CAPE CANAVERAL, Fla. (AP) NASA and its Russian counterpart worked on two minor problems Monday before starting the countdown clock for Thursday night's launch of space shuttle Discovery on a mission to rewire the international space station.
Engineers reported to their consoles Monday night as the three-day countdown clock began ticking at 11 p.m. EST. The launch is scheduled for 9:35 p.m. EST on Thursday.
Hours before the countdown began, Russian flight controllers boosted the space station's orbit by firing the engine on a supply vehicle docked to the space lab for 23 minutes. An effort to do that was aborted last week after only three minutes because of a software problem. The boost will help Discovery dock with the space lab on the third day of the flight.
``It was a flawless firing,'' said NASA spokeswoman Lynnette Madison.
Meanwhile in Houston, NASA worked on a software problem that had caused a breaker to open on a circuit to the motor that causes giant solar arrays to rotate at the space station in the direction of the sun. The solar arrays will generate power to the space station after Discovery's mission.
NASA planned to test the software fix on Tuesday.
The chances of favorable weather for liftoff Thursday were put at 80 percent.
During their 12-day mission, Discovery's seven astronauts planned to rewire the space station, deliver a 2-ton addition and replace one of the space station's three crew members.
Discovery's liftoff will be NASA's first night shuttle launch in four years.
NASA required daylight liftoffs for the three flights after the 2003 Columbia accident to make sure the agency could get good photos of the external fuel tank. Foam breaking off the tank at liftoff caused the damage that killed Columbia's seven astronauts.