A Comprehensive Digital Simulation Fortheverification of Apollo Flight Software

The flight software for the on-board Apollo Primary Guidance, Navigation and Control System provides attitude and trajectory control, recursive navigation, targetting, inertial subsystem moding and alignment, prelaunch checkout, crew interaction and telemetry processing for each spacecraft. To develop and flightqualify this complex software package, an all-digital, instruction-by-instruction simulation of the on-board computer’s operation has been implemented, along with a powerful set of software diagnostics. This computer simulation is coupled to a comprehensive digital simulation of the computer’s environment, including the sensor systems. The simulator is described and design considerations, advantages and limitations are discussed. A simulated powered flight maneuver is compared with telemetry obtained during the actual performance of the maneuver in flight. The telemetry data revealed a potentially significant effect which had not been modeled. As a result the environment simulation was upgraded to more accurately represent the flight environment. By: F.K. Glick S.R. Femino January 1970