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Starlink, Amazon, One Web - Ruining the sky?

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#1 Trackerthedog

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Posted 26 February 2020 - 02:02 PM

Can anyone give me a helpful answer about the concerns surrounding Musk's Starlink satellites - as well as Amazon's (and others') intended launches. There are currently 8,000 satellites in orbit and these additional launches are supposed to raise that figure to 40,000 (with Space X) ... and eventually 120,000. ... Apparently professional astronomers don't think that Musk is taking their concerns seriously - at least that is what a recent article from Forbes implied. https://www.forbes.c...cA#ffda88f6a577 . . . . Since I have invested a lot of money in an observatory and in astrophotography equipment - and I want to open the observatory to the public (especially school children and teachers) for free, I would be very, very appreciative of any comments and information that you can share. Thank you for any comments and information that you can share here.


Edited by Trackerthedog, 26 February 2020 - 05:31 PM.

 

#2 Cali

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Posted 26 February 2020 - 02:08 PM

There are a few threads regarding this in the Light Pollution forum.

 

- Cal


 

#3 aa6ww

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Posted 26 February 2020 - 02:23 PM

From what I've read, the only time the Starlink satellites will be visible in the dark skies are when they are first deployed off the rockets which put them into orbit.

Once they are on their set orbits, they will only be visible for a very short period of time before sunrise or just before sunset. This is because of the low orbit they will be on, and during those times, the steep angle of the suns light could reflect off the satellites at that time. Also, I read that these satellites are now painted flat black to made it even harder for sunlight to reflect off of these.

Based on that information, this shouldn't effect astronomers at all since the skies aren't dark at those times.

Its a good subject to talk about however, and cause panic to some. Fortunately, Spring time is almost here, though it does feel like its here already, so hopefully, astronomers will be spending more time observing and less time in these forums creating fake new.

...Ralph
 

#4 bobzeq25

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Posted 26 February 2020 - 02:27 PM

Light pollution and its increase is still more of an issue.  The satellites are common targets, but less important.  Now.


 

#5 TMO

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Posted 26 February 2020 - 02:28 PM

To recap, within the next few years, over 30,000 satellites will be launched, almost all in Low Earth Orbit (LEO), a few hundred kilometers above the Earth's surface.  They move roughly 1 degree per sec across the sky (as seen from the ground), and most will be fainter than 6th mag (once they arrive in their final orbit).  Within the decade, there will be roughly 1 satellite per square degree.

 

Statement from the American Astronomical Society:

https://aas.org/post...based-observing

 

Forbes article is accurate:

https://www.forbes.c...zc#44dec5eb287e

 

These LEO satellites will be mostly invisible to the naked eye, but they are easily visible in the eyepiece of any amateur telescope (and binoculars) and worse they will contaminate long exposures in astrophotography.  These satellites shine by reflected light from the Sun.  So, they are visible primarily for about 1.5 hours after sunset and 1.5 hours before sunrise.  Otherwise, they are dark in the Earth's shadow.

For astrophotography, this tsunami of satellites will force us to avoid imaging within 1.5 hours of sunset or sunrise. With an eyepiece, we will occasionally see a white streak flash though the field of view, within 1.5 hours of sunset.


 

#6 ngc7319_20

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Posted 26 February 2020 - 02:33 PM

 So, they are visible primarily for about 1.5 hours after sunset and 1.5 hours before sunrise.  Otherwise, they are dark in the Earth's shadow.

For astrophotography, this tsunami of satellites will force us to avoid imaging within 1.5 hours of sunset or sunrise. With an eyepiece, we will occasionally see a white streak flash though the field of view, within 1.5 hours of sunset.

Given that astronomical twilight is about 1.5 hours after sunset / 1.5 hours before sunrise... I'm not sure this is such a big deal.


Edited by ngc7319_20, 26 February 2020 - 02:35 PM.

 

#7 Astrojensen

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Posted 26 February 2020 - 02:38 PM

To recap, within the next few years, over 30,000 satellites will be launched, almost all in Low Earth Orbit (LEO), a few hundred kilometers above the Earth's surface.  They move roughly 1 degree per sec across the sky (as seen from the ground), and most will be fainter than 6th mag (once they arrive in their final orbit).  Within the decade, there will be roughly 1 satellite per square degree.

 

Statement from the American Astronomical Society:

https://aas.org/post...based-observing

 

Forbes article is accurate:

https://www.forbes.c...zc#44dec5eb287e

 

These LEO satellites will be mostly invisible to the naked eye, but they are easily visible in the eyepiece of any amateur telescope (and binoculars) and worse they will contaminate long exposures in astrophotography.  These satellites shine by reflected light from the Sun.  So, they are visible primarily for about 1.5 hours after sunset and 1.5 hours before sunrise.  Otherwise, they are dark in the Earth's shadow.

For astrophotography, this tsunami of satellites will force us to avoid imaging within 1.5 hours of sunset or sunrise. With an eyepiece, we will occasionally see a white streak flash though the field of view, within 1.5 hours of sunset.

 

Given that astronomical twilight is 1.5 hours after sunset / 1.5 hours before sunrise... I'm not sure this is such a big deal.

From some parts of the Earth, this means that deep-sky astrophotography will be impossible for a quarter of the year, or longer. Here at 55°N, the Sun never sinks below 18° under the horizon from May 5th to August 6th. During this period, twilight lasts all night.

 

 

Clear skies!
Thomas, Denmark 


 

#8 Astrojensen

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Posted 26 February 2020 - 03:11 PM

Just did a back-of-the-envelope calculation (please correct me, if I'm wrong, my trigonometry is a little rusty) and it seems to me, that if we want the whole sky to be COMPLETELY free from any illuminated satellites in a LEO as high as 550km, then the Sun needs to be more than 46° below the horizon. If we are satisfied with just the southern horizon free, then 23° below the horizon is sufficient. 

 

18° doesn't cut it at all. Large swaths of the sky, including the zenith, will become unusable for deep-sky imaging for common amateurs in the evening hours. 

 

 

Clear skies!
Thomas, Denmark


Edited by Astrojensen, 26 February 2020 - 03:14 PM.

 

#9 dcollier

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Posted 26 February 2020 - 03:28 PM

They seem to be showing up in more and more of my subs.  So far, I have been able to process them out. But, it is a trend and is growing rapidly.  As far as I can tell there is no one with a balanced point of view on this is in a decision making capacity.   FCC is the one that grants licences in the US and they are in the business of promoting/developing communication infrastructure.  I think it is a problem.  It is an area in need of International regulation. Given the current political climate, what do you think are the chances of that happening? 

 

                   -Dave 


 

#10 Astrojensen

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Posted 26 February 2020 - 03:57 PM

 

It is an area in need of International regulation. Given the current political climate, what do you think are the chances of that happening?

None whatsoever.  

 

 

Clear skies!
Thomas, Denmark 


 

#11 OldManSky

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Posted 26 February 2020 - 04:00 PM

18° doesn't cut it at all. Large swaths of the sky, including the zenith, will become unusable for deep-sky imaging for common amateurs in the evening hours. 

 

Possibly, except that satellites occasionally passing through the FOV of a deep-sky imaging target doesn't mean "unusable for deep-sky imaging."  Stacking methods easily remove satellite trails from subs.

For example, I recently did about 6 hours of exposure on M42 (and surrounding area) through a variety of filters.  Just about 1 of every 5 images had satellite trails (mostly from geo-sync sats, not Starlinks) in it.  I threw none of them out, included them all in the stacks -- and none of the stacks show any sign of them.

 

So while increased satellite trails in images are annoying, and for professional astronomical research potentially more damaging, for amateur deep-sky astrophotography it's certainly not anything close to "unusable."


 

#12 chubster4

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Posted 26 February 2020 - 04:32 PM

Sorry to get off topic, but speaking of ruining the sky…what really scares me is something mentioned in the news a few times over the past several years – the proposed use of space-based advertising – basically huge billboards in space. Since some foreign entities are among those who seem to think this is a good idea, an even better idea might be an international treaty prohibiting it.

I can live with Starlink satellites if they're only visible around twilight, but the 'golden arches' lighting up an otherwise moonless sky? No way.
  https://www.nbcnews....idea-ncna960296


 

#13 ngc7319_20

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Posted 26 February 2020 - 04:52 PM

Just did a back-of-the-envelope calculation (please correct me, if I'm wrong, my trigonometry is a little rusty) and it seems to me, that if we want the whole sky to be COMPLETELY free from any illuminated satellites in a LEO as high as 550km, then the Sun needs to be more than 46° below the horizon. If we are satisfied with just the southern horizon free, then 23° below the horizon is sufficient. 

Not quite sure where you are getting the 46 degrees below the horizon for the sun.  I'm getting 23 degrees for objects at the zenith and 550km altitude. 

 

I agree that for people at high latitudes, in the summer you will be seeing these things all night long -- but then there is not really any "night" anyway.  Twilight is a dark as it gets in the summer.

 

I think even now the sky is not "completely free" of illuminated satellites.  There are plenty at geosynchronous. I think "completely free" is an overly restrictive standard. 

 

Another point is that there are only a few visible at any one time for any location on earth.  Its not like there will be 20,000 above your horizon.

 

So I'm not ready to sell the scopes just yet over Starlink....

 

Theres lots you can do to eliminate moving and transient objects from images -- more sub-frames, better artifact rejection, etc.


 

#14 dhkaiser

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Posted 26 February 2020 - 05:08 PM

No one seems to consider the impact on the science of astronomy.  Radar, radio, large land based and space based telescopes will be far more impacted than amateur astrophotography.


 

#15 bobzeq25

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Posted 26 February 2020 - 05:26 PM

They seem to be showing up in more and more of my subs.  So far, I have been able to process them out. But, it is a trend and is growing rapidly.  As far as I can tell there is no one with a balanced point of view on this is in a decision making capacity.   FCC is the one that grants licences in the US and they are in the business of promoting/developing communication infrastructure.  I think it is a problem.  It is an area in need of International regulation. Given the current political climate, what do you think are the chances of that happening? 

 

                   -Dave 

Less than zero.


 

#16 Astrojensen

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Posted 27 February 2020 - 10:48 AM

Not quite sure where you are getting the 46 degrees below the horizon for the sun.  I'm getting 23 degrees for objects at the zenith and 550km altitude. 

 

I agree that for people at high latitudes, in the summer you will be seeing these things all night long -- but then there is not really any "night" anyway.  Twilight is a dark as it gets in the summer.

 

I think even now the sky is not "completely free" of illuminated satellites.  There are plenty at geosynchronous. I think "completely free" is an overly restrictive standard. 

 

Another point is that there are only a few visible at any one time for any location on earth.  Its not like there will be 20,000 above your horizon.

 

So I'm not ready to sell the scopes just yet over Starlink....

 

Theres lots you can do to eliminate moving and transient objects from images -- more sub-frames, better artifact rejection, etc.

The Sun needs to be 46° below the horizon, if the WHOLE sky needs to be free from illuminated satellites in a 550km LEO. If the Sun is 23° below the horizon, you can still see satellites in this orbit from the zenith and down to the horizon in the direction of the Sun. 

 

We may not get more than twilight here in summer, but some imagers are still trying to grab what little they can for an hour or so around midnight, perhaps using narrowband filters to darken the sky. 

 

The satellites in geosynchronous orbits are MUCH fainter than the Starlink satellites are going to be. 

 

And there is a great difference between having a faint-ish satelitte crossing your imaging field once in a while, and having a fairly bright one cross the field every few seconds. I know we won't be able to see ALL of them at the same time, or even half of them, but a rough estimate tells me that, if they all have an altitude of 550km (I know they won't, but I don't know how many there will be at any given altitude), around 4% of them will be visible at any given location at any given time. This means that there will be a staggering 1,600+ satellites above the horizon at the same time, all the time. Fewer, of course, if many of them have lower altitude orbits.   

 

 

Clear skies!
Thomas, Denmark


 

#17 ngc7319_20

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Posted 27 February 2020 - 11:30 AM

The Sun needs to be 46° below the horizon, if the WHOLE sky needs to be free from illuminated satellites in a 550km LEO. 

...

This means that there will be a staggering 1,600+ satellites above the horizon at the same time, all the time. Fewer, of course, if many of them have lower altitude orbits.   

Yes, I agree the situation seems dire if you require the sky to be "completely free" of satellites, the "whole" sky, and down to the "horizon".  But I think it is not so terrible if you consider the area within say 20 or 30 degrees of the zenith.  I guess that is where I do most of my observing anyway -- since there is less haze, light pollution from street lights, etc.  To see other areas of the sky, maybe one needs to wait a few hours or months, or get on an airplane to change the latitude.


 

#18 SteveGR

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Posted 27 February 2020 - 04:44 PM

Can anyone give me a helpful answer about the concerns surrounding Musk's Starlink satellites - as well as Amazon's (and others') intended launches. There are currently 8,000 satellites in orbit and these additional launches are supposed to raise that figure to 40,000 (with Space X) ... and eventually 120,000. ... Apparently professional astronomers don't think that Musk is taking their concerns seriously - at least that is what a recent article from Forbes implied. https://www.forbes.c...cA#ffda88f6a577 . . . . Since I have invested a lot of money in an observatory and in astrophotography equipment - and I want to open the observatory to the public (especially school children and teachers) for free, I would be very, very appreciative of any comments and information that you can share. Thank you for any comments and information that you can share here.

I recently heard a talk by the president of the AAS and they are talking with Musk, and he seemed somewhat sympathetic... once he had the situation explained to him.  His early solution of "just put telescopes in orbit" isn't exactly practical, his views may be evolving now.  But it ultimately won't matter that much, even if they reduce the reflectivity, they won't be able to do so completely.  That business is in motion, and they aren't going to stop it. 

 

It is going to play hell with the Large Synoptic Survey, especially since there is some persistence for a period of time in the sensors after the satellite over-saturates it.

 

There is another issue for our radio astronomer friends.  It won't be good for them either.  It is also a question of whether the satellites will even operate in the spectrum they are supposed to, the Iridium satellites don't.

 

On a tangent, anyone want to start a pool on when Kessler Sydrome starts?


Edited by SteveGR, 27 February 2020 - 04:47 PM.

 

#19 Trackerthedog

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Posted 27 February 2020 - 05:38 PM

Thank you all for your feedback and opinions (and facts). ... I find it very sad that many people I have spoken with about Musk's plans don't seem to give a crap. They would much rather look down at their phones (with faster internet speed) than up at the magnificent night skies. ... Too many people have never experienced the joy of staring up at the stars from a dark sky site or of looking through a high quality telescope - even in a city. ... Thank you again for the comments and discussion.

 

Cheers.


 

#20 jfgout

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Posted 27 February 2020 - 06:08 PM

To recap, within the next few years, over 30,000 satellites will be launched, almost all in Low Earth Orbit (LEO), a few hundred kilometers above the Earth's surface.  They move roughly 1 degree per sec across the sky (as seen from the ground), and most will be fainter than 6th mag (once they arrive in their final orbit).  Within the decade, there will be roughly 1 satellite per square degree.

 

Statement from the American Astronomical Society:

https://aas.org/post...based-observing

 

Forbes article is accurate:

https://www.forbes.c...zc#44dec5eb287e

 

These LEO satellites will be mostly invisible to the naked eye, but they are easily visible in the eyepiece of any amateur telescope (and binoculars) and worse they will contaminate long exposures in astrophotography.  These satellites shine by reflected light from the Sun.  So, they are visible primarily for about 1.5 hours after sunset and 1.5 hours before sunrise.  Otherwise, they are dark in the Earth's shadow.

For astrophotography, this tsunami of satellites will force us to avoid imaging within 1.5 hours of sunset or sunrise. With an eyepiece, we will occasionally see a white streak flash though the field of view, within 1.5 hours of sunset.

French astronomer Nicolas Bivier reports magnitude ~2.5 for Starlink satellites that have already reached the 550 km altitude (including the "darksat" which was supposed to be darker but if anything is actually even brighter than the other ones). If they keep launching satellites at this  pace, sitting on the porch to look at the stars after sunset will become an activity from the past...

 

jf


 

#21 ngc7319_20

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Posted 27 February 2020 - 07:16 PM

French astronomer Nicolas Bivier reports magnitude ~2.5 for Starlink satellites that have already reached the 550 km altitude (including the "darksat" which was supposed to be darker but if anything is actually even brighter than the other ones). If they keep launching satellites at this  pace, sitting on the porch to look at the stars after sunset will become an activity from the past...

 

Can you provide a reference for this magnitude number?  It is interesting...


 

#22 Tom K

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Posted 28 February 2020 - 12:48 AM

With modern CMOS cameras in anything but Bortle 1 or 2 skies, the most efficient subs are quite short and therefore numerous to get enough signal for a decent image.   Even if you get trails in a good percentage of your subs, it is unlikely that they will be in the same exact track as the others, so some of the stacking routines should take them out of the image.   I live on the flight path for a regional airport and get planes all the time through subs and they calibrate out pretty well.


 

#23 rimcrazy

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Posted 28 February 2020 - 12:31 PM

Per a recent article in Science Magazine, 

 

"The Rubin Observatory, with an 8.4-meter mirror that will take pictures of the sky the size of 40 full Moons in 30-second exposures, “is the perfect machine for running into these satellites,” Tyson says.

He and his team conducted simulations that suggested the track of a satellite image across their camera would saturate each camera pixel as it passes, and cause leak- age into neighboring ones. The resulting artifacts “cannot be removed in software. We have failed in doing that,” Tyson says. The team looked at altering schedules to avoid satellite trails, but with such a wide field of view, avoiding thousands of satel- lites would end up as “a wild goose chase,” he says.
So Tyson is pinning his hopes on SpaceX darkening its future satellites. He and his team speak several times a week with en- gineers at SpaceX, which launched one darkened satellite in January that is just now reaching its final orbit. Tyson’s team calculated that if the company can reduce reflections by a factor of 15, the issue will be manageable. Images would still contain trails, but they wouldn’t saturate pixels and could be removed digitally. SpaceX and its chief, Elon Musk, are “totally committed to solving this problem,” Tyson says, and his team has worked with them to “narrow to a design that may work.” Several satel- lites with this updated dark design will be launched in coming weeks. SpaceX did not respond to requests for comment."   Science Magazine, 28 February 2020, Vol 367 Issue 6481

 

The reference to the individual Tyson is Tony Tyson, chief scientist of the Rubin Observatory.

 

So according to at least one source if the reflections can be reduced by a factor of at least 15 there may be software solutions to overcome the effects of the satellites.  Lets hope they can come to a solution that works.


 

#24 mccarthymark

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Posted 28 February 2020 - 01:28 PM

I hope they do find a solution to reduce the reflections.  But it would only be truly effective if SpaceX released the patent to the world -- so that all the companies and countries deploying LEO satellites can use it.  It won't be enough if it is "just" the SpaceX satellites which are dark.

 

Better yet, if they can find such a solution, it becomes international law (somehow) that all satellites have to use it. How to make that happen?


 

#25 dawziecat

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Posted 28 February 2020 - 01:33 PM

This is humanity insanity of a sort! That it is somehow even remotely controversial that launching a hundred thousand LEO satellites is not going to essentially wipe out amateur astrophotography is absurd! 

Yes, very much colour me in "the sky is falling" camp. IMO, no amount of digital hocus pocus in SW is going to be entirely successful in removing these things from DSO images of several minutes and longer! 

Kessler Syndrome? I don't know. Maybe a story for apocalyptic sci-fi . . . and maybe not. The author of this book sees it happening anyway and he could just be right. I do know the bean counters will not care a fig though. There's money to be made! They can smell it! And there's no one to stop them!

 

Like Jurassic Park, far too much emphasis on "can we" and not nearly enough on "should we?"

Who foresaw that reaching LEO would ever become so easy and so cheap that this would ever become a problem?


Edited by dawziecat, 28 February 2020 - 01:34 PM.

 


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