Flight controllers sent commands to enable a large joint to begin rotating around 7 p.m. CST, moving the solar arrays on the P4 truss like a giant paddle wheel to track the sun as the station moves from daylight to darkness in orbit. A few hours later, just before 10 p.m. CST, valves were opened to allow 300 pounds of ammonia to flow into the truss segments of the station and its radiators, the first step toward providing permanent cooling for the avionics and electronics on the complex.
Those vital activation tasks occurred after a day-long effort by Discoveryís crew to retract the port array on the P6 solar array truss structure, which was installed six years ago to provide early electrical power for the station.
The crew spent six hours today sending as many as 45 commands in a start-stop fashion to retract, then redeploy, then retract the balky Venetian-blind like array panels in an effort to fold them into a narrow blanket box at the base of the array. But guide wires that help fold the arrays flat into the box apparently became snagged with only 17 out of 31 bays of the port array retracted. That was enough, however, to provide enough clearance to enable the new P4 arrays to begin rotating as planned.
Mission managers met tonight to discuss various options for completing the P6 array retraction, and decided to press ahead with the second of three scheduled spacewalks Thursday by Bob Curbeam and Christer Fuglesang during which they will rewire the first pair of electrical channels for the permanent power system on the station.
Managers will convene over the next few days to determine whether additional spacewalk activity by Discoveryís crew will be scheduled to complete the retraction of the P6 array, although they have concluded that the array is in a safe configuration for the remainder of this mission, Discoveryís undocking next week, and if necessary, for the arrival of a new Russian Progress resupply ship in January should a spacewalking task be added to the Expedition 14 crew following Discoveryís flight.
Late tonight, to gather data for a future decision, Mission Control asked Discovery Commander Mark Polansky and Station Commander Mike Lopez-Alegria to consider which flight day would be best for a fourth spacewalk if one is ordered to complete the P6 array retraction. Polansky and Lopez-Alegria asked for more details about what such a spacewalk would entail before offering their thoughts.
With the stationís new solar arrays rotating and its permanent cooling system operating as advertised, Discoveryís crew members will begin an eight-hour sleep period at 1:17 a.m. CST and will wake up Thursday at 9:17 a.m. CST to begin preparations for the second spacewalk of the flight. The station crew members will be awakened thirty minutes later.