Starlink Satellite Brightness -- Characterized From 100,000 Visible Light Magnitudes

Abstract: Magnitudes for the VisorSat and Original-design types were analyzed separately and by time. Mean values are compared with those from other large-scale photometric studies, and some signficant differences are noted. The illumination phase functions for Starlink satellites indicate strong forward scattering of sunlight. They are also time-dependent on a scale of months and years. These phase functions improve the predictability of satellite magnitudes. A Starlink Brightness Function tailored to the satellite shape also improves magnitude predictions. Brightness flares lasting a few seconds are characterized and the mean rate of magnitude variation during a pass is determined. Observation planning tools, including graphs and statistics of predicted magnitudes, are discussed and illustrated.