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Thread: Starlink Interference

  1. #1
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    Starlink Interference

    How much interference does the starlink satellite system pose to ground based observations? Not necessary only starlink but any satellite. Seems like it's similar to a bug on the windshield. If you focus on the bug that's all you see. But if your focusing in the distance you don't see the bug. Does making them non-reflective reduce photo streaking?
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    Quote Originally Posted by DaCaptain View Post
    How much interference does the starlink satellite system pose to ground based observations? Not necessary only starlink but any satellite. Seems like it's similar to a bug on the windshield. If you focus on the bug that's all you see. But if your focusing in the distance you don't see the bug. Does making them non-reflective reduce photo streaking?
    From what I understand, it does not in fact work that way at all. The problem is that even with some of the mitigations in place and the final orbits being acheived, many of the satellites have been very much interfereing in scientific (not just aesthetic) images of the sky. One issue is that many instruments work outside the wavelengths of light the mitigations and design were done for. Another is that there's a natural variability in the actual reflections vs. the idealized modeling done prior to launch and orbit finalizations. And (and) there was always gonig to be some places at some times of the year that no mitigation was going to do much to remove the satelitte interference. As I further understand it (from the scientists and engineers I follow around social media), there are ongoing discussions with SpaceX on what to do with future satellites. Thankfully, the satellites have a somewhat limited lifespan before reentering and being replaced by new ones, so if a solution can be found to mollify all the stakeholders, it'll come before too long. Unfortunately, I have also seen some proposed changes to operational orbits that are likely to increase their brightness when visibile, and I am not sure how much traction various mitigating coatings and designs are getting vs. getting the consetallation operational and generating revenue.

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  3. #3
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    Quote Originally Posted by DaCaptain View Post
    How much interference does the starlink satellite system pose to ground based observations? Not necessary only starlink but any satellite. Seems like it's similar to a bug on the windshield. If you focus on the bug that's all you see. But if your focusing in the distance you don't see the bug. Does making them non-reflective reduce photo streaking?
    The satellites are far enough away that there is essentially no difference in focus, there are no telescopes large enough to "see around them" as you suggest. Which is a good thing, because they are far brighter when in sunlight than typical observation targets...if they were blurred, they'd make a fat smudge across the image instead of a trail a couple pixels wide. Thin trails can be detected and deleted, fat smears would wipe out much more data.

    The effect of the satellites has been wildly exaggerated. The satellites are only visible near dawn and dusk, when a telescope can see them while they're still outside Earth's shadow. Because of their low orbits, the vast majority of them will be below the horizon at any time, and most of what's visible will be low in the sky, barely above the horizon...a bad location to be doing astronomy anyway, especially near dawn/dusk in the direction of the sun. They are primarily a problem for telescopes doing wide angle, long-exposure observations near the horizon, mainly the LSST, and in their own words:

    A very conservative upper limit on the number of LSST pixels affected by Starlink satellites is about 0.01%, and quite likely significantly smaller. Therefore, for LSST, Starlink satellites will be a nuisance rather than a real problem.

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    Quote Originally Posted by cjameshuff View Post
    The satellites are far enough away that there is essentially no difference in focus, there are no telescopes large enough to "see around them" as you suggest. Which is a good thing, because they are far brighter when in sunlight than typical observation targets...if they were blurred, they'd make a fat smudge across the image instead of a trail a couple pixels wide. Thin trails can be detected and deleted, fat smears would wipe out much more data.

    The effect of the satellites has been wildly exaggerated. The satellites are only visible near dawn and dusk, when a telescope can see them while they're still outside Earth's shadow. Because of their low orbits, the vast majority of them will be below the horizon at any time, and most of what's visible will be low in the sky, barely above the horizon...a bad location to be doing astronomy anyway, especially near dawn/dusk in the direction of the sun. They are primarily a problem for telescopes doing wide angle, long-exposure observations near the horizon, mainly the LSST, and in their own words:
    It's funny how depending on one's circle of information, the interpretation differs. I'll have a look through my contacts again and see what people think, more up-to-the-minute. The last few comments I saw on Twitter, for example, by professional astronomers (or academics/research I guess) were not favorable - though not catastrophic.

    CJSF
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  5. #5
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    Just an example, here is a night sky picture from the Cerro Tololo Inter-American Observatory in Chile including StarLink

    https://www.faz.net/aktuell/wissen/w...-16674105.html
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    Quote Originally Posted by tusenfem View Post
    Just an example, here is a night sky picture from the Cerro Tololo Inter-American Observatory in Chile including StarLink

    https://www.faz.net/aktuell/wissen/w...-16674105.html
    That's a Starlink post-launch "train". This is not typical of how they will appear in their operational orbits, they are closely packed, at lower altitude and thus brighter, and in a different orientation than they would have in operation, but for some reason people using this image as an example of Starlink's impact rarely mention these facts...

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    I still like the idea of the Orbital Antenna Farm where you have a few really large sats as opposed to lots of little ones.

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    Quote Originally Posted by publiusr View Post
    I still like the idea of the Orbital Antenna Farm where you have a few really large sats as opposed to lots of little ones.
    Covering Earth with a small number of satellites requires the satellites to be in high orbit, with high latency, low link budgets, and very limited system capacity. That's what we have now for satellite internet, and it's awful.

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    Quote Originally Posted by cjameshuff View Post
    Covering Earth with a small number of satellites requires the satellites to be in high orbit, with high latency, low link budgets, and very limited system capacity. That's what we have now for satellite internet, and it's awful.
    With the thousands of them that are planned, they will need to make replacement launches often. If anything happens to collide with just one of them, it could cause a chain reaction that we may not be able to recover a safe launch window for a long time. Our plentiful meteor showers comes to mind as a significant threat.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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    Quote Originally Posted by DaCaptain View Post
    With the thousands of them that are planned, they will need to make replacement launches often. If anything happens to collide with just one of them, it could cause a chain reaction that we may not be able to recover a safe launch window for a long time. Our plentiful meteor showers comes to mind as a significant threat.
    Do you have a source for that? It sounds like an argument based on that scene from Wall-E. SpaceX has gotten their deployment plan approved which includes risk management of debris and collision and all their satellites are orbiting very low (they are abandoning their 1000+ km shells) and and both broken satellites and any debris should de-orbit fast.

  11. #11
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    Quote Originally Posted by glappkaeft View Post
    Do you have a source for that? It sounds like an argument based on that scene from Wall-E. SpaceX has gotten their deployment plan approved which includes risk management of debris and collision and all their satellites are orbiting very low (they are abandoning their 1000+ km shells) and and both broken satellites and any debris should de-orbit fast.
    No sources, just a thought. Have never seen Wall-E.
    I know that I know nothing, so I question everything. - Socrates/Descartes

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