Method for calibrating spatial errors, and method and system for estimating the attitude of a vehicle
First Claim
1. A method for 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 steps of:
- calibrating spatial errors induced by phase biases affecting measurements of the phase differences of the radio-electric signals received by said at least three non-aligned reception antennas of the craft, said phase biases depending on a direction of incidence of the radio-electric signals with respect to the craft, comprising 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;
calculating by at least one processor, 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;
calculating by said at least one processor, 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;
calculating by said at least one processor, 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
calculating by said at least one processor, 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; and
compensating the spatial errors calculated during a calculation of the attitude of the craft.
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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.
10 Citations
14 Claims
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1. A method for 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 steps of:
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calibrating spatial errors induced by phase biases affecting measurements of the phase differences of the radio-electric signals received by said at least three non-aligned reception antennas of the craft, said phase biases depending on a direction of incidence of the radio-electric signals with respect to the craft, comprising 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; calculating by at least one processor, 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; calculating by said at least one processor, 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; calculating by said at least one processor, 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 calculating by said at least one processor, 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; and compensating the spatial errors calculated during a calculation of the attitude of the craft. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A system to calculate an attitude of a craft as a function of measurements of phase differences of radio-electric signals, comprising:
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at least three non-aligned reception antennas on the craft for receiving the radio-electric signals; a processing unit comprising at least one processor configured to; obtain 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 calculate 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; calculate 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 calculate 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 a calculated inter-satellite angular distance; calculate 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 calculated inter-satellite angular distance determined for said pair of satellites; and compensate the spatial errors calculated during a calculation of the attitude of the craft. - View Dependent Claims (12, 13, 14)
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Specification