Distributed formation SAR satellite group multi-angle scattering characteristic spectrum measurement system and method

Abstract

The invention provides a distributed formation SAR satellite group multi-angle scattering characteristic spectrum measurement system and method. The distributed formation SAR satellite group multi-angle scattering characteristic spectrum measurement system comprises a satellite formation subsystem, a load collaborative observation subsystem, a signal processing subsystem and a spectrum construction subsystem, the satellite formation subsystem is used for constructing an initial satellite formation and dynamically reconstructing the initial satellite formation; the load collaborative observation subsystem is used for collaborative observation of multiple satellites on the same area; the signal processing subsystem is used for realizing distributed holographic imaging processing of multi-satellite echo signals; and the map construction subsystem is used for constructing a multi-dimensional space map. According to the invention, through the concentric ring-spiral composite formation configuration and in combination with the real-time dynamic optimization algorithm, continuous full coverage of the azimuth angle and the pitch angle of the three-dimensional space of the ground target is realized, and highly coincident irradiation of multi-star radar beams on the same ground feature area is ensured; the bottleneck of scattering feature capture caused by traditional formation angle discretization is fundamentally broken through.

Description

Technical Field

[0001] This invention relates to the field of spaceborne radar system design and signal processing technology, specifically to a distributed formation SAR satellite swarm multi-angle scattering feature map measurement system and method. Background Technology

[0002] Spaceborne synthetic aperture radar (SAR) is an active microwave imaging sensor based on a satellite platform. It achieves high-resolution range imaging through the transmission of broadband frequency-modulated signals and pulse compression technology, and high-resolution azimuth imaging through azimuth virtual synthetic aperture technology. Spaceborne SAR images contain rich geometric, radiometric, and phase information, making them a primary technique for all-weather, all-day Earth observation. The electromagnetic scattering information acquired is of great significance for resource exploration, environmental monitoring, and military reconnaissance. However, traditional SAR imaging methods have significant limitations: single-satellite or fixed-array systems are limited by the single observation perspective, only able to capture scattering responses at discrete angles, and cannot continuously cover the full-domain scattering characteristics of targets in three-dimensional space; simultaneously, they lack the ability to synchronously extract multi-dimensional physical parameters and suffer from insufficient inter-satellite synchronization accuracy, preventing traditional SAR systems from constructing spatial scattering feature maps of targets. Therefore, researching techniques to achieve comprehensive perception of target spatial scattering characteristics and construct multi-angle scattering feature spatial maps is crucial for improving the performance of SAR systems.

[0003] The paper "First Bistatic Spaceborne SAR Experiments With TanDEM-X" (Rodriguez-Cassola, M. et al. IEEE geoscience and remote sensing letters 9.1(2012): 33–37. Print.) verified the viewing limitations of traditional SAR systems through a two-satellite experiment: the fixed formation configuration leads to discretized sampling of target scattering responses, making continuous three-dimensional spatial coverage impossible. In the experiment, even with only small bistatic angles between satellites, the scattering characteristics of man-made structures showed significant differences, demonstrating that the scattering evolution process is affected by continuous changes in azimuth angle. In the vertical dimension, short baseline constraints severely limit the elevation angle coverage. This result confirms that the discrete sampling mode of the fixed formation system restricts the continuous sensing capability of the target's global scattering characteristics.

[0004] The paper "Water Body Information Extraction Based on GF-3 Fully Polarimetric SAR Index Features" (Song Wei, Shi Mengchen, Yang Yang. Bulletin of Surveying and Mapping, 2025(1):78-82. DOI:10.13474 / j.cnki.11-2246.2025.0113.) proposes a water body information extraction method based on Gaofen-3 (GF-3) imagery of fully polarimetric monostatic SAR. By analyzing the differences in scattering characteristics of different polarization modes (HH, HV, VH, VV), two water body index features are constructed and combined into a new feature image. Combined with object-oriented classification technology, water body extraction is achieved quickly and with high precision. The advantage of this method is that it fully explores the complementarity of fully polarimetric data, significantly improves the ability to distinguish between water bodies and non-water bodies, and effectively solves the problem of confusion between water bodies and similar scattering features in monopolar SAR. However, it does not explicitly utilize the spatial information of azimuth and elevation angles (such as terrain-related features) and does not further explore the monitoring potential of multi-temporal polarimetric features for dynamic water bodies.

[0005] The paper "Research on Polarimetric SAR Target Detection Algorithm Combining Polarimetric Scattering Characteristics and Deep Feature Learning" (Xu Xinyu, Xi'an University of Electronic Science and Technology, 2024. DOI:10.27389 / d.cnki.gxadu.2024.000370.) proposes a polarimetric SAR target detection framework that integrates physical scattering mechanisms and deep learning. In the first stage, a superpixel segmentation method is used to extract rotational domain polarimetric-related features for pre-detection and false alarm suppression. In the second stage, unsupervised anomaly detection and polarimetric scattering characteristics are combined to complete target localization. This approach utilizes rotational domain polarimetric patterns to extract multi-scale features, enhancing target separability, and integrates prior polarimetric features in an unsupervised network to reduce the false alarm rate. This method uses a monostatic backscattering model to extract azimuth information to construct rotationally invariant features and utilizes HH / VV co-polarimetric channels to construct polarimetric features. However, it does not fully utilize elevation angle information and ignores the phase information of cross-polarimetric channels (HV / VH), failing to construct coherent features for fully polarimetric data.

[0006] The patent "A High-Resolution Wide-Swept Imaging Mode Design Method and Device for Multi-Based Spaceborne SAR" (CN202510611248.X) proposes a high-resolution wide-swept imaging method based on a distributed spaceborne SAR system. It constructs a nested spiral orbit constellation (one primary and multiple secondary satellites) and employs a collaborative mechanism of wide-beam transmission from the primary satellite and narrow-beam reception from multiple satellites to achieve high-resolution wide-swept imaging. While this method overcomes the limitations of single-satellite quality factor through a distributed receiving architecture, it only develops the spatial dimension of azimuth through beam control, lacking terrain correlation modeling for elevation angles. Furthermore, it does not develop polarization information based on single-channel data processing, thus limiting its applicability in complex terrain monitoring scenarios.

[0007] The patent "A Polarimetric SAR Change Detection Method, Device, Equipment and Medium" (CN202510713506.5) proposes a polarimetric SAR change detection method based on edge-constrained superpixel segmentation and graph structure energy optimization. It generates an edge intensity map through multi-temporal polarimetric covariance matrix similarity measurement; incorporates edge constraints and feature space similarity into superpixel segmentation to construct clustering criteria; and constructs a graph structure based on the fusion of temporal and cross-temporal features from superpixel blocks, achieving change detection through energy optimization. This method utilizes azimuth information for edge detection and Gaussian window direction control to optimize positioning accuracy, and leverages the statistical characteristics of polarization amplitude in the covariance matrix to quantify matrix differences, reducing regional discontinuities and boundary ambiguity errors in superpixel segmentation. It exhibits strong robustness in natural and complex urban scenes, but its computational complexity is high. Furthermore, it does not utilize the phase information of elevation angle and polarimetric coherence matrix, limiting its ability to discriminate scattering changes.

[0008] In summary, traditional single-satellite or fixed-array systems are limited by their singular observation perspective, failing to continuously cover the full-domain scattering characteristics of three-dimensional space. Furthermore, orbital drift caused by J2 perturbation further restricts the continuous sensing capability of scattering evolution. Moreover, existing technologies have significant shortcomings in multi-dimensional fusion, and the impact of spatial and polarization dimensions on interference scattering has not been fully explored. Therefore, overcoming the limitations of discrete sampling and achieving multi-dimensional fusion of azimuth, elevation, and polarization channels has become a key challenge in improving the full-domain sensing capability of distributed SAR systems. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the purpose of this invention is to provide a system and method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation.

[0010] A distributed SAR satellite constellation multi-angle scattering feature map measurement system according to the present invention includes: a satellite constellation subsystem, a payload collaborative observation subsystem, a signal processing subsystem, and a map construction subsystem; the satellite constellation subsystem is used to construct an initial satellite constellation and dynamically reconstruct it; the payload collaborative observation subsystem is used for collaborative observation of the same area by multiple satellites; the signal processing subsystem is used to realize distributed holographic imaging processing of multi-satellite echo signals; and the map construction subsystem is used to construct a multi-dimensional spatial map.

[0011] Preferably, the satellite formation subsystem consists of a concentric ring-spiral composite formation configuration composed of M launching satellites and N receiving satellites. The concentric ring-spiral composite formation configuration projects as concentric rings onto the vertical trajectory plane and exhibits a spiral-angle topology along the flight path, enabling continuous coverage of multiple azimuth and elevation angles. The formation baseline length of the satellite formation subsystem is dynamically adjustable, with the relative positions of the satellites adjusted in real time through an optimization algorithm to meet minimum safety distance and orbital stability constraints. The formation reconfiguration mechanism of the satellite formation subsystem is used to autonomously switch configuration modes according to observation mission requirements, including along-track baseline, tangential baseline, and multi-baseline combination modes.

[0012] Preferably, in the payload-coordinated observation subsystem, satellite T is equipped with a multi-band fully polarimetric SAR transmitter for signal encoding transmission and adaptive adjustment of pulse repetition frequency; satellite R is equipped with a multi-band fully polarimetric DBF SAR receiver for digital beamforming and coherent signal synthesis; satellite T and satellite R in the payload-coordinated observation subsystem have a time synchronization module, a phase synchronization module, and a beam synchronization module. The time synchronization module is used to compensate for carrier frequency phase noise, the phase synchronization module is used to correct frequency source phase offset, and the beam synchronization module is used to coordinate the attitude and radio beam of the two satellites to achieve overlapping imaging areas of the two satellites.

[0013] Preferably, the signal processing subsystem includes an echo signal separation module, used to achieve echo separation corresponding to different transmitting satellites of the same receiving satellite using digital beamforming and signal coding techniques; the signal processing subsystem includes an imaging processing module, used to perform imaging processing on each echo data using a monostatic / bistatic imaging processing algorithm; the signal processing subsystem includes a multi-angle sub-aperture segmentation module, used to segment the image data into sub-image sets according to azimuth and elevation angles, and extract pixel-level scattering feature parameters.

[0014] Preferably, the map construction subsystem includes a scattering feature extraction module for calculating the scattering direction and scattering amplitude of each imaging unit. The scattering direction is determined by radar observation geometry and external DEM positioning, and the scattering amplitude is determined by the radiometrically corrected SAR image. Scattering coherence angle and scattering amplitude ,in,

[0015]

[0016]

[0017] in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. ; The map construction subsystem includes a multi-dimensional spatial mapping module, which is used to fuse azimuth, elevation, and polarization channel dimensional information to generate a multi-dimensional spatial map.

[0018] The present invention also provides a method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation, comprising: step S1, satellite formation construction and dynamic reconstruction; step S2, multi-satellite collaborative observation and synchronization control; step S3, distributed holographic signal processing; and step S4, multi-dimensional spatial map construction.

[0019] Preferably, the satellite formation construction and dynamic reconstruction includes: Step S1.1, constructing a concentric ring-spiral composite formation configuration, with the vertical trajectory plane projection being a concentric ring distribution and a spiral angle topology along the flight path, wherein the concentric ring radius and spiral angle are dynamically adjusted according to the Earth's rotation compensation requirements; Step S1.2, autonomously switching between in-orbit baseline, tangential baseline, or multi-baseline combination mode according to mission requirements; Step S1.3, optimizing the formation baseline length in real time based on an optimization algorithm, and reducing measurement errors. The following constraints must be met:

[0020] in, Represents the satellite position vector. Number the satellite. Indicates the minimum allowable distance. Indicates the maximum allowed distance. Indicates fuel consumption. This indicates the upper limit of fuel consumption.

[0021] Preferably, the multi-satellite collaborative observation and synchronization control includes: step S2.1, T satellite transmits multi-band fully polarimetric SAR signals, and R satellite collects echoes through a fully polarimetric DBF receiver; step S2.2, time synchronization is achieved by adopting a two-way pulse transmission protocol, and phase synchronization is achieved by designing a common frequency source for radar and GNSS; step S2.3, the beam pointing angle is adjusted based on the overlap rate feedback of the imaging area to ensure the overlap of the coverage area of ​​the two satellite beams.

[0022] Preferably, the distributed holographic signal processing includes: step S3.1, using a phase center mapping matrix. The calculation employs bistatic distance migration correction to map the non-uniformly distributed receiver satellite positions into a virtual, equally spaced phase center array.

[0023] in, Indicates the coordinates of the virtual equally spaced phase centers. Indicates the actual satellite position coordinates. The phase center mapping matrix is ​​represented; in step S3.2, the full aperture data is divided into sub-image sets according to the azimuth and elevation angles, and pixel-level scattering feature parameters are extracted.

[0024] Preferably, the construction of the multidimensional spatial map includes: step S4.1, calculating the scattering direction and scattering amplitude of each imaging unit, wherein the scattering direction is determined by radar observation geometry and external DEM positioning, and the scattering amplitude is determined by the radiometrically corrected SAR image, and the scattering direction of each imaging unit is calculated. Scattering coherence angle and scattering amplitude ,in,

[0025]

[0026]

[0027] in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. Step S4.2: Integrate azimuth, elevation, and polarization channel dimensional information to generate a multidimensional spatial map.

[0028] Compared with existing technologies, this invention has the following advantages: By employing a concentric ring-spiral composite formation configuration, this invention achieves continuous full coverage of the three-dimensional spatial azimuth and elevation angles of ground targets, fundamentally overcoming the bottleneck of scattering feature capture caused by the discrete angles of traditional formations. By combining real-time dynamic optimization algorithms, it effectively suppresses configuration distortion caused by orbital perturbations and autonomously switches between multiple observation modes according to mission requirements, significantly improving formation stability and mission adaptability. Through the innovative use of high-precision time synchronization and phase synchronization technologies, combined with a real-time feedback control mechanism for beam overlap areas, it ensures a high degree of overlap of multiple radar beams illuminating the same ground object area, laying a crucial foundation for data coherence in subsequent distributed holographic signal processing. Based on this, this invention proposes a multi-dimensional information fusion method based on virtual phase center mapping and HSI color space conversion, for the first time fusing azimuth, elevation, and four polarization channels to construct a multi-dimensional spatial map, achieving full-domain perception and visualization of target scattering characteristics. Attached Figure Description

[0029] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of a distributed formation SAR satellite constellation multi-angle scattering feature map measurement system provided by the present invention.

[0030] Figure 2 The flowchart illustrates a method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation, as provided by this invention.

[0031] Figure 3 This is a schematic diagram of the formation configuration of a distributed formation SAR satellite constellation provided by the present invention. Detailed Implementation

[0032] 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.

[0033] like Figure 1 As shown, the present invention provides a distributed formation SAR satellite constellation multi-angle scattering feature map measurement system, which includes the following modules: Module M1: Satellite Formation Subsystem; Module M2: Load Co-observation Subsystem; Module M3: Signal Processing Subsystem; Module M4: Graph Construction Subsystem.

[0034] Furthermore, the M1 satellite formation subsystem consists of M launching satellites (T satellites) and N receiving satellites (R satellites) forming a concentric ring-spiral composite formation, as shown below. Figure 3 As shown, it includes: Module M1.1: The concentric ring-spiral composite formation configuration is projected onto the vertical trajectory plane as a concentric ring distribution, and exhibits a spiral angle topology along the flight path, achieving continuous coverage of multiple azimuth and pitch angles; Module M1.2: The formation baseline length is dynamically adjustable. The relative positions of satellites are adjusted in real time through optimization algorithms to meet the constraints of minimum safe distance and orbital stability. Module M1.3: The formation reconfiguration mechanism supports autonomous switching of configuration modes (such as along-track baseline, tangent-track baseline, or multiple baseline combinations) according to the needs of the observation mission.

[0035] Furthermore, the module M2 payload collaborative observation subsystem includes: Module M2.1: The T satellite is equipped with a multi-band fully polarimetric SAR transmitter, supporting signal encoding transmission, adaptive adjustment of pulse repetition frequency, etc. Module M2.2: The R satellite is equipped with a multi-band fully polarized DBF SAR receiver, supporting digital beamforming and coherent signal synthesis; Module M2.3: The inter-satellite time synchronization module compensates for carrier frequency phase noise, the phase synchronization module corrects frequency source phase offset, and the beam synchronization module achieves overlapping of the two-satellite imaging areas through attitude and radio beam pointing coordinated control.

[0036] Furthermore, the module M3 signal processing subsystem is used to realize distributed holographic imaging processing of multi-satellite echo signals, including: Module M3.1: Echo signal separation module, used to achieve echo separation for different transmitting satellites from the same receiving satellite using digital beamforming and signal coding technology; Module M3.2: Imaging processing module, used to process each echo data using monostatic / bistatic imaging processing algorithms; Module M3.3: Multi-angle sub-aperture segmentation module, used to segment image data into sub-image sets according to azimuth and elevation angles, and extract pixel-level scattering feature parameters.

[0037] Furthermore, the module M4 map construction subsystem includes: Module M4.1: Scattering Feature Extraction Module, used to calculate the scattering direction and scattering amplitude of each imaging unit. The scattering direction is determined by radar observation geometry and external DEM positioning, while the scattering amplitude is determined by the radiometrically corrected SAR image. The scattering direction of each imaging unit is calculated. Scattering coherence angle and scattering amplitude ,in,

[0038]

[0039]

[0040] in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. ; Module M4.2: Multidimensional spatial mapping module, used to fuse azimuth, elevation, and polarization channel dimensional information to generate multidimensional spatial maps.

[0041] Through the above specific implementation steps, by constructing a closed-loop system of flexible formation, collaborative observation, holographic processing, and map construction, the raw data of the distributed SAR satellite constellation was successfully transformed into a high-dimensional information product capable of perceiving the physical scattering characteristics of targets across the entire domain and in all dimensions. This fundamentally solves the bottleneck problem of traditional SAR's incomplete capture and limited descriptive capabilities of complex three-dimensional target features.

[0042] like Figure 2 As shown, the present invention also provides a method for measuring the multi-angle scattering feature map of a distributed SAR satellite constellation, comprising the following steps: Step S1: Satellite formation construction and dynamic reconstruction.

[0043] Furthermore, in step S1, the radius of the concentric rings and helix angle Dynamically adjust according to the Earth's rotation compensation requirements to suppress configurational distortion caused by J2 perturbation.

[0044] Step S1.1: Construct a concentric ring-spiral composite formation configuration, with the vertical trajectory plane projection being a concentric ring distribution and a spiral angle topology along the flight path; Step S1.2: Automatically switch between the following baseline, the cutting baseline, or the multi-baseline combination mode according to the task requirements; Step S1.3: Optimize the formation baseline length in real time based on the optimization algorithm, and measure the error. The following constraints must be met:

[0045] in, Represents the satellite position vector ( (for satellite numbering) Indicates the minimum allowable distance. Indicates the maximum allowed distance. Indicates fuel consumption. This indicates the upper limit of fuel consumption.

[0046] Step S2: Multi-satellite collaborative observation and synchronization control.

[0047] Step S2.1: Satellite T transmits multi-band fully polarimetric SAR signals, and satellite R collects the echoes through a fully polarimetric DBF receiver; Step S2.2: Time synchronization is achieved using a two-way pulse transmission protocol, and phase synchronization is achieved through a common frequency source design between the radar and GNSS. Step S2.3: Adjust the beam pointing angle based on the overlap rate feedback of the imaging area to ensure the overlap of the coverage area of ​​the two-star beams.

[0048] Step S3: Distributed holographic signal processing.

[0049] Step S3.1: Map the non-uniformly distributed receiving satellite positions into a virtual equally spaced phase center array, using the phase center mapping matrix. The calculation employs bistatic distance migration correction;

[0050] in Indicates the coordinates of the virtual equally spaced phase centers. Indicates the actual satellite position coordinates. This represents the phase center mapping matrix.

[0051] Step S3.2: Divide the full aperture data into sub-image sets according to azimuth and elevation angles, and extract pixel-level scattering feature parameters.

[0052] Step S4: Construction of multidimensional spatial map.

[0053] Step S4.1: Scattering feature extraction. Calculate the scattering direction and amplitude of each imaging unit. The scattering direction is determined by radar observation geometry and external DEM positioning, and the scattering amplitude is determined by the radiometrically corrected SAR image. Calculate the scattering direction of each imaging unit. Scattering coherence angle and scattering amplitude :

[0054]

[0055]

[0056] in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. ; Step S4.2: Multidimensional spatial mapping, fusing azimuth angle, elevation angle, and polarization channel (HH / HV / VH / VV) dimensional information to generate a multidimensional spatial map.

[0057] Through the above specific implementation steps, an end-to-end solution from the physical layer (formation) to the information layer (map) is provided. Through the deep integration of a dynamically reconfigurable observation network and holographic multidimensional signal processing, continuous, quantitative, and structured perception of the scattering characteristics of ground targets from all angles, three dimensions, and multiple polarizations is realized for the first time. This advances the observation capability of synthetic aperture radar from the era of "two-dimensional imaging" to a new stage of "multidimensional physical field perception".

[0058] 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.

[0059] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0060] 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 distributed formation SAR satellite swarm multi-angle scattering feature map measurement system, characterized in that, include: Satellite formation subsystem, payload collaborative observation subsystem, signal processing subsystem, and map construction subsystem; The satellite formation subsystem is used to construct an initial satellite formation and dynamically reconstruct it. The payload collaborative observation subsystem is used for collaborative observation of the same region by multiple satellites; The signal processing subsystem is used to realize distributed holographic imaging processing of multi-star echo signals; The map construction subsystem is used to construct multidimensional spatial maps.

2. The distributed formation SAR satellite constellation multi-angle scattering feature map measurement system according to claim 1, characterized in that, The satellite formation subsystem consists of M launching satellites and N receiving satellites forming a concentric ring-spiral composite formation configuration. The concentric ring-spiral composite formation configuration is distributed as concentric rings when projected onto the vertical trajectory plane and has a spiral angle topology along the flight path, which is used to achieve continuous coverage of multiple azimuth angles and multiple pitch angles. The formation baseline length of the satellite formation subsystem is dynamically adjustable, and the relative positions of the satellites are adjusted in real time through optimization algorithms to meet the constraints of minimum safe distance and orbital stability. The formation reconfiguration mechanism of the satellite formation subsystem is used to autonomously switch configuration modes according to the needs of the observation mission, including in-orbit baseline, out-of-orbit baseline and multi-baseline combination mode.

3. The distributed formation SAR satellite constellation multi-angle scattering feature map measurement system according to claim 1, characterized in that, The payload collaborative observation subsystem is equipped with a multi-band fully polarimetric SAR transmitter for signal encoding transmission and adaptive adjustment of pulse repetition frequency. The payload collaborative observation subsystem is equipped with a multi-band fully polarized DBF SAR receiver for digital beamforming and coherent signal synthesis on the R satellite. The payload collaborative observation subsystem includes a time synchronization module, a phase synchronization module, and a beam synchronization module between the T satellite and the R satellite. The time synchronization module is used to compensate for carrier frequency phase noise, the phase synchronization module is used to correct frequency source phase offset, and the beam synchronization module is used to coordinate the attitude and radio beam of the two satellites to achieve overlapping imaging regions of the two satellites.

4. The distributed formation SAR satellite constellation multi-angle scattering feature map measurement system according to claim 1, characterized in that, The signal processing subsystem includes an echo signal separation module, which uses digital beamforming and signal coding techniques to achieve echo separation for different transmitting satellites corresponding to the same receiving satellite. The signal processing subsystem includes an imaging processing module, which is used to perform imaging processing on each echo data using a monostatic / bistatic imaging processing algorithm; The signal processing subsystem includes a multi-angle sub-aperture segmentation module, which is used to segment image data into sub-image sets according to azimuth and elevation angles and extract pixel-level scattering feature parameters.

5. A distributed formation SAR satellite constellation multi-angle scattering feature map measurement system according to claim 1, characterized in that, The map construction subsystem includes a scattering feature extraction module, used to calculate the scattering direction and scattering amplitude of each imaging unit. The scattering direction is determined by radar observation geometry and external DEM positioning, while the scattering amplitude is determined by the radiometrically corrected SAR image. The calculation of the scattering direction for each imaging unit... Scattering coherence angle and scattering amplitude ,in, in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. ; The map construction subsystem includes a multi-dimensional spatial mapping module, which is used to fuse azimuth, elevation, and polarization channel dimensional information to generate a multi-dimensional spatial map.

6. A method for measuring the multi-angle scattering feature map of a distributed SAR satellite constellation, characterized in that, include: Step S1, Satellite formation construction and dynamic reconfiguration; Step S2: Multi-satellite collaborative observation and synchronization control; Step S3, distributed holographic signal processing; Step S4: Construction of multidimensional spatial map.

7. The method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation according to claim 6, characterized in that, The satellite formation construction and dynamic reconfiguration include: Step S1.1: Construct a concentric ring-spiral composite formation configuration. The vertical trajectory plane projection is a concentric ring distribution, and the spiral angle topology is formed along the flight path. The radius of the concentric rings and the spiral angle are dynamically adjusted according to the Earth's rotation compensation requirements. Step S1.2: Automatically switch between the following baseline, the cutting baseline, or the multi-baseline combination mode according to the task requirements; Step S1.3: Optimize the formation baseline length in real time based on the optimization algorithm, and measure the error. The following constraints must be met: in, Represents the satellite position vector. Number the satellite. Indicates the minimum allowable distance. Indicates the maximum allowed distance. Indicates fuel consumption. This indicates the upper limit of fuel consumption.

8. The method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation according to claim 6, characterized in that, The multi-satellite collaborative observation and synchronization control includes: Step S2.1: Satellite T transmits multi-band fully polarimetric SAR signals, and satellite R collects the echoes through a fully polarimetric DBF receiver; Step S2.2: Time synchronization is achieved using a two-way pulse transmission protocol, and phase synchronization is achieved through a common frequency source design between the radar and GNSS. Step S2.3: Adjust the beam pointing angle based on the overlap rate feedback of the imaging area to ensure the overlap of the coverage area of ​​the two-star beams.

9. A method for measuring the multi-angle scattering feature map of a distributed formation SAR satellite constellation according to claim 6, characterized in that, The distributed holographic signal processing includes: Step S3.1, through the phase center mapping matrix The calculation employs bistatic distance migration correction to map the non-uniformly distributed receiver satellite positions into a virtual, equally spaced phase center array. in, Indicates the coordinates of the virtual equally spaced phase centers. Indicates the actual satellite position coordinates. Represents the phase center mapping matrix; Step S3.2: Divide the full aperture data into sub-image sets according to azimuth and elevation angles, and extract pixel-level scattering feature parameters.

10. A method for measuring the multi-angle scattering feature map of a distributed SAR satellite constellation according to claim 6, characterized in that, The construction of the multidimensional spatial map includes: Step S4.1: Calculate the scattering direction and scattering amplitude of each imaging unit. The scattering direction is determined by radar observation geometry and external DEM positioning, and the scattering amplitude is determined by the radiometrically corrected SAR image. Scattering coherence angle and scattering amplitude ,in, in, Indicates angle The scattering intensity function of the direction, Indicates the radar wavelength. Indicates the equivalent aperture length. Indicates the range of the complex number. This means finding the independent variable that makes the function reach its maximum value. ; Step S4.2: Integrate azimuth, elevation, and polarization channel dimensional information to generate a multidimensional spatial map.

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