Thermal Testing and Analysis of the CASE Engineering Model Subsystem

The Contribution to Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) Spectroscopy of Exoplanets (CASE) is a passively cooled cryogenic subsystem consisting of two detector packages, two cryogenic flex cables and an accompanying focal plane electronics box containing two separate sidecar electronics packages which will be delivered to the Space Research Centre of the Polish Academy of Sciences (CBK). CASE will be used in its Fine Guidance Sensor (FGS) instrument as part of the European Space Agency’s (ESA) ARIEL mission. NASA’s Jet Propulsion Laboratory is delivering the hardware with coordination and detector testing services provided by NASA Headquarters and Goddard Spaceflight Center (GSFC). To test the system in a flight like environment over a long period of time with a small team supporting the experiment a custom test fixture and test setup had to be designed. The test setup needed to achieve 37 K on the optical bench simulator for environmental qualification and thermal model validation purposes. A black, <50 K radiation sink was required to achieve a radiation environment cold enough to simulate deep space well enough for model correlation. A fixture was designed to create the appropriate environment and it was cooled by two dual stage 4K Gifford-McMahon cryocoolers. The test setup was operated continuously for six months of thermal, functional, firmware and electromagnetic compatibility testing. This paper will report the thermal design, analysis and test process for the CASE engineering model (EM) hardware in a cryogenic environment and the plans for flight testing.