The two men spent about six hours outside
Russian cosmonauts have completed a spacewalk to remove an explosive bolt from a Soyuz capsule attached to the International Space Station (ISS).
Officials believe the recent off-target returns to Earth made by Soyuz craft could have been the result of faulty pyrobolts on the vehicles.
Sergei Volkov and Oleg Kononenko spent six hours outside the station carefully removing the device.
It was put inside a blast-proof box and will be sent for examination on Earth.
Pyrobolts are used to separate the Soyuz crew compartment from its propulsion module prior to re-entry. If the bolts fail, the descent capsule will not adopt the correct orientation to go through the atmosphere.
April's re-entry was again off-target
This can lead to unshielded surfaces being exposed to excessive heating.
Soyuz landings in October last year and April this year both underwent what are termed ballistic entries, resulting in high-G rides for the crews and landings that were hundreds of kilometres short of the planned recovery area on the Kazakh steppe.
Commander Volkov and Flight Engineer Kononenko had a particular interest in their job: the Soyuz TMA-12 spacecraft on which they were working is the one that will return them to Earth in three months' time.
During the spacewalk, US astronaut Greg Chamitoff sat inside the Soyuz in case an emergency required the two Russians to join him in the capsule (whilst attached to the ISS, the Soyuz acts as the station's "lifeboat").