Official ring-bound NASA checklist entitled "(July 26 Launch), Apollo 15, CSM 112, Change A, CSM G&C Checklist" used by Russell A. Larson of MIT's Charles Stark Draper Laboratory, prepared by the Manned Spacecraft Center's Guidance & Control Systems Procedures Branch, 6 x 8, July 14, 1971, marked on the front cover in felt tip, "#15, MIT/CSDL, R. Larson." The abbreviated checklist contains sections for "CMC General," "Alarm Codes," "EXT Verbs," "G&C Systems Management," "Navigation," "Prethrust (P30's & 70's)," "△V vs △0 Long," "P37 Block Data," "Thrusting (P40's)," "Prop Cons," "SPS vs RCS Criteria," "GIMB ANGS vs WT," "Alignments (P50's)," "Star Charts," "Initialization Procedures," "PTC/ORB Rate," "Erasable Load Update," and "Planet Vectors." In very good condition, with heavy wear to the cover and tabs. Russ Larson worked as a program engineer and astronaut liaison at MIT's Instrumentation Lab, where he was involved in programming the Lunar Module's Apollo Guidance Computer; he worked directly with the astronaut crews, training them on the simulators and guidance system.
The G&C Checklist provides the crew with a quick reference to the actions needed to operate the Command Module Primary Guidance, Navigation and Control System (PGNCS). The PGNCS provides the spacecraft with an onboard means of measuring orientation, position, velocity, and trajectory, in addition to providing automatic control over parts of the spacecraft via the Command Module Computer. The PGNCS is a tightly interwoven system that consists of three main subsystems: the Inertial Subsystem (ISS), the Computer Subsystem (CSS), and the Optics Subsystem (OSS). The ISS measures information on the spacecraft orientation and velocity by providing a stable platform of reference, the Inertial Measuring Unit (IMU). The CSS applies this information to its current knowledge of the spacecraft's position and calculates a new estimate, called the state-vector; the CSS also behaves as an integrated auto-pilot. The OSS consists of a sextant and telescope for crew navigation sightings in aligning the IMU.
