The Endeavour astronauts are preparing to undock from the international space station this afternoon, leaving a fresh three-man crew behind and bringing the lab's fifth full-time crew home after six months in space.

All 10 astronauts and cosmonauts plan to meet in the U.S. Destiny laboratory module around 12:15 p.m. EST for a final round of hugs and hangshakes. Twenty minutes later, Endeavour's crew, which now includes Expedition 5 commander Valery Korzun, Sergei Treschev and science officer Peggy Whitson, will float out of the station and into the shuttle, leaving Expedition 6 commander Kennedy Bowersox, Nikolai Budarin and science officer Donald Pettit behind for a four-month tour of duty.

With pilot Paul Lockhart at the controls, Endeavour is scheduled to undock from a port on the forward end of the Destiny module at 3:05 p.m. EST. After pulling away to a point about 400 feet directly in front of the station, Lockhart will guide Endeavour through a quarter loop to a point directly above the outpost before firing the ship's maneuvering jets to leave the area for good.

"We'll back off to the 400-foot range and then initiate a fly around," said flight director Paul Dye. "It's a great chance for us to get some video and some still pictures of the station in its new configuration and that helps us on the ground when we're working problems in the future."

Lockhart originally hoped to fly Endeavour through a full loop around the station. But after three reboost sessions to increase the station's altitude by nearly 6.5 miles, Endeavour only has enough discretionary fuel left for a quarter of a loop.

Two-and-a-half hours after undocking, Lockhart will oversee deployment of two small Air Force "picosats" designed to test technology intended for future spacecraft that could be used to remotely inspect other satellites.

If all goes well, Endeavour will glide to a touchdown at the Kennedy Space Center at 3:48 p.m. Wednesday. For readers who bother to pay attention to long-range Florida forecasts, the Spaceflight Meteorology Group at the Johnson Space Center is predicting a chance of showers and thundershowers near the spaceport Wednesday and Thursday with improving conditions Friday.

Astronaut Joan Higginbotham told shuttle commander James Wetherbee early today that Endeavour has enough on-board supplies for four additional days in space beyond Wednesday if the weather causes any delays. Even so, she advised the shuttle crew "not to share the food too much with your ISS crew members before you close the hatch."

"Good call," Wetherbee replied.