Power subsystem design for the Montana EaRth Orbiting Pico-Explorer (MEROPE) CubeSat-class satellite

Montana State University's Space Science and Engineering Laboratory (SSEL) under support from the Montana NASA Space Grant Consortium is engaged in an Earth orbiting satellite student project that will carry a reproduction, using current-day technology, of the scientific payload flown on Explorer-1 in 1958 into a 650 km sun-synchronous polar orbit. The off-the-shelf emphasis of the MEROPE component selections has required the power system to adapt to widely different electrical needs across subsystems. The size limitations of the CubeSat-class specifications confine body-mounted solar arrays to approximately 64 cm/sup 2/ per side, restricting overall power production and necessitating the use of an extremely efficient power bus. MEROPE will employ dual junction GaAs solar cells (19% efficiency) to produce the 5 W necessary for satellite operation and battery maintenance. Included in the system will be two Li-ion battery cells chosen for their high energy density, rapid charge characteristics, low mass, and lack of memory effects. The power system is responsible for providing a highly regulated 5 V bus to the microcontroller subsystem and a 6 V bus to the communication subsystem. In addition, the Geiger tube scientific payload aboard MEROPE requires a stable 500 V high voltage power supply (HVPS) to operate the experiment. This will be accomplished using a prototype HVPS requiring +/- 5 V buses.