Thermal Vacuum Tests and Thermal Properties on ESA’s OPS-SAT mission

OPS-SAT is a 3U CubeSat, designed for versatile use as an experimental platform for industry and universities, to demonstrate new operational concepts and prototype software in a real space environment. The satellite offers numerous payloads alongside the satellite bus, all of which might be used by an OPS-SAT experiment. The unpredictable nature of experiments with respect to the use of payload components raises certain unknowns, in particular concerning power consumption. As a result, the thermal behaviour throughout the satellite depends largely on which of the several on-board experiments and the associated payloads are switched on. OPS-SAT offers a variety of communication modules, such as a UHF transceiver, an S-Band transceiver, a Software Defined Radio (SDR), an X-Band transmitter and an optical receiver. The peak power consumption of OPS-SAT may exceed 30 watts during high power experiments. The S-Band transceiver consumes up to 10 watts during ground station passes and the so-called Satellite Experimental Processing Platform (SEPP), the heart of OPS-SAT experiments, consumes up to 8 watts constantly. This work provides an overview of the design and the thermal considerations on OPS-SAT and the results of the thermal vacuum (TVAC) test campaign. The results yield an average thermo-optical emissivity of 0.79 to 0.84 and the thermal power distribution on the spacecraft surface, and demonstrate the special case of the thermally isolated S-Band and X-Band patch antennas. Based on the derived results, predictions can be made about the thermal behaviour during various load cases and during periods with an active S-Band transmitter.