Satellite megaconstellations will threaten space-based astronomy

Rapidly growing satellite constellations have raised strong concerns among the scientific community^1-4. 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 Telescope⁵. 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mn>5.6</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>0.3</mml:mn></mml:mrow> <mml:mrow><mml:mo>+</mml:mo> <mml:mn>0.3</mml:mn></mml:mrow> </mml:msubsup> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mn>69</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>22</mml:mn></mml:mrow> <mml:mrow><mml:mo>+</mml:mo> <mml:mn>21</mml:mn></mml:mrow> </mml:msubsup> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msubsup><mml:mrow><mml:mn>92</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>10</mml:mn></mml:mrow> <mml:mrow><mml:mo>+</mml:mo> <mml:mn>11</mml:mn></mml:mrow> </mml:msubsup> </mml:math> trails per exposure, respectively, with an average surface brightness of μ = 19 ± 2 mag arcsec^-2. 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.