NASA has reserved time for a later launch in case it can't meet its Oct. 28, 2008 target date to send the Lunar Reconnaissance Orbiter (LRO) to the moon.

Rick Gilbrech, associate administrator for exploration systems, said Dec. 10 the planned orbiter and its piggyback Lunar Crater Observation and Sensing Satellite (LCROSS) impactor face "a very challenging schedule."

While NASA is sticking to the target date and has "a chance" of launching then, "we've also booked alternate launch dates in November as backup plans."

Gilbrech said it is "a little too early to start talking about any slips" based on the briefings he has received.

"It's just basically the amount of integration and test that has to happen at Goddard [Space Flight Center]," he said during an end-of-year briefing for reporters in Washington. "They are doing this as an in-house project, and all these instruments have to come in together."

LRO has a suite of six instruments, plus an experimental lightweight X- and S-band radar, that are designed to give NASA a global map of the lunar surface and its resources. The "Mini-RF" radar is intended to demonstrate the technology needed to look for the signatures of water ice that may exist in the deep freeze of permanently dark polar craters.

The LCROSS spacecraft is designed to help that search for ice by sending the LRO's one-ton spent upper stage crashing into a dark polar crater, observing the resulting ejecta, then crashing nearby to generate a second debris cloud. Telescopes on the ground and in space will also collect data from the two impacts.

Gilbrech said Goddard is running two shifts and using best practices from other programs to pull the LRO spacecraft together, with the bus and propulsion system already in hand and other hardware trickling in.

Carl Walz, an astronaut who is director of advanced capabilities for NASA's Exploration Systems Mission Directorate, said there are very few "slack days" remaining for LRO, while the LCROSS project managed at Ames Research Center is carrying about a 20-day schedule cushion.

"As we go through our testing we're looking constantly for efficiencies that might help us there," Walz said, adding that there are some problem components in common with both LRO and LCROSS, including an inertial measurement unit.

"We're looking at when that problem will be resolved, or if there're other solutions out there," he said.