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Proceedings Paper

Correction of errors due to profile shape in static Earth horizon sensors
Author(s): Vladimir Alperovich; Jeremy M. Topaz
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Paper Abstract

Earth horizon sensors, used on satellites for determining orientation, usually operate on the principle of detecting the discontinuity in the infrared radiance at the limb. Most such sensors make use of radiant emission from the upper atmosphere in the 15 micrometers CO2 absorption band and locate the 50% point on the horizon radiance profile, normalized to the maximum radiance value. Their accuracy is affected by errors due to seasonal, latitudinal, and random climatic variations in the shape of this profile. A method is presented for reducing the errors due to these variations, based on determining a specific profile shape which best fits the data obtained, and using this shape to estimate the position on the profile of a chosen tangent height. This method has been developed especially for a new type of static horizon sensor to be used in the Techsat-1 micro-satellite. This sensor gives a multi-point characterization of the profile, from which the shape can be ascertained and compared with a selection of representative profiles stored in the on-board computer. The profile best matching the data is then selected and used in the computation. The method could also be applied to those types of dynamic sensor which scan the profile with adequate resolution. The theory and application of the method is described together with computer analysis showing the degree of improvement in accuracy which can be achieved compared to traditional methods. It is shown that accuracies better than +/- 0.1 degree(s) can be obtained in low earth orbits.

Paper Details

Date Published: 6 June 1995
PDF: 9 pages
Proc. SPIE 2426, 9th Meeting on Optical Engineering in Israel, (6 June 1995); doi: 10.1117/12.211207
Show Author Affiliations
Vladimir Alperovich, EL-OP Electrooptics Industries Ltd. (Israel)
Jeremy M. Topaz, EL-OP Electrooptics Industries Ltd. (Israel)

Published in SPIE Proceedings Vol. 2426:
9th Meeting on Optical Engineering in Israel
Itzhak Shladov; Yitzhak Wiessman; Natan Kopeika, Editor(s)

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