Thermal Design and Analysis of a Next-Generation Hyper-Angular Rainbow Polarimeter (HARP) Instrument

Abstract

MegaHARP is a next-generation Hyper-Angular Rainbow Polarimeter (HARP) instrument. It is targeted to fly on NASA's Atmospheric Observation System (AOS) Sky satellite. Although MegaHARP leverages its design and technology from predecessor instruments, including HARP2, which is currently operating in orbit, this latest HARP instrument features key improvements. With these improvements come significant engineering challenges; the thermal system is one such challenge. This work explores the design and validation of a conceptual MegaHARP thermal system that achieves two goals: maintaining the instrument's electronics within their temperature ranges, and stabilizing its focal plane arrays (FPAs) while the instrument is acquiring images. The instrument's radiators and heaters are first ideally sized using a steady-state, orbital averaged heat load approximation. A subsequent calculation accounts for the FPA-radiator thermal path using information obtained from the HARP2 thermal model, which is correlated experimentally. Finally, MegaHARP’s thermal design is validated using a transient orbital thermal model. The model shows that the passive thermal system presented here accomplishes both design requirements.