CAPE CANAVERAL, Fla. (AP) — Spacewalking astronauts installed new pumps on a cosmic ray detector outside the International Space Station on Monday in a bid to extend its scientific life.

It was the third spacewalk in nearly three weeks for Italy's Luca Parmitano and NASA's Andrew Morgan. One more spacewalk remains before NASA can declare the Alpha Magnetic Spectrometer successfully repaired.

The $2 billion spectrometer has been up there hunting for antimatter and dark matter for 8 ½ years, longer than anticipated. Without four new pumps for cooling, the device would be crippled and, ultimately...