ISS astronauts take spacewalk to replace Canadarm2 part

Spacewalking astronauts gavetheInternational Space Station's big robot arm a new hand Thursday.

NASA Commander Randy Bresnik and Mark Vande Heifloated out around 8 a.m. ET and stayed out for nearly seven hoursto replace one of two Latching EndEffectors(LEE) on the Canadarm2.It's the first of three NASA spacewalks planned over the next two weeks.

The latching mechanism on one end of the 17.7-metre Canadarm2 malfunctioned in August. It had to be replaced before the arrival of an OrbitalATK supply ship in November.

Hustling through their work, the spacewalkers unbolted the old mechanism and promptly installed the spare. Initial testing by ground controllers indicated success.

"All right, gentlemen, we show a good arm," Mission Control radioed.

"That is great news, Houston," Bresnik said. "Much rejoicing."

Canadarm2 in use for 16 years

Canadarm2has two identicalLEEsthat areused to grab visiting spacecraft, as well asprovide data and telemetry to the rest of the Canadian-built Mobile Base System.This bundle of latches more than a metre long also attaches to grapple fixtures outside the space station. That way, the arm can move likean inchworm across the sprawling structure.

The Canadian-built arm has been in orbit for 16 years. The two latchingmechanisms, one on each end of the arm, have been used nearly 400times, and engineersattribute the recent trouble to wear and tear.

The latching mechanism on the opposite end will be replaced earlynext year.

It was the first spacewalk for Vande Hei, a rookie astronaut whoarrived at the orbiting outpost a few weeks ago.

"Congratulations, my friend, on becoming the 221st human to exitin your own personal spacecraft into the void of space," saidBresnik, a veteran spacewalker.

As the duo worked, they marvelled over the views of Earth belowand the full moon above.They'll venture back out on Tuesday tolubricate the new mechanism and do other chores.

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