Oxygen Ion Implantation in the Solar Panel Coverglass of GPS Satellites

Summary form only given. Global positioning satellites (GPS) have been experiencing an anomalous, accelerated degradation of solar array power. This phenomenon, analyzed since the early 80´s, remains unexplained. Recently, low-energy (<50 keV) oxygen ions (O⁺) have been identified as a possible, still unexplored, cause of degradation of solar panel coverglass materials. Oxygen ion implantation in the (100-nm-thick) anti-reflection coating of the coverglass could cause darkening, and associated transmission loss. We investigate this hypothesis by irradiating various GPS flight configuration coverglass samples in simulated O⁺ environments. The latter are based on modeling of the average oxygen environment at GPS orbit (20,000 km altitude). The O⁺ implants will complement proton, electron, and UV irradiation on the same coverglass samples. The O⁺ implants (ion energies from 0.1 to 50 keV, yearly doses up to 10¹⁴ cm^-2) are performed in steps, up to a 20-year-equivalent final dose. About 70 different samples are implanted with two facilities: a plasma immersion ion implanter (<10 keV) and an ion beam implanter (>10 keV). After each implant step, the optical properties of the samples are measured. Results of this investigation will be presented