The preliminary design of the Comet Nucleus Tour spacecraft power subsystem

The power subsystem for the Johns Hopkins University, Applied Physics Laboratory, Comet Nucleus Tour (CONTOUR) mission spacecraft which will visit two comets is described. The spacecraft is octagonal shaped with body mounted solar panels. The power system is an unregulated bus direct energy transfer system with a "Super" NiCd battery and utilizes triple junction solar cells. The power control is performed by digital and linear sequential shunts. The Sun distance, the temperature variations, the shadowing on the solar panels and the requirements on the power subsystem to support the spinning and the inertially stabilized modes of operation of the spacecraft make the solar array and power subsystem design a challenging task. The power system design uses heritage circuits and emphasizes reliability with low cost, weight and power consumption.