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Description
The Copernicus Imaging Microwave Radiometer (CIMR) is part of ESA’s Copernicus Sentinel Expansion missions and is designed to monitor Earth’s surfaces through radiometric measurements of parameters such as sea surface temperature, sea-ice concentration, and salinity. CIMR operates in a quasi-polar, near-circular, Sun-synchronous orbit, ensuring global coverage including polar regions. The spacecraft includes a rotating microwave radiometer crate and a deployable mesh reflector. The instrument crate thermal control relies on heat pipes (HPs), which spread the heat dissipated by onboard electronic units over a radiating surface. This paper presents the HP architecture developed to withstand the centrifugal forces generated by the instrument rotation. The HPs are mounted along a flat panel at the crate perimeter, parallel to the rotation axis. Differential centrifugal accelerations affect HP performance and, at high force levels, may drive the working fluid towards both ends of the pipe, depleting the central section. The initial design was based on HP performance under a constant acceleration field because data for the actual flight configuration were unavailable. This imposed limitations on pipe length and reduced thermal performance. To overcome these limitations, a dedicated test campaign was conducted in a centrifuge facility to evaluate HP performance under a realistic rotation-induced acceleration field. Different pipe designs were tested under various spin rates and adverse conditions, while residual performance margins were assessed. This paper presents and discusses the test setup and results. Based on the experimental data, system-level analyses were conducted. The thermal conductance of the HPs was degraded with rotational speed, especially for the longest HPs. In spite of that, the results showed better performance than tilted configuration, leading to an optimized heat pipe layout that maximizes overall efficiency while minimizing losses, system complexity, and cost.