Impacts of Large Satellite Constellations on Astronomy

[su27k]

These tracks are all deterministic. If astronomical imaging systems are sufficiently disrupted by satellite constellations they could be engineered to not record for the brief intervals the satellites track across the individual detector chips or, for some detector architectures, strips or areas of those arrays. That would result in some small degradation of sensitivity, but not massive loss.

That’s not to say there is no problem. It just seems manageable.

It was manageable until now. But, it probably won' t be in the future, with all this constellations.

Citation needed. Since we're talking about science here, we need numbers not speculation.

I don' t think the majority of observatories have enough money to anticipate the satellites nor to manage and use this contaminated data. Probably they will lost the observation.

How much money do they need to write this software? Can't they share the same software for doing this? That's just one of the many questions need to be answered before we can properly evaluate the impact on astronomy.

[high road]

So all telescopes on earth go through clean room maintenance with maintenance precision after their initial construction? By which I mean, the telescopes that are so much cheaper than their in-space counterparts that were now doomed according to the post I responded to.

Yes, they are. Check it on the net.

Here a picture of a complex instrument on one of ESO's VLT. It is a very complex instrument. I disagree with your comment intention of " much cheaper than their in-space counterparts". This instruments aren' t cheap. They are expensive. The problem is that space counterpart will be incredible expensive (compared to ground instruments)

¿could you imagine an astronaut trying to fix something on this instrument?

That's the definition of cheaper. Less expensive. And yes, I can imagine the reduction in launch costs and increase in launcher size and flexibility to result in designs that can be serviced after launch either robotically, or that they can be picked up, brought home, serviced in that same clean room, and launched again. Or if there's enough denand, unlikely in the short run, a dedicated pressurized clean room in space is not impossible IMO. No clumsy space suits required

[jebbo]

Here a picture of a complex instrument on one of ESO's VLT. It is a very complex instrument. I disagree with your comment intention of " much cheaper than their in-space counterparts". This instruments aren't cheap. They are expensive. The problem is that space counterpart will be incredible expensive (compared to ground instruments)

KMOS (on Antu) isn't even the most complex :-)

I think part of the problem is a lack of understanding on how these large instruments are used. They are not "low touch". Although they are high precision, most require frequent maintenance and calibration. Not only that, there are multiple focii (Nasmyth A/B, Cassegrain, and at the VLT the combined Coudé focus) on each of the 4 UT, and often a choice of instrument. So maintenance is significant. Swapping instruments usually means reconfiguring the hardware (unplugging fibres, etc; sometimes much more), and some instruments require different hardware each run (e.g. fibre plates for multi-object spectrographs).

Which is why there are multiple observational astronomers on site. They aren't there as PIs and collecting data; they are instrument specialists and there to manage them.

Trying to do this in orbit is frankly impossible. In the future (and I mean decades), the lunar surface is a good location even though it's a much more extreme environment, but you need a huge sustained human presence first.

--- Tony

[pochimax]

If an asteroid that has our number on it is missed because of all the satellites above interfered with viewing when it was best visible (low down at the horizon during dawn or dusk), then it could be a very big deal. A civilisation ending big deal!

It could also happen that Starlink provides enough economic benefit to let SpaceX finish development of Starship and Starship's ability to launch large amounts of mass to orbit on short notice lets us deflect an asteroid that we otherwise wouldn't have been able to deflect.

I think the best  solution will be to charge the benefits of Starlink with taxes, and direct this money to fiber optic the remote regions until no more constellations are needed.

[Star One]

Here a picture of a complex instrument on one of ESO's VLT. It is a very complex instrument. I disagree with your comment intention of " much cheaper than their in-space counterparts". This instruments aren't cheap. They are expensive. The problem is that space counterpart will be incredible expensive (compared to ground instruments)

KMOS (on Antu) isn't even the most complex :-)

I think part of the problem is a lack of understanding on how these large instruments are used. They are not "low touch". Although they are high precision, most require frequent maintenance and calibration. Not only that, there are multiple focii (Nasmyth A/B, Cassegrain, and at the VLT the combined Coudé focus) on each of the 4 UT, and often a choice of instrument. So maintenance is significant. Swapping instruments usually means reconfiguring the hardware (unplugging fibres, etc; sometimes much more), and some instruments require different hardware each run (e.g. fibre plates for multi-object spectrographs).

Which is why there are multiple observational astronomers on site. They aren't there as PIs and collecting data; they are instrument specialists and there to manage them.

Trying to do this in orbit is frankly impossible. In the future (and I mean decades), the lunar surface is a good location even though it's a much more extreme environment, but you need a huge sustained human presence first.

--- Tony

Considering you speak from a position of greater knowledge on this topic than most of us on this thread. I am a bit bemused why some posters appear to be posting as if they better know this area than you.

[high road]

Here a picture of a complex instrument on one of ESO's VLT. It is a very complex instrument. I disagree with your comment intention of " much cheaper than their in-space counterparts". This instruments aren't cheap. They are expensive. The problem is that space counterpart will be incredible expensive (compared to ground instruments)

KMOS (on Antu) isn't even the most complex :-)

I think part of the problem is a lack of understanding on how these large instruments are used. They are not "low touch". Although they are high precision, most require frequent maintenance and calibration. Not only that, there are multiple focii (Nasmyth A/B, Cassegrain, and at the VLT the combined Coudé focus) on each of the 4 UT, and often a choice of instrument. So maintenance is significant. Swapping instruments usually means reconfiguring the hardware (unplugging fibres, etc; sometimes much more), and some instruments require different hardware each run (e.g. fibre plates for multi-object spectrographs).

Which is why there are multiple observational astronomers on site. They aren't there as PIs and collecting data; they are instrument specialists and there to manage them.

Trying to do this in orbit is frankly impossible. In the future (and I mean decades), the lunar surface is a good location even though it's a much more extreme environment, but you need a huge sustained human presence first.

--- Tony

Ah, now this is an informative post. So we're not even talking about space telescopes being more expensive than ground based high-end telescopes, but the merits of high end telescopes that can't be easily replaced by in-space variants and are hindered by space constellations. Agreed, that is a problem in need of a solution.

However, I don't quite understand yet why instruments and hardware couldn't be swapped on a space station? (with the telescope being either on a space station that's used for other stuff or the telescope containing enough pressurized volume for easy maintenance, or even sustained presence of said instrument specialists). Or why they could not be launched for a single run, brought back, refurbished for the next run, and launched again? Especially if their design would be done specifically for this kind of use?

This would be quite more clumsy and expensive to do than the telescopes we've spent hundreds of years improving for their current use case. But not impossible, and other types of research become more feasilbe. It seems to me like a shift in research would be more likely than purely negative consequences. With the end result maybe a net gain.

If an asteroid that has our number on it is missed because of all the satellites above interfered with viewing when it was best visible (low down at the horizon during dawn or dusk), then it could be a very big deal. A civilisation ending big deal!

It could also happen that Starlink provides enough economic benefit to let SpaceX finish development of Starship and Starship's ability to launch large amounts of mass to orbit on short notice lets us deflect an asteroid that we otherwise wouldn't have been able to deflect.

I think the best  solution will be to charge the benefits of Starlink with taxes, and direct this money to fiber optic the remote regions until no more constellations are needed.

So all that remains is all those other satellites that are likely to be launched as launch costs come down? Earth observation sats, that is. Can't replace those with fiber optic. Or are they less of a problem, even in case they eventually outnumber Starlink satellites?

Taxing sat constellations to pay for the construction (and operation?) of the aforementioned manned space telescopes, now that would be an interesting idea. ;-)

[edzieba]

One thing I would still be interested in know is how observatories currently deal with the thousands of existing satellites (and tens to hundreds of thousands of bits of shiny tumbling debris) already in orbit.

These tracks are all deterministic. If astronomical imaging systems are sufficiently disrupted by satellite constellations they could be engineered to not record for the brief intervals the satellites track across the individual detector chips or, for some detector architectures, strips or areas of those arrays. That would result in some small degradation of sensitivity, but not massive loss.

Unfortunately that is not an option with CCDs, you must physically block incoming light if you want to prevent them gathering electrons generated by incident photons.

[Star One]

Causing more trouble for astronomers.

STARLINK SATELLITES PHOTOBOMB A METEOR SHOWER: Yes, there was an outburst of alpha Monocerotid meteors on Nov. 22nd. As predicted by forecasters Esko Lyytinen and Peter Jenniskens (NASA/Ames), Earth grazed a filament of comet dust, prompting a flurry of meteors to emerge from the constellation Monoceros (the Unicorn). In La Palma on the Canary islands, a Global Meteor Network camera captured the display--and something more. Starlink photobombed the meteor shower:

https://www.spaceweather.com/archive.php?view=1&day=23&month=11&year=2019

[Comga]

One thing I would still be interested in know is how observatories currently deal with the thousands of existing satellites (and tens to hundreds of thousands of bits of shiny tumbling debris) already in orbit.

These tracks are all deterministic. If astronomical imaging systems are sufficiently disrupted by satellite constellations they could be engineered to not record for the brief intervals the satellites track across the individual detector chips or, for some detector architectures, strips or areas of those arrays. That would result in some small degradation of sensitivity, but not massive loss.

Unfortunately that is not an option with CCDs, you must physically block incoming light if you want to prevent them gathering electrons generated by incident photons.

I design optical instruments for a living.  It is an option.
One would need to read the first part of the exposure and resume after the specific satellite tracks across the array or sub-array.  That would incur read noise penalties and create other issues.  This is not ideal, and requires some sophisticated automation, but it's better than discarding entire images.

[Asteroza]

One thing I would still be interested in know is how observatories currently deal with the thousands of existing satellites (and tens to hundreds of thousands of bits of shiny tumbling debris) already in orbit.

These tracks are all deterministic. If astronomical imaging systems are sufficiently disrupted by satellite constellations they could be engineered to not record for the brief intervals the satellites track across the individual detector chips or, for some detector architectures, strips or areas of those arrays. That would result in some small degradation of sensitivity, but not massive loss.

Unfortunately that is not an option with CCDs, you must physically block incoming light if you want to prevent them gathering electrons generated by incident photons.

I design optical instruments for a living.  It is an option.
One would need to read the first part of the exposure and resume after the specific satellite tracks across the array or sub-array.  That would incur read noise penalties and create other issues.  This is not ideal, and requires some sophisticated automation, but it's better than discarding entire images.

Is that automation something suitable for SpaceX to underwrite as open source software, to facilitate the astronomical community developing measures to deal with increased obstruction by manmade obstructions?

[su27k]

NASA administrator Jim Bridenstine on whether SpaceX low-orbit satellites are blocking stargazing (Fox News video)

Rough transcript from reddit user NeuralPlanet:

HOST:

Astronomers aren’t too happy with this SpaceX company. They say a lot of their low earth orbit satellites are actually blocking their view of the stars. Is it mostly his stuff that’s the problem here?

JIM:

No, not at all, we have a lot of satellites in low earth orbit. SpaceX is a very great partner with NASA, they are very responsible space actors. Some of these problems can be mitigated very easily by just reducing the reflectivity of the satellites. I know Elon personally, and he has no interest in blocking for astronomers.

[pochimax]

This Is Why We Can't Just Do All Of Our Astronomy From Space
https://www.forbes.com/sites/startswithabang/2019/11/27/this-is-why-we-cant-just-do-all-of-our-astronomy-from-space/

While it's easy to point to the ways that space-based astronomy has superiority to ground-based astronomy, there are still substantial advantages that being on the ground offers, and that astronomers continue to take advantage of even in a post-Hubble era. We can create images, collect data, and perform scientific investigations that simply cannot occur with space-based observatories alone.

There are five major metrics where ground-based observatories should always remain leaps and bounds ahead of space-based ones, and they generally include:

size,
reliability,
versatility,
maintenance,
and upgradeability.

If we can keep our skies dark, clear, and unobstructed, ground-based astronomy is sure to enter a golden age as the 21st century unfolds. Here's what's great about the ground.

Losing the benefits of ground-based astronomy would be both catastrophic and unnecessary, as even a small effort can prevent it. But if we continue to be reckless and careless with our skies — two all-too-human traits — they'll disappear, along with ground-based astronomy, before we know it.

[pochimax]

One thing I would still be interested in know is how observatories currently deal with [...]

Again, the main problem is not with current observatories. The real risk is that we are preventing succesful FUTURE observatories, and preventing the expansion of ground astronomy
(example: deploying large numbers of LSST replicas, a large number of large field of view telescopes)

[edzieba]

One thing I would still be interested in know is how observatories currently deal with [...]

Again, the main problem is not with current observatories.

Then if the current swarm of LEO satellites and other LEO junk is such a nonissue for ground astronomy that no mitigation measures must be taken, what is special about Starlink that makes it so much of an issue?

[pochimax]

Problem is constellations, generally speaking.
Not only Starlink.

[edzieba]

And again, we already have LEO constellations in orbit (e.g. Iridium).
Once more: other than "there are more", what is different with Starlink (and OneWeb, etc) that requires special mitigations, while existing constellations (and other satellites and other objects like spent stages, dead satellites, and general debris) do not? And if there is no difference beyond quantity, why are whatever current mitigations for satellite passes over ground-based telescopes viable for the current several hundreds to thousands of objects but not for additional objects?

[high road]

This Is Why We Can't Just Do All Of Our Astronomy From Space
https://www.forbes.com/sites/startswithabang/2019/11/27/this-is-why-we-cant-just-do-all-of-our-astronomy-from-space/

While it's easy to point to the ways that space-based astronomy has superiority to ground-based astronomy, there are still substantial advantages that being on the ground offers, and that astronomers continue to take advantage of even in a post-Hubble era. We can create images, collect data, and perform scientific investigations that simply cannot occur with space-based observatories alone.

There are five major metrics where ground-based observatories should always remain leaps and bounds ahead of space-based ones, and they generally include:

size,
reliability,
versatility,
maintenance,
and upgradeability.

If we can keep our skies dark, clear, and unobstructed, ground-based astronomy is sure to enter a golden age as the 21st century unfolds. Here's what's great about the ground.

Losing the benefits of ground-based astronomy would be both catastrophic and unnecessary, as even a small effort can prevent it. But if we continue to be reckless and careless with our skies — two all-too-human traits — they'll disappear, along with ground-based astronomy, before we know it.

I still don't see any showstoppers in the article, but that could be because they don't explain why future (rather than old ones designed for prohibitively expensive and small launchers) space infrastructure couldn't solve many (or even all) of the problems listed. Yes, to replace high end telescopes with lots of support infrastructure, you'd need an equally large telescope with equally large support infrastructure in space, which comes at a hefty premium. But it doesn't seem inherently impossible. New technology shifting the relative cost of different research techniques doesn't stop research. It just favours alternative ways of doing research. Seems like the golden age of astronomy is coming.

[pochimax]

This future solutions are more or less sci-fi. With little possibilities for being  a reallity in the near future.

And, even if they will be possible in the long future, they allways be more expensive than ground based solutions. It doesn' t matter how cheaper you go with space solutions, ground based alternatives will also evolve and be more cheaper, again. But we will be prevented of using it.

[pochimax]

And again, we already have LEO constellations in orbit (e.g. Iridium).
Once more: other than "there are more", what is different with Starlink (and OneWeb, etc) that requires special mitigations, while existing constellations (and other satellites and other objects like spent stages, dead satellites, and general debris) do not? And if there is no difference beyond quantity, why are whatever current mitigations for satellite passes over ground-based telescopes viable for the current several hundreds to thousands of objects but not for additional objects?

1) they are not radio emitting.
2) the important quantity is not only numbers, but apparent magnitude.

[pochimax]

It is not sure this constellations will blockade astronomers sky. The problem is that nobody has study properly this potential impact and how it will affect ground astronomy (current and future). It is wrong to do this things in that way.