Spacewalkers complete overnight excursion
BY JUSTIN RAY
Posted: July 27, 2010
Two Russian cosmonauts working outside the International Space Station in the wee hours this morning wired up the autopilot homing beacon on the newest docking compartment and threw away a broken television camera on the outpost's back-end.
The excursion began at 12:11 a.m, lasted six hours, 42 minutes and concluded when the hatchway was resealed at 6:53 a.m. EDT.
It was the fourth spacewalk in Yurchikhin's three-mission career and the first for rookie Kornienko.
After emerging from Pirs, the duo traversed along Zvezda's hull to the station's rear docking port to remove and replace an old TV camera needed for receiving European 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," said Chris Edelen, Expedition 24 lead spacewalk flight director.
The camera's picture quality had degraded because of numerous bad pixels, Edelen explained, requiring the changeout to fix the system before the next ATV arrives for docking in December.
The new camera was plugged in and bolted down less than an hour into the EVA.
"We have the confirmation that all electrical circuitry is operating nominally," Russian mission control radioed the spacewalkers. "We'll just have to check the image, but the camera itself is alive."
"That's great news," one of the spacewalkers replied.
The cosmonauts then started tackling the laborious work of stringing umbilicals to the new Rassvet module that shuttle Atlantis attached to the space station in May.
"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," Edelen previewed before the EVA. "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."
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 flown manually by Yurchikhin a month ago, Rassvet needed today's spacewalk to hook up the automated rendezvous equipment for autopilot dockings using the Russian KURS system.
While gathering equipment at the airlock to start the work, something resembling a handle got away from the spacewalkers just before 1:45 a.m. EDT. External TV cameras also spotted a few other unknown objects floating away later in the day.
The cosmonauts began the wiring of Rassvet by plugging in command-and-control cables to a panel on the ball-shaped forward area of Zvezda. The spacewalkers then unspooled the umbilicals on Zarya's exterior, securing them onto handrails along the way and eventually mating the cabling to Rassvet.
The other reel held the wiring to link the KURS antennas on Rassvet to the station's computers. Those short umbilicals were run between Rassvet and Zarya.
One connector initially showed signs of a problem and Yurchikhin double-checked it was properly seated.
"Are you positive that all the connectors have been mated?" a flight controller radioed.
"Well, I do have fairly good assurance," Yurchikhin responded. "Are there any issues?"
"You know, for some reason, when we did the first activation we received nothing," the controller said.
As the spacewalk was continuing, Russian ground controllers were testing the newly installed TV camera before giving the cosmonauts permission to toss the old one away in the EVA's final minutes.
Experts determined it the safest option for disposing of the camera was throwing it overboard instead of carrying it indoors for packing in the trash.
"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," said Edelen.
"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."
Perched in a foot restraint at the Strela crane, Yurchikhin threw the camera in a retrograde direction behind and below the space station at 6:40 a.m. EDT.
"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."
Yurchikhin and Kornienko ingressed the airlock and closed the hatchway, marking the official conclusion of the EVA.
This was the 147th spacewalk devoted to station assembly and maintenance and the 11th so far this year. Total space station EVA time since construction began in 1998 now stands at 921 hours and 35 minutes.
The next EVA is planned for August 5 when NASA astronauts Doug Wheelock and Tracy Caldwell-Dyson perform a spacewalk from the Quest airlock module. They'll install an operating base on the Zarya module for the station's robotic arm and lay power lines outside the Unity node for use by the Leonardo storage module when it's delivered for permanent attachment during the November shuttle mission.