Miniature high-resolution Fabry–Perot guided-wave spectrometer for planetary atmospheric remote sensing

Abstract

Infrared (IR) remote sensing of planetary atmospheres typically requires spectral resolution below 0.1 nm to resolve the fine structure of the optical absorption characteristics of relevant gas-phase species and minimize interferences. This is currently accomplished using large bulk-optic Fourier transform infrared (FT IR) or dispersive spectrometers with complex optomechanics to provide the required spectral discrimination through the selection of a large optical path length. However, the resultant large mass and power requirements carry a high cost penalty and risk for spaceborne missions, requiring costly, large space platforms. This paper describes the breadboarding of an innovative spectrometer concept, the Fabry–Perot (FP) guided-wave integrated optical spectrometer (IOSPEC), which synergistically combines two mature technologies to provide a miniature spectrometer capable of broadband operation at high spectral resolution to below 0.03 nm full width half maximum (FWHM) with a net mass under 3 kg. A special, tailored tunable FP filter is employed to provide the high spectral discrimination, allowing a large spectrometer input aperture. This is matched with a high-performance guided-wave IR spectrometer based on MPB Communications Inc. patented IOSPEC technologies to simultaneously provide the measurement of 256–512 high-resolution spectral channels over a relatively broad spectral range. By tuning the FP filter, a continuum of spectral measurement points can be obtained with a signal-to-noise ratio (SNR) advantage of at least SQRT(256) over scanned spectrometer systems. The guided-wave optics integration provides robust, long-term optical alignment and minimizes the system mechanical complexity. The FP–IOSPEC spectrometer volume and mass minimization enable multiple spectrometers to be accommodated on a low-cost microsat, optimized for selected measurement tasks and views, thereby enabling significantly improved data acquisition for remote sensing and science while minimizing the mission cost. The application of this innovative technology to the requirements of the potential Miniature Earth Observation Satellite (MEOS) mission to study critical aspects of the carbon and hydrologic cycles associated with climate change is discussed.