Satellite megaconstellations will threaten space-based astronomy.

Borlaff, Alejandro S; Marcum, Pamela M; Howell, Steve B · Nature · 2025

other · Level V

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Abstract

Rapidly growing satellite constellations have raised strong concerns among the scientific community<sup>1-4</sup>. Reflections from satellites can be visible to the unaided eye and extremely bright for professional telescopes. These trails already affect astronomical images across the complete electromagnetic spectrum, with a noticeable cost for operations and mitigation efforts. Contrary to popular perception, satellite trails affect not only ground-based observatories but also space observatories such as the Hubble Space Telescope<sup>5</sup>. However, the current number of satellites is only a fraction (less than 3%) of those to be launched in the next decade. Here we show a forecast of the satellite trail contamination levels for a series of international low-Earth-orbit telescopes on the basis of the proposed telecommunication industry constellations. Our results show that if these constellations are completed, one-third of the images of the Hubble Space Telescope will be contaminated, while the SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer), ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys) and Xuntian space telescopes will have more than 96% of their exposures affected, with <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mn>5.6</mn></mrow> <mrow><mo>-</mo> <mn>0.3</mn></mrow> <mrow><mo>+</mo> <mn>0.3</mn></mrow> </msubsup> </math> , <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mn>69</mn></mrow> <mrow><mo>-</mo> <mn>22</mn></mrow> <mrow><mo>+</mo> <mn>21</mn></mrow> </msubsup> </math> and <math xmlns="http://www.w3.org/1998/Math/MathML"> <msubsup><mrow><mn>92</mn></mrow> <mrow><mo>-</mo> <mn>10</mn></mrow> <mrow><mo>+</mo> <mn>11</mn></mrow> </msubsup> </math> trails per exposure, respectively, with an average surface brightness of μ = 19 ± 2 mag arcsec<sup>-2</sup>. Our results demonstrate that light contamination is a growing threat for space telescope operations. We propose a series of actions to minimize the impact of satellite constellations, allowing researchers to predict, model and correct unwanted satellite light pollution from science observations.