A method for optical detection and guidance of space targets based on star positioning

Abstract

The present invention provides a method for optical detection and guidance of space targets based on star positioning, comprising the following steps: Step 1: Using a tracking camera to capture a star map and transmit it to a test device; Step 2: Recording the attitude quaternion output by a star sensor, and having the test device extract star points from the star map; Step 3: Projecting the star points based on the attitude quaternion of the star sensor and the theoretical installation quaternion of the star sensor and tracking camera to obtain calibration installation quaternions for the star sensor and tracking camera, and correcting the pointing deviation of the tracking camera; Step 4: Uploading the calibration installation quaternion to an electronic circuit box, which calculates the sky area pointed by the tracking camera based on the attitude of the star sensor and opens a wave gate when there are stars in the field of view, extracts star points, calculates the stellar vectors of the star points, and completes ground verification of the astronomical calibration function. The present invention solves the problem of finding stars with a tracking camera with a small field of view, and calibrates the pointing deviation of the tracking camera based on star positioning.

Description

Technical Field

[0001] The present invention proposes a method for optical detection and guidance of space targets based on star positioning, mainly focusing on ground verification of on-orbit astronomical calibration of star attitude sensors and tracking cameras. Background Art

[0002] A star sensor is a high-precision, fast-response, highly reliable, and long-life attitude sensor, serving as a crucial component for satellite attitude determination. A small-field-of-view tracking camera is a camera used for tracking and tracking cooperative or non-cooperative targets in space, providing pointing information for satellite payloads. To calibrate the on-orbit star sensor and tracking camera, a quaternion is installed between them for optical precision measurement on the ground. However, due to factors such as vibration during rocket launch and the release of gravity on orbit, the actual on-orbit installation quaternions between the star sensor and tracking camera deviate from the ground-based precision measurement. Furthermore, due to on-orbit temperature fluctuations, which cause thermal deformation of the satellite's cabin panels and mounting platform, the installation quaternions also vary to a certain extent. Therefore, to ensure the smooth execution of the entire satellite mission, it is necessary to calibrate the installation relationship between the star sensor and tracking camera on-orbit using star sensor guidance and to calibrate the tracking camera's pointing deviation. Summary of the Invention

[0003] The purpose of the present invention is to propose a space target optical detection and guidance method based on star positioning, so as to realize ground verification of the joint astronomical calibration of a star sensor and a tracking camera.

[0004] To achieve the above object, the present invention adopts the following technical solution, and the steps are as follows:

[0005] Step 1: Use the tracking camera to take a star map and transfer it to the test equipment;

[0006] Step 2: Record the attitude quaternion output by the star sensor, and the test equipment extracts star points from the star map;

[0007] Step 3: Perform star point projection based on the star sensor attitude quaternion and the theoretical installation quaternion of the star sensor and the tracking camera to obtain the calibration installation quaternion of the star sensor and the tracking camera, and correct the pointing deviation of the tracking camera;

[0008] Step 4: Upload the calibration installation quaternion to the electronic circuit box. The electronic circuit box calculates the star sensor attitude and points the aiming camera to the sky area. When there are stars in the field of view, the wave gate is opened and the star point is extracted. The star vector of the star point is calculated to complete the ground verification of the astronomical calibration function.

[0009] Furthermore, there are no fewer than five stars within the field of view of the star sensor.

[0010] Furthermore, the tracking camera and the star sensor are respectively equipped with a first multi-star simulator and a second multi-star simulator, and the two star simulators are set in linkage, that is, when the quaternion driven by the second multi-star simulator equipped with the star sensor changes, the quaternion driven by the first multi-star simulator equipped with the tracking camera changes accordingly.

[0011] Furthermore, the theoretical installation quaternion of the first multi-star simulator and the tracking camera is consistent with the theoretical installation quaternion of the second multi-star simulator and the star sensor.

[0012] Furthermore, the installation quaternion Q from the inertial system to the tracking camera system is converted into the installation matrix A. The standard vector R of the star in the star catalog is used. The imaging position of the star on the camera image plane is:

[0013]

[0014] Where f is the focal length of the tracking camera lens, (x0, y0) is the principal point coordinate; assuming that the rotation is α radians around the X axis, β radians around the Y axis, and γ radians around the Z axis, the rotation sequence is 123. The installation quaternion Q from the star sensor measurement system to the tracking camera measurement system is known. xg , rotate the tracking camera measurement system along three axes, and use the steepest descent method based on the distance between the projected star point and the measured star point to obtain the calibration installation quaternion of the star sensor measurement system and the tracking camera measurement system according to the following rotation formula;

[0015]

[0016] Where qx ​​is the rotation quaternion of α radians around the X axis, qy is the rotation quaternion of β radians around the Y axis, qz is the rotation quaternion of γ radians around the Z axis, and qrec is the rotation quaternion from the star sensor to the tracking camera. is quaternion multiplication.

[0017] The present invention has the following beneficial effects:

[0018] (1) There is a high probability that there are no stars in the field of view of the small field of view and the aiming camera, which solves the problem of finding stars in the small field of view and the aiming camera.

[0019] (2) According to the attitude of the star sensor, the theoretical installation matrix of the star sensor and the tracking camera, and the image of the tracking camera, the on-orbit astronomical calibration of the star sensor and the small field of view tracking camera is completed, and the pointing deviation of the tracking camera is calibrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a flow chart of the space target optical detection and guidance method of the present invention;

[0021] Figure 2 This is a star point diagram within the star-sensing field of view of the present invention;

[0022] Figure 3 This is the calibration front projection star point and tracking camera field of view star point diagram of the present invention;

[0023] Figure 4 This is the star point diagram of the calibration-post-projection and tracking camera field of view of the present invention. DETAILED DESCRIPTION

[0024] The following is a further detailed description of the optical detection and guidance method for space targets based on star positioning proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description.

[0025] The present invention proposes a method for optical detection and guidance of space targets based on star positioning, which is implemented based on a verification system. The verification system includes a star sensor, an electronic circuit box, a tracking and aiming camera, a multi-star simulator supporting the star sensor, and a multi-star simulator supporting the tracking and aiming camera.

[0026] The star sensor's maximum detection magnitude is 6 Mv, its effective field of view is 20°, and its detector array is 1024×1024. However, the number of stars required for star sensor attitude determination is ≥5. The tracking camera's maximum detection magnitude is 6 Mv, its effective field of view is 2°×2°, and its detector array is 2048×2048. The tracking camera can only capture and transmit star maps and does not have the ability to independently perform attitude recognition. The star sensor head and tracking camera are both connected to the electronic circuit box via cables. The star sensor extracts star points and other information and transmits it to the electronic circuit box for attitude calculation. The tracking camera's full-frame image is then transmitted to the test equipment for star map processing and star point extraction.

[0027] Using the Hipparcos star catalog simulation, the probability that the number of stars in the star sensor's field of view is ≥15 is 99.9950%, the probability that the number of stars in the field of view is 14 is 0.0045%, and the probability that the number of stars in the field of view is 13 is 0.0005%. The star sensor can track stably in all directions; the probability that there are no stars in the tracking camera's field of view is 68.962%, the probability that there is 1 star in the field of view is 24.784%, the probability that there are 2 stars in the field of view is 5.138%, the probability that there are 3-4 stars in the field of view is 1.020%, and the probability that there are ≥5 stars in the field of view is 0.096%. To meet the number of stars required for attitude determination, astronomical calibration is performed on ≥5 stars.

[0028] This ground calibration test simulates on-orbit application. First, the installation of the star sensor and its accompanying multi-star simulator was calibrated. The simulated sky areas of the two multi-star simulators matched the installation angles of the star sensor and tracking camera. The tracking camera's pointing direction was ensured by tooling and was not calibrated. As a result, the installation quaternions of the star sensor and tracking camera deviated from the theoretical values. This test calibrated the installation deviations using the ground-based verification method proposed in this invention, in which a space target is guided by a star sensor.

[0029] The theoretical quaternion of the star sensor and tracking camera is (0.6220658808710200.169957214345132-0.253552437224016 0.721013074084929), and the quaternion of the simulated sky area of ​​the star sensor equipped with the multi-star simulator is (0.325196 0.52329-0.685326

[0030] -0.388256, the tracking camera is now pointing to the multi-star area (0.219528-0.211782-0.952058)

[0031] -0.0232556, record the quaternion of the star sensor at this time (0.325196 00.52329-0.685326

[0032] -0.388256), the star point image in the star sensor field of view is shown in Figure 2 , the star points extracted from the star map taken by the tracking camera and the star points projected by the star sensor and the theoretical installation matrix are shown in Figure 3 , the steepest descent method is used to optimize the distance between the projected star point and the image extracted star point to minimize the distance. The results are shown in Figure 4 The installed quaternion calibration results for the star sensor and tracking camera are (0.6243062289108860.171343032742692-0.2522759636147880.719194279617797). The calibration results are injected into the electronic circuit box. The star sensor predicts the star position in the tracking camera field of view based on the star sensor attitude and the installed quaternion calibration value, opens the wave gate, and extracts the star point. The star vector of this star point in the measurement system is calculated to be (0.0095703 0.00186429 0.999952).

[0033] Based on the above verification system, see Figure 1 The present invention provides a method for optical detection and guidance of space targets based on star positioning, comprising the following steps:

[0034] Step 1: Use the tracking camera to take a star map and transfer it to the test equipment;

[0035] Step 2: Record the attitude quaternion output by the star sensor, and the test equipment extracts star points from the star map;

[0036] Step 3: Perform star point projection based on the star sensor attitude quaternion and the theoretical installation quaternion of the star sensor and the tracking camera to obtain the calibration installation quaternion of the star sensor and the tracking camera, and correct the pointing deviation of the tracking camera;

[0037] Step 4: Upload the calibration installation quaternion to the electronic circuit box. The electronic circuit box calculates the star sensor attitude and points the aiming camera to the sky area. When there are stars in the field of view, the wave gate is opened and the star point is extracted. The star vector of the star point is calculated to complete the ground verification of the astronomical calibration function.

[0038] Furthermore, the tracking camera and the star sensor are respectively equipped with a first multi-star simulator and a second multi-star simulator, and the two star simulators are set in linkage, that is, when the quaternion driven by the second multi-star simulator equipped with the star sensor changes, the quaternion driven by the first multi-star simulator equipped with the tracking camera changes accordingly.

[0039] Furthermore, the theoretical quaternions for the first multi-star simulator and the tracking camera match the theoretical quaternions for the second multi-star simulator and the star sensor. The optical axis orientation of the star sensor is determined through simulation when multiple stars are within the tracking camera's field of view. The sky area simulated by the second multi-star simulator, which is used with the star sensor, is then adjusted to ensure that multiple stars are within the tracking camera's field of view.

[0040] Furthermore, the attitude quaternion of the star sensor is recorded, and an image is taken and saved with the tracking camera. The quaternion in the star sensor telemetry and the image data of the tracking camera are aligned by timestamp.

[0041] The tracking camera image data is processed to extract the coordinate information of the star point on the detector surface.

[0042] Given the installation quaternion Q from the inertial system to the tracking camera system, convert it into the installation matrix A, and the standard vector R of the star in the star catalog, the imaging position of the star on the camera image plane is:

[0043]

[0044] Where f is the focal length of the tracking camera lens, and (x0, y0) is the coordinate of the principal point. Due to the deviation on the track, there is a certain deviation between the projected star points and the star points extracted in the image.

[0045] Assume that the rotation is α radians about the X axis, β radians about the Y axis, and γ radians about the Z axis, with a rotation order of 123, that is, first rotate the X axis, then the Y axis, and finally the Z axis. Given the installation quaternion of the star sensor measurement system to the tracking camera measurement system, perform a three-axis rotation on the tracking camera measurement system. According to the following rotation formula, use the steepest descent method with the minimum sum of the distances between the projected star point and the measured star point as the goal to obtain the calibration installation quaternion of the star sensor measurement system and the tracking camera measurement system.

[0046]

[0047] Where qx ​​is the rotation quaternion of α radians around the X axis, qy is the rotation quaternion of β radians around the Y axis, qz is the rotation quaternion of γ radians around the Z axis, and qrec is the rotation quaternion from the star sensor to the tracking camera. is quaternion multiplication.

[0048] The present invention has the following beneficial effects:

[0049] (1) There is a high probability that there are no stars in the field of view of the small field of view and the aiming camera, which solves the problem of finding stars in the small field of view and the aiming camera.

[0050] (2) According to the attitude of the star sensor, the theoretical installation matrix of the star sensor and the tracking camera, and the image of the tracking camera, the on-orbit astronomical calibration of the star sensor and the small field of view tracking camera is completed, and the pointing deviation of the tracking camera is calibrated.

[0051] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for optical detection and guidance of space targets based on star positioning, characterized in that: The following steps are involved: Step 1: Use the tracking camera to take a star map and transfer it to the test equipment; Step 2: Record the attitude quaternion output by the star sensor, and the test equipment extracts star points from the star map; Step 3: Perform star point projection based on the star sensor attitude quaternion and the theoretical installation quaternion of the star sensor and the tracking camera to obtain the calibration installation quaternion of the star sensor and the tracking camera, and correct the pointing deviation of the tracking camera; Step 4: Upload the calibration installation quaternion to the electronic circuit box. The electronic circuit box calculates the direction of the tracking camera according to the attitude of the star sensor. When there are stars in the field of view, it opens the wave gate and extracts the star point. It calculates the star vector of the star point, completing the ground verification of the astronomical calibration function. The installation quaternion Q from the inertial system to the tracking camera system is converted into the installation matrix A. The standard vector R of the star in the star catalog, then the imaging position of the star on the camera image plane is: Where f is the focal length of the tracking camera lens, (x0, y0) is the principal point coordinate; assuming that the rotation is α radians around the X axis, β radians around the Y axis, and γ radians around the Z axis, the rotation sequence is 123. The installation quaternion Q from the star sensor measurement system to the tracking camera measurement system is known. xg , rotate the tracking camera measurement system along three axes, and use the steepest descent method based on the distance between the projected star point and the measured star point to obtain the calibration installation quaternion of the star sensor measurement system and the tracking camera measurement system according to the following rotation formula; Where qx ​​is the rotation quaternion of α radians around the X axis, qy is the rotation quaternion of β radians around the Y axis, qz is the rotation quaternion of γ radians around the Z axis, and qrec is the rotation quaternion from the star sensor to the tracking camera. is quaternion multiplication.

2. The method for optical detection and guidance of space targets based on star positioning according to claim 1, characterized in that: There are no fewer than five stars within the star sensor's field of view.

3. The method for optical detection and guidance of space targets based on star positioning according to claim 1, characterized in that: The tracking camera and the star sensor are respectively equipped with a first multi-star simulator and a second multi-star simulator. The two star simulators are set in linkage, that is, when the quaternion driven by the second multi-star simulator equipped with the star sensor changes, the quaternion driven by the first multi-star simulator equipped with the tracking camera changes accordingly.

4. The method for optical detection and guidance of space targets based on star positioning according to claim 2, characterized in that: The theoretical installation quaternion of the first multi-star simulator and the tracking camera is consistent with the theoretical installation quaternion of the second multi-star simulator and the star sensor.

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