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Monday, 13 December, 1999, 16:15 GMT
Shuttle fuel pipe repaired

Fuel The pipe helps circulate hydrogen during the prelaunch sequence

By BBC News Online Science Editor Dr David Whitehouse

After a weekend of repairs, Nasa has finally cleared the space shuttle Discovery for lift-off on its mission to repair the Hubble Space Telescope (HST).

If no more problems are uncovered, Discovery will blast off at 0218GMT on Friday, 17 December.

Technicians had to replace a dented fuel line. The pipe carries liquid hydrogen for the shuttle's three main engines. Officials are unsure how it got damaged. The flight is already two months late because of shuttle wiring repairs.

Nasa has only three chances to launch Discovery this month: Thursday, Friday and Saturday. If the shuttle is not up by then, the mission will be put off until January to avoid having the shuttle fly over New Year period which could pose Y2K problems.

A seven-strong crew of astronauts will be on Discovery. They will replace the faulty navigational gyroscopes that have put Hubble and its systems in a "sleep" mode since 13 November.

 See how Discovery will grab the HST

Experienced crew

It will be this shuttle's 27th flight and will be commanded by US Air Force Colonel Curt Brown, who will be flying for the sixth time. Scott Kelly is serving as the pilot on his first shuttle mission. The five mission specialists for STS- 103 are:
  • Steve Smith - Payload Commander on his third shuttle mission;
  • Michael Foale - Mir veteran making his fifth flight into space;
  • John Grunsfeld - He has made two previous space flights;
  • Claude Nicollier - Esa astronaut flying on the shuttle for the fourth time;
  • Jean-Francois Clervoy - Another Esa astronaut who will operate Discovery's robot arm during the mission.
Smith, Foale, Grunsfeld and Nicollier will do the arduous, six-hour spacewalks during which vital equipment on Hubble will be changed.

They have to replace the telescope's six gyroscopes, a fine-guidance sensor, a transmitter, a spare solid-state recorder and a high-voltage/temperature kit for protecting the batteries from overheating.

 The BBC's Sue Nelson hears from Michael Foale

They will also install a more advanced computer that is 20 times faster and has six times the memory of the current HST computer.

The Hubble telescope, the size of a bus, was launched into orbit in 1990. So far, the observatory has taken 259,000 shots of more than 13,000 objects in space, some of them 12 billion light-years away.

Two more servicing missions are planned before the nominal end of Hubble's life in 2010. A mission will be sent to it in mid-2001 and another in 2003 with new solar arrays and scientific equipment.

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See also:
09 Nov 99 |  Sci/Tech
Hubble's house call
 |  Sci/Tech
Hubble shuts its eyes
24 Apr 99 |  Sci/Tech
Another Hubble gyroscope fails

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