Nasa has cleared the space shuttle Discoveryto return home after dismissing lingering concerns about its condition, and told the crew to pack up their spacesuits because there was no need for a fourth spacewalk.
Discovery's scheduled return to Cape Canaveral in Florida on Monday will be the first shuttle landing since Columbiadisintegrated over Texas in 2003 as it glided through the atmosphere on re-entry.
"I will not tell you that it is zero risk," shuttle deputy program manager Wayne Hale told reporters. "(But) it is the lowest risk, the best choice and the unanimous decision of the engineers and the management team that we should re-enter as is."
Nasa's shuttle deputy program manager Wayne Hale
Engineers had been studying whether a piece of damaged cloth insulation beneath the commander's left cockpit window could break off and damage a part of the shuttle critical for flight, such as the rudder speed brake located on the tail.
Wind tunnel tests at the Ames Research Center in California, however, convinced managers that the blanket should stay attached to the shuttle during its descent. In a worst-case scenario, there was a 1.5 per cent chance that the fabric would hit the shuttle if it ripped off, Mr Hale said.
If Nasa had decided to repair or remove the damaged blanket, Discovery's13-day mission would likely have been extended another day so astronauts Soichi Noguchi of Japan and Nasa's Steve Robinson could make a fourth spacewalk today.
The shuttle has been parked at the International Space Station since July 28th and was scheduled to depart from the orbiting outpost tomorrow.
During their spacewalks, Noguchi and Robinson restored the space station's prime steering system, installed a storage platform and removed two protruding cloth strips from the shuttle's heat shield in the shuttle program's first spacewalk to the underside of an orbiter.
Nasa feared the strips could cause dangerous heat damage as the shuttle plunges through the atmosphere for landing.