International Space Station crew members Chris Cassidy and Tom Marsburn began preparations early Friday for a weekend spacewalk to investigate a coolant leak on the station’s oldest solar power system module.
The excursion could come as soon as Saturday, ISS commander Chris Hadfield said by Twitter early Friday.
Preparations unfolded as Hadfield, Marshburn and cosmonaut Roman Romanenko were preparing to depart the ISS in their Soyuz TMA-07M spacecraft for Earth late Monday to conclude a 146-day expedition.
“Good morning, Earth! Big change in plans, spacewalk tomorrow. Chris Cassidy and Tom Marshburn are getting suits and airlock ready,” Hadfield said by Twitter. “The whole team is clicking like clockwork, readying for tomorrow.”
Meanwhile, NASA’s mission control team was preparing for a shutdown of the leaking cooling loop on the 13-year-old P-6 solar power module positioned on the far port side of the orbiting lab. That meant powering down non-essential equipment and transferring cooling responsibilities to a second cooling apparatus.
NASA stated Hadfield, Marshburn, Cassidy and cosmonauts Pavel Vinogradov, Alexander Misurkin and Romanenko were in no danger.
Hadfield notice the surging leak Thursday morning, alerting Mission Control.
Cosmonaut Pavel Vinogradov reported to Russia’s Mission Control early Friday that the leak was continuing and described the size of the frozen “drops” coming from the area of the P-6 radiator as 1 to 3 centimeters. The veteran cosmonaut also transmitted a photo of a suspicious “mark” on the solar module to ground controllers.
Initially, NASA’s experts estimated the leak rate would trigger an automatic shutdown of the port side cooling loop within 48 hours. By late Thursday that estimate had advanced to 24 hours, or sometime Friday.
On Nov. 1, previous ISS crew members Sunita Williams and Akihiko Hoshide carried out a near-seven hour spacewalk to install jumper cabling in an effort to circumvent a persistent low rate coolant leak on the P-6. The work included the re-activation of a radiator panel that had been active during the station’s early assembly phase.
The departing crew members are scheduled to be replaced on May 28 by cosmonaut Fyodor Yurchikhin, NASA astronaut Karen Nyberg and European Space Agency astronaut Luca Parmitano.
U.S., European and Japanese ISS crew members are trained to deal with a range of spacewalk repairs that might be required on the station's U.S. segment.