Ares I-X Trajectory Reconstruction: Methodology and Results

The Ares I-X trajectory reconstruction produced best-estimated trajectories of the flight-test vehicle ascent through stage separation and of the first- and upper-stage entries after separation. The trajectory-reconstruction process combines onboard, ground-based, and atmospheric measurements to produce the trajectory estimates, using an iterated extended Kalman filter algorithm. The Ares I-X vehicle had a number of onboard and ground-based sensors that were available, including inertial measurement units, radar, air data, and weather balloons. However, due to problems with calibrations and/or data, not all of the sensor data were used. This paper describes the methodology and results of the trajectory-reconstruction process, including flight-data preprocessing and input uncertainties, trajectory-estimation algorithms and dynamic models, output transformations, and comparisons with preflight predictions. The results of the reconstruction indicate nominal vehicle performance that is well within the range o...