Second, astronomers already use image stacking to reject any number of transient artifacts, like satellites, airplanes, cosmic rays, etc.

Third, while these constellations are going to greatly increase the number of satellites in orbit, it's only by about an order of magnitude. Yes, that's worse, but it's not like it's a problem that hasn't existed before.

The type of observations that are likely to be most affected are surveys that actually search for moving near-Earth objects, especially near the Sun (and radio astronomy which apparently can detect terrestrial emissions scattering off of satellites) but I fail to see how this will mean anything like "the end of astronomy" (and I have a Ph.D. in astronomy.)

As new launch systems like Falcon 9, Starship, New Glenn and New Armstrong eliminate these constraints it will eventually be cheaper to build telescopes in space than on the ground.

Other “pusher” motivations include worsening access to real estate, reduced control over light pollution, recognition of indigenous rights, etc.

I don't think the next 5-10 companies launching constellation satellites will be quite as considerate, so one order of magnitude could creep on to two over 15 years.

I think image stacking has been simulated to work somewhere from okay to unusable even for 15s exposures - I think the trails are actually pretty bad due both due to quantity, velocity in the sky, and brighter-fatter.

It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based.

I'm on the fence on this whole issue. It's not exactly clear what impact it will have on astronomy. Nor what impact it will have on making the internet pricing and availability. Where I used to live, the only options for internet access were expensive and really bad, the positive impact this might have is potentially quite big.

It's hard with a story like this to suss out what the long term effects will be so it's a big grey area.

I'm not an astronomer but I'm not convinced that that's the case. The number of space telescopes pales in comparison to the number of terrestrial observatories. Moreover, advances like adaptive optics have done a lot to close the gap between ground and space capabilities (for optical telescopes). Even once you've invested in expensive tech like adaptove optics, a telescope in space still costs an order of magnitude more than one on the ground (thats being really conservative. JWST has already cost ~10x more than the most expensive ground telescope ever, and the thing hasn't even launched yet)

There were a few space based radio telescopes in the past, but I don't think there are any now. Imagine building something like the Arecibo Observatory[1] or VLA[2] in space. And speaking of the VLA, some of the techniques for getting high quality results (e.g. interferometry without physically conjoining the receivers) are difficult if not impossible to do in space.

[1]: https://en.wikipedia.org/wiki/Arecibo_Observatory

[2]: 27 of these guys, which are able to move around precisely on rails to generate constructive interference with the different waves they're receiving: https://public.nrao.edu/wp-content/uploads/2016/04/vla_panor...

I'm not entirely certain what the balance is here. I don't think my post made it clear that I'm not certain how big the effect would be, only that there is a tradeoff here which is hard to quantify.

I do know there is a lot of significant astronomy done by space telescope and that the importance of space astronomy is only growing.

Seems to me the answer is that those who benefit from the new satellite constellations (SpaceX, etc) should finance additional investment in astronomy to mitigate the effects.

Former astronomer here. I would argue that the importance of space astronomy is actually decreasing. Satellite telescopes are most important at wavelengths that the Earth's atmosphere absorbs like IR, UV, and X-ray. At visible wavelengths satellite telescopes have been much less important over the past couple of decades due to the development of adaptive optics.

The main reason to put a visible wavelength telescope in space is that you avoid the smearing out of the source by the atmosphere. Adaptive optics solves this problem by correcting for the distortions induced by the atmosphere and bringing images to resolutions that are comparable to (though still not quite as good as) what you can achieve in space.

Since space telescopes no longer have the advantage of much greater resolution, there's much less of a compelling reason to use them for most research problems. (Some questions, of course, can only be tackled by using the highest resolution available.) On every other dimension space-based telescopes are inferior to ground-based telescopes. They are more expensive by many orders of magnitude, much, much smaller, and they cannot be changed once they're up (at least not easily). By contrast a ground based observatory can get substantially better over the course of a year by installing better detectors.

IMO, over the next 30 years space based telescopes are going to play an ever larger role.

I'd be curious to know what the impact is on impactful amateur astronomy (as opposed to backyard hobbyists who are just engaged for personal pleasure). I know some amateurs use images created by public telescopes, I'm not sure how much meaningful work is done by amateurs using backyard equipment anymore.

Not being dismissive, genuinely curious.

"Since professional astronomers do not have the time or the resources to monitor every variable star, astronomy is one of the few sciences where amateurs can make genuine contributions to scientific research." [0]

[0] https://en.wikipedia.org/wiki/American_Association_of_Variab...

A decent number of asteroids and comets are still found by backyard astronomers.

I'd trade amateur ground astronomy for that.

There are plenty of good pictures on wikipedia already, do looking at those compare to going out on a clear night and looking at the stars yourself?

Imagine if a painter in Greece in some century BC convinced his fellow Grecians that building a harbor in the cove by their town was a bad idea because it ruined his paintings of the cove. How was he supposed to look at the marine life if you stuck wood and industry in the water???

You need old distant objects for cosmology, observing the structure if the universe, big bang and stuff. You need variability for finding exoplanets, measuring distance and observing transitions such as supernovae.

Oh, and then a huge part is taking spectra, which means bouncing the light directly off a grating. Filtering transients is hard to impossible there. You need spectra for relative motion, magnetic fields, composition of matter and radiation and of course temperature.

Needing such filters would set astronomy back a few decades

Wow.

You’re shocked at my statement, as if StarLink is entitled. Consider the alternative argument: why should astronomy slow global comms progress? If astronomy is more valuable than the ~$30 billion/year global comms market, shouldn’t someone bear that cost?

Technically, a human life has an economic value. And yes such value is used every day to decide health policies and insurance coverage. Would this mean that SpaceX killing N humans (where N=30B*number of years of operation planned for starlink/value of a human live) is ok? Absolutely not.

https://en.wikipedia.org/wiki/Extraterrestrial_real_estate

And then there is also the vulnerability of the lauch site and control center...

It is true that spacex can put a significant amount of satllites in orbit witha single launch though, so it probably evens it out.

First-mover advantage is real.

The US is not a super power because it asked politely and a committee granted it permission. Similarly, SpaceX will move forward because anyone with the authority to challenge them allows them to proceed.

You replied "Optical, RF, or Xray?"

Then I said, "Let's start with optical." but then you disappeared!

So, what's your solution for long-slit optical spectroscopy?

To be clear, I think we're well in the realm of academic discussion; no one is stopping any global constellation due to astronomy concerns. As I've said many times in this thread and elsewhere, I think it's a growth opportunity for the astronomy community to move towards space based observation platforms, and with the plummeting cost of lift (ie SpaceX Falcon and Starship) I don't think that's an unreasonable position to hold.

Not true at all. Ground based is much cheaper and easier to maintain and reconfigure with new and different equipment. Just look at the cost of the upcoming >30m telescopes vs the James Webb or Hubble.

And since you are going to spend so much money to launch it, you also add extra hardware to do other type of observations, so the cost of the telescope balloons upward but you are get more bang for the buck.

If on the other hand you have cheap launches then you can send up the minimum telescope needed since you can always send up a better one or even a very different one if you later discover the need.

Today because of high costs, we need to design the scopes to meet all the possible needs we can think of and afford, result very expensive space scopes.

Why make this more expensive than it needs to be? Researchers are already strapped for cash.

You're going to have to point out which source you pulled that out of! As a simple example, more than half of the Nobel prizes awarded for astronomy since 2000 are for discoveries made with ground based detectors. And of those awarded to satellite experiments, none was actually competing with a ground based experiment, so satellites mainly bring different, not better, capabilities.

When I encounter this phrase I think of things like the neutrino detector in Antarctica, which of course isn't affected by satellites at all. How much contemporary astronomy relies on visible-light telescopy?

The key point is usable observation time. Our current handful of satellite telescopes provide 24h of time a day. Each terrestrial telescope provides maybe 8h. However, there are a magnitude more telescopes on Hawaii alone than in space. You would need to get a hundred satellite telescopes to begin to replace earthbased observation time.

And that doesn't even begin to talk about the possible instruments, mirror sizes, astronomical costs of buulding and running satellites, etc.

Satellites are invisible if they're in the Earth's shadow. By the time useful observation can begin, there's an enormous swath of the sky that will have zero visible satellites in it.

Diversify your observation targets. There's more than one interesting thing to science at any given moment. If that means spreading out your observations so you spend two hours a night observing four targets as opposed to four hours a night on two targets, so be it.

At the very worst, this means astronomers will need to do more work during the day shift scheduling and prioritizing. This isn't a new problem. I remember reading a back page article in Astronomer magazine sometime in the late 90s with a page of BASIC code. Someone wanted to optimize a computer controlled telescope to make one observation of 100 or so stars every night. You need to roughly minimize the total Manhatten distance between every two observations, while also eliminating observations below the horizon and penalize observations low in the sky. So the author wrote a program to roughly approximate the traveling salesman problem with the additional constraints. In the 90s. In BASIC. In one page. It might be NP complete to get the perfect solution, but good enough is pretty good.

Add an additional constraints penalising observations where they might be impacted by satellites. Hire an intern working on their degree who's taken an optimization course and have them do it for you.

We're going to have to start thinking bigger if we want to leave this rock. Might as well start now.

The real risk is Elon's companies dissolving and the satellites adding pollution for no real gain. If I could trade observatory time for (working) world-wide internet, I'd take the latter with no hesitation.

As much as I sympathize, most of the cosmos aren't really going anywhere. It'll be there after we build hundreds of telescopes.

/s (jeez, your sense of humor folks...)

Of course, the reason why people who enjoy lecturing others about why something can't be done differently or shouldn't be done differently seem to gravitate to a site called "Hacker News" is one of those universal mysteries that can't be answered with a computer or a telescope.

Don't fight the people who are trying to fix this.

But never mind, we've been told that digital imaging is "functionally identical to film," and we're "losing the discussion."

A generation or two in the future astronomy will probably get redefined quite a bit via remote telescopes and adventure vacations to space and so forth.

Even now there are plenty of enthusiasts who are excited to take pictures of rockets during take off or explore satellites as they pass by. So it actually get more people interested in space and astronomy.

And there will always be people on either side supporting or opposing technological advances - as we have seen thought history. The one thing that is certain in my opinion though is that things will change.

Does the proliferation of high speed Internet to every part of the world outweigh the cheapness of current land based astronomy tooling?

If not, maybe spacex can compensate by providing some launch load for space bound telescopes.

https://www.cnet.com/news/in-rural-farm-country-forget-broad...

Moreover, I think mega-constellations will actually be a boon for astronomy. Think of it as a platform, while initial iterations will be focused on communication systems, what is stopping them from adding sensor packages looking both inwards and outwards? They already have the bandwidth to downlink all of that. Once on the ground those streams could be combined to produce datasets of unprecedented coverage and fidelity.

Once the sun is set in their orbit, they should be invisible both to the eye and telescopes.

That's where it can shade 24h/day.

These are not geosynchronous satellites, but instead are 200-500 miles above the Earth, moving many, many thousands of mph. No, it isn't blocking anything 100 light years away unless your shutter speed is in the single-digit nanoseconds.

In fact if, as you believe, these satellites would actually occlude things beyond them, they sound very useful for calibration and education.

Why is that? Almost everything astronomy studies isn't fast-moving. Shouldn't it be easy to filter out that noise?

Fast-moving = more likely for it to traverse your field of view while the shutter is open

First is the impact to "professional astronomers", and from what I've seen this group won't be impacted nearly as much as the other. This group has the ability to use satellite based telescopes, or has the tech already to be able to filter/post-process the images to remove satellites, planes, meteor showers, and any other stuff that might get in the way.

Then you have "amateur astronomers", this groups is likely to be impacted by starlink. This group doesn't have access to the digital filtering stuff that the "big guys" do, from what i've seen, most of the people in this group just use normal long-exposure setups and adding in a processing step would mean a pretty significant change to their process, and probably a lot of additional costs.

Even still, the impact to amateur astronomers seems limited to when the sats are in sunlight, which traditionally isn't a super popular time for stargazing (although I may be wildly wrong on this, as I've read that these sats are removing up to 1/3 of the normal viewing time for some astronomers, so don't take this as gospel), and I still think the impacts will be a lot less doom and gloom than some are saying, but I still hope that SpaceX can work with the astronomy community to see if there are solutions or mitigations that can help everyone out.

Filtering is less advanced, but masking outliers (and their neighbors) and replacing them with an average of the others isn't advanced filtering.

It's annoying the way getting cut off in traffic is annoying, not the way getting T-boned is annoying.

If we were to employ the reversal test[1], the concern about astronomy would be a non-problem. Imagine if the entire planet was covered by the equivalent of 4G cell networks. And imagine if some astronomers asked us to destroy those networks so that some of their work could be made more convenient. Imagine all of the people affected by this network. All of the lives saved by emergency calls, all of the remote locations made digitally accessible to the rest of humanity, all of the scientific experiments in jungles, deserts, tundra… cameras and microphones and sensors reporting data through this global satellite network… imagine all of that destroyed so that some astronomers could be relieved of an inconvenience. That is absurd. Yet that is the world that some people want to live in.

It's so clear to anyone whose view isn't so parochial, so local in time and space, so blinkered by where and when they were born. Does anyone think that astronomers will still be preventing the launch of satellite constellations in the year 2100? In 2200? In 2500? Clearly not.

I'd rather the improvement happen in my lifetime than after. Launch away.

1. https://en.wikipedia.org/wiki/Reversal_test

A very simple and common way is to stack all of the static images aligned on top of each other such that you have a set of values for each pixel corresponding to the same region of sky. Then sort the values of each pixel by brightness and keep the median value for that pixel. Or throw out that top and bottom 10% and average the rest, or throw out the top and bottom N, etc.

This is a standard feature of essentially all astronomical image processing software and has been for a long time.

Remember you don't need to throw away the whole frame, only the pixels that were obstructed. One track across a frame will obstruct less than 1% of the data in that frame.

There is no way to see Starlink at night. You can potentially see them for a short period around twilight.

Starlink satellites directly overhead are in sunlight for about 1.5 hours after sunset, and the same before sunrise. Including observing on an angle, you probably lose 4 hours per night out of 12. With 300km satellites, you probably lose 3 hours. I think the situation will be worse away from the equator in summer.

The satellites you can easily see at any time are much higher up.

The time window is limited, yes. So it is not the end of the world. It is still a problem.