Noise measurements at different Satellite Interfaces due to Solar Array Switching Strings

Switching of solar array strings is a well-known source of electromagnetic emissions on Spacecraft. In order to regulate the bus voltage, the switching strings have Pulse Frequency Modulation (PFM) and Pulse Width Modulation (PWM) to cater to the spacecraft power requirement. High frequency content present in the switching circuitry couples to various interfaces of the spacecraft interfaces that are in close proximity. During disassembled mode testing phase of some of the high power satellites, certain circuits nearby had deviation from nominal performance. To understand the amount of noise coupled to the interfaces, practical measurements have been carried out for the various configurations of the solar array harness types employed in satellite as well as some of the standard interfaces present. The entire practical setup of the solar array simulators with the harness and the switching circuitry have been placed by employing the hardware used for spacecrafts. The switching strings have three types of harness configurations i.e. first is the live and return bundle separately routed, second is the manual twisting of shielded live and return bundle and third is bundle of Twisted pair shielded cable. Six different types of victims have been identified for measurement. The measurements are described and presented in this paper.