Aeronautics and astronautics – Spacecraft – With payload accommodation
Reexamination Certificate
2000-04-27
2002-11-05
Poon, Peter M. (Department: 3643)
Aeronautics and astronautics
Spacecraft
With payload accommodation
C244S164000
Reexamination Certificate
active
06474602
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to satellites, and more particularly, to an improved solar array orientation for satellite systems.
BACKGROUND
Historically, satellite systems use solar arrays (wings) deployed from the body of a satellite in order to power the satellite for normal operations. The solar arrays contain solar panels that receive sunlight and convert the sunlight to solar energy by known methods. The solar energy is then used to power the various components of the satellite.
Each solar array of the satellite is deployed on opposite sides of the main satellite and is oriented in a way that it is substantially coplanar with respect to the other array.
Satellite systems having solar arrays deployed as described above experience symmetric and asymmetric mode frequency changes as the solar arrays flex in response to operational disturbances. Symmetric mode frequency changes (flexing), when the solar arrays synchronously flex up and down (i.e. both up or both down at the same time), cause the body of the satellite to dynamically move up and down in response to the array flexure. This movement typically has little effect on the performance of the satellite.
Asymmetric mode frequency changes (flexing), when one solar array flexes upward and the other flexes downward (or asynchronously in the same direction), may add a rotational dynamical response by the satellite body. This rotational dynamic response negatively affects the performance of satellites that require a rotationally fixed reference point relative to some other object. For example, a photogrammetry camera contained within a satellite may need a fixed reference point on the earth or some other celestial body with which to take its photogrammetric measurements, and rotation may result in inaccurate measurements.
To alleviate or remedy the problem of asymmetric mode frequency changes, satellite stability is typically enhanced by resorting to “brute force” structural stiffening designs of the solar arrays. These stiffer solar arrays do not flex as much in response to operational disturbances of the satellite, and thus lessen rotational dynamic response correspondingly required by the satellite body. This structure adds excess weight to the satellite, which increases costs to place a satellite in orbit. Further, research and development costs to add structural integrity to the satellite may be significant. Also, adding structure to the satellite increases the complexity of the satellite, which in turn may increase the risk of malfunctioning or broken equipment in the manufacture or deployment of the solar arrays.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to lessen or eliminate the amount of structural stiffening in solar arrays that is required to limit or eliminate the dynamical rotational response of a satellite body.
The above object is accomplished by clocking (rotating) one solar array relative to the other, thus creating an “X” array configuration as viewed down the pitch axis of the satellite. The pair of solar arrays are then rotated to a position in which the maximum surface area of solar panels contained on the solar arrays receive direct sunlight from the sun.
The advantage of the present invention is the ability to maintain high precision angular stability without resorting to structural stiffening solutions with their associated complexity, risks and development costs.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.
REFERENCES:
patent: 4728061 (1988-03-01), Johnson et al.
Hughes Electronics Corporation
Poon Peter M.
Steele George L.
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