Advanced Celestial Tracker Techniques Gimbal Position Readout

摘要

The purpose of the project was the development of an ultraprecise, optical, shaft-angle encoding system of minimum size and weight for use in star trackers, inertial platforms and guidance systems, precision servos, and other aerospace applications. Presented herein are descriptions of methods which were considered for increasing the resolution of the Theodosyn shaft-angle encoder from its basic 18 bits to 20 bits, a description of the prototype system which was built under the contract, and experimental data demonstrating the feasibility of accomplishing the stated objective using the selected technique. A prototype encoder and breadboard interpolation electronic circuits were built and tested, showing maximum rms errors of less than 0.6 arc second. These results indicate that the design concepts employed in the prototype are feasible for production of 20- or 21-bit Theodosyns using the same disc pattern and, moreover, that the same techniques could be used to produce a 20- or 21-bit absolute encoder without increasing the size of the housing.