By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - A pair of Russian cosmonauts wrapped up a 6-1/2 hour spacewalk outside the International Space Station on Friday, the first of up to eight outings this year to install experiments and prepare the orbital outpost for a new module, officials said.
Flight engineers Pavel Vinogradov, 59, a veteran of seven spacewalks and Roman Romanenko, 41, a second-generation cosmonaut on his debut spacewalk, floated outside the station's airlock at 10:03 a.m. EDT/1403 GMT as the station soared 262 miles over the southern Pacific Ocean.
The primary purpose of the 6-1/2 hour excursion was to set up an experiment that monitors plasma waves in Earth's ionosphere, the outer layer of the planet's atmosphere that extends to about 370 miles into space.
Instruments on two boxes attached to handrails on the forward portion of the station's Zvezda module will measure low-frequency electromagnetic radiation, which, among other triggers, has been tied to earthquakes.
At the other end of the Zvezda module, Vinogradov and Romanenko replaced a faulty laser retroreflector that is part of an automated docking system used by the European Space Agency's cargo transports. The next ship is due to launch in June.
Before heading back into the station, the cosmonauts retrieved another experiment designed to study how microbes affect spacecraft structures and whether microbes are affected by solar activity.
The day's only glitch occurred just before the men wrapped up their six-hour, 38-minute spacewalk. Vinogradov lost his grip on a science experiment that was slated to be returned to Earth. It floated away in the gravity-free world of space.
The lost aluminum panel, which measured about 18 inches by 12 inches and weighed about 6.5 pounds (3 kg), had been anchored outside the station to test how various metals wear in the harsh space environment.
It floated off in the direction of the Zvezda module's solar arrays, but engineers determined it did not hit or threaten the station, NASA mission commentator Rob Navias said.
A second panel remains attached to the outside of the station and is slated to be retrieved on a later spacewalk.
"So all is not lost," Navias said. "It was a minor fly in the ointment to what has been a successful spaceflight up that moment."
While his crewmates worked outside, station commander Chris Hadfield, a Canadian astronaut, had the less glamorous task of replacing a pump separator in one of the station's toilets.
Two more spacewalks by Russian cosmonauts are scheduled for June to prepare for the arrival of a Russian laboratory and docking module that is to be launched in December.
The station, which is staffed by rotating crews of six astronauts and cosmonauts, is a $100 billion research outpost owned by the United States and Russia in partnership with Europe, Japan and Canada.
(Editing by Eric Walsh, Kevin Gray and Stacey Joyce)