STS-104, Mission Control Center Status Report # 15 Thursday, July 19, 2001 – 6 a.m. CDT

Astronauts aboard the International Space Station complex successfully replaced a leaky air circulation
valve and moved a hatch into position for the first space walk out of the new Quest airlock.

That space walk is scheduled to begin about 10:30 p.m. Friday, pending a successful leak check of the
crew lock while the crew sleeps today. Mission Specialists Mike Gernhardt and Jim Reilly will attach a fourth
and final supply tank to the airlock’s exterior, and move on to some get-ahead tasks made possible when
they were able to attach a bonus third tank during Wednesday’s space walk. Tasks added to Friday’s space
walk include an inspection of one of the station’s solar array swivels and inspection of the Floating Potential
Probe that measures plasma levels around the solar arrays.

STS-104 Commander Steve Lindsey and Expedition Two Flight Engineer Jim Voss finished replacing the
Intermodule Ventilation (IMV) Assembly valve in the station’s Unity module about 7:30 p.m. Wednesday.
With help from station Commander Yury Usachev, they replaced the leaking valve with another from the
Destiny laboratory that won’t be needed until the station’s second node arrives in 2003.

Voss, Mission Specialist Janet Kavandi and Susan Helms moved the hatch from its initial location between
the Unity module and the airlock’s Equipment Lock to between the Equipment Lock and Crew Lock. The
Equipment Lock will be used for storing and servicing space suits, while the Crew Lock will serve as the exit
to space.

Usachev also worked with one of the station’s payload computers, performing maintenance on several of
the station’s Russian systems, and Kavandi, Gernhardt and Reilly worked to transfer items between the
shuttle and station while getting equipment and space suits squared away in the airlock. Helms also
changed out a Command and Control computer that had been temporarily installed in place of a payload
data computer in Destiny. The payload computer was cannibalized during the STS-100 mission and
retasked when all three of the station’s command computers broke down. The old computer will be returned
to Earth on Atlantis for testing and analysis.

Lindsey and Pilot Charlie Hobaugh gave the station another boost using the shuttle’s reaction control
system jets, increasing the station’s orbit about 5 miles to 244 x 240 statute miles. It was the final reboost
planned for this mission. Atlantis will leave the station later this week about 10 miles higher than when it
arrived.

The next mission status report will be issued about 6 p.m. or as events warrant.