Planned satellite constellations may swamp future orbiting telescopes

Planned orbital observatories would see satellites cross nearly all of their images.

See full article...

 

[monkeywrench76]

This is like building 50 freeways thru Yosemite National Park. You never get it back.

 

[Maury Markowitz]

It seems to me this issue could be "solved" by demanding that the people launching the constellations also launch a high-throughput orbital telescope above the altitude of their satellites. Maybe more than one. Or maybe a share on a really big one. After all, we demand mining companies put aside money for remediation, this seems similar.

Falcon 9 can launch Hubble, and Heavy can launch it into lunar orbit or the L points. If we simply required 1 of these per, say, 10,000 satellites, we'd have more throughput than we know what to do with.

 

[1Zach1]

I wish this image, or a description of it had been placed in the article. It shows the orbits of the various space telescopes mentioned and orbits of satellite constellations. This seems like a key point that isn't actually in the article.

 

[jscottars]

Could a workaround be made by changing 600-second exposures to 600 one second exposures, blacking out the satellites from each and then combining? Seems like a process could be made to automate that. Maybe the hardware is not equipped to save that many images.

A one second exposure does not collect near the amount of light/photons as 600s...kind of the whole point of a long exposure.

 

[monkeywrench76]

Could a workaround be made by changing 600-second exposures to 600 one second exposures, blacking out the satellites from each and then combining? Seems like a process could be made to automate that. Maybe the hardware is not equipped to save that many images.

problem is the SNR ratio for each 1 sec exposure is much lower than the SNR ration of long exposure on these sensors so no amount of image stacking can restore the signal

 

[fenncruz]

Could a workaround be made by changing 600-second exposures to 600 one second exposures, blacking out the satellites from each and then combining? Seems like a process could be made to automate that. Maybe the hardware is not equipped to save that many images.

It's all about the signal to noise and how different noise sources scale with what your doing. There's a noise term based on simply measuring the data in the CCD out. So 600 hundred exposures has 600 times the read noise in the CCD's as 1 long exposure.

 

[cbrubaker]

I am curious about one thing - they state that the constellations should be launched to lower orbits. Is there a reason why the observatories can't be raised to higher orbits? This is a serious question - do the observatories need a specific period that only occur with a limited array of orbits?

 

[monkeywrench76]

It seems to me this issue could be "solved" by demanding that the people launching the constellations also launch a high-throughput orbital telescope above the altitude of their satellites. Maybe more than one. Or maybe a share on a really big one. After all, we demand mining companies put aside money for remediation, this seems similar.

Falcon 9 can launch Hubble, and Heavy can launch it into lunar orbit or the L points. If we simply required 1 of these per, say, 10,000 satellites, we'd have more throughput than we know what to do with.

we should at least charge them for the orbital spots and use that money to fund bigger and newer scopes at L points and also deorbit projects for space garbage.

 

[monkeywrench76]

I am curious about one thing - they state that the constellations should be launched to lower orbits. Is there a reason why the observatories can't be raised to higher orbits? This is a serious question - do the observatories need a specific period that only occur with a limited array of orbits?

very hard to move and existing observatory that was not designed for a different orbit.

 

[LordEOD]

Despite warnings of the various potential issues (including a rather catastrophic one in the Kessler Syndrome) it seems nothing is really getting in the way of these constellations going up anyways.

I won't necessarily cast a shadow on them (we do need infrastructure for communications, etc) but I can't help but to wonder..
..when and if something goes wrong, I am betting that is will be 99% on the public (i.e. taxpayer dollars) to fix. Not only ours, but globally.

It's a shame that cynicism has to be the order of the day, but I can't help but feeling we're heading into yet another situation wherein the profits are privatized and the losses will be socialized.

 

[redleader]

A one second exposure does not collect near the amount of light/photons as 600s...kind of the whole point of a long exposure.

600 1 second exposures do actually capture (very nearly) the same amount of light as 1 600 second exposure. Unfortunately they also capture 600 times as much read noise (although that will add in quadrature so "only" sqrt(600) times as much). In the long term this is likely to become more common, but sensor read noise is going to have to improve before that is a good solution.

 

[wagnerrp]

very hard to move and existing observatory that was not designed for a different orbit.

Per the article...

may swamp future orbiting telescopes​

So we're not concerned with existing telescopes right now. Future ones can and should be placed higher, and constellations can and should be pushed lower. Particularly ones like OneWeb, Qianfan, and Guowang.

 

[Wickwick]

Despite warnings of the various potential issues (including a rather catastrophic one in the Kessler Syndrome) it seems nothing is really getting in the way of these constellations going up anyways.

I won't necessarily cast a shadow on them (we do need infrastructure for communications, etc) but I can't help but to wonder..
..when and if something goes wrong, I am betting that is will be 99% on the public (i.e. taxpayer dollars) to fix. Not only ours, but globally.

It's a shame that cynicism has to be the order of the day, but I can't help but feeling we're heading into yet another situation wherein the profits are privatized and the losses will be socialized.

The very lowest orbits will never suffer a Kessler Syndrome scenario. Unpowered objects will decay and fall to the earth faster than they can collide with something else to create more debris. So there's always a workable solution even if the higher orbits are denied at some point in the future.

 

[wagnerrp]

Despite warnings of the various potential issues (including a rather catastrophic one in the Kessler Syndrome) it seems nothing is really getting in the way of these constellations going up anyways.

Because Kessler System is an absolute worst case situation requiring gross stupidity on all parts, including these constellation builders not actually worrying about their own best interests, and any one who brings it up is either ignorant, stupid, or spewing FUD for attention.

 

[lurknomore]

There's a real problem, but also, isn't 550000 sats a bit too high to model ?
We know People have Plans, but starting at 100k would have made the point while being actually achievable reasonably soon.
The gap between a handful of US and Chinese sustained constellations adding up to 100k, and actually having 500k sats, is really really a big one to cross.
If you go too big, you lose the urgency factor.

 

[Wickwick]

There's a real problem, but also, isn't 550000 sats a bit too high to model ?
We know People have Plans, but starting at 100k would have made the point while being actually achievable reasonably soon.
The gap between a handful of US and Chinese sustained constellations adding up to 100k, and actually having 500k sats, is really really a big one to cross.
If you go too big, you lose the urgency factor.

But if you don't over-model by a factor of five then you only get 20 tracks per image instead of 100.

Of course, what fraction of the sensor area is 100 tracks anyways? 0.8%?

 

[wagnerrp]

I am curious about one thing - they state that the constellations should be launched to lower orbits. Is there a reason why the observatories can't be raised to higher orbits? This is a serious question - do the observatories need a specific period that only occur with a limited array of orbits?

The telescopes should be launched to higher orbits. They're discussing asteroid spotting, and needing to observe the horizon at dawn to capture these asteroids in similar orbits to Earth. That means it's a bad design. They should be in high orbit, or somewhere like L1 inside of Earth's orbit, rather than one so obviously ill suited to their needs.

"Oh, but it costs more to get there, and it costs more to communicate with there."

Cheaper launches are a thing, and they're getting cheaper continuously. Laser communications are a thing, and no longer require dedicated time on the DSN.

 

[Wickwick]

The telescopes should be launched to higher orbits. They're discussing asteroid spotting, and needing to observe the horizon at dawn to capture these asteroids in similar orbits to Earth. That means it's a bad design. They should be in high orbit, or somewhere like L1 inside of Earth's orbit, rather than one so obviously ill suited to their needs.

"Oh, but it costs more to get there, and it costs more to communicate with there."

Cheaper launches are a thing, and they're getting cheaper continuously. Laser communications are a thing, and no longer require dedicated time on the DSN.

Literally the enabling technology for deployment of megaconstellations is the solution to avoiding their impact for in-space observatories.

 

[Dioptase]

Part of the problem is going to be an overcapacity issue. The most obvious is the duplication of capacity caused by the Chinese and US constellations. It's safe to assume each country isn't going to permit ground stations or terminals from the other.

One possible solution is permitting some sort of version of internet peering or transit. The constellation owners make some sort of deal (blessed by their respective governments) that allows encrypted data links between satellites and ground that are only decrypted once they have reached an approved decryption gateway to the internet.

For example, a Starlink terminal in the US might link to a Chinese satellite using a Starlink account. The Chinese satellite links to a Chinese owned ground-station (maybe in the US, maybe not). The ground station connects to the approved gateway (much like an IPX). In theory, the Chinese portion of the network can't tell what the data is, but now Starlink can get by with fewer satellites. And visa versa.

Obviously you'd restrict such links to only non critical stuff. For example, nothing national security related.

Basically a satellite equivalent to internet peering that avoids every company needing to run fiber from coast to coast.

But I don't see this happening any time soon.

 

[cbrubaker]

I wish this image, or a description of it had been placed in the article. It shows the orbits of the various space telescopes mentioned and orbits of satellite constellations. This seems like a key point that isn't actually in the article.

View attachment 123500

That chart seems intended to viscerally exaggerate the issue.

First, by misrepresenting the true physical distribution of the satellites. Most of these are roughly car sized; how many millions of cars are there just in the LA Metro area, which mostly exist in a single layer with a roughly 80-mile diameter (especially be including the highly speculative (and frankly, extremely unlikely to occur). Compare this to the 40 million square miles of the Earth between the Arctic and Antarctic circles (since polar orbits are pretty sparse). And that's just a single layer; the diagram above shows ~0.5 million satellites in layers 1000 miles thick., which represents a volume equal >50% of the volume of the entire planet (which has how many billions of cars creeping around just on the surface).

Second, and probably worse, is to be including the highly speculative (and frankly, extremely unlikely to occur) Semaphore and Cinnamon-937 constellations, which account for >80% of the satellites shown. So the actual likely number of satellites to occur is ~100K; still a lot, but not "polluted" as the graph above implies.

If we go a step further, and observe that <1/3 of those remaining (32K) are proposed to exist above 600 km, and most of these are not flown by the US (21K between PRC and OneWeb, which was British and is now French), and this is being presented by an American group to an American audience, I have to wonder at the actual target of this chart.

Seems to me that the real answer is to lift the observatories to 800 km or higher, since then you are only moving a handful.

 

[YetAnotherAnonymousAppellation]

A one second exposure does not collect near the amount of light/photons as 600s...kind of the whole point of a long exposure.

That's true, but why not have a physical shutter that blocks the light for the duration of the satellite's passage? With the "super black" processes available it should be possible to have a shutter that you can rotate into position without producing reflections that disrupt the image.

 

[Erbium168]

Reminds me of Ogden Nash:
"I think that I will never see
A billboard lovely as a tree.
In fact, unless the billboards fall
I'll never see a tree at all."

 

[Veritas super omens]

Of course the astronomers' solution is for everyone to adapt to their needs. That's the m.o. of astronomers across the world. Heaven forbid they acknowledge the solution is to just go above all the satellites.

One has to realize that the cat is out of the bag. Even if all the civilian megaconstellations were cancelled tomorrow, the military applications are enough to demand their growth. Astronomers may as well adapt to reality and start planning to fly above the noise sources or adapt to them on the ground

Hell, you have the ephemeris information for every noise source before its in your image. If you're dead set on imaging through them then find a way to deal with the noise - physical blockers or selective amplification drops as noise sources go past.

That is like asking the people in the post above that enjoy Yosemite to build their own park.

As David Byrne says:

"Most beautiful, most intelligent criminals you've ever seen. Now you're paying top dollar. For what you used to get for free."

 

[dmsilev]

I wish this image, or a description of it had been placed in the article. It shows the orbits of the various space telescopes mentioned and orbits of satellite constellations. This seems like a key point that isn't actually in the article.

View attachment 123500

I wonder about the two biggest contributors. Cinnamon-937 is from the Rwandan government, and at least as far as I can tell with a bit of searching, doesn't seem to exist as anything beyond an ITU filing. Semaphore-C apparently came from the same people, this time via France. It's not really clear that that actually exists as a serious effort either. Take those two out, and what's left is a lot lot smaller.

 

[fenris_uy]

There's a real problem, but also, isn't 550000 sats a bit too high to model ?
We know People have Plans, but starting at 100k would have made the point while being actually achievable reasonably soon.
The gap between a handful of US and Chinese sustained constellations adding up to 100k, and actually having 500k sats, is really really a big one to cross.
If you go too big, you lose the urgency factor.

Yeah, I was thinking something similar the majority of those 550,000 sats appears to be from the constellations named Semaphore at 116,000 sats and Cinnamon-937 with 330,000. Haven't read the paper, but I hope that they also study the scenario in which those 2 huge constellations don't get made.

 

[wagnerrp]

Part of the problem is going to be an overcapacity issue. The most obvious is the duplication of capacity caused by the Chinese and US constellations. It's safe to assume each country isn't going to permit ground stations or terminals from the other.

The US and EU constellations provide internet access. The Chinese constellations provide Chinese network access. They're not duplication of capacity because they're not offering the same thing.

 

[ashypans]

Greg Wylers Cinnamon constellation (337,323) is dead. He's second proposal Semaphore (116,640) isn't dead yet but probability of success is so low that its inclusion in this study is reckless. So that is half a million satellites that will never exist included in this study. I expect some more of these are paper satellites, but even if every other proposal goes through that's only 20% of what this team modelled.

 

[jfconde]

600 1 second exposures do actually capture (very nearly) the same amount of light as 1 600 second exposure. Unfortunately they also capture 600 times as much read noise (although that will add in quadrature so "only" sqrt(600) times as much). In the long term this is likely to become more common, but sensor read noise is going to have to improve before that is a good solution.

While 600 1 second exposures wouldn't work, they could just close the shutter for the few seconds it takes for a satellite to pass their view and then resume the long exposure. It might not be ideal, but it should be simple enough since all the satellite tracks are known. So the interference can be predicted and consequent shutter closures can be programmed in advance.

 

[jhodge]

Yeah, I was thinking something similar the majority of those 550,000 sats appears to be from the constellations named Semaphore at 116,000 sats and Cinnamon-937 with 330,000. Haven't read the paper, but I hope that they also study the scenario in which those 2 huge constellations don't get made.

And the constellation that is most fully-realized, Starlink, is relatively low and getting lower with the Gen-2, Part-2 satellites. SpaceX obviously shouldn't have a monopoly, but maybe part of the answer is to force future constellations lower and future telescopes higher with a buffer zone in the middle.

 

[ashypans]

And now a second comment where I admit to not knowing how digital photography works. With these long exposures shots is it operating just like a film camera or is it taking hundreds of readings per second and then adding them together as a sort of timelapse composite? So each pixel is the sum of light received at that pixels location of the duration of the shot from thousands of samples or like one long single reading on that one pixel?

 

[ridgeguy]

I'm greatful that I'm not an astronomer, and that I was born early enough to have great memories of the night sky before humans made it to space. And as an admission of my hypocrisy, I depend on Starlink in my rural area. Life involves tradeoffs.

 

[1Zach1]

And now a second comment where I admit to not knowing how digital photography works. With these long exposures shots is it operating just like a film camera or is it taking hundreds of readings per second and then adding them together as a sort of timelapse composite? So each pixel is the sum of light received at that pixels location of the duration of the shot from thousands of samples or like one long single reading on that one pixel?

Each exposure is a single shot. I don't know the technical details of these future space scopes, but most use image stacking which removes the issues with satellite crossing as they get subtracted out. The real issue is for wide field telescopes that are used for tracking objects in space, as they use changes between each image to do their science, which satellites can't be subtracted from.

 

[wagnerrp]

Yes, yes, we'll just resign ourselves to losing satellites and astronauts that have to transition those higher orbits lacking 'workable solutions', including the very observatories that you argue should simply be placed above an innumerable horde semi-disposable communications satellites that absolutely must be made and operated as cheaply as possible because...

There it is. The FUD. You've been around here long enough that ignorance is not an excuse, so it's either stupidity, or intentional disinformation. Your choice.

DRJlaw here is taking a lesson out of the playbook of prestigious groups such as Moon-landing deniers. One of their favorite arguments is that the Van Allen radiation belts are lethal, and anyone trying to cross through them would instantly die. This is a variation, claiming Kessler Syndrome will produce a similarly instantaneously lethal shell of debris around the planet. In reality, it's a statistical function of time. It's a hazard zone, and the longer you stay there, the higher your risk. Pass through it quickly enough, and your risk is negligible.

How do we know this to be factual? If you were guaranteed to be impacted while passing through said region, the region would very rapidly cease to exist. Debris would impact debris, turning to dust, deorbiting most of the mass, and producing a ring. Yes. This is how planetary rings are created. If it's low density, then it's low density, and you just don't linger there. If it's high density, then it forms a ring, and you just don't fly through the ring.

 

[ashypans]

Each exposure is a single shot. I don't know the technical details of these future space scopes, but most use image stacking which removes the issues with satellite crossing as they get subtracted out. The real issue is for wide field telescopes that are used for tracking objects in space, as they use changes between each image to do their science, which satellites can't be subtracted from.

Thank you for not only quickly answering my question but anticipating my next one and answering it too.

 

[brionl]

I'm on my phone, or I would post the Disco Stu "If these trends continue" meme.
As other people have already pointed out, 90% of these satellites are purely imaginary and will never be launched.