METHOD OF GUIDANCE FOR PLACING A SATELLITE ON STATION

• US 20160178750A1
• Filed: 12/11/2015
• Published: 06/23/2016
• Est. Priority Date: 12/17/2014
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: AMALRIC, Jol, DARGENT, Thierry, LE BRIS, Christophe
• Granted Patent: US 9,798,008 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B64G 1/2427 Transfer orbits
• CPC Class Codes: B64G 1/405 Ion or plasma engines per se F03H1/00
• CPC Class Codes: G01S 19/02 Details of the space or ground control segments

Abstract

A method of guidance for placing a satellite on station comprises the following steps carried out during a predefined current cycle: A) determining on the ground a law of orientation of the thrust vector, and a history of state variables and of adjoint state variables of the satellite for the transfer from a starting orbit to a target orbit using optimal control theory, B) determining on the ground a law of evolution of the rotation of the satellite about the thrust vector, on the basis of the orientation law and of the history, C) representing according to a predetermined format the evolution of the state variables and adjoint state variables so as to obtain first parameters, D) representing according to a predetermined format a law of evolution of the rotation so as to obtain second parameters, E) concatenating the first and second parameters so as to obtain a guidance plan for the satellite, F) downloading onboard the guidance plan, G) periodically repeating according to a predefined period which is smaller than the duration of the guidance cycle: g1) reconstructing onboard the satellite a guidance instruction, g2) executing onboard the satellite the instruction by applying a closed control loop, H) measuring on the ground the real orbital trajectory of the satellite, I) repeating steps A) to H) with the trajectory measured at the end of the cycle as starting orbit of the following cycle, until the target orbit is attained.

Claims

1. A method of guidance for the placement on station of a satellite equipped with means of communication with a ground station, comprising the following steps carried out during a predefined current cycle:

A) determining on the ground for a predetermined cycle, a law of orientation of the thrust vector of the satellite, and a history of state variables and of adjoint state variables of the satellite for the transfer from a starting orbit to a predetermined target orbit using optimal control theory,

B) determining on the ground for the said cycle period, on the basis of the law of orientation of the thrust vector of the satellite and of the history of state variables and of adjoint state variables of the satellite, represented in an inertial reference frame, a law of evolution of the rotation of the satellite about the thrust vector,

C) representing according to a predetermined format the evolution of the state variables and adjoint state variables so as to obtain first parameters,

D) representing according to a predetermined format a law of evolution of the rotation so as to obtain second parameters,

E) concatenating the first and second parameters so as to obtain a guidance plan for the satellite,

F) downloading onboard the satellite the guidance plan for the satellite,

G) during the current cycle, periodically repeating the following sub-steps according to a predefined period which is smaller than the duration of the guidance cycle;

g1) reconstructing onboard the satellite a guidance instruction for the satellite,

g2) executing onboard the satellite the guidance instruction by applying a closed control loop,

H) measuring on the ground the real orbital trajectory of the satellite,

I) repeating steps A) to H) periodically from cycle to cycle, with the trajectory measured at the end of the previous cycle as starting orbit of the following cycle, until the target orbit is attained.

2. The method according to claim 1, wherein the target orbit is an operational orbit.

3. The method according to claim 1, wherein the starting orbit is an injection orbit.

4. The method according to claim 1, wherein the evolution of the state variables and adjoint state variables is represented using a polynomial representation.

5. The method according to claim 1, wherein the law of evolution of the rotation is represented in the form of a sampling table.

6. The method according to claim 5, wherein the current cycle is of a week.

7. A computer program product, the computer program comprising code instructions to perform the steps of the method according to claim 1, when the program is executed on a computer.