images will be affected, and likewise future LEO-based science missions, such as the Xuntian wide field observatory being built for the Chinese Space Station.
Fig.5. An observation made using the Hubble Space Telescope in November 2020. The streak seems likely to have been made by Starlink 1619, only a few km above Hubble, thus creating a wide out of focus trail. (Image credit: Mikulski Archive for Space Telescopes (MAST). Science PI: Simon Porter.)
Mitigations, damage and their cost
The international astronomical community has had multiple meetings to discuss how to address the new landscape of increasing numbers of bright LEO satellites, leading to key reports [6–10]. A report by the US Government independent advisory body JASON was also commissioned by the National Science Foundation [4]. Astronomers have engaged with satellite companies to discuss ways to mitigate the problems. For optical astronomy, this has included ideas such as painting satellites black, changing their orbits and orientations, adding sun visors, and providing detailed positions and trajectories so that observatories can avoid pointing at them. For radio astronomy, key mitigations further include redirecting beams away from major observatory facilities and employing sophisticated signal filtering. None of these mitigations can fully avoid LEO satellite constellations harming astronomical science however [7, 8, 10]. Launching significantly fewer satellites is the only mitigation that could do this.
The consequences of the current and proposed growth of satellite constellations have a direct cost from repeating or extending observations, wasting scientist time, and even negatively affecting their careers. Implementing mitigations will also impose significant costs, either on the astronomical community (and so the taxpayer), or on the satellite operator companies, or on both. We do not attempt to assess those costs here. Rather, we point out that this is a classic example of environmental damage, externalising true costs. To give one example, one significant conclusion from the SATCON2 Observations Working Group [8] is
