Power degradation studies of the Mir solar array return experiment

A Russian solar array was recently returned from the Mir space station after 125 months on-orbit and made available to US investigators for detailed post-flight analysis. The array, consisting of eight panels of silicon cells, was deployed on June 16, 1987 as one of four segments of an array located directly above the Kvant-2 module. After removal and packaging by Russian cosmonauts in November, 1997, it was brought back to Earth by the STS-89 mission two months later. Detailed post-flight performance measurements of one panel show that its overall power conversion efficiency degraded from a BOL value of about 9% to 4.8%, due not to an overall degradation in cell conversion efficiency but rather to circuit disruptions in several of the parallel connected strings. In this paper, the photovoltaic post-flight analysis is presented, as well as a detailed description of the array technology.