Results of the Solar Cell Experiments Aboard the NTS-2 Satellite After 447 Days in Orbit.

Results after 447 days in orbit of the solar cell experiments aboard the NTS-2 satellite are presented. The objective of the solar cell experiment, consisting of 15 separate experiments of five cells each, is to evaluate the performance of state-of-the-art solar cells in the space environment. Telemetered data from the 14 silicon and one gallium arsenide modules indicate a more severe radiation environment in the 63 degree, 20,190 km circular orbit than was predicted. Based on the NTS-2 data, the solar power array containing Spectrolab Helios cells will degrade 27 in maximum power over the three-year mission. Solar cell panel temperatures have reached 104 C providing ideal conditions for annealing of the radiation-induced damage in the gallium arsenide cells. After 15 months of operation these cells have suffered the least power degradation, with a maximum power loss of 14.0. After 447 days in orbit, the loss in power ranged from 14.0 to 59.5 with the exception of the Solarex low-cost space cell which became open-circuited on the 69th day. The average value of I sub sc measured in space on the first day of exposure agreed with prelaunch solar simulator values to within 1 or - 0.99. The agreement between V sub oc in space and solar simulator values was 1.24 or - 1.08. Results are summarized of the changes in the photovoltaic parameters of each of the experiments. Author