Cape Canaveral, Fla. ? Two spacewalking astronauts improved the parking situation at the international space station on Tuesday, putting up the latest devices for guiding in a brand new line of cargo ships.

Russian Gennady Padalka and American Mike Fincke installed laser reflectors and antennas for the cargo carrier that’s due to arrive in another year, and hung out fresh science experiments in place of old ones.

It was their third spacewalk in just over a month, This time, they zipped through the work and finished in a snappy 4 1/2 hours.

At the end of June, the men had to make their way across the entire space station to reach a fried circuit breaker that needed to be replaced on the U.S. side of the orbiting outpost. It took two spacewalks to accomplish the job; a spacesuit problem cut short their first foray.

Tuesday’s tasks were on the Russian side of the 220-mile-high complex, just a short hop from the main exit, making for a much easier endeavor.

Padalka and Fincke left the station empty during their spacewalk. In what is becoming routine, although not preferred, flight controllers in Moscow and Houston kept watch over the vacated outpost.

Midway through the excursion, however, communication was lost.

A NASA official said the main U.S. radio link was inadvertently turned off by flight controllers in a power-conserving effort involving other equipment, which was prompted by the expected brief shutdown of station steering. Controllers eventually activated the backup radio line, sending commands through Russian ground stations, then got the main system working again.

To prepare for the arrival of a European supply ship that has been in the pipeline for years and is running late, Padalka and Fincke replaced outdated laser reflectors with newer models. The six old reflectors were built in the late 1990s and have been in orbit since 2000, and the new ones will make it easier for the unmanned ships to close in and pull up, NASA officials said.

Expedition 9 Commander Gennady Padalka, facing camera on left, works on the exterior of the Zvezda module during a televised spacewalk. Padalka and astronaut Mike Fincke, on right with back to camera, installed reflectors and communications equipment on the exterior of the International Space Station on Tuesday.

In addition, a TV camera needed for the docking of the new line of supply ships already is broken, and the spacewalkers had to disconnect its electrical cable. The camera will be replaced by a future crew.

The European Space Agency’s cargo ship — scheduled for a fall 2005 launch — will supplement the U.S. and Russian vessels that fly to the space station. The grounding of NASA’s shuttles following the Columbia accident highlighted the need for a more diversified fleet.

Padalka and Fincke — more than halfway through a six-month mission — will venture out once more, early next month.