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US 6,285,395 B1Granted
Earth sensor for satellite
AssigneeHughes Electonics Corporation
InventorThomas J. Firpo
Life of this patent
Estimating the term…
Abstract
An earth sensor for a communication satellite is provided which utilizes a camera for viewing the earth from the satellite and an optical correlator which optically processes the video data from the camera to provide attitude information to a satellite attitude control computer.
Claims6
An earth sensor for a satellite, said sensor comprising:
- a first camera mounted on the satellite for viewing a first scene and a second scene including an image of the earth against a background of space, said first camera generating video data,
- an image processor for processing the video data from said first camera to develop output pixel data containing pitch, roll and yaw information representing movement of the earth from said first and second scenes, said yaw information derived from the image of the earth, and
- wherein said image processor comprises:
- storage means for storing video data from said first camera representing said first scene, and
- an optical correlator for comparing video data representing the first and second scene, to detect movement of the earth relative to the first camera and to provide said output pixel data defining the distance and direction of said movement, which said optical correlator rejects the background of space as viewed by said first camera.
2 more elements
An earth sensor for a satellite, said sensor comprising;
- a first camera mounted on the satellite for viewing a first scene and a second scene including an image of the earth against a background of space, said first camera generating video data,
- an image processor for processing the video data from said first camera to develop output pixel data containing pitch, roll and yaw information representing movement of the earth from said first and second scenes, said yaw information derived from the image of the earth, and
- wherein said image processor comprises:
- an optical correlator including first and second magneto-optical light modulators having pixel locations, and first, second and third light polarizers, said first magneto-optical light modulator being located between said first and second light polarizers and said second magneto-optical light modulator being located between said second and third light polarizers, a light source for providing parallel light rays through said first and second magneto-optical light modulators, said optical correlator emitting polarized light,
- a correlator camera responsive to the polarized light emitting from said optical correlator for providing pixel output data,
- a translator having video data from said first and second scenes, said translator controlling said first magneto-optical light modulator to rotate, by 90 degrees, the parallel light rays passing through the pixel locations corresponding to the second scene while passing the parallel light rays, without rotation, at other pixel locations,
- said translator also controlling said second magneto-optical light modulator to rotate, by 90 degrees, the parallel light rays passing through the pixel locations corresponding to the first scene while passing the parallel light rays, without rotation, at said other pixel locations, and
- said first, second, and third light polarizers being effective to block passage of light rays from said source to said correlator camera whereby a difference in the first and second scenes as viewed by said first camera is presented to said correlator camera.
5 more elements
A method of sensing movement of the earth relative to a first camera mounted on a spacecraft for viewing a first and second scene of the earth against a background of space, comprising the steps of;
- producing pixel data from said first camera representing the first and second scenes of the earth including the background of space,
- optically processing the pixel data to remove the background while producing a correlated image representing a difference between said first and second scenes, and
- viewing said correlated image with a second camera to produce pixel data representing said difference.
Dependencies are inferred from the claim text.