Communication system utiliizing a constellation of satellites and method therefor

• US 20020102939A1
• Filed: 01/29/2001
• Published: 08/01/2002
• Est. Priority Date: 01/29/2001
• Status: Active Grant

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Shaneyfelt, James T.
• Granted Patent: US 6,745,006 B2
• Time in Patent Office: Days
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/18521 Systems of inter linked satellites, i.e. inter satellite service for optical links between satellites H04B10/118
• CPC Class Codes: H04B 7/19 Earth-synchronous stations

Abstract

A communication system (20) utilizing a constellation (22) of satellites (24) is presented. A source ground station (52) transmits an uplink signal (34) containing source payload data (32) to a primary satellite (26) located in an orbit (70) about the Earth (56). The primary satellite (26) conveys the source payload data (32) to a secondary satellite (28) located proximate the primary satellite (26) in the orbit (70), where the source payload data (32) is baseband processed to produce destination payload data (42), which is then conveyed back to the primary satellite (26). The primary satellite (26) transmits a downlink signal (50) containing the destination payload data (42) to a destination ground station (54). The primary satellite (26) and secondary satellites are configured to expend majorities of their energy budgets in downlink transmissions and payload data processing, respectively.

Claims

1. A communication system utilizing a constellation of satellites, said communication system comprising:

a plurality of destination ground stations configured to receive a multiplicity of downlink signals;

a primary satellite configured to transmit one of said multiplicity of downlink signals to one of said plurality of destination ground stations, and configured to expend a majority of a primary-satellite energy budget in transmitting said multiplicity of downlink signals during a lifetime of said constellation of satellites;

a secondary satellite configured to baseband process source payload data contained in an uplink signal to produce destination payload data to be contained in said one downlink signal, configured to convey said payload data to said primary satellite, and configured to expend a majority of a secondary-satellite energy budget in baseband processing payload data to be contained in a plurality of said multiplicity of said downlink signals during a lifetime of said constellation of satellites; and

a source ground station configured to transmit an uplink signal containing said source payload data to one of said primary satellite and said secondary satellite.

2. A communication system as claimed in claim 1 wherein:

said majority of said primary-satellite energy budget is at least seventy percent thereof; and

said majority of said secondary-satellite energy budget is at least seventy percent thereof.

3. A communication system as claimed in claim 1 wherein:

said primary satellite is located at a first position in an orbit about the Earth, and

said secondary satellite is located at a second position in said orbit, said second position being proximate said first position.

4. A communication system as claimed in claim 3 wherein said orbit is a geosynchronous orbit.

5. A communication system as claimed in claim 1 wherein said secondary satellite comprises:

a demodulator configured to demodulate a source intermediate-frequency signal containing said source payload data into a source baseband signal containing said source payload data;

a processor configured to process said source baseband signal to produce a destination baseband signal containing said destination payload data in response to said source payload data;

a modulator configured to modulate said destination baseband signal into a destination intermediate-frequency signal containing said destination payload data; and

an intersatellite transmitter configured to transmit said destination intermediate-frequency signal to said primary satellite.

6. A communication system as claimed in claim 5 wherein said secondary satellite additionally comprises an intersatellite receiver configured to receive said source intermediate-frequency signal from said primary satellite.

7. A communication system as claimed in claim 5 wherein said secondary satellite additionally comprises:

an uplink receiver configured to receive said uplink signal from said source ground station; and

a down-converter configured to convert said uplink signal into said source intermediate-frequency signal.

8. A communication system as claimed in claim 1 wherein said primary satellite comprises:

an intersatellite receiver configured to receive a destination intermediate-frequency signal containing said destination payload data from said secondary satellite;

an up-converter configured to convert said destination intermediate-frequency signal into said one downlink signal; and

a downlink transmitter configured to transmit said one downlink signal to said one destination ground station.

9. A communication system as claimed in claim 8 wherein said primary satellite additionally comprises:

an uplink receiver configured to receive said uplink signal from said source ground station;

a down-converter configured to convert said uplink signal into a source intermediate-frequency signal containing said source payload data; and

an intersatellite transmitter configured to transmit said source intermediate-frequency signal to said secondary satellite.

10. A communication system as claimed in claim 1 wherein an intersatellite transmitter in a first one of said primary and secondary satellites and an intersatellite receiver in a second one of said primary and secondary satellites together comprise a free-space optical transmission link configured to convey said payload data.

11. A method of communication utilizing a constellation of satellites, said method comprising:

a) conveying an uplink signal containing source payload data from a source ground station to one of a primary satellite and a secondary satellite;

b) determining if said source payload data is to be baseband processed;

c) processing, when said determining activity determines said source payload data is to be baseband processed, said source payload data in said secondary satellite to produce destination payload data; and

d) conveying a downlink signal containing said destination payload data from said primary satellite to a destination ground station.

12. A method as claimed in claim 11 additionally comprising:

converting said uplink signal into a source intermediate-frequency signal containing said source payload data; and

converting, when said determining activity b) determines said source payload data is not to be baseband processed, said intermediate-frequency signal into said downlink signal, wherein said destination payload data is substantially identical to said source payload data.

13. A method as claimed in claim 11 wherein said processing activity c) comprises:

e) converting said uplink signal into a first intermediate-frequency signal containing said source payload data;

f) conveying, when said conveying activity a) conveys said uplink signal to said primary satellite, said first intermediate-frequency signal from said primary satellite to said secondary satellite;

g) demodulating said first intermediate-frequency signal to produce a first baseband signal containing said source payload data;

h) processing said first baseband signal to produce a second baseband signal containing said destination payload data;

i) modulating said second baseband signal to produce a second intermediate-frequency signal containing said destination payload data;

j) conveying said second intermediate-frequency signal from said secondary satellite to said primary satellite; and

k) converting said second intermediate-frequency signal into said downlink signal.

14. A method as claimed in claim 13 wherein said conveying activity f) comprises:

transmitting said first intermediate-frequency signal from said primary satellite; and

receiving said first intermediate-frequency signal at said secondary satellite.

15. A method as claimed in claim 13 wherein said conveying activity j) comprises:

transmitting said second intermediate-frequency signal from said secondary satellite; and

receiving said second intermediate-frequency signal at said primary satellite.

16. A method as claimed in claim 13 wherein:

said conveying activity f) and said conveying activity j) convey said first and second intermediate-frequency signals between said primary and secondary satellites utilizing lasers.

17. A method as claimed in claim 11 wherein, when said conveying activity a) conveys said uplink signal to said secondary satellite, said determining activity b) is performed prior to said conveying activity a).

18. A communication method as claimed in claim 11 wherein said conveying activity a) comprises:

transmitting said uplink signal from said source ground station; and

receiving said uplink signal at one of said primary satellite and said secondary satellite.

19. A communication method as claimed in claim 11 wherein said conveying activity d) comprises:

transmitting said downlink signal from said primary satellite; and

receiving said downlink signal at said destination ground station.

20. A point-to-point communication system utilizing a constellation of satellites, said communication system comprising:

a source ground station configured to transmit an uplink signal containing source payload data;

a primary satellite located at a first position in an orbit about the Earth, said primary satellite expending greater than fifty percent of its energy in transmitting a multiplicity of downlink signals containing destination payload data during a lifetime of said constellation, and said primary satellite comprising;

an uplink receiver configured to receive said uplink signal from said source ground station;

an up-converter configured to convert said uplink signal into a source intermediate-frequency signal containing said source payload data;

an intersatellite transmitter configured to transmit said source intermediate-frequency signal;

an intersatellite receiver configured to receive a destination intermediate-frequency signal containing said destination payload data;

a down-converter configured to convert said destination intermediate-frequency signal into one of said multiplicity of downlink signals, said one downlink signal containing said destination payload data; and

a downlink transmitter configured to transmit said one downlink signal;

a secondary satellite located at a second position in said orbit proximate said first position, said secondary satellite expending greater than fifty percent of its energy in producing said destination payload data for each of said multiplicity of said downlink signals during said lifetime of said constellation, and said secondary satellite comprising;

an intersatellite receiver configured to receive said source intermediate-frequency signal from said primary satellite.;

a demodulator configured to demodulate said source intermediate-frequency signal into a source baseband signal containing said source payload data;

a processor configured to process said source baseband signal to produce a destination baseband signal containing said destination payload data for said one downlink signal in response to said source payload data;

a modulator configured to modulate said destination baseband signal into said destination intermediate-frequency signal; and

an intersatellite transmitter configured to transmit said destination intermediate-frequency signal to said primary satellite; and

a destination ground station configured to receive said one downlink signal from said primary satellite.