Endeavour will be ready to lift off on February 9, but a Delta rocket launch and a dress rehearsal for an upcoming Air Force satellite-delivery mission could delay the flight until February 12. In light of the jammed schedule, NASA officials still are examining options for Endeavours next launch attempt.

"Were going back to Houston while they think about it," Endeavour commander Janice Voss told SPACE.com before she and three crewmates climbed aboard T 38 jets for the trip back to NASAs Johnson Space Center (JSC).

"Were not really sure of the actual launch date, but hopefully in a week or two well be heading off to do this mapping mission," added mission commander Kevin Kregel.

Voss and Kregel, along with Endeavour pilot Dom Gorie and mission specialist Gerhard Thiele, flew back to Houston from Kennedy Space Centers (KSC) Shuttle Landing Facility. Flight engineer Janet Kavandi and mission specialist Mamoru Mohri escorted family members back to Texas aboard a NASA plane that took off from nearby Patrick Air Force Base.

Once in orbit, the astronauts plan to raise a 200-foot- (60-meter-) tall radar antenna that will be used to make a 3-D map of as much as 80 percent of Earths land mass, which is home to 95 percent of the planets population.

Rainy weather forced NASA to scrub an initial launch attempt Monday. The agency decided to forgo a launch attempt Tuesday so technicians could replace a faulty signal relayer that plays a crucial role in a shuttles eight-and-a-half minute climb into orbit.

The so-called Master Events Controller (MEC) is one of two units designed to route computer commands that ignite the shuttles twin solid rocket boosters and then jettison them two minutes into flight.

About the size of a small suitcase, the 65-pound devices also send commands to separate the shuttle from its 15-story external tank once the ship and its crew reach an initial orbit.

NASA flight rules call for both of the MECs to be operating properly before a shuttle is given a green light for flight. One of Endeavours signal relayers malfunctioned during Mondays scrubbed countdown, prompting mission managers to order its replacement.

"They take the Master Events Controllers very seriously," Kregel told SPACE.com. "They made the right decision."

While workers here press ahead with the signal relayer replacement work, Endeavours crew will spend the day Thursday boning up for launch in a mission flight simulator at JSC.

"Were going to head back and keep training and well go when we have a good vehicle," Kregel said. "So see you in a couple of days."

The astronauts will return to Kennedy Space Center Saturday if a decision is made to make a launch attempt February 9.

Their return to Florida, however, will be delayed until next Monday or Tuesday if their next launch attempt is pushed back to February 12. KSC spokesman George Diller said a launch date decision is expected Thursday.