Two Russian cosmonauts on board the International Space Station (ISS) have successfully completed a spacewalk, Russia’s Mission Control Center reported on Saturday.

During their more than six-and-a-half-hour extra-vehicular activity, flight engineers Pavel Vinogradov and Roman Romanenko carried out a number of maintenance tasks and returned to the space station.

The spacewalk lasted longer than the initially planned six hours because during the installation of the Obstanovka experiment package on the station’s Zvezda service module, one unit failed to switch on. Later the problem was solved.

Obstanovka will study plasma waves and the effect of space weather on the Earth’s ionosphere.

The cosmonauts also retrieved the second container from the Biorisk experiment, which studied the effect of microbes on spacecraft structures, and replaced a reflector device that will facilitate the docking of the European Space Agency’s Automated Transfer Vehicle-4 when it arrives at the orbital outpost in June.

The cosmonauts did not fulfill an additional task, to retrieve a section of the Vynoslivost experiment apparatus, as the section was lost.

Space flight veteran Vinogradov had already logged a total of 31 hours 41 minutes in open space in his previous six spacewalks, while Romanenko ventured outside the ISS for the first time in his career.