Aerospatiale Societe Nationale Industrielle

Societe Nationale Industrielle Et Aerospatiale

Patrick Flament

Michel Perdu

Pierre Brunet

Jean Portier

Miguel Molina-Cobos

A satellite embodying at least one surface intended mainly for exposure to solar radiation and extending away from the satellite in a predetermined direction (Y), an on board computer having connected thereto an attitude sensing system, an orbit control system for imparting thrust to the satellite along predetermined axes, and an attitude control system. The satellite further embodies a device for controlling the tilt of the surface in parallel with a plurality of planes containing the predetermined direction; and, therefore, particularly in parallel with the plane of a solar panel forming the surface. The tilt control device is controlled by the on-board computer. The tilting can generate a moment of pitch or relocate the center of gravity onto the axis of the orbit control system.

Method for controlling the pitch attitude of a satellite by means of

A satellite embodying at least one surface intended mainly for exposure to solar radiation and extending away from the satellite in a predetermined direction (Y), an onboard computer having connected thereto an attitude sensing system, an orbit control system for imparting thrust to the satellite along predetermined axes, and an attitude control system. The satellite further embodies a device for controlling the tilt of the surface in parallel with a plurality of planes containing the predetermined direction; and, therefore, particularly in parallel with the plane of a solar panel forming the surface. The tilt control device is controlled by the onboard computer. The tilting can generate a moment of pitch or relocate the center of gravity onto the axis of the orbit control system.

Apparatus controlling the pitch attitude of a satellite by means of

A method of controlling the attitude of a satellite according to which the direction of a predetermined celestial object is defined in a frame of reference related to the satellite, the instantaneous angular velocity vector of the satellite is detected and, by means of an actuating assembly, torques are applied to the satellite which are defined by a control law so as to rotate the satellite about the direction while orienting an aiming axis related to the satellite in the same direction, involves defining the direction of the predetermined celestial object in a frame of reference related to the satellite by a first quantity representing a first angle measured between an axis of sight and the projection of the direction onto a first reference plane containing the axis of sight and by a second quantity representing a second angle defined by the axis of sight and the projection of the direction onto a second reference plane containing the axis of sight, the second angle being calculated from the first angle and from the instantaneous angular velocity vector of the satellite, while a satellite for implementing the method includes a body; a sensor having the axis of sight; an actuating assembly; an attitude control unit for generating signals for applying the torques to the satellite; a unit for measuring the rotation velocity; and a processing unit calculating the second quantity.

Method for controlling the attitude of a satellite aimed towards a

To reacquire the attitude of a satellite wholly or partially stabilized on three axes a test is executed to determine if a terrestrial sensor is sensing the Earth (test 1) and if a star sensor is sensing a star whose magnitude is at least approximately equal to that of a given reference star (test 2).

Method of attitude reacquisition for three-axis stabilized satellites

Roll and yaw attitude control method for a satellite stabilized about its roll, yaw and pitch axes embodying a momentum wheel system generating a continuous angular momentum substantially parallel to the pitch axis and having a variable component at least approximately parallel to the roll-yaw plane and a continuously acting actuator system in which the roll and/or yaw attitude of the satellite is sensed. Control signals are applied to the momentum wheel system that are produced by a fast control loop using a known fast control law and second control signals are applied to the continuously acting actuator system that are produced by a slow control loop using a known slow control law. The continuously acting actuator system is loaded in fixed direction of the satellite parallel to the variable component if the latter has a fixed direction. At least a first additional control signal is applied to the momentum wheel system, chosen to yield a value of the fixed direction component of the angular momentum adapted to compensate in the long term drift of a second fixed direction component of the angular momentum. A second additional control signal is applied to the continuously acting actuator system that is adapted to cancel the effect of the first signal on the attitude with respect to the second fixed direction.

Continuously acting one-way satellite roll-yaw attitude control method

A method to control the attitude in roll (X) and in yaw (Z) of a satellite including two solar generator panels adapted to be oriented independently of each other about a pitch axis. In a preliminary stage: two geometrical axes x and z are selected in the plane of the roll and yaw axes, there being associated with the z axis a tolerable command torque error much lower than for the x axis, and a correlation law is established between satellite panel depointing angles .gamma..sub.N and .gamma..sub.S and possible command torques due to solar radiation pressure. Then cyclically while the satellite performs its orbit: a theoretical attitude correction torque in the plane of the roll and yaw axes is calculated, a possible torque is identified having on the z axis, a component substantially identical to that of the theoretical torque, and on the x axis, a component as close as possible to the theoretical torque component, and there are applied to the panels the depointing angles associated with the possible torque in accordance with the correlation law.

Satellite roll and yaw attitude control method

An attitude control device for a satellite stabilized on three axes including a pitch axis comprises two solar generator wings extending in opposite directions away from a satellite body on respective longitudinal axes at least approximately parallel to the pitch axis. Two drive motors drive these wings independently of each other in rotation about rotation axes at least approximately parallel to the pitch axis to keep the wings facing the Sun with a depointing angle at most equal to a predetermined maximum depointing value. Sensors measure attitude angles and a computation system commands the drive motors according to the attitude angles. On each wing an additional surface in the form at least one vane extends longitudinally beyond the end of the wing parallel to its longitudinal axis. These additional surfaces have substantially the same surface area and are inclined about this axis relative to the wings in opposite directions by at least approximately the same angle which is less than the 90.degree. complement of the maximum amplitude of wing depointing.

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Le Cannet, France

Patrick Flament