Two US astronauts aboard the International Space Station successfully completed a spacewalk Thursday to make repairs and install new equipment.

"NASA astronauts completed all planned tasks + a few extra," the US space agency said on Twitter.

Americans Jeff Williams, 58, and Kate Rubins, 37, completed their mission at 1841 GMT after six hours and 48 minutes in space.

It was their first time in space in nearly two weeks. At that time, they attached an international docking adaptor in anticipation of increased private spaceship traffic.

This time, Williams and Rubins retracted one of the thermal radiators outside the space station. Astronauts unsuccessfully tried to push it back into position last year.

They also "installed two enhanced high definition cameras on the station's truss and tightened bolts on a joint that enables one of the station's solar arrays to rotate," NASA said.

The cameras will be used to monitor spaceships transporting freight and astronauts.

The mission was the 195th spacewalk undertaken to build and maintain the ISS.

It was the fifth spacewalk for Williams, a veteran astronaut who on August 19 surpassed US astronaut Scott Kelly's record for the most cumulative days in space for an American.

Kelly has 520 days in space over his career.

Williams will have 534 days in space by the time he wraps up his stint at the ISS and returns to Earth next week.

It was the second spacewalk for Rubins. She is the 12th woman to walk in space.

In their August 19 spacewalk, Williams and Rubins installed a special parking spot on the ISS and connected power and data cables for the docking adaptor.

The fittings will enable the space station to share power and data with visiting spaceships.

NASA describes the docking adaptor as a "metaphorical gateway to a future" that will allow a new generation of US spacecraft -- the first since the space shuttle program ended in 2011 -- to carry astronauts to the space station.

The second docking adaptor is expected to be launched in late 2017.

The adaptors will work with Boeing's CST-100 Starliner and SpaceX's Crew Dragon, two spaceships under construction that are planned to ferry astronauts to the space station.