Real-time monitoring system and method for mapping camera pose changes

Abstract

The present application belongs to the technical field of attitude change detection, and particularly relates to a real-time monitoring system and method for monitoring attitude change of front and rear view mapping cameras. The method comprises the following steps: firstly, ground calibration is performed; then, a reference time is determined as the time when the real-time monitoring system starts to work; next, a monitoring link at the reference time is constructed; a corresponding matrix obtained at a working time is measured; finally, the monitoring link at the working time is confirmed, and a transformation matrix of the front and rear view ground cameras in the J2000 coordinate system is derived. The present application can guarantee the geometric accuracy of the mapping cameras, and can also take into account the real-time performance of the measurement process and the comprehensiveness of the system monitoring.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of visual axis included angle detection, and particularly relates to a real-time monitoring system and method for mapping camera attitude changes. BACKGROUND

[0002] In the field of satellite photogrammetry, the exterior orientation element angle of the earth mapping camera is a key factor affecting the positioning accuracy, especially the positioning accuracy without ground control points. Due to the influence of various environmental factors during the launch and on-orbit operation of the space camera, the included angle between the main optical axes of the satellite camera may change, which will directly affect the accuracy of the obtained attitude angle. The positioning accuracy error of the mapping camera without control points mainly comes from the following aspects: the geometric calibration error of the camera itself in the ground stage, the orbit measurement error of the satellite itself and the attitude determination error of the star sensor, and the non-uniform thermal deformation of the sun illumination, which causes the front and rear view visual axis included angle to be no longer stable, and the low-frequency error generated by other factors accumulates in a long period, thereby seriously restricting the geometric accuracy of the mapping camera.

[0003] In order to ensure that the earth mapping camera can work for a long time with high precision, a special monitoring system is urgently needed: in the scene without control points, the changes of the front and rear view visual axis included angle of the camera are monitored in real time, as well as the change relationship between the included angle and the absolute pointing.

[0004] The determination of the front and rear view visual axis included angle of the mapping camera is usually realized through two calibration methods, namely laboratory calibration method and on-orbit geometric calibration method. The laboratory calibration method obtains the rotation matrix of the front / rear view camera relative to the satellite body coordinate system and the rotation matrix of the star sensor relative to the camera body system through ground calibration, and solves the included angle of the front / rear view camera visual axis in the inertial space and its absolute pointing vector through the rotation matrix transmission link. The on-orbit geometric calibration method directly obtains the visual axis included angle and the inertial pointing at the calibration time by using the ground control points to solve the installation matrix of the front / rear view camera relative to the star sensor. It should be particularly pointed out that during on-orbit operation, the installation matrix between the star sensor and the mapping camera will be affected by time-varying effects such as structural thermal deformation and low-frequency jitter, and its elements show non-stationary characteristics. At the same time, the on-orbit calibration method is also affected by external factors such as weather and terrain, and the calibration period is once every few months, which is difficult to accurately reflect the visual axis pointing and camera attitude changes in a short period, leading to the deviation of the camera visual axis included angle from the calibration reference value, and further introducing the system pointing error, and finally degrading the geometric positioning accuracy.

[0005] In addition, the existing attitude monitoring system often adopts a double vector scheme, and the yaw angle perpendicular to the target surface has poor robustness, the error range is larger than the two Euler angles of the pitch angle and the roll angle, and the accuracy and robustness of the algorithm are affected by multiple factors such as the angle between the double beams, the stability of the laser beam, the shape of the spot centroid, and the centroid extraction accuracy. These factors jointly limit the further improvement of the accuracy of the angle monitoring system. SUMMARY

[0006] Therefore, the present application aims to provide a real-time monitoring system and method for mapping camera attitude changes, which solves the technical problem that the geometric accuracy of the front and rear view mapping cameras is limited by the pointing direction under the condition of no control. The present application constructs a multi-spot monitoring system, uses multiple vectors in combination with the Quest algorithm, and effectively improves the robustness and accuracy of the algorithm. At the same time, the attitude change range of the front and rear view camera optical system is effectively calculated to carry out real-time monitoring of the on-orbit boresight change of the space remote sensing camera. The real-time and comprehensiveness of the measurement process are taken into account while ensuring the geometric accuracy of the mapping camera.

[0007] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] The present application provides a real-time monitoring system for mapping camera attitude changes, which includes a front view camera, a rear view camera, a star sensor, a reference prism, a first quartz mirror, a second quartz mirror, a third quartz mirror, a fourth quartz mirror, a fifth quartz mirror, a sixth quartz mirror, and a Daman grating. The first laser beam emitted by the laser inside the front view camera is reflected by the first quartz mirror and the second quartz mirror in turn and then enters the reference prism. The second laser beam emitted by the laser inside the rear view camera is reflected by the third quartz mirror and the fourth quartz mirror in turn and then enters the reference prism. The reference prism causes the first laser beam and the second laser beam to irradiate the fifth quartz mirror. The fifth quartz mirror reflects the first laser beam and the second laser beam to the Daman grating for light splitting. Each split beam obtained after light splitting by the Daman grating is reflected by the sixth quartz mirror to the detector focal plane of the star sensor.

[0009] The present application provides a real-time monitoring method for mapping camera attitude changes, which is realized by using the real-time monitoring system for mapping camera attitude changes. The method specifically includes the following steps:

[0010] S1: In the ground calibration stage, the real-time monitoring system for mapping camera attitude changes obtains the representation of the star sensor pointing vector in the satellite body coordinate system , the representation of the star sensor pointing vector in the star sensor focal plane coordinate system , representation of the vector perpendicular to the star sensor pointing vector in the satellite body coordinate system , representation of the vector perpendicular to the star sensor pointing vector in the star sensor focal plane coordinate system , representation of the reference prism normal vector in the satellite body coordinate system , representation of the reference prism normal vector in the reference prism coordinate system , representation of the vector perpendicular to the reference prism normal vector in the satellite body coordinate system , representation of the vector perpendicular to the reference prism normal vector in the reference prism coordinate system , and calculate the rotation matrix from the reference prism coordinate system to the star sensor focal plane coordinate system ;

[0011] S2: At the time of imaging calibration of the star sensor, the satellite platform is yawed to make the star sensor image the sky, and the star sensor is used to continuously capture the starry sky that meets the imaging condition to obtain an actual observation star chart, and the satellite body coordinate system to the J2000 coordinate system transformation matrix is obtained by using the actual observation star chart ;

[0012] S3: The first laser beam is split by the Dammam grating to obtain a first single-beam vector set ; the second laser beam is split by the Dammam grating to obtain a second single-beam vector set ;

[0013] S4: Based on the first single-beam vector set and the second single-beam vector set, the forward-looking ground camera coordinate system to the star sensor focal plane coordinate system transformation matrix and the rear-looking ground camera coordinate system to the star sensor focal plane coordinate system transformation matrix ;

[0014] S5: The link change relationship of the real-time monitoring system at the reference time is constructed by the following formula:

[0015] ;

[0016] ;

[0017] ;

[0018] ;

[0019] wherein, is the first intermediate variable, is the second intermediate variable;

[0020] S6: Based on the link change relation formula constructed in step S5, the transformation matrix of the forward-looking ground camera to the rear-looking ground camera in the J2000 coordinate system is calculated :

[0021] ;

[0022] S7: At the measurement moment, the first laser beam obtains a third single-beam vector set after being split by the Dammam grating ; the second laser beam obtains a fourth single-beam vector set after being split by the Dammam grating ;

[0023] S8: Based on the third single-beam vector set and the fourth single-beam vector set, the QUEST algorithm is used to calculate the transformation matrix of the forward-looking ground camera coordinate system to the star sensor focal plane coordinate system in the satellite body coordinate system and the transformation matrix of the rear-looking ground camera coordinate system to the star sensor focal plane coordinate system ;

[0024] S9: Based on the calibration results of S8, the transformation matrix of the forward-looking ground camera to the rear-looking ground camera in the J2000 coordinate system is calculated :

[0025] ;

[0026] S10: According to the transformation matrix of the forward-looking ground camera to the rear-looking ground camera at the reference moment and the transformation matrix of the forward-looking ground camera to the rear-looking ground camera at the measurement moment , the attitude change of the forward-looking ground camera and the rear-looking ground camera is obtained :

[0027] .

[0028] Further, step S1 specifically includes:

[0029] S11: Based on the representation of the star sensor pointing vector in the satellite body coordinate system and the representation of the star sensor pointing vector in the star sensor focal plane coordinate system , an orthogonal coordinate basis is constructed in the satellite body coordinate system :

[0030] ;

[0031] ;

[0032] ;

[0033] Wherein, ||·|| is the vector modulus operation;

[0034] S12: representation of a vector normal to the star sensor pointing vector in the satellite body frame and representation of a vector normal to the star sensor pointing vector in the star sensor focal plane frame constructing an orthogonal coordinate basis in the star sensor focal plane frame :

[0035] ;

[0036] ;

[0037] ;

[0038] S13: computing the transformation matrix from the satellite body frame to the star sensor focal plane frame by :

[0039] ;

[0040] S14: representation of the reference prism normal vector in the satellite body frame and representation of the reference prism normal vector in the reference prism frame constructing an orthogonal coordinate basis in the satellite body frame :

[0041] ;

[0042] ;

[0043] ;

[0044] S15: representation of a vector normal to the reference prism normal vector in the satellite body frame and representation of a vector normal to the reference prism normal vector in the reference prism frame constructing an orthogonal coordinate basis in the reference prism frame :

[0045] ;

[0046] ;

[0047] ;

[0048] S16: computing the transformation matrix from the satellite body frame to the reference prism frame by :

[0049] ;

[0050] S17: Calculate the rotation matrix from the reference prism coordinate system to the star sensor focal plane coordinate system by the following formula :

[0051] .

[0052] Further, in step S2, the imaging condition is met if the target sky area aligned by the star sensor includes at least N stars with magnitudes ≤ M, and the target sky area is not blocked by the sun, the earth and the earth atmosphere during the observation period of the star sensor.

[0053] Further, step S2 specifically includes:

[0054] S21: Select at least three non-collinear stars in the actual star observation map of the star sensor, and perform centroid extraction on each selected star to obtain the included angle between each star and the optical axis, and obtain a one-dimensional vector group based on the calculation result of the included angle , where n is the total number of selected stars:

[0055] ;

[0056] wherein is the included angle between the i-th star and the optical axis, is the centroid coordinates of the i-th star, is the focal length of the star sensor;

[0057] S22: Based on the built-in star catalog of the star sensor, use the one-dimensional vector group to obtain a real-time pointing vector group of each star in the star sensor focal plane coordinate system , and use a star map matching algorithm to process the real-time pointing vector group to obtain a real-time pointing vector group of each star in the J2000 coordinate system ;

[0058] S23: Input the real-time pointing vector group and the real-time pointing vector group to the QUEST algorithm, and obtain the transformation matrix from the star sensor focal plane coordinate system to the J2000 coordinate system based on the quaternion returned by the QUEST algorithm ;

[0059] S24: Based on the transformation matrix from the satellite body coordinate system to the star sensor focal plane coordinate system solved in S13 , calculate the transformation matrix from the satellite body coordinate system to the J2000 coordinate system by the following formula :

[0060] .

[0061] Further, in step S4, the representation of the first set of single beam vectors in the forward-looking camera coordinate system and the representation of the first set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and the transformation matrix from the forward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm ;

[0062] The representation of the second set of single beam vectors in the backward-looking camera coordinate system and the representation of the second set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and the transformation matrix from the backward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm .

[0063] Further, in step S8, the representation of the third set of single beam vectors in the forward-looking camera coordinate system and the representation of the third set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and the transformation matrix from the forward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm ;

[0064] The representation of the fourth set of single beam vectors in the backward-looking camera coordinate system and the representation of the fourth set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and the transformation matrix from the backward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm .

[0065] Further, the star sensor focal plane coordinate system is a three-dimensional coordinate system established with the projection center of the star sensor as the origin, the Z-axis of the star sensor focal plane coordinate system coincides with the direction of the optical axis of the star sensor, the X-axis of the star sensor focal plane coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the star sensor, and the Y-axis of the star sensor focal plane coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the star sensor;

[0066] The forward-looking camera coordinate system is a three-dimensional coordinate system established with the projection center of the forward-looking camera as the origin, the Z-axis of the forward-looking camera coordinate system coincides with the optical axis of the forward-looking camera, the X-axis of the forward-looking camera coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the forward-looking camera, and the Y-axis of the forward-looking camera coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the forward-looking camera;

[0067] The rear-view ground camera coordinate system is a three-dimensional coordinate system with the projection center of the rear-view ground camera as the origin, the Z-axis of the rear-view ground camera coordinate system coincides with the optical axis of the rear-view ground camera, the X-axis of the rear-view ground camera coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the rear-view ground camera, and the Y-axis of the rear-view ground camera coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the rear-view ground camera.

[0068] Compared with the prior art, the application can achieve the following beneficial effects:

[0069] (1) The real-time monitoring system and method for attitude change of front and rear view mapping cameras can realize uncontrolled monitoring of the included angle and absolute pointing of the viewing axes of the double-head mapping cameras, and improve the geometric positioning accuracy of the mapping cameras.

[0070] (2) The real-time monitoring system and method for attitude change of front and rear view mapping cameras based on the light splitting principle can significantly improve the robustness and anti-interference of the algorithm, so that the application has smaller error and wider application range compared with the prior art.

[0071] (3) The real-time monitoring system and method for attitude change of front and rear view mapping cameras can monitor the attitude of multiple loads and instruments on the satellite.

[0072] (4) The real-time monitoring system and method for attitude change of front and rear view mapping cameras adopts Daman grating light splitting, improves the imaging quality of the monitoring light beam and the centroid calculation accuracy, and thus realizes precise monitoring of the viewing axes. BRIEF DESCRIPTION OF DRAWINGS

[0073] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the present application, and the schematic embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0074] Figure 1 The structural schematic diagram of the real-time monitoring system for attitude change of front and rear view mapping cameras according to the embodiments of the present application;

[0075] Figure 2 The flowchart of the real-time monitoring method for attitude change of front and rear view mapping cameras according to the embodiments of the present application;

[0076] Figure 3 The construction principle diagram of the reference prism coordinate system according to the embodiments of the present application.

[0077] Reference signs:

[0078] 1, forward-looking camera; 2, rear-looking camera; 3, star sensor; 4, reference prism; 5, first quartz mirror; 6, second quartz mirror; 7, third quartz mirror; 8, fourth quartz mirror; 9, fifth quartz mirror; 10, sixth quartz mirror; 11, Daman grating; 12, laser. DETAILED DESCRIPTION

[0079] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not constitute a limitation on the present application.

[0080] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0081] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only used to facilitate the description of the present application and simplify the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used for description purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited by "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0082] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the communication between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0083] The present application will be described in detail below with reference to the drawings and embodiments.

[0084] As Figure 1As shown, the present application provides a real-time monitoring system for mapping camera pose changes, comprising a forward-looking camera 1, a backward-looking camera 2, a star sensor 3, a reference prism 4, a first quartz reflector 5, a second quartz reflector 6, a third quartz reflector 7, a fourth quartz reflector 8, a fifth quartz reflector 9, a sixth quartz reflector 10, and a Daman grating 11, wherein a first laser beam emitted by a laser 12 inside the forward-looking camera 1 is incident on the reference prism 4 after being reflected by the first quartz reflector 5 and the second quartz reflector 6 in turn, a second laser beam emitted by the laser 12 inside the backward-looking camera 2 is incident on the reference prism 4 after being reflected by the third quartz reflector 7 and the fourth quartz reflector 8 in turn, the reference prism 4 causes the first laser beam and the second laser beam to be incident on the fifth quartz reflector 9, the fifth quartz reflector 9 reflects the first laser beam and the second laser beam to the Daman grating 11 for light splitting, and each light beam obtained after light splitting by the Daman grating 11 is reflected by the sixth quartz reflector 10 to the detector focal plane of the star sensor 3.

[0085] It should be noted that the monitoring system for the absolute pointing of the forward and backward-looking cameras includes the Daman grating 11, the star sensor 3, the forward-looking camera 1, the backward-looking camera 2, the reference prism 4, etc. The monitoring light path is divided into two parts, the laser beams are emitted from the focal planes of the forward-looking camera 1 and the backward-looking camera 2, respectively, and are collimated after passing through the optical systems of the forward-looking camera 1 and the backward-looking camera 2 to enter the quartz reflectors rigidly connected to the outer wall. Since the thermal deformation of the quartz reflectors is very small, they can be regarded as stable references. The light path passes through the quartz reflectors and reaches the reference prism 4, and then the light is split by the Daman grating 11 to obtain multiple beams and is finally imaged on the focal plane of the star sensor 3 after being folded. The star sensor 3 provides the absolute pointing and establishes the monitoring link from the star sensor 3 to the reference prism 4. Then, the monitoring links from the reference prism 4 to the forward-looking camera 1 and the backward-looking camera 2 are established, respectively, and the angle change between the forward-looking camera 1 and the backward-looking camera 2 can be indirectly monitored by the change relative to the reference prism 4.

[0086] Further, for the Daman grating 11 for light splitting, a prism or other light splitter can be considered for replacement, and any optical device that can split the light beam into several parts with a clear pointing direction can be used. In addition, the laser 12 does not necessarily need to be installed at the focal plane position of the forward-looking and backward-looking mapping cameras, and the folding light path can be changed. Finally, the monitoring link between the star sensor 3 with absolute pointing function and the mapping camera needs to be established.

[0087] The real-time monitoring method for mapping camera pose changes provided by the present application is realized by using the real-time monitoring system for mapping camera pose changes, and specifically includes the following steps:

[0088] S1: In the ground calibration stage, the real-time monitoring system based on the front and rear view mapping camera pose changes obtains the representation of the star sensor pointing vector in the satellite body coordinate system , the representation of the star sensor pointing vector in the star sensor focal plane coordinate system , the representation of the vector perpendicular to the star sensor pointing vector in the satellite body coordinate system , the representation of the vector perpendicular to the star sensor pointing vector in the star sensor focal plane coordinate system , the representation of the reference prism normal vector in the satellite body coordinate system , the representation of the reference prism normal vector in the reference prism coordinate system , the representation of the vector perpendicular to the reference prism normal vector in the satellite body coordinate system , the representation of the vector perpendicular to the reference prism normal vector in the reference prism coordinate system , and the rotation matrix of the reference prism coordinate system to the star sensor focal plane coordinate system ;

[0089] S2: By satellite platform yaw, the star sensor 3 images the sky at the time of calibration as the reference time, and uses the star sensor 3 to continuously shoot the starry sky that meets the imaging conditions to obtain the actual observation chart, and uses the actual observation chart to obtain the transformation matrix of the satellite body coordinate system to the J2000 coordinate system ;

[0090] S3: The first laser beam is split by the Dammam grating 11 to obtain a first single beam vector set ; the second laser beam is split by the Dammam grating 11 to obtain a second single beam vector set ;

[0091] S4: Based on the first single beam vector set and the second single beam vector set, the transformation matrix of the front view ground camera 1 coordinate system to the star sensor focal plane coordinate system and the transformation matrix of the rear view ground camera 2 coordinate system to the star sensor focal plane coordinate system ;

[0092] S5: The link change relationship formula of the real-time monitoring system at the reference time is constructed by the following formula:

[0093] ;

[0094] ;

[0095] ;

[0096] ;

[0097] wherein, is a first intermediate variable, is a second intermediate variable;

[0098] S6: Based on the link change relationship formula constructed in step S5, the transformation matrix of the forward-looking ground camera to the rear-looking ground camera in the J2000 coordinate system is calculated :

[0099] ;

[0100] S7: At the measurement time, the first laser beam obtains a third single-beam vector set after being split by the Dammam grating 11 ; the second laser beam obtains a fourth single-beam vector set after being split by the Dammam grating 11 ;

[0101] S8: Based on the third single-beam vector set and the fourth single-beam vector set, the QUEST algorithm is used to calculate the transformation matrix of the forward-looking ground camera 1 coordinate system to the star sensor focal plane coordinate system in the satellite body coordinate system and the transformation matrix of the rear-looking ground camera 2 coordinate system to the star sensor focal plane coordinate system ;

[0102] S9: Based on the calibration results of S8, the transformation matrix of the forward-looking ground camera 1 to the rear-looking ground camera 2 in the J2000 coordinate system is calculated :

[0103] ;

[0104] S10: According to the transformation matrix of the forward-looking ground camera 1 to the rear-looking ground camera 2 at the reference time and the transformation matrix of the forward-looking ground camera 1 to the rear-looking ground camera 2 at the measurement time , the attitude change of the forward-looking and rear-looking mapping cameras is obtained :

[0105] .

[0106] It should be noted that the detection process of the multi-spot real-time monitoring system of the forward and rear viewing mapping cameras is as follows: first, ground calibration is performed, then the reference time is determined as the time when the multi-spot real-time monitoring system starts to start, then the monitoring link at the reference time is constructed, the corresponding matrix obtained at the measurement time is measured, and finally the monitoring link at the working time is confirmed and the transformation matrix of the forward-looking ground camera 1 (cam1) and the rear-looking ground camera 2 (cam2) in the J2000 coordinate system is calculated.

[0107] Further, as Figure 3As shown, the reference prism coordinate system takes the common vertex of three mutually perpendicular edges as the origin, and establishes a right-handed space rectangular coordinate system along the direction of the three edges.

[0108] In addition, on the UG software, after modeling the multi-spot real-time monitoring system of the front and rear view mapping camera view axis included angle, the vector representation on the satellite body coordinate system, the reference prism coordinate system and the star sensor focal plane coordinate system can be obtained through data, and after building the multi-spot real-time monitoring system of the front and rear view mapping camera view axis included angle, the vector representation on the satellite body coordinate system, the reference prism coordinate system and the star sensor focal plane coordinate system are obtained by using a laser range finder, a total station, a theodolite, a vernier caliper and the like, which is prior art and will not be described in detail.

[0109] In some embodiments, step S1 specifically comprises:

[0110] S11: representation of the star sensor pointing vector in the satellite body coordinate system and representation of the star sensor pointing vector in the star sensor focal plane coordinate system , constructing an orthogonal coordinate base in the satellite body coordinate system :

[0111] ;

[0112] ;

[0113] ;

[0114] wherein ||·|| is a vector modulus operation;

[0115] S12: representation of the vector perpendicular to the star sensor pointing vector in the satellite body coordinate system and representation of the vector perpendicular to the star sensor pointing vector in the star sensor focal plane coordinate system , constructing an orthogonal coordinate base in the star sensor focal plane coordinate system :

[0116] ;

[0117] ;

[0118] ;

[0119] S13: calculating the transformation matrix from the satellite body coordinate system to the star sensor focal plane coordinate system by the following formula :

[0120] ;

[0121] S14: representation of the reference prism normal vector in the satellite body coordinate system and representation of the reference prism normal vector in the reference prism coordinate system constructing an orthogonal coordinate basis in the satellite body coordinate system :

[0122] ;

[0123] ;

[0124] ;

[0125] S15: representation of the vector perpendicular to the reference prism normal vector in the satellite body coordinate system and representation of the vector perpendicular to the reference prism normal vector in the reference prism coordinate system constructing an orthogonal coordinate basis in the reference prism coordinate system :

[0126] ;

[0127] ;

[0128] ;

[0129] S16: calculating the transformation matrix from the satellite body coordinate system to the reference prism coordinate system by :

[0130] ;

[0131] S17: calculating the rotation matrix from the reference prism coordinate system to the star sensor focal plane coordinate system by :

[0132] .

[0133] In some embodiments, in step S2, the imaging condition is satisfied in that the target sky region aligned by the star sensor 3 at least includes N stars with a magnitude ≤ M, and the target sky region is not blocked by the sun, the earth and the earth atmosphere glow in the observation period of the star sensor 3.

[0134] It should be noted that M is a specific value of the magnitude, and M depends on the specific observation condition of the day, and is generally between 5-6.

[0135] In some embodiments, step S2 specifically includes:

[0136] S21: select at least three non-collinear stars in the actual star observation map of the star sensor 3, and perform centroid extraction on each selected star to obtain the included angle between each star and the optical axis, and obtain a one-dimensional vector group based on the included angle calculation result , n is the total number of selected stars:

[0137] ;

[0138] wherein, is the included angle between the i-th star and the optical axis, is the centroid coordinates of the i-th star, is the focal length of the star sensor;

[0139] S22: based on the built-in star table of the star sensor, a one-dimensional vector group is obtained, and the real-time pointing vector group is processed using a star map matching algorithm to obtain a real-time pointing vector group of each star in the J2000 coordinate system ;

[0140] S23: input the real-time pointing vector group and the real-time pointing vector group into the QUEST algorithm, and obtain the transformation matrix from the star sensor focal plane coordinate system to the J2000 coordinate system based on the quaternion returned by the QUEST algorithm;

[0141] S24: based on the transformation matrix from the satellite body coordinate system to the star sensor focal plane coordinate system solved in S13, the transformation matrix from the satellite body coordinate system to the J2000 coordinate system is calculated by the following formula:

[0142] .

[0143] Further, it should be noted that the star sensor 3 is built-in with a high-precision star table which stores the accurate coordinates of tens of thousands of stars in the inertial coordinate system J2000. The principle of invariability of interstellar angular distance is used, that is, the included angle of the angular distance vector of any two stars in the inertial system is fixed and independent of the observer's attitude.

[0144] In some embodiments, in step S4, the representation of the first single-beam vector set in the forward-looking camera 1 coordinate system and the representation of the first single-beam vector set in the star sensor focal plane coordinate system are input into the QUEST algorithm, and the transformation matrix from the forward-looking camera 1 coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm.

[0145] The representation of the second set of single beam vectors in the rear-view camera 2 coordinate system and the representation of the second set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and a transformation matrix from the rear-view camera 2 coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm .

[0146] In some embodiments, in step S8, the representation of the third set of single beam vectors in the front-view camera 1 coordinate system and the representation of the third set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and a transformation matrix from the front-view camera 1 coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm ;

[0147] The representation of the fourth set of single beam vectors in the rear-view camera 2 coordinate system and the representation of the fourth set of single beam vectors in the star sensor focal plane coordinate system are input to the QUEST algorithm, and a transformation matrix from the rear-view camera 2 coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternion returned by the QUEST algorithm .

[0148] It should be noted that the above-mentioned QUEST algorithm is specifically: the QUEST algorithm returns the best quaternion based on the input of two one-dimensional matrices , so as to obtain the corresponding matrix R based on the quaternion:

[0149] ;

[0150] wherein, are all elements corresponding to the quaternion.

[0151] In some embodiments, the star sensor focal plane coordinate system is a three-dimensional coordinate system established with the projection center of the star sensor 3 as the origin, the Z axis of the star sensor focal plane coordinate system coincides with the direction of the optical axis of the star sensor 3, the X axis of the star sensor focal plane coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the star sensor 3, and the Y axis of the star sensor focal plane coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the star sensor 3;

[0152] The front-view camera 1 coordinate system is a three-dimensional coordinate system established with the projection center of the front-view camera 1 as the origin, the Z axis of the front-view camera 1 coordinate system coincides with the optical axis of the front-view camera 1, the X axis of the front-view camera 1 coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the front-view camera 1, and the Y axis of the front-view camera 1 coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the front-view camera 1;

[0153] The rear-view ground camera 2 coordinate system is a three-dimensional coordinate system established with the projection center of the rear-view ground camera 2 as the origin, the Z axis of the rear-view ground camera 2 coordinate system coincides with the optical axis of the rear-view ground camera 2, the X axis of the rear-view ground camera 2 coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the rear-view ground camera 2, and the Y axis of the rear-view ground camera 2 coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the rear-view ground camera 2.

[0154] At the reference time, the laser emitted from the focal plane of the front and rear-view ground cameras 2 is split into multiple vectors after passing through the reference prism 4 and the Dammam grating 11, and is respectively denoted as and According to the QUEST algorithm, the transformation matrix of the current mapping camera (front and rear-view ground cameras 2) to the focal plane of the star sensor 3 in the satellite body coordinate system is calculated using the multiple vectors and ;

[0155] The link change relationship of the multi-spot real-time monitoring system at the reference time is established as follows:

[0156]

[0157] Thus, the absolute pointing of the front and rear-view ground cameras cam1 and cam2 in the J2000 coordinate system at the reference time is obtained, and the transformation matrix of the front and rear-view ground cameras cam1 and cam2 in the J2000 coordinate system is further derived:

[0158] ;

[0159] At the measurement time, due to the running track and pointing reasons, one side of the double-head mapping camera often faces direct sunlight, leading to uneven heating and thermal deformation, and the satellite will have residual kinetic energy after maneuvering, causing slight low-frequency vibration of the camera. These errors will eventually cause changes in the spot position of the focal plane of the star sensor 3, which are respectively denoted as and According to the QUEST algorithm, the transformation matrix of the current double-head mapping camera to the focal plane of the star sensor 3 in the satellite body coordinate system is calculated and Meanwhile, the star sensor 3 can also obtain the transformation matrix of the measurement time relative to the satellite body coordinate system to the coordinate system , thereby establishing the monitoring link:

[0160]

[0161] Similarly, the transformation matrix of the front and rear-view mapping cameras cam1 and cam2 in the J2000 coordinate system at this time can also be easily obtained:

[0162] .

[0163] Since the rotation amplitude is small, the rotation sequence can be ignored, and the roll angle is assumed to be... The pitch angle is The heading angle is ， It can be represented as: ;

[0164] The solution can be found:

[0165] ;

[0166] ;

[0167] ;

[0168] Thus, the change in relative attitude between the front-view and rear-view cameras is obtained. for The element in the third row and first column of the matrix, and the others are similar (including...). ).

[0169] In summary, this invention, under the condition of on-orbit independent measurement points of the dual-head mapping camera (forward and backward looking), uses real-time monitoring of multiple light spots combined with the QUEST algorithm to determine the absolute pointing of the dual-head mapping camera in the global coordinate system. Furthermore, the invention employs a Damman grating 11 for beam splitting, which effectively improves the quality of the light spot, thereby enhancing the accuracy of the light spot centroid extraction and achieving precise measurement of the line-of-sight pointing. In addition, the laser 12 is deployed at the focal plane of the dual-head mapping camera, and its final light spot hits the focal plane of the star sensor 3, representing a special case of a focal plane on a focal plane, thus simplifying the algorithm and achieving the final result without matrix multiplication.

[0170] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0171] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A real-time monitoring system for attitude changes of a forward and backward surveying camera, characterized in that: The system includes a forward-looking ground-view camera, a rear-looking ground-view camera, a star sensor, a reference prism, a first quartz mirror, a second quartz mirror, a third quartz mirror, a fourth quartz mirror, a fifth quartz mirror, a sixth quartz mirror, and a Dammann grating. A first laser beam emitted from a laser inside the forward-looking ground-view camera is reflected sequentially by the first and second quartz mirrors before entering the reference prism. A second laser beam emitted from a laser inside the rear-looking ground-view camera is reflected sequentially by the third and fourth quartz mirrors before entering the reference prism. The reference prism causes the first and second laser beams to illuminate the fifth quartz mirror. The fifth quartz mirror reflects the first and second laser beams to the Dammann grating for beam splitting. The split beams obtained after beam splitting by the Dammann grating are reflected by the sixth quartz mirror to the detector focal plane of the star sensor.

2. A method for real-time monitoring of attitude changes of a forward and backward looking mapping camera, implemented using the real-time monitoring system for attitude changes of a forward and backward looking mapping camera as described in claim 1, characterized in that: Specifically, the steps include the following: S1: During the ground calibration phase, the star sensor pointing vector in the satellite body coordinate system is obtained based on the real-time monitoring system for the attitude changes of the forward and backward looking mapping cameras. Representation of the star sensor pointing vector in the star sensor focal plane coordinate system The representation of the vector perpendicular to the star sensor pointing vector in the satellite body coordinate system. The representation of a vector perpendicular to the star sensor pointing vector in the star sensor focal plane coordinate system. Representation of the reference prism normal vector in the satellite body coordinate system Representation of the reference prism normal vector in the reference prism coordinate system Representation of the vector perpendicular to the reference prism normal vector in the satellite body coordinate system The representation of a vector perpendicular to the normal vector of the reference prism in the reference prism coordinate system. And calculate the rotation matrix from the reference prism coordinate system to the star sensor focal plane coordinate system. ; S2: By tilting the satellite platform to the side, the time when the star sensor calibrates its image against the sky is used as the reference time. The star sensor is then used to continuously photograph the night sky that meets the imaging conditions to obtain an actual star map. The transformation matrix from the satellite's coordinate system to the J2000 coordinate system is then obtained from the actual star map. ; S3: The first laser beam is split by a Damman grating to obtain the first single-beam vector set. The second laser beam is split by a Dammann grating to obtain a second single-beam vector set. ; S4: Based on the first and second single-beam vector sets, obtain the transformation matrix from the forward-looking ground camera coordinate system to the star sensor focal plane coordinate system. And the transformation matrix from the rear-view camera coordinate system to the star sensor focal plane coordinate system. ; S5: The link change relationship of the real-time monitoring system at the reference time is constructed by the following formula: ； ； ； ； in, As the first intermediate parameter, This is the second intermediate parameter; S6: Based on the link change relationship established in step S5, calculate the transformation matrix from the forward-looking ground camera to the backward-looking ground camera in the J2000 coordinate system. : ； S7: At the measurement moment, the first laser beam is split by the Dammann grating to obtain the third single-beam vector set. The second laser beam is split by a Dammann grating to obtain the fourth single-beam vector set. ; S8: Based on the third and fourth single-beam vector sets, the QUEST algorithm is used to calculate the transformation matrix from the forward-looking ground camera coordinate system to the star sensor focal plane coordinate system in the satellite body coordinate system. And the transformation matrix from the rear-view camera coordinate system to the star sensor focal plane coordinate system. ; S9: Based on the calibration results of S8, calculate the transformation matrix from the forward-looking ground camera to the backward-looking ground camera in the J2000 coordinate system. : ； S10: Based on the transformation matrix from the forward-looking camera to the backward-looking camera at the reference time. The transformation matrix from the forward-looking ground camera to the backward-looking ground camera at the measurement time. Obtain the attitude changes of the forward and backward looking ground cameras. : 。 3. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 2, characterized in that: Step S1 specifically includes: S11: Representation of the star sensor pointing vector in the satellite body coordinate system Representation of the star sensor pointing vector in the star sensor focal plane coordinate system Construct an orthogonal coordinate base within the satellite's body coordinate system. : ； ； ； Where ||·|| is the vector modulo operation; S12: Representation of the vector perpendicular to the star sensor pointing vector in the satellite body coordinate system The representation of the vector perpendicular to the star sensor pointing vector in the star sensor focal plane coordinate system Construct an orthogonal coordinate base within the focal plane coordinate system of the star sensor. : ； ； ； S13: Calculate the transformation matrix from the satellite body coordinate system to the star sensor focal plane coordinate system using the following formula. : ； S14: Representation of the reference prism normal vector in the satellite body coordinate system Representation of the reference prism normal vector in the reference prism coordinate system Construct an orthogonal coordinate base within the satellite's body coordinate system. : ； ； ； S15: Representation of a vector perpendicular to the reference prism normal vector in the satellite body coordinate system The representation of a vector perpendicular to the normal vector of the reference prism in the reference prism coordinate system Construct an orthogonal coordinate base within the reference prism coordinate system. : ； ； ； S16: Calculate the transformation matrix from the satellite body coordinate system to the reference prism coordinate system using the following formula. : ； S17: Calculate the rotation matrix from the reference prism coordinate system to the star sensor focal plane coordinate system using the following formula. : 。 4. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 2, characterized in that: In step S2, satisfying the imaging conditions means that the target sky area pointed at by the star sensor includes at least N stars with magnitude ≤ M, and the target sky area is not obscured by the Sun, the Earth, or the Earth's atmospheric glow during the observation period of the star sensor.

5. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 3, characterized in that: Step S2 specifically includes: S21: Select at least three non-collinear stars from the actual star chart of the star sensor, extract the barycenter of each selected star, obtain the angle between each star and the optical axis, and obtain a one-dimensional vector group based on the angle calculation results. , where n is the total number of stars selected: ； in, Let be the angle between the i-th star and the optical axis. Let be the coordinates of the barycenter of the i-th star. The focal length of the star sensor; S22: Based on the built-in star catalog of the star sensor, utilizing a one-dimensional vector group Obtain the real-time pointing vector set of each star in the focal plane coordinate system of the star sensor. Furthermore, the star map matching algorithm is used to analyze the real-time pointing vector group. The data is processed to obtain the real-time pointing vector set of each star in the J2000 coordinate system. ; S23: Set up the real-time pointing vectors of each star in the focal plane coordinate system of the star sensor. Real-time pointing vectors of each star in the J2000 coordinate system The input is fed into the QUEST algorithm, and the transformation matrix from the star sensor focal plane coordinate system to the J2000 coordinate system is obtained based on the quaternion returned by the QUEST algorithm. ; S24: Transformation matrix from the satellite body coordinate system to the star sensor focal plane coordinate system obtained based on S13. The transformation matrix from the satellite body coordinate system to the J2000 coordinate system is calculated using the following formula. : 。 6. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 2, characterized in that: In step S4, the representations of the first single-beam vector set in the forward-looking camera coordinate system and the representations of the first single-beam vector set in the star sensor focal plane coordinate system are input into the QUEST algorithm, and the transformation matrix from the forward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternions returned by the QUEST algorithm. ; The representations of the second single-beam vector set in the rear-view camera coordinate system and the representations of the second single-beam vector set in the star sensor focal plane coordinate system are input into the QUEST algorithm, and the transformation matrix from the rear-view camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternions returned by the QUEST algorithm. .

7. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 2, characterized in that: In step S8, the representations of the third single-beam vector set in the forward-looking camera coordinate system and the representations of the third single-beam vector set in the star sensor focal plane coordinate system are input into the QUEST algorithm, and the transformation matrix from the forward-looking camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternions returned by the QUEST algorithm. ; The representations of the fourth single-beam vector set in the rear-view camera coordinate system and the representation of the fourth single-beam vector set in the star sensor focal plane coordinate system are input into the QUEST algorithm, and the transformation matrix from the rear-view camera coordinate system to the star sensor focal plane coordinate system is obtained based on the quaternions returned by the QUEST algorithm. .

8. The real-time monitoring method for attitude changes of forward and backward surveying cameras according to claim 2, characterized in that: The star sensor focal plane coordinate system is a three-dimensional coordinate system established with the projection center of the star sensor as the origin. The Z-axis of the star sensor focal plane coordinate system coincides with the optical axis of the star sensor. The X-axis of the star sensor focal plane coordinate system is parallel to the horizontal pixel arrangement direction of the star sensor focal plane. The Y-axis of the star sensor focal plane coordinate system is parallel to the vertical pixel arrangement direction of the star sensor focal plane. The forward-looking camera coordinate system is a three-dimensional coordinate system established with the projection center of the forward-looking camera as the origin. The Z-axis of the forward-looking camera coordinate system coincides with the optical axis of the forward-looking camera. The X-axis of the forward-looking camera coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the forward-looking camera. The Y-axis of the forward-looking camera coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the forward-looking camera. The rear-view camera coordinate system is a three-dimensional coordinate system established with the projection center of the rear-view camera as the origin. The Z-axis of the rear-view camera coordinate system coincides with the optical axis of the rear-view camera. The X-axis of the rear-view camera coordinate system is parallel to the horizontal pixel arrangement direction of the focal plane of the rear-view camera. The Y-axis of the rear-view camera coordinate system is parallel to the vertical pixel arrangement direction of the focal plane of the rear-view camera.

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