The multi-billion-dollar instrument could get back to hunting for elusive antimatter and dark matter by midweek.
The spectrometer was never meant for hands-on repairs like this and was designed to last just three years.
The spectrometer was never meant to undergo space surgery but after 8 ½ years in orbit, its cooling system is almost dead.
A record-shattering NASA astronaut is set to return to Earth on Saturday, finishing a 288-day mission that put her over the top as the American who has spent the most cumulative amount of time in space.
It was the ninth spacewalk for NASA's Whitson, who already holds the American record for most spacewalks by a female astronaut, and the first for Fischer.