The space shuttle Discovery touched down in Florida yesterday with a satellite carrying a bounty of data about the Earth's protective ozone layer.
Passing a full moon in the blue morning sky, the $2 billion gliding spaceship set down on its landing strip at the Kennedy Space Centre.
"Welcome home. This looked like a perfect mission from start to finish," mission control's Dom Gorie radioed as Discovery stopped on the runway.
Cradled in the shuttle's cargo bay was an ozone-monitoring satellite, holding enough atmospheric data to fill a half-ton of computer floppy disks. The German-built spacecraft flew free of the shuttle for nine days and took nearly 50,000 atmospheric measurements to aid scientists studying ozone-layer depletion.
The satellite also provided evidence to support a controversial theory that Earth is being bombarded daily by thousands of house-sized, water-laden comets.
The threat of fog had delayed Discovery's homecoming by a day, but the weather co-operated for the sole landing opportunity yesterday.
The shuttle made a rare southerly approach to the Florida spaceport, entering the atmosphere over the South Pacific, passing high over the Yucatan Peninsula, and crossing the Gulf of Mexico west of Cuba.
The shuttle entered US air space near Tampa Bay and shook the central Florida area with double sonic booms.
The crew of six, which included a Canadian researcher, had a busy 12-day mission. In addition to setting free the ozone-monitoring satellite and returning to pick it up later, the astronauts worked on 24 other major objectives.
They tested a Japanese prototype robot arm for the planned international space station; grew colon cancer cells for medical research and pointed a telescope at the Hale Bopp comet as it raced away from the sun.
NASA officials described the mission as a complete success.
Discovery's crew of six enjoyed their extra day aloft on Monday by watching Earth speed by 256 km (160 miles) below and scientists took the opportunity to cram in some last-minute observations with cargo bay instruments. The first landing attempt was waived on Monday because of a chance of fog.