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CAPE CANAVERAL (CBSMiami/AP) — American astronauts performed an emergency spacewalk Tuesday to make a critical repair to the International Space Station.

Over the weekend, one of the station’s two data relay boxes abruptly stopped working. Even though a second unit managed the data load just fine, NASA scrambled to put together a spacewalk in order to restore backup capability.

The system is vital for operating the station’s solar panels, radiators, and robotic equipment. The failed data-relay box was just installed in March.

While Whitson focuses on the 250-mile-high replacement job, Fischer will install a pair of wireless communication antennas that should have been hooked up earlier this month. That May 12th spacewalk was cut short by leaking station equipment.

Whitson, who has now performed 10 spacewalks, has tied the record for most spacewalks by an American.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)