A Ground Based Optical Survey for GPS Solar Panel Arcing

Abstract

In an attempt to confirm electrostatic discharge induced contamination as responsible for the excess power loss of GPS solar arrays, three GPS satellites were observed at the MMT using a sensitive Electron Multiplying CCD (EMCCD) with the aim of catching the microsecond optical emission of solar panel arcing. One of these satellites (NAVSTAR 48) was concurrently observed with the Arecibo radio telescope in the hopes that coincident optical and radio detections would all but confirm the hypothesis. Unfortunately, owing to ∼ 75% transmission losses, optical arc detections could not be conclusively confirmed or ruled out. Detections above the nominal threshold were present more frequently than expected from random fluctuations, but the lack of coincidence with Arecibo detections and the similar number of detections away from the satellite imply a cause other than arcs, most likely non-Gaussian noise behavior. One of the other satellites, NAVSTAR 65, yielded a promising candidate with a brightness consistent with a fully discharging arc of a Block II-F solar array. However, without external confirmation from satellite telemetry, the detection significance is not sufficient to unambiguously label this event as an arc. If the observations could be repeated with transmission losses of 30% or less, the 50% detection efficiency of arcs would improve from 200-photon arcs to 70-photons or better. This would make the difference between being sensitive to some full discharge arcs or most partial discharge arcs, although requiring substantial redesign of the observing strategy.