Harrison Krantz, University of Arizona Steward Observatory; Eric Pearce, University of Arizona Steward Observatory; Adam Block, University of Arizona Steward Observatory
Keywords: mega-constellation, starlink, oneweb, darksat, visorsat, LEO, photometry, astronomy, light pollution, autonomous,
Abstract:
Measuring the photometric brightness is a common tool for characterizing satellites. However, characterizing satellite mega-constellations and their impact on astronomy research requires a new approach and methodology. A few measurements of singular satellites are not sufficient to fully describe a mega-constellation and assess its impact to modern astronomical systems. Characterizing the brightness and impact of a satellite mega-constellation requires a comprehensive measurement program conducting numerous observations over the entire set of critical variables. Doing so requires not only a complete observing program but also the development of techniques for photometric measurements of low-Earth orbit (LEO) satellites. While photometry of deep space satellites is common, doing the same with LEO satellites presents certain technical challenges.
Utilizing Pomenis, a small-aperture and wide field-of-view astrograph, we developed an automated observing program to measure the photometric brightness of mega-constellation satellites including Starlink and OneWeb. We created software to intelligently schedule daily observations with an optimizing algorithm to observe as many satellites as possible while prioritizing particular satellites and geometries to satisfy project goals. The telescope autonomously executes the observing schedule every twilight imaging up to 60 images of satellites per hour. For each satellite we measure its photometric brightness and astrometric position. However, the most valuable insights come from analyzing the ensemble of satellites over a comprehensive range of geometries and phase angles. We characterize the all-sky brightness of satellite mega-constellations through the distribution of measurements and correlate the satellite brightness with time of day, on-sky position, solar geometry etc. We also compare the brightness of different satellite designs and report the efficacy of brightness reduction efforts including Starlink’s DarkSat and VisorSat.
We aim to measure the potential impact of mega-constellation satellite obtrusion through an assessment of all-sky brightness: a combination of likelihood of satellite appearance and brightness distributions as a function of sky position and time. Analytical studies done by members of the astronomy community show that the impact on astronomy research is real and potentially very significant, particularly for wide-field surveys like the Rubin Observatory (formerly LSST). Our project benefits the astronomy community by characterizing the overall impact of satellite mega-constellations in terms of sky availability and the probability of incidental satellites during planned observations.
Date of Conference: September 14-17, 2021
Track: Non-Resolved Object Characterization