A NASA-led study published in Nature warns that sunlight reflected from the rapidly growing number of satellites in Earth orbit could spoil a large fraction of observations from upcoming space telescopes — in some cases more than 95% of images within the next decade. Reflected light appears as streaks, called satellite trails, which have already shown up in Hubble Space Telescope exposures.
The study identifies missions at particular risk, including NASA’s recently launched SPHEREx, ESA’s planned ARRAKIHS and China’s Xuntian Space Telescope. Lead author Alejandro S. Borlaff, a NASA scientist, cautions that transient or rare events — for example, a sudden stellar explosion seen while observing a distant galaxy — could be permanently missed if a satellite crosses the field of view.
Satellite deployment has surged: more satellites were launched in the past four years than in the preceding 70 years, and as of Dec. 1 there were over 10,000 active satellites in orbit, with SpaceX operating more than 7,800 Starlink satellites. The International Telecommunication Union says thousands more are planned.
Previous work found roughly 4% of Hubble images from 2018–2021 contained satellite streaks; the new analysis predicts that rate could rise substantially — to at least one in three Hubble images — and reach about 96% contamination for some instruments on next-generation missions.
The problem also affects ground-based observatories. The American Astronomical Society has warned that large constellations raise collision and debris risks and produce glare and streaks that degrade astronomical data. The ITU is calling for tighter international rules and better management of satellite networks to protect orbital sustainability. Satellite operators say they are taking steps to dim or shield satellites — testing darker coatings, adding visors and adjusting orbits — and the AAS says it will keep working with agencies and industry to reduce impacts on astronomy.