Three generations of DC power systems for experimental small satellites

The University of Surrey has launched 12 small satellites into orbit since 1981, demonstrating convincingly that low cost, reliable spacecraft can be engineered using standard components and techniques, as opposed to the expensive approach practiced by space agencies. Moreover, initial design to orbital operation takes only 12 to 18 months. The power system is a critical part of the spacecraft infrastructure. Three generations of satellite de power systems are presented: the original system used on the 50 kg microsatellites UoSAT-1 and UoSAT-2; the system introduced on UoSAT-3 and used for current designs; and a new system for a 350 kg minisatellite due for launch in late 1996. The solar arrays, battery charge regulators, batteries, power processing and power distribution are described. Careful incremental development has ensured that no power system failure has occurred to date.