A Data-Driven Evaluation of the Viability of Solar Arrays at Saturn

Solar arrays are a low-cost, readily available, and highly reliable power source for space exploration, which makes them attractive to multiple NASA mission concepts up to and including the orbit of Saturn (9.5 AU). This paper addresses the viability of currently available solar cell and solar array technologies under extremely low irradiance and low temperature (LILT) conditions. We present ground-based measurements of solar cell performance in laboratory environments relevant to Saturn missions. Several space-qualified cell products were evaluated, including Spectrolab UTJ, SolAero ZTJ, and Azur 3G28-LILT. Test conditions consisted of irradiances corresponding to sun distances from 1 AU to 9.5 AU, and junction temperatures from + 150 degrees C to -165 degrees C. The various cell options were all found to have highly viable average efficiencies under Saturn LILT conditions, in the similar to 30-34% range. We also present in-flight solar array telemetry data obtained by the Juno mission under Saturn-like environmental conditions. Juno is a solar-powered spacecraft, currently in polar orbit around Jupiter. During the Jupiter orbit insertion maneuver, the Juno solar array temporarily experienced effective irradiances and temperatures comparable to those that would be experienced by a solar array at Saturn. We evaluate the actual array performance under those conditions and compare it to the ground-based laboratory data.