An optical computer has been constructed employing an artificial intelligence, early vision, processing technique to perform precision horizon location in scanning horizon sensors. It is well known that the second derivative of the horizon signal crosses zero at the point of maximum slope and is thus an optimum point to minimize instrument errors. In contrast to conventional techniques the Bulls EyeTM Locator performs the double differentiation optically, thus circumventing most of the noise limitations imposed by electronic differentiation and analog/digital signal processing. Differentiation is implemented spatially by subtracting the signals from an inner circular and an outer annular field of view (FOV). The result is a method of horizon location which is insensitive to scan speed and crossing angle variations, along with inherently rejecting radiance errors. Optimization of on-orbit performance is reviewed in detail. Several embodiments of the locator are discussed, including a proprietary single-element pyroelectric detector. Technical implications are explored, specifically, our development of an extremely low cost, high accuracy, wide dynamic range family of horizon sensing instruments.

Date Published: 1 July 1991
PDF: 12 pages
Proc. SPIE 1495, Small-Satellite Technology and Applications, (1 July 1991); doi: 10.1117/12.45891

Published in SPIE Proceedings Vol. 1495:
Small-Satellite Technology and Applications
Brian J. Horais, Editor(s)