Preliminary Thermal Design of the Planned Venus Synthetic Aperture Radar Instrument

The Venus Synthetic Aperture Radar (VenSAR) is a planned science instrument that would be part of the EnVision mission managed by the European Space Agency. EnVision would launch in 2031 on an Ariane 64 to Venus. VenSAR would consist of a two-pol S-band radio frequency feed, a three-panel reflectarray, and various electronics. The instrument would collect imaging data of the surface and allow for time comparisons with data from the past Magellan mission. After cruise from Earth to Venus, the spacecraft would begin aerobraking to transition into a 1.5-hour polar orbit for science operations. The science phase would last four Earth years. The thermal design of the feed and reflectarray has the primary challenge of accommodating short duration, high aerothermal flux heat loads during aerobraking and persistently high environmental heat loads at Venus. The feed assembly would be thermally isolated from the spacecraft interface and mostly covered with MLI. The reflectarray panels would also be thermally isolated from the spacecraft and would have a white thermal control coating on the RF side and MLI on the opposite side. Some of the VenSAR electronics inside the spacecraft would have high power dissipations that require thermal interface material to provide additional thermal conductance for heat rejection. Furthermore, the spacecraft would have heat pipes and radiators to redistribute and reject heat. The antenna thermal design would also be a key contributor to the integrated structural thermal electrical performance of the instrument. This paper will describe the VenSAR preliminary thermal environments, requirements, design, analysis, and hardware.