Spacewalkers complete ISS repairs

Astronaut Peggy Whitson on Tuesday repaired a critical International Space Station system during a nearly three-hour spacewalk that moved her into second place on NASA’s career list for most spacewalking time.

Joined by NASA’s Jack Fischer, Whitson swapped out a computer relay box that had failed on Saturday.

Known as a multiplexer-demultiplexer, or MDM, the box helped control the station’s solar arrays, radiators and cooling loops, among other systems.

A backup box remained in good shape, but NASA on Sunday ordered the unplanned "contingency" spacewalk to minimize the risk of a backup failure.

Whitson, the 57-year-old commander of the station’s five-person Expedition 51 crew, unbolted the failed relay box and installed a spare as the football field-length research complex orbited 250 miles above the planet.

Trump calls ISS to congratulate Whitson on NASA record

Fischer, meanwhile, installed wireless communications antennas on the station’s Destiny lab module.

The two-hour, 46-minute spacewalk added to Whitson’s record-breaking resume.

Last month, she set a new NASA mark for most cumulative days in space with more than 534 days, an achievement celebrated with a call from President Donald Trump.

Tuesday’s spacewalk was her 10th, tying the most by a NASA astronaut. In the course of it she passed two retired NASA colleagues, Jerry Ross and John Grunsfeld, for most time performing spacewalks.

Whitson’s career total of 60 hours and 21 minutes of “extra-vehicular activity,” or EVA, trails NASA’s Michael Lopez-Alegria by more than seven hours and Russian cosmonaut Anatoly Solovyev — the all-time leader — by about 20 hours.

No more spacewalks are scheduled before Whitson's planned return to Earth in September with Fischer, a 43-year-old flight engineer who completed his second spacewalk Tuesday.

Contact Dean at 321-242-3668 orjdean@floridatoday.com. And follow on Twitter at@flatoday_jdeanand on Facebook atfacebook.com/jamesdeanspace.