Shannon Walker is an American physicist and NASA astronaut selected in 2004. She launched on her first mission on June 25th, 2010 onboard Soyuz TMA-19 and has currently logged 163 days in space over one long-duration mission to the International Space Station. She is scheduled to return to the ISS for a second long-duration flight in late 2020 onboard USCV-1, the first operational flight of SpaceX's Crew Dragon spacecraft.