NASASpaceFlight.com Forum
Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: Tywin on 04/12/2019 02:53 am
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Well the mission DART, to the asteroid Didymos, will be launch by SpaceX...
https://spacenews.com/nasa-awards-dart-launch-contract-to-spacex/
“SpaceX is proud to continue our successful partnership with NASA in support of this important interplanetary mission,” SpaceX President Gwynne Shotwell said in a company statement. “This award underscores NASA’s confidence in Falcon 9’s capability to perform critical science missions while providing the best launch value in the industry.”
https://www.nasa.gov/planetarydefense/dart
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Some news on DART:
DART remains on schedule for launch in July 2021 on a Falcon 9 despite the pandemic, said Elena Adams, mission systems engineer for DART at the Johns Hopkins University Applied Physics Lab, which is managing the mission, during the webinar. The spacecraft bus, with its electric propulsion systems installed, recently arrived at the lab for integration and testing.
https://spacenews.com/nasa-planetary-defense-efforts-continue-during-pandemic/
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As of February, the launch has been postponed - NET November 24, 2021
https://www.nasa.gov/feature/dart-launch-moves-to-secondary-window (https://www.nasa.gov/feature/dart-launch-moves-to-secondary-window)
The ROSA solar panels had some supply-chain issues and the navigation camera needed more work to make sure it could handle launch.
EDIT: Today (April 18th) I stumbled upon this video showing them testing out the high gain antenna - which is a flat disk shaped Radial Line Slot Array, rather than the usual parabolic dish. I decided to attach it to this post instead of writing a new one because JHUAPL released it in February:
https://www.youtube.com/watch?v=iTWdya4wBzw
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This came in yesterday:
https://www.nasa.gov/feature/nasa-selects-four-scientists-to-join-the-dart-planetary-defense-mission (https://www.nasa.gov/feature/nasa-selects-four-scientists-to-join-the-dart-planetary-defense-mission)
Dr. Bonnie Buratti of the Jet Propulsion Laboratory will use Earth-based telescopic observations of Didymos and Dimorphos to better characterize the surface reflectivity and roughness of both objects before DART’s arrival, and later will use observations from DART itself to further refine this knowledge, in order to aid in mapping the geological features of the asteroids.
Dr. Ludmilla Kolokolova of the University of Maryland, College Park will use sophisticated radiative-transfer models to analyze and interpret images of the ejecta plume taken by LICIACube’s cameras, in order to better understand the distribution of ejecta momentum enhancing the effect of DART’s kinetic impact.
Dr. Jay McMahon of the University of Colorado, Boulder will apply the dynamical theory of interacting non-spherical bodies and radiative forces to better understand the changes in Dimorphos’s orbit caused by physical effects other than DART’s kinetic impact, in order to help interpret the post-impact Earth-based observations.
Dr. Stephen Schwartz of the University of Arizona will develop a new computational approach to link fluid-based simulations of impacts to particle-based simulations of the resulting ejecta, in order to better connect the observed properties of the ejecta plume to the physical properties of Dimorphos’s surface
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November 16, 2021
MEDIA ADVISORY M21-154
NASA TV to Air DART Prelaunch Activities, Launch
NASA will provide coverage of the upcoming prelaunch and launch activities for the agency’s first planetary defense test mission, the Double Asteroid Redirection Test (DART). The mission will help determine if intentionally crashing a spacecraft into an asteroid is an effective way to change its course. DART’s target asteroid is not a threat to Earth.
DART is scheduled to launch no earlier than 1:20 a.m. EST Wednesday, Nov. 24 (10:20 p.m. PST Tuesday, Nov. 23) on a SpaceX Falcon 9 rocket from Vandenberg Space Force Base in California.
Live launch coverage will begin at 12:30 a.m. EST Wednesday, Nov. 24, 2021 (9:30 p.m. PST Tuesday, Nov. 23, 2021), on NASA Television, the NASA app, and the agency’s website, with prelaunch and science briefings beginning Sunday, Nov. 21.
The spacecraft is designed to direct itself to impact an asteroid while traveling at a speed of roughly 15,000 miles per hour (24,000 kilometers per hour). Its target is the asteroid moonlet Dimorphos (Greek for “two forms”), which orbits a larger asteroid named Didymos (Greek for “twin”). In fall 2022, DART will impact Dimorphos to change its orbit within the Didymos binary asteroid system. The Didymos system is the ideal candidate for DART because it poses no actual impact threat to Earth, and scientists can measure the change in Dimorphos’ orbit with ground-based telescopes.
Due to the coronavirus (COVID-19) pandemic, all media participation in news conferences will be remote. Please refer to NASA’s media accreditation policy for teleconferences and onsite activities. A phone bridge will be provided for each briefing. Media and the public also may refer to the DART press kit for more information on the mission.
Full mission coverage is as follows (all times Eastern):
Sunday, Nov. 21
4 p.m. – DART investigation and engineering briefing with the following participants:
Lori Glaze, director of NASA's Science Mission Directorate's Planetary Science Division at NASA Headquarters in Washington
Tom Statler, DART program scientist, NASA’s Science Mission Directorate’s Planetary Science Division, NASA Headquarters
Andy Rivkin, DART investigation team lead, Johns Hopkins Applied Physics Laboratory
Betsy Congdon, DART mechanical systems engineer, Johns Hopkins Applied Physics Laboratory
Simone Pirrotta, Light Italian Cubesat for Imaging of Asteroids (LICIACube) project manager, Italian Space Agency
This event is open to media with valid credentials. Media who would like to ask questions during the investigation briefing must provide their name and affiliation by 4 p.m. EST (1 p.m. PST) Friday, Nov. 19, to the newsroom at the Kennedy Space Center in Florida at: [email protected]. Media and the public also may ask questions on social media using #AskNASA.
Monday, Nov. 22
7 p.m. – DART prelaunch news conference, with the following participants:
Thomas Zurbuchen, associate administrator, NASA’s Science Mission Directorate, NASA Headquarters
Lindley Johnson, planetary defense officer, NASA’s Planetary Defense Coordination Office, NASA Headquarters
Ed Reynolds, DART project manager, Johns Hopkins Applied Physics Laboratory
Omar Baez, senior launch director, Launch Services Program, NASA’s Kennedy Space Center in Florida
Julianna Scheiman, director for civil satellite missions, SpaceX
Capt. Maximillian Rush, weather officer, Space Launch Delta 30, Vandenberg Space Force Base
This event is open to media with valid credentials. Media who would like to ask questions during the prelaunch briefing must provide their name and affiliation by 1 p.m. EST (10 a.m. PST) Monday, Nov. 22, to the Kennedy newsroom at: [email protected]. Media may also ask questions on social media using #AskNASA.
Tuesday, Nov. 23
4 p.m. – NASA Science Live, with the following participants:
Lori Glaze, director of NASA's Science Mission Directorate's Planetary Science Division at NASA Headquarters
Nancy Chabot, DART coordination lead, John Hopkins University Applied Physics Laboratory
Joshua Ramirez Rodriguez, telecommunications subsystem integration and test lead engineer, Johns Hopkins Applied Physics Laboratory
This event will stream live on the agency’s Facebook, Twitter and YouTube channels. Members of the public can participate live by submitting questions in the comment section of the streams, or by using #AskNASA.
Wednesday, Nov. 24
12:30 a.m. – NASA TV live launch coverage begins.
Audio only of the news conferences and launch coverage will be carried on the NASA “V” circuits, which may be accessed by dialing 321-867-1220, -1240, -1260 or -7135. On launch day, "mission audio," the launch conductor’s countdown activities without NASA TV launch commentary, will be carried on 321-867-7135.
Planetary Defender Campaign
To allow the public to share in the excitement of DART, NASA has launched the Planetary Defenders campaign. Participants can answer a short series of questions about planetary defense to earn their planetary defender certificate, which they can download or print, as well as a digital badge to share on social media using the hashtag #PlanetaryDefender.
Public Participation
Members of the public can register to attend the launch virtually. NASA’s virtual guest program for DART includes curated launch resources, a behind-the-scenes look at the mission, and the opportunity for a virtual guest launch passport stamp.
Virtual NASA Social
As we finalize launch preparations, we are excited to invite the public to join our virtual NASA Social for the #DARTMission on Facebook. Stay up to date on the latest mission activities, interact with NASA and DART team members in real-time, and watch the launch of the SpaceX Falcon 9 rocket that will boost DART toward its destination.
Watch and Engage on Social Media
Stay connected with the mission on social media, and let people know you're following it on Twitter, Facebook, and Instagram using the hashtag #DARTMission and tag these accounts:
Twitter: @NASA, @AsteroidWatch, @NASASocial and @NASA_LSP
Facebook: NASA and NASA LSP
Instagram: NASA
Para obtener información sobre cobertura en español en el Centro Espacial Kennedy o si desea solicitar entrevistas en español, comuníquese con Antonia Jaramillo 321-501-8425.
The Johns Hopkins Applied Physics Laboratory has been directed to manage the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency’s Planetary Missions Program Office. The agency provides support for the mission from several centers, including the Jet Propulsion Laboratory in Southern California, Goddard Space Flight Center in Greenbelt, Maryland, Johnson Space Center in Houston, Glenn Research Center in Cleveland, and Langley Research Center in Hampton, Virginia. The launch is managed by NASA’s Launch Services Program, based at the agency’s Kennedy Space Center in Florida. SpaceX is the rocket provider for the DART launch.
For more information about DART, visit:
https://www.nasa.gov/dartmission
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This press conference was a couple of weeks ago and is pretty interesting:
https://youtu.be/EMwB0QERjEw
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Press conference of today: DART investigation and engineering briefing
https://youtu.be/zinTjeOVfpY
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Good animations of the relevant maneuvers and phases.
NASA hopes to hit an asteroid now in case we really need to knock one away later
https://www.washingtonpost.com/science/interactive/2021/nasa-rams-an-asteroid-planetary-defense/
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And on NSF
https://www.nasaspaceflight.com/2021/11/falcon-9-dart-launch/
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https://twitter.com/DrPhiltill/status/1463661046615392259
BTW, the reason we need to experimentally slam a spaceship into an asteroid rather than simply *calculate* how much it will deflect the asteroid, is because regolith physics is UNSOLVED and too hard to calculate! The splash of regolith on impact determines the deflection. 1/2
2/2 Because the splash flies *back* the opposite direction that the asteroid is being nudged, so it actually increases the change of momentum of the asteroid. But how much? Nobody can calculate a splash of sand. Sand physics is unsolved and super hard. https://nytimes.com/2020/11/09/science/what-makes-sand-soft.amp.html
The factor of the momentum change due to regolith splash is known as the “beta” of the impact. It is super important to measure so we can deflect an asteroid enough to miss the Earth, considering that spacecraft kinetics are not infinite.
Sample the math in this seminal paper. This is sand (in a simplified case). https://eweb.unex.es/eweb/fisteor/vicente/publicaciones/preb07.pdf
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Seems to me this test will need to be repeated on each type of near Earth asteroid. Surely you will get quite different ejecta depending on whether the spacecraft slams into a solid rock, a pile of rubble, a sandy surface, and so on.
Also, for a real mission, I'd imagine you would want to leave the spacecraft attached to the second stage. It requires more maneuvering oomph, but increases your impact mass (or gravity tractor mass) for free. This is a quite different engineering problem (especially if you want to support a wide variety of launch providers, as you would in a real emergency). Maybe the next planetary defense mission can try this.
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Seems to me this test will need to be repeated on each type of near Earth asteroid. Surely you will get quite different ejecta depending on whether the spacecraft slams into a solid rock, a pile of rubble, a sandy surface, and so on.
Also, for a real mission, I'd imagine you would want to leave the spacecraft attached to the second stage. It requires more maneuvering oomph, but increases your impact mass (or gravity tractor mass) for free. This is a quite different engineering problem (especially if you want to support a wide variety of launch providers, as you would in a real emergency). Maybe the next planetary defense mission can try this.
Heh. Will really like to see a real impactor like "Rods from God" for asteroid composition survey. All that is needed is attaching some ion thrusters for the cruise phase plus some hypergolic thrusters for the terminal phase to a 10 tonne metal rod. Along with some parasite post impact observation SmallSats that doubles up as vehicle flight control systems.
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Seems to me this test will need to be repeated on each type of near Earth asteroid. Surely you will get quite different ejecta depending on whether the spacecraft slams into a solid rock, a pile of rubble, a sandy surface, and so on.
Also, for a real mission, I'd imagine you would want to leave the spacecraft attached to the second stage. It requires more maneuvering oomph, but increases your impact mass (or gravity tractor mass) for free. This is a quite different engineering problem (especially if you want to support a wide variety of launch providers, as you would in a real emergency). Maybe the next planetary defense mission can try this.
Heh. Will really like to see a real impactor like "Rods from God" for asteroid composition survey. All that is needed is attaching some ion thrusters for the cruise phase plus some hypergolic thrusters for the terminal phase to a 10 tonne metal rod. Along with some parasite post impact observation SmallSats that doubles up as vehicle flight control systems.
“asteroid composition survey” sounds like science
DART is out of NASA’s Space Technology Mission Directorate
The composition is “on topic” so far as it affects the momentum coupling
The foolishly named “rods from God” form assumes a lot about what kind of impact is targeted and that leaving behind most of the mass would actually help. Not likely.
Doing some homework might bring you to the mass installed in the Impactor spacecraft for NASA’s Deep Impact mission. It was a layered and pocketed copper mass designed to maximize the coupling. It did not need to look like any particular weapon.
(Copper was chosen for its lack of emission lines within the wavelength range of the Spectral Imaging Module.)
I actually possess a disk from the original Impactor mass, which Ball Aerospace scrapped and then paid NASA back for the scrap metal value. It’s just a disk.
If you read the paper you will see that the coupling coefficient is anticipated to be between 1.5 and 2.0 for the Didymos impact. Getting a good value from thus experiment will go a long way to refining a future prediction for a different asteroid.
And in the end, in the unlikely case that such a deflection was needed, it would be over-designed for the worst case amplification factor and the worst case targeting.
So another test is not needed, which is good because another mission is unlikely.
edit: correction
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....the coupling coefficient is anticipated to be between 1.5 and 2.0 for the Didymos impact. Getting a good value from thus experiment will go a long way to refining a future prediction for a different asteroid.
And in the end, in the unlikely case that such a deflection was needed, it would be over-designed for the worst case amplification factor and the worst case targeting.
So another test is not needed, which is good because another mission is unlikely.
Think there might be similar missions to other classes of asteroids if they are cheap enough.
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DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
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DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
Information like this is PRECISELY why I like this forum. You'd never know this from the NASA description of the mission, of course. Even reading the previous studies and noting DART was not there would not tell you why. But someone involved in the process does know, and now we know too. Thanks!
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DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
That's quite the leading comment. Care to share WHO the Congress member was? A Google search was fruitless. Link to the studies? Any opinion on WHY the earmark was inserted?
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DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
That's quite the leading comment. Care to share WHO the Congress member was? A Google search was fruitless. Link to the studies? Any opinion on WHY the earmark was inserted?
It's an APL mission. It was earmarked by somebody in the Maryland congressional delegation.
Ideally, the way you want these things to happen is that a group of subject matter experts (in this case, asteroid experts) would meet, identify a problem, then identify a set of solutions to that problem:
Finding: X is a problem.
Recommendation: NASA should do Y to fix that problem.
You can't find that in this case. The mission sort of just sprang up in the middle of the last decade, without any independent pedigree. I believe that it first appeared in congressional language and not a president's budget request, but even if it had been the later it could have been a favor to a member of Congress. Rather surprisingly, the last administration did not kill it, but that's because Republicans like blowing stuff up, whereas the higher priority for asteroid defense has long been a better means of detecting them (you can't blow up what you have not detected). If you look back several years, you'll see that DART was supposed to be done in conjunction with a European mission, but that European mission never got approved, making DART really dubious. But it was always dubious.
As to the studies:
https://www.nap.edu/catalog/12842/defending-planet-earth-near-earth-object-surveys-and-hazard-mitigation
https://www.nap.edu/catalog/25476/finding-hazardous-asteroids-using-infrared-and-visible-wavelength-telescopes
There was also a STPI/IDA study that's public, but I don't know if it's on the internet. And there have been numerous other studies as well. Feel free to research the subject and report back on what you find.
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DART was an earmarked mission inserted into NASA's budget by a member of Congress. There have been numerous expert studies done over a number of years on dealing with the hazard posed by NEOs (I was study director on two of them). You won't find this mission recommended in those studies.
If you’re willing, would you mind briefly describing the kinds of missions which were recommended, if any? For those of us who don’t want to read the whole study (sorry :)).
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“asteroid composition survey” sounds like science
DART is out of NASA’s Space Technology Mission Directorate
DART is funded under "Planetary Defense" budget line, which is under "Planetary Science" in the NASA budget.
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Planetary Society has a good article about the funding increase for Planetary Defense: How NASA's Planetary Defense Budget Grew By More Than 4000% in 10 years (https://www.planetary.org/articles/nasas-planetary-defense-budget-growth), work for APL is the direct reason for DART funding as explained in the article, but that happened under the general trend of increasing funding for Planetary Defense, it didn't happen alone.
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As to the studies:
https://www.nap.edu/catalog/12842/defending-planet-earth-near-earth-object-surveys-and-hazard-mitigation
https://www.nap.edu/catalog/25476/finding-hazardous-asteroids-using-infrared-and-visible-wavelength-telescopes
The fact that the 2nd study didn't recommend anything like DART is to be expected, since the reason this study is done in the first place is because "NASA’s chief scientist asked the National Academies of Sciences, Engineering, and Medicine to establish a study to address the issue of the relative advantages and disadvantages of infrared and visible observations of near Earth objects (NEOs).", so of course the study is not going to recommend anything like DART because the study is entirely focused on finding asteroids, mitigation is not even part of the study.
The 1st study however did have the following recommendation from Chapter 5 Mitigation:
Recommendation: If Congress chooses to fund mitigation research at an appropriately high level, the first priority for a space mission in the mitigation area is an experimental test of a kinetic impactor along with a characterization, monitoring, and verification system, such as the Don Quijote mission that was previously considered, but not funded, by the European Space Agency. This mission would produce the most significant advances in understanding and provide an ideal chance for international collaboration in a realistic mitigation scenario.
This looks very much like a recommendation for DART.
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It's not often that you find a member of Congress doing such thorough homework:
Galvez, A., Carnelli, I., Michel, P., Cheng, A.F., Reed, C., Ulamec, S., Biele, J., Zbrll, P. and Landis, R., 2013, September. AIDA: The asteroid impact and deflection assessment mission. In European Planetary Science Congress (Vol. 8).
Cheng, A.F., Michel, P., Reed, C., Galvez, A., Carnelli, I. and Headquarters, P., 2012, September. Dart: Double asteroid redirection test. In European Planetary Science Congress (Vol. 7, pp. 23-28).
Cheng, A., Stickle, A., Atchison, J., Barnouin, O., Rivkin, A., Michel, P., Ulamec, S. and AIDA Team, 2015, October. Asteroid impact and deflection assessment mission: Double asteroid redirection test (dart). In Proceedings of the 4th IAA Planetary Defense Conference, Frascati, Italy.
Michel, P., Kueppers, M., Sierks, H., Carnelli, I., Cheng, A.F., Mellab, K., Granvik, M., Kestilä, A., Kohout, T., Muinonen, K. and Näsilä, A., 2018. European component of the AIDA mission to a binary asteroid: Characterization and interpretation of the impact of the DART mission. Advances in Space Research, 62(8), pp.2261-2272.
Cheng, A.F., Rivkin, A.S., Michel, P., Atchison, J., Barnouin, O., Benner, L., Chabot, N.L., Ernst, C., Fahnestock, E.G., Kueppers, M. and Pravec, P., 2018. AIDA DART asteroid deflection test: Planetary defense and science objectives. Planetary and Space Science, 157, pp.104-115.
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As to the studies:
https://www.nap.edu/catalog/12842/defending-planet-earth-near-earth-object-surveys-and-hazard-mitigation
https://www.nap.edu/catalog/25476/finding-hazardous-asteroids-using-infrared-and-visible-wavelength-telescopes
The fact that the 2nd study didn't recommend anything like DART is to be expected, since the reason this study is done in the first place is because "NASA’s chief scientist asked the National Academies of Sciences, Engineering, and Medicine to establish a study to address the issue of the relative advantages and disadvantages of infrared and visible observations of near Earth objects (NEOs).", so of course the study is not going to recommend anything like DART because the study is entirely focused on finding asteroids, mitigation is not even part of the study.
The 1st study however did have the following recommendation from Chapter 5 Mitigation:
Recommendation: If Congress chooses to fund mitigation research at an appropriately high level, the first priority for a space mission in the mitigation area is an experimental test of a kinetic impactor along with a characterization, monitoring, and verification system, such as the Don Quijote mission that was previously considered, but not funded, by the European Space Agency. This mission would produce the most significant advances in understanding and provide an ideal chance for international collaboration in a realistic mitigation scenario.
This looks very much like a recommendation for DART.
Thanks for posting that as it certainly gives a rather different prospective than you would get if you just read some of the posts above.
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There's a lot of context left out. The most relevant issue is the 2005 George E. Brown Act, which directed NASA to find 90% of potentially hazardous asteroids 140 meters in diameter or greater by 2020. (Note: it's technically part of a different piece of legislation and not a stand-alone act, but it is generally referred to as the George E. Brown Act.) By 2020--the deadline in the act--NASA had detected about 30% of those asteroids. Even only a few years after the act was signed, it was clear that NASA was not going to accomplish that goal, and by 2020 it was clear that existing asteroid detection systems were never going accomplish that goal even by 2035.
The only way to accomplish the goal is to build an in-space infrared telescope specifically designed for the purpose. The leading proposal for that telescope was the NEOCam spacecraft, first proposed in the 2000s. NEOCam has now been renamed as the NEO Surveyor, but is essentially the same project. The problem was that NEOCam just never got funding. There are a lot of reasons for that, but I won't go into them here. The bottom line was that even a decade after the passage of the act (mid-2010s), NASA was not making any progress at accomplishing that goal. But then along came DART, and if you go digging deep enough in congressional legislation (and draft congressional legislation) you find that DART was lobbied by APL and then added into the NASA budget by a member of Congress. That's where it came from. If you had asked members of the asteroid defense community during the last 16 years what they believed should be their highest priority, it would have been the survey telescope, not an impact mission. If you had gone to SBAG meetings throughout the 2010s, most of the focus would have been on asteroid science missions, not planetary defense, but the people there talked about the requirements for an NEO survey telescope.
As for Casey Dreier's article, he misunderstood a number of key issues (he updated that article after I pointed out some important events that he left out, but there are still some problems with his interpretation of the cause-effect relationships.). He was looking at top-line budget numbers for "Planetary Defense/NEO Observation Funding," but not what was actually in those budgets, and then drew conclusions that the top-line budgets increased primarily because of the human spaceflight program. Simply taking his argument at face value, one could ask why, if the Asteroid Redirect Mission was a major cause of increase in that budget, the budget did not go down after ARM was canceled? Furthermore, the biggest overall increase to the budget was DART procurement, and DART has nothing at all to do with the human spaceflight program. Even further, the most important precursor to the ARM mission was a survey telescope to find asteroids that astronauts could realistically visit, and yet that did not get funded. The human spaceflight and planetary defense subjects weren't linked and increases in the planetary defense budget were not caused by events in the human spaceflight program. In fact, one of the problems with NASA's human mission to an asteroid effort was that they were not talking to the actual asteroid experts. MIT's Richard Binzel made a lot of noise about this at SBAG meetings in the last decade.
In order to understand increases in the planetary defense budget, you have to look at what was actually in the budget. There were a bunch of things that were either increased or added to that budget from elsewhere. For instance, the Antarctic meteorite collection effort was previously book-kept elsewhere in NASA and that was then added to the planetary defense budget, increasing the total. I believe that NASA's portion of Arecibo funding was added to the planetary defense budget. A number of projects for ground-telescope support, upkeep, and observing time were added to the budget (not all of them were related to asteroids--I think NASA funding for the IRTF was in there--but neither was the Antarctica program). There were also infrastructure upgrades that were added into the budget--I was told, dunno if it's totally accurate, that the Minor Planet Center's (they track asteroids) outdated equipment was also upgraded at NASA expense. So those budget increases came from a lot of things added into the planetary defense budget and you'd really have to get down into the weeds to see what all of them were. (There's one other minor issue that I told Dreier about, but it's difficult to find information on. That is that the increase in the budget first occurred in late 2009, not 2011. It happened after the NRC produced the interim report to its 2010 report. The NEO budget increased from about $4.5 million to $6.5 million. But that extra $2 million came out of somebody's existing discretionary reserve account. I cannot remember if it was the NASA administrator's discretionary account or if it was the AA for science discretionary account, but it didn't show in the overall top-line budget because the money came from elsewhere. [Sidenote: people like the NASA administrator and the AAs for various directorates usually have a few million dollars in a discretionary reserve budget that they can allocate however they want. This is actually common to many organizations.])
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I thought the single biggest advance in asteroid detection will be the Vera Rubin (formerly Large Synoptic Survey Telescope), which can do the bulk of the work of discovering unknown asteroids. In its first year of operation, it is expected to double the number of known Earth-crossing asteroids (https://b612foundation.org/how-many-asteroids-will-lsst-find-we-now-have-that-number-by-dr-ed-lu/). Is Planetary defense contributing to this project?
NeoWise, or equivalent, will still be needed, since Rubin cannot look too close to the Sun, nor spend the bulk of it's time looking at spots where threatening asteroids are most likely to be found. But it will up the detected fraction by a lot.
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From what I remember, ideally NEOSurvey would be flown in a close orbit to Venus so it could look "out". I don't know if SEL1 would be a second best. So it's not only how close but how you look, from what I understand. Looking "outwards" gives you the view with the most brightness. Looking close to the sun you are looking sideways to a hot plate. At least that's what I understood.
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...DART was supposed to be done in conjunction with a European mission, but that European mission never got approved...
Ummm...
Hera?
https://www.esa.int/Safety_Security/Hera (https://www.esa.int/Safety_Security/Hera)
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Hera?
AIM.
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I was under the probably mistaken impression that AIM became Hera.
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I was under the probably mistaken impression that AIM became Hera.
It's different. AIM was more extensive. Whether the current setup produces good data I have no knowledge.
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I was under the probably mistaken impression that AIM became Hera.
It's different. AIM was more extensive. Whether the current setup produces good data I have no knowledge.
Why would it had been approved if it wasn't expected to produce good (enough) data?
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I was under the probably mistaken impression that AIM became Hera.
It's different. AIM was more extensive. Whether the current setup produces good data I have no knowledge.
Why would it had been approved if it wasn't expected to produce good (enough) data?
People have different definitions of "enough."
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I thought the single biggest advance in asteroid detection will be the Vera Rubin (formerly Large Synoptic Survey Telescope), which can do the bulk of the work of discovering unknown asteroids. In its first year of operation, it is expected to double the number of known Earth-crossing asteroids (https://b612foundation.org/how-many-asteroids-will-lsst-find-we-now-have-that-number-by-dr-ed-lu/). Is Planetary defense contributing to this project?
NeoWise, or equivalent, will still be needed, since Rubin cannot look too close to the Sun, nor spend the bulk of it's time looking at spots where threatening asteroids are most likely to be found. But it will up the detected fraction by a lot.
Won't NeoSurveyor also see things too dark for the LSST survey, since its an IR camera?
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I thought the single biggest advance in asteroid detection will be the Vera Rubin (formerly Large Synoptic Survey Telescope), which can do the bulk of the work of discovering unknown asteroids. In its first year of operation, it is expected to double the number of known Earth-crossing asteroids (https://b612foundation.org/how-many-asteroids-will-lsst-find-we-now-have-that-number-by-dr-ed-lu/). Is Planetary defense contributing to this project?
NeoWise, or equivalent, will still be needed, since Rubin cannot look too close to the Sun, nor spend the bulk of it's time looking at spots where threatening asteroids are most likely to be found. But it will up the detected fraction by a lot.
Won't NeoSurveyor also see things too dark for the LSST survey, since its an IR camera?
I think this depends on the asteroid. If it has a high albedo, it's bright in the visible, and LSST sees it more easily. But if it's low albedo (and I think some asteroids are as low a 3%) then there is little reflected light, and LSST has problems. But that absorbed energy has to go somewhere, and such asteroids are bright in the thermal infrared even though dark in the visible. So these are more visible to NEO Surveyor. The combination is better than either alone.
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https://www.nasa.gov/feature/with-its-single-eye-nasa-s-dart-returns-first-images-from-space
Dec 22, 2021
With Its Single “Eye,” NASA’s DART Returns First Images from Space
Just two weeks after launching from Vandenberg Space Force Base in California, NASA’s Double Asteroid Redirection Test (DART) spacecraft has opened its “eye” and returned its first images from space — a major operational milestone for the spacecraft and DART team.
image of about a dozen stars near where the constellations Perseus, Aries and Taurus intersect
On Dec. 7, after opening the circular door to its telescopic imager, NASA’s DART captured this image of about a dozen stars near where the constellations Perseus, Aries and Taurus intersect.
Credits: NASA/Johns Hopkins APL
image of the stars in Messier 38, or the Starfish Cluster
On Dec. 10, DART’s DRACO camera captured and returned this image of the stars in Messier 38, or the Starfish Cluster, which lies some 4,200 light years away.
Credits: NASA/Johns Hopkins APL
After the violent vibrations of launch and the extreme temperature shift to minus 80 degrees C in space, scientists and engineers at the mission operations center at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, held their breath in anticipation. Because components of the spacecraft’s telescopic instrument are sensitive to movements as small as 5 millionths of a meter, even a tiny shift of something in the instrument could be very serious.
On Tuesday, Dec. 7, the spacecraft popped open the circular door covering the aperture of its DRACO telescopic camera and, to everyone’s glee, streamed back the first image of its surrounding environment. Taken about 2 million miles (11 light seconds) from Earth — very close, astronomically speaking —the image shows about a dozen stars, crystal-clear and sharp against the black backdrop of space, near where the constellations Perseus, Aries and Taurus intersect.
The DART navigation team at NASA’s Jet Propulsion Laboratory in California used the stars in the image to determine precisely how DRACO was oriented, providing the first measurements of how the camera is pointed relative to the spacecraft. With those measurements in hand, the DART team could accurately move the spacecraft to point DRACO at objects of interest, such as Messier 38 (M38), also known as the Starfish Cluster, that DART captured in another image on Dec. 10. Located in the constellation Auriga, the cluster of stars lies some 4,200 light years from Earth. Intentionally capturing images with many stars like M38 helps the team characterize optical imperfections in the images as well as calibrate how absolutely bright an object is — all important details for accurate measurements when DRACO starts imaging the spacecraft’s destination, the binary asteroid system Didymos.
DRACO (short for Didymos Reconnaissance and Asteroid Camera for Optical navigation) is a high-resolution camera inspired by the imager on NASA’s New Horizons spacecraft that returned the first close-up images of the Pluto system and of a Kuiper Belt object, Arrokoth. As DART’s only instrument, DRACO will capture images of the asteroid Didymos and its moonlet asteroid Dimorphos, as well as support the spacecraft’s autonomous guidance system to direct DART to its final kinetic impact.
DART was developed and is managed by Johns Hopkins APL for NASA’s Planetary Defense Coordination Office. DART is the world's first planetary defense test mission, intentionally executing a kinetic impact into Dimorphos to slightly change its motion in space. While neither asteroid poses a threat to Earth, the DART mission will demonstrate that a spacecraft can autonomously navigate to a kinetic impact on a relatively small target asteroid, and that this is a viable technique to deflect a genuinely dangerous asteroid, if one is ever discovered. DART will reach its target on Sept. 26, 2022.
For more information about the DART mission, visit:
https://www.nasa.gov/dartmission
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Tenuously on topic question, that I did not find an answer for elsewhere:
Did Deep Impact produce a measurable change in the orbit of comet Tempel-1? From what I've read it may pass too close to Jupiter for any conclusions to be drawn.
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Tenuously on topic question, that I did not find an answer for elsewhere:
Did Deep Impact produce a measurable change in the orbit of comet Tempel-1? From what I've read it may pass too close to Jupiter for any conclusions to be drawn.
It produced no measurable change to the orbit of the comet.
DART is hitting a much smaller object, and the change is expected to be easily measurable from Earth.
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Tenuously on topic question, that I did not find an answer for elsewhere:
Did Deep Impact produce a measurable change in the orbit of comet Tempel-1? From what I've read it may pass too close to Jupiter for any conclusions to be drawn.
It produced no measurable change to the orbit of the comet.
DART is hitting a much smaller object, and the change is expected to be easily measurable from Earth.
Partially because not only is it a relatively very small asteroid but it is in orbit around another asteroid which allows us to observe the change in period of asteroid orbit around the other asteroid.
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At today's SBAG meeting it was noted that the Dimorphos impact will be at 7:14 PM EST on September 26.
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At today's SBAG meeting it was noted that the Dimorphos impact will be at 7:14 PM EST on September 26.
added to my calendar ;D
Google probably isn't sure what to make of the location "asteroid Dimorphos"
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At today's SBAG meeting it was noted that the Dimorphos impact will be at 7:14 PM EST on September 26.
In late September Daylight Savings Time will be in effect.
How was it specified at the SBAG?
Will the impact be 7:14 PM EST or EDT?
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https://www.nasa.gov/feature/with-its-single-eye-nasa-s-dart-returns-first-images-from-space
Dec 22, 2021
With Its Single “Eye,” NASA’s DART Returns First Images from Space
Attaching the image here. Also available on JHUAPL site:
https://www.jhuapl.edu/NewsStory/211222-DART-DRACO-returns-first-images-of-stars-from-space (https://www.jhuapl.edu/NewsStory/211222-DART-DRACO-returns-first-images-of-stars-from-space)
and the DART image archive:
https://dart.jhuapl.edu/Gallery/ (https://dart.jhuapl.edu/Gallery/)
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Why does one star look elongated? Is it in motion? A planet?
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Why does one star look elongated? Is it in motion? A planet?
It could be a cosmic ray.
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Dart and Didymos trajectories plotted as per NASA Horizons data.
Unfortunately I am not able to get the relative distance as I can't get Didymos as the central body; in case anybody wants to give it a try:
Dart: -135
Didymos: DES=2065803
I used these urls and manually overlayed the results:
Dart url (http://win98.altervista.org/space/exploration/3d/space-explorer-tracker.html?orbiter=-135¢er=@0&bodyname=Sun&orbitername=DART&start=2021-12-31&stop=2022-10-17&step=1d&3dzoom=300000000&radius=1000000)
Didymos url (http://win98.altervista.org/space/exploration/3d/space-explorer-tracker.html?orbiter=DES=2065803¢er=@0&bodyname=Sun&orbitername=Didymos&start=2021-12-31&stop=2022-10-17&step=1d&3dzoom=300000000&radius=1000000)
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I also found a guide (https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/req/naif_ids.html#NAIF%20Object%20ID%20numbers) to NAIF SPICE system about asteroids and their moons, with a specific example about Didymos (last lines):
Asteroids
According to the original schema, NAIF ID codes for permanently numbered asteroids registered in the JPL Solar System Dynamics (SSD) Group database are 7-digit numbers determined using the algorithm
NAIF ID code = 2000000 + Permanent Asteroid Number
limited to the 2000001 to 2999999 range and allowing up to 1 million asteroids.
For newly discovered asteroids with provisional numbers SSD internally uses 7-digit numbers determined via the algorithm
NAIF ID code = 3000000 + Provisional Asteroid Number
limited to the 3000001 to 3999999 range and also allowing up to 1 million asteroids.
Given the need to accommodate many more asteroids expected to be discovered by surveys coming on-line in the near future and the desire to encode in the NAIF ID codes the roles of individual asteroids and barycenters in binary and multi-body asteroid systems in a way similar to planetary systems, in 2019 SSD and NAIF agreed to extend the original schema.
Under the extended schema all permanently numbered singular asteroids have 8-digit NAIF ID codes with the original 7-digit IDs still allowed to be used. Such asteroids are assigned NAIF ID codes using the algorithm
NAIF ID code = 20000000 + Permanent Asteroid Number
limited to the 20000001 to 49999999 range and allowing up to 30 million asteroids.
For asteroid systems with two or more bodies the 8-digit NAIF ID code represents the barycenter. Individual satellites have a prepended number 1 through 8, while the primary body uses the ``last available'' prefix 9, resulting in 9-digit NAIF ID codes. This is analogous to the planetary system approach except a single extra number is added as a prefix rather than two numbers added as a suffix. In the case of ID codes presented by strings, a 0 prefix could be added to the ID of the barycenter, if printing out uniform 9 digits is desired.
For newly discovered singular asteroids and asteroid system barycenters with provisional numbers NAIF ID codes are also 8-digit numbers determined via the algorithm:
NAIF ID code = 50000000 + Provisional Asteroid Number
limited to the 50000001 to 99999999 range and allowing up to 50 million asteroids, with the same prefix rule used to derive the 9-digit IDs for the primary and satellite bodies in multi-body systems.
For example, asteroid Yeomans (2956) has NAIF ID number 2002956 according to the original schema and NAIF ID number 20002956 according to the extended schema, while asteroids Didymos (65803) and its satellite Dimorphos can be accommodated only using the extended schema with IDs 920065803 and 120065803, and Didymos system barycenter with ID 20065803.
NAIF ID NAME
________ ____________________
20065803 'DIDYMOS_BARYCENTER'
120065803 'DIMORPHOS'
920065803 'DIDYMOS'
These info should be useful to figure out how to track Didymos, Didymoon and DART using one of the pages below, but I didn't succeed yet (I cant find the right kernels):
https://wgc.jpl.nasa.gov:8443/webgeocalc/#StateVector
https://wgc2.jpl.nasa.gov:8443/webgeocalc/example/perform-calculation.html
https://ssd.jpl.nasa.gov/horizons/app.html#/
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Found the right parameters (http://win98.altervista.org/space/exploration/3d/space-explorer-tracker.html?orbiter=-135¢er=@20065803&bodyname=Didymos&orbitername=Didymos&start=2021-11-25&stop=2022-10-18&%2005:00step=1d&3dzoom=100000000&radius=0.1) to plot Dart vs Didymos: "center" must be "@20065803" rather than "@2065803" (one zero added, don't know why).
Closest approach is currently.... the impact (planned at 26-Sep-2022 23:14:18.1108 UTC), but trajectory continues afterwards.
No luck in tracking Dymorphos (120065803) vs Didymos yet.
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Very cool updated on Horizons system just yesterday, March 3rd!
Horizons On-Line System News
March 3, 2022
-- The 65803 Didymos system, containing the DART mission's satellite impact
target (Dimorphos), has been elaborated and can be accessed under the
following ID codes:
Didymos system barycenter : 20065803
Primary body (Didymos) center: 920065803
Secondary (Dimorphos) center : 120065803
Thus one can generate ephemerides such as ...
target center
Dimorphos wrt DART: 120065803 @ dart (or "@-175")
Dimorphos wrt Didymos primary: 120065803 @ 920065803
Dimorphos wrt Didymos bary : 120065803 @ 20065803
... and so on.
A mass model for the system and rotation model for Dimorphos are also
defined to generate orbital elements and cartographic data.
However, DART will be using optical navigation and maneuvering to
refine the trajectory to impact, so this prediction-based model is
only a nominal guide.
https://ssd.jpl.nasa.gov/horizons/news.html
This allows plotting the current typical orbit of Dymorphos around Didymos, to compare it to new orbit after impact:
http://win98.altervista.org/space/exploration/3d/space-explorer-tracker.html?orbiter=120065803¢er=@20065803&start=2022-MAR-04&stop=2022-03-05&step=1m
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.@NASA's #DARTMission is set to deflect an asteroid soon, but #PlanetaryDefense is a global effort - 150 international scientists are meeting to prepare for @ESA's #HeraMission, which will examine the deflected mass & determine if humans can indeed divert threatening asteroids.
https://twitter.com/AschbacherJosef/status/1531199271239819266
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In T minus *60* days time, @NASA and @JHUAPL's #DARTMission will impact the smaller of the 2 #Didymos #asteroids - and perform humankind's first orbital deflection for #PlanetaryDefense test.
https://twitter.com/ESA_Tech/status/1552694876453715968
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
For small low density asteroids. Think a high surface area impactor might work for "asteroid redirection". Essentially deploying a solar sail like structure as impactor.
Hopefully DART will not have a no show by passing through Didimoon with nothing to see. Of course DART might survive a fly through scenario enough to be detectable afterwards.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
For small low density asteroids. Think a high surface area impactor might work for "asteroid redirection". Essentially deploying a solar sail like structure as impactor.
Hopefully DART will not have a no show by passing through Didimoon with nothing to see. Of course DART might survive a fly through scenario enough to be detectable afterwards.
No ship that far out is detectable on its own. We can only see the radio transmissions from it.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
There is no way DART will pass through it, or will "disassemble" - not even if Dimorphos is only a heap of dust.
The lowest constraint for the density of Dimorphos is 1150 kg m^−3.
see Rivkin, Andrew & Chabot, Nancy & Stickle, Angela & Thomas, Cristina & Richardson, Derek & Barnouin, Olivier & Fahnestock, Eugene & Ernst, Carolyn & Cheng, Andrew & Chesley, Steven & Naidu, Shantanu & Statler, Thomas & Barbee, Brent & Agrusa, Harrison & Moskovitz, Nicholas & Daly, Ronald & Pravec, Petr & Scheirich, Peter & Dotto, Elisabetta & Hirabayashi, Masatoshi. (2021). The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements. The Planetary Science Journal. 2. 173. 10.3847/PSJ/ac063e.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
For small low density asteroids. Think a high surface area impactor might work for "asteroid redirection". Essentially deploying a solar sail like structure as impactor.
Hopefully DART will not have a no show by passing through Didimoon with nothing to see. Of course DART might survive a fly through scenario enough to be detectable afterwards.
No ship that far out is detectable on its own. We can only see the radio transmissions from it.
It's a pity that HERA is so late that it will be only be able to see the remains; original mission was to have HERA looking while DART impacting.
Is LICIACube "observer" still part of the mission?
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Looking for info on LICIACube (found nothing :( ) I found this interesting, very recent paper.
Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions (https://iopscience.iop.org/article/10.3847/PSJ/ac67a7)
Sabina D. Raducan, Martin Jutzi
Summary:
We predict that the DART impact is likely to produce morphologies that are dissimilar to cratering and change the global morphology of the asteroid. In such cases, Hera will not find a classical crater morphology.
[...] We find that for the current energy of the DART impact, the catastrophic disruption of the target is not possible. However, the DART impact may probe not only the surface but also the interior of the asteroid.
So maybe the asteroid will not be destroyed, but very likely "something more" than just a crater will be caused.
(https://cfn-live-content-bucket-iop-org.s3.amazonaws.com/journals/2632-3338/3/6/128/revision1/psjac67a7f8_lr.jpg?AWSAccessKeyId=AKIAYDKQL6LTV7YY2HIK&Expires=1659780763&Signature=BBf5mljThf2LoI9gq2T%2FvwURPLg%3D)
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I can't find any official source about canceling of 2001 CB21 flyby planned for 3-6 march 2022, apart from one line in this page (https://echo.jpl.nasa.gov/asteroids/radar.small.body.mission.targets.html).
Why was it canceled? It was needed for camera calibration!
Instead, I found a paper (https://az659834.vo.msecnd.net/eventsairwesteuprod/production-atpi-public/00fb1a0e860041bbadf8a37f7040194e)which assures that the DART mission will not cause Didymos impacting on Earth due to the deviation...
Interstingly, paper was published after launch.
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I can't find any official source about canceling of 2001 CB21 flyby planned for 3-6 march 2022, apart from one line in this page (https://echo.jpl.nasa.gov/asteroids/radar.small.body.mission.targets.html).
Why was it canceled? It was needed for camera calibration!
Instead, I found a paper (https://az659834.vo.msecnd.net/eventsairwesteuprod/production-atpi-public/00fb1a0e860041bbadf8a37f7040194e)which assures that the DART mission will not cause Didymos impacting on Earth due to the deviation...
Interstingly, paper was published after launch.
There already had been studies showing that there was zero risk of earth impact before the asteroid was selected. It was kind of a requirement.
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There already had been studies showing that there was zero risk of earth impact before the asteroid was selected. It was kind of a requirement.
I think you didn't get the point: I am talking about what will happen to the binary system after the impact; it's weird they calculated it only after launching the mission, and it's creepy that only 2 months from the impact they figured out that the impact will have way different effect w.r.t what they supposed at the time of mission designing (it won't be a redirection, it will be an explosion).
As far as I can understand, the binary system will be turned into a huge debris cloud, with a lot of material leaving the original system orbit at escape velocity, something similar to what happens when an Earth-orbiting satellite is intentionally destroyed by an impact, but at "km scale".
I also understood that they are currently working at a graphical simulation of such a cloud debris and its evolution... then I got lost on details.
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I think you didn't get the point: I am talking about what will happen to the binary system after the impact; it's weird they calculated it only after launching the mission, and it's creepy that only 2 months from the impact they figured out that the impact will have way different effect w.r.t what they supposed at the time of mission designing (it won't be a redirection, it will be an explosion).
Publication date is not the same thing as the completion of the study. It can take months to over a year for a paper to be published.
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It looks like DART could become a "shooting stars generator". ;)
Because the closest point of approach
of Didymos to Earth’s orbit is only 6 million km (about 16 times the Earth–Moon distance), some ejected material
will make its way sooner or later to our planet, and the observation of these particles as meteors would increase the
scientific payout of the DART mission. The DART project may also represent the first human-generated
meteoroids to reach Earth and is a test case for human activity on asteroids and its eventual contribution to the
meteoroid environment and spacecraft impact risk. This study examines the amount and timing of the delivery of
meteoroids from Didymos to near-Earth space. This study finds that very little DART-ejected material will reach
our planet, and most of that only after thousands of years. But some material ejected at the highest velocities could
be delivered to Earth-crossing trajectories almost immediately, though at very low fluxes
On the Delivery of DART-ejected Material from Asteroid (65803) Didymos to Earth, Paul Wiegert (https://iopscience.iop.org/article/10.3847/PSJ/ab75bf/pdf)
And this is a paper dated 2019, when they thought the impact would have caused just a "plume".
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There already had been studies showing that there was zero risk of earth impact before the asteroid was selected. It was kind of a requirement.
I think you didn't get the point: I am talking about what will happen to the binary system after the impact; it's weird they calculated it only after launching the mission, and it's creepy that only 2 months from the impact they figured out that the impact will have way different effect w.r.t what they supposed at the time of mission designing (it won't be a redirection, it will be an explosion).
As far as I can understand, the binary system will be turned into a huge debris cloud, with a lot of material leaving the original system orbit at escape velocity, something similar to what happens when an Earth-orbiting satellite is intentionally destroyed by an impact, but at "km scale".
I also understood that they are currently working at a graphical simulation of such a cloud debris and its evolution... then I got lost on details.
This paper says that, but it certainly wasn't the only one. You can go back and listen to Dart PR from before it launched, they are very clear that there is NO possibility of the redirection causing an earth impact. This was known many years ago.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
Emphasis mine
That's not how physics works. If one body impacts another, there is always a transfer of momentum.
A grain of sand impacting a huge pile of sand in space will still transfer its momentum to it.
Also, a grain of sand impacting a solid mountain in space will still transfer its momentum to it.
Regardless of the actual physical interaction that occurs between the probe and the asteroid body, we will see a change in the orbit of Dimorphos, which is the entire point of the mission.
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Given the recent findings about Bennu (https://www.nasaspaceflight.com/2022/07/osiris-rex-bennu-aging/), I think that we have to rethink from scratch any "asteroid redirection mission": shooting a small asteroid would probably "deviate" it as much as shooting a cloud deviates it. :( And if the asteroid is massive enough to be compact enough not to "absorb" the bullet, it won't be probably affected anyway by the impact due to huge mass difference.
And Dimorphos/Didimoon is 3 times smaller than Bennu, 50-100m: possibly the 650 kg bullet will pass through it, or will "disassemble" it!
It will be a great show.
There is no way DART will pass through it, or will "disassemble" - not even if Dimorphos is only a heap of dust.
The lowest constraint for the density of Dimorphos is 1150 kg m^−3.
see Rivkin, Andrew & Chabot, Nancy & Stickle, Angela & Thomas, Cristina & Richardson, Derek & Barnouin, Olivier & Fahnestock, Eugene & Ernst, Carolyn & Cheng, Andrew & Chesley, Steven & Naidu, Shantanu & Statler, Thomas & Barbee, Brent & Agrusa, Harrison & Moskovitz, Nicholas & Daly, Ronald & Pravec, Petr & Scheirich, Peter & Dotto, Elisabetta & Hirabayashi, Masatoshi. (2021). The Double Asteroid Redirection Test (DART): Planetary Defense Investigations and Requirements. The Planetary Science Journal. 2. 173. 10.3847/PSJ/ac063e.
For reference,
Ice: 920 kg/m3
Coal: 700-1500 kg/m3
Pure water: 1000 kg/m3
Sand: 1520-1680 kg/m3
Rock: 1600-3500 kg/m3
Dimorphos is probably a loosely bound aggregate of small rocks, similar to Bennu.
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We are less than 50 days away from the impact of the #DART probe with Dimorphos, the moon of the asteroid Didymos. This is intended to demonstrate the ability to deflect future asteroids dangerous to Earth.
https://twitter.com/SpaceNosey/status/1556583227812466689
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August 23, 2022
MEDIA ADVISORY M22-119
NASA Invites Media to Witness World’s First Planetary Defense Test
NASA’s Double Asteroid Redirection Test (DART), the world’s first mission to test technology for defending Earth against potential asteroid or comet hazards, will impact its target asteroid—which poses no threat to Earth—at 7:14 p.m. EDT on Monday, Sept. 26.
Among other activities, NASA will host a televised briefing beginning at 6 p.m. on Sept. 26 from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. APL is the builder and manager of the DART spacecraft for NASA.
This test will show a spacecraft can autonomously navigate to a target asteroid and intentionally collide with it to change the asteroid’s motion in a way that can be measured using ground-based telescopes. DART will provide important data to help better prepare for an asteroid that might pose an impact hazard to Earth, should one ever be discovered.
The following is a list of activities for DART’s impact with the asteroid Dimorphos (all times Eastern):
Monday, Sept. 12
9 a.m. – NASA will host a hybrid media day at APL focused on the technology enabling the DART spacecraft to autonomously navigate to and impact its target asteroid. Participants include leaders from NASA and the DART mission team. In-person attendees will have an opportunity to tour the DART mission operations center at APL, located at 11100 Johns Hopkins Road in Laurel, Maryland.
Media interested in participating must RSVP by completing this form no later than 3 p.m. on Tuesday, Aug. 30. NASA’s media accreditation policy for on-site and virtual activities is available online.
Thursday, Sept. 22
3 p.m. – Media briefing at NASA Headquarters to preview DART’s final activities before its impact with Dimorphos. The media briefing will take place in the Webb Auditorium at NASA Headquarters in the Mary W. Jackson building, 300 E. Street, SW in Washington and include senior leaders from NASA and APL.
Media interested in participating must RSVP by completing this form no later than 3 p.m. on Thursday, Sept. 15.
Monday, Sept. 26 (DART Impact Day)
Media interested in covering the DART impact from APL must complete this form by 3 p.m. on Friday, Sept. 2.
6 p.m. – Live coverage of DART’s impact with the asteroid Dimorphos will air on NASA TV and the agency’s website. The public also can watch live on agency social media accounts on Facebook, Twitter, and YouTube.
7:14 p.m. – DART’s kinetic impact with asteroid Dimorphos.
Interview Opportunities
Remote live and taped interviews via Zoom will be offered from 6 a.m. to 1 p.m. on Monday, Sept. 26. To book a live shot window, media should fill out this form by 3 p.m. on Thursday, Sept. 22.
A series of panels featuring NASA and APL mission experts will take place at APL on Monday, Sept. 26. Opportunities for interviews before and after DART’s asteroid impact will be available by filling out this form.
NASA Social
Stay connected with the DART mission and share your experience watching DART’s impact with an asteroid on Twitter, Facebook, and Instagram with #DARTMission and #PlanetaryDefender. Follow and tag these accounts:
Twitter: @NASA, @NASASolarSystem, @AsteroidWatch, @JHUAPL
Facebook: NASA, NASA Solar System Exploration, Johns Hopkins University Applied Physics Lab
Instagram: @NASA, @NASASolarSystem, @JohnsHopkinsAPL
Become a Planetary Defender
Support the DART mission by becoming a “Planetary Defender!” Participants who take a short quiz will earn a certificate and badge they can download, print, and share on social media.
For more information about the DART mission, visit:
https://www.nasa.gov/dartmission
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Spotted this on the DSN status page:
SPACECRAFT
NAME
LICIACube
RANGE
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ROUND-TRIP LIGHT TIME
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ANTENNA NAME
DSS 35
AZIMUTH
0.10 deg
ELEVATION
89.98 deg
WIND SPEED
0.00 km/hr
MODE
-
DOWN SIGNAL
SOURCE
LICIACUBE
TYPE
DATA
DATA RATE
1.00 kb/sec
FREQUENCY
8.44 GHz
POWER RECEIVED
-98.95 dBm
(1.27 x 10-16 kW)
Since the DART cubesat has not separated, is this a real test?
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https://twitter.com/NASASolarSystem/status/1563223967208353797
T-minus 30 days to impact! The #DARTmission is a first-of-a-kind mission: a demonstration of asteroid deflection by kinetic impactor, to test whether this is a viable means of defending the Earth from asteroids, should the need ever arise. Don't miss it: http://nasa.gov/dart
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How Will We Know if NASA’s DART Mission Successfully Changed an Asteroid’s Orbit?
https://youtu.be/uUaiMvnW6dY
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Any news about foreseen visibility/magnitude of the impact from Earth?
Dymorphos will be high enough on my horizon (https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Didymos%20%27&CENTER=%27034@399%27&OBJ_DATA=%27yes%27&MAKE_EPHEM=%27yes%27&TABLE_TYPE=%27OBSERVER%27&REF_PLANE=%27ECLIPTIC%27&COORD_TYPE=%27GEODETIC%27&SITE_COORD=%2712,42,0.150%27&START_TIME=%272022/9/26%2023:00%27&STOP_TIME=%272022/9/27%2002:00%27&STEP_SIZE=%275m%27&QUANTITIES=%274,9,10,13,21,29,35%27&FIXED_QUANTITIES=%27Custom%27&REF_SYSTEM=%27J2000%27&OUT_UNITS=%27KM-S%27&VECT_TABLE=%273%27&VECT_CORR=%27NONE%27&CAL_FORMAT=%27CAL%27&ANG_FORMAT=%27DEG%27&APPARENT=%27AIRLESS%27&TIME_TYPE=%27UTC%27&TIME_DIGITS=%27MINUTES%27&RANGE_UNITS=%27AU%27&SUPPRESS_RANGE_RATE=%27no%27&SKIP_DAYLT=%27no%27&EXTRA_PREC=%27yes%27&CSV_FORMAT=%27yes%27&VEC_LABELS=%27yes%27&ELM_LABELS=%27yes%27&TP_TYPE=%27ABSOLUTE%27&R_T_S_ONLY=%27NO%27&CA_TABLE_TYPE=%27STANDARD%27) to be visible at the time of the impact.
(Change string "12,42,0.150" to your "lon,lat,altitude" to tune it to your location; altitude is in km.)
Output columns:
Date__(UT)__
HR:MN, , ,
Azimuth_(a-app),
Elevation_(a-app),
APmag, (Apparent magnitude)
S-brt, (The asteroids' approximate apparent airless visual magnitude and surface brightness using the standard IAU H-G system magnitude model)
Illu%, (illuminated fraction)
Ang-diam, (angular diameter)
1-way_down_LT, (light time 1-way down in minutes)
Cnst, (nearest constellation)
399_ins_LT, (Light time to Earth in minutes)
Sky simulator: https://stellarium-web.org/
Tracking Didymos: https://theskylive.com/planetarium?objects=sun-moon-didymos-mercury-venus-mars-jupiter-saturn-uranus-neptune-pluto&obj=didymos&h=23&m=14&date=2022-09-26#ra%7C3.588357170121647%7Cdec%7C-32.7892890447576%7Cfov%7C50
Telescope simulator: https://telescopius.com/telescope-simulator
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This month there are 25 days until @NASA and their #DARTmission will impact the asteroid Dimorphos performing humanity's first #PlanetaryDefense test , then the @ESA will continue with #HeraMission will carry out its own detailed study of the impacted body..
https://twitter.com/SergioMartinGu3/status/1567887872816037890
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The #DARTMission will crash into a non-hazardous asteroid on Sept. 26 as the world's 1st planetary defense test. But how will we know it worked? Watch how @LowellObs, one of many observatories will monitor the impact.
https://twitter.com/Dr_ThomasZ/status/1568618171506065409
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https://twitter.com/planet4589/status/1569188159677759489
GT: The Italian probe @LICIACube
by @ASI_spazio
split as expected from NASA's DART spacecraft. Here is the first image from the @Argotec_Space control room
in Turin. On the night between 26 and 27 September it will document the impact against an asteroid
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From the horse's mouth:
https://mobile.twitter.com/ASI_spazio/status/1569214382122438656
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https://twitter.com/ASI_spazio/status/1569217806926757889/photo/1
The first signal taken from @SSDC_ASI @LICIACube
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Its reported that @LICIACube was successfully deployed and in a nominal state. It was an amazing effort today by the folks at the stations and JPL who moved mountains to get this outcome. It makes me very proud to be part of the team. I'm going home now for a big glass of wine.
https://twitter.com/nascom1/status/1569232671183884289
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There's a reference to stations moving mountains...
Some mission declared a spacecraft emergency and requested 70m support overnight US time.
I wonder if DART is that mission.
It will be interesting to hear what the full deployment details are.
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Some mission declared a spacecraft emergency and requested 70m support overnight US time.
I wonder if DART is that mission.
Most probably it's about CAPSTONE.
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Media Briefing: Behind the Technologies Enabling NASA’s DART Mission
https://youtu.be/Z9eGVV4B5UA
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AFAIK deployment was planned 10 days before impact, but we are still at -14, being the impact planned for 26th.
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#DART mission is still intimidated - hopefully, it will be resolved soon!
https://twitter.com/SpaceIntellige3/status/1569281668221140992
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NASA DART Mission LIVE: Spacecraft to Crash Into an Asteroid..
https://youtu.be/ZEMoGo4DPqY
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Some mission declared a spacecraft emergency and requested 70m support overnight US time.
I wonder if DART is that mission.
Most probably it's about CAPSTONE.
I do not believe it was CAPSTONE.
I wonder why no mention was made during the press event today about LICIACube declaring an emergency...
You'd think that would be relevant...
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I have no knowledge of the details, but if LICIACube was not mentioned and CAPSTONE is known to have experienced a serious problem, is it not reasonable to assume the emergency was CAPSTONE?
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I'm quoting the bold portion of the tweet below (from up-thread post by centaurinasa, quoting Richard Stephenson).
That is combined with a well-supported belief that at least one station participated in supporting a declared spacecraft emergency *today*.
That would have been at least 5 hours before the press event.
Its reported that @LICIACube was successfully deployed and in a nominal state. It was an amazing effort today by the folks at the stations and JPL who moved mountains to get this outcome. It makes me very proud to be part of the team. I'm going home now for a big glass of wine.
EDIT: I see other posts indicating that CAPSTONE did, in fact, have an anomaly. Perhaps I'm in error in my belief that LICIACube had a declared emergency. I'll wait for first-hand information.
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I suspect the bolded text just referred to getting the DSN to do anything else while they were working on the CAPSTONE emergency, which sounds like it was pretty dire. But DSN Now has been down all day so it's hard to tell.
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https://youtu.be/Z9eGVV4B5UA
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Watch the online briefing this afternoon on the planned impact of @NASA’s #DARTmission with an #asteroid, covering Europe's contribution, including ESA's follow-on #HeraMission.
Live from 13:00 BST/14:00 CEST on #ESAwebTV..
https://twitter.com/esa/status/1570323214185676800
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Is there an archive of this briefing available?
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LICIACube, the Light Italian Cubesat for Imaging of Asteroids which was riding along with DART successfully conducted the first of 3 orbital maneuvers over Canberra's DSS43. Think of it as making its way to the best seat in the house for the upcoming DART vs Dimorphos fight..
https://twitter.com/nascom1/status/1571281347968405504
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“It's vital for mission success that there are no coverage gaps in #DART’s terminal phase. Antennas around the world will work in unison, backing each other up & filling gaps in the NASA DSN” – Daniel Firre, ESA’s DART Service Manager.
"– we can't lose DART for a moment."
https://twitter.com/esaoperations/status/1572232040698847233?cxt=HHwWgoC9pcCt2NErAAAA
“Our giant dish in Australia will be in touch with #DART as it crashes into #Dimorphos. In the last minutes, data will stream that'll be used by scientists to estimate the asteroid's mass, surface type & impact site” - Suzy Jackson, New Norcia Maintenance & Ops Manager at @CSIRO
https://twitter.com/esaoperations/status/1572234044200427523?cxt=HHwWhoC9xY-i2dErAAAA
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https://youtu.be/xv2t-yv7H2o
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I think this was the highlight of the conference, I am excited that DART will be the focus of Hubble, JWST and Lucy.
https://twitter.com/spcplcyonline/status/1573029427348488194
https://twitter.com/spcplcyonline/status/1573032369333862400
https://twitter.com/spcplcyonline/status/1573040879979626496
https://twitter.com/spcplcyonline/status/1573043189706985472
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Just. Three. Days.
https://twitter.com/esaoperations/status/1573207929553141760
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From Earth all these telescopes will also be aware of the impact and the evolution in the following weeks.
https://twitter.com/SpaceNosey/status/1573228127857381377
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Tom Statler, DART program scientist at NASA HQ, says he would be surprised if astronomers can determine the new orbit of Dimorphos sooner than a few days after impact, and also surprised if it takes more than a few weeks. Rivalry between optical and radar observers.
https://twitter.com/jeff_foust/status/1573036862796693504
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DLR Press Release, 23 September 2022
Planetary defence - Impact 11 million kilometres away
Full article with image: https://www.dlr.de/content/en/articles/news/2022/03/20220923_impact-11-million-kilometres-away.html
In the early hours of Tuesday morning, NASA's Double Asteroid Redirection Test (DART) mission, which was launched in November last year, will test whether it is possible to change the course of an asteroid. DART will then reach the Didymos-Dimorphos asteroid binary system and impact the 170-metre wide 'moonlet' Dimorphos during a targeted approach. The 'kinetic momentum' transferred in the process is expected to alter the orbit of Dimorphos around its larger companion, Didymos. This is the first time in the history of spaceflight that an attempt is being made to influence the orbit of a celestial body by a human-made body. The German Aerospace Center (Deutsches Zentrum fuer Luft- und Raumfahrt; DLR) is involved in the analysis of the impact. In 2026, the ESA mission Hera, in which Germany is significantly involved through the German Space Agency at DLR, is to explore the asteroid system and its shifted orbit.
Earth has always been threatened by asteroid collisions. Although almost all of the approximately one million 'known' celestial bodies over 100 metres in size move in stable orbits between Mars and Jupiter, about 30,000 of these have orbits that intersect with Earth's orbit around the Sun. It is these bodies that could potentially collide with our planet. A collision of a body even a few hundred metres in size with Earth would cause quite considerable damage. Such danger may be averted by using space probes to alter the course of a potential Earth-colliding asteroid very early on so that it simply flies past our planet.
"We live in the age of space travel. This gives us the opportunity to use space probes to deflect an asteroid that may potentially collide with Earth," says Jean-Baptiste Vincent from the DLR Institute of Planetary Research. DLR has been observing and characterising Earth-crossing asteroids for decades. "On the one hand, we try to characterise these small, but sometimes dangerous, celestial bodies to understand their physical properties, and on the other hand we observe them to be able to draw conclusions on how we could ward them off should our calculations show that they could collide with Earth in the future," explains Stephan Ulamec from the DLR Microgravity User Support Center (MUSC) in Cologne.
Change in orbital period by a few minutes
The two DLR scientists are involved in NASA's DART mission. DART is a cube-shaped satellite with an edge length of just under two metres and a mass of 610 kilograms. The mission was launched on 24 November 2021 and steered on an elliptical orbit to its target, the asteroid pair Didymos and Dimorphos. Didymos, the larger of the two bodies, has an irregular diameter of nearly 800 metres, Dimorphos of about 170 metres. Dimorphos orbits Didymos – Greek for twin – in 12 hours at a distance of 1200 metres. Together, the two asteroids orbit the Sun in 25 months on an orbit that crosses Earth's orbit, making them potentially dangerous Near-Earth Objects (NEOs). In 2003, the two asteroids came within six million kilometres of Earth.
"We assume that Dimorphos' orbital period around Didymos will change by a few minutes due to DART's momentum," predicts DLR researcher Stephan Ulamec. "However, we do not know what Dimorphos is like," adds Jean-Baptiste Vincent. "Is it a compact body or are its components only very loosely assembled? In other words, is Dimorphos maybe just a pile of rock fragments, a 'rubble pile' as we say in asteroid research?" The task of the two DLR scientists in the DART team is to determine the exact shape of the small asteroid, its precise mass and to analyse the crater and the transmission of the momentum and ejecta produced by the impact.
The spacecraft will, of course, be completely destroyed in the process, but the impact of DART on Dimorphos will be observed by two small cubesats which were deployed on 11 September. The two LICIACubes were developed by the Italian Space Agency (ASI) to make flyby observations of the Didymos binary asteroid system following DART’s impact. The small satellites will communicate directly with Earth before, during and after the impact. Two cameras (LUKE and LEIA) will confirm the impact and capture images of the ejecta cloud and possibly a crater. Three minutes after DART's impact, they will have flown past Dimorphos, turning and still taking pictures of the far side of Dimorphos, which of course DART will not get to see up close. LICIACube is the first all-Italian autonomous space probe in space. NASA's Lucy mission, launched last year to the 'Trojan' asteroids in Jupiter's orbit, will also observe the impact from a distance of 19 million kilometres.
Will we be able to deflect asteroids in the future?
The targeted collision of the DART spacecraft with Dimorphos will occur on 27 September 2022 at 01:14 CEST at a distance of just over 11 million kilometres from Earth, the closest the binary asteroid system will be to Earth in the near future (the asteroid pair will not pass Earth at a similarly close distance again until 2062). Being this 'close' to Earth also provides good observing opportunities for telescopes on the planet's night side, especially from Europe; observations that will be used for complementary analyses during and after the collision. These and other telescopes will also record light curves of the binary asteroid system in the nights after the event to contribute data on Dimorphos’ orbital alteration to the overall analysis.
Nearly 140 million kilojoules of energy are converted during DART's impact with Dimorphos. The researchers assume that the impact will create a crater several tens of metres in diameter and that the asteroid's orbital period will change measurably, by a few minutes. This corresponds roughly to a change in velocity of half a millimetre per second. "How efficiently an asteroid is deflected by colliding with a space probe is decisively influenced by the physical properties of the body, in other words, it depends on how porous and solid the rock is," explains Kai Wuennemann from the Museum fuer Naturkunde Berlin, whose team has been developing computer simulations of the impact process in order to make predictions that are as precise as possible. At the Museum für Naturkunde Berlin, various scenarios of the nature of Dimorphos are run and simulated in order to predict the size of the crater, among other things.
In October 2024, the European Space Agency (ESA) will launch Hera, a mission coordinated with NASA, which will be developed and built largely in Germany, to study the impact and its consequences in detail. The German Space Agency at DLR, based in Bonn, manages the German ESA contributions for Hera. Hera will reach the binary asteroid system in December 2026, approximately four years after the impact of DART. Hera's detailed investigations will then significantly expand knowledge about the possibilities afforded by asteroid deflection. DART and Hera are missions of the international research project AIDA (Asteroid Impact and Deflection Assessment).
Repeated asteroid impacts in Earth's history
In the foreseeable future, there is currently no reason to worry about an asteroid hitting Earth. But asteroid collisions have happened again and again in Earth's four-and-a-half billion years of history. Traces of these can be found in the craters left behind when asteroids hit, such as the Nördlinger Ries in southern Germany or the Barringer Crater in Arizona. The Moon, littered with impact craters, makes it clear that asteroid collisions used to be much more frequent. However, on the dynamically ever-changing Earth, almost all traces of impacts have been erased. The extinction of the dinosaurs was caused by an asteroid collision 65 million years ago. That the danger of an asteroid hitting Earth remains real today, albeit on a much smaller scale, became clear on 15 February 2013. At that time, an unknown asteroid entered Earth's atmosphere and exploded over the Russian city of Chelyabinsk. The shockwave of compressed air from Earth's atmosphere caused considerable damage in the city. Thousands of window panes were shattered, injuring more than 1600 people. The total damage was estimated at 30 million euros. Yet the asteroid in Chelyabinsk was only about 18 metres in diameter.
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The DART probe is now half a million kilometers from the Didymos system, and just over 24 hours to impact.
https://twitter.com/planet4589/status/1574171325257682946
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Didymos is an X-type silicate asteroid. Its moon, Dimorphos, is the target. The mass of Dimorphos is about 5 million tons; its Kepler speed around Didymos is only about 1 km/hr and will be changed by about 1 mm/s by the impact..
https://twitter.com/planet4589/status/1574183883712569344
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T -24 hours for the impact of the #Dart probe with the asteroid Dimorphos. The small 550kg probe hopes to slightly deflect the trajectory of this mole.
https://twitter.com/SpaceNosey/status/1574175490805489664
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Simulation of the last moments of #Dart before impact with Dimorphos within 32 hours.
https://twitter.com/SpaceNosey/status/1574044075761999873
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Representation of how #Dart can slightly deflect Dimorphos's orbit around Didymos. This would show that we are capable of deflecting a future threat to Earth.
https://twitter.com/SpaceNosey/status/1574295997546745857
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For anyone wanting it:
The DART spacecraft image feed will be available on impact day without commentary at https://youtube.com/watch?v=-6Z1E0mW2ag.
As live a feed as it can be with light travel time and rapid processing through the Deep Space Network.
https://twitter.com/michael_w_busch/status/1573354428337463298
https://youtu.be/-6Z1E0mW2ag
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https://youtu.be/yrxPT8UFJRM
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NASA trailer!
https://youtu.be/nHBuVbGkmBY
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https://twitter.com/jeff_foust/status/1574485638233178134
APL’s Andy Cheng says there are 20, maybe 30 telescopes worldwide that plan to monitor the Didymos system after the impact to measure the change in the orbit of Dimorphos.
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Current view of the Didymos system:
https://www.youtube.com/watch?v=-6Z1E0mW2ag (https://www.youtube.com/watch?v=-6Z1E0mW2ag)
Currently I-1h
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1 hour before impact, NASA TV feed reported that the spacecraft has spotted Dimorphos.
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Dimorphos is reportedly already visible in the DART images (around 7 pixels, same relative brightness as its parent Didymos). I believe it's
the image on the small FoV (right box) on the previous post. EDIT: Actually no, the right image is just where in DRACO's full FoV the region of interest (ROI) is at.
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LICIACube being controlled from Argotec's MCC in Turin, in coordination with ASI :)
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Target lock confirmed.
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DART's main instrument camera, DRACO, is a direct descendent of LORRI, New Horizon's imager which took the first close-up pictures of Pluto a few years ago.
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Dimorphos is finally clearly visible on the live feed.
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Great situational awareness diagram:
https://twitter.com/planet4589/status/1574529830514839558 (https://twitter.com/planet4589/status/1574529564793098242)
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Final poll conducted, everything's looking good for impact, plenty of margins on all sides, including DSN and ground.
I-26 min.
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Pointing right now 30 m away from Dymorphos' bullseye.
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Now very properly clear. About 25 minutes before impact.
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JWST now observing: https://twitter.com/JWSTObservation/status/1574513893245964289 (https://twitter.com/JWSTObservation/status/1574513893245964289)
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Precision target lock (on Dimorphos) now established and confirmed.
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Around 7000 km away from impact, I-18 min.
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Interesting structure in Didymos... looks like it's brighter on the side facing Dimorphos - wonder if it's just a lighting artifact or something else.
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Meaningful feature resolution on Dimorphos. Impact in 14 minutes.
Interesting structure in Didymos... looks like it's brighter on the side facing Dimorphos - wonder if it's just a lighting artifact or something else.
Pretty sure that's lighting, e.g., the daylit/sunward side.
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I-9 min.
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I-6 mins. Craters now appreciable on Didymos.
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Final comms opportunity just passed. MCC is just another spectator at this point. I-5 mins.
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Note the clock on NASA TV is time to the actual impact in "absolute time", lightspeed and image processing lag means there's about a minute of difference between the actual events in space and when we see them.
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Impact in 5 minutes. 60 seconds until the start of the final correction burn. Clear detail visible on Didymos and some on Dimorphos. DART is about as far from Dimorphos as New York City is from Cape Canaveral.
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SmartNAV has now stopped maneuvering. Coasting for impact.
Some boulders resembling Itokawa are visible?
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Projected miss: 17 m.
Didymos now getting out of frame.
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Dimorphos getting sharp!
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Boulders in Dimorphos!
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IMPACT
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Last few images, of roughly the last 10 seconds of approach. Looks like a rubble pile to me! Can't wait for the aftermath from LICIACube :)
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The decoded part of the last (partially) transmitted image overlaid on the penultimate image, i.e. the last full frame before impact. I've also overlaid the frame's size, which gives a good idea of where the DART's CoM, or at least center-of-camera, has impacted.
Seems it targeted the one of the largest boulders in the area ;D
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After LICIACube, let's remember ESA's Hera, led by Italy and later Germany, to be launched in about two years' time. Hera will also carry CubeSats to complement the main S/C's views.
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Does anyone know when we might have images from LICIACube? I may have missed it, but I didn't see it get discussed on the NASA broadcast.
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Does anyone know when we might have images from LICIACube? I may have missed it, but I didn't see it get discussed on the NASA broadcast.
S/C is much smaller so it will take a few days to downlink the images through its X-band antenna. Maybe we'll have something by tomorrow?
On the other hand, it's already done its job, maybe taking a few last departure images.
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IMPACT SUCCESS! Watch from #DARTMIssion’s DRACO Camera, as the vending machine-sized spacecraft successfully collides with asteroid Dimorphos, which is the size of a football stadium and poses no threat to Earth.
https://twitter.com/NASA/status/1574539270987173903?cxt=HHwWnsC-wf3H8dkrAAAA
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Reminder of DART's former incarnation as a knight errand fighting giants (asteroidal giants in fact) dressed as windmills.
https://twitter.com/ESA_Tech/status/1574486060104663055
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Does anyone know when we might have images from LICIACube? I may have missed it, but I didn't see it get discussed on the NASA broadcast.
Sometime during the NSF broacast (https://www.youtube.com/watch?v=yrxPT8UFJRM), Scott Bellamy, the DART Mission Manager, said they would be available in 24 to 48 hours.
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Surely, some Earth-based telescopes have captured images already, right?
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Does anyone see a resemblance between Dimorphos and Bennu, i.e. with the dense concentration of boulders? If Dimorphos is, in fact, just a loose aggregation of rocks and boulders, the impact may have created a large 'cloud' of a spreading debris, much more so than would be caused by a solid body. I too can't wait for the first images.
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https://www.virtualtelescope.eu/2022/09/11/dart-slams-into-dimorphos-online-live-observation-of-the-impact-26-sept-2022/ (https://www.virtualtelescope.eu/2022/09/11/dart-slams-into-dimorphos-online-live-observation-of-the-impact-26-sept-2022/)
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Does anyone see a resemblance between Dimorphos and Bennu, i.e. with the dense concentration of boulders? If Dimorphos is, in fact, just a loose aggregation of rocks and boulders, the impact may have created a large 'cloud' of spreading debris, much more so than would be caused by a solid body. I too can't wait for the first images.
Another reason not to use explosive materials to destroy one of these, is as it only generates thousands of bolder size projectiles.
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Congrats NASA, well done! Really one for the books. Thank you NSF for the great coverage!
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Is there something wrong with the youtube video or was the post mission briefing shot on a potato? The image quality downlinked across millions of kms from the spacecraft was better (albeit not great framerate).
https://www.youtube.com/watch?v=fsZo1cxMqck&t=513s
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Final poll conducted, everything's looking good for impact, plenty of margins on all sides, including DSN and ground.
I-26 min.
I'm confused, was this a go/no go poll? I assumed this was the only impact opportunity.
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https://twitter.com/fallingstarIfA/status/1574583529731670021
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https://twitter.com/cbs_spacenews/status/1574586823791230979
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"Last partial frame layed over the last complete frame."
https://twitter.com/Darktemp/status/1574540052151128071 (https://twitter.com/Darktemp/status/1574540052151128071)
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LICIACube, the Light Italian Cubesat for Imaging of Asteroids which was riding along with DART successfully conducted the first of 3 orbital maneuvers over Canberra's DSS43. Think of it as making its way to the best seat in the house for the upcoming DART vs Dimorphos fight..
https://twitter.com/nascom1/status/1571281347968405504
So did this Cubsat provide the alternate view??
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Final poll conducted, everything's looking good for impact, plenty of margins on all sides, including DSN and ground.
I-26 min.
I'm confused, was this a go/no go poll? I assumed this was the only impact opportunity.
Yes, but the impact went through with the nominal mission scenario, while there were contingency scenarios, probably many, depending on different S/C conditions that didn't come to pass. They also had the opportunity to directly control the S/C from Earth, with a several-tens-of-seconds delay, until the very final approach.
EDIT: And actually, I just found out there was the possibility to forego the impact altogether and try again in 2 years! https://twitter.com/genejm29/status/1574557368960024593
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What I believe is the highest resolution composite image available right now of Dimorphos:
https://twitter.com/doug_ellison/status/1574646223591481345
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LICIACube, the Light Italian Cubesat for Imaging of Asteroids which was riding along with DART successfully conducted the first of 3 orbital maneuvers over Canberra's DSS43. Think of it as making its way to the best seat in the house for the upcoming DART vs Dimorphos fight..
https://twitter.com/nascom1/status/1571281347968405504 (https://twitter.com/nascom1/status/1571281347968405504)
So did this Cubsat provide the alternate view??
Should be on the ground, at least a downsampled first look:
https://twitter.com/coastal8049/status/1574621663341445126 (https://twitter.com/coastal8049/status/1574621663341445126)
https://twitter.com/Argotec_Space/status/1574603106502967296 (https://twitter.com/Argotec_Space/status/1574603106502967296)
MCC-Turin has gone into idling at 7.30 am local, when the teams went home to rest after a red-eye night controlling LICIACube and receiving the data. First images were received at 4.23 am. Should get something published soon.
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After DART comes Hera:
https://youtu.be/1NY2Eudymo0
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Another great look from the ground-based SAAO telescopes in South Africa:
https://twitter.com/astrosnapper/status/1574578176214196225
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Should be on the ground, at least a downsampled first look:
Thanks, eeergo.
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DART was launched atop a SpaceX Falcon 9 rocket.
https://twitter.com/nextspaceflight/status/1574545040910692352
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JWST NIRCAM images before and after impact. You can clearly see the dust halo after the mission's end:
https://twitter.com/thecolomb7710/status/1574695638943793152
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What I believe is the highest resolution composite image available right now of Dimorphos:
https://twitter.com/doug_ellison/status/1574646223591481345
It looks foreshortened, not sure how much of this is geometric distortion. Hopefully
the LICIAcube images will help to constrain the true shape.
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https://twitter.com/saao/status/1574688994201255936
Last night, Nicolas Erasmus (SAAO) and Amanda Sickafoose (@planetarysci) successfully observed DART's impact with Dimorphos using the Mookodi instrument on the SAAO's 1-m Lesedi telescope.
@fallingstarIfA also did a very similar measurement using ATLAS-Sutherland.
#DART #NASA
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Images from LICIACube to be released in approximately 45 mins.
https://twitter.com/ASI_spazio/status/1574747976706031618
At 16.00 [CEST] the press conference in which the first images of LICIACube will be released, witnessing the impact of NASA's DART probe against the asteroid Dimorphos. Follow the live streaming on ASITV: https://asitv.it/media/live
Information: https://tinyurl.com/5n66d3b8
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First look at JWST's images:
https://twitter.com/CeuProfundo/status/1574740198256164865
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https://twitter.com/willgater/status/1574684733287542784
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More images acquired also from China: https://twitter.com/CNSpaceflight/status/1574751669857841152
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160cm? how about more like the average 175cm to give a better perspective?
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160cm? how about more like the average 175cm to give a better perspective?
Yep - you can do that. Enlarge the human by about 9%.
Although using just my eyeball, I'm not sure that small of an adjustment will make much difference. It's all relative.
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LICIACube press conference:
- Upwards of 620 images taken.
- Some of them downloaded, many are still onboard.
- Scientists are already looking at them.
- LICIACube's precursor should have been ArgoMoon (currently loaded on SLS's SCA along with other EM-1 CubeSats), which will hopefully take proximity images of the ICPS after the Artemis I launch.
- The CubeSat's navigation and target lock system is based on an Argotec proprietary AI neural network trained on the ground for this task, to ensure the satellite "turned its head" and kept staring at the evolving scene.
[rant] [Show us the imagessss... instead of talking VIPs on a Teams window, not even in full-screen mode :) ] [/rant]
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Ehm... (excuse the abysmal quality, but after all the compressions they're going through, they are a bit underwhelming - EDIT: I have substituted the poor-quality screengrabs with the official versions from here (https://www.asi.it/2022/09/liciacube-conferenza-stampa-con-le-prime-immagini/); the last one in particular is much more interesting without the compression blur).
LEIA took the B&W images, LUKE the colored ones.
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[rant] [Show us the imagessss... instead of talking VIPs on a Teams window, not even in full-screen mode :) ] [/rant]
Sort of like last night - the emcee was clearly not comfortable on camera, and the entire planned portion of the event was asking two on the panel how they felt... That was a bit of a letdown.
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Better-resolution versions of the first couple of images (before/after) from someone who must have access to the un-streamed files:
https://twitter.com/alexwitze/status/1574770713273442306
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More from JWST (not sure what the "squarey" afterimage arc is):
EDIT: Explanation here: https://twitter.com/marshallperrin/status/1574740013992009728 (https://twitter.com/marshallperrin/status/1574740013992009728)
EDIT2: And an animation of all images except the "faulty" one showing the ejecta tendrils: https://twitter.com/landru79/status/1574776954070437889
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From an observatory in Réunion Island (Indian Ocean), area over which the Didymos system was most optimally visible during yesterday's impact:
https://twitter.com/esaoperations/status/1574774088794521600
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[Comparison of DART's last full frame with a human silhouette]
Perhaps a more useful metric:
https://twitter.com/interplanetary/status/1574770111369691136
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LEIA took the B&W images, LUKE the colored ones.
Wow, those last 2 LUKE images with the filamentary streamers are the last thing I expected to see in an impact like this :o It now makes me kinda sad we don't have a 3d profile of the ejecta curtain.
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To my untrained eye this looks very different from the Deep Impact results. Was that expected at all?
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To my untrained eye this looks very different from the Deep Impact results. Was that expected at all?
I'm not an expert, but DI hit a cometary nucleus rich with all kinds of volatiles tentatively just under the surface layer, just waiting to escape. This is a baked-out asteroid surface with a lot of very large boulders and gravel so at least some differences were to be expected with regards to ejecta curtain asymmetry.
Not sure that's enough to account for that amount of spatial variation in the ejecta skirt, though.
<Spock>Fascinating.</Spock>
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To my untrained eye this looks very different from the Deep Impact results. Was that expected at all?
I'm not an expert, but DI hit a cometary nucleus rich with all kinds of volatiles tentatively just under the surface layer, just waiting to escape. This is a baked-out asteroid surface with a lot of very large boulders and gravel so at least some differences were to be expected with regards to ejecta curtain asymmetry.
Not sure that's enough to account for that amount of spatial variation in the ejecta skirt, though.
<Spock>Fascinating.</Spock>
Can I get a sanity check here, folks?
The equation for the first-order approximation of the gravitational binding energy of an astronomical object is (3GM2)/(5R), where G is the gravitational constant, M is the mass of the object, and R is the radius. Using the estimate of Dimorphos's mass at 5 billion kg (per JHAPL (https://dart.jhuapl.edu/Mission/index.php)) and a mean radius of 85 meters, that would give a gravitational binding energy of 1.18e7 Joules (https://www.wolframalpha.com/input?i=%283*G*%285e9+kg%29%5E2%29%2F%285*85+m%29).
DART had a mass of 570 kg at impact and a relative impact velocity of 6.1 km/s (again per JHAPL above). Based on the kinetic energy equation, that's 1.06e10 J.
Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
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Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
I'm not any sort of scientist, but I'm getting the same numbers as you. My guess is that a significant part of the impact energy is "spent" on vaporizing rock instead of doing work against Dimorphos' gravity. Heating can soak up a whole lot of energy.
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To my untrained eye this looks very different from the Deep Impact results. Was that expected at all?
I'm not an expert, but DI hit a cometary nucleus rich with all kinds of volatiles tentatively just under the surface layer, just waiting to escape. This is a baked-out asteroid surface with a lot of very large boulders and gravel so at least some differences were to be expected with regards to ejecta curtain asymmetry.
Not sure that's enough to account for that amount of spatial variation in the ejecta skirt, though.
<Spock>Fascinating.</Spock>
Can I get a sanity check here, folks?
The equation for the first-order approximation of the gravitational binding energy of an astronomical object is (3GM2)/(5R), where G is the gravitational constant, M is the mass of the object, and R is the radius. Using the estimate of Dimorphos's mass at 5 billion kg (per JHAPL (https://dart.jhuapl.edu/Mission/index.php)) and a mean radius of 85 meters, that would give a gravitational binding energy of 1.18e7 Joules (https://www.wolframalpha.com/input?i=%283*G*%285e9+kg%29%5E2%29%2F%285*85+m%29).
DART had a mass of 570 kg at impact and a relative impact velocity of 6.1 km/s (again per JHAPL above). Based on the kinetic energy equation, that's 1.06e10 J.
Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
Doesn't this ignore all the materials of what dimorphos was? Its not a pile of unbound equal sized spherical particles with zero friction all sitting next to each other.
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Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
I'm not any sort of scientist, but I'm getting the same numbers as you. My guess is that a significant part of the impact energy is "spent" on vaporizing rock instead of doing work against Dimorphos' gravity. Heating can soak up a whole lot of energy.
A significant amount, yes.
But 99.89% of it?
Because if even 0.11% of the kinetic energy was actually delivered into the moon itself, that's still equal to the GBE.
The equation for the first-order approximation of the gravitational binding energy of an astronomical object is (3GM2)/(5R), where G is the gravitational constant, M is the mass of the object, and R is the radius. Using the estimate of Dimorphos's mass at 5 billion kg (per JHAPL (https://dart.jhuapl.edu/Mission/index.php)) and a mean radius of 85 meters, that would give a gravitational binding energy of 1.18e7 Joules (https://www.wolframalpha.com/input?i=%283*G*%285e9+kg%29%5E2%29%2F%285*85+m%29).
DART had a mass of 570 kg at impact and a relative impact velocity of 6.1 km/s (again per JHAPL above). Based on the kinetic energy equation, that's 1.06e10 J.
Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
Doesn't this ignore all the materials of what dimorphos was? Its not a pile of equal sized spherical particles with zero friction all sitting next to each other.
A rubble pile (which it appears to be) is basically precisely that in comparison to a projectile moving at ~6 km/s.
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The equation for the first-order approximation of the gravitational binding energy of an astronomical object is (3GM2)/(5R), where G is the gravitational constant, M is the mass of the object, and R is the radius. Using the estimate of Dimorphos's mass at 5 billion kg (per JHAPL (https://dart.jhuapl.edu/Mission/index.php)) and a mean radius of 85 meters, that would give a gravitational binding energy of 1.18e7 Joules (https://www.wolframalpha.com/input?i=%283*G*%285e9+kg%29%5E2%29%2F%285*85+m%29).
DART had a mass of 570 kg at impact and a relative impact velocity of 6.1 km/s (again per JHAPL above). Based on the kinetic energy equation, that's 1.06e10 J.
Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
Doesn't this ignore all the materials of what dimorphos was? Its not a pile of equal sized spherical particles with zero friction all sitting next to each other.
A rubble pile (which it appears to be) is basically precisely that in comparison to a projectile moving at ~6 km/s.
Energy of impact doesn't mean that you can assume dimorphos was composed of totally unbound atoms. The asteroid will still physically interact with the impact. We cannot reject this idea because the basic idea is obviously flawed as the impact didn't obliterate dimorphos.
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This abstract from last year's LPSC quotes an estimate of 0.25% of the KE being transferred in what is a highly inelastic collision (so KE is not conserved).
https://www.hou.usra.edu/meetings/lpsc2021/pdf/2041.pdf
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A significant amount, yes.
But 99.89% of it?
Because if even 0.11% of the kinetic energy was actually delivered into the moon itself, that's still equal to the GBE.
I'll have to leave that question to those who are some sort of scientist. For comparison, if my calculation is roughly correct, Dimorphos' GBE is slighty less than the energy needed to boil and vaporize five litres of water (starting out at 4 °C). Not sure whether that makes non-disintegration more or less mysterious.
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A significant amount, yes.
But 99.89% of it?
Because if even 0.11% of the kinetic energy was actually delivered into the moon itself, that's still equal to the GBE.
I'll have to leave that question to those who are some sort of scientist. For comparison, if my calculation is roughly correct, Dimorphos' GBE is slighty less than the energy needed to boil and vaporize five litres of water (starting out at 4 °C). Not sure whether that makes non-disintegration more or less mysterious.
Let's see.
The specific heat of water is 4.184 kJ/kg*K, so heating 5 liters (5 kg) of water from 4°C to 100°C takes 4.184*5*(100-4)=2008 kJ. Water's enthalpy of vaporization is 40.66 kJ/mol and its molar mass is 55.49 moles/kg so its mass-specific enthalpy is 2256 kJ/kg which gives us 1.13e7 J. Add on the specific heat required and it only goes up to 1.33e7 J.
But yes, it looks like your observation is precisely correct.
Maybe the concept of gravitational binding energy is simply not applicable to very small bodies? That couldn't make sense, could it?
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A significant amount, yes.
But 99.89% of it?
Because if even 0.11% of the kinetic energy was actually delivered into the moon itself, that's still equal to the GBE.
I'll have to leave that question to those who are some sort of scientist. For comparison, if my calculation is roughly correct, Dimorphos' GBE is slighty less than the energy needed to boil and vaporize five litres of water (starting out at 4 °C). Not sure whether that makes non-disintegration more or less mysterious.
Let's see.
The specific heat of water is 4.184 kJ/kg*K, so heating 5 liters (5 kg) of water from 4°C to 100°C takes 4.184*5*(100-4)=2008 kJ. Water's enthalpy of vaporization is 40.66 kJ/mol and its molar mass is 55.49 moles/kg so its mass-specific enthalpy is 2256 kJ/kg which gives us 1.13e7 J. Add on the specific heat required and it only goes up to 1.33e7 J.
But yes, it looks like your observation is precisely correct.
Maybe the concept of gravitational binding energy is simply not applicable to very small bodies? That couldn't make sense, could it?
You basically just said "maybe gravity isn't applicable to small bodies"...
Your problem is the spherical cows in a vacuum.
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Maybe the concept of gravitational binding energy is simply not applicable to very small bodies? That couldn't make sense, could it?
You basically just said "maybe gravity isn't applicable to small bodies"...
Your problem is the spherical cows in a vacuum.
No, that is not basically what I just said.
Small bodies certainly have gravity and so they certainly have gravitational binding energy. It is certainly useful in investigating, for example, spin bursting caused by the YORP effect. However, that doesn't mean the concept of gravitational binding energy is applicable to very small bodies in the context of high-velocity collisions.
It could be that although small rubble pile bodies have a calculable gravitational binding energy, their surface gravity is so low that the energy dissipated by fragmentation in a high-velocity collision is going to be many orders of magnitude higher than the amount of kinetic energy transferred "deeper" into the rubble pile.
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Kinetic energy is not efficiently converted into tearing apart the Moon.
If you could capture all the kinetic energy of DART in a big battery and use that energy to eject chunks of the moonlet at just the right escape velocity, sure, you could tear it apart with energy to spare. But that’s not the case. The high speed of the impact is very energy-inefficient in tearing apart the moon. The ejecta is moving way faster than escape velocity. A lot of the energy ends up as heat or vaporizing stuff.
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Interesting that the Earth-based observations are quite a bit better than the space-based ones. Still hoping that some image wizards can *enhance* the cubesat pics.
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What I believe is the highest resolution composite image available right now of Dimorphos:
https://twitter.com/doug_ellison/status/1574646223591481345
It looks foreshortened, not sure how much of this is geometric distortion. Hopefully
the LICIAcube images will help to constrain the true shape.
That image stack was captured something like 68 kilometers away, according to the Wikipedia page where Doug's stacked image is posted in full resolution.
The Dart camera has a tele-lens objective, so there won't be much geometric distortion in the image, it is pretty close to isometric, I should think.
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Is the binding energy the energy required to accelerate all of the particles to escape velocity? For an object that size, escape velocity is incredibly small. A collision will give some particles a pretty large velocity and energy, with little energy left over.
John
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GREAT Thread here. Quite long but a good read. Particularly like item 15
https://twitter.com/DrPhiltill/status/1574905023888334858
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I have a feeling that this mission is going to create more new questions than answers for existing ones. I see the need for followup missions beyond the Hera mission from ESA. I am looking forward to what the scientists will be able to tell us from this mission. I also am looking forward to what they will propose for followup missions.
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Not really as unusual as it might appear. The pattern of rays around a lunar crater like Kepler forms as 'streamers' like these in the ejecta cone fall to the surface.
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Not really as unusual as it might appear. The pattern of rays around a lunar crater like Kepler forms as 'streamers' like these in the ejecta cone fall to the surface.
But surely the ejecta should be moving in almost straight lines, curved in one plane only?
The crooked ejecta paths suggests something very strage going on, maybe volatiles being released from the ejecta itself so that it changes course post impact?
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Does anyone see a resemblance between Dimorphos and Bennu, i.e. with the dense concentration of boulders? If Dimorphos is, in fact, just a loose aggregation of rocks and boulders, the impact may have created a large 'cloud' of a spreading debris, much more so than would be caused by a solid body. I too can't wait for the first images.
To my untrained eye this looks very different from the Deep Impact results. Was that expected at all?
Recent (2021) paper about this topic (with many videosimulations), written after Osiris Rex experiment revealed that a faint air burst caused a 10 m crater due to rubble-pile composition of Bennu: https://www.sciencedirect.com/science/article/pii/S0019103521001172
These tiny asteroids are mor "ball pools" than solid rocks.
(https://5.imimg.com/data5/GC/KS/MY-21361694/ball-pool-500x500.jpg)
Old videos by Paul Weigert about dust cloud behavior (but based on assumption of 10m crater):
https://www.youtube.com/watch?v=oet6VN_Fvp4
https://www.youtube.com/watch?v=QxpqDYLHf0g
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Some math:
DART mass: 500 kg (https://it.wikipedia.org/wiki/Double_Asteroid_Redirection_Test)
DART impact speed: 6600 m/s (https://www.space.com/dart-asteroid-mission#:~:text=DART%20deliberately%20impacted%20the%20moonlet,14%2C760%20mph%20(23%2C760%20kph).)
Dymorphos mass: 5e9 kg (https://en.wikipedia.org/wiki/Dimorphos)
Dymoprhos orbital speed: 0.174 m/s (https://en.wikipedia.org/wiki/Dimorphos)
DART kinetic energy:
0.5 * 500 * 6600 * 6600 =~ 11E9
Dymorphos kinetic energy: 0.5 * 5e9 * v^2
11e9 = 0.5 * 5e9 * v^2
v = sqrt(2 * 11e9 / 5e9) = sqrt(4.4) = 2.1 m/s
Does this mean that if Dymoprhos were rock-solid, it would have been stopped in its orbit by DART, and would have even started moving the other way?!?
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GREAT Thread here. Quite long but a good read. Particularly like item 15
Indeed, thanks for the link. It boils down to: diversity is what makes things get interesting. Hyper-pure samples give you "boring" results hardly seen in Nature, with little potential for complex (and useful) behavior. Mix and match a bit though, and statistics starts becoming fun, leading to complexity and much richer phenomena.
TL;DR: seems likely at least part of the explanation is single-sized particle distributions create homogeneous ejecta, but "granular collapse" (being actively study at Station and suborbital flights) in widely heterogeneous particle distributions causes clumping.
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Some math:
DART mass: 500 kg (https://it.wikipedia.org/wiki/Double_Asteroid_Redirection_Test)
DART impact speed: 6600 m/s (https://www.space.com/dart-asteroid-mission#:~:text=DART%20deliberately%20impacted%20the%20moonlet,14%2C760%20mph%20(23%2C760%20kph).)
Dymorphos mass: 5e9 kg (https://en.wikipedia.org/wiki/Dimorphos)
Dymoprhos orbital speed: 0.174 m/s (https://en.wikipedia.org/wiki/Dimorphos) and https://www.sciencedirect.com/science/article/pii/S0012821X22003491 (https://www.sciencedirect.com/science/article/pii/S0012821X22003491)
DART kinetic energy:
0.5 * 500 * 6600 * 6600 =~ 11E9
Dymorphos kinetic energy: 0.5 * 5e9 * v^2
11e9 = 0.5 * 5e9 * v^2
v = sqrt(2 * 11e9 / 5e9) = sqrt(4.4) = 2.1 m/s
Does this mean that if Dymoprhos were rock-solid, it would have been stopped in its orbit by DART, and would have even started moving the other way?!?
In a collision there is conservation of energy and conservation of momentum. In Dymorphos reference frame, Dymorphos, m1=5e9, is at rest, v1=0. Dart, m2=500, v2=6600. m1*v1+m2*v2 is total momentum before. Afterwards most of the mass stays together but some unknown amount gets blasted backwards so the collision is not completely inelastic. If it was fully inelastic, all the mass would move with a single post-collision velocity, v3. Momentum after would be (m1+m2)*v3. Can ignore m2 in this since it's so small. momentum before = momentum after. So basically the momentum of Dart is fully transferred to Dymorphos. m2*v2=m1*v3. Then v3=(m2*v2)/m1.
When its somewhat elastic/explosive, you have to account for the blasted-backwards mass and its velocity. Some of the KE of dart would go into material deformation, some into radiation, and some into the KE of the ejected material, so it would not be easy to account for. Some of the ejecta KE is off-axis and wouldn't add/subtract from the axial momentum.
Edit to add a recent paper: https://arxiv.org/pdf/2111.10108.pdf (https://arxiv.org/pdf/2111.10108.pdf) and https://www.sciencedirect.com/science/article/pii/S0012821X22003491 (https://www.sciencedirect.com/science/article/pii/S0012821X22003491)
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Some math:
DART mass: 500 kg (https://it.wikipedia.org/wiki/Double_Asteroid_Redirection_Test)
DART impact speed: 6600 m/s (https://www.space.com/dart-asteroid-mission#:~:text=DART%20deliberately%20impacted%20the%20moonlet,14%2C760%20mph%20(23%2C760%20kph).)
Dymorphos mass: 5e9 kg (https://en.wikipedia.org/wiki/Dimorphos)
Dymoprhos orbital speed: 0.174 m/s (https://en.wikipedia.org/wiki/Dimorphos) and https://www.sciencedirect.com/science/article/pii/S0012821X22003491 (https://www.sciencedirect.com/science/article/pii/S0012821X22003491)
DART kinetic energy:
0.5 * 500 * 6600 * 6600 =~ 11E9
Dymorphos kinetic energy: 0.5 * 5e9 * v^2
11e9 = 0.5 * 5e9 * v^2
v = sqrt(2 * 11e9 / 5e9) = sqrt(4.4) = 2.1 m/s
Does this mean that if Dymoprhos were rock-solid, it would have been stopped in its orbit by DART, and would have even started moving the other way?!?
In a collision there is conservation of energy and conservation of momentum. In Dymorphos reference frame, Dymorphos, m1=5e9, is at rest, v1=0. Dart, m2=500, v2=6600. m1*v1+m2*v2 is total momentum before. Afterwards most of the mass stays together but some unknown amount gets blasted backwards so the collision is not completely inelastic. If it was fully inelastic, all the mass would move with a single post-collision velocity, v3. Momentum after would be (m1+m2)*v3. Can ignore m2 in this since it's so small. momentum before = momentum after. So basically the momentum of Dart is fully transferred to Dymorphos. m2*v2=m1*v3. Then v3=(m2*v2)/m1.
When its somewhat elastic/explosive, you have to account for the blasted-backwards mass and its velocity. Some of the KE of dart would go into material deformation, some into radiation, and some into the KE of the ejected material, so it would not be easy to account for. Some of the ejecta KE is off-axis and wouldn't add/subtract from the axial momentum.
Edit to add a recent paper: https://arxiv.org/pdf/2111.10108.pdf (https://arxiv.org/pdf/2111.10108.pdf) and https://www.sciencedirect.com/science/article/pii/S0012821X22003491 (https://www.sciencedirect.com/science/article/pii/S0012821X22003491)
In other words @spacexplorer, conservation of kinetic energy does not apply to inelastic collisions - just to elastic ones. If you assume an unbreakable DART just clumped with a solid Dimorphos, it is an inelastic collision (there must be some binding energy to prevent DART recoiling upon contact), which by definition implies a loss of kinetic energy, so only mv(initial) = mv(final) applies, not Ek(initial) = Ek(final).
The situation you described where energy conservation would apply would be an unbreakable DART colliding with Dimorphos, to then remain at rest in the initial Dimorphos frame, having transferred all momentum to the asteroid, which would then move backwards at 2 m/s - which is obviously quite removed from the real scenario, even neglecting the important ejecta and heating.
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GREAT Thread here. Quite long but a good read.
That was a great read; thanks for sharing! I wonder if the DART team had any scientific expectations other than "can we deflect an asteroid"? They sure got some!
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Just an opinion:
All the dust and pebbles we see in the pre-impact images could have been surrounding a hard iron or chondrite mass. The outer layers would have been blown off, but the center would have absorbed the KE, thus solving the binding energy question. Then, the physical structure of the core could have influenced the ejecta pattern, creating the streamers we see.
To paraphrase Bill Cosby: it may have been a slush ball with a rock in the middle, not a snowball.
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https://twitter.com/AntonioParis/status/1574702478221660160
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Not really as unusual as it might appear. The pattern of rays around a lunar crater like Kepler forms as 'streamers' like these in the ejecta cone fall to the surface.
But surely the ejecta should be moving in almost straight lines, curved in one plane only?
The crooked ejecta paths suggests something very strage going on, maybe volatiles being released from the ejecta itself so that it changes course post impact?
The 'curved/crooked' paths may just be a visual effect. Similar to the 'spirals' formed during upper stage propellant dumps: all the material involved moves only in straight lines, but there is a visual impression of a spinning spiral because of discontinuous and inhomogeneous material emission.
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Not really as unusual as it might appear. The pattern of rays around a lunar crater like Kepler forms as 'streamers' like these in the ejecta cone fall to the surface.
But surely the ejecta should be moving in almost straight lines, curved in one plane only?
The crooked ejecta paths suggests something very strage going on, maybe volatiles being released from the ejecta itself so that it changes course post impact?
The 'curved/crooked' paths may just be a visual effect. Similar to the 'spirals' formed during upper stage propellant dumps: all the material involved moves only in straight lines, but there is a visual impression of a spinning spiral because of discontinuous and inhomogeneous material emission.
The ejecta could be spinning and throwing off debris
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Did DART really hit Dimorphos with almost 900 times as much kinetic energy as its GBE? If so, wouldn't Dimorphos be completely obliterated?
I'm not any sort of scientist, but I'm getting the same numbers as you. My guess is that a significant part of the impact energy is "spent" on vaporizing rock instead of doing work against Dimorphos' gravity. Heating can soak up a whole lot of energy.
There's lots of ways to get rid of energy without disrupting Dimorphos. For the same amount of energy you can eject:
(1) 500 kg at 6000 m/s (opposite of impact)
(2) 50,000 kg at 600 m/s
(3) 5,000,000 kg at 6 m/s
(4) 500,000,000 kg at 0.6 m/s (1/10 of Dimorphos mass)
(5) 5,000,000,000 kg at 0.2 m/s (entire mass of Dimorphos)
Considering the escape velocity of debris is about 0.09 m/s (assuming mass = 5e9 kg and r=80 m) there is way more energy than needed to disrupt Dimorphos. But the most likely scenario is more like case (2) above - a small fraction of rocks given way more than escape velocity.
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Osiris-REX displaced 6 tons of material on Bennu, with just a puff of gas.
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In this news article (https://www.nytimes.com/2022/09/27/science/nasa-dart-asteroid-photos.html), an astronomer estimates the debris moving at 1800 m/s, a little less than a third of incoming velocity. Depending on the mass of the material, this could potentially carry away several times the momentum of the incoming spacecraft. I'm going to guess the amplification of the impact momentum will be on the high side, perhaps a factor of 2 or more. That's good news if you are trying to deflect rubble-pile asteroids.
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In this news article (https://www.nytimes.com/2022/09/27/science/nasa-dart-asteroid-photos.html), an astronomer estimates the debris moving at 1800 m/s, a little less than a third of incoming velocity. Depending on the mass of the material, this could potentially carry away several times the momentum of the incoming spacecraft. I'm going to guess the amplification of the impact momentum will be on the high side, perhaps a factor of 2 or more. That's good news if you are trying to deflect rubble-pile asteroids.
This depends on your goals. The trajectory of the center of mass of spacecraft+target is unchanged, but the target is now in multiple pieces. The big piece is deflected, but the little pieces now form a wide pattern which will sweep along the orbit.
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In this news article (https://www.nytimes.com/2022/09/27/science/nasa-dart-asteroid-photos.html), an astronomer estimates the debris moving at 1800 m/s, a little less than a third of incoming velocity. Depending on the mass of the material, this could potentially carry away several times the momentum of the incoming spacecraft. I'm going to guess the amplification of the impact momentum will be on the high side, perhaps a factor of 2 or more. That's good news if you are trying to deflect rubble-pile asteroids.
How could the debris carry away "several times the momentum of the incoming spacecraft". Conservation of momentum is generally a thing - there can't be more going out of the system than was put in.
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In this news article (https://www.nytimes.com/2022/09/27/science/nasa-dart-asteroid-photos.html), an astronomer estimates the debris moving at 1800 m/s, a little less than a third of incoming velocity. Depending on the mass of the material, this could potentially carry away several times the momentum of the incoming spacecraft. I'm going to guess the amplification of the impact momentum will be on the high side, perhaps a factor of 2 or more. That's good news if you are trying to deflect rubble-pile asteroids.
How could the debris carry away "several times the momentum of the incoming spacecraft". Conservation of momentum is generally a thing - there can't be more going out of the system than was put in.
Momentum is conserved for the system as a whole (spacecraft + Dimorphos + debris). But from the point of view of Dimorphos, its momentum is reduced by the momentum of the debris headed in the other direction (the direction the spacecraft came in). How big this factor might be is unclear, since it depends on how much mass is ejected by the impact, and its velocity and direction. Measuring this factor is one of the main objectives of the mission (https://www.nasa.gov/feature/predicting-the-unpredictable-the-dynamics-of-dart-s-dive-into-an-asteroid).
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The angle of the ejected material is quite wide. Would that suggest the crater would be quite deep?
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does anyone knows where to find the list of astronomical observatories that actually acquired the events?
There is a map online with a list of about 40 astronomical observatories involved in the hit and the followup worldwide, but the event was visible only to a minority of them because of visibility (African and Southern Asia should have been in the right geographical position), weather, engineering time, etc. Plus JWST, HST and Lucy.
thanks!
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The angle of the ejected material is quite wide. Would that suggest the crater would be quite deep?
More than just a crater, I would expect virtually the entire surface of Dimorphos to be disrupted. Didymos will likely have a bunch of new craters.
I dearly wish that Hera had been around to observe them before the impactor arrived.
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Probably no craters at all. There were none to begin with despite unavoidable impacts. On small objects like this most impacts will just move stuff around, not make a crater. The impact on Ryugu left a vague pit and a visible ejecta field, but not a standard crater, and Dimorphos is much smaller than Ryugu.
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Not really as unusual as it might appear. The pattern of rays around a lunar crater like Kepler forms as 'streamers' like these in the ejecta cone fall to the surface.
But surely the ejecta should be moving in almost straight lines, curved in one plane only?
The crooked ejecta paths suggests something very strage going on, maybe volatiles being released from the ejecta itself so that it changes course post impact?
The ejecta curtain is made irregular by flow instabilities, by breakup of rotating clumps, all sorts of messy phenomema. Straight lines (like spherical cows and frictionless particles) are for physics, but this is geology. I repeat, the pattern of lunar crater rays is formed as streamers in the expanding ejecta curtain (basically an expanding conical sheet) fall onto the surface. If ejecta moves in perfect straight lines how do you account for complex ray patterns on the Moon? If you want an example look at the rays of Copernicus.
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https://twitter.com/comets77/status/1575118862978355201
Significance of this, apart from the coolness factor:
https://twitter.com/DrPhiltill/status/1574791409785524224
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So if one of these rubble pile asteroids was to head toward Earth would they break up once they reach the atmosphere, forming many small asteroids that would burn up before they reach the surface?
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NASA blog post on DART impact modelling for various compositions and resulting Beta (impact momentum coupling factor):
https://www.nasa.gov/feature/predicting-the-unpredictable-the-dynamics-of-dart-s-dive-into-an-asteroid/
Well worth a read, and the 'rubble pile' impact visualisation near the bottom (the one with the 'exploding boulders') would explain some of the odd looking plume shape.
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So if one of these rubble pile asteroids was to head toward Earth would they break up once they reach the atmosphere, forming many small asteroids that would burn up before they reach the surface?
Probably, but you still have that amount of mass interacting with the Earth's environment. So even if nothing reached the Earth's surface it'll still have an enormous effect on the atmosphere.
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Teamwork makes the dream work For the first time, @ESA_Webb and @HUBBLE_space have observed the same target at the same time. And it's not just any target... it's the aftermath of the #DARTMission collision with #asteroid Dimorphos!
https://twitter.com/esascience/status/1575478446515400704
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This gif shows Hubble's view of the collision: ejecta, material thrown out from the impact, appears as rays stretching out from the body of the asteroid. The bolder, fanned-out spike of ejecta to the left of the asteroid is where DART impacted.
https://twitter.com/HUBBLE_space/status/1575478402538258432
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This gif shows Webb's view of the impact, a tight, compact core, with plumes of material appearing as wisps streaming away from the centre of where the impact took place.
https://twitter.com/ESA_Webb/status/1575478701780779009
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.@NASAWebb & @NASAHubble caught the DART impact on camera – the 1st time that Webb & Hubble were used to simultaneously observe the same celestial target.
Looking forward to what we’ll learn about #DARTmission from our telescopes on Earth soon.
https://twitter.com/SenBillNelson/status/1575489623333122049
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Larger image of the Hubble and JWST views
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Webb and Hubble Capture Detailed Views of DART Impact
First Time Webb, Hubble Make Simultaneous Observations of the Same Target
29 September 2022
Two of the great observatories, the NASA/ESA/CSA James Webb Space Telescope and the NASA/ESA Hubble Space Telescope, have captured views of a unique experiment to smash a spacecraft into a small asteroid. NASA’s Double Asteroid Redirection Test (DART) impact observations mark the first time that Webb and Hubble were used to simultaneously observe the same celestial target.
On 27 September 2022 at 01:14 CEST, DART intentionally crashed into Dimorphos, the asteroid moonlet in the double-asteroid system of Didymos. It was the world’s first test of the kinetic impact technique using a spacecraft to deflect an asteroid by modifying the object’s orbit. DART is a test for defending Earth against potential asteroid or comet hazards.
The observations are more than just an operational milestone for each telescope—there are also key science questions relating to the makeup and history of our solar system that researchers can explore when combining the capabilities of these observatories.
Observations from Webb and Hubble together will allow scientists to gain knowledge about the nature of the surface of Dimorphos, how much material was ejected by the collision, and how fast it was ejected. Additionally, observing the impact across a wide array of wavelengths between Webb and Hubble will reveal the distribution of particle sizes in the expanding dust cloud, helping to determine whether it threw off lots of big chunks or mostly fine dust. Combining this information will help scientists to understand how effectively a kinetic impact can modify an asteroid’s orbit.
Webb Captures Impact Site Before and After Collision
Webb took one observation of the impact location before the collision took place, then several observations over the next few hours. Images from Webb’s Near-Infrared Camera (NIRCam) show a tight, compact core, with plumes of material appearing as wisps streaming away from the centre of where the impact took place.
Observing the impact with Webb presented the flight operations, planning, and science teams with very unique challenges. Because of the asteroid’s speed of travel across the sky, the teams worked in the weeks leading up to the impact to enable and test a method of tracking asteroids moving over 3 times faster than the original speed limit set for Webb.
Scientists also plan to observe the asteroid in the coming months using Webb’s Mid-Infrared Instrument (MIRI) and Webb’s Near-Infrared Spectrograph (NIRSpec). Spectroscopic data will provide researchers with insight into the asteroid’s chemical composition.
Webb observed the impact over five hours total and captured 10 images. The data were collected as part of Webb’s Cycle 1 Guaranteed Time Observation Program 1245 led by Heidi Hammel of Association of Universities for Research in Astronomy (AURA).
Hubble Images Show Movement of Ejecta After Impact
Hubble also managed to capture observations of the moonlet ahead of the impact, then again 15 minutes after DART met the surface of Dimorphos. Images from Hubble’s Wide Field Camera 3 show the impact in visible light. Ejecta from the impact appear as rays stretching out from the body of the asteroid. The bolder, fanned-out spike of ejecta to the left of the asteroid is where DART impacted.
Some of the rays appear to be curved slightly, but astronomers need to take a closer look to determine what this could mean. In the Hubble images, astronomers estimate that the brightness of Didymos increased by 3 times after impact, and are also particularly intrigued by how that brightness then held steady, even eight hours after impact.
Hubble will monitor Dimorphos ten more times over the next three weeks. These regular, relatively long-term observations as the ejecta cloud expands and fades over time will paint a more complete picture of the cloud’s expansion from the ejection to its disappearance.
Hubble captured 45 images in the time immediately before and following DART’s impact with Dimorphos. The Hubble data was collected as part of Cycle 29 General Observers Program 16674.
Follow Up with ESA’s Hera Mission
Due to launch in October 2024, ESA’s Hera mission will perform a detailed post-impact survey of the target asteroid Dimorphos. Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique that might one day be carried out for real.
Just like Webb and Hubble, NASA’s DART and ESA’s Hera missions are a great example of what international collaboration can achieve: the two missions are supported by the same teams of scientists and astronomers, and take place through an international collaboration called AIDA – the Asteroid Impact and Deflection Assessment.
NASA and ESA worked together in the early 2000s to develop asteroid monitoring systems, but recognised there was a missing link in the chain from asteroid threat identification to ways of addressing that threat. In response NASA oversaw the DART mission while ESA developed the Hera mission to gather additional data on DART’s impact. With the Hera mission, ESA is assuming even greater responsibility for protecting our planet and ensuring that Europe plays a leading role in the common effort to tackle asteroid risks. As Europe’s flagship planetary defender, Hera is supported through the Agency’s Space Safety programme, part of the Operations Directorate. Read about future plans to be proposed at ESA’s Council at Ministerial Level this November.
More information
The James Webb Space Telescope is an international partnership between NASA, ESA and the Canadian Space Agency (CSA).
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.
Webb is the largest, most powerful telescope ever launched into space. Under an international collaboration agreement, ESA provided the telescope’s launch service, using the Ariane 5 launch vehicle. Working with partners, ESA was responsible for the development and qualification of Ariane 5 adaptations for the Webb mission and for the procurement of the launch service by Arianespace. ESA also provided the workhorse spectrograph NIRSpec and 50% of the mid-infrared instrument MIRI, which was designed and built by a consortium of nationally funded European Institutes (The MIRI European Consortium) in partnership with JPL and the University of Arizona.
Image Credit: NASA, ESA, CSA, and STScI
Links
Collection of Webb’s First Images
ESA Webb Seeing Farther Interactive Brochure
Hera Mission
DART Mission
ESA’s Vision for Space Safety
Release on STScI website
Release on NASA website
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Getting greedy here, but why no preliminary results from DART yet?
The orbital period of Dimorphos was about 12 hours, and measured quite precisely (much better than a second) The most conservative estimate of period change is 7 minutes. So the very first eclipse (and certainly the second) should easily reveal the approximate period change. It's not that hard of an observation, and with telescopes around the world it should occur at night for at least some.
So why no results yet? Of course they will get more accurate the longer the span of observations, but I'd think they'd want to take advantage of the public interest and announce at least something.
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Getting greedy here, but why no preliminary results from DART yet?
The orbital period of Dimorphos was about 12 hours, and measured quite precisely (much better than a second) The most conservative estimate of period change is 7 minutes. So the very first eclipse (and certainly the second) should easily reveal the approximate period change. It's not that hard of an observation, and with telescopes around the world it should occur at night for at least some.
So why no results yet? Of course they will get more accurate the longer the span of observations, but I'd think they'd want to take advantage of the public interest and announce at least something.
Are they actually eclipsing at this time?
From Photometric Observations of the Binary Near-Earth Asteroid (65803) Didymos in 2015–2021 Prior to DART Impact
P. Pravec et. al, (https://iopscience.iop.org/article/10.3847/PSJ/ac7be1)
Abstract
We performed photometric observations of the binary near-Earth asteroid (65803) Didymos in support of the Double Asteroid Redirection Test (DART) mission that will test the Kinetic Impactor technology for diverting dangerous asteroids. It will hit the Didymos secondary, called Dimorphos, on 2022 September 26. We observed Didymos with 11 telescopes with diameters from 3.5 to 10.4 m during four apparitions in 2015–2021, obtaining data with rms residuals from 0.006 to 0.030 mag. We analyzed the light-curve data and decomposed them into the primary rotational and secondary orbital light curves. We detected 37 mutual eclipse/occultation events between the binary system components. The data presented here, in combination with 18 mutual events detected in 2003, provide the basis for modeling the Dimorphos orbit around the Didymos primary. The orbit modeling is discussed in detail by Scheirich & Pravec and Naidu et al. The primary light curves were complex, showing multiple extrema on some epochs. They suggest a presence of complex topography on the primary's surface that is apparent in specific viewing/illumination geometries; the primary shape model by Naidu et al. (Icarus 348, 113777, 2020) needs to be refined. The secondary rotational light-curve data were limited and did not provide a clear solution for the rotation period and equatorial elongation of Dimorphos. We define the requirements for observations of the secondary light curve to provide the needed information on Dimorphos's rotation and elongation when Didymos is bright in 2022 July–September before the DART impact.
So only a few dozen eclipses were identified over several apparitions (closest approaches) and they were picked out of a complex light curve measured with significant noise.
Astronomers are unlikely to nail down two with precision in the immediate aftermath of the impact.
Patience, Grasshopper!
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https://twitter.com/ngc3314/status/1575964911523729408
Last night, @SARA_Obs Chile: Didymos/Dimorphos dust trails. 7x5m tracked on asteroids, stars filtered. WNW trail extends to 165", projecting to ~8600 km. (0410-0500 UT 30 Sept., ~78 hours after impact, R band)
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Foreseen tail length: https://academic.oup.com/mnras/article/515/2/2178/6634251
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DART AFTERMATH: The SOAR Telescope in Chile, operated by NSF’s NOIRLab, imaged the more than 10,000 kilometers long trail of debris blasted from the surface of Dimorphos two days after the asteroid was impacted by NASA’s DART spacecraft.
https://twitter.com/marsboy/status/1577014935317422080
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DART impact observed by telescopes:
https://youtu.be/ANXsCdMGzeo
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So how long is the analysis of the orbit disruption going to take before some conclusions can be drawn?
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A couple of weeks was suggested earlier. The difference of position in one orbit is presumably too little to measure, so you have to accumulate enough orbits to give you a measurable difference. And one data point is not enough so you keep doing it until the statistics are reliable.
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I'd love to know what is taking the LUCIE (sp) images so long to come down? There must have been more than just 3?
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About 600, I believe. Patience is a virtue, though admittedly it's deeply unfashionable in the 21st Century.
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I'd love to know what is taking the LUCIE (sp) images so long to come down? There must have been more than just 3?
Downlink speed is 64 to 256 kbit/s, and they have 1.5 hour comms sessions. so they're downloading ~1-10 photos per session.
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I'd love to know what is taking the LUCIE (sp) images so long to come down? There must have been more than just 3?
Downlink speed is 64 to 256 kbit/s, and they have 1.5 hour comms sessions. so they're downloading ~1-10 photos per session.
I read that paper (https://www.nasa.gov/sites/default/files/atoms/files/argomoon_and_liciacube_ops.pdf) to, but I didn't understand why just 1.5 hours per day are available for transmission (page 38).
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From this paper (https://iopscience.iop.org/article/10.3847/PSJ/ac6509/pdf):
Since the data downlink will last for several months, the
public release of data to the Planetary Data System is planned
for 9 months after the closest approach. At that point, all of the
data collected will also be made available to the public by
means of MATISSE (https://tools.ssdc.asi.it/Matisse/).
Let's hope something will be published before delivery to PDS...
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I read that paper (https://www.nasa.gov/sites/default/files/atoms/files/argomoon_and_liciacube_ops.pdf) to, but I didn't understand why just 1.5 hours per day are available for transmission (page 38).
I think I got it: onboard panels and antenna are not steerable, hence LICIAcube must spend most of the time oriented toward the sun to charge the battery, to have enough energy to transmit data for 80 minutes.
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Meanwhile, the NEO Surveyor mission is being killed. Well, not totally killed, but placed into a coma.
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Meanwhile, the NEO Surveyor mission is being killed. Well, not totally killed, but placed into a coma.
As is traditional, at this point.
How many times has NEO Surveyor (nee NEO Surveillance nee NEOCam) been killed and revived now? Until congress actually funds it at something beyond a shoestring level, it will continue to limp on and repeatedly be killed and then revived at a bare minimum level.
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DART Update
Oct. 11 at 18:00 UTC
https://twitter.com/NASA/status/1578478396568657926
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https://twitter.com/jeff_foust/status/1579895826071293952
NASA Administrator Bill Nelson says DART successfully changed the orbit of Dimorphos, decreasing its orbital period around Didymos from 11hrs 55 mins to 11hrs 23mins, a 32-minute change.
https://twitter.com/joroulette/status/1579896040794513408
NASA chief Bill Nelson tells reporters that the agency's DART impactor spacecraft successfully moved the orbit of the Didymos asteroid by 32 minutes, proving a key planetary defense method.
"This is a watershed moment for planetary defense, and a watershed moment for humanity"
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https://youtu.be/Zhzn0U2m5wQ
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https://twitter.com/jeff_foust/status/1579897974657757184
The precision of that orbital change ±2 minutes, says NASa’s Lori Glaze, planetary science division director.
The minimal requirement was 73-sec change, but models estimated a change of a few minutes to several tens of minutes, so on the upper end of those models.
Fantastic result, congratulations to the Dart team!
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https://twitter.com/jeff_foust/status/1579898545556967425
A new Hubble image of the asteroid system post-impact. The tail is ~10,000 km long.
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https://www.nasa.gov/press-release/nasa-confirms-dart-mission-impact-changed-asteroid-s-motion-in-space
Oct 11, 2022
RELEASE 22-105
NASA Confirms DART Mission Impact Changed Asteroid’s Motion in Space
Analysis of data obtained over the past two weeks by NASA’s Double Asteroid Redirection Test (DART) investigation team shows the spacecraft's kinetic impact with its target asteroid, Dimorphos, successfully altered the asteroid’s orbit. This marks humanity’s first time purposely changing the motion of a celestial object and the first full-scale demonstration of asteroid deflection technology.
“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” said NASA Administrator Bill Nelson. “This mission shows that NASA is trying to be ready for whatever the universe throws at us. NASA has proven we are serious as a defender of the planet. This is a watershed moment for planetary defense and all of humanity, demonstrating commitment from NASA's exceptional team and partners from around the world.”
Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11 hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.
Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.
“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid” said Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters in Washington. “As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.”
The investigation team is still acquiring data with ground-based observatories around the world – as well as with radar facilities at NASA Jet Propulsion Laboratory’s Goldstone planetary radar in California and the National Science Foundation’s Green Bank Observatory in West Virginia. They are updating the period measurement with frequent observations to improve its precision.
Focus now is shifting toward measuring the efficiency of momentum transfer from DART’s roughly 14,000-mile (22,530-kilometer) per hour collision with its target. This includes further analysis of the "ejecta” – the many tons of asteroidal rock displaced and launched into space by the impact. The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos – a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction.
To successfully understand the effect of the recoil from the ejecta, more information on of the asteroid’s physical properties, such as the characteristics of its surface, and how strong or weak it is, is needed. These issues are still being investigated.
“DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defense technology,” said Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. “The DART team is continuing to work on this rich dataset to fully understand this first planetary defense test of asteroid deflection.”
For this analysis, astronomers will continue to study imagery of Dimorphos from DART’s terminal approach and from the Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency, to approximate the asteroid’s mass and shape. Roughly four years from now, the European Space Agency’s Hera project is also planned to conduct detailed surveys of both Dimorphos and Didymos, with a particular focus on the crater left by DART’s collision and a precise measurement of Dimorphos’ mass.
Johns Hopkins APL built and operated the DART spacecraft and manages the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency's Planetary Missions Program Office. Telescopic facilities contributing to the observations used by the DART team to determine this result include: Goldstone, Green Bank Observatory, Swope Telescope at the Las Campanas Observatory in Chile, the Danish Telescope at the La Silla Observatory in Chile, and the Las Cumbres Observatory global telescope network facilities in Chile and in South Africa.
Neither Dimorphos nor Didymos poses any hazard to Earth before or after DART’s controlled collision with Dimorphos.
For more information about the DART mission, visit:
https://www.nasa.gov/dart
-end-
Image caption:
This imagery from NASA’s Hubble Space Telescope from Oct. 8, 2022, shows the debris blasted from the surface of Dimorphos 285 hours after the asteroid was intentionally impacted by NASA’s DART spacecraft on Sept. 26. The shape of that tail has changed over time. Scientists are continuing to study this material and how it moves in space, in order to better understand the asteroid.
Credits: NASA/ESA/STScI/Hubble
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LICIACube's video of the impact:
https://twitter.com/LICIACube/status/1579897633258508288 (https://twitter.com/LICIACube/status/1579897633258508288)
And excellent photo of the binary shortly after the impact, before closest approach:
https://twitter.com/elena_epifani/status/1579899481990258690
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Nasa's Dart spacecraft 'changed path of asteroid' https://www.bbc.co.uk/news/science-environment-63221577
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I would call this now a very successful mission. Knowing how much a rubble pile asteroid of fairly well known mass was slowed is a pretty good starting point. I think we need a few more data points with new missions in the coming years to see how consistent the results will be with different size targets with different makeup.
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DART impact successfully moved asteroid Dimorphos! NASA chief explains
https://youtu.be/N-q2z4N_Rsk
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The results are in.
@NASA crashed the #DARTMission into asteroid #Dimorphos. They altered its orbit by 4%.
Orig. orbit around central: 11hr 55mins
Models expected: a few-10 mins difference
Post impact: 11hr 23mins. A 32 min orbital change!
https://twitter.com/esaoperations/status/1579902243016671234
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Unless I've miscalculated, this means the rubble blasting out increased the momentum transfer by a factor of about 4.
Here's my back of the envelope calculation. Central mass is 5.55x10^11 kg. Dimorphos is 5x10^9 kg. Orbital radius is 1200 meters. Initial orbit just under 12 hours. All of these are from pre-impact papers. Assuming a circular orbit, this gives an orbital velocity of 0.176 m/s.
Delta speed caused by an inelastic impact would be (spacecraft speed - 6100 m/s) x spacecraft mass (570 kg) / mass of Dimorphos. This is about 6.95e-4 m/s (or -0.4% of the original speed). This causes a change in 'a', the semi-major axis, of -0.79%. This causes an orbital period change of about -1.18%, or about -8.5 minutes.
In order to get the observed change of 32 minutes, you need the delta speed imparted to be about 4x the calculation above. This implies the momentum transfer was about 4x that of an inelastic impact. So the debris blasted out added about 3x the momentum of the incoming spacecraft, for a total of 4x. If I recall correctly, the pre-impact guess (so little was known it was hard to call it a prediction) was about 2x for the total momentum transfer. So it was somewhat bigger than expected.
EDIT: All this assumes the spacecraft velocity vector was exactly opposite Dimorphos's orbital velocity. It was presumably not exactly aligned, so some momentum went into an inclination change instead of an orbital velocity change. I have no idea of the magnitude of the misalignment, but it must make the multiplication factor a little larger yet.
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I'm thrilled this worked.
As an added bonus, the change in mass and orbital period of the smaller asteroid (Dimorphos) will affect the larger asteroid (Didymos) it orbits over time as well.
So we get to see success both with direct bombardment, and also with "gravitational tug" methods for deflecting asteroids!
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Unless I've miscalculated, this means the rubble blasting out increased the momentum transfer by a factor of about 4.
Here's my back of the envelope calculation. Central mass is 5.55x10^11 kg. Dimorphos is 5x10^9 kg. Orbital radius is 1200 meters. Initial orbit just under 12 hours. All of these are from pre-impact papers. Assuming a circular orbit, this gives an orbital velocity of 0.176 m/s.
Delta speed caused by an inelastic impact would be (spacecraft speed - 6100 m/s) x spacecraft mass (570 kg) / mass of Dimorphos. This is about 6.95e-4 m/s (or -0.4% of the original speed). This causes a change in 'a', the semi-minor axis, of -0.79%. This causes an orbital period change of about -1.18%, or about -8.5 minutes.
In order to get the observed change of 32 minutes, you need the delta speed imparted to be about 4x the calculation above. This implies the momentum transfer was about 4x that of an inelastic impact. So the debris blasted out added about 3x the momentum of the incoming spacecraft, for a total of 4x. If I recall correctly, the pre-impact guess (so little was known it was hard to call it a prediction) was about 2x for the total momentum transfer. So it was somewhat bigger than expected.
EDIT: All this assumes the spacecraft velocity vector was exactly opposite Dimorphos's orbital velocity. It was presumably not exactly aligned, so some momentum went into an inclination change instead of an orbital velocity change. I have no idea of the magnitude of the misalignment, but it must make the multiplication factor a little larger yet.
Can we determine the ejected mass?
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So the debris blasted out added about 3x the momentum of the incoming spacecraft,
I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
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So the debris blasted out added about 3x the momentum of the incoming spacecraft,
I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
Energy isn't the same as momentum. Energy is indeed conserved, even if messy (big bodies + debris + chemical + light).
Momentum is also conserved but can be distributed in different ways after collision.
One ball of gloop hitting another ball of gloop - they join together and combine momentum.
One small steel ball hitting a much larger steel ball - the small one ricochets backwards at nearly the same speed. The big ball has equal but opposite momentum to the small ball, so it goes forward at very low speed.
Suppose you can transfer the KE of the impactor m1 into moving a much larger mass of debris backwards, e.g. 100 times the mass. By conservation of energy, energy before = energy after (and ignore the much larger mass of the the asteroid for now), so 0.5*m1*v1^2 = 0.5*(100*m1)v2^2. Then v2 = v1/sqrt(100), v2 = v1/10. Impactor can push 100 times its mass backwards at 1/10th of the velocity. Now looking at how much momentum is sent backwards: (100*m1)*v1/10 which is 10*m1*v1. That would be 10 times the momentum sent backwards. This is over simplified since some energy goes forward with the very large asteroid.
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I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
Total energy is conserved. Kinetic energy is not conserved.
It is almost certain that almost all the initial kinetic energy goes into heat, light and turning big rocks into small rocks.
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So the debris blasted out added about 3x the momentum of the incoming spacecraft,
I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
We already answered you at length in replies #200-201. Not sure why you insist with a quantity that isn't conserved in inelastic collisions (Ek), choosing to ignore the far more important energy conversion and momentum conservation.
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I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
Total energy is conserved. Kinetic energy is not conserved.
It is almost certain that almost all the initial kinetic energy goes into heat, light and turning big rocks into small rocks.
Sure, and this is why I am asking which is the mechanism/formula which cause Dimorphos momentum to "increase by 4x", if part of the energy is converted into heat (i.e. lost in space):
This implies the momentum transfer was about 4x that of an inelastic impact. So the debris blasted out added about 3x the momentum of the incoming spacecraft, for a total of 4x.
But maybe I got it: "increase" is not referred to Asteroid momentum, but to expected transfer of momentum.
"Inventing" some numbers, just for understanding:
- elastic collision: 100% momentum transfer from DART to static Asteroid (let's say 100 "momentum units"); DART stops, Asteroid starts moving;
- inelastic collision: 0% momentum transfer from DART to static Asteroid (0 units); DART burns up; Asteroid heats up without moving;
- real collision:
- expected momentum transfer: 10 units; 70 units lost in heat; 20 units cause debris; DART increases speed by K units;
- measured momentum transfer: 10x4 = 40 units; 10 units lost in heat; 40 units cause debris; DART increases speed by "K+something" units.
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A very impressive animation obtained by centering frames on Dimorphos.
It's a little hard to see: in some cases the animation appears "wrong", with big asteroid (Didymos) rotating in one direction and small one (Dimorphos) rotating in opposite direction, but it's just an optical illusion, like the one which makes sometimes craters appears as bubbles; so I attach an explanatory image which shows what you should see. If it "does not work", try changing the direction of light coming to your screen (move your phone or your monitor), so your brain does not get fooled by "wrong light direction".
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https://twitter.com/esa/status/1583120023786524672
📷This NASA/ESA @HUBBLE_space Telescope image shows the two tails of dust ejected from the Didymos-Dimorphos asteroid system, documenting the lingering aftermath of the NASA’s #DARTMission impact on 27 September 2022.
👉 esa.int/ESA_Multimedia…
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I don't understand how.
Dart has energy Ed.
Asteroid has energy Ea.
Why, after the impact, isn't the total energy just Ed+Ea? The debris are not "spontaneously" ejected by the asteroid, they are just a consequence of DART energy.
Total energy is conserved. Kinetic energy is not conserved.
It is almost certain that almost all the initial kinetic energy goes into heat, light and turning big rocks into small rocks.
Sure, and this is why I am asking which is the mechanism/formula which cause Dimorphos momentum to "increase by 4x", if part of the energy is converted into heat (i.e. lost in space):
This implies the momentum transfer was about 4x that of an inelastic impact. So the debris blasted out added about 3x the momentum of the incoming spacecraft, for a total of 4x.
But maybe I got it: "increase" is not referred to Asteroid momentum, but to expected transfer of momentum.
"Inventing" some numbers, just for understanding:
- elastic collision: 100% momentum transfer from DART to static Asteroid (let's say 100 "momentum units"); DART stops, Asteroid starts moving;
- inelastic collision: 0% momentum transfer from DART to static Asteroid (0 units); DART burns up; Asteroid heats up without moving;
- real collision:
- expected momentum transfer: 10 units; 70 units lost in heat; 20 units cause debris; DART increases speed by K units;
- measured momentum transfer: 10x4 = 40 units; 10 units lost in heat; 40 units cause debris; DART increases speed by "K+something" units.
Ok so I was thinking this through myself, so here is my take.
Energy is a scalar, Momentum is a vector quantity, that is, you can start with an object with 0 momentum in its rest frame, bust it up and send some relatively small pieces flying off in one direction, and then the big piece goes slowly in another direction. The total momentum (i.e vector addition of the momentum of all the pieces) can remain zero. This is how a rocket works. You need energy to do this. So for Dart you have the momentum of Dart, which is non-zero in the frame of reference of Dimorphos while Dimorphos momentum is 0. You also have the kinetic energy of Dart, which gets transformed in Heat and Kinetic energy and a lot of small pieces which fly off.
So at the end in the rest frame of the original Moon, You still have the momentum of Dart, plus some momentum of smaller pieces and some of the big piece which when you add it up add to momentum of Dart + 0.
So now when we talk about the momentum of Dimorphos at the end, we are doing a slight of hand, we are only talking about the momentum of the big piece, and not the stuff that flew off. In the original frame of reference the big piece is the main part plus what is left of Dart, and it has non-zero momentum in the original frame, That momentum is the Momentum of Dart plus the momentum given by the vector addition of the momentum of all the small pieces. It looks like the second part turns out to be several times that of the momentum of Dart itself.
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https://twitter.com/jeff_foust/status/1603471764704661529
At an #AGU22 press briefing, Andy Cheng of JHUAPL says the DART impact of Dimorphos had a momentum enhancement factor (called beta) of 3.6, because of the large amount of ejecta the impact produced. Means could use a smaller impactor, or longer lead times, for deflection.
Edit to add:
https://twitter.com/jeff_foust/status/1603478050917830657
One other note from the briefing: the tail of ejecta from Dimorphos created by the DART impact is at least 30,000 kilometers long, says Andy Rivkin of JHUAPL, with a mass of at least 1,000 metric tons, and possibly up to 10 times that much.
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https://www.nasa.gov/feature/early-results-from-nasa-s-dart-mission
Dec 15, 2022
Early Results from NASA’s DART Mission
Since NASA’s Double Asteroid Redirection Test (DART) spacecraft intentionally slammed into the asteroid moonlet Dimorphos on Sept. 26 – altering its orbit by 33 minutes – the investigation team has been digging into the implications of how this planetary defense technique could be used in the future, if such a need should ever arise. This has included further analysis of the “ejecta” — the many tons of asteroidal rock displaced and launched into space by the impact – the recoil from which substantially enhanced DART’s push against Dimorphos.
Continued observations of that evolving ejecta have given the investigation team better understanding of what the DART spacecraft achieved at the impact site. DART team members provided a preliminary interpretation of their findings during the American Geophysical Union’s Fall Meeting on Thursday, Dec. 15, in Chicago.
“What we can learn from the DART mission is all part of a NASA’s overarching work to understand asteroids and other small bodies in our Solar System,” said Tom Statler, the program scientist for DART at NASA headquarters in Washington, and one of the presenters at the briefing. “Impacting the asteroid was just the start. Now we use the observations to study what these bodies are made of and how they were formed – as well as how to defend our planet should there ever be an asteroid headed our way.”
Central to this effort are detailed, post-impact science and engineering analyses of data from the world’s first planetary defense technology demonstration. In the weeks after impact, scientists turned their focus toward measuring the momentum transfer from DART’s roughly 14,000 mile per hour (22,530 kilometer per hour) collision with its target asteroid.
Scientists estimate DART’s impact displaced over two million pounds (one million kilograms) of the dusty rock into space – enough to fill six or seven rail cars. The team is using that data – as well as new information on the composition of the asteroid moonlet and the characteristics of the ejecta, gained from telescope observations and images from DART’s ride-along Light Italian CubeSat for Imaging of Asteroids (LICIACube) contributed by the Italian Space Agency (ASI) – to learn just how much DART’s initial hit moved the asteroid, and how much came from the recoil.
“We know the initial experiment worked. Now we can start to apply this knowledge,” said Andy Rivkin, DART investigation team co-lead at the Johns Hopkins Applied Physics Lab (APL). “Studying the ejecta made in the kinetic impact – all of it derived from Dimorphos – is a key way of gaining further insights into the nature of its surface.”
Observations before and after impact, reveal that Dimorphos and its larger parent asteroid, Didymos, have similar makeup and are composed of the same material – material that has been linked to ordinary chondrites, similar to the most common type of meteorite to impact the Earth. These measurements also took advantage of the ejecta from Dimorphos, which dominated the reflected light from the system in the days after impact. Even now, telescope images of the Didymos system show how solar radiation pressure has stretched the ejecta stream into a comet-like tail tens of thousands of miles in length.
Putting those pieces together, and assuming that Didymos and Dimorphos have the same densities, the team calculates that the momentum transferred when DART hit Dimorphos was roughly 3.6 times greater than if the asteroid had simply absorbed the spacecraft and produced no ejecta at all – indicating the ejecta contributed to moving the asteroid more than the spacecraft did.
Accurately predicting momentum transfer is central to planning a future kinetic impact mission if one is ever needed, including determining the size of the impactor spacecraft and estimating the amount of lead-time necessary to ensure that a small deflection would move a potentially dangerous asteroid off its path.
“Momentum transfer is one of the most important things we can measure, because it is information we would need to develop an impactor mission to divert a threating asteroid,” said Andy Cheng, DART investigation team lead from Johns Hopkins APL. “Understanding how a spacecraft impact will change an asteroid’s momentum is key to designing a mitigation strategy for a planetary defense scenario.”
Neither Dimorphos nor Didymos poses any hazard to Earth before or after DART’s controlled collision with Dimorphos.
Johns Hopkins APL built and operated the DART spacecraft and manages the DART mission for NASA's Planetary Defense Coordination Office as a project of the agency's Planetary Missions Program Office.
For more information about the DART mission, visit:
https://www.nasa.gov/dart
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Image captions:
Banner image: This image is constructed from several images taken on November 30, 2022 by astronomers at Magdalena Ridge Observatory in New Mexico, USA. It holds Didymos still in the frame, and thus the background stars are seen as linear trails of dots. Average images like this can provide additional details to astronomers studying faint structures in the ejecta tail. This image is roughly 32,000 kilometers across the field of view at the distance of Didymos. Credit: Magdalena Ridge Observatory/NM Tech
The last complete image of asteroid moonlet Dimorphos, taken by the DRACO imager on NASA’s DART mission from ~7 miles (12 kilometers) from the asteroid and 2 seconds before impact. The image shows a patch of the asteroid that is 100 feet (31 meters) across. Ecliptic north is toward the bottom of the image. This image is shown as it appears on the DRACO detector and is mirror flipped across the x-axis from reality.
Credits: NASA/Johns Hopkins APL
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Wonder if the Dart spacecraft generated a subsurface plasma bubble in Dimorphos after penetrating the fluffy outer crust? Resulting in the greater than expected amount of ejecta.
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Wait
Putting those pieces together, and assuming that Didymos and Dimorphos have the same densities, the team calculates that the momentum transferred when DART hit Dimorphos was roughly 3.6 times greater than if the asteroid had simply absorbed the spacecraft and produced no ejecta at all.
In spaceexplorer’s terms DART had 100% of its momentum (by definition).
If it has smushed into Dimprphos like a raisin falling into oatmeal it would have transferred that 100% to Dimorphos.
If it bounced off like two steel ball bearings, it would have transferred 200% of that momentum to Dimorphos.
But it transferred 360%, according to that quote.
That’s all fine, and a useful number to have if NASA was planning a real asteroid deflection for Planetary Defense.
But elsewhere the DART team stated that the change in orbital period, which is directly related to momentum for small changes, was 30 times their “success criterion”.
Doesn’t that means their threshold for “success” was 360%/30=12%~1/8?
That is, the DART team would have declared success if the impact coupled in 1/8 of its momentum but carried away the remaining 7/8?
The only ways to get a coupling that SMALL would be for DART to fly THROUGH Didimous mostly unscathed, or to almost miss the moon and just nick the edge.
That’s a pretty low threshold.
I would have thought that 30X the expected transfer would have been a coupling coefficient of 30-60, as their predictions were between 1 and 2, IIRC, not 3.6
Were they just sandbagging “success”?
Edit: Perhaps not
I may have figured this out.
It may be that “success” was the press release version of “resolvable”. As long as the measurement of the modified orbit period had a resolvable change, the test would be declared a success.
From the calculations above it looks like they have a resolution in terms of coupling coefficient of about one eighth (1/8).
From a paper on the mission the team expected a coupling coefficient ob between 1 and 2, or 8 to 16 times the resolution.
The actual result was a coefficient of 3.6, or 30 resolution elements.
That would be good, in terms of both test design and result
Why the result was about three times the expected result is another question.
Modeling this kind if interaction is hard!
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Were they just sandbagging “success”?
I'm not sure any level of momentum transfer is relevant to success. It's an experiment, whatever the result you learn something. The more surprising the result the more you learn. If Dart hit and transferred no momentum, you still learn something (also WTF?). Failure would be not having any measurements.
Also we did not learn how impacts transfer momentum to asteroids. We learned how one impact transferred momentum to one asteroid. More than we knew before, but hardly justification for gross generalization.
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https://youtu.be/vMu5bNadlGo
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DART: Six Months After Impact
Streamed live March 14, 2023
On September 26, 2022, the Double Asteroid Redirection Test (DART) spacecraft successfully collided with the asteroid Dimorphos, making history as humanity’s first demonstration of asteroid deflection. Since then, the team has been busy analyzing the data from the camera onboard the DART spacecraft and the Italian Space Agency’s Light Italian CubeSat for Imaging of Asteroids (LICIACube); making continued observations with Earth- and space-based telescopes; and modeling DART’s impact event, the ejecta evolution, and dynamics.
The team previously announced that Dimorphos’ orbital period was changed by the DART impact by 33 minutes, indicating that the ejecta contributed significantly to enhance the deflection produced by the spacecraft. This press event will share the latest results, from reconstructing the details of DART’s impact with the asteroid’s surface and simulating DART’s kinetic impact using that information to analyzing the rich LICIACube dataset and sharing the latest Hubble Space Telescope observations of the Didymos-Dimorphos system. These results are being used to fully understand DART’s impact event and its implications for future planetary defense applications if such a need should arise.
Note: The video was not edited so skip over to 17:00 where introductions start.
https://www.youtube.com/watch?v=h7HJj-X-tyM
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Altering Orbit: The Impact of NASA's DART Mission
May 23, 2023
"If an asteroid one day is discovered heading for the Earth, what would you do?" The impetus for the DART mission was to answer that question, says Andy Cheng, DART investigation team lead.
Developed and led for NASA by the Johns Hopkins APL, DART demonstrated the planetary defense technique known as the kinetic impact on Sep 26, 2022. The DART spacecraft slammed into the moon of an asteroid and shifted its orbit, taking a critical step in demonstrating ways to protect our planet from a potentially hazardous impact. DART used an autonomous targeting system to aim itself at Dimorphos. The spacecraft, roughly the size of a small car, struck the smaller body at about 4 miles per second. Telescopes on Earth observed the asteroid system and measured the change in Dimorphos’ orbit around Didymos. A ride-along CubeSat named LICIACube, built by the Italian Space Agency, separated from DART before impact to observe the collision.
Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit its larger parent asteroid, Didymos. Since DART’s intentional collision with Dimorphos on Sept. 26, astronomers have been using telescopes on Earth to measure how much that time has changed. Now, the investigation team has confirmed the spacecraft’s impact altered Dimorphos’ orbit around Didymos by 32 minutes, shortening the 11-hour and 55-minute orbit to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.
Before its encounter, NASA had defined a minimum successful orbit period change of Dimorphos as a change of 73 seconds or more. This early data show DART surpassed this minimum benchmark by more than 25 times.
In this video, the DART team looks back on the success of the world's first Planetary Defense test mission. https://dart.jhuapl.edu/
https://youtu.be/OaF-c9-utC0
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However, a team of high school students led by teacher Jonathan Swift at Thacher School in California have discovered that Dimorphos’ orbit continued to shrink by another minute more than a month after the collision.
One possibility is that the asteroid is now tumbling, having previously been tidally locked to Didymos.
Another possibility is that material kicked up by the impact, including boulders up to a few meters across, stayed in orbit near Dimorphos and fell back onto the surface, slowing its orbit more.
Harrison Agrusa, a DART team member at the Côte d’Azur Observatory in France, thinks the second theory is more likely.
The DART team is continuing to observe Dimorphos and will publish their own results in the coming weeks.
https://metro.co.uk/2023/09/08/asteroid-behaving-weirdly-after-nasa-crash-19468023/
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I can't see how tumbling would change the orbital period. It's just a function of the semi-major axis, which is unchanged by tumbing. So additional material impacting Dimorphos seems more likely.
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I can't see how tumbling would change the orbital period. It's just a function of the semi-major axis, which is unchanged by tumbing. So additional material impacting Dimorphos seems more likely.
The process of an object becoming tidally locked raises its orbit (and thus increases its orbital period) due to conservation of angular momentum of the system as a whole. If Dimorphos was orbiting retrograde it would be an orbit lowering (period decrease) instead. Once Dimorphos becomes tidally locked, that orbit raising will cease.
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I can't see how tumbling would change the orbital period. It's just a function of the semi-major axis, which is unchanged by tumbing. So additional material impacting Dimorphos seems more likely.
The process of an object becoming tidally locked raises its orbit(and thus reduces its orbital period) due to conservation of angular momentum of the system as a whole. If Dimorphos was orbiting retrograde it would be an orbit lowering (period decrease) instead. Once Dimorphos becomes tidally locked, that orbit raising will cease.
Minor nit but probably worth pointing out to help somebody where this is at the edge of their understanding.
Per Kepler's third law raising the orbit increases the period.
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I'd initially written things as orbital velocity, edited to period, and forget to swap both signs. Fixed.
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I can't see how tumbling would change the orbital period. It's just a function of the semi-major axis, which is unchanged by tumbing. So additional material impacting Dimorphos seems more likely.
The process of an object becoming tidally locked raises its orbit (and thus increases its orbital period) due to conservation of angular momentum of the system as a whole. If Dimorphos was orbiting retrograde it would be an orbit lowering (period decrease) instead. Once Dimorphos becomes tidally locked, that orbit raising will cease.
Nothing wrong with the theory, but this effect is far too small to cause the reported change, of about 1 minute in a 700 minute orbit. This is a change of about 1.3 x 10^-3. The angular momentum available in the spin of Dimorphos is much less. From the paper The Excited Spin State of Dimorphos Resulting from the DART Impact (https://arxiv.org/pdf/2107.07996.pdf) they look at the comparative energy, then note:
A similar approach can be used for the spin and orbital angular momenta, where we get L_dimorphos/L_orbital ≃ 2 × 10^−5.
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Amazing how many wonders some appropriate alignment and sequential animation can do to aid spatial recognition! Look at how planar that ejecta is!
https://twitter.com/landru79/status/1721575172581347692
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I don't know if it has already been discussed, but can the shortening of the orbit period of such a great amount of time (32mins w.r.t. 12 hours period) lead to orbit decay and didymoon crashing on didymos? And in how much time?
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Some of the debris produced from this mission may end up hitting Mars in the future.
https://www.iflscience.com/nasa-may-have-inadvertently-redirected-an-asteroid-at-mars-73675