Parallel sessions

The unprecedented deployment of large satellite constellations in low Earth orbit has a significant impact on optical and radio astronomy, and on both ground- and space-based observatories. This session will explore the effect of satellites, the response from the astronomical community, governments, international organisations and industry. Since 2019 we have seen a paradigm shift in the commercial use of space, and the deployment of communications satellites in low Earth orbit (below an altitude of 2,000 km) on an unprecedented scale. At the time of writing (December 2021) SpaceX has 1844 satellites in orbit and the part-UK owned OneWeb has 358. By the end of the decade there could be 100,000 or more satellites in this region of space, with even that number a small fraction of those requested in licence applications. The astronomical community in the UK and around the world now has a significant body of published work highlighting the impact of large satellite constellations. The effect on optical observations is particularly important for widefield survey telescopes, with instruments like the Vera Rubin Observatory set to have up to two fifths of its images affected, and for scientists attempting to observe transient phenomena, such as the optical counterparts to gamma ray bursts and meteor showers. For radio astronomy, observers will be dealing with downlink signals that are trillions of times more powerful than remote astronomical sources. Unlike other forms of interference and light pollution, satellites in the new constellations are visible everywhere in the world, compromising astronomy in even the most remote locations chosen to avoid artificial light and radio signals. Beyond professional astronomy the voice of the amateur astronomical community and the wider public have so far rarely been heard on this issue. The "ownership" of the night sky is seen by many as a cultural heritage issue. In this session we will cover these topics, and structure the programme around them: the observed impact of satellites at optical and radio wavelengths; Recommended mitigation measures by satellite operators from an industry and academic perspective; Policy responses in the UK, Europe and UN, including the work of the new IAU Centre for the Protection of the Dark Sky from Satellite Constellation Interference; The cultural ownership of the night sky and how this can be protected.