Lunar crater ejecta detection method and system based on synthetic aperture radar image, storage medium and electronic device

Abstract

The application discloses a kind of lunar meteorite crater sputtering layer detection method, system, storage medium and electronic equipment based on synthetic aperture radar image, comprising: by polarimetric decomposition to the SAR image of study area, obtain the scattering characteristics including the inner wall and bottom of meteorite crater, sputtering layer and lunar surface background weathering layer area;Extract the lunar surface background level of polarized component in sample as the threshold value for distinguishing sputtering layer and lunar surface background weathering layer;Extract the crater boundary in SAR image;Extract the boundary of sputtering layer;The crater boundary and sputtering layer boundary extracted in all samples are combined to represent the range of sputtering layer in SAR image.The application can well characterize the sputtering layer of lunar meteorite crater, reduce the influence of other meteorite craters and sputtering layer, and has important significance for studying the impact history of moon and future lunar landing.

Description

Technical Field

[0001] This invention relates to the field of geographic detection technology, and in particular to a method, system, storage medium, and electronic device for detecting lunar crater ejecta based on synthetic aperture radar imagery. Background Technology

[0002] Currently, Synthetic Aperture Radar (SAR) is an advanced active microwave imaging device used for topographic mapping and imaging of the lunar surface. Based on the penetration characteristics and polarization features of radar electromagnetic waves, analyzing radar backscattered echoes can also detect subsurface characteristics of the Moon (such as lunar regolith thickness, dielectric constant, and geological structure). SAR systems currently used in lunar exploration projects include the Mini-SAR aboard Chandrayaan-1, the Mini-RF aboard the LRO, and the DFSAR aboard Chandrayaan-2.

[0003] The study of lunar crater ejecta provides information about impact processes and subsurface materials of the lunar regolith, influencing future lunar landing plans and playing a crucial role in lunar exploration. Optical images are an important data source for characterizing lunar surface morphology, and optical-based crater identification methods have been extensively studied. However, optical images are limited to characterizing the outermost layer of the lunar regolith. The degradation of the regolith surface means that optical images cannot accurately characterize the boundary between the ejecta and the background regolith. The lunar surface is highly covered by craters, and the superposition of ejecta from different craters significantly increases the difficulty of characterizing the ejecta of a single crater. The inherent speckle noise in SAR images also blurs the boundary between the ejecta and the background regolith. Therefore, traditional methods of characterizing ejecta using SAR images struggle to clearly define the boundary between the ejecta and the background regolith.

[0004] Therefore, how to reduce the influence of other impact craters and ejecta, and how to effectively characterize the extent of ejecta in SAR images, are urgent problems that need to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a method, system, storage medium, and electronic device for detecting lunar crater ejecta based on synthetic aperture radar (SAR) images, which can effectively characterize the extent of ejecta in SAR images and reduce the influence of other craters and ejecta.

[0006] The technical solution adopted in this invention is as follows:

[0007] A method for detecting lunar crater ejecta based on synthetic aperture radar imagery includes the following steps:

[0008] Step S101: Perform polarization decomposition on the SAR remote sensing image of the study area to obtain the distribution and variation patterns of scattering characteristics of the bottom of the crater, the inner wall, the ejecta layer, and the lunar background weathering layer.

[0009] Step S102: Following the direction of ejecta ejection, extract samples starting from the bottom of the crater to obtain the samples needed for subsequent analysis. The samples should include scattering characteristic information from the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith. In this method, this specifically refers to the component m representing the volumetric scattering process in the compressed three-component decomposition used. v ;

[0010] Step S103: Extract the lunar background level of the polarization component in the sample as a criterion for distinguishing between the sputtering layer and the lunar background weathering layer;

[0011] Step S104: Define the research scope for crater boundary analysis in the sample and extract the crater boundaries from the SAR image;

[0012] Step S105: Based on the lunar surface background level of polarization components in the sample and the extracted crater boundary information, analyze the variation law of sputtering layer scattering characteristics, and optimize the abnormal data on the sputtering layer that do not conform to the variation law of scattering characteristics.

[0013] Step S106: Fit the optimized data and combine it with the lunar background level of the polarization component in the sample to analyze the boundary between the sputtering layer and the lunar background weathering layer.

[0014] Step S107: Combine the crater boundaries and ejecta boundaries obtained from all samples to analyze the center location of the crater, and use circle fitting to fit the crater boundaries and ejecta boundaries to characterize the extent of the ejecta.

[0015] Step S101 specifically involves: using polarization decomposition technology to process the radar echo data, decomposing the received data into two parts: fully polarized and fully non-polarized, representing the deterministic scattering process and the volume scattering process, respectively.

[0016] We selected Mini-RF S-band data as the data source, which can be displayed in Stokes vector form:

[0017]

[0018] Where S1 represents the total power of radar backscattering, E represents the electric field, and H and V represent the received horizontally or vertically polarized echoes; a partially polarized wave can be decomposed into the sum of a completely unpolarized wave and a completely polarized wave, represented as a Stokes vector, mathematically:

[0019]

[0020] Where m is the polarizability, I1 represents a unit of completely nonpolarized state, I2 represents a unit of completely polarized state, and we have:

[0021]

[0022] The compact polarization three-component decomposition model assumes that volume scattering is completely nonpolar, which can be represented in the form of Stokes vectors as follows:

[0023]

[0024] Where, m v To represent the process of volume scattering, m s I3 represents a unit completely nonpolarized state, and I4 represents a unit completely polarized state.

[0025] From (3) and (4), we can obtain:

[0026]

[0027] Since the research objective of this application is sputtered layers, component m is selected. v Remote sensing data for subsequent use:

[0028] The lunar background regolith primarily undergoes surface scattering;

[0029] Because the sputtered layer contains scatterers on a higher scale (from centimeters to decimeters), it has a higher roughness and primarily undergoes volume scattering and secondary scattering; therefore, in the image, the m on the sputtered layer... v The value is relatively high, and it gradually decreases and flattens out from the crater boundary along the direction of the ejecta, eventually dropping to the level of the lunar background regolith. The m value at the bottom of the crater is... v The value is close to the background regolith on the lunar surface, and the m value of the inner wall of the crater is similar. v The value level rises continuously from the bottom in the direction of the ejected material, until it reaches m at the boundary of the crater. v Value level;

[0030] The scattering characteristics of the study area were analyzed using polarization decomposition technology. The main research object was the ejecta layer of the impact crater. The polarization features used should be able to distinguish the ejecta layer from other areas. Based on the distribution characteristics of the scattering characteristics of the lunar regolith, the parameters representing volume scattering after polarization decomposition were used to characterize the scattering characteristics of the lunar surface and distinguish the ejecta layer from other areas.

[0031] Step S102 is as follows:

[0032] First, a 3*3 mean filter is used to process the signal and reduce the impact of speckle noise.

[0033] Then, for the data of the study area after polarization decomposition, sampling is carried out outward from a point at the bottom of the crater as the starting sampling point, following the direction of the ejected material. The sampling area is the boundary from the starting sampling point to the study area, and should include information on the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith.

[0034] Step S103 is as follows:

[0035] Based on the variation patterns of scattering characteristics at the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith, the m-shaped particles representing the ejecta flow direction in the sample were analyzed. v The probability density of the value is used as the parameter representing the scattering characteristics of the lunar background regolith and the distinguishing criterion between the sputtering layer and the lunar background regolith.

[0036] Step S104 is as follows:

[0037] Based on the crater radius obtained from the optical image, the range for analyzing the crater boundary in the SAR image is defined as the area from the initial sampling point to twice the crater radius. A Gaussian function is used to fit the data within this range, and the location of the highest value is taken as the location of the crater boundary in the sample. The fitting function is:

[0038]

[0039] Where, f(r) crater The values ​​represent the fitted data, where a1, a2, b1, b2, c1, and c2 are constants, and r represents the distance from the fitted position to the original sampling point.

[0040] Step S105 is as follows:

[0041] Based on the location information of the crater boundaries in the samples obtained in step S104, the range of the boundary between the ejecta layer and the lunar background regolith is defined. Specifically, the range is from the location of the crater boundary to the boundary of the study area. A power function is used to fit the data within this range, and outliers are suppressed. The fitting function is:

[0042] f(r) ejecta =d×r e +f (7)

[0043] Where, f(r) ejecta The fitted data values ​​are represented by d, e, and f, which are constants, and r represents the distance from the fitted position to the boundary of the crater in the sample.

[0044] The anomalous data is manifested in the fact that small impact craters on the ejecta layer affect the variation of the scattering characteristics in that region, specifically in the polarization decomposition component m. v The increase in the value will affect the fitting of the data within the range in step S105, resulting in a failure to conform to the variation law of the sputtered layer scattering characteristics.

[0045] The suppression of outlier data is specifically manifested in the following way: by comparing the original sample data with the fitted data, the portion of the original data that is greater than the fitted data is reduced to the value of the parameter representing the scattering characteristics of the lunar background weathering layer.

[0046] Step S107, the specific steps are as follows:

[0047] Calculate the average of the coordinates of all crater boundary locations as the coordinates of the crater center location;

[0048] The average distance from the boundary of all the craters to the center of the crater is calculated and used as the radius of the circle that fits the crater boundary.

[0049] The average distance from all sputtering layer boundaries obtained from the sample to the center of the crater is calculated and used as the radius of the circle fitted to the sputtering layer boundaries;

[0050] The fitted circles are used to characterize the start and end ranges of the sputtered layer, respectively.

[0051] A lunar crater ejecta detection system based on synthetic aperture radar imagery includes:

[0052] The polarization decomposition unit is configured to perform polarization decomposition on SAR data images to obtain images with different polarization components; the sample extraction unit is configured to extract samples from the polarization component images, including information on the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith.

[0053] The lunar background level extraction unit is configured to perform an overall analysis of the sample data, taking the value with the highest probability density among all data as the lunar background level of the polarization component, and using it as the threshold to distinguish between the lunar background weathering layer and the ejecta layer; the crater boundary extraction unit is configured to set the range of the crater boundary in the sample based on the radius of the craters in the research object, and use a Gaussian function to fit the data within the range, taking the position of the highest value point within the range after fitting as the position of the crater boundary in the sample;

[0054] The ejector layer boundary extraction unit is configured to set the range of the ejector layer boundary analysis based on the crater boundary position obtained by the crater boundary extraction unit, fit the data within the range by a power function and suppress outlier data, fit the suppressed data by a power function again, and combine the threshold obtained by the lunar surface background level extraction unit to determine the boundary of the ejector layer in the sample.

[0055] Sputtering layer extent characterization unit: Combining the crater boundary position and the sputtering layer boundary position obtained from all samples, the two boundaries are fitted into a circle to characterize the extent of the sputtering layer.

[0056] A computer-readable storage medium having a computer program stored thereon, the program being the lunar crater ejecta detection method based on synthetic aperture radar imagery as described above.

[0057] An electronic device includes: a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the lunar crater ejecta detection method based on synthetic aperture radar imagery as described above.

[0058] This invention distinguishes the ejecta layer from other regions by analyzing the distribution patterns of the scattering characteristics of the lunar regolith, thus mitigating the problem of unclear boundaries between the ejecta layer and other regions caused by the degradation of lunar surface morphology. Furthermore, by analyzing and fitting the variation patterns of the ejecta layer's scattering characteristics, the influence of anomalous data caused by other impact craters on the ejecta layer is suppressed. Therefore, it can effectively characterize the starting and ending ranges of the ejecta layer, which will also be helpful for future lunar exploration work such as landing site selection and cruise route planning. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0060] Figure 1 This is a schematic diagram of the process of the present invention;

[0061] Figure 2 This is a system structure block diagram of the present invention;

[0062] Figure 3 A schematic diagram of the polarization decomposition image and the extracted sample provided as an example of the present invention;

[0063] Figure 4 A comparison chart of the original sample data and the filtered data provided for an example of the present invention;

[0064] Figure 5 The probability density curve of the data in the sample provided for the example of the present invention;

[0065] Figure 6A schematic diagram illustrating the results of fitting data to a crater region, provided as an example of the present invention.

[0066] Figure 7 A schematic diagram showing the results of fitting sputtered layer data as an example of the present invention;

[0067] Figure 8 A schematic diagram illustrating the characterization results of the sputtering layer range provided in this embodiment of the invention. Detailed Implementation

[0068] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0069] like Figure 1 , 2 As shown in Figures 3 and 4, the present invention includes the following steps:

[0070] Step S101: Polarization decomposition is performed on the SAR remote sensing images of the study area to obtain the distribution and variation patterns of scattering characteristics of the bottom of the crater, the inner wall, the ejecta layer, and the lunar background weathering layer.

[0071] Polarization decomposition technology is used to process radar echo data, decomposing the received data into fully polarized and fully non-polarized parts, representing the deterministic scattering process (surface scattering and secondary scattering) and the volume scattering process, respectively. This application focuses on lunar crater ejecta. Among currently available lunar SAR systems, the Mini-RF system mounted on the LRO provides the widest S-band data coverage; therefore, Mini-RF S-band data is chosen as the data source. This data can be represented in the form of Stokes vectors.

[0072]

[0073] Where S1 represents the total power of radar backscattering, E represents the electric field, and H and V represent the received horizontally or vertically polarized echoes. A partially polarized wave can be decomposed into the sum of a completely unpolarized wave and a completely polarized wave, represented as a Stokes vector, mathematically as follows:

[0074]

[0075] Where m is the polarizability, I1 represents a unit of completely nonpolarized state, I2 represents a unit of completely polarized state, and we have:

[0076]

[0077] The compact polarization three-component decomposition model assumes that volume scattering is completely nonpolar, which can be represented in the form of Stokes vectors as follows:

[0078]

[0079] Where, m v To represent the process of volume scattering, m s I3 represents a unit completely nonpolarized state, and I4 represents a unit completely polarized state.

[0080] From (3) and (4), we can obtain:

[0081]

[0082] Since the research objective of this application is sputtered layers, component m is selected. v This data will be used for subsequent remote sensing applications. The lunar background regolith primarily undergoes surface scattering; the sputtered layer, containing scatterers ranging from centimeters to decimeters in size, has a higher roughness and primarily undergoes volume scattering and secondary scattering. Therefore, in the image, the m... v The value is relatively high, and it gradually decreases and flattens out from the crater boundary along the direction of the ejecta, eventually dropping to the level of the lunar background regolith. The m value at the bottom of the crater is... v The value is close to the background regolith on the lunar surface, and the m value of the inner wall of the crater is similar. v The value level rises continuously from the bottom in the direction of the ejected material, until it reaches m at the boundary of the crater. v Value level.

[0083] Step S102: Extract samples from the data after evolutionary decomposition.

[0084] After polarization decomposition, the study area data is first processed using a 3*3 mean filter to reduce the impact of speckle noise. Starting from a point at the bottom of the crater, sampling is performed outwards along the direction of the ejecta. The sampling area is the boundary from the starting point to the study area, including information on the crater bottom, crater walls, ejecta layer, and lunar background regolith.

[0085] Step S103: Extract the lunar background level of polarization components in the sample.

[0086] Based on the variation patterns of scattering characteristics at the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith, the probability density of all data in the sample was analyzed, and the data with the highest probability density was taken as the m representing the lunar background regolith. v The value level can also serve as a criterion for distinguishing between the sputtering layer and the background weathering layer on the lunar surface.

[0087] Step S104: Define the research scope for crater boundary analysis in the sample and extract the location of the crater boundary.

[0088] Based on the crater radius obtained from the optical image, the range for analyzing the crater boundary in the SAR image is limited to the area from the initial sampling point to twice the crater radius. A Gaussian function is used to fit the data within this range, and the location of the highest value is taken as the location of the crater boundary in the sample. The fitting function is:

[0089]

[0090] Where, f(r) crater The values ​​represent the fitted data, where a1, a2, b1, b2, c1, and c2 are constants, and r represents the distance from the fitted position to the original sampling point.

[0091] Step S105: Suppress outliers on the sputtered layer.

[0092] Based on the location information of the crater boundaries in the samples obtained in step S104, the range of the boundary between the ejecta layer and the lunar background regolith is defined. Specifically, the range is from the location of the crater boundary to the boundary of the study area. A power function is used to fit the data within this range, and outliers are suppressed. The fitting function is:

[0093] f(r) ejecta =d×r e +f (7)

[0094] Where, f(r) ejecta The fitted data values ​​are represented by d, e, and f, which are constants, and r represents the distance from the fitted position to the boundary of the crater in the sample.

[0095] The anomalous data is manifested in the fact that small impact craters on the ejecta layer affect the variation of the scattering characteristics in that region, specifically in the m value representing volume scattering. v An increase in the value will affect the fitting of the data within the range in step S105, resulting in a change that does not conform to the variation law of the sputtered layer scattering characteristics.

[0096] The suppression of outliers is specifically manifested in the following way: by comparing the original sample data with the fitted data, the portion of the original data that is greater than the fitted data is reduced to m, which represents the background weathering layer of the lunar surface. v Values ​​at the value level.

[0097] Step S106: Extract the location of the sputtering layer boundary. Fit the optimized data and combine it with the lunar background level of the polarization component in the sample to analyze the boundary between the sputtering layer and the lunar background weathering layer;

[0098] The outlier-suppressed data from step S105 is fitted using a power function. Combined with the distinction criteria between the lunar background weathering layer and the sputtering layer obtained in step S103, the boundary between the sputtering layer and the lunar background weathering layer is obtained. The fitting function used is the same as that used in step S105.

[0099] Step S107: Characterization of the ejecta layer extent. Combining the crater boundaries and ejecta layer boundaries obtained from all samples, analyze the center position of the crater and use a circle to fit the crater boundaries and ejecta layer boundaries to characterize the extent of the ejecta layer. Specifically, calculate the average coordinates of all crater boundary positions as the coordinates of the crater center. Use a circle to fit the crater boundaries and ejecta layer boundaries. Specifically, calculate the average distance from all crater boundaries obtained from the samples to the crater center, using this as the radius of the circle fitting the crater boundaries; calculate the average distance from all ejecta layer boundaries obtained from the samples to the crater center, using this as the radius of the circle fitting the ejecta layer boundaries. These two circles are used to characterize the start and end extent of the ejecta layer, respectively.

[0100] This method distinguishes the ejecta layer from other regions by analyzing the distribution patterns of the scattering characteristics of the lunar regolith, reducing the problem of unclear boundaries between the ejecta layer and other regions caused by the degradation of lunar surface morphology. By analyzing and fitting the variation patterns of the ejecta layer's scattering characteristics, the influence of anomalous data from other impact craters on the ejecta layer is suppressed. Therefore, it can effectively characterize the starting and ending ranges of the ejecta layer, which is helpful for future lunar exploration work such as landing site selection and cruise route planning. Compared to traditional methods using synthetic aperture radar (SAR) imagery for ejecta layer range detection, this method, based on the variation patterns of the scattering characteristics expressed by the ejecta layer in SAR imagery and fitting its variation curves, reduces the problem of the ejecta layer range shrinking due to the degradation of lunar surface morphology, resulting in more accurate detection results.

[0101] Figure 2 This is a schematic diagram of a lunar crater ejecta detection system based on synthetic aperture radar imagery, according to this application; Figure 2As shown, the lunar crater ejecta extent characterization system includes: a polarization decomposition unit, configured to perform polarization decomposition on SAR data images to obtain images with different polarization components; a sample extraction unit, configured to extract samples from the polarization-decomposed SAR data images, including information on the crater bottom, crater inner wall, ejecta layer, and lunar background regolith; a ejecta layer and lunar background regolith differentiation criterion parameter extraction unit, configured to perform overall analysis of the sample data and take the value with the highest probability density among all data as the differentiation criterion between the ejecta layer and the lunar background regolith; and a crater boundary extraction unit, configured to... The range of crater boundaries in the sample is set based on the radius of the craters in the research object. A Gaussian function is used to fit the data within this range, and the location of the highest fitted point within the range is taken as the location of the crater boundary in the sample. The ejecta boundary extraction unit is configured to set the range of ejecta boundary analysis based on the crater boundary positions obtained from the ejecta boundary extraction unit. A power function is used to fit the data within this range, and outlier data is suppressed. The suppressed data is then fitted with a power function again, and the boundary of the ejecta layer in the sample is determined by combining the distinction criteria obtained from the ejecta layer and lunar background regolith extraction unit. The ejecta range characterization unit combines the crater boundary positions and ejecta boundary positions obtained from all samples, fitting the two boundaries as circles to characterize the start and end ranges of the ejecta layer.

[0102] The lunar crater ejecta detection system based on synthetic aperture radar imagery provided in this application can realize the steps, processes and beneficial effects of any of the above-described embodiments of the lunar crater ejecta detection method based on synthetic aperture radar imagery, which will not be repeated here.

[0103] exist Figure 3 (a) is the study region after the three-component decomposition by compressional polarization. v image, Figure 3 (b) is the set of extracted samples. Figure 4 Yes Figure 3 The image shows the original data of the medium sample S1 and the data after mean filtering. In the Q1, Q2 and Q3 regions, there are fluctuations that do not conform to the distribution pattern of scattering characteristics in the sputtering layer region. These are images of small meteorite craters on the sputtering layer. Figure 5 It is a display of the probability density of all data in S1. Figure 6 This is the data fitting result from the analysis of the crater boundary, representing the m value of the region from the crater bottom to the outer edge of the crater in S1. v The changes in value, where m v It reaches its maximum value at the edge of the meteorite crater. Figure 6 The value is displayed as 0.1698. Figure 7(a) and (b) are the data fitting results and the results of the data set after suppression when suppressing abnormal data on the sputtering layer, respectively. The comparison of abnormal fluctuations on the sputtering layer before and after suppression is shown in Q4-Q9. Figure 8 (a) and (b) respectively depict the sputtering layer range extracted from all samples and the final characterization result using circle fitting.

[0104] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0105] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0106] Note that the above description is merely a preferred embodiment and application of the technical principles of the present invention. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the specific embodiments described herein, and may include many other effective embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for detecting lunar crater ejecta based on synthetic aperture radar imagery, characterized in that, include: Step S101: Perform polarization decomposition on the SAR remote sensing image of the study area to obtain the distribution and variation patterns of scattering characteristics of the bottom of the crater, the inner wall, the ejecta layer, and the lunar background weathering layer; Step S101 specifically involves: using polarization decomposition technology to process the radar echo data, decomposing the received data into two parts: fully polarized and fully non-polarized, representing the deterministic scattering process and the volume scattering process, respectively. Mini-RF S-band data was selected as the data source, and this data is presented in Stokes vector format: ; in, The total power of radar backscattering is represented by E, the electric field is represented by H and V, and the horizontal or vertical polarized echoes are represented by H and V. A partially polarized wave is decomposed into the sum of a completely unpolarized wave and a completely polarized wave, represented as a Stokes vector, mathematically as follows: ; Where m is the polarizability. This indicates a completely nonpolar state. This represents the unit of complete polarization, and we have: ; The compact polarization ternary decomposition model treats volume scattering as completely nonpolar, represented in the form of Stokes vectors as follows: ; in, This represents the process of volume scattering. This represents a deterministic scattering process. This indicates a completely nonpolar state. Indicates the unit's fully polarized state; From (3) and (4), we can obtain: ; Since the research objective of this application is sputtered layers, the component is selected. Remote sensing data for subsequent use: The lunar background regolith primarily undergoes surface scattering; Sputtered layers, containing scatterers on the centimeter to decimeter scale, have higher roughness and primarily undergo volume scattering and secondary scattering; therefore, in images, the sputtered layer... The value is relatively high, and it gradually decreases and flattens out from the crater boundary along the direction of the ejecta, eventually dropping to the level of the lunar background regolith. The bottom of the crater... The values ​​are close to the background regolith on the lunar surface, and the inner walls of the crater are... The value level rises continuously from the bottom in the direction of the ejected material, until it reaches the boundary of the crater. Value level; The scattering characteristics of the study area were analyzed using polarization decomposition technology. The main research object was the ejecta layer of the impact crater. The polarization features used were used to distinguish the ejecta layer from other areas. Based on the distribution characteristics of the scattering characteristics of the lunar regolith, the parameters representing volume scattering after polarization decomposition were used to characterize the scattering characteristics of the lunar surface and to distinguish the ejecta layer from other areas. Step S102: Following the direction of ejecta ejection, extract samples starting from the bottom of the crater to obtain the samples needed for subsequent analysis. The samples should include scattering characteristic information from the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith. In this method, this specifically refers to the component representing the volumetric scattering process in the compact scheme three-component decomposition used. ; Step S103: Extract the lunar background level of the polarization component in the sample as a criterion for distinguishing between the sputtering layer and the lunar background weathering layer; Step S104: Define the research scope for crater boundary analysis in the sample and extract the crater boundaries from the SAR image; Step S104 specifically involves: Based on the crater radius obtained from the optical image, the range for analyzing the crater boundary in the SAR image is limited to the area from the initial sampling point to twice the crater radius. A Gaussian function is used to fit the data within this range, and the location of the highest value is taken as the location of the crater boundary in the sample. The fitting function is: ; in, This represents the fitted data values. , , , , , It is a constant. This represents the distance from the fitted position to the original sampling point; Step S105: Based on the lunar surface background level of polarization components in the sample and the extracted crater boundary information, analyze the variation law of sputtering layer scattering characteristics, and optimize the abnormal data on the sputtering layer that do not conform to the variation law of scattering characteristics. Step S106: Fit the optimized data and combine it with the lunar background level of the polarization component in the sample to analyze the boundary between the sputtering layer and the lunar background weathering layer. Step S107: Combine the crater boundaries and ejecta boundaries obtained from all samples to analyze the center location of the crater, and use circle fitting to fit the crater boundaries and ejecta boundaries to characterize the extent of the ejecta.

2. The method for detecting lunar crater ejecta based on synthetic aperture radar imagery according to claim 1, characterized in that, Step S102 is as follows: First, a 3*3 mean filter is used to process the signal and reduce the impact of speckle noise. Then, for the data of the study area after polarization decomposition, sampling is carried out outward from a point at the bottom of the crater as the starting sampling point, following the direction of the ejected material. The sampling area is the boundary from the starting sampling point to the study area, and should include information on the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith.

3. The method for detecting lunar crater ejecta based on synthetic aperture radar imagery according to claim 1, characterized in that, Step S103 is as follows: Based on the variation patterns of scattering characteristics at the bottom of the crater, the inner wall of the crater, the ejecta layer, and the lunar background regolith, the analysis of the sample representing the ejecta flow direction was performed. The probability density of the value is used as the parameter representing the scattering characteristics of the lunar background regolith and the distinguishing criterion between the sputtering layer and the lunar background regolith.

4. The method for detecting lunar crater ejecta based on synthetic aperture radar imagery according to claim 1, characterized in that, Step S105 is as follows: Based on the location information of the crater boundaries in the samples obtained in step S104, the range of the boundary between the ejecta layer and the lunar background regolith is defined. Specifically, the range is from the location of the crater boundary to the boundary of the study area. A power function is used to fit the data within this range, and outliers are suppressed. The fitting function is: ; in, This represents the fitted data values. , , It is a constant. This represents the distance from the fitted location to the crater boundary in the sample; The anomalous data is manifested in the fact that small impact craters on the ejecta layer affect the variation of its regional scattering characteristics, specifically in the polarization decomposition components. The increase in the value will affect the fitting of the data within the range in step S105, resulting in a failure to conform to the variation law of the sputtered layer scattering characteristics. The suppression of outlier data is specifically manifested in the following way: by comparing the original sample data with the fitted data, the portion of the original data that is greater than the fitted data is reduced to the value of the parameter representing the scattering characteristics of the lunar background weathering layer.

5. The method for detecting lunar crater ejecta based on synthetic aperture radar imagery according to claim 1, characterized in that, Step S107, the specific steps are as follows: Calculate the average of the coordinates of all crater boundary locations as the coordinates of the crater center location; The average distance from the boundary of all the craters to the center of the crater is calculated and used as the radius of the circle that fits the crater boundary. The average distance from all sputtering layer boundaries obtained from the sample to the center of the crater is calculated and used as the radius of the circle fitted to the sputtering layer boundaries; The fitted circles are used to characterize the start and end ranges of the sputtered layer, respectively.

6. A lunar crater ejecta detection system based on synthetic aperture radar imagery, characterized in that, include: The polarization decomposition unit is configured to perform polarization decomposition on SAR data images to obtain images with different polarization components. The radar echo data is processed using polarization decomposition technology, which decomposes the received data into two parts: fully polarized and fully non-polarized, representing the deterministic scattering process and the volume scattering process, respectively. Mini-RF S-band data was selected as the data source, and this data is presented in Stokes vector format: ; in, The total power of radar backscattering is represented by E, the electric field is represented by H and V, and the horizontal or vertical polarized echoes are represented by H and V. A partially polarized wave is decomposed into the sum of a completely unpolarized wave and a completely polarized wave, represented as a Stokes vector, mathematically as follows: ; Where m is the polarizability. This indicates a completely nonpolar state. This represents the unit of complete polarization, and we have: ; The compact polarization ternary decomposition model treats volume scattering as completely nonpolar, represented in the form of Stokes vectors as follows: ; in, This represents the process of volume scattering. This represents a deterministic scattering process. This indicates a completely nonpolar state. Indicates the unit's fully polarized state; From (3) and (4), we can obtain: ; Since the research objective of this application is sputtered layers, the component is selected. For subsequent use of remote sensing data: The lunar background regolith primarily undergoes surface scattering; Sputtered layers, containing scatterers on the centimeter to decimeter scale, have higher roughness and primarily undergo volume scattering and secondary scattering; therefore, in images, the sputtered layer... The value is relatively high, and it gradually decreases and flattens out from the crater boundary along the direction of the ejecta, eventually dropping to the level of the lunar background regolith. The bottom of the crater... The values ​​are close to the background regolith on the lunar surface, and the inner walls of the crater are... The value level rises continuously from the bottom in the direction of the ejected material, until it reaches the boundary of the crater. Value level; The scattering characteristics of the study area were analyzed using polarization decomposition technology. The main research object was the ejecta layer of the impact crater. The polarization features used were used to distinguish the ejecta layer from other areas. Based on the distribution characteristics of the scattering characteristics of the lunar regolith, the parameters representing volume scattering after polarization decomposition were used to characterize the scattering characteristics of the lunar surface and to distinguish the ejecta layer from other areas. The sample extraction unit is configured to extract samples from the polarization component image, and the samples include information on the bottom of the crater, the inner wall of the crater, the ejecta layer and the lunar background regolith. The lunar background level extraction unit is configured to perform an overall analysis of the sample data, taking the value with the highest probability density among all data as the lunar background level of the polarization component, and using it as the threshold to distinguish between the lunar background weathering layer and the sputtering layer. The crater boundary extraction unit is configured to set the range of the analyzed crater boundaries in the sample based on the radius of the craters in the research object. It uses a Gaussian function to fit the data within this range, and takes the location of the highest fitted point within the range as the location of the crater boundary in the sample; specifically: Based on the crater radius obtained from the optical image, the range for analyzing the crater boundary in the SAR image is limited to the area from the initial sampling point to twice the crater radius. A Gaussian function is used to fit the data within this range, and the location of the highest value is taken as the location of the crater boundary in the sample. The fitting function is: ; in, This represents the fitted data values. , , , , , It is a constant. This represents the distance from the fitted position to the original sampling point; The ejector layer boundary extraction unit is configured to set the range of the ejector layer boundary analysis based on the crater boundary position obtained by the crater boundary extraction unit, fit the data within the range by a power function and suppress outlier data, fit the suppressed data by a power function again, and combine the threshold obtained by the lunar surface background level extraction unit to determine the boundary of the ejector layer in the sample. Sputtering layer extent characterization unit: Combining the crater boundary position and the sputtering layer boundary position obtained from all samples, the two boundaries are fitted into a circle to characterize the extent of the sputtering layer.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, The procedure is the lunar crater ejecta detection method based on synthetic aperture radar imagery as described in any one of claims 1-5 above.

8. An electronic device, characterized in that, include: The method includes a memory, a processor, and a program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the lunar crater ejecta detection method based on synthetic aperture radar imagery as described in any one of claims 1-5 above.

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