Space shuttle's landing marks the end of a successful year for NASA

CAPE CANAVERAL, Fla. -- NASA began 2006 having flown only a single space shuttle mission since the Columbia disaster three years earlier.

After Friday's landing of space shuttle Discovery and its seven astronauts, the U.S. space agency will end the year with three successful shuttle missions under its belt and the resumption of construction on the international space station.

"Yes, this was a big year," NASA administrator Michael Griffin said after Discovery touched down. "Each and every time we do this, it is a minor miracle. It is the hardest thing that human being have yet learned how to do."

Discovery safely returned to Earth after some last-minute suspense over which landing site to use, ending a smooth, 13-day mission during which the astronauts rewired the space station and delivered U.S. astronaut Sunita "Suni" Williams to the orbiting outpost for a six-month stay.

It was not until about an hour before the landing that NASA decided where to bring the shuttle home. There were showers over Florida, which forced NASA to bypass the first opportunity to land, and crosswinds at the usual back-up landing site, Edwards Air Force Base in California's Mojave Desert.

NASA was not thrilled about the next-best landing site, White Sands Missile Range in New Mexico, where the weather looked good.

Ultimately, NASA gave the go-ahead for a Florida landing when it appeared the rain would not reach Cape Canaveral. The shuttle came in through scattered clouds and touched down on a floodlit runway in the early evening darkness.

"We've had a fantastic year," said Kirk Shireman, space station program deputy manager. "Next year is going to be bigger."