Satellites Overwhelm Space Telescopes With “Railroad” Tracks

NASA’s SPHEREx space telescope found that 73.3 percent of its images collected between May and September last year were contaminated by artificial satellite trails, according to a preprint from the agency’s Ames Research Center [1]. The telescope, which orbits roughly 700 kilometers above Earth, recorded an average of 2.18 trails per exposure [1]. SPHEREx was designed to map the entire sky in near-infrared light, a mission that requires long exposures and wide sky coverage — conditions that make interference from orbiting objects more likely [1]. Most of the trails appear in an “X” pattern that mirrors the orbital paths of satellite megaconstellations [1]. The contamination is not limited to ground-based observatories. NASA, an independent U.S. agency established in 1958, operates a range of astrophysics investigations using space-based observatories, including the Hubble Space Telescope and the James Webb Space Telescope [5]. A 2023 study led by an astronomer at the European Space Agency found that the fraction of Hubble images crossed by satellites rose from 2.8 percent in the early 2000s to 5.9 percent in 2021 [1]. ESA organizes its science missions into budgetary programs, with its current Cosmic Vision Programme supporting space telescopes that contribute to interstellar astronomy [7]. The SPHEREx instrument uses an automated algorithm to protect itself from stray cosmic rays by halting data collection on affected pixels [1]. Commercial satellites are now bright enough to trigger this protection system on their own, carving permanent “railroad” tracks into the science imagery and erasing photometric data beneath them [1]. Satellite designers have tested dark coatings and specialized visors to reduce optical brightness, but newer systems with large antennas are negating those gains [1]. Recent filings with the U.S. Federal Communications Commission seek approval for up to 2 million satellites in low Earth orbit, compared with roughly 20,000 currently in orbit [1]. Simulations in the new paper forecast that if those constellations are approved and launched, 100 percent of SPHEREx images would be polluted by satellite trails, with an average of 189 trails per image [1].