The Apollo program began as part of the National Aeronautics and Space Administration's (NASA) long-term plan for lunar exploration. Apollo 11 (16 July - 24 July 1969) was the fourth crewed flight of the program and the first crewed landing on the moon. The mission objectives were to "perform a manned lunar landing and return; conduct scientific experiments; [and] collect soil and rock samples for return to Earth." The three-person crew, Neil A. Armstrong (Commander), Michael Collins (Command Module Pilot), and Edward E. Aldrin, Jr. (Lunar Module Pilot) accomplished all mission objectives. Armstrong and Aldrin landed on the moon in the Sea of Tranquility at 3:17pm on July 20, 1969, and, six hours later, Armstrong became the first person to set foot on the moon at 9:55pm. The two men spent two hours outside the lunar module and gathered 21kg of lunar samples before lifting off at 12:54am July 21, 1969, to rendezvous with Collins.