Space Walk Underway For Final Fix Of International Space Station Device

"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."

"NASA flight engineer Andrew Morgan and the commander of the space station's Expedition 61, Luca Parmitano of the European Space Agency, are doing leak checks on their installation of a new cooling system meant to extend the lifespan of the externally-attached Alpha Magnetic Spectrometer dark matter and antimatter detector."

"They are being assisted by two other Expedition 61 crew members, NASA flight engineers Jessica Meir and Christina Koch, who are operating a Canadarm2 robotic arm capable of fine-tuned maneuvers."

"The AMS, as the cosmic ray detector is known, was installed about nine years ago on the spacecraft and was designed to function for only three years. It was not meant to be serviced in flight."