Live In Orbit: Big Day In Space

NASA will stage a critical test of a repaired solar wing rotary mechanism on the International Space Station early today as the agency strives to fix problems with the outpost's power-production system.

The joined crew of shuttle Endeavour and the station also aim to overcome start-up problems with a newly delivered treatment system designed to convert urine, sweat and condensate into potable drinking water -- a capability key to plans to double station crew size to six next May.

And you can watch all the action unfold here in The Flame Trench. Simply click the NASA TV box on the righthand side of the page to launch our NASA TV viewer and live 24/7 coverage of Endeavour's ongoing mission to the station.

Look for the test of the starboard Solar Alpha Rotary Joint to begin at 5:30 a.m. EST as the shuttle-station complex soars some 220 statute miles above planet Earth.

Specialists in NASA's Mission Control Center will beam up commands to turn the station's single starboard solar wing like a steamboat paddlewheel so it can constantly track the sun as the outpost circles Earth, maximizing electrical output.

The test will show whether unprecedented repairs to a 10-foot-diameter rotary joint were successful. The repairs were made during a series of four spacewalks over the past week.

Inside the station, astronauts will continue working with a urine processor assembly that has been plagued with start-up problems since its delivery aboard Endeavour. The system must be operating properly for NASA and its international partners to expand the size of resident crews to six from three next May.

Endeavour and its astronauts will be staying an extra day at the station. Mission managers decided to keep the shuttle crew at the station so the astronauts could help troubleshoot the start-up problems with the water treatment system.

NASA engineers on the ground are making preliminary plans to bring parts of the urine processor assembly back to Earth if ongoing fix-it attempts don't work. Doing so would make it difficult to maintain the schedule for crew expansion in May.

Replacement parts would not arrive at the station until Discovery arrived in mid-February, and a 90-day checkout period is required before the size of resident crews on the station can be increased.