Moscow, April 20 : Russian cosmonauts Oleg Artemyev and Denis Matveyev completed their spacewalk after completing work in the outer space and have returned to the Russian segment of the International Space Station (ISS), Russia's state space corporation Roscosmos said. The astronauts opened the hatch of the Poisk module at 18:00 Moscow time (1500 GMT) on Tuesday, Roscosmos said on Tuesday, Xinhua news agency reported. They spent a total of six hours and 37 minutes in the outer space, and completed the first phase that aimed at preparing the European Robotic Arm remote manipulator system for operation on the Russian segment of the ISS. Roscosmos cosmonaut Sergei Korsakov, who was the third member of the expedition, controlled the manipulator from the internal control panel of the Nauka multi-purpose laboratory module, Roscosmos said. The agency said the next spacewalk is scheduled for April 28. /IANS