The TSS‐1R Mission: Overview and scientific context

The Tethered Satellite System (TSS) program is a binational collaboration between NASA and the Italian Space Agency (ASI) with NASA providing the Shuttle‐based deployer and tether and ASI providing a satellite especially designed for tethered deployment. Twelve science investigations (see Table 1) were supported by NASA, ASI, or the Air Force Philips Laboratory. The goals of the TSS‐IR mission, which was the second flight of the TSS hardware, were to provide unique opportunities to explore (1) certain space plasma‐electrodynamic processes—particularly those involved in the generation of ionospheric currents, and (2) the orbital mechanics of a gravity‐gradient stabilized system of two satellites linked by a long conducting tether. TSS‐IR was launched February 22, 1996 on STS‐75 into a 300‐km, circular orbit at 28.5° inclination. Satellite flyaway occurred at MET 3/00:27 and a unique data set was obtained over the next 5 hours as the tether was deployed to a length of 19,695 m. At MET 3/05:11, during a day pass, the tether suddenly broke near the top of the deployer boom. The break resulted from a flaw in the tether insulation which allowed the ignition of a strong electrical discharge that melted the tether. The operations that had begun at satellite flyaway, however, allowed significant science to be accomplished.