Work to repair suspect wiring between Discovery's external tank and boosters will push back the launch date from Dec. 6 to around Dec. 9, NASA officials said Tuesday. The problem was discovered last week.
The mission originally was scheduled for mid-October, but was delayed along with everything else in order to fix exposed wires found throughout the shuttle fleet. Liftoff slipped to Dec. 2, then Dec. 6, because of additional wiring problems and a contaminated engine.
Discovery's flight has taken on an added urgency: Hubble cannot conduct any astronomical observations until the shuttle arrives with new gyroscopes for pointing. Spacewalking astronauts also will install a new computer, radio transmitter, battery voltage kits and thermal insulation.
A supplemental flight readiness review will be held on Dec. 1 to assess the progress of repairs and to set a firm launch date. Until then, engineers are targeting launch for 1:10 a.m. on Dec. 9.
Under that scenario, Discovery's crew would grapple the space telescope around 1:37 a.m. on Dec. 11. The first of four back-to-back spacewalks to install new gyroscopes and other equipment would get under way at 8 p.m. that night. Hubble would be released into open space around 10:18 p.m. on Dec. 15 and Discovery would land back at the Kennedy Space Center around 10:30 p.m. on Dec. 18.
Shuttle program manager Ron Dittemore said earlier this month that Discovery would not be launched past Dec. 14 to avoid any chance, due to landing weather delays or other issues, of having a shuttle in orbit over the New Year holiday. While no one at NASA believes any Y2K problems exist in the shuttle's ground or flight control software, no one wants to take any unnecessary chances, either.
But sources said Tuesday if worse came to worse Dittemore might, in fact, consider launching Discovery one or two days past Dec. 14 to get Hubble back in operation as soon as possible if the only other choice is delaying until next year.
Should that happen, however, one or two of the four planned Hubble repair spacewalks would be cancelled to get the orbiter back on the ground by Dec. 26 or 27 (including possible landing weather delays) at the latest. All of the high-priority repair items are scheduled for the first two spacewalks; the other work could be deferred to the next scheduled repair mission in 2001 if necessary.