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How bad are satellite megaconstellations for astronomy?

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Re: How bad are satellite megaconstellations for astronomy?

#81

Post by dheera »

StellarScience wrote: post #42

There certainly is a real concern for astronomers, but the photo illustrations used in the article are selected to make things seem worse than they really are. They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, with film systems a century ago. But these days astronomical telescopes tend to have much narrower fields of view (like tiny soda straws peering into one par…

> the photo illustrations used in the article are selected to make things seem worse than they really are

Exactly. I do a LOT of astrophotography and satellite trails are actually very easy to get rid of. Even the stupidest, most naive outlier rejection techniques, such as taking a stack of tracked images, finding their mean and standard deviation, throwing out any data points outside of 2 standard deviations, and then re-averaging, will get rid of the satellites very cleanly. You can go to more advanced techniques such as doing linear fits and RANSAC and whatnot, but you get the idea.

NOT doing any outlier rejection, just taking the mean of all the images will show the satellite tracks, but very dimly. The people who are trying to make noise on social media deliberately and disingenuously take the max() instead of the mean() to make the problem seem worse than it is.

That said -- in all of my imaging sessions, aircraft are a much, much, much bigger problem than satellites, and still easy to deal with. Yet nobody makes any noise about aircraft.

Re: How bad are satellite megaconstellations for astronomy?

#82

Post by palata »

FredPret wrote: post #80
palata wrote: post #73

Earlier quoted context omitted.

Starlink is not there to bring Internet in places that don't have it. It's here to bring fast Internet in places that already have slow Internet. The question is: how fast an Internet connection do we need? Do we really need to swipe 4k videos on social network, or to download 50G of docker containers for every build? I don't think so.

Is there some maximum level of development you want? And what is that level, and why? Where do you want to draw the line? The wheel, fire, hand tools, struggling to survive in the middle ages, slow internet, fast internet? I say there is no line.

> I say there is no line.

I say there is one: survival. Not only of our species, but of the others, too. We're failing at that, and the vast majority of the technology that got developed in the last decades is making things worse.

Re: How bad are satellite megaconstellations for astronomy?

#83

Post by palata »

Turing_Machine wrote: post #78
palata wrote: post #72

Earlier quoted context omitted.

> To me, these were built for the sole purpose of surveillance, and internet is an afterthought. Growth! Growth no matter the cost! Why would anyone question the need for always faster internet connections everywhere? /s

Let us know when you switch back to a 300 bps audio modem.

Sure, because that is the only alternative to fiber. /s

Re: How bad are satellite megaconstellations for astronomy?

#84

Post by schiffern »

Havoc wrote: post #13

As much as I sympathize this feels like a necessary evil to me in a sense vaguely accerlationism like. I do think starlink can do more to help the situation though. Sure they tweaked some of the satellites to minimise it, but they could do more. Presumably the know the precise location and orientation of each sat. Surely that can be packaged into a data stream that helps unfk the images? Maybe with a sprinkling of th…

  >they could do more. Presumably the know the precise location and orientation of each sat. Surely that can be packaged into a data stream
SpaceX already does that.

https://youtu.be/MNc5yCYth5E?t=1717

https://arxiv.org/abs/2305.11123

Re: How bad are satellite megaconstellations for astronomy?

#85

Post by SaberTail »

shadowgovt wrote: post #44

I'm sure it's inconvenient, but it's hard for me to believe that this isn't a solvable problem. Satellites have extremely predictable paths and are very well-tracked by every government with a space program. If you can know a source of noise is there, you can trim the noise out of the signal. Sure, this impacts the fidelity of your signal for the three-dimensional coordinates of image where the noise was present, but…

When counting photons, the noise in your signal scales with the square root of the total count. If the satellite is dumping 100 ± 10 photons in every pixel it passes through, you can no longer distinguish objects so faint that they'd only leave 10 photons in a pixel during your exposure.

Re: How bad are satellite megaconstellations for astronomy?

#86

Post by TeMPOraL »

stouset wrote: post #18
hehdhdjehehegwv wrote: post #15

Earlier quoted context omitted.

[flagged]

Megaconstellations are not a problem for kids looking through telescopes. If anything it’s additional things to wonder at in amazement.

Exactly. My fondest memories of childhood stargazing was gathering people around me, pointing at the sky and asking them to look, just as a high-magnitude Iridium flare was starting. Heavens Above was my secret weapon for showing off in high school.

Re: How bad are satellite megaconstellations for astronomy?

#87

Post by TeMPOraL »

stevage wrote: post #71
pfdietz wrote: post #55

Earlier quoted context omitted.

Propellant is very cheap.

Yeah but it is still mass and volume that might reduce available payload?

Doesn't matter. The point is that, thanks to reusable boosters, launching satellite constellations, and other recent developments, space is becoming much cheaper - so if you can't fit 8 JWSTs in one Starship, just launch the rest on another, and it'll still come out cheaper than the original JWST.

Re: How bad are satellite megaconstellations for astronomy?

#88

Post by TeMPOraL »

Retric wrote: post #38
mercutio2 wrote: post #20

Earlier quoted context omitted.

Are there really a lot of ground based telescope components larger than Starship's fairing? I'm just not seeing the argument for there being any telescope function that wouldn't be better done in orbit, at Starship payload prices.

Yes, though I guess it depends on what you mean by lots: https://en.wikipedia.org/wiki/List_of_largest_optical_reflec... . Critically the 30+m monsters under construction have only recently become feasible on the Earh let alone in space, and much smaller instruments still provide significant value today. There’s a much longer list of large radio based telescopes which have minimal advantages in space to the point whe…

> There’s a much longer list of large radio based telescopes which have minimal advantages in space to the point where we haven’t launched any

What if they could be put behind the Moon, completely shielding them from Earth RF emissions? It's been a cost-prohibitive idea now, but might not be for much longer.

Re: How bad are satellite megaconstellations for astronomy?

#89

Post by rickydroll »

_dain_ wrote: post #61
rickydroll wrote: post #43

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Extremely_Large_Telescope The 39-meter primary mirror has 798 1.4-meter segments, each individually adjustable. The scaffolding required to hold all the segments is "significant" and must be assembled in orbit. We would stick this out next to the James Webb at L2, which means we would need the ability to travel to L2 to construct this mythical orbital extremely large telescope. With our…

For one thing, before this decade is out we will have the lift capacity to get an ELT-worth of mass to L2. And the lack of need to correct for atmospheric distortion would simplify the design considerably. But it's beside the point. Such a singular mega-telescope would no longer be the only way to do astronomy in space. A world of radically lower launch costs gives more possibilities. We could have a fleet of thousan…

It doesn't simplify the design; it increases its complexity. All the problems of telescopes on Earth become significantly more problematic in space: temperature, flexure, warping, backlash, pointing models, optical alignment, and collimation are some of the issues.

Electronics, sensors, and consumables fail or run out, which means you need to be able to get there to fix things. Then, as research projects change, you need to change instruments.

Yes, one could have thousands of 1-5 m telescopes. A terrestrial scope is about an order of magnitude cheaper than an orbiting telescope. So, the big question is who will pay to replace the thousands of scopes in that size range that are already operating on Earth.

Rationing will still needed (Research projects always exceed the number of available scopes). High-quality data, will not be as cheap or abundant as you think it might be. With the number of scopes we are talking about and the sensors that astronomers use, we can expect hundreds or thousands of petabytes a second of data. How will we get that data down from orbit?

A practical example this volume of data comes from the event horizon telescope. I could describe the firehose of firehoses but this paper from supermicro does a much better job of it https://www.supermicro.com/white_paper/white_paper_Black_Hol...

This is just one project. Could you imagine a thousand of these astronomical fire hoses running at the same time in orbit?

The next issue is where these telescopes should be placed. The more we learn about running telescopes in orbit, the more we realize that they need to be placed very far from Earth to increase the observable sky and the length of time one can study a chunk of it. As I said above, consumables need to be replaced, sensors need to be changed for the observing program, boils down to how you are going to get a repair crew out to wherever the telescopes are.

Re: How bad are satellite megaconstellations for astronomy?

#90

Post by rickydroll »

feoren wrote: post #49
rickydroll wrote: post #43

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Extremely_Large_Telescope The 39-meter primary mirror has 798 1.4-meter segments, each individually adjustable. The scaffolding required to hold all the segments is "significant" and must be assembled in orbit. We would stick this out next to the James Webb at L2, which means we would need the ability to travel to L2 to construct this mythical orbital extremely large telescope. With our…

Why would you assemble it at L2 instead of assembling it in LEO and then sending it out on its own?

It is not impossible. But you would have to design the telescope to be a rocketship complete with motors, fuel tanks, and all that other fun stuff. That would significantly increase the telescope's complexity to withstand the force and vibration of a rocket engine. Theoretically, one could use ion drives, but the engineering challenges of creating ion drives capable of moving a few hundred tons of telescope are significant.

It is much simpler to build the telescope equivalent of IKEA flatpack furniture and assemble it on-site than it is to build it and then move it.

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