Reflections from a growing number of satellites could spoil more than 95% of images taken by some space telescopes over the next decade, a NASA-led study published in Nature warns. The stray sunlight appears as streaks, known as satellite trails, which have already been seen in images from the Hubble Space Telescope and are expected to worsen as orbital satellite counts rise.
The study predicts severe contamination for several telescopes, including NASA’s recently launched SPHEREx, the European Space Agency’s upcoming ARRAKIHS and China’s planned Xuntian Space Telescope. Lead author Alejandro S. Borlaff, a NASA scientist, noted that transient events—like a distant exploding star—could be lost forever if a satellite crosses the field of view during the observation.
Satellite launches have surged in recent years. As of Dec. 1, more than 10,000 active satellites were in orbit, according to data from astrophysicist Jonathan McDowell; SpaceX alone operates over 7,800 Starlink satellites. The International Telecommunication Union (ITU) says thousands more are planned. Between 2018 and 2021, when there were fewer satellites, about 4% of Hubble images showed satellite streaks, per a 2023 Nature Astronomy study. Borlaff and colleagues now estimate that at least one in three Hubble images could show a streak, and that SPHEREx, ARRAKIHS and Xuntian could have roughly 96% of images contaminated.
Astronomers and scientific organizations have long raised concerns. The American Astronomical Society (AAS) has warned that large satellite constellations could increase collision risks and create glare and streaks that harm observations. The AAS says it will work with federal agencies and the satellite industry to understand and minimize impacts.
SpaceX has said it is testing measures to reduce satellite brightness, including darker coatings, visors to block sunlight and orbital adjustments to limit reflected light. The ITU has urged stricter international regulation of satellite numbers and better management of orbital networks, citing risks to space sustainability, collisions, debris generation and the long-term viability of orbital resources.