Space station crew steps out to catch cosmic rays

Yuri Onufrienko doing exterior work on his temporary home

By Richard Stenger
CNN Sci-Tech

(CNN) -- Two crewmembers of the international space station stepped outside their orbiting home on Friday to install a ham radio antenna, thruster deflectors and a handful of cool experiments.

Cosmonaut Yuri Onufrienko and astronaut Dan Bursch began the six-hour float from the Russian-built Pirs docking compartment shortly before 10:30 a.m. EST.

Astronaut Carl Walz, who took part in a spacewalk with Onufrienko last week, remained inside to assist his crewmates by operating the space station's robotic arm.

"The sunrise is beautiful," observed station skipper Onufrienko, minutes after venturing into space.

Working on the Russian service module, Onufrienko and Bursch will position the second of four antennas, which will allow them to make contact with amateur radio operators more than 200 miles (322 km) below on Earth; and place six thruster plume deflectors, which should protect the exterior from harmful fuel exhaust.

The deflectors are designed to block Alpha control thrusters from blasting onto parts of the station where spacewalkers must work.

Alpha crew, from left, Carl Walz, Daniel Bursch and Yuri Onufrienko

Station flight managers have expressed concern that residue might build up and cling to the suits of passing spacewalkers, posing a minor health risk when they return inside.

The retired Russian space station Mir experienced a similar residue problem, which cosmonauts resolved by installing deflectors.

The floating construction workers, both wearing Russian spacesuits, will also install a device that collects thruster contaminants for future study and a physics experiment designed to detect cosmic rays from the sun and beyond.

The measurements could help improve procedures to protect Alpha and its hardware from intense space radiation.

The spacewalk is the second of the crew, which began their five-month tour in December. The crew is the fourth to reside on Alpha. Walz and Bursch will conduct another one next month to prepare for an April space shuttle visit.

The spacewalk is the 33rd in support of space station assembly and the eighth conducted from Alpha, a multi-billion dollar partnership of the United States, Russia, Europe, Canada and Japan.

The spacewalk was Onufrienko's eighth and his second from Alpha. He conducted the others from the retired Russian space station Mir. The float was the first for Bursch.