Global space radiopositioning and radionavigation system, beacon and receiver used in this system

• US 5,995,040 A
• Filed: 07/14/1997
• Issued: 11/30/1999
• Est. Priority Date: 11/14/1995
• Status: Expired due to Fees

• Current Assignee: Centre National D'Etudes Spatiales
• Original Assignee: Centre National D'Etudes Spatiales
• Inventors: Issler, Jean Luc, Berges, Dominique, Aguttes, Jean Paul, Cugny, Bruno
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/860,715
• Time in Patent Office: 869 Days
• Field of Search: 342/352, 455/12.1, 455/13.1
• US Class Current: 342/352
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments

Abstract

This invention relates to a global system dedicated to radionavigation and radiopositioning and includes:

a land segment comprising:

a global network of ground beacons (RBS) emitting an upwards wide spectrum radioelectric signal to user satellites,

a mission and control center (CMC) which creates work plans for some user satellites and transmits them when they fly over the master beacons,

a processing center (CT) that receives remote measures sorted by the mission and control center (CMC), separates remote measurements into remote measurements necessary for processing specific to the processing center (CT), and remote measurements specific to some clients of services offered by the said system;

a space segment composed of mater satellites (SM) participating closely in operation of the system and client satellites;

a user segment composed of client beacons and fixed or mobile client receivers.

Claims

1. A global system dedicated to radionavigation and radiopositioning, having a land segment, a space segment and a user segment, the land segment comprising:

a global network of beacons on the ground emitting an upwards single-directional radioelectric wide spectrum signal towards user satellites, each of the global network of beacons transmitting a message containing an identification code;

a control center configured to prepare work plans for some user satellites and transmit the work plans when the user satellites overfly master beacons, each of said work plans including at least one of a client beacon number and an observation period;

a processing center configured to receive remote measurements sorted by mission and control center, separate remote measurements into two groups, one containing remote measurements necessary for processing information specific to the processing center, and the other containing remote measurements specific to some clients of services offered by the system, wherein

the space segment being composed of master satellites and client satellites, the master satellites participating closely in operation of the system, and

the user segment is composed of client beacons and client receivers, and associated fixed or mobile carriers.

2. The system according to claim 1, wherein:

the beacons on the ground are of different types including,

orbitography beacons, the position of which being known and that permanently transmit a signal and transmit a position thereof periodically;

client beacons including positioning beacons, whose exact position being unknown when put into service; and

master beacons that transmit at least one of useful information and work plans to some user satellites and an accepting part of the system.

3. The system according to claim 1, wherein:

outputs produced by the processing center include;

precise orbitography and routine orders for some user satellites;

a precise attitude of some user satellites;

parameters representative of the ionosphere;

clock coefficients for some beacons referenced with respect to the system time;

the system time being produced by the processing center and being distributed partly to clients of services of the system and returned to the control center which uses the system time to prepare the work plan and to provide routine orbits to at least one of remote measurement stations and remote control stations using the services of the system.

4. The system according to claim 1, wherein:

the master satellites being equipped with a receiver capable of processing the message transmitted by the master beacons, and being connected to an ultra-stable oscillator,

unprocessed measurements made by the master beacons being formatted in a form of remote receiver and the data originating from the measurements received by the ground, with the processing center as a final destination.

5. The system according to claim 4, wherein:

the master satellites have at least one of a quasiheliosynchronous orbit a low each orbit and a geostationary orbit.

6. The system according to claim 1, wherein:

client satellites do not send remote measurements therefrom to the processing center and are not capable of processing the message transmitted by master beacons.

7. The system according to claim 6, wherein:

client satellites being in any type of orbit and form part of the space segment and of the system user segment.

8. The system according to claim 1, wherein:

client beacons include positioning beacons, and time beacons.

9. The system according to claim 1, wherein:

a set of the beacons being connected to a microcomputer, used to program some beacon parameters and to verify that the beacons are working correctly.

10. The system according to claim 9, wherein:

the microcomputer being connected to local measurement sensors, including,

meteorological data sensors,

GNSS unprocessed measurement sensors, or GNSS differential correction sensors;

clock coefficient sensors,

sensors determining a condition of the various elements making up the beacon in order to make remote diagnoses of failures, from the control center, and

calibration sensors.

11. The system according to claim 1, in which beacons are single frequency or dual frequency.

12. The system according to claim 1, wherein:

said beacons include precision beacons.

13. The system according to claim 1, wherein:

two beacons being assigned with an identical PN code so as to be tracked by the same satellite and are separated by a range exceeding a diameter of a visibility circle associated with the satellite.

14. The system according to claim 1, wherein:

carriers transmitted by beacons are all modulated by a reference spectrum spreading code.

15. The system according to claim 1, comprising:

a client receiver that includes at least one of a single frequency receiver and a dual frequency receiver.

16. The system according to claim 1, wherein:

precision beacons of said network of beacons are dual frequency and that at least one of the transmitted carriers is modulated by a precision spectrum spreading code in addition to a reference code, a code length of said precision spectrum spreading code being greater than that of the reference code.

17. The system according to claim 1, which includes receivers in at least one of orbit close to the land surface and ground based.

18. The system according to claim 1, further comprising:

basic receivers;

navigation receivers having a predetermined cost;

navigation and attitude detection receivers having a predetermined cost;

navigation and attitude receivers;

navigation, orbitography and precision attitude detection receivers; and

mixed receivers capable of processing signals transmitted by beacons in the system, and by satellites in GNSS constellations.

19. The system according to claim 1, comprising:

receivers configured to process reference codes only; and

receivers configured to simultaneously process reference codes and precision codes.

20. The system according to claim 1, further comprising:

a subsystem for precise monitoring of a drift of an orbiting cold atomic clock.

21. The system according to claim 1, wherein:

sequencing of transmissions from client beacons is managed according to a daily cycle described by week words, wherein each week word including a transmit indicator for each day of the week.

22. The system according to claim 1, wherein:

beacons on the ground have a common electrical and antenna architecture, except for,

beacons adapted for precise monitoring of a drift of an orbiting cold atomic clock, which have a directional diagram instead of a hemispherical type antenna diagram, and

beacons in local autonomous cells which have a specific antenna diagram.

23. The system according to claim 1, being configured for use with an interferrometric imagery technique using S.A.R. radar satellites for monitoring precise deformations of a terrain covered by a mesh of beacons received by a receiver forming part of the system installed on radar satellites.

24. The system according to claim 1, configured to determine precise variations between beacon clocks, and time beacons in particular, using orbiting and geostationary satellites carrying a receiver of the system.

25. The system according to claim 1, including GNSS2 navigation satellites configured to use a receiver of the system for navigation, and for deriving orbit and time ephemeris tables to be broadcast to users of the GNSS2 satellites.

26. The system according to claim 1, including a local autonomous beacon and receiver cells, and said receiver cells being radioelectrically connected to master or client satellites.

27. Beacon used in the system according to claim 1, which comprises:

at least one local data sensor;

a control computer connected to the said data sensor;

a reference signal generator controlled by the said oscillator;

a signal generation and transmission module for each transmitted carrier frequency controlled by the reference signal generator, this module comprising;

a carrier generator;

a short spectral spreading code generator;

a data formatter controlled by the control computer, the said data modulating the said short code in the base band through an integrator, the assembly modulating the carrier with a modulator;

an antenna, connected to the modulator through an RF amplifier.

28. The system having the beacon according to claim 27, wherein the transmitted carrier frequency being included as a frequency used in the system.

29. The system having the beacon according to claim 27, wherein said beacon being configured to transmit one of a dual frequency and a single frequency signal.

30. The system having the beacon according to claim 27, wherein:

the beacon includes a precision beacon and includes at least one of the signal generation and transmission modules, which further comprises,

a spectrum spreading code generator that generates a long code having a predetermined code length lower than that produced by said short spectral spreading code generator;

an integrator configured to modulate said long code by a message output from the data formatter;

a carrier modulated by the long code integrated with data;

a phase shifter configured to input a π

/4 phase shift of the modulated carrier; and

an adder configured to integrate the carrier modulated by the long code in quadrature with the carrier modulated by the short code.

31. The system having the beacon according to claim 27, wherein:

said beacon being a precision beacon configured to transmit long codes having a code length longer than that produced by said short spectral spreading code generator at a frequency specific to the system.

32. The system having a receiver used in the system according to claim 1, comprising for each received carrier frequency:

one to four reception antennas;

one to four radiofrequency reception and intermediate frequency transposition modules, connected to an analogue digital converter, and being specific to the received carrier frequency of the system;

at least one ASIC circuit configured to process a short spectrum spreading code that modulates the received carrier, said short spectrum spreading code having a predetermined code length;

a microprocessor assembly interconnected firstly to the at least one ASIC circuit and secondly to a memory assembly and to a digital interface;

an oscillator configured to control radiofrequency reception and intermediate frequency transposition modules, the at least one ASIC circuit and the microprocessor assembly.

33. The system having the receiver according to claim 32, comprising a radiofrequency reception and transposition module configured to process a signal from each antenna in a parallel RF architecture.

34. The system having the receiver according to claim 32, wherein:

a single radiofrequency reception and intermediate frequency transposition module is interconnected to all of the one to four antennas through a fast switch for receivers with sequenced RF architecture.

35. The system having the receiver according to claim 32, wherein:

a mixed receiver being one of the radiofrequency reception and intermediate frequency transposition modules and being adapted to operate at one of two operating frequencies of the system; and

another RF reception and IF transposition module being adapted to operate in a frequency band distributed by satellites in GNSS constellations.

36. The system having the receiver according to claim 32, wherein:

said receiver being a precision receiver adapted to receive a long code used in said system, at the received carrier of the system, said long code having a longer code length than the predetermined code length of said short spectrum spreading code, the ASIC circuit being capable of simultaneously processing the short spectrum spreading code and the long code.