Astronomers fret over ‘debilitating threat’ of thousands of satellites cluttering the sky

The promise of today’s nascent communications satellite constellations is real: connecting everyone on the globe, no exceptions. But the dark side, or rather bright side, of these satellites threatens to pollute the sky with innumerable points of moving light. Astronomers warn that this may pose a “debilitating threat” if not addressed by regulators or industry.

The International Astronomical Union, a group of over ten thousand astronomers and researchers all over the world, issued a statement this week politely but firmly pointing out the risks of this “new and largely unregulated frontier of space utilisation.”

The problem is that we have graduated from an era where we were launching a satellite every month or so to one where dozens might be launched every week. The competing communications constellations from Starlink, OneWeb, and others will number in the tens of thousands once deployed, outnumbering by far every other satellite in the sky.

This isn’t a question of maybe seeing one little blip out of the corner of your eye — eventually there may be hundreds of these satellites visible at any given time from nearly anywhere on the planet.

Not only that, but these satellites are frequently in relatively low orbits, making them much more visible than distant geosynchronous ones like GPS satellites — not to mention they’re shiny, the IAU writes:

The surfaces of these satellites are often made of highly reflective metal, and reflections from the Sun in the hours after sunset and before sunrise make them appear as slow-moving dots in the night sky.

Are they visible to the naked eye? Depends on a lot of circumstances — the time of day, the position of the craft, the light pollution in your area, and so on. But it’s certainly possible. And astrophotographers and observatories have already noted the problem. You can see the trails of the Starlink satellites in the image at top, and photographer Xplode captured similar trails in this shot — if you look closely you can see there are lots.

High-powered telescopes and sensitive imaging devices are even more susceptible to the issue; the Large Synoptic Survey Telescope team said Starlink was merely a “nuisance,” but acknowledged that for others it may be a far greater threat, and referred to the IAU statement as more representative of the global community.

Naturally there are countermeasures — timing, postprocessing, and other tools for shooters and researchers who don’t want the satellites to interfere. But this will become progressively harder, even impossible for some surveys and exposures, as more satellites are deployed.

SpaceX (which runs Starlink) founder and CEO Elon Musk has tentatively addressed the issue online, promising the team will look into reducing the visibility of the satellites, but that may or may not amount to anything. Any modifications the company makes would be entirely voluntary.

In addition to the visual component, the satellites will be beaming strong radio signals towards the Earth, which can interfere with radio telescopes if the spectrum is not partitioned carefully. This is perhaps a more tractable problem but still must be considered.

This is another case where the industry has long since passed up the regulations that bind it. There’s simply no law against putting thousands of satellites into space — no upper limit on how many, or on how prominent they can be in the sky. The IAU begs that the powers that be look into it:

Satellite constellations can pose a significant or debilitating threat to important existing and future astronomical infrastructures, and we urge their designers and deployers as well as policy-makers to work with the astronomical community in a concerted effort to analyse and understand the impact of satellite constellations. We also urge appropriate agencies to devise a regulatory framework to mitigate or eliminate the detrimental impacts on scientific exploration as soon as practical.

At the speed new regulations are adopted, there will likely be hundreds more satellites in orbit before anything is done, but it’s important to pursue nevertheless. I’ve also asked the American Astronomical Society for their opinion on the topic, and will update this post if I hear back.