Abstract

Honeywell's Earth Reference Attitude Determination Sensor (ERADS) is a wide field of view ultraviolet imaging sensor for satellite attitude determination. The sensor was designed for small satellite applications¹, where size, weight, and cost are the primary drivers. Use of the ultraviolet region of the spectrum provides a unique capability to simultaneously image stars, Earth's limb (day or night), and other celestial objects, and to tolerate the sun in the field of view. This is because the solar output is lower relative to the other objects of interest in this waveband, and eliminates the need for expensive and cumbersome sun shields. The field of view consists of a 10° annular region at 71° from axis, and a 10 degree center field. Higher accuracy attitude information is obtained from measurements of stellar location. The accuracy with which these measurements can be made is limited by the number of pixels on the focal plane, the blur spot dimensions, and the photon count rates. The detector array of the sensor was a megapixel CCD. The field of view of the sensor was effectively increased by making use of an array of six folding mirrors, and the field remapping effectively increased the pixel density in the area of interest. The optimal blur diameter for the centroiding algorithms proved to be the width of three pixels, if a photon rate of 50 per star for fourth magnitude stars could be maintained.

© 1996 Optical Society of America