Outline of 500kg-class small satellite system study

Abstract On 1992 we started the study of 500kg-class satellite mainly for technology demonstration mission which contributes to mitigate the project risk. It goes without saying that this class of satellite is characterized by low cost and fast turn-around-time, but are different from the same class satellites which we'd developed in the '80s. In this paper, we present the outline of this class of satellites, and focusing to Space Environments and Effects Observation Satellite(SEES) under pre-phase A. A lot of failures which have happened on orbit are caused by space environments. So it is necessary to understand in detail the behavior, and to develop technology to endure them.