TERSat: Trapped Energetic Radiation Satellite

Abstract

Radiation damage caused by interactions with high-energy particles in the Van Allen Radiation Belts is a leading cause of component failures for satellites in low and medium Earth orbits (LEO, MEO). Very Low Frequency (VLF) electromagnetic waves have been shown to couple energy to high energy radiation belt particles and change their properties. For example, data from the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite suggest that the gap between the inner and outer Van Allen belts is caused by lightning, which naturally generates VLF waves that scatter the pitch angle of high energy particles, such that they rejoin the neutral lower atmosphere.14 It has been proposed that space-based antennas transmitting VLF waves could similarly help reduce the effects of radiation by scattering particles. However, the interaction between a VLF transmitter and the plasma environment is not sufficiently well understood, thus on-orbit experimentation and demonstration are needed to analyze how best to tune and couple VLF energy to the electrons and ions even though terrestrial VLF equipment is well understood and low-risk. TERSat is a 50 kg student-built nanosatellite that will analyze how VLF waves interact with the radiation environment at 550 km altitude by deploying two 2.5 m antennas to form a 5 m dipole, using a transmitter to radiate VLF waves over a range of voltage levels up to at least 600 V, frequencies from 3—50 kHz, and a range of magnetic field orientations. TERSat will also measure the strengths of the echoes with a VLF receiver. The spacecraft bus consists of a skinned isogrid structure, body-mounted solar cells for power generation, a reaction wheel attitude determination and control system (ADCS), and a customized student-built avionics board. TERSat is under development as part of the Air Force Research Laboratory (AFRL) University Nanosatellite Program 7 (UNP- 7) competition. TERSat’s science mission complements that of AFRL’s Demonstration and Science Experiments (DSX) satellite. TERSat has the potential to occasionally interact and perform bistatic experiments with DSX, which will be in MEO, if both have overlapping operational periods. TERSat will support technology development of systems that can interact with and potentially reduce Van Allen Belt radiation by improving our understanding of transmitting and receiving VLF waves in a LEO satellite plasma environment.