Author Topic: Impacts of Large Satellite Constellations on Astronomy  (Read 174031 times)

Offline su27k

  • Senior Member
  • *****
  • Posts: 6414
  • Liked: 9104
  • Likes Given: 885
[edit/gongora:  We needed a specific thread for this topic so I split this post from the Starlink thread to get it started.  Please keep this civil, hysterical posts will be deleted.  This is for all of the constellations, not just Starlink.  Any posts on this topic made in the threads for specific constellations may be moved here.]

Don't want to start an argument, but this is important news: Statement on NSF and SpaceX Radio Spectrum Coordination Agreement

Quote
June 4, 2019

In late May, SpaceX launched its first 60 Starlink satellites into orbit. SpaceX plans to launch a much larger satellite constellation into low-Earth orbit with the goal of providing terrestrial internet service. The operation of these satellites will utilize frequencies that neighbor some radio astronomy assets in the 10.6 - 10.7 GHz band. SpaceX coordinated with NSF and its radio astronomy observatories regarding potential interference from their use of the radio spectrum. After working closely with SpaceX, NSF has finalized a coordination agreement to ensure the company’s Starlink satellite network plans will meet international radio astronomy protection standards, limiting interference in this radio astronomy band. Additionally, NSF and SpaceX will continue to explore methods to further protect radio astronomy. Together we are setting the stage for a successful partnership between commercial and public endeavors that allows important science research to flourish alongside satellite communication.

-NSF-

BTW, in this context NSF is the National Science Foundation
« Last Edit: 06/07/2019 05:11 pm by gongora »

Offline intelati

Don't want to start an argument, but this is important news: Statement on NSF and SpaceX Radio Spectrum Coordination Agreement

Considering SpaceX's mantra is typically literally move fast and break things. Good thing that SpaceX isn't completely burning the bridges here
Starships are meant to fly

Offline gongora

  • Global Moderator
  • Senior Member
  • *****
  • Posts: 10426
  • US
  • Liked: 14326
  • Likes Given: 6134
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #2 on: 06/07/2019 05:17 pm »
RAS statement on Starlink satellite constellation

The Royal Astronomical Society notes with concern the launch of the new SpaceX Starlink constellation of satellites into low-Earth orbit, and the potential impact of this and other programmes on views of the night sky and on astronomical research.

Starlink, and other similar networks planned by OneWeb, Amazon and Telesat, aim to provide global commercial internet coverage. Each network consists of thousands of satellites in low-Earth orbit – less than 2,000 kilometres altitude – that when fully deployed will be visible over a significant proportion of the sky from most of the inhabited world.

In their final orbits, the satellites will be relatively faint most of the time. Initial images of the constellation though suggest that they will exhibit frequent reflective flaring, where transient alignment with sunlight leads to temporary surges in brightness.

Increasing the number of satellites so significantly presents a challenge to ground-based astronomy. The deployed networks could make it much harder to obtain images of the sky without the streaks associated with satellites, and thus compromise astronomical research.

Given the scale of these projects, there is also the prospect of a significant and lasting change to the views of the night sky until now enjoyed throughout human history and pre-history. The night sky is part of the cultural heritage of humanity, and the Society believes that it deserves protection.

There appears to have been no consultation between SpaceX and the scientific community in advance of the Starlink launch, though since initial press reports we note that Elon Musk has responded indicating he wishes to minimise the impact on astronomy.

The Society welcomes this offer. We urge SpaceX, and other satellite providers, to work with scientists, engineers and others to mitigate the effects of the new constellations. We also ask that the provider companies consider the impact on human heritage too – an issue that goes far beyond the concerns of the astronomical community.

Offline AJW

  • Full Member
  • ****
  • Posts: 811
  • Liked: 1323
  • Likes Given: 136
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #3 on: 06/07/2019 06:39 pm »
When my boys were Scouts, during the Summer I would join them at their Scout Camp in the Sierras and teach a variety of Merit Badges.  There was no internet access from camp so I would bring printouts of any significant satellite passes for the week.   

After one campfire I told my group to hang around for a few minutes and we watched the ISS rise from the horizon and cross overhead.  Another time I took them to the field sports area and told them to watch the sky to the North just as an Iridium flare lit up the sky.  A group hiking that night stopped by asking if we had seen the flash, and the boys from my group explained to them what they had seen.  Neither group had ever seen anything like this before and they were all fascinated that these events were predictable.

Two weeks ago and my kids were over for dinner and afterwards we went outside to watch the Starlink train cross through the bowl of the Big Dipper.   Even though they are in their 20's, they would call out as each satellite briefly appeared and then faded.

I suppose it is upsetting when someone keeps moving your cheese.  If it isn't bad weather, it is city lights and now satellites.  I can also see this as the start of a new golden age of astronomy as private and university telescopes can affordably move into orbit and the next generation grow up seeing the sky as a doorway not a ceiling.
We are all interested in the future, for that is where you and I are going to spend the rest of our lives.

Offline ChrisWilson68

  • Senior Member
  • *****
  • Posts: 5266
  • Sunnyvale, CA
  • Liked: 4991
  • Likes Given: 6459
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #4 on: 06/07/2019 06:56 pm »
Lets not forget that any low-Earth satellites are only an issue to visible-light astronomy for the periods when the surface of the Earth is dark but the satellites are still in the sun.  In the middle of the night, no low Earth satellites will be an issue at all.  How long after dusk and before dawn they are visible depends on the altitude.  And for part of that period only satellites in part of the sky can be visible, with those in other parts of the sky in the Earth's shadow.

Does anyone have numbers for Starlink's altitudes for the curve over time of how much of the sky can be affected?  For example, 1 hour after sunset, what percentage of the sky at each altitude is out of the Earth's shadow?  What about 1 hour five minutes?  1 hour ten minutes?  And so on.

It's hard to form an opinion about the possible impact on astronomy without these hard upper limits on the light pollution from Starlink.

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #5 on: 06/07/2019 07:29 pm »
To strictly address the thread title.
The recent Event Horizon Telescope publications were significantly delayed because moving data from many of the telescopes was intractable.
If it was possible to move a petabyte a day from a very remote scope site in the antarctic, that may considerably improve the performance.
It would also allow data to be processed in a timely manner, so as to (for example) alert other observers to changes they might be able to have useful observations of.

The TESS sky survey satelite as another example, takes 2s frames and while downloading every single frame might not quite have a useful science case, a very reasonable argument could be made  that a very much faster framerate than the 30 minute full-frame images downloaded every couple of weeks would be nice.

(TESS in ~lunar orbit is clearly out of the range of the current starlink system, but free space LASER comms would be enormously easier to a space-based target.)

Offline Joseph Peterson

  • Full Member
  • ****
  • Posts: 752
  • Pittsburgh, PA
  • Liked: 578
  • Likes Given: 14356
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #6 on: 06/07/2019 08:19 pm »
I took a tour of Allegheny Observatory last night.  It was a fascinating tour and I'm kicking myself for believing the ex-girlfriend who lived a couple blocks away when she told me the Observatory was closed two decades ago.  It turns out it isn't.  The 16" scope is still being used for followup exoplanet studies.  I highly recommend free tour.  These are every Thursday and Friday(April through November 1st for Fridays) starting at 8 PM, with a lecture series starting at 7 PM on the third Friday of every month.  My girlfriend called it the best date night ever and is looking for the telescope she got as a child.

https://www.pitt.edu/~aobsvtry/tours.html

As to the effects of Starlink, the word straight from the horse's mouth is dealing with the extra satellites will be a pain, but doable.  [edit/gongora: removed poorly expressed thought]  Gaia wouldn't even be that much of a problem, but astronomy dollars are being concentrated on flagship telescopes like JWST.

Edit: I will edit again once I know how to accurately report to gongora's satisfaction.  This comment now is missing a crucial detail.

Edit 2:  So apparently the problem is that I did not interject my opinion into a facts only paragraph.  Since providing only the facts obviously isn't good enough, here is some opinion based on my inferences.  From the link I provided we can tell that funding dried up, probably at the end of 2005.  Furthermore, based on the deleted fact I can infer that Gaia is directly competing for funding with the Allegheny Observatory.  Additionally we can infer that the telescope that lost work is the 30" Thaw.  This seems to be a likely reason why the tour guide was salty about space telescopes.  Take the previous statements with a grain of salt as they are my opinion, not confirmed facts.

With the opinion out of the way I can now repost the deleted fact.  The fact is our tour guide(not naming names here) said a missile is the solution to Gaia.

Back to opinion.  I do agree that was a poorly expressed thought.  I believe the Observatory staff is salty they aren't doing work with a perfectly good telescope.  I believe this is a strong indicator of disagreement within the astronomy community.  Your mileage may vary.

Back to fact.  Yes, I am very annoyed that I am expected to add a paragraph's worth of my opinion as a disclaimer when I post what was said in a purely factual paragraph.  Good night everybody.  I'm now at least 50 pages behind on homework I wanted to get done tonight.  I have learning to do.
« Last Edit: 06/08/2019 02:19 am by Joseph Peterson »

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8906
  • South coast of England
  • Liked: 500
  • Likes Given: 223
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #7 on: 06/07/2019 11:45 pm »
If we want to base telescopes on the far side of the Moon to avoid light pollution from the Earth the far side will have to be protected. Rules need passing that:
 * Force satellites to switch off their transmitters when on the far side.
 * Encase satellites in a Faraday cage and filter any external wires.
 * Make satellites hide their infrared emissions, possibly with a moon facing curtain made from material similar to the James Webb's sun shield.
 * Little or no radio communication with bases and rovers on the far side, possibly by relaying lases through special communications satellites.

The rules could be based on the military TEMPEST specification (telescopes have very sensitive receivers) or the FCC Part 15.
https://en.wikipedia.org/wiki/Title_47_CFR_Part_15

edit: grammar of filter plus added 'similar to'
« Last Edit: 06/09/2019 02:10 am by A_M_Swallow »

Offline ChrisWilson68

  • Senior Member
  • *****
  • Posts: 5266
  • Sunnyvale, CA
  • Liked: 4991
  • Likes Given: 6459
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #8 on: 06/08/2019 06:54 am »
If we want to base telescopes on the far side of the Moon to avoid light pollution from the Earth the far side will have to be protected. Rules need passing that:
 * Force satellites to switch off their transmitters when on the far side.

I don't get it.  When the satellites are on the far side of the Moon?  What sort of satellite are you imaging that would be on the far side of the Moon?

Offline A_M_Swallow

  • Elite Veteran
  • Senior Member
  • *****
  • Posts: 8906
  • South coast of England
  • Liked: 500
  • Likes Given: 223
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #9 on: 06/08/2019 07:55 am »
If we want to base telescopes on the far side of the Moon to avoid light pollution from the Earth the far side will have to be protected. Rules need passing that:
 * Force satellites to switch off their transmitters when on the far side.

I don't get it.  When the satellites are on the far side of the Moon?  What sort of satellite are you imaging that would be on the far side of the Moon?


Plans exist to put communication satellites around the Moon. These ideas always come back. Here is an old article on it.
https://spectrum.ieee.org/aerospace/satellites/commercial-communications-satellites-for-the-moon

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #10 on: 06/08/2019 11:45 am »
Plans exist to put communication satellites around the Moon. These ideas always come back. Here is an old article on it.
https://spectrum.ieee.org/aerospace/satellites/commercial-communications-satellites-for-the-moon

In many ways, the far side of the moon isn't a very great location unless it's free or negative cost compared to other near-earth orbits. - intermittent power, variable temperature, possible dust.
Given a base, this cost reduction may actually happen.

The wavelengths you care about for comms are in many ways lots less interesting for astronomy.
0 through ~2GHz can easily be carved out as a protected band, and that's the frequency range that is problematic to observe from earth.

Requiring an absolutely pristine environment for astronomy may increase the cost of operations on the farside, reducing the total amount of astronomy done.

Many reasons for the large constellation of satellites (~7000 or whatever) in the final earth Starlink constellation simply do not apply at all.
The prime one is that for the life of any conceivable satellite comms system, the number of people on the moon is going to be well under 10K.

A dozen satellites at ~1500km orbits is simply not a very huge issue.

Offline jstrotha0975

  • Full Member
  • ****
  • Posts: 606
  • United States
  • Liked: 356
  • Likes Given: 2769
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #11 on: 06/08/2019 05:51 pm »
Maybe Spacex can create some kind of clear, non reflective coating for their satellites?
« Last Edit: 06/08/2019 05:52 pm by jstrotha0975 »

Offline Dizzy_RHESSI

  • Full Member
  • *
  • Posts: 113
  • United Kingdom
  • Liked: 113
  • Likes Given: 109
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #12 on: 06/08/2019 10:37 pm »
From the link I provided we can tell that funding dried up, probably at the end of 2005.  Furthermore, based on the deleted fact I can infer that Gaia is directly competing for funding with the Allegheny Observatory.  Additionally we can infer that the telescope that lost work is the 30" Thaw.  This seems to be a likely reason why the tour guide was salty about space telescopes.  Take the previous statements with a grain of salt as they are my opinion, not confirmed facts.

With the opinion out of the way I can now repost the deleted fact.  The fact is our tour guide(not naming names here) said a missile is the solution to Gaia.

Back to opinion.  I do agree that was a poorly expressed thought.  I believe the Observatory staff is salty they aren't doing work with a perfectly good telescope.  I believe this is a strong indicator of disagreement within the astronomy community.  Your mileage may vary.

Gaia is a European mission with no significant contribution from NASA, the money for these two things isn't even coming from the same counties. They are absolutely not competing for funding. Furthermore in both the US and Europe space and most ground based astronomy is handled by different organisations with different budgets.

I'm quite sure they mentioned Gaia because it seems they used to do Parallax measurements there. Gaia did not steal there funding, it made their continued work obsolete. Gaia made the measurements they were doing but with much higher precision and for 100 million stars instead of tens to hundreds. It's not really a competition. It has nothing to do with disagreement in the community, it has everything to do with observatory staff sad to see the end and worried for their jobs. If someone was truly enthusiastic about the science that was done at the observatory then they should be thrilled with Gaia, as many astronomers are.

Offline Joseph Peterson

  • Full Member
  • ****
  • Posts: 752
  • Pittsburgh, PA
  • Liked: 578
  • Likes Given: 14356
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #13 on: 06/08/2019 11:03 pm »
Farside radio telescope fan here.  I actually made a rough image showing how I prefer to deploy Lunar comms sats not too long ago.  Enjoy.


Offline Joseph Peterson

  • Full Member
  • ****
  • Posts: 752
  • Pittsburgh, PA
  • Liked: 578
  • Likes Given: 14356
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #14 on: 06/08/2019 11:16 pm »
From the link I provided we can tell that funding dried up, probably at the end of 2005.  Furthermore, based on the deleted fact I can infer that Gaia is directly competing for funding with the Allegheny Observatory.  Additionally we can infer that the telescope that lost work is the 30" Thaw.  This seems to be a likely reason why the tour guide was salty about space telescopes.  Take the previous statements with a grain of salt as they are my opinion, not confirmed facts.

With the opinion out of the way I can now repost the deleted fact.  The fact is our tour guide(not naming names here) said a missile is the solution to Gaia.

Back to opinion.  I do agree that was a poorly expressed thought.  I believe the Observatory staff is salty they aren't doing work with a perfectly good telescope.  I believe this is a strong indicator of disagreement within the astronomy community.  Your mileage may vary.

Gaia is a European mission with no significant contribution from NASA, the money for these two things isn't even coming from the same counties. They are absolutely not competing for funding. Furthermore in both the US and Europe space and most ground based astronomy is handled by different organisations with different budgets.

I'm quite sure they mentioned Gaia because it seems they used to do Parallax measurements there. Gaia did not steal there funding, it made their continued work obsolete. Gaia made the measurements they were doing but with much higher precision and for 100 million stars instead of tens to hundreds. It's not really a competition. It has nothing to do with disagreement in the community, it has everything to do with observatory staff sad to see the end and worried for their jobs. If someone was truly enthusiastic about the science that was done at the observatory then they should be thrilled with Gaia, as many astronomers are.

Thanks.  I really didn't want to post that paragraph of my only partly informed opinion but gongora insisted I introduce opinion when reporting what was said.  I still don't get it but gongora is a mod so I added the opinion.

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #15 on: 06/08/2019 11:18 pm »
Farside radio telescope fan here.  I actually made a rough image showing how I prefer to deploy Lunar comms sats not too long ago.  Enjoy.
The lack of atmosphere also means you could implement the same cutoff with more close in sats, just by turning off emissions.

Offline Robotbeat

  • Senior Member
  • *****
  • Posts: 39351
  • Minnesota
  • Liked: 25382
  • Likes Given: 12161
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #16 on: 06/08/2019 11:46 pm »
Laser comms work all the way to the surface on the far side. An interesting option.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline Joseph Peterson

  • Full Member
  • ****
  • Posts: 752
  • Pittsburgh, PA
  • Liked: 578
  • Likes Given: 14356
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #17 on: 06/08/2019 11:50 pm »
Farside radio telescope fan here.  I actually made a rough image showing how I prefer to deploy Lunar comms sats not too long ago.  Enjoy.
The lack of atmosphere also means you could implement the same cutoff with more close in sats, just by turning off emissions.

Communications signals aren't the primary concern.  The telescope would be looking at wavelengths far longer than what we use for communications.  The primary concern is radiated heat.  A_M_Swallow already posted how we want to go about "turning off" emissions.

Disclaimer:  I don't understand why so many people want to go back to the Moon.  There simply isn't much there worth going for.  My position is that if we are going back to the Moon we should not be destroying one of the few plausible reasons to go before we get there.

Edit: added missing negative
« Last Edit: 06/09/2019 02:33 am by Joseph Peterson »

Offline speedevil

  • Senior Member
  • *****
  • Posts: 4406
  • Fife
  • Liked: 2762
  • Likes Given: 3369
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #18 on: 06/09/2019 10:12 am »
Farside radio telescope fan here.  I actually made a rough image showing how I prefer to deploy Lunar comms sats not too long ago.  Enjoy.
The lack of atmosphere also means you could implement the same cutoff with more close in sats, just by turning off emissions.

Communications signals aren't the primary concern.  The telescope would be looking at wavelengths far longer than what we use for communications.  The primary concern is radiated heat.  A_M_Swallow already posted how we want to go about "turning off" emissions.

I have real problems believing ~5kW of omnidirectional heat emitted at 500km from a handful of sources is going to be a significant issue for imaging.
They already have to deal with 1kW/m^2 of heating directly, unless they want to give up half their observing time and be blind to large areas for months.

Offline ChrisWilson68

  • Senior Member
  • *****
  • Posts: 5266
  • Sunnyvale, CA
  • Liked: 4991
  • Likes Given: 6459
Re: Impacts of Large Satellite Constellations on Astronomy
« Reply #19 on: 06/10/2019 03:51 pm »
I'd like to remind everyone of the subject of this thread.  It's the impacts of large satellite constellations on astronomy.  That means the large LEO constellations currently being proposed and, in some cases, already being deployed.  There are concrete, well-funded plans for these constellations, and there are particular, immediate concerns that have been expressed about their impact on astronomy.

What it doesn't cover is an idea someone once had that maybe someday someone would put communication satellites around the moon.  I think anyone interested in discussing that should create a new thread for the purpose.

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
0