METHOD FOR CALIBRATING SPATIAL ERRORS, AND METHOD AND SYSTEM FOR ESTIMATING THE ATTITUDE OF A VEHICLE

• US 20150015436A1
• Filed: 03/28/2013
• Published: 01/15/2015
• Est. Priority Date: 03/29/2012
• Status: Active Grant

• Current Assignee: Airbus Defence and Space GmbH, Centre National D'Etudes Spatiales
• Original Assignee: Airbus Defence and Space GmbH
• Inventors: Polle, Bernard, Broquet, Renaud, Montel, Johan
• Granted Patent: US 9,846,243 B2
• Time in Patent Office: Days
• US Class Current: 342/357.38
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/53 Determining attitude
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry
• CPC Class Codes: G01S 19/55 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 3/46 using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 5/0247 Determining attitude
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence

Abstract

A method for calibrating spatial errors induced by phase biases having a detrimental effect on the measurements of phase differences of radio signals received by three unaligned receiving antennas of a vehicle. An inter-satellite angular deviation of a pair of satellites is estimated in two different ways: on the basis of the respective positions of the vehicle and of the satellites to obtain a theoretical inter-satellite angular deviation; and on the basis of the respective directions of incidence of the satellites relative to the vehicle, which are determined from phase measurements, to obtain an estimated inter-satellite angular deviation. The space errors are estimated on the basis of said theoretical and estimated inter-satellite angular deviations. Also, a method and system for estimating the attitude of a vehicle, in particular a spacecraft.

Claims

1-15. -15. (canceled)

16. A method for calibrating spatial errors induced by phase biases affecting measurements of phase differences of radio-electric signals received by at least three non-aligned reception antennas of a craft, said phase biases depending on a direction of incidence of the radio-electric signals with respect to the craft, comprises, comprising the steps of:

obtaining respective positions of the craft and a pair of satellites situated at a given instant in a radio-electric field of view of the craft;

estimating an inter-satellite angular distance of said pair of satellites as a function of the respective positions of the craft and said pair of satellites to obtain a theoretical inter-satellite angular distance;

estimating respective directions of incidence of said pair of satellites with respect to the craft as a function of phase measurements of radio-electric signals received from said pair of satellites by the three non-aligned reception antennas of the craft;

estimating the inter-satellite angular distance of said pair of satellites as a function of the respective directions of incidence of said pair of satellites with respect to the craft to obtain an estimated inter-satellite angular distance; and

estimating the spatial errors for the respective directions of incidence of the said pair of satellites with respect to the craft as a function of the theoretical inter-satellite angular distance and of the estimated inter-satellite angular distance determined for said pair of satellites.

17. The method as claimed in claim 16, further comprising the step of estimating the spatial errors in a form of a parametric model whose parameters are estimated as a function of theoretical inter-satellite angular distances and of estimated inter-satellite angular distances determined for pairs of satellites.

18. The method as claimed in claim 17, further comprising the step of pre-partitioning the radio-electric field of view of the craft into a plurality of distinct cones of incidence of radio-electric signals with respect to the craft;

and wherein the spatial errors are considered to be the same for any direction of incidence inside same incidence cone.

19. The method as claimed in claim 18, wherein the cones of incidence of low elevation with respect to a plane determined by phase centers of the three non-aligned reception antennas of the craft are of smaller respective solid angles than those of cones of incidence of high elevation with respect to said plane.

20. The method as claimed in claim 17, further comprising the step of estimating the spatial errors in a form of a parametric model whose basis functions are spherical harmonics.

21. The method as claimed in claim 16, wherein the satellites belong to a global satellite navigation system and the three non-aligned reception antennas are antennas of receivers of said global satellite navigation system;

and further comprising the step of determining the respective positions of the satellites and of the craft in accordance with navigation information included in the radio-electric signals received from said satellites.

22. The method as claimed in claim 16, further comprising the step of estimating the spatial errors in a recursive manner, a pair of satellites by a pair of satellites or a group of pairs of satellites by a group of pairs of satellites.

23. The method as claimed in claim 16, wherein Ns satellites organized into Np pairs being situated simultaneously in a radio-electric field of view of the craft;

and further comprising the step of estimating the spatial errors for each of the respective directions of incidence of the Ns satellites with respect to the craft simultaneously as a function of the theoretical inter-satellite angular distances and of the estimated inter-satellite angular distances determined for said Np pairs of satellites.

24. The method as claimed in claim 16, further comprising the step of utilizing at least one of:

new pairs of satellites entering the radio-electric field of view of the craft in a course of time or a same pair of satellites several times in the course of time.

25. A method of estimating attitude of a craft as a function of measurements of phase differences of radio-electric signals received by at least three non-aligned reception antennas of the craft, comprising the steps of calibrating the spatial errors in accordance with the method as claimed in claim 16;

and compensating the spatial errors estimated during an estimation of the attitude of the craft.

26. A non-transitory computer readable medium comprising a set of program code instructions, when executed by a processor, implement the steps of calibrating the spatial errors in accordance with the method as claimed in claim 16

27. A system for estimating attitude of a craft as a function of measurements of phase differences of radio-electric signals, comprising:

at least three non-aligned reception antennas on the craft for receiving the radio-electric signals;

a first processing unit obtains respective positions of the craft and a pair of satellites situated at a given instant in a radio-electric field of view of the craft, and estimates an inter-satellite angular distance of said pair of satellites as a function of the respective positions of the craft and said pair of satellites to obtain a theoretical inter-satellite angular distance;

a second processing unit estimates respective directions of incidence of said pair of satellites with respect to the craft as a function of phase measurements of radio-electric signals received from said pair of satellites by the three non-aligned reception antennas of the craft, and estimates the inter-satellite angular distance of said pair of satellites as a function of the respective directions of incidence of said pair of satellites with respect to the craft to obtain an estimated inter-satellite angular distance; and

a third processing unit estimates the spatial errors for the respective directions of incidence of the said pair of satellites with respect to the craft as a function of the theoretical inter-satellite angular distance and of the estimated inter-satellite angular distance determined for said pair of satellites.

28. The attitude estimation system as claimed in claim 27, wherein the three non-aligned reception antennas are antennas of receivers of a global satellite navigation system.

29. A spacecraft comprising an attitude estimation system as claimed in claim 27.

30. The spacecraft as claimed in claim 29, further comprising a body comprising a plurality of substantially plane external faces;

and wherein the three non-aligned reception antennas are arranged on same external face of said body.