Peggy Annette Whitson (born 9 February 1960) is an American biochemistry researcher and a NASA astronaut. Her first space mission was in 2002, with an extended stay aboard the International Space Station as a member of Expedition 5. Her second mission launched October 10, 2007, as the first female commander of the ISS with Expedition 16. With her two long-duration stays abroad the ISS, Whitson is NASA's most experienced astronaut, with just over 376 days in space. This also places her twentieth among all space flyers.