Impacts of Large Satellite Constellations on Astronomy

[Dizzy_RHESSI]

And another complete non-sequiter. Read the recommendation #1 and #3 for observatories that were listed in the report attached to this post:
https://forum.nasaspaceflight.com/index.php?topic=48302.msg2124381#msg2124381

Nothing in those 2 bullets requires modelling 4000 satellites. It is talking about software processing to remove known trails from an image and detailed SNR calculations to determine how much residual error would be present in the images after the trails are removed. Bullet 3 explicitly requests figuring out the signal to noise that would remain present in a single image after the trail is removed, which is an operation that would be done on a single frame. Actually doing this full SNR calculation correctly is non-trivial, sure there may be undergrad level back of the envelope versions, but it is rarely that simple.

The first part of recommendation 3 is: "Support selected detailed simulations of the effects on data analysis systematics and data reduction signal-to-noise impacts of masked trails on scientific programs affected by satellite constellations." It says simulate the effect of satellite constellations on scientific programs. You cannot model the effect on a program without simulating a constellation, of e.g. ~4000 satellites. And it isn't talking about removing trails from single frames, it clearly says "masked trails", which means that portion of the data has been masked in further analysis and stacks. I did not say this could be done by undergrad level calculations, you are mixing completely separate statements. In fact, I explicitly said this could not be done with pen and paper.

What in the world are you talking about? I said nothing about adaptive optics at all.

My mistake, I pasted a comment from somewhere else into the quote. Apologies.

[AnalogMan]

Radio Astronomers at the Square Kilometer Array (SKA) Organisation have released the initial findings of a study they are carrying out.

SKAO needs corrective measures from satellite ‘mega-constellation’ operators to minimise impact on its telescopes

SKA Global Headquarters, 7 October 2020 – The SKA Organisation (SKAO) – which leads the delivery of the international Square Kilometre Array (SKA) project – has undertaken a preliminary analysis of the potential impact of current satellite mega-constellations on its telescopes. The analysis quantifies this impact and identifies possible mitigations. The SKA project is an intergovernmental collaboration between 15 countries involving thousands of scientists and engineers to build and operate the world’s largest radio observatory, with two telescopes located in Australia and South Africa.

The study focuses on the impact of the deployment of the principal currently planned space-based systems, totalling 6,400 satellites, on the SKA-Mid telescope soon to be erected in South Africa, which will consist of an array of 197 dishes1.

SKAO’s low-frequency telescope in Western Australia, which uses a different antenna technology and will operate at lower frequencies, is not the subject of the analysis reported here.

Key points and findings (based on deployment of 6,400 satellites)

 • The satellites in the various constellation projects will transmit signals within the frequency range
    covered by the Band 5b receivers of the SKA-Mid telescope in South Africa (one of seven bands planned
    for the telescope).

 • Without specific mitigation actions by the constellation operators, there is likely to be an impact on
    all astronomical observations in Band 5b.

 • This impact includes a loss of sensitivity in the frequency range used by the constellations, leading
    to astronomical observations in that range taking 70% longer.

 • The science impact is most significant for studies of molecular and atomic spectral lines in that
    range, including complex organic molecules; Class II methanol masers; and a wide range of
    extragalactic molecular lines.

 • Viable mitigation techniques identified by SKAO can reduce this impact on SKA-Mid by a factor of 10,
    if implemented by relevant satellite operators.

 • SKAO remains committed to minimising the loss of scientific discovery through all available avenues.
    SKAO will continue to work closely with industry on ways to minimise the damage caused by
    mega-constellation transmissions and is looking forward to a positive response on these
    proposed solutions.

 • For significantly larger constellations, of up to 100,000 satellites, the effect on the SKA would be
    much worse, potentially threatening the viability of the complete Band 5b for 100% of the time, unless
    stringent mitigation actions are put in place.

[... continues]

https://www.skatelescope.org/news/skao-satellite-impact-analysis/

BBC write-up by Jonathan Amos:
Square Kilometre Array project frets about satellite interference
https://www.bbc.co.uk/news/science-environment-54457344

[Steven Pietrobon]

As the areas where the SKA will operate have little to no population, it should be relatively simple for the satellite operators to turn off their transmit antennas while flying over those areas.

[Semmel]

Today and tomorrow, the impact of satellite constellations on astronomy are discussed:

Program schedule is here:
https://www.unoosa.org/oosa/en/ourwork/psa/schedule/2020/2020_dark_skies.html

The conference is sort of public but requires registration which is closed. They will release a report some time after the conference, I am sure though we will hear plenty of it in the press. I had a quick look at the draft reports, its going to be interesting.

[NaN]

As the areas where the SKA will operate have little to no population, it should be relatively simple for the satellite operators to turn off their transmit antennas while flying over those areas.

For Starlink perhaps, but OneWeb spots are non-steerable ellipses >1000 kilometers wide, so if they turned off all spots intersecting that area, they could lose coverage to a large swath of South Africa.


Here's a brief summary of the SKA article:

* They are about to start building a large radio observatory which covers a broad frequency range
* Very little of this range is protected for astronomy and parts are licensed for satellite downlinks
* With a small number of fixed (GEO) sources, this is not a meaningful problem. Sounds like this is what they planned against
* Now they are worried about the effects of constellations, particularly on 10.7 - 12.7 GHz range (Ku band)
* They model that the impact is likely to be meaningful with currently launching SL & OW, and quite serious with the longer term planned (>10k) constellation sizes
* The request is to potentially treat a certain geographic area in South Africa as a dark zone, such as by not steering spot beams in the area
* Sounds like a lot of uncertainty in their modeling and this is an invitation to more investigation

[eeergo]

Peter Beck weighing in:

https://twitter.com/jackiewattles/status/1313888143133700096

[eeergo]

Interesting points from the DarkAndQuietSkies initiative, including hammering in the point that the electromagnetic spectrum is a very limited and non-renewable resource:

https://mobile.twitter.com/JohnBarentine/status/1314601550929489920

https://mobile.twitter.com/planet4589/status/1314603461292560385

https://mobile.twitter.com/JareelSkaj/status/1314623772176113671

[su27k]

https://mobile.twitter.com/JareelSkaj/status/1314623772176113671

That's an incredibly stupid take, only two LEO constellations are funded by billionaires, the others (OneWeb, Telesat, Chinese ones) are owned or funded by national governments.

And how do you know SpaceX wouldn't help the radio astronomers? Starship would make it very easy to build a lunar farside radio telescope.

That doesn't even touch the point that constellation operators got the spectrum fair and square, entirely legally, both according to local law and international law, this makes the complaint about supposed billionaire outsourcing cost even more idiotic.

[ncb1397]

That's an incredibly stupid take, only two LEO constellations are funded by billionaires, the others (OneWeb, Telesat, Chinese ones) are owned or funded by national governments.

Well, the founder/chairman of Bharti Enterprises, Sunil Bharti Mittal, is worth ~$9 billion. Not sure how much of that is tied up in Bharti Enterprises, but probably most of it. And Bharti Enterprises is one of the most significant funders if not the most significant funder of OneWeb. So, if SpaceX gets counted, you should probably count OneWeb as well as the situations are pretty similar.

[niwax]

That's an incredibly stupid take, only two LEO constellations are funded by billionaires, the others (OneWeb, Telesat, Chinese ones) are owned or funded by national governments.

Well, the founder/chairman of Bharti Enterprises, Sunil Bharti Mittal, is worth ~$9 billion. Not sure how much of that is tied up in Bharti Enterprises, but probably most of it. And Bharti Enterprises is one of the most significant if not the most significant funders of OneWeb. So, if SpaceX gets counted, you should probably count OneWeb as well as the situations are pretty similar.

It's also a stupid take in many other ways. By the same metric, why shouldn't SpaceX seek money from astronomers who caused them to go through multiple risky design iterations of multi-billion-dollar hardware?

[Frogstar_Robot]

Yeah, if only these billionaires didn't exist everything would be perfect. 

The social and environmental problems caused by large multi-national companies have been known for several decades, nothing new there. Governments turn a blind eye to their activities, as long as they provide at least some benefit in the form of jobs or taxes.

I'm reminded of that saying "they came for the X, but I was not an X,  so I didn't speak out...". I guess most people are not concerned until the Invisible Hand gives them a slap, and then ask "why isn't anyone doing something about this??" Nice to see the astronomy community getting into some political activism, even if a bit late to the party. They might check with their climate scientist colleagues to see how the fight with "the billionaires" (Koch brothers) goes.

[ZChris13]

Yeah, if only these billionaires didn't exist everything would be perfect. 

The social and environmental problems caused by large multi-national companies have been known for several decades, nothing new there. Governments turn a blind eye to their activities, as long as they provide at least some benefit in the form of jobs or taxes.

I'm reminded of that saying "they came for the X, but I was not an X,  so I didn't speak out...". I guess most people are not concerned until the Invisible Hand gives them a slap, and then ask "why isn't anyone doing something about this??" Nice to see the astronomy community getting into some political activism, even if a bit late to the party. They might check with their climate scientist colleagues to see how the fight with "the billionaires" (Koch brothers) goes.

One could just as easily call out the social and environmental problems caused by governments, but these sorts of opinions are politics and have absolutely no place here.

[Frogstar_Robot]

One could just as easily call out the social and environmental problems caused by governments, but these sorts of opinions are politics and have absolutely no place here.

Yeah, if all those governments didn't exist everything would be perfect 

[FinalFrontier]

Solution:
Switch to space based astronomy. Many have been saying for decades that we need more space based radio and optical telescopes and not albatrosses like James Webb either.

Perhaps the pace of LEO super constellation technology is further proof that the frontline for astronomy ought to be in space based instruments not with terrestrial instruments.
The science has also approached the limit of what can be learned/observed with terrestrial based fixed position observatories anyway.

So here's a possible compromise I could easily see happening in the future. Congress passes a law that says "if you as company X want to operate a LEO super constellation you must pay a tax to uncle sam in exchange for operating it. That tax money is then used explicitly to fund the construction of space based (or non earth planetary based) astronomical instruments. "

It will probably be years before we see something like this but I am beginning to think it's a given.
There is not going to be a blanket ban on LEO super constellations or probably any ban for that matter. You can't just ban emerging technologies when they become inconvenient, nor would it be in the best interest of any future congress to do so.

Even if the US government prohibited the construction of these things other countries would just build their own eventually. There are to many advantages to this technology someone is going to build it regardless.

Short version: it's not getting banned or restricted people will have to find other solutions.

[eeergo]

Solution:
Switch to space based astronomy. [...]

This has been explained, proven and repeated ad-nauseam not to be a solution, in this very thread among other places, just a far-future declaration of intentions. You cannot (should not, rather) deny access to a natural resource, especially for private profit, when no options exist to do without it. Just the single topic of hazardous NEOs would be enough to justify this, let alone with the myriad other facets on the table.

Even if the US government prohibited the construction of these things other countries would just build their own eventually. There are to many advantages to this technology someone is going to build it regardless.
Short version: it's not getting banned or restricted people will have to find other solutions.

Other countries are following on the footsteps of a non-elegant, brute force solution - anyway, it would be off-topic to delve into megaconstellations' business model in this thread. However, saying "it's not going to get banned or restricted" after a few years' development of a completely new paradigm is, apart from extremely arrogant, also a bit like claiming, I don't know, dumping radioactive waste in the oceanic abysses in the 50s is just going to grow as an unavoidable consequence to energy production, or river diversion in the central Asian steppes will be the future of agriculture, so "people" will have to suck it up and quit whining about whales, disappearing seas or other minutiae in the name of "progress".

[ncb1397]

Things are getting slightly out of hand....



It is almost like a dyson sphere/dyson swarm (just surrounding a planet rather than a star). If we aren't smart about it, space based internet won't be a thing...and ground based astronomy...and space based astronomy or space based anything really. And there needs to be a better justification than fortnite ping times.

[aquanaut99]

Things are getting slightly out of hand....



It is almost like a dyson sphere/dyson swarm (just surrounding a planet rather than a star). If we aren't smart about it, space based internet won't be a thing...and ground based astronomy...and space based astronomy or space based anything really. And there needs to be a better justification than fortnite ping times.

Yes, ironic if the “game-changer” of “cheap access to space” which SpaceX and others have promised (and at least somewhat delivered) ends up destroying all access to space for everyone and for ever...

[leetdan]

Things are getting slightly out of hand....

This video, from six years ago, has zero relevance to the topic at hand.  And of course it looks scary, if every piece of space debris is represented as a kilometer sized pixel.

eeergo's post is an example of an excellent, well-thought case against limitless LEO constellations.  The video you posted is not.

[ncb1397]

Yes, ironic if the “game-changer” of “cheap access to space” which SpaceX and others have promised (and at least somewhat delivered) ends up destroying all access to space for everyone and for ever...

There is a lot of concern about space debris. It isn't just me. That video was originally produced by NASA. Again, it isn't fearmongering and while out of date, the situation hasn't improved over time - additional objects from "megaconstellations" will be overlaid over the existing population. Of course, space debris and operational satellites are going to impact ground astronomy as well (as we have seen). Internet megaconstellations are going to affect space debris and multiply the number of satellites out there. Space debris is going to affect the conduct of space based astronomy (additional risk to launches, additional in space maneuvers, possibly drastically in a kessler syndrome like scenario). All these topics are inter-related.

I mean, the proof that you have to be very careful is out there. A decade after Iridium was put up there, an accidental hypervelocity impact occured and that was with a system with under 100 satellites. Within months of SpaceX launching satellites, coordination issues between satellite operators started to crop up where operator B couldn't get a hold of operator A. The warning signs are out there.

[Redclaws]

Yes, ironic if the “game-changer” of “cheap access to space” which SpaceX and others have promised (and at least somewhat delivered) ends up destroying all access to space for everyone and for ever...

This has been discussed here previously, but these satellites will reenter in a few years if they lose control.  As will *everything* in LEO.  It would be possible to wreck the GEO ring indefinitely, but not LEO.  That’s not how LEO works.