Impacts of Large Satellite Constellations on Astronomy

[meekGee]

An example of the impact.

Obviously, this will get better as the satellites orient themselves correctly and disperse to their final orbits.

https://twitter.com/lcjohnso/status/1196370554414125056

--- Tony

"example" is misleading.  To get this shot, you have to aim, time, and choose your location very carefully...

The satellites are lit against a dark sky only near sunset/sunrise, or for longer times when low on the horizon in the direction of the sun.

Neither of these scenarios make for acceptable observing conditions.

Also, when grouped together, they are only affecting one region at any given time...  So you really have to get them intentionally for a picture like this.

So this is "a shot of the satellite train", not "an example of impact on astronomy".

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, but the ~300 km deployment altitude will greatly reduce the times then the "train" is visible.

But as long as SpaceX is releasing the latest orbital data, which they are doing now, it's pretty trivial to predict a pass like this several days in advance and plan around it.

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

Can we talk about numbers instead of insults?

These satellites, in shell form, appear to me to be spaced really far apart when viewed from an earth location, if we ignore the near-horizon direction of view.

They are much denser near the horizon, and much likelier to be actually lit, but that's not where astronomers look.

When launched, they are clumped, but this only means that for every place/time/direction they appear as a group, there all these other places where they don't appear at all..

So what exactly is the problem?

[Star One]

An example of the impact.

Obviously, this will get better as the satellites orient themselves correctly and disperse to their final orbits.

https://twitter.com/lcjohnso/status/1196370554414125056

--- Tony

"example" is misleading.  To get this shot, you have to aim, time, and choose your location very carefully...

The satellites are lit against a dark sky only near sunset/sunrise, or for longer times when low on the horizon in the direction of the sun.

Neither of these scenarios make for acceptable observing conditions.

Also, when grouped together, they are only affecting one region at any given time...  So you really have to get them intentionally for a picture like this.

So this is "a shot of the satellite train", not "an example of impact on astronomy".

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, but the ~300 km deployment altitude will greatly reduce the times then the "train" is visible.

But as long as SpaceX is releasing the latest orbital data, which they are doing now, it's pretty trivial to predict a pass like this several days in advance and plan around it.

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

Can we talk about numbers instead of insults?

These satellites, in shell form, appear to me to be spaced really far apart when viewed from an earth location, if we ignore the near-horizon direction of view.

They are much denser near the horizon, and much likelier to be actually lit, but that's not where astronomers look.

When launched, they are clumped, but this only means that for every place/time/direction they appear as a group, there all these other places where they don't appear at all..

So what exactly is the problem?

Yet again you seem to be forgetting the impact on something like LSST, let alone radio astronomers.

[Yellowstone10]

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

This isn't just a SpaceX or a Starlink problem. More lights in the sky is the inevitable result of expanding humanity's presence in space, whether that's a commsat constellation, solar power satellites, habitats, orbital foundries, etc. (Imagine what the night sky would look like in the Star Trek or The Expanse universes.) I think that's why (certain) space advocates see (certain) astronomers as arrogant - the arguments against Starlink, if taken to their logical conclusion, imply that only astronomers can make legitimate use of space, and any other human use of space beyond the current small scale should be restricted.

[meekGee]

An example of the impact.

Obviously, this will get better as the satellites orient themselves correctly and disperse to their final orbits.

https://twitter.com/lcjohnso/status/1196370554414125056

--- Tony

"example" is misleading.  To get this shot, you have to aim, time, and choose your location very carefully...

The satellites are lit against a dark sky only near sunset/sunrise, or for longer times when low on the horizon in the direction of the sun.

Neither of these scenarios make for acceptable observing conditions.

Also, when grouped together, they are only affecting one region at any given time...  So you really have to get them intentionally for a picture like this.

So this is "a shot of the satellite train", not "an example of impact on astronomy".

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, but the ~300 km deployment altitude will greatly reduce the times then the "train" is visible.

But as long as SpaceX is releasing the latest orbital data, which they are doing now, it's pretty trivial to predict a pass like this several days in advance and plan around it.

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

Can we talk about numbers instead of insults?

These satellites, in shell form, appear to me to be spaced really far apart when viewed from an earth location, if we ignore the near-horizon direction of view.

They are much denser near the horizon, and much likelier to be actually lit, but that's not where astronomers look.

When launched, they are clumped, but this only means that for every place/time/direction they appear as a group, there all these other places where they don't appear at all..

So what exactly is the problem?

Yet again you seem to be forgetting the impact on something like LSST, let alone radio astronomers.

Again, numbers.
LSST has a FOV of under 4 degres.  The satellites are (IIUC) about 40 degrees apart except near the horizon.

Also, if you discard to peripheral 30 degrees above the horizon in the sun direction, they are mostly dark.

[envy887]

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, ...

Why?

I don't think this is true at all.  ISS is only visible for a brief time just after sunset and 550km isn't much higher than ISS, relative to the planet's diameter of 12,700km.

See this simulation:

[Star One]

An example of the impact.

Obviously, this will get better as the satellites orient themselves correctly and disperse to their final orbits.

https://twitter.com/lcjohnso/status/1196370554414125056

--- Tony

"example" is misleading.  To get this shot, you have to aim, time, and choose your location very carefully...

The satellites are lit against a dark sky only near sunset/sunrise, or for longer times when low on the horizon in the direction of the sun.

Neither of these scenarios make for acceptable observing conditions.

Also, when grouped together, they are only affecting one region at any given time...  So you really have to get them intentionally for a picture like this.

So this is "a shot of the satellite train", not "an example of impact on astronomy".

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, but the ~300 km deployment altitude will greatly reduce the times then the "train" is visible.

But as long as SpaceX is releasing the latest orbital data, which they are doing now, it's pretty trivial to predict a pass like this several days in advance and plan around it.

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

Can we talk about numbers instead of insults?

These satellites, in shell form, appear to me to be spaced really far apart when viewed from an earth location, if we ignore the near-horizon direction of view.

They are much denser near the horizon, and much likelier to be actually lit, but that's not where astronomers look.

When launched, they are clumped, but this only means that for every place/time/direction they appear as a group, there all these other places where they don't appear at all..

So what exactly is the problem?

Yet again you seem to be forgetting the impact on something like LSST, let alone radio astronomers.

Again, numbers.
LSST has a FOV of under 4 degres.  The satellites are (IIUC) about 40 degrees apart except near the horizon.

Also, if you discard to peripheral 30 degrees above the horizon in the sun direction, they are mostly dark.

I notice you didn’t answer the radio astronomy question?

[envy887]

Even 40,000 sats, say 200 planes of 200, represent a mesh of satellites 200 km apart.  At an altitude of 300 km, that's 40 degrees apart to an observer on the ground. (LSST is under 4 degrees)

So except for near the horizon (where you view the shell edge on) you'll have a hard time catching even one satellite, even if it happens to be lit, which is rarely to begin with.

No.

They're moving, and telescopes typically take long exposures.  So, if they're going to cross your FOV, you're going to see them.

Yes, they are moving, but not very fast - it takes them over 100 seconds to transit the whole sky. For exposures on the order of 10-100 seconds, even a 4 square degree FOV probably won't capture any. On the order of 100-1000 s, it will probably get a couple Starlinks, and probably a couple other satellites as well.

Given good TLEs, which we now have, for any particular set of exposure start and stop times and any particular patch of sky, it is possible (even trivial) to calculate whether or not you will catch a Starlink pass, and exactly where in the FOV it will be. This is a challenge, but hardly the end of astronomy as we know it.

[meekGee]

An example of the impact.

Obviously, this will get better as the satellites orient themselves correctly and disperse to their final orbits.

https://twitter.com/lcjohnso/status/1196370554414125056

--- Tony

"example" is misleading.  To get this shot, you have to aim, time, and choose your location very carefully...

The satellites are lit against a dark sky only near sunset/sunrise, or for longer times when low on the horizon in the direction of the sun.

Neither of these scenarios make for acceptable observing conditions.

Also, when grouped together, they are only affecting one region at any given time...  So you really have to get them intentionally for a picture like this.

So this is "a shot of the satellite train", not "an example of impact on astronomy".

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, but the ~300 km deployment altitude will greatly reduce the times then the "train" is visible.

But as long as SpaceX is releasing the latest orbital data, which they are doing now, it's pretty trivial to predict a pass like this several days in advance and plan around it.

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Neither does Space X own the heavens. You seemingly miss the irony of condemning astronomers for arrogance whilst arrogantly telling them they will just have to get used to the new reality. Maybe some space advocates need to take a lesson in humility before making accusations against the astronomy community.

Can we talk about numbers instead of insults?

These satellites, in shell form, appear to me to be spaced really far apart when viewed from an earth location, if we ignore the near-horizon direction of view.

They are much denser near the horizon, and much likelier to be actually lit, but that's not where astronomers look.

When launched, they are clumped, but this only means that for every place/time/direction they appear as a group, there all these other places where they don't appear at all..

So what exactly is the problem?

Yet again you seem to be forgetting the impact on something like LSST, let alone radio astronomers.

Again, numbers.
LSST has a FOV of under 4 degres.  The satellites are (IIUC) about 40 degrees apart except near the horizon.

Also, if you discard to peripheral 30 degrees above the horizon in the sun direction, they are mostly dark.

I notice you didn’t answer the radio astronomy question?

One at a time.  I'm less familiar with their constraints, but know SpaceX has been working with them. But the images above are all about optical..

So how about it?  How do satellites that are about 40 degrees apart and usually dark create a problem?

[Rondaz]

Professional astronomers starting to be affected by Starlink. This kind of problem will be rare for now, but once the full constell is up it will be an everyday occurrence.

https://twitter.com/planet4589/status/1196456228886589440

[Rondaz]

Here’s the Starlink plagued DECam frame:

https://twitter.com/lcjohnso/status/1196370554414125056

[Lee Jay]

It's close to the summer solstice in Chile, so Starlinks will be visible for a good part of the night. At 550 km they would be visible nearly all night, ...

Why?

I don't think this is true at all.  ISS is only visible for a brief time just after sunset and 550km isn't much higher than ISS, relative to the planet's diameter of 12,700km.

See this simulation:

https://www.youtube.com/watch?v=vZiUsNQiJ1I?t=70

Yes, about what I thought - the illuminated ones are near the terminator leaving most of the night sky clear most of the time.

[Lar]

Professional astronomers starting to be affected by Starlink. This kind of problem will be rare for now, but once the full constell is up it will be an everyday occurrence.

https://twitter.com/planet4589/status/1196456228886589440

Please don't repost the same tweet we are already in the midst of discussion.

And please do trim your quote blocks back from time to time. Thanks

[Bubbinski]

I am an amateur astronomer but also a space advocate as well. The Starlink constellation and others like it will be highly beneficial for rural areas where some family members live as well as countries where local dictators shut down or curb the local telecom’s internet access. On the whole I think the emerging space economy will benefit humanity.

However, the astronomy community has raised legitimate concerns about the impacts on the night sky, and in time these mega-constellations could impact my ability to take certain Astro photos, and professional observatories (radio and visible) can be impacted, and I don’t want to see their work affected. There is also a legitimate space debris concern. I’m not too concerned about my astrophotography hobby, and I can work around satellite passes, but I’m more concerned about the professional observatories and especially preventing a Kessler cascade.

I would hope that a “grand meeting” can be arranged between Elon Musk, OneWeb, NRAO, Mauna Kea, ESO, and other interested parties to hammer out workable solutions (i.e. stealth coatings or flat black/non-reflective coatings on satellites, a central “space control” facility to plot orbits that won’t conflict with others, perhaps trimming the number of satellites needed for full coverage, etc.).  As humanity expands out into space how this issue is handled could well set the precedent for future expansions of space activity, so it’s vital we get this one right.

[eeergo]

And otherwise some proper software-guided masking technology can blot them out.

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

Have you looked at the simulation by a professional I posted a while back? Here it is for reference https://forum.nasaspaceflight.com/index.php?topic=48302.msg2006942#msg2006942 (by the way, it just takes into account visible light, impacts to radio will compound on top of those)

"Astronomers" don't own the sky, in spite of being a more diverse and numerous group than Mr Musk or his *private* corporation, or his competition accolites. Nor should any of those, or other groups, own it because it's universal public heritage.

It doesn't mean it has to be kept pristine, but I'd say there's a difference between a guy using a fishing rod and crab cages to sell in his town market, and a huge Japanese whaler with drag nets to pass the time while a whale appears - if you allow me the sea-faring metaphor. The first isn't the problem here. The second is, especially when it incentivizes other such ships and mostly unnecessary prestige-driven whale meat consumption. Should there be famine maybe they'd be a good option - in times of abundance it's just mindless destruction. Replace hunger with need for data and less impactful alternatives for delivering it.

[su27k]

I would hope that a “grand meeting” can be arranged between Elon Musk, OneWeb, NRAO, Mauna Kea, ESO, and other interested parties to hammer out workable solutions (i.e. stealth coatings or flat black/non-reflective coatings on satellites, a central “space control” facility to plot orbits that won’t conflict with others, perhaps trimming the number of satellites needed for full coverage, etc.).  As humanity expands out into space how this issue is handled could well set the precedent for future expansions of space activity, so it’s vital we get this one right.

Again, SpaceX is already doing this, there're monthly meetings between SpaceX and astronomers discussing this issue per https://www.nytimes.com/2019/11/11/science/spacex-starlink-satellites.html

Since May, the American Astronomical Society has convened an ad hoc committee with Dr. Lowenthal and other experts to discuss their concerns with SpaceX representatives once a month.

And they're planning to paint the bottom of Starlink satellite black: https://www.nature.com/articles/d41586-019-03446-y

SpaceX says that it is “taking steps to make the base of Starlink satellites black to help mitigate impacts on the astronomy community”, but did not say whether the upcoming launch will involve darkened Starlinks. The company also told Nature that it is sharing information on the position of its satellites in the US military catalogue, and talking with astronomy groups around the world to assess the effects and evaluate mitigation strategies.

So everything you suggested is already being done by SpaceX, they're being very responsive in this matter, despite anti-Musk fanatics' attempt to paint him as some sort of greedy capitalist.

[Bubbinski]

Again, SpaceX is already doing this, there're monthly meetings between SpaceX and astronomers discussing this issue per https://www.nytimes.com/2019/11/11/science/spacex-starlink-satellites.html

Since May, the American Astronomical Society has convened an ad hoc committee with Dr. Lowenthal and other experts to discuss their concerns with SpaceX representatives once a month.

And they're planning to paint the bottom of Starlink satellite black: https://www.nature.com/articles/d41586-019-03446-y

SpaceX says that it is “taking steps to make the base of Starlink satellites black to help mitigate impacts on the astronomy community”, but did not say whether the upcoming launch will involve darkened Starlinks. The company also told Nature that it is sharing information on the position of its satellites in the US military catalogue, and talking with astronomy groups around the world to assess the effects and evaluate mitigation strategies.

So everything you suggested is already being done by SpaceX, they're being very responsive in this matter, despite anti-Musk fanatics' attempt to paint him as some sort of greedy capitalist.

That’s very good news, I’m glad SpaceX is doing these things. Let’s hope other mega constellation providers follow suit. I believe they will, because they will need to in order to be a “good neighbor”.

[eeergo]

Again, SpaceX is already doing this, there're monthly meetings between SpaceX and astronomers discussing this issue per https://www.nytimes.com/2019/11/11/science/spacex-starlink-satellites.html

Since May, the American Astronomical Society has convened an ad hoc committee with Dr. Lowenthal and other experts to discuss their concerns with SpaceX representatives once a month.

That's good. Are all companies planning to deploy large constellations going, or indeed required, to do the same? Would it be mandatory to work out plans for sky light pollution mitigation that are not in their best economic interest, or just not of negligible impact for them, should it be required (decided by whom)? In other words: should we just accept they'll be good? Telecoms don't have such a good track record...

That's the issue, not *just* Starlink, although it IS the farthest-advanced constellation out there, so it is, and will be, setting precedents and implicitly establishing what is acceptable, how much they can stretch limits, where regulations can be modeled in their favor. Now it's the time to think things through - not when pulling one's hair out is the only thing left to do: when there'll be a multi-billion dollar infrastructure in place, upon which millions might rely, is obviously not the time to be "responsive".

And they're planning to paint the bottom of Starlink satellite black: https://www.nature.com/articles/d41586-019-03446-y

SpaceX says that it is “taking steps to make the base of Starlink satellites black to help mitigate impacts on the astronomy community”, but did not say whether the upcoming launch will involve darkened Starlinks. The company also told Nature that it is sharing information on the position of its satellites in the US military catalogue, and talking with astronomy groups around the world to assess the effects and evaluate mitigation strategies.

Will that help? Just painting a flat surface black is not going to change that much their specular reflectivity, as any flat tinted window will show you on a sunny day.

So everything you suggested is already being done by SpaceX, they're being very responsive in this matter, despite anti-Musk fanatics' attempt to paint him as some sort of greedy capitalist.

So far their effective mitigation measures wrt the one hundred and twenty real hardware units currently in space are zero. In fact, the bottom of their birds now is mostly painted white or is reflective.

No comment to your "Musk's under attack again" unwarranted trigger, except to note you'll agree with me he can certainly be described as a capitalist (not sure that's a bad thing, and indeed it's difficult to be a billionare nowadays otherwise), and an ambitious one at that. Probably a tad more than the astronomy community. The boundary between greed and ambition is fuzzy and subject to interpretation, but can be better gleaned in situations such as the one under discussion.

[edzieba]

We've seen lots of dramatic photos of the 'trains' of satellites during orbit-raising and seperation where they are actively orienting to keep their panels as insolated as possible to power the ion thrusters.

How much of a visual impact are the first-launch Starlinks now having after having assumed their final orbits? While they will be less frequently passing once a full Starlink deployment is complete, do existing satellites in similar orbits (e.g. Iridium and Orbcomm) already have to be taken into account during observation time?

[woods170]

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

A perfect example of why astronomers detest a lot of space advocates ... this "suck it up" attitude is hardly helpful.

Astronomers should also realize that without spaceflight and satellites several fields of astronomy would not nearly be as far along as they are today. Particularly visible (Hubble!) infrared, X-ray, ultraviolet.

Which reminds me of a little incident which took place at the University of Groningen (the Netherlands) in 1983. A resident visible light astronomer discovered that one of his long-exposures had a satellite streak going over it from south to north. He discussed his dismay with some of his fellow astronomers at the university. When one of his colleagues discovered that the streak was caused by IRAS (InfraRed Astronomical Satellite) the dismayed astronomer immediately refrained from any further complaints.
You see, some of his fellow astronomers had worked on DAX, one of the two main instruments on IRAS.

Hubble has shown up in ground-based long exposures. So has (in the past) Compton and other astronomy satellites. Why is that I don't hear the astronomers complaining about THAT?
Hypocrisy?

[eeergo]

Astronomers do not own the heavens. They will have to learn to deal with a new reality.

A perfect example of why astronomers detest a lot of space advocates ... this "suck it up" attitude is hardly helpful.

Astronomers should also realize that without spaceflight and satellites several fields of astronomy would not nearly be as far along as they are today. Particularly visible (Hubble!) infrared, X-ray, ultraviolet.

Which reminds me of a little incident which took place at the University of Groningen (the Netherlands) in 1983. A resident visible light astronomer discovered that one of his long-exposures had a satellite streak going over it from south to north. He discussed his dismay with some of his fellow astronomers at the university. When one of his colleagues discovered that the streak was caused by IRAS (InfraRed Astronomical Satellite) the dismayed astronomer immediately refrained from any further complaints.
You see, some of his fellow astronomers had worked on DAX, one of the two main instruments on IRAS.

Hubble has shown up in ground-based long exposures. So has (in the past) Compton and other astronomy satellites. Why is that I don't hear the astronomers complaining about THAT?
Hypocrisy?

That answer is just willful anumerism - what's the relative impact of each?

As I explained a few replies back and you chose to ignore (boring), the issue here is whose plans call for a massive deterioration of natural heritage, furthermore for private profit reasons and moreover setting jurisprudence for other such actors - not a handful of unique, non-profit scientific instruments.