12 Celestial Navigation
12.1 INTRODUCTION
This chapter discusses the principles of celestial navigation, and in particular, high-precision stellar-inertial navigation. Since the time of the ancient mariners, stars have been used as a means of navigating on the Earth's surface using night-time manual celestial fixes. Until the 1970s, manual celestial fixes were used on transoceanic commercial aircraft. Since the 1960s, high-precision stellar-inertial navigation systems have been developed with automatic daylight and night-time star-tracking capability. These stellar-inertial navigators are highly useful for military aircraft in that they provide accurate position and attitude information, are autonomous, nonradiating, and invulnerable to jamming. They have been used on such aircraft as the SR-71 and U-2 reconnaissance aircraft and the B-2 and B-58 bombers. The development of these high-precision daylight stellar-inertial navigators has been brought about by (1) improved star-light detection devices, (2) techniques for improving star signal to sky background noise ratios, (3) advances in the throughput and memory of airborne digital processors, and (4) the development of algorithms for optimally combining the star observation with the inertial navigator output.
12.1.1 Evolution of Celestial Navigation
The nearly fixed positions of the stars in space, and the predictable motion of the Earth, make stars an obvious measurement source for navigation. The North Star (Polaris) can be used ...
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