Fecha de publicación: 02/12/1986 Fuente: WIPO "honey" When producing images of the earth using rotating planar mirrors mounted in an aircraft, errors are introduced by roll, pitch and yaw of the aircraft. These errors are overcome in one of two ways. In the first way, the scanning planar mirror (30) is mounted on a shaft (54), the axis of which can be moved through small angles during the rotation of the shaft. This movement of the shaft is achieved by supporting the shaft (54) so that the end which does not carry the mirror is located within a cylindrical hollow region (60) at the end of an outer shaft (50). The two shafts rotate together. A pair of permanent magnets (51,52), each mounted axially in a respective shaft, have opposite poles adjacent to each other. The attraction of the magnets is perturbed by a transverse magnetic field established by an electromagnet (57,58,59) mounted outside the outer shaft (50). The current in the winding of the electromagnet depends upon the value of signals which are proportional to pitch and yaw of the aircraft. Those signals are derived from a gyroscope system (70). The second mechanism for overcoming errors involves mounting the scanning, planar mirror (12) in a cylinder (10) which is part of an inertial system that, in turn, is mounted on gimbals. Radiation received by the mirror is reflected by a system of mirrors which is similar to a Cassegrain telescope. The radiation is finally reflected by an elliptical mirror (18) to radiation monitoring equipment (21). In each case, signals indicative of the roll of the aircraft are used to control the time at which samples of the incoming radiation are first monitored.