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The Visible Mid-wave Dyson Imaging Spectrometer (VMDIS) is a JPL-developed prototype instrument whose main goal is to address three key technical challenges for the next generation of imaging spectrometers for solar system exploration: (1) High signal-to-noise ratio (SNR) measurements for mapping of minerals and volatiles on solar system targets including comets, asteroids, rocky moons, icy moons, and planets especially Mars; (2) Miniaturization for low-cost mission platforms (reducing the size, mass, and power requirements compared to current options); and (3) excellent spectral cross-track and spectral-spatial uniformity required by todays advanced algorithms for rigorous quantitation with uncertainties. The core of VMDIS is the imaging spectrometer instrument: an optically fast F/1.8 Dyson imaging spectrometer covering a spectral range from 600 nm to 3600 nm, with a spectral sampling of 7 nm. Different telescopes can be used with different implementations of VMDIS to tailor the IFOV and FOV of the instrument. With its prototype telescope, the instrument enables a field of view (FOV) of 28°, with an instantaneous FOV of 0.5 milliradians subtended by each 18 μm cross-track pixel. The size of the VMDIS prototype including the telescope and heritage electronics is roughly equal to 3U (3 units – 1 unit measuring approximately 10×10×10 cm), with a mass < 8 kg and payload power < 40 W. With next generation electronics in development this mass falls below 3 kg. We present an overview of the optical, mechanical, and thermal design of VMDIS, which is required to fabricate this instrument within very demanding resource allocations. The design of the signal chain electronics is also detailed. In addition, preliminary alignment, characterization, and calibration measurements, obtained with the instrument operating in relevant space-type environment, are also discussed. While tested with an available 30-μm detector array, VMDIS is designed for a 18-μm digital readout detector array. VMDIS is intended to pave the way for future low-cost, small form factor imaging spectrometers with state-of-the-art performance in terms of combination of spectral range, high throughput, exceptional uniformity, as well as configuration flexibility for both orbital and landed mission, for the next decade and beyond.
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