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.

Abstract: For providing video-on-demand (VOD) a set comprising a plurality of N video programs at staggered time intervals is repeatedly transmitting from a VOD server to a network for access by a view box of an user; responsive to a request for access to a selected program by the user, there is selection of that in-progress transmission of the selected program for which a lead-in portion is shortest and storage of the program in a buffer associated with the view box as it is transmitted. A previously stored beginning portion of the selected program having a time length sufficient to compensate for that time interval is selected, in a memory associated with the view box, and outputting to the view box for display. The in-progress transmission stored in the buffer is continuously spliced to a conclusion of the beginning portion. All different video programs in a same set are transmitted with mutual time shifts equal to a fraction of the staggered interval.

Abstract: For controlling the attitude of a satellite placed on a low earth orbit, components of a vector Bm of the earth's magnetic field along three measurement axes of a frame of reference bound with the satellite (typically by means of a three-axis magnetometer) are measured. The orientation of the earth's magnetic field in the frame of reference is computed and a derivative {dot over (B)}m of the vector is also computed. Magneto-couplers carried by the satellite are energized to create a torque for spinning the satellite at an angular frequency &ohgr;c about a determined spin axis of the satellite, where &ohgr;c is greater than an orbital angular frequency 2&ohgr;0 of the satellite.

Abstract: A system for managing electrical energy and for controlling attitide of a satellite has an attitude control unit which controls a plurality of reaction wheels oriented about different axes for instance three wheels. An on-board electricity power supply network has a solar array, a payload and a storage unit connected to a power line. The storage unit comprises a buffer supercapacitor and one inertia wheel unit with a respective motor/generator and typically two contra-rotating wheels. Interchanges between the storage units and the power supply line are controlled by a regulator which attenuates power demand transients and thus torque transients on the inertia wheel or wheels.

Abstract: The photosensitive device implements charge coupling and accumulation for analyzing a light signal. A sensor has an image zone M rows and N columns of photosensitive sites for receiving a light signal during successive acquisition periods, a transfer zone of P rows and N columns of non-photosensitive sites for receiving, in each site of a first row, the sum of the charges in a respective column of the image zone at the end of each successive sampling period. It also has a storage zone of P rows an N columns in which each column is adjacent to a respective column of the transfer zone and each site is arranged to receive charges contained in an adjacent site of the transfer zone and to accumulate it. The sensor is clocked for a sequence.

Abstract: The circuit has a power busbar, a solar generator made up of a plurality of sections that can be connected individually to the busbar via switches and a storage battery. The busbar is permanently connected to an energy-storage capacitor having a capacitance of at least 0.1 F. The busbar is powered from the battery via at least one discharge module controlled in on/off mode by a regulator which also controls the switches. The circuit is particularly suitable for use on low earth orbit (LEO) satellites.