A new generation of rockets democratizes access to space, and that’s a good thing – for the most part. Astronomers have been sounding the alarm for months that new mega-constellations of satellites may interfere with important observations, and fundamentally change the way we study the cosmos. A new report from a group of astronomers explains the scale of the problem, but the good news is that the companies launching the missions are at least ready to listen to these concerns.
The American Astronomical Society (AAS) recently organized a virtual conference to explain how satellites interfere with astronomy and give recommendations on how to repair 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 want to saturate the sky with mirrored small spaceships. Amazon, OneWeb, and others want to bring massive space fleets online to connect 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 did not take long for astronomers to reach unsightly streaks in image data that rendered their observations useless. SpaceX has started looking for the darkening or shadowing of its satellites, but it is unclear how well that will work.
According to the AAS, SpaceX is just an early sign of how bad things can get. Starlink could eventually have more than 40,000 satellites. With OneWeb and others, astronomers could get stuck with more than 100,000 objects cluttering the sky. University of Michigan professor Patrick Seitzer claims that a constellation of 47,000 satellites like the one proposed by OneWeb would produce at least one light path in every 32 exposures. In the summer southern hemisphere, attempting to observe the Great Magellanic Cloud would be virtually impossible with at least one track in each frame.
The group came up with a series of recommendations, 10 of them for astronomers to deal with the increase in space travel and six for the private space industry. The AAS recommendations for satellite companies include:
- Start less than no LEO rate. As impractical as it is unlikely, this is the only identified option that can achieve zero astronomical impact.
- Insert satellites at orbital altitudes not exceeding ~ 600 km.
- Darker satellites are used as sunshades to shade their reflecting surfaces.
- Check the orientation of each satellite in space to reflect less sunlight to Earth.
- Minimize if eventually can eliminate the effect of satellite paths when processing astronomical images.
- Make more accurate orbital information available to satellites so that observers can avoid aiming telescopes at them.
SpaceX, Amazon and OneWeb were all involved in the AAS report, so they are at least aware of how seriously astronomers take this. Scientists may assume that there were no mega-constellations, but no one expects that to happen. Instead, astronomers and operators should simply do what they can to limit the impact.
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