TABLE OF CONTENTS Originally appeared as Chapter 14 of the book Theory and Application of Kalman Filtering a publication of the Advisory Group for Aerospace Research and Development of the North Atlantic Treaty Organization published in February 1970 as AGARDograph 139 and edited by Cornelius T. Leondes. It was prepared at the request of the Guidance and Control Panel of AGARD-NATO. The chapter was entitled "Application of Kalman Filtering Techniques to the Apollo Program" and was co-authored by Richard H. Battin and Gerald M. Levine.
The first manned trip to the vicinity of the moon of Apollo 8 during December 1968 gave an excellent test of the Apollo system's onboard navigation capability. Although ground tracking navigation was the primary system, the onboard navigation system had the task of confirming a safe trajectory and providing a back-up for return to earth in the remote chance that ground assistance became unavailable for onboard use.
Apollo 8 was to use sun illuminated visual horizons rather than landmarks for operational simplicity, even though, as confirmed from earth orbit by Astronaut Donn Eisele in Apollo 7, the earth's horizon does not provide a distinct target for visual use. Moreover, the filter in the sextant beamsplitter, designed originally to enhance the contrast between water and land when looking down at the earth, filters out the blue in such a way as to make the horizon even more indistinct. Originally a blue sensitive photometer had been designed for horizon detection in the prototype sextant models, but...
