Ep. 555: Satellite Constellations and the Future of Astronomy

The other big issue at the AAS was the challenge that astronomy is going to face from all the new satellite constellations coming shortly. There are already 180 Starlinks in orbit, and thousands more are coming, not to mention the other constellations in the works. What will be the impact on astronomy, and what can we do about it?

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Fraser:                         Astronomy Cast, episode 555, “Satellite Constellations and the Future of Astronomy”. Welcome to Astronomy Cast, a weekly, facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, as always, is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute and the Director of CosmoQuest. And so, again, this week we are at the American Astronomical Society Meeting, and the other big issue that was hanging over the entire conference is the impact of Starlink and the various satellite constellations that are in the process of getting launched.

                                    There’s already 180 satellites in space from Starlink, making it the largest satellite provider in the world, and there’s gonna be thousands, tens of thousands more satellites. So, astronomers wanna know what was gonna be the impact, what mitigation strategies are there, and what does the future look like when there are tens of thousands of satellites orbiting the Earth; what does it mean for astronomy? All right, let’s get into the episode. All right, so here we are back at the American Astronomical Society Meeting in Honolulu, Hawaii, and we – the last episode we talked about the big controversy of the… construction of the Thirty Meter Telescope here on the Hawaiian Islands.

                                    The other big controversy that’s going on is, of course, the Starlink constellation. And literally, just a couple of days ago, SpaceX launched the third batch of Starlink satellites, another 60 satellites, into space, and it is safe to say that astronomers are outraged.

Dr. Gay:                      I think that’s an understatement.


Fraser:                         Understatement, yeah.

Dr. Gay:                      And… there were three different arguments put forward, and I have to admit at the top of this episode, I am somewhat biased. I desperately want to see the digital divide be overcome and low-cost internet to be available globally, and Starlink promises that. And so, a lot of what we’re gonna talk about today, the issue comes down to whether or not you trust Elon Musk to actually implement the low-cost internet. So, the three arguments that we heard today against Starlink, one was a cultural problem of “Oh but the children.” If you see satellites zipping around in the sky, will people still fall in love with the stars?

                                     Will your experience visiting a dark sky site turn you off to astronomy if you see satellites? And the cry of outrage we heard was that people won’t be inspired by the sky if they see manmade objects. Now, I have to admit, I distinctly remember exactly where I was the first time I saw a satellite. I was up in the mountains of the Caucasus camping beside a glacier. And I was sitting on a rock all by myself because being a teenager is hard, and I was 15, and sometimes you need to sit on a rock by yourself when you’re 15. And this satellite – I just saw something moving in the sky and I realized what it was and that realization of “I’m alone on a rock beside a glacier… but there’s a satellite moving through my stars,” that, at the age of 15, was an amazing moment.

                                    And this idea that satellites make it impossible for people to fall in love with the stars, I don’t think that’s the case, but it was one of the arguments put forward.

Fraser:                         Yeah, and we’ll get into the other arguments in a second, but sorta from a practical, technical standpoint, when the Starlinks are first launched, they are actually very bright. They’re above magnitude 2 or 3, which makes them easily visible to the unaided eye from many spots on the Earth, and they look like this train of – that’s moving across the sky. They call this… “string of pearls”. And then, as the Starlinks raise their altitude up to their final position of about 550 kilometers altitude, they’ve dimmed back to about a 5 magnitude, which is at the very limits of what the human eye can see in nice, dark skies.

                                    But, of course, in the eyes of an astronomer, that is incredibly bright; a fifth magnitude star is a very bright star in the eyes of a telescope. And then, the other problem is that when they pass across the sky, they will really only be visible to astronomy when they are low on the horizon during the summer months; so, when the night is the shortest, you’re gonna get – really, you’re only gonna be able to see these satellites right after twilight and right before sunrise and that’s it. And then, for the rest of the night there – won’t see any of these satellites.

                                    But as the nights get longer, the satellites get brighter over the entire night’s sky; and so, they’re anticipating that, over some of the big observatories in Chile and in the Northern Hemisphere when you’re in the middle of the longest nights, you’re gonna see these satellites run across the entire sky. So, there’s no question that these are gonna be very bright objects that are gonna move through your field of view and leave streaks.

Dr. Gay:                      And one of the things that people keep bringing up is, there’s already thousands of pieces of stuff.

Fraser:                         There’s 18,000 tracked pieces that you can pull from the database, right – 18,007, I think, you can pull from the database. And you can track the position using Celestis and other things like that. Yeah, so they’re – we know – and so adding another 1,200, which is the goal for Starlink.

Dr. Gay:                      Well, so let’s narrow this down even further. So, there’s 18,000 things up there. Prior to the launch of Starlink, only 200 objects were naked-eye visible. So, you could only look up 200 different things in heavens above and go outside and see them with your unaided eye. With Starlink, they’re adding well over 1,000 by the end of this year to the list of things that will be visible to the unaided eye, and it’s this brightness that is really the problem. I was an observational astronomer for a number of years before realizing I am “the Rain God.” In those years that I was still an observational astronomer, I had myriad satellites go through my images.

                                    But because they were low-brightness objects, there would be this straight line of pixels that, well, I couldn’t see stars in. But that line was the size on the sky that the satellite was on the sky. With Starlink what’s happening is these… well, captured photons that are reflected off of the satellite, there are so many of them that they saturate the pixels, spill over to adjacent pixels wiping out a larger swath of your detector than the satellite alone would wipe out. And when you saturate a pixel, that saturation can cause the next several images to have ghosts of that satellite’s passage still visible.

                                    So, not only are you wiping out the larger percentage of pixels with that satellite, but you’re wiping them out across multiple images.

Fraser:                         Yeah, and so a lot of these satellites, as they pass of field of view, can overwhelm the sensor and essentially make an entire observing frame worthless. And the speed that they’re moving is of great concern to the astronomers; as they move through, it’s about how quickly is this thing moving through your field of view and how long do you have to not be able to take data while this satellite is moving through. So, they’re quite concerned just about, overall, in the time domain as well. And, of course, the big observatory that’s gonna be the most affected is the newly… renamed

Dr. Gay:                      Oh, that’s a different controversy.

Fraser:                         – no, I know that’s like the third controversy, but we won’t get into that. But we – I think we can all agree that the Vera Rubin Observatory –


Dr. Gay:                      Observatory.

Fraser:                         – is a wonderful name for an observatory and –


Dr. Gay:                      Facility.

Fraser:                         – that’s gonna be the facility that’s gonna be deeply affected because it just is staring wide-eyed at the sky for – all night capturing as much as it can and as deeply as it can. And so, every frame is gonna have Starlinks and OneWebs and all that’s passing through them.

Dr. Gay:                      And this is a problem of because it has a giant field of view, the probability that there’s going to be a Starlink in any one image goes up. If you have a small field of view, there’s the potential that you can time your images to avoid having a Starlink in them, but because this is a huge field of view your ability to do that is greatly reduced, and they’re gonna end up picking up Starlinks left and right. And here, the question starts to become one of mitigation. So, folks are working with SpaceX to see, “Okay, what do we need to do to reduce the brightness of these objects so that they aren’t blowing out the detectors?”

Fraser:                         Yeah, and there’s more to it than that. So, someone from SpaceX actually gave a presentation this morning, and that was actually a bit of a surprise. And they didn’t do a very good job of letting us know that this was gonna happen; there weren’t a lot of people. We had the whole ballroom and there wasn’t a lot of people there listening to her talk. But they mentioned, essentially, a couple of mitigation strategies. So, the first thing is, with this first launch, they have applied some darkening materials to one of the 60 satellites to see if they’ve – some of their ideas to have a lower LB or a lower reflectivity.

Dr. Gay:                      And before you laugh at the fact that it’s only one, the thing you have to take into mind is these suckers were already largely built in preparation, and… turning around and refabricating, that takes time. And so, my suspicion, my hope… is that they were only able to fabricate one with the new materials fast enough to be able to test.

Fraser:                         And I think it’s – this is how you perform an experiment –

Dr. Gay:                      Yeah.

Fraser:                         – right, is you isolate the variable? “Does putting all this material on one of the satellites make it darker than the rest?” And we’ll find out what happens. So, that’s the first thing they did is they’re experimenting. And this is a good sign. This is the first time, I think, that any satellite constellation has ever had a conversation with astronomers and said, “What can we do to minimize our impact on your science?” There’s Iridium’s, the 200 others that we mentioned, plus all the 18,000; no one’s ever tried to make them not bright in the eyes of astronomers. So, the first strategy is to try to paint them, so they’re a little darker.

                                    The second thing is to provide an open-sourced, real time location of all of the satellites and their constellation, and to communicate with the other networks and anyone out there who is gonna be relying on knowing the position of these Starlinks. So, in theory, as the constellation gets built, you’re – if you’re a telescope operator, you are going to know when a Starlink is gonna be passing through your detector, and you’ll be able to shut the detector down, wait for the Starlink to pass, open the detector again, and continue to get your data.

                                    So, you won’t necessarily get that – if you’ve got a very precise amount of time; you’ll be able to use it carefully navigating around satellites as they’re coming by. The other thing is they’re going to provide very specific – and I forget what the technical term was, but essentially the launch trajectory of each new constellation as they go up. So, when that first trail is starting to head off into space – and it is gonna cause horrible streaks in any telescope, any amateur astrophotographer is gonna get this as well – they’re going to set – you’re going to know when that constellation is gonna be passing through, where it’s gonna be, and just to plan your observing time around those Starlink launches.

                                    It’s only a few months – or really, it’s only a few days a week… that they’re in this trail, and then they sort of spread out and shift themselves to that higher orbit.

Dr. Gay:                      But the second problem that we’re talking about, one of the additional parts to this is, while so far SpaceX has been extraordinarily – in terms of trying to build a relationship, saying, “Look, yes, we’re gonna work with you. Here’s all the ways we’re going to work with you,” SpaceX is just one of a myriad of companies looking to do this. And so, is China, when they start launching their constellations, are they going to do the same thing… with open source abilities to track?

Fraser:                         Did you know that China launched more rockets last year than the United States?

Dr. Gay:                      Yes.

Fraser:                         Yeah. So, this is – whatever happens with Starlink, there will be a Chinese version of Starlink.

Dr. Gay:                      And what is going to happen with all the other companies looking to do this? Because you know if SpaceX is doing this, it’s just a matter of time before we see the same coming from Amazon and, well, from everyone else. So, while, things so far – if you’re willing to trust that they will do what they say – and this is the sticking point for a lot of people, I understand – while it’s promising for SpaceX, we don’t know what the future will hold, and this is honestly terrifying to a lot of people.

Fraser:                         Yeah, yeah. There’s a lot of really mad people because they’re anticipating and it is… so interesting and I hope you’re – this is already starting to kind of echo the previous conversation that we had. It is completely flipped around. You have got astronomers who have this resource, the night sky, that they’re using to gather data, and it is sacred to them. And you have someone coming in and… wanting –

Dr. Gay:                      Saying, “Oh, but the internet.”

Fraser:                         – yeah, “Oh, but the internet” – wanting to utilize this resource, and the astronomers being concerned and wanting more dialogue and wanting to have their concerns taken very seriously. So, obviously, the whole irony of the situation is not lost on me.


Dr. Gay:                      They’re using the same words. There was an individual today –

Fraser:                         Yeah, they really are. Yeah.

Dr. Gay:                      – making a purely emotional argument saying, “But this is our cultural heritage. This is sacred to us.” It’s the exact same arguments.

Fraser:                         Yeah. Yeah, it absolutely is. So, you can see the same method for being able to resolve what’s happening with Hawaii is gonna be the same method that’s gonna be resolved – there was a couple of really interesting things. One is… the opportunity to be able to resolve this with regulation, that ship has sailed, that horse is out of the barn. And, in fact, the astronomers who are working with SpaceX on this have said, right now, there is no regulation option to be able to stop SpaceX from doing what they’re doing, to stop these – there was one issue, which was that in the radio spectrum –

Dr. Gay:                      And this is the third problem.

Fraser:                         – right. Okay, so in the radio spectrum – there was a very specific set of the radio spectrum that the satellite constellations aren’t allowed to use. It’s this 300 – 250 megahertz, and it counts for about 1/8of the spectrum that these constellations are able to use. And they were able to get them to cede… that part of the spectrum for radio astronomy, which has already sort of partly been… sort of defined by regulation. And so, they were able to rachet that back, and so you’ve got this part of the spectrum, which originally the satellite constellations were wanting to use and they have agreed to not use in order to continue protecting that spectrum for astronomy.

Dr. Gay:                      And this gets back to the relationship issue because one of the things that we heard over and over was, “But they haven’t turned on the satellites and we don’t trust them to have actually done what they said.” So, there’s a lot of fear right now because there isn’t the relationship that these constellations aren’t going to do what they promised and are instead going to do as the Iridium satellites did and just stomp all over the astronomical protected parts of the radio spectrum. And so, again, these two problems completely parallel each other, where because there is a lack of trust, because there is a lack of relationship, the… communications companies are saying, “We’re just trying to get internet to remote parts of the world, people,” and the astronomers are saying, “We don’t trust you.”

Fraser:                         Yeah, and “You could have at least told us what your plans were and we could have worked with you over years to come up with strategies and use all that engineering capability that you have to minimize the impact on both the night sky for everybody and ” because I think that… yeah, we’ve lucked out with this batch. Right? Yes. If you go outside, in almost any circumstance, you will not be able to see Starlinks. They are not gonna be this grid of dots in the sky that you are going to see and it is going to besmirch your vision of the heavens. But as we enter the Space Age and we get our gigantic rotating… space stations, as we get our –

Dr. Gay:                      We’re going to lose the sky eventually.

Fraser:                         – we are going to lose the sky, yeah. And so that is the downside. The downside of that Star Trek future is watching the Starship Enterprise… shine brightly in the night sky while you’re just trying to watch the meteor shower, as the Enterprise flies overhead.

Dr. Gay:                      And I’m kind of okay with that.

Fraser:                         No, I’m not. No. No.

Dr. Gay:                      But what we’re saying is, a lot of this comes down to, people are currently afraid and fear isn’t facts. So, when you hear people with both Mauna Kea, as we talked about in the last episode, and with Starlink, as we’re talking about today, saying, “But we don’t trust… but we are concerned that… this is sacred to us,” what you’re hearing is one group of people who just wanna try something new and amazing and advance society, and another group is saying, “But we don’t care about your advancements. We’re happy the way we are. Please go away.”

                                    And we need to build relationships if we do want to move forward, so that we can move forward together and sometimes be able to say, “I don’t agree with you but we’ve talked this out and you’ve heard what I have to say, so I’m gonna now sit down and support you.” And this is something that comes out of the software community a lot. You hash everything out, figure out how you’re gonna move forward; you have all the disagreements, but once you come to that conclusion you support the path forward. But you have to have the relationship. So, let’s work on building the relationships.

Fraser:                         Yeah, and I think obviously the position that I’ve had for quite a while is that it is now inevitable that everyone on Earth is gonna want access to the internet. It is the way that we as human beings will connect, and so then the question is “What is the way? Are we gonna build millions –l” right now there’s five million cell towers around the world, and it will take more five million more cell towers to complete the last mile to get everybody online, or “How many cell towers? Do we wanna go with 5G? What’s the impact on –” sorry, is it – yeah, is it –

Dr. Gay:                      5G, well –


Fraser:                         – yeah, 5G. “What’s the impact of 5G on –” it looks like those are actually pretty serious transmission power and we don’t know what that’s gonna do; if those birds –


Dr. Gay:                      Those eradicate weather… satellites.

Fraser:                         – yeah, the bird strikes on – there are millions of birds that hit cell towers. Right?

Dr. Gay:                      And beyond that, just the fact that… it is cost… prohibitive to run fiber optics to all the little islands of the world, to run the wires to every world village in, well, Canada.

Fraser:                         Yeah, you gotta lay cable through sensitive marine environments. You’ve gotta dig big, long fiber optic tunnels through permafrost, through – it’s madness to consider the engineering to planet Earth that will be required to provide the same level of internet access that these satellite constellations are going to provide. And… one thing that we did talk about a bit is that there’s gonna be multiple constellations. There’s not just Starlink. There’s the one from Amazon; OneWeb has already launched six satellites. The OneWeb ones are at an altitude of 1,200 kilometers, and they are visible for the entire pass through the field of view.

                                    There’s no time that they’re not visible; they’re always visible, but they’re dimmer because they’re farther. So, they’re only eighth magnitude but – which is still highly bright in any telescope. And there’s gonna be more of those. And, as you said, there’s the Chinese ones, there’s the Amazon – Amazon is planning 3,000-plus satellites.

Dr. Gay:                      One of the phrases that was used today is, “This is an existential crisis.” Do we protect the skies at the cost of our environment as we lay new communications, lines and towers across the world? Do we sacrifice the astronomy to erase the digital divide? Do we find a way to maybe compromise both and protect a few places? There are after all places in, I believe, Virginia where you can’t use a cellphone because of the Radio Quiet Zone. There are compromises, but they require relationships.

Fraser:                         Yeah, and I – there are 150 dark-sky preserves around the world. They account for 100,000 square kilometers of space in 20 different countries that you can go to, and you can see the Milky Way, you can see the night sky in a way that the vast majority of humanity will never see it. And if we lose those spaces, we will lose that connection to the night sky; if light pollution… peeks into every single corner of planet Earth and there’s no place you can go to be able to see the sky as it’s meant to be seen, that will be an absolute shame.

                                    And I really hope that we can figure out some kinda compromise that allows us to continue enjoying the sky and continue to do science, but also be able to connect to people around the world. And I don’t think anyone knows the solution yet. One quick additional comment. I know people are asking about this idea of painting the satellites black or using Vantablack or stealth technologies. And so, someone actually brought this up in a conversation – or it was in one of the press conferences, and they were saying that the problem is, is if you paint the telescope black, it now radiates in the infrared.

                                    So, the visible astronomers have an easier time with the night sky, but now the infrared astronomers have a worse time. And, of course, this whole time the radio astronomers are just screaming in pain from the shouting telescopes. So, it is gonna be a thorny issue, and I sort of wish we had started this conversation ten years ago as opposed to now, as these constellations are going up one after the other.

Dr. Gay:                      And this is really a case that was brought about because the astronomers were off sitting doing their astronomy quite happily not worried about how do you get the internet to the rest of the world. Whereas the communications companies that… well, make their money off of how do we get more people on the internet, they were thinking through this. And Dr. Phil Metzger is someone who’s actually done some interesting writing on this and just points out that this is a necessary step in the communications infrastructure of building a society.

                                    In the future, we will probably figure out how to do things that are lower latency, which means there’s less lag time between the two – between sending and receiving the signals… that they can be handled in a different than just sticking satellites in low enough orbits to drop the latency while also not having huge power requirements. We’re not there yet… and so this is a temporary step and… we don’t know what the future’s going to be.

Fraser:                         It’s gonna be bright.

Dr. Gay:                      Well –

Fraser:                         It’s gonna be light-polluted. Yeah.

Dr. Gay:                      – so, here’s the thing, though. You’ll still be able to see the Milky Way. These aren’t providing the kind of light pollution that a city provides. This is the kind of light pollution of, you’re looking at the Milky Way and it’s like there’s an airplane dashing across it, except it’s moving much faster and isn’t as bright as an airplane. So, if you can imagine – if you’ve ever gone camping someplace that isn’t a dark-sky preserve, that doesn’t have air traffic above it; if you’ve ever gone out to a farm, if you’ve ever gone out to Yellowstone, you can see that Milky Way, and then you also see all the air traffic.

                                    That’s what we’re looking to is, it’s going to be like a lot more air traffic, but you can by eye still see all the faint things. If you’re trying to take images, you’re doomed. It’s the people who are imagers that are doomed.

Fraser:                         Yeah. Yeah. I already have to… throw away so many frames from my astrophotos. I just can’t imagine how – where this is gonna go next. All right, well, so I hope that gives everyone the update, which is… Starlink marches on. Astronomers are – continue to be outraged. And we will continue this conversation over time as more and more of these satellites go up and more, hopefully, mitigation strategies are figured out. Well, thanks Pamela. It was super fun to, as always, hang out with you in-person here in one of these American Astronomical Society Meetings. It’s been ten years since I’ve been in one. I don’t know how recent you –

Dr. Gay:                      It’s been a few years for me as well.

Fraser:                         Yeah. Yeah, this was an important one. But I hope people enjoy all of the content that we’ve been streaming, bringing back. And who knows? Maybe we’ll go and do the next one.

Dr. Gay:                      And he didn’t do it, so I will. His “Guide to Space” and question and answer shows are about to have a flood… of amazing content. So, check those out, if you haven’t already. And if you want to hear more about the news that has come out this week, check out the “Daily Space” that we’re putting out with CosmoQuest.

Fraser:                         All right, and we’ll see you next week.

Dr. Gay:                      We will see you all next week. Buh-bye.

Announcer:                 Thank you for listening to Astronomy Cast, a non-profit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@astronomycast.com, tweet us @AstronomyCast, “Like” us on Facebook, and watch us on YouTube. We record our show live on YouTube every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 19:00 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Sorel, and the show was edited by Susie Murph.

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