Radiant energy – Invisible radiant energy responsive electric signalling – Infrared responsive
Patent
1985-06-13
1987-05-19
Fields, Carolyn E.
Radiant energy
Invisible radiant energy responsive electric signalling
Infrared responsive
250342, 250347, 250351, G01J 134
Patent
active
046671048
ABSTRACT:
A method and apparatus for deriving an off-course signal for an orbiting th satellite, preferably a geostationary satellite, by an earth-horizon sensor. The earth-horizon sensor operates in the infrared range and comprises, in the focal plane of an input lens, a chopper disk, which is periodically reciprocated with a determined chopper frequency (f) and which has a diameter corresponding to the image of the earth, and a detector (1) receiving the periodically interrupted radiation of opposite earth rims. The output signal of the detector is demodulated synchronously with the chopper frequency (f) and corrected with a correction signal corresponding to different temperatures of opposite earth rims (earth anomaly). In order to be able to use the earth-horizon sensor not only as a ZERO-seeking sensor, but also as an angle-measuring sensor the amplified detector output signal is additionally demodulated synchronously with the second harmonic wave of the chopper frequency (2f) thereby producing a presence signal (U.sub.p). This presence signal, or a reference signal produced from the presence signal and the amount of the corrected off-course signal (.vertline.U.sub.DO .vertline.), respectively, are used in order to draw the characteristic line of the earth-horizon sensor into the desired characteristic line of the earth-horizon sensor, also during a "off-pointing", by controlling the amplification factor for the detector output signal, which is applicable for the instance when the line of sight of the earth-horizon sensor, which line of sight is fixed with respect to the satellite, is aligned with the earth central point.
REFERENCES:
patent: 3486024 (1969-12-01), Astheimer
patent: 3551681 (1970-12-01), Astheimer
patent: 3638021 (1972-01-01), Hickerson
patent: 3714432 (1973-01-01), Jalink, Jr.
patent: 3920994 (1975-11-01), Cargille
Fields Carolyn E.
Hanig Richard
Messerschmitt-Bolkow-Blohm Gesellschaft mit beschrankter Haftung
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