SpaceX's second crew launch is slated for this weekend and this time there are twice as many astronauts as the test flight earlier this year, and the mission will last for a full six months.The three Americans and one Japanese astronaut arrived at Kennedy Space Center from Houston earlier this week. They're scheduled to rocket away Saturday night to the International Space Station. For NASA, it marks the long-awaited start of regular crew rotations, with private companies providing the lifts.These are the four astronauts that will be making the trip: Mike HopkinsMichael S. Hopkins was selected by NASA as an astronaut in 2009. The mission will be the Missouri native’s second long duration mission aboard the International Space Station.Previously, Hopkins was member of the Expedition 37/38 crew and has logged 166 days in space. He launched from the Baikonur Cosmodrome in Kazakhstan to the International Space Station in September 2013. During his stay aboard the station, he conducted two spacewalks totaling 12 hours and 58 minutes to change out a degraded pump module.He holds a Bachelor of Science in Aerospace Engineering from the University of Illinois, where he was captain of the school’s football team in 1991, and a Master of Science in Aerospace Engineering from Stanford University.He and his wife, Julie, have two sons. Shannon WalkerShannon Walker was selected by NASA to be an astronaut in 2004. She holds a Bachelor of Arts degree in Physics, a Master of Science and a Doctorate of Philosophy in Space Physics from Rice University.Walker began her professional career at the Johnson Space Center (JSC) in 1987 as a Robotics Flight Controller for the Space Shuttle Program. This mission will be her second extended stay at the International Space Station. In 2010, she served as Flight Engineer for Expedition 24/25, a long-duration mission aboard the International Space Station that lasted 163 days.She is married to NASA astronaut Andy Thomas. Victor GloverVictor J. Glover, Jr. was selected as an astronaut in 2013 while serving as a Legislative Fellow in the United States Senate.The California native holds a Bachelor of Science in General Engineering, a Master of Science in Flight Test Engineering, a Master of Science in Systems Engineering and a Master of Military Operational Art and Science. Glover is a Naval Aviator and was a test pilot in the F/A‐18 Hornet, Super Hornet and EA‐18G Growler.He and his wife Dionna have four children. Soichi NoguchiSoichi Noguchi was selected as an astronaut candidate by the National Space Development Agency of Japan (NASDA, currently Japan Aerospace Exploration Agency) in May 1996 and joined NASDA in June 1996. He completed two years of Astronaut Candidate Training at NASA's Johnson Space Center, and was qualified for flight assignments aboard the space shuttle as a Mission Specialist in April 1998.He previously flew the STS-114 mission by the space shuttle Discovery in 2005, and in 2010 he was launched to the ISS aboard the Soyuz TMA-17 from the Baikonur Cosmodrome in Kazakhstan. He spent 161 days aboard the ISS as a Flight Engineer for the Expedition 22/23 Mission, and returned to Earth in June 2010.