Shuttle’s Bay Doors Opened to Remove Batteries, Fix Part

NASA opened Discovery’s payload bay doors Saturday to remove the Hubble Space Telescope’s batteries for recharging and to replace a faulty part in preparation for an April 25 launch.

Technicians took out a faulty auxiliary power unit responsible for grounding the shuttle last week. A new unit was being installed to be tested today and fired up briefly later this week.

“We haven’t run into any problem,” said Lisa Malone, a spokeswoman for the National Aeronautics and Space Administration. “We’re looking good for the 25th.”

Hubble’s six nickel-hydrogen batteries will be recharged for 5 1/2 days in a laboratory at the Vehicle Assembly Building. NASA decided to take the batteries there because they can be recharged at a cooler temperature and thus retain more power.

The batteries will power Hubble from the time it is disconnected from the shuttle’s power system during deployment until its energy-collecting solar panels are unfurled.

Discovery was poised for launch Tuesday, but the mission was scrubbed four minutes before liftoff when the auxiliary power unit failed.

NASA was not sure how long it would take to replace the 88-pound unit because the procedure had never been performed before at the launch pad. The work went smoothly, Malone said.

The defective power unit was returned to the manufacturer, Sunstrand Corp. of Rockford, Ill., for testing.

The shuttle’s three auxiliary power units pressurize the hydraulic system, which is used to move wing and rudder surfaces and in the ship’s braking and steering systems.

NASA planned to close Discovery’s payload bay doors today as soon as the lengthy process of removing the batteries was completed. The chamber will remain sealed to reduce the risk of getting too much dust on the telescope’s 94-inch mirror.