On-orbit agile satellite in-motion imaging attitude planning method and system

Abstract

This invention provides a method and system for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, comprising: determining an image plane reference point based on a recursive period, imaging line frequency, and camera line-of-sight; and based on... t n Calculate the satellite's position coordinates and the line-of-sight vector of the image plane reference point using the six orbital roots and three-axis attitude calculations; calculate... t n The coordinates of the object point corresponding to the image plane reference point at any given time; calculation t n The tangent vector along the orbit or perpendicular to the orbit to the object point corresponding to the image plane reference point at any given time; calculate t n+1 The satellite orbit six-root number, satellite position coordinates, and line-of-sight vector of the camera's line-of-sight point are calculated at the given time. t n+1 At any given time, the satellite maintains its imaging matrix along its orbit or vertically along its orbit; calculation t n+1 The three-axis attitude of the orbital system required for the satellite to maintain motion imaging along its orbit or vertically during the entire imaging period is determined. The above steps are repeated to obtain the three-axis attitude of the orbital system required for the satellite to maintain motion imaging along its orbit or vertically during the entire imaging period.

Description

Technical Field

[0001] This invention relates to the field of aerospace optical remote sensing imaging technology, specifically to a method and system for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit. Background Technology

[0002] In the field of aerospace optical remote sensing imaging, image signal-to-noise ratio and sharpness are the core indicators of optical remote sensing satellites, which determine the user's evaluation level of the entire satellite.

[0003] Optical remote sensing satellites mostly employ a linear array pushbroom system, accumulating ground object signals over a longer period through time delay integration (TDI) of the detector during the pushbroom process to achieve remote sensing imaging of the Earth. However, with the rapid development of optical remote sensing satellites, imaging conditions have been continuously shifting from daytime to dawn / dusk, and the imaging spectral bands have been continuously expanding from multispectral to hyperspectral. Simply relying on multi-stage integration of the detector using TDI is no longer sufficient to meet the signal-to-noise ratio requirements of the exposure time. Satellite attitude retracement compensation is necessary to further extend the exposure time in order to ensure that the remote sensing image has a sufficient signal-to-noise ratio.

[0004] Unlike conventional pushbroom imaging, retrace compensation imaging adds one-dimensional motion, primarily attitude retracement around the pitch axis. This reduces the relative velocity between the camera's line of sight and ground features, extending the exposure time. To obtain high-resolution images, retrace compensation imaging must address two key issues: camera line frequency matching and satellite attitude matching. Camera line frequency matching ensures that the camera's imaging line frequency matches the relative velocity between the satellite and the ground, thereby reducing image shift along the orbital direction. Satellite attitude matching involves minimizing residual image shift after camera line frequency matching through appropriate attitude planning. When the satellite attitude is inappropriate or the camera line frequency is mismatched, retrace compensation imaging will increase image shift during the exposure time, leading to a decrease in the sharpness of the remote sensing image.

[0005] Satellite backflash compensation imaging is a type of on-the-moment imaging. To achieve attitude planning for on-the-moment imaging, related technologies have been proposed:

[0006] Patent application CN116228846A discloses a method for adjusting the attitude of a moving imaging system applicable to TDICCD optical satellites. This method presets the attitude and calculates the moving speed and line frequency of the imaging target point relative to the image plane to determine whether the TDICCD camera meets the imaging conditions. If not, it iterates and replans. This method achieves moving imaging attitude planning and drift angle correction, but the iterative method is not suitable for scenarios with high real-time requirements.

[0007] Patent application CN116242317A discloses an agile optical satellite linear array imaging method in motion. This method, by setting an evaluation function, performs orbit calculation and attitude planning using multiple combinations of imaging parameters for a given imaging task, and selects the one with the highest evaluation parameter value to execute the imaging task. This method solves the problems of improper attitude control planning methods and improper selection and setting of imaging parameters for optical satellites, but it is a trial-and-error method.

[0008] Patent application CN118683757A discloses a high-frequency integration time adjustment method suitable for in-motion imaging. This method calculates the maximum image shift error caused by the integration time adjustment and the minimum MTF value during imaging by setting a preset integration time adjustment frequency. If the MTF threshold is not met, the preset frequency is modified and recalculated. This method achieves high-frequency integration time adjustment, ensuring imaging quality throughout the push-broom imaging process, but it does not involve attitude planning.

[0009] Patent document CN113868594B discloses a method and system for calculating the drift angle during in-motion imaging using a two-way pushbroom method. This method uses the current target attitude of the imaging satellite as a reference to calculate the drift angle during forward and reverse pushbroom imaging along the satellite's flight trajectory, and updates the target attitude matrix with the increment of the drift angle, thus achieving multi-strip stitching within a single imaging interval. While this method implements the calculation of the drift angle during forward and reverse pushbroom imaging, it does not involve attitude planning for in-motion imaging.

[0010] Patent application CN118494789A discloses a dynamic pushbroom imaging attitude maneuver method for space targets. This method performs initial screening of imaging time based on imaging conditions, and then uses a constant attitude angular velocity to perform pushbroom imaging along a given direction, realizing active attitude pushbroom imaging of rapidly moving cooperative targets in space. This method expands the application scope of dynamic pushbroom imaging, belongs to space target imaging, and does not belong to Earth observation. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the purpose of this invention is to provide an agile satellite attitude planning method and system for maintaining imaging in motion along or vertically.

[0012] The agile satellite attitude planning method for maintaining imaging in motion along or vertically to orbit, provided by the present invention, includes: Step S1: Determine the image plane reference point A based on the recursive period, imaging line frequency, and camera line of sight point O; Step S2: According to t n Satellite position coordinates in the reference ellipsoidal coordinate system for calculating the six orbital roots and three-axis attitude of the satellite at any given time. The line-of-sight vector of the image plane reference point A ; Step S3: Calculationt n At time, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoid coordinate system ; Step S4: Calculation t n At time, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system Or, the object point A corresponding to the image plane reference point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system ; Step S5: Calculation t n+1 At any given time, the satellite's orbital root numbers and its position coordinates in the reference ellipsoidal coordinate system. and the view axis vector of the camera's view axis point O ; Step S6: Calculation t n+1 At any given moment, the satellite maintains its imaging matrix along its orbit. Or satellite vertical orbit maintains imaging matrix ; Step S7: Calculation t n+1 At any given time, the satellite maintains the three-axis attitude of the orbital system required for imaging along its orbit or the satellite maintains the three-axis attitude of the orbital system required for imaging perpendicular to its orbital path. Step S8: Repeat steps S2 to S7 to obtain the three-axis attitude of the orbital system required for the satellite to maintain dynamic imaging along or perpendicular to the orbit throughout the entire imaging time period.

[0013] Preferably, in step S1, the coordinates of the image plane reference point A in the camera coordinate system are... The expression is:

[0014]

[0015] In the formula, Let O be the coordinates of the camera's line-of-sight point in the camera coordinate system. t d For the recursion period, f p For imaging line frequency, d pixel For pixel angular resolution, β off The camera's off-axis angle.

[0016] Preferably, in step S2, t n Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0017]

[0018]

[0019] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. r n for t n The distance between the Earth's center and the orbital center at any given moment; oh e This is the angular rate of Earth's rotation; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n for t n The true closest angle at any given moment; , , Rotate clockwise around the +X axis, +Y axis, and +Z axis respectively. α The transformation matrix, where the superscript T denotes the transpose; In step S2, t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system The expression is:

[0020]

[0021] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for tn The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. Let A be the coordinates of the image plane reference point A in the camera coordinate system; f n , i n , ψ n They are respectively t n The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3.

[0022] Preferably, in step S3, t n At any given moment, the image plane reference point A corresponds to the object point A. n The coordinate expression in the reference ellipsoid coordinate system is:

[0023]

[0024]

[0025] In the formula, l The coefficient is dimensionless. for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. , , These are the components of the line-of-sight vector on the three coordinate axes; for t n Satellite position coordinates in the time reference ellipsoidal coordinate system , , The components of the satellite's position on the three coordinate axes; r a , r b These are the major and minor semi-axises of the reference ellipsoid, respectively; a , b , c These are the coefficients of the quadratic equation.

[0026] Preferably, in step S4, t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system The expression is:

[0027] In the formula, for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Camera in time reference ellipsoidal coordinate system + x Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Normal vector in the reference ellipsoid coordinate system ;

[0028]

[0029] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. In camera coordinate system + x Axial unit vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system , , These are the components of the coordinates on the three coordinate axes in the reference ellipsoidal coordinate system; r a , r b These are the major and minor semi-axises of the reference ellipsoid, respectively; t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system The expression is:

[0030] In the formula, for t nCamera in time reference ellipsoidal coordinate system + y Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Normal vector in the reference ellipsoid coordinate system ;

[0031] In the formula, In camera coordinate system + y Axial unit vector.

[0032] Preferably, in step S5, t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0033]

[0034]

[0035]

[0036]

[0037] In the formula, for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. r n+1 for t n+1 The distance between the Earth's center and the orbital center at any given moment; oh e This is the angular rate of Earth's rotation; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n+1 for t n+1 The true closest angle at any given moment; t d For the recursion period, oh s It is the orbital angular velocity; In step S5, t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system The expression is:

[0038] In the formula, for t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system.

[0039] Preferably, in step S6, t n+1 The satellite maintains its imaging matrix along its orbit at all times. The expression is:

[0040]

[0041] In the formula, for t n+1 The unit tangent vector along / perpendicular to the rail at time [time]. for t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system.

[0042] Preferably, in step S6, t n+1 Constant-time satellite vertical orbit maintains imaging matrix The expression is:

[0043]

[0044] In the formula, for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system.

[0045] Preferably, in step S7, t n+1 The orbital system's three-axis attitude must satisfy the following conditions to maintain imaging along or perpendicular to the orbit:

[0046] In the formula, ( f n+1 , i n+1 , ψ n+1 ) are respectively t n+1 The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3. When using track-holding imaging, we have:

[0047] When using vertical track-held imaging, we have:

[0048] In the formula, for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The satellite maintains its imaging matrix along its orbit at all times. for t n+1 The satellite maintains its imaging matrix in its vertical orbit at all times. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. β off The camera's off-axis angle.

[0049] Preferably, in steps S2 to S7, the semi-major axis of the reference ellipsoid... r a and short half shaft r b The expression is:

[0050]

[0051] In the formula, R a , R b These are the major and minor semi-axises of the WGS84 ellipsoid, respectively. l hThis is the proportionality coefficient. h This represents the elevation of ground features in the WGS84 coordinate system.

[0052] Preferably, in steps S2 to S7, when on-board computing resources are limited, the tangent vector along or perpendicular to the orbit of the object point corresponding to the image plane reference point A in the reference ellipsoidal coordinate system remains approximately constant, that is:

[0053]

[0054] In the formula, for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 The perpendicular tangent vector in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system.

[0055] The agile satellite attitude planning system for maintaining dynamic imaging along or perpendicular to the orbit provided by the present invention employs the aforementioned agile satellite attitude planning method for maintaining dynamic imaging along or perpendicular to the orbit.

[0056] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention proposes a method for planning the attitude of agile satellites to maintain imaging in motion along or perpendicular to the orbit, which realizes image shift compensation during the imaging process of agile satellites in motion and ensures imaging quality: The on-the-track attitude planning method for maintaining imaging attitude during the imaging process: By keeping the image motion vector of the camera's line of sight parallel to the detector's integration direction during imaging, the satellite achieves real-time correction of the drift angle during the imaging process, reduces the image motion introduced by the drift angle correction residual, and ensures imaging quality. Vertical orbit maintaining on-the-moment imaging attitude planning method: By keeping the projections of each level of the TDI detector parallel during the multi-level integration of the satellite during imaging, line frequency matching of each pixel is achieved, avoiding image shift caused by line frequency matching residuals of different pixels of each detector, ensuring imaging quality and improving the consistency of image quality across the entire field of view.

[0057] (2) The agile satellite attitude planning method for maintaining imaging in motion along or perpendicular to the orbit proposed in this invention achieves constant line frequency across the entire field of view, significantly reduces the difficulty of camera line frequency matching, and avoids the image shift blur problem between different TDI levels caused by line frequency changes during long exposures: The method for maintaining the attitude planning of imaging in motion along the track: By using a fixed reference point on the meridional image plane for attitude planning during imaging, the line frequency of the central field of view detector is kept constant, and the line frequency of each detector in the entire field of view is kept constant (but different for each detector). Vertical track-maintaining dynamic imaging attitude planning method: By fixing the reference point of the meridional image plane during imaging, and tolerating small drift angle residuals, the line frequency of each detector in the entire field of view is kept constant and the same.

[0058] (3) The present invention proposes an agile satellite attitude planning method for maintaining imaging in motion along the orbit, which realizes the correction of the drift angle and is particularly suitable for situations where the number of pixels of a single detector of a camera is small and the line frequency of each detector can be adjusted individually.

[0059] (4) The present invention proposes an agile satellite vertical orbit maintaining dynamic imaging attitude planning method, which realizes the matching of line frequencies of each pixel, and is particularly suitable for situations where the number of pixels of a single camera detector is large or the overall line frequency of the detector is adjusted. Attached Figure Description

[0060] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Workflow diagram for planning a method to maintain the attitude of agile satellites in motion for imaging along orbit; Figure 2 Schematic diagram of the working principle of the planning method for maintaining the attitude of agile satellites in motion for imaging along the orbit; Figure 3 Example diagram of the planning results for maintaining the attitude of retrace compensation imaging along the orbit of agile satellites; Figure 4 Example image showing the coverage area of ​​the retrace compensation imaging along the orbit of the agile satellite; Figure 5 Example diagram of the line frequency of each detector segment for maintaining retrace compensation imaging along the orbit of an agile satellite; Figure 6 Example diagram of planning results for maintaining accelerated push-broom imaging attitude along orbit for agile satellites; Figure 7 Example image showing how agile satellites maintain accelerated pushbroom imaging coverage along their orbit; Figure 8 Example diagram showing how to maintain the line frequency of each detector segment for accelerated pushbroom imaging along the orbit of an agile satellite; Figure 9Workflow diagram for planning a method to maintain the dynamic imaging attitude of agile satellites in vertical orbit; Figure 10 Schematic diagram of the working principle of the planning method for maintaining the attitude of agile satellites in motion for imaging on vertical orbit; Figure 11 Example of planning results for maintaining the retrace compensation imaging attitude of agile satellites in vertical orbit; Figure 12 Example image showing the coverage area of ​​the retrace compensation imaging for agile satellites in vertical orbit; Figure 13 Example diagram of the line frequency of each detector for maintaining retrace compensation imaging in vertical orbit of agile satellites; Figure 14 Example figure of planning results for maintaining accelerated pushbroom imaging attitude in vertical orbit of agile satellites; Figure 15 Example image showing the area covered by accelerated pushbroom imaging for agile satellites in vertical orbit; Figure 16 Example diagram showing the line frequency of each detector segment for accelerated pushbroom imaging in the vertical orbit of an agile satellite. Detailed Implementation

[0061] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0062] (1) Linear scan camera A line scan camera is an imaging device that contains only one row of pixels (arranged in a line), relying on the movement of the target or the camera itself to complete the scanning and imaging of the entire image. It is widely used in high-precision remote sensing, industrial inspection and other fields, and is characterized by high imaging resolution and expandable imaging width.

[0063] (2) Detector The imaging sensor in a line scan camera, typically a CCD or CMOS image sensor, is responsible for acquiring light signals and converting them into digital image signals.

[0064] Each detector contains multiple linearly arranged pixels; each pixel has multiple levels of photosensitive elements to achieve time delay integration (TDI); multiple detectors are stitched together in a collinear / interlaced / mechanical manner to expand the imaging swath.

[0065] (3) Deflection angle During the imaging process of a line array camera, in order to compensate for the image motion caused by the Earth's rotation, a deflection angle correction is required so that the direction of motion of the ground image on the image plane is parallel to the TDI integration direction.

[0066] The angle between the direction of motion of the ground feature image on the image plane and the TDI integration direction is the drift angle compensation residual.

[0067] (4) Imaging in motion Remote sensing satellites continuously observe and image targets while performing their own attitude maneuvers, typically including: Backscan compensation imaging: During the imaging process, the satellite attitude is backscanned around the pitch axis, and the pitch angular velocity is negative, thereby extending the exposure time and improving the imaging signal-to-noise ratio; Accelerated push-broom imaging: During the imaging process, the satellite attitude is scanned forward around the pitch axis, and the pitch angular velocity is positive, thereby achieving rapid scanning and shortening the scanning time.

[0068] (5) Maintaining dynamic imaging along the track In this invention, track-based motion imaging is defined as: During in-motion imaging, the satellite always maintains the image displacement vector of the camera's line of sight parallel to the detector's integration direction; During the imaging process, the satellite maintains a constant line frequency for the detector in the center field of view of the camera.

[0069] In this invention, the working principle of the orbit-keeping dynamic imaging attitude planning method is as follows: Figure 2 As shown. Point O is the camera's line-of-sight point on the image plane, and point A is the image plane reference point; a virtual TDI detector is established using points O and A, with point O located in the final stage of the TDI and point A located in the first stage of the TDI. t n At time 10, the projections of points O and A on the virtual TDI detector onto the ground are O. n A n ; t n+1 At time 10, the projections of points O and A on the virtual TDI detector onto the ground are O. n+1 A n+1 ; Maintaining motion imaging along the track enables O n+1 and A n Points coincide, and O n A n With O n+1 A n+1 parallel.

[0070] In this invention, the working principle of the vertical track-maintaining dynamic imaging attitude planning method is as follows: Figure 10 As shown. Point O is the camera's line-of-sight point on the image plane, and point A is the image plane reference point; a virtual TDI detector is established using points O and A, with point O located in the final stage of the TDI and point A located in the first stage of the TDI. t n At time 10, the projections of points O and A on the virtual TDI detector onto the ground are O. n A nThe final projection of TDI is O n The perpendicular tangent to the orbital line at point A, the primary projection of TDI is A n The perpendicular tangent to the rail; t n+1 At time 10, the projections of points O and A on the virtual TDI detector onto the ground are O. n+1 A n+1 The final projection of TDI is O n+1 The perpendicular tangent to the orbital line at point A, the primary projection of TDI is A n+1 The perpendicular tangent to the orbit; the orbit remains in motion for imaging, making O n+1 and A n Points coincide, and O n+1 With A n The perpendicular tangent to the rail is parallel, that is... t n+1 The final projection of TDI at time t and t n The TDI primary projection is parallel at any given time.

[0071] Example 1 A certain agile satellite has an orbital altitude of 500km and is equipped with an optical camera payload. The nadir resolution is 0.5m, and the focal plane is formed by stitching together 5 collinear detectors with a swath width of 10km. It needs to perform on-the-moment imaging attitude planning to achieve backscan compensation imaging.

[0072] The following describes the application of this invention in planning the attitude maintenance of an agile satellite along its orbit while it is in motion for imaging. The implementation process is as follows: Figure 1 As shown, it includes: Step S1: Determine the image plane reference point A based on the recursive period, imaging line frequency, and camera line of sight point O; Step S2: According to t n The six roots of the satellite orbit at any given time ( a c , e c , i c , oh c , Oh c , f n ) and orbital system three-axis attitude ( f n , i n , ψ n Calculate the satellite position coordinates in the reference ellipsoidal coordinate system. The line-of-sight vector of the image plane reference point A ; Step S3: Calculation tn At time, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoid coordinate system ; Step S4: Calculation t n At time, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system ; Step S5: Calculation t n+1 At any given time, the satellite orbit has six root numbers ( a c , e c , i c , oh c , Oh c , f n+1 Satellite position coordinates in the reference ellipsoidal coordinate system and the view axis vector of the camera's view axis point O ; Step S6: Calculation t n+1 At any given moment, the satellite maintains its imaging matrix along its orbit. ; Step S7: Calculation t n+1 At any given moment, the satellite maintains the three-axis attitude of the orbital system required for imaging. f n+1 , i n+1 , ψ n+1 ); Step S8: Repeat steps S2 to S7 to obtain the three-axis attitude of the orbital system required for the satellite to maintain dynamic imaging along its orbit throughout the entire imaging period.

[0073] In step S1, the coordinates of the image plane reference point A in the camera coordinate system are... The expression is:

[0074] in,

[0075] In the formula, Let O be the coordinates of the camera's line-of-sight point in the camera coordinate system. t d For the recursion period, f p For imaging line frequency, d pixel For pixel angular resolution, β off The camera's off-axis angle.

[0076] In step S2, t n Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0077] in,

[0078]

[0079] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. r n for t n The distance between the Earth's center and the orbital center at any given moment; oh e This is the Earth's rotational angular rate. oh e =7.2921151467e-5 rad / s; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n for t n The true closest angle at any given moment; , , Rotate clockwise around the +X axis, +Y axis, and +Z axis respectively. α The transformation matrix, where the superscript T represents the transpose.

[0080] In step S2, t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system The expression is:

[0081] in,

[0082] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. Let A be the coordinates of the image plane reference point A in the camera coordinate system; f n , i n , ψ n ) are respectively t n The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3.

[0083] In step S3, t n At any given moment, the image plane reference point A corresponds to the object point A. n The coordinates in the reference ellipsoid coordinate system are:

[0084] in,

[0085]

[0086] In the formula, l The coefficient is dimensionless. for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Satellite position coordinates in the time reference ellipsoidal coordinate system r a , r b These are the major and minor axes of the reference ellipsoid, respectively.

[0087] In step S4, t nAt any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system The expression is:

[0088] In the formula, for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Camera in time reference ellipsoidal coordinate system + x Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n The expression for the normal vector in the reference ellipsoid coordinate system is:

[0089]

[0090] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. In camera coordinate system + x Axial unit vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system; r a , r b These are the major and minor axes of the reference ellipsoid, respectively.

[0091] In step S5, t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0092] in,

[0093]

[0094]

[0095]

[0096] In the formula, for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. r n+1 for t n+1 The distance between the Earth's center and the orbital center at any given moment; oh e This is the angular rate of Earth's rotation; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n+1 for t n+1 The true closest angle at any given moment; t d For the recursion period, oh s ω represents the orbital angular velocity.

[0097] In step S5, t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system The expression is:

[0098] In the formula, for t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system.

[0099] In step S6, t n+1The satellite maintains its imaging matrix along its orbit at all times. The expression is:

[0100] in,

[0101] In the formula, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system.

[0102] In step S7, t n+1 The satellite maintains the required three-axis attitude of its orbital system for imaging at all times. f n+1 , i n+1 , ψ n+1 )satisfy:

[0103] In the formula, ( f n+1 , i n+1 , ψ n+1 ) are respectively t n+1 The satellite's orbital system maintains its roll, pitch, and yaw attitude along three axes, with the sequence 1-2-3. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t;

[0104] In the formula, for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The satellite maintains its imaging matrix along its orbit at all times. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. β off The camera's off-axis angle.

[0105] In steps S2-S7, the semi-major axis of the reference ellipsoid r a and short half shaft r b The expression is:

[0106] in,

[0107] In the formula, R a , R b These are the major and minor semi-axises of the WGS84 ellipsoid, respectively. l h This is the proportionality coefficient. h This represents the elevation of ground features in the WGS84 coordinate system.

[0108] In steps S2-S7, when on-board computing resources are limited, the orbital tangent vector of the object point corresponding to the image plane reference point A in the reference ellipsoidal coordinate system can be approximately kept constant, that is:

[0109] In the formula, for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n The tangent vector along the orbit in the reference ellipsoidal coordinate system.

[0110] The agile satellite pixel angular resolution d pixel =0.5m / 500km=1μrad, camera off-axis angle β off =0.5°, retrace compensation imaging line frequency is 2.56kHz, recursion period t d =0.05s, from which we obtain the coordinates of the image plane reference point A in the camera coordinate system. The elevation of features in the satellite imaging area is 0m, therefore the semi-major axis of the reference ellipsoid is... r a =R a = 6378.137km, short half-shaft r b =R b= 6356.752km.

[0111] The total imaging duration for satellite in motion is 10 seconds, with the imaging period recorded as -5 seconds to +5 seconds; at the start of in motion imaging, the satellite's orbital six roots ( a c , e c , i c , oh c , Oh c , f The orbital system has a three-axis attitude of (6871.004km, 0, 97.3°, 180°, 0°, -0.3176°). f , i , ψ The values ​​are (29.8036°, 2.8079°, 0.1592°).

[0112] Through recursion, the attitude planning result for maintaining backscan compensation imaging along the orbit of this agile satellite is obtained as follows: Figure 3 As shown. Due to satellite retrace compensation imaging, the satellite retraces around the pitch axis during imaging, the pitch angle gradually decreases, and the pitch angular velocity is negative.

[0113] The agile satellite maintains its scan-compensation imaging coverage area along its orbit, such as... Figure 4 As shown, the coverage area maintained by the backscan along the track is approximately trapezoidal, with the longer side being the side closer to the nadir point. Within 10 seconds, a coverage area of ​​13.7km (vertical track) × 14.8km (along the track) was completed.

[0114] The agile satellite maintains along-orbit retrace compensation imaging, with each detector's flight frequency as follows: Figure 5 As shown, the line frequency of each detector in the camera remains constant during the on-the-go imaging process along the track, but there are differences between detectors; the line frequency of the center field of view is 2.56 kHz, consistent with the setting.

[0115] Example 2 A certain agile satellite has an orbital altitude of 500km and is equipped with an optical camera payload. The nadir resolution is 0.5m, and the focal plane is formed by stitching together 5 collinear detectors with a swath width of 10km. It needs to perform on-the-moment imaging attitude planning to achieve accelerated push-broom imaging.

[0116] The following describes the application of this invention in planning the attitude maintenance of an agile satellite along its orbit while it is in motion for imaging. The implementation process is as follows: Figure 1 As shown, except for some parameter differences, the implementation steps are completely consistent with those in Example 1.

[0117] The agile satellite pixel angular resolution d pixel=0.5m / 500km=1μrad, camera off-axis angle β off =0.5°, accelerated push-broom imaging line frequency is 25.6kHz, recursion period t d = 0.005s, from which we obtain the coordinates of the image plane reference point A in the camera coordinate system. The elevation of features in the satellite imaging area is 0m, therefore the semi-major axis of the reference ellipsoid is... r a =R a = 6378.137km, short half-shaft r b =R b = 6356.752km.

[0118] The total imaging duration for satellite imaging in motion is 1 second, with the imaging period recorded as -0.5s to +0.5s; at the start of imaging in motion, the satellite's orbital six roots ( a c , e c , i c , oh c , Oh c , f The coordinates are (6871.004km, 0, 97.3°, 180°, 0°, -0.0318°), and the three-axis attitude of the orbital system is ( f , i , ψ The range is (29.9808°, -0.3795°, 0.0160°).

[0119] Through recursion, the attitude planning results for maintaining accelerated push-broom imaging along the orbit of this agile satellite are obtained as follows: Figure 6 As shown. Due to the satellite's accelerated push-broom imaging, the satellite scans forward around the pitch axis during imaging, with the pitch angle gradually increasing and the pitch angular velocity being positive.

[0120] The agile satellite maintains accelerated push-broom imaging coverage along its orbit, such as... Figure 7 As shown, due to accelerated sweeping, a 13.7km (vertical rail) × 14.8km (along rail) area coverage was completed within 1 second.

[0121] The agile satellite maintains accelerated push-broom imaging along its orbit, with each detector segment's travel frequency as... Figure 8 As shown, the line frequency of each detector in the camera remains constant during the on-the-go imaging process along the track, but there are differences between detectors; the line frequency of the center field of view is 25.6 kHz, consistent with the setting.

[0122] Example 3 A certain agile satellite has an orbital altitude of 500km and is equipped with an optical camera payload. The nadir resolution is 0.5m, and the focal plane is formed by stitching together 5 collinear detectors with a swath width of 10km. It needs to perform on-the-moment imaging attitude planning to achieve backscan compensation imaging.

[0123] The following describes the application of this invention in agile satellite vertical orbit maintenance imaging attitude planning, as follows: Figure 9 As shown, it includes: Step S1: Determine the image plane reference point A based on the recursive period, imaging line frequency, and camera line of sight point O; Step S2: According to t n The six roots of the satellite orbit at any given time ( a c , e c , i c , oh c , Oh c , f n ) and orbital system three-axis attitude ( f n , i n , ψ n Calculate the satellite position coordinates in the reference ellipsoidal coordinate system. The line-of-sight vector of the image plane reference point A ; Step S3: Calculation t n At time, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoid coordinate system ; Step S4: Calculation t n At time, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system ; Step S5: Calculation t n+1 At any given time, the satellite orbit has six root numbers ( a c , e c , i c , oh c , Oh c ,f n+1 Satellite position coordinates in the reference ellipsoidal coordinate system and the view axis vector of the camera's view axis point O ; Step S6: Calculation t n+1 At any given time, the satellite maintains its imaging matrix in its vertical orbit. ; Step S7: Calculation t n+1 At any given moment, the satellite's vertical orbit maintains the three-axis attitude of the orbital system required for imaging. f n+1 , i n+1 , ψ n+1 ); Step S8: Repeat steps S2 to S7 to obtain the required three-axis attitude of the satellite's orbital system during the entire imaging time period.

[0124] In step S1, the coordinates of the image plane reference point A in the camera coordinate system are... The expression is:

[0125] in,

[0126] In the formula, Let O be the coordinates of the camera's line-of-sight point in the camera coordinate system. t d For the recursion period, f p For imaging line frequency, d pixel For pixel angular resolution, β off The camera's off-axis angle.

[0127] In step S2, t n Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0128] in,

[0129]

[0130] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. r n for t n The distance between the Earth's center and the orbital center at any given moment; oh e This is the Earth's rotational angular rate. oh e =7.2921151467e-5 rad / s; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n for t n The true closest angle at any given moment; , , Rotate clockwise around the +X axis, +Y axis, and +Z axis respectively. α The transformation matrix, where the superscript T represents the transpose.

[0131] In step S2, t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system The expression is:

[0132] in,

[0133] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. Let A be the coordinates of the image plane reference point A in the camera coordinate system; f n , i n , ψ n ) are respectively t n The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3.

[0134] In step S3, t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system:

[0135] in,

[0136]

[0137] In the formula, l The coefficient is dimensionless. for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Satellite position coordinates in the time reference ellipsoidal coordinate system r a , r b These are the major and minor axes of the reference ellipsoid, respectively.

[0138] In step S4, t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system The expression is:

[0139] In the formula, for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Camera in time reference ellipsoidal coordinate system + y Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Normal vector in the reference ellipsoid coordinate system ;

[0140]

[0141] In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. In camera coordinate system + y Axial unit vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system; r a , r b These are the major and minor axes of the reference ellipsoid, respectively.

[0142] In step S5, t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is:

[0143] in,

[0144]

[0145]

[0146]

[0147] In the formula, for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. r n+1 for t n+1 The distance between the Earth's center and the orbital center at any given moment; oh e This is the angular rate of Earth's rotation;a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, oh c The perigee argument, Oh c Right ascension of the ascending node, f n+1 for t n+1 The true closest angle at any given moment; t d For the recursion period, oh s ω represents the orbital angular velocity.

[0148] In step S5, t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system The expression is:

[0149] In the formula, for t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system.

[0150] In step S6, t n+1 Constant-time satellite vertical orbit maintains imaging matrix The expression is:

[0151] in,

[0152] In the formula, for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system for t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system.

[0153] In step S7, t n+1The satellite maintains the required three-axis attitude of its orbital system for imaging at all times. f n+1 , i n+1 , ψ n+1 )satisfy:

[0154] In the formula, ( f n+1 , i n+1 , ψ n+1 ) are respectively t n+1 The satellite's orbital system maintains its roll, pitch, and yaw attitude along three axes, with the sequence 1-2-3. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t;

[0155] In the formula, for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The satellite maintains its imaging matrix in its vertical orbit at all times. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. β off The camera's off-axis angle.

[0156] In steps S2-S7, the semi-major axis of the reference ellipsoid r a and short half shaft r b The expression is:

[0157] in,

[0158] In the formula, R a , R b These are the major and minor semi-axises of the WGS84 ellipsoid, respectively. l h This is the proportionality coefficient. h This represents the elevation of ground features in the WGS84 coordinate system.

[0159] In steps S2 to S7, when on-board computing resources are limited and a certain line frequency difference can be tolerated, the perpendicular tangent vector of the object point corresponding to the image plane reference point A in the reference ellipsoidal coordinate system can be approximately constant, that is:

[0160] In the formula, for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 The perpendicular tangent vector in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system.

[0161] The agile satellite pixel angular resolution d pixel =0.5m / 500km=1μrad, camera off-axis angle β off =0.5°, retrace compensation imaging line frequency is 2.56kHz, recursion period t d = 0.05s, from which we obtain the coordinates of the image plane reference point A in the camera coordinate system. The elevation of features in the satellite imaging area is 0m, therefore the semi-major axis of the reference ellipsoid is... r a = R a = 6378.137km, short half-shaft r b =R b = 6356.752km.

[0162] The total imaging duration for satellite in motion is 10 seconds, with the imaging period recorded as -5 seconds to +5 seconds; at the start of in motion imaging, the satellite's orbital six roots ( a c , e c , i c , oh c , Oh c , f The orbital system has a three-axis attitude of (6871.004km, 0, 97.3°, 180°, 0°, -0.3176°). f , i , ψ The range is (29.7865°, 2.8082°, -1.7932°).

[0163] Through recursion, the attitude planning result for the vertical orbit-maintaining retrace compensation imaging of this agile satellite is obtained as follows: Figure 11 As shown. Due to satellite retrace compensation imaging, the satellite retraces around the pitch axis during imaging, the pitch angle gradually decreases, and the pitch angular velocity is negative.

[0164] The agile satellite maintains a vertical orbit and retains a scan compensation imaging coverage area, such as... Figure 12 As shown, the vertical rail maintains a backscan compensation coverage area that is approximately arc-shaped, with the arc opening facing the nadir point. Within 10 seconds, it completed area coverage of 13.7km (vertical rail) × 14.8km (along the rail).

[0165] The agile satellite maintains vertical orbit and performs retrace compensation imaging, with each detector's line frequency as follows: Figure 13 As shown, the center field of view line frequency is 2.56kHz during the motion imaging period of the vertical track, which is consistent with the setting; the difference and change in line frequency of each detector of the camera is less than 0.2Hz, which can be ignored. That is, the line frequency is constant and the line frequency is the same throughout the entire field of view. The image shift caused by the line frequency matching deviation at the edge of each detector is less than 0.01 pixels, which has no effect on MTF.

[0166] When onboard computing resources are limited and a certain degree of line frequency difference can be tolerated, the vertical orbit tangent vector remains approximately constant. In this case, the line frequency of the central field of view during the vertical orbit's motion imaging is 2.56 kHz, consistent with the setting. The line frequencies of each detector are as follows: 2.547 kHz for the first detector (left edge field of view), 2.553 kHz for the second detector, 2.560 kHz for the third detector (central field of view), 2.567 kHz for the fourth detector, and 2.573 kHz for the fifth detector (right edge field of view). During 128-level integration, the image shift caused by the line frequency matching deviation at the edges of each detector is 0.33 pixels, resulting in an MTF impact factor of 0.956, which is acceptable.

[0167] Example 4 A certain agile satellite has an orbital altitude of 500km and is equipped with an optical camera payload. The nadir resolution is 0.5m, and the focal plane is formed by stitching together 5 collinear detectors with a swath width of 10km. It needs to perform on-the-moment imaging attitude planning to achieve accelerated push-broom imaging.

[0168] The following describes the application of this invention in agile satellite vertical orbit maintenance imaging attitude planning, as follows: Figure 9 As shown, except for some parameter differences, the implementation steps are completely consistent with those in Example 3.

[0169] The agile satellite pixel angular resolution d pixel =0.5m / 500km=1μrad, camera off-axis angleβ off =0.5°, accelerated push-broom imaging line frequency is 25.6kHz, recursion period t d = 0.005s, from which we obtain the coordinates of the image plane reference point A in the camera coordinate system. The elevation of features in the satellite imaging area is 0m, therefore the semi-major axis of the reference ellipsoid is... r a = R a = 6378.137km, short half-shaft r b =R b = 6356.752km.

[0170] The total imaging duration for satellite imaging in motion is 1 second, with the imaging period recorded as -0.5s to +0.5s; at the start of imaging in motion, the satellite's orbital six roots ( a c , e c , i c , oh c , Oh c , f The coordinates are (6871.004km, 0, 97.3°, 180°, 0°, -0.0318°), and the three-axis attitude of the orbital system is ( f , i , ψ The range is (29.9828°, -0.3795°, 0.2409°).

[0171] Through recursion, the attitude planning results for the agile satellite's vertical orbit maintenance accelerated push-broom imaging are obtained as follows: Figure 14 As shown. Due to the satellite's accelerated push-broom imaging, the satellite scans forward around the pitch axis during imaging, with the pitch angle gradually increasing and the pitch angular velocity being positive.

[0172] The agile satellite maintains accelerated push-broom imaging coverage in its vertical orbit, such as... Figure 15 As shown, due to accelerated sweeping, a 13.7km (vertical rail) × 14.8km (along rail) area coverage was completed within 1 second.

[0173] The agile satellite maintains accelerated pushbroom imaging at its vertical orbit, with each detector segment's flight frequency as... Figure 16As shown, during the motion imaging period, the central field of view line frequency is 25.6kHz, consistent with the setting; the difference and variation in line frequency among the camera's detectors is less than 0.2Hz, which is negligible, meaning the line frequency is constant and parallel across the entire field of view. The image shift caused by line frequency matching deviation at the edges of each detector is less than 0.01 pixels, which has no impact on MTF.

[0174] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0175] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, characterized in that, include: Step S1: Determine the image plane reference point A based on the recursive period, imaging line frequency, and camera line of sight point O; Step S2: According to t n Satellite position coordinates in the reference ellipsoidal coordinate system for calculating the six orbital roots and three-axis attitude of the satellite at any given time. The line-of-sight vector of the image plane reference point A ; Step S3: Calculation t n At time, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoid coordinate system ; Step S4: Calculation t n At time, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system Or, the object point A corresponding to the image plane reference point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system ; Step S5: Calculation t n+1 At any given time, the satellite's orbital root numbers and its position coordinates in the reference ellipsoidal coordinate system. and the view axis vector of the camera's view axis point O ; Step S6: Calculation t n+1 At any given moment, the satellite maintains its imaging matrix along its orbit. Or satellite vertical orbit maintains imaging matrix ; Step S7: Calculation t n+1 At any given time, the satellite maintains the three-axis attitude of the orbital system required for imaging along its orbit or the satellite maintains the three-axis attitude of the orbital system required for imaging perpendicular to its orbital path. Step S8: Repeat steps S2 to S7 to obtain the three-axis attitude of the orbital system required for the satellite to maintain dynamic imaging along or perpendicular to the orbit throughout the entire imaging time period.

2. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S1, the coordinates of the image plane reference point A in the camera coordinate system are... The expression is: In the formula, Let O be the coordinates of the camera's line-of-sight point in the camera coordinate system. t d For the recursion period, f p For imaging line frequency, δ pixel For pixel angular resolution, β off The camera's off-axis angle.

3. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S2, t n Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is: In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. r n for t n The distance between the Earth's center and the orbital center at any given moment; ω e This is the angular rate of Earth's rotation; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, ω c The perigee argument, Ω c Right ascension of the ascending node, f n for t n The true closest angle at any given moment; , , Rotate clockwise around the +X axis, +Y axis, and +Z axis respectively. α The transformation matrix, where the superscript T denotes the transpose; In step S2, t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system The expression is: In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. Let A be the coordinates of the image plane reference point A in the camera coordinate system; φ n , θ n , ψ n They are respectively t n The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3.

4. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S3, t n At any given moment, the image plane reference point A corresponds to the object point A. n The coordinate expression in the reference ellipsoid coordinate system is: In the formula, λ The coefficient is dimensionless. for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. , , These are the components of the line-of-sight vector on the three coordinate axes; for t n Satellite position coordinates in the time reference ellipsoidal coordinate system , , The components of the satellite's position on the three coordinate axes; r a , r b α, β, and γ represent the major and minor axes of the reference ellipsoid, respectively; a, b, and c are the coefficients of the quadratic equation.

5. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S4, t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoid coordinate system The expression is: In the formula, for t n The line-of-sight vector of the image plane reference point A in the time reference ellipsoidal coordinate system. for t n Camera in time reference ellipsoidal coordinate system + x Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Normal vector in the reference ellipsoid coordinate system ; In the formula, for t n The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n The transformation matrix from the orbital frame to the inertial frame at time t. for t n The transformation matrix from the satellite's body coordinate system to its orbital system at any given time. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. In camera coordinate system + x Axial unit vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system , , These are the components of the coordinates on the three coordinate axes in the reference ellipsoidal coordinate system; r a , r b These are the major and minor semi-axises of the reference ellipsoid, respectively; t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoid coordinate system The expression is: In the formula, for t n Camera in time reference ellipsoidal coordinate system + y Axis vector, for t n At any given moment, the image plane reference point A corresponds to the object point A. n Normal vector in the reference ellipsoid coordinate system ; In the formula, In camera coordinate system + y Axial unit vector.

6. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S5, t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system The expression is: In the formula, for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. r n+1 for t n+1 The distance between the Earth's center and the orbital center at any given moment; ω e This is the angular rate of Earth's rotation; a c For the semi-major axis of the track, e c For orbital eccentricity, i c For the track inclination angle, ω c The perigee argument, Ω c Right ascension of the ascending node, f n+1 for t n+1 The true closest angle at any given moment; t d For the recursion period, ω s It is the orbital angular velocity; In step S5, t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system The expression is: In the formula, for t n+1 Satellite position coordinates in the time reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Coordinates in the reference ellipsoidal coordinate system.

7. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S6, t n+1 The satellite maintains its imaging matrix along its orbit at all times. The expression is: In the formula, for t n+1 The unit tangent vector along / perpendicular to the rail at time [time]. for t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n+1 The line-of-sight vector of the camera's line-of-sight point O in the time reference ellipsoidal coordinate system.

8. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S6, t n+1 Constant-time satellite vertical orbit maintains imaging matrix The expression is: In the formula, for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system.

9. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In step S7, t n+1 The orbital system's three-axis attitude must satisfy the following conditions to maintain imaging along or perpendicular to the orbit: In the formula, ( φ n+1 , θ n+1 , ψ n+1 ) are respectively t n+1 The satellite's orbital system is constantly in the roll, pitch, and yaw three-axis attitude sequence, which is 1-2-3. When using track-holding imaging, we have: When using vertical track-held imaging, we have: In the formula, for t n+1 The transformation matrix from the orbital frame to the inertial frame at time t. for t n+1 The transformation matrix from the inertial frame to the reference ellipsoidal coordinate system at time t. for t n+1 The satellite maintains its imaging matrix along its orbit at all times. for t n+1 The satellite maintains its imaging matrix in its vertical orbit at all times. This is the transformation matrix from the camera coordinate system to the satellite coordinate system. β off The camera's off-axis angle.

10. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In steps S2 to S7, the semi-major axis of the reference ellipsoid r a and short half shaft r b The expression is: In the formula, R a , R b These are the major and minor semi-axises of the WGS84 ellipsoid, respectively. λ h This is the proportionality coefficient. h This represents the elevation of ground features in the WGS84 coordinate system.

11. The method for planning the attitude of an agile satellite to maintain imaging in motion along or perpendicular to its orbit, as described in claim 1, is characterized in that... In steps S2 to S7, when on-board computing resources are limited, the tangent vector along or perpendicular to the orbit of the object point corresponding to the image plane reference point A in the reference ellipsoidal coordinate system remains approximately constant, that is: In the formula, for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n Tangent vector along the orbit in the reference ellipsoidal coordinate system for t n+1 At any given moment, the image plane reference point A corresponds to the object point A. n+1 The perpendicular tangent vector in the reference ellipsoidal coordinate system for t n At any given moment, the image plane reference point A corresponds to the object point A. n The perpendicular tangent vector in the reference ellipsoidal coordinate system.

12. An agile satellite attitude planning system for maintaining imaging in motion along or perpendicular to orbit, characterized in that, The agile satellite attitude planning method for maintaining in-motion imaging along or vertically using any one of claims 1 to 11 is adopted.

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