Endeavour cleared for Wednesday launch try

NASA managers Monday formally cleared the shuttle Endeavour for a delayed launch Wednesday on a space station assembly mission. Launch of the agency's Lunar Reconnaissance Orbiter atop an unmanned Atlas 5 rocket was delayed to Thursday or Friday to make room for the shuttle in an effort to maximize launch opportunities for both missions.

Endeavour was grounded Saturday when a gaseous hydrogen vent line umbilical seal leaked potentially dangerous vapor during fueling. Engineers replaced the seal and while the schedule is tight, NASA managers decided Monday to retarget the shuttle for launch at 5:40:50 a.m. EDT Wednesday. The shuttle's countdown will be restarted at the T-minus 11-hour mark at 1:15 p.m. Tuesday and forecasters are predicting an 80 percent chance of good launch weather.

As it now stands, the Endeavour astronauts will have one shot at getting off the ground Wednesday. If the shuttle runs into additional problems, the flight likely will be delayed to July 11 because of temperature constraints related to the International Space Station's orbit.

While the shuttle team presses ahead with work to ready Endeavour for launch, the LRO/LCROSS team is continuing processing for takeoff aboard a United Launch Alliance Atlas 5 rocket at launch complex 41 at the nearby Cape Canaveral Air Force Station. Liftoff is targeted for 6:41 p.m. Friday.

Charles Dovale, the NASA launch manager for the LRO/LCROSS mission, said today the agency looked into the possibility of a launch on June 18. But the Air Force Eastern Range, which provides tracking and telemetry support, could not reset its systems in time.

"We will monitor shuttle's progress," Dovale said. "If the shuttle (team) were to begin their count and scrub for any reason prior to midnight (Tuesday), LRO/LCROSS and Atlas can maintain June 18 as the earliest date."

But if the shuttle's countdown proceeds past midnight Tuesday, launch of the Lunar Reconnaissance Orbiter will remain on June 19.

The LRO spacecraft is scheduled to map the moon's surface in unprecedented detail from an orbit around the lunar poles just 31 miles above the cratered terrain. A companion mission, the Lunar Crater Observation and Sensing Satellite, or LCROSS, is designed to look for evidence of water ice and other materials by crashing the Atlas 5's Centaur upper stage into a crater near the moon's south pole.

A small "shepherding satellite" will monitor the Centaur's demise, flying through the cloud of debris thrown up by the crash, before following it to a similar fate.

The primary goals of Endeavour's 16-day five-spacewalk mission are to attach an experiment platform to a Japanese research module, to replace aging solar array batteries, to mount critical spare parts on the station, and to replace station flight engineer Koichi Wakata with NASA astronaut Timothy Kopra.

Endeavour's launch window opened June 13 and closes June 20. A launch on June 21 is possible, but one of the crew's spacewalks likely would have to be skipped to ensure an undocking before temperature constraints were violated.

The LRO/LCROSS launch window also closes on June 20. The decision to give the shuttle a launch opportunity Wednesday still leaves at least two opportunities to launch LRO/LCROSS before its window closes.

Correction at 3:24 p.m.: This story initially gave the wrong manufacturer of the rocket that will carry the Lunar Reconnaissance Orbiter into space. It is a United Launch Alliance Atlas 5.

Updated at 3:37 p.m. PDT: The Air Force Eastern Range has now ruled out a launch for the Atlas on Thursday if the shuttle countdown remains on track.