Current-voltage characteristics of a long tethered system observed in the ionosphere

Summary form only given, as follows. Presents measurements taken by the Shuttle Potential and Return Electron Experiment (SPREE) in the shuttle payload bay during the deployed-satellite phases of the Tethered Satellite System (TSS) mission. The shuttle flew in an inverse airplane mode with the engine bells facing the ram direction to facilitate ion current collection. The authors study intervals in which the tether was electrically connected to the shuttle by low to medium impedance shunts and thruster firings occurred. During TSS-1 the satellite was deployed to 256 m. Ion spectra measured by SPREE indicate that with no thrusters firing the shuttle charged to a few tens of volts negative. In previously reported examples of neutral gas releases from charged spacecraft the magnitude of the vehicle potential decreased. Thruster firings during TSS-1 events either left the circuit unchanged or caused the current measured in the tether to diminish and the shuttle to become more negatively charged. In the latter case, thruster gas impeded access of ambient ions to the current collecting surfaces of the shuttle. During the longer tether deployment of TSS-1R (reflight), the authors anticipate that stronger shuttle potential will result in occasional breakdowns of ejected neutral gas and subsequent reductions of the shuttle potential.