Satellite-borne navigation receiver multi-antenna phase center on-orbit calibration method

Abstract

The application provides a kind of on-orbit calibration method for multi-antenna phase center of spaceborne navigation receiver, comprising the following steps: S1, selecting an on-orbit coarse measurement target antenna from the antenna to be calibrated, adjusting the attitude of the satellite platform, so that the reference antenna and the on-orbit coarse measurement target antenna are deviated to the pointing direction; S2, calculating the RTK coarse measurement vector; the satellite platform collects the original measurement data; S3, the on-orbit measurement information of the on-orbit coarse measurement target antenna is transmitted to the ground station; S4, repeating steps S1-S3, traversing all antennas to be calibrated; S5, the ground station performs offline processing based on the on-orbit measurement information, and calculates the phase center position deviation of each antenna to be calibrated; S6, uploading the satellite platform to complete on-orbit calibration. The application uses dual-antenna on-orbit differential positioning combined with real-time satellite attitude measurement information, through post-ground processing and uploading, which can effectively avoid the influence of ground environment multipath effect, and solves the technical problem of absolute phase center calibration after multi-antenna installation.

Description

Technical Field

[0001] This invention relates to multi-antenna fusion RTK (carrier phase measurement) technology for navigation receivers, specifically to an on-orbit calibration method for the phase center of multiple antennas in a spaceborne navigation receiver. Background Technology

[0002] With the widespread application of various GNSS (Global Navigation Satellite Systems) such as BeiDou and GPS (Global Positioning System), navigation receivers have become the primary sensors for satellite absolute and relative navigation. Limited by the navigation and positioning principles of GNSS, when satellite platforms undergo frequent attitude maneuvers, continuous high-precision navigation measurements are achieved using multi-antenna fusion RTK technology. RTK is a millimeter-level measurement method based on the antenna phase center position. For formation satellite systems undergoing frequent attitude maneuvers in orbit, the near-hemispherical coverage pattern of conventional antennas often necessitates configuring multiple antennas in different quadrants and orientations for multi-antenna fusion RTK. This technology involves the conversion of raw measurement information; therefore, its success rate and accuracy largely depend on the accuracy of the phase centers of each antenna. The antenna phase center is the center of curvature of the curve where the equiphase surface of the far-field radiation field intersects the plane passing through the antenna axis; that is, the equivalent radiation source center of the antenna's radiated electromagnetic waves.

[0003] Currently, there are three methods for calibrating the antenna phase center: simulation calculation, anechoic chamber measurement, and receiver system testing. Among these, simulation calculation cannot accurately assess the phase center characteristics because interference from the satellite itself after installation can distort the characteristics. Anechoic chamber measurement requires a high-quality measurement site and is generally suitable for small, independent antennas, but is unsuitable for multi-antenna satellite navigation receiver systems that are too large after installation. Receiver system testing is affected by multipath effects from the ground environment, resulting in poor calibration accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide an on-orbit calibration method for the phase center of a multi-antenna satellite navigation receiver. By using dual-antenna on-orbit differential positioning combined with real-time satellite attitude measurement information, and through post-processing and uploading on the ground, the influence of multipath effects in the ground environment can be effectively avoided, thus solving the problem of inaccurate calibration of the absolute phase center after multiple antennas are installed on the satellite.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for on-orbit calibration of the phase center of multiple antennas in a spaceborne navigation receiver, wherein the spaceborne navigation receiver is mounted on a satellite platform, and the satellite platform further includes a navigation receiving antenna electrically connected to the spaceborne navigation receiver. The navigation receiving antenna includes one reference antenna and multiple antennas to be calibrated. The on-orbit calibration method is used to calibrate the relative phase center of each antenna to be calibrated with respect to the reference antenna, using the phase center of the reference antenna as a reference. The satellite platform can communicate with a ground station. The method includes the following steps:

[0007] S1. Select an on-orbit coarse measurement target antenna from the antennas to be calibrated, adjust the attitude of the satellite platform so that the reference antenna and the on-orbit coarse measurement target antenna are biased towards the sky, so that the reference antenna and the on-orbit coarse measurement target antenna have enough common view of the satellite;

[0008] S2. Based on the reference antenna and the on-orbit coarse measurement target antenna, the satellite navigation receiver performs calculations using dual-antenna RTK technology to generate the RTK coarse measurement vector of the on-orbit coarse measurement target antenna; and simultaneously enables the reference antenna and the on-orbit coarse measurement target antenna to independently receive satellite signals and position themselves, while the satellite platform collects the raw measurement data of the reference antenna and the on-orbit coarse measurement target antenna.

[0009] S3. The generated RTK coarse measurement vector of the on-orbit coarse measurement target antenna, the original measurement data of the collected reference antenna and the on-orbit coarse measurement target antenna, as well as the ephemeris information, satellite platform attitude information and reference antenna absolute position information are transmitted to the ground station as the on-orbit measurement information of the on-orbit coarse measurement target antenna.

[0010] S4. Repeat steps S1 to S3 until all the antennas to be calibrated have been traversed;

[0011] S5. The ground station performs offline processing based on the on-orbit measurement information of each antenna to be calibrated, and calculates the phase center position deviation of each antenna to be calibrated relative to the reference antenna.

[0012] S6. Upload the phase center position deviation of each of the antennas to be calibrated to the satellite platform via parameter uploading to complete the on-orbit calibration.

[0013] Preferably, step S5 includes:

[0014] S51. Select a ground-optimized target antenna from the antennas to be calibrated. Based on the on-orbit measurement information of the ground-optimized target antenna, perform post-optimization processing on the coarse RTK measurement vector of the ground-optimized target antenna according to the dual-antenna RTK technology. After removing outliers and smoothing, obtain the fine ground-fixed system measurement vector.

[0015]

[0016] S52. Based on the observation data periodically released by IERS, and according to the IAU 2000A / B precession nutation model, calculate the transformation matrix from the Earth-fixed frame to the inertial frame at a certain epoch UTC.

[0017] S53. Based on the on-orbit measurement information of the ground-optimized target antenna and the precise ground-fixed system vector... Transformation matrix from Earth-fixed frame to inertial frame The vector of the ground-optimized target antenna relative to the reference antenna in the body coordinate system is calculated. The solution formula is as follows:

[0018]

[0019] in, The gyro attitude in the satellite platform attitude information of the on-orbit measurement information is obtained by the satellite platform attitude sensor.

[0020] S54. Based on the absolute position information of the reference antenna in the on-orbit measurement information of the ground-optimized target antenna, and the vector of the ground-optimized target antenna relative to the reference antenna in the body coordinate system. The phase center position deviation of the ground-optimized target antenna relative to the reference antenna is calculated;

[0021] S55. Repeat steps S51 to S54 until all the antennas to be calibrated have been traversed.

[0022] Preferably, the calculation formula for step S52 is:

[0023]

[0024] Where W(t), R(t), and Q(t) are the polar motion matrix, the Earth rotation matrix, and the precession-nutation transformation matrix, respectively, and t is the time variable;

[0025] Furthermore, the formula for calculating the polar shift matrix W(t) in formula (1) is as follows:

[0026]

[0027] Wherein, polar displacement x p y p Published regularly by IERS based on astronomical observations; R x (θ), R y (θ), R z (θ) is the transformation matrix during coordinate system transformation, as shown below:

[0028]

[0029]

[0030]

[0031] Furthermore, the formula for calculating the Earth's rotation matrix R(t) in formula (1) is as follows:

[0032]

[0033] in, The Earth's rotation angle can be obtained using the Fortran source code provided by IERS;

[0034] Furthermore, the formula for calculating the precession nutation matrix Q(t) in formula (1) is as follows:

[0035]

[0036] Where α = 1 / 2 + 1 / 8(X) 2 +Y 2 ); in formula (4) (X, Y) = (X, Y) IAU2000 +(dX,dY) IERS ; where (X,Y) IAU2000 s and s can be solved from the Fortran source code provided by IERS, (dX, dY) IERS It is a correction term for the high-frequency motion of the Earth's axis, which is published periodically by IERS based on astronomical observations.

[0037] Preferably, in step S1, the step of deflecting the reference antenna and the on-orbit coarse measurement target antenna toward the sky direction means that...

[0038] The first angle between the axis direction of the reference antenna and the opposite direction of the geocentric vector is equal to the second angle between the axis direction of the on-orbit coarse measurement target antenna and the opposite direction of the geocentric vector, and both the first and second angles are less than or equal to 90°.

[0039] Preferably, the RTK coarse measurement vector of the on-orbit coarse measurement target antenna refers to the unoptimized RTK result vector of the on-orbit coarse measurement target antenna relative to the reference antenna in the ground-fixed system.

[0040] Preferably, the raw measurement data includes pseudorange, carrier phase, and Doppler data.

[0041] Preferably, the satellite platform attitude information is the satellite platform attitude quaternion of the local system relative to the inertial frame at each epoch.

[0042] In summary, compared with the prior art, the on-orbit calibration method for the phase center of a multi-antenna satellite navigation receiver provided by this invention has the following beneficial effects:

[0043] 1. This invention greatly improves the success rate and accuracy of multi-antenna fusion RTK by adopting on-orbit measurement and post-event ground optimization and uploading, and is suitable for satellite platforms with frequent attitude maneuvers, ultra-short-range measurement and high-precision formation flight in orbit;

[0044] 2. This invention has no special requirements on the type of receiving antenna, installation location, satellite platform size, structural complexity, etc. As long as a good field of view is guaranteed, this method can be applied and has good engineering feasibility. Attached Figure Description

[0045] Figure 1 This is a flowchart of the on-orbit calibration method for the phase center of multiple antennas in a spaceborne navigation receiver according to the present invention. Detailed Implementation

[0046] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a more detailed explanation of the on-orbit calibration method for the phase center of a multi-antenna satellite navigation receiver proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clarify the illustration of the embodiments of this invention, and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0047] It should be noted that, in this invention, relational terms such as "and" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0048] Combined with appendix Figure 1 As shown, this embodiment provides an on-orbit calibration method for the phase center of multiple antennas in a spaceborne navigation receiver. The spaceborne navigation receiver is mounted on a satellite platform, which also includes a navigation receiving antenna electrically connected to the spaceborne navigation receiver. The navigation receiving antenna includes one reference antenna and multiple antennas to be calibrated. The on-orbit calibration method is used to calibrate the relative phase center of each antenna to be calibrated with respect to the reference antenna, using the phase center of the reference antenna as a reference. The satellite platform can communicate with a ground station. The method includes the following steps:

[0049] S1. Select one on-orbit coarse measurement target antenna from the antennas to be calibrated, and adjust the attitude of the satellite platform so that the reference antenna and the on-orbit coarse measurement target antenna are biased towards the sky (i.e., the first angle between the axis direction of the reference antenna and the opposite direction of the geocentric vector is equal to the second angle between the axis direction of the on-orbit coarse measurement target antenna and the opposite direction of the geocentric vector, and both the first and second angles are less than or equal to 90°). This is to ensure that the reference antenna and the on-orbit coarse measurement target antenna have enough common-view satellites for subsequent dual-antenna RTK calculation operations.

[0050] S2. Based on the reference antenna and the on-orbit coarse measurement target antenna, the satellite navigation receiver performs calculations according to the existing dual-antenna RTK technology to generate the RTK coarse measurement vector of the on-orbit coarse measurement target antenna; and simultaneously enables the reference antenna and the on-orbit coarse measurement target antenna to independently receive satellite positioning, and the satellite platform collects the raw measurement data of the reference antenna and the on-orbit coarse measurement target antenna.

[0051] The RTK coarse measurement vector of the on-orbit coarse measurement target antenna refers to the unoptimized RTK result vector of the on-orbit coarse measurement target antenna relative to the reference antenna in the ground-fixed system. The original measurement data includes pseudorange, carrier phase, Doppler, and other data. The satellite positioning of the reference antenna and the on-orbit coarse measurement target antenna needs to be maintained for a certain period of time. On the one hand, this ensures the stability and continuity of the dual-antenna RTK solution. On the other hand, it is necessary to collect a large amount of original measurement data, thereby providing a sufficient number of sampling factors for the subsequent optimization processing of the RTK coarse measurement vector. The specific duration of this maintenance is related to the specific satellite conditions of the GNSS and the measurement accuracy of the satellite navigation receiver during on-orbit implementation.

[0052] S3. The generated RTK coarse measurement vector of the on-orbit coarse measurement target antenna, the original measurement data of the collected reference antenna and the on-orbit coarse measurement target antenna, as well as the ephemeris information, satellite platform attitude information and reference antenna absolute position information are transmitted to the ground station as the on-orbit measurement information of the on-orbit coarse measurement target antenna.

[0053] Among them, the satellite platform attitude information refers to the satellite platform attitude quaternion at each epoch (relative to the inertial frame).

[0054] S4. Repeat steps S1 to S3 until all antennas to be calibrated have been traversed.

[0055] S5. The ground station performs offline processing based on the on-orbit measurement information of each antenna to be calibrated, and calculates the phase center position deviation of each antenna relative to the reference antenna; specifically including the following steps:

[0056] S51. Select a ground-optimized target antenna from the antennas to be calibrated. Based on the on-orbit measurement information of this ground-optimized target antenna, perform post-optimization processing on the coarse RTK measurement vector of the ground-optimized target antenna according to the existing dual-antenna RTK technology. After removing outliers and smoothing, obtain the fine ground-fixed system measurement vector.

[0057] S52. Based on observational data regularly released by IERS (International Earth Rotation and Reference Systems Service), and according to the IAU 2000A / B precession nutation model, calculate the transformation matrix from the Earth-fixed frame to the inertial frame at a certain epoch UTC. The calculation formula is:

[0058]

[0059] Where W(t), R(t), and Q(t) are the polar motion matrix, the Earth rotation matrix, and the precession-nutation transformation matrix, respectively, and t is the time variable;

[0060] Furthermore, the formula for calculating the polar shift matrix W(t) in formula (1) is as follows:

[0061] Wherein, polar displacement x p y p Published regularly by IERS based on astronomical observations; mas is an abbreviation for millisecond, the unit of measurement; R x (θ), R y (θ), R z (θ) is the transformation matrix during coordinate system transformation, as shown below:

[0062]

[0063]

[0064]

[0065] Furthermore, the formula for calculating the Earth's rotation matrix R(t) in formula (1) is as follows:

[0066]

[0067] Where θ is the Earth's rotation angle, which can be obtained using the Fortran source code provided by IERS;

[0068] Furthermore, the precession nutation matrix Q(t) in formula (1) is calculated according to the formula proposed by the IAU (International Association of Universities) as follows:

[0069]

[0070] Where α = 1 / 2 + 1 / 8(X) 2 +Y 2 ); in formula (4) (X, Y) = (X, Y) IAU2000 +(dX,dY) IERS ; where (X,Y) IAU2000 s and s can be solved from the Fortran source code provided by IERS, (dX, dY) IERS It is a correction term for the high-frequency motion of the Earth's axis, and is also published regularly by IERS based on astronomical observations.

[0071] S53. Based on the on-orbit measurement information of the ground-optimized target antenna and the ground-fixed system precision measurement vector generated in step S51. The transformation matrix from the Earth-fixed frame to the inertial frame obtained in step S52. The vector of the optimized ground target antenna relative to the reference antenna in the body coordinate system is calculated. The specific solution formula is as follows:

[0072]

[0073] in, The gyroscope attitude in the satellite platform attitude information of the on-orbit measurement information is obtained by the satellite platform attitude sensor; the geometric center and phase center of the reference antenna are assumed to coincide (the actual error is included in the RTK measurement accuracy, and this assumption has no impact on the success rate of multi-antenna fusion RTK and the actual accuracy of the relative measurement).

[0074] S54. Based on the absolute position information of the reference antenna in the on-orbit measurement information of the ground-optimized target antenna, and the vector of the ground-optimized target antenna relative to the reference antenna in the body coordinate system calculated in step S53. The phase center position deviation of the ground-optimized target antenna relative to the reference antenna can be calculated using existing technical methods;

[0075] S55. Repeat steps S51 to S54 until all antennas to be calibrated have been traversed.

[0076] S6. Upload the phase center position deviation of each antenna to be calibrated to the satellite platform via parameter uploading to complete the on-orbit calibration.

[0077] In summary, the present invention provides an on-orbit calibration method for the phase center of a multi-antenna satellite navigation receiver. By adopting on-orbit measurement and subsequent ground optimization and uploading, it greatly improves the success rate and accuracy of multi-antenna fusion RTK. It is suitable for satellite platforms that have frequent attitude maneuvers, ultra-short-range measurements, and high-precision formation flights in orbit. The present invention has no special requirements on the type of receiving antenna, installation location, satellite platform size, structural complexity, etc. As long as a good field of view is guaranteed, this method can be applied and has good engineering feasibility.

[0078] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for on-orbit calibration of the phase center of multiple antennas in a spaceborne navigation receiver, wherein the spaceborne navigation receiver is mounted on a satellite platform, the satellite platform further includes a navigation receiving antenna electrically connected to the spaceborne navigation receiver, the navigation receiving antenna includes one reference antenna and multiple antennas to be calibrated, the on-orbit calibration method is used to calibrate the relative phase center of each antenna to be calibrated with respect to the reference antenna using the phase center of the reference antenna as a reference; the satellite platform can communicate with a ground station; characterized in that... Including the following steps: S1. Select an on-orbit coarse measurement target antenna from the antennas to be calibrated, adjust the attitude of the satellite platform so that the reference antenna and the on-orbit coarse measurement target antenna are biased towards the sky, so that the reference antenna and the on-orbit coarse measurement target antenna have enough common view of the satellite; S2. Based on the reference antenna and the on-orbit coarse measurement target antenna, the spaceborne navigation receiver performs calculations using dual-antenna RTK technology to generate the RTK coarse measurement vector of the on-orbit coarse measurement target antenna. In addition, the reference antenna and the on-orbit coarse measurement target antenna are simultaneously enabled to independently receive satellite signals and locate themselves, and the satellite platform collects the raw measurement data of the reference antenna and the on-orbit coarse measurement target antenna; S3. The generated RTK coarse measurement vector of the on-orbit coarse measurement target antenna, the original measurement data of the collected reference antenna and the on-orbit coarse measurement target antenna, as well as the ephemeris information, satellite platform attitude information and reference antenna absolute position information are transmitted to the ground station as the on-orbit measurement information of the on-orbit coarse measurement target antenna. S4. Repeat steps S1 to S3 until all the antennas to be calibrated have been traversed; S5. The ground station performs offline processing based on the on-orbit measurement information of each antenna to be calibrated, and calculates the phase center position deviation of each antenna to be calibrated relative to the reference antenna. S6. Upload the phase center position deviation of each of the antennas to be calibrated to the satellite platform via parameter uploading to complete the on-orbit calibration.

2. The on-orbit calibration method as described in claim 1, characterized in that, Step S5 includes: S51. Select a ground-optimized target antenna from the antennas to be calibrated. Based on the on-orbit measurement information of the ground-optimized target antenna, perform post-optimization processing on the coarse RTK measurement vector of the ground-optimized target antenna according to the dual-antenna RTK technology. After removing outliers and smoothing, obtain the fine ground-fixed system measurement vector. S52. Based on the observation data periodically released by IERS, and according to the IAU 2000A / B precession nutation model, calculate the transformation matrix from the Earth-fixed frame to the inertial frame at a certain epoch UTC. S53. Based on the on-orbit measurement information of the ground-optimized target antenna and the precise ground-fixed system vector... Transformation matrix from Earth-fixed frame to inertial frame The vector of the ground-optimized target antenna relative to the reference antenna in the body coordinate system is calculated. The solution formula is as follows: in, The gyro attitude in the satellite platform attitude information of the on-orbit measurement information is obtained by the satellite platform attitude sensor. S54. Based on the absolute position information of the reference antenna in the on-orbit measurement information of the ground-optimized target antenna, and the vector of the ground-optimized target antenna relative to the reference antenna in the body coordinate system. The phase center position deviation of the ground-optimized target antenna relative to the reference antenna is calculated; S55. Repeat steps S51 to S54 until all the antennas to be calibrated have been traversed.

3. The on-orbit calibration method as described in claim 2, characterized in that, The calculation formula for step S52 is as follows: Where W(t), R(t), and Q(t) are the polar motion matrix, the Earth rotation matrix, and the precession-nutation transformation matrix, respectively, and t is the time variable; Furthermore, the formula for calculating the polar shift matrix W(t) in formula (1) is as follows: W(t)=R z (-s′)R y (x p )R x (y p ); (2) s′=0.047mas×t; Wherein, polar displacement x p y p Published regularly by IERS based on astronomical observations; R x (θ), R y (θ), R z (θ) is the transformation matrix during coordinate system transformation, as shown below: Furthermore, the formula for calculating the Earth's rotation matrix R(t) in formula (1) is as follows: in, The Earth's rotation angle can be obtained using the Fortran source code provided by IERS; Furthermore, the formula for calculating the precession nutation matrix Q(t) in formula (1) is as follows: Where α = 1 / 2 + 1 / 8(X) 2 +Y 2 ); in formula (4) (X, Y) = (X, Y) IAU2000 +(dX,dY) IERS ; where (X,Y) IAU2000 s and s can be solved from the Fortran source code provided by IERS, (dX, dY) IERS It is a correction term for the high-frequency motion of the Earth's axis, which is published periodically by IERS based on astronomical observations.

4. The on-orbit calibration method as described in claim 1, characterized in that, In step S1, the phrase "bias the reference antenna and the on-orbit coarse measurement target antenna toward the sky" means that... The first angle between the axis direction of the reference antenna and the opposite direction of the geocentric vector is equal to the second angle between the axis direction of the on-orbit coarse measurement target antenna and the opposite direction of the geocentric vector, and both the first and second angles are less than or equal to 90°.

5. The on-orbit calibration method as described in claim 1, characterized in that, The RTK coarse measurement vector of the on-orbit coarse measurement target antenna refers to the unoptimized RTK result vector of the on-orbit coarse measurement target antenna relative to the reference antenna in the ground-fixed system.

6. The on-orbit calibration method as described in claim 1, characterized in that, The raw measurement data includes pseudorange, carrier phase, and Doppler data.

7. The on-orbit calibration method as described in claim 1, characterized in that, The satellite platform attitude information is the satellite platform attitude quaternion of the local system relative to the inertial frame at each epoch.

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