SAR satellite azimuth agile observation mode multi-target task planning method and system

Abstract

The application provides a SAR satellite azimuth agile observation mode multi-target task planning method and system, comprising the following steps: calculating the downward angle of each target observation according to target position information and orbit prediction information, and obtaining corresponding wave position parameters; calculating the azimuth observation angle of the satellite relative to the target at any time; screening the reachable observation center time according to the maximum scanning capacity of the SAR satellite and the scanning angle required by the target observation; calculating the starting and ending time of each target observation based on the wave position parameters, and forming an observation time array; sorting each target according to the starting time sequence to form an observable target sequence array; taking the imaging ending time of the last target in the observable target sequence as the time reference value for the next screening; removing the observable target, and continuing to select the smallest imaging starting time greater than the time reference value from the remaining to-be-observed target time array, so that the task planning efficiency is improved, and the efficiency of the SAR satellite ground observation is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of SAR satellite mission planning, in particular to a SAR satellite azimuth agile observation mode multi-target mission planning method and system. BACKGROUND

[0002] Space-borne active phased array synthetic aperture radar (SAR) is an all-weather and all-day observation means, with the continuous development of space-borne active phased array SAR technology, two-dimensional large scanning and wideband signal are becoming the necessary conditions for SAR satellites to obtain high-resolution wide observation bands, especially the azimuth large scanning capability can not only realize high-resolution in the azimuth direction, but also can realize the observation of a large number of targets in one pass, especially in the background of close distance in the azimuth direction and far distance in the range direction, by using the azimuth large scanning capability of SAR antenna, the front squint, the side-looking and the back squint means can be used to realize the observation of a large number of target clusters in one pass, which greatly improves the observation efficiency of SAR satellites.

[0003] For the observation of a large number of target clusters in one pass, how to maximize the number of observation targets is a problem that needs to be solved in SAR satellite mission planning, therefore, the SAR satellite azimuth agile observation mode multi-target mission planning is the basic work to ensure and improve the full play of the efficiency of two-dimensional active phased array SAR satellites. At the same time, with the increasing demand for the normal application of new observation modes of SAR satellites in orbit, in order to realize the efficient application of the function of SAR satellite azimuth agile observation mode, it is necessary to give a SAR satellite azimuth agile observation mode multi-target mission micro-planning method based on the previous satellite macro-mission planning method combined with the characteristics of space-borne SAR, so as to adapt to the optimal observation combination under different side-looking angles.

[0004] The SAR satellite mission planning design is mainly two types. One is the on-board autonomous mission planning. Due to the limited computing resources and computing capacity on board, the on-board autonomous mission planning usually targets user task demand or on-orbit events, and according to the running state and usage constraints of the platform and payload, the satellite autonomously arranges the mission plan, formulates the action sequence and generates the control instruction, which belongs to the macro task planning in the running process of a single satellite or multi-satellite cluster. There is no planning solution for maximizing the number of observation targets using the azimuth direction agile observation mode in the multi-target dense area. The other is the observation task arrangement on the ground. First, the observation time is calculated according to the target latitude and longitude information and the satellite orbit prediction value. Then, combined with the satellite energy balance requirement and the attitude maneuver time length and other constraint conditions, the target observation priority order is pruned until the task execution condition can be met. In the past, it was mainly for the forward-looking and side-looking observation mode. Through the calculation of the satellite over-target normal top time, the planning and sorting of each target were carried out. With the flexibility of the SAR system on board, the constraint conditions considered by the conventional planning method are not suitable for the current development level of SAR satellite and the new application mode of azimuth agile observation. Moreover, the past SAR satellite mission planning mainly focuses on the macro level and lacks micro detail level.

[0005] After investigation, the domestic published patents and papers on SAR satellite azimuth agile observation mode multi-target task planning are listed as follows:

[0006] The DHIP method of SAR satellite imaging mission planning (paper, Computer Engineering and Science, Vol. 33, No. 9, 2011), which proposes a double-layer insertion planning (DHIP) method, inserts the tasks to be planned at the on-board SAR switch-on information tuple level and the imaging information tuple level two levels in turn, and uses the method of constructing and detecting to obtain the optimization solution of the problem.

[0007] Autonomous mission planning design and on-orbit verification of GF-3 satellite (paper, Spacecraft Engineering, Vol. 26, No. 6, 2017), which introduces the working mode of GF-3 satellite and the form of ground operation instruction, and on this basis designs the autonomous mission planning, and proposes nine kinds of autonomous mission planning arrangement instruction templates such as single recording, single antenna single station recording and placing, single antenna double station recording and placing.

[0008] This paper, titled "On-board Real-time Mission Planning and Design for Agile SAR Satellites" (published in *Spacecraft Engineering*, Vol. 29, No. 5, 2020), designs on-board real-time mission planning for agile synthetic aperture radar (SAR) satellites with on-orbit collaborative guided imaging missions. Considering the collaborative mission process and characteristics, a framework for on-board real-time mission planning combining rolling planning and dynamic replanning is constructed. A planning-decision strategy with rolling advancements of long planning windows and short decision windows is formulated, and an on-board real-time mission planning process based on event triggering or fixed-cycle advancements is designed. For the multi-point target imaging planning problem during operation, a depth-first tree search algorithm is used to search for the optimal imaging target sequence. Conflict resolution rules and benefit prediction rules are used to prune the search tree to accelerate the search speed.

[0009] Research on In-orbit Real-time Guided Multi-Satellite Imaging Mission Planning Method (Paper, Spacecraft Engineering, Vol. 28, No. 5, 2019) This paper addresses the high timeliness requirements and reliance on ground systems for in-orbit autonomous mission planning of remote sensing satellites. By analyzing the satellite's orbital characteristics and the coordination of multiple payloads, a multi-satellite autonomous mission planning method for in-orbit real-time guided imaging is proposed.

[0010] Chinese patent document CN106647262B discloses a differential evolution method for multi-objective mission planning of agile satellites. The differential evolution method includes: converting the solution set space composed of decision variables into a population; initializing the population and its algorithm parameters; generating donation vectors, trial vectors, and offspring based on the population's algorithm parameters; adding offspring to the population to obtain a mutant population, and decoding the fitness of individuals; determining whether the current iteration number i is less than the total number of iterations; if so, selecting individuals from the mutant population to generate a new population and updating the corresponding population's algorithm parameters; otherwise, removing dominated solutions from the elite solution set and adding non-dominated solutions from the mutant population to the solutions not dominated by individuals in the elite solution set to update the elite solution set; sorting the individuals in the elite solution set and outputting a specified number of individuals according to the order.

[0011] With the improvement of azimuth scanning capability of SAR satellites, the azimuth agile observation mode can realize multi-target observation in one flight. However, no specific planning method for multi-target mission of SAR satellite azimuth agile observation mode has been found in the currently published papers and patents. Summary of the Invention

[0012] To address the shortcomings of existing technologies, the purpose of this invention is to provide a multi-target mission planning method and system for SAR satellite azimuth agile observation mode.

[0013] A multi-target mission planning method for a SAR satellite azimuth-agile observation mode, provided by the present invention, includes the following steps:

[0014] Step S1: Obtain the position information of the target to be observed and the predicted satellite position information, and unify the target and satellite position information data into the same coordinate system;

[0015] Step S2: Calculate the downward viewing angle of each observed target and obtain the corresponding wavefront parameters;

[0016] Step S3: Calculate the azimuth observation angle of the satellite relative to all the targets to be observed at any given time;

[0017] Step S4: Select the available observation center time based on the maximum scanning capability of the SAR satellite and the scanning angle required for target observation;

[0018] Step S5: Calculate the start and end times of each target observation based on the wave position parameter information to form an observation time array;

[0019] Step S6: Sort the targets according to their starting time to form an array of observable targets;

[0020] Step S7: Use the imaging end time of the last target in the observable target sequence as the time reference value for the next screening;

[0021] Step S8: Remove the observable targets that have completed the planning, continue to select targets that meet the time sorting from the remaining target time array, and determine them as continuous observation targets, until the remaining target times do not meet the time conflict judgment.

[0022] Step S9: Generate multi-objective observation planning results.

[0023] Preferably, step S1 includes the following sub-steps:

[0024] Step S1.1: Obtain the location information of the target to be observed, including latitude, longitude and elevation information, and convert the location information of the target to be observed into location information in the WGS-84 coordinate system;

[0025] Step S1.2: Obtain satellite orbit position prediction information over a period of time, convert the predicted satellite position data into position information in the WGS-84 coordinate system, and perform interpolation processing on the satellite position information.

[0026] Preferably, step S2 includes the following sub-steps:

[0027] Step S2.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system;

[0028] Step S2.2: Calculate the downward angle of the satellite relative to each target based on the position information of the target to be observed and the satellite orbit position prediction information;

[0029] Step S2.3: Select the nearest wave positions corresponding to each target under test based on the calculated downward angle and obtain the wave position information, including PRF value, azimuth scan angle range required for observation and number of dwell pulses.

[0030] Preferably, step S3 includes the following sub-steps:

[0031] Step S3.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system;

[0032] Step S3.2: Calculate the azimuth observation angle of the satellite relative to all the targets at any given time based on the satellite orbit prediction position information and the position information of each target to be observed.

[0033] Preferably, step S4 includes the following sub-steps:

[0034] Step S4.1: Determine the limit value of the azimuth observation angle based on the maximum azimuth scanning capability of the SAR satellite;

[0035] Step S4.2: Take any time as the center time of the image;

[0036] Step S4.3: Calculate the maximum azimuth angle during the target observation imaging time based on the azimuth scanning angle range required for target observation and the azimuth observation angle of the satellite relative to the target at the center time;

[0037] Step S4.4: Use the extreme values ​​of the azimuth observation angles as threshold values ​​to determine and filter out the available observation center times.

[0038] Preferably, step S5 includes the following sub-steps:

[0039] Step S5.1: Obtain the PRF value, dwell pulse number, azimuth scanning angle range, and scanning step value based on the target wave position parameter information;

[0040] Step S5.2: Calculate the imaging duration for each target;

[0041] Step S5.3: Calculate the start and end times of observation for each target based on the imaging center time and imaging duration;

[0042] Step S5.4: Round the start and end times to ensure that the interval between the two imaging operations is greater than the control requirement of the set time.

[0043] Step S5.5: Generate the observation time array for each target.

[0044] Preferably, step S6 includes the following sub-steps:

[0045] Step S6.1: Find the smallest imaging start time from the observation time array and determine the target at the corresponding position as the first observation target;

[0046] Step S6.2: Based on the imaging start time, form an observable target sequence array and record the corresponding target number, the corresponding imaging start time and end time.

[0047] Preferably, step S8 includes the following sub-steps:

[0048] Step S8.1: Remove observable targets that have already been planned;

[0049] Step S8.2: Continue to search for the smallest imaging start time that is greater than the time decision reference value from the remaining target time array, and determine the target at the corresponding position as the next observation target;

[0050] Step S8.3: Continue until the remaining time of the target to be observed does not meet the time conflict decision.

[0051] Preferably, step S9 includes the following sub-steps:

[0052] Step S9.1: Generate the corresponding observable target sequence number based on the observable target sequence array;

[0053] Step S9.2: Based on the observable target sequence array, generate the imaging start time and end time corresponding to the observable targets for use in SAR satellite power-on / off imaging control;

[0054] Step S9.3: Based on the observable target sequence array, obtain the scanning angle range and corresponding wavefront parameters corresponding to the observable targets for SAR satellite imaging parameter setting.

[0055] A multi-target mission planning system for SAR satellite azimuth-agile observation mode, provided by the present invention, includes the following modules:

[0056] Module M1: Acquires the position information of the target to be observed and the predicted satellite position information, and unifies the target and satellite position information data into the same coordinate system;

[0057] Module M2: Calculates the downward viewing angle of each observed target and obtains the corresponding wavefront parameters;

[0058] Module M3: Calculates the azimuth observation angle of the satellite relative to all the targets to be observed at any given time;

[0059] Module M4: Filters the available observation center times based on the maximum scanning capability of SAR satellites and the scanning angle required for target observation;

[0060] Module M5: Calculates the start and end times of observations for each target based on wave position parameter information, forming an observation time array;

[0061] Module M6: Sorts the targets according to their starting time to form an array of observable target sequences;

[0062] Module M7: Uses the imaging end time of the last target in the observable target sequence as the time reference value for the next screening;

[0063] Module M8: Remove observable targets that have completed planning, continue to select targets that meet the time sorting from the remaining target time array, and determine them as the next observation targets, until the remaining target times do not meet the time conflict judgment.

[0064] Module M9: Generates multi-objective observation planning results.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. The multi-target mission planning method of the SAR satellite azimuth agile observation mode of the present invention allows for the free combination of target observations under different azimuth observation angles in the azimuth agile observation mode, which can fully realize the ability to observe multiple targets in one flight and improve the on-orbit observation efficiency of SAR satellites.

[0067] 2. The multi-target mission planning of the SAR satellite azimuth agile observation mode of the present invention adopts the method of screening the minimum imaging start time and sorting by time size, which realizes the optimal combination of observable targets. First, it optimizes and simplifies the combination strategy; second, it simplifies the decision method; and third, it greatly improves the planning efficiency.

[0068] 3. The multi-target mission planning method of the SAR satellite azimuth agile observation mode of the present invention realizes mission planning at the micro level and has strong intuitiveness and operability. Attached Figure Description

[0069] 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:

[0070] Figure 1 This is a step diagram of the multi-target mission planning method for the SAR satellite azimuth agile observation mode of the present invention;

[0071] Figure 2 This is a schematic diagram of the SAR satellite azimuth agile observation mode of the present invention;

[0072] Figure 3 This is a schematic diagram of the SAR satellite ground geometry model of the present invention;

[0073] Figure 4 This is a flowchart of the multi-target mission planning algorithm for the SAR satellite azimuth agile observation mode of the present invention;

[0074] Figure 5 This is a graph showing the predicted orbital position of the satellite according to the present invention.

[0075] Figure 6 This is a graph showing the predicted orbital velocity of the satellite according to the present invention.

[0076] Figure 7 This is a schematic diagram of the target planning results under the observation requirement of 0.3m / 5km in this invention;

[0077] Figure 8 This is a schematic diagram of the target planning results under the observation requirements of 0.5m / 3.5km in this invention. Detailed Implementation

[0078] 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.

[0079] This invention relates to SAR satellite mission planning, and more particularly to a highly efficient SAR satellite azimuth-agile observation mode multi-target mission planning technology, specifically involving mission planning for a two-dimensional active phased array SAR satellite to pass over densely distributed targets in a single flight. With the rapid development of active phased array antenna technology and the improvement of two-dimensional large-scan capability, especially azimuth-oriented large-scan, SAR satellites have gained the ability to perform forward and backward squint observations in addition to traditional frontal and side-looking observations, forming a new application mode of azimuth-agile observation. To maximize the number of target observations in a single flight, this invention presents a SAR satellite azimuth-agile observation mode mission planning method. First, it analyzes the azimuth-oriented large-scan capability and spaceborne SAR imaging control method based on the working principle of the azimuth-agile observation mode. Then, it establishes a satellite-ground geometric model, provides calculation formulas for the azimuth observation angle and the viewing angle under observation, and achieves the optimal combination of observable targets by using a method of selecting the minimum starting imaging time and sorting by time. Simulation results show that the SAR satellite azimuth-agile observation mode multi-target mission planning method can efficiently complete the planning and design of maximizing the multi-target observation capability in a single flight, effectively improving the efficiency of SAR satellite Earth observation. The purpose of this invention is to provide a multi-target mission planning method for a SAR satellite azimuth agile observation mode. First, it realizes the transformation of mission planning from the macro level to the micro level, making it more operable. Second, it enhances the on-orbit observation capabilities of high-resolution SAR satellites and fully utilizes their effectiveness.

[0080] This invention discloses a multi-target mission planning method for SAR satellite azimuth-agile observation mode, comprising the following steps:

[0081] Step S1: Obtain the position information of the target to be observed and the predicted satellite on-orbit position information, and unify the target and satellite position information data into the same coordinate system. In this embodiment, the WGS-84 coordinate system is used. Details are as follows:

[0082] Step S1.1: Obtain the location information of the target to be observed, including latitude, longitude and elevation information, and convert the location information of the target to be observed into location information in the WGS-84 coordinate system;

[0083] Step S1.2: Obtain satellite orbit position prediction information over a period of time, generally in 1-second increments. Convert the predicted satellite position data into position information in the WGS-84 coordinate system and perform interpolation on the satellite position information. Update the time step to 10ms or less.

[0084] Step S2: Calculate the downward viewing angle of each observed target and obtain the corresponding wavefront parameters, including PRF, scan angle range, and dwell pulse number. Details are as follows:

[0085] Step S2.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system;

[0086] Step S2.2: Calculate the downward angle of the satellite relative to each target based on the position information of the target to be observed and the satellite orbit position prediction information;

[0087] Step S2.3: Select the nearest wave positions corresponding to each target under test based on the calculated downward angle and obtain the wave position information, including PRF value, azimuth scan angle range required for observation and number of dwell pulses.

[0088] Step S3: Calculate the azimuth observation angle of the satellite relative to all the targets to be observed at any given time, as follows:

[0089] Step S3.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system;

[0090] Step S3.2: Calculate the azimuth observation angle of the satellite relative to all the targets at any given time based on the satellite orbit prediction position information and the position information of each target to be observed.

[0091] Step S4: Based on the maximum scanning capability of the SAR satellite and the scanning angle required for target observation, select the reachable observation center time, as follows:

[0092] Step S4.1: Determine the limit value of the azimuth observation angle based on the maximum azimuth scanning capability of the SAR satellite;

[0093] Step S4.2: Take any time as the center time of the image;

[0094] Step S4.3: Calculate the maximum azimuth angle during the target observation imaging time based on the azimuth scanning angle range required for target observation and the azimuth observation angle of the satellite relative to the target at the center time;

[0095] Step S4.4: Use the extreme values ​​of the azimuth observation angles as threshold values ​​to determine and filter out the available observation center times.

[0096] Step S5: Calculate the start and end times of each target observation based on the wave position parameter information to form an observation time array, as follows:

[0097] Step S5.1: Obtain the PRF value, dwell pulse number, azimuth scanning angle range, and scanning step value based on the target wave position parameter information;

[0098] Step S5.2: Calculate the imaging duration for each target;

[0099] Step S5.3: Calculate the start and end times of observation for each target based on the imaging center time and imaging duration;

[0100] Step S5.4: Round the start and end times to ensure that the interval between the two imaging operations is greater than the control requirement of the set time.

[0101] Step S5.5: Generate the observation time array for each target.

[0102] Step S6: Sort the targets in chronological order of their start times, select the smallest imaging start time, and determine it as the first observation target, forming an array of observable target sequences, as follows:

[0103] Step S6.1: Find the smallest imaging start time from the observation time array and determine the target at the corresponding position as the first observation target;

[0104] Step S6.2: Based on the imaging start time, form an observable target sequence array and record the corresponding target number, the corresponding imaging start time and end time.

[0105] Step S7: Use the imaging end time of the last target in the observable target sequence as the time reference value for the next screening.

[0106] Step S8: Remove the observable targets that have completed the planning, and continue to select targets that meet the time sorting from the remaining target time array and determine them as the next observation targets, until the remaining target times no longer meet the time conflict judgment, as follows:

[0107] Step S8.1: Remove observable targets that have already been planned;

[0108] Step S8.2: Continue to search for the smallest imaging start time that is greater than the time decision reference value from the remaining target time array, and determine the target at the corresponding position as the next observation target;

[0109] Step S8.3: Continue until the remaining time of the target to be observed does not meet the time conflict decision.

[0110] Step S9: Generate multi-target observation planning results, specifically: generate corresponding observable target numbers based on the observable target sequence array; generate imaging start and end times corresponding to the observable targets based on the observable target sequence array, for use in SAR satellite power-on / off imaging control; obtain the scanning angle range and corresponding wavefront parameters corresponding to the observable targets based on the observable target sequence array, for use in SAR satellite imaging parameter settings.

[0111] More specifically, the main contents of this invention are as follows:

[0112] 1. Agile directional observation mode

[0113] To fully utilize the two-dimensional large scanning angle characteristics of planar active phased array antennas, especially the large azimuth scanning, continuous multi-target observation can be achieved through forward-looking, side-looking, and backward-looking imaging. (See also...) Figure 2 During a single flight, there are a large number of targets to be observed. Given that the targets are close in azimuth and far in distance, the SAR antenna's azimuth scanning capability can be utilized to achieve dense observation of multiple target clusters during a single flight by using forward-looking, side-looking, and backward-looking methods.

[0114] 2. Azimuth-oriented large scan

[0115] To achieve high-resolution Earth observation, high-resolution SAR satellites need to transmit wide-range signals to achieve high range resolution, and simultaneously accumulate Doppler bandwidth through large azimuth scanning to achieve high azimuth resolution. Therefore, azimuth-agile observation mode is a characteristic and advantage of high-resolution SAR satellites. Large azimuth scanning capability can be achieved through satellite attitude control or through active phased array electronic scanning. The former has lower control efficiency and accuracy, failing to meet the application requirements of agile observation mode. The latter, employing an active phased array antenna, can quickly and accurately switch between different azimuth angles, which is a fundamental condition for improving the performance of azimuth-agile observation mode and an important trend for future development.

[0116] 3. Spaceborne SAR Imaging Control

[0117] The azimuth-agile observation mode is mainly used for high-resolution, high-resolution observations, generally based on spotlight imaging or sliding spotlight imaging modes for multi-target observations at different angles. Addressing the drawback of long on / off intervals (approximately 60 seconds) between previous single imaging sessions, and to meet the application requirements of dense multi-target observations during a single flight, high-resolution SAR satellites have designed a working mode that allows for multiple imaging sessions with a single power-on. The time interval between images within the same imaging mode can be controlled to be 10 ms to 10 seconds, fully adapting to the short and unequal imaging intervals characteristic of the azimuth-agile observation mode, effectively avoiding the problem of missed targets due to long on / off intervals.

[0118] 4. Space-to-Ground Geometric Model

[0119] The spaceborne SAR antenna is fixedly mounted to the satellite body, with its azimuth aligned with the satellite's flight direction. The satellite uses a ground-fixed coordinate system (WGS-84) as a reference, with the Earth's center as the origin, and the satellite-ground geometric relationship is referenced. Figure 3 As shown. The black dot represents the target to be observed, where θ represents the satellite's azimuth angle relative to the target. V represents the observation angle of the satellite relative to the target (i.e., the corresponding wave position angle), V represents the satellite's flight velocity vector, R represents the slant range vector from the target to the satellite, and H represents the distance vector from the Earth's center to the satellite.

[0120] In the WGS-84 coordinate system, let the position value of a certain target to be observed be (x... p ,y p ,z p The satellite's position and velocity values ​​at any given time are (x, y, x) and (v, v), respectively. x ,v y ,x z Taking the direction of satellite flight as the positive observation azimuth, the V vector, R vector, and H vector are respectively expressed as V = (v x ,v y ,x z ), R = (x p -x,y p -y,z p -z), H=(-x,-y,-z), the formulas for calculating the downward angle and azimuth angle of the satellite relative to the target at any given time are:

[0121]

[0122]

[0123] 5. Task planning algorithm

[0124] In the azimuth-agile observation mode, using the target location information and satellite orbital position prediction information as inputs, and combining specific wavefront parameters, the system plans and designs the sequence and time periods for multi-target detection in a single flight, based on the principles of SAR satellite field of view reachability, time conflict-free operation, and maximizing detection capability. It also employs a method of sequentially selecting the minimum imaging start time and ranking the time for each step to improve planning efficiency and meet the required timeliness. (Refer to...) Figure 4 The specific algorithm steps are as follows:

[0125] 1) Obtain target location information and satellite orbit prediction information, convert them to the WGS-84 coordinate system, and interpolate the satellite position and velocity values;

[0126] 2) Calculate the downward angle of each target observation based on the target position value, satellite position value, and velocity value, and obtain the corresponding wavefront parameters (including PRF, scan angle range, number of dwell pulses, etc.);

[0127] 3) Calculate the azimuth angle of the satellite relative to the target at any given moment based on the target position value, satellite position value, and velocity value;

[0128] 4) Select available observation center times based on the maximum scanning capability of SAR satellites and the scanning angle required for target observation;

[0129] 5) Calculate the start and end times of each target observation based on the wave position parameters, and round the start and end times according to the 10ms step value to meet the control requirement that the interval between two imaging is greater than 10ms, thus forming an observation time array;

[0130] 6) Select the smallest imaging start time from the observation time array of all targets to be observed, and determine that target as the first observation target to form an observable target sequence;

[0131] 7) Use the imaging end time of the last target in the observable target sequence as the time reference value for the next screening;

[0132] 8) Remove observable targets, continue to select the smallest imaging start time greater than the time reference value from the remaining target time array, and determine it as the next observation target, until the remaining target time does not meet the time conflict decision.

[0133] The algorithm described in this invention is used for multi-target mission planning, design, and calculation in a azimuth-agile observation mode, with target position, satellite orbital position, and velocity prediction information referenced. Figures 5 to 6 And Table 1. Based on the calculation results, under the requirements of 0.3m / 5km observation resolution and swath width, a maximum of 5 targets can be observed in a single flight. For specific planning results, please refer to Table 1. Figure 7With an observation resolution of 0.5m / 3.5km and a swath width requirement, a maximum of 11 targets can be observed in a single flight. For specific planning results, please refer to... Figure 8 Referring to Table 1, the 15 targets are geographically dispersed. If a frontal and side-view observation is adopted, and the target is required to be in the center of the scene, only one target can be observed on the ground in a single flight. In comparison, the agile azimuth observation mode and the algorithm proposed in this plan can greatly improve the observation efficiency.

[0134] Table 1

[0135]

[0136] In summary, the multi-target mission planning method of the SAR satellite azimuth agile observation mode of the present invention mainly utilizes the SAR satellite's large azimuth scanning capability and flexible imaging start-up control capability to complete the SAR satellite's single-pass flight over densely distributed target observation mission planning. It solves the optimization problem under the combination of frontal side-view, forward oblique view, and backward oblique view, maximizes the number of observed targets, greatly improves the observation efficiency of active phased array SAR satellites, and meets the normalized, high-frequency, and effective application of the current SAR satellite azimuth agile observation mode for multi-target observation in a single flight.

[0137] This invention also discloses a multi-target mission planning system for SAR satellite azimuth agile observation mode, comprising the following modules:

[0138] Module M1: Acquires the position information of the target to be observed and the predicted satellite position information, and unifies the target and satellite position information data into the same coordinate system;

[0139] Module M2: Calculates the downward viewing angle of each observed target and obtains the corresponding wavefront parameters;

[0140] Module M3: Calculates the azimuth observation angle of the satellite relative to all the targets to be observed at any given time;

[0141] Module M4: Filters the available observation center times based on the maximum scanning capability of SAR satellites and the scanning angle required for target observation;

[0142] Module M5: Calculates the start and end times of observations for each target based on wave position parameter information, forming an observation time array;

[0143] Module M6: Sorts the targets according to their starting time to form an array of observable target sequences;

[0144] Module M7: Uses the imaging end time of the last target in the observable target sequence as the time reference value for the next screening;

[0145] Module M8: Remove observable targets that have completed planning, continue to select targets that meet the time sorting from the remaining target time array, and determine them as the next observation targets, until the remaining target times do not meet the time conflict judgment.

[0146] Module M9: Generates multi-objective observation planning results.

[0147] Those skilled in the art will understand that, besides implementing the system and its various devices, modules, and units provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices, modules, and units of this invention function in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices, modules, and units provided by this invention can be considered as a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices, modules, and units for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0148] 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 multi-target mission planning method for a SAR satellite azimuth-agile observation mode, characterized in that, Includes the following steps: Step S1: Obtain the position information of the target to be observed and the predicted satellite position information, and unify the target and satellite position information data into the same coordinate system; Step S2: Calculate the downward viewing angle of each observed target and obtain the corresponding wavefront parameters; Step S3: Calculate the azimuth observation angle of the satellite relative to all the targets to be observed at any given time; Step S4: Select the available observation center time based on the maximum scanning capability of the SAR satellite and the scanning angle required for target observation; Step S5: Calculate the start and end times of each target observation based on the wave position parameter information to form an observation time array; Step S6: Sort the targets according to their starting time to form an array of observable targets; Step S7: Use the imaging end time of the last target in the observable target sequence as the time reference value for the next screening; Step S8: Remove the observable targets that have completed the planning, continue to select targets that meet the time sorting from the remaining target time array, and determine them as continuous observation targets, until the remaining target time does not meet the time conflict judgment. Step S9: Generate multi-objective observation planning results.

2. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S1 includes the following sub-steps: Step S1.1: Obtain the location information of the target to be observed, including latitude, longitude and elevation information, and convert the location information of the target to be observed into location information in the WGS-84 coordinate system; Step S1.2: Obtain satellite orbit position prediction information over a period of time, convert the predicted satellite position data into position information in the WGS-84 coordinate system, and perform interpolation processing on the satellite position information.

3. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S2 includes the following sub-steps: Step S2.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system; Step S2.2: Calculate the downward angle of the satellite relative to each target based on the position information of the target to be observed and the satellite orbit position prediction information; Step S2.3: Select the nearest wave positions corresponding to each target under test based on the calculated downward angle and obtain the wave position information, including PRF value, azimuth scan angle range required for observation and number of dwell pulses.

4. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S3 includes the following sub-steps: Step S3.1: Establish a satellite-ground geometric model in the WGS-84 coordinate system; Step S3.2: Calculate the azimuth observation angle of the satellite relative to all the targets at any given time based on the satellite orbit prediction position information and the position information of each target to be observed.

5. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S4 includes the following sub-steps: Step S4.1: Determine the limit value of the azimuth observation angle based on the maximum azimuth scanning capability of the SAR satellite; Step S4.2: Take any time as the center time of the image; Step S4.3: Calculate the maximum azimuth angle during the target observation imaging time based on the azimuth scanning angle range required for target observation and the azimuth observation angle of the satellite relative to the target at the center time; Step S4.4: Use the extreme values ​​of the azimuth observation angles as threshold values ​​to determine and filter out the available observation center times.

6. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S5 includes the following sub-steps: Step S5.1: Obtain the PRF value, dwell pulse number, azimuth scanning angle range, and scanning step value based on the target wave position parameter information; Step S5.2: Calculate the imaging duration for each target; Step S5.3: Calculate the start and end times of observation for each target based on the imaging center time and imaging duration; Step S5.4: Round the start and end times to ensure that the interval between the two imaging operations is greater than the control requirement of the set time. Step S5.5: Generate the observation time array for each target.

7. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S6 includes the following sub-steps: Step S6.1: Find the smallest imaging start time from the observation time array and determine the target at the corresponding position as the first observation target; Step S6.2: Based on the imaging start time, form an observable target sequence array and record the corresponding target number, the corresponding imaging start time and end time.

8. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S8 includes the following sub-steps: Step S8.1: Remove observable targets that have already been planned; Step S8.2: Continue to search for the smallest imaging start time that is greater than the time decision reference value from the remaining target time array, and determine the target at the corresponding position as the next observation target; Step S8.3: Continue until the remaining time of the target to be observed does not meet the time conflict decision.

9. The multi-target mission planning method for SAR satellite azimuth-agile observation mode according to claim 1, characterized in that: Step S9 includes the following sub-steps: Step S9.1: Generate the corresponding observable target sequence number based on the observable target sequence array; Step S9.2: Based on the observable target sequence array, generate the imaging start time and end time corresponding to the observable targets for use in SAR satellite power-on / off imaging control; Step S9.3: Based on the observable target sequence array, obtain the scanning angle range and corresponding wavefront parameters corresponding to the observable targets for SAR satellite imaging parameter setting.

10. A multi-target mission planning system for a SAR satellite azimuth-agile observation mode, characterized in that: Includes the following modules: Module M1: Acquires the position information of the target to be observed and the predicted satellite position information, and unifies the target and satellite position information data into the same coordinate system; Module M2: Calculates the downward viewing angle of each observed target and obtains the corresponding wavefront parameters; Module M3: Calculates the azimuth observation angle of the satellite relative to all the targets to be observed at any given time; Module M4: Filters the available observation center times based on the maximum scanning capability of SAR satellites and the scanning angle required for target observation; Module M5: Calculates the start and end times of observations for each target based on wave position parameter information, forming an observation time array; Module M6: Sorts the targets according to their starting time to form an array of observable target sequences; Module M7: Uses the imaging end time of the last target in the observable target sequence as the time reference value for the next screening; Module M8: Remove observable targets that have completed planning, continue to select targets that meet the time sorting from the remaining target time array, and determine them as the next observation targets, until the remaining target times do not meet the time conflict judgment. Module M9: Generates multi-objective observation planning results.

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