Using an electrodynamic tethered satellite as an ionospheric electric double probe to estimate tethered satellite motion and measure vertical electric field

This research develops new techniques for estimating tethered satellite motion and for measuring the large scale electric field in the F-region ionosphere. Accurate measurement of induced potential across the tether, while deployed as a long electric double probe, is necessary to characterize fundamental electrodynamic properties of tethered satellite systems. Measurements of induced tether potential were obtained using the Tether Current and Voltage Monitor (TCVM) during the two missions of the Tethered Satellite System (TSS) in August 1992 and February 1996.; An accurate model of the electromotive force (EMF) from the tether's motion through the Earth's magnetic field was developed. A tethered satellite dynamics model, the motional EMF model, induced tether potential measurements, and other TSS deployer measurements, were used in a Kalman filter to estimate tethered satellite motion relative to the Space Shuttle Orbiter. Results with and without the tether potential measurement were compared with the best estimates of the relative satellite trajectories provided by NASA, demonstrating a new method for estimating tethered satellite motion. The induced tether potential measurements and the motional EMF model were then compared to determine the component of the average ambient electric field between each end of the tether.; Experimental results confirm that the induced tether potential was measured by the TCVM with sufficient accuracy to characterize tether system electrodynamic properties. The electric fields derived from the potential measurements were found to be consistent with previous satellite and ground-based measurements of the F-region electric field for similar ionospheric conditions. Comparison of the measured electric field at different deployment lengths for corresponding local times reveal that the average vertical component of the ambient electric field existed on scales >10 km. The TSS tether's ability to act as a double probe varying two orders of magnitude in length makes the data particularly unique and demonstrates a new capability for measuring the vertical ionospheric electric field.