Abstract: An optical system including a telescope and a principal pointing device for selecting a direction of observation is disclosed. The system furthermore includes at least one secondary pointing device arranged ahead of a part of the entrance of the telescope and oriented fixedly with respect to the principal pointing device. A set of photodetectors records a secondary image formed by the telescope from light rays directed by the secondary pointing device toward the entrance of the telescope The secondary image makes it possible to accurately determine the direction of observation.

Abstract: An optical splitting device is intended to receive at an input two beams of different wavelengths. The device includes a polarizing beam splitter designed to selectively transmit part of the beam having one of the wavelengths towards a first output or a second output depending on the polarization of said beam. The device further includes a polarization variation system placed upstream of the polarizing beam splitter. By combining the polarization variation device with the polarizing beam splitter it is possible to adjust the distribution of the energy of a beam between the two outputs of the device. Such a splitting device is advantageously incorporated into an optical communication terminal.

Abstract: The invention relates to a method of controlling the attitude of a satellite (1) comprising two gyrodynes (3,4) and a third main actuator (2) which delivers torques at least along the Z axis.

Abstract: A control moment gyro comprising a wheel support structure which is mounted on a base by a motor, which is used to rotate the support around a first axis and bearing a wheel arrangement for driving the wheel spinner at a high speed around a second axis perpendicuIar to the first. The support structure includes a tubular part which rotates on the base and a flange which is disposed on only one side of the wheel and which is fixed both to the wheel and the tubular part. The diameter of the wheel and the point at which the wheel is fixed to the flange are proportioned such that the wheel penetrates the tubular part.

Abstract: In order to control the attitude of a satellite having at least four gyroscopic actuators with respective spinners mounted on gimbals steerable about axes parallel to one or the other of only two different directions that are fixed relative to the satellite, the attitude of the satellite is measured using sensors on board the satellite, the control torque required to perform an attitude-changing maneuver is calculated, local linearization calculation is performed based on pseudo-inversion of the Jacobean matrix of the function associating the orientations of the actuator gimbals with the total angular momentum of the cluster in order to determine a new gimbal orientation, and precession speeds of at least one of the gimbals of the actuators are controlled to deliver the control torque for reaching the desired configuration.

Abstract: The invention concerns an optical instrument, designed to be used on a satellite, for simultaneously or quasi-simultaneously observing in two opposite angularly separated directions. It comprises at least two telescopes (TA, TB) having angularly spaced apart observation directions, each having a real and accessible exit pupil and respective planar or superimposable image fields, with a width at least five times more than that of the pupil in a specific direction. Optical means provided at the exit pupil are arranged so as to form the image fields in a common overlapping focal plane except in lateral zones whereof the width is substantially equal to that of the exit pupil of the telescopes. In the common focal plane, an assembly of several matrix detectors are arranged and oriented on the superimposition zone of the image fields of the telescopes in the wavefront.

Abstract: An optical splitting device is intended to receive at an input two beams of different wavelengths. The device includes a polarizing beam splitter designed to selectively transmit part of the beam having one of the wavelengths towards a first output or a second output depending on the polarization of said beam. The device further includes a polarization variation system placed upstream of the polarizing beam splitter. By combining the polarization variation device with the polarizing beam splitter it is possible to adjust the distribution of the energy of a beam between the two outputs of the device. Such a splitting device is advantageously incorporated into an optical communication terminal.

Abstract: An optical system with variable pointing comprises a telescope and a principal pointing device selecting a direction of observation. The system furthermore comprises at least one secondary pointing device arranged ahead of a part of the entrance of the telescope and oriented fixedly with respect to the principal pointing device. A set of photodetectors records a secondary image formed by at least a part of the telescope from light rays directed by the secondary pointing device toward the entrance of the telescope. The secondary image makes it possible to accurately determine the direction of observation.

Abstract: The invention concerns a space craft, such as a telecommunication geostationary satellite, comprising a body, at least one main telecommunication antenna having a specific orientation relative to the body, at least a omnidirectional antenna having a field of view opposite to that of the main antennae and at least a radiator extensible by tilting about an axis linked to the craft body between a stowing position wherein it is pressed against the body and an extended position. The axis is positioned substantially in the plane of one surface of the body parallel to the orientation of the omnidirectional antenna and to the surfaces or the surface bearing the main antenna. The radiator tilts at an angle close to 180° from a position wherein it is pressed against one surface bearing a solar panel to a position wherein it extends substantially in the plane of the surface which bears it when it is stowed.