Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) for Sunrise III: Thermal-Vacuum Test of the SCIP Optical Unit

The Sunrise Chromospheric Infrared spectroPolarimeter (SCIP) is an instrument for the third flight of the Sunrise balloon-borne solar observatory planned for 2022. To verify the high spatial and spectral resolutions required in the balloon flight, the SCIP optical unit was subjected to a thermal-vacuum test in which the SCIP optical unit was installed in a vacuum chamber and was exposed to the thermal vacuum environment expected in the balloon flight. We verified the heater control performance and the temperature distribution in the SCIP optical unit in hot and cold conditions created by the shrouds in the vacuum chamber. We confirmed the optical performance, such as spatial and spectral resolution, and an air-to-vacuum difference of the optics by injecting the laser and white lights through a vacuum window.