Think Out Loud

Why a University of Washington astronomer thinks environmental protections need to extend to space

By Sheraz Sadiq (OPB)
May 16, 2022 8:46 p.m. Updated: May 24, 2022 7 p.m.

Broadcast: Tuesday, May 17

This image shows satellites, visible as vertical streaks, in the night sky. The highly reflective satellites and exponential increase in them in the Low Earth Orbit can hamper celestial observations by astronomers and amateur sky gazers alike.

This image shows satellites, visible as vertical streaks, in the night sky. The highly reflective satellites and exponential increase in them in the Low Earth Orbit can hamper celestial observations by astronomers and amateur sky gazers alike.

T. Hansen/IAU OAE, Creative Commons Attribution / T. Hansen/IAU OAE/Creative Commo


Satellites whizzing above Earth have revolutionized how we communicate, navigate and even monitor the greenhouse gas emissions that are driving climate change. But the number of satellites being launched into orbit is expected to increase by tens of thousands in just a few years, and are already making it harder for astronomers and amateur sky gazers to peer deep into the night sky. Meredith Rawls is an astronomer and research scientist at the University of Washington. She and a team of international astronomers argue in a recent paper that space needs environmental protections, much like establishing marine protected reserves or biodiversity hotspots. She joins us to talk about making the case for space environmentalism.

This transcript was created by a computer and edited by a volunteer.

Dave Miller:  Satellites whizzing above the earth have revolutionized how we communicate, navigate and even monitor the greenhouse gas emissions that are driving climate change Satellites are not exactly new Sputnik was put into orbit back in 1957 but the number of satellites being launched above our heads is expected to increase by tens of thousands in just a few years. Satellites are already making it harder for astronomers and amateur sky gazers to see stars and planets and all the other non-human stuff in the night sky. Meredith Rawls is an astronomer and research scientist at the University of Washington. She and a team of international astronomers argue in a recent paper that space needs environmental protections, much like marine protected reserves or biodiversity hotspots. Meredith Rawls joins us now. You have a graph at the top of your recent paper in Nature that shows the total number of tracked human made objects in space over time since the 1960 or so. And in the last five years, the line representing the number of active satellites has gone almost straight up. What has been happening?

Meredith Rawls:  It’s really the last three years that it has gone from kind of a steady state slow increase because lots of, you know, a few satellites are being launched here and there to this really unsustainable rapid increase due to the new commercial low earth orbit satellite constellations that are starting to be launched. The two that are currently up most right now is SpaceX’s Starlink and also theUK based Oneweb.

Miller:  So [partly] as a result of Startling, Elon Musk’s company, to provide satellite based internet globally at some point, what’s the increase of satellites orbiting above our heads right now that we’ve already had and what’s expected in the coming years?

Rawls:  Yeah. So right now there’s something like five or 6000 active satellites and when you take a look at all of the different companies and organizations that have filed an intention to launch satellites from places around the world, it is not at all unreasonable to say wow. In 5 to 10 years we might be looking at a population of 100,000 satellites and that doesn’t even assume that every single project proposed gets off the ground because they probably won’t. But there are hundreds of thousands of filed intentions with the FCC here in the US and the International Telecommunications Union for International filers. [Those] are the two main bodies that we keep an eye on and it’s a huge increase.

Miller:  A 20 fold increase is possible in not that many years?

Rawls:  Yeah.

Miller:  You said that these are in lower earth orbit mainly?

Rawls:  That’s right. Yeah. So you can kind of divide the different regions of orbital space above the Earth and the three different segments. Low Earth orbit is the one closest to Earth’s atmosphere and it goes until about 2000 kilometers above Earth.And then there’s medium Earth orbit which is higher still and there’s geosynchronous orbit which is up at like 36,000 kilometers and that’s the location at which a satellite appears to not move at all in the sky and hovers over your position because it orbits at the same rate that the Earth spins.

Miller:  Which one of those versions, a satellite that appears fixed because we’re moving with it or one that whizzes around us. Which one is more problematic for an astronomer like you who’s looking up to try to understand the universe?

Rawls:  Well, if you ask some of my radio astronomer colleagues, they’re not particularly thrilled about a huge number of geosynchronous satellites to be honest. But the real increase that we’re seeing right now and that I’m most concerned about is the low Earth orbit satellites from these various commercial companies. And that’s because as you say, they whiz across the sky super fast. So they reflect sunlight and they leave bright streaks on our images and other data products and you can often see them shortly after they’ve launched. They appear as these kind of beads or pearls moving across the sky as they’re getting up higher into their final orbital altitude and people more and more, when they go out to stargaze or looked at the lunar eclipse the other night if they didn’t have clouds, you’re able to see a whole bunch of kind of surprise satellites.

Miller:  Is there a way to digitally erase satellites from the images you get from your sophisticated telescopes or does optics not work that way?

Rawls:  So to a point, you can use some clever algorithms to identify and kind of ignore the pixels in your image that are affected by a satellite streak. But you’re not able to recover the things that are behind it. And you also wind up in a situation where, if you’re trying to do statistics on your image to figure out how things are distributed across the sky and you suddenly introduce a whole bunch of stripes every which way, you’re not able to really get a robust statistical measurement of distributions in the sky. There’s a whole bunch of missing stripes everywhere.

Miller:  Can you give us a sense for what the worst case scenario - meaning the status quo continuing - 100,000 satellites in low Earth orbit in a decade or so. What would that mean in terms of a huge project that you’re a part of - the Vera C. Rubin observatory that’s going to be going online in Chile in just a couple of years. What would that mean for the data you’re hoping to get from that gigantic telescope?


Rawls:  Yeah, it’s a real concern. This telescope is particularly vulnerable to large numbers of bright satellites because it has a wide field of view. It looks like a large swath of sky all at once and it has a very sensitive camera and a big mirror so it can collect a lot of light. All of these features make it really great for discovering cool new things in the universe. But they also make it highly vulnerable to lots of bright satellites whizzing across. And so it’s difficult to predict the exact impact for different versions of a future with different kinds of satellite populations. But we do know that it’s not great if there’s a whole bunch [of satellites] because it contaminates our data products, where we’re doing the best we can to build robust data pipelines that will not accidentally alert on our satellite when we say ‘hey, it’s a supernova [when] actually it was a satellite or whatever the situation may be. But we will not discover as many things and we will have more contaminated data products if we’re in a situation with 100,000 satellites in the sky, which is not unrealistic at all if things continue as they currently are.

Miller:  If I’m looking up in a place that doesn’t have much light pollution in the sky and I’m lucky enough to get a clear night where I can really see the universe above me, I’m thinking just as a layperson, not about contaminated data products. I’m thinking about the majesty and awe and sort of terrifying immensity of the universe. So I’m curious how you think about what this means for the rest of us, the rest of us who both could benefit from what you’re learning as a scientist about the universe, but also could benefit or enjoy looking up and not just seeing versions of ourselves up there. What’s at stake in this, broadly, for humans?

Rawls:  So I got into this originally as an astronomer who wanted to be able to have, as you say, uncontaminated data products. But that really is as a small piece of this larger issue, which as you say, is really about [being] on the cusp of fundamentally changing the night sky, which has been roughly the same for human ancestors for generations and generations. Sure there’s been localized light pollution, right? You’re not going to be able to see the Milky Way from downtown Portland or Seattle. That’s a given. But you can drive to a more remote site for the most part and, if the weather cooperates, see how it’s always looked - an amazing sky. And it’s not just scientists who use the sky, right? There’s all kinds of different cultures and storytelling traditions, indigenous people and others who use the night sky for all kinds of things - for way finding, for different practices. So when you’re talking about just unilaterally launching a bunch of really bright things that will permanently alter a part of the fabric of our night across the entire globe, that really concerns me.

Miller:  If you’re just tuning in, we’re talking right now with Meredith Rawls, an astronomer and research scientist at the University of Washington. And we’re talking about a particular kind of light pollution, the one that comes from the reflection of the sun off of satellites that are orbiting above us. What are the regulations that currently exist that govern how satellites end up above us?

Rawls:  There are some but there’s not enough. Essentially, you have to get a permit to launch and you have to get a permit to operate. And these constrain things such as radio frequencies that are allowed to transmit at. So, you can’t just blast over the entire electromagnetic radio spectrum. You have to have transmitters that are licensed in certain bands and what have you. But there’s currently no regulation of the maximum number of satellites that any one operator can have or how bright they are in any kind of optical visible wavelength. The only regulations right now are in the radio spectrum. And as many of my radio astronomers will tell you they are insufficient there as well.

Miller:  This is embarrassing to say, but it was news to me, until I was preparing for this conversation, that satellites don’t have lights - that all we see is just a reflection. I think I just assumed they were sort of like airplanes with lights.

Rawls:  Well some can have lights. There actually are some. We’re also concerned about the potential for future space billboards. At the moment, thankfully, the commercial satellites that are being launched don’t have anything like that and it’s all reflected sunlight. But even just the reflected sunlight is a big issue.

Miller:  Is it possible to construct them in ways where they will actually reflect less light?

Rawls:  Sure. To a point that is absolutely helpful. And we’ve actually been very pleased. Astronomers have been very pleased that some folks at SpaceX have iterated on their engineering designs to make different darkening mitigations. So they painted one a little bit more black and it was a little bit darker. Unfortunately, it was also too hot so they weren’t able to continue doing that. They manufacture these little visors that can kind of block some of the reflected sunlight and that helps make them dimmer as well. My understanding is that those visors weren’t more feasible for the long term going forward. So now they’re back to iterating on some different kinds of darkening coatings. But a lot of these details are very proprietary and company specific. So I don’t get to know about the details as they’re happening. We kind of have to observe and say, ‘oh they’re darker. Maybe they change something or oh, they’re brighter. Maybe they did something else’. [That] can be a little frustrating when you’re just trying to get your images or see the sky.

Miller:  Can you describe the regulatory system that in your dreams we would have globally, what would happen if someone came to this regulatory body and said, ‘I want to send 50 more satellites up into space because I want to provide better weather forecasting or satellite internet for subsistence farmers in sub Saharan Africa’. They go to you and they’re ready to launch and what’s the process you’d like to see in place?

Rawls:  Wow. Yeah. I do think there’s a need for satellites. Just to be clear, I’m not saying shoot them all down or anything like that. Satellites have absolutely improved our quality of life on Earth and are essential for lots of various purposes. But I think that in a perfect world, we could have some kind of international regulatory procedure where before you launch, you have to submit an application of some kind describing what the need is that your satellite will fulfill, that existing satellites don’t fulfill, how you’re going to be mitigating various impacts on astronomy and other ecological areas, and maybe even what your plan is for making your satellites shared with other companies or groups. You know, if you have a little space for another sensor or something, it could be both an internet providing satellite and an Earth observing satellite, instead of having a whole bunch of independent ones that have a possibility of running into each other as well, which is a whole other issue that’s very connected. [This] so that we have a more reasonable cap on the total number of things up there and can keep tabs on it a little better versus kind of the more wild west situation - a new space race characterization that we have right now.

Miller:  Is it possible to see this as a kind of celestial version of the Tragedy of the Commons - that this is everybody’s place. But it’s sort of, as a result, also nobody’s place. And so it actually ends up being very hard to govern?

Rawls:  Oh, yeah, absolutely. And I think a lot of the default decisions that are being made right now - let’s get up as fast as we can [with] individual companies trying to launch as much as they can right now to beat any kind of regulation. [This] is very typical of the kinds of patterns that you see in other industries. Getting out ahead of regulations and asking for forgiveness instead of permission.

Miller:  What is the long term lifespan of these low orbit bodies? I mean, what happens to a satellite after 10 or 15 or 50 years?

Rawls:  Sure. So one benefit of low Earth orbit is that if something becomes defunct or stops working it will eventually, on a timescale of save weeks to months, burn up in Earth’s atmosphere and not just linger as space junk forever. Whereas higher orbit stuff would hang out and does hang out forever which could be a problem for debris. That being said, the expected lifetime for low Earth orbit satellites is around five years. So if a company wants to maintain a population of say 50,000 satellites, which many companies would love to do, they’re going to be constantly launching and de-orbiting to maintain that population. And that’s something that people don’t often think about. They think, okay well there’s satellites up there and they’re just staying up there whatever they can be there no big deal. But in reality they’re the brightest and they have the most likely atmospheric pollution potential when they’re constantly being launched and constantly being de-orbited. Because that’s when they’re brightest. Basically you’re getting a fake meteor shower all the time when they’re de-orbited as well.

Miller:  A different version of human made phenomena that we’ll maybe be forced to just find beautiful because it’s what we’re left with.

Rawls:  I suppose.

Miller:  Meredith Rawls, it was a pleasure talking to you.

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