SUBMITTED BY ARTHUR N1ORC - AMSAT A/C #31468

Spacewalkers to Jettison Ammonia Reservoir

07.19.07

Two International Space Station crew members will remove and jettison a refrigerator-size ammonia reservoir Monday during a six-hour-plus spacewalk from the Quest Airlock of the International Space Station.

The spacewalk is scheduled to begin at about 6:30 a.m. EDT.(1030 UTC)

Image to right: Cosmonaut Fyodor N. Yurchikhin (left), Expedition 15 commander representing Russia's Federal Space Agency, and astronaut Clayton C. Anderson, flight engineer, work with an Extravehicular Mobility Unit (EMU) spacesuit in the Quest Airlock of the International Space Station. Image credit: NASA TO VIEW IMAGE GO TO: http://www.nasa.gov/mission_pages/station/expeditions/expedition15/e15_eva_0...

Astronaut Clay Anderson will be the lead spacewalker, EV1, and will wear the spacesuit with red stripes. Fyodor Yurchikhin, the cosmonaut and station commander, will be EV2 and wear the all-white suit. Cosmonaut Oleg Kotov, in the U.S. laboratory Destiny, will operate the Canadarm2.

After leaving the airlock and setting up equipment, the first task is installation of a television camera stanchion. The spacewalkers will take it from an external stowage platform and then install it on the Earth-facing side of the station's main truss at the interface Starboard 0-Port 1 (S0-P1) truss segments.

Next they will move to separate tasks. Anderson will reconfigure a power supply for an S-Band Antenna Assembly, and then set up and get on a foot restraint at the end of Canadarm2. Yurchikhin will replace a circuit breaker, called a remote power controller module. It will ensure power redundancy for a move of the Mobile Transporter rail car on the station's truss.

Back together, Anderson and Yurchikhin will remove flight support equipment, where the camera stanchion had been mounted, and an attached Flight Releasable Attachment Mechanism. Together they have a mass of about 212 pounds.

While Anderson jettisons them from the end of the arm, Yurchikhin will move to the Z1 truss, where he will disconnect and stow cabling associated with the ammonia reservoir, called the Early Ammonia Servicer (EAS).

The EAS was installed on the P6 truss during STS-105 in August 2001, as an ammonia reservoir if a leak had occurred. It was never used, and was no longer needed after the permanent cooling system was activated last December. The EAS has to be removed before the P6 truss can be moved to the end of the station's main truss.

With Anderson still on the arm, both crew members will move to the P6 Truss and release its remaining connections to the station. Once it is free, Anderson will hold it while the arm maneuvers him to the jettison point, below the right side of the ISS main truss.

The EAS weighs a little over 1,400 pounds on Earth. The jettison will be much like that of the stanchion equipment. Anderson will shove the EAS opposite the station's direction of travel at a minimum velocity of about seven inches (17 cm) per second.

A few hours later, Russian thrusters will reboost the station to provide clearance from the EAS. The reboost also will prepare for the Aug. 2 launch of the Progress 26 cargo carrier and the Aug. 7 launch of Discovery to the station.

The final scheduled spacewalk task is cleaning the Earth-facing docking port, or Common Berthing Mechanism (CBM) of the Unity node. That is being done in preparation for the relocation of Pressurized Mating Adapter-3 (PMA-3), scheduled for late August.

The move is being made to clear the PMA-3's present position, on the starboard CBM of Unity, for a series of events that will culminate with the arrival of the Harmony node and its preparation to receive future space shuttles.

After cleanup Anderson and Yurchikhin will re-enter the Quest Airlock and conclude the spacewalk a little after noon.

The spacewalk is the first for Anderson and the third for Yurchikhin.