U.S. astronauts conclude 7-hour spacewalk, 250 miles above Earth

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Scott Kelly tries on his spacesuit at the International Space Station ahead of his spacewalk Wednesday..

Two U.S. astronauts have completed a seven-hour spacewalk to carry out maintenance on the International Space Station, 250 miles above Earth.

Expedition 45 commander Scott Kelly and flight engineer Kjell Lindgren returned to the space station’s airlock where repressurization began about 3:19 p.m ET, marking the official end of the spacewalk, NASA said in a live broadcast of the event.

The spacewalk took seven hours and 16 minutes, about 45 minutes longer than NASA had predicted.

The astronauts were tasked with “station upgrades and maintenance tasks, including installing a thermal cover on the Alpha Magnetic Spectrometer, which is a state-of-the-art particle physics detector that has been attached to the station since 2011,” the space agency said.

The thermal cover was successfully fitted about 2½ hours into the spacewalk.

It was the first spacewalk for both astronauts.

The astronauts will carry out a second spacewalk November 6, two days after the 15-year anniversary of continuous human presence aboard the space station.

An international crew of six people live in the station, which orbits Earth every 90 minutes.

In a tweet, NASA astronaut Douglas H. Wheelock explained that the frequent orbits meant half of Wednesday’s spacewalk took place in darkness, with a sunrise or sunset every 45 minutes.

342 days in space

Kelly arrived at the station in May. He plans to spend 342 days there — the longest stretch in space for any U.S. astronaut.

Kelly’s mission will allow scientists to study how the human body responds to long-duration space flights. On Earth, scientists will perform parallel studies on Kelly’s identical twin brother, retired astronaut Mark Kelly.

Mark Kelly is the husband of former U.S. Rep. Gabrielle Giffords of Arizona, who left office after being wounded in a January 2011 assassination attempt.