MicroMAS: A First Step Towards a Nanosatellite Constellation for Global Storm Observation

The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a dual-spinning 3U CubeSat equipped with a nine-channel passive microwave spectrometer observing near the 118.75-GHz oxygen absorption line. The focus of this first MicroMAS mission is to observe convective thunderstorms, tropical cyclones, and hurricanes. The payload, housed in the “lower” 1U of the dual-spinning 3U CubeSat, is mechanically rotated approximately once per second as the spacecraft orbits the Earth, resulting in a cross-track scanned beam with a FWHM beamwidth of 2.5 degrees and an approximately 20-km diameter footprint at nadir incidence from a nominal altitude of 400 km. The MicroMAS flight unit is currently being developed by MIT Lincoln Laboratory, the MIT Space Systems Laboratory, the MIT Department of Earth and Planetary Sciences, and the University of Massachusetts-Amherst Department of Radio Astronomy for a 2013 launch on the Cygnus-2 ISS resupply mission. INTRODUCTION AND MISSION OVERVIEW Accurate monitoring and forecasting of severe weather provides enormous societal and economic benefit. High revisit-rate measurements provided by infrared (IR) imagers and sounders on satellites operating in geostationary orbit have proven to be a critically important asset. These observations, however, are blind to the most important meteorological phenomena relevant to severe weather events—clouds and the underlying precipitation. A low-Earth orbiting (LEO) constellation of passive microwave sensors could provide all-weather observations with revisit rates of approximately 30 minutes for advanced forecasting and nowcasting techniques and applications that are needed to study full hydrologic cycle processes. The goal of the MicroMAS mission is to demonstrate a core element of the constellation at very low cost – a 3U cross-track-scanning CubeSat hosting a microwave spectrometer with nine channels near the 118.75-GHz oxygen absorption line for sensing of temperature and precipitation at approximately 20-km spatial resolution with full Nyquist sampling. MicroMAS will launch on the Cygnus-2 ISS resupply mission, currently scheduled for December 8, 2013. The CubeSat will be delivered to the ISS as Cygnus cargo and will be deployed from the Japanese Experiment Module (JEM) Small Satellite Orbital Deployer (J-SSOD). J-SSOD is capable of launching small satellites from the station using the JEM Remote Manipulator System. MIT has contracted with SpaceFlight Services and NanoRacks to provide this service. The initial orbit altitude will be approximately 400 km, and MicroMAS will decay to 300 km in approximately 75 days. Orbit inclination will be 51.6 degrees. Spacecraft de-tumbling, initial checkout, and radiometer calibration and validation will occur in the first 30 days of the mission. The NASA Wallops Flight Facility will provide ground segment services in collaboration with the Utah State University