TRANSIENT-RESPONSE OF AN ELECTRODYNAMIC TETHER SYSTEM IN THE IONOSPHERE - TSS-1 FIRST RESULTS

The electrical transient response of an electrodynamic tether system i n low earth orbit has been investigated experimentally and by computer simulation. Our experimental results come from the first Tethered Sat ellite System (TSS-1) mission flown on the space shuttle in 1992. Duri ng this mission a tethered satellite was deployed to a distance of 267 m above the shuttle using a conducting, insulated cable. It is shown by computer simulation that the electrical transient response of the s ystem is due to a combination of both the tether electrical circuit an d the interaction of the tether system with the space plasma. In gener al, ground measurements showed that the TSS-1 electrical circuit is ap proximately second order and underdamped. However, it was found that o n-orbit transient decay as well as the symmetry of transient oscillati ons could be dramatically altered, following closely with ionospheric plasma density variations. Combined electrical circuit and plasma inte raction modeling shows that these differences can be explained by acco unting for ion and electron current collection capabilities of the tet her end connections with the space plasma. These results have implicat ions for the use of electrodynamic tethers for high current switched a pplications including direct generation of low-frequency electromagnet ic signals and high electrical power generation as well as detection o f natural electric field transient signatures.