Launching of Shuttle, Telescope Set for April 25

NASA on Thursday set April 25 as the new launching date for the space shuttle Discovery and the $1.5-billion Hubble Space Telescope, the agency’s most expensive and complex payload.

The first launching attempt was scrubbed Tuesday, four minutes before liftoff when one of Discovery’s three auxiliary power units failed.

“The date is based on the decision to remove and replace APU No. 1 on space shuttle Discovery and to allow time for recharging the Hubble Space Telescope batteries,” NASA said in a statement.

The National Aeronautics and Space Administration said a new power unit was expected to arrive here this week. Shuttle managers estimate it will take two to three days to replace the unit, NASA spokesman Bruce Buckingham said.

It will be the first time that NASA has ever replaced an auxiliary power unit on the launching pad.

NASA shipped the unit’s 15-pound controller, which adjusts speed, back to the manufacturer for testing. The manufacturer informed NASA that the controller was fine, indicating an unknown problem elsewhere in the unit.

Auxiliary power units steer the ship’s three main engines, control the movements of flaps on the wings and the rudder, lower the main and nose landing gears, and provide the hydraulics for the main landing gear brakes.

NASA will remove the telescope’s nickel-hydrogen batteries and recharge them in a laboratory starting Saturday. The batteries will power the space telescope from the time it is disconnected from the shuttle’s power system during deployment until its energy-collecting solar panels are unfurled.

Discovery’s five astronauts will place Hubble in space on the second day of their five-day mission, delayed since 1983 by technical problems and the 1986 Challenger explosion. The telescope is to orbit 380 miles high for 15 years, enabling astronomers to look back to almost the beginning of time.