A planning method and system for autonomous imaging of a satellite

Abstract

The application relates to a satellite autonomous imaging planning method and system, and relates to the aerospace technical field, and solves the problems of insufficient overtop prediction accuracy, low autonomy and large satellite resource consumption in the prior art method based on high-precision orbit low orbit and accurate search overtop time. Based on satellite orbit information obtained through orbit recursion and longitude and latitude data of a ground target point, an included angle between a flight direction and a satellite-target point connecting vector is calculated, orbit recursion step length is dynamically adjusted according to the included angle value, and orbit data of the satellite overtop time is determined; according to the orbit data of the overtop time, it is judged whether the overtop orbit is located in the side swing shooting capability range of the satellite, if the requirement is not met, the orbit recursion is returned and continued, and if the requirement is met, the best imaging time and the satellite attitude are calculated respectively; the best imaging time, the satellite attitude and related orbit information are returned to a ground central computer, and are used for task storage and scheduling.

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and more specifically to a planning method and system for satellite autonomous imaging. Background Technology

[0002] As the operationalization of Earth remote sensing increases, users are increasingly demanding diverse geographical, temporal, and geometric constraints on imaging targets. Agile satellites' optical payloads can maneuver around roll, pitch, and yaw axes, enabling them to point at targets in any orientation within their capabilities. Their observable area is a strip centered on the nadir trajectory, and ground targets within this strip can potentially be observed. However, due to limitations in the payload's field of view and attitude / angular rate constraints, the satellite's coverage is finite, requiring meticulous mission orchestration.

[0003] Traditional imaging mission workflows rely on unified planning by ground control centers. If orbit control is performed while the satellite is in orbit (or orbital deviations caused by environmental disturbances), changes in orbital information may lead to wasted window time and mission failure.

[0004] To address this, Chinese patent CN112945242A discloses "A method for satellite autonomously planning the optimal time and attitude for on-orbit missions." This method allows the satellite to perform the following functions after receiving only two inputs from the ground: "target latitude and longitude" and "planned imaging time." First, based on the latest orbital information after orbit control, it autonomously recursively calculates and geometrically solves to quickly locate the target's imageable time. Second, it combines attitude / yaw capability and angular rate constraints to solve for the optimal observation time and attitude that satisfy the constraints. Third, it automatically generates and issues command sequences to complete imaging and transmits the autonomous mission actions and results back to the ground. Simulation and ground / satellite testing have verified that this method is simple, has good real-time performance, requires minimal ground intervention, effectively reduces window waste, and improves the efficiency and success rate of integrated satellite-ground mission scheduling.

[0005] However, this technical solution uses the J4 perturbation model and adopts a geometric threshold to determine the overshoot condition. Its method is essentially a proximity judgment mechanism under finite precision recursion, which makes it difficult to guarantee the orbit-attitude geometric consistency in high-resolution autonomous imaging scenarios. Summary of the Invention

[0006] This invention solves the problems of insufficient over-the-top prediction accuracy, low autonomy, and high on-board resource consumption in existing methods.

[0007] The satellite autonomous imaging planning method of the present invention includes the following steps: Step S1: Based on satellite orbit information and latitude and longitude data of ground target points, calculate the relative distance between the satellite and the ground target points. When the relative distance is less than a set threshold, use the Earth's gravitational field spherical harmonic expansion model to perform orbit recursion. Step S2: Based on the satellite orbit information obtained by orbit recursion and the latitude and longitude data of the ground target point, calculate the angle between the flight direction and the vector connecting the satellite and the target point. According to the angle value, dynamically adjust the orbit recursion step size to determine the orbit data at the time of satellite overpass. Step S3: Based on the orbit data at the overhead moment, determine whether the overhead orbit is within the satellite's side-swing imaging capability range. If the requirement is not met, return and continue orbit recursion. If the requirement is met, calculate the optimal imaging moment and satellite attitude respectively. Step S4: The optimal imaging time, satellite attitude, and relevant orbital information are returned to the ground center computer for mission storage and scheduling.

[0008] Furthermore, in one embodiment of the present invention, the determination of satellite overhead is achieved by constructing an objective function. ; ; when When the value is 0, the satellite passes overhead; in, Calculate the unit vector of the target point in the Earth-fixed system based on its latitude and longitude. To calculate the unit vector of the satellite's current position in the Earth-fixed system.

[0009] Furthermore, in one embodiment of the present invention, the orbital recursion is a multi-level recursion stopping condition.

[0010] Furthermore, in one embodiment of the present invention, the multi-level recursion stopping condition is specifically as follows: Set three threshold levels These correspond to the three stages: coarse search, interval determination, and precise solution.

[0011] Furthermore, in one embodiment of the present invention, the coarse search stage specifically comprises: The search is performed using a large step size recursive method, when the condition is met... ; in, This is the coarse search phase. For the k-th step, The objective function value at time t; The compensation is switched from a large step size to a smaller step size, and the interval determination stage begins.

[0012] Furthermore, in one embodiment of the present invention, the interval determination stage specifically comprises: Constructing the precise search interval using monotonic changes: ; When it appears ; in, For the first Step and the first The difference in the objective function of each step. For the first Step and the first The difference in the objective function of each step. For the first step, The corresponding objective function value, For the first step, The corresponding objective function value; Then in the interval If there is a local minimum in memory, use that as the search interval.

[0013] Furthermore, in one embodiment of the present invention, the precise solution stage specifically comprises: A fine step size is used to accurately locate the overshoot time, and the process stops when the objective function is less than the third-level threshold or the step size is less than the time resolution. or ; in, This represents the time resolution threshold for the satellite's onboard system. Let be the objective function value at time t*. For the accurate solution stage, The maximum value in the current time interval. This is the minimum value of the current time interval. This represents the time resolution threshold for the satellite's onboard system.

[0014] The present invention discloses a satellite autonomous imaging planning system, which is implemented based on the satellite autonomous imaging planning method described above, and includes the following modules: Module S1 calculates the relative distance between the satellite and the ground target point based on satellite orbit information and latitude and longitude data of the ground target point. When the relative distance is less than a set threshold, the orbit is recursively calculated using the Earth's gravitational field spherical harmonic expansion model. Module S2 calculates the angle between the flight direction and the vector connecting the satellite and the target point based on the satellite orbit information obtained by orbit recursion and the latitude and longitude data of the ground target point. Based on the angle value, it dynamically adjusts the orbit recursion step size to determine the orbit data at the time of satellite overpass. Module S3 determines whether the overpass orbit is within the satellite's side-swing imaging capability based on the orbit data at the overpass moment. If the requirement is not met, it returns and continues the orbit recursion. If the requirement is met, it calculates the optimal imaging moment and satellite attitude respectively. Module S4 returns the optimal imaging time, satellite attitude, and relevant orbital information to the ground control computer for mission storage and scheduling.

[0015] This invention solves the problems of insufficient over-the-top prediction accuracy, low autonomy, and high on-board resource consumption in existing methods. Specific beneficial effects include: 1. The satellite autonomous imaging planning method described in this invention, to meet specific user imaging needs, proposes an on-board autonomous planning method that relies solely on the latitude, longitude, and altitude information of target points annotated on the ground to complete mission planning in orbit and quickly calculate the optimal imaging time and corresponding three-axis attitude. This method is simple in process and highly real-time, enabling rapid response in emergency imaging scenarios while significantly reducing ground-based manual intervention and communication burden, improving on-board resource utilization efficiency, and promoting integrated satellite-ground mission scheduling and operational use. 2. The satellite autonomous imaging planning method described in this invention introduces a high-order zonal spherical harmonic function to finely model the Earth's gravity field and constructs a continuously optimizable overpass objective function, transforming the overpass determination problem into an extreme value search problem. This achieves the unification of dynamic model accuracy and overpass determination accuracy, and improves the autonomous imaging accuracy and algorithm stability. 3. The satellite autonomous imaging planning method described in this invention is applicable to Earth observation satellites with agile pointing capabilities. After orbit control, it can autonomously complete the optimal time and attitude determination for mission replanning on-board based on the latest orbit information. Attached Figure Description

[0016] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a flowchart of the overall task planning scheme described in Implementation Method 1; Figure 2 This is a schematic diagram illustrating the relationship between the satellite orbit and the target point as described in Implementation Method 1; Figure 3 This is a schematic diagram showing the angle between the satellite's flight direction and the target point as described in Implementation Method 1; Figure 4 This is a schematic diagram illustrating the calculation of the desired attitude from the vertex trajectory information and the geographical information of the target point as described in Implementation Method 1. Figure 5 This is a flowchart of the optimal time and attitude for autonomously planning satellite missions as described in Implementation Method 1; Figure 6 This is a schematic diagram of the relationship between the satellite and the target point as described in Implementation Method 1; Figure 7 This is a schematic diagram of the relationship between the satellite and the target point as described in Implementation Method 1. Detailed Implementation

[0017] Various embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. The embodiments described with reference to the drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0018] Implementation Method 1: To address the technical problems existing in the prior art, this implementation method proposes a satellite autonomous imaging planning method, specifically as follows: After orbit control, ensure that the satellite can accurately photograph the target point and rationally plan the imaging task to avoid wasting the imaging window. The input and output of the scheme are shown in Table 1.

[0019] Table 1 Inputs and Outputs of the Autonomous Imaging Scheme

[0020] The latitude and longitude are in units of 200000 (hexadecimal), which is 2^21 in decimal. The corresponding ground accuracy is calculated as (1 / 2^21)*111319≈5.31cm = 0.0531m, and the push-broom imaging accuracy is 0.0319 m.

[0021] The overall implementation process of the autonomous mission planning scheme after satellite orbit control is as follows: Figure 1 As shown.

[0022] 1) Ground surface injection According to the satellite's autonomous planning function, the uplink mission information on the ground only includes latitude, longitude, and time information (latest image acquisition time). The instruction refresh flag is carried in the 512 / 64-byte service instruction; 0x55 indicates the service needs refresh, and 0xAA indicates the service does not need refresh. If the instruction refreshes, it means the satellite has undergone autonomous orbit control, its actual orbit has been updated, and the imaging service needs to be replanned; if the instruction does not refresh, the service is executed according to the original uploaded information. Based on the above requirements, the designed target point instruction parameter format is shown in Table 2.

[0023] Table 2 Target Point Command Parameter Format

[0024] 2) Attitude control calculation After receiving the target point information, the target point is identified by its identifier. Once the target reception is complete, the target point information is cached and sent to the relevant attitude control computing unit, triggering the background task of autonomous attitude control computing planning.

[0025] In the attitude control main program, the time when orbit recursion begins and the satellite's initial position and velocity information are first recorded. The background program uses a high-precision orbit recursion model for forward calculations lasting up to two days. This model employs a high-order Earth gravitational field model, considering spherical harmonic expansions exceeding J4, and incorporates multiple perturbations such as three-body gravity, atmospheric drag, and solar radiation pressure, thereby improving the accuracy of orbit calculations. High-order numerical integration methods are used during the recursion process, and the calculation accuracy and efficiency are optimized by dynamically adjusting the step size. Figure 3 and 4 As shown, the distance between the satellite and the target point is determined by the included angle; the smaller the angle, the closer the satellite is to the target. By judging the included angle value, the system adaptively adjusts the recursive step size: when the included angle is large (e.g., below 50°), the step size is large to quickly approach the target and reduce computational burden; when the included angle decreases (e.g., between 50° and 80°), the step size gradually decreases, and the accuracy gradually increases; when the included angle further decreases (e.g., between 80° and 88°), the step size is minimized to accurately pinpoint the overpass time. Finally, when the satellite approaches the target point, the step size is set to a minimum value, and the overpass time is accurately calculated.

[0026] The output information after attitude control calculation includes overhead time, lateral swing angle (including output in quaternion form), and a "capable of being photographed" flag (0xAA); or an output "capable of being photographed but in the shadow area" flag (0x11), "unable to be photographed at 45° lateral swing" flag, or "planning failed due to insufficient maneuver time" flag (0x00).

[0027] like Figure 5 As shown, the method for satellites to autonomously plan the optimal time and attitude for their on-orbit missions is as follows: The orbital recursion is performed using a spherical harmonic expansion model of Earth's gravitational field, specifically as follows: The equation of motion of the satellite in the geocentric inertial coordinate system is: ; (1) in, For satellite position vectors, For velocity vector, This is the resultant acceleration.

[0028] The Earth's gravitational potential function is expanded using a spherical harmonic expansion of order N with a truncation: (2) in, The gravitational constant of Earth, For the Earth's radius, , The latitude of the Earth's core. Longitude of the Earth's core To associate Legendre functions, and These are the normalized spherical harmonic coefficients.

[0029] The gravitational acceleration can be calculated from the potential function. (3) The combined acceleration of the satellite can be expressed as (4) in, To account for the gravitational acceleration due to the Sun and Moon as a third body, Atmospheric drag acceleration, The perturbation acceleration of solar radiation pressure: ; ; (5) in, The solar radiation pressure constant. This is the shadow function.

[0030] The criteria for determining satellite overhead are as follows: When the satellite passes directly above the target point, the lines of sight between the satellite and the target point should be perfectly aligned; that is, the satellite's projection in the Earth-fixed system should completely coincide with the target point's projection. First, calculate the target point's unit vector in the Earth-fixed system based on its latitude and longitude. Then calculate the unit vector of the satellite's current position in the Earth-fixed system. The formula for calculating the coordinates of the target point in the Earth-fixed coordinate system is: ; (6) in, and These are the geographical latitude and longitude of the target point. The height of the target point, It is the radius of curvature of the target point.

[0031] Define the unit vector of a satellite in the Earth-fixed coordinate system: (7) The unit vector of the target point in the Earth-fixed system is (8) The angle between the satellite and the target point Defined as the angle between two unit vectors (9) To improve computational efficiency and accuracy, this implementation method constructs an objective function. Used to determine whether a satellite has passed overhead. (10) when When the value is 0, the satellite is directly above the target point.

[0032] The stopping condition for orbital recursion is as follows: This implementation method employs a multi-level recursive stopping condition. First, the satellite orbit is rapidly recursively calculated using a large step size. When approaching the target point, the step size is reduced to improve accuracy, thereby achieving precise positioning at the time of overpass.

[0033] Set three threshold levels These correspond to the three stages: coarse search, interval determination, and precise solution.

[0034] First, a large-step recursive search is performed, until the condition is met. (11) At this point, the compensation will be adjusted by the larger step size. Switch to smaller step size Then, the interval determination stage begins.

[0035] After a coarse search initially determines the time of the top crossing, the search interval is further narrowed by reducing the step size to find adjacent times. This ensures that the objective function has a local minimum point close to 0 within this interval. This invention uses monotonicity variation to construct the precise search interval: (12) When it appears (13) Then it is considered to be in the interval Memory in a local minimum Use it as the precise search interval .

[0036] After determining the precise search interval through intervals, a fine step size is finally used to accurately locate the overshoot time, stopping when the objective function is less than the third-level threshold or the step size is less than the time resolution. (14) or (15) in, This represents the time resolution threshold for the satellite's onboard system.

[0037] 3) Task Planning After receiving the calculated overpass time and side-slip angle information for the target point, the satellite service generates the target point mission during the planning phase. This phase is also performed through a background task to avoid conflicts with normal onboard tasks. The attitude information configuration follows the standard pushbroom mission configuration, and the attitude maneuver time is configured according to the maximum envelope of the mission maneuver time. The payload configuration follows the default payload configuration pre-stored onboard. The mission file number uses a specific file number range planned autonomously to avoid conflicts with ground-planned missions. The mission priority information utilizes the priority from previously cached target point information. Autonomously planned missions uniformly enable mission combination switches, enabling rapid imaging of the target point. Considering the satellite's pre-grounding capability, the mission generation phase checks whether the target point is within the pre-grounding area. For target points meeting the criteria, the maneuver time for mission generation is dynamically configured based on the side-slip angle information, achieving rapid maneuver imaging.

[0038] The side-swing angle calculation at the imaging moment is as follows: At the moment when the satellite passes over the target point The satellite's position and velocity vectors are ; (16) The Earth-fixed coordinates of the target point are: (17) Calculate and normalize the line-of-sight vector from the satellite to the target point: (18) Construct the Z-axis of the target pointing to the attitude matrix (19) Construct a temporary reference vector using the local north direction ; (20) Constructing the X and Y axes of the pose matrix ; ;(twenty one) Construct the desired pose matrix

[0039] ;(twenty two) Euler angles are extracted from the attitude matrix based on the 3-2-1 rotation sequence. ; ;(twenty three) ; in, pose matrix The element in the i-th row and j-th column, Yaw angle The pitch angle, This is the roll angle.

[0040] 4) Task storage Once task planning is complete, the generated tasks are stored using the existing task storage mechanism. The subsequent task mechanism will be able to perform task conflict detection. Since the autonomously planned tasks and the ground-planned tasks are subject to unified priority management, users can achieve unified management of various types of requirements during use.

[0041] 5) Imaging task execution After the autonomously planned mission is executed, the satellite will transmit mission execution information via BeiDou short message / telemetry and control. The transmitted information includes basic mission information such as file number, imaging duration, and target point information, thereby guiding the ground to complete the planning of subsequent data transmission missions.

[0042] Therefore, this embodiment proposes a satellite autonomous imaging planning method. First, based on the satellite orbit information and the latitude and longitude data of the ground target point, the relative distance between the satellite and the target point is calculated. When this distance is less than a set threshold, it indicates that the satellite is approaching the target point, and orbit recursion for subsequent time intervals is initiated. To ensure orbit accuracy, this embodiment uses a high-precision J4 orbit model to virtually recursively calculate the satellite orbit. Next, based on the recursed orbit information and the latitude and longitude of the target point, the angle between the flight direction and the vector connecting the satellite and the target point is calculated. According to this angle value, this embodiment dynamically adjusts the orbit recursion step size to accurately determine the orbit information at the satellite's overhead transit time. Then, based on the orbit data at that time, it is determined whether the overhead transit orbit is within the satellite's side-swing imaging capability range. If the overhead transit orbit does not meet the imaging capability range requirements, the process returns and continues recursion; if it meets the requirements, the optimal imaging time and satellite attitude are further determined. Finally, the calculated optimal observation time, attitude, and related orbit information are returned to the ground control computer for mission storage and scheduling.

[0043] To better illustrate the satellite autonomous imaging planning method described in this embodiment, the following examples will be used for detailed description: Example 1: Southern Latitude Imaging Satellite orbital parameters: orbital altitude 535.35km, orbital inclination 97.54°.

[0044] The target point's latitude, longitude, and altitude are [93.74° -16.50° 0].

[0045] According to the ground control center's plan, the satellite reached position 802197361 (4:36:01 AM Beijing time on June 3, 2025), with a side tilt of 19.4°. The actual imaging time was 4:36:03 AM on June 3, 2025, with a time error of 2 seconds and a side tilt angle error of 0.05°. Figure 6 As shown, the blue curve represents the satellite trajectory, the blue circle represents the satellite sensor range, and the purple letter represents the target point.

[0046] Example 2: Northern Latitude Imaging Satellite orbital parameters: orbital altitude 535.35km, orbital inclination 97.54°.

[0047] The target point's latitude, longitude, and altitude are [-128.14° 34.30° 0].

[0048] According to the ground control center's plan, the satellite reached 802120325 (7:12:05 AM Beijing time on June 2, 2025), with a side tilt of 0.0039°. The actual imaging time was 7:12:05.202 AM on July 12, 2025, with a time error of 0.202 seconds and a side tilt angle error of 0.05°. Figure 7 As shown, the blue curve represents the satellite trajectory, the blue circle represents the satellite sensor range, and the purple letter represents the target point.

[0049] Implementation Method Two: A satellite autonomous imaging planning system according to this implementation method is implemented based on the satellite autonomous imaging planning method described in Implementation Method One, and includes the following modules: Module S1 calculates the relative distance between the satellite and the ground target point based on satellite orbit information and latitude and longitude data of the ground target point. When the relative distance is less than a set threshold, the orbit is recursively calculated using the Earth's gravitational field spherical harmonic expansion model. Module S2 calculates the angle between the flight direction and the vector connecting the satellite and the target point based on the satellite orbit information obtained by orbit recursion and the latitude and longitude data of the ground target point. Based on the angle value, it dynamically adjusts the orbit recursion step size to determine the orbit data at the time of satellite overpass. Module S3 determines whether the overpass orbit is within the satellite's side-swing imaging capability based on the orbit data at the overpass moment. If the requirement is not met, it returns and continues the orbit recursion. If the requirement is met, it calculates the optimal imaging moment and satellite attitude respectively. Module S4 returns the optimal imaging time, satellite attitude, and relevant orbital information to the ground control computer for mission storage and scheduling.

[0050] The above provides a detailed description of the satellite autonomous imaging planning method and system proposed in this invention. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A planning method for satellite autonomous imaging, characterized in that, Includes the following steps: Step S1: Based on satellite orbit information and latitude and longitude data of ground target points, calculate the relative distance between the satellite and the ground target points. When the relative distance is less than a set threshold, use the Earth's gravitational field spherical harmonic expansion model to perform orbit recursion. Step S2: Based on the satellite orbit information obtained by orbit recursion and the latitude and longitude data of the ground target point, calculate the angle between the flight direction and the vector connecting the satellite and the target point. According to the angle value, dynamically adjust the orbit recursion step size to determine the orbit data at the time of satellite overpass. Step S3: Based on the orbit data at the overhead moment, determine whether the overhead orbit is within the satellite's side-swing imaging capability range. If the requirement is not met, return and continue orbit recursion. If the requirement is met, calculate the optimal imaging moment and satellite attitude respectively. Step S4: The optimal imaging time, satellite attitude, and relevant orbital information are returned to the ground center computer for mission storage and scheduling.

2. The satellite autonomous imaging planning method according to claim 1, characterized in that, The determination of satellite overhead is based on the construction of an objective function. ; ； when When the value is 0, the satellite passes overhead; in, Calculate the unit vector of the target point in the Earth-fixed system based on its latitude and longitude. To calculate the unit vector of the satellite's current position in the Earth-fixed system.

3. The satellite autonomous imaging planning method according to claim 1, characterized in that, The aforementioned orbital recursion is a multi-level recursion stopping condition.

4. The satellite autonomous imaging planning method according to claim 3, characterized in that, The aforementioned multi-level recursion stopping condition is specifically as follows: Set three threshold levels These correspond to the three stages: coarse search, interval determination, and precise solution.

5. The satellite autonomous imaging planning method according to claim 4, characterized in that, The coarse search phase, as described above, specifically includes: The search is performed using a large step size recursive method, when the condition is met... ； in, This is the coarse search phase. For the k-th step, The objective function value at time t; The compensation is switched from a large step size to a smaller step size, and the interval determination stage begins.

6. The satellite autonomous imaging planning method according to claim 4, characterized in that, The interval determination stage specifically includes: Constructing the precise search interval using monotonic changes: ； When it appears ； in, For the first Step and the first The difference in the objective function of each step. For the first Step and the first The difference in the objective function of each step. For the first step, The corresponding objective function value, For the first step, The corresponding objective function value; Then in the interval If there is a local minimum in memory, use that as the search interval.

7. The satellite autonomous imaging planning method according to claim 4, characterized in that, The precise solution stage, as described above, specifically includes: A fine step size is used to accurately locate the overshoot time, and the process stops when the objective function is less than the third-level threshold or the step size is less than the time resolution. or ; in, This represents the time resolution threshold for the satellite's onboard system. Let be the objective function value at time t*. For the accurate solution stage, The maximum value in the current time interval. This is the minimum value of the current time interval. This represents the time resolution threshold for the satellite's onboard system.

8. A satellite autonomous imaging planning system, said system being implemented based on the satellite autonomous imaging planning method according to claim 1, characterized in that, Includes the following modules: Module S1 calculates the relative distance between the satellite and the ground target point based on satellite orbit information and latitude and longitude data of the ground target point. When the relative distance is less than a set threshold, the orbit is recursively calculated using the Earth's gravitational field spherical harmonic expansion model. Module S2 calculates the angle between the flight direction and the vector connecting the satellite and the target point based on the satellite orbit information obtained by orbit recursion and the latitude and longitude data of the ground target point. Based on the angle value, it dynamically adjusts the orbit recursion step size to determine the orbit data at the time of satellite overpass. Module S3 determines whether the overpass orbit is within the satellite's side-swing imaging capability based on the orbit data at the overpass moment. If the requirement is not met, it returns and continues the orbit recursion. If the requirement is met, it calculates the optimal imaging moment and satellite attitude respectively. Module S4 returns the optimal imaging time, satellite attitude, and relevant orbital information to the ground control computer for mission storage and scheduling.

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