CAPE CANAVERAL - Space Shuttle Discovery was all but cleared Thursday for a quarter-mile move into Kennedy Space Centers (KSC) cavernous assembly building next week -- a short trip considered a key milestone in an agency campaign to launch a Hubble Space Telescope repair mission.
Discovery and seven astronauts are scheduled to blast off December 2 on a mission to fix Hubbles troubled pointing system, which remains one failure away from triggering an automatic telescope shutdown.
In that case, all telescope observations would be temporarily halted until spacewalking astronauts could make repairs.
Senior shuttle program managers held a teleconference Thursday and decided to schedule Discoverys move from its processing hangar into KSCs 52-story Vehicle Assembly Building for Tuesday. A final go-ahead is expected Monday.
The move had been targeted for Monday but was pushed back so technicians can repair a faulty temperature sensor on one of the shuttles nitrogen tanks. The sensor, which measures the temperature of nitrogen gas within the tank, failed a recent test, prompting managers to order the repair work.
"Its not a safety of flight issue and its not something that is a major concern," said KSC spokesman Joel Wells. "But if you have access (to the sensor in the hangar), you might as well go ahead and make the repair."
The move to the assembly building is considered a big step in NASAs launch campaign. Once inside the building, Discovery will be hoisted atop a mobile launcher platform and outfitted with a 15-story external tank and attached solid rocket boosters.
Technicians then will verify mechanical and electrical connections between Discovery and its fuel tank, boosters and launch platform before the assembled ship is moved out to launch pad 39-B around November 7 or 8.
The $3 billion Hubble observatory ran into potential trouble earlier this year when problems cropped up with the telescopes pointing control system, threatening its ability to lock onto stars, planets, galaxies and other celestial objects.
Key to the system is a set of six gyroscopes. A minimum three are needed to operate the observatory. Two of the gyroscopes already had failed and a third broke in January.
Should a fourth fail, Hubble would automatically shut itself down, and the most powerful space telescope ever launched would be at least temporarily out of business.
Astronauts aboard Discovery will conduct a quartet of spacewalks to replace the faulty gyroscopes and service the observatory, which was launched in April 1990. The servicing work includes the installation of a new flight computer, new voltage regulators, a new radio transmitter and a new solid-state recorder.
NASA had hoped to launch the repair mission in October, but those plans were dashed after the July 23 launch of sister ship Columbia.
A short circuit, five seconds into that flight, knocked out two engine computers, prompting fleet-wide electrical wiring inspections. The inspections and subsequent repair work have temporarily grounded the Hubble mission and all other shuttle flights.
Wiring inspections and repairs on Discovery are complete, but agency officials still must finish up an extensive series of tests to the shuttles electrical power and distribution system. The tentatively scheduled December 2 launch might slip a couple of days as a result.
A firm launch date will be set November 19 when shuttle program managers meet in a traditional flight readiness review.
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