Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
2000-02-15
2001-03-27
Wimer, Michael C. (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C343S840000
Reexamination Certificate
active
06208317
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to spacecraft antenna reflectors and, more particularly, to a hub mounted bending beam for shape adjustment of springback reflectors.
2. Description of the Related Art
Spacecraft antenna reflectors are typically constructed as concave disks. Electrical specifications for the reflector dictate disk dimensions, specifically diameter and cross-sectional curvature. Spacecraft payload weight limits often constrain the reflector thickness to a level that renders the reflector vulnerable to dynamic forces associated with the spacecraft launch. Atmosphere drag and launch booster vibration may be particularly damaging to the reflector if the reflector is mounted in a typical operational configuration (i.e., on support collars on the external surface of the spacecraft) during launch. It is therefore desirable to store the reflectors in a confining envelope designed to protect the reflectors from launch stress.
The shape of the confining envelope requires temporary modification of the intrinsic antenna reflector shape to fit inside the envelope during launch. After launch, the reflectors are released from the envelope and returned to the original shape thereof on deployment. One approach for temporarily modifying the reflector shape is disclosed in Robinson, Simplified Spacecraft Antenna Reflector for Stowage and Confined Envelopes, U.S. Pat. No. 5,574,472, which is expressly incorporated in its entirety by reference herein. In the Robinson patent, a concave reflector fabricated from a flexible, semi-rigid material is deformed by application of a uniform force at diametrically opposed points at the periphery of the reflector. These forces cause the reflector to assume a shape similar to a taco shell which is maintained while the reflector is stowed. Upon deployment, the forces are removed from the reflector and the reflector reassumes its concave shape.
Deforming and stowing the reflector in this manner can cause distortion of the reflector from its desired shape. Additionally, other factors can cause distortion of the reflector from its desired shape. These factors include the predisposition of the reflector to fold on its own after fabrication, and thermal effects on and moisture absorption by the material from which the reflector is fabricated. The distorted shape ultimately results in the degradation of the performance of the reflector after the reflector is deployed and in use by the satellite.
Therefore, there is a need for an improved apparatus and method for adjusting the shape of springback reflectors to correct distortions caused by storage of the reflectors, fabrication of the reflectors, thermal effects and moisture absorption by the reflector material.
SUMMARY OF THE INVENTION
The present invention is directed to a method of and a device for adjusting the concavity of a springback antenna reflector. The method and device of the present invention can be used to adjust the concavity of the springback reflector prior to stowage within a satellite to correct actual or anticipated variations in the desired shape of reflector that are caused by storage of the reflector, fabrication of the reflector, thermal effects on the reflector, and moisture absorption by the material from which the reflector is fabricated. By adjusting the concavity of the reflector to correct the variations in the shape of the reflector, degradation of the performance of the reflector due to distortions in the shape of the reflector may be greatly reduced.
According to one aspect of the present invention, a shape adjustment mechanism is provided for a concave antenna reflector fabricated from a resilient material and having a surface and a coupling member attached to the surface proximate the center of the reflector. The shape adjustment mechanism includes a first support member rigidly mounted on the coupling member, and a resilient member rigidly connected to the first support member. The resilient member has a proximal end that is connected to the first support member, and a free distal end that is offset from the surface of the reflector by a distance. The shape adjustment mechanism further includes a second support member that has a first end rigidly connected to the reflector and a second end proximate the distal end of the resilient member. The shape adjustment mechanism further includes an adjustment member coupled to the second support member and adapted to engage the distal end of the resilient member. When the adjustment member is moved longitudinally along the second support member, the adjustment member engages the distal end of the resilient member such that the distance between the distal end of the resilient member and the surface of the reflector is varied as the adjustment member moves toward or away from the reflector.
In one alternative embodiment of the present invention, the resilient member of the shape adjustment mechanism may be in the form of a leaf spring having an aperture proximate the distal end with the second end of the second support member passing through the aperture. In this embodiment, the shape adjustment member may engage the leaf spring in the area proximate the aperture in order to vary the distance between the distal end of the leaf spring and the surface of the reflector. In another alternative embodiment, the second support member includes external threads and the adjustment member is a pair of threaded nuts disposed on either side of the resilient member. The nuts move longitudinally along the second support member as the nuts are rotated and engage the resilient member in either direction to vary the distance between the distal end and the reflector. In yet another alternative embodiment, the adjustment mechanism is disposed on the concave side of the reflector.
According to another aspect of the present invention, an antenna reflector is provided that includes a concave dish fabricated from a resilient material and a coupling member attached to a surface of the dish proximate the center of the dish. The antenna reflector further includes a first support member rigidly mounted on the coupling member, and a resilient member rigidly connected to the first support member. The resilient member has a proximal end that is connected to the first support member, and a free distal end that is offset from the surface of the dish by a distance. The antenna reflector further includes a second support member that has a first end rigidly connected to the dish and a second end proximate the distal end of the resilient member. The antenna reflector further includes an adjustment member coupled to the second support member and adapted to engage the distal end of the resilient member. When the adjustment member is moved longitudinally along the second support member, the adjustment member engages the distal end of the resilient member such that the distance between the distal end of the resilient member and the surface of the dish is varied as the adjustment member moves toward or away from the dish.
In one alternative embodiment of the present invention, the resilient member of the antenna reflector may be in the form of a leaf spring having an aperture proximate the distal end with the second end of the second support member passing through the aperture. In this embodiment, the shape adjustment member may engage the leaf spring in the area proximate the aperture in order to vary the distance between the distal end of the leaf spring and the surface of the dish. In another alternative embodiment, the second support member includes external threads and the adjustment member includes a pair of threaded nuts disposed on either side of the resilient member. The nuts move longitudinally along the second support member as the nuts are rotated and engage the resilient member in either direction to vary the distance between the distal end and the dish. In yet another alternative embodiment, the adjustment mechanism is disposed on the concave side of the dish.
According to a still further aspect
Gillett James R.
Naepflin Hans P.
Robinson Stephen A.
Taylor Robert M.
Gudmestad T.
Hughes Electronics Corporation
Wimer Michael C.
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