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by Jerry Oltion

Starlink, Star Junk


In May of 2019, the private corporation SpaceX launched 60 satellites into low Earth orbit. They were released in a long stream, like paratroopers rushing out the back of a cargo plane, creating a train of satellites that swept across the sky in a formation that scared the bejeezus out of a fair portion of the world and delighted quite a few more. They eventually drifted apart and went their separate ways, becoming the first parts of an eventual network of 42,000 similar satellites designed to provide broadband Internet to everyone on the planet.

No, that's not a typo. 42,000 of them. The first phase of the deployment calls for "just" 12,000 satellites, but SpaceX plans to launch 30,000 more eventually. They're already up to 300, with more scheduled to be lauched every few weeks.

And not to be outdone, four other companies plan to orbit their own constellations of communication satellites. Within a decade, we could see well over 100,000 new satellites in space.


So What?


To put that in perspective, there are fewer than 5,000 satellites in space at the moment. (Of those, fewer than 2,000 of them are operational.) So the Starlink constellation will increase the total by a factor of 8. If everyone gets in on the act with a similar number, we could see a 20-fold increase in the number of satellites in orbit.

Why should we care? As SpaceX founder and CEO Elon Musk tweeted after the launch of his first 60, "There are already 4,900 satellites in orbit, which people notice ~0% of the time." He has a point. Most people live in cities, where due to light pollution the sky is gray rather than black, and they can barely see even the brightest stars, much less satellites.

That is precisely why they should care. They—we, all of us—have already lost the battle against light pollution here on Earth. There are so few places left on our planet with truly pristine sky that about a third of the people alive today have never seen the Milky Way. However it's still possible to drive out of town and see the night sky...whereupon you also see satellites. Quite a few of them, in fact. I spend a lot of time outdoors at night and I see one every couple of minutes, slowly drifting across the sky. They're usually not very bright, maybe 4th or 5th magnitude, about the same brightness as the average stars you see by naked eye. But they're there, and easy to spot.

Multiply that by 20. We'll be seeing a new satellite every six seconds. And since satellites stay in view for about five minutes, there will be about 50 satellites in view at any given moment.

The sky will quite literally be crawling with satellites.




If that were the only impact, we might say "Maybe it's worth it in order to provide Internet access to everyone in the world." But it's not the only impact, nor will the Starlink network provide access to anyone who can't afford the downlink antenna and a computer.

The biggest impact by far will be to professional astronomy. Professional astronomers do almost all their work with long-duration photographs that gather light from extremely dim objects over extended periods of time. Remember the Hubble Deep Field photograph that revealed thousands of unknown galaxies in one image? That was a 140-hour exposure. Granted it was done in smaller increments that were stacked together at the end, but the telescope got 140 hours of useful data out of 140 hours of observing time. There were a few satellite tracks through a few images, but they were rare.

Also, the Hubble Deep Field looked into a very narrow (0.002 square degrees) area of sky. Nowadays one of the major focuses of professional astronomy is the wide-field survey, in which automated telescopes scan the entire sky each night in search of transient phenomena like supernovae, gamma ray bursts, and transiting exoplanets. The impact on those wide-field observations will be nearly continual.

Speaking of impact, one of the areas of astronomy that will be hardest hit is the search for near-Earth asteroids, the ones that could strike our planet and send us the way of the dinosaurs. The telescopes and cameras that search for potential dangers are looking for streaks of light against the stellar background. When there are dozens of those streaks in every photograph, finding the ones that belong to asteroids becomes a tough job. And ironically, the better SpaceX does at lowering their satellites' reflectivity, the worse the problem becomes for the asteroid searchers. They want to catch asteroids while they're still a long ways out, which means while they're still dim. So they're most interested in dim streaks, which even the best-shielded SpaceX constellation will provide aplenty.


Radio Noise


It gets worse. Way worse. Radio astronomy is an even bigger field than visual astronomy, in part because radio waves aren't affected by clouds or turbulence in the atmosphere. A radio telescope on Earth is just as good as a radio telescope in space, except for one thing: radio interference.

Our planet is awash in radio signals. The entire radio spectrum, from long-wave navigation frequencies to microwaves, is in continuous use. There are tiny notches reserved for radio astronomy, but the universe doesn't care about that. It broadcasts in all frequencies, most of which we can no longer hear because of the background noise. And transmitters that are designed for different frequencies often still radiate harmonics in these "protected" bands.

Because you can pack more data into higher frequencies, the Starlink constellation will be using the highest ones they can. Those are precisely the frequencies that radio astronomy has been driven into by the relentless increase in radio use already. And a satellite doesn't have to be directly in line with the antenna to interfere with an observation; it merely needs to be above the horizon. When all 42,000 Starlink satellites are launched, there will be more than 2,000 of them above the horizon at any given moment. Even if they stop at 12,000, there will be more than 60 always within range. Radio astronomy is going to become very difficult indeed.


The Tragedy of the Commons


What can we do about it? At this point, nothing. International treaties governing the use of space only forbid military use; all else is fair game. And that leads us to a concept that you're undoubtedly familiar with, even if you've never heard of it before. It's called "The tragedy of the commons."

Put simply, it's the idea that when there's a common resource that everybody can use, if there's no regulation of how many people can use it nor how much of it any individual can use, then there's no incentive for anyone to be good stewards of that resource. It makes the most sense to take as much of it as you can until it's all gone, because if you don't, then someone else will. Everyone involved knows that they're wrecking that resource, but they also know it's going to disappear anyway, so they might as well get as much as they can out of it while it still exists.

Sometimes it's not that bad. People running cows on a common pasture, for instance, know how many cows the pasture can support before it's overgrazed. Ranchers can, and do, come to agreements on how many cows each one can run on the pasture. Then someone figures, "I can run one more cow and nobody will notice." They'll get extra money at the end of the year for that cow. It's practically free money. A lot of people can't resist that sort of temptation, so they run the extra cow. Get enough people doing that and the pasture gets overgrazed even with regulations designed to prevent it.

Earth orbit is another common resource. Until recently, it was too expensive for anyone to use more than a tiny fraction of it. But SpaceX and its competitors are poised to use it all, and quickly, before any kind of regulation can take effect. Musk tells us that SpaceX will work with astronomers to reduce the impact of its satellites, but that's entirely voluntary and if it doesn't produce the desired result (which is probably physically impossible), they're most likely going to send them into space anyway. They've invested too much money in it to stop now.

And of course SpaceX's competitors, and any new companies that want a piece of the action, will be pushing hard to get their constellations into place ASAP, too. Whether or not they can mitigate their impact on the night sky.

Yet even that isn't the worst thing that can happen.


The Kessler Syndrome


You probably saw the movie Gravity. The writers got a lot of their science wrong, but they got one thing right: If you blow up a satellite in orbit, the pieces will fly off in every direction, creating a big cloud of debris that could whack into another satellite, blowing it to bits that could hit another one, and so on until "could" becomes "will." That's called the Kessler Syndrome, after NASA scientist Donald Kessler who figured this out clear back in 1978.

How many satellites would it take to initiate a Kessler scenario?

Umm...about 5,000. In other words, we're probably already at the beginning of one. Two satellites did indeed crash into one another back in 2009, generating about 2,000 pieces of debris. Those pieces are flying every which way, most of them too small to track reliably. And they're in a polar orbit, which has two very tight bottlenecks for satellites to pass through. It's nearly inevitable that some of those fragments of satellite will hit more satellites.

So let's throw 12,000 more satellites up there. Or 42,000, or 100,000. What can we expect to happen?

Oddly enough, in low orbit the effect won't be as bad as higher up. When you blow something up in low orbit, a lot of the ejecta flies off in the direction of Earth and burns up in the atmosphere. A lot more of it flies up away from the Earth, then falls back down and burns up in the atmosphere half an orbit later. It's only the stuff that blows out sideways that stays in orbit.

The farther away you are, the smaller a target Earth becomes, so more debris stays in orbit. The Starlink satellites, at 340 miles altitude for the first wave and 710 miles for the second wave, are high enough that debris could stay there for a long time. A lot of it would be in highly elliptical orbits, too, dipping down toward Earth and outward toward geostationary orbit, contaminating every orbit in between. We could lose our current constellation of geosynchronous satellites, which could create another Kessler cloud extending all the way to the Moon. If the debris cloud got bad enough, it could wall off access to space for centuries.

Will it get that bad? Probably not. But how much do we want to risk it? For what gain? Internet access? We can provide that with ground-based expansion at a fraction of the cost.


Take Away


As I said earlier, we've already lost the battle against light pollution. When porch lights and street lights first became possible, most people thought it was a great thing. They hardly noticed the loss of their beautiful night sky, and those who did were ridiculed as anti-progress sticks-in-the-mud. By the time the problem grew bad enough for the average person to notice, too many people had become accustomed to the lights to change back. Nowadays we're discovering serious medical issue with light pollution, yet most people are now so used to continuous nighttime lighting that there's no hope of giving it up. And new technology has just made it worse: When LEDs made lighting cheaper, people simply put in more (and brighter) lights.

We're poised at the beginning of a similar battle. And we may have already lost this one, too. We have become so accustomed to our satellite TV and satellite phone connections and satellite weather observations, etc., that we would be loath to give them up. We're loath to even restrict them to our current level of usage. Rather, just about every non-astronomer I talk to about the Starlink satellites simply shrugs and says, "Extra lights in the night sky? Who cares?" One asked me, "Should we outlaw airplanes, too?"

It's a thorny problem, and ours is the generation that's going to decide what Earth orbit looks like for centuries to come.

What does this all mean to us reading this magazine, science fiction and fantasy readers and writers?

For writers, if you're setting a story at night in the not-too-distant future, remember to put in lots of satellites crawling along overhead. More satellites than stars, probably. (There are only 2,500 stars visible at any given time.) And if you're writing farther into the future, you'll probably want to explain either why we can't go into space anymore, or how we avoided that catastrophe.

For readers, expect a lot of stories about how private enterprise screws up yet another resource, this one right over our heads. And probably some rebuttals about how wonderful it will be when we can order ice cream bars delivered by Amazon drone in the Sahara desert.

Me, I'm hoping for that one visionary story that describes how we can solve this problem before it's too late.


Jerry Oltion has been a science nut since he was old enough to spell "curious." He has written science fiction almost as long, and has done astronomy somewhat less. He writes a regular column on amateur telescope making for Sky & Telescope magazine, and spends many, many nights a year out under the stars.

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