A team of astronomers has used archival images from a survey telescope to look for Starlink tracks over the past two years. Over that time, the number of images affected rose by a factor of 35, and the researchers estimate that by the time the planned Starlink constellation is complete, pretty much every image from their hardware will have at least one track in it. Ars Technica reports: SpaceX’s Starlink Internet service will require a dense constellation of satellites to provide consistent, low-latency connectivity. The system already has over 1,500 satellites in orbit and has received approval to operate 12,000 of them. And that has astronomers worried. Although SpaceX has taken steps to reduce the impact of its hardware, there’s no way to completely eliminate the tracks the satellites leave across ground-based observations. […] In response to complaints from the astronomy community, SpaceX put visors on later generations of Starlink satellites. The research team was able to compare the visibility of these different generations and found that the visors worked — satellites with visors dropped in brightness by a factor of roughly 4.6 (the precise number depended upon the wavelength). The visibility, however, was still higher than the target set at a workshop that was meant to address this issue.
Because these tracks are small and software already identifies and handles them, they don’t have much of an effect on observations. The researchers estimate that, at present, there’s only a 0.04 percent chance that a rare event will be missed because it coincides with a track. But because the problem is most acute in twilight observations, it’s more likely to impact searches for objects within the Solar System. This would include comets and asteroids — including asteroids that originated around other stars. But again, the problem is likely to get worse. SpaceX already has approval to increase the number of Starlink satellites to well over 10,000; the authors estimate that at 10,000, every image at twilight will likely contain a Starlink track. SpaceX has indicated it would eventually like to boost the numbers to over 40,000 satellites, at which point all twilight images are likely to have four tracks.
And SpaceX isn’t the only company planning on this sort of satellite service. If all the companies involved follow through on their plans, low Earth orbit could see as many as 100,000 of these satellites. Overall, the picture is mixed. The ZTF’s main mission — to pick out rare events caused by distant, energetic phenomena — is largely unaffected by the growing number of satellite tracks. And because the percentage of events is currently small, tripling the number of satellites won’t have a dramatic impact on observations. But a secondary science mission is already seeing a lot of light contamination, and matters are only going to get worse. The findings have been published in the journal Astrophysical Journal Letters.