Method for synchronizing a space telecommunications system comprising at least one satellite

• US 6,725,034 B1
• Filed: 10/20/2000
• Issued: 04/20/2004
• Est. Priority Date: 02/06/1998
• Status: Expired due to Term

• Current Assignee: Centre National D'Etudes Spatiales
• Original Assignee: Centre National D'Etudes Spatiales
• Inventors: Diris, Jean-Pierre
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): RAMPURIA, SHARAD K
• Application Number:
  US09/601,324
• Time in Patent Office: 1,278 Days
• Field of Search: 455/13.1, 455/13.2, 455/12.1, 455/427, 370/318, 370/324, 244/158.R
• US Class Current: 455/427
• CPC Class Codes: H04B 7/1855 using a telephonic control signal, e.g. propagation delay variation, Doppler frequency variation, power variation, beam identification

Abstract

The invention relates to a method for synchronizing a space telecommunications system comprising at least one satellite and several user terminals, each satellite comprising:

off-line and real time means (20) delivering tracking measurements;

a means for processing these measurements so as to smooth them through an orbit model in order to provide accurate orbit restitution and real time synchronization information; and

a means (21) for transmitting the information to the user terminals (22).

Claims

1. A method of synchronizing a telecommunications space system comprising at least one satellite and at least two user terminals, each satellite comprising means for transmitting synchronization information to user terminals, means for delivering off-line and real time tracking measurements, and means for processing the tracking measurements to smooth them through an orbit model, said method comprising the steps of:

performing an accurate and real time orbit restitution measurement aboard each satellite;

transmitting the satellite orbit restitution measurement and an on-board reference time to each of the user terminals; and

synchronizing transmissions between each of the user terminals and a given satellite of the at least one satellite, with respect to the on-board reference time.

2. The method according to claim 1, wherein is the performing step performs the orbit restitution measurement based on Doppler measurements produced by a DORIS system.

3. The method according to claim 1,

wherein the performing step performs orbit restitution measurement based on pseudo-distances and pseudo-speeds produced by a GPS system.

4. The method according to claim 1,

wherein each terminal communicating with a the at least one satellite performs the following operations:

identifying a time shift of a time reference of the at least one satellite with respect to satellite time;

theoretically calculating a terminal/satellite propagation delay from the orbit restitution measurement and a terminal position; and

transmitting a terminal/satellite up-link information telecommunication signal at a date required by the at least one satellite, the signal being pre-compensated for Doppler frequency and synchronization offset time.

5. A synchronizing system for synchronizing a telecommunications space system comprising at least one satellite and at least two user terminals, each satellite comprising means for transmitting synchronization information to each of the user terminals, means for delivering off-line and real time tracking measurements, and means for processing the tracking measurements to smooth them through an orbit model, said synchronizing system comprising:

means for performing an accurate and real time orbit restitution measurement aboard each satellite;

means for transmitting the satellite orbit restitution measurement and an on-board reference time to each of the user terminals; and

means for synchronizing transmissions between each of the user terminals and a given satellite of the at least one satellite, with respect to the on-board reference time.

6. A synchronizing system for synchronizing a telecommunications space system, said synchronizing system comprising:

at least one satellite; and

at least two user terminals,

wherein each satellite is configured to transmit synchronization information to each of the user terminals, deliver off-line and real time tracking measurements, process the tracking measurements to smooth them through an orbit model, perform an accurate and real time orbit restitution measurement, and transmit the satellite orbit restitution measurement and an on-board reference time to each of the user terminals, and

wherein each user terminal is configured to synchronize transmissions to a given satellite of the at least one satellite, with respect to the on-board reference time.