Endeavour Astronauts Philippe Perrin and Franklin Chang-Díaz are set to step out into the vacuum of space this morning for the first of three spacewalks to help install a platform for the transport of the International Space Station’s robotic arm and to replace a faulty joint in the arm itself.

With the help of Endeavour Pilot Paul Lockhart, who will help coordinate the spacewalk from inside Endeavour, Chang-Díaz and Perrin will leave the Quest Airlock this morning for a planned six-hour spacewalk to first install a Power and Data Grapple Fixture to the station’s P6 truss for its future relocation. The two first-time space walkers will then temporarily park micrometeoroid debris shields on the Russian segment of the station. Expedition Five Flight Engineer Peggy Whitson and ISS Commander Valery Korzun will install the shields on the Zvezda Service Module during a spacewalk set for late July.

The final task of the spacewalk will involve the removal of thermal blankets from the Mobile Base System. That component will be mated tomorrow to the Mobile Transporter on the S0 (S-Zero) Truss of the ISS to enable the Canadarm2 robotic arm to “walk off” the Destiny Laboratory onto the station’s railcar system for transport up and down the length of the complex. Chang-Díaz will be identifiable by solid red stripes on the legs of his spacesuit. Perrin will wear the pure white suit with no stripes.

Commander Ken Cockrell will use the shuttle robotic arm’s cameras to monitor the activities outside. Whitson and Endeavour Astronaut Carl Walz will transport Chang-Díaz on the end of Canadarm2 during the spacewalk.

During the spacewalk, Chang-Díaz will conduct a visual and photographic inspection of one of the station’s four control moment gyroscopes (CMGs) on the station’s Z1 Truss. The gyroscope experienced a mechanical failure of its spin bearing yesterday and will no longer be able to be used to assist in station attitude control.

Three other CMGs are operating normally to provide full attitude control for the ISS. If necessary, station control can be maintained with only two functioning CMGs, with other backup attitude control systems also available. The CMG failure will have no impact on ISS operations. A substitute CMG is available on the ground and program managers are evaluating future replacement options. To accommodate the use of three CMGs and varying thermal conditions, the orientation of the shuttle and station will be altered slightly for today’s spacewalk.

Once the protective blankets are removed from the Mobile Base System, Whitson and Walz will latch onto the platform in Endeavour’s cargo bay with Canadarm2, remove it from its carrier, and maneuver it to a position just above the Mobile Transporter, which was installed on the S-Zero Truss in April. Canadarm2 will be left in a parked position overnight to thermally condition the Mobile Base System before it is mated to the Transporter railcar Monday.

At the start of their fifth day in space, Endeavour’s crew was awakened at 4:23 a.m. Central time to the sound of “Drops of Jupiter” by Train, a tune selected for Cockrell.

The next STS-111 status report will be issued Sunday evening following the spacewalk, or earlier, if events warrant.

- end -

text-only version of this release