Article Posted on : - Aug 06, 2010

WASHINGTON (BNS): NASA astronauts in the International Space Station, who were planning their first spacewalk on Friday to replace a faulty cooling system of the orbital station, have reset their mission for Saturday and Wednesday.

The first spacewalk by NASA astronauts Doug Wheelock and Tracy Caldwell Dyson is scheduled at 1055 GMT on Saturday which will be followed by another one on Wednesday to complete replacement of the ammonia pump module that failed last Saturday.

“Teams of flight controllers, engineers, and spacewalk and robotics experts have made significant progress in preparing for the spacewalk, but need an additional day to finish working out all the details,” NASA said.

The additional day will allow the final procedures to be uplinked and give the station crew time to review the plans made by the Mission Control, it said.

During the first spacewalk, the pump module will be removed and replaced. The crew will complete connecting fluid ammonia lines to the replacement pump during the second excursion Wednesday.

The spacewalks are challenging because the crew will be handling ammonia lines at full operating pressure, which makes the lines stiff during reconnection and mating.

The timeline for the spacewalk will require numerous “off ramps” to ensure there is enough time to complete decontamination procedures if the crew comes in contact with ammonia, NASA said.

One of the ISS's two cooling systems suddenly shut down last Saturday. Serving the US, European and Japanese laboratories, the cooling system was being used to keep electronic equipment from overheating.

Earlier, NASA was planning the first spacewalk on Friday and the second one on Monday which were put off as workers on the ground needed more time to work on the repair plan.