May 23, 2013
HOUSTON — NASA’s Mission Control restored full distribution of solar power throughout the International Space Station on May 22, adding back in an eighth channel that was temporarily taken offline in response to a port-side ammonia coolant system leak that required a spacewalk repair earlier this month.
The return to normal eight-channel distribution comes days before the scheduled May 28 launch of Russia’s Soyuz TMA-09M spacecraft with new Expedition 36 ISS crewmembers — cosmonaut Fyodor Yurchikhin, NASA’s Karen Nyberg and the European Space Agency’s Luca Parmitano. Liftoff from the Baikonur Cosmodrome in Kazakhstan is scheduled for 4:31 p.m. EST.
A May 11 spacewalk in response to the ammonia coolant leak by previous ISS crewmember Tom Marshburn and current NASA flight engineer Chris Cassidy replaced a suspect Pump and Flow Control Systems (PFCS) electronics box on the oldest of the orbiting lab’s four U.S. solar power modules, the 13-year-old P-6.
While NASA’s flight control team intends to monitor the system closely for weeks, flight controllers have already noted that residual coolant in the older PFCS unit has since drained away, suggesting the pump unit was indeed the source of a worrisome 5-lb.-per-day coolant loss first noted on May 9.
“That leak rate is gone,” Mike Suffredini, NASA’s ISS program manager, told a May 22 news briefing at the Johnson Space Center. However, controllers will continue to monitor the P-6 cooling system for a pair of previously known leaks, deemed small enough to replenish with ammonia during NASA-led maintenance spacewalks.