Friday marks 100 days in space for the three crewmembers, Commander Yury Usachev, and Flight Engineers Jim Voss and Susan Helms, since launch on March 8 to replace the Expedition One crew.
Meanwhile, plans are in place for a complete checkout of the station's robotic arm, called Canadarm2, on Thursday to check all of the positions through which it will be maneuvered to support the installation of the next pressurized component - the Joint Airlock - scheduled for launch aboard Space Shuttle Atlantis about July 12 from the Kennedy Space Center, FL.
The scheduled 4-hour checkout, set to begin about 10 a.m. Central time, effectively will serve two functions. First, the operation will verify the arm's ability to support the Airlock installation on the Unity module of the station. Second, to continue to investigate the reason for an intermittent loss of communication between the arm's shoulder pitch joint and its computer commanding unit. A diagnostic software patch has been loaded in the station's onboard computers to attempt to obtain additional data on the arm's operation.
Meanwhile, shuttle and station managers have elected to delay the rollout of Atlantis to the launch pad while the robotic arm troubleshooting continues. At present, the rollout is scheduled for Tuesday to support a launch around 4 a.m. Central on July 12. The option still exists to postpone the mission until September and fly Discovery to the station first on the STS-105 flight no earlier than August 5 to deliver the Expedition Three crew as a replacement for Expedition Two.
This week has been the busiest so far aboard the station for science investigations with more than 25 hours of experiment work budgeted for the crew.
The International Space Station is orbiting at an altitude of around 240 miles (385 km).