Adaptive controller for a Fourier Transform Spectrometer with space applications

This paper presents an adaptive controller for CIRIS (Compositional InfraRed Interferometric Spectrometer) implemented on a stand-alone field programmable gate array (FPGA) architecture with emphasis on space applications in radiation environments such as Europa. CIRIS is a novel take on traditional Fourier Transform Spectrometers (FTS) and replaces linearly moving mirrors (characteristic of Michelson interferometers) with a constant-velocity rotating refractor to variably phase shift and alter the path length of incoming light. This design allows for a compact and robust device, making it ideal for spaceborne measurements in the near-IR to thermal-IR band (2-12 μm) on planetary exploration missions. The instrument's embedded microcontroller is implemented on a VIRTEX-5 FPGA and a PowerPC with the aim of sampling the instrument's detector and optical rotary encoder in order to construct an interferogram. Subsequent signal processing provides spectral immunity from the noise effects of radiation encountered during space flight to destinations such as Europa. A variety of signal processing techniques, including radiation peak removal, resampling, Fast Fourier Transform (FFT), filtering, dispersion correction, and spectral calibration processes are applied in real-time to compose the sample spectrum. The instrument's FPGA controller is demonstrated with the FTS to highlight its suitability for implementation in space systems.