Shuttle charging by fixed energy beam emissions

We present environmental responses observed by the Shuttle Potential and Return Electron Experiment during 13 prolonged electron beam emissions from the Fast Pulsed Electron Generator (FPEG) during the TSS 1R deployment. As the tether lengthened from 0.18 to 2.5 km, FPEG fired nine times at a nominal current of 100 mA at 1 keV. The motional potential induced across the system increased from 24 to 225 V. With a 15 Omega resistor connecting the tether to shuttle ground, current was higher and the degree of negative shuttle charging lower when FPEG was off than when it was on. While most FPEG firings left the shuttle uncharged, two created significant potentials: one to +70 V in a nighttime, equatorial plasma depletion and one to -60 V, with the tether ∼ 15 km.