In-flight Hipparcos solar array performance degradation after three and a half years in GTO

This paper compares the in-flight and predicted performance degradation of the Hipparcos spacecraft´s solar array three and half years on from being stranded at launch in the very damaging radiation environment of its geostationary transfer orbit (GTO). The very severe radiation environment has provided a unique opportunity to study the on-board silicon solar cells up to equivalent 1 MeV electron fluence levels (Ø=1.26E16 e/cm² for Isc and 2E16e/cm² for Pmax/Voc) seldom attained by other spacecraft