NASA delays launch to Wednesday

CAPE CANAVERAL, Florida (Reuters) - NASA is planning to delay the launch of its new moon probe for two days so it can try to launch space shuttle Endeavour Wednesday on a construction mission to the International Space Station, officials said on Sunday.

The U.S. space agency postponed Endeavour's launch on Saturday due to a potentially dangerous hydrogen leak. Repairs were expected to take four days.

NASA managers decided on Sunday to try to make one attempt to launch Endeavour this week, on Wednesday at 5:40 a.m. EDT. If weather or technical problems interfere, the shuttle mission likely would be delayed until next month to allow the moon probe flight.

Wednesday had been reserved for launch of an unmanned Atlas rocket carrying the Lunar Reconnaissance Orbiter (LRO) spacecraft. The probe is the debut mission in a new U.S. space exploration initiative aimed at returning astronauts to the surface of the moon by 2020.

The probe's launch would be delayed until Friday.

NASA has to choose between the missions because Cape Canaveral Air Force Station can support only one type of rocket at a time. The range, which provides tracking, safety and other support services, needs two days to configure equipment for use by different types of rockets.

"It really is better for both missions to try to go during this launch period," said LeRoy Cain, shuttle deputy program manager.

NASA said delaying LRO beyond this week would affect its science objectives, as well as delay future satellites launching on Atlas rockets at Cape Canaveral.

LRO is designed to map the moon's surface and scout for landing spots for future human missions. The spacecraft includes a companion satellite known as L/CROSS that will crash into a lunar crater, allowing scientists to scan ejected material for signs of water.

Endeavour is due to deliver the last segment of Japan's Kibo laboratory and dozens of spare parts to the station. NASA is on deadline to complete station assembly and retire the shuttle fleet by September 30, 2010. Eight missions remain on the schedule.

"Each delay that we have ... puts us closer to the point where I can no longer finish my mission from an overall perspective," Cain said.

If Endeavour doesn't launch this week, the mission would have to be delayed until July. After June 20, the sun angle would overheat the shuttle while it was docked at the station. The next launch opportunity would be on July 11.

A delay until July would push back NASA's next space station construction mission from early to late August.

Also this week, a presidential commission is schedule to begin a review of the U.S. human space program. The findings, which are due in August, could impact the time, scope and plans for the lunar mission and use of the space station.

(Editing by Jim Loney and Philip Barbara)