Angie Crews
Massachusetts Institute of Technology
The rapidly advancing capabilities of small satellite systems and instrument miniaturization provides an opportunity to use CubeSats as a cost effective weather monitoring platform that can provide increased temporal resolution over current weather satellites. In this work, we consider both visible and microwave radiometer instruments. A significant gap occurs in visible observations that are critical for extreme weather events and natural disasters [1]. Revisit times for MODIS and MISR are 9 days and 2 days, respectively; revisit time for Landsat is 16 days. A constellation of CubeSats with visible imagers could provide a daily revisit time that would improve disaster monitoring for extreme weather events. Improving revisit time of microwave radiometers would also significantly improve weather forecasting, as stated in the NASA Earth Science Decadal Survey [2]. Current microwave radiometers such as the Advanced Technology Microwave Sounder (ATMS) provide global coverage twice a day; however, a constellation of six CubeSats with microwave radiometers such as the Time-Resolved Observations of Precipitations structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission could provide a rapid refresh rate of better than 60 minutes. A future constellation of CubeSats with visible imagers and radiometers could drastically improve revisit times and thus address gaps in monitoring extreme weather events.
In order to effectively use CubeSats in a constellation as a weather monitoring platform, calibration of the sensors, particularly intersatellite calibration, must be used to provide consistent measurements. We will use the Community Radiative Transfer Model (CRTM) [3] to determine intersatellite radiometric biases by comparing actual radiances, such as from the Microwave Radiometer Technology Acceleration (MiRaTA), with ground truth that is developed using sources such as Numerical Weather Prediction (NWP) models, radiosondes, and GPS Radio Occultation (GPSRO) measurements. Calibration opportunities between CubeSat constellations and GPSRO measurements will be analyzed, as well as opportunities for satellite to satellite calibration for constellations of microwave radiometers and visible imagers. Visible imager calibration techniques such as lunar and ground-based calibration will be investigated, and we will determine vicarious calibration opportunities between visible imager sensors in a constellation and stable ground targets. We additionally propose to compare data from CubeSats and traditional weather satellites and develop metrics of performance between the sensors, and we will assess the system level utility of CubeSat sensor performance to the weather forecasting community for monitoring large scale weather events. In this manner, the proposed research will develop tools for designing and architecting constellations that have high utility to weather forecasting systems, as well as tools that allow intersatellite and cross satellite calibrations in a constellation of CubeSats with visible imagers and microwave radiometers.