Theory of Three-Axis Stable Systems Employing External Information

Abstract

I (l) and astronomical (2) systems may be used to compute x, y, z (coordinates in three-dimensional space) and x, y, z (the corresponding velocities). An inertial system can give the velocities reliably, but the coordinates are subject to major errors because of drift in the gyros and instability in the system generally. An astronomical system can give the coordinates accurately, but the velocities, which are deduced b} differentiation, are subject to very large errors. A combined (astro-inertial) system can give coordinates and velocities with the desired accuracy. Previous work (1-3) forms the basis of the present treatment of a three-axis astro-inertial system; we assume that the astronomical information is used not merely to correct the coordinate readings but also to control the response of the inertial system (to suppress instability, to cause damping, and to reduce the response time).