This manual was prepared to provide the astronaut with a single source reference as to the characteristics and functions of the SA-503 launch vehicle and the AS-503 manned flight mission. A revision to the manual, incorporating the latest released data on the vehicle and mission, will be released approximately 30 days prior to the scheduled launch date. The manual provides general mission and performance data, emergency detection system information, a description of each stage and the IU, and a general discussion of ground support facilities, equipment, and mission control. A bibliography identifies additional references if a more comprehensive study is desired.