The Copernicus Imaging Microwave Radiometer (CIMR): Thermal Control System Design, Challenges and Solutions for a Large Rotating Instrument

The Copernicus Imaging Microwave Radiometer (CIMR) is one of the six Copernicus Expansion Missions, that are part of the Copernicus Space Component being implemented by the European Space Agency (ESA) and the European Commission. The primary mission objectives of CIMR are to measure Sea Ice Concentration and Sea Ice Extent at a spatial resolution of ≤5 km and Sea Surface Temperature at a spatial resolution of ≤15 km with a focus on sub-daily coverage of Polar Regions and daily coverage of Adjacent Seas. CIMR will additionally ensure European operational continuity of L-band measurement capability to enhance monitoring of the Polar Regions. CIMR is a complex mission involving a rotating microwave radiometer working in L/C/X/K/Ka bands with a deployable antenna with a mesh reflector. This paper aims to introduce the instrument thermal control: its design drivers, challenges and technical solutions. Due to the complex interfaces between the instrument, its subsystems and spacecraft platform, an advanced and innovative thermal management approach is applied, consisting of both active and passive thermal control. Several challenges have been identified, including the environment definition for the rotating scan mechanism, the behavior of heat pipes under centrifugal forces and the temperature gradients and thermal stability requirements of the sensitive elements. This paper describes the instrument thermal control system design, often driven by the instrument rotation, and the solutions which have been identified to properly manage the complex interfaces and the challenging environment. It is foreseen that the CIMR thermal control design will serve as heritage for future Earth observation missions involving large rotating payloads.