It's perfectly reasonable for scientists to want to capture accurate data on the space surrounding the main subject being imaged. Simply erasing the satellites from photos does not recover the data on the space behind. Any data from behind the satellites is lost forever. This photo keeps the satellites in order to visually demonstrate this problem.
Remember that astronomy today is often done on a single pixel of data. Starlink blocks multiple pixels, and even ruins entire exposures when they flare up. This will make astronomical research, like searching for exoplanets, far harder and more expensive than it is today. Space telescopes are, and will always be, orders of magnitude more expensive than ground telescopes to launch, maintain and operate.
I understand for any specific image, there's going to be some lost background because of Starlink satellites, but that's not what this is showing, this is showing something that's not possible, right? Shifting all the satellites temporally so they appear together, arbitrarily maximizing the problem beyond what is real isn't an accurate depiction of the problem, IMO.
Put another way, if you erase the Starlink satellites from the images before stacking them, you then get a fairly accurate representation of the sky without any Starlink satellites, and you still have the data behind them (from the other pictures where that portion of the sky was not occluded). You can also probably fix the intensity of anything occluded in a few of the pictures but not others through some math.
Typically, you want to use one single integration time, if possible. Doing so can limit readout noise, for one thing. (Note that ground-based astrophotographers, with consumer cameras, often take multiple exposures to cool down the detectors. This is not a factor with the actively-cooled detectors in astronomical telescopes.)
For instance, the observations leading to the recent discovery of the two-planet exosystem  used roughly 15-minute integration times [2, sec. 2] across an 8 meter (!) aperture. This is a longer integration time than the 17, 30-second integrations that produced OP.
I think the above considerations about stacking vs single exposures are a side issue, though.
The saving grace is that many astronomical observations are narrow-field-of-view, and are done away from the illuminated part of the StarLink constellation. But, surveys or wide-field images could really be affected strongly, at the 30-40% level .
That’s not what bias frames  are doing. Bias frames measure a systematic effect in the conversion of stored charge to a digital number in the CCD device. You can then subtract it out.
The calibration offered by bias frames does not fix readout noise, which is a random, not systematic, effect that is inherent in the same conversion.
You can use the bias frames to compute the strength of the readout noise (i.e., the rms magnitude of its random part) but you can’t remove the random noise itself.
See sec. 1.1 of the linked reference for more.
As he mentioned, flare can cover a broader area of the sensor.
It's worse than any single image that's used to make it, so why make it at all?
It's like taking a picture of the one car every day driving on some empty road and then coadding them and claiming you're demonstrating density of traffic.
If you're doing a narrow field long exposure with tracking, that will be problematic and you'll loose data. Most scientific observations don't do long exposures, especially measuring highly variable things like exoplanet transits.
It's more effective to stack a large number of short exposures for scientific measurements. It's much easier to eliminate noise because everything that is not noise will be transient for a single frame in the stack. You can also remove frames with things like satellites, clouds, or airplanes without losing much data.
Knowing the ephemeris of satellites also allows observations to time short exposures to avoid occultations. Astronomers have been dealing with satellites, clouds, and airplanes for a long time. Amateur astronomers might have a harder time with Starlink satellites but they will adapt just like they did with the ISS and Iridium.
Not quite the whole truth, I think you're speaking a tad beyond your expertise. While you're right that transient science generally does short exposures (TESS is 2 seconds, Kepler was 6.5, LSST will be ~20 iirc), the vast majority of astrophysical science I've been exposed to (mechanical engineer at an astrophysics research institute), 10 or 20 minute exposures are more the norm. Especially when looking at faint objects.
Doesn't take away from your main point - astronomers will adapt. I think they're perturbed by this because Starlink makes their jobs even more complex, and thus more expensive. A cost that SpaceX doesn't bear at all.
I think astronomers have a right to be perturbed about Starlink et al. SpaceX seeming to not care about the effect Starlink satellites would have on astronomy is ridiculous. At the same time stupid mis/disinformation like this tweet is also ridiculous.
“Because of scattered light in the optics by the bright satellites, the scientific usefulness of an entire exposure can sometimes be negated,” AURA said in a statement last month. “Detection of near-Earth asteroids, normally surveyed for during twilight, would be particularly impacted. Dark energy surveys are also sensitive to the satellites because of streaks caused in the images. Avoiding saturation of streaks is vital.”"
That may have worked with analog film before we had satellites, but Starlink is just the latest and brightest addition to the sky that makes that an increasingly bad idea. Change is hard, but it's not that difficult.
Instead, AND a bunch of shorter exposures. Then, your streaks are not streaks, but a series of point sources that can be removed trivially.
If I poo in your front yard, would you be happy with me telling you simply "well you can just remove it, what's the big deal?" Or rather, pooing regularly somewhere on a lawn in a public park that you really like and visit daily.
Satellites move fast. Not only that, but you know exactly where and when they will cross your field of view, and for how long they'll remain within it. If the astronomy community can't muster the rudimentary image processing technology needed to reject satellites and other transient objects, I'm not exactly confident in their ability to finally figure out the whole origin-of-the-Universe thing.
Science is not just difficult because the research being done is hard; it's also difficult because everything you're trying to do is being done in spite of the fact 95% of the rest of the world could give a care leas that you're doing, so that last 5% of support you can count has to go a long way.
I can understand the bitterness perfectly, and to be frank, your response is exactly the reason they deserve to be irate.
(And I really couldn't care less how many astronomers disagree with the assertion that it's trivial to avoid interference to observations from satellite passes. If I want to know something about astronomy, I'll ask an astronomer. Astronomers, by the same token, should consult digital imaging experts before concluding that the rest of the world is out to wreck their careers with unreasonably-expensive or technically-insurmountable roadblocks. You guys can afford to lose a frame or two now and then in exchange for what Starlink offers the rest of humanity.)
Then again, I am also not a fan of putting more satellites into orbit either... mostly just struck by your comment as being not terribly odd to me.
Travelling to exoplanets is not hard, it just takes 1000 - 10,000 years.
There will be no FTL untill we can manipulate black holes, if ever at all.
So the first trip to exoplanels will be in a multi-hundred year hybernation, or a genration ship, or people that are so different from us that they don't mind the journey.
point me to the data behind the occlusion on a single frame.
I get the frustration, and no doubt I'll be pissed when I have a shot that's more affected, but amateur astrophotography seems like the least-important reason to be concerned about Starlink.
But then, the photo is going to get more attention, for sure.
I go further.
I myself think we need to take a second look at city light. I'd like us to begin working on making the milky way visible again.
The other side is to reduce emissions of aerosols and particles that scatter light in the atmosphere.
Yes, but when doing that, let's also take into account the fact that Starlink exists to open up space access. Starlink doesn't exist (just) to provide Internet access, it exists primarily to fund Starship and further reduce costs of space missions. This makes it one of the most important thing happening for astronomy.
Textbook example for tragedy of the commons. Luckily we didn't do the same with earthly resources like water, air, wild animals, ... oh wait
Space based telescopes give a much clearer picture than land based ones. You can't have ubiquitous and/or (relatively) cheap space based telescopes without a thriving launch industry that reduces costs. You can't have that without innovation and competition in the space launch industry. You are unlikely to innovation or competition in that industry the without a market need. Starlink is the market need right now.
Want lots of space telescopes to give you even better pictures? Don't kill off what's going to take you there before it begins. The astronomy industry needs to work with SpaceX to minimize the problem while also encouraging them (and anyone else working to drop costs to launch something into orbit) to succeed, not killing off or greatly delaying the oncoming age of ubiquitous and easy access to space telescopes because they are short sighted.
Aren't those far more expensive to launch and operate?
Moreover, you only need a guy with a wrench to fix a telescope on the ground. If your telescope is in orbit then the problem is a tad more expensive to fix.
Is the field of astronomy facing death because of Starlink? That seems a bit excessive.
I would say it's more like a national healthcare system covering only poor quality glasses for vision for a decade while they pump money into research and training for laser corrective surgery to both reduce the downsides and make it much more affordable, in preparation for covering laser reconstructive surgery at the end of that period.
> I already have a ton of money invested in earth telescopes. What good does it do me if you argue that in the future I might gain some capabilities if I scrap everything and buy a whole new infrastructure?
Again, telescopes aren't scrapping everything, astronomers aren't going to disappear. They're at most some percentage less useful than they thought they would be prior to this. That sucks, but homeowners have complained about other people moving in and obstructing their perfect view for a long time, so it's not entirely new. I don't support Starlink because I think SpaceX has some right over astronomers, but because I think humanity as a whole benefits from more industry in space, and there's a solution for astronomy on the other side of this, and I don't want humanity held back because astronomers feel it infringes on a domain with a problem they've generally not had to worry about (even if they would probably argue that they are doing it for the benefit of humanity by providing knowledge).
Bottom line, I think the benefit to humanity from increased space industry is greater than the benefit unhampered astronomy provides in a case where we impede that industry.
But the problem here is with the way that this debate is being framed. There is a false dichotomy that has been repeated here which I sum up as basically "Space-X is trying to solve humanitarian problem A, and astronomers are getting in the way! Deal with it astronomers, you are not more important than humanitarian issue A." but that's not at all what's actually happening. This is a monumentally impactful project undertaken by Space-X in secret, with enormous ramifications on science that -- despite the simplistic claims here -- are not something that can be worked around (LSST and other projects cannot be done in space, regardless of the cost of space delivery). Instead of responsibly investigating the impact, consulting with scientific agencies to either mitigate them, or prepare for the impact (as they are doing now after a huge outcry, but there is little that can be done now), they have instead opted to completely blindside entire branches of science, ruining decades of work around the globe and impacting tens or hundreds of billions of dollars in R&D. Even their press releases now say things like they are "learning how astronomical detectors work" -- that is extremely disturbing. That should basically never happen. There are responsible ways to do what Space-X has done, and they have shirked those responsibilities.
I'm not trying to really frame it as SpaceX. I think it's a bit more fundamental than that. There are benefits to lots of satellites providing services, there are benefits to decreased launch costs. SpaceX is only really in the discussion because they've leveraged the latter to achieve the former for their own benefit (and hopefully the benefit of others).
Put another way, even if Starlink wasn't a thing, do we think there wouldn't be the same amount of more satellites in the sky for other reasons and for a hundred different companies 20 years from now? If this is an inevitable problem (and I think it is, unless we decide Space industry is just not worth it), then what's the solution for astronomy? Whatever it is, we should just do it now, and maybe try to get some more money out of SpaceX for it, because it needs to be done anyway. This is a "the world is changing because of technology, I wish it wouldn't" type of problem, and we've seen how those play out. You're much better off if you work with the flow than against it. That is, coal miners can complain all they want and try to get intervention, but those that see the writing on the wall and jump into those retraining programs sooner than later will be much better off. That doesn't mean they shouldn't petition the government for more subsidies to help with that though...
> This is a monumentally impactful project undertaken by Space-X in secret
Secret? Starlink was publicly announced in early 2015, filed with the FCC in late 2016, and the maiden flight to deploy satellites was in 2018, according to wikiperdia. Maybe you're referring to something else? I'm confused as to what you're referring to.
> are not something that can be worked around (LSST and other projects cannot be done in space, regardless of the cost of space delivery).
Okay, but why? I can accept this is the case, and even likely for some things (I suspected not everything could be done exactly the same in space), but without details how am I or anyone else to weigh whether they think that specific task is more or less important than the alternative?
> Instead of responsibly investigating the impact, consulting with scientific agencies to either mitigate them, or prepare for the impact ... they have instead opted to completely blindside entire branches of science
They announced publicly and filed with the FCC 4-5 years ago. The first criticism I'm seeing about telescopes or astronomy is in late 2018 and 2019, and is more worried that they won't be able to avoid collisions and we'll have kessler syndrome, but maybe you know of earlier criticism. Was there criticism from the astronomy community prior to this? It seems like if they thought it would be a problem, they should have spoken up. If they didn't, why didn't they? The number of satellites is increasing, has this been an entirely non-issue for that community?
> Even their press releases now say things like they are "learning how astronomical detectors work" -- that is extremely disturbing. That should basically never happen.
Why? Has it been the responsibility of launching companies in the past to check with the astronomy community on whether they're impacted? Is publicly announcing your plans for years (and hyping them around the world) and filing with government agencies not sufficient in giving warning to people that might be impacted, and know better than anyone else - including the people launching the satellites - whether their specific jobs are impacted, to speak up?
To be clear, I'm not trying to be snide in these questions. Where I ask these questions, I'm actually asking these questions. For example, are space agencies in the habit of asking astronomers if a satellite will cause problems? I can see how NASA traditionally might have done that, but that might not have occurred to a company whose mandate doesn't also include a lot of astronomy work. In that case, maybe what we need are some legal frameworks to make sure this is assessed ahead of time (not that we can enforce anything the space agencies or companies in other countries).
you're right that this isn't just spaceX, this is a much larger problem. Not of satellites in general, mind you, we've been successfully contending with those for many decades now (they do have a detrimental effect from an astronomical perspective, but we can deal with them for the most part or incorporate them when designing instruments/experiments). The difference is the brightness and number of satellites in a constellation like starlink. They are brighter than >99% of other satellites.
> Put another way, even if Starlink wasn't a thing, do we think there wouldn't be the same amount of more satellites in the sky for other reasons and for a hundred different companies 20 years from now? If this is an inevitable problem (and I think it is, unless we decide Space industry is just not worth it), then what's the solution for astronomy?
The solution is more oversight, disclosure, and planning. Space-X is obviously going to do everything to the letter of the law and no further, because they are a competitive business. What you do in circumstances like that is add regulation and oversight so everyone is subject to the same rules and standards.
^ the above shows the results from some collaboration that, if Starlink follows through, could mitigate some of the effects in LSST (not completely). But this is the sort of thing that needs to be done before companies like Space-X start launching things.
> They announced publicly and filed with the FCC 4-5 years ago. The first criticism I'm seeing about telescopes or astronomy is in late 2018 and 2019, and is more worried that they won't be able to avoid collisions and we'll have kessler syndrome, but maybe you know of earlier criticism. Was there criticism from the astronomy community prior to this? It seems like if they thought it would be a problem, they should have spoken up. If they didn't, why didn't they? The number of satellites is increasing, has this been an entirely non-issue for that community?
Actually, yea the collisions are a problem for a variety of reasons, but I'm not even talking about that, I just mean the problems arising from the combination of very bright and very numerous constellation satellites. But that is another good point, and another good argument for international regulation to prevent catastrophes like that.
Back to your point: Space-X actually didn't release any relevant technical info that astronomers could use, so the brightness was quite a nauseating shock. Space-X was actually surprised by the brightness themselves (which is astounding to me). Here's a quote
"However, even at fifth magnitude the satellites are bright enough to pose a problem for professional astronomers who require long exposures on large telescopes to observe faint celestial objects. Seitzer said that, before Starlink, only about 200 objects in Earth orbit were that bright, but by the end of 2020 that could increase by a factor of nine because of Starlink. “So, life is going to get really interesting,” he said."
"While astronomers may have been aware that SpaceX was planning to launch Starlink satellites, they didn’t expect them to be that bright. “What caught everyone, principally, by surprise was the sheer brightness of the ‘string of pearls’ going across the sky,” said Jeff Hall, director of the Lowell Observatory in Arizona and chair of an AAS committee that handles light pollution and space debris issues." -- [https://spacenews.com/starlink-vs-the-astronomers/](https://...
The point is that the current legal frameworks in place are from a different era and are not prepared to deal with Starlink-like constellations, so astronomers don't really have much they can do at this point (there's a suit against the FCC right now, but who knows if or when that will succeed). There needs to be a collaborative solution and better oversight because completely destroying billions of dollars of R&D may sound like draining the swamp but all you are really doing is needlessly destroying billions of dollars in R&D. There's no reason why there can't be an oversight committee that enforces certain limits on constellation manufacturers (e.g. albedo limits, etc).
"There is a long history of international regulations for radio interference via the International
Telecommunications Union (ITU) going back to the 1930s. However, there are no regulations in place for light pollution from space as there are for the radio spectrum....While
the willingness of SpaceX to help is a sign of hope, without federal and international requirements for space light pollution, it is far from guaranteed that others would follow suit."
> Whatever it is, we should just do it now, and maybe try to get some more money out of SpaceX for it, because it needs to be done anyway. This is a "the world is changing because of technology, I wish it wouldn't" type of problem, and we've seen how those play out. You're much better off if you work with the flow than against it. That is, coal miners can complain all they want and try to get intervention, but those that see the writing on the wall and jump into those retraining programs sooner than later will be much better off. That doesn't mean they shouldn't petition the government for more subsidies to help with that though...
There fundamentally no real solution, only partial mitigations, and those are only possible with cooperation. Things like transient detections (useful for broad swaths of astronomy like cosmology, but also for near-earth object detection (i.e. asteroids) that has some very important practical benefits) will suffer greatly. Astronomers are simply asking to "work with the flow" -- we're doing absolutely everything we can to do that.
Astronomers are trying to get the word out now that this is a huge problem that needs a solution, otherwise we will lose an insane amount of pricey (and priceless) research. Right now astronomical organizations are playing extremely nicely with Space-X, not because we like them (I think a lot of people are rightly furious, some of these issues were due to pure incompetence and recklessness on Space-X's part), but because we have no other good option available to us. Luckily in this case, Space-X is relatively cooperative and supposedly "on track" to make some changes to partially mitigate some of these issues, but fundamentally some instruments are just SOL. And it will get much, much worse without interventions by governments.
This is very different than a "coal-miners" situation — we have no alternative. We either do the research, or we don't. Not to mention, there are currently billions of dollars of research being affected right now. That's already been payed for by you, the taxpayer.
> Okay, but why? I can accept this is the case, and even likely for some things (I suspected not everything could be done exactly the same in space), but without details how am I or anyone else to weigh whether they think that specific task is more or less important than the alternative?
Well, multiple things: ground based observatories have the ability to upgrade/maintain instrumentation (very very important), more sensitive/larger apertures that aren't really possible to put into space (these make it possible to do, e.g. LSST), extreme environmental conditions in space mean the addition of expensive complex engineering challenges, etc. Some things are possible to do from space, but mean 10-100x multiplier on the cost and/or development time of an already expensive project, regardless of delivery costs. Some things, like 8.3 meter mirrors that involve large machines to carefully assemble in place are just never going to be feasible to do in space.
> In that case, maybe what we need are some legal frameworks to make sure this is assessed ahead of time (not that we can enforce anything the space agencies or companies in other countries).
yea thats exactly what we need!
Extreme expense and complexity of space based telescopes is one large downside (saying "well space x will make that cheaper" um, maybe? but that will not happen for quite some time, and you realize you are parroting a PR department known for being hyperbolic? While ignoring the actual, real impact these satellites are currently having on billions of dollars of astronomy research, which happens on 10-20 year timescales?).
There are numerous benefits conferred by ground based telescopes that cannot be accomplished in space. Ground based telescopes allow you to have much larger collecting area, allow you the option to maintain + upgrade instrumentation (not possible in space, and if someone mentions "hey they replaced the hubble mirror, didn't they?" yes, at the cost of 250 million dollars), not to mention the barrier to entry for building ground based instruments is much lower and allows smaller projects to have a large impact without requiring a ridiculous amount of funding. See, e.g. https://www.astro.princeton.edu/~gbakos/satellites/ <- one astronomer's page detailing the impact these satellites currently have on his work; this is just one example. Lots of links, e.g. https://www.forbes.com/sites/startswithabang/2019/11/27/this... that will confirm the bare basics of what I'm saying here.
People thinking "oh well ML should fix that" may also be completely unaware that: no it cannot, unless you just want a pretty picture, because astrophysics is done on pixel-level brightnesses and once you saturate a pixel, there is no more information there, not to mention that even non-saturated pixels will have an insane amount of noise now, which degrades the SNR of otherwise good observations. Astronomy is done with some of the most sensitive optical/IR/radio equipment that exists (a large motivation to fund astronomy is for the innovation here that is relevant to other applications).
People saying "oh but space x is going to add some anti-reflectivity coating so it'll all be alright, Elon will fix it." Ohhh boy. Yikes. Here's the incredible page addressing this on space-x: https://www.spacex.com/updates/starlink-update-04-28-2020/ <- it's incredible because it flat out admits to an astounding level of ignorance about the impact of this, and makes several promises that may seem nice to a non-astronomer but basically amount to "we'll do something but it will not really change anything at all for any astronomy research, but we totally understand now that someone has finally educated us on the bare basics of operating in space."
> For example, earlier this year we launched DarkSat, which is an experimental satellite where we darkened the phased array and parabolic antennas designed to tackle on-station brightness. This reduced the brightness of the satellite by about 55%,
To give you an idea of how completely meaningless this is to astronomy: these satellites currently have an average magnitude of 5.5, brighter than the brightest stars, and virtually all of astronomy tries to be sensitive to > 10th mag (i.e. 1.5% of the brightness of 5.5 mag, so we're looking for > 99% brightness reduction before this even begins to mean anything) + this coating will affect IR measurements because black coatings are black because they absorb light, and things that absorb light get hot and things that are hot emit IR radiation. LSST will have a 5-sigma single exposure sensitivity of at least 22 mag (0.000025% of the current satellite brightness, no that is not a typo, so we would need 99.99997% brightness reduction).
> The huge collecting area of a larger telescopes like Vera C. Rubin Observatory leads to a sensitivity that will render even the darkest satellites visible.They are so sensitive that it won't be possible to build a satellite that will not produce streaks, in a typical long integration. There is much that can be done to reduce the impact of satellite streaks, and that starts with an understanding of how astronomical sensors work.
So nice of them to think of that, um, now? The rest of that section is a goldmine, saying basically "here is why we really can't mitigate this for CCD detectors used by all of astronomy because, well, they are looking at dim things and bright things ruin a large portion of the observations" while also concluding with
> While it will not be possible to create satellites that are invisible to the most advanced optical equipment on Earth, by reducing the brightness of the satellites, we can make the existing strategies for dealing with similar issues, such as frame-stacking, dramatically more effective.
No, no, no, no, no and no. There is absolutely nothing you can do with 30,000 5-6th mag satellites in the sky at all times. They will be in your images. Frame stacking will help to a point, but not even close to what you would need (not even within a few orders of magnitude). We will lose a large amount of effective sensitivity and a large amount of science will be completely lost.
People still shrugging this off should remember: instruments like LSST cost the taxpayer half a billion dollars and took 20 years of development, countless and priceless time investment from a large fraction of astrophysicists and astronomers (many at the top of their field), and would allow us to do incredibly impactful science, both from a philosophical standpoint (being able to observe 20 billion galaxies + stars allows you to do cosmology and other astrophysics that is otherwise impossible, see the science book: https://arxiv.org/abs/0912.0201), and from a practical standpoint (like NEO's)
So: even if you don't think astronomy is important, you should still care about this. It's a colossal waste of money due to the complete arrogance and ignorance of one rich guy. Absolutely did not have to be this way.
Elon Musk's entire MO is appealing to non-experts to drive the narrative, whether he's talking about Full-Self-Driving cars, or underground car tunnels, or Hyperloops, or a brain implant curing dementia, or these satellites. It's scary.
Look at some of the replies in that Twitter thread, "He's literally bringing internet to under-served locations!" as if any of this project is even functioning today, or there is no other way to provide telecoms to these places.
I've seen plenty of people saying some variation of "there are only 600 of these now, imagine what it will be like when there are 42k of them..." If I understand correctly, the number of bright satellites will be proportional to the launch rate, not the total quantity in orbit. Going off Wikipedia, they have launched about 1/8th of their 2024 goal, and the majority of the remaining satellites are destined for much higher (and dimmer) orbits.
Because the constellation needs constant replenishment, the launch rate (and hence the # of brighter satellites) will have to reach a steady state that is directly proportional to the size of the constellation.
We can extrapolate that in the future this rate will actually be significantly higher than it is currently:
They currently have permission to launch around 12,000 sats. They're launching around 250 per year. The current launch rate is only sustainable if each satellite lasts for 50 years.
If you expand that to the proposed 42,000 constellation, 250 new satellites per year is only sustainable with a MTBF of around 150-200 years per satellite, which is nigh impossible in low Earth orbit. Using a lower (but still very generous and optimistic) MTBF of 10 years, Starlink will need to launch 4,200 satellites every year, about ~15x higher their current launch cadence.
> the majority of the remaining satellites are destined for much higher (and dimmer) orbit
Just about all of the satellites they've orbited so far are hanging out around 550km. SpaceX initially got permission to go as high as 1300km, but they've since changed their mind. The new plan (still pending FCC approval I believe) is to keep all of the satellites between 300-550km. So the future satellites will be as low or lower than the current ones.
You have to actively tweak your settings to create this kind of photo.
> Almost every modern astronomical post-processing program has a rejection process (sometimes referred to as sigma-reject) to remove unwanted signals, though the exact sequence will depend on which program you use.
> The way this process works is that, while averaging all of the pixels in a series of, say, 10 images, the program mathematically calculates which pixels fall far away from the mean value because they're much brighter (or much fainter) compared to the same pixels in other frames. The algorithm then discards those out-of-range pixel values so they don’t affect the final image.
Wouldn't this process remove part of the comet trails as well as the satellite trails?
I mean, I get how it works if all you care about is relatively static like distant stars, but would it work for this specific use case?
In other words, the process works wonderfully to get rid of the starlink-emitted photons, but you lose that subframe's signal, lowering your signal to noise ratio. Not the end of the world. But inconvenient and sometimes costly to professional astronomers.
No, the most basic stacking is just to add the images together, resulting in trails. I don't see this as bad faith at all.
Unless you actually want to have the satellites there, then the stacking would just cut the region with the satellite from each photo and simply glue them together. That's how you can get this image.
I actually just tried it in Hugin. Normal stacking from 2 pictures by default made the objects that appeared only on one of the pictures semi-transparent. If I did this with more pictures, they would be so transparent that I wouldn't see them at all. But I could manually select a mask to cut out the portions that I don't want. If I select and exclude the object (satellite streak) it would disappear completely. But I could also purposefully include the streak and in that case all the satellite streaks would be included in full brightness in the result. That's most likely how this photo was made.
Presumably to the point where people who want to can subscribe to a Hubble-like satellite service and get all the space photos their hearts desire.
Also, we made a similar trade-off a long time ago - most people live in heavily light-polluted cities, because we value having street lighting more than being able to see the stars.
1. Space is a hostile place, and developing telescope that works there is much harder.
2. There are very real limits on size and weight of what can be put there right now, and rocket equation is ruthless.
3. Any type of maintenance or upgrades are basically impossible, compared to earth based.
4. Adaptive optics were such a huge breakthrough, that basically negated need for most of space based telescopes.
There's a feedback loop in space launches: they're expensive, therefore you launch less, so you need to add redundancies and spend more time ensuring the payload will work, which raises the development cost and increases mass, which makes launches less frequent and more expensive.
Conversely, reducing the cost of access to space means you can send more stuff that's less robust, which shortens development time and makes it less expensive, and of course makes technological progress faster.
Which translates to: suddenly space telescopes may be more affordable, and more of them will be launched.
Even with cheaper launches it's much harder to get that benefit in space--servicing missions are much more expensive than driving up a mountain...
We should be fair and acknowledge all the downsides, and if you disagree I would ask to waste a bit of effort and explain why we should ignore this costs on the public(maybe the costs are worth it in the long run but we should not ignore them)
Ground-based telescopes have a number of very significant advantages over space-based telescopes. You can build much larger and heavier telescopes and instruments on the ground. If you want to observe faint objects, you need more photons. To capture more photons, you need a larger primary mirror.
Space-based telescopes used to give higher resolution, but adaptive optics undo much of that advantage. In fact, because the diffraction limit is dependent on the size of the primary mirror, ground-based telescopes can achieve better resolution than space-based telescopes.
You can attach large, heavy instruments, such as massively multiplexed spectrometers, to ground-based telescopes. And you can switch instruments out and do periodic upgrades and maintenance.
Space-based telescopes have advantages in certain specific areas. They can observe wavelengths that Earth's atmosphere absorbs or emits at (such as the ultraviolet and infrared). They can achieve much better calibration, because there's no atmosphere to calibrate out. They can achieve high resolution across a wide field of view (adaptive optics negates the effects of the atmosphere in a small field of view). Sometimes you need these particular advantages, so space telescopes are critical. Often you don't, and ground-based telescopes are superior.
To me it seems like the moment we got a proper space telescope( Hubble) there was a ton of low-hanging fruit to discover at such a degree that so many years later we are still finding out new stuff. Compared to that Earth based telescopes seem to have to go through massive efforts to make headline discoveries( not that any other less discussed paper isn't important, it's just that... how would we know about e.g. the acceleration of the universe from an Earth based observatory?).
That's a function of how the media works. Ground-based telescopes are extremely important for astronomy, and I would even venture to say are involved in most major discoveries. Space telescopes are also extremely useful, but they're also much flashier than ground-based telescopes.
> how would we know about e.g. the acceleration of the universe from an Earth based observatory?
By observing type-Ia supernovae (SNe Ia), for example. Not only is it possible to do this with ground-based telescopes, but ground-based telescopes are the primary way it is done. Most of the SNe Ia observations that went into the discovery of the acceleration of cosmic expansion were done from the ground.
Isn't there a way of multiplexing lots of small telescopes together to gather more photons and effectively emulate a larger telescope in software?
If so, could you launch 1000 small telescopes into space and effectively have a (set of <1000) larger telescope(s)?
There are telescopes formed from arrangement of smaller telescopes (like mentioned Very Large Telescope of European Southern Observatory), but these have to be connected optically (by a system of precise mirrors), not just digitally.
Interferometry is much easier with radio telescopes. You can record the waveform at each dish, and then digitally combine the signals afterwards (there is specialized "correlator" hardware that is purpose-built to do this very efficiently). That means you can put receivers anywhere (on Earth or even in space), as long as you are able to synchronize the timestamps in the data well enough to digitally combine the signals afterwards. One of the major technical challenges faced by the Event Horizon Telescope, which imaged the black hole at the center of M87, was synchronizing clocks at stations on opposite sides of the Earth. They had to physically bring atomic clocks from one location to another. After they took their observations, they flew hard drives with the recorded signals to a centralized location to do the correlation.
The article on interferometry implied that this is "just" a matter of computational difficulty - the higher frequency means that more accuracy and computing power is needed to resolve an image. Is that right?
If so, surely this is a Moore's Law problem, solved by waiting a few years for the needed computing power to be cheap enough to use?
CCDs just count photons (incoming photons kick electrons into the conduction band, and you count electrons after each exposure). There are more advanced detectors that tell you the energy of the photons, but not their phase. If you can't measure the phase of individual photons, you can combine light from different telescopes directly, and let nature do the correlation for you. That's what optical interferometers do.
See European Southern Observatory's very large telescope.
Let me know if somehow I am wrong and for example Hubble is superior to all telescopes on the ground at the time it was launched. The best thing is to have it all, giant telescope arrays on the ground, telescopes in orbit, on the moon, on the other side of the sun/
All of these things are coming, in subsequent revisions of hardware.
Everyone on HN should recognise the pattern - it's very much a launch of a minimum viable product.
Truth is people never look at the sky period. Ask people when the moon is visible and most will say "during the night." But about half of the time, the moon is actually visible during the day. Wouldn't people realize this if they simply looked up?
You're going to say it's not a trick question; but it is a short question and expects a short answer "it's visible when X", and there isn't one, except the common approximation "Day: sun, Night: moon". Apart from that it's just a list of things which might be in the way of seeing it, and there's lots of them: "When it's above the horizon, enough not to be blocked by trees or hills, and the sky is clear, and the sun isn't too bright, and you're outside, and it's not behind a tall building, and your eyes are open, and you're facing the right way, and you aren't blind, and..."?
No, I don't think that's the reason. The moon is frequently very bright during the day, not even remotely hard to see. Moreover, people are mostly outside during the day, meaning that most of the time they have the opportunity to see the moon will be during the day.
I think the reason is that a supposed sun/moon - day/night dichotomy is perpetuated by culture (for instance, clock dials that use an image of the moon to symbolize the night) and that culture has a stronger impact on people's perception of the moon than their personal observations of the sky. I think they have seen the moon during the day, but the moon is very rarely the object of their attention. They see it, but rarely do they notice it.
The reason for such a culture emerging seems obvious to me; the Sun's presence in the sky obviously correlates with daylight perfectly, making the sun an obvious symbol to associate with the day. But then what symbol would you use for the night? There's a clear day/night dichotomy, creating a demand for a symbol that's inverse of the sun. However there's no object in the sky that correlates so perfectly with the night. The moon isn't there half the time, but neither is any particular star. You could use generic stars, and sometimes that's done, but stars aren't necessarily visually distinctive. The moon is visually distinctive and so it's pressed into the roll of being the symbolic opposite of the Sun, even though a trivial glance into the sky reveals that it isn't actually opposite of the sun.
I'd expect that from something like the East India Company in the 1700's or something. Not a modern company in a modern society.
A US company airplane passing over my house doesn't impact people in India, for example.
Airplanes have proven utility. Airplanes proved their utility before bothering people worldwide.
The country can still decide against it and now allow any more launches, and the satellites that are up there will come down naturally in a few years time. You may even be able to forcibly deorbit them if they still have propellant left (not sure if they do or not).
No-fly zones are almost always created for the government to do government things, and not for the direct benefit of the public (ie reducing airport noise for nearby residents).
A US plane passing over your house doesn't impact people in India either negatively or positively(except for the consequences of global warming). These satellites passing over the US and India can equally benefit people in the US and India. It's not like starlink is a US only service and SpaceX is going to prevent anyone in India from having access.
Satellites also have proven utility, as does the internet, which is why groups like the UN General Assembly HRC declared access to the internet as a basic human right.
I'm not sure this is entirely true. SpaceX is US corporation. They could easily decide to deny access, or otherwise limit what people can do, based on policies set by the US government.
See also, the GP post, referencing the East India Company.
EDIT: The point here is not whether StarLink is a net benefit or not. It's that it's a predatory capture of resources, fuelled by capital and advantages, which won't be passed down, but have a good chance of being used for further leverage.
EDIT2: I'm not against advancement, far from it, but if there are no tools to manage it, then we end up with oil companies again.
I don't understand how starlink is a predatory capture of resources. It's not like they are saturating LEO and no other satellites are allowed to be launched. There are multiple companies planning high speed satellite based internet, including one backed by the richest person in the world.
I think Jesse Pinkman said it best, "dolla dolla bills yo"
EDIT: It's not whether the technology is useful or not, it's about whether you are be ok with a handful people using natural resources in the pursuit of more wealth and influence, with no regard for the consequences. If you can't see any parallels in history, then :shrug:
Who would you suggest gets paid for putting satellites up? Who does American Airlines, or the random dude in the Cessna pay in order to fly over my house?
And yes, they can profit, just like telecom and other companies that use satellites do.
> with no regard for the consequences
The consequences being globally available internet, at the cost of a couple hundred scientists having a harder time doing the observation. If you can't see the upside because of the downside, then :shrug:
It's like how people have been upset recently about secret police; it can't be reduced to the specific actions that we know about, it's the process being unacceptable to some.
Not to mention there's already ways to get very high-speed internet to remote villages that want it. The only barrier is cost - but for motivated villages and/or governments, it's not very expensive ($10's of thousands up front cost, trivial long-term costs). I've sat in many conferences with people building out wireless networks in remote regions - very fascinating work.
There's some pretty non-trivial chance Starlink was only approved because of the Cult of Elon.
SpaceX wants to put 1,584 satellites in orbit to the cost of around $10 Billion USD, and will need to replace these routinely due to orbital decay.
There's only 2,666 satellites in orbit currently. 1,327 of which are from the US.
Re: No fly zones - they can be established for all sorts of things. There's no fly zones around many amusement parks, for example, and not just because of the remote possibility of some terrorist attack.
> UN General Assembly HRC declared access to the internet as a basic human right
That seems simply to be virtue signaling. Of course everyone should have access to information and knowledge, but that's not exclusive to the internet.
It costs money to provide internet access. Basic Human Rights don't cost money to exercise. The Right to be Free doesn't require a monthly payment to some mega-corp. If it did, you would not be free, would you?
> People in these remote places of the world are unlikely to be able to afford internet... not have a need or desire for it. They have other priorities.
Not my experience visiting some remote areas of India, Nepal, and Tibet. A single anecdote, but I gave a man a ride to the top of a mountain near Ganden monastery so he could use his cell phone. He went with a list of messages of various people in his family and who to send the messages to. He would normally walk 3 hours uphill in order to get service to send those messages (This was in 2007, maybe things have changed since then).
> The only barrier is cost - but for motivated villages and/or governments, it's not very expensive ($10's of thousands up front cost, trivial long-term costs).
Many places in the world wouldn't be able to drum up tens of thousands of dollars, and it isn't for a lack of motivation. But they might be able to drum up $500 and then $60/mo.
> There's some pretty non-trivial chance Starlink was only approved because of the Cult of Elon.
The FCC isn't composed of the twitter mob or the spacex subreddit.
I'm not really interested in debating positive or negative rights, or whether the UN was virtue signaling. My point was that many people view internet access as extremely important for humanity, and starlink and other projects may be an incredible boon for the world, at the expense of some astronomy observations.
So before 3G, when AT&T had an exclusive deal to sell a locked iPhone.
I mean I remember having to use dial up for the first time in years when I lived in Spain in 2005!
Actually maybe a white line is simpler to remove than a black one on a black background.
Seems like this is light pollution taken to a completely new level.
Less reflective. I don't think there's a way to make them not reflective, and many, many astronomical objects are very dim.
> Less reflective. I don't think there's a way to make them not reflective, and many, many astronomical objects are very dim.
Vantablack would probably be adequate for the timescales involved, at least for most terrestrial observations:
 eg. I can easily imagine a similar but more severe problem for a lunar farside observatory if (when?) Starlink is expanded to provide internet coverage for the Moon's surface. Of course, the main reason for a farside observatory would be shielding from Earth's RF emissions, so just people needing and wanting internet access on farside is probably going to be a problem first.
Even if that weren't the case, it's easy for the human eye to distinguish a star from a LEO satellite; the satellite is the one that's moving fast. I see no reason the sailors couldn't simply ignore the satellites.
I don't think astronavigation is used in any serious capacity anymore, so in that sense it's a moot point. Still, it's a cool practice and it would've been too bad to see that go away.
I'm sure there's other ways of solving the broadband problem. I'm sure there are other ways of getting the astronomical data. I'm also pretty sure that all of them would have their own trade offs. Everything does.
In this case, I think the unilateral approach that Musk is taking has hurt perception of the project as much as the trade offs represented by the project itself.
Starlink satellites are also only visible low on the horizon, and only for brief periods after sunset and before sunrise, because their low orbits keep them in the Earths shadow the rest of the night.
Also, the comet is a wide object. A wide image is just more likely to have any satellite in view.
> Why (on Earth) do you want to become a multi planetary species??
That's just an un-neccesarily foolish question. Why does a dog swim when you place him in a lake?
> Have you ever tried to live in Antarctica or in the Atacama desert (I have)? I support science, exploration, tech development but not foolishness. Do you surround your house with roads to explore distant locations?
Isn't that exactly what we've done as a society already?
On Twitter there seem to be a lot of people on who expect to live in other worlds soon, and not just to explore and study them. He's likely rhetorically responding to that idea. And I think it's worthwhile to confront those ideas critically. IMO as well, living off of Earth sounds hellish, given what we know now.
The person the Twitter poster is talking with is now suggesting that many people will abandon their physical bodies, and those that won't will live in cylindrical space colonies. He's speaking fantasies.
On Twitter there seem to be a lot of people who currently live on other worlds.
Assuming humanity exists long enough, it will expand throughout the solar system. At very least to the moon.
We can argue about how long that might take, but not about it ever happening.
That's a big assumption.
There's also the why question. What's on the moon that would make it worth all the difficulty to get there? I suppose we might have a semi-permanent research station on the moon or even Mars, but colonization? Unless we make some really unlikely discovery like unobtanium is only found on Europa and it's really super useful, we're not going to have space colonies.
The other potential industry will be moon tourism. It could become something like the new Mt Everest. Obviously only for the very rich at first.
Once it becomes a real possibility and not some crazy sci-fi project, governments may start competing, so as to not get “left behind”, even if it is not immediately profitable.
One way or another, unless we destroy ourselves, it will happen eventually. There’s a percentage of people who are just absurdly curious and adventurous, and want to go where no one has gone before, even if the cost is immense. Hell, for some, I’m sure even just desire to get away from their situation on Earth will be a big part of why they go for it. People like this will build the first settlements and bases on the moon and elsewhere in the solar system.
Edit: sorry for the constant edits. It’s a bad habit — I don’t always get my thoughts out on the first try.
And I'm not entirely sure how you turn water (H₂O) into Methane (CH₄). Granted I barely passed freshman chemistry 33 years ago so my chemistry knowledge isn't so good, but as near as I can recall, there is no process that will turn that input into that output.
And again, even if the moon is a source of water, there's not a significant need for any water mining operation at the poles to have a colony around it or even any human staffing. Putting people there on even a semi-permanent basis would likely eliminate any gains to be had from using the moon as a source of water.
Even the space tourism doesn't call for settling the moon. No one lives on top of Mount Everest either.
Also, the Lunar Gateway  is a key part of the plans by NASA/SLS. It's not about settling on the moon, it's about making it a stop off point to refuel or pickup supplies before going on to a further off destination like Mars. Instead of having to have all your fuel and payload when taking off from Earth, you can have a lot of your supplies and weight on the Moon. This means your trip off Earth can be cheaper. Getting out of Earths gravity and getting to escape velocity is the hard part. Getting off the moon is a lot easier.
"OP" refers to the OP of the Twitter thread.
I'm just the submitter and do not share their view on being a multi-planetary species at all (I agree that it sucks to have streaks on your astro-photos, as I started taking them recently).
We have to boldly go where no man has gone before.
Edit: changed wording to restore split infinitive.
evidence: Brazil's rainforest. Indonesian palm oil. Chinese mines. African, well, everything.
For most of human history, nature has been trying to kill us (if that's too anthropomorphic, we can go with the longer-form "The processes of nature are ambivalent to the survival of our species and individuals in that species, and there is no guarantee that the natural world is one habitable by humanity. Our species' history is shot through with plagues, floods, famines, and predation, and much of our technology was created to minimize that.")
All these talks about “multi-planetary species” are bunk in the long term, anyway. We will probably have observation outposts scattered across the solar system, but that’ll be about it for quite a long time.
The only realistically reachable planet in the foreseeable future is Mars. We could fix our issues with Earth for a fraction of what it would take to make it inhabitable.
We’ll send our billionaire pioneers to the moon alright. With a scientific base as a side effect. It still won’t improve anything that’s wrong with Homo Sapiens.
See, e.g., this link for comments by Musk: https://www.space.com/spacex-starlink-internet-satellites-ma...
Without actually venturing out there, we might never develop viable star travel.
"Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith."
If you wouldn't mind reviewing https://news.ycombinator.com/newsguidelines.html and sticking to the rules when posting here, we'd be grateful.
Fixing the image is not a matter of "editing it out in photoshop". It's a matter of processing the data correctly in the first place, e.g. not editing it in. The author of the tweet stacked his images to show every satellite instead of removing every satellite, which is ass-backwards.
Note that simply putting telescopes in space is not a viable solution to these problems.
Several observatories were built near cities. As light pollution from terrestrial sources have increased, they've found their expensive optical telescopes become toys, and have moved their scientific collection utility over to radio.
I'm looking forward to someone launching a satellite telescope network with the collection radius of an Earth orbit.
>Space junk. There HAS to be another way to improve internet communications, does Humanity and planet Earth's livestock need this (5G)? Really?
It's mostly the media, who care's not for science at all pushing this 'we should be outraged', but we eat it up.
Starlink and others helping the world will also create a whole new genre for ground based space photography the super rich can get into, but this drama is so tiring.
People's comments here are generally insane to me.
Let's go to other planets.
Let's build a Dyson swarms of O'Neil cylinders with a quadrillion humans living in luxury.
Let's keep the light of consciousness alive.
Some things will change along the way, like amateur photography.
To me it's like complaining that your photography hobby is harder now that more people can afford to travel and they get in the way of your favorite tourist shots.
I'm sure there are good examples of trade-offs that matter here like the impact on terrestrial research telescopes, but a guy snapping a pic of a comet and ranting about it on Twitter frankly has the opposite effect on me.
Your sympathy or lack thereof is your business, but astronomy is one of the rare sciences where amateurs still do a great deal of work and make important discoveries.
> I'm sure there are good examples of trade-offs that matter here like the impact on terrestrial research telescopes, but a guy snapping a pic of a comet and ranting about it on Twitter frankly has the opposite effect on me.
It's a shame you would allow your opinion on an important subject to be swayed by a single tweet on an issue you apparently know little or nothing about.
I believe that's part of the goal of SpaceX
There are also reasons for humans and animals to not want new, moving stars for reasons other than pure utility. At the very least, these shiny beacons are an insulting advertisement for Musk.
Next, people will be defending a Pepsi ad on the moon or something. https://www.theatlantic.com/science/archive/2019/04/pepsi-ad...
The cost to put the thing into orbit is minuscule compared to the equipment and operation itself.
Put another way - SpaceX isn't solving any problems here.
Interference with GPS and other signals overwhelmingly comes from ground based sources.