The NACHOS CubeSat-based hyperspectral imager: laboratory and field performance characterization

Hyperspectral imaging with sufficient resolution and sensitivity for scientifically useful space-based mapping of trace gases has long required large and expensive satellite instruments. Miniaturizing this capability to a CubeSat configuration is a major challenge, but opens up more agile and far less expensive observing strategies. A major step in this direction is our development of NACHOS, an ultra-compact (1.5U instrument, 3U complete CubeSat) hyperspectral imager covering the 300-500nm spectral range in 400 channels. Here we describe laboratory and field performance characterization of this new instrument. Laboratory tests demonstrate spatial and spectral resolutions of <0.8 mrad and 1.3 nm, respectively, with good resolution of the spectral lines of our SO₂ and NO₂ target gases. Outdoor field tests under realistic illumination conditions provide real-world signal-to-noise benchmarks, and yield hyperspectral images displaying high quality solar and atmospheric spectra. To estimate on-orbit gas retrieval sensitivities, we computationally implanted plumes of varying concentrations into acquired hyperspectral datacubes. Applying our adaptive matched filter gas-retrieval algorithms to the generated scene, we predict NACHOS will be able to distinguish 35 and 7 ppm⋅m plumes of SO₂ and NO₂ (respectively) with high sensitivity; a capability well-suited to address scientific goals related to monitoring both passive SO₂ degassing from volcanoes and NO₂ emissions from anthropogenic sources. Lastly, we will show findings from thermal and vibrational environmental tests, performed in preparation for a scheduled early-2022 launch, demonstrating the extremely robust spectrometer design is well-suited for satellite-based deployment.