Sharipov and Chiao are set to step outside early Monday for nearly six hours to continue the external outfitting of the Station with antennas for the European Automated Transfer Vehicle (ATV). They also will deploy a small Russian technology satellite, Nanosatellite, to test control techniques.
NASA Television will broadcast the spacewalk live beginning at 11 p.m. CST Sunday. The spacewalk is scheduled to begin at about 12:25 a.m. CST Monday.
It is planned to be the second and final planned spacewalk of the expedition. They began preparations last Friday with a spacewalk timeline review. They also gathered tools they will use to install the antennas on the exterior of the Station's Zvezda living quarters module. On Monday, the crew worked out on a stationary bicycle while doctors on the ground monitored their health and they were pronounced physically fit for the spacewalk. The crew also checked the health of the breadbox-sized satellite, finding it in good order.
The spacewalkers will install the fourth, fifth and sixth in a series of communications antennas for the European ATV. They also will install a Global Positioning System antenna on Zvezda and inspect and photograph the large "Lira" antenna on Zvezda to insure it is in the correct position.
Early today, a thermal control loop panel in Zvezda that provides cooling to the Pirs airlock failed, and its backup system was activated to provide the necessary cooling. There are two circulating pumps associated with each panel. Both pump panels are needed to provide adequate backup capability for the spacewalk. The crew will troubleshoot the pump panel early Saturday, and replace one or both of the pumps in the degraded panel.
The crew will close hatches between the U.S. and Russian segments of the Station at 4:55 p.m. Sunday, deactivate nonessential systems on the Station at 5:30 p.m. and perform preliminary spacesuit tests at 7 p.m. Airlock systems checks are set for 9:20 p.m., and final suit checks at 9:50 p.m.
Chiao and Sharipov will climb into their Orlan suits at 10:10 p.m. Sunday and will begin depressurizing the airlock at 10:40 p.m. The spacewalk will officially begin when they open the Pirs hatch about 12:25 a.m. CST Monday.
Also this week, the crew repressurized the Station using oxygen from tanks on the attached Progress supply ship. Mission managers elected to postpone any further troubleshooting of the balky Elektron oxygen-generating system until after the spacewalk. The Elektron, which converts water into oxygen, is one of several methods that can be used to provide oxygen.
Ground controllers powered up the Mobile Servicing System on Wednesday and confirmed software was working properly after an update last week. The Canadarm2 robotic arm is in position for its cameras to provide television views of the spacewalk.
Russian flight controllers commanded Station thrusters to fire and increase the altitude of the complex by about 1.8 statute miles. The reboost places the Station at the correct altitude and trajectory for the launch of the next crew, Expedition 11, and a European Space Agency astronaut on April 15.
On Thursday, managers approved a plan to make connections that will bypass a failed circuit breaker, called a Remote Power Controller, on the first spacewalk to be conducted during Shuttle mission STS-114. The job is planned to be a five-minute task on that spacewalk, the first of three to be conducted by the Shuttle Return-to- Flight crew while Discovery is docked to the Station. STS-114 spacewalker Steve Robinson will reconfigure power cables to bypass that circuit breaker, providing power to restart a Station Control Moment Gyroscope. Power was removed from that gyroscope last week when the circuit breaker failed.
Later on the Shuttle mission, Robinson and fellow spacewalker Soichi Noguchi will replace another gyroscope that failed in June 2002. Once complete, the work will restore the Station to four operating gyroscopes. The Station's orientation is being maintained well now by only two gyroscopes, but more will be needed as assembly of the complex resumes and its size increases.