Attitude Determination of a Spinning and Tumbling Rocket Using Data from Two Orthogonal Magnetometers

Shu T. Lai

Jan 1981 · Air Force Geophysics Laboratory, Air Force Systems Command, United States Air Force

About this ebook

This technical note reports on the attitude determination of Air Force Rocket No. A31.603 on which an ion emission experiment was performed. Two orthogonal magnetometers, one facing forward along the rocket spin axis and the other facing sideways, provide magnetic field component data. The bias-offset and scaling (signal conversion) factor are not given, but can be determined in a sinusoidal approximation. The algorithm used for generating magnetic pitch angles is discussed and an error analysis is provided. In a local vertical coordinate system, two sets of elevation angles are found for the tumbling rocket, and the set that satisfies an initial condition exactly is the correct one. The deviation of the rocket tumbling plane from the vertical plane can be determined at the times of closest encounter of the magnetic field vector and rocket vector. The deviation at all times can be approximately determined by sinusoidal curve fitting with tumbling frequency. The angles between the rocket vector and moonlight vector during the instants of moonviews at the onboard camera are also calculated. (Author).