The GTOSat CubeSat: scientific objectives and instrumentation

GTOSat is a 6U CubeSat mission that will pave the way for highly reliable, capable CubeSat constellations and missions beyond low Earth orbit (LEO). GTOSat will study Earth’s dynamic radiation belts, acting as a follow-on to NASA’s Van Allen Probe mission and demonstrating the potential utility of SmallSats for both science and space weather monitoring. While a number of previous CubeSats have studied the radiation belts from LEO, GTOSat will launch into a low inclination geosynchronous transfer orbit (GTO) to directly sample 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. High-heritage instrumentation includes the Relativistic Electron Magnetic Spectrometer (REMS), measuring energetic electrons and ions, and a boom-mounted fluxgate magnetometer (MAG) 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 including parts selection and shielding to reduce the total dose for 1 year on orbit to less than ~30 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).