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According to a comment by user @J:

With that said, other than aesthetics, machine vision algorithms are wildly more advanced today than in the past - strategies to remove passing satellites don't really seem to be anything other than trivial. It's annoying because it requires land based observatories to correct for the new noise, but it doesn't seem anything fundamentally more disruptive than that - a mild annoyance.

Is it true that machine learning (and other) algorithms are so good these days that you can automatically eliminate the impact of any satellites passing overhead? Perhaps not the ideal solution for a casual astronomer but perhaps easy to do for a professional observatory?

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    $\begingroup$ I'll add that the context of that comment was strictly about UV-VIS-NIR imaging. The radio pollution created by Starlink is a different matter altogether and I think it's worth stating that I was not trivializing that problem (ie; Starlink RF frying high-gain ground based receivers, etc). That's a more serious problem. $\endgroup$
    – J...
    Commented Apr 20, 2021 at 20:22
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    $\begingroup$ @J's comment suggests a profound misunderstanding of the purpose of obtaining astronomical data, which is to obtain data we do not already know, not to make pretty pictures that casual non-scientists think look fine. $\endgroup$
    – Peter Erwin
    Commented Apr 20, 2021 at 20:32
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    $\begingroup$ @PeterErwin care to expand this into an answer? $\endgroup$
    – JonathanReez
    Commented Apr 20, 2021 at 20:43
  • $\begingroup$ Great question! These are different but related: How do observational astronomers manage streaks and other artifacts from objects in Earth Orbit? and Do large telescopes, especially plans for the LSST, avoid saturation artifacts from the brightest stars and planets? If so, how? $\endgroup$
    – uhoh
    Commented Apr 21, 2021 at 0:58
  • $\begingroup$ @PeterErwin Whether or not the data captured is in the visual part of the electromagnetic spectrum isn't all that relevant per se though, is it? Noise filtering algorithms don't have any wavelength-specific restrictions AFAIK. What does seem relevant though, is the durations of the astronomic events being measured VS satellite traversal time; but yeah, an answer with a specific example of such an issue would be quite welcome I think. $\endgroup$
    – Will
    Commented Apr 21, 2021 at 10:05

2 Answers 2

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No, automated algorithms won't ever be able to completely eliminate the effect of passing satellites.

  1. Some of the light reflected from the satellites into the atmosphere will then scatter and cause some amount of light pollution. The pollution isn't limited to just in the direction of observing. See: https://photo.stackexchange.com/questions/41722/can-you-photograph-the-milky-way-with-a-full-moon-out.

  2. Whenever automated algorithms remove the presence of satellites from images, some of the underlying data will be removed as well.

  3. As the number of satellites increases, eventually it will render some data for stellar occultation light curves unusable as the occultations from satellites coincide with the occultations from asteroids. See: Is 486958 Arrokoth (2014 MU69 aka Ultima Thule) the only solar-system object determined to be binary by occultation?. This particular effect will occur even if the satellites have zero reflectivity.

Elon Musk says:

I am confident that we will not cause any impact whatsoever in astronomical discoveries, zero [...] That's my prediction, we will take corrective action if it's above zero.

But he is confident in an impossibility. We can minimize the effect by reducing satellite reflectivity, but we can't make the effect zero, even with advanced algorithms.

Note: The above list is not meant to be comprehensive.

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  • $\begingroup$ we will take corrective action if it's above zero I wonder what Elon had in mind and I'm curious if SpaceX would, or could, ever accommodate "making space" for specific observations. As in, having the swarm make minor orbital adjustments to stay clear of some area of sky within whatever solid angle is under observation. I think this could probably be done up to some limit depending on how much RCS fuel the satellites have for their 4-year life. $\endgroup$
    – J...
    Commented Apr 21, 2021 at 23:20
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    $\begingroup$ @J... Re: what Elon has in mind, my money would be on either him no caring, or something in the line of "once I get us on Mars we'll have even better skies for your telescopes" $\endgroup$
    – Luris
    Commented Apr 22, 2021 at 12:37
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    $\begingroup$ @Luris which is of course true in the long run. If we manage to build a lunar/Mars colony (which is a major step towards colonizing space, which is in turn the end goal of human civilization), space observations will be a no-brainer. $\endgroup$
    – JonathanReez
    Commented Apr 22, 2021 at 17:30
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No, you can't perfectly subtract out satellite trails from images. The root problem is that astronomical cameras are essentially photon counters. Any time you are counting, you are limited by Poisson statistics. So, even if you have a fantastic model that says a Starlink satellite will deposit 10,000 photons in a pixel, Poisson statistics say the actual number of photons from the satellite will be 10,000 plus or minus 100. You can subtract off that 10,000 signal, but the 100 noise remains.

This is also why we can't use telescopes during the day. You could make a model of how bright you think the daytime sky should be and subtract it off. But the Poisson noise from all those photons remains.

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