5. NASA’s Hyperspectral Thermal Emission Spectrometer (HyTES)

The Hyperspectral Thermal Emission Spectrometer (HyTES) is being developed as part of the risk reduction activities associated with the Hyperspectral Infrared Imager (HyspIRI). HyspIRI is one of the NASA’s Tier 2 Decadal Survey Missions for earth science. HyTES will provide information on how to place the spectral filters on the HyspIRI Thermal Infrared Instrument as well as provide antecedent science data. The HyTES pushbroom design has 512 spatial pixels over a 50-degree field of view and 256 contiguous spectral bands between 7.5 and 12 μm in the thermal infrared (TIR) wavelength region. HyTES includes many key enabling state-of-the-art technologies including a high performance concave diffraction grating, a quantum well infrared photodetector (QWIP) focal plane array, and a compact Dyson-based optical design. The Dyson optical design allows for a very compact and optically fast system (F/1.6). It also minimizes cooling requirements due to the fact it has a single monolithic prism-like grating design which allows baffling for stray light suppression. The monolithic configuration eases mechanical tolerancing requirements which are a concern since the complete optical assembly is operated at cryogenic temperatures. The QWIP allows for optimum spatial and spectral uniformity and provides adequate responsivity or D-star to allow 200 mK noise equivalent temperature difference (NEDT) operation across the TIR passband. The system uses two mechanical cryocoolers to maintain instrument temperature. The first cooler holds the focal plane array at 40 K and the second cooler holds the remainder of the cryovacuum system at 100 K. Assembly of the system is now complete and the system is undergoing alignment and laboratory testing. Once laboratory testing is complete the system will be used to acquire airborne data from a Twin Otter aircraft over the southwestern USA in late 2012.