Insat power bus characterization in the presence of switching load

Indian National Satellites (INSATs) are a series of multi purpose satellites, with a thrust on communication pay-loads, operating in Geo synchronous orbit. They employ Dual sun-lit, ripple regulated bus to power the loads during sunlit period, and Chemical batteries during eclipse. Voltage ripple on the bus can get influenced in the presence of switching loads such as operating the Traveling Wave Tube Amplifiers (TWTA) in Time Division multiple Access (TDMA) modes. The focus of this paper is to simulate the effect of Switching loads on the Power bus during Sunlit, & Eclipse conditions and also to estimate the Bus Impedance. The result of this exercise forms an input for performance analysis (such as EMI/EMC) of other loads connected to the power bus and also gives confidence to conduct such tests on spacecraft. The results of this exercise would be applicable to all space crafts, having similar power system design.