Current collection model characterizing shuttle charging during the tethered satellite system missions

This research presents a new mathematical model characterizing the negative potential electrical charging behavior of large spacecraft in low Earth orbit that are actively collecting charge, such as part of an electrodynamic tether system. The analysis was carried out to identify significant plasma current sources affecting steady-state spacecraft charging using data from the tethered satellite system missions. During both tethered satellite missions (Aug. 1992 and Feb. 1996), Space Shuttle Orbiter charging was lower than expected, The current collected by the Orbiter greatly exceeded premission predictions based on thin sheath, ram-dominated current collection, Our investigation revealed that the tethered satellite deployer boom was conducting and was grounded to the Orbiter providing a significant current path from the plasma. Modeling results suggest that the plasma sheath significantly augmented the ram current collected by the main engine nozzles and the satellite deployer boom by expanding the effective current collecting area.