Cellular Interferometer for Continuous Earth Remote Observation (CICERO)

• US 20100063733A1
• Filed: 09/09/2008
• Published: 03/11/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: GeoOptics, Inc.
• Original Assignee: GeoOptics, Inc.
• Inventors: Yunck, Thomas Patrick
• Granted Patent: US 9,857,475 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: B64G 1/1021 Earth observation satellites
• CPC Class Codes: B64G 1/1085 Swarms and constellations
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 13/9023 combined with interferometric techniques
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

A fleet of small spacecraft (“cells”) in low Earth orbit combine to form an integrated Earth observing system providing many observations previously requiring distinct sensing systems. Each cell performs a few relatively primitive functions, including emission, reception, sampling, and recording of radio and microwave signals. Each cell observes over a spherical field of view, samples the received signals independently at many small antenna elements, and stores the data from each element. Data from all cells are sent to a common location where they can be combined in diverse ways to realize a wide range of observing functions. These functions may include ionosphere and gravity field mapping; atmospheric radio occultation; ocean, ice, and land altimetry; ocean scatterometry; synthetic aperture radar (SAR) imaging; radar sensing of soil moisture, land cover, and geological surface properties; and interferometric SAR sensing of surface change. The system can also provide real-time messaging, navigation and surveillance functions.

Claims

1. Designs and orbit configurations for a plurality of small Earth satellites, or “

cells,”

each said cell performing a set of relatively primitive functions, including emission, reception, sampling, and recording of radio and microwave signals for subsequent combination and processing to produce a diversity of observations of the earth system, its atmosphere, ionosphere, surface, potential fields, and climate.

2. The cells of claim 1 wherein reception of radio and microwave signals by each said cell is performed in selected frequency bands within up to a 4 pi steradian field of view, or spherical shell, surrounding said cell.

3. The cells of claim 2 wherein said emission of radio and microwave signals is performed in select frequency bands over a broad, downward-directed conical field of view centered approximately at the nadir and extending at least 1000 km beyond the earth limb in all directions, as viewed from said cells.

4. The cells of claim 3 wherein reception of radio and microwave signals by each said cell is performed by means of a plurality of antenna elements on the surface of each said cell.

5. The cells of claim 4 wherein the signals received at each said antenna element are individually amplified, filtered, downconverted, and digitally sampled at the Nyquist rates for the selected bands for each said antenna element.

6. The cells of claim 5 wherein said digital samples of said signals received at each said antenna element may optionally be further processed to reduce bit volume and/or to extract specific information from said signals before the data are stored and rendered for use.

7. The cells of claim 6 wherein said information extracted from said received signals at each said antenna element may include, but is not limited to, time histories of signal voltages, signal carrier phases and frequencies, signal amplitudes, signal-to-noise ratios, signal polarizations, telemetry information, and other information modulated onto said signals.

8. The cells of claim 7 wherein the signals emitted by any and all global navigation satellites, including signals in the L1, L2, and L5 frequency bands from GPS, Galileo, Glonass, and any future such systems, observable anywhere above the earth'"'"'s limb by said cells, may be received and processed by said cells to compute each cell'"'"'s real-time position, velocity, acceleration, attitude, clock offset, and clock rate, and to extract and store any data messages carried by said global navigation satellite system (GNSS) signals.

9. The cells of claim 8 wherein wide-area differential GNSS correction signals broadcast either by Earth satellites or from the ground may be received and processed by said cells to enhance their real-time navigation solutions.

10. The cells of claim 9 wherein said radio signals emitted by each said cell may carry any and all data and information extracted from all said received signals, including but not limited to all navigation solutions, signal parameters, science data, and other data and communications received either from other satellites or from emitters on the ground.

11. The cells of claim 10 wherein said emissions may also include infrared and optical laser signals directed towards the earth'"'"'s limb over a full 360 degrees of azimuth with respect to said cells.

12. The cells of claim 11 wherein said cells are deployed in numbers ranging from twelve to two thousand and are placed in widely distributed low earth orbits that offer continuous GNSS radio occultation coverage of the earth between at least plus-and-minus 75 degrees latitude.

13. A particular realization of the cells of claim 12 wherein said signals emitted and received by said cells include signals in the 20-megahertz (MHz) L1, L2, and L5 frequency bands of the Global Positioning System, as well as in a plurality of bands centered at frequencies ranging from 100 MHz to 250 gigahertz (GHz), which center frequencies may include but are not limited to 150 MHz, 400 MHz, 10 GHz, 14 GHz, 17 GHz, 20 GHz, 22.5 GHz, 60 GHz, 112 GHz, 165 GHz, 183 GHz, and 195 GHz.

14. A particular realization of the cells of claim 13 wherein said signals emitted by each said cell are modulated by unique pseudorandom noise (PN) codes that disperse their power over a broader frequency band and permit multiple said signals emitted by multiple said cells on a common carrier frequency to be individually distinguished and tracked by receivers on other said cells by the method of code division multiple access (CDMA).

15. A particular realization of the cells of claim 14 wherein each said cell is equipped with electronics and a processor enabling said cell to detect, distinguish, and track the emissions of all other said cells in the constellation by the CDMA method, and to extract from each said received signal the signal features cited in claim 7.

16. A particular realization of the cells of claim 15 wherein each said cell may transmit any and all data it has extracted, and may receive the data collected or re-transmitted by other said cells of the constellation (“

secondary data”

), to either re-transmit said data or perform onboard combining and processing of said data collected from other said cells of the constellation.

17. A particular deployment of the cells of claim 16 wherein three or more said cells fly in an arc formation (“

chain”

) within or near the same low Earth orbit, emitting signals at two or more radio frequencies, such as, but not restricted to, 22.5 GHz, 60 GHz, 112 GHz, 183 GHz, and 195 GHz, where each said emission is modulated by a unique PN code so that said emissions can be received, distinguished, and tracked by all other said cells in said chain that are within line-of-sight view of said emissions.

18. A particular deployment of cells wherein two such chains as set forth in claim 17 travel in opposing directions within the same or nearly the same orbit plane, giving rise to multiple rising and setting crosslink atmospheric occultations between said cells of the two said chains.

19. A variation of the orbit configuration of claim 18 wherein the said cells of one chain are dispersed within the plane around the full orbit, providing daily global coverage of crosslink atmospheric occultations between said cells of the two said chains.

20. A particular realization of the orbit configuration of claim 19 wherein the said cells of one said chain are dispersed non-uniformly within the plane around the orbit in such a way as to compensate for the convergence of high-inclination orbits near the poles, providing nearly uniform geographical daily coverage of crosslink atmospheric occultations between said cells of the two said chains.

21. A particular realization of the orbit configurations of claims 17-20 wherein one or more pairs of cells within a given chain are spaced in such a way that crosslinks exchanged between said cell pairs always or nearly always pass through the earth'"'"'s atmosphere throughout the orbit to provide a continuous or nearly continuous atmospheric radio occultation.