Magazine article Science News

TSS-1: The Science Mission That Got Away

Magazine article Science News

TSS-1: The Science Mission That Got Away

Article excerpt

Any fisherman knows that a line on a reel can snag. Stretch the average fishing line over 20 kilometers, take away the familiarity of gravity, add a 518-kilogram satellite: Then things begin to get really difficult.

Shuttle astronauts hit mechanical snags from the start of their attempts to deploy the first tethered satellite last week. As originally designed, the Tethered Satellite System (TSS-1) resembles a giant fishing kit, with the 5-foot-diameter satellite attached to the shuttle by a shoelace-thin, 20-kilometer-long cord. The TSS-1 team managed to unreel only 256 meters of this tether before several knotty problems halted all progress, forcing them to retrieve the satellite with its primary scientific goals unaccomplished.

"The science team was very disappointed in the results of the mission," said TSS-1 mission scientist Nobie Stone of Marshall Space Flight Center in Huntsville, Ala., speaking at a NASA briefing last week. "We did not achieve our primary objectives. ... We didn't approach those."

A joint venture between NASA and the Italian Space Agency, the mission set out to test the physical stability of long-tethered systems and to conduct electro-dynamic experiments in the space environment.

Although the unreeled tether stretched less than 2 percent of its planned distance, the mission still achieved two major engineering objectives: the deployment and docking of the satellite, noted lead flight director Chuck Shaw of Johnson Space Center in Houston at the briefing. The system was easier to control in space and more stable than predicted, he added.

The problems encountered involved the satellite-deployment mechanism, built by Martin Marietta Astronautics Group of Denver. After several delays due to technical glitches, deployment stopped entirely when a snag seemed to develop at the end of the deployment boom. …

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