Aeronautics and astronautics – Spacecraft – Attitude control
Patent
1992-07-24
1994-05-17
Barefoot, Galen L.
Aeronautics and astronautics
Spacecraft
Attitude control
244173, B64G 124
Patent
active
053120736
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of The Invention
The invention concerns controlling the attitude of a satellite about its three axes, usually a geostationary satellite stabilized about the three axes, with optional compensation of disturbing torques acting on the satellite about the roll/yaw axes during orbit control maneuvers.
It is also concerned with the general configuration of satellites whose attitude is stabilized about their three geometrical axes in geostationary orbit, whether for civil or military, commercial or scientific purposes, or combinations thereof.
2. Description of the Prior Art
In the present context a satellite is any artificial object in the solar system in orbit around the Earth or any other planet or object of the solar system, or, in solar orbit, possibly a transfer orbit between two planets.
Satellites in orbit are known to be subjected to disturbing torques which make it necessary to control their attitude. The most important causes of disturbing torques are the lack of symmetry about the center of gravity (in space the expression "center of mass" is more appropriate) of the effects of solar radiation pressure (solar pressure for short) due to the angle of incidence (not 90.degree.) of the pitch axis of the satellite to the Sun, different reflectivity characteristics of parts of the satellite and geometrical asymmetries of the satellite; the action of the local (for example terrestrial) magnetic field; the aerodynamic effect of the environment (in low orbits); and the distance from the center of gravity of the satellite to the resultant thrust vector axis of the thrusters used to modify the Satellite orbit.
It is possible to distinguish between disturbances related to the environment: solar pressure, interaction of the satellite magnetic dipole with the surrounding magnetic field, gravitational gradient, etc.; these disturbances are weak (order of magnitude=10.sup.-5 N.m) but act on the satellite at all times, and disturbances related to misalignment of the thrust vector of the orbit control chemical thrusters relative to the center of gravity of the satellite; these disturbances are stronger (order of magnitude=10 N.m.s per day for a geostationary satellite) but limited in time.
It is essential to provide means for controlling the attitude of a satellite in its orbit. Various active means have already been proposed for this purpose, using a plurality of reaction wheels or thrusters of the mass ejection type, but the principle of ejecting mass requires that the satellite carry a reserve of mass, which increases the weight of the satellite at launch. Further, gas jet thrusters cause intense disturbances which excite the flexible and nutation modes of the satellite, degrading pointing accuracy. Additionally, low-thrust type thrusters such as ion thrusters or electrical arc ionization thrusters consume considerable electrical power and require warm-up phases which generally lead those skilled in the art to avoid using them for attitude control, and reaction wheels are not sufficient in themselves because the wheels must be desaturated to bring their speed to a value near the nominal value from time to time and this requires the application of external torque to the satellite.
To control the attitude of a satellite for an optimal mass budget use is made of disturbing forces due to solar pressure, by appropriately orienting surfaces attached to the satellite, or the local, for example terrestrial, magnetic field, by creating magnetic dipoles on board the satellite by means of pairs of currents.
Various prior art references have already put forward the use of solar radiation pressure for satellite attitude control and orbit control (stationkeeping) using mobile surfaces which can be oriented by means of dedicated actuators or using orientation thrusters already on board.
French Patent 2,513,589 describes a method and a device for aligning with a required direction the roll axis of a satellite which is spin-stabilized and fitted with a plurality of fixed solar panels; mobile sur
REFERENCES:
patent: 4288051 (1981-09-01), Goschel
patent: 4508297 (1985-04-01), Mouilhayrat
patent: 4630790 (1986-12-01), Williams, Jr.
patent: 4684084 (1987-08-01), Fuldner et al.
patent: 4767084 (1988-08-01), Chan et al.
patent: 4825646 (1989-05-01), Challoner et al.
patent: 4909460 (1990-03-01), Moura et al.
patent: 4949922 (1990-08-01), Rosen
patent: 5020746 (1991-06-01), Anzel
patent: 5149022 (1992-09-01), Flament
Brunet Pierre
Flament Patrick
Perdu Michel
Portier Jean
Aerospatiale - Societe Nationale Industrielle
Barefoot Galen L.
VanOphem Remy J.
LandOfFree
Method for controlling the pitch attitude of a satellite by mean does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling the pitch attitude of a satellite by mean, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling the pitch attitude of a satellite by mean will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-871377