The first item on the agenda for Gorie and company is to rendezvous and dock with the space station. At liftoff, the station will be flying along a northeasterly trajectory near Newfoundland.

A space shuttle can only catch up with the station if it launches within five minutes of the moment Earth's rotation carries the launch pad into the plane of the lab's orbit.

But in recent years, NASA managers decided to give up the first five minutes of the 10-minute launch window to improve the odds of a reaching an East Coast runway in the event of multiple main engine failures that otherwise would force a crew to bail out.

By waiting five minutes, Earth's rotation results in a trajectory that carries the shuttle closer to the East Coast, thus improving the odds of pulling off an East Coast abort and landing, or ECAL. Fifteen civilian and military runways from Myrtle Beach, S.C., to Newfoundland are available for emergency use if needed.

Assuming an on-time liftoff and a trouble-free ascent, Endeavour will spend two days catching up with the station, using a series of rocket firings to fine-tune the approach. The terminal phase of the rendezvous procedure will begin when the shuttle reaches a point about 9.2 miles behind the station.

To visualize the shuttle's approach, it is useful to recall the current configuration of the space station.

The 150-ton complex is made up of four connected pressurized modules and a truss extending upward with respect to Earth that supports the huge P6 solar arrays. The solar panels extend at right angles to the long axis made up of the pressurized modules.

For Endeavour's docking, the station will be oriented with its long axis in the direction of travel. The forward-most module is the U.S. Destiny laboratory. Destiny, in turn, is connected to a multi-hatch module known as Unity, which is connected to the Russian-built NASA-financed Zarya module.

Zarya, in turn, is connected to the Russian Zvezda command module. Zvezda's aft port is used by unmanned Progress supply ships. A new docking compartment known as Pirs is connected to a downward facing hatch in the command module.

The station's three-man Soyuz lifeboat is docked to a downward facing hatch in the Zarya module.

The Unity module has six hatchways - one on each end and four around its circumference. A large airlock is attached to Unity's starboard hatch and the Z1 truss that serves as the base of the P6 solar array extends upward from Unity's zenith port.

Endeavour will approach the station from behind and below. When it reaches a point about 600 feet directly below the lab complex, Gorie will begin a maneuver to position the shuttle 400 feet or so directly ahead of the station with its tail pointing toward Earth and its payload bay facing a docking module on Destiny's front end.

The view from Endeavour during the final approach to docking. Photo: NASA

"Then we back into the space station at about a quarter of a foot per second to start with, and it slows down to be a tenth of a foot per second at the very end," Gorie said in a NASA interview. "That's a very slow pace ... so it's very controllable."

Tani will be in charge of the rendezvous checklist, making sure no one inadvertently misses a procedure. Godwin will use a handheld laser to measure the shuttle's distance from the station and its closing velocity while Kelly oversees rendezvous computers showing Endeavour's current and projected positions.

"It's a very slow ballet of a maneuver," Gorie said. "You're not forcing anything like you would with an F-18 that I'm used to, slamming an airplane on an aircraft carrier deck, but you are just very smoothly and precisely flying this thing with very slow and controlled rates. And I think 'delicate' is probably one of the best words you could use."

Once the docking systems have engaged and leak checks are complete, hatches between Endeavour and the Destiny module will be opened and Culbertson, Dezhurov and Tyurin will welcome their shuttle colleagues and Expedition Four replacements aboard.

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