Antenna on-orbit calibration method and system based on dual-star sensor and self-tracking combination

Abstract

This invention provides an on-orbit antenna calibration method and system based on a combination of dual-star sensors and self-tracking. Star sensors are configured on both the satellite body and the deployed antenna. First, astronomical calibration is performed through dual-star pattern matching to obtain a high-precision initial reference for the antenna's mechanical axis. Then, the antenna is controlled to self-track a cooperative target in orbit, acquiring electrical axis pointing data. Finally, the astronomical calibration results and self-tracking data are fused to accurately separate the mechanical axis deviation and electrical axis deviation, establishing a comprehensive error compensation model. This invention overcomes the limitations of single calibration methods, achieving joint, high-precision, on-orbit real-time calibration of the mechanical and electrical axes of spaceborne antennas, significantly improving pointing accuracy and stability. It is particularly suitable for satellite missions with extremely demanding pointing requirements, such as laser communication and high-resolution SAR.

Description

Technical Field

[0001] This invention relates to the field of spacecraft telemetry and control technology, specifically to a high-precision on-orbit calibration method and system for a spaceborne antenna based on a combination of dual-satellite sensors and self-tracking. Background Technology

[0002] High-precision spaceborne antennas are core components of modern satellite communication, data relay, Earth observation (especially synthetic aperture radar SAR), and space laser communication systems. Their performance directly depends on the antenna's pointing accuracy, which is determined by both the antenna's mechanical axis pointing (followed by its structure and pointing mechanism) and electrical axis pointing (followed by its electromagnetic radiation characteristics). However, due to factors such as launch dynamics, extreme on-orbit thermal cycling, weightlessness, and material aging, the antenna's on-orbit pointing accuracy can be significantly worse than its ground-based calibration value.

[0003] Currently, traditional on-orbit calibration methods have the following limitations: 1. Beacon calibration method: High accuracy but relies on ground stations, cannot achieve real-time and continuous calibration, and has limited coverage.

[0004] 2. Earth edge sensitive method: It can be carried out autonomously, but the accuracy is low and it is easily affected by the atmosphere and clouds.

[0005] 3. Single star sensor method: Only a star sensor is installed on the satellite body. The antenna pointing is calculated by theoretically installing the matrix. It cannot sense and compensate for the relative deformation between the satellite body and the antenna (especially high-frequency micro-vibrations).

[0006] 4. Standalone self-tracking method: It can only calibrate the overall pointing deviation of the electric shaft, and cannot distinguish whether the deviation is caused by deformation of the mechanical structure, radio wave propagation, or problems with the feed itself.

[0007] Therefore, there is an urgent need in this field for a comprehensive on-orbit calibration solution that can achieve high precision, real-time or near real-time calibration, and simultaneously calibrate mechanical and electric axes.

[0008] A review of existing technologies reveals that there are currently several research approaches for on-orbit calibration technology of spaceborne antennas, but each has its own limitations and cannot simultaneously meet the requirements of high precision, real-time performance, autonomy, and comprehensiveness.

[0009] Patent document CN112468211A, titled "Method for Correcting On-Orbit Pointing Error of Tracking Antenna and Space-Based Telemetry, Tracking and Communication System," provides a method for correcting on-orbit pointing error of a tracking antenna and a space-based telemetry, tracking, and communication system. This invention relies on a ground station sending tracking commands to the satellite and receiving telemetry data of the antenna's theoretical and actual angles. After calculating error correction parameters on the ground, the data is uploaded to the satellite for execution. While this method can utilize the powerful computing capabilities of the ground, it is heavily dependent on ground telemetry and control resources, cannot achieve autonomous satellite operation, and cannot perform calibration after the satellite leaves the ground station's visible arc, resulting in poor real-time performance. Furthermore, this method cannot distinguish between mechanical and electrical axis errors, and cannot separate or diagnose error sources.

[0010] The paper "On-orbit Calibration Method for Star-Sensor-Based Tracking and Aiming Systems" (Gao Yuan et al., Journal of Terahertz Science and Electronic Information, 2019) proposes a multi-star-sensor optical axis calibration algorithm. Simulations verify that its dual-star-sensor calibration accuracy can reach within 25 arcseconds. This method focuses on the calibration of the optical axis of the optical payload (tracking and aiming camera), but its core is determining the relative installation matrix between different star sensors, without addressing the calibration of the antenna's electrical axis. For spaceborne antennas, calibrating only the mechanical axis without calibrating the electrical axis cannot reflect the actual electromagnetic radiation pointing direction of the antenna.

[0011] Patent document CN115507880B, titled "Method for On-Orbit Pointing Calibration of Spacecraft Using Multiple Ground-Based Antennas," provides a method for on-orbit pointing calibration of spacecraft using multiple ground-based antennas. It proposes using multiple ground-deployed antennas to receive satellite downlink signals and estimating antenna pointing deviation by constructing an observation model. Compared to a single antenna, this method can obtain more measurement data, improving calibration accuracy. However, it is essentially still an external calibration method dependent on ground facilities, and it also suffers from limited coverage, lack of real-time autonomy, and its calibration results still represent the overall performance of the electrical axis, failing to distinguish between mechanical and electrical deviations.

[0012] The paper "Wide-Field-of-View Star Map Matching Accelerated by CenterLocalization Based on Red and Black Tree" (Liu et al., Acta Optica Sinica, 2024) primarily addresses the computational complexity and slow speed of wide-field-of-view star map matching by proposing a fast matching algorithm based on RB-Tree and GeoHash encoding, significantly improving matching efficiency. These works provide powerful tools for rapid attitude determination of star sensors at the underlying algorithm level. However, these studies are limited to attitude determination and have not extended this high-precision attitude determination capability to system-level applications such as pointing calibration and error separation for spaceborne antennas. How to utilize the fast attitude determination results for antenna calibration remains an unsolved system application problem.

[0013] The paper "On-orbit Self-calibration Method for Star Sensors Based on Models and Splines" (Yan Haodong et al., Acta Optica Sinica, 2024) focuses on the on-orbit correction of optical distortions in star sensors. This type of technique aims to ensure the original accuracy of star sensor output data and is fundamental to the entire high-precision attitude determination chain. However, it only addresses the issue of "star sensor accuracy itself" and does not address how to use a high-precision star sensor to calibrate another system (such as an antenna). Summary of the Invention

[0014] To address the shortcomings of existing technologies, the purpose of this invention is to provide an on-orbit calibration method and system for antennas based on a combination of dual-star sensors and self-tracking.

[0015] According to the present invention, an on-orbit antenna calibration system based on a dual-satellite sensor and self-tracking combination includes: The satellite body star sensor is fixedly installed on the satellite body and is used to determine the satellite body's first attitude in inertial space; The antenna star sensor is fixedly mounted on the antenna's back frame and rigidly connected to the antenna. It is used to directly determine the antenna's second attitude in inertial space. The data processing and control unit is communicatively connected to the satellite body star sensor, the antenna star sensor, and the antenna self-tracking receiver, respectively. The data processing and control unit is configured to perform the following steps: Step A: Based on the first attitude and the second attitude, determine the real-time relative attitude matrix of the antenna's mechanical axis relative to the satellite body reference through star map matching calculation; Step B: When the antenna is self-tracking the on-orbit cooperative target, obtain the antenna's electrical axis pointing data from the self-tracking receiver; Step C: Integrate the real-time relative attitude matrix with the electrical axis pointing data to establish a comprehensive error model of the antenna's electrical axis deviation and mechanical axis deviation.

[0016] Furthermore, in step A, the data processing and control unit calculates the low-frequency and high-frequency pointing errors caused by the deformation of the satellite body structure by comparing the real-time relative attitude matrix with the preset nominal installation matrix.

[0017] Furthermore, in step C, the data processing and control unit uses a Kalman filter or a least squares algorithm to perform spatiotemporal alignment and fusion processing on the astronomical calibration data from the binary star sensor and the radio frequency calibration data from the self-tracking sensor.

[0018] Furthermore, the on-orbit cooperative targets include geostationary communication satellites, relay satellites, or ground beacon stations.

[0019] According to the present invention, an on-orbit antenna calibration method based on a dual-star sensor and self-tracking combination is provided, which employs the aforementioned on-orbit antenna calibration system based on a dual-star sensor and self-tracking combination to perform the following steps: Step S1: During the on-orbit initialization phase, the observation data of the satellite body star sensor and the antenna star sensor are acquired synchronously. Through star map matching and attitude calculation, the high-precision initial pointing of the antenna mechanical axis is obtained. Step S2: Control the antenna to perform angle self-tracking on the known on-orbit cooperative target, and record the electric axis pointing data and the corresponding satellite orbit and attitude information throughout the process; Step S3: Combine the results obtained in step S1 with those obtained in step S2 to calculate and separate the electric axis error related to the mechanical installation error of the antenna and the radio wave propagation. Step S4: Based on the solution results of step S3, construct a pointing error compensation model that causes structural deformation, and upload the pointing error compensation model to the satellite service computer for real-time feedforward compensation of subsequent pointing commands of the antenna.

[0020] Furthermore, steps S1 and S2 are repeated under different satellite attitude and temperature conditions to obtain calibration data covering the entire mission scenario.

[0021] Further, step S1 includes: When the satellite is in a stable attitude, star images are captured simultaneously using the satellite's own star sensor and the antenna star sensor. By matching and solving the two star charts respectively, the precise attitude quaternions Q of the satellite body coordinate system and antenna coordinate system in inertial space are obtained. body and Q ant ; Calculate the real-time relative attitude matrix M of the antenna relative to the body. real = Q ant * Q body -1 ; M real The nominal installation matrix M obtained by precise ground measurement nominal By comparison, the attitude deviation angles (Δφ, Δθ, Δψ) caused by structural deformation are obtained, where Δφ is the roll deviation angle, Δθ is the pitch deviation angle, and Δψ is the yaw deviation angle.

[0022] Further, step S2 includes: Select an in-orbit cooperative target whose precise location is known; The control antenna enters self-tracking mode, and the antenna automatically adjusts its direction according to the received signal strength to align the electric axis with the target on the rail. After the self-tracking stabilizes, the angle information output by the self-tracking receiver is recorded at this time, along with the satellite's orbital position and attitude, thereby deducing the actual direction of the electric axis in inertial space.

[0023] Further, step S3 includes: The mechanical axis pointing (AZ) obtained at the same time or in S1 after interpolation alignment mech EL mech ) and the electric axis direction (AZ) obtained in step S2 elec EL elec ) for comparison; The difference between the two (ΔAZ = AZ) elec - AZ mech , ΔEL = EL elec - EL mech ) represents the electrical axis deviation of the antenna.

[0024] Further, step S4 includes: The data processing unit uses calibration data from multiple tests and under multiple operating conditions, employs the least squares fitting method, to construct a comprehensive pointing error compensation model, which is then injected into the satellite's attitude control system or antenna controller. When a satellite needs its antenna to point at a target, it first calculates the theoretical pointing command based on its orbit and attitude, then calls the pointing error compensation model to pre-correct the theoretical pointing command, and adjusts the antenna pointing according to the corrected pointing command.

[0025] Compared with the prior art, the present invention has the following beneficial effects: 1. High precision: Dual-star sensitive star map matching provides an absolute mechanical axis reference at the arcsecond or even sub-arcsecond level, fundamentally eliminating the influence of satellite platform deformation.

[0026] 2. Full functionality: It realizes the separation and joint calibration of mechanical axis deviation and electrical axis deviation, and provides a comprehensive diagnostic capability for antenna pointing error.

[0027] 3. High reliability: The two independent calibration methods verify each other, avoiding the systematic errors or failure risks that may exist in a single method, resulting in more reliable results.

[0028] 4. Good real-time performance: The dual-star agile system can provide a near-continuous attitude reference, enabling the calibration model to be dynamically updated and used for real-time compensation of high-frequency jitter.

[0029] 5. High autonomy: Reduces dependence on ground stations and enhances the satellite's ability to operate autonomously. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the on-orbit high-precision calibration system for a spaceborne antenna that combines a dual-star sensor with self-tracking, as described in this invention. Figure 2 This is a flowchart of the on-orbit calibration method for antennas based on a combination of dual-star sensors and self-tracking, as described in this invention.

[0031] In the picture: 101-Satellite body star sensor; 102-Antenna star sensor; 103-Data processing and control unit; 104-Antenna self-tracking receiver. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0033] like Figure 1 As shown, an on-orbit antenna calibration system based on a dual-star sensor and self-tracking combination includes: The satellite body star sensor 101 is fixedly installed on the satellite body and is used to determine the satellite body's initial attitude in inertial space. The satellite body star sensor 101 is a high-precision star sensor, and its field of view is approximately the same as the antenna direction to avoid being blocked by the antenna.

[0034] Antenna star sensor 102 is fixedly mounted on the antenna's back frame and rigidly connected to the antenna. It is used to directly determine the antenna's second attitude in inertial space. Antenna star sensor 102 is selected from star sensors of the same or higher precision. It is directly mounted on the back frame or near the feed of the deployed antenna through a high-rigidity, high-stability bracket to ensure that it moves together with the antenna.

[0035] The self-tracking receiver 104, an integral part of the antenna, is used to calculate and output the pointing error signal of the electrical axis relative to the cooperative target in self-tracking mode. Cooperative targets in orbit include geostationary communication satellites, relay satellites, or ground beacon stations.

[0036] The data processing and control unit 103 is communicatively connected to the satellite's own star sensor 101, the antenna star sensor 102, and the antenna's self-tracking receiver 104. The data processing and control unit 103 can be a satellite central computer or a dedicated processing module. It connects to both star sensors and the self-tracking receiver via a high-speed data bus to ensure data time synchronization (e.g., through hardware triggering or high-precision timestamps).

[0037] The data processing and control unit 103 is configured to perform the following steps: Step A: Based on the first and second attitudes, determine the real-time relative attitude matrix of the antenna's mechanical axis relative to the satellite body reference through star map matching calculation. By comparing the real-time relative attitude matrix with the preset nominal installation matrix, calculate the low-frequency and high-frequency pointing errors caused by the deformation of the satellite body structure.

[0038] Step B: When the antenna is self-tracking the on-orbit cooperative target, obtain the antenna's electrical axis pointing data from the self-tracking receiver 104.

[0039] Step C: Fuse the real-time relative attitude matrix and electrical axis pointing data to establish a comprehensive error model of the antenna's electrical axis deviation and mechanical axis deviation. Use a Kalman filter or least squares algorithm to perform spatiotemporal alignment and fusion processing on the astronomical calibration data from the dual-star sensor and the RF calibration data from the self-tracking sensor.

[0040] like Figure 2 As shown, an on-orbit antenna calibration method based on a dual-star sensor and self-tracking combination includes: Step S1: During the on-orbit initialization phase, the observation data of the satellite body star sensor 101 and the antenna star sensor 102 are acquired synchronously. Through star map matching and attitude calculation, the high-precision initial pointing of the antenna mechanical axis is obtained.

[0041] When the satellite is in a stable attitude, star images are simultaneously captured using the satellite's own star sensor 101 and the antenna star sensor 102. The two star images are then matched and calculated to obtain the precise attitude quaternions Q of the satellite's own coordinate system and the antenna coordinate system in inertial space. body and Q ant ; Calculate the real-time relative attitude matrix M of the antenna relative to the body. real = Q ant * Q body -1 ; M real The nominal installation matrix M obtained by precise ground measurement nominal By comparison, the attitude deviation angles (Δφ, Δθ, Δψ) caused by structural deformation are obtained, where Δφ is the roll deviation angle, Δθ is the pitch deviation angle, and Δψ is the yaw deviation angle.

[0042] Step S2: Control the antenna to perform angle self-tracking on the known on-orbit cooperative target, and record the electric axis pointing data and corresponding satellite orbit and attitude information throughout the process.

[0043] Select an on-orbit cooperative target with a precisely known location. Control the antenna to enter self-tracking mode; the antenna automatically adjusts its pointing based on the received signal strength, aligning its electrical axis with the on-orbit cooperative target.

[0044] After the self-tracking stabilizes, the angle information output by the self-tracking receiver is recorded at this time, along with the satellite's orbital position and attitude, thereby deducing the actual direction of the electric axis in inertial space.

[0045] Steps S1 and S2 are repeated under different satellite attitude and temperature conditions to obtain calibration data covering the entire mission scenario.

[0046] Step S3: Combine the results obtained in step S1 with those obtained in step S2 to calculate and separate the electric axis error related to the mechanical installation error of the antenna and the propagation of radio waves.

[0047] The mechanical axis pointing (AZ) obtained at the same time or in S1 after interpolation alignment mech EL mech ) and the electric axis direction (AZ) obtained in step S2 elec EL elec Compare the two. The difference between them (ΔAZ = AZ) is... elec - AZ mech , ΔEL =EL elec - EL mech ) represents the electrical axis deviation of the antenna.

[0048] Step S4: Based on the solution results of step S3, construct a pointing error compensation model that causes structural deformation, and upload the pointing error compensation model to the satellite service computer for real-time feedforward compensation of subsequent pointing commands of the antenna.

[0049] The data processing unit utilizes calibration data from multiple scenarios and under various operating conditions, employing methods such as least-squares fitting, to construct a comprehensive pointing error compensation model, which is then injected into the satellite's attitude control system or antenna controller. When the satellite needs its antenna to point at a target, it first calculates the theoretical pointing command based on the orbit and attitude, then calls the pointing error compensation model to pre-correct the theoretical pointing command, and finally adjusts the antenna pointing according to the corrected pointing command.

[0050] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. An on-orbit antenna calibration system based on a dual-star sensor and self-tracking combination, characterized in that, include: The satellite body star sensor (101) is fixedly installed on the satellite body and is used to determine the first attitude of the satellite body in inertial space; Antenna star sensor (102) is fixedly mounted on the antenna back frame and rigidly connected to the antenna, and is used to directly determine the second attitude of the antenna in inertial space; The data processing and control unit (103) is communicatively connected to the satellite body star sensor (101), the antenna star sensor (102), and the antenna self-tracking receiver (104), respectively. The data processing and control unit (103) is configured to perform the following steps: Step A: Based on the first attitude and the second attitude, determine the real-time relative attitude matrix of the antenna's mechanical axis relative to the satellite body reference through star map matching calculation; Step B: When the antenna performs self-tracking on-orbit cooperative target, obtain the antenna's electrical axis pointing data from the self-tracking receiver (104); Step C: Integrate the real-time relative attitude matrix with the electrical axis pointing data to establish a comprehensive error model of the antenna's electrical axis deviation and mechanical axis deviation.

2. The on-orbit calibration system for an antenna based on a dual-star sensor and self-tracking combination as described in claim 1, characterized in that, In step A, the data processing and control unit (103) calculates the low-frequency and high-frequency pointing errors caused by the deformation of the satellite body structure by comparing the real-time relative attitude matrix with the preset nominal installation matrix.

3. The on-orbit calibration system for an antenna based on a dual-star sensor and self-tracking combination as described in claim 1, characterized in that, In step C, the data processing and control unit (103) uses a Kalman filter or least squares algorithm to perform spatiotemporal alignment and fusion processing on the astronomical calibration data from the binary star sensor and the radio frequency calibration data from the self-tracking sensor.

4. The on-orbit calibration system for an antenna based on a dual-star sensor and self-tracking combination as described in claim 1, characterized in that, The on-orbit cooperation targets include geostationary communication satellites, relay satellites, or ground beacon stations.

5. An on-orbit antenna calibration method based on a dual-star sensor and self-tracking combination, characterized in that, Using the on-orbit antenna calibration system based on dual-star sensors and self-tracking as described in claim 1, the following steps are performed: Step S1: During the on-orbit initialization phase, the observation data of the satellite body star sensor (101) and the antenna star sensor (102) are acquired synchronously. Through star map matching and attitude calculation, the high-precision initial pointing of the antenna mechanical axis is obtained. Step S2: Control the antenna to perform angle self-tracking on the known on-orbit cooperative target, and record the electric axis pointing data and the corresponding satellite orbit and attitude information throughout the process; Step S3: Combine the results obtained in step S1 with those obtained in step S2 to calculate and separate the electric axis error related to the mechanical installation error of the antenna and the radio wave propagation. Step S4: Based on the solution results of step S3, construct a pointing error compensation model that causes structural deformation, and upload the pointing error compensation model to the satellite service computer for real-time feedforward compensation of subsequent pointing commands of the antenna.

6. The on-orbit calibration method for antennas based on a dual-star sensor and self-tracking combination as described in claim 5, characterized in that, Steps S1 and S2 are repeated under different satellite attitude and temperature conditions to obtain calibration data covering the entire mission scenario.

7. The on-orbit calibration method for antennas based on a dual-star sensor and self-tracking combination as described in claim 5, characterized in that, Step S1 includes: When the satellite is in a stable attitude, star images are captured simultaneously by the satellite body star sensor (101) and the antenna star sensor (102); By matching and solving the two star charts respectively, the precise attitude quaternions Q of the satellite body coordinate system and antenna coordinate system in inertial space are obtained. body and Q ant ; Calculate the real-time relative attitude matrix M of the antenna relative to the body. real = Q ant * Q body -1 ; M real The nominal installation matrix M obtained by precise ground measurement nominal By comparison, the attitude deviation angles (Δφ, Δθ, Δψ) caused by structural deformation are obtained, where Δφ is the roll deviation angle, Δθ is the pitch deviation angle, and Δψ is the yaw deviation angle.

8. The on-orbit calibration method for antennas based on a dual-star sensor and self-tracking combination as described in claim 5, characterized in that, Step S2 includes: Select an in-orbit cooperative target whose precise location is known; The control antenna enters self-tracking mode, and the antenna automatically adjusts its direction according to the received signal strength to align the electric axis with the target on the rail. After the self-tracking stabilizes, the angle information output by the self-tracking receiver is recorded at this time, along with the satellite's orbital position and attitude, thereby deducing the actual direction of the electric axis in inertial space.

9. The on-orbit calibration method for antennas based on a dual-star sensor and self-tracking combination as described in claim 5, characterized in that, Step S3 includes: The mechanical axis pointing (AZ) obtained at the same time or in S1 after interpolation alignment mech EL mech ) and the electric axis direction (AZ) obtained in step S2 elec EL elec ) for comparison; The difference between the two (ΔAZ = AZ) elec - AZ mech , ΔEL = EL elec - EL mech ) represents the electrical axis deviation of the antenna.

10. The on-orbit calibration method for antennas based on a dual-star sensor and self-tracking combination as described in claim 5, characterized in that, Step S4 includes: The data processing unit uses calibration data from multiple tests and under multiple operating conditions, employs the least squares fitting method, to construct a comprehensive pointing error compensation model, which is then injected into the satellite's attitude control system or antenna controller. When a satellite needs its antenna to point at a target, it first calculates the theoretical pointing command based on its orbit and attitude, then calls the pointing error compensation model to pre-correct the theoretical pointing command, and adjusts the antenna pointing according to the corrected pointing command.

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