Cellular interferometer for continuous earth remote observation (CICERO)

• US 9,857,475 B2
• Filed: 09/09/2008
• Issued: 01/02/2018
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: GeoOptics, Inc.
• Original Assignee: GeoOptics, Inc.
• Inventors: Yunck, Thomas Patrick
• Primary Examiner(s): Dinh, Tien Q
• Assistant Examiner(s): Fabula, Michael A.
• Application Number:
  US12/206,927
• Publication Number:
  US 20100063733A1
• Time in Patent Office: 3,402 Days
• Field of Search: 2441584
• 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. A system for generating a set of Earth observations comprising:

a constellation of at least three satellites, wherein;

(i) each satellite in the constellation of satellites individually includes;

a Global Navigation Satellite System (GNSS) antenna to receive a GNSS signal;

(ii) at least two satellites in the constellation of satellites individually include;

a first crosslink antenna that points in a first direction,

wherein a first crosslink module feeds a first received signal from the first crosslink antenna to a digital signal processor; and

a second crosslink antenna that points in a second direction opposite the first direction,

wherein a second crosslink module feeds a second received signal from the second crosslink antenna to the digital signal processor; and

(iii) each satellite in the constellation of satellites individually includes a down-looking receiving antenna;

wherein the first crosslink module is programmed to conduct an encoding of a first transmission signal for transmission in the first direction;

wherein the second crosslink module is programmed to conduct an encoding of a second transmission signal for transmission in the second direction;

wherein the encoding of the first transmission signal and the encoding of the second transmission signal use a unique code;

wherein the unique code is unique to the satellite; and

wherein the system processes recorded data from the constellation of at least three satellites to generate the set of Earth observations;

wherein the system determines a first distance and a second distance using the GNSS signal, the first transmission signal, and the second transmission signal; and

wherein at least one Earth observation in the set of Earth observations is derived from the first distance and the second distance.

2. The system of claim 1, wherein the digital signal processor is programmed to:

distinguish the first received signal from a third received signal received from the first direction based on a second code; and

distinguish the second received signal from a fourth received signal received from the second direction based on a third code.

3. The system of claim 2, wherein:

the unique code, the second code, and the third code are pseudonoise spread spectrum codes;

the third code and the second code are different; and

the encoding modulates the unique code with the first transmission signal and the second transmission signal.

4. The system of claim 1, wherein:

the unique code is a pseudonoise spread spectrum code; and

the encoding modulates the pseudonoise spread spectrum code with the first transmission signal and the second transmission signal.

5. The system of claim 1, wherein:

the first crosslink module feeds a third received signal from the first crosslink antenna to the digital signal processor; and

the digital signal processor is programmed to;

determine an amplitude of the third received signal; and

set a frequency of the first transmission signal to target a Radio Frequency (RF) absorption line of a first species in the atmosphere.

6. The system of claim 5, at least one satellite in the constellation of satellites further comprising

a first Global Navigation Satellite System Radio Occultation (GNSS-RO) antenna that points in the first direction, wherein a first GNSS front end module feeds a fourth received signal from the first GNSS-RO antenna to the digital signal processor.

7. The system of claim 5, where the digital signal processor is programmed to:

conduct a precise orbit determination using the GNSS signal received on the upward-looking GNSS antenna;

determine a first relative velocity to a second satellite using the first received signal; and

determine a second relative velocity to a third satellite using the second received signal.

8. The system of claim 5, wherein:

the first crosslink module is programmed to;

(i) conduct an encoding of a third transmission signal for transmission in the first direction; and

(ii) set a frequency of the third transmission signal to target a second RF absorption line of a second species in the atmosphere;

the first RF absorption line is 22.7 GHz; and

the first species is water.

9. The system of claim 1, wherein:

the second received signal and the first transmission signal share a first frequency;

the first received signal and the second transmission signal share a second frequency; and

the first frequency and the second frequency are different.

10. The system of claim 1, at least one satellite in the constellation of satellites further comprising:

a first means for measuring a relative velocity variation which operates in the first direction; and

a second means for measuring a second relative velocity variation which operates in the second direction.

11. The system of claim 1, wherein:

the first crosslink module feeds a first set of received signals from the first crosslink antenna to the digital signal processor;

the second crosslink module feeds a second set of received signal from the second crosslink antenna to the digital signal processor;

the digital signal processor includes a set of processing channels to simultaneously process the first set of received signals and the second set of received signals; and

the first and second sets of received signals each includes greater than three signals.

12. The system of claim 1, each satellite in the constellation of satellites further comprising:

an accelerometer;

wherein the memory stores the output of the accelerometer.

13. A system for generating a set of Earth observations, comprising:

a constellation of at least three satellites, wherein;

(i) each satellite in the constellation of satellites individually includes

a Global Navigation Satellite System (GNSS) antenna to receive a GNSS signal;

(ii) at least two satellites in the constellation of satellites individually include

a first crosslink antenna that points in a first direction,

wherein a first crosslink module feeds a first received signal from the first crosslink antenna to a digital signal processor; and

a second crosslink antenna that points in a second direction opposite the first direction,

wherein a second crosslink module feeds a second received signal from the second crosslink antenna to the digital signal processor; and

(iii) each satellite in the constellation of satellites individually includes

a down-looking receiving antenna

wherein the first crosslink module is programmed to;

(i) conduct an encoding of a first transmission signal for transmission in the first direction using a first code; and

(ii) distinguish the first received signal from a third received signal received from the first direction based on a second code;

wherein the second crosslink module is programmed to;

(i) conduct an encoding of a second transmission signal for transmission in the second direction using the first code; and

(ii) distinguish the second received signal from a fourth received signal received from the second direction based on a third code;

wherein the first code is a unique code that is unique to the satellite;

wherein the system processes recorded data from the constellation of at least three satellites to generate the set of Earth observations; and

wherein the recorded data is derived from the first transmission signal and the second transmission signal.

14. The system of claim 13, wherein:

the unique code is a pseudonoise spread spectrum code; and

the encoding modulates the pseudonoise spread spectrum code with the first transmission signal and the second transmission signal.

15. The system of claim 13, wherein:

the first crosslink module feeds the third received signal from the first crosslink antenna to the digital signal processor; and

the digital signal processor is programmed to;

determine an amplitude of the third received signal; and

set a frequency of the first transmission signal to target an RF absorption line of a first species in the atmosphere.

16. The system of claim 15, at least one satellite in the constellation of satellites further comprising:

a first GNSS RO antenna that points in the first direction, wherein a first GNSS front end module feeds a fifth received signal from the first GNSS-RO antenna to the digital signal processor.

17. The system of claim 15, where the digital signal processor is programmed to:

conduct a precise orbit determination using the GNSS signal received on the upward-looking GNSS antenna;

determine a first relative velocity to a second satellite using the first received signal; and

determine a second relative velocity to a third satellite using the second received signal.

18. The system of claim 15, wherein:

the first crosslink module is programmed to;

(i) conduct an encoding of a third transmission signal for transmission in the first direction; and

(ii) set a frequency of the third transmission signal to target a second RF absorption line of a second species in the atmosphere;

the first RF absorption line is 22.7 GHz; and

the first species is water.

19. The system of claim 13, wherein:

the second received signal, the fourth received signal, and the first transmission signal share a first frequency;

the first received signal, the third received signal, and the second transmission signal share a second frequency; and

the first frequency and the second frequency are different.

20. The system of claim 13, at least one satellite in the constellation of satellites further comprising:

a first means for measuring a relative velocity variation which operates in the first direction; and

a second means for measuring a second relative velocity variation which operates in the second direction.

21. The system of claim 13, wherein:

the first crosslink module feeds a first set of received signals from the first crosslink antenna to the digital signal processor;

the second crosslink module feeds a second set of received signal from the second crosslink antenna to the digital signal processor;

the digital signal processor includes a set of processing channels to simultaneously process the first set of received signals and the second set of received signals; and

the first and second sets of received signals each includes greater than three signals.

22. The system of claim 13, at least one satellite in the constellation of satellites further comprising:

an accelerometer;

wherein the memory stores the output of the accelerometer.

23. A system for generating a set of Earth observations, comprising:

a constellation of at least three satellites, wherein;

(i) each satellite in the constellation of satellites includes

a Global Navigation Satellite System (GNSS) antenna to receive a GNSS signal;

(ii) at least two satellites in the constellation of satellites individually include

a first crosslink antenna that points in a first direction,

wherein a first crosslink module feeds a first received signal from the first crosslink antenna to a digital signal processor; and

a second crosslink antenna that points in a second direction opposite the first direction,

wherein a second crosslink module feeds a second received signal from the second crosslink antenna to the digital signal processor; and

(iii) each satellite in the constellation of satellites individually includes

a down-looking receiving antenna; and

wherein the first crosslink module is programmed to conduct an encoding of a first transmission signal for transmission in the first direction;

wherein the second crosslink module is programmed to conduct an encoding of a second transmission signal for transmission in the second direction;

wherein the system processes recorded data from the constellation of at least three satellites to generate the set of Earth observations; and

wherein the recorded data is derived from the first transmission signal and the second transmission signal.

24. The system of claim 23, wherein:

the encoding modulates the first transmission signal and the second transmission signal with a single pseudonoise spread spectrum code; and

the single pseudonoise spread spectrum code is unique to the satellite.

25. The system of claim 24, wherein:

the first crosslink module feeds a third received signal from the forward-looking crosslink antenna to the digital signal processor; and

the digital signal processor is programmed to;

determine an amplitude of the third received signal; and

set a frequency of the first transmission signal to target an RF absorption line of a first species in the atmosphere.

26. The system of claim 25, at least one satellite in the constellation of satellites further comprising:

a first GNSS-RO antenna that points in the first direction, wherein a first GNSS front end module feeds a fourth received signal from first GNSS-RO antenna to the digital signal processor.

27. The system of claim 25, where the digital signal processor is programmed to:

conduct a precise orbit determination using the GNSS signal received on the upward-looking GNSS antenna;

determine a first relative velocity to a second satellite using the first received signal; and

determine a second relative velocity to a third satellite using the second received signal.

28. The system of claim 25, wherein:

the first crosslink module is programmed to;

(i) conduct an encoding of a third transmission signal for transmission in the first direction; and

(ii) set a frequency of the third transmission signal to target a second RF absorption line of a second species in the atmosphere;

the first RF absorption line is 22.7 GHz; and

the first species is water.

29. The system of claim 24, wherein:

the second received signal and the first transmission signal share a first frequency;

the first received signal and the second transmission signal share a second frequency; and

the first frequency and the second frequency are different.

30. The system of claim 24, at least one satellite in the constellation of satellites further comprising:

a first means for measuring a relative velocity variation which operates in the first direction; and

a second means for measuring a second relative velocity variation which operates in the second direction.

31. The system of claim 24, wherein:

the first crosslink module feeds a first set of received signals from the first crosslink antenna to the digital signal processor;

the second crosslink module feeds a second set of received signal from the second crosslink antenna to the digital signal processor;

the digital signal processor includes a set of processing channels to simultaneously process the first set of received signals and the second set of received signals; and

the first and second sets of received signals each includes greater than three signals.

32. The system of claim 24, at least one satellite in the constellation of satellites further comprising:

an accelerometer;

wherein the memory stores the output of the accelerometer.