Thermal vacuum performance testing of the CubeSat Infrared Atmospheric Sounder (CIRAS)

Abstract

Hyperspectral infrared sounders measure the profiles of temperature and water vapor in the atmosphere and the concentration of trace gas species. Instruments such as NASA Atmospheric Infrared Sounder (AIRS) 1 on the Aqua spacecraft have proven their value for weather and climate research, atmospheric composition research, and high impact to the operational forecast at NWP centers worldwide. Reducing the size, weight and power of these instruments is key to enabling more rapid revisit when deployed in Low Earth Orbit (LEO), enabling new measurements such as 3D Atmospheric Motion Vector (AMV) winds, and reducing the cost of these instrument for future deployment in LEO, Geostationary Earth Orbit (GEO) and aircraft platforms. NASA and NOAA have sponsored technology maturation at JPL of the CubeSat Infrared Atmospheric Sounder (CIRAS) to demonstrate the use of wide field grating spectrometer optics and large format FPA technologies included in CIRAS for infrared sounding. These include a 2D format High Operating Temperature-Barrier Infrared Detector (HOT-BIRD), a silicon Immersion Grating, and Black Silicon for the CIRAS entrance slit and blackbody. Thermal Vacuum (TVac) performance testing of CIRAS has been completed achieving TRL 5 for a full scale brassboard of the instrument. Testing included spatial, spectral, and radiometric response of the instrument including measurements of the transmission in a gas cell. Results show excellent performance from the system with the exception of a high background flux from the Integrated Dewar Cryocooler Assembly (IDCA). The IDCA is not planned for flight use and projections of the performance in the flight configuration are discussed. Through this testing the instrument has reached TRL 5. Recently, the NASA Earth Science Technology Office (ESTO) awarded JPL a contract to fly the CIRAS in an aircraft, called the Pyro-atmosphere Infrared Sounder (PIRS), to measure the convective environment around wildfires.