Cloud Imaging and Environmental Monitoring Results from the CUbesat MULtispectral Observing System, CUMULOS

CUMULOS is a tiny three-camera VIS/SWIR/LWIR sensor system flying as a hosted payload on the NASA/JPL ISARA mission, a 3U CubeSat. CUMULOS provides a small-aperture, large field-of-view, remote sensing payload suitable for testing the performance of passively-cooled commercial sensors for weather and environmental monitoring missions. The CUMULOS consists of a 0.4-0.9 µm visible CMOS camera, a 0.9 -1.7 µm short-wave infrared InGaAs CMOS camera, and a 7.5-13.5 long-wave infrared VOx microbolometer camera. All three cameras and associated electronics fit into less than 1U of spacecraft volume and were accommodated on the ISARA mission on a non-interference basis. CUMULOS is designed for point-and-stare imaging and acquires almost simultaneous 3-band coverage of regions approximately 200 x 150 kilometers (km) in size, at ground sample distances from 130 to 400 meters from an orbital altitude of 450km. Remote sensing applications that we are investigating include: cloud imaging, surface temperature characterization, hotspot detection (including fires, gas flares, and volcanic activity), detection of nighttime lights, and airglow phenomenology. Operational since June 2018, the sensors have proven capable of daytime and nighttime cloud imaging including, notably, the nighttime detection of airglow-illuminated clouds by the SWIR camera. The LWIR microbolometer camera provides useful single-band cloud and earth surface thermal imagery. The combination of all three cameras working together are very useful for researching compact sensor nighttime weather imaging capabilities and limitations and mapping nightlights and thermal hotspots in manner similar to the VIIRS sensor, but from a different orbit. The high sensitivity performance of the CUMULOS small aperture imagers is enabled by the ability of the spacecraft bus to accurately point and stay pointed during the camera exposure as well as the fast optics. We present example results on nighttime cloud detection, as well as nightlights applications including mapping of urban development and road networks, detection of gas flares and other industrial heat sources, detection of urban heat islands and demonstrating how the combination of sensors work together. CubeSats sensors, such as CUMULOS, can complement existing larger space sensors, such as VIIRS, by acting as testbeds for new spectral bands, imaging at higher resolution over smaller fields of view, and flying in different orbits to measure nighttime lights signals at different times of night. The CUMULOS is also an engineering test bed for developing techniques for the calibration of small sensors in space, demonstrating a calibration and georegistration data pipeline, and automating CubeSat remote sensing data collection. These experiences, lessons and procedures will be described as well. The results from the CUMULOS experiments should be useful in scaling larger, but still very small payloads for weather applications in CubeSat or SmallSat form factors.