Astronomers Warn Massive Satellite Fleets Could Change Astronomy Forever

A new generation of rockets is democratizing access to space, and that’s a good thing — mostly. Astronomers have been sounding the alarm for months that new mega-constellations of satellites could interfere with important observations, and fundamentally alter the way we study the cosmos. A new report from a group of astronomers lays out the scale of the problem, but the good news is the companies launching the missions are at least willing to listen to these concerns. 

The American Astronomical Society (AAS) hosted a virtual conference recently to explain how satellites interfere with astronomy and provide recommendations on how to fix it. We’ve seen a few examples of SpaceX’s Starlink satellites spoiling astrophotography and telescope observations, but it’s just one of several companies that wants to saturate the sky with reflective little spacecraft. Amazon, OneWeb, and others want to begin bringing massive space fleets online to deliver connectivity to every corner of the globe. 

SpaceX already has hundreds of satellites in orbit, making it the largest single satellite operator in the world. It didn’t take long for astronomers to run into unsightly streaks in image data that made their observations useless. SpaceX has started looking into darkening or shading its satellites, but it’s unclear how well that will work. 

According to the AAS, SpaceX is just an early sign of how bad things could get. Starlink could eventually feature more than 40,000 satellites. With OneWeb and others, astronomers could be stuck with more than 100,000 objects cluttering the sky. University of Michigan professor Patrick Seitzer claims that a 47,000-satellite constellation like the one proposed by OneWeb would produce at least one light trail in every 32 exposures. In the summer southern hemisphere, attempting to observe the Large Magellanic Cloud would be virtually impossible with at least one trail in every frame. 

The group came up with a series of recommendations, 10 of them for astronomers to cope with the increase in space traffic and six for the private space industry. The AAS recommendations for satellite operators include:

1. Launch fewer or no LEO sats. However impractical or unlikely, this is the only option identified that can achieve zero astronomical impact.
2. Deploy satellites at orbital altitudes no higher than ~600 km.
3. Darken satellites or use sunshades to shadow their reflective surfaces.
4. Control each satellite’s orientation in space to reflect less sunlight to Earth.
5. Minimize or eventually be able to eliminate the effect of satellite trails during the processing of astronomical images.
6. Make more accurate orbital information available for satellites so that observers can avoid pointing telescopes at them.

SpaceX, Amazon, and OneWeb were all involved with the AAS report, so they’re at least aware of how seriously astronomers are taking this. Scientists might prefer there were no mega-constellations, but no one expects that to happen. Instead, astronomers and operators might just need to do whatever they can to mitigate the impact.

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