Following Two Spacewalks To Replace A Degraded Pump Module On The Truss, Or Backbone, Of The International Space Station, Flight Controllers In The Mission Control Center At Nasa's Johnson Space Center In Houston Successfully Restarted The New Pump Tuesday Night.

The Pump Module Controls The Flow Of Ammonia Through Cooling Loops And Radiators Outside The Space Station, And, Combined With Water-Based Cooling Loops Inside The Station, Removes Excess Heat Into The Vacuum Of Space.

The New Pump Now Is Considered Fully Functional, But It Will Take Some Time To Fully Reintegrate The Pump And Loop A Of The Two-Loop External Cooling System. Teams At Mission Control Are Following A Schedule That Should Allow The Restored Cooling Loop To Be Fully Activated And Integrated Into The Station'S Cooling System On Christmas Day, Dec. 25.

Electrical Systems That Depend On Cooling From Loop A Will Be Repowered Or Moved Back From Temporary Support On Loop B Gradually On Thursday, Friday And Throughout The Weekend.

Expedition 38 Flight Engineers Mike Hopkins And Rick Mastracchio Removed The Degraded Pump Module During A 5 Hour, 28 Minute Spacewalk Saturday, Dec. 22. They Retrieved A Replacement Pump From An External Stowage Platform Near The End Of The Station'S Backbone, And Installed It During A 7 Hour, 30 Minute Spacewalk On Christmas Eve, Dec. 24.

Engineers At Mission Control Sent A Series Of Commands To The New Pump Module At The End Of Tuesday'S Spacewalk To Ensure That Ammonia - An Excellent Thermal Conductor - Was Flowing To The New Pump Module.

Beginning About 4:30 P.M. Est Today, Remote Commands Started The Process Of Pressurizing The New Pump. Reactivation Of The Pump Is Now Complete, And It Is Performing Its Job Regulating The Flow And Temperature Of The Ammonia In Loop A Of The Two-Loop Cooling System.

On Saturday, The Crew Had Moved The Old Pump Module To A Temporary Stowage Platform On A Rail Car On The Station'S Mobile Base System, Where It Can Remain Indefinitely.