NASA has cleared the space shuttle Discovery for launch on 31 May to deliver the centrepiece of Japan鈥檚 space programme, a massive laboratory named Kibo, to the International Space Station.
Lift-off is scheduled for 1702 EDT (2102 GMT) from the Kennedy Space Center in Florida, with docking at the space station expected two days later. 鈥淩ight now we鈥檙e in great shape,鈥� said launch director Mike Leinbach.
Officials said they were not expecting any delay to the shuttle mission due to the ongoing investigation of Russian Soyuz spacecraft that malfunctioned while returning space station crew members to Earth.
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During the last two Soyuz landings, in April 2008 and October 2007, the craft descended more steeply than planned and landed off course.
That has raised questions about the use of a Soyuz spacecraft currently attached to the station as a means of escape for the station crew in an emergency.
But the agency鈥檚 associate administrator for space operations, Bill Gerstenmaier, said that despite the two problematic Soyuz flights, the vehicle is considered safe enough to rely on for emergency returns.
He said he had visited Russia during the previous week to meet with the investigation team and did not see any concerns big enough to delay the shuttle launch. 鈥淚 talked to [the team] about us setting up for the 31st launch,鈥� he said. 鈥淭hey told us that they were ready for us to go fly.鈥�
In any case, NASA believes there is less than a 1% chance of an emergency requiring the crew to return on the Soyuz vehicle, he said. 鈥淔or a backup emergency system that has a low probability of use, you will take a lower reliability of that component,鈥� he said. 鈥淚t has the reliability that we think it needs for a backup system.鈥�
Further investigation will be needed to determine whether NASA can commit to using the Soyuz to return crew to Earth in October as part of a regularly scheduled rotation, he said.
Expanded crew
In addition to installing Kibo onto the orbital complex, the Discovery astronauts plan to tackle an assortment of maintenance jobs to help prepare the station for an expanded six-member crew. Three people now live aboard the station full time, in staggered increments ranging from three to six months.
NASA is in the process of figuring out how to repair a paddle wheel that turns one of the station鈥檚 solar wing panels which will be needed to fully power the outpost.
Astronauts Michael Fossum and Ronald Garan are scheduled to make three spacewalks during Discovery鈥檚 nine-day stay at the station.
In addition to installing and outfitting Kibo, the spacewalkers will inspect and troubleshoot the broken solar array rotary joint and replace nitrogen tanks needed to pressurise the station鈥檚 ammonia cooling system.
鈥淚t鈥檚 an extremely complicated mission,鈥� Gerstenmaier said.
NASA has two years to complete the space station before retiring the shuttle fleet. Eleven flights, including Discovery鈥檚, are planned.
Delays building the shuttle鈥檚 fuel tanks, which were extensively remodelled after the 2003 Columbia shuttle accident, forced NASA to drop one of two more missions to the space station planned this year following Kibo鈥檚 arrival.
The agency still plans to fly a final servicing call to the Hubble Space Telescope in October.
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