An innovative onboard computer for CNES microsatellites

Since the end of 1998, CNES has been developing a new Microsatellite product line in the 100 kg range, called MYRIADE, based on the "smaller, faster, cheaper" concept. As far as the onboard control/command subsystem is concerned, this innovative approach deeply relies on lightweight/low cost equipment developments using commercial miniaturized parts and non-space qualified technologies. The Microsatellite central on board computer (OBC) has thus been designed through a CNES R&D development phase, started in 1997, and then manufactured and space qualified in partnership with a small French high-tech firm, STEEL Electronique: the challenge was to obtain the best compromise between a low cost/low mass/low power objective and computing and communication performances similar to the state-of-the-art computers used in standard satellite projects. The OBC directly manages the attitude and orbit control system (AOCS) actuators and sensors, as well as the power unit, and it interfaces with the payload. The satellite remote control (TC) and telemetry (TM) are transmitted through the OBC.