Session
Technical Session I: The Horizon
Abstract
The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a dual-spinning 3U CubeSat equipped with a passive microwave spectrometer that observes nine channels near the 118.75-GHz oxygen absorption line. The focus of this MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit. The MicroMAS-1 flight unit is currently being developed by MIT Lincoln Laboratory, the MIT Space Systems Laboratory, and the MIT Department of Earth and Planetary Sciences for a 2014 launch to be provided by the NASA CubeSat Launch Initiative program. As a low cost platform, MicroMAS offers the potential to deploy multiple satellites than can provide near-continuous views of severe weather. The existing architecture of few, high-cost platforms, infrequently view the same earth area which can miss rapid changes in the strength and direction of evolving storms thus degrading forecast accuracy. The 3U CubeSat has dimensions of 10 x 10 x 34.05 cm3 and a mass of approximately 4 kg. The payload is housed in the “lower” 1U of the dualspinning 3U CubeSat, and is mechanically rotated approximately once per second as the spacecraft orbits the Earth. The resulting cross-track scanned beam has a FWHM beam width of 2.4º, and has an approximately 20-km diameter footprint at nadir incidence from a nominal altitude of 500 km. Radiometric calibration is carried out using observations of cold space, the Earth's limb, and an internal noise diode that is weakly coupled through the RF front-end electronics. In addition to the dual-spinning CubeSat, a key technology development is the ultra-compact intermediate frequency processor (IFP) module for channelization, detection, and analog-to-digital conversion. The payload antenna system and RF front-end electronics are highly integrated, miniaturized, and optimized for low-power operation. To support the spinning radiometer payload, the structures subsystem incorporates a brushless DC zerocogging motor, an optical encoder and disk, a slip ring, and a motor controller. The attitude determination and control system (ADCS) utilizes reaction wheels, magnetorquers, Earth horizon sensors, peak power tracking, a magnetometer, and a gyroscope. The communications system operates at S-band using the Open System of Agile Ground Stations (OSAGS) with a 2.025—2.120 GHz uplink and 2.200—2.300 GHz downlink at 230 kbps. MicroMAS-1 uses a Pumpkin CubeSat Motherboard with a Microchip PIC24 microcontroller as the flight computer running Pumpkin’s Salvo Real Time Operating System. Thermal management includes monitoring with thermistors, heating, and passive cooling. Power is generated using four double-sided deployable 3U solar panels and one 2U bodymounted panel with UTJ cells and an electrical power system (EPS) with 30 W-hr lithium polymer batteries from Clyde Space. Tests with the MicroMAS-1 Engineering Design Model (EDM) have resulted in modifications to the spinning assembly, stack and ADCS system and have informed the development of the flight model subsystems.
Presentation Slides
Nanosatellites for Earth Environmental Monitoring: The MicroMAS Project
The Micro-sized Microwave Atmospheric Satellite (MicroMAS) is a dual-spinning 3U CubeSat equipped with a passive microwave spectrometer that observes nine channels near the 118.75-GHz oxygen absorption line. The focus of this MicroMAS mission (hereafter, MicroMAS-1) is to observe convective thunderstorms, tropical cyclones, and hurricanes from a near-equatorial orbit. The MicroMAS-1 flight unit is currently being developed by MIT Lincoln Laboratory, the MIT Space Systems Laboratory, and the MIT Department of Earth and Planetary Sciences for a 2014 launch to be provided by the NASA CubeSat Launch Initiative program. As a low cost platform, MicroMAS offers the potential to deploy multiple satellites than can provide near-continuous views of severe weather. The existing architecture of few, high-cost platforms, infrequently view the same earth area which can miss rapid changes in the strength and direction of evolving storms thus degrading forecast accuracy. The 3U CubeSat has dimensions of 10 x 10 x 34.05 cm3 and a mass of approximately 4 kg. The payload is housed in the “lower” 1U of the dualspinning 3U CubeSat, and is mechanically rotated approximately once per second as the spacecraft orbits the Earth. The resulting cross-track scanned beam has a FWHM beam width of 2.4º, and has an approximately 20-km diameter footprint at nadir incidence from a nominal altitude of 500 km. Radiometric calibration is carried out using observations of cold space, the Earth's limb, and an internal noise diode that is weakly coupled through the RF front-end electronics. In addition to the dual-spinning CubeSat, a key technology development is the ultra-compact intermediate frequency processor (IFP) module for channelization, detection, and analog-to-digital conversion. The payload antenna system and RF front-end electronics are highly integrated, miniaturized, and optimized for low-power operation. To support the spinning radiometer payload, the structures subsystem incorporates a brushless DC zerocogging motor, an optical encoder and disk, a slip ring, and a motor controller. The attitude determination and control system (ADCS) utilizes reaction wheels, magnetorquers, Earth horizon sensors, peak power tracking, a magnetometer, and a gyroscope. The communications system operates at S-band using the Open System of Agile Ground Stations (OSAGS) with a 2.025—2.120 GHz uplink and 2.200—2.300 GHz downlink at 230 kbps. MicroMAS-1 uses a Pumpkin CubeSat Motherboard with a Microchip PIC24 microcontroller as the flight computer running Pumpkin’s Salvo Real Time Operating System. Thermal management includes monitoring with thermistors, heating, and passive cooling. Power is generated using four double-sided deployable 3U solar panels and one 2U bodymounted panel with UTJ cells and an electrical power system (EPS) with 30 W-hr lithium polymer batteries from Clyde Space. Tests with the MicroMAS-1 Engineering Design Model (EDM) have resulted in modifications to the spinning assembly, stack and ADCS system and have informed the development of the flight model subsystems.
