HOUSTON — Spacewalking cosmonauts Pavel Vinogradov and Roman Romanenko replaced a faulty docking aid outside the Russian segment of the International Space Station on April 19, a repair that sets the stage for the arrival of the European Space Agency’s ATV-4 resupply ship, the Albert Einstein, in mid-June.

The excursion got under way at 10:02 a.m. EDT, marking the first of eight planned U.S. and Russian spacewalks in the coming months, a level of extravehicular activity not seen since the assembly of the U.S. segment of the six-person orbiting lab drew to a close in mid-2011. The Russian spacewalk concluded at 4:41 p.m. EDT, after 6 hr., 38 min.

The long-term spacewalk agenda includes the installations of external data and solar-power cabling for Russia’s Nauka Multipurpose Laboratory Module, which is tentatively scheduled for launching atop a Proton rocket in December. The external activities will include preparations for the jettisoning of Russia’s Pirs module to clear a docking port for Nauka.

U.S. outings, planned for July, will likely embrace a range of maintenance tasks, including inspections of the big gearing mechanisms that rotate the outstretched solar arrays and the installation of recently delivered grapple bars on the inboard external radiators. There is a list of communications upgrades, camera replacements and insulation repairs awaiting attention as well.

The U.S.-led ISS mission management team slowed the pace of spacewalks in the post-assembly period to focus more of the station crew’s time on science experiments and engineering demonstrations.

Vinogradov and Romanenko replaced one of three laser reflectors on the Russian segment Zvezda service module, the parking spot for ATV-4, which is currently scheduled for a June 5 lift off from French Guiana. The reflectors are part of the range and range-rate measurements made by the European freighter’s automated docking system. Docking is planned for June 15.

The departure of Russia’s 49 Progress cargo capsule on April 15 exposed the work site. Russia’s Progress 51, which is scheduled to come and go from the same docking port ahead of the ATV-4, does not require the laser reflectors.

Vinogradov and Romanenko’s first task was the installation of the Obstanovka experiment, a two-antenna sensor for studies of plasma waves linked to interactions between the Sun and the Earth’s magnetic field as well as the plasma environment around the space station.

The spacewalkers also retrieved a Biorisk enclosure, part of an experiment installed outside their airlock in August 2011 to assess the effects of bacteria and fungi on spaceflight structures.

On the way into the airlock, the cosmonauts attempted to retrieve Vinoslivost, a materials-exposure experiment installed outside the Poisk module in February 2012. However, the 18 x 12-in. aluminum experiment panel slipped away from Vinogradov. Mission Control reports the 6.5-lb. panel moved away from the station on a retrograde trajectory and is not expected to pose a collision threat to the station.