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How satellite ‘megaconstellations’ will photobomb astronomy images

nature.com

221–230 of 395 posts

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#221
post #163

Earlier quoted context omitted.

Sure. And for small field of view things that might be the future. But if you are looking at large chunks of the sky at some point with enough satellites the shutter will have to stay shut for the whole duration of the exposure.. so not really a good solution for that.

(can't reply below) If you had a localised shutter covering pattern X for 6 seconds, could you compensate for that by covering the inverse pattern of X for 6 seconds to get the same exposure for all pixels? So if you covered 3 satellite streaks of 6 seconds each using non-verlapping patterns (A,B,C) you could compensate for that by ending your exposure with covering the inverse of A+B+C for 6 seconds, adding only 6 s…

Herein lies the problem. Your proposed solutions are ever more complicated as you begin to grasp the magnitude of the issue. Implementing this idea, and I'm not saying that it's good enough, would require modifications to pretty much every major telescope in the world. And there's no economy of scale because most of them are custom builds. Who's gonna pay for that?

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#222
post #37

Living in a city, I didn't understand how big a deal this was until I got a view of the clear night sky in a less populated area recently. The satellites are already visible by eye everywhere, and there are only 655 Starlink satellites. There's approval for 12000, and SpaceX is seeking approval for 30000! If they're all going to be this reflective, satellites will be the main thing we see in the night sky a few years…

Starlink is only ever visible at dusk or dawn. It’s orbits are so low they are in the earths shadow for the rest of the night.

And new Starlink have visits limiting their reflectivity even during dusk and dawn.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#223
post #52

Earlier quoted context omitted.

I personally believe that pervasive high speed internet even in remote locations will do more for humanity than the scientific cost of these satellites. However, this conversation has basically been skipped over. Maybe you're right and I'm wrong. The constellations are being launched, and there's zero chance of shutting them down once they're serving a commercial role. Considering the abundant red tape in the modern…

> I personally believe that pervasive high speed internet even in remote locations will do more for humanity than the scientific cost of these satellites. I've had faster Internet than the average Starlink speedtest says, in rural Romania, at the foot of a mountain, wild bears and all: https://twitter.com/q3k/status/1172621386977861632 . Internet access in rural areas is pretty much a solved problem, it just now hing…

> Internet access in rural areas is pretty much a solved problem.

No it isn't. Just because it works for you it doesn't mean the same solutions can apply everywhere.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#224

Earlier quoted context omitted.

Sure, you'll be able to see the most recent launch, just as you can now. But you won't see 30,000 in the sky, which is what everyone assumes. Also note that you can't see them at all in the middle of the night; only for an hour or so around sunset and sunrise.

Isn't sunrise and sunset the prime time for people looking at the sky for aesthetic reasons?

People yes, who will enjoy seeing satellites.

Prime astronomy hours are when Starlink is in the earths shadow.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#225
post #86

Earlier quoted context omitted.

The final orbits are approved in advance by the government; there's no mystery. They are not visible to the naked eye in their final orbits because they are farther away and they maintain an orientation that allows their sunshade to reflect sunlight away from Earth instead of toward it.

There's actually a good primary source for this cited in the article [0], stating: "However, at low elevations near twilight at intermediate latitudes (45°–55°, e.g., much of Europe) hundreds of satellites may be visible at once to naked-eye observers at dark sites." This is referring to Starlink's 12000 satellite constellation, so thousands absolutely is the order of magnitude we're talking about when (if) they go t…

Only at dusk and dawn, and not when they have visors.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#226
post #207

Earlier quoted context omitted.

Space based observation of objects on potential collision course with Earth is far superior to earth observatio. For example you can't really observe anything coming from the direction of the sun. Look up NEOCam project that aims to have a near Earth asteroid telescope in solar orbit.

how many space-based telescopes are there? And how many will where be, once 9/10 launches fail?

> And how many will where be, once 9/10 launches fail?

This is not a real thing that will happen.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#227

The article covers the mitigations already in place and how they only partially resolve the issue. These satellites are low, bright (at dawn/dusk) and very soon to be incredibly numerous. Yes, it is possible for data workflows to post-process these streaks away, but not all configurations allow this, and whereas previous intrusions were somewhat rare and could be ignored that simply won't be the case due to three com…

As a counterpoint, I'll die on the opposite hill with, I suspect, the large majority of the public. And I say that as someone who has been a lifelong space enthusiast. Ubiquitous access to cheap internet has done more for humanity in the last 20 years by far than any contribution from ground-based astronomy. If the choice is between Starlink and more difficult ground-based astronomy, I'll choose Starlink.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#228

I'm not expressing a pro or con opinion here, but I'm curious. Did this same conversation happen when we started light polluting the city? Was this why observatories adapted by moving to darker locations? On the surface this seems a wee bit absurd, but I wonder if a case could be made that it's time for more space-based telescopes.

That is exactly what happened. It's clear even to the naked eye - people still freak out when power grids get knocked out at night. They see far more stars and think that's what caused the failure. To be more technical, the EM radiation signals that astronomers are interested in is very faint and barely above the background noise level. This is why they have to use large aperture and long exposure to essentially amplify the difference between signal and noise. They can resolve fainter signals (images) if the noise floor (light pollution) is less.

Compared to space telescopes, ground telescopes were limited by atmospheric interference. This has improved much lately with adaptive optics. Space telescopes are better, but it's too costly. You will never see a mega telescope constellation, because there is no money to be made. Ground telescopes still generate considerable valuable data (in scientific terms. corporates wouldn't care any less). Even individuals have ground telescopes that do this. Some projects like Sloan Digital Sky Survey (https://www.sdss.org/) puts massive amounts of data in the public domain. SDSS also does observations that are impossible with space telescopes.

Space telescopes are good, but are complementary to ground telescopes - not a replacement. When (some) people say that we should simply forget ground telescopes in favor of space telescopes, they are actually asking to throw away cheap, accessible, democratic, inclusive and sometimes unique way of astronomical observations in favour of an incredibly costly, elitist and closed methods which is viable only to big corps who have little interest in it because of lack of short term profits.

An aside, there are some people in this thread asking astronomers to stop complaining and just remove the streaks from the image. I would say that's incredibly philistine stance - science has long term benefits that is underrated compared to commercially motivated projects with perceived short-term social benefits. An approach suggested is to statistically remove the streaks from image. That's against the whole purpose of these observations - astronomers are interested in the details that cannot yet be statistically predicted. Another approach is to use multiple exposures and combine them. Again - the signals they are interested in often takes night long exposure before signal is sufficiently amplified above and noise. This can't be solved with multiple exposure. The third approach is to close the sensor (usually CCD) with a shutter when a satellite is in the vicinity. This is more viable. However, this is going to be hard and is going to waste a lot of exposure time.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#229

This is bad. This is really really bad. The EU has invested billions in telescopes and that's now going to go to waste. Instead advancing human knowledge it's just going to fill rich guy pockets even more.

No, it’s not.

Starlink satellites are only visible at dusk and dawn, they are in the earths shadow during prime viewing hours.

And SoaceX has already added visors to make new Starlink satellites nearly invisible.

Re: How satellite ‘megaconstellations’ will photobomb astronomy images

#230

Hopefully they can come up with some sort of 'vanta black' coating for the sats that reduces this issue. I agree with there needing to be a tax on bright, private sats in orbit. Space is getting more democratized, but not nearly so much so that an international body wouldn't be able to slap fines on companies putting 'disco balls' in orbit. Another thing is that our skies will probably get brighter overall when we re…

Vanta Black would make the satellites too hot. SpaceX is using visors to solve the problem .
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