US3676581A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Optical scanning spacecraft system
Assignee: United States Department of the Navy
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Filing: 1971-02-01
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Granted: 1972-07-11
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Expires: 1991-02-01
Abstract
Abstract A method and apparatus for mapping the surface of a celestial body employs a spin stabilized spacecraft which is placed in a highly eccentric orbit about the celestial body to be mapped and whose spin axis is always Earth oriented. An optical linescanning system is mounted aboard the spacecraft normal to the spacecraft spin axis and repeatedly sweeps out an elongated image strip or swath on the surface of the celestial body; the image swath advancing over the surface of the body as the spacecraft spins during its orbit about said body. The optical scanning system includes a mechanical slit which is dimensioned such that when it is projected onto the surface of the celestial body it forms one line of the desired image swath. Suitable spectral dispersing means receives the light passing through the mechanical slit and disperses it onto a mosaic of photosensors. The photosensor mosaic is arranged to produce output voltages indicative of the light intensity of the light image occurring at preselected spectral regions of the image. The highly eccentric orbit into which the spacecraft is placed about the celestial body permits close-up and broader coverage pictures to be obtained during each orbit of the spacecraft. It also helps to reduce the velocity change requirements for planetary capture, and lengthens the orbital period to permit continuous transmission to Earth of a complete picture at modest data rates.
Inventors
- 👤 Charles J Swet
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 00:28
CPC Classifications
B; B64; B64G; B64G3/00; G; G01; G01C; G01C11/00; G01C11/02; G01C11/025
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
184 words
A System for optically mapping the surface of a planet or the like comprising, a spin stabilized spacecraft which is launched from Earth and whose spin axis is oriented towards Earth, said spacecraft having an eccentric orbit about said planet, and an optical system mounted aboard said spacecraft to scan normal to said spacecraft spin axis an elongated image swath which advances over the surface of said planet due at least in part to the spinning of said spacecraft about said spin axis, said elongated image swath being formed from a succession of instantaneous line images each having a length corresponding to the width of the image swath and being dimensioned to contain a predetermined number of resolution elements associated with said optical system and to provide an instantaneous coverage of the planetary surface determined by the distance of said spacecraft from said surface, said optical system including means for converting the light incoming from each of said line images into corresponding video voltage signals representing the light intensity at selected spectral regions of each of said line images forming said elongated image swath.
Claim 2
Independent Claim
184 words
A System for optically mapping the surface of a planet or the like comprising, a spin stabilized spacecraft which is launched from Earth and whose spin axis is oriented towards Earth, said spacecraft having an eccentric orbit about said planet, and an optical system mounted aboard said spacecraft to scan normal to said spacecraft spin axis an elongated image swath which advances over the surface of said planet due at least in part to the spinning of said spacecraft about said spin axis, said elongated image swath being formed from a succession of instantaneous line images each having a length corresponding to the width of the image swath and being dimensioned to contain a predetermined number of resolution elements associated with said optical system and to provide an instantaneous coverage of the planetary surface determined by the distance of said spacecraft from said surface, said optical system including means for converting the light incoming from each of said line images into corresponding video voltage signals representing the light intensity at selected spectral regions of each of said line images forming said elongated image swath.
Claim 3
Dependent Claim
112 words
The system specified in claim 1 wherein said optical system comprises, a mechanical slit representing a light passage which when projected onto the surface of said planet defines the dimensions of said instantaneous line image and being effective to pass the light incoming from said line image, means receptive of the line image light passing through said mechanical slit for dispersing said line image transversely of its length according to the spectral content of said line image, and photosensor means disposed to receive said spectrally dispersed line image for generating an output voltage signal indicative of the spectral content of said image at each preselected spectral region of interest within said image.
Claim 4
Dependent Claim
14 words
The system specified in claim 2 wherein said image dispersing means is prism means.
Claim 5
Dependent Claim
38 words
The system specified in claim 2 wherein said photosensor means is a plurality of solid state photosensors arranged as a mosaic, said mosaic containing a predetermined number of said photosensors for each resolution element in said line image.
Claim 6
Dependent Claim
11 words
The system specified in claim 4 wherein said photosensors are phototransistors.
Claim 7
Dependent Claim
121 words
The system specified in claim 4 wherein the individual photosensors within said predetermined number of photosensors associated with each resolution element of said input light image are disposed to receive and be associated with different wavelength components of interest within said spectrally dispersed light image, each photosensor producing a voltage output signal indicative of the light image intensity occurring at the associated wavelength for the associated resolution element of said light image, and further including, means connected to combine the voltage output signals from the photosensors associated with adjacent wavelengths for producing, for each spectral region of interest, a digital signal representing the average value of the input image light intensity within the associated spectral region of said incoming light image.
Claim 8
Dependent Claim
53 words
The system specified in claim 6 and further including, storage means for storing said digital signal for each spectral region of interest in said incoming light image, and means operably connected to said storage means for communicating to a receiving station on Earth information regarding the digital signals stored in said storage means.
Claim 9
Dependent Claim
41 words
The optical mapping system specified in claim 1 wherein said spacecraft is launched when the Earth approaches intercept with the orbital plane of the planet to be mapped and the interplanetary trajectory of said spacecraft traverses substantially 180* of heliocentric travel.
Claim 10
Dependent Claim
42 words
The optical mapping system specified in claim 1 wherein said eccentric orbit is dimensioned such that the ratio of the distances from the spacecraft to the surface of Said planet to be mapped at apo-apsis and peri-apsis is substantially twenty to one.
Claim 11
Dependent Claim
27 words
The optical mapping system specified in claim 1 wherein each line image forming said image swath is one resolution element wide and one thousand resolution elements long.
References Cited (Backward Citations)
US3504975A
Cited
US3560642A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-11 | 1976-01-10 | 1976-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-11 | 1980-01-10 | 1980-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-11 | 1984-01-10 | 1984-07-11 | $7700.00 | Window Closed / Lapsed |