Piers J. Sellers, a climate scientist who flew to the International Space Station three times in NASA’s shuttle program, became a leading figure in the agency’s scientific research initiatives and continued while terminally ill to devote himself to the challenges posed by global warming, died on Friday in Houston. He was 61.

NASA said the cause was pancreatic cancer.

Mr. Sellers, who was born and educated in England, had been deputy director of sciences and exploration at NASA’s Goddard Space Flight Center in Greenbelt, Md., since 2011.

He flew to the space station on the space shuttle Atlantis in 2002 and 2010 and on Discovery in 2006 to perform research and carry out repair work, and made a total of six spacewalks.

“I’ve spent much of my professional life thinking about the science of climate change,” Mr. Sellers wrote in The New York Times in January, shortly after learning he had cancer. “Now that my personal horizon has been steeply foreshortened, I was forced to decide how to spend my remaining time.”