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Astronomy

Dealing With All Of The Lights In The Sky

By Keith Cowing
NASA Watch
January 8, 2020
Filed under , ,

Keith’s note: There was a session and a media briefing today at the AAS meeting about large satellite constellations and their impact on astronomy. The SpaceX Starlink constellation got the most attention. It seems that people are either in the BAD or NO BIG DEAL camps. But there is a place in between where a bigger picture – an emergent property – presents itself. Pamela Gay from Cosmoquest managed to capture it. I experienced it in Nepal. We are becoming a spacefaring species – and that is now expanding to all corners of our planet. We can be smart about this and manage the impact, but there is no turning back. Space is useful.

My Star Trek Episode at Everest
“One night in April 2009, as I trekked through the Khumbu region toward Everest, I stayed in Dingboche (elevation 14,470 feet) at the aforementioned Hotel Arizona. I went outside to call my wife on the Iridium satphone. It was impossibly dark with a sky full of stars unlike any I had ever seen. I was just mesmerized. It was so dark that I literally walked right into a small yak that was wandering around the Hotel Arizona.
At one point my Sherpa Tashi came out. Tashi asked me why I was looking up at the sky. He had seen satellite phones before, so he knew what they did. I explained to him that it was hard to get a signal for more than a few minutes due to the high peaks surrounding us. So, I waited to see if I could spot an Iridium satellite (easy to do) and then dialed my wife. I knew I’d lose the call as soon as the satellite passed behind a mountain – but having the satellite in sight allowed me to parse my conversation.
Tashi is a very smart guy. But he was a bit perplexed about my satellite spotting. So I taught him how to do it and explained the different types of satellites and their orbits. Like his neighbors, Tashi had always assumed that all of the moving lights in the night sky were airplanes. When I told him that they were satellites lit by sunlight he asked how they could be lit by the sun at night. I asked him why some mountain peaks were still visible well after the sun goes down or glow before the sun rises. He answered matter of factly that this was because the mountains were very high. I then asked him to imagine a mountain 100 km tall – where satellites are – and said that this is why they were still visible. Having had the experience of 12 Everest summits under his belt and gazing out over vast expanses, Tashi immediately got the concept. Several days later I saw him teaching and explaining my satellite hunting tricks to several other Sherpas.
To this day I get a shiver from this – it was a very Star Trek moment – teaching someone what the “lights in the sky” were – with a piece of the Moon in my pocket on my way to meet a space traveller. Tashi was very psyched about that. But this was not my only Star Trek moment in Nepal.”

NASA Watch founder, Explorers Club Fellow, ex-NASA, Away Teams, Journalist, Space & Astrobiology, Lapsed climber.

54 responses to “Dealing With All Of The Lights In The Sky”

  1. ThomasLMatula says:
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    “The needs of the many outweighs the needs of the few or even one.-Spock.

    On one hand you have the billions who need access to the Internet to improve their life. On the other 10,000 or so astronomers who find it makes their work harder.

    • sunman42 says:
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      There are many ways to access the Internet on this planet. There’s only one sky.

      • ThomasLMatula says:
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        In urban areas, but try accessing it from rural areas. Plus once the satellites are in their operating orbit they will be too dim to be seen by most folks without optics. It’s only astronomers that will be inconvenienced by them.

        • Jeff2Space says:
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          But these LEO constellations will allow for Internet access in rural locations. 😉

          • SpaceGhost says:
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            I live in a rural area and have high-speed internet without starlink. Did you actually think us rural folks don’t have the internet?

          • kcowing says:
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            Have you ever been to Nepal?

          • SpaceGhost says:
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            A quick search reveals that broadband internet is available in Nepal.

            Also, the average person in Nepal likely won’t be able to afford a subscription to starlink ($40-50 per month seems to be the speculation).

          • kcowing says:
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            You have no idea how Nepal’s economy works nor how things are priced there. I do.

          • SpaceGhost says:
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            It never ceases to amaze me how many westerners are experts in developing countries and know what is best for them.

          • kcowing says:
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            Easy for you to sit there with a fake name to pontificate. What, pray tell, is your expertise in this regard, Mr. Ghost?

          • kcowing says:
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            A rural area in what country?

          • fcrary says:
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            I think anyone with enough money can have internet access just about anywhere. But, correct me if I’m mistaken, wasn’t _affordable_ high speed internet in rural Canada one of Mr. Trudeau campaign promises in the recent election? That’s what Starlink is about, not access but affordable access.

        • SpaceGhost says:
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          In the Canadian arctic, communities already have broadband connections. That is about as rural as you can get.

          • kcowing says:
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            Yea and how big are the dishes used and what is the size of the satellite that powers them and how much of the operation is underwritten by the government?

      • Not Invented Here says:
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        There’re other ways to look at the sky too, for example in orbit.

        • PsiSquared says:
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          How much time is spent on the sky by all terrestrial observatories each year? It’s not reasonable to think that any loss in viewing on Earth can necessarily be completely made up with many fewer space based telescopes. Consider the cost of a terrestrial observatory vs. the cost of a space based telescope.

          • fcrary says:
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            All the observatories on Earth? Including little 20 inch telescopes in light polluted areas (these days generally just used to teach astronomy students)? I’m not sure, but the issue isn’t as clear as you might think.

            First, terrestrial observatories can only observe for about nine hours or less per day (counting from astronomical twilight not sunrise and sunset.) Given weather, I doubt they average six hours per day of usable time. Possibly less due to scheduling issues and targets which don’t conveniently rise at twilight and stay above the horizon all night. Those problems are not issue for orbital telescopes. There are similar ones, but they can mostly be worked around.

            Second, these constellations only affect observations shortly before dawn and dusk. So, even at worst, the terrestrial observatories aren’t losing the whole night.

            Between those two factors, I’d guess it would take less than 5% as much glass in orbit to make up for the impact on terrestrial observatories. That’s still a lot, but also less than it might seem at first glance.

          • Michael Spencer says:
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            “How much time is spent on the sky by all terrestrial observatories each year?”

            Answer, in just a few short years: NONE. Because the heavens will not be visible. To anyone.

  2. Dewey Vanderhoff says:
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    Last I knew there were at least four other giant companies and numerous smaller outfits preparing to launch swarms of websats to LEO and MEO. Iridium’s 75 NEXT birds are already up there . Besides SpaceX Starlink there is Amazon’s Kuiper, One Web , Samsung, China’s YinHe… then the list gets huge and convoluted . Check out a rolling roster of satellite constellations here: https://www.newspace.im/

    One other thought is maybe the best place to put astronomical instruments going forward is also space. The potential observational rewards of major telescopes on the Moon is huge, especially on the far side. The astronomers might collectively adopt the ” if you can’t beat them , join them “. Just don’t use the James Webb ST as a role model.

  3. chuckc192000 says:
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    I heard they were planning to paint future Starlink satellites (maybe including this past launch?) to make them less reflective.

    • fcrary says:
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      One of the sixty they just launched was painted, at least on the Earth-facing side, to make it less reflective. That can mess with the thermal design of the spacecraft and it isn’t clear how much it will help. So they’re flying one to see how well this works. The final results will take a few months, since it takes that long for the spacecraft to work its way up to its operational orbit.

  4. james w barnard says:
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    Light pollution from the ground is so bad around many cities that you can barely see the Big Dipper! Best things the astronomers can do is wait until we put both optical and radio observatories where there will be no interference…on the far side of the Moon! Come on, SpaceX, let’s get that star ship going!
    Ad Luna! Ad Ares! Ad Astra!

  5. Mike Oliver says:
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    “Don’t it always seem to go
    That you don’t know what you’ve got til its gone
    They paved paradise
    And put up a parking lot” Big Yellow Taxi Joni Mitchell

    Yeah, I’ll appreciate the convenience of multiple internet providers and worldwide coverage, but I’ll miss the dark sky when its gone.

    • ThomasLMatula says:
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      The sky will still be dark, there will just be more satellites visible among the stars. BTW Starlink satellites are already starting to show up on the UFO reporting sites as UFOs. I expect they will be the next group to complain about them. ?

      • sunman42 says:
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        Sorry, but that’s a remarkably narrow view of what astronomy consists of. Please look up the Vera C. Rubin Observatory and then reconsider what the reckless Mr. Musk may have done. I say “may,” because a lot of astronomers are clever people and eventually some of them may come up with a way of scrubbing the multi-Pbyte time series data of the time dependent effects of these satellites — and removing any systematic residuals — as the satellites’ orbits constantly decay. I just hope that if there is such a solution, it doesn’t require the energy of the Bitcoin mining industry. The NSF doesn’t have that kind of budget for astronomy (and hates paying for the operation of facilities in any case).

        Oh, and in this case, “astronomy” includes tracking 90% of near-earth objects down to ~ 300 m in size. Maybe not as important as pictures of cats….

        • ThomasLMatula says:
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          If NASA was doing its job on searching for NEO, with requests by Congress going back to the 1990’s to search for them, they would have satellites in orbit searching for them. Satellites are especially needed for identify the ones with orbits mostly interior to the Earth’s orbit, a problem with all Earth based observatories. Hopefully Starlink will push NASA, or more likely the new U.S Space Force to do build such a network.

          • sunman42 says:
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            Do you really think it’s a reasonable use for the taxpayers’ hard-earned money to do it from space when it can be done from he ground, and as a by-product of observational effort with other, primary objectives? Even if Mr, Musk launches such spacecraft, the missions will cost far more than groundbased efforts, even those involving 3 Gpixel detectors.

          • ThomasLMatula says:
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            Ground based observatories are not able to identify well threats that come NEOs with orbits between the Earth and the Sun. Moving observatories into space closes this gap. In terms of Starlink, SpaceX indicated they are specifically working with the Vera C Rubin Observatory.

          • sunman42 says:
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            And one can only hope they can come up with a solution that (1) doesn’t degrade the data too much and (2) as noted above, doesn’t pass the energy requirements of worldwide Bitcoin mining.
            Whatever the solution(s) may be, processing even fainter satellite tracks enabled by less reflective coatings with require processing 15 Tbyte of data per night, every night, just to keep up. If better or different algorithms become available later, that’s a minimum of ~ 5.5 Pbyte a year.

          • fcrary says:
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            Visible light observations don’t give you the size of an asteroid, at least not better than an order of magnitude guess. That takes thermal IR spectra, and that can’t be done from the ground. And being able to observe both the northern and southern skies for more than nine hours a day also helps.

          • sunman42 says:
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            The LSST/Vera C. Rubin Observatory will operate with five of a possible six filters at any given time, at wavelengths up to 1080 nm. Could you please explain why thermal IR is necessary for size determination?

            As for northern and southern coverage, there’s nothing to stop interested parties from duplication the telescope design in the northern hemisphere — at, one suspects, considerably less cost than the original.

          • fcrary says:
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            1080 nm is barely out of the visible range. You need the thermal IR data because otherwise, you don’t know the albedo of the object. Visible light just gives you the amount of sunlight it reflects. It could be big and dark or small and shiny. You can guess at the albedo, but that’s only an uncertain guess not a measurement. The thermal IR spectra give you the amount of heat the object is radiating, and therefore the amount of sunlight it is absorbing. With that and the visible brightness, you can determine whether it’s big and dark or small and shiny. And that lets you determine the object’s size.

          • sunman42 says:
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            Thanks. And you can’t get an approximation to the total albedo from UGRIZY photometry? Most of the sun’s output falls in that range, doesn’t it?

          • fcrary says:
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            I’d call that an educated guess rather than a complete guess. From that, you can get a fair spectral classification and assume the object’s albedo is similar to that of other asteroids in the same spectra class. But the more asteroids we see up close, the more it seems like they are a very diverse group. Even within a given class, they can be different enough that I’m not sure about assuming they all have similar albedos.

            But I suppose that depends on the requirements for finding potentially hazardous asteroids. Is a factor of two in size (effective radius) good enough? Would that mean finding everything down to an estimated size of 70 m diameter, just to make sure we had everything with an actual size of at least 140? If so, would IR spectra and more reliable size estimates be more practical option?

        • Not Invented Here says:
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          Stop spreading FUD about Starlink, Elon Musk hasn’t done anything, reckless or otherwise. Astronomers in AAS235 already admitted 1,500 satellites in the initial Starlink constellation is not going to be a problem, they can handle it.

          There’re concerns once the total number of new satellites (not just Starlink, but OneWeb and others too) become too many, there’re also concerns about the brightness of the Starlink. The former is a problem for every satellite operator in the world, the latter is being resolved by SpaceX.

          Jeff Hall, director of Lowell Observatory and chair of the AAS committee, said: “We have not had to cajole SpaceX in any way. They’ve been very receptive and very proactive”.

          Oh, just FYI, NASA is already funding Near Earth Object Surveillance Mission (NEOSM) to find all near-Earth asteroids and comets equal to or greater than 140 meters in diameter, which BTW is a task assigned by Congress to NASA, not NSF.

    • Not Invented Here says:
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      A sky full of glittering space based platforms is the sign that we have truly become a spacefaring species.

      This won’t be about Starlink: SpaceX already promised they’ll reduce the albedo of the satellites so that its magnitude would be below what a naked eye can see. So they’ll keep the sky as it is, just temporarily added a few hundred satellites at magnitude 5 which will be replaced after 5 years.

      No, this is about what a future spacefaring civilization will put in orbit: large spaceships, space habitats, orbital factories, solar power satellites, etc. All these wonders we wanted to see, they will be bright and change the dark sky, and I think we should welcome it.

  6. TiminSoCal says:
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    I would assume that satellites are not lit up once in shadow, so wouldn’t this only be an issue near sunrise and sunset?
    Or is the concern that a tiny satellite would “eclipse” a star being observed and that would be a problem?
    I don’t get why the existing other satellites in orbit are not causing the same problem. Space is quite large.

    • fcrary says:
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      The satellites are only visible in twilight, not all night. But there are only so many hours in a night, and astronomers wouldn’t want to give up a couple of them.

      I haven’t heard any concerns over eclipsing. I suppose there is a potential to mess with high precision photometry, like transit searches for exoplanets. But that sort of work already involves weeding out brief, random drops in stellar brightness.

      One other concern I have heard is the radio emissions themselves. Even though the frequencies are regulated and almost all the transmitted power goes out in a very narrow frequency band, a very tiny fraction of the power goes out across a broad range of frequencies. That’s usually not a problem. But if you’re looking at a faint radio source, say a millionth of the intensity of the satellite’s peak emissions, and there are a few dozen of them overhead, all the time, it can add up to a problem. China discovered this with their Five-hundred-meter Aperture Spherical Telescope. The local government decided it would be great for the local economy to use it as a tourist attraction, and set up a big, high-tech theme park (or something similar) a few kilometers away. Of course, that sort of tourist will have a cell phone. Tens of thousands of cell phones isn’t consistent with the sort of radio-quiet zone the telescope needs. I’m not sure how that played out; I haven’t heard anything new in a year or so.

      As far as other satellites are concerned, sure. They are a similar problem. But there aren’t many of them. Thousands, not hundreds of thousands (if all the plans for all the mega-constellations materialize.) I think it’s the numbers which are the main concern.

  7. Daniel Woodard says:
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    We still have no idea how the user terminals are supposed to work. Even the possibility of a phased array antenna has been thrown into doubt.

    • Not Invented Here says:
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      Not sure what this is about, Elon Musk mentioned how user terminal would work in a recent tweet, SpaceX also has multiple patents already filed for this. Yes, it does use phased array.

  8. Michael Spencer says:
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    What exactly is the difference between what Elon is doing and, say, dumping mine tailings into a water supply? Nothing. It is pollution. And like pollution, rationale is often in terms of jobs, or life styles, or some great benefit.

    Mr. Musk’s plan is to basically steal a clear sky from the rest of humanity. By what right? By simply being able to launch satellites does this give the right to do it? And at huge expense to the rest of humanity? He can own the orbit because he’s capable of getting there?

    • fcrary says:
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      It isn’t clear that there is a problem. The initial satellites certainly would be, but SpaceX is trying to fix that. In any case, Mr. Musk wouldn’t be doing this by himself. I don’t think the business plan is sustainable without a large number of customers. They can’t charge a very high rate to a small number of people, because expensive, satellite internet is already available. I think they are planning on charging a modest rate to a very large number of people. And those people might decide they like seeing the stars more than they like Starlink. Or they might be convinced of that by friends and neighbors. People voting with their wallets has been effective in a wide range of things, from helping unions establish themselves to promoting non-polluting farming (“organic”, although I dislike the term, since the alternative isn’t inorganic…) If SpaceX can’t solve the problem, they may not have a customer base.

    • ThomasLMatula says:
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      No. Let’s look at the facts and not buy into the hype.

      When they reach orbit the Starlink satellites will only shine at around magnitude 6. That is dimmer than the planet Uranus at opposition. Which means they will be barely visible in a perfectly clear dark sky IF you have good vision. Also they will only be that bright for a short period about 30 minutes before and after sunrise/sunset.

      When the full 40,000 satellites are deployed there might be at most 30-40 satellites in the sky at once. Now it sounds like a lot but the sky is very big and they will be very dim. Even in a dark sky region you will really need a small wide-field telescope or binoculars to see them and you will need to know where to look. Unless you are very experienced in satellite hunting and have a finder chart you probably won’t be able to see a single one. If you don’t believe me start looking for the Starlink satellites already in their operation orbit. Note that all the pictures the astronomers are using to scare folks are of them starting their journey to their operational orbit. This only represents a very short (a few weeks) and a very predictable part of their deployment.

      So Elon Musk is not stealing the night sky from anyone. All he is doing is requiring professional astronomers to take one more variable into account when they image the sky.

      • fcrary says:
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        While looking at the facts, I can’t reproduce that 6th magnitude number I’ve seen in various places. They are currently (i.e. immediately after launch) around 2.5. The operating altitude is only a factor of two higher, and that would make them 4th magnitude, unless I’ve gotten the math wrong. SpaceX will need to do something to get their brightness down by another factor of five or so, before the’ll be 6th magnitude at their operational altitude. But that’s certainly possible and SpaceX is working on it.

        • Not Invented Here says:
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          It should be magnitude 5 in operational orbit. Immediately after launch, its solar array is not tracking the sun, instead it’s oriented to minimize atmosphere drag, which may cause it to reflect light to Earth and becomes unusually bright.

          There’s a Nature article about this: https://www.nature.com/arti

          • ThomasLMatula says:
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            That article was a good one, but I couldn’t find any information on the brightness of the operational satellites other than they could be brighter that 99% of objects in the sky, but it doesn’t define if its objects visible to the unaided eye, or all objects including very dim galaxies and dwarft stars, or the objects the Ruben Telescope is imaging in its survey.

          • Not Invented Here says:
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            This spacenews article has the brightness in operational orbit: https://spacenews.com/space…, the information comes from a presentation about Starlink and astronomy at AAS235

          • ThomasLMatula says:
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            I wonder if it is based on an actual measurement or just an estimate.

            This also reminds of the Iridium flare issue and how folks claim that would destroy astronomy. After a few years it was forgotten and the new generation of Iridium satellites don’t show the bright flares like the old one did.

        • ThomasLMatula says:
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          The 6th Magnitude was from an article in Sky & Telescope. That appears to be the magnitude the first batch is shining at now that they reached orbit and oriented themselves properly. Remember orientation also effects brightness. I will post the link tomorrow when I go online.

          • ThomasLMatula says:
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            Here is the Sky & Telescope article that references that the Starlink satellites from Spring are now at Magnitude 6. I imagine it would be easy for someone with the proper equipment to vertify this, but for now I accept what Sky & Telescope says as they have a good track record for reporting on astronomy. The article also views them as a threat, so I imagine if they were brighter it would have reported it.

            https://www.skyandtelescope

            The Starlink Situation
            By: Monica Young | December 3, 2019

            “The satellites launched in May first appeared around magnitude 2, similar in brightness to Polaris, but by July they appeared around magnitude 6, just within reach of the unaided eye at dark-sky sites.”

    • Not Invented Here says:
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      “What exactly is the difference between what Elon is doing and, say, dumping mine tailings into a water supply?”: Simple, mine tailing in water harms the general public, which is why there’re rules against it. Seeing a few more lights in the sky won’t harm the general public, which is why there’s no regulation against it. If it’s not forbidden, then it is allowed.

      “Mr. Musk’s plan is to basically steal a clear sky from the rest of humanity. By what right?”: That’s an absurd notion, by this logic airplane manufacturer and operators stole the sky first. Who give them the right to fly those big metal birds around the sky? Not me that’s for sure. (this part is sarcastic, the whole idea that sky can be stolen is insane)

      But seriously, who give him the right? The federal government of course, specifically the FCC and FAA. The former gave him the right to use the orbit and frequency, the latter gave him permit for launch. This is telecom industry, it’s heavily regulated, so I don’t get the outrage at all. There was a public commenting period when FCC is considering Starlink’s case, where are you when FCC was asking for comments from the public?

      “And at huge expense to the rest of humanity?”: What huge expense? There is no expense, if there is, there would be a law regulating it.

      “He can own the orbit because he’s capable of getting there?”: He doesn’t own the orbit, nobody does. But if nobody else is using it, then he can use it, it’s first come first serve, as it should be. Why shouldn’t he use it if nobody else is using it?

  9. cb450sc says:
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    I don’t think people entirely understand how sensitive modern astronomical instruments are. 5th magnitude is blinding. A small (1-meter class) telescope easily reaches 20th magnitude in a 30-second exposure, and is “pinned” at levels 100x fainter than the Starlink satellites. Even when in the Earth shadow they still shine in the infrared. Painting them won’t do anything at all. Even the existing satellites are annoying for current survey telescopes, but at least it’s livable. Increase that number by an order of magnitude and it’s a real problem. I headed such a project for years.

    In any case, no, there is no regulation for the constellation as a whole, and that’s a real problem. Yes, the broadcast frequencies fall under international telegraphy law, and the launch of the rocket itself falls under the purview of the FAA. But the release of the constellation falls between the cracks of all these agencies. Honestly, no one ever really thought a person could just hurl thousands of satellites into orbit because they wanted to. The law evolved around notions of spaceflight occurring at the national government level.

    • Not Invented Here says:
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      “Painting them won’t do anything at all.”: That’s not what the astronomers are saying at AAS235, Patrick Seitzer’s presentation shows the current Starlink satellite is bright enough to saturate LSST detectors, there’s a joint LSST-SpaceX engineering team to mitigate this, making satellite fainter is one of the solutions.

      “But the release of the constellation falls between the cracks of all these agencies. Honestly, no one ever really thought a person could just hurl thousands of satellites into orbit because they wanted to.”: No one? Teledesic was proposed in 1994 and has 840 satellites. And Brilliant Pebbles would place 10,000 anti-ballistic missile satellites in orbit, that was proposed in 1990. Constellation didn’t fall between the cracks, it’s just we as a society do not see adding a few lights in the sky as a big enough issue to regulate.

  10. Bill Housley says:
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    While I agree with you, Keith, we are going to bemoan the loss of the still night sky.

    There are only about 4000 stars visible to the human eye.