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How bad are satellite megaconstellations for astronomy?

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Re: How bad are satellite megaconstellations for astronomy?

#91

Post by pfdietz »

TeMPOraL wrote: post #87
stevage wrote: post #71

Earlier quoted context omitted.

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.

Ultimately it becomes so cheap we'll be able to put workers up there to assemble and maintain the telescopes, just like on Earth. We might see telescopes in telescope farms near a small station for the workers. It might even be possible to send workers out to the Sun-Earth L2 point to maintain telescopes there.

Re: How bad are satellite megaconstellations for astronomy?

#92

Post by astrodust »

philomath_mn wrote: post #4
tetris11 wrote: post #2

I know it's a blessing for people who live out in the sticks to have internet.... but is that really such a large use-case to justify entire fleets of these things? How hard is it to run km of wire from the nearest town? To me, these were built for the sole purpose of surveillance, and internet is an afterthought. Edit: yes yes it's expensive, but the easiest solution the world came up with was for some guy to invest…

> How hard is it to run km of wire from the nearest town? Very hard, especially when the towns are much more dispersed than a km apart.

The hardest part is not the cable, or even the installation thereof, it's finding a contiguous right-of-way you can install it on, or having to fuss around with thousands of land owners who want their cut for the rights.

This is why most cables are laid alongside train tracks, not unlike telegram wires of years past. You negotiate with a handful of entities and can get permission relatively easily.

Of course, this presumes there's tracks, which is less and less likely as they keep getting ripped out.

If there's anything modern infrastructure build needs, it's more right-of-way access where you can provision dark fibre without getting mired in the legal issues.

Re: How bad are satellite megaconstellations for astronomy?

#93

Post by FredPret »

palata wrote: post #82
FredPret wrote: post #80

Earlier quoted context omitted.

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.

OK, but I don’t think tech progress = dead ecosystem.

In fact, newer tech tends to be cleaner. We use less land than we would’ve using 1800’s farming techniques, for instance. Nuclear is cleaner than coal.

Also, everybody having more money is a huge help for the environment. Compare the size of the green movements between say, Sweden and the DRC.

Yes, more money = more consumption, but it also means we can do innovative things in a better way.

In this particular case, surely extra-planetary infrastructure is better than millions of miles of ditches with lead cables in them.

Either way, our current state of development isn’t sustainable. It has to be millions of times smaller, or an unknown amount larger. I vote for more tech.

Re: How bad are satellite megaconstellations for astronomy?

#94

Post by FredPret »

amelius wrote: post #52
FredPret wrote: post #46

It'd be so cool if we can put up a huge antenna / scope on the far side of the moon. You'd be completely shielded from all human noise

Until we put satellites around the Moon.

I wonder if it could be made practical to have a radio interferometer made up of several spacecraft flying in various directions.

Re: How bad are satellite megaconstellations for astronomy?

#95

Post by sapiogram »

TeMPOraL wrote: post #88
Retric wrote: post #38

Earlier quoted context omitted.

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.

The largest filled-aperture radio telescope in the world has a 500-meter diameter, and reportedly only cost $180 million. For comparison, the International Space Station costs $3 billion per year just to operate. Doing stuff in space is expensive.

Re: How bad are satellite megaconstellations for astronomy?

#96

Post by p_j_w »

delichon wrote: post #32
bmitc wrote: post #27

Earlier quoted context omitted.

The theoretical part is whether that's actually useful for not. Cost per kilo to orbit doesn't magically solve astronomical observation problems.

Don't Chandra, Webb and Hubble, et. al. sufficiently prove the usefulness?

The cost of getting those into space is a relatively small part of the overall cost. The amount of cost benefit one of these telescopes would see just to the cost reductions gained specifically because of Starlink are insignificant.

Re: How bad are satellite megaconstellations for astronomy?

#97

Post by malfist »

dheera wrote: post #81
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 th…

Seriously, any time you have >3 images to stack satellites and planes are a complete non issue. The median pixel value is always going to exclude those. Five images is enough to eliminate any trails even if they overlap between images.

Re: How bad are satellite megaconstellations for astronomy?

#98

Post by nomel »

gammarator wrote: post #67
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…

> They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, Sorry, but one of the two example images ( https://noirlab.edu/public/images/iotw1946a/ ) is a single 333-second exposure with a modern survey camera, the Dark Energy Camera. This is not particularly long nor does it represent some outmoded observational strategy. Large, wide-field imaging sky surveys (such as the…

> Masking and stacking can mitigate the problem but it does not of course compensate for the lost area and sensitivity. And the brightest satellites (like BlueWalker) saturate the readout electronics and spoil the whole exposure.

Is this only a problem in systems that aren't aware of where the satellites will be? I naively assume that, if the system knew, it could start exposing in the next clear window. I naively assume that the window is almost always clear, especially for an individual sensor.

Re: How bad are satellite megaconstellations for astronomy?

#99

Post by malfist »

gammarator wrote: post #67
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…

> They're wide field of view, long-duration exposures. That used to be the way astronomers imaged space, Sorry, but one of the two example images ( https://noirlab.edu/public/images/iotw1946a/ ) is a single 333-second exposure with a modern survey camera, the Dark Energy Camera. This is not particularly long nor does it represent some outmoded observational strategy. Large, wide-field imaging sky surveys (such as the…

Where do you see that the full well of those CCDs are fully saturated by a single satellite streak?

Even if that was the case, that seems a very poor design for a sensor and not really an issue of satellites. If a satellite streak can saturate your well, then so could a decently dense star field.

Do they blow out the individual pixels? Sure. But you just stack.

You don't lose sensitivity just because your stack rejected pixels, that's not how stacking works. You wind up with a tiny bit more noise, how much more depends on your capture. But not lower sensitivity, stacking isn't just average an area

Re: How bad are satellite megaconstellations for astronomy?

#100

Post by ggreer »

palata wrote: post #74
ggreer wrote: post #65

Earlier quoted context omitted.

Useful for anything? Starlink useful to its 2.7 million subscribers. And it's already profitable. As of last year, SpaceX makes more in subscription fees than it costs to build and launch the satellites. The economics will only become more favorable when SpaceX improves their launch capabilities with Starship.

> The economics will only become more favorable when SpaceX improves their launch capabilities with Starship. Until we start making them pay for the environmental impact, that is.

What environmental impact? So far there have been 162 Starlink launches. Each launch uses around 200 tons of RP-1, which is equivalent to the fuel capacity of a Boeing 747. In other words: A single 747 burns more fuel in a year than all the Starlink launches in the past five years.
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