Analog sun sensor

Abstract

Continuous positional information for an orbiting body such as a spacecraft, satellite, or the like with respect to a reference body, for example, the sun, is provided by a first continuous sensor which continually views the sun from the orbiting body and generates electrical signals which provide two axis information on the orbiting body's position. Analog sensors of this type have low accuracy because of transfer function non-linearity, degradation due to environmental aging, or radiation effects and others. A second periodic sensor is directed at the reference body to provide periodic positional updates. These updates are used as references to which the instantaneous output of a continuous sensor are compared so that error associated with the output of the continuous sensor can be eliminated to the accuracy of the calibration. The first continuous sensor preferably utilizes a first and second double triangle detector arranged to form first and second rectangles each having a slot aperture mounted thereon for projecting a line image normal to each rectangle. The first and second double triangle detectors are arranged orthogonally with respect to each other. An algorithm is used to accurately locate the position of the slit shadows on the first and second detectors on the continuous sensor, and thus provide a continuous position for the reference body such as the sun. The second periodic sensor has a patterned detector mask positioned over a very small area detector for producing periodic positional updates which information can be used to correct the continuous sensor errors and provide an accurate analog sun position sensor.