The space shuttle Endeavour's launch to the International Space Station has been put off for at least a week, due to a troublesome glitch with an onboard heater system, NASA said Sunday.
"It's not going to be any earlier than the 8th," said Mike Moses, who heads up the mission management team for Endeavour's launch. "Don't take that as a launch date, take that as a target."
Moses said the precise date for the next launch opportunity would be announced on Monday or Tuesday.
Wounded U.S. Rep. Gabrielle Giffords, the wife of Endeavour commander Mark Kelly, flew back to her rehabilitation center in Texas on Sunday but will return to Florida for the next launch attempt, her staff said.
Endeavour's launch-pad team is currently in the midst of repairing a faulty heater in one of the orbiter's three auxiliary power units. The units provide hydraulic pressure for the aerodynamic control system, and NASA's rules say all three must be working for launch.
Launch had been set for last Friday — but the countdown was stopped even as hundreds of thousands of people, including President Barack Obama and his family, were converging on Kennedy Space Center. The postponement was required when the launch team reported the heater problem.
A week of waiting
The additional delay means Endeavour's six crew members and their families — including Giffords — will have to wait at least a week longer for liftoff.
The astronauts flew back to Houston on Sunday.
Giffords presents a special case due to the head injury she sustained during an assassin's attack in January. The Arizona Democrat was flown from her Houston rehabilitation center to Florida last week, expressly to watch the launch of the mission headed up by her husband.
Giffords was kept out of the public eye during her stay in Florida, but she reportedly kept up with her rehabilitation routine during her stay in Florida. In a Facebook update, her staff said she was back in Texas.
"Team Giffords had an easy flight back to Houston today," Sunday's update reported. "Gabby will have a couple days of good therapy. ... Then back to FL for the launch!"
Giffords' spokesman, C.J. Karamargin, told msnbc.com that the congresswoman took the delay in stride. "No question there's a little disappointment that Endeavour didn't take off, but safety has to come first," he said.
Complicated repair
NASA had been hoping that the cause of Endeavour's glitch was a bad thermostat, which could have been replaced easily and quickly. That would have put Endeavour on track for a 2:34 p.m. ET launch attempt on Monday.
However, technicians found out that the problem involved a switchbox — basically, a 40- to 50-pound fuse box — inside an aft section of the shuttle. Launch director Mike Leinbach said replacing and testing a new box, and then testing all the components connected to that box, would take two full days. Only then could a new countdown proceed.
"There still are numerous factors to be worked out, but just based on the amount of time needed to do the fix, a new launch attempt wouldn’t happen before the end of the week, at the soonest," NASA said in a statement.
NASA also has to avoid a conflict with the scheduled May 6 launch of an Air Force satellite on an Atlas 5 rocket. Moses said the combination of constraints led mission managers to conclude that the next launch opportunity would not come before May 8, on Mother's Day.
This mission represents Endeavour's final spaceflight before retirement, and the second-to-last flight of the 30-year space shuttle program. The six-man crew will bring up a $2 billion particle-physics experiment for installation on the International Space Station and conduct four spacewalks to do station maintenance.
During Obama's visit to Kennedy Space Center on Friday, the president said he could not return to the Cape for a Monday launch, according to center director Bob Cabana. But Obama and his wife, Michelle, still hope to see a shuttle launch — if not Endeavour's liftoff, then Atlantis' shuttle program finale, currently scheduled for late June.
"It's a priority for us," Michelle Obama said.
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