SHUTTLE CHARGING BY FIXED-ENERGY BEAM EMISSIONS

We present environmental responses observed by the Shuttle Potential a nd Return Electron Experiment during 13 prolonged electron beam emissi ons from the Fast Pulsed Electron Generator (FPEG) during the TSS 1R d eployment. As the tether lengthened from 0.18 to 2.5 km, FPEG fired ni ne times at a nominal current of 100 mA at 1 keV. The motional potenti al induced across the system increased from 24 to 225 V. With a 15 Ohm resistor connecting the tether to shuttle ground, current was higher and the degree of negative shuttle charging lower when FPEG was off th an when it was on. While most FPEG firings left the shuttle uncharged, two created significant potentials: one to +70 V in a nighttime, equa torial plasma depletion and one to -60 V, with the tether similar to 1 5 km.