An artist's concept of the Shuttle Radar Topography Mission aboard Endeavour's upcoming flight. Photo: NASA

NASA has secured February 11 as space shuttle Endeavour's new launch date after a scheduling conflict with an unrelated rocket test at Cape Canaveral was resolved, NASA officials confirmed late Wednesday.

Endeavour's 11-day Earth radar mapping mission was stalled earlier this week by a faulty avionics unit and bad weather.

The U.S. space agency had thought the earliest Endeavour could try again was February 12 because of a countdown rehearsal for a U.S. Air Force Titan 4B rocket scheduled for February 10.

The rehearsal requires use of the Eastern Range, which needs 48 hours to reconfigure its systems from one launch vehicle to another. The Air Force-controlled Range is a vast network of tracking, computer and safety systems that supports all space shuttle and unmanned rocket launches from Florida's Kennedy Space Center and Cape Canaveral Air Station.

But the Air Force said Wednesday a hardware problem will delay the Titan's planned February 21 launch of a $250 million missile detection satellite, allowing the countdown test to be delayed too.

No further details on the Titan rocket's problem were immediately available, an Air Force spokeswoman said.

The test delay also allows Boeing to have a backup launch opportunity on February 9 for its Delta 2 rocket. The booster is scheduled for launch on February 8 carrying four spare satellites for the space-based Globalstar cellular telephone network.

NASA now says February 11 is the earliest it can have Endeavour repaired and prepped to launch. Previously, officials believed the shuttle might be ready by February 9.

At KSC's launch pad 39A, preparations are underway to remove the faulty Enhanced Master Events Controllers No. 2 from Endeavour's aft engine compartment. The suspect unit failed a health check during Monday's countdown.

Endeavour is equipped with two EMECs, which send vital commands to ignite the twin solid rocket boosters at liftoff, and later separate the spent boosters and external tank during launch.

The shuttle launch team will have a two-hour, 12-minute window to get Endeavour airborne on February 11 beginning at 12:28 p.m. EST (1728 GMT).

Mission specialists Gerhard Thiele and Janice Voss, commander Kevin Kregel and pilot Dom Gorie talk to the media before leaving for Houston. The other astronauts left separately. Photo: NASA

The six international astronauts that will fly aboard Endeavour left KSC on Wednesday, heading back to their home base in Houston, Texas. They will return to the Cape on February 7.

"The crew is still in good spirits. We got to spend some quality time with our family," commander Kevin Kregel told reporters prior to leaving KSC. "They are going to replace the Master Events Controller, and that is the right thing to do to make sure we have a good vehicle."

Once in space, Endeavour will use a sophisticated radar payload to map a majority of the Earth's surface. Researchers will take the information to generate the highest resolution 3-D map of the planet's topography.