Peggy Whitson (born 1960), American astronaut and biochemist. Before serving as an astronaut, Whitson worked as a Research Biochemist in the Biomedical Operations and Research Branch at NASA?檚 Johnson Space Center, Houston, Texas, USA. In 1996, she was selected as an astronaut candidate. Whitson was a flight engineer on her first mission to space on Expedition 5. In 2016, Whitson became the first female commander of the International Space Station (ISS) on Expedition 16. On her final spaceflight in 2017, she served as a commander of the ISS on Expedition 51. Whitson retired in 2018 and she still holds the American record for the longest cumulative days in space at 665 days. Photographed on 28th November 2001.