New York, Jan 30 (IANS): US space agency NASA on Thursday announced that Indian-origin astronaut Sunita Williams, along with colleague Butch Wilmore, have begun their second spacewalk for maintenance and scientific experiments.

"Astronaut Suni Williams is conducting her ninth career spacewalk and Butch Wilmore is conducting his fifth career spacewalk today," NASA said in a blog post.

This is Williams' second spacewalk in 12 years.

The first took place earlier this month, where Williams undertook the spacewalk along with colleague Nick Hague.

The latest mission is expected to last around six and a half hours.

During the mission, the astronaut duo will remove a radio frequency group antenna assembly from the station’s truss, as per NASA.

They will also collect samples of surface material for analysis from the Destiny laboratory and the Quest airlock to see whether microorganisms may exist on the exterior of the orbital complex.

The two spacewalkers will swab sites outside the orbital outpost to collect samples of potential microbes for analysis.

The duo will also prepare a spare elbow joint for the Canadarm2 robotic arm.

Williams is crew member 1, wearing a suit with red stripes. Wilmore is spacewalk crew member 2, wearing an unmarked suit, NASA said.

Both Williams and Willmore, who became the first to ride the faulty Starliner by Boeing, are stuck in space since June last year.

While NASA is yet to announce a date to bring them back, President Donald Trump has urged SpaceX founder and billionaire Elon Musk to bring the astronauts back.

NASA replied that it is "working expeditiously" and will bring them back "as soon as it is practical".