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CAPE CANAVERAL (CBSMiami/AP) —  NASA Astronaut Scott Kelly took his first spacewalk Wednesday ahead of setting a new U.S. flight record.

Kelly and Kjell Lindgren floated out of the International Space Station for a bit of maintenance work. Their to-do list included greasing the station’s big robot arm, routing cables, removing insulation from an electronic switching unit and covering an antimatter and dark matter detector.

Kelly’s identical twin, Mark, a retired astronaut, urged his brother to be careful but still have fun outside.

“Don’t forget to take a good selfie!” Mark said via Twitter. He commanded the mission that delivered the antimatter-hunting Alpha Magnetic Spectrometer in 2011; it was the next-to-last shuttle flight. Scientists want the device covered with a thermal blanket to keep it cooler and prolong its life.

The spacewalk was held up slightly after Lindgren inadvertently switched on the water flow in his suit too soon. Mission Control wanted to make certain the suit would be safe, before giving the all-clear. Water is needed to cool the suit; a malfunction two years ago caused a spacewalker’s helmet to flood and almost drowned him.

A second spacewalk — to further whittle down a backlog of station chores — will be conducted Nov. 6th by the same two men.

In the wee hours of Thursday morning, just after midnight Eastern Time, Kelly will break the American record for NASA’s longest single space shot. That 215-day record — more than seven months — was set in 2007.

Kelly has been living at the orbiting lab since March. He’ll remain there until March 2016. Russian Mikhail Kornienko is also part of the one-year experiment in preparation for eventual Mars expeditions, although it will fall shy of the 14-month world record held by a fellow cosmonaut, Valery Polyakov, who lived on Russia’s old Mir space station in 1994 and 1995.

Former space station resident Michael Lopez-Alegria has been counting down the days until Kelly surpasses his record of 215 days, eight hours and 22 minutes. “The countdown clock is ticking,” he said last week in a tweet.

President Barack Obama already has relayed congratulations. In a phone call last week, Obama told Kelly his feat is “nothing to sneeze at.” Kelly assured the president that even though he feels like he’s been in orbit a long time and still has a long way to go, “it shouldn’t be a problem getting to the end with enough energy and enthusiasm to complete the job.”

“Records are made to be broken,” Kelly noted.

Earlier this month, Kelly broke the U.S. record for the most accumulative time in space: 383 days and counting over four missions. It will total 522 days by the time he returns to Earth, well short of the Russian record.

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