“We have good news,” said astronaut Julie Payette, radioing the message to her colleagues on board the spacecraft from mission control.
“The MMT (Mission Management Team) just got to the conclusion that the blanket underneath the commander’s window is safe for return.”
Since taking-off from Cape Canaveral on July 26, there have been fears for the safety of the aging shuttle after pieces of insulation foam from an external fuel tank broke off during the launch.
Then concerns about protruding strips of gap filler between heat shield tiles on Discovery’s underbelly prompted an unprecedented spacewalk operation.
Astronaut Steve Robinson ventured underneath the spacecraft to extract the strips equipped with a hacksaw and forceps.
“Like a lot of Americans, I was amazed at the procedures that took place to repair the craft. It was pretty remarkable,” US President George W Bush said of the feat.
Damage to a section of cloth insulation beneath one of the shuttle’s cockpit windows brought fresh anxiety that part of the blanket could tear off on re-entry and affect critical structures such as the tail or a movable flap.
But after getting aerodynamic engineers to test sample blankets in a wind tunnel to simulate a shuttle’s re-entry into Earth’s atmosphere, it was decided that another repair mission would not be needed.
Discovery’s seven crew have resumed the task of restocking the International Space Station (ISS) for its two crew who were left without fresh supplies for two and a half years after the loss of Columbia in February 2003.
NASA has put future shuttle flights on hold until it solves the problem of foam debris coming loose during lift-off.
The same type of event caused damage to Columbia’s wing heat shield and led to the shuttle’s disintegration as it passed through Earth’s atmosphere on February 1, 2003.
NASA spent A$1.3 billion on safety upgrades after the disaster, but, according to documents published by The New York Times newspaper, the space agency went ahead with the Discovery mission despite warnings a year ago that problems with insulation foam still posed a risk.
An internal paper reportedly written by retired NASA division chief for quality engineering at the Johnson Space Centre said: “There will continue to be the threat of critical debris generation.”
Without any delays anticipated, Discovery will start its return journey on Saturday and touch down two days later.