# Compact Midwave Imaging System: Results from an Airborne Demonstration
## 5 Conclusions  
The results presented in this paper from the CMIS aircraft flights demonstrated the advanced capability of the instrument for multi-angle, multi-spectral wide-field of view observations to support earth science. The accuracy of the airborne stereo observations of cloud heights and winds confirmed that this technique applied to the CMIS 3.75-\(\upmu\)m bands can be used effectively for spaceflight. The CMIS observations with MWIR bands demonstrated that the instrument delivers scientifically useful day/night stereo observations for AMVs and their heights. The MWIR imaging has an advantage over the thermal bands in the dimension of instrument optics for the same pixel resolution, which allows the compact design of CMIS. Although the MWIR bands have been flown on LEO and GEO, the key enabling technology is the high-sensitivity Type-2 Superlattice (T2 SL) detector used by CMIS that operates at 150 K. The high detector operation temperature will significantly lower the instrument power, prolong the cooler lifetime, and simplify the system design. The CMIS flights proved that its technology and design are ready for spaceflight. The current detector format for CMIS is 640 \(\times\) 512 pixels with a 50\({}^{\circ}\) field of view. At a nominal altitude of 410 km, the GSD is approximately 545 m as indicated in Table 6. However, the technology has subsequently improved so that the detector can now be scaled up to 1280 \(\times\) 1024 pixels, which would improve the GSD to 272 m. This provides sufficienthorizontal resolution to observe mesoscale features associated with such features as outflow boundaries and PBL structures. The low SWaP (size, weight, and power) of CMIS makes it a cost-effective solution to the need for high-resolution spatiotemporal sampling from CubeSat or SmallSat constellations. Its compact design will fit the instrument to a 6U CubeSat or as a hosted payload on a SmallSat, to meet the Earth Science 2017-2027 needs for high-resolution tropospheric and PBL winds. With the improved SWaP, CMIS provides an attractive, affordable option to fly a satellite constellation of 10-15 satellites for a potential Earth System Explorer mission to meet requirements for the Atmospheric Winds Targeted Observable (TO-4 in Appendix C of ESAS 2017) or a potential Earth Venture science mission. If the objective is to obtain stereo cloud motion vectors only, highly accurate radiometric calibration would not be required. A calibration need only be accurate enough to enable pattern matching between cloud scenes taken within 5-15 min of each other. As demonstrated from the CMIS flights, the instrument also proved its capability for monitoring fires. The 4.05-um band provides data in combination with the 2.25-um band to estimate temperature and fire radiative power if both bands remain unsaturated. The CMIS instrument can utilize dual gains to achieve a wider dynamic range so as to avoid saturation. Depending on wildfire measurement requirements, the instrument can be upgraded to increase the number of spectral channels to ~10 within the range of 1.8 um to 5 um. Accurate radiometric calibration, plus a large dynamic range would be required to enable sensing of large, hot fires, as well as volcanic plumes. For a potential future mission, it might also be advisable to include a 2048-pixel visible band with time-delay integration to serve as a low-light imager. On moonlit nights, it might be possible to obtain stereo products at better than 250-m and 375-m GSD with a low-light imager and CMIS, respectively. The high data rates for these imagers would drive the need for on-board processing to process the datasets into disparities, which are an intermediate-level stereo product. The stereo-bit FPGA has already demonstrated the capability to do this [11]. Finally, because of the high operating temperature of the FPA, a potential design enhancement for CMIS would be to replace its cryocooler with a TE cooler.