SPREE measurements of wave-particle interactions generated by the electron guns on TSS-1 and TSS-1R

Abstract The Shuttle Potential and Return Electron Experiment (SPREE) was flown in the orbiter bay during TSS-1 and TSS-1R flights. Measurements presented here correspond to times of DC electron firings of the Shuttle Electrodynamic Tether System (SETS) fast pulsed electron generator (FPEG). SPREE included particle correlators measuring particle modulations in the 0–10kHz and 0–10MHz frequency ranges. Wave Particle Interactions, WPI, were observed on TSS-1 & TSS-1R in both frequency ranges: around a few MHz whenever the emitted beams were close to 90° pitch angle; and at a few kHz at many other beam pitch angles. On both missions problems with the tether deployment lead to more of the mission timeline being dedicated to the SPREE/FPEG active plasma studies reported here. The strong MHz waves occur when the 90° FPEG beam has the same low parallel velocity component, V par values as the thermal electrons. Then both the beam source and the thermal sink can interact with the same waves. The strong kHz waves are generated directly by the passage of the FPEG beam through the ionospheric plasma at the orbiter velocity with a period determined by the geometry of the disturbance.