Washington, Nov 7 (IANS): NASA astronauts Scott Kelly and Kjell Lindgren on the International Space Station (ISS) ended their seven hour and 48 minute spacewalk on Friday, successfully completing some key tasks in the outer space.

The astronauts restored the ammonia cooling system to its original configuration and also returned ammonia to the desired levels in both the prime and back-up systems, NASA said in a statement.

In a minor departure from the planned tasks, the astronauts ran out of time to cinch and cover a spare radiator known as the Trailing Thermal Control Radiator.

The radiator, which Lindgren retracted earlier in the spacewalk, was fully redeployed and locked into place in a dormant state.

The radiator had been deployed during a November 2012 spacewalk by astronauts Sunita Williams and Aki Hoshide as they tried to isolate a leak in the truss’ cooling supply by re-plumbing the system to the backup radiator.

The leak persisted and was subsequently traced to a different component that was replaced during a spacewalk in May 2013.

The spacewalk was the second for both astronauts and the 190th in support of assembly and maintenance of the orbiting laboratory.

Crew members have now spent a total of 1,192 hours and 4 minutes working outside the orbital laboratory.