The viewing window is actually pretty small. For most of the night the satellites are not visible because they are in Earth's shadow. There is an impact on astronomy but it is being overstated by journalists hungry for yet another "Big Tech bad" story.
No, it’s not. This hurts survey telescopes and it’s an orders of magnitude issue.
A rule of astronomy is that if you can see it with your eyes near a city than it’s really really fucking bright, if you can see it with your eyes in the wilderness after your eyes have adjusted for 10 minutes, than it’s still extremely bright.
Bright, fast-moving things are pretty terrible.
Even if Starlink doesn’t kill astronomy, the next 4 companies with similar deployment will definitely exclude types of sciences and ruin billions of dollars of investments in new observatories.
First, satellites are only visible in the optical when they are illuminated by the Sun, which is only for a fairly short window after sunset and before sunrise. The exact size of the window depends on how high they are, but most of the good "dark" time should be unaffected.
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.)
Just to add to this, the satellites can still cause problems during the night after sunset, as they can occlude other objects being observed as they pass overhead.
Terrestrial telescopes, which we've invested a bunch of money in terms of observatories in, receive interference from Starlink satellites. Telescopes in space, like the Hubble, don't have the same problem, but they're on the magnitude of 100x more expensive and its difficult to have the same missions.
Noting that the orders of magnitude increase in cost are directly caused by infrequent launches by launch systems with tight mass and volume constraints, and the need to build a space telescope on the ground, have the equipment survive launch, and then survive with no intervention for a decade or two in space.
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.
correct - I didn't think I meant Starlink would kill astronomy (I thought I was addressing some of the hyperbole rather than extending it) - but probably even at the level to be deployed in the near future we would see severely degraded quality of observations for solar system objects. Furthermore - I do think SpaceX is the "good citizen" here.
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.
Saying it will "Kill astronomy" is pretty hyperbolic.
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.
>It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based.
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.
> I'm not an astronomer but I'm not convinced that that's the case.
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.
> I do know there is a lot of significant astronomy done by space telescope and that the importance of space astronomy is only growing.
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.
Adaptive optics have zero issues if you’re looking to make a cool picture, but they do introduce bias which is an issue for scientific instruments. That’s largely offset by more and larger telescopes for the same price, but it is very much a tradeoff based in launch costs which are falling.
IMO, over the next 30 years space based telescopes are going to play an ever larger role.
Are you an amateur astronomer or just trying to be the devil's advocate?
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.
Variable star observing is actually a place where amateurs really help, since it's about observation time, and not necessarily some hugely powerful telescope. And the more powerful a telescope is, the more people want to use it to point at all sorts of things, which makes it kind of expensive to use those telescopes for variable star observations which take a lot of time.
"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]
In recent news, the only confirmed interstellar comet in our solar system was found by a dude who worked at an observatory (not as an astronomer) and decided to build own telescope for fun in his spare time. It's one of only two known interstellar visitors we've had, and because he found it early enough the pros were able to make very detailed observations.
A decent number of asteroids and comets are still found by backyard astronomers.
If SpaceX works out, we'll probably see a lot more telescopes in space. Wouldn't be that expensive at that point for, say, a school class to launch a telescope cubesat.
The dead of night will be fine. But during (astronomical) twilight, the time when you are most likely awake and looking up, it will have ugly extra dots.
Also I'm sorry but I really, really don't care about a hobby if it gets in the way of the progress of the entire human race.
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???
Don't think so. Adaptive optics works by changing the physical shape of the mirror. If you measure the atmosphere continuously and bend the mirror the right way, you can remove atmospheric distortion from the image. If anything, AO just gets you sharper images of the starlink satellites (or significantly worse ones if a satellite flies in front of the guidestar that you're using as a reference point to measure atmospheric distortions).
Modern astronomy works at the edges of whats possible, a single frame might take hours. Needing multiple frames would mean multiple days per observation. It would mean no longer seeing faint and distant objects, limiting us to younger, closer and frankly far more boring objects. It would make observing variability impossible for certain timescales.
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
If someone doesn’t manage or govern it with economic incentives, no one does (see: most of the “public good” rainforest slashed and burned in South America and Asia that we desperately needed managed better, through private ownership and conservation management, to avert climate change).
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?
Because ultimately, arguments relying solely on economics are moot.
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.
No it doesn't. If you know something will kill people, economic arguments are not considered sufficient. This was famously decided when it was revealed Ford elected not to recall the Pinto on the basis of paying compensation was cheaper then the fleet maintenance they had to do.
Not considered sufficient to avoid penalties in a court of law. But even that example can be reframed as a failure to calculate total risk in the cost / benefit analysis (i.e. they should have factored in the risk of a lawsuit and federal fine).
This is actually one of the more interesting questions in space exploration in general. It has been ever since someone tried charging NASA for parking on the section of the moon they claim ownership of.
Defense would actually be quite easy. Just undesirable. There are working antisat weapons in the major powers' arsenals. However, they would produce nasty debris clouds.
And then there is also the vulnerability of the lauch site and control center...
Not in general. A kinetic striker would require as much energy to reach the satellite as the satellite used to get there. Something fancier, like a targeted laser, to my knowledge doesn't exist with anything like the wattage needed to punch through atmo and still have effective kill on anything that far out (assuming you could solve the targeting problem to resolve the beam that tightly in the first place).
The satellite is in orbit. It requires significantly more energy to put something in orbit than merely reachin that altitude. Satellite killers are relatively small rockets that can use a small supersonic fighter jet as first stage, while it requires a much bigger rocket to put a satellite in space (it would depend on the orbit of course).
It is true that spacex can put a significant amount of satllites in orbit witha single launch though, so it probably evens it out.
That makes the relationship sound adversarial, when really there's mutual benefit to SpaceX and the international astronomy community. Astronomy can use cheap lifting capabilities.
It's a complicated question, but there are echoes of it in "Why does the US get the privilege of having their flag on the moon, just because they could get it there and nobody can take it back down?" or "Why do people have any right to the land they occupy, merely because they got there before other people did?"
It’s not complicated. The answers to your questions are, “Because they can.” Possession, control, and force carry much more weight than some would like. It just makes those without power, authority, or any other stakeholder equity uncomfortable.
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.
Hey! I'm still waiting to hear back from the astronomer I paid to do the research. I still intend to report back with their DOI from the resulting paper. I recognize when I've exceeded my domain knowledge and need an expert.
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.
No, they are too bright and will saturate the detector with even very short exposures. Best you can do is just discard the affected area, at worst you have to discard several exposures because the saturation effected the readout electronics.
Arecibo and VLA aren't affected by starlink at all. Those are radio telescopes. They don't even need to wait until nighttime to observe. It's only an optical/ir problem.
Starlink uses radio to communicate with the ground. A common complaint from radio astronomers is new radio satellite operators promising to not interfere with radio astronomy and then making no effort to follow through in that promise.
“It will likely affect some earthbound astronomy significantly, but much (most?) of the most important work in modern astronomy is satellite based.”
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.
On the plus side, SpaceX is making launches much bigger and cheaper, which will make space-based telescopes much more affordable. Cheaper launches = more, cheaper satellites.
You are right, but also wrong. Because the launch cost so much you spend even more move on the space telescope because you want it to work for a very long time to get the best value for your money.
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.
I guess we would have to look at the actual costs and trade offs. Personally I am still not convinced that launch cost is the biggest problem but I am sure astronomers are crunching budget numbers right now and will adjust plans if it makes sense.
> but much (most?) of the most important work in modern astronomy is satellite based.
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?
A very large fraction. Optical is still the most important band, probably followed by radio, x-ray, IR and gamma ray in that order. And less then 10% of optical is done using satellites.
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.
>And that doesn't even begin to talk about the possible instruments, mirror sizes, astronomical costs of buulding and running satellites, etc.
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.
Well, he is. For the Luddites in these threads, it's enough to cite the JWST as a reason to keep doing things the same old way, over and over, in space and on Earth.
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.
Most astronomy is long exposure which the eventual mega constellation is particularly harmful too because there's no way currently to deal with the light reflecting off them.
You know they don't use film plates for those exposures anymore, right? They stack images digitally. Removing satellite trails is the easiest part of the post processing flow, or it damned well should be.
Digit and film single long exposures are functionally identical and for very dim objects you still need long exposures because the amount of light reaching the sensor is very low. You can't image stack if the object is too dim to appear in the shorter exposure's you're stacking.
Astronomical sensors typically are 12 bit. So anything 4000 times brighter will overflow the sensor and can not be subtracted. And of course you have perfect solutions to Poisson noise, bleeding pixels, and increased dead time caused by shorter read out intervals as well, right? We are done here. But not for the reasons you think. You did not win this discussion.
A simple median filter will take care of it. Have you seen what an unprocessed image from the Hubble Space Telescope looks like? It's riddled with cosmic ray tracks, and they all get filtered out.
There are any number of ways to correct observations for satellite trails, not the least because their appearance and duration are both transient and 100% predictable in any given field of view, and can be gated out of the exposure series. Cosmic rays don't even give us the latter break. (To be fair, the rabbit hole does go deeper than the usual places where a median filter alone will save you, but the general problem is far from intractable.)
But never mind, we've been told that digital imaging is "functionally identical to film," and we're "losing the discussion."
My impression is that a lot of interesting "leads" are generated by ground based telescopes and only then examined in more detailed by space based telescopes. If you kill off the generating mechanism, then effectiveness of space telescopes could also decline a lot.
It's nothing really new and the same dynamics can be observed throughout history. Imagine there was a time one could look over and see the bay without the Golden Gate bridge or high rise buildings. And now, its even an iconic thing!
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.
OP is talking about affecting astronomy the science, not astrophotography the hobby. Land-based survey telescopes are incredibly useful cheap tools that do not have alternatives.
No, we don't. There are tons of places right around me, in central Europe, where people will benefit greatly from Starlink. A lot of rural-based people are excitedly talking about it, even older people who you would not expect to know what it is - and they don't, but they're excited about their access to the Internet.
Ok, then Tesla should really prove they can provide that or find ways to compensate those with land based astronomy tooling. They have done neither and have not communicated in any form that they want to.
Staring at a night sky in a designated dark sky area is amazing. Given the pace of SpaceX launches amount of time you can do that without sky crawling with LEO constellations is pretty limited. So days of humans experiencing night sky raw are pretty limited (some would argue it is already impossible). However, I think astronomers will find a way to operate even in a noisy environment of mega-constellations. Given that the objects are bright they can be tracked extremely well. Filtering out them out of the datasets does not seem intractable. Am I missing anything here?
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.
"Invisible" isn't quite correct. They won't be visible as white spots, they'll be black spots blocking out the things behind them. Not a big deal for human eyes. Quite a big deal for astronomers.
It'll block a star for ~1/2500th of a second (assuming a three meter blocking radius, and 7500m/s) - I wouldn't be surprised if that went undetected 99% of the time. At most it would read as a minor brightness fluctuation, right?
Not only that, but it first has to actually pass in front of the star. This gets increasingly likely as you look at fainter and fainter stars, but the sky is still mostly empty and is not as common as you might think. (Olber's paradox and all that.)
The satellites are not only small, they are also fast. A fast moving satellite can only occlude a 100 light years away object for a couple of microseconds before it passes. This is absolutely negligible for an astronomical observation lasting seconds to minutes. And even if you launched billions of opaque satellites they couldn't come close to blocking a big enough percentage of the sky for this to matter at all.
It'd be in front of an object 100 light years away for an absurdly tiny amount of time. The percentage of the sky occluded by these satellites is absolutely minuscule. This is not a rational notion.
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.
The relative (apparent) motion differences and the fact that the locations of the satellites are known should take care of that, no? It’s unlikely that the motions are going to track each other exactly in most cases.
In fact if, as you believe, these satellites would actually occlude things beyond them, they sound very useful for calibration and education.
It's bright because it's in a low orbit and a lot closer to us. Because it's in a low orbit it's in the earth's shadow for most of the night. It's not bright while in shadow.
I think there are 2 issues here, and it's making the conversation around it difficult.
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.
We absolutely use short exposures. It's actually more important for us than the pros because the mounts are a lot less stable and polar assignment is far worse. Doing a lot of short exposures is a lot easier than nailing your polar assignment. It also help with bad seeing; you throw away the blurriest quarter of your images and the stack looks a lot better.
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.
So, you clear your CCD, collect photons for 30 minutes, then some satellite sprays you with a multiple of the number of photons collected thus far, and then ... what?
Instead of exposing for 30 minutes, astronomers take lots of shorter exposures and stack them. Otherwise you'd get tons of noise from CCD hot spots, cosmic rays, aircraft, meteors, satellites, etc.
Well, but then, you also get noise from CCD readout, so it's not like you can just take 18000 100ms exposures and stack them to get the same result as a 30 minute exposure minus the "broken frames". Stacking frames is a workaround for disturbances, but it comes at a cost in the form of readout noise. The shorter you make the exposures, the more disturbances you can filter out without wasting observing time, but the more readout noise you get. So, if you have more disturbances, you either need more telescope time so that you still have enough frames left to see your signal after you have thrown out all the bad frames, or you need to reduce exposure times so you can throw out frames as higher granularity, but then you have to accept more readout noise, which makes it harder to see the signal.
There are already enough disturbances that a 30 minute exposure is impractical. Astrophotographers tend to use exposures around 30 seconds. It's true that more satellites mean that astronomers will have to tweak their observation methods and/or reduce their observation windows, but it's not a showstopper. At worst it's an inconvenience to them.
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.
Absolutely, in fact it's pretty easy and is routinely done by amateur and professional astronomers alike. We've had satellites, airplanes, and meteors obstructing astronomical images ever since we began taking them.
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.
Sure. But increasing the number of frames with tracks increased the number of datapoints you need to throw away, reducing the effective time on target and therefore sensitivity of your observations. Astronomers are not idiots. They know how to deal with obstructions. But that is not free of cost. Neither in observational limits nor computer time nor required brain power.
Sure it's not without cost, but in most cases the cost is not very high.
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.
One of the key assumptions that's being made, throughout this thread, is that astronomy is mostly imaging. Taking or stacking images. A ton of astronomy is spectroscopy, which is nothing like a stack of static images with one that has a streak in it.
Personally, I don't want to be limited to observing the stars from planet Earth for too much longer. The development of commercially viable space technology will fund and fuel investment in interplanetary expeditions and help us move to the next stage of human progress.
Like most other satellites, it can be seen when it reflects the Sun. Satellites tend to be shiny. For an extreme case, check out "Iridium flares" - a brief but bright flares on the sky caused by old Iridium satellites, whose antennas were essentially large, rectangular mirrors.
Here is the actual geometry at the equator, ignoring axial tilt (the blue/black circle is Earth, the red/black circle is a satellite at 500km, and the radial lines are hours): https://www.desmos.com/calculator/3br1snafmj
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.
You've really never looked into a night sky and seen a satellite? Unless you live underground or never leave a big city, it's quite easy and there are dozens of apps that will help you understand what you're looking at.
I guess the point they are trying to make is that 500km (or 300km) is essentially hugging the planet. Which means that, if it is night, they will be in the shadow for the majority of the time.
The satellites you can easily see at any time are much higher up.
A shortsighted attitude, IMO. Terrestrial observatories are in a good position to clean up satellite artifacts digitally. They already have to do more image processing than the staff at Playboy. Meanwhile, cheaper access to orbit can only be a good thing for astronomy, given that we've picked most of the low-hanging fruit in terrestrial-bound optical observations.
Depending on source class and telescope location it ruins between 1/3 and 1/2 of the available observing time. Are you willing to pay $1 more in taxes to to fund the extra telescopes we need to make up the short fall? Please write to your representatives and senators if you do.
Satellites and space-based telescopes are still monumentally expensive even if you ignore launch cost. The James Web Space Telescope has cost almost 10 billion dollars in development and won't even launch until (unless the schedule slips again) next year.
One of the reasons JWST is expensive is its complex folding mechanism. Starship could launch a mirror bigger than JWST's in one piece.
Another reason is that they're only launching one and it has to work perfectly the first and only time it's launched. That level of reliability in a one-off product is incredibly expensive to achieve. With dramatically cheaper launches it would make sense to launch a much larger number of less reliable but much less expensive telescopes.
Another reason is politics, but SpaceX can't solve that one.
> it would make sense to launch a much larger number of less reliable but much less expensive telescopes
What if... SpaceX made up for the pollution they introduce by making the Starlink satellites look up the other way and push the captured data back to earth?
The lens and CCD would be small, but with the massive volume (and clear sky) it could add up. Like the amateur set ups using an array of consumer grade cameras.
Space based works for optical, but not all other wave length. For example it will also reduce the sensitivity of air cherenkov telescopes that detect gamma rays and that can not be moved to space.
Would air cherenkov telescopes be significantly affected by additional satellites in orbit? It sounds like they're designed to detect high energy gamma rays striking the atmosphere, so probably not?
is cherenkov radiation even observable during dawn/dusk +/- 2 hours? I imagine that the atmospheric refraction of the sun would seriously hamper those observations during that time period.
On traditional telescope using photomultipliers such as Magic, Hess or Veritas: no. But systems with solid state detectors such as FACT are moving in that direction.
Because cherenkov radiation is only observable in a transparent medium like air or water. Space doesn't work because the speed of light in space equals the speed of light in vacuum, therefore no cherenkov radiation.
Cherenkov telescopes for neutrinos do look down for reasons of schielding. Neutrinos can pass the earth, other particles not so much.
But those are a special case, air cherenkov telescopes are looking for "less weird" particles like photons or protons. Those can only be seen looking up, since the primary particles moving down focuses the cherenkov light down in a narrow cone.
While this certainly requires non trivial large scale space engineering, you should be able to build in in principle.
Basically a big bubble filled with the most useful gas for this + bunch of photodetectors inside at the appropriate places. You could also make the whole detection chamber much larger, than the ~30 km (?) of reasonably thick atmosphere you get on Earth.
Tonight. And what about when SpaceX gets all 11,000 satellites up there? And then Amazon's constellation. and then all the other American companies planning to do the same thing. And the European companies. And the Chinese companies and the Indian companies, and on and on and on.
Dropping a piece of plastic in a lake isn't a big deal. Until it's 11,000 pieces of plastic. And then hundreds of other people do it, too.
The viewing window is the same length no matter how many satellites there are at the same altitude, because Earth's shadow is the same for all of them.
Astronomers are already criticizing such ideas, and have already created an international appeal by professional astronomers open for subscription to ask for an intervention from institutions and governments. See: https://astronomersappeal.wordpress.com/
Isn't this exactly the same view as "if we regulate the use of fossil fuels, China will use way more than us and outcompete us economically" and "if we limit the number of nuclear weapons we create, there's going to be a gap between our nuclear firepower and Russia's"?
Creating a livable planet is not easy, but nationalistic thinking makes it a hundred times harder.
Which do you think has more capability to improve and save lives?
1. Cheaper internet available everywhere for anybody willing to pay
2. Better data on the cosmos
1. The response isn't really relevant, because I was pointing out an argumentative mistake in my parent comment. They said, "if we don't do X the Chinese will"; I was not making a point about the relative positives / negatives of doing X.
2. I'd go with #2.
3. Even if #1 is right, jumping to the conclusion that Musk's project is a good idea is a complete non-sequitur. As far as I know, no one has argued that putting 10000 satellites into space is the only way to provide widely available cheaper internet. As you can see from discussions elsewhere in the thread, it's not likely to even do that. Will SpaceX provide service to China?
Then we get blasted by a gamma ray burst from Betelgeuse and we're all dead. Studying the cosmos is extremely important, and studying threats (asteroids, supernovae, etc.) are just one part of that.
What is the point of studying the cosmos if we never leave our planet? Space is coming. Admittedly much slower than we expected. However SpaceX's satellites are just the beginning. Astronomy will continue, just much more so. Imagine a telescope array the size of the earth scanning the stars from orbit. Why look at an asteroid when you can GO there and do something with it?
You believe there's no use in developing global cooperation to regulate issues like this? Because if so, we have far more to worry about than satellites.
What useful science has been achieved in the last 100 years thanks to astronomy?
Meanwhile, what kind of useful science do you think can be facilitated by globally accessible high-speed internet? The value generated by such a network is clearly orders of magnitude more useful than observing the cosmos, at this juncture of human endeavor. Not too mention that Starlink will allow SpaceX to re-invest more and more money into space launches / space travel. I'd much prefer humans actually visit other celestial bodies rather than just staring at them.
In the last 100 years, advances in particle physics have been aided by our study of high-energy mechanisms in the universe (nuclear fusion in star systems, supernovae, acceleration of the expansion of the universe, etc.)..
so you have internet thanks, in part, to astronomy..
We did not discover nuclear fusion from the stars, we realized the possibility of nuclear fusion and subsequently realized that this is what must power the sun (and every other star).
Ditto for everything else on that list. We made discoveries by looking at things and performing experiments here on earth and then realized that these things must be what is causing X and Y out in the cosmos.
Part of what you say is true, we make discoveries by looking at things.. Astronomy gives us more things to look at, and in energy regimes that cost many $$ to replicate in experiments on Earth..
Your claim is not substantiated by the source, while mine actually is.
Without Einstein's E = mc^2, Arthur Eddington would not have realized that the fusing of nuclei could power the sun. In other words, he realized that fusing two atoms would release a lot of energy thanks to terrestrial research, and then hypothesized that this is what must power the sun. He did not come to this theory from staring at the sun through a telescope. Astronomy clearly did not lead to fusion - atomic theory did, which did not come from astronomy.
And neither did Einstein formulate E = mc^2 because he was an avid astronomer who wanted to understand the sun.
I am well aware this happened more than 100 years ago, not sure why you would be under the impression that I thought otherwise or needed to hear that for some reason.
The discovery and confirmation of relativistic physics has resulted in more efficient materials research and led to space technology (communications) and microprocessor improvements here on earth.
We absolutely do not have globally accessible high speed internet.
Starlink means you can be doing research in the middle of the Amazon and have good internet. Antarctica. Middle of the ocean. Wherever. Sure, population centres are all connected to the internet by now, but that's really not what I'm talking about.
Also, a good way to make internet cheaper (so that those in poverty have access) is to provide more alternatives to access / competition.
Third time I'm saying this, but starlink is not for consumers. It's not a "cheaper" alternative to your current ISP. None of your comment is based on any of the information put out by SpaceX.
None of those noble cases are actually what it's being built for though, the 100 scientists in the Amazonas aren't the reason you put up 1500 satellites in one year.
Likewise, those in poverty living far from population centres (by the way, those are the places with most of the people) are better served by being gifted 10 bricks so they can build an actual stove.
What is it being built for, if not globally available (as in, actually anywhere in the globe), high-speed, low latency, low cost internet?
It's built for whoever gets utility out of it and will pay for it, those "noble cases" included. It's not for them, but it enables them.
The internet can tell you how to build a better stove, farm better, raise animals better, discourage you from barbaric rituals that don't actually have the effect you believe them to have, etc. Arguably the poorest, most ignorant of the world are the same people that need the knowledge the internet can provide the most.
Internet access gives you access to actual knowledge. Yes, it also gives access to fake news and farmville, but I think those latter concerns are less important when you are having sex with babies to make your AIDS go away.
The discovery of the CMBR did not lead to the theory of the Big Bang. But astronomy in general certainly did, for sure.
That doesn't really answer my question though, but that's probably my fault for using a word as subjective as "useful", so let me rephrase:
How has astronomical knowledge of the CMBR/Big Bang/Black Holes/Pulsars/Galaxies/etc. fundamentally improved the human condition? What specifically have we been able to do (not "know") that we would not have been able to do without terrestrial astronomy?
The internet produced thousands of wonderful things. Your argument is 100% baseless.
Astronomy is nice too, but I will choose the internet every time, if forced to choose. We have wonderful images of the whole sky in all kinds of spectrum in incredible resolution.
SpaceX could provide a handful of at-cost launches for astronomy projects per year. It wouldn't fix anything for the ground telescopes but could be a bit of an olive branch for the community.
Starlink satellites cost < 500k each, compared to hundreds of millions for traditional sats.
If you mass produced space telescopes they wouldn't cost the ridiculous sums spent on JWST, which is a terrible example of the wasteful cost plus contracts of nasa. They've been planning it since 1996, and costs have risen from 1 billion to 10 billion.
I wonder how much it would cost to get a decent camera on one of those Starlink launch missions just so it would beam down some distortion free, high-resolution pictures to the masses.
Although I doubt that would provide meaningful data to professional astronomer.
One of the targeted markets of VantaBlack was the aerospace industry to paint the inside of baffles on telescopes and optical sensors. It is currently being used in some star trackers on satellites [1].
Overheating is definitely a big concern for painting your satellite back. There is a lot of work that goes in to thermal design of satellites and that surfaces have the proper optical properties for absorption, reflection and emission.
It's possible, although it's kind of tricky to use in practice.
From the Vantablack wikipedia article:
When light strikes Vantablack, instead of bouncing off, it becomes trapped and is continually deflected amongst the tubes, eventually becoming absorbed and dissipating into heat.[7]
Dealing with heat in space isn't easy, since you have no air to dissipate heat into.
Right, but that means that stealth costs mass (weight) and means less satellites per launch. So that means making them less visible costs more money.
For non spy satellites where stealth isn't one of the top goals, that might mean people don't do it.
Also, typically one does not simply ask a surveillance agency how they do things. They would probably respond with something like, "NO SUCH PERSON AT THIS ADDRESS, RETURN TO SENDER."
From what i read they are going with "partially painted black" Makes sense to only have the underside facing earth black. Also the satellites underside is only exposed to the sun with an steep angle because most of the time when it would be exposed to sunlight it's going to be in earths shadow. Reducing the extra heating even more..
Black radiates heat faster than white as well as absorbin it faster, so ostensibly the side in shadow should dump heat quickly if you have something like heatpipes to move it there.
Question: If SpaceX is successful in developing the Starship, couldn't they launch huge space telescopes for a very low cost? I'd imagine that SpaceXs efforts will be a net positive for astronomers in the end. If the satellite problems becomes too big, maybe they should offer discounts for launching space telescopes.
Another question.. if you are building a radio telescope in space, could you just use a thin foil that folds out like origami for the reflector?
> If SpaceX is successful in developing the Starship, couldn't they launch huge space telescopes for a very low cost?
If the BFR (the rocket behind the starship) is successful then yes it could mean the ability to launch very large telescopes in to space. The scientific community would be very exited about this possibility. However, this doesn't necessarily make it very low cost. One launch of the BFR would still likely be much more than an a Falcon Heavy launch.
> if you are building a radio telescope in space, could you just use a thin foil that folds out like origami for the reflector?
Yes! This technology already exists and it is really pretty amazing to see in action. Right now most of them are used on communications satellites or for synthetic aperture radar satellites. See the videos below:
BFR isn't a name that's still in use. Poster you're responding to was correct in calling it Starship: "SpaceX's Starship spacecraft and Super Heavy rocket (collectively referred to as Starship)" (from https://www.spacex.com/starship).
Starship projects to be significantly less expensive than Falcon Heavy _or_ Falcon 9. With total reusability of both stages and a construction built toward little to no refurbish or rehab, the cost per launch is nearly completely dictated (order of magnitude) by fuel costs, and project to be ~$2 million. This is an order of magnitude reduction in $/kg over the Falcon 9.
The article you pointed to said that is would be $2 million that SpaceX would have to spend on each launch. That would not be the amount for someone to purchase a launch with that rocket. Considering Elon estimated that development would cost $5 billion to $10 billion [1], the cost of launch would likely be much higher based on recouping the intial development and manufacturing costs.
As a side note, I don't really believe the $2 million price tag either based on my own experiences. Mission specific planning/services/verification tend to push prices of launches 10s of millions of dollars above the "sticker prices" that SpaceX puts on their website.
Nothing against SpaceX, I am a fan of everything they have done to decrease launch costs. They have significantly changed the game in terms of lowering launch costs. But it is really hard to take Elon's wild numbers that he gives the press at face value.
I know it’s extremely far fetched, but part of me hopes that if Starship is successful and they have they room, they could capture the Hubble and bring it back down to put in a museum.
Launch costs are a relatively small part of the cost of space telescopes. Pretty much always less than 10%, sometimes as low as 2% of the program's cost. The expensive part is building something that can run for years at a time with no maintenance. Things that are relatively easy on the ground (keeping some parts at cryogenic temperatures, having enough electricity) get significantly more complicated (and expensive) in space.
Is there a specific reason we're still doing ground based astronomy? With satellites becoming ever cheaper, sure we at some point should be able to get a significant telescope up there right? Are we waiting for the bigger rockets to accomplish that?
Yeah. Depending on the spectrum, the telescope might need to be really big. Not to mention at the moment a telescope in orbit would hard, if not impossible, to service.
It seems possible to launch multiple small telescopes and operate them as one large scope using aperture synthesis. I don't know if there are any existing designs or plans for this.
Also: somewhat ninja'd, see other replies as well.
> It seems possible to launch multiple small telescopes and operate them as one large scope using aperture synthesis. I don't know if there are any existing designs or plans for this.
We know how to do that in radio (VLBI), have some experience in IR (ALMA), are doing research on how to do that in optical. But in practice that is much harder than you think. The relative distances of the telescopes have to be known and constant to within a few fractions of the wavelength you are using. Hard when you are using centimeter radiowaves, insanely hard with optical light that has 600 nanometers wavelength.
We've been doing optical interferometry for quite some time. Homodyne techniques (see facilities, CHARA, VLTI, COAST, NPOI, SUSI) in which the light is interfered with itself are quite common. Heterodyne methods (one facility, ISI) in which the incoming light is mixed with a stable laser and downconverted to longer wavelengths are uncommon though.
Launch a bunch of small telescopes, connect them with a rigid structure. Keep it shaded. Shouldn't be impossible. And with no gravity and no atmosphere, even a light structure will keep it all positioned very precisely.
Innumberable reasons. Data transfer, stability, power, heat dissipation, ability to use large area parts, accessibility for fixing and upgrades, and on and on.
It's very expensive to build (especially large) space telescopes (JWST is already costing more than 8 billion at this point), and astronomy is not very well funded.
It's fascinating to me that the telescope costs so much more than the launch.
A high-quality 24" or 1-meter university-grade observatory telescope can be had for well under $1 million. If you multiply that by a factor of 100 to mount it on a satellite, you're still at 'just' $0.1 billion and can buy a whole Ariane-5 launch just like the JWST to put it at your desired orbit for $0.15B, for a total of $0.25B (a Falcon Heavy runs about half the cost for a launch). You could launch 30 of those (hopefully improving your factor-of-100 cost increase to something more manageable) for less than what the JWST will cost.
I get that JWST is a 6.5 meter telescope, not a piddly backyard 24" device, but why do we have to launch the best single scope possible?
JWST is being built to do things that are truly impossible on Earth. It is an infrared telescope that will image things that cannot be seen through Earth's atmosphere.
JWST is not the first IR telescope (Spitzer Space telescope, retiring this month comes to mind, 0.85 m diameter primary), but its size will allow both improved resolution (diffraction limit falls like 1/diameter) and improved collection efficiency (grows like diameter^2). Without constellation-flying and interferometric telescopes (see Keck Observatory), one cannot get either one from an array of small telescopes.
There are a lot of scientists grumpy about JWST because of its huge budget, but as long as JWST works, the view it gives of our universe will be spectacular. At this point, I think everyone really wants JWST to work, as so much has been sacrificed to make it possible.
Your $1 million university telescope probably wouldn't work long in space without maintenance, the ability to regulate temps, and rad-hard electronics.
See https://doi.org/10.1117/1.2031216 for the scaling of cost with size. It is very much not linear. Rather if you double the diameter the cost goes up by about a factor of 3.5 (closer to the area that went up by 4).
The university grade telescope, not sure what the entails, but I'm guessing it isn't hardened for radiation exposure and heat cycles seen in space. You can't use some off the shelf product unfortunately.
Making things survive in space is hard. Working functionally for the lifespan of the telescope is really hard. There's not a lot you can do once it's up there.
Aren't they mainly large so they have less hindrance of earth's atmosphere? Couldn't telescopes that are in space be smaller and have similar performance?
The are mainly large to increase resolution and sensitivity. Atmosphere limits how large you can make the mirror before hitting diminishing returns, but that is mitigated by good site selection, adaptive optics and lucky imaging (taking many exposures and keeping the least blurry ones).
Telescopes in space could have better performance, because you are not limited by atmospheric conditions for your angular resolution. But you still need a larger aperture to increase your theoretical angular resolution (see the Rayleigh criterion), and increase light gathering power.
For radio we might be able to make it work. But we currently don't have the ability to position satellites to within 10 nanometers, which would be required to make this work in the optical range that you have just killed off on the ground.
Large aperture means more light makes it into the telescope. JWST has a mirror assembly bigger than most ground based systems. It comes down to cost vs performance. For the cost of putting a small-mid sized satellite in orbit you can build one hell of an observatory that will function longer and have a much bigger tube. At a certain point it makes more sense to use orbital systems but only for certain types of experiments.
Is there a specific reason we're still doing ground based datacenters? With satellites becoming ever cheaper, sure we at some point should be able to get a significant datacenter up there right? Are we waiting for the bigger rockets to accomplish that?
That thought exercise should give you 90% of the answers to your question. The atmosphere and light pollution from cities are pretty easy to counteract with location and bigger optics.
The viewing window is actually pretty small. For most of the night the satellites are not visible because they are in Earth's shadow. There is an impact on astronomy but it is being overstated by journalists hungry for yet another "Big Tech bad" story.