Weather permitting, Discovery will end its 13 days in orbit Monday morning with the first shuttle landing at the Kennedy Space Center since 2002.
Discovery’s six astronauts are scheduled to touch down at 8:14 a.m. CDT to complete a supply flight to the International Space Station that included a repair to the station and delivery of a new crewman. Weather is expected to be acceptable despite a chance of showers near Cape Canaveral.
“My experience is that at the Kennedy Space Center, [weather] is always a challenge,” said Steve Stich, the flight director who will oversee Discovery’s return. “I think we have a pretty good shot.”
Discovery’s crew packed up Sunday to prepare for landing after checking out the shuttle’s flight control systems. Part of the checkout included activation of an auxiliary power unit that has been slowly leaking small amounts of either flammable hydrazine fuel or harmless nitrogen gas. Engineers suspect the leak is nitrogen but cannot be certain.
The unit is one of three aboard Discovery that powers the orbiter’s hydraulics system and operates the body flaps, steering and brakes during landing. Only one unit is needed to return safely.
Mission managers monitored the leaking unit during Sunday’s checkout and determined the rate of the leak did not increase after the test. As a result, the plan is to operate all three units as usual during Monday’s landing.
“We’re not going to try to start it early or do anything unusual,” astronaut Steve Frick told the crew from Mission Control. “We’ll be looking at it close like we did [Sunday].” In an interview from orbit Sunday, Discovery pilot Mark Kelly told reporters the unit wasn’t an issue as far as the crew was concerned.
“It’s working great,” he said. “We don’t expect any problems for landing.”
Engineers also cleared Discovery’s heat shield Sunday for the return to Earth after reviewing data from two days of late inspections done with a sensor-laden boom held by the shuttle’s robot arm. No evidence of significant damage was found.
Monday, Discovery’s astronauts were to don their flight suits for the trip home at about 5:45 a.m. If the weather looks good for the shuttle to land on its 202nd orbit of the Earth, Mission Control will give the go-ahead an hour later for a three-minute firing of Discovery’s twin braking rockets.
The firing, scheduled to take place at 7:07 a.m., will slow the shuttle’s speed and begin its fiery plunge home through the atmosphere.
If an 8:14 a.m. landing isn’t possible, Discovery has another opportunity one orbit later, at 9:50 a.m.
Discovery will stay in space for an additional day if adverse weather thwarts both Florida landing opportunities. Backup runways at Edwards Air Force Base in Southern California and White Sands Missile Range in New Mexico would be activated Tuesday.
The weather forecast for Edwards predicts optimal conditions Monday and Tuesday. However, mission managers prefer to return Discovery to Kennedy to save a week or so in turnaround time and the $1 million cost of ferrying the shuttle back to Florida atop a jumbo jet. Last year, bad weather forced Discovery to land in California to complete the first shuttle flight since the Columbia accident in February 2003.
Discovery can stay in space until Wednesday, when the ship will begin to run low on its supply of liquid oxygen needed to generate electricity that powers the orbiter’s systems. The shuttle would land at White Sands only if the weather looked bleak in Florida and California for all three days.
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On the shuttle
SUNDAY: Discovery’s crew packed up after checking the shuttle’s flight control systems and engineers gave the heat shield an OK for the return to Earth. An auxiliary power unit for the orbiter’s hydraulics system has been leaking small amounts of either flammable hydrazine fuel or harmless nitrogen gas. NASA decided to use the unit during Monday’s landing.
COMING UP: An 8:14 a.m. CDT landing at Kennedy Space Center. Weather permitting, it would be the first landing there since 2002.