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US3609374A Expired / Lapsed US ⏱️ 0.0 years remaining

Weighted scan star scanner

Assignee: Kearfott Guidance and Navigation Corp
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Filing: 1967-02-24
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Granted: 1971-09-28
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Expires: 1987-02-24
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Abstract

Abstract Possible incident star energy is directed onto a deflecting mirror as a beam which will systematically reflect said beam upon one of a plurality of detector elements arranged in a linear array, generating a signal. This signal is amplified and fed to a level detector. When a predetermined threshold is exceeded, the output of the level detector activates a trigger. The trigger activates a flip-flop which causes the scanner to reverse and rescan the limited area where the possible stars occurred. This time, the signal is passed through another channel wherein the time constant for the filter is increased by about three, (the number of rescans). This results in an improvement in the signal to noise ratio of about at the point in question. The level detector trigger associated with the second channel is set at a higher threshold. When this trigger is activated, the acquisition problem is solved and the probability of star presence is over 0.99. This second channel trigger enables a second flip-flop switching the scanner to the fine mode, whose purpose is merely of more accurately defining the position of the star in the search field. In the fine mode, when the signal from the star is centered, an output at one frequency may be provided whereas an increasingly large off-axis error signal in another frequency may be provided for offcenter both in azimuth and elevator. These error signals act on the scanner so as to move the scanner in line with the star scanned.

Inventors

  • 👤 Philip Gevas

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-26 23:04
CPC Classifications
G; G01; G01S; G01S3/00; G01S3/78; G01S3/782; G01S3/789

Claims Analysis

Total Claims: 9
Claim 1
Independent Claim 129 words
In a star-scanning system, a linear array of detectors; first means to cause said array to scan along a path to sample a first field of view until a presumed star signal is detected; and, second means for rescanning only a small segment of said field where said presumed signal is located, the signal to noise ratio during rescan being higher and matched filter band being different than during the scan so that any signal appearing during the rescan will almost undoubtedly be a star, whereby the system performance gain of this invention over the prior state of the art, which art is based on a nonvariable, optimum or linear matched filter is achieved without an increase in to total time required to acquire a star with high probability.
Claim 2
Dependent Claim 129 words
In a star-scanning system, a linear array of detectors; first means to cause said array to scan along a path to sample a first field of view until a presumed star signal is detected; and, second means for rescanning only a small segment of said field where said presumed signal is located, the signal to noise ratio during rescan being higher and matched filter band being different than during the scan so that any signal appearing during the rescan will almost undoubtedly be a star, whereby the system performance gain of this invention over the prior state of the art, which art is based on a nonvariable, optimum or linear matched filter is achieved without an increase in to total time required to acquire a star with high probability.
Claim 3
Dependent Claim 153 words
In a star detector wherein suspected star energy is received by optical means and directed along a path across a plurality of detector elements, the improvement therein comprising in combination, first level detector means responsive to a certain level signal to which the output of said detector elements if fed; electronic and/or magnetic and/or servo means responsive to said first level detector means causing the rescan of a portion of the previously scanned path in a second scanning mode, and, second level detector means in said second scanning mode set at a higher threshold than in the first scanning mode with matched filter bandwidth corresponding to second scanning speed, whereby the system performance gain of this invention over the prior state of the art, which art is based on a nonvariable, optimum or linear matched filter is achieved without an increase in the total time required to acquire a star with high probability.
Claim 4
Dependent Claim 153 words
In a star detector wherein suspected star energy is received by optical means and directed along a path across a plurality of detector elements, the improvement therein comprising in combination, first level detector means responsive to a certain level signal to which the output of said detector elements if fed; electronic and/or magnetic and/or servo means responsive to said first level detector means causing the rescan of a portion of the previously scanned path in a second scanning mode, and, second level detector means in said second scanning mode set at a higher threshold than in the first scanning mode with matched filter bandwidth corresponding to second scanning speed, whereby the system performance gain of this invention over the prior state of the art, which art is based on a nonvariable, optimum or linear matched filter is achieved without an increase in the total time required to acquire a star with high probability.
Claim 5
Dependent Claim 27 words
In a star detector as claimed in claim 2, said star energy being directed into a scanning mirror as a beam which is deflected along said path.
Claim 6
Dependent Claim 25 words
In a star detector as claimed in claim 3, said mirror scan in said second scanning mode being slower than in said first scanning mode.
Claim 7
Dependent Claim 33 words
In a star detector as claimed in claim 4, the scanning speed in the second scanning mode being of the order of one third the scanning speed in the first mode of scanning.
Claim 8
Dependent Claim 63 words
A star detector as claimed in claim 5 wherein the detector elements comprise at least three detector units in parallel so as to provide pulsating output, a band-pass amplifier responsive to said pulsating output a demodulator and filter receiving said amplified pulsating output and supplying a rectified filtered output, and, a Schmitt trigger including level setting means responsive to said rectified filtered output.
Claim 9
Dependent Claim 38 words
A star detector as claimed in claim 5 said second scanning mode enabling a fine mode including angularly disposed detector means, said detector means providing informatiOn as to whether said star energy is on axis or off axis.

References Cited (Backward Citations)

No citation records indexed.

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1974-09-27 1975-03-29 1975-09-28 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1978-09-27 1979-03-29 1979-09-28 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1982-09-27 1983-03-29 1983-09-28 $7700.00 Window Closed / Lapsed

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