Encyclopedia Astronautica
2001.06.27 - ISS Status Report: ISS 01-21


As Shuttle and International Space Station Program managers prepare to meet to select an official target launch date for Atlantis' STS-104 mission to the complex, the Expedition Two crew continues to test the station's robotic arm in preparation for its first official task of permanently installing the Airlock onto the Unity module.

The face-to-face Flight Readiness Review at the Kennedy Space Center Thursday is expected to result in a launch target date for Atlantis at 4:04 a.m. CDT, July 12. Pending completion of the robotic arm checkout on orbit, Atlantis will arrive with the newest component of the station late in the evening of July 13. The Airlock is a critical component allowing Extravehicular Activity (EVA), or space walks to be conducted using U.S. spacesuits or Russian Orlan spacesuits without the presence of the shuttle.

The Airlock also will add an additional 1,200 cubic feet of volume to the station, bringing its size to about 12,000 cubic feet of volume. The six-and-a-half-ton module, built by Boeing at NASA's Marshall Space Flight Center, can only be attached to the station using the new Canadian-built robot arm that was delivered to the station on the most recent shuttle mission in April.

Since that time, the Canadarm2, as it's known, has been undergoing an extensive on-orbit checkout. Several problems with the testing led to launch delays, but those issues have been resolved and the arm has operated flawlessly for several weeks. In the event of a recurrence of the most serious of the problems, which was a communications error in the shoulder pitch joint's backup electronics, a software patch essentially telling the robotic arm's electronics to bypass the nuisance fault has been loaded into station computers, which likely will solve the problem should it surface again.

Extensive reviews by engineers from NASA, the Canadian Space Agency and its prime robotics contractor - MD Robotics - concluded that the communications error between Canadarm2's shoulder pitch joint and the arm's main computer commanding unit was attributable to an intermittent problem with a computer chip in the joint's electronic system and not a problem with joint itself.

Expedition Two Flight Engineers Jim Voss and Susan Helms will conduct an additional dress rehearsal of the Airlock installation task Thursday, following an identical run a week ago.

In preparation for launch, the STS-104 crew is at the Florida spaceport for its traditional countdown dress rehearsal that concludes Friday.

Expedition Two Commander Yury Usachev, Voss and Helms continued a variety of science investigations this week with more than 25 hours of experiment work budgeted for the crew.

The International Space Station is orbiting at an altitude averaging 240 miles (385 km).

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