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Overnight spacewalk coming up for station cosmonauts BY JUSTIN RAY SPACEFLIGHT NOW Posted: July 26, 2010 
Playing repairmen and electricians outside the International Space Station, two Russian cosmonauts will conduct a spacewalk late tonight to replace a bad television camera and wire up the outpost's newest module. Expedition 24 crewmates Fyodor Yurchikhin and Mikhail Kornienko are scheduled to begin the six-hour EVA at 11:45 p.m. EDT.
After emerging from the Pirs module's side door, the duo will traverse along Zvezda's hull to the back-end of the station where an old TV camera is located. They'll remove and replace that camera, which is used for docking Europe's Automated Transfer Vehicle cargo delivery craft. "The ATV is an unmanned spacecraft that brings supplies to the station, and the video camera is used to monitor the approach as it comes in and docks on the aft-end of the Zvezda module. The video camera currently on-orbit has numerous bad pixels, resulting in degraded picture quality. So the new camera is expected to restore the system to its full functionality in time for next the ATV mission. ATV-2 is scheduled for December of this year," said Chris Edelen, Expedition 24 lead spacewalk flight director. As the spacewalk continues, Russian ground controllers will test the newly installed camera before the old one is thrown away. "After a ground checkout of the new camera, the old camera will be jettisoned. It will not be brought back inside the station due to concerns the insulation around the camera has degraded in the space environment and could result in fiberglass particles being shed inside the station resulting in a breathing hazard for the crew. So at the end of the EVA, we will jettison the old ATV video camera," said Edelen. The camera swapout job should be finished by 1 a.m. EDT. Then begins the cosmonauts' work of stringing umbilicals to the Rassvet module that arrived at the space station aboard shuttle Atlantis in May. Rassvet doubles as a science room and a docking compartment for Russian Soyuz crew capsules and Progress resupply ships. The module protrudes downward from the Earth-facing side of Zarya to afford approaching vehicles good clearance from other structures as the station expands. Although the compartment received its first Soyuz a month ago, Rassvet does not yet have the ability to support autopilot dockings using the Russian KURS system. This spacewalk will connect the wires needed for the automated rendezvous equipment. "First, a cable bundle will be run from the Zvezda and Zarya modules to connect the Rassvet to the Russian command and data handling computers. Then, a second set of cables will be run from Rassvet to Zarya to provide full functionality of the KURS docking system to allow automated vehicle dockings of Progress and Soyuz spacecraft to the docking port at the bottom of the Rassvet module," said Edelen. The chore starts with hooking up electrical connectors on the command and data handling cables to a panel on the ball-shaped forward area of Zvezda. The spacewalkers will unspool the umbilicals on Zarya's exterior, securing them onto handrails along the way and eventually mating the wires to Rassvet. The other reel holds the cabling to link the KURS antennas on Rassvet to the station's computers. Those short umbilicals will be run between Rassvet and Zarya. Russian flight controllers expect the wiring work should be wrapped up by 5:30 a.m. EDT. Assuming checkout of the new camera has gone well, the cosmonauts will untether the old camera from a temporary stowage spot outside the airlock and then toss it overboard in retrograde direction at about 0.5-meters per second (1.12 mph). "Since its drag deceleration is greater than the overall station, it will slowly lose altitude," said Edelen. "And after about 120 days, it is expected to re-enter the Earth's atmosphere and burn up." Experts determined it wasn't safe to bring the camera inside the space station for disposal aboard a departing cargo ship, meaning a spacewalk jettison was the best option. "The concern is that insulation could flake loose inside the cabin, resulting in fibers that the crew could breathe in. Once that determination was made, then it was clear jettisoning was the right thing to do," said Edelen. Yurchikhin and Kornienko will ingress the airlock and close the hatchway, marking the official conclusion of the planned EVA around 5:45 a.m. EDT. It'll be the 25th Russian-based excursion from the station to date. Live television of the spacewalk is expected to be limited and the cosmonauts won't be wearing helmet-mounted TV cameras.
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VIDEO:
STEP-BY-STEP PREVIEW OF SPACEWALK 