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Station Spacewalk Set for Thursday

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Old June 24th 04, 04:07 PM
Jacques van Oene
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Default Station Spacewalk Set for Thursday

Station Spacewalk Emphasizes the International

It takes a planet-wide effort to run the International Space Station, and
that cross-cultural cooperation will be showcased this week. On Thursday at
5:50 p.m. EDT (2150 GMT), the American and Russian crew members are
scheduled to leave the Station's interior and float through differences in
language, culture and national borders during a first-of-its-kind spacewalk.

It will be the first time a spacewalk has been conducted in Russian
spacesuits to replace a U.S. component on the U.S. segment of the Station.
Starting from the Russian airlock, the main task for NASA Science Officer
Mike Fincke and Expedition 9 Commander Gennady Padalka is to replace a type
of circuit breaker on the U.S.-built truss, restoring power to a gyroscope
that can help control the Station's orientation.

An effort across many miles has taken place to plan the spacewalk, drawing
on experts in both the U.S. and Russia. And that effort will be echoed
during the journey outside for Fincke and Padalka, with the spacewalkers
switching languages as they conduct communications with flight controllers
on opposite sides of the planet.

"This is the real stuff that the Station was built for," said Paul Boehm,
the lead Extravehicular Activity (EVA) Officer for the spacewalk. "It allows
us to test this cooperation, the techniques, and the technology of these two
different space countries and to determine how to make joint space travel
work. It's the only way to the future of human exploration."

When outside the Russian segment of the Station, ground controllers outside
Moscow will speak to Fincke and Padalka in Russian. When they are outside
the U.S. segment of the Station, the team in Houston will speak in English.
The spacewalkers, proficient in both languages, will use whichever language
is appropriate to the time or the task. And, sometimes, Fincke and Padalka
may not speak to each other at all. They may use a set of predetermined hand
signals, much like deep sea divers and paratroopers, during periods when
radio communications are not available.

This will be the first spacewalk in history to have the primary support
switch in real time between ground controllers in Russia and the U.S.
Because the crewmembers will be wearing the Russian spacesuits, exiting and
returning to the Russian Pirs airlock, and using a Russian crane to aid them
in climbing to the repair site, the first and last parts of the spacewalk
will be coordinated by engineers in Russia's Mission Control Center outside
of Moscow.

Once the pair gets as far as the junction of the Russian and American-built
segments of the Station, flight controllers at Mission Control in Houston
will take over. They'll guide the spacewalkers the rest of the way to the
repair site as they move, using handholds and tethers. Then they'll help the
spacewalkers replace a faulty Remote Power Control Module (RPCM). When that
is done, and Fincke and Padalka return to the Russian crane, Russian ground
controllers will again take over primary support.

Throughout the spacewalk, flight controllers in Houston and Moscow will be
in constant contact with each other, virtually working side by side on
opposite sides of the world. Although not always visible, this is the way
day-to-day International Space Station operations have been accomplished
since the first pieces of the complex were launched in 1998. During all
previous spacewalks, however, there has been only one lead control center,
be it in Russia or the U.S.

"Interaction with our Russian friends has never been more productive because
both sides are highly motivated to succeed," said John Curry, the lead U.S.
flight director for the spacewalk. "The team is very excited to work this
spacewalk because space exploration is at its best when we push the
boundaries a little and do new things. If this bi-lateral EVA goes as well
as we expect it will, I am sure we'll use that fact to help optimize
scheduling for future spacewalks."

The goal of the spacewalk is to restore electricity to one of three
operational Control Moment Gyroscopes (CMG) that control the Station's
orientation. CMG 2 went off-line April 21 when it lost power. The two
gyroscopes that are working can control the Station's attitude, but a third
functioning CMG will provide greater backup capabilities. The fourth CMG
failed two years ago, and will be replaced when Space Shuttle flights resume
next year.

The spacewalk plan initially called for American spacesuits and the U.S.
Quest Airlock to be used. But the crew could not get the cooling system of
one of the U.S. spacesuits to work. Managers in America and Russia then
agreed to do the spacewalk using Russian suits.

Using the Russian spacesuits poses some additional challenges. The
spacewalkers will use communication antennas on the Russian segment of the
Station, and the truss structure may interfere at times with those radio
signals. The spacewalkers also will have to travel about twice as far to get
to the work site as they would have had to travel if they began from the
U.S. airlock. That means they have to be outside the station longer and use
the Russian Strela cargo crane to reduce their travel time. Also, the
Russian spacesuit gloves are not as supple as those of the American suits,
so additional preparation will need to be made inside the Station in advance
to avoid too many fine tasks.

The communications problems are not just between the crewmembers and the
ground. If the signal is blocked, Padalka and Fincke may not be able to talk
to each other because the spacesuit radios require the Russian segment
antennas to relay the signal. If communications are interrupted, the control
teams have developed the system of hand signals and have identified a
special, unblocked communications location.

The spacewalkers may use four simple hand signals to communicate in that
case, and one simple "pager" signal that Mission Control can use to alert
Padalka and Fincke. The pager signal involves turning off the light at the
end of Canadarm2, which will be positioned to provide camera views of the
repair work. If communications are blocked and Mission Control needs the
pair to go to the unblocked location, the Robotics Officer (ROBO) in Mission
Control will simply turn off the light.


Jacques :-)



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