Ground-Based Surveillance Campaign to Detect Global Positioning System Arcing: First Preliminary Results

Abstract

Excess power degradation on global positioning system (GPS) solar arrays has been ascribed to arc-induced contamination. Arcs have also been proposed as one source of spurious signals in Los Alamos National Laboratory’s radiofrequency detectors on GPS satellites. Both ideas may be confirmed by detecting such arcs with large ground-based optical- and radiotelescopes. Correlation of these signals with each other and/or the event times onboard would cement both hypotheses. In this paper, preliminary positive results of a coordinated campaign of large optical- and radiotelescope observations on tracked GPS satellites are presented. Coordinated observations were carried out with the Arecibo 305 m and long wavelength array radiotelescopes and a 3.5 m optical telescope. Correlations of event rates, with predictions based on the U.S. Air Force, Aerospace, National Reconnaissance Office AE9/AP9/SPM empirical standard trapped radiation climatology model, show that daily variations in the undispersed event rates track variations in the charging electron flux with a delay appropriate for solar cell cover-glass conduction times. Additionally, Arecibo observations at 327 MHz show narrow autocorrelation features ($\sim 140\mu \mathrm{s}$ wide) for one GPS satellite on two different days. Ground testing of a GPS-like solar array reveals arc voltage thresholds and contamination rates sufficient to produce the observed power degradation. Implications are discussed for GPS spacecraft and other satellites.