Titan IIIC preflight and postflight trajectory analyses

Abstract

The Titan IIIC launch vehicle uses a carousel inertial measurement unit to provide acceleration and attitude information during its flight to geosynchronous orbit. The four-gimbal inertial measurement unit imposes certain middle gimbal angle constraint on trajectory design. To meet this constraint, various maneuver times and vehicle orientations are optimized during engineering trade studies. The preflight trajectory analysis ensures that all mission specifications, trajectory requirements, and instrument constraints are satisfied for a particular Titan IIIC launch vehicle and spacecraft combination. In-flight recording of guidance, navigation, and performance variables in a telemetry stream enables postflight reconstruction of art instrument-sensed trajectory. An independent trajectory reconstruction is achieved by using the recursive Kalman minimum variance filtering algorithms to fit the equations of motion to radar tracking data. A comparison between the preflight, instrument-sensed, and postflight reconstructed trajectories, together with orbital error bounds determined by a statistical error analysis, provides the mission accuracy. The purpose of this paper is to provide an overview of the preflight, postflight, and accuracy analyses of the Titan IIIC launch vehicle.