The space shuttle Atlantis, with a preliminary clean bill of health, is about to make a 17 1/2-ton delivery.
Astronauts Monday morning will use the shuttle's robotic arm to remove a giant truss with two attached solar wings from the shuttle's cargo bay and hand it over to the international space station. With that cosmic delivery, Atlantis, just two days off the launch pad, will have accomplished a big chunk of its main mission.
Atlantis' mission is to resume construction on the international space station after a three-year hiatus following the loss of the space shuttle Columbia. More parts will be added in 14 other flights.
The more than 300-foot-long truss will provide power, data and temperature control to the station's electronics.
There's a lot of work to be done after the truss is delivered. Just like the delivery of a washing machine to a home, astronauts have to hook up the plumbing and electricity. But it's no easy task 213 miles above Earth, so it will take four astronauts three spacewalks over the next week to get the truss hooked up and unfurl the solar wings.
But before any of that is to happen, Atlantis has to hook up with the space station in a docking maneuver that has become routine yet remains delicate and could be dangerous with a wrong move.
Early Monday morning, commander Brent Jett will guide Atlantis slowly toward the space station until they are separated by 600 feet. Then Atlantis will make a giant backflip, snuggle up to and then connect with the orbital outpost.
"It's a busy day," lead flight director Paul Dye said Sunday morning. "There's an awful lot going on and it'll be nonstop work from start to finish."
Monday and Tuesday are "the most critical time frame" for the construction, said space station deputy manager Kirk Shireman.
So far, NASA has reported no serious problems with Atlantis' critical heat shield. Astronauts spent much of Sunday using the shuttle's robotic arm to take pictures of the shuttle's wing leading edge and nose area. On Monday, during the backflip, the shuttle's underbelly will be examined. It's still early to tell if everything is free from debris hits _ like the ones that caused the disintegration of Columbia in 2003 _ but NASA managers declared Sunday afternoon that the areas already examined are "not suspect," mission management team in-flight chairman John Shannon.
The shuttle had minor problems with a speed brake and switches on the latches to the cargo bay door, but nothing that worried engineers, Shannon said.
"We have a really good start to this really complex mission," he said.