U.S. space officials have extended the visit of the shuttle Discovery to the International Space Station one day so astronauts can spend more time retracting a stubborn solar panel. Mission managers have added a fourth spacewalk for this purpose on Monday. VOA's David McAlary reports that the third spacewalk on Saturday completed the task of rewiring the station for a new power system.
In three spacewalks since Tuesday, Discovery astronauts have successfully rewired the station to accept two big new solar energy arrays brought up on the previous shuttle mission. On Saturday, crewmembers Robert Curbeam and Sunita Williams completed the task of rerouting power from an old system that had been supplying electricity to the station since 1999 to the new one that will serve future modules supplied by the European and Japanese space agencies.
After the first spacewalk completed a partial rewiring Tuesday, ground officials successfully activated ammonia pumps to cool the equipment that converts the solar energy into electricity.
Lead space station flight director John Curry says the new system is working well. He says "It's a major change in the space station architecture. We're powering up a whole other system that had not been powered up before and everything went flawlessly. We got good power, we got good flow to the ammonia system, and this vehicle is ready to accept the international partner modules now."
After finishing the rewiring, astronauts Curbeam and Williams spent 90 minutes longer than planned on Saturday's spacewalk trying to complete the folding of an old solar panel that has refused to retract all the way. Earlier in the week, astronauts had mechanically pulled it back halfway from inside the orbiter, but its accordion folds did not compress further. Mission controllers say the wires pulling on the sides of the array got stuck on grommets through which they pass.
So on Saturday's outing, Curbeam repeatedly shook the assembly to loosen the wires. He freed the cable on his side and was able to push the panel back some more, but the cable on Sunita Williams' side got stuck and they could not force it back any more.
Spacewalk official Tricia Mack says the astronauts had to abandon the task before they ran out of life support supplies and had to end the spacewalk, or as flight controllers call it, an EVA for extra vehicular activity.
Mack told reporters, "For a while, we really thought we were going to get this retracted on this EVA and it just did not want to come loose. We all firmly believe that had we had we had more time on today's EVA, we would have been able to get it in there, but since we didn't, we did run out of time."
As a result, mission officials have added a fourth spacewalk for Monday to try to finish the solar panel pullback. Fortunately for the space station, they did move far enough back last week to give the new solar arrays room to rotate to follow the sun.
The extra spacewalk means Discovery will undock from the space station one day later than planned. Departure is now set for Tuesday.