Starlink Questions

I got a great couple of questions on an earlier post about Starlink. My good friend Tobi asked about concerns that massive satellite internet constellations could lead to a bunch of space junk in orbit and also concerns that these constellations will cause problems for astronomers.

SpaceX, with 12,000 or more Starlink satellites in it’s completed constellation, won’t be the only company in the low-flying internet satellite game. OneWeb already has satellites in orbit and they want to put up at least 7,000 total up there. Amazon’s Kuiper hasn’t put anything in orbit yet but they want to launch at least 3,000 satellites pretty soon. And don’t expect major governments to stay out of this game. In just a few years we will have more internet satellites in low Earth orbit than all other orbiting satellites combined, working and dead. And these satellites have a fairly short lifetime, 5 years or so before they run low on fuel and must spend their last remaining fuel to de-orbit.

SpaceX is planning for the largest constellation of the companies I know about and they’re doing it seemingly responsibly. They have built Starlink satellites out of materials that will burn up completely when they de-orbit. The Starlink satellites have onboard ion propulsion thrusters powered by krypton gas. They use these thrusters to achieve their orbits, maintain those orbits against the drag of the upper atmosphere, and to de-orbit the satellites at the end of their lifetimes. Even if something goes wrong with a Starlink satellite’s thrusters, the constellation is low enough that it will only take a few years for the satellite’s orbit to decay and the satellite succumb to drag and burn up.

SpaceX is also working to mitigate Starlink’s impact on astronomy. You may have seen photos or videos of “Starlink trains” rows of lights moving across the sky. These bright satellite trains are only that bright while they’re in the process of raising their orbits. SpaceX launches the satellites into a very low orbit, about 155 miles up, and they then use precession to spread out and use their ion thrusters to raise their orbits to about 335 miles. That process takes a few months and during that time the satellites are low and clumped up and so fairly bright. SpaceX has cut down on that brightness a lot by changing the orientation of the satellites during orbit raise so they don’t reflect as much sunlight. But even when they reach their ultimate orbits, higher up and spread out, they still reflect some sunlight at dusk and dawn. SpaceX has mitigated a bunch of by outfitting all of their recently launched Starlink satellites with sun shades that eliminate a lot, but not all, of the reflection.

I think SpaceX has a firm handle on the problem of space junk. They’ve designed and built satellites and a process for replacing old satellites with new ones that will not lead to space junk. I think they’ve got less of a grip on the problems they may be creating for astronomers, especially hobbyists who may not have the tools to remove any Starlink interference from their data and images. They are working on it though and have made some real progress.

One idea I had was that SpaceX, which is after all a rocket company, could remediate some of the harm they may cause to terrestrial astronomy by offering free launch services to publicly funded (universities!) space telescopes. It costs anywhere from tens of millions to hundreds of millions of dollars just to launch a space telescope into orbit. If that barrier was gone, think about how many new space telescopes might be built, from great big ones like James Webb or Hubble to miniature ones like the BRITE nanosatellites, and everything in between.

I know that space telescopes can be more expensive to build and they can’t replace terrestrial ones for every use case, but by eliminating most or all of the launch costs, SpaceX could help usher in a new era of space-based astronomy. I think that could really help build some bridges with the astronomy community.

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