Satellite attitude sensor using thermal imaging

Abstract

The present invention provides a method for distinguishing a boundary of an object, and the object itself, from its background. In the method electromagnetic radiation is detected from at least one field of view substantially spanning the boundary of the object and background adjacent to the boundary and superimposed or overlaid as images onto a detector. The method includes correlating spatial transitions in intensity of the overlaid images on the detector with a boundary of the object. When used for determining the attitude of a satellite with respect to the earth, the detector is a thermal infrared detector thereby providing a sharp contrast between the thermal emission of the earth and cold space. The invention provides a simple, effective method and device for determining satellite orientation and/or attitude with respect to a thermal infrared-emitting target body. The sensor includes a segmented limb-looking mirror to provide multiple fields-of-view within the field-of-regard and superimposing these fields-of-view as images onto a common detector. The required resolution can be obtained while providing a wide range of operational orbital altitudes. The attitude of the satellite can vary by a large angle from the minimal orientation while still permitting an accurate determination of attitude. Multiple channels in a modular form provide redundancy, improved accuracy, and the opportunity of providing more diverse configurations. The utilization of uncooled microbolometer arrays as imaging detectors removes the requirement for additional cooling equipment thereby providing a low cost, small size and low mass sensor with configurational flexibility and no moving parts.