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TSS

TSS mission graphic

Tethered Satellite System

Phase: Past

Launch Date: June 26, 1992

Mission Project Home Page - http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-75.html

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The Tethered Satellite System (TSS) consists of a satellite, a conducting tether, and a tether deployment/retrieval system to be flown on the Space Shuttle. The objectives of the TSS-1 mission were to: (1) verify engineering performance of the Tethered Satellite System (TSS); (2) determine and understand the electro-magnetic interaction between the tether/satellite/orbiter system and the ambient space plasma; (3) investigate and understand the dynamical forces acting upon a tethered satellite; and, (4) develop the capability for future tether applications on the Shuttle and Space Station.

The TSS released a satellite while remaining attached to a reel in the orbiter payload bay. This mission was intended to demonstrate control of the satellite during deployment, aerodynamic stability at flight altitude, and the ability of the system to collect meaningful scientific data and to return the data to the Orbiter, and then to the Payload Operations Control Center (POCC). The satellite was to be deployed 20 Km (12.5 miles) above the Orbiter. The deploying equipment consisted of a Spacelab pallet, a reel for tether deployment, an extendible/retractable boom for initial deployment and final retrieval of the satellite, an electrical power and distribution subsystem, a communications and data management subsystem, and a tether control capability. A separate support structure carried science instrumentation.

The spherical satellite was 1.6 meters in diameter, with the upper hemisphere containing some of the scientific payload, and the lower hemisphere containing the support equipment. The satellite contained cold gas (nitrogen) thrusters used for deployment, retrieval, and attitude control. The 2.54 mm diameter conducting tether cowas constructed using Kevlar and Nomex with 10 strands of 34 AWG copper wire and a Teflon sheath.

NASA was reponsible for the TSS deployer and systems integration, and Italy for building the satellite. Five investigations from Italy and five from the USA were selected for the first mission. Because of a technical problem (a protruding bolt) the tether could only be released to about 840 feet. A reflight of the tether system (TSS-1R) happened in 1996.

The TSS-1R mission is a reflight of the Tethered Satellite TSS-1 that had been flown on the Space Shuttle mission STS-46 in July of 1992. A protruding bolt had prevented full release of the tether during the TSS-1 mission. The TSS mission equipment consists of the deployer system, the Italian-build satellite, the electrically conductive tether (22km total length) and 6 science instruments. The TSS-1 is to be deployed from a reel in the orbiter payload bay upward (away from Earth) to up to 20 Km (12.5 miles) above the Orbiter. The objectives of this mission are: (1) to verify engineering performance of the Tethered Satellite System (TSS); (2) to determine and to understand the electro-magnetic interaction between the tether/satellite/orbiter system and the ambient space plasma; (3) to investigate and to understand the dynamical forces acting upon a tethered satellite; (4) to demonstrate electrical power generation; and, (5) to develop the capability for future tether applications on the Shuttle and Space Station. The deploying system consists of a motor- driven tether storage reel and level wind system.

Five hours after deployment began on February 25, 1996, with 19.7 km (of 20.7 planned) of tether released, the tether cable suddenly snapped near the top of the deployment boom. The TSS satellite shot away into a higher orbit. TSS instruments could be re-actived and produced science data for three days until battery power ran out.