Broadband thermal infrared spectrometry for the polar radiant energy in the Far-InfraRed Experiment (PREFIRE)

The thermal land-atmosphere interaction at the poles is modulated by a weak atmospheric greenhouse effect accentuating the impact of poorly characterized longwave surface emissivities on local energy balance. The PREFIRE mission is examining whether model biases in these interactions drive variability in projections of sea level rise, ice sheet loss and weather severity. Measurements of the spectral thermal emission to space are being made using two Thermal InfraRed Spectrometers (TIRS) aboard each of the twin NASA PREFIRE CubeSats, now in low-Earth orbit. These instruments provide us with broad observational bandwidth covering mid- and far-infrared wavelengths, and allow systematic sampling of polar conditions at sub-diurnal to seasonal scales. We will discuss the design, assembly and testing of these compact infrared sensors which required miniaturization of existing technologies including an ambient thermopile array detection system embedded in an Offner spectrometer. Challenges of calibration and geolocation for our CubeSat operations will also be presented.