System for determining and controlling the attitude of a moving airborne or spaceborne platform or the like

摘要

A system for determining the attitude of an airborne or spaceborne platform such as a terrain image sensor or an energy beam pointer includes a digital image correlator for comparing successive overlapping, instantaneous images of the terrain which are recorded by a second, two- dimensional image sensor whose image plane is oriented parallel to that of the platform or terrain image sensor. The second sensor generates an instantaneous master image and a subsequent slave image which at least partially overlaps the master image in terms of the terrain which is viewed. The master and slave images are approximately registered and a correlation is performed. A plurality of points on the slave image are correlated with the corresponding terrain points on the master image. The relative orientation of the slave image with respect to the master image characterizes the attitude change of the platform. The technique also reveals changes in altitude and velocity of the platform when mean altitude and velocity are known. The image produced by the terrain image sensor or the attitude of the beam pointer can be altered on a real time basis using the information relating to the change in platform attitude, or the master and slave image data can be recorded for subsequent use in modifying the image data recorded by the terrain image sensor. A multispectral scanner is employed to detect in advance regions that cannot be properly imaged due to clouds and the like and a computer controlled mirror directs images onto the sensor from regions that the scanner has determined to produce meaningful image data.