The Van Allen Probes Power System Launch and Early Mission Performance

The Van Allen Probes are twin NASA spacecraft that were launched August 30, 2012, into lapping highly elliptical earth orbits. The twin spacecraft will operate within the Van Allen radiation belts throughout their two-year mission. The Van Allen Probes are sponsored by NASA\textquoterights Living With a Star (LWS) Program. The Johns Hopkins University, Applied Physics Laboratory designed, fabricated, and operates the twin spacecraft for NASA. The power systems of the twin spacecraft are identical. A direct energy transfer topology was selected for the power system. The loads are connected directly to the eight-cell Lithium Ion battery. The solar panels consist of triple junction cells. The design average power of each spacecraft is about 350 Watts, nominal 28.8 volt bus. A single 50 AH Lithium Ion battery is used to support the spacecraft loads during launch and eclipse periods. The battery charge control is performed using constant current/constant voltage taper charging. The two Van Allen Probes are performing as designed. This paper will describe the power system launch and early mission performance results.