Hughes Aircraft Company

Hughes Electronics Corporation

The Boeing Company

John W Smay

John F Yocum, Jr

William F Hummel

Harold A Rosen

Thomas R Parks

John P Harrell

Loren I Slafer

David J Rosmann

Carl L Chen

Salma Saeed

Eugene Gonzalez, Jr

A method, apparatus, article of manufacture, and a memory structure for controlling an attitude and a nutation of a spacecraft spinning about a first axis. The method comprises the steps of measuring a spacecraft attitude rate &ohgr; (t) about a second axis substantially orthogonal to the first axis; generating a rate correction value &agr;&ohgr; (t)/&lgr; , wherein &lgr; is an inertial nutation frequency of the spinning spacecraft, and &agr; is a proportionality factor; determining a spacecraft attitude angle &phgr; (t) about a third axis substantially orthogonal to the first axis and the second axis; generating an error signal e(t) as &phgr; (t)&plus;&agr;&ohgr; (t)/&lgr; ; and applying a torque to rotate the spacecraft along the second axis. The article of manufacture comprises a program storage device storing instructions implementing the instructions described above. The apparatus comprises an attitude rate sensor for measuring the spacecraft attitude rate &ohgr; (t) about a second axis substantially orthogonal to the first axis; means for measuring a spacecraft attitude angle &phgr; (t) about a third axis substantially orthogonal to the first axis; a processor, in communication with the attitude rate sensor, for generating an error signal e(t)&equals;&phgr; (t)&plus;&agr;&ohgr; (t)/&lgr; , wherein &lgr; is an inertial nutation frequency of the spinning spacecraft, and a is a proportionality factor; and a torquer for applying a torque to the spacecraft along the second axis in accordance with the generated error signal e(t).

Minimum fuel attitude and nutation controller for spinning spacecraft

A method and apparatus for controlling a spacecraft having a first axis is disclosed. The apparatus comprises a momentum wheel unidirectionally rotatable about a spin axis substantially co-aligned with the first axis; a momentum wheel mount for tilting the momentum wheel about at least one of two axes substantially orthogonal to the spin axis; and a processor in communication with the momentum wheel and the momentum wheel mount. The processor commands either the momentum wheel speed or the momentum wheel tilting to control the attitude of the spacecraft in a first orientation and in a second orientation inverted from the first along the first axis, using the same control law. The method comprises the steps of tilting the momentum wheel according to the control law as applied to a spacecraft attitude command and a measured attitude of the spacecraft; angularly displacing the spacecraft from a first orientation to a second orientation substantially inverted from the first orientation, and tilting the momentum wheel according to the same control law applied to the spacecraft altitude command or a new command and the measured attitude of the spacecraft. The article of manufacture comprises a program or data storage device tangibly embodying instructions to perform the method steps described above.

Bi-directional momentum bias spacecraft attitude control

An apparatus for storing energy and actuating the attitude of a spacecraft includes a first gimbaled flywheel assembly having a first rotor rotating in a first direction, and a second gimbaled flywheel assembly having a second rotor rotating in a second direction opposing the first direction. The first and second gimbaled flywheel assemblies are adapted to store and release energy and to actuate the attitude of the spacecraft. The apparatus includes one or more non-gimbaled counter-rotating flywheel pairs that are adapted to store and release energy.

Combined flywheel energy storage and attitude control apparatus for

A method and system of attitude steering and momentum management for a spacecraft suitable over a wide range of orbit altitude and inclination parameters and a similar wide range of mission steering profiles is provided. The system utilizes two active momentum wheels positioned with their spin axes nominally coaligned on the spacecraft pitch axis. Each wheel is pivoted by jackscrew type mechanisms which allow the angular momentum to be tilted (e.g. within the range 0-45.degree. from the nominal alignment with respect to the spacecraft body). The spacecraft control processor generates wheel torque commands for the wheel speed electronics and jackscrew drive commands for the platform assemblies in order to adjust the speed and amount of tilt of the momentum wheels. The invention provides a two-momentum wheel array that allows use of either momentum bias steering or large angle zero-momentum steering and accommodates multiple orbit geometries and varying degrees of attitude steering agility.

Universal spacecraft attitude steering control system

A method of and system for applying single gimbal control moment gyros to spacecraft attitude control employing two control moment gyros with nominal spin axes anti-parallel and gimbal axes displaced at a fixed angle in the plane normal to the nominal spin axes to achieve two orthogonal body fixed control torques using two wheels. If the gimbal axis displacement of each of three wheels is 120 degrees, two wheels provide independent uncoupled orthogonal two-axis control, and the third can substitute, in the event of failure, for either of the two requiring no change in control law or performance.

Spacecraft control with skewed control moment gyros

A system for providing energy storage, attitude steering, and momentum management of a spacecraft is shown using a pair of gimbaled flywheels. Two flywheels are positioned with spin axes nominally co-aligned along the spacecraft pitch axis and are spun in opposite or the same direction at differential or equal speeds to store spacecraft momentum as desired. Angular momentum can be tilted from the normal alignment with respect to the spacecraft body. This system will reduce the weight of conventional spacecraft and also reduce the cost.

Spacecraft energy storage, attitude steering and momentum management

A control system and method for causing a spacecraft (10) initially spinning about a principal axis of inertia (H) to transition to spin about an arbitrary command axis (3) is presented in which the capture maneuver is performed in a way to preserve spacecraft attitude knowledge without sensor or attitude propagation by using a simple rate feedback loop. The capture is accomplished by applying a step torque about axes (1) and (2) transverse to the desired spin axis (3) creating an initial nutation. The nutation is subsequently damped actively by closing a rate feedback loop with a low pass filter and applying transverse torques proportional to the transverse nutational rate.

Spacecraft spin axis capture system and method

A method for acquiring Earth-pointing attitude of a three-axis, body-stabilized spacecraft orbiting the Earth in a prescribed orbit plane, e.g. a geosynchronous communications satellite, including the steps of aligning the roll axis of the spacecraft with the sun line (which is the vector directed from the spacecraft to the Sun); then, orienting the spacecraft such that the angle formed between the yaw axis and the sun line is equal to the Earth-Sun angle (which is the angle formed between the sun line and a vector directed from the origin of the spacecraft internal coordinate system to the Earth); then, orienting the spacecraft such that the yaw axis is aligned with the center of the Earth; and finally, rotating the spacecraft about its yaw axis until its pitch axis is oriented at a desired attitude relative to the orbit plane, e.g., normal to the orbit plane, to thereby complete acquisition of the Earth-pointing attitude.

Spacecraft earth-pointing attitude acquisition method

A system located on board a geosynchronous satellite for detecting spin axis precession and developing thruster control signals for restoring the spin axis to the desired attitude. Fuel economy is enhanced by performing the major attitude correction at a time when the fuel expended contributes to that required for orbit inclination control.

Method for controlling the spin axis attitude of a spinning spacecraft

A nutation sensor and nutation control system using a relative spin phase sensor in a dual-spin stabilized satellite is disclosed. The relative spin phase sensor provides index pulses indicative of the relative spin phase and rate between the satellite rotor and platform. Nutation of the satellite perturbs the relative spin position of the rotor and platform and means are provided for analyzing index pulse arrive times to calculate nutation of the satellite. In the nutation control system, means are provided to apply a nutation damping torque to the satellite.

Nutation sensor and nutation control system for a dual-spin stabilized

Apparatus for controlling the pointing position of the payload platform of a dual-spin satellite. A torque motor which controls the relative position of the payload platform is controlled by means of a closed-loop feedback system which points the line-of-sight of the platform at a predetermined position on the earth. The control circuitry comprises position and rate sensing devices which monitor the relative position of the line-of-sight and the relative rotational rate of the payload platform. The line-of-sight of the platform is compared to signals indicative of the angular subtense of the earth. If the line-of-sight is pointed at the earth, then position command signals control the torque motor. If, however, the line-of-sight of the platform is not directed at the earth, then rate command signals are summed with the position command signals and subsequently applied to the motor. The combination of the position and rate command signals provides for a system in which the equilibrium state of the system is such that the platform will be despun and earth-pointed. A method of controlling the pointing position of the satellite is also disclosed.

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Redondo Beach, CA, United States of America

John W Smay