Method for multi-parameter joint agile design of spaceborne sar in large elliptical orbit and storage medium

Abstract

The present disclosure relates to a large elliptical orbit satellite SAR multi-parameter joint maneuvering design method and a storage medium. The joint maneuvering parameters include distance beam pointing, pulse repetition frequency, echo sampling start time and echo sampling point number. The method comprises: determining the motion characteristics of the satellite by analyzing the basic parameters of the large eccentric orbit and the working time of the satellite; determining the distance beam pointing maneuvering law according to the imaging swath position; designing the pulse repetition frequency time maneuvering law; obtaining the sampling start time and sampling point number time maneuvering law. Through the embodiments of the present disclosure, the SAR satellite can accurately obtain the radar echo data of the imaging area, and reduce the subsequent data processing difficulty and system data rate of the SAR satellite.

Description

Technical Field

[0001] This disclosure relates to a synthetic aperture radar parameter design method for high-resolution wide-scan imaging of the ground in the field of microwave remote sensing, specifically to a multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit and a computer-readable storage medium. Background Technology

[0002] In existing technologies, in highly elliptical orbit spaceborne SAR (Synthetic Aperture Radar), the large eccentricity causes continuous changes in satellite orbital altitude and relative velocity between the satellite and the ground during the radar imaging process. Traditional fixed-parameter design methods for spaceborne SAR pose significant challenges to the accurate and efficient acquisition of SAR echo data in highly eccentric orbits. First, the continuous changes in orbital altitude will significantly alter the geometric relationship between the satellite and the mapping zone. Fixed range beam pointing will lead to deviations in the illumination direction of the spaceborne SAR radar beam, thereby drastically reducing the radiometric quality of the SAR image. Simultaneously, when acquiring ground radar echo data, the continuous changes in satellite velocity result in non-uniform sampling of azimuth signals in the fixed pulse repetition frequency (PRF) transceiver system, significantly increasing the difficulty of subsequent SAR imaging processing and reducing azimuth focusing effectiveness. Furthermore, changes in orbital altitude during radar echo data acquisition cause significant range migration in the echo data. Traditional fixed sampling start and sampling point number data acquisition methods will inevitably lead to an increase in invalid data and a significant increase in data rate, severely impacting the efficiency of spaceborne SAR data acquisition. Therefore, the traditional parameter design methods for circular orbit spaceborne SAR systems are no longer applicable to the design of SAR systems with large eccentricity orbits. Summary of the Invention

[0003] This disclosure aims to provide a multi-parameter joint agile design method for spaceborne SAR in a highly elliptical orbit and a computer-readable storage medium, which enables SAR satellites to accurately acquire radar echo data of the imaging area, reducing the difficulty of subsequent data processing and the system data rate.

[0004] According to one of the solutions disclosed herein, a multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit is provided. The joint agility parameters include range beam pointing, pulse repetition frequency, echo sampling start time, and number of echo sampling points. The method includes: By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined. Determine the range beam pointing agility law based on the location of the imaging mapping zone; Design the pulse repetition frequency to change abruptly over time; The agility of the sampling start time and the number of sampling points over time was obtained.

[0005] In some embodiments, the determination of the satellite's motion characteristics by analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time includes: Calculate the satellite's orbital period; Calculate the pericentric angle; Calculate the time-varying true centripetal angle of large eccentricity orbit SAR; Determine the satellite's altitude; Calculate the satellite velocity in a spaceborne SAR in a highly elliptical orbit.

[0006] In some embodiments, determining the range beam pointing agility rule based on the location of the imaging mapping strip includes: calculating the range beam scanning angle based on the satellite altitude.

[0007] In some embodiments, designing the pulse repetition frequency to vary with time includes: The pulse repetition frequency at the initial moment is obtained; The parameters are obtained based at least on the change in pulse repetition frequency from the start time to the end time, which represent the number of times the pulse repetition frequency needs to be reset during the entire observation period. Based at least on the satellite velocity in a highly elliptical orbit spaceborne SAR, the velocity change for each variation sequence is obtained; A reset operation is performed after the pulse repetition frequency reaches a predefined threshold to ensure that the change in pulse repetition frequency remains within an acceptable range, thereby maintaining the quality of radar signal sampling.

[0008] In some embodiments, the initial pulse repetition frequency is obtained based on the satellite's reference velocity and azimuth antenna length; the parameter is obtained based on the change in pulse repetition frequency from the initial time to the final time, the initial pulse repetition frequency, and a threshold, which is at least related to the degrees of freedom selectable for the pulse repetition frequency.

[0009] In some embodiments, the reset operation after the pulse repetition frequency reaches a predefined threshold includes: Obtain the pulse repetition frequency at any given time; If the pulse repetition frequency at any time exceeds the threshold condition, the pulse repetition frequency at any time is reset to the pulse repetition frequency at the starting time.

[0010] In some embodiments, determining whether the pulse repetition frequency at any given time exceeds the threshold condition includes: Obtain the absolute value of the difference between the pulse repetition frequency at any given time and the pulse repetition frequency at the beginning time; Determine whether the ratio of this absolute value to the pulse repetition frequency at the start time is greater than the threshold.

[0011] In some embodiments, where the absolute value is less than the threshold, the variation in the pulse repetition frequency at any given time remains within an acceptable range.

[0012] In some embodiments, obtaining the agility of the sampling start time and the number of sampling points over time includes: Calculate the near-end slope angle to the geocentric angle and the far-end slope angle to the geocentric angle; Calculate the near-end slope distance and the far-end slope distance; Calculate the start time of the time-varying distance-direction sampling; Calculate the time-varying number of sampling points.

[0013] According to one of the solutions of this disclosure, a computer-readable storage medium is provided, having stored thereon computer-executable instructions, which, when executed by a processor, implement: Based on the above-mentioned multi-parameter joint agility design method for spaceborne SAR in highly elliptical orbits.

[0014] This disclosure presents various embodiments of a multi-parameter joint agility design method for spaceborne SAR in highly elliptical orbits, along with a computer-readable storage medium. The joint agility parameters include range beam pointing, pulse repetition frequency (PRF), echo sampling start time, and the number of echo sampling points. The method determines the satellite's motion characteristics by analyzing the basic parameters of the highly eccentric orbit and the satellite's operating time. It determines the range beam pointing agility law based on the imaging mapping zone location. It designs the pulse repetition frequency agility law over time and obtains the agility laws for the sampling start time and the number of sampling points over time. Therefore, for the orbital characteristics of highly elliptical orbit SAR satellites, it achieves accurate illumination of the mapping zone through agility design of the range beam scanning angle, reduces the non-uniformity of azimuth signal sampling caused by satellite velocity changes through agility design of the pulse repetition frequency (PRF), and improves the accuracy of echo data sampling and reduces the instantaneous data rate of the SAR satellite through agility design of the radar echo sampling start time and the number of sampling points. The embodiments of this disclosure not only enable SAR satellites to accurately acquire radar echo data of the imaging area, but also help reduce the difficulty of subsequent data processing and the system data rate of SAR satellites through multi-parameter joint agility design.

[0015] It should be understood that the foregoing general description and the following detailed description are exemplary and illustrative only, and are not intended to limit the scope of this disclosure. Attached Figure Description

[0016] In drawings that are not necessarily drawn to scale, similar reference numerals in different views may indicate similar components. Similar reference numerals with letter suffixes or similar reference numerals with different letter suffixes may indicate different instances of similar components. The drawings are generally used to illustrate various embodiments by way of example rather than limitation, and are used together with the specification and claims to explain the disclosed embodiments.

[0017] Figure 1 A flowchart of a multi-parameter joint agile design method for spaceborne SAR in a highly elliptical orbit, according to an embodiment of this disclosure, is shown. Figure 2 A signal processing flowchart according to an embodiment of this disclosure is shown; Figure 3 A schematic diagram of the elliptical cross section of a spaceborne SAR in a highly elliptical orbit is shown. Figure 4 A flowchart illustrating a reset operation after the pulse repetition frequency reaches a predefined threshold, according to an embodiment of this disclosure, is shown. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0019] In conjunction with the preceding background section, this disclosure provides illustrative examples of solutions to address the deficiencies in the prior art, but these are not intended to limit the scope of patent protection claimed in this disclosure.

[0020] Spaceborne synthetic aperture radar (SAR) is a primary means of spaceborne Earth observation, capable of providing high-resolution, all-weather, all-day imaging of surface targets, and has wide applications in the civilian sector. Due to the unique orbital characteristics of highly elliptical orbits, spaceborne SAR in these orbits can not only achieve long-term, large-area continuous observation of regions of interest at higher orbits, but also provide high-resolution, high-signal-to-noise ratio imaging of targets at lower orbits. Therefore, highly elliptical orbit SAR satellites combine the large-area coverage and continuous imaging capabilities of medium / high orbit SAR satellites with the fine-grained perception capabilities of low orbit SAR satellites in key areas, significantly enhancing their ability to respond to differentiated observations. This capability gives highly elliptical orbit SAR satellites a significant advantage in handling complex and variable geographical environments and addressing diverse mission requirements. However, the orbital altitude and relative velocity between the satellite and the ground of highly elliptical orbit SAR satellites change continuously over time, posing challenges to the accurate and efficient acquisition of radar echo data.

[0021] In light of the preceding content, and to overcome some of the aforementioned technical shortcomings, as one possible solution is... Figure 1 and Figure 2 As shown, embodiments of this disclosure provide a multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit. The joint agility parameters include range beam pointing, pulse repetition frequency, echo sampling start time, and the number of echo sampling points. The method includes: S1: By analyzing the basic parameters of the large eccentricity orbit and the satellite's working time, the satellite's motion characteristics are determined; S2: Determine the range beam pointing agility law based on the location of the imaging mapping zone; S3: Design the pulse repetition frequency to change agilely with time; S4: Obtain the agility pattern of the sampling start time and the number of sampling points over time.

[0022] To address the problems mentioned above, the embodiments of this disclosure aim to propose a multi-parameter joint agility system design method based on a highly elliptical orbit spaceborne SAR. The parameters for joint agility include range beam pointing, PRF, echo sampling start time, and the number of echo sampling points. The embodiments of this disclosure first calculate the altitude and velocity changes of the highly elliptical orbit SAR based on the six orbital elements; then, based on the imaging geometry, determine the range beam pointing agility mode to ensure that the range beam center is always aligned with the mapping zone; then, based on the satellite orbit velocity variation law, design the system PRF agility mode; finally, based on the time-varying geometric relationship between the satellite and the mapping zone, design the agility mode for the range sampling start and the number of sampling points of the radar echo signal.

[0023] By employing agile design of the range beam scanning angle to achieve accurate illumination of the mapping zone, agile design of the pulse repetition frequency (PRF) to reduce the non-uniformity of azimuth signal sampling caused by satellite velocity changes, and agile design of the radar echo sampling start time and number of sampling points to improve the accuracy of echo data sampling and reduce the instantaneous data rate of the SAR satellite, combined with the method exemplified in steps S1 to S4, the embodiments of this disclosure not only enable the SAR satellite to accurately acquire radar echo data of the imaging area, but also the multi-parameter joint agile design helps to reduce the difficulty of subsequent data processing and the system data rate of the SAR satellite.

[0024] In some implementations, the method of this disclosure may include: determining the satellite's motion characteristics by analyzing the basic parameters of a large eccentricity orbit and the satellite's operating time, including: Calculate the satellite's orbital period; Calculate the pericentric angle; Calculate the time-varying true centripetal angle of large eccentricity orbit SAR; Determine the satellite's altitude; Calculate the satellite velocity in a spaceborne SAR in a highly elliptical orbit.

[0025] For example, in combination Figure 3 The schematic diagram shown is of the elliptical cross section of a spaceborne SAR in a highly elliptical orbit. The specific implementation of the method step S1 in this embodiment may include steps S11 to S15.

[0026] Step S1: By analyzing the six basic parameters of the large eccentricity orbit and the satellite's working time, the satellite's motion characteristics are determined in detail. The specific processing steps are as follows.

[0027] Step S11: Calculate the satellite's orbital period T .

[0028] Operating time of spaceborne SAR ,in and These represent the start and end times of echo acquisition, respectively. A reference time point is also set. This time point corresponds to the moment when the satellite passes a specific location on its orbit. (1), Among them, parameters α The semi-major axis representing the elliptical orbit. is the Kepler constant.

[0029] Step S12: Calculate the pericentric angle E : (2), in, eThe eccentricity of a spaceborne SAR in a highly elliptical orbit is given. This nonlinear equation is typically solved using an approximate iterative method, as follows: (3).

[0030] Step S13: Calculate the time-varying true pericentric angle of the large eccentricity orbit SAR. : (4).

[0031] Step S14: Based on the true proximal angle The value determines the satellite altitude : (5), During the operation of a spaceborne SAR satellite in a highly elliptical orbit, the satellite's altitude is not constant but changes over time. During the satellite's operational period... In the calculation, the satellite altitude at the initial moment is as follows: (6), in, And the true pericentric angle representing the initial moment.

[0032] Step S15: Calculate the satellite velocity in a highly elliptical orbit spaceborne SAR : (7), The satellite velocity at the initial moment is calculated as follows: It is also set as the reference velocity for satellites: (8).

[0033] In some implementations, the method of this disclosure may be: determining the range beam pointing agility law based on the location of the imaging mapping zone, including: calculating the range beam scanning angle based on the satellite altitude.

[0034] For example, a specific implementation of method step S2 in this embodiment may include: Step S2: Determine the range beam pointing agility law based on the imaging mapping zone position, and calculate the range beam scanning angle. : (9), Among them, the geocentric angle is Known It is the Earth's radius. This refers to the ground distance. During operation in an elliptical orbit, the range beam scanning angle changes accordingly as the satellite's altitude changes.

[0035] In some implementations, the method of this disclosure may include: designing a pulse repetition frequency that varies with time, including: The pulse repetition frequency at the initial moment is obtained; The parameters are obtained at least based on the change in pulse repetition frequency from the start time to the end time. It represents the number of times the pulse repetition frequency needs to be reset during the entire observation period; Based at least on the satellite velocity in a highly elliptical orbit spaceborne SAR, the velocity change for each variation sequence is obtained; A reset operation is performed after the pulse repetition frequency reaches a predefined threshold to ensure that the change in pulse repetition frequency remains within an acceptable range, thereby maintaining the quality of radar signal sampling.

[0036] For example, a specific implementation of method step S3 in this embodiment may include steps S31 to S34.

[0037] Step S3: Design the pulse repetition frequency (PRF) as a time-dependent variable. The specific processing steps are as follows.

[0038] Step S31: The initial pulse repetition frequency can be obtained based on the satellite's reference velocity and azimuth antenna length. For example, this embodiment calculates the initial pulse repetition frequency. It can be: (10), Among them, the azimuth antenna length is known. The oversampling rate is typically between 1.3 and 1.8 under spaceborne SAR conditions. , parameter It is obtained based on the change in pulse repetition frequency from the start time to the end time, the pulse repetition frequency at the start time, and a threshold, which is at least related to the degrees of freedom that the pulse repetition frequency can be selected.

[0039] Step S32: Parameters This is derived from the change in pulse repetition frequency from the start time to the end time, the pulse repetition frequency at the start time, and a threshold, which is at least related to the degrees of freedom for selecting the pulse repetition frequency. For example, the calculation parameters... The specific processing steps are as follows.

[0040] Step S321: Calculate the change in PRF from the start time to the end time. : (11).

[0041] Step S322: Calculate parameters : (12), in, This indicates rounding up, with a known threshold. The purpose of this threshold is to ensure that the variation in PRF remains within an acceptable range. This threshold is primarily related to the degrees of freedom selectable for the PRF in the zebra plot and is typically set between 5% and 20%. In some embodiments, 10% can be chosen as the threshold. .

[0042] Step S323: Determine the speed of the first... n PRF change sequence parameters n : (13), in, This represents the rounding operation.

[0043] Step S33: Calculate the velocity change for each changing sequence. : (14), in, This represents taking the remainder, because the remainder of a negative number is also a positive number. Hengzheng.

[0044] In some implementations, the method of this disclosure may include: performing a reset operation after the pulse repetition frequency reaches a predefined threshold, including: Obtain the pulse repetition frequency at any given time; If the pulse repetition frequency at any time exceeds the threshold condition, the pulse repetition frequency at any time is reset to the pulse repetition frequency at the starting time.

[0045] In some implementations, the method of this disclosure may include: determining whether the pulse repetition frequency at any given time exceeds the condition defined by the threshold, including: Obtain the absolute value of the difference between the pulse repetition frequency at any given time and the pulse repetition frequency at the beginning time; Determine whether the ratio of this absolute value to the pulse repetition frequency at the start time is greater than the threshold.

[0046] Based on step S33 above, it can be combined with Figure 4 This diagram illustrates a reset operation after the pulse repetition frequency reaches a predefined threshold, which is repeated throughout the imaging process in step S34 to ensure high quality and consistency of radar signal sampling.

[0047] Step S34: Reset operation after PRF reaches a predefined threshold to ensure that the change of PRF remains within an acceptable range, thereby maintaining the quality of radar signal sampling. The specific process is as follows.

[0048] Step S341: Calculate the pulse repetition frequency at any given time. : (15), in, As the satellite's orbital altitude gradually increases, its speed will decrease accordingly. Conversely, as the satellite's orbital altitude gradually decreases, its speed increases due to gravitational acceleration. .

[0049] Step S342: Use the following formula to determine the calculated Does it exceed the set threshold? ,if The following conditions must be met: (16), but The change did not exceed the threshold. The changes are kept within an acceptable range. if The following conditions must be met: (17), but The change exceeds the threshold , Reset to the value at the start time .

[0050] In some implementations, the method of this disclosure can be: obtaining the agility pattern of the sampling start time and the number of sampling points over time, including: Calculate the near-end slope angle to the geocentric angle and the far-end slope angle to the geocentric angle; Calculate the near-end slope distance and the far-end slope distance; Calculate the start time of the time-varying distance-direction sampling; Calculate the time-varying number of sampling points.

[0051] For example, a specific implementation of method step S4 in this embodiment may include steps S41 to S44.

[0052] Step S4: Calculate the agility of the sampling start time and the number of sampling points over time. The specific processing steps are as follows.

[0053] Step S41: Calculate the near-end slope distance from the geocentric angle and the far-end slope angle to the geocentric point : (18), Among them, it is known It is the ground distance. It refers to the width of the radar's mapping band.

[0054] Step S42: Calculate the proximal slope distance and distal slant distance for: (19), in, The radius is the Earth's radius.

[0055] Step S43: Calculate the time-varying distance-direction sampling start time. : (20), in, c It's the speed of light.

[0056] Step S44: Calculate the number of time-varying sampling points : (twenty one), in, It is a known pulse width. This is the number of additional sampling points, typically 256 points.

[0057] Compared with existing design methods, the multi-parameter joint agile design method for spaceborne SAR in highly elliptical orbits disclosed in various embodiments has the following advantages: 1) The methods of the various embodiments of this disclosure overcome the problem that the altitude and velocity of large eccentric orbit spaceborne SAR will change significantly throughout the imaging process. By agilely changing the range beam scanning angle, the mapping zone and the imaging area can be matched, ensuring that the mapping zone always matches the imaging area, effectively overcoming the problem of mismatch between the mapping zone and the target area in large eccentric orbit spaceborne SAR. 2) By jointly adjusting multiple parameters and optimizing parameters such as pulse repetition frequency, sampling start, and number of sampling points, the non-uniform sampling problem in spaceborne SAR with highly elliptical orbits is solved. The design methods of the various embodiments of this disclosure can not only effectively eliminate excessive invalid data and reduce the complexity of data processing, but also significantly improve the efficiency of data processing and imaging quality; 3) It has excellent adaptability, and can dynamically adjust various parameters according to actual observation needs and environmental conditions, enabling the system to achieve excellent performance in different operating modes. This allows large eccentric orbit spaceborne SAR to adapt to a wider range of application scenarios, such as resource exploration and disaster monitoring.

[0058] As one solution, embodiments of this disclosure provide a multi-parameter joint agile design device for spaceborne SAR in a highly elliptical orbit, comprising one or more design modules configured as follows: By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined. Determine the range beam pointing agility law based on the location of the imaging mapping zone; Design the pulse repetition frequency to change abruptly over time; The agility of the sampling start time and the number of sampling points over time was obtained.

[0059] As one implementation method, one or more design modules of this disclosure are further configured as follows: By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined, including: Calculate the satellite's orbital period; Calculate the pericentric angle; Calculate the time-varying true centripetal angle of large eccentricity orbit SAR; Determine the satellite's altitude; Calculate the satellite velocity in a spaceborne SAR in a highly elliptical orbit.

[0060] As one implementation, one or more design modules of this disclosure are further configured to: determine the range beam pointing agility law based on the position of the imaging mapping zone, including: calculating the range beam scanning angle based on the satellite altitude.

[0061] As one implementation method, one or more design modules of this disclosure are further configured to: design the pulse repetition frequency as a function of time agility, including: The pulse repetition frequency at the initial moment is obtained; The parameters are obtained at least based on the change in pulse repetition frequency from the start time to the end time. It represents the number of times the pulse repetition frequency needs to be reset during the entire observation period; Based at least on the satellite velocity in a highly elliptical orbit spaceborne SAR, the velocity change for each variation sequence is obtained; A reset operation is performed after the pulse repetition frequency reaches a predefined threshold to ensure that the change in pulse repetition frequency remains within an acceptable range, thereby maintaining the quality of radar signal sampling.

[0062] As one implementation, one or more design modules of this disclosure are further configured as follows: the pulse repetition frequency at the start time is obtained based on the satellite's reference velocity and the azimuth antenna length; parameter It is obtained based on the change in pulse repetition frequency from the start time to the end time, the pulse repetition frequency at the start time, and a threshold, which is at least related to the degrees of freedom that the pulse repetition frequency can be selected.

[0063] As one implementation, one or more design modules of this disclosure are further configured to: perform a reset operation after the pulse repetition frequency reaches a predefined threshold, including: Obtain the pulse repetition frequency at any given time; If the pulse repetition frequency at any time exceeds the threshold condition, the pulse repetition frequency at any time is reset to the pulse repetition frequency at the starting time.

[0064] As one implementation, one or more design modules of this disclosure are further configured to: determine whether the pulse repetition frequency at any given time exceeds the condition defined by the threshold, including: Obtain the absolute value of the difference between the pulse repetition frequency at any given time and the pulse repetition frequency at the beginning time; Determine whether the ratio of this absolute value to the pulse repetition frequency at the start time is greater than the threshold.

[0065] As one implementation, one or more design modules of this disclosure are further configured such that, when the absolute value is less than the threshold, the change in the pulse repetition frequency at any time remains within an acceptable range.

[0066] As one implementation method, one or more design modules of this disclosure are further configured to: obtain the agility law of sampling start time and number of sampling points over time, including: Calculate the near-end slope angle to the geocentric angle and the far-end slope angle to the geocentric angle; Calculate the near-end slope distance and the far-end slope distance; Calculate the start time of the time-varying distance-direction sampling; Calculate the time-varying number of sampling points.

[0067] In some specific implementations, one or more design modules of this disclosure are configured to perform specific implementations of steps S1 to S4 above.

[0068] Specifically, one of the inventive concepts of this disclosure aims to determine the motion characteristics of a satellite by analyzing at least the basic parameters of a highly eccentric orbit and the satellite's operating time; determine the range beam pointing agility law based on the location of the imaging mapping zone; design the pulse repetition frequency (PRF) agility law over time; and obtain the agility laws of the sampling start time and the number of sampling points over time. Thus, for the orbital characteristics of a highly elliptical orbit SAR satellite, accurate illumination of the mapping zone is achieved through agility design of the range beam scanning angle; non-uniformity of azimuth signal sampling caused by satellite velocity changes is reduced through agility design of the pulse repetition frequency (PRF); and accuracy of echo data sampling and instantaneous data rate of the SAR satellite are improved through agility design of the radar echo sampling start time and the number of sampling points. The embodiments of this disclosure not only enable SAR satellites to accurately acquire radar echo data of the imaging area, but also the multi-parameter joint agility design helps reduce the difficulty of subsequent data processing and the system data rate of the SAR satellite.

[0069] This disclosure also provides a computer-readable storage medium storing computer-executable instructions thereon. When executed by a processor, the computer-executable instructions mainly implement the multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit described above. The parameters of the joint agility include range beam pointing, pulse repetition frequency, echo sampling start time, and number of echo sampling points. The method includes: The parameters of the joint agile beamforming include range beam pointing, pulse repetition frequency, echo sampling start time, and number of echo sampling points; the method includes: By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined. Determine the range beam pointing agility law based on the location of the imaging mapping zone; Design the pulse repetition frequency to change abruptly over time; The agility of the sampling start time and the number of sampling points over time was obtained.

[0070] The above embodiments are merely exemplary embodiments of this disclosure and are not intended to limit this disclosure. The scope of protection of this disclosure is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this disclosure within its substance and scope, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this disclosure.

Claims

1. A multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit, wherein the joint agility parameters include range beam pointing, pulse repetition frequency, echo sampling start time, and number of echo sampling points; the method includes: By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined. Determine the range beam pointing agility law based on the location of the imaging mapping zone; Design the pulse repetition frequency to change abruptly over time; The agility of the sampling start time and the number of sampling points over time was obtained; in, By analyzing the basic parameters of the large eccentricity orbit and the satellite's operating time, the satellite's motion characteristics are determined, including: Calculate the satellite's orbital period; Calculate the pericentric angle; Calculate the time-varying true centripetal angle of large eccentricity orbit SAR; Determine the satellite's altitude; Calculate the satellite velocity in a spaceborne SAR in a highly elliptical orbit; Determining the range beam pointing agility rule based on the location of the imaging mapping zone includes: calculating the range beam scanning angle based on satellite altitude; Design the pulse repetition frequency as a function of time, including: Obtain the pulse repetition frequency at the initial moment; The parameters are obtained at least based on the change in pulse repetition frequency from the start time to the end time. It represents the number of times the pulse repetition frequency needs to be reset during the entire observation period; Based at least on the satellite velocity in a highly elliptical orbit spaceborne SAR, the velocity change for each variation sequence is obtained; A reset operation is performed after the pulse repetition frequency reaches a predefined threshold to ensure that the change in pulse repetition frequency remains within an acceptable range, thereby maintaining the quality of radar signal sampling.

2. The method according to claim 1, wherein, The pulse repetition frequency at the start time is obtained based on the satellite's reference velocity and the azimuth antenna length; parameter It is obtained based on the change in pulse repetition frequency from the start time to the end time, the pulse repetition frequency at the start time, and a threshold, which is at least related to the degrees of freedom that the pulse repetition frequency can be selected.

3. The method according to claim 2, wherein, Perform a reset operation after the pulse repetition frequency reaches a predefined threshold, including: Obtain the pulse repetition frequency at any given time; If the pulse repetition frequency at any time exceeds the threshold condition, the pulse repetition frequency at any time is reset to the pulse repetition frequency at the starting time.

4. The method according to claim 3, wherein, Determining whether the pulse repetition frequency at any given time exceeds the threshold condition includes: Obtain the absolute value of the difference between the pulse repetition frequency at any given time and the pulse repetition frequency at the beginning time; Determine whether the ratio of this absolute value to the pulse repetition frequency at the start time is greater than the threshold.

5. The method according to claim 4, wherein, If the absolute value is less than the threshold, the change in pulse repetition frequency at any given time remains within an acceptable range.

6. The method according to claim 5, wherein, The agility of the sampling start time and the number of sampling points over time was obtained, including: Calculate the near-end slope angle to the geocentric angle and the far-end slope angle to the geocentric angle; Calculate the near-end slope distance and the far-end slope distance; Calculate the start time of the time-varying distance-direction sampling; Calculate the time-varying number of sampling points.

7. A computer-readable storage medium having stored thereon computer-executable instructions, which, when executed by a processor, implement: The multi-parameter joint agility design method for spaceborne SAR in a highly elliptical orbit as described in any one of claims 1 to 6.

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