This paper describes the analysis of NASDA's various space solar cells by analyzing the data measured in space. NASDA launched the Engineering Test Satellite-V (ETS-V) on August 27, 1987 and put into the geostationary orbit at a longitude 150 degreesE. This satellite was in operation until electronics stopped on September 12, 1997. On this satellite, the solar cell monitor (SCM) was equipped as a part of the Technical Data Acquisition Equipment (TEDA) for observation of the space environment. SCM consisted of 24 kinds of solar cells including silicon (Si) cells and gallium arsenide (GaAs) cells as shown in Table 1. The short-circuit current (I-sc) characteristic of each cell were measured in the radiation environment of geostationary orbit for 10 years. The degradation data due to a solar flare, occurred in October 19, 1989, were also recorded. All flight data agree qualitatively with ground test data. (C) 2001 Elsevier Science B.V. All rights reserved.