Daimler-benz Aerospace Ag

Deutsche Aerospace Ag

Diamler-benz Aerospace Ag

Globalstar L.p. and Daimler-benz Aerospace Ag

Walter Fichter

Michael Surauer

Helmut Bittner

Horst-Dieter Fischer

Ernst Bruederle

John James Rodden

Nobuo Furumoto

Oliver Juckenhoefel

Christian Roche

Peter Zentgraf

An attitude controller for a 3-axis stabilized, Earth oriented bias momentum spacecraft is described, where only 2-axis attitude measurements from the Earth sensor are available. In contrast to the classical spacecrafts that are controlled w.r.t. a fixed orbital Earth pointing reference frame, (possibly large angle) time varying reference signals are considered here, i.e. the control task consists of a tracking problem. The controller design consists of a decoupling controller and axis-related PID controllers based on yaw observer estimates.

Method for controlling the attitude of a three-axis stabilized, earth

A system for autonomous on-board determination of the position of an earth orbiting satellite consists of a biaxially measuring earth sensor which defines the z-axis (yaw axis) of the satellite and of several biaxially measuring sun sensor measuring heads which are arranged on the satellite structure such that, with the exception of earth shadow phases, they supply a direction vector measurement. Out-of-plane movement of the satellite is propagated by means of a precise model of the satellite dynamics including natural disturbance forces and thrusts during maneuvers on board. In order to compensate sensor uncertainties and the effects of thermal deformations, the satellite orbit is precisely measured at regular intervals (approximately 3 months), and by means of this information, a calibration function (time function for a day) for compensating measured values is determined. The in-plane movement of the satellite is not only propagated, but the propagation is supported by measured data (estimation), and the effects of out-of-plane movement and thermal deformations are taken into account, by means of the data of the calibration function (k(t) or of the propagation out-of-plane movement.

Method and system for the autonomous on-board determination of the

A low earth orbiting satellite control arrangement according to the invention has an earth sensor for measuring roll and pitch of the satellite relative to an earth oriented moving reference system, a spin wheel mounted along an axis perpendicular to the orbital plane of the satellite for measuring spin of the satellite, and two magnet coils for generating control. A first of the two magnet coils is aligned substantially in parallel to a roll axis of the satellite, and the second is aligned substantially parallel to the yaw axis. Alternative control algorithms are disclosed for controlling attitude, nutation and spin of the satellite based on information from the earth sensor, spin wheel and an observer which is also mounted on the satellite.

Earth oriented satellite and process for controlling the position,

The sun search method for a satellite stabilized in three axes according to the invention uses a sun sensor device with a visual field possibly containing gaps, and a rotational speed gyro which measures in a measuring axis that is oriented arbitrarily. A regulating law with the form .tau.=-kGG.sup.T .omega. is used (.tau.=regulating torque, k=amplification factor, G=directional vector of measuring axis of rotational speed gyro, .omega.=rotational speed vector of the satellite). A rotational wheel momentum H which is not parallel to the measuring axis, is generated with the aid of an additional flywheel device.

Sun search method and apparatus for a satellite stabilized in three axes

A method and apparatus for steering a low-earth-orbit communication satellite requiring sun-orientation for solar-power accumulation is disclosed. Momentum-bias both maintains nadir pointing and adds yaw-steering moments for sun-trackig attitude control, simultaneously. The method has two principal steps: 1) open-loop momentum decoupling, for correcting the calculated steering torque, and closed-loop attitude compensation, to correct for perturbations about the calculated attitude in accordance with one of two control law definitions. This combines the advantage of stable gyroscopic attitude control with those of open-loop yaw steering.

Dynamic bias for orbital yaw steering

Measuring arrangement useful for controlling the attitude of a

Three-axis stabilized, earth-oriented satellite and a corresponding sun

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Munich, Germany

Walter Fichter