HOUSTON — Spacewalking cosmonauts Gennady Padalka and Yuri Malenchenko prepped the outside of the International Space Station on Aug. 20 for the anticipated 2013 arrival of Russia’s Nauka Multi-purpose Laboratory Module (MLM) as they multitasked outside the orbital lab’s Russian segment.

The scheduled 6.5-hr. excursion, which began at 11:37 a.m. EDT — an hour late because of a small airlock leak — will be followed by a U.S. excursion on Aug. 30, the first spacewalk orchestrated by NASA in more than a year.

Padalka and Malenchenko uprooted Strela-2, a hand-cranked cargo crane, from the Pirs docking module and moved the mechanism to Zarya, the 14-year-old station’s cornerstone module. The transfer prepared the 11-year-old Pirs compartment for future unberthing to open a docking port for Russia’s 44,000-lb. MLM.

Nauka, accompanied by the European Robot Arm, is expected to be launched next year.

Strela-1, a second crane used to move bulky equipment and even spacewalkers around the outside the station, was transferred from Pirs to the Zvezda service module during the most recent previous Russian spacewalk on Feb. 16. The task became so taxing for less-experienced spacewalkers Oleg Kononenko and Anton Shkaplerov that they were forced to defer the installation of five micrometeoroid debris panels on Zvezda, the Russian segment’s nerve center.

Padalka and Malenchenko skipped scheduled rest periods to begin latching down panels intended to lower the risk of a potentially catastrophic penetration by an impact from man-made debris or a micrometeoroid strike.

The U.S.-led station partnership intends to extend operations of the six-person orbiting science laboratory until 2020 and perhaps beyond.

The cosmonauts also hand-launched a small satellite, “Sfera,” aft and toward the Earth. The passive, 20-lb. satellite will be tracked by Russian ground stations for about three months to model the behavior of orbital debris.

The spacewalk’s start was slowed by an hour when airlock pressure checks indicated a small leak in the transfer compartment separating the Poisk and Pirs modules. Padalka and Malenchenko were using Pirs as their airlock. The leak, eventually traced to an internal valve, was stopped after a round of troubleshooting by Russia’s Mission Control.

The Aug. 30 U.S. spacewalk will pair NASA’s Sunita Williams and Japanese astronaut Akihiko Hoshide for the replacement of the Main Bus Switching Unit (MBSU) No. 1., one of four U.S. segment external circuit breaker boxes. The MBSU experienced a partial failure in October 2011.

The relay functions, but the telemetry that provides ground control teams with insight into the MBSU itself has ceased.