Endeaovur fuel cells loaded for final flight

Six Endeavour astronauts awoke at midnight to continue preparations for an 8:56 a.m. Monday launch of the next-to-last shuttle mission.

Kennedy Space Center teams are preparing to load supercold reactants into Endeavour's full cell system, which will generate electrical power during the shuttle's planned 16-day flight to the International Space Station.

Three fuel cells will combine liquid hydrogen and liquid oxygen to generate power. The process also produces potable water as a byproduct, some of which will be transferred to the station.

The countdown to the mission's second launch attempt, following a scrubbed attempt April 29, began at 7 a.m. Friday.

The pad was to be cleared of nonessential personnel at 11 p.m. before the hazardous fuel cell-loading operation begins around 3 a.m. today.

Endeavour commander Mark Kelly and pilot Greg "Box" Johnson are slated to practice landings in a modified Gulfstream 2 jet at 5 a.m. and later transition to T-38 jets for more flight time. The crew will undergo medical exams at 8 a.m.

The pad should reopen around 1:30 p.m. Checkouts and inspections will follow throughout the afternoon and evening of the shuttle main engines, external tank and twin solid rocket boosters.

NASA at 4 p.m. will hold a pre-launch news conference featuring Mike Moses, the shuttle launch integration manager; Mike Leinbach, the shuttle launch director; and Kathy Winters, the shuttle weather officer.

It's the last briefing scheduled before launch, and you can watch it here by clicking on the NASA TV image at right to launch a viewer.

On its 25th and final flight, Endeavour will deliver spare parts and a $2 billion particle physics detector to the space station.