An astronomical calibration method for synchronizing a small field of view camera with a star measurement reference

Abstract

The application discloses an astronomical calibration method for synchronizing a small field-of-view camera with a star sensor reference, comprising the following steps: S1, simultaneously exposing and scanning the corresponding sky area of each field of view of the space-based small field-of-view camera and the star sensor, obtaining the expected star image shot by the small field-of-view camera and the satellite inertial quaternion under the star sensor measurement coordinate system; S2, the star sensor calculates the star vector coordinates of the star in the star sensor measurement coordinate system and the space-based small field-of-view camera measurement coordinate system according to the measurement information of the space-based small field-of-view camera and the star sensor; S3, the optimal estimation algorithm is used to calculate the estimated value of the measurement deviation angle of the space-based small field-of-view camera and the star sensor; S4, the limitation condition of the estimation algorithm in step S3 is set, including the amplitude limitation of the estimated value and the timing of the estimation algorithm. The application has high recognition precision, the recognition data can be directly used for the next load task, the attitude determination and the task precision are improved, and the application has strong engineering practicability.

Description

Technical Field

[0001] This invention relates to satellite attitude determination and reference identification technology, specifically to an astronomical calibration method for synchronizing a space-based small field-of-view camera with a star-sensitive period measurement reference. Background Technology

[0002] Space security satellites need to obtain the position and attitude information of target satellites. The process of acquiring attitude information involves the measurement reference error of the star sensor (star attitude sensor) relative to the satellite's coordinate system and the measurement reference deviation of the tracking and aiming unit (space-based small field-of-view camera) relative to the satellite's coordinate system.

[0003] Star-sensors and space-based small-field-of-view cameras are high-precision optical instruments with various error sources, such as installation errors, thermal deformation errors, optical system imaging errors, manufacturing and assembly errors, optical axis instability, CCD noise, dark current, response inhomogeneity, electronic circuit noise, and calibration errors. Therefore, error calibration compensation is necessary to obtain high-precision angle measurement. Currently, the calibration of star-sensors and small-field-of-view cameras is generally performed using ground-based calibration test equipment. However, the corresponding laboratories and telemetry and control systems for ground calibration are quite complex and expensive, and the ground calibration environment cannot completely simulate the various space environments in which the satellite operates in orbit.

[0004] Secondly, as the satellite operates under irradiation conditions for an extended period, the aberrations of the internal optical systems of the star-sensor and the space-based small field-of-view camera increase, and structural deformation occurs, leading to changes in various ground calibration parameters of the star-sensor and the small field-of-view camera. During actual on-orbit measurements, the star-sensor and the space-based small field-of-view camera are affected by various factors such as installation errors and calibration accuracy, resulting in increased measurement errors and reduced measurement accuracy.

[0005] Furthermore, space-based small field-of-view cameras are generally limited by the size of their field of view and cannot directly output the satellite inertial quaternion information in their measurement system. However, in the attitude pointing control of space safety satellites, the measurement information of space-based small field-of-view cameras and star sensors is often used to determine the satellite attitude. Therefore, it is necessary to calibrate the installation deviation between star sensors and space-based small field-of-view cameras and reflect it in the high-precision attitude determination. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of large errors and low measurement accuracy in current star-sensor and space-based small field-of-view camera calibration methods.

[0007] To achieve the above objectives, this invention proposes an astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference, comprising the following steps:

[0008] S1. Simultaneous exposure scanning of the sky region corresponding to the field of view of the space-based small field-of-view camera and the star sensor is adopted. The desired star is near the center of the field of view of the space-based small field-of-view camera. The satellite inertial quaternion in the star sensor measurement coordinate system and the image of the desired star in the small field-of-view camera measurement coordinate system are obtained.

[0009] S2 and StarAgence calculate the stellar vector coordinates of the same star in the StarAgence measurement coordinate system and the space-based small field-of-view camera measurement coordinate system, respectively, based on the measurement information from the space-based small field-of-view camera and StarAgence.

[0010] S3. Calculate the estimated values ​​of the measurement deviation angles of the space-based small field-of-view camera and star sensor using the optimal estimation algorithm;

[0011] S4. Set the limiting conditions for the estimation algorithm in step S3, including limiting the amplitude of the estimated value and timing the estimation algorithm.

[0012] Step S1 further includes the following steps:

[0013] S11. Utilizing the satellite's pointing capability in any inertial space, the optical axis of the space-based small field-of-view camera on the satellite is rotated to point towards the desired star in space. During this process, the satellite performs a three-axis attitude scan within a fixed speed and angle range, ensuring that the field of view of the space-based small field-of-view camera fixed to the satellite always covers the desired star. The desired star moves in a cross-shaped trajectory near the center of the image captured by the space-based small field-of-view camera. During the movement, the star sensor processes the measurement image information of the small field-of-view camera in real time to obtain the vector position r of the desired star in the measurement coordinate system of the space-based small field-of-view camera.

[0014] S12. When the space-based small field-of-view camera captures an image of the sky region containing the desired star, the star-sensor synchronously exposes to obtain the sky region image corresponding to its own field of view, and obtains the satellite inertial quaternion q in the star-sensor measurement coordinate system. is .

[0015] Among them, the star sensor sends the internal exposure signal to the space-based small field-of-view camera in real time, so that the falling edges of the two are synchronized.

[0016] Specifically, step S2 is as follows:

[0017] The space-based small field-of-view camera transmits image information to the star sensor in real time. After loading the optical system parameters of the space-based small field-of-view camera, the star sensor identifies the image through a star recognition algorithm and provides the star vector coordinates of the stars in the image in the measurement coordinate system of the space-based small field-of-view camera.

[0018] A high-speed communication interface is provided between the space-based small field-of-view camera and the star sensor.

[0019] The stellar vector coordinates in the star-sensing measurement coordinate system are: in A represents the stellar vector position in the inertial coordinate system stored in the StarMin star database. is The measurement information q from the star sensor can be used is Calculated;

[0020] Star vector coordinates in the coordinate system measured by the space-based small field-of-view camera Images captured by a camera can be directly obtained through star-aware star recognition algorithms.

[0021] Step S3 further includes the following steps:

[0022] S31. Establish a reference plane perpendicular to the star-sensor measurement plane, with the basis vector of the reference plane being H(k);

[0023] S32. Establish observations

[0024] S33. Calculate the measurement reference deviation angle between the small field-of-view camera and the star sensor. in Let Δθ(k) be the measurement roll deviation angle of the small field-of-view camera and the star sensor, Δψ(k) be the measurement roll pitch angle of the small field-of-view camera and the star sensor, and Δψ(k) be the measurement yaw deviation angle of the small field-of-view camera and the star sensor.

[0025] in, in

[0026]

[0027]

[0028]

[0029] Among them, A bxj The transformation matrix from the coordinate system of the space-based small field-of-view camera to the satellite's intrinsic coordinate system can be directly obtained from the ground-based precision measurement information of the camera; A sb The transformation matrix from the star-sensor measurement coordinate system to the satellite's own coordinate system can be directly obtained from the precise measurement information obtained from the ground installation of the star-sensor.

[0030] Where Fai(k)=H T (k)·H(k)+Fai(k-1), Fai(0)=zeros(3,3),Y(0)=[0 0 0] T Fai -1 (k) is the inverse matrix of matrix Fai(k).

[0031] Specifically, step S4 involves: limiting the estimated value of the measurement deviation angle between the space-based small field-of-view camera and the star sensor to an amplitude of 0.1 / 57.3 rad; setting a counter for the estimation algorithm in step S3; when the optimal estimation algorithm is enabled, starting the counter to count; after counting for 50 seconds, taking the output value of the optimal estimation algorithm as the measurement reference deviation angle between the small field-of-view camera and the star sensor; then exiting the algorithm and resetting the counter to zero.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention discloses an autonomous astronomical calibration method for synchronizing the measurement reference of a space-based small field-of-view camera and a star sensor. After the satellite's attitude maneuver to a designated sky region, the space-based small field-of-view camera takes an image, extracts the image, and compares it with the measurement values ​​of the star sensor to identify the measurement reference deviation between the camera and the star sensor. The identification accuracy is high, and the identification data can be directly used for the next payload mission, improving attitude determination and mission accuracy, and has strong engineering applicability.

[0034] Design a high-speed image communication interface between a space-based small field-of-view camera and a star sensor. Make full use of the mature star point extraction and image recognition technology of the star sensor to extract the real-time star vector captured by the small field-of-view camera, simplify the camera design, and the camera does not need to have functions such as gate image extraction, star point extraction and recognition, and star map matching, which has practical value for on-orbit application.

[0035] An observation equation for the installation error angle between the star sensor and the space-based small field-of-view camera was constructed. Based on the reference vector information of the star in inertial space in the camera, the observation information of the star vector on the platform, and the platform attitude information obtained by the star sensor, the relative installation error angle information between the two was identified through the optimal estimation method. The identified installation error was corrected in orbit to improve the consistency between the platform measurement reference and the camera pointing. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference according to the present invention. Detailed Implementation

[0037] The technical solutions, structural features, achieved objectives, and effects of the present invention will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention.

[0038] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.

[0039] It should be noted that, in this invention, relational terms such as "first" and "second" 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.

[0040] This embodiment discloses an astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference. The small field-of-view camera generally refers to a camera with a field of view not exceeding φ4°, such as... Figure 1 As shown, the method includes the following steps:

[0041] S1. Simultaneously expose the sky region corresponding to their respective fields of view using a space-based small field-of-view camera and a star sensor to obtain the satellite inertial quaternion in the star sensor measurement coordinate system and the image of the desired star in the small field-of-view camera measurement coordinate system, wherein the desired star is near the center of the field of view of the space-based small field-of-view camera, including the following steps;

[0042] S11. Utilizing the satellite's pointing capability in arbitrary inertial space, the optical axis of the space-based small field-of-view camera on the satellite is turned to the desired star in space. During this process, by designing the three-axis attitude scanning capability of the GNC subsystem (guidance, navigation and control subsystem), the satellite performs a three-axis attitude scan within a fixed speed and angle range, ensuring that the field of view of the space-based small field-of-view camera fixed to the satellite always covers the desired star. The desired star moves in a cross-shaped trajectory near the center of the image captured by the space-based small field-of-view camera. During the movement, the star sensor processes the measurement image information of the small field-of-view camera in real time to obtain the vector position r of the desired star in the measurement coordinate system of the space-based small field-of-view camera.

[0043] S12. While the space-based small field-of-view camera is scanning the desired star, the star-sensor synchronously exposes to acquire the sky image corresponding to its own field of view, and calculates the satellite inertial quaternion q in the star-sensor measurement coordinate system. is ;

[0044] The star sensor's own exposure cycle and data update frequency is 10Hz. In order to achieve real-time synchronous exposure between the star sensor and the space-based small field-of-view camera, the star sensor sends the internal exposure signal (ITR) to the space-based small field-of-view camera in real time to ensure that the falling edges of the two are synchronized and to complete the unification of the exposure timing.

[0045] S2 and StarSense calculate the stellar vector coordinates in the StarSense measurement coordinate system and the Space-based Small Field-of-View Camera measurement coordinate system, respectively, based on the measurement information from the Space-based Small Field-of-View Camera and StarSense.

[0046] A high-speed communication interface (spacewire) is set up between the space-based small field-of-view camera and the star sensor. Through this high-speed communication interface, the image information of the space-based small field-of-view camera is transmitted to the star sensor in real time. After loading the optical system parameters of the space-based small field-of-view camera, the star sensor identifies the image through the star recognition algorithm in the application software, and at the same time provides the star vector coordinates of the stars in the image in the measurement coordinate system of the space-based small field-of-view camera. This process makes full use of the star sensor's mature star point extraction and image recognition technology to extract the real-time star vectors captured by the small field-of-view camera, simplifying the camera design. The camera does not need to have functions such as gate image extraction, star point extraction and recognition, and star map matching.

[0047] Specifically, calculate the stellar vector coordinates in the star-sensor measurement coordinate system: in A represents the stellar vector position in the inertial coordinate system stored in the StarMin star database. is The measurement information q from the star sensor can be used is Calculated;

[0048] Star vector coordinates in the coordinate system measured by the space-based small field-of-view camera Images captured by a camera can be directly obtained through star-aware star recognition algorithms.

[0049] The S3 and GNC subsystems calculate the estimated values ​​of the measurement deviation angles of the space-based small field-of-view camera and star sensor using an optimal estimation algorithm. This step applies a least-squares estimation model and includes the following steps:

[0050] S31. Establish a reference plane perpendicular to the star-sensitive measurement plane, with the basis vector H(k) of this reference plane. in

[0051] S32. Establish observations in

[0052]

[0053]

[0054]

[0055] Among them, A bxj The transformation matrix from the coordinate system of the space-based small field-of-view camera to the satellite's intrinsic coordinate system can be directly obtained from the ground-based precision measurement information of the camera; A sb The transformation matrix from the star-sensor measurement coordinate system to the satellite's own coordinate system can be directly obtained from the ground-based precision measurement information of the star-sensor. These two transformation matrices are the theoretical installation matrices between the space-based small field-of-view camera and the star-sensor.

[0056] S33. Calculate the measurement reference deviation angle between the small field-of-view camera and the star sensor. in Let Δθ(k) be the measurement roll deviation angle of the small field-of-view camera and the star sensor, Δψ(k) be the measurement roll pitch angle of the small field-of-view camera and the star sensor, and Δψ(k) be the measurement yaw deviation angle of the small field-of-view camera and the star sensor. Specifically...

[0057]

[0058] Where Fai(k)=H T (k)·H(k)+Fai(k-1), Fai(0)=zeros(3,3),Y(0)=[0 0 0] T Fai -1 (k) is the inverse matrix of matrix Fai(k).

[0059] S4. Set the constraints for the estimation algorithm in step S3, including limiting the range of the estimated value and timing the estimation algorithm;

[0060] Specifically, the estimated values ​​of the measurement deviation angles of the space-based small field-of-view camera and the star sensor are subjected to amplitude limiting processing, with an amplitude of 0.1 / 57.3 rad; a counter is set for the estimation algorithm in step S3. When the optimal estimation algorithm is enabled, the counter starts counting. After counting for 50 seconds, the output value of the optimal estimation algorithm is taken as the measurement reference deviation angle between the small field-of-view camera and the star sensor. At this time, the algorithm is exited and the counter is cleared to zero.

[0061] 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. An astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference, characterized in that, Includes the following steps: S1. Simultaneously scan the sky region containing the desired star using a space-based small field-of-view camera and a star sensor to obtain the star map of the desired star captured by the small field-of-view camera and the satellite inertial quaternion in the star sensor's measurement coordinate system; S2. The star sensor calculates the stellar vector coordinates in the star sensor's measurement coordinate system and the space-based small field-of-view camera's measurement coordinate system based on the measurement information from the space-based small field-of-view camera and the star sensor, respectively; S3. Calculate the estimated value of the measurement deviation angle of the space-based small field-of-view camera and the star sensor using an optimal estimation algorithm; S4. Set the constraints for the estimation algorithm in step S3, including limiting the amplitude of the estimated value and timing the estimation algorithm; wherein, step S2 specifically involves: the space-based small field-of-view camera transmitting image information to the star sensor in real time; after loading the optical system parameters of the space-based small field-of-view camera, the star sensor identifies the image using a star recognition algorithm, and simultaneously provides the stellar vector coordinates of the star in the image in the star sensor's measurement coordinate system and the space-based small field-of-view camera's measurement coordinate system, respectively; the stellar vector coordinates in the star sensor's measurement coordinate system are: ,in These are the stellar vectors in the inertial frame stored in the StarMiner database. Satellite inertial quaternions Calculated stellar vector coordinates in the space-based small field-of-view camera measurement coordinate system. The images of stars captured by space-based small field-of-view cameras can be directly obtained by star sensors using mature star recognition algorithms. Step S3 further includes the following steps: S31, establishing a reference plane perpendicular to the star-sensor measurement plane, the basis vector of which is H(k); S32, establishing the observation measurement... S33. Calculate the measurement reference deviation angle between the small field-of-view camera and the star sensor. ,in The measurement of the roll deviation angle between the small field-of-view camera and the star sensor. The pitch deviation angle is measured by the small field-of-view camera and the star sensor. The yaw deviation angle is measured for the small field-of-view camera and the star sensor; in, For matrix The inverse matrix.

2. The astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference as described in claim 1, characterized in that, Step S1 further includes the following steps: S11. Utilizing the pointing capability of the satellite in any inertial space, the optical axis of the space-based small field-of-view camera on the satellite is rotated to point towards the desired star in space. During this process, the satellite's three-axis attitude is scanned within a fixed speed and angle range, causing the optical axis of the space-based small field-of-view camera to perform a cross-shaped trajectory scan centered on the desired star. The image of the desired star is acquired in real time using the measurement information from the small field-of-view camera; S12. While the space-based small field-of-view camera is scanning the desired star, the star sensor simultaneously exposes the sky region corresponding to its own field of view and acquires the satellite's inertial quaternion in the star sensor's measurement coordinate system at this time. .

3. The astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference as described in claim 2, characterized in that, The star sensor sends the internal exposure signal to the space-based small field-of-view camera in real time, synchronizing the falling edges of the two.

4. The astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference as described in claim 1, characterized in that, A high-speed communication interface is provided between the space-based small field-of-view camera and the star sensor.

5. The astronomical calibration method for synchronizing a small field-of-view camera with a star-sensitive measurement reference as described in claim 1, characterized in that, Step S4 specifically involves: limiting the estimated value of the measurement deviation angle between the space-based small field-of-view camera and the star sensor to an amplitude of 0.1 / 57.3 rad; setting a counter for the estimation algorithm in step S3; when the optimal estimation algorithm is enabled, starting the counter to count; after counting for 50 seconds, taking the output value of the optimal estimation algorithm as the measurement reference deviation angle between the small field-of-view camera and the star sensor; at this point, exiting the algorithm and resetting the counter to zero.

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