In this image take from NASA video, astronauts Christina Koch, left, moves away as Jessica Meir, right, exits a hatch as they prepare to install batteries for the International Space Station's solar power grid during a space walk, Monday, Jan. 20. In this image take from NASA video, astronauts Christina Koch, left, moves away as Jessica Meir, right, exits a hatch as they prepare to install batteries for the International Space Station's solar power grid during a space walk, Monday, Jan. 20. Two astronauts aboard the International Space Station began their fourth and final space walk early Saturday to finish a series of repairs aimed at extending the functioning of a cosmic ray detector attached to the spacecraft. The planned six-and-a-half-hour foray outside the space capsule began shortly after 7:00 a.m. ET and was being shown in a live video feed from NASA.