A method for enhancing azimuth resolution of spaceborne microwave scatterometer based on image reconstruction technique

Abstract

The application discloses a kind of based on image reconstruction technology's spaceborne microwave scatterometer azimuth resolution enhancement method, according to the demand of range resolution, range beam footprint is divided into several resolution units, by scaling, the power of resolution unit is converted into backscattering coefficient, simultaneously based on observation geometry information, the observation position corresponding to backscattering coefficient is determined by geographic positioning;Along the ground footprint track formed by the beam center corresponding to each range resolution unit along antenna scanning section is continuously divided into one-dimensional uniform grid, based on range high-resolution backscattering coefficient and corresponding spatial response function, scatterometer image reconstruction algorithm is used to realize backscattering coefficient reconstruction in grid area by projecting information in grid area.The application can realize the azimuth resolution improvement of spaceborne microwave scatterometer in real time, reliably and efficiently by overcoming the limitations of existing processing method, and is a practical spaceborne microwave scatterometer data processing method.

Description

TECHNICAL FIELD

[0001] The application relates to a kind of spaceborne microwave scatterometer resolution enhancement methods, belong to space microwave remote sensing technical field. BACKGROUND

[0002] The spaceborne microwave scatterometer of fan beam and pencil beam system usually uses linear frequency modulation signal to realize distance direction pulse compression by dechirp processing technology, and the echo power is divided into multiple high-resolution measurement units in distance direction by using the correspondence between dechirp signal frequency and time delay (distance), but it cannot realize high-resolution measurement in azimuth direction due to the limitation of antenna inherent beam width. In order to improve the azimuth resolution of backscattering coefficient observation data, two processing methods are currently mainly used:

[0003] (1) Scatterometer image reconstruction method: by introducing numerical iterative algorithm to solve the observation equation model, the noise signal amplification in the reconstruction process is suppressed, and the two-dimensional high-resolution reconstruction in distance and azimuth is realized, but this method needs to accumulate multi-track or multi-sky or the same track forward and backward observation data in the reconstruction area, so it cannot meet the real-time high-resolution detection demand of sea surface wind field, and can only be applied to land and south and north poles and other areas where the scattering characteristics are basically unchanged for a long time and are not sensitive to instrument observation azimuth. In addition, this method has low processing efficiency due to the need for data accumulation.

[0004] (2) Azimuth one-dimensional high-resolution processing method based on strip measurement data: used to solve the problem of insufficient azimuth resolution in forward and backward observation areas of high-resolution high-precision scatterometer using distance-doppler processing technology. This method is based on the over-determined or completely determined observation equation model established by scatterometer in the forward and backward areas under high sampling rate, and uses improved adaptive normalization algorithm to realize azimuth one-dimensional high-resolution reconstruction, but this method depends on high pulse sampling rate to ensure the positive or over-determined nature of the observation matrix model, and is only applied to forward and backward area observation data. SUMMARY

[0005] The application provides a spaceborne microwave scatterometer azimuth resolution enhancement method, which can produce backscattering coefficient with high resolution in distance and azimuth at all scanning azimuth positions of the scatterometer, and can realize real-time, reliable and efficient azimuth resolution enhancement of the spaceborne microwave scatterometer.

[0006] The technical solution of the application comprises:

[0007] A spaceborne microwave scatterometer azimuth resolution enhancement method based on image reconstruction technology, comprising:

[0008] Step one, distance direction high resolution processing: through distance direction resolution unit subdivision, distance direction resolution unit backscattering coefficient scaling and distance direction resolution unit geographic positioning processing, distance direction resolution unit backscattering coefficient is obtained, and each distance direction resolution unit footprint center latitude Lat p and Lon p is determined, and corresponding ground incident angle Eia p and geographic azimuth angle Azi p are determined, and antenna scanning angle Scan p reflecting observation data forward and backward state is reserved.

[0009] Step two, azimuth direction one-dimensional resolution enhancement processing: through azimuth direction one-dimensional reconstruction parameter calculation, original observation data reorganization, azimuth direction high resolution reconstruction and reconstructed data geographic geometry auxiliary information;

[0010] backscattering coefficient with high resolution in distance direction and azimuth direction is obtained, and longitude, latitude, ground incident angle, geographic azimuth angle and antenna scanning angle information corresponding to the high resolution backscattering coefficient are obtained.

[0011] Optionally, step one, distance direction high resolution processing specifically includes:

[0012] distance direction beam footprint is divided into a plurality of resolution units according to distance direction resolution requirement, resolution unit power is converted into backscattering coefficient through scaling based on echo power slice distribution and distance direction resolution unit corresponding relationship and system parameters, and observation position corresponding to the backscattering coefficient is determined through geographic positioning based on observation geometry information; the number of measurement units that can be provided by scatterometer in distance direction for each observation is calculated, that is, the number of distance direction resolution units, each distance direction resolution unit corresponds to a power slice in a certain range of echo measurement value. The power slice corresponding to each distance direction resolution unit is accumulated and scaled to determine the backscattering coefficient corresponding to the distance direction resolution unit through the distance direction resolution unit backscattering coefficient scaling step. Finally, the geographic position information of each distance direction resolution unit backscattering coefficient is determined through the distance direction resolution unit geographic positioning step, including latitude, longitude, ground incident angle, geographic azimuth angle and antenna scanning angle, which provides input for azimuth direction one-dimensional resolution enhancement processing. The backscattering coefficient of each distance direction resolution unit and the corresponding geographic position data are arranged in order of original scanning observation time of the scatterometer.

[0013] Optionally, step two, azimuth direction one-dimensional resolution enhancement processing specifically includes:

[0014] The specific distance direction resolution unit ground surface coverage range of each participating azimuth direction resolution enhancement processing is determined by the azimuth direction one-dimensional reconstruction parameter calculation step, and the number of specific distance direction resolution units observed in each participating azimuth direction high resolution reconstruction is determined; after the antenna scanning angle and the geographic azimuth angle are converted in angle before the azimuth direction high resolution reconstruction, the distance direction resolution unit backscattering coefficient, the latitude, the longitude, the adjusted antenna scanning angle and the geographic azimuth angle, and the incident angle are reorganized in four dimensions as the input of the azimuth direction high resolution reconstruction processing step according to the scanning starting angle and the front and rear view identification in the scanning period; the high resolution reconstruction processing step traverses the input data in the distance direction resolution unit dimension, the scanning period dimension and the front and rear view dimension in turn, processes the distance direction resolution unit backscattering coefficient based on the reconstruction parameter and the spatial response function information by using the scatterometer image reconstruction algorithm, and realizes the azimuth direction resolution enhancement of each distance direction resolution unit backscattering coefficient; the latitude, the longitude, the adjusted antenna scanning angle and the geographic azimuth angle information corresponding to the azimuth direction resolution enhancement processed backscattering coefficient are calculated by the reconstruction data geographic geometry auxiliary information calculation step from the distance direction resolution unit latitude, longitude, adjusted antenna scanning angle and geographic azimuth angle, and finally the backscattering coefficient with enhanced distance direction and azimuth direction resolution, and the corresponding latitude, longitude, antenna scanning angle and geographic azimuth angle information are obtained.

[0015] Optionally, the distance direction high resolution processing includes:

[0016] (1) Distance direction resolution unit subdivision

[0017] The ground footprint is subdivided into a plurality of ground resolution units N Ele :

[0018]

[0019] S Ele is the ground footprint size of the antenna distance direction 3dB beam, ΔR Ele is the distance direction required resolution;

[0020] (2) Distance direction resolution unit backscattering coefficient calibration

[0021] In real-time processing of remote sensing data, the echo power slice accumulation range and the irradiation integration parameter I 0r corresponding to each distance direction resolution unit in each pulse observation are obtained by looking up the power slice accumulation range and the irradiation integration parameter table based on the real-time subspace point latitude and the antenna scanning angle, and the echo power P 0r,p of each pulse distance direction resolution unit is calculated:

[0022]

[0023] r1 and r2 respectively represent the start and end sequence numbers corresponding to the echo power slice contained by the rth distance direction resolution unit, i represents the echo power slice sequence number, the above formula means that the echo power slices selected from r1 to r2 are accumulated, r=1, 2…N Ele , p represents the scanning observation point sequence number;

[0024] Based on the internal calibration data, the P 0r,p is denoised to obtain a pure signal power P sr,p , and the range resolution unit is obtained by combining the irradiation integral factor and the radar system parameters

[0025]

[0026] X1 is a fixed parameter related to the system, and X2 is a parameter related to the internal calibration of the system;

[0027] (3) Geographical positioning of the range direction resolution unit

[0028] The geographical positioning of each range direction resolution unit is performed for each pulse observation, and the latitude Lat p and the longitude Lon p of the footprint center of each range direction resolution unit are determined p , the corresponding ground incidence angle Eia p and the geographical azimuth angle Azi p are determined, and the antenna scanning angle Scan EA reflecting the forward and backward states of the observation data is retained.

[0029] Optionally, the azimuth direction one-dimensional resolution enhancement processing includes:

[0030] (1) Azimuth direction one-dimensional reconstruction parameter calculation

[0031] When the satellite position vector and the velocity vector , the antenna beam center elevation angle and the antenna beam center azimuth angle are θ0 and respectively, the conversion matrix M EA from the earth fixed coordinate system to the antenna coordinate system is calculated:

[0032] M EA =M Ecf2Ant M Ins (4);

[0033] Where M Ecf2Ant is a conversion matrix related to the satellite position vector, the velocity vector, the beam center elevation angle and the beam center azimuth angle, and M Ins represents an instrument installation offset matrix;

[0034] Let the beam angle corresponding to each resolution unit be θ. r r = 1, 2…N Ele The azimuth angle of each resolution element is consistent with the azimuth angle of the antenna beam center. Assuming the beamwidth of the azimuth antenna of the resolving element is 2φ0, the azimuth traversal range used for the azimuth projection of the resolving element is... The traversal interval is Δφ. The location of the first null point in the azimuth pattern of the coverage antenna; based on the satellite position vector. velocity vector Radar instrument mounting matrix, resolution unit beam angle θ r 1. Resolve the azimuth angle of the projection of the unit. j = 1, 2…M, where M is the number of azimuth subdivisions of the resolution unit. The ground projection point corresponding to the distance resolution unit is calculated. from arrive The connecting vector is:

[0035]

[0036] vector The modulus is the distance from the satellite to the ground projection point:

[0037]

[0038] Transformation matrix M from Earth fixed coordinate system to antenna coordinate system EA Will Transform to the antenna coordinate system;

[0039]

[0040] Depend on Calculated vector Elevation and azimuth angles in the antenna coordinate system:

[0041]

[0042]

[0043] This can be determined by looking up the table. The corresponding antenna two-way gain G rj Combined with slant distance R rj The azimuth spatial response function (RSF) of each range-resolved cell was obtained. rj :

[0044]

[0045] For RSF rj according to Normalization yields the normalized spatial response function RSF. rj,n :

[0046]

[0047] Accordingly, based on the coordinates of the ground projection point of the distance resolution unit Calculate the projection points along the azimuth direction relative to the central projection point. Distance D Rsf,rj The relative distance D between the center projection points Rsf,cen =0; the sign will be converted to correspond to the azimuth angle. Part D Rsf,rj Convert to a negative value to facilitate the reconstruction of the spatial function in the orientation direction, i.e.:

[0048]

[0049] When the microwave scatterometer is working normally, the satellite position corresponding to different observation points changes with the movement of the satellite platform. When using the conical scan observation method, the satellite position corresponding to any fixed observation point... Other scanning observation points and (m=nM, n-M+1…n+M,m≠n) The connecting vector is, where n represents the index of any fixed observation point, and m represents the index of the 2M observation points that are adjacent to this observation point in time:

[0050]

[0051] The corresponding beam angle is:

[0052]

[0053] Corresponding beam angle α mn The variation should be controlled within the Δα range of each distance resolution angle. r Within this range, and thereby determine the observation points involved in the reconstruction. Within the 2M observation points that are adjacent in time as described above, M0 observation points satisfy the condition that the coverage area is located within the same range resolution cell. The width ΔS of the effective reconstruction area in the azimuth direction is:

[0054] ΔS=M0ΔP (15);

[0055] ΔP is the distance on the ground from the center of the footprint of the adjacent pulse beam along the scanning direction;

[0056] (2) Reassembly of raw observation data

[0057] The original data antenna scan angle and geographic azimuth angle were adjusted and converted to a range of ±180°:

[0058]

[0059] Scan p and Azi p respectively represent the corresponding scan azimuth and beam footprint center geographic azimuth of the backscatter coefficient obtained by range-dependent high resolution processing, p represents the scan observation point sequence number;

[0060] According to the antenna scan angle, the forward and backward view identifiers of each scan observation are calculated:

[0061]

[0062] The backscatter coefficient, latitude, longitude, adjusted antenna scan angle and geographic azimuth, incident angle, forward and backward view identifier of each range-dependent resolution unit obtained by range-dependent high resolution processing are arranged according to the scatterometer periodic scan observation timing;

[0063] The data obtained by range-dependent high resolution processing is reorganized according to the following method: the nearest forward scan azimuth to-90° in each scan period is taken as the scan starting angle, and the backscatter coefficient, latitude, longitude, adjusted antenna scan angle and geographic azimuth, incident angle, forward and backward view identifier are periodically arranged according to the scan starting angle value, and in each period, the data is divided into forward and backward view state data according to the forward and backward view identifiers;

[0064] The reorganized data is divided into four dimensions, the first dimension corresponds to different distance resolution units, the second dimension corresponds to different scan periods, the third dimension corresponds to forward and backward view, and the fourth dimension corresponds to different observation points in forward or backward view;

[0065] (3) Azimuth high resolution reconstruction

[0066] Select the forward or backward view observation data in a specific distance resolution unit and scan period, and uniformly divide the coverage range of the beam footprint of the continuous scan observation points into N P intervals, each interval has an azimuth reconstruction region width ΔS, the Pth interval is represented as [S P S P +ΔS], S P represents the distance of the starting point of the Pth reconstruction interval along the scan trajectory relative to the footprint center of the first scan point;

[0067] According to the ground projection coordinates of the scan observation points covering the reconstruction region [S P S P +ΔS] Calculate Distance D between the footprint center of the starting observation point of the scan observation section and the scan trajectory Azi,p ;

[0068] According to the azimuthal one-dimensional reconstruction target resolution requirement, the Pth to be reconstructed interval [S P S P +ΔS] is uniformly divided into N Q intervals, each interval [R q R q +ΔR] represents an azimuthal resolution unit with a size of ΔR, and the starting point R q represents the distance between the starting point of the azimuthal resolution unit and the footprint center of the starting observation point of the scan observation section.

[0069] For each observation point , its normalized spatial response function RSF ij,n , the corresponding relative distance is D Rsf,j , then RSF ij,n , the distance from the starting point of the scan observation section is D Azi,p +D Rsf,j , and the search distance value D Azi,p +D Rsf,j is located in the interval [R q R q +ΔR] and is averaged as the spatial response function value of the Pth observation point falling into the qth azimuthal resolution unit.

[0070]

[0071] Ind1 and Ind2 represent the starting and ending ranges of the sequence number located in the interval [R q R q +ΔR] with a distance value D Azi,p +D Rsf,j , Q p =Ind2-Ind1+1.

[0072] The observation point corresponding to the backscatter coefficient , combined with the spatial response function RSF ij,n , the scatterometer image reconstruction algorithm SIR is applied to realize the backscatter coefficient reconstruction of each azimuthal resolution unit [R P S P +ΔS] in the interval [R q R q +ΔR].

[0073] (4) Calculation of geographical geometric auxiliary information of reconstructed data

[0074] The azimuthal resolution unit [R q Rq The center position of +ΔR] is taken as the center of the reconstructed scattering coefficient position, that is The corresponding Lon at this position q Lat q Antenna Scan Angle q Geographic azimuth Azi q and the angle of incidence Eia q Lon information can be based on the original observation data used to reconstruct the backscattering coefficients in this region. p Lat p Antenna Scan Angle p Geographic azimuth Azi p and the angle of incidence Eia p Determined by interpolation;

[0075] Finally, repeat steps (3) to (4) to traverse all range resolution cells, scanning cycles, forward-looking and backward-looking observation data to achieve one-dimensional azimuth high-resolution reconstruction of all observation data. The processed backscattering coefficients have high resolution in both range and azimuth directions.

[0076] Optionally, the SIR implementation interval of the scatterometer image reconstruction algorithm [S p S p Each azimuth resolution unit within +ΔS] [R] q R q The backscattering coefficients of +ΔR] are reconstructed, and the specific reconstruction process is as follows:

[0077] a. The vector composed of the backscattering coefficients of each resolution cell in the azimuth direction is S, s q Let S represent the scattering coefficient of the q-th resolving unit, and initialize the vector to any vector S. 0 ;

[0078] b. The (k+1)th iteration:

[0079]

[0080] in:

[0081] λ is the iterative tuning factor, h pq The average value of the normalized spatial response function of the p-th original observation point participating in the reconstruction falls within the q-th resolution cell;

[0082] In each iteration, the original observation data participates in the update of the backscattering coefficients of the azimuth resolution unit;

[0083] c. Repeat step b. As the number of iterations increases, the difference between the results of the previous and subsequent iterations gradually decreases until convergence.

[0084] Compared with the prior art, the application has the advantages of:

[0085] The application divides the reconfiguration grid area in real time along the central track of the beam footprint formed by antenna scanning and applies the SIR algorithm for resolution enhancement processing, and does not need to accumulate multi-day or multi-track or front and rear observation data, has higher real-time performance relative to the existing two-dimensional reconfiguration processing method, and simplifies the two-dimensional reconfiguration problem into a one-dimensional problem.

[0086] The method provided by the application performs azimuth resolution enhancement processing at all scanning positions in each scanning period, has higher coverage relative to the existing method of processing only in the front and rear regions,

[0087] All scanning positions in each scanning period can be covered except for internal calibration measurement.

[0088] The data after azimuth resolution enhancement processing by the method provided by the application synchronously retains the observation geometry information in the original data, facilitates the multi-aspect application of the data after resolution enhancement, and the traditional processing method discards the observation geometry information of the original data participating in reconfiguration. BRIEF DESCRIPTION OF DRAWINGS

[0089] The accompanying drawings are included to provide a further understanding of the present disclosure and constitute a part of the specification, and together with the following specific embodiments, serve to explain the present disclosure but do not constitute a limitation on the present disclosure. In the drawings:

[0090] Figure 1 The flowchart of the azimuth resolution enhancement method of the spaceborne microwave scatterometer based on the image reconfiguration technology of the application;

[0091] Figure 2 The result graph before the distance high-resolution processing of example one;

[0092] Figure 3 The result graph after the distance high-resolution processing of example one;

[0093] Figure 4 The result graph after the azimuth one-dimensional high-resolution reconfiguration of example one;

[0094] Figure 5 The scatter coefficient distribution graph before and after the azimuth one-dimensional resolution enhancement processing of the isolated island near the South Pole processed by example one; the forward scatter coefficient distribution graph before and after the azimuth one-dimensional reconfiguration;

[0095] Figure 6 The scatter coefficient distribution graph before and after the azimuth one-dimensional resolution enhancement processing of the isolated island near the South Pole processed by example one; the scatter coefficient distribution graph after the azimuth one-dimensional reconfiguration. DETAILED DESCRIPTION

[0096] The application is further explained and described in conjunction with the accompanying drawings and detailed description.

[0097] The application discloses a spaceborne microwave scatterometer azimuth resolution enhancement method based on an image reconstruction technology, relates to spaceborne microwave scatterometer data processing, and belongs to the technical field of space microwave remote sensing. The application comprises the following steps: firstly, dividing a distance direction beam footprint into a plurality of resolution units according to distance direction resolution requirements; converting resolution unit power into backscatter coefficients by calibration based on the correspondence between echo power slice distribution and the distance direction resolution unit and system parameters; and determining the observation positions corresponding to the backscatter coefficients by geographic positioning based on observation geometry information. The distance direction high-resolution backscatter coefficients corresponding to the beam footprint have a certain overlap degree in the scanning direction, the ground footprint track formed by the beam centers corresponding to the distance direction resolution units is continuously divided into a one-dimensional uniform grid in sections along antenna scanning, the scatterometer image reconstruction (SIR) algorithm is applied to realize backscatter coefficient reconstruction in the grid based on the projection information of the distance direction high-resolution backscatter coefficients and the corresponding spatial response function in the grid area, so that the azimuth resolution is improved, and finally, the backscatter coefficient product with high resolution in the distance direction and the azimuth direction is obtained. The application can realize real-time, reliable and efficient enhancement of the azimuth resolution of the spaceborne microwave scatterometer by overcoming the limitations of the existing processing method, and is a practical spaceborne microwave scatterometer data processing method.

[0098] The technical solution of the application comprises the following two steps in sequence:

[0099] Step one, distance direction high-resolution processing. The distance direction high-resolution processing comprises the following steps: distance direction resolution unit subdivision, distance direction resolution unit backscatter coefficient calibration and distance direction resolution unit geographic positioning processing, so as to produce the backscatter coefficient product with high spatial resolution in the distance direction, which serves as the basis for the azimuth one-dimensional resolution enhancement processing.

[0100] Step two, azimuth one-dimensional resolution enhancement processing. The azimuth one-dimensional resolution enhancement processing comprises the following steps: azimuth one-dimensional reconstruction parameter calculation, original observation data reorganization, azimuth high-resolution reconstruction and reconstructed data geographic geometry auxiliary information calculation, so as to produce the backscatter coefficient product with high spatial resolution in the azimuth direction.

[0101] Specifically, the application comprises the following steps:

[0102] The azimuth resolution enhancement method of the spaceborne microwave scatterometer based on image reconstruction technology processes the scatterometer original data in the range direction and the azimuth direction in turn, and finally obtains the backscatter coefficient and related information with high resolution in the range direction and the azimuth direction.

[0103] The distance direction resolution unit subdivision step calculates the number of measurement units that the scatterometer can provide in the distance direction for each observation, i.e. the number of distance direction resolution units, and each distance direction resolution unit corresponds to a certain range of power slices in the echo measurement value. The distance direction resolution unit backscatter coefficient scaling step accumulates and scales the power slices corresponding to each distance direction resolution unit to determine the backscatter coefficient of the distance direction resolution unit. Finally, the distance direction resolution unit geographic positioning step determines the geographic position information corresponding to the backscatter coefficient of each distance direction resolution unit, including latitude, longitude, ground incidence angle, geographic azimuth angle and antenna scanning angle, which provides input for the azimuth one-dimensional resolution enhancement processing. The backscatter coefficient of each distance direction resolution unit and the corresponding geographic position data are arranged in the order of the original scanning observation time of the scatterometer.

[0104] The azimuth one-dimensional resolution enhancement processing first determines the ground surface coverage range of the specific distance direction resolution unit along the scanning footprint direction participating in the azimuth resolution enhancement processing each time through the azimuth one-dimensional reconstruction parameter calculation step, and then determines the number of specific distance direction resolution units participating in the azimuth high-resolution reconstruction each time. After the angle conversion of the antenna scanning angle and the geographic azimuth angle, the distance direction resolution unit backscatter coefficient, latitude, longitude, adjusted antenna scanning angle and geographic azimuth angle, and incidence angle are reorganized in four dimensions according to the scanning starting angle and the front and rear view identification within the scanning period as input for the azimuth high-resolution reconstruction processing step. The high-resolution reconstruction processing step traverses the input data in the distance resolution unit dimension, the scanning period dimension and the front and rear view dimension in turn, processes the distance direction resolution unit backscatter coefficient based on the reconstruction parameters and the spatial response function information using the scatterometer image reconstruction algorithm, and realizes the azimuth resolution enhancement of each distance direction resolution unit backscatter coefficient. The latitude, longitude, adjusted antenna scanning angle and geographic azimuth angle corresponding to the azimuth resolution enhancement processed backscatter coefficient are calculated by the reconstruction data geographic geometry auxiliary information calculation step. After the above processing steps, the backscatter coefficient with enhanced resolution in the range direction and the azimuth direction, and the corresponding latitude, longitude, antenna scanning angle and geographic azimuth angle information are finally obtained.

[0105] The above processing steps obtain the backscatter coefficient product with high resolution in the range direction and the azimuth direction.

[0106] 1. Distance direction high-resolution processing

[0107] (1)Distance resolution unit subdivision

[0108] According to the actual satellite orbit parameters and wind field radar scanning observation geometry information, the distance 3dB beam width is projected to obtain the distance beam ground footprint, and according to the sea surface wind field inversion application to the backscattering coefficient distance resolution requirement, the ground footprint is subdivided into a plurality of ground resolution units N Ele , N Ele The antenna distance 3dB beam ground footprint and the application requirement resolution are determined:

[0109]

[0110] S Ele is the antenna distance 3dB beam ground footprint size, ΔR Ele is the distance requirement resolution, and different distance resolution units have the same size ground footprint.

[0111] According to the corresponding relationship between the ground footprint unit and the observation angle, slant range, antenna gain and echo power slice position, a resolution unit echo power slice accumulation range, illumination integral parameter and beam angle lookup table is established.

[0112] (2) Distance resolution unit backscattering coefficient calibration

[0113] In real-time processing of remote sensing data, based on the real-time subsatellite point latitude and antenna scanning angle, the power slice accumulation range and illumination integral parameter table is looked up to obtain the corresponding echo power slice accumulation range and illumination integral parameter I 0r of each distance resolution unit for each pulse observation, and the echo power P 0r,p of each pulse distance resolution unit is calculated:

[0114]

[0115] r1 and r2 respectively represent the start and end serial numbers of the echo power slice contained by the rth distance resolution unit, p represents the pulse observation serial number; i represents the echo power slice serial number, and the above formula means that the echo power slices with the range from r1 to r2 are selected for accumulation, r = 1, 2…N Ele , p represents the pulse observation serial number;

[0116] Based on the internal calibration data, the noise reduction processing is performed on P 0r,p to obtain the pure signal power P sr,p , and the illumination integral factor and radar system parameters are combined to obtain the distance resolution unit backscattering coefficient:

[0117]

[0118] X1 is a fixed parameter related to the system, and X2 is a parameter related to the calibration in the system.

[0119] (3) Geographical positioning of the range direction resolution unit

[0120] Based on the information such as the antenna scanning angle at the pulse observation time, the satellite ephemeris, and the radar installation offset matrix, and in combination with the beam view angle obtained by table lookup, the geographical positioning of each range direction resolution unit is performed for each pulse observation, the latitude Lat p , Lon p of the footprint center of each range direction resolution unit is determined p , the corresponding ground incidence angle Eia p and the geographical azimuth angle Azi p are determined, and the antenna scanning angle Scan p reflecting the forward and backward states of the observation data is retained.

[0121] 2. Azimuth direction one-dimensional resolution enhancement processing

[0122] (1) Azimuth direction one-dimensional reconstruction parameter calculation

[0123] When the satellite position vector and the velocity vector , the antenna beam center elevation angle is θ0, and the antenna beam center azimuth angle is , the conversion matrix M EA from the earth fixed coordinate system to the antenna coordinate system is calculated:

[0124] M EA = M Ecf2Ant M Ins (4);

[0125] wherein M Ecf2Ant is a conversion matrix related to the satellite position vector, the velocity vector, the beam center elevation angle, and the beam center azimuth angle, and M Ins represents the instrument installation offset matrix.

[0126] Let the beam elevation angle corresponding to each resolution unit be θ r , r = 1, 2, …, N Ele , and the azimuth angle of each resolution unit is consistent with the antenna beam center azimuth angle, which is Let the azimuth direction antenna beam width of the resolution unit be 2φ0, and the azimuth angle range used for the resolution unit projection is The traversal interval is covering the first zero point position of the antenna azimuth direction pattern. According to the satellite position vector , the velocity vector , the radar instrument installation matrix, the resolution unit beam pointing angle θ r , and the resolution unit projection traversal azimuth angle j = 1, 2…M, where M is the number of azimuth subdivisions of the resolution unit; calculate the ground projection point corresponding to the distance resolution unit. from arrive The connecting vector is:

[0127]

[0128] vector The modulus is the distance from the satellite to the ground projection point:

[0129]

[0130] Transformation matrix M from Earth fixed coordinate system to antenna coordinate system EA Will Transform to antenna coordinate system

[0131]

[0132] Depend on Calculated vector Elevation and azimuth angles in the antenna coordinate system:

[0133]

[0134]

[0135] This can be determined by looking up the table. The corresponding antenna two-way gain G rj Combined with slant distance R rj The azimuth spatial response function (RSF) of each range-resolved cell was obtained. rj :

[0136]

[0137] For RSF rj according to Normalization yields the normalized spatial response function RSF. rj,n :

[0138]

[0139] Accordingly, based on the coordinates of the ground projection point of the distance resolution unit Calculate the projection points along the azimuth direction relative to the central projection point. Distance D R sf,rj, the relative distance D between the center projection points Rsf,cen =0. The sign will be changed to correspond to the azimuth angle. Part D Rsf,rj Convert to a negative value to facilitate the reconstruction of the spatial function in the orientation direction, i.e.:

[0140]

[0141] When the microwave scatterometer is working normally, the satellite position corresponding to different observation points changes with the movement of the satellite platform. When the conical scanning observation mode is adopted, for any fixed observation point, the satellite position corresponding to the observation point changes with the movement of the satellite platform Other scanning observation points and The line vector is:

[0142]

[0143] The corresponding beam view angle is:

[0144]

[0145] To ensure the azimuth one-dimensional high-resolution reconstruction accuracy, the area covered by the observation points participating in the reconstruction must be located in the same distance resolution unit, that is, the corresponding view angle α mn should be controlled within each distance resolution view angle range Δα r , and the observation points participating in the reconstruction are determined accordingly. The azimuth effective reconstruction area width is ΔS, and in the above 2M observation points adjacent in time, there are M0 observation points satisfying the condition that the covered area is located in the same distance resolution unit:

[0146] ΔS = M0ΔP (15)

[0147] ΔP is the ground distance of the center of the adjacent pulse beam footprint along the scanning direction.

[0148] (2) Original observation data reorganization

[0149] To ensure the continuity of the high-resolution data antenna scanning angle and geographical azimuth angle after reconstruction, and to avoid the antenna scanning angle and geographical azimuth angle jump problem caused by interpolation when the reconstruction is performed in the area formed by the continuous scanning footprint, the original data antenna scanning angle and geographical azimuth angle are converted to the range of ±180°:

[0150]

[0151]

[0152] Scan p and Azi p respectively represent the scanning azimuth angle and the geographical azimuth angle of the center of the pulse observation point.

[0153] According to the antenna scanning angle, the front view and rear view marks of each original observation data are calculated:

[0154]

[0155] The backscattering coefficients, latitude, longitude, adjusted antenna scan angle and geographic azimuth, incident angle, and fore- and back-look markers of each range-resolved unit obtained after range-oriented high-resolution processing are arranged according to the periodic scanning observation sequence of the scatterometer. The data obtained after range-oriented high-resolution processing are reorganized according to the following method: the nearest fore-look scanning azimuth within each scanning cycle is taken as the scanning starting angle. Based on this scanning starting angle value, the backscattering coefficients, latitude, longitude, adjusted antenna scan angle and geographic azimuth, incident angle, and fore- and back-look markers are periodically arranged. Within each cycle, the data is divided into fore-look and back-look state data according to the fore-look and back-look markers. The original data (backscattering coefficients, latitude, longitude, antenna scan angle, geographic azimuth) are arranged according to the periodic scanning sequence of the antenna. The data of each scanning cycle consists of fore-look and back-look state observation data. The starting point of each scanning cycle data corresponds to the nearest fore-look scanning azimuth at -90°. The reconstructed data is divided into four dimensions: the first dimension corresponds to different distance resolution units, the second dimension corresponds to different scanning cycles, the third dimension corresponds to forward and backward looking within a cycle, and the fourth dimension corresponds to different observation points in forward or backward looking.

[0156] (3) High-resolution reconstruction in azimuth direction

[0157] By selecting specific range-resolved cells and forward-looking or backward-looking observation data within a scanning period, the beam footprint coverage of continuous scanning observation points is uniformly divided into N. P There are intervals, each interval having a length equal to the width ΔS of the azimuth reconstruction region. p The interval is represented as [S] p S p +ΔS],S p Indicates the sequence along the scan trajectory. p The distance between the starting point of the interval to be reconstructed and the center of the footprint of the first scan point.

[0158] Based on the coverage reconstruction area [S] p S p Ground projection coordinates of the pulse observation point [+ΔS] calculate The distance D from the center of the footprint along the scanning trajectory relative to the starting observation point of the scanning observation segment (forward observation segment and backsight observation segment) Azi,p .

[0159] Based on the one-dimensional reconstruction target resolution requirements in the orientation direction, the p-th interval [S p S p +ΔS] is uniformly divided into N QThere are intervals, each interval [R] q R q +ΔR] represents a azimuth resolution cell of size ΔR, with the interval starting point R. q This indicates the distance from the starting point of the azimuth resolution unit to the center of the footprint of the starting observation point of the scanning observation segment (forward observation segment and backward observation segment).

[0160] For each observation point Its normalized spatial response function RSF ij,n The corresponding relative distance is D Rsf,j Then RSF ij,n The distance relative to the starting point of the scanning observation segment (forward observation segment and backsight observation segment) is D. Azi,p +D Rsf,j Search distance value D Azi,p +D Rsf,j Located in the interval [R q R q The spatial response function within +ΔR] is averaged and used as the spatial response function value of the p-th observation point falling into the q-th azimuth resolution unit.

[0161]

[0162] Ind1 and Ind2 respectively represent the interval [R] q R q +ΔR] Inner distance value D Azi,p +D Rsf,j The start and end range of the sequence number, Q p =Ind2-Ind1+1.

[0163] Observation point corresponding backscattering coefficient Combining the spatial response function RSF ij,n The Scattermeter Image Reconstruction (SIR) algorithm can be used to reconstruct images in the range [S]. p S p Each azimuth resolution unit within +ΔS] [R] q R q +ΔR] Backscattering coefficient reconstruction. The SIR algorithm uses a numerical iterative method to reconstruct the azimuth resolution cell [R]. q R q +ΔR] backscattering coefficients, the specific reconstruction process is as follows:

[0164] a. The vector composed of the backscattering coefficients of each resolution cell in the azimuth direction is S, s q This represents the scattering coefficient of the q-th resolving unit. The vector is initialized to an arbitrary vector S. 0 .

[0165] b. the k+1th iteration

[0166]

[0167] wherein:

[0168] λ is the iteration tuning factor, h pq is the average value of the normalized spatial response function of the pth original observation point participating in the reconstruction falling into the qth resolution cell.

[0169] In each iteration, the original observation data participates in the azimuth resolution cell backward scattering coefficient update.

[0170] c. Repeat step b, as the number of iterations increases, the difference between the front and back iterations gradually decreases until convergence.

[0171] (4) Reconstruction data geographic geometry auxiliary information calculation

[0172] Select the center position of the azimuth resolution cell [R q R q +ΔR] as the center position of the reconstructed backscattering coefficient, that is The corresponding Lon q , Lat q , antenna scan angle Scan q , geographic azimuth angle Azi q and incident angle Eia q can be determined by interpolation based on the corresponding information Lon p , Lat p , antenna scan angle Scan p , geographic azimuth angle Azi p and incident angle Eia p of the original observation data participating in the reconstruction of the area backward scattering coefficient.

[0173] Finally, repeat steps (3)-(4) to traverse all distance resolution cells, scan periods, forward and backward observation data, and realize one-dimensional azimuth high-resolution reconstruction of all observation data. The processed backscattering coefficient has high resolution in distance and azimuth. Because the reconstruction processing is along the antenna beam scanning footprint, the reconstructed data has the same observation geometry characteristics as the original data, and there is no need to separately locate the reconstruction area and calculate the observation geometry auxiliary information, which improves the data processing efficiency.

[0174] Example one:

[0175] The test and verification of the azimuth resolution enhancement method of the spaceborne microwave scatterometer based on the image reconstruction technology is carried out on a Windows system PC (memory 129G, main frequency 3.1GHz, Core i7 processor, hard disk space 100G or more). The data processing software code is written and tested by using the Matlab software.

[0176] The original measured data of the spaceborne microwave scatterometer are taken as input, and the data are processed according to the method described above. The effectiveness of the azimuth resolution enhancement method of the spaceborne microwave scatterometer based on the image reconstruction technology is verified by comparing the changes of the backscattering coefficient distribution before and after each main processing step.

[0177] The backscattering coefficient distributions of the original observation data of the spaceborne microwave scatterometer in the Greenland region before the distance high-resolution processing, after the distance high-resolution processing and after the azimuth one-dimensional high-resolution reconstruction processing are shown in Figs. Figure 2 、 3 and 4. Figure 2 Before the distance high-resolution processing, Figure 3 After the distance high-resolution processing, Figure 4 After the azimuth one-dimensional high-resolution reconstruction processing; by comparing the backscattering coefficient distribution maps of the Greenland region before the distance high-resolution processing, after the distance high-resolution processing and after the azimuth one-dimensional high-resolution reconstruction processing, it can be seen that after the processing of the azimuth resolution enhancement method of the spaceborne microwave scatterometer based on the image reconstruction technology, the island boundary coastline is clearer, and the local backscattering distribution details of the island are more obvious.

[0178] The backscattering coefficient distributions of the isolated islands near the South Pole before and after the azimuth one-dimensional resolution enhancement processing are shown in Figs. Figure 5 and 6 . Figure 5 is the backscattering coefficient distribution before the azimuth one-dimensional reconstruction processing, Figure 6 is the backscattering coefficient distribution after the azimuth one-dimensional reconstruction processing; by comparing the changes of the backscattering coefficient distribution of the isolated islands before and after the azimuth one-dimensional high-resolution reconstruction processing, it is shown that after the azimuth one-dimensional high-resolution reconstruction processing, the scattering characteristics of the isolated islands are more obvious, and the purpose of resolution enhancement is achieved.

[0179] The above data processing test results verify the effectiveness of the azimuth resolution enhancement method of the spaceborne microwave scatterometer based on the image reconstruction technology for realizing the spatial resolution enhancement of the backscattering coefficient.

[0180] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

[0181] Although the present application has been described in detail with particular references to illustrative embodiments thereof, it should be understood that modifications and / or improvements can be made to the present application which fall within the scope of the present application. Accordingly, no limitation is intended to the details of construction or the arrangement of parts illustrated, other than as described in the claims below and any equivalents thereto.

Claims

1. A method for enhancing the azimuth resolution of a spaceborne microwave scatterometer based on image reconstruction technology, characterized in that, include: Step 1, Range-oriented high-resolution processing: After subdividing the range-oriented resolution cells, calibrating the backscattering coefficients of the range-oriented resolution cells, and geolocating the range-oriented resolution cells, the backscattering coefficients of the range-oriented resolution cells are obtained, and the latitude of the footprint center of each range-oriented resolution cell is determined. and At the same time, determine the corresponding ground incident angle. and geographical azimuth It also retains the antenna scanning angle that reflects the foresight and backsight states of the observation data. Specifically, the process includes: dividing the range beam footprint into several resolution units based on range resolution requirements; converting the power of each resolution unit into backscattering coefficients through calibration based on the correspondence between the echo power slice distribution and the range resolution units, as well as system parameters; simultaneously determining the observation location corresponding to the backscattering coefficients through geolocation based on observation geometry information; calculating the number of measurement units available in the range direction for each observation by the scatterometer through the range resolution unit subdivision step, i.e., the number of range resolution units, with each range resolution unit corresponding to a power slice within a certain range of the echo measurement value; accumulating and calibrating the power slices corresponding to each range resolution unit through the range resolution unit backscattering coefficient calibration step to determine the backscattering coefficient corresponding to that range resolution unit; finally, determining the geographical location information corresponding to the backscattering coefficient of each range resolution unit through the range resolution unit geolocation step, including latitude, longitude, ground incident angle, geographical azimuth angle, and antenna scanning angle, providing input for azimuth one-dimensional resolution enhancement processing; and arranging the backscattering coefficients and corresponding geographical location data of each range resolution unit in the order of the original scanning observation time of the scatterometer. Step 2, Azimuth-oriented one-dimensional resolution enhancement processing: Through azimuth-oriented one-dimensional reconstruction parameter calculation, original observation data reconstruction, azimuth-oriented high-resolution reconstruction, and geographic geometric auxiliary information of the reconstructed data, the backscattering coefficient with high resolution in both range and azimuth directions is obtained. Simultaneously, the longitude, latitude, ground incidence angle, geographic azimuth angle, and antenna scan angle information corresponding to the high-resolution backscattering coefficient are obtained. Specifically, this includes: determining the surface coverage of specific range-oriented resolution cells along the scan footprint direction for each azimuth-oriented resolution enhancement process through the azimuth-oriented one-dimensional reconstruction parameter calculation step, thereby determining the number of specific range-oriented resolution cells observed for each azimuth-oriented high-resolution reconstruction; after angle conversion of the antenna scan angle and geographic azimuth angle before azimuth-oriented high-resolution reconstruction, the backscattering coefficient, latitude, longitude, and other parameters of the range-oriented resolution cells are adjusted according to the scan start angle and foresight markers within the scan cycle. The antenna scan angle, geographic azimuth, and incident angle are reconstructed according to four dimensions and used as inputs for the azimuth-oriented high-resolution reconstruction process. The high-resolution reconstruction process sequentially traverses the input data in the range-resolved cell dimension, scan period dimension, and forward and backward look dimensions. Based on the reconstruction parameters and spatial response function information, the backscattering coefficients of the range-resolved cells are processed using a scatterometer image reconstruction algorithm to enhance the azimuth resolution of the backscattering coefficients of each range-resolved cell. The latitude, longitude, antenna scan angle, and geographic azimuth information corresponding to the azimuth resolution-enhanced backscattering coefficients are calculated from the latitude, longitude, antenna scan angle, and geographic azimuth of the range-resolved cells through the geographic geometric auxiliary information calculation step of the reconstructed data. Finally, the backscattering coefficients with enhanced resolution in both the range and azimuth directions, as well as the corresponding latitude, longitude, antenna scan angle, and geographic azimuth information, are obtained.

2. The method for enhancing the azimuth resolution of a spaceborne microwave scatterometer based on image reconstruction technology according to claim 1, characterized in that, The aforementioned high-resolution range processing includes: (1) Range-oriented resolution unit subdivision The ground footprint is subdivided into several ground resolution units. : (1)； The antenna distance represents the size of the 3dB beam footprint on the ground. To meet the required resolution for distance; (2) Calibration of backscattering coefficients of range-resolved cells In real-time remote sensing data processing, the echo power slice accumulation range and illumination integration parameters corresponding to each range resolution cell for each pulse observation are obtained by looking up the power slice accumulation range and illumination integration parameter table based on the real-time nadir latitude and antenna scan angle. The echo power of each pulse range resolution unit was calculated. : (2)； and They represent the first The range resolution cell contains the start and end numbers of the echo power slices, where i represents the echo power slice number. The above formula represents the selection range from... Arrived The echo power slices are accumulated. =1,2… p represents the scan observation point number; Based on internal calibration data After noise reduction processing to obtain clean signal power The backscattering coefficient of the range resolution cell is obtained by combining the illumination integration factor and radar system parameters. : (3)； These are fixed parameters related to the system. These are parameters related to system calibration. (3) Geographic location of distance-resolved unit For each pulse observation range, geolocation is performed for each resolution cell to determine the latitude of the footprint center in each range resolution cell. and At the same time, determine the corresponding ground incident angle. and geographical azimuth It also retains the antenna scanning angle that reflects the foresight and backsight states of the observation data. .

3. The method for enhancing the azimuth resolution of a spaceborne microwave scatterometer based on image reconstruction technology according to claim 1 or 2, characterized in that, The aforementioned azimuth-oriented one-dimensional resolution enhancement processing includes: (1) Calculation of one-dimensional reconstruction parameters in azimuth direction At a specific satellite position vector and velocity vector When the antenna beam center viewing angle and the antenna beam center azimuth angle are respectively and At that time, the transformation matrix from the Earth fixed coordinate system to the antenna coordinate system is calculated. : (4)； in This is the transformation matrix related to the satellite position vector, velocity vector, beam center view angle, and beam center azimuth angle. Represents the instrument installation offset matrix; Let the beam angle corresponding to each resolution unit be set as r=1,2… The azimuth angle of each resolution element is consistent with the azimuth angle of the antenna beam center. Let the beamwidth of the azimuth antenna of the resolving element be... The azimuth traversal range used for resolving the azimuth projection of the unit is as follows: The traversal interval is , The location of the first null point in the azimuth pattern of the coverage antenna; based on the satellite position vector. Velocity vector Radar instrument installation matrix, resolution unit beam angle 1. Resolve the azimuth angle of the projection of the unit. j=1,2…M, where M is the number of azimuth subdivisions of the resolution unit, and the ground projection point corresponding to the distance resolution unit is calculated. ,from arrive The connecting vector is: (5)； vector The modulus is the distance from the satellite to the ground projection point: (6)； Transformation matrix from Earth fixed coordinate system to antenna coordinate system Will Transform to the antenna coordinate system; (7)； Depend on Calculated vector Elevation and azimuth angles in the antenna coordinate system: (8)； (9)； This can be determined by looking up the table. Corresponding antenna two-way gain , combined The azimuth spatial response function of each range-resolved unit was obtained. : (10)； right according to Normalization yields the normalized spatial response function. : (11)； Accordingly, based on the coordinates of the ground projection point of the distance resolution unit Calculate the projection points along the azimuth direction relative to the central projection point. distance Relative distance of the center projection point ; By converting the sign, the corresponding azimuth angle Part Convert to a negative value to facilitate the reconstruction of the spatial function in the azimuth direction, i.e.: (12)； When the microwave scatterometer is working normally, the satellite position corresponding to different observation points changes with the movement of the satellite platform. When using the conical scan observation method, the satellite position corresponding to any fixed observation point... Other scanning observation points and (m=nM,n-M+1…n+M, The connecting vector is given by n, where n represents the index of any fixed observation point, and m represents the indices of the 2M observation points that are adjacent to this observation point in time. Project the azimuth angles for the j-th resolution unit; (13)； The corresponding beam angle is: (m=n-M, n-M+1…n+M, )(14); Corresponding beam angle Changes should be controlled within the resolution range at each distance. Within this range, and thereby determine the observation points involved in the reconstruction. (p=n- ,n- +1…n+ Within the aforementioned 2M adjacent observation points, M0 observation points satisfy the condition that the coverage area is located within the same range resolution cell, and the width of the effective reconstruction area in the azimuth direction is... for: (15)； The distance on the ground surface between the centers of the footprints of adjacent pulse beams along the scanning direction; (2) Reassembly of raw observation data The original data antenna scan angle and geographic azimuth angle were adjusted and converted to... Within the range: (16)； (17)； and , respectively represent the scanning azimuth angle and the geographic azimuth angle of the beam footprint center corresponding to the backscattering coefficients obtained after range-axis high-resolution processing, and p represents the scanning observation point number; Calculate the foresight and backsight markers for each scan based on the antenna scan angle: (18)； The backscattering coefficients, latitudes, longitudes, adjusted antenna scan angles and geographic azimuths, incident angles, and foresight and backsight markers of each range-resolved unit obtained after range-resolved high-resolution processing are all arranged according to the scatterometer periodic scanning observation sequence. The data obtained after range-to-high resolution processing is reconstructed using the following method: the distance within each scan cycle is... The most recent forward-looking azimuth angle is used as the scanning start angle. Based on this scanning start angle value, the backscattering coefficient, latitude, longitude, adjusted antenna scanning angle and geographic azimuth angle, incident angle, and forward and backward look marks are periodically arranged. In each period, the data is divided into two parts: forward-looking and backward-looking status data, based on the forward-looking and backward-looking marks. The reconstructed data is divided into four dimensions: the first dimension corresponds to different distance resolution units, the second dimension corresponds to different scanning cycles, the third dimension corresponds to forward-looking and backward-looking, and the fourth dimension corresponds to different observation points in forward-looking or backward-looking. (3) Azimuth-oriented high-resolution reconstruction By selecting specific range-resolved cells and forward-looking or backward-looking observation data within a scanning period, the beam footprint coverage of continuous scanning observation points is uniformly divided into... There are several intervals, each with a length equal to the width of the effective reconstruction region in the azimuth direction. , No. Each interval is represented as , Indicates the sequence along the scan trajectory. The distance between the starting point of the interval to be reconstructed and the center of the footprint of the first scan point; Based on the coverage reconstruction area Ground projection coordinates of the scanning observation point (p=n- , n- +1…n+ ),calculate Distance from the center of the footprint along the scanning trajectory relative to the starting observation point of the scanning observation segment ; Based on the one-dimensional reconstruction target resolution requirements in the orientation direction, the first... One interval to be reconstructed Evenly divided into Each interval Indicates size is The azimuth resolution unit, the starting point of the interval This indicates the distance between the starting point of the azimuth resolution unit and the center of the footprint of the starting observation point of the scanning observation segment; For each observation point Its normalized spatial response function The corresponding relative distance is ,but The distance relative to the starting point of the scanning observation segment is Search distance value Located in the interval The spatial response function within the range is averaged and used as the first... The observation point falls into the first Spatial response function values ​​of each azimuth resolution unit; (19)； and They respectively represent the intervals Inner distance value The start and end range of the serial number, ; Observation point corresponding backscattering coefficient Combined with spatial response function Applying the SIR scatterometer image reconstruction algorithm to achieve interval Internal azimuth resolution units Backscattering coefficient reconstruction; (4) Reconstructing data geographic geometry-aided information calculation Select azimuth resolution unit The center position is taken as the center of the reconstructed scattering coefficient position, that is The position corresponding to , Antenna scanning angle Geographical azimuth and angle of incidence Information can be obtained from the original observation data used to reconstruct the backscattering coefficients in this region. , Antenna scanning angle Geographical azimuth and angle of incidence Determined by interpolation; Finally, repeat steps (3) to (4) to traverse all range resolution cells, scanning cycles, forward-looking and backward-looking observation data to achieve one-dimensional azimuth high-resolution reconstruction of all observation data. The processed backscattering coefficients have high resolution in both range and azimuth directions.

4. The method for enhancing the azimuth resolution of a spaceborne microwave scatterometer based on image reconstruction technology according to claim 3, characterized in that, The SIR scatterometer image reconstruction algorithm described above achieves the interval Internal azimuth resolution units Backscattering coefficient reconstruction, the specific reconstruction process is as follows: a. The vector composed of the backscattering coefficients of each resolution cell in the azimuth direction is: , This represents the scattering coefficient of the q-th resolving unit, and the vector is initialized to an arbitrary vector. ; b. The (k+1)th iteration: (20)； in: , , ; For the iterative tuning factor, For the first The normalized spatial response function of the original observation point participating in the reconstruction falls into the first... The average value within each resolution unit; For interval Number of interior orientation resolvable cells For the k-th iteration Calculation results of backscattering coefficients for each azimuth-resolved element The number of original observation points participating in the reconstruction; In each iteration, the original observation data participates in the update of the backscattering coefficients of the azimuth resolution unit; c. Repeat step b. As the number of iterations increases, the difference between the results of the previous and subsequent iterations gradually decreases until convergence.

Images