On-orbit automatic calibration device and method for satellite-borne composite imaging system

Abstract

According to an automatic calibration algorithm, a satellite platform control system completes index decomposition and drives attitude adjusting equipment such as a momentum wheel and the like, and orderly change of pointing of a main shaft (such as an optical axis of a narrow-view-field visible light sensor, an electric axis of an imaging radar and the like) of an accurate imaging sensor is realized; according to the signal response quality and related azimuth information (such as an image maximum average D / N value or a target angle measurement value and an echo signal-to-noise ratio calibration graph), the deviation between a main axis (such as an optical axis of a narrow-view-field visible light sensor, an electric axis of an imaging radar and the like) of an accurate imaging sensor and an optical axis of a large-view-field wide-angle guide sensor (such as an optical wide-angle camera) is calculated; and convergence is realized through several times of scanning, so that on-orbit automatic calibration is completed.

Description

TECHNICAL FIELD

[0001] The application relates to an on-orbit automatic calibration device and method of a satellite-borne composite imaging system, in particular to an on-orbit automatic calibration device and method of a high-resolution narrow-beam microwave imaging radar and a high-resolution small-view optical composite imaging system, and belongs to the technical field of on-orbit automatic calibration of a satellite-borne composite imaging system. BACKGROUND

[0002] The satellite-borne composite imaging system is composed of a wide-angle guide sensor (such as an optical wide-angle camera) and precise imaging sensors, such as a high-resolution small-sized visible light camera (with a small field of view and angle measurement and imaging functions), a high-frequency microwave imaging radar (with a fixed narrow beam and only distance measurement and imaging functions after deleting a differential channel for weight optimization), and the like. The precise imaging sensors also include, but are not limited to, other narrow-beam imaging infrared sensors, multi-band optical composite imaging detection systems and the like.

[0003] After being launched into orbit, the satellite is subjected to the mechanical conditions of the launch section and the thermal conditions in orbit, so that the optical axis of the visible light camera, the radar antenna, the mounting surface cabin plate and the optical axis of the guide camera all change. The narrow-beam antenna electric axis and the narrow-view visible light camera optical axis need to be calibrated in orbit according to the optical axis of the wide-angle guide camera to achieve accurate pointing.

[0004] The visible light camera optical axis calibration is usually performed in the "man-in-the-loop" mode, that is, in the real-time imaging downlink mode, which is low in efficiency and occupies human resources and orbital resources. The microwave radar with a narrow beam and lacking a differential channel cannot usually complete on-orbit calibration.

[0005] The current calibration of the imaging system of the satellite in orbit needs "man-in-the-loop", that is, real-time imaging and real-time image downlink. The ground operator manually judges the image definition to guide the momentum wheel to change the satellite platform attitude, and finds the target through multiple optimization. The experience of the ground operator is fully relied on. Meanwhile, under normal circumstances, the low-frequency microwave radar beam is relatively wide, and the on-orbit calibration is completed through multiple iterations according to the angle measurement value and the guide camera. When the radar beam is very narrow, the deviation between the radar electric axis pointing and the ground calibration is large under the action of the on-orbit mechanical and thermal conditions, and it is difficult to achieve target locking without angle measurement capability. SUMMARY

[0006] The technical problem solved by the application is to overcome the shortcomings of the prior art and provide an on-orbit automatic calibration device and method of a satellite-borne composite imaging system. The on-orbit calibration of the visible light camera and the microwave radar can be completed in one key through the automatic calibration method, the calibration target is sent after being marked on the ground, and the existing resources of the composite imaging system and the satellite platform are utilized.

[0007] The technical solution of the application is: In a first aspect, an on-orbit automatic calibration device of a spaceborne compound imaging system is provided, comprising: a visible light camera, a microwave radar, a compound imaging processor, a guide camera, a control computer, and a pose adjustment mechanism; wherein: the visible light camera is configured to monitor a target, perform image processing on the target after imaging, obtain an azimuth angle and an elevation angle of the target in a camera coordinate system, and send the azimuth angle and the elevation angle to the compound imaging processor; the microwave radar is configured to perform microwave imaging when a relative motion angle between the target and the microwave radar meets an imaging requirement, and send a ranging result of the target to the compound imaging processor; the compound imaging processor stores an automatic calibration algorithm, determines a target pointing vector using detection results of the visible light camera and the microwave radar, and calculates a scanning index and sends the scanning index to the control computer; the control computer receives the scanning index from the compound imaging processor, decomposes the scanning index, and sends the scanning index to the pose adjustment mechanism; the guide camera provides an initial direction of a target for the visible light camera and the microwave radar; the pose adjustment mechanism receives instructions from the control computer, and drives the visible light camera and the microwave radar to adjust the azimuth angle and the elevation angle.

[0008] Preferably, the scanning index comprises: a scanning step, a scanning point dwell time, and a scanning range.

[0009] Preferably, a field of view of the guide camera is larger than those of the visible light camera and the microwave radar. Ideally, an optical axis of the guide camera is consistent with an optical axis of the visible light camera and an electrical axis of the microwave radar; due to assembly errors, an angle between a mechanical axis of the radar antenna or the optical axis of the camera and the optical axis of the guide camera is calibrated on the ground.

[0010] In a second aspect, an on-orbit automatic calibration method of a spaceborne compound imaging system is provided, comprising: visible light camera optical axis calibration and microwave radar electrical axis calibration; wherein: the visible light camera optical axis calibration method comprises: the visible light camera optical axis is directed to a target according to an initial direction provided by the guide camera; S1-1, the compound imaging processor calculates a grid scanning index and sends the grid scanning index to the control computer; the control computer generates a scanning instruction according to the grid scanning index, and controls the pose adjustment mechanism to drive the visible light camera to perform grid scanning; at each grid scanning point, the visible light camera feeds back a grid scanning result to the compound imaging processor; S1-2, the compound imaging processor calculates a spiral scanning center and a spiral scanning index of spiral scanning by counting DN values at all grid points, and sends the spiral scanning center and the spiral scanning index to the control computer; S1-3, the control computer controls the attitude adjusting mechanism to drive the visible light camera to complete two spiral scans according to the spiral scan center and the spiral scan index; at each spiral scan point, the visible light camera feeds the azimuth angle and the elevation angle of the target in the camera coordinate system to the composite imaging processor; S1-4, the composite imaging processor statistically analyzes the azimuth angle and the elevation angle of the target at all spiral scan points in the two spiral scans, determines the target pointing vector of the two spiral scans, and judges whether the two target pointing vectors satisfy the scan end condition; when the scan end condition is satisfied, the time corresponding to the second target pointing vector is recorded and sent to the control computer, and step S1-5 is entered; if the scan end condition is not satisfied, step S1-3 is returned to reiterate; S1-5, the control computer obtains the satellite three-axis attitude angle offset amount corresponding to the time of the second target pointing vector, and completes the visible light camera calibration; The microwave radar electric axis calibration method comprises: According to the initial direction provided by the guide camera, the radar electric axis is directed to the target; S2-1, the composite imaging processor calculates the grid scan index and sends it to the control computer, the control computer generates a grid scan instruction according to the grid scan index, and controls the attitude adjusting mechanism to drive the microwave radar to perform grid scanning; at each grid scan point, the microwave radar feeds the grid scan result to the composite imaging processor; S2-2, the composite imaging processor statistically analyzes the signal-to-noise ratio at all grid points, and determines the spiral scan center and the spiral scan index of the spiral scan; S2-3, the control computer controls the attitude adjusting mechanism to drive the microwave radar to complete two spiral scans according to the scan center and the spiral scan index; at each spiral scan point, the microwave radar feeds the ranging result vector of the target to the composite imaging processor; S2-4, the composite imaging processor statistically analyzes the ranging result of the microwave radar at all spiral scan points in the two spiral scans, determines the target pointing vector of the two spiral scans, and judges whether the two target pointing vectors satisfy the scan end condition; when the scan end condition is satisfied, the time corresponding to the second target pointing vector is recorded and sent to the control computer, and step S2-5 is entered; if the scan end condition is not satisfied, step S2-3 is returned to reiterate; S2-5, the control computer obtains the satellite three-axis attitude angle offset amount corresponding to the time of the second target pointing vector, and completes the microwave radar calibration.

[0011] Preferably, during ground calibration, the included angle between the microwave radar electric axis or the visible light camera optical axis and the guide camera optical axis is θ1 and θ2, respectively; The grid scan range of the microwave radar and the visible light camera is ±M*θ1 and ±N*θ2, respectively; Wherein, M represents the amplification coefficient of the microwave radar electric axis grid scanning range, and N represents the amplification coefficient of the visible light camera optical axis grid scanning range.

[0012] Preferably, the spiral scanning ranges of the microwave radar and the grid visible light camera are ±(M / 2)*θ1 and ±(N / 2)*θ2 respectively.

[0013] Preferably, the center point of the spiral scanning refers to the grid point with the maximum microwave radar ranging signal-to-noise ratio or the maximum visible light camera imaging DN value in the grid scanning result.

[0014] Preferably, the scanning step of the spiral scanning is P times of the microwave radar beam width or the visible light camera field of view, and 0

[0015] Preferably, the scanning end condition is that the angle difference between the target pointing vectors of two spiral scans is less than the scanning step of the spiral scanning.

[0016] Preferably, during the grid scanning, the control computer takes the results of the ground calibration of the visible light camera and the microwave radar as the initial scanning points.

[0017] Compared with the prior art, the present application has the following advantages: (1) The present application designs an automatic calibration method and process, which does not need ground participation and completes on-orbit calibration in one key. (2) The on-orbit automatic calibration method designed by the present application does not depend on radar angle measurement function, and only through extracting radar ranging signal-to-noise ratio, the electric axis automatic calibration can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a block diagram of the satellite-borne composite imaging system of the present application. Figure 2 It is a calibration flowchart of the present application. Figure 3 It is a radar calibration graphical schematic diagram of the present application. Figure 4 It is a schematic diagram of the maximum average DN value of each scanning point during the optical axis calibration of the visible light camera in the embodiment of the present application. DETAILED DESCRIPTION

[0019] The application provides a device and method for on-orbit calibration of a satellite-borne compound imaging system, according to an automatic calibration algorithm, a satellite platform control system completes index decomposition and drives a momentum wheel and other attitude adjustment devices to realize ordered changes in the pointing of a main shaft of an accurate imaging sensor (such as an optical axis of a narrow field of view visible light sensor, an electric axis of an imaging radar, etc.), according to signal response quality and related azimuth information (such as an image maximum average D / N value or target angle measurement value and echo signal-to-noise ratio calibration chart), the deviation of the main shaft of the accurate imaging sensor (such as the optical axis of the narrow field of view visible light sensor, the electric axis of the imaging radar, etc.) from the optical axis of a wide field of view wide-angle guide sensor (such as an optical wide-angle camera) is calculated, convergence is realized through several scans, and on-orbit automatic calibration is completed.

[0020] The application is realized by the following technical solutions: The device for on-orbit automatic calibration of the satellite-borne compound imaging system comprises the following software / hardware: A visible light camera is used to complete conversion of light signals of a specified spectral range into electrical signals, realize high-resolution imaging of a monitoring target, and give an azimuth angle and an elevation angle of the target in a camera coordinate system through processing of the exposure image, and send the azimuth angle and the elevation angle to a compound imaging processor.

[0021] A microwave radar is used to detect the presence or absence of a target and the distance of the target by actively radiating a radio frequency signal and receiving a return wave (in order to adapt to the light weight requirement of the system, the radar in the application has only two channels, and the speed measurement and angle measurement functions are cut), and realize high-resolution microwave imaging when a relative motion angle of the target and the microwave radar meets the imaging requirement, and send the distance measurement result of the target to the compound imaging processor.

[0022] A guide camera provides an initial direction for target imaging for the visible light camera and the microwave radar. A compound imaging processor is an interface of the compound imaging system to the platform, and is internally provided with automatic calibration software to complete calculation of control requirements of a grid scan and a spiral scan on the satellite platform, obtain scan indexes (including scan steps, dwell time, scan range, etc.), and make a decision on whether the grid scan / spiral scan is completed. The compound imaging processor can also focus the visible light camera.

[0023] A control computer belongs to the satellite platform, and interfaces with the compound imaging processor to decompose and send the scan indexes of the compound imaging processor to an actuator such as a momentum wheel.

[0024] A momentum wheel and other attitude adjustment mechanisms belong to the satellite platform, and are responsible for receiving instructions from the control computer and driving the satellite platform to realize changes in an azimuth angle and a pitch angle.

[0025] Multi-band optical composite imaging detection system: the system comprises a beam splitter, a visible light objective lens, a visible light sensor, a medium wave infrared objective lens, a micro scanner and a medium wave infrared sensor. The system can divide light signals into two beams of visible light and medium infrared light, and realize imaging through corresponding objective lenses and sensors.

[0026] The technical solution solved by the application is: An on-orbit automatic calibration device and method for a satellite-borne composite imaging system, the implementation steps are as shown in the figure, in particular: Figure 2 1. Visible light camera optical axis or microwave radar electric axis calibration: the composite imaging processor gives the range of grid scanning, scanning step and grid point residence time according to the automatic calibration algorithm, controls the computer to take the ground calibration result as the initial scanning point, decomposes the scanning index to the momentum wheel to complete scanning, and the radar realizes ranging in the residence time of each grid point or the camera completes imaging in the scanning process.

[0027] 2. After the grid scanning is completed, the composite imaging processor calculates the starting point of the next spiral scanning, the scanning range, the step and the residence time, and after three scans are completed, the composite imaging processor calculates the scanning point where the target is located.

[0028] 3. The control subsystem gives the offset amount of the coordinate axis attitude angle at this time according to the time mark, so as to complete the visible light camera optical axis or microwave radar electric axis calibration.

[0029] The above step 1 specifically comprises: 1.1. The composite imaging processor calculates the step of grid scanning, the residence time of the scanning point and the scanning range; 1.2. The control computer realizes the pointing of the optical axis / electric axis to the target according to the instruction of the composite imaging processor, and starts grid scanning; 1.3. In the residence time of each grid point, the microwave radar completes ranging and gives the maximum signal-to-noise ratio, or the camera completes imaging and gives the maximum average DN value.

[0030] The above step 1.1 specifically comprises: 1.1.1. The step of grid scanning refers to the microwave radar beam width or the camera field of view P times (0 1.1.2. The residence time of the grid scanning point refers to the time greater than the response time of the microwave radar ranging or the camera imaging; 1.1.3. It is assumed that the included angles between the radar antenna mechanical axis or the camera optical axis and the guiding camera optical axis are θ1 and θ2 respectively through ground calibration, and then the grid scanning ranges are ±M*θ1 and ±N*θ2 respectively; M represents the magnification multiple of the microwave radar electric axis grid scanning range, and N represents the magnification multiple of the camera optical axis grid scanning range; The above step 2 specifically comprises:​ 2.1 The compound imaging processor calculates the signal-to-noise ratio or DN value at all grid points, determines the center point, the scanning step and the scanning range of the next spiral scan.

[0031] 2.2 The control computer directs the optical / electrical axis to point at the target according to the instruction of the compound imaging processor, and starts the spiral scan. 2.3 During the dwell time at each scanning point, the microwave radar completes the ranging and gives the maximum signal-to-noise ratio, or the camera completes the imaging and gives the azimuth and elevation of the target in the camera coordinate system.

[0032] 2.4 The compound imaging processor calculates the signal-to-noise ratio or azimuth / elevation at all spiral scanning points, and determines whether the end scanning condition is met.

[0033] The above step 2.1 specifically includes: 2.1.1 The center point of the spiral scan refers to the grid point with the maximum signal-to-noise ratio or DN value. 2.1.2 The step of the spiral scan refers to the microwave radar beam width or P times (P≤0.1) of the camera field of view. 2.1.3 The range of the spiral scan is ±(M / 2)*θ1 and ±(N / 2)*θ2, respectively. The above step 2.4 specifically includes: 2.4.1 The compound imaging processor calculates the vector pointing at the target (i.e. the scanning point with the maximum signal-to-noise ratio or the minimum azimuth / elevation value) determined by the radar or the camera each time the spiral scan is performed. When the angle difference between two vectors (the angle difference between the vectors pointing at the target obtained by two spiral scans) is less than the scanning step of the spiral scan, it is determined that the end scanning condition is met.

[0034] The above step 3 specifically includes: 3.1 The compound imaging processor transmits the target pointing (i.e. the scanning point with a time mark) obtained by the second spiral scan to the control computer, and the control computer gives the satellite three-axis attitude angle offset at this time under the same time standard, and the microwave radar electrical axis / camera optical axis calibration is completed.

[0035] The application will be described in detail below through specific examples.

[0036] A satellite-borne compound imaging system as shown in Fig. 1 includes a microwave radar 1, a camera 2, a control computer 3, a compound imaging processor 4 and a satellite 5. Figure 1The composite imaging system is shown in Fig. 1. It consists of a narrow-beam microwave radar and a narrow field of view optical camera. The microwave radar has the functions of ranging (not angle measurement) and microwave imaging, and the optical camera has the functions of angle measurement and visible light imaging. The antenna of the microwave radar and the lens of the optical camera are fixedly installed on the satellite platform, the electrical axis of the antenna and the optical axis of the camera are consistent with the pointing direction of the optical camera, and the pointing direction is preliminarily calibrated on the ground. The composite imaging processor is an interface between the subsystem and the satellite platform control computer, which is responsible for calculating the grid scanning / spiral scanning range, scanning step and scanning point dwell time according to the calibration algorithm, and sending scanning instructions to the control computer and judging whether the scanning is completed. The control computer is responsible for guiding the momentum wheel and other attitude driving mechanisms to realize the change of the satellite attitude according to the instructions.

[0037] Example 1, visible light camera optical axis calibration, the steps are as follows: (1) Perform grid scanning.

[0038] a) Calculate the grid scanning parameters according to the camera field of view, camera exposure time and ground calibration results. As shown in Table 1: Table 1 Visible light camera specifications and grid scanning parameters

[0039] b) Statistics of the maximum average DN value at each grid point and determination of the parameters of spiral scanning.

[0040] Figure 4 The maximum average DN value at each scanning point of the grid scanning; According to the automatic calibration algorithm, the parameters of the next spiral scanning are as follows: as shown in Table 2: Table 2 Visible light camera grid scanning results and spiral scanning parameters

[0041] (2) Perform spiral scanning a) Statistics of the azimuth angle and elevation angle at each scanning point, this case carried out two spiral scans according to the automatic calibration algorithm, the scanning point of the target is B n , the included angle of the two scanning vectors pointing to the target is 0°, which meets the algorithm convergence condition, and the scanning is completed.

[0042] b) Record the X-axis attitude angle offset, Y-axis attitude angle offset and Z-axis attitude angle offset of B n point as 0°, 0.5° and 0.5° respectively.

[0043] Example 2, microwave radar electrical axis calibration, the steps are as follows: (1) Perform grid scanning.

[0044] a) According to the radar beam width, radar ranging response time and ground calibration results, the grid scanning parameters are calculated. As shown in Table 3: Table 3 Microwave radar index and grid scanning parameters

[0045] b) The signal-to-noise ratio at each grid point is counted and the parameters of the spiral scanning are determined.

[0046] The signal-to-noise ratio at each scanning point of the grid scanning is as follows:

[0047] According to the automatic calibration algorithm, the parameters of the next spiral scanning are as follows: as shown in Table 4: Table 4 Microwave radar grid scanning results and spiral scanning parameters

[0048] c) Continue to carry out spiral scanning with Bn as the scanning center, count the maximum signal-to-noise ratio at each scanning point, and the signal-to-noise ratio at each scanning point of the spiral scanning is as follows:

[0049] According to the automatic calibration algorithm, two spiral scans are carried out, and the scanning center points determined according to the maximum signal-to-noise ratio are both B n+q , and the final vector angle pointing to the target is 0°, which meets the algorithm convergence condition, and the scanning is completed. The radar calibration diagram is shown in Figure 3 .

[0050] The X-axis attitude angle offset, Y-axis attitude angle offset and Z-axis attitude angle offset of the B n point are 0°, 0.35° and 0.25°, respectively.

[0051] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art.

Claims

1. An on-orbit automatic calibration device for a spaceborne composite imaging system, characterized in that... include: Visible light camera, microwave radar, composite imaging processor, guide camera, control computer, attitude adjustment mechanism; among which: Visible light cameras are used to monitor targets. After imaging the target, image processing is performed to obtain the target's azimuth and elevation angles in the camera coordinate system, which are then sent to a composite imaging processor. Microwave radar is used to perform microwave imaging after the relative motion angle between the target and the microwave radar meets the imaging requirements, and sends the ranging results of the target to the composite imaging processor. The composite imaging processor stores the automatic calibration algorithm, uses the detection results of the visible light camera and microwave radar to determine the target pointing vector, calculates the scanning index, and sends it to the control computer; The control computer receives the scanning parameters from the composite imaging processor, decomposes the scanning parameters, and sends them to the attitude adjustment actuator. The camera is guided to provide the initial direction of the visible light camera and microwave radar towards the target; The attitude adjustment mechanism receives instructions from the control computer and drives the visible light camera and microwave radar to adjust their azimuth and elevation angles.

2. The on-orbit automatic calibration device for a spaceborne composite imaging system according to claim 1, characterized in that: Scan indicators include: Scan step, scan point dwell time, and scan range.

3. The on-orbit automatic calibration device for a spaceborne composite imaging system according to claim 1, characterized in that: The field of view of the guiding camera is larger than that of the visible light camera and microwave radar; Ideally, the optical axis of the guide camera should be aligned with the optical axis of the visible light camera and the electrical axis of the microwave radar. However, due to assembly errors, the angle between the mechanical axis of the radar antenna or the optical axis of the camera and the optical axis of the guide camera should be calibrated on the ground.

4. An on-orbit automatic calibration method for a spaceborne composite imaging system, characterized in that... include: Optical axis calibration for visible light cameras and electrical axis calibration for microwave radar; where: Methods for calibrating the optical axis of a visible light camera include: Point the optical axis of the visible light camera toward the target based on the initial orientation provided by the guide camera; S1-1. The composite imaging processor calculates the grid scanning index and sends it to the control computer. The control computer generates scanning instructions based on the grid scanning index and controls the attitude adjustment actuator to drive the visible light camera to perform grid scanning. At each grid scanning point, the visible light camera feeds back the grid scanning result to the composite imaging processor. S1-2. The composite imaging processor counts the DN values ​​at all grid points, determines the spiral scanning center and spiral scanning parameters, and sends them to the control computer. S1-3. The control computer controls the attitude adjustment mechanism to drive the visible light camera to complete two spiral scans based on the spiral scan center and spiral scan index. At each spiral scan point, the visible light camera feeds back the azimuth and elevation angles of the target in the camera coordinate system to the composite imaging processor. S1-4: The composite imaging processor statistically analyzes the azimuth and elevation angles of all spiral scanning points in the two spiral scans of the visible light camera to determine the target pointing vectors of the two spiral scans and to determine whether the two target pointing vectors meet the scan end condition. When the scan end condition is met, the time corresponding to the second target pointing vector is recorded and sent to the control computer, and the process proceeds to step S1-5. If the scan end condition is not met, the process returns to step S1-3 and iterates again. S1-5. The control computer obtains the satellite's three-axis attitude angle offset at the moment corresponding to the second target pointing vector, and completes the visible light camera calibration. Microwave radar electric axis calibration methods include: Point the radar axis toward the target based on the initial orientation provided by the guidance camera; S2-1. The composite imaging processor calculates the grid scanning index and sends it to the control computer. The control computer generates a grid scanning command based on the grid scanning index and controls the attitude adjustment actuator to drive the microwave radar to perform grid scanning. At each grid scanning point, the microwave radar feeds back the grid scanning result to the composite imaging processor. S2-2, The composite imaging processor calculates the signal-to-noise ratio at all grid points to determine the spiral scanning center and spiral scanning parameters; S2-3. The control computer controls the attitude adjustment mechanism to drive the microwave radar to complete two spiral scans based on the scanning center and spiral scan parameters. At each spiral scan point, the microwave radar feeds back the target ranging result vector to the composite imaging processor. S2-4. The composite imaging processor statistically analyzes the ranging results at all spiral scanning points of the microwave radar in the two spiral scans, determines the target pointing vector of the two spiral scans, and judges whether the target pointing vectors of the two scans meet the scan end condition. When the scan end condition is met, the time corresponding to the second target pointing vector is recorded and sent to the control computer, and the process proceeds to step S2-5. If the scan end condition is not met, the process returns to step S2-3 and iterates again. S2-5. The control computer obtains the satellite's three-axis attitude angle offset at the moment corresponding to the second target pointing vector, and completes the microwave radar calibration.

5. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 4, characterized in that: When calibrating on the ground, the angles between the microwave radar electrical axis or the visible light camera optical axis and the guide camera optical axis are θ1 and θ2, respectively. The grid scanning ranges of the microwave radar and the visible light camera are ±M*θ1 and ±N*θ2, respectively; Where M represents the magnification factor of the microwave radar's electrical axis grid scanning range, and N represents the magnification factor of the visible light camera's optical axis grid scanning range.

6. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 5, characterized in that: The spiral scanning ranges of the microwave radar and the grid visible light camera are ±(M / 2)*θ1 and ±(N / 2)*θ2, respectively.

7. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 4, characterized in that: The center point of a spiral scan refers to the grid point in the grid scan result that has the highest signal-to-noise ratio in microwave radar ranging or the highest DN value in visible light camera imaging.

8. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 4, characterized in that: The scanning step of the helical scan is P times the microwave radar beamwidth or the field of view of the visible light camera, where 0 < P ≤ 0.

1.

9. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 8, characterized in that: The scan ends when the angle difference between the target pointing vectors of two helical scans is less than the scan step of the helical scan.

10. The on-orbit automatic calibration method for a spaceborne composite imaging system according to claim 4, characterized in that: During grid scanning, the control computer uses the results of ground calibration by the visible light camera and microwave radar as the initial scan points.

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