(CNN) -- Astronaut Scott Carpenter, the second American to orbit Earth, has died, NASA said on Thursday. He was 88.

"We, the whole NASA family, are mourning with Scott's family. We have lost a true pioneer. I shall long remember him not only for his smarts and courage but his incredible humor. He kept us all grounded," said NASA Administrator Charlie Bolden. "We will miss him greatly."

Carpenter was one of the Mercury Seven astronauts chosen by NASA. He was a backup pilot for John Glenn in the preparation for America's first manned orbital space flight in February 1962.

Carpenter flew the second American manned orbital flight in May of that year.

He was born in Boulder, Colorado.