## 5 Conclusions  
A new space-borne weather remote sensing approach, MISTiC Winds, employing miniature infrared spectral imaging sounders in a microsatellite-hosted constellation is described in this paper. This observation approach would provide individual high-resolution infrared spectral soundings in a dense array, with image quality characteristics of spatial sampling, spatial resolution, and sensitivity that enable high-quality atmospheric feature tracking. These attributes, together with the small size of these instruments enable a small number of them to be deployed in a common orbital plane in LEO short with time-separation, providing a feature-track wind observation, with the improved feature height assignment accuracy provided by hyperspectral infrared sounding. The vertically resolved tropospheric wind observations enabled by MISTiC Winds are directly responsive to the need identified by the National Academy in its 2018 Decadal Survey for Earth Sciences and identified as a targeted observable. Such observations would enable research for an improved understanding of key atmospheric processes, especially for severe weather, and improved numerical weather prediction. This proposed observation builds on the experience of the NASA AIRS Program, as well as the requirements, design, and technology developments of the NASA GIFTS Program and the NASA/NOAA GOES-R HES Formulation Phase Program. The specific requirements, mission concept, and instrument design concept were developed under the NASA Instrument Incubator Program and BAE Systems internal funding. A program of critical risk reduction testing was also completed. Specific accomplishments under these efforts include:  
Development of key instrument and mission requirements, observing system architecture and instrument detailed concept design tailored to focus on dynamic weather characterization in the troposphere with miniature instruments in a constellation:  
Cloud and water vapor motion vector winds with rms wind-speed errors <2 m/s at 6+ levels in the troposphere,  
High-resolution IR soundings of temperature and vertically resolved moisture gradients in the troposphere,  
15 kg/50 W instrument is 60x smaller in volume, 10x lower mass, and 4x lower power demand than NASA's AIRS instrument,  
Performance of critical technology risk reduction through laboratory and airborne testing:  
APD-mode 640x480 IRFPA with Proton total dose tolerance for four-year LEO mission life demonstrated,  
Ultra-low distortion brass-board IR spectrometer assembly demonstrates >700:1 spectral resolving power and high spectral calibration temperature stability (dJ/dT <2.5% of spectral response function FWHM per 100 mK),Conducted several airborne observation demonstration flights on ER2 (\(\sim\)30 h) multi-pass observations over land sites in southern California, and over the nearby ocean,  
Analyzed the airborne data to show vertically resolved moisture gradients, and hyperspectral cloud AMVs matching radiosonde wind speed observations to within 2.5 m/s under challenging high wind-shear conditions. Conceptualization, K.M. and J.P.; Formal analysis, K.M. ; Investigation, J.P., H.A., J.S., D.B., C.G., M.J. and S.F. ; Project administration, D.B. ; Software, S.F. ; Writing--original draft, K.M. The financial support of this work by the NASA Earth Science Technology Office, under grants NNX14 AG86G and 80 NSSC18K0568, overseen by NASA Earth Science Technology Office by Mr [PERSON] and Ms [PERSON] is gratefully acknowledged. Significant contributions to the design, fabrication, alignment, and calibration of the airborne instrument used for data acquisition for this work were provided by BAE Systems staff members [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON]. Dr [PERSON] at NASA GSFC provided IR retrieval analysis for the spectral cutoff trade studies, and for correlations between AIRS observations and the airborne observations reported here.