The space shuttle Discovery undocked from the International Space Station without a hitch on Saturday.
"We had a by-the-book undocking with the station," said lead flight director Tony Ceccacci.
The three ISS crew bid the shuttle astronauts farewell. "Have a safe journey back, and soft landing, and we'll see you in a few months," said ISS crew member Jeff Williams.
Discovery had dropped off European Space Agency astronaut Thomas Reiter, who will stay aboard the ISS for at least six months. They also delivered tonnes of supplies, fixed a railcar on the outside of the ISS and tested new ways of repairing a damaged heat shield while in space.
After backing away from the ISS, Discovery's astronauts began inspecting its right wing and the nose cap for potential damage from micrometeoroids and space junk. They had checked out the left wing the night before. This is the first time NASA has tried an in-space inspection for orbital debris. NASA does not yet have any results from those inspections.
Landing is scheduled for 0914 EDT (1314 GMT) on Monday at the Kennedy Space Center in Florida, US. But unsuitable weather could postpone landing or even shift it from Florida to Edwards Air Force Base in California.
Shuttle managers are keeping an eye on a small leak in one of the orbiter's three Auxiliary Power Units (APU). The leak could either be nitrogen, which is harmless, or hydrazine fuel, which could be dangerous in large quantities.
"We can't tell right now if it's GN2 [gaseous nitrogen] or if it's hydrazine," deputy shuttle manager John Shannon said on Friday. "The team is treating it like it's hydrazine because if it's GN2 we're done talking."
They will use the leaking APU for some flight control check-outs on Sunday. If the leak gets worse during this activity, they may not use that APU to land. The APUs control the hydraulic systems, such as the rudder/speed brake and nose landing gear steering.
If they chose to land with only two APUs, they would have small explosive devices to deploy the landing gear rather than the hydraulics. They may also employ more stringent weather restrictions for landing, to increase the safety margin.
During an early shuttle mission in 1983 (STS-9), a lot of hydrazine leaked out of the APU fuel tank and sprayed on a hot region. This started a fire in the aft compartment of the shuttle.
The team will decide whether Discovery is officially cleared for landing on Sunday morning.
Keep up-to-date on the mission by visiting our special report on the space shuttle.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
11:17 21 August 2008
