Television – Special applications – Observation of or from a specific location
Reexamination Certificate
1996-07-31
2001-09-04
Lee, Richard (Department: 2613)
Television
Special applications
Observation of or from a specific location
Reexamination Certificate
active
06285395
ABSTRACT:
TECHNICAL FIELD
This invention relates to earth sensors for providing spacecraft attitude information and more particularly to an earth sensor for a satellite which utilizes a camera for viewing the earth from the satellite and an optical correlator which optically processes the data from the camera to provide accurate attitude information to the satellite attitude control system.
BACKGROUND ART
An earth sensor is a critical component of a communication or remote sensing satellite's attitude control subsystem. It is generally desirable to maintain a communications or remote sensing satellite in a geosynchronous orbit about the earth so as to enable a communication beam or sensor field of view from the satellite to accurately cover a desirable area, such as a particular country, on the surface of the earth. Any deviations from this orbit will alter the coverage of the beam or view. Accordingly, satellites are provided with sensors for sensing changes in orientation of the satellite relative to the earth.
One prior art earth sensor relies on infrared radiation focused on thermally sensitive detectors. Another relies on the intensity of visible and ultraviolet radiation from the earth disk. The earth as seen from space does not always have the same shape in the visible light spectrum. It is therefore difficult to design a video earth sensor which accommodates this characteristic without providing prohibitively large and complex data processing capabilities.
SUMMARY OF THE INVENTION
According to the present invention a video earth sensor for a geosynchronous 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 accurate attitude information to the satellite attitude control system. The optical correlator uses two Magneto-Optic Spatial Light Modulators (MOSLMs). MOSLMs are well known in the art and have been used in target and pattern recognition applications. In contrast to the prior art pattern recognition systems, the pattern of interest in the present invention, namely the earth as seen from orbit, is of a known and slowly changing shape. It is the shape and orientation of the earth as seen by the camera which gives the satellite attitude control system the attitude information it requires. The sensor of the present invention relies on the fact that although the earth does change shape over the course of a day, as well as over the course of a year, it does so relatively slowly. The rate at which MOSLMs can be readdressed is very fast (120 frames per second) and thus real-time or near real-time comparison from one frame to the next is possible. Comparison of the current picture of earth with those of the very recent past can give data on the location of the earth within the scene as well as orientation. The changing shape of the earth is essentially filtered out or eliminated.
REFERENCES:
patent: 3869705 (1975-03-01), Woywood
patent: 4364085 (1982-12-01), Dalke
patent: 4679753 (1987-07-01), Landecker
patent: 4688091 (1987-08-01), Kamel et al.
patent: 4688092 (1987-08-01), Kamel et al.
patent: 4689748 (1987-08-01), Hofmann
patent: 4746976 (1988-05-01), Kamel et al.
patent: 4944587 (1990-07-01), Harique
patent: 5029220 (1991-07-01), Juday
patent: 5107351 (1992-04-01), Leib et al.
patent: 5189295 (1993-02-01), Falbel
Gudmestad T.
Hughes Electonics Corporation
Lee Richard
LandOfFree
Earth sensor for satellite does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Earth sensor for satellite, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Earth sensor for satellite will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2444602