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EXP 12 CREW COMPLETES SPACEWALK



SUBMITTED BY ARTHUR N1ORC - AMSAT A/C #31468

Spacewalkers Install New Camera Assembly, Jettison FPP

    11.07.2005

Space station Commander and NASA Science Officer Bill McArthur and 
Flight Engineer Valery Tokarev installed a new camera assembly and 
jettisoned the Floating Potential Probe during a 5-hour, 22 minute 
spacewalk Monday.

McArthur, designated EV1 (for Extravehicular Activity) and wearing the 
spacesuit with red stripes, and Tokarev, EV2, in the all-white suit, 
also completed two get-ahead tasks.

TO VIEW PHOTOS GO 
TO:http://www.nasa.gov/mission_pages/station/expeditions/expedition12/exp12_eva.html

Expedition 12 spacewalk Image to left: Expedition 12 Flight Engineer 
Valery Tokarev (upper left) assists Commander Bill McArthur with a task 
during the spacewalk. Image credit: NASA TV

The camera assembly installation on the Port 1 Truss was the first of 
the two primary tasks. The new device is similar to the camera assembly 
on the Starboard 1 Truss, and was installed on a P1 lower outboard 
stanchion. It will have a big role in future station assembly.

The camera assembly will be used after arrival of the P3 and P4 truss 
segment during STS-115, station assembly flight 12A, next year. It will 
offer visual perspective to arm operator Steve MacLean, a Canadian 
astronaut, as he maneuvers the truss segment for installation.

The truss segment brings with it another radiator and another set of 
solar wings. Stretching 240 feet from tip to tip, the solar assembly 
will almost double the total electricity generating capacity of the station.

McArthur and Tokarev spent about 2 hours, 10 minutes on the camera 
assembly installation. In order to have daylight for the Floating 
Potential Probe jettison, they moved on to one of the get-ahead tasks, 
the retrieval of a failed remote joint motor controller. Engineers are 
anxious to get this one back to see what went wrong before others are 
sent to the space station.

Expedition 12 spacewalkImage to right: Commander Bill McArthur (lower 
right) and Flight Engineer Valery Tokarev inspect a camera assembly on 
the lower outboard stanchion of the P1 truss. Credit: NASA TV

After taking the RJMC and tools from the first task back to the airlock, 
they then moved, with McArthur in the lead, up the P6 truss to the 
Floating Potential Probe.

The FPP was situated atop the P6 Truss between the station's solar 
wings. It was designed to measure the station's electrical potential and 
compare it to the surrounding plasma. It wasn't working.

Photos showed FPP fasteners had backed out. That raised concerns that 
the fasteners could become detached and perhaps cause damage.

McArthur and Tokarev released and stowed a grounding wire, then released 
the FPP housing from its stanchion. They checked its condition and then 
report lighting conditions to Houston with an eye to jettisoning the FPP.

McArthur jettisons the FPP Image to left: The FPP moves away from the 
station moments after being jettisoned by Commander Bill McArthur. This 
view is from the camera mounted on Flight Engineer Valery Tokarev's 
helmet. Credit: NASA TV

Getting rid of the FPP was a little more complicated than just tossing 
it away. To ensure its safe departure, McArthur jettisoned the device 
backwards in relation to the direction the station is moving with a 
smooth motion. He aimed for a velocity of at least half a foot per 
second. He tried to throw the FPP 30 degrees upward and 10 degrees to 
the left of the back of the station, a target he apparently came close 
to hitting.

The spacewalkers spent about an hour on the FPP, wrapping up the second 
major task of the spacewalk.

That done, crewmembers completed a second get-ahead task: removal and 
replacement of a remote power controller module, a kind of circuit 
breaker. This one is on the mobile transporter, which moves along 
railroad-like tracks on the station's main truss.

It was the first U.S. Quest airlock-based spacewalk since an Expedition 
6 spacewalk by Commander Ken Bowersox and NASA Science Officer Don 
Pettit on April 8, 2003.

The beginning of the spacewalk was delayed about an hour to repressurize 
the Quest airlock's crew compartment so the crew could check the 
position of a pressurization valve in Quest's equipment lock.

The spacewalk officially ended at 3:54 p.m. EST.
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