Expedition 4 Commander Yury Onufrienko and astronauts Carl Walz and Dan Bursch were launched last Dec. 5 aboard Endeavour's STS-108 mission, and have been on the ISS since Dec. 7.
Endeavour is scheduled for launch on May 30. That would result in a docking with the station on June 1. Endeavour Commander Ken Cockrell, Pilot Paul Lockhart, and mission specialists Chang-Diaz and Perrin are bringing the Expedition 5 crew to the station. That crew is commanded by Valery Korzun and includes astronaut Peggy Whitson and cosmonaut Sergei Treschev.
The first two of the three spacewalks by Chang-Diaz and Perrin will focus on installation of a new Mobile Base System for the station's robotic arm, Canadarm2. It will allow the arm to move along the railroad-like tracks of station's main truss, eventually to reach a length of more than 350 feet. The third spacewalk is to change out the wrist roll joint of Canadarm2.
On Friday, Dan Bursch worked with the Biomass Production System, a plant growth experiment using wheat and a plant related to cabbage and radishes. Each crewmember was scheduled for an hour to pack personal possessions, as they have been for much of this week. On Thursday Walz and Bursch completed their final session with the PuFF (pulmonary function in flight) experiment, which looks at effects of microgravity on lung function.
Several experiments have been deactivated, including the Physics of Colloids in Space, which was shut down Tuesday and which will be returned to Earth on Endeavour. It is a study of fine particles suspended in a fluid. An example of such fluids is paint.
Major systems aboard the station continue to function well as the ISS orbits at an average altitude of about 243 statute miles.