Astronauts plug leak, finish fixing detector

CAPE CANAVERAL, Fla. — Spacewalking astronauts plugged a leak in a cosmic ray detector outside the International Space Station on Saturday, completing a series of complex repairs to give the instrument new life.

The $2 billion Alpha Magnetic Spectrometer could resume its hunt for elusive antimatter and dark matter by midweek.

Team members around the world expressed relief as NASA’s Andrew Morgan and Italy’s Luca Parmitano wrapped up work on the spectrometer. It was their fourth and final spacewalk since November to revive the instrument’s crippled cooling system.

“Congratulations the AMS pump system is now leak tight,” tweeted the European Organization for Nuclear Research, or CERN, which helps run the spectrometer.

Mission Control cautioned it was too soon to declare success with the space station’s premier science instrument, but noted “It still has a good heartbeat.”

Last month, Morgan and Parmitano installed new coolant pumps on the spectrometer. They went back out Saturday to check for any leaks in the plumbing.

Parmitano quickly discovered a leak in one of the eight coolant lines — the first one he tested — and tightened the fitting.

“Our day just got a little more challenging,” Mission

Control observed.

The line still leaked after a mandatory one-hour wait, and Parmitano tightened it again. Finally, success — the leak was gone.

“Let us all take a breath,” Mission Control urged. By then, the astronauts were already halfway into their six-hour spacewalk.

Mission Control acknowledged the leak added some unwanted “drama” to the spacewalk.

“Everybody’s hearts stopped,” Mission Control told the astronauts.

NASA This photo shows the view from NASA’s Andrew Morgan’s helmet cam as Italian astronaut Luca Parmitano works outside the space station during a spacewalk Saturday.