Computational Reconfigurable Imaging Spectrometer
Presenting Author: Adam Milstein
Organization: MIT Lincoln Laboratory
Co-Author(s): Yaron Rachlin, Corrie Smeaton, Charles Wynn, Ryan Sullenberger, Philip Chapnik, Steven Leman
Spaceborne infrared spectral imagers and sounders provide critical data for a wide range of Earth science applications, such as weather, climate, air quality, and land/water usage. For example, hyperspectral sounders such as Atmospheric Infrared Sounder (AIRS) and the Cross-Track Infrared Sounder (CrIS) observe the Earth's atmosphere with dense spectral coverage, enabling significantly improved weather forecasts and unprecedented measurements of atmospheric composition. Despite the high value of such infrared imaging spectrometers, high cost and complexity have limited the number of fielded instruments, and dramatically increased the impact of losing anyone instrument. Longwave instruments in particular require significant size, weight, and power (SWaP) due to the need for cryocooling, with the cost of existing instruments typically in the hundreds of millions of dollars. As a result, revisit intervals for instruments in low Earth orbit are typically no greater than 12 hours, limiting observations of dynamic phenomena such as severe weather events. To address this, we present the Computational Reconfigurable Imaging Spectrometer (CRISP), a new imaging spectrometer suitable for hyperspectral and multispectral missions. The design of this system will enable high performance from smaller and less- expensive components such as uncooled microbolometers, and thus be more suitable for small satellites that can be deployed in constellations. CRISP is a novel design that exploits platform motion, dispersive elements, and coded sensing techniques to make a time series of encoded measurements of the optical spectrum at each pixel. This encoding is inverted using specialized processing to recover the spectrum. The proposed effort will demonstrate significant sensitivity and other advantages over existing imaging spectrometer designs, enabling miniaturization and improved area coverage. Spectral and spatial resolution and coverage can be traded off with a simple configuration change to encompass multiple mission types. As a particular example, the effort will demonstrate that an uncooled CRISP system can provide longwave sensitivity and spectral resolution comparable to existing IR imaging and sounding instruments.