GTOSat: A Next-Generation CubeSat to study Earth’s Radiation Belts

GTOSat is a 6U CubeSat mission currently under development and targeting a launch ~2021. While a number of previous CubeSats have studied the radiation belts from low-Earth orbit (LEO), GTOSat will launch into a low inclination geosynchronous transfer orbit (GTO) to directly study the core trapped particle population. From this orbit, it will measure energy spectra and pitch angles of ~hundreds keV - few MeV electrons and ions, with the primary science goal of advancing our quantitative understanding of particle acceleration and loss in the outer radiation belt. Instrumentation includes the high-heritage Relativistic Electron Magnetic Spectrometer (REMS), which is a customized version of the MagEIS instrument onboard NASA’s Van Allen Probes mission, and a boom-mounted fluxgate magnetometer to provide 3-axis knowledge of the local ambient magnetic field. The GTOSat bus consists of a 6U spin-stabilized structure with a Sun-pointing spin axis. Mitigation of radiation effects is accomplished through a multi-pronged systems approach consisting of spot shielding, parts selection, and a ‘vault’ that utilizes a novel z-graded radiation shielding developed by NASA LaRC to reduce the total dose for 1 year on orbit to less than 25 krad. Communication is achieved via an S-band transceiver, enabling high data throughput through the Near-Earth Network (NEN) and low-latency radiation belt monitoring via the Tracking and Data Relay Satellite System (TDRSS). GTOSat will pave the way for highly reliable, capable CubeSat constellations and missions beyond low earth orbit (LEO).