SPHEREx Confirms Predictions for Artificial Satellite Trail Pollution in Low Earth Orbit

The number of artificial satellites in low Earth orbit (LEO) has been increasing at an exponential rate since 2019. Satellites are visible to both ground and space telescopes, and their bright emission in optical, infrared, and radio wavelengths contaminates astronomical observations, degrading the data’s scientific value. Recent simulations forecast that if all satellite constellations listed in current launch manifests are deployed to LEO, satellite trails will appear in up to 96% of the images obtained by most space telescopes. In this article, we use the recently launched Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx) space telescope to corroborate these models. SPHEREx observations obtained between 2025 May and September indicate that 73. 3 − 1.2 + 1.3 % of the images already show satellite-trail contamination, with an average number of N = 2.1 8 − 0.09 + 0.11 trails per exposure, providing observational validation of the published light contamination models. The observed satellite trails display highly inclined trajectories in agreement with the simulated ones. We discuss potential data-reduction mitigation methods, and provide an updated satellite light pollution forecast for Hubble and SPHEREx including the newer satellite constellations proposed in early 2026.