Author Topic: ESA - Rosetta updates  (Read 97134 times)

Offline Alpha Control

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Re: ESA - Rosetta updates
« Reply #160 on: 01/20/2014 09:54 PM »

Wtf? Why so complex?

the nucleus is not spherical, so the gravity field itself is not symmetrical and quite complicated. moreover, there are constraints of Sun and Earth visibility.

Correct, but maybe I can shed some more light here. Keep in mind that the motion is relative to the comet.

During the triangular patterns (up till about 30s in the video), Rosetta is not yet in a real orbit around the comet. Think of it more as 'formation flying' with the comet instead; those patterns allow us to get a good view of the sunlit part of the comet.

After that, we transfer into a 'global mapping' orbit at around 30 km. This is almost a terminator orbit, meaning we stay almost precisely above the day-night border. This is because we don't want to get into the coma - those 14m solar panels don't like getting sandblasted!

Finally, we go down to a 20km and then a 10km orbit, if circumstances (comet activity) allow. And, if all goes well, there are a few even more intricate manoeuvres (not depicted in the video) before lander delivery at about 3km altitude.

All in all, it's going to be an exciting mission and I'm really happy Rosetta phoned home today!

Thank you for the excellent clarification. That was most helpful. And welcome to the Forum!
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Re: ESA - Rosetta updates
« Reply #161 on: 01/21/2014 01:56 AM »
Video highlight showing receipt of signal from ESA's Rosetta comet chaser after 31 months of deep-space hibernation. Teams at ESA's operations centre in Darmstadt, Germany, leapt for joy as the signal was confirmed via NASA's 70m tracking stations in California and Australia.

"Earth is the cradle of humanity, but one cannot live in a cradle forever." - Konstantin Eduardovich Tsiolkovsky.

Offline clongton

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Re: ESA - Rosetta updates
« Reply #162 on: 01/21/2014 03:44 PM »
There is something I'm not getting from Chris's story. It speaks of the southern hemesphere as the landing spot as being the most consistant receiver of solar radiation for the lander's arrays. Is the comet approaching the sun south pole first? That would somewhat explain the comment about Rosetta orbiting at the day-night terminator to maintain consistant solar energy in Rosetta's arrays. Perhaps it is explained in the video but I was not able to view it. I'm getting an error trying to access it.
« Last Edit: 01/21/2014 03:46 PM by clongton »
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Offline bolun

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Re: ESA - Rosetta updates
« Reply #163 on: 01/22/2014 08:20 AM »

Online eeergo

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Re: ESA - Rosetta updates
« Reply #164 on: 01/22/2014 08:35 AM »
EDIT: Bolun was faster than me ;)

Update from Rosetta's Ops Manager Andrea Accomazzo (the tense/happy guy during the coverage):

http://blogs.esa.int/rosetta/2014/01/21/rosetta-update-from-mission-control/


To sum up, everything looks nominal, the temperatures are just a few degrees lower than average predictions but ok. Little to no degradation found anywhere that has been checked so far. Delay in receiving the signal was due to Rosetta rebooting shortly after wake-up.

During these days, apart from systems checks, the reaction wheels will be heat up and spun to working revolutions.
« Last Edit: 01/22/2014 08:36 AM by eeergo »
-DaviD-

Online eeergo

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Re: ESA - Rosetta updates
« Reply #165 on: 01/22/2014 08:58 AM »
There is something I'm not getting from Chris's story. It speaks of the southern hemesphere as the landing spot as being the most consistant receiver of solar radiation for the lander's arrays. Is the comet approaching the sun south pole first? That would somewhat explain the comment about Rosetta orbiting at the day-night terminator to maintain consistant solar energy in Rosetta's arrays. Perhaps it is explained in the video but I was not able to view it. I'm getting an error trying to access it.

Perhaps somebody actually studying comets (not me) can expand on this with more authority, but according to this paper modelling the expected activities at 67P (paywall): http://www.sciencedirect.com.ezproxy.lib.vt.edu:8080/science/article/pii/S0019103509004497#

Quote
The colatitude is defined equal to zero at the north pole and increases up to 180
at the south pole of the comet; the longitude is given between 0 and 360, in a body fixed coordinate system, and 0 is the subsolar meridian at perihelion.

For a "spherical harmonics" comet shape (bulbous):
Quote
On the present orbit, the water flux comes directly from the surface of the comet and produces different spots of activity that follow the day/night variation and the shadows caused by the comet shape. [...] the water flux is shown in relation with the illumination of the surface during a comet rotation at the perihelion and aphelion of orbit. The water gas activity is directly dependent on the solar illumination. The gas activity main modulation is due to the seasonal effects: the maximum of the activity is in the southern hemisphere at perihelion and in the northern hemisphere atthe aphelion.

Quote
The gas and dust activity at the perihelion is concentrated in the southern regions that are subjected to a strong ablation, while the northern hemisphere remains ‘‘untouched” by this activity.
The nucleus that results from this odd activity, concentrated in the south polar regions, has a peculiar internal structure, with old, devolatilized terrains in the northern hemisphere and fresh, less altered terrains in the southern areas.
-DaviD-

Offline Star One

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ESA - Rosetta updates
« Reply #166 on: 01/22/2014 11:12 AM »
EDIT: Bolun was faster than me ;)

Update from Rosetta's Ops Manager Andrea Accomazzo (the tense/happy guy during the coverage):

http://blogs.esa.int/rosetta/2014/01/21/rosetta-update-from-mission-control/


To sum up, everything looks nominal, the temperatures are just a few degrees lower than average predictions but ok. Little to no degradation found anywhere that has been checked so far. Delay in receiving the signal was due to Rosetta rebooting shortly after wake-up.

During these days, apart from systems checks, the reaction wheels will be heat up and spun to working revolutions.

I bet they'll be watching those reaction wheels very carefully after previous reports about them.

http://www.spacenews.com/article/esa-controllers-buy-time-fix-glitches-comet-chaser
« Last Edit: 01/22/2014 11:13 AM by Star One »

Offline Hobbes-22

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Re: ESA - Rosetta updates
« Reply #167 on: 01/23/2014 03:07 PM »
ESA commissioned this excellent video explaining how Philae works using lots of Lego:


Offline woods170

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Re: ESA - Rosetta updates
« Reply #168 on: 01/23/2014 06:06 PM »
ESA commissioned this excellent video explaining how Philae works using lots of Lego:



Yeah, we get to do some excellent little projects in the Netherlands...  :)

Check out http://vimeo.com/channels/lightcurvefilms for more of Maarten's excellent films. He's an astrophysicist and film-maker
« Last Edit: 01/23/2014 06:09 PM by woods170 »

Offline dsmillman

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Re: ESA - Rosetta updates
« Reply #169 on: 01/24/2014 02:52 PM »
Will someone please post the phone number to listen to a repeat of this teleconference? 
This number is usually announced at the end of the call.

January 23, 2014
MEDIA ADVISORY M14-020

NASA, ESA Discuss Rosetta Comet Mission in Media Teleconference

NASA will host a media teleconference at noon EST Friday, Jan. 24, to discuss the road ahead for the three U.S. science instruments, as well as other NASA support, that are part of the European Space Agency's (ESA) Rosetta mission.
Having been reactivated Monday after a record 957 days in hibernation, the spacecraft will be the first to orbit a comet and land a probe on its nucleus.
The Rosetta mission could help inform NASA's asteroid initiative, which will be the first mission to identify, capture and relocate an asteroid for astronauts to explore.
The teleconference participants are:
--James Green, director of planetary science, NASA Headquarters, Washington
--Mark McCaughrean, ESA senior scientific advisor, Noordwijk, Netherlands
--Matthew Taylor, ESA Rosetta project scientist, Noordwijk
--Claudia Alexander, U.S. Rosetta project scientist, Jet Propulsion Laboratory (JPL), Pasadena, Calif.
--Art Chmielewski, U.S. Rosetta project manager, JPL
To participate by phone, reporters must send an email providing name, media affiliation and telephone number to Dwayne Brown at dwayne.c.brown@nasa.gov or call Brown at 202-358-1726 by 11:45 a.m. EST Friday.
The teleconference will be streamed live at:
http://www.nasa.gov/newsaudio
Related images will be available at the start of the teleconference at:
http://go.nasa.gov/1jqyKG7
For more information about Rosetta, visit:
http://www.esa.int/rosetta
and
http://rosetta.jpl.nasa.gov
-end-
Dwayne Brown
Headquarters, Washington
202-358-1726
dwayne.c.brown@nasa.gov
DC Agle/Jia-Rui Cook
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-9011/818-354-0850
agle@jpl.nasa.gov / jia-rui.c.cook@jpl.nasa.gov
________________________________________
NASA news releases and other information are available automatically by sending an e-mail message with the subject line subscribe to hqnews-request@newsletters.nasa.gov.
To unsubscribe from the list, send an e-mail message with the subject line unsubscribe to hqnews-request@newsletters.nasa.gov.
 
 
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« Last Edit: 01/24/2014 02:54 PM by dsmillman »

Offline AJA

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Re: ESA - Rosetta updates
« Reply #170 on: 01/24/2014 05:15 PM »

...
I bet they'll be watching those reaction wheels very carefully after previous reports about them.


http://www.spacenews.com/article/esa-controllers-buy-time-fix-glitches-comet-chaser


That article seems to be all over the place.


Quote
The propulsion problem aboard Rosetta is in the form of a leak in a helium-pressurization system that enables the propellant reservoir to direct fuel to the probe’s on-board thruster engines.


Ferri said ESA had planned to repressurize Rosetta for future operations, allowing the satellite to maximize fuel efficiency. They have now decided against that because of the risk of aggravating the leak. The resulting operations will mean Rosetta will use more fuel than it would otherwise and will fly a less-efficient route. But Ferri said the consensus is that it will still have enough fuel to complete its comet rendezvous in mid-2014.


What leak? Haven't heard anything about this recently. ESA says that the propellant tank temperature is now running at 7-9 deg C instead of the 10-15 deg C, but that that was normal.


How d'you have a leak in the Helium pressurisation without the propellant boiling away? Over TWO YEARS? Is there a bladder between the He and the fuel?


Quote
It may be the first time a three-axis-stabilized satellite with such large solar arrays, which are not designed to be spun, has performed such a maneuver.
Umm.. what? The hibernation requirement surely didn't suddenly sneak up on the mission designers. So does this mean that the design didn't plan on spin-stabilisation during the hibernation period? And banked on there being enough power to run the reaction wheels, to perform attitude changes for thermal control?


It seems extremely unlikely, given all the ancillary stuff which would be required to keep the reaction wheels running. Heaters, periodic de-saturation, costing propellant (especially with that leak) etc.. A PTC and attitude stabilising spin is much more likely to have been planned and accounted for.


Btw - here are the twitter handles for the various instruments: https://twitter.com/RosettaMIDAS/status/425958216816934912


Btw2, @dsmillman - the number's 800-839-2235.

Offline dsmillman

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Re: ESA - Rosetta updates
« Reply #171 on: 01/24/2014 07:31 PM »
Thank you  AJA.

Offline bolun

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Re: ESA - Rosetta updates
« Reply #172 on: 01/31/2014 01:26 PM »

Offline bolun

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Re: ESA - Rosetta updates
« Reply #173 on: 01/31/2014 01:37 PM »
Rosetta wide awake as check-up continues

31 Jan 2014

http://www.bis.gov.uk/ukspaceagency/news-and-events/2014/Jan/rosetta-wide-awake

Quote
After its long deep-space hibernation, Europe’s Rosetta spacecraft woke up on 20 January to begin the final leg of its 10-year journey to comet 67P/Churyumov–Gerasimenko.

Its first signal was received at 18:18 GMT (19:18 CET) at ESA’s control centre in Darmstadt, Germany. Receipt confirmed that Rosetta had exited hibernation, warmed up and – as planned – switched itself into ‘safe mode’, a basic level of functionality, transmitting a simple radio tone via its S-band transmitter and waiting for instructions from Earth.

Within several hours, the Flight Control Team had established full control, switching on the more powerful X-band transmitter. This allowed high-rate housekeeping information to provide a detailed look at the health and status of crucial propulsion, attitude-keeping and power systems, among many others.

Back online

After several days of detailed checks, the team have determined that the rest of the comet-chaser’s systems are also working as expected.

Reactivation of three of the four reaction wheels – spinning gyroscopes used to control attitude – went flawlessly. The fourth wheel should be reactivated in the coming weeks.

The next few weeks will be dedicated to testing and configuring onboard flight systems, including the solid-state mass memory, used to store science and operations data prior to download.

Quote
Science instrument commissioning

The next phase, lasting through April, will see science teams recommissioning Rosetta’s 11 scientific instruments. This will be done on individual schedules coordinated by the Rosetta Mission Operations Centre in ESOC.

In March, Rosetta’s lander, Philae, will also be switched on for the first time since hibernation. It, too, will be recommissioned to confirm its control systems and 10 instruments are working.

Offline bolun

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Re: ESA - Rosetta updates
« Reply #174 on: 03/01/2014 04:41 PM »
A decade of Rosetta mission highlights… and we’re not even there yet!

http://blogs.esa.int/rosetta/2014/02/28/a-decade-of-rosetta-mission-highlights-and-were-not-even-there-yet/

Offline bolun

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Re: ESA - Rosetta updates
« Reply #175 on: 03/05/2014 11:29 AM »
Rosetta ready for payload check-out

http://blogs.esa.int/rosetta/2014/03/05/rosetta-ready-for-payload-check-out/

Quote
Rosetta is operating nominally in 'Normal Mode' and all platform systems have been fully re-activated. The Thermal, Power and Data Handling systems are all working. The reaction wheels – spinning wheels used to maintain Rosetta's orientation in space – are being exercised at very low speed to characterise their behaviour in this regime.

All instruments are off except for:

- The Ultra Stable Oscillator for the Radio Science Investigation
- Standard Radiation Monitor

Quote
Here is an overview of upcoming activities, with the ever-present proviso that dates, times and events may change due to operational requirements:

- 17 March – Switch on the OSIRIS imaging system; all other instruments will be switched on in the following approximately 6 weeks
- 24 March – Pending successful re-activation, OSIRIS will take a first look in the direction of the comet. The comet will be too far away (around 5 million kilometres) to resolve in these first images and its light will be seen in just a couple of pixels. These images will be acquired regularly for navigation purposes and to already start planning the trajectory corrections planned for  May.


Offline bolun

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Re: ESA - Rosetta updates
« Reply #176 on: 03/05/2014 11:33 AM »
Rosetta NavCam image 23 Feb 2014

The image was acquired on 23 February 2014 and is pointed roughly in the direction of the constellation Aries (almost in the direction opposite to comet 67P). The bright star to the right of the centre is delta Arietis (δ Ari) the bright star at the top left is epsilon Arietis, ε Ari. The NavCam field of view is 5×5 degrees.

http://blogs.esa.int/rosetta/2014/03/05/rosetta-ready-for-payload-check-out/cam1/

Image Credit: ESA/Rosetta/NavCam

Offline bolun

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Offline bolun

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Re: ESA - Rosetta updates
« Reply #178 on: 03/28/2014 10:26 AM »
Gotcha! Rosetta sets sights on comet

Rosetta has caught a first glimpse of its destination comet since waking up from deep-space hibernation. These two ‘first light’ images were taken on 20 and 21 March by the OSIRIS wide-angle camera and narrow-angle camera, as part of the six-week instrument commissioning period.

http://blogs.esa.int/rosetta/2014/03/27/gotcha-rosetta-sets-sights-on-comet/

Article: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_sets_sights_on_destination_comet

Images credit: ESA © 2014 MPS for OSIRIS-Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Offline bolun

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Re: ESA - Rosetta updates
« Reply #179 on: 03/28/2014 08:54 PM »
Philae lander back in contact with Earth
 
http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10081/151_read-9894/#gallery/9150

Quote
On 28 March, the lander was successfully reactivated and broke its planned radio silence by sending data to Earth from a distance of about 655 million kilometres. At 15:40 CET, packet after packet of data started to arrive for the team in the Lander Control Centre (LCC) at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). The result: "Philae is operational and ready for the next few months," said lander project manager Stephan Ulamec of DLR. In November, the lander will be deployed onto the target comet, 67P/Churyumov-Gerasimenko, while the Rosetta spacecraft continues to orbit the comet. The orbiter and lander will be the first to witness a comet's 'awakening' as it approaches the Sun first hand.

Rosetta’s lander is awake!

http://blogs.esa.int/rosetta/2014/03/28/rosettas-lander-is-awake/

Quote
Today’s activities confirm that Philae is alive and well; the lander and its ten scientific instruments will undergo much more extensive checks throughout April.

Meanwhile, Rosetta’s MIDAS , COSIMA and ROSINA instruments are also being tested today. The instruments ALICE, CONSERT, GIADA, RPC, and RSI also began testing this week. And one instrument – the OSIRIS imaging system – has already passed the commissioning phase with a clean bill of health.



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