Design and Test of the SAS-A Power System.

The SAS-A power system consists of a solar cell array, a rechargeable nickel-cadmium battery, and two redundant charge control systems. The unique feature of this system is that there are a wide range of battery charge currents from the solar array, complicating the task of the charge control elements. The first part of the report describes the design of the power system with emphasis on the predicted solar cell array currents for different positions of the satellite with respect to the sun. The second part of the report presents the results of the power system test. Curves describing system operation are presented. A comparison between the two redundant charge control elements is made to show the advantages and disadvantages of each. A battery current and voltage limiter has the advantage of being simple and lightweight. However, the heavier electronic coulometer has the advantage of accommodating changes in the battery characteristics and of allowing more accurate predictions of the heat dissipated in the battery. Author