The shuttle Discovery crew fired steering rockets today to dodge a piece of space debris during what was expected to be the final day of a successful resupply run to the International Space Station.
Nasa did not know what the space junk was, except that it likely came from the shuttle or the space station on Saturday during the last of the Discovery crew's three spacewalks.
"Exactly what (the debris) is is not known, but it's been moving toward the orbiter so it is a concern," said mission commentator Pat Ryan.
As the astronauts prepared for a 7.05pm EDT (2305 GMT) touchdown at the Kennedy Space Center in Florida, a Japanese station cargo ship lifted off on a debut flight to the orbital outpost.
The H-2 Transfer Vehicle, known as HTV, blasted off from the Tanegashima Space Center in southern Japan at 1.01 pm EDT (1703 GMT) aboard an H-2B rocket, also making its maiden flight.
The launch, which was televised by Nasa, marks a major milestone for Japan's aerospace industry and a key resource for the space station program, which will soon lose the enormous cargo capacity of the US space shuttles. The shuttle fleet is being retired due to safety concerns and high operating expenses after six more missions to the space station.
"We are so proud of taking this new responsibility to provide cargo transportation capability to ISS program," said Masazumi Miyake, a project manager with the Japan Aerospace Exploration Agency. "JAXA is now entering a new era."
The HTV, which is expected to reach the station on September 17th, is loaded with more than 3 tons of food, equipment, supplies and experiments, including two Earth-monitoring devices that will help track climate change.
Nasa meanwhile kept watch on weather at the Kennedy Space Center in hopes of bringing the shuttle Discovery back to Earth after 13 days in orbit.
The astronauts' first task of the day was to fire Discovery's twin maneuvering engines to avoid coming too close to a piece of mystery debris later in the afternoon.
During Discovery's nine-day stay at the station, two other pieces of orbital debris sent engineers scrambling to prepare avoidance manoeuvers, which were later determined to be unnecessary. Those pieces of space junk were identified as part of a spent upper-stage European rocket motor and a fragment from an obsolete weather satellite China destroyed in January 2007 during a widely condemned weapons test.
Discovery blasted off a minute before midnight on August 28th with more than 7.5 tons of food, laboratory equipment, science experiments, spare parts and a new treadmill and crew quarters for the space station, a $100 billion project of 16 nations, which is nearing completion after more than a decade of construction.
Reuters