Expedition 51 was a mission to the International Space Station (ISS) that began in December 2016 and ended in April 2017. It was the 51st expedition to the ISS, and was comprised of six crew members from NASA, the Russian Federal Space Agency, and the European Space Agency. The expedition was launched aboard a Soyuz spacecraft, and the crew members spent approximately four months living and working on the ISS. During their time on the station, the crew members conducted a variety of scientific experiments, performed maintenance and repair work, and welcomed several visiting spacecraft, including the SpaceX Dragon and Orbital ATK Cygnus. The crew of Expedition 51 included NASA astronaut Peggy Whitson, Russian cosmonauts Oleg Novitskiy and Fyodor Yurchikhin, and European Space Agency astronaut Thomas Pesquet.