Small Satellite Power System Design

Recently, there has been extensive interest in Special Purpose Inexpensive Satellite’s (SPINSAT) that perform cost effective space oriented missions. Reduced reliability and short delivery schedules are two key issues relating to the design of such satellites for minimizing acquisition costs. These issues are important factors in the design of a spacecraft power system which can be considered to be the heart of the entire satellite. The power system constitutes a substantial portion of the overall satellite system cost that must be reduced for SPINSAT missions. Minimum cost or inexpensive satellite implies prudent power system design with minimal redundancy, inexpensive energy source and battery with high cycle life. All of these factors must be considered during the design phase of a small SPINSAT and in particular, of the power system. Fairchild Space Company was recently awarded a contract to build such a small satellite for the Profile (Passive Radio Frequency Interference Location Experiment) program. The power system for the Profile program has gone through the considerations mentioned above in terms of cost, reliability, mission life and requirements compliance. Some of the major factors that were addressed during the design phase for Profile are the selection of battery type, battery charge control, main bus voltage level, power control and conditioning, dependence on other parts of the satellite, and system redundancy. Various trade-off studies were conducted in order to achieve an optimum design for minimizing the satellite acquisition costs. This paper describes the Profile power system design, the rationale for component selection (including system topology and bus voltage), and how the system design satisfies the primary SPINSAT objectives