Abstract: An electromagnetic precision rotary drive for a disk-shaped rotor. Along a peripheral annular zone of the rotor an armature band with a periodical pattern is disposed, which, within each period, varies continuously between the inner and the outer edge of the annular zone. The rotor is surrounded by a magent support, which carries at least one permanent magnet. If the magnet support is moved back and forth substantially radially, a torque is exerted on the rotor due to the interaction between the permanent magnet and the armature band.

Abstract: A method and an apparatus for processing the output signals of an optical rth-horizon sensor (1) operating in the infrared range of an orbiting, e.g. stationary earth satellite with respect to variously warm oppositely located earth rims (earth anomaly). With the earth-horizon sensor (1), an off-course signal is formed which is a measurement of the off-course angle of the line of sight of the earth-horizon sensor in relation to the satellite/earth central point connection line and is used for the attitude control of the earth satellite. This off-course signal is corrected in dependence on the earth anomaly.

Abstract: A mechanical vibrator for resonance operation, and particularly well suited for use with a beam chopper, comprises a mechanically stiff vibrator arm representing a fixed mass. A spring with a fixed spring constant is attached to and acts upon the vibrator arm. The vibrator arm and the spring comprise a mass/spring system. A drive means is connected to the vibrator arm and has a positive feedback circuit for self-excitation at the resonance frequency of the mass/spring system. At least one first magnetic system is arranged on the vibrator arm and at least one second magnetic system is located off the vibrator arm in operational connection with the first magnetic system for measuring and/or influencing the time ratio of the two half waves (t.sub.o, t.sub.g) of the vibration amplitude waveform of the vibration arm.

Abstract: The invention is directed to a method for determining the anomaly portion the output signal of a zero-seeking earth-horizon sensor for a geostationary satellite. The horizon sensor comprises a chopper disk operated with constant frequency, which chopper disk pictures the image of oppositely located earth horizons on a common infrared detector. When the thermal radiation of the two earth horizons is different the anomaly portion contained in the detector output signal can be determined in that the off-course signals are measured for different amplitudes of the chopper disk. Since the anomaly-dependent portion in the detector output signal depends on this chopper amplitude, correcting amounts can be determined for the measured values corresponding to the anomaly portion.

Abstract: A method and apparatus for deriving an off-course signal for an orbiting th satellite, preferably a geostationary satellite, by an earth-horizon sensor. The earth-horizon sensor operates in the infrared range and comprises, in the focal plane of an input lens, a chopper disk, which is periodically reciprocated with a determined chopper frequency (f) and which has a diameter corresponding to the image of the earth, and a detector (1) receiving the periodically interrupted radiation of opposite earth rims. The output signal of the detector is demodulated synchronously with the chopper frequency (f) and corrected with a correction signal corresponding to different temperatures of opposite earth rims (earth anomaly).