Concept for a low cost MWIR Imaging Sounder for Low Earth Orbit

NASA's Atmospheric Infrared Sounder (AIRS) is a hyperspectral infrared instrument that covers the infrared spectrum from 3.7-15.4 um with 2378 channels and flies on the EOS Aqua spacecraft. NASA's MODIS instrument is the workhorse imaging instrument with its global daily coverage of 36 bands from 0.4-14.4 um at spatial resolutions ranging from 0.25 to 1.0 km at nadir. Both AIRS and MODIS have demonstrated considerable value to NWP centers world wide with AIRS having among the highest impact to operational forecasts, and MODIS providing water vapor derived winds in the polar regions. These instruments provide many other invaluable measurements and have been succeeded by the Cross-track Infrared Sounder (CrIS) and the Visible and Infrared Imaging Radiometer Suite (VIIRS) on NPP and JPSS.

The current state-of-the art large format detector arrays and wide field optics now available within industry allow imaging and spectroscopy to be acquired simultaneously at the full resolution of the imager. In particular, JPL has been working on the design of an low cost MWIR imaging spectrometer capable of meeting the performance of the MWIR bands of MODIS and VIIRS as well as the temperature and water vapor sounding performance of the AIRS and CrIS. Learning from the AIRS experience, the spectrometer covers the spectral range from 1950 cm-1 to 2450 cm-1 with 0.5 cm-1 sampling and 1.0 cm-1 spectral resolution. The very high spectral resolution will improve spectral and radiometric calibration accuracy and enable accurate surface temperature measurements using “superwindow” channels. The instrument design concept, size, mass, power, and performance will be presented with results from a retrieval performance simulation for key parameters including temperature profiles, water vapor profiles, cloud and surface imagery.