Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer will exit the station's Quest airlock around 7:00 a.m. central time.
The astronauts also completed additional tasks to install a connector that will route data to a device called the Alpha Magnetic Spectrometer, fix insulation at the connecting point of the Japanese robotic arm, and install a protective shield on the Pressurised Mating Adapter-3, which will host a new global docking port for the arrival of commercial crew spacecraft.
Whitson already holds the record for most spacewalks by a female astronaut, according to NASA.
NASA chose to shorten the mission from the original six and a half hour plan, due to a glitch during earlier spacewalk preparations.
The airlock is equipped with two such umbilicals to provide cooling water, power and data while the astronauts are inside the station, preserving the suits' batteries for the actual EVA.
This is the 9th spacewalk for the veteran Whitson, the most of any female USA astronaut, and for Fischer, it's the very first. Find us on Facebook too!
The duo also planned to add shielding to Pressurized Mating Adapter No. 3, which was recently relocated from the Tranquility module to the Harmony module, where it will receive a new docking mechanism next year for future link-ups with commercial crew spaceships developed by Boeing and SpaceX.
NASA posted the spacewalk on its official Twitter account.
An issue with some gear inside the airlock ahead of the spacewalk forced mission managers to delay the start time and shorten the walk in space. That prompted the U.S. space agency to shorten the outing and assign the astronauts just one task. This was her ninth.
"It is a huge honor to work with all of you".
"Only because of legends like Peggy, and Jerry Ross and [Jim] Newman [who took that first station spacewalk] and the guys who started this, that made this possible", Fischer replied.
The first ISS spacewalk was performed by a pair of NASA astronauts back in 1998. "It's humbling to be a part of their legacy".