A method for constructing a space brightness temperature radiation model for an on-orbit satellite antenna

Abstract

This invention discloses a method for constructing a space brightness temperature radiation model for on-orbit satellite antennas, specifically in the field of remote sensing measurement. It completes multi-coordinate system transformation of antenna radiation patterns; preprocesses cold-space brightness temperature mapping data, and constructs a cold-space radiation background database by combining piecewise binary linear interpolation and linear fitting. Based on brightness temperature thresholds, the Milky Way region is identified, and the upper and lower boundaries are solved by fitting the center line of the Milky Way strip using weighted least squares, thus establishing a Milky Way brightness temperature strip model. A land-sea segmentation model is used to classify land and sea using latitude and longitude coordinates, generating surface brightness temperature data. A standardized surface brightness temperature background database is constructed through interpolation and surface fitting. The spatial pointing of each radiometer beam is determined; surface-pointing beams are matched with surface brightness temperature data, while non-surface-pointing beams use cold-space background data to solve for the spatial brightness temperature of each beam, generating a satellite antenna background radiation value vector. The antenna brightness temperature integral effect is numerically calculated using the brightness temperature integral formula, completing the overall construction of the space brightness temperature radiation background model.

Description

Technical Field

[0001] This invention relates to the field of remote sensing measurement, and more specifically to a method for constructing a space brightness temperature radiation model for on-orbit satellite antennas. Background Technology

[0002] Accurate calculation of the impact of the space brightness temperature radiation background on the 2D L-band ASMR and the MICAP of the active / passive sounder is crucial for the stable on-orbit operation of ocean salinity sounding satellites, significantly affecting the quality of salinity remote sensing monitoring. The onboard radiometer antenna is subjected to microwave radiation from the Earth's surface, atmosphere, and the cold space background, typically manifested as brightness temperature. On one hand, accurately assessing the impact of the space brightness temperature radiation background on the 2D L-band ASMR and MICAP of the active / passive sounder under specific satellite conditions helps quantify the quality of payload missions. On the other hand, accurately solving the brightness temperature radiation integral provides important feedback for the on-orbit instrument planning and design. Therefore, high-precision antenna brightness temperature modeling and correction is a key research direction in the field of satellite remote sensing.

[0003] Existing research indicates that the calculation and calibration process for brightness temperature has the following problems: On the one hand, the coupling of multiple uncertainties limits the accuracy of brightness temperature simulation; when using the radiative transfer model (RTM) for brightness temperature simulation, there are often small-scale uncertainties (such as on the order of 10−410^{-4}) in data from different sensors or multiple sources, and the fitting and correction accuracy of brightness temperature may further decrease under the combined effects of orbital thermal effects, antenna cross-polarization coupling and Faraday rotation angle error.

[0004] On the other hand, antenna mode correction and data processing are highly complex. Calculating antenna temperature involves coupling integration between the antenna gain function and different brightness temperature backgrounds (such as ocean, land, and galactic stripes), requiring consideration of antenna sidelobes and cross-polarization, as well as handling spatiotemporal dynamic background changes caused by solar radiation and relative motion of celestial bodies. Some tasks (such as SMOS, Aquarius, AMSU-A, and ATMS) have improved measurement accuracy by refining antenna mode correction algorithms, introducing neural networks, or employing weight allocation based on the Backus-Gilbert method, but still face challenges such as low computational efficiency and high model maintenance costs.

[0005] Furthermore, the thermal deformation of the on-orbit antenna and changes in background radiation place higher demands on brightness temperature modeling and correction. Temperature field modeling studies show that the antenna reflector deforms under the influence of the heat conduction equation and boundary conditions. If such effects are ignored or underestimated, it can easily lead to non-negligible deviations in the brightness temperature data.

[0006] Given the aforementioned technical challenges, constructing a unified and efficient model for the space brightness-temperature radiation of on-orbit satellite antennas has become a crucial issue that urgently needs to be addressed. On one hand, it is necessary to consider the radiation characteristics of a large celestial background (including the Milky Way, cold space, and land and sea regions) to reduce singularity issues caused by uneven distribution of edge data. On the other hand, it is necessary to combine the antenna's own power pattern and thermal field variation patterns to construct a rapid numerical calculation method for the effects of on-orbit brightness-temperature radiation, thereby balancing simulation accuracy and computational efficiency, and improving on-orbit real-time correction and calibration capabilities.

[0007] Currently, L-band spaceborne radiometer antennas require precise sensing of the space brightness temperature background during in-orbit operation to perform integrated calculations of the brightness temperature radiation values ​​pointed to by the antenna beam. However, in a large celestial scene, the raw brightness temperature radiation data suffers from uneven distribution and anomalous banding, and there is a discrepancy between the accuracy of the antenna power pattern and the amount of data. This results in high complexity in the antenna's integration calculation of brightness temperature radiation and a tendency for insufficient fitting accuracy. Constructing a space brightness temperature radiation model and database that combines high accuracy and high efficiency is a core technical challenge in meeting the brightness temperature background sensing requirements of in-orbit satellite antennas. Summary of the Invention

[0008] Therefore, this invention provides a method for constructing a space brightness temperature radiation model for on-orbit satellite antennas. This method is of great significance for ensuring the long-term on-orbit calibration accuracy of spaceborne radiometers and improving the reliability of remote sensing data. It can achieve efficient matching between a multi-source brightness temperature background database (containing information on the cold universe, the Milky Way, and the emissivity of land and sea surfaces) and antenna pattern data, thereby solving the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for constructing a space brightness temperature radiation model for on-orbit satellite antennas, comprising: converting the radiation pattern of a spaceborne radiometer antenna between different coordinate systems; The cold air brightness temperature mapping data were preprocessed, and a cold air brightness temperature radiation background database was constructed by piecewise binary linear interpolation and linear function fitting. The Milky Way region is located by brightness temperature threshold, and the center line of the Milky Way band is fitted by weighted least squares. The upper and lower boundaries of the band are fitted with the center line as the reference to obtain the Milky Way brightness temperature band model. The geographic latitude and longitude coordinate set is classified into land and sea by the land surface segmentation model to obtain a formatted land surface brightness temperature data table. After interpolation and fitting of a continuous surface, a standardized land surface brightness temperature background database is obtained. The spatial pointing direction of each beam in the radiation pattern of the satellite radiometer antenna is determined. For beams pointing towards the ground, the brightness temperature value is matched using a standardized ground brightness temperature background database. Conversely, for beams pointing away from the ground, the brightness temperature value is matched using a cold air brightness temperature radiation background database. This process is repeated to obtain the spatial brightness temperature radiation value in the direction of each beam, forming a vector of radiation values ​​received by the satellite antenna from the spatial brightness temperature background at the current satellite state. The final numerical solution of the effect of the spatial brightness temperature radiation background on the antenna brightness temperature integral is obtained using the brightness temperature integral formula, thus completing the construction of the spatial brightness temperature radiation model.

[0010] Preferably, the antenna pattern of the spaceborne radiometer is transformed between different coordinate systems, including: First, generate the nominal direction map pointing set. Mapping radiation pattern using a spaceborne radiometer antenna Based on the nominal direction chart pointing set Perform formatted calibration to generate a formatted power radiation pattern. ; In Cartesian coordinates, the formatted power pattern is determined using the load installation matrix. Representation in the spacecraft's body coordinate system, i.e. And it is transformed to the reference inertial frame using the spacecraft attitude rotation matrix. The representation of beam pointing in the reference inertial frame forms the basis for subsequent matching of database brightness temperature radiation values ​​in the celestial coordinate system. The formatted antenna pattern under the celestial sphere is denoted as... .

[0011] Preferably, the nominal radiation pattern beam pointing is generated based on the antenna coordinate system, and the specified resolution scale is set to... Take the lower azimuth angle of the antenna coordinate system polar angle ,by For the distance of the walk, for the first Discretizing the azimuth angles yields: ; Polar angle discretization yields: ; The coordinates of each grid point are the azimuth angle. and polar angle The combination is represented as the set pointed to by the nominal coordinates. : ; The total number of grid points is: ; Based on the direction of the calibration coordinates, the power pattern is matched; assuming the measured L-band power pattern of a certain radiometer antenna is as follows: Regarding the power pattern No. Each direction can be represented in spherical coordinates as follows: ; in, This represents the highest resolution scale actually measured. for Beam power corresponding to angular coordinates; to obtain the calibrated beam angular coordinates Corresponding beam power ,right Zhongyu Matching is performed using the beam coordinates with the minimum angular distance. Defined as: ; For each calibrated beam angle coordinate Find the actual measurement Make distance The smallest point is denoted as: ; in, These are the indices that satisfy the minimum angular distance condition; The matched angular coordinate data is used for beam power allocation mapping, and the measured radiation pattern data table is indexed. Beam power in angular coordinates Mapped to the nearest beam coordinates ,get That is to say, it is believed = And form a formatted power pattern function: ; The relative rotation relationship between the known antenna coordinate system and the spacecraft body coordinate system is established using the spaceborne antenna installation mode; Let the antenna coordinate system be... The spacecraft's body coordinate system is The coordinate bases of both consist of two sets of vector arrays, each containing three orthogonal unit vectors. and composition: ; Relative installation relationship matrix of antenna relative to satellite body Defined by the following formula: ; Formatted power pattern function In the antenna coordinate system, beam vectors are defined using spherical coordinates. In the spacecraft body coordinate system, the beam vectors are transformed from the antenna coordinate system to the body coordinate system, given a beam coordinate system in the antenna coordinate system. It has a corresponding power in the beam direction. Its beam coordinates in the antenna coordinate system can be expressed in Cartesian coordinates as follows: The calculation is as follows: ; Using rotation matrix , In the spacecraft's body coordinate system, it is represented as: ; Based on this, the power beam pointing can be represented in the spacecraft's body coordinate system; where each power value still maintains its orientation relative to the original antenna coordinate system. The correspondence is such that only the coordinate system direction changes. This mapping method facilitates subsequent matrix calculations, avoids the need to process and accumulate coordinates in each direction independently, thereby improving computational efficiency and enhancing the algorithm's adaptability to matrix calculations in actual computer software. Similarly, given the current situation Transformation matrix from spacecraft body coordinate system to reference inertial frame at any given time This allows the formatted power directional beam to be represented as a vector in the reference inertial frame. : ; This completes the antenna pattern beam formatting calibration and its solution with the attitude coupling model, so that the beam pairs can be matched with the space brightness and temperature data in the reference inertial frame.

[0012] Preferably, the preprocessing of cold air brightness temperature mapping data includes: firstly generating a set of nominal right ascension and declination coordinates. Data table of brightness and temperature measurement of cold air Based on the nominal right ascension and declination coordinates, a formatted calibration is performed to generate a formatted cold air brightness temperature data table. Subsequently, a piecewise bivariate linear interpolation method was used to obtain high-resolution interpolated cold air brightness temperature data, and a two-dimensional convolutional smoothing window was used to smooth the periodic data to obtain high-resolution smoothed cold air brightness temperature data. Next, piecewise bivariate linear fitting was performed on this data. While preserving the integrity of the original data, the discrete data coordinates were fitted into a continuous surface, resulting in a cold air brightness temperature radiation background database in the form of a piecewise bivariate linear fitting function. .

[0013] Preferably, a nominal right ascension and declination grid coordinate system is constructed, and the original cold air brightness temperature radiation mapping data is formatted, with a specified resolution scale set as follows: Right ascension in the celestial coordinate system declination by For the distance from the walking distance, the right ascension discretization is as follows: ; Declination discretization yields: ; The discretized coordinates of the nominal celestial right ascension and declination are: ; The total number of grid points is: ; Match the cold air brightness temperature radiation background data; and convert the original cold air brightness temperature data table. Represented as: ; in, This represents the highest resolution scale actually measured. for The cold air brightness temperature radiation corresponding to the coordinates; To obtain the nominal right ascension and declination coordinates Corresponding cold air brightness temperature radiation ,right Zhongyu Matching is performed using the celestial coordinates with the smallest angular distance. Defined as: ; For each formatted celestial grid coordinate Find the actual measurement Make distance The smallest point is denoted as: ; in, These are the indices that satisfy the minimum angular distance condition; The matched angular coordinate data is used for the allocation and mapping of cold air brightness temperature radiation background values, and the measured cold air brightness temperature radiation data is used for this purpose. Map to the nearest grid point ,get And generate a formatted cold air brightness temperature radiation background data table. : ; A cold air brightness temperature radiation background database is obtained by piecewise fitting based on linear interpolation and boundary data smoothing methods; the method is designed as follows: The known formatted cold air brightness temperature radiation background database consists of discretized data points represented by right ascension and declination. These data points can be represented as... ,in It has a periodicity, with a period of 1 / 2. ; It does not have a periodicity; Constructing a periodic bivariate interpolation function The function satisfies: exist The direction satisfies the periodic boundary condition: ; Linear interpolation is used for each segment, while the overall process is smooth and the boundaries are continuous. To achieve Periodic boundary conditions in the direction will cause discrete data points to... The direction is periodically expanded, and the expansion rule is as follows: right Directional expansion: ; in For the extended width; The expanded data points are represented as That is, the expanded brightness temperature data points are composed of the expanded right ascension coordinates and the original declination coordinates; due to the periodicity of the coordinate system, the expanded combined coordinate points are still within the dataset range when obtaining brightness temperature data based on the original database. For the expanded data point set In each two-dimensional matrix unit Construct a linear fitting function. : ; in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries; After interpolation, perform a two-dimensional sliding window smoothing operation on the result; define the two-dimensional smoothing kernel. : ; in They are respectively Direction, the set window width; Smoothed result Achieved through two-dimensional convolution: ; Ultimately, the cold air brightness temperature radiation background fitting database is represented as a piecewise bivariate linear fitting function, in each It contains: ; in, Indicates that in the number A linear fitting function for cold air brightness temperature within a two-dimensional matrix unit; the boundaries of each two-dimensional matrix unit are continuous, forming a continuous fitting function. That is, the cold air brightness temperature radiation background fitting database. Given any right ascension and declination coordinates, the brightness temperature radiation data corresponding to the right ascension and declination coordinates can be calculated. Preferably, the construction of the galactic brightness-temperature banding model includes: Set the threshold for abnormal brightness temperature detection. The cold air brightness temperature measurement data table that exceeds this threshold The brightness temperature coordinates are considered to be abnormal brightness temperature coordinates; For the anomalous brightness temperature coordinates under the Mercator projection, weighted least squares regression was used to obtain the centerline that best represents the galactic brightness temperature band. ; with the center line To reference the upper and lower boundaries of the fitted brightness temperature bands .

[0014] Preferably, a weighted least squares curve fitting method is used to fit the distribution of outlier bands in the cold space data; through outlier identification and weighted polynomial fitting, the center curve and its boundary that best represent the distribution of brightness temperature outlier bands caused by the Milky Way in the cold space database are determined: First, set the threshold for abnormal brightness temperature points in the cold air brightness temperature radiation background database. The anomalous brightness temperature data set in the cold air brightness temperature radiation background database is represented as: ; Considering the brightness temperature values ​​of the coordinates of the above abnormal brightness temperature data, weighted least squares regression is used to regress the center lines of the stripes, letting... Let the center line of the Milky Way band on the Mercator projection be given, and set... Represented by a polynomial expansion, the highest order is : ; set up For each Constructing a matrix The superscript k is used to indicate the coordinates of the kth anomaly: ; remember For each The vector formed This is a column vector of polynomial coefficients; brightness temperature As weights, the weight matrix is: ; The objective function of weighted least squares is: ; Its closed-form solution is: ; Obtain the centerline function of the Milky Way band Its polynomial coefficients are derived from The decision is made to use brightness temperature as a weight because the band distribution is mainly dominated by anomalies with higher brightness temperatures, thus giving them a greater regression influence to obtain more reliable centerline positions. Further steps are needed to define the Milky Way bands in the Mercator projection coordinates of the celestial sphere, and to assign each anomaly... The value given by the center line is , and The difference is ;like The indication point is above the center line, if Then it lies below the center line; regressing on the upper boundary, for all and Let the deviations of the sampling coordinate points relative to the center line satisfy the polynomials: ; Similarly, using weighted least squares, the weight matrix is ​​changed to an exponentially decaying form to suppress excessive expansion of the boundary by extreme brightness temperature points: ; in This is the exponential decay factor that needs to be set; The upper and lower boundaries were obtained through fitting: ; Preferably, a nominal geographic latitude and longitude grid coordinate system is constructed to prepare for a further binary brightness temperature model for land-sea separation, with the specified resolution scale set as follows: Take the longitude in the geographic latitude and longitude coordinate system ,latitude by For the distance from the walk, longitude discretization yields: ; Latitude discretization includes: ; The coordinates of the discretized geographic latitude and longitude grid points are: ; The total number of grid points is: ; The brightness temperature values ​​are assigned using a land-sea separation model, with the brightness temperature radiation value corresponding to the ocean coordinate point being... Land brightness temperature value set to This forms a formatted database of Earth's surface brightness temperature radiation background. ; in, , These represent the sets of ocean latitude and longitude coordinates in the land-sea separation model; For the data point set of the formatted surface brightness temperature radiation background database In each two-dimensional matrix unit Construct a linear fitting function. : ; in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries; Ultimately, the surface brightness temperature radiation background fitting database was represented as a piecewise bivariate linear fitting function, in each It contains: ; in, Indicates that in the number The linear fitting function of surface brightness temperature within a two-dimensional matrix cell; the boundaries of each two-dimensional matrix cell are continuous, thus forming a continuous fitting function. This refers to a database for fitting the background brightness temperature radiation of the Earth's surface. Given any geographic latitude and longitude coordinates, the brightness temperature radiation data corresponding to those coordinates can be calculated.

[0015] Preferably, based on current satellite telemetry information, including the position of the reference inertial frame, the attitude relative to the inertial frame, and the latitude and longitude coordinates of the current satellite nadir point, the spatial brightness temperature radiation value pointing upwards for each beam is calculated using a formatted onboard antenna pattern and a fitted database. First, the pattern beam pointing is formatted and determined based on the current spacecraft attitude under the actual orbital space environment; assuming the nominal orbit is... At any given moment, a celestial coordinate system exists for the satellite. Under the celestial sphere, the satellite receives spatial brightness and temperature radiation from all directions, contributed by the visible area of ​​the Earth's surface and cold air. The origin of the spherical coordinate system under the celestial coordinate system is the center of the satellite, and the spherical coordinate angles are described as follows: Meanwhile, the origin of the spherical coordinate system for surface brightness temperature is the Earth's center, and the spherical coordinate angle is described as follows: Therefore, the stitching of celestial brightness temperature data needs to consider the visible range of the surface brightness temperature data in the celestial coordinate system and... Coordinates; the following geometric relationships are used to determine and process the data, assuming the celestial coordinate system is a celestial coordinate system with the satellite center as the origin. Its coordinate axes Orientation and J2000 reference inertial frame parallel; set up The angular coordinate system of the next point is It has its Cartesian coordinate system vector: ; To determine whether it points to a cold space region or an area on the Earth's surface, let the satellite's current orbital position vector be... ,like If the following equation is satisfied, the angular coordinates point to the Earth's surface region; otherwise, they point to the cold air region: ; in, The semi-cone angle of the visible area on the Earth's surface relative to the satellite is given by the Earth's radius. Atmospheric thickness is , It is expressed as follows: ; When angular coordinates When pointing to the cold air region, the brightness temperature gain corresponding to that angular coordinate system is calculated directly using the fitted cold air database function. ; When angular coordinates When pointing to a region on the Earth's surface, the following further calculations are performed: Calculate the latitude and longitude of angular coordinates pointing towards the Earth's surface; angular coordinate vector. There are two intersections with the Earth's surface Select intersection point Obtain its latitude and longitude The brightness temperature gain corresponding to this angular coordinate system is calculated using the fitted surface brightness temperature database function. The direction of each formatted beam is determined, and the brightness temperature value is calculated using a brightness temperature background fitting database to obtain the brightness temperature radiation value vector. This vector contains the brightness temperature radiation values ​​of the spatial background at the current moment, pointing towards the N beams of the formatted antenna pattern. The numerical solution of the effect of the final spatial brightness temperature radiation background on the antenna brightness temperature integral is performed using the brightness temperature integral formula. Given the original antenna power pattern, the formula for calculating the brightness temperature integral of its spatial brightness temperature radiation background effect is as follows: ; in, The power pattern after conversion to an inertial frame is shown. and Completed with The matching correspondence, Represents a surface in the celestial coordinate system. ; set up It can be used as a constant for preliminary calculations, for formatted radiation patterns and their solved radiation matrix. The integral formula, discretized into a summative form, can be represented using matrix multiplication as follows: ; in, The element in the i-th row is This completes the numerical integration of the radiation value matrix generated from the fitted database with respect to the effect of the space brightness temperature radiation background on the on-orbit satellite.

[0016] Beneficial effects: 1. This invention achieves synchronous matching between the beam pointing of LASMR and MICAP payloads and the brightness temperature background pointing of the space background, thereby reducing the data matching dimensionality of the two payloads during the brightness temperature integration calculation process: Based on the specified formatted pattern beam, the two measured pattern data are formatted and calibrated to match their power distribution to the direction of the formatted pattern beam. The formatted LASMR and MICAP power patterns share the same pattern coordinate matrix, differing only in power gain in each direction.

[0017] 2. This invention establishes a brightness temperature radiation fitting database, significantly reducing the complexity of data dimensionality and radiation value matching: By formatting the antenna power pattern and constructing a brightness temperature radiation fitting database, efficient matching and matrix-based rapid numerical solution of antenna beam pointing brightness temperature radiation information were achieved.

[0018] 3. This invention ensures the continuity of the brightness temperature fitting database, achieving highly stable and accurate brightness temperature integral calculation: By employing methods such as formatted interpolation, sliding convolution window smoothing, and piecewise binary fitting on the original brightness temperature data, the fitting singularity problem caused by uneven edge distribution can be effectively avoided, thereby ensuring the stability and accuracy of subsequent matrix-based brightness temperature integral solutions.

[0019] 4. This invention achieves efficient dynamic solution of the brightness temperature integral of a spaceborne antenna driven by a fitting database: In actual on-orbit scenarios, the dynamic adjustment of brightness temperature background due to changes in the relative position of the Earth is fully considered, and the dynamic calculation of the space brightness temperature radiation matrix under different times and different satellite attitudes is realized, thereby ensuring the accuracy and stability of the integral solution of the on-board antenna brightness temperature under continuous attitude changes during the satellite's on-orbit operation.

[0020] Overall, this model construction method is both innovative and practical in engineering. It efficiently generates a brightness temperature radiation matrix pointing to the antenna beam, meeting the requirement of simultaneously sensing the on-orbit brightness temperature background with multiple antenna payloads. Combined with the antenna power pattern, it enables rapid calculation of the antenna brightness temperature integral value, thus providing crucial support for improving the accuracy and calibration of spaceborne radiometer antennas. In actual calculations, compared to the original data table index matching method, this method significantly improves computational efficiency. Attached Figure Description

[0021] Figure 1 This invention provides a data preprocessing method flow configuration based on antenna and space mapping data. Figure 2 This invention provides a flowchart for the method of solving the brightness temperature integral of on-orbit satellite antennas based on a fitted database. Figure 3 This is the X-polarized LASMR antenna pattern provided by the present invention; Figure 4 This is the MICAP antenna pattern provided by the present invention; Figure 5 This invention provides Figure 3 The installation configuration within the spacecraft's core system was obtained through a formatted calibration method. Figure 6 This invention provides Figure 4 The installation configuration within the spacecraft's core system was obtained through a formatted calibration method. Figure 7 This invention provides a continuous function surface (Mercator projection) for fitting data of cold air brightness temperature radiation background. Figure 8 This invention provides a continuous function surface (spherical envelope diagram) for fitting cold air brightness temperature radiation background data. Figure 9 This is a 2D visualization of the Milky Way brightness temperature band fitting database provided by this invention, plotted against a cold space background. Figure 10 This is a 3D visualization of the Milky Way brightness temperature band fitting database provided by this invention, plotted against a cold space background. Figure 11 It is a continuous surface (Mercator projection) drawn from the land and sea brightness temperature segmentation fitting database provided by this invention. Figure 12 This is a schematic diagram of the right ascension and declination of the beam pointing provided by the present invention in the celestial coordinate system; Figure 13 This is a schematic diagram illustrating the geometric relationship between the satellite beam pointing towards cold air and towards the Earth's surface, provided by the present invention. Detailed Implementation

[0022] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0023] This invention proposes a method for constructing a space brightness temperature radiation model for on-orbit satellite antennas. This method can be widely applied to satellite remote sensing systems, especially for brightness temperature data processing and calculation of L-band radiometers.

[0024] This invention specifically includes two aspects: 1. Data preprocessing methods based on antenna and space mapping data; Preprocessing is performed on the antenna radiation pattern, firstly generating a nominal radiation pattern pointing set. Mapping radiation pattern using a spaceborne radiometer antenna Based on the direction of the pointer, a formatted calibration is performed to generate a formatted power radiation pattern. In the Cartesian coordinate system, the representation of the radiation pattern in the spacecraft body coordinate system is determined using the load installation matrix. And it is transformed to the reference inertial frame using the spacecraft attitude rotation matrix. The representation of beam pointing in the reference inertial frame forms the basis for subsequent matching of database brightness temperature radiation values ​​in the celestial coordinate system. The formatted antenna pattern under the celestial sphere is denoted as... .

[0025] Preprocessing is performed on the cold air brightness temperature mapping data, firstly generating a set of nominal right ascension and declination coordinates. Data table of brightness and temperature measurement of cold air Based on the nominal right ascension and declination coordinates, a formatted calibration is performed to generate a formatted cold air brightness temperature data table. Subsequently, a piecewise bivariate linear interpolation method was used to obtain high-resolution interpolated cold air brightness temperature data, and a two-dimensional convolutional smoothing window was used to smooth the periodic data to obtain high-resolution smoothed cold air brightness temperature data. Next, piecewise bivariate linear fitting was performed on this data. While preserving the integrity of the original data, the discrete data coordinates were fitted into a continuous surface, resulting in a cold air brightness temperature radiation background database in the form of a piecewise bivariate linear fitting function. .

[0026] To generate the brightness temperature banding model of the Milky Way, the threshold for detecting abnormal brightness temperature is first set. The cold air brightness temperature measurement data table that exceeds this threshold The brightness temperature coordinates were considered anomalous brightness temperature coordinates; then, weighted least squares regression was performed on the anomalous brightness temperature coordinates under the Mercator projection to obtain the centerline that best represents the brightness temperature band of the Milky Way. Similarly, the upper and lower boundaries of the brightness temperature bands are fitted with the center line as a reference. .

[0027] To generate a surface land-sea brightness temperature segmentation model, the first step is to generate a set of nominal geographic latitude and longitude coordinates. The surface land-sea segmentation model is used to determine whether each coordinate in the calibration geographic latitude and longitude matrix is ​​located in the ocean or on land. Specific brightness temperature values ​​are assigned to ocean coordinates and land coordinates respectively, forming a formatted surface brightness temperature data table. Subsequently, a piecewise bivariate linear interpolation method is used to obtain a high-resolution interpolated cold air brightness temperature data table. Next, piecewise bivariate linear fitting is performed on the data table. While preserving the integrity of the original data, the discrete data coordinates are fitted into a continuous surface, resulting in a surface brightness temperature radiation background database in the form of a piecewise bivariate linear fitting function. .

[0028] Aspect 2: A method for solving the brightness temperature integral of on-orbit satellite antennas based on a fitting database.

[0029] Based on the aforementioned data, a method for calculating the brightness temperature integral of the satellite's on-orbit antenna is developed. Given telemetry information, the spatial pointing of each beam in the antenna pattern is determined; the beam pointing towards the Earth's surface uses... Match the brightness temperature value, otherwise use By iterating through the matched brightness temperature values, the spatial brightness temperature radiation values ​​pointing upwards for each beam are obtained, forming a vector of radiation values ​​received by the satellite antenna from the spatial brightness temperature background at the current satellite state. Finally, the brightness temperature integral formula was used to numerically calculate the effect of the final spatial brightness temperature radiation background on the antenna brightness temperature integral. .

[0030] This invention fully integrates the background data required for brightness temperature background integration calculation using L-band radiometers, significantly reducing the complexity of brightness temperature integration calculation. The efficiency of brightness temperature integration calculation is improved by 20,000% compared to general database matching methods. At the same time, it takes into account data integrity, computational complexity, and accuracy of brightness temperature integration calculation, with an accuracy loss of less than 0.12%. The model method has been verified by actual satellite on-orbit telemetry and control, providing efficient and accurate technical support for related applications.

[0031] like Figure 1 As shown, the first aspect of the present invention is described below, namely, an implementation method for data preprocessing based on antenna and space mapping data, specifically including steps 1 to 4: Step 1: Generate the nominal radiation pattern beam pointing based on the antenna coordinate system, assuming the specified resolution scale is... Take the lower azimuth angle of the antenna coordinate system polar angle by Given the distance from the walk distance, the azimuth angle is discretized as follows: ; Polar angle discretization yields: ; The coordinates of each grid point are the azimuth angle. and polar angle The combination is represented as the set pointed to by the nominal coordinates. : ; The total number of grid points is: .

[0032] The power pattern is matched based on the direction of the calibration coordinates. Assume that the measured L-band power pattern of a certain radiometer antenna is as follows: It is expressed in spherical coordinates as: ; in, This represents the highest resolution scale actually measured. for The beam power corresponding to the angular coordinates. The following is how to obtain the calibrated beam angular coordinates. Corresponding beam power ,right Zhongyu Matching is performed using the beam coordinates with the minimum angular distance. Defined as: ; For each calibrated beam angle coordinate Find the actual measurement Make distance The smallest point is denoted as: ; in, These are the indices that satisfy the minimum angular distance condition.

[0033] The matched angular coordinate data is used for beam power allocation mapping, and the measured radiation pattern data table is indexed. Beam power in angular coordinates Mapped to the nearest nominal grid point ,get That is to say, it is believed = And form a formatted power pattern function: ; Next, the relative rotation relationship between the known antenna coordinate system and the spacecraft body coordinate system is established using the spaceborne antenna installation mode. Let the antenna coordinate system be... The spacecraft's body coordinate system is The coordinate bases of both consist of two sets of vector arrays, each containing three orthogonal unit vectors. and composition: ; Relative installation relationship matrix of antenna relative to satellite body Defined by the following formula: ; Formatted power pattern function In the antenna coordinate system, beam vectors are defined using spherical coordinates. In the spacecraft body coordinate system, it is necessary to transform the beam vectors from the antenna coordinate system to the body coordinate system, given beam coordinates in an antenna coordinate system. It has a corresponding power in the beam direction. Its beam coordinates in the antenna coordinate system can be expressed in Cartesian coordinates as follows: The calculation is as follows: ; Using rotation matrix , In the spacecraft's body coordinate system, it is represented as: ; Based on this, the power beam pointing can be represented in the spacecraft's body coordinate system. Each power value retains its orientation relative to the original antenna coordinate system. The correspondence is such that only the coordinate system direction changes. This mapping method facilitates subsequent matrix calculations, avoids the need to process and accumulate coordinates in each direction independently, thereby improving computational efficiency and enhancing the algorithm's adaptability to matrix calculations in actual computer software.

[0034] Similarly, given the current situation Transformation matrix from spacecraft body coordinate system to reference inertial frame at any given time This allows the formatted power directional beam to be represented as a vector in the reference inertial frame. : ; This completes the antenna pattern beam formatting calibration and its solution with the attitude coupling model, so that the beam pairs can be matched with the space brightness and temperature data in the reference inertial frame.

[0035] For example Figures 3-4 The LASMR antenna and MICAP antenna shown are synchronously used with the pattern formatting calibration method to obtain the formatted pattern installation configuration of the spacecraft's main system. The results are as follows: Figures 5-6 As shown.

[0036] Step 2: Construct a nominal right ascension and declination grid coordinate system, format the original cold air brightness temperature radiation mapping data, and set the specified resolution scale as... Right ascension in celestial coordinate system declination by For the distance from the walking distance, the right ascension discretization is as follows: ; Declination discretization yields: ; The discretized coordinates of the nominal celestial right ascension and declination are: ; The total number of grid points is: .

[0037] Furthermore, the cold air brightness temperature radiation background data were matched. The original cold air brightness temperature data table was then used. Represented as: ; in, This represents the highest resolution scale actually measured. for The coordinates correspond to the cold air brightness temperature radiation. Below is the method for obtaining the nominal right ascension and declination coordinates. Corresponding cold air brightness temperature radiation ,right Zhongyu Matching is performed using the celestial coordinates with the smallest angular distance. Defined as: ; For each formatted celestial grid coordinate Find the actual measurement Make distance The smallest point is denoted as: ; in, These are the indices that satisfy the minimum angular distance condition.

[0038] The matched angular coordinate data is used for the allocation and mapping of cold air brightness temperature radiation background values, and the measured cold air brightness temperature radiation data is used for this purpose. Map to the nearest grid point ,get And generate a formatted cold air brightness temperature radiation background data table. : ; A cold air brightness temperature radiation background database was obtained by piecewise fitting based on linear interpolation and boundary data smoothing methods. The piecewise interpolation method using linear interpolation and sliding convolution smoothing is designed as follows: The known formatted cold air brightness temperature radiation background database consists of discretized data points represented by right ascension and declination. These data points can be represented as... ,in It has a periodicity, with a period of 1 / 2. ; It does not have a periodicity.

[0039] Constructing a periodic bivariate interpolation function The function satisfies: 1. In The direction satisfies the periodic boundary condition: ; 2. Linear interpolation is used for each segment, while the overall result is smooth and the boundaries are continuous.

[0040] To achieve Periodic boundary conditions in the direction will cause discrete data points to... The direction is periodically expanded, and the expansion rule is as follows: right Directional expansion: ; in For the extended width.

[0041] Therefore, the expanded data points are represented as That is, the expanded brightness temperature data points are composed of the expanded right ascension coordinates and the original declination coordinates. Due to the periodicity of the coordinate system, the expanded combined coordinate points are still within the dataset range when obtaining brightness temperature data based on the original database.

[0042] For the expanded data point set In each two-dimensional matrix unit Construct a linear fitting function. : ; in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries.

[0043] After interpolation, a two-dimensional sliding window smoothing operation is performed on the result. Define the two-dimensional smoothing kernel. : ; in They are respectively The window width that needs to be set in the direction.

[0044] Smoothed result Achieved through two-dimensional convolution: ; Ultimately, the cold air brightness temperature radiation background fitting database is represented as a piecewise bivariate linear fitting function, in each It contains: ; in, Indicates that in the number The linear fitting function for cold air brightness temperature within a two-dimensional matrix cell. Since the boundaries of each two-dimensional matrix cell are continuous, a continuous fitting function is formed. This refers to the cold air brightness temperature radiation background fitting database, which allows the calculation of brightness temperature radiation data corresponding to any right ascension and declination coordinates.

[0045] This method combines piecewise linear interpolation and two-dimensional sliding window smoothing. Through periodic expansion and convolution operations, it effectively handles the smoothing and interpolation problems of two-dimensional periodic data. It is suitable for data modeling scenarios with periodic boundary conditions and can achieve feature data fitting and data boundary optimization for cold air brightness temperature background databases, Milky Way brightness temperature stripes, and surface brightness temperature background databases. The resulting continuous function surface of the cold air brightness temperature radiation background fitting data is shown below. Figures 7-8 As shown.

[0046] Step 3: Based on the weighted least squares curve fitting method, fit the distribution of outlier bands in the cold space data. Through outlier identification and weighted polynomial fitting, determine the center curve and its boundary that best represent the distribution of brightness temperature outlier bands caused by the Milky Way's influence in the cold space database. First, set the threshold for abnormal brightness temperature points in the cold air brightness temperature radiation background database. The anomalous brightness temperature data set in the cold air brightness temperature radiation background database is represented as: ; Furthermore, considering the brightness temperature values ​​of the coordinates of the aforementioned abnormal brightness temperature data, weighted least squares regression is used to regress the center lines of the stripes, letting... Let the center line of the Milky Way band on the Mercator projection be given, and set... Represented by a polynomial expansion, the highest order is : ; set up For each Constructing a matrix The superscript k is used to indicate the coordinates of the kth anomaly: ; remember For each The vector formed This is a column vector of polynomial coefficients. The brightness temperature... As weights, the weight matrix is: ; The objective function of weighted least squares is written as: ; Its closed-form solution is: ; Therefore, we can obtain the function for the centerline of the Milky Way band. Its polynomial coefficients are derived from The decision is made. Brightness temperature is used as a weight here because the band distribution is mainly dominated by anomalies with higher brightness temperatures, thus giving them a greater regression influence to obtain more reliable centerline positions. Further steps are needed to define the Milky Way bands in the Mercator projection coordinates of the celestial sphere, and for each anomaly... The value given by the center line is , and The difference is like The indication point is located "above the center line", if Then it is "below the center line". Regression is performed on the upper boundary for all... and Let their deviations from the centerline satisfy the polynomial: ; Similarly, using weighted least squares, the weight matrix is ​​changed to an exponentially decaying form to suppress excessive expansion of the boundary by extreme brightness temperature points: ; in This is the exponential decay factor that needs to be set.

[0047] The upper and lower boundaries were obtained through fitting: ; The coordinate curves of the obtained Milky Way brightness temperature band fitting database under a cold space background are as follows: Figures 9-10 As shown: Step 4: Construct a nominal geographic latitude and longitude grid coordinate system to prepare for the further development of a binary brightness temperature model for land-sea separation. Let the specified resolution scale be... Take longitude in the geographic latitude and longitude coordinate system ,latitude by For the distance from the walk, longitude discretization yields: ; Latitude discretization includes: ; The coordinates of the discretized geographic latitude and longitude grid points are: ; The total number of grid points is: .

[0048] Furthermore, a land-sea separation model was used to assign brightness temperature values, with the brightness temperature radiation value corresponding to the ocean coordinate point being... Land brightness temperature value set to This forms a formatted database of Earth's surface brightness temperature radiation background. ; in, , These represent the set of ocean latitude and longitude coordinates in the land-sea separation model.

[0049] Similarly, for the data point set of the formatted surface brightness temperature radiation background database In each two-dimensional matrix unit Construct a linear fitting function. : in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries.

[0050] Ultimately, the surface brightness temperature radiation background fitting database was represented as a piecewise bivariate linear fitting function, in each It contains: ; in, Indicates that in the number The linear fitting function for surface brightness temperature within a two-dimensional matrix cell. Since the boundaries of each two-dimensional matrix cell are continuous, a continuous fitting function is formed. This refers to a database for fitting the background brightness temperature radiation of the Earth's surface. Given any geographic latitude and longitude coordinates, the brightness temperature radiation data corresponding to those coordinates can be calculated.

[0051] The obtained fitting model of the Earth's surface land-sea segmentation brightness temperature radiation background is as follows: Figure 11 As shown: like Figure 2As shown, the second aspect of the present invention is described below, namely, the implementation method of the on-orbit satellite antenna brightness temperature integral solution method driven by the fitting database, specifically including steps 5 to 6: Step 5: Based on the current satellite telemetry information, including the position of the reference inertial frame, the attitude relative to the inertial frame, and the latitude and longitude coordinates of the current satellite nadir point, the spatial brightness temperature radiation value pointing upwards for each beam can be calculated using the formatted onboard antenna pattern and the fitted database. First, the pattern beam pointing is formatted to determine the pattern beam pointing under the current attitude of the spacecraft in the actual orbital space environment. Assume that in the nominal orbit... A celestial coordinate system exists at all times. At this moment, the satellite receives space brightness and temperature radiation from all directions beneath the celestial sphere, contributed by the visible area of ​​the Earth's surface and cold air. The origin of the spherical coordinate system under the celestial coordinate system is the satellite center, and the spherical coordinate angles are described as follows: Meanwhile, the origin of the spherical coordinate system for surface brightness temperature is the Earth's center, and the spherical coordinate angle is described as follows: Therefore, the stitching of celestial brightness temperature data needs to consider the visible range of the surface brightness temperature data in the celestial coordinate system and... Coordinates. This invention uses the following geometric relationships to process and determine data, assuming the celestial coordinate system is a celestial coordinate system with the satellite center as the origin. Its coordinate axes Orientation and J2000 reference inertial frame Parallel, such as Figure 12 As shown.

[0052] set up The angular coordinate system of the next point is It has its Cartesian coordinate system vector: ; To determine whether it points to a cold space region or an area on the Earth's surface, let the satellite's current orbital position vector be... ,like If the following equation is satisfied, the angular coordinates point to the Earth's surface region; otherwise, they point to the cold air region: ; in, The semi-cone angle of the visible area on the Earth's surface relative to the satellite is given by the Earth's radius. Atmospheric thickness is , It is expressed as follows: ; Furthermore, when angular coordinates When pointing to a cold air region, the brightness temperature gain corresponding to that angular coordinate system can be calculated directly using the fitted cold air database function. ; When angular coordinates When pointing to a region on the Earth's surface, the following further calculations are performed: like Figure 13 As shown, to calculate the latitude and longitude of angular coordinates pointing towards the Earth's surface, the angular coordinate vector... There are two intersections with the Earth's surface Select intersection point Obtain its latitude and longitude The brightness temperature gain corresponding to this angular coordinate system is calculated using the fitted surface brightness temperature database function. Therefore, based on Figure 1 The process shown determines the direction of each formatted beam and uses a brightness temperature background fitting database to calculate the brightness temperature value vector. This vector contains the brightness temperature radiation values ​​of the spatial background at the current moment, which are directed upwards by the N beams of the formatted antenna pattern.

[0053] Step 6: Use the brightness temperature integral formula to perform a numerical calculation of the final spatial brightness temperature radiation background effect on the antenna brightness temperature integral.

[0054] The formula for calculating the brightness temperature integral of the original antenna power pattern with respect to its spatial brightness temperature radiation background is given as follows: ; in, The power pattern after conversion to an inertial frame is shown. and Completed with The matching correspondence, Represents a surface in the celestial coordinate system. .

[0055] set up It can be used as a constant for preliminary calculations, for formatted radiation patterns and their solved radiation matrix. The integral formula, discretized into a summative form, can be represented using matrix multiplication as follows: ; in, The element in the i-th row is This completes the numerical integration of the radiation value matrix generated from the fitted database with respect to the space brightness temperature radiation background effect of the on-orbit satellite.

[0056] In summary, a method for constructing a space brightness temperature radiation background model for an on-orbit satellite antenna was completed, and the engineering model parameter settings used are as follows: Table 1 Model Parameter Settings

[0057] Simultaneously, the performance of the test process for matching brightness temperature radiation information using the fitted database was compared with that of the general differential matching process. The computer CPU configuration was an Intel(R) Xeon(R) Gold 6226R CPU @ 2.90GHz, and the single-core performance is shown in the table below. Table 2 Model Operation Performance Parameters

[0058] The model fitted in this study has been tested and found to be highly efficient with minimal loss of accuracy, demonstrating significant advantages.

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for constructing a space brightness-temperature radiation model for on-orbit satellite antennas, characterized in that: include: Transform the radiation pattern of the spaceborne radiometer antenna between different coordinate systems; The cold air brightness temperature mapping data were preprocessed, and a cold air brightness temperature radiation background database was constructed by piecewise binary linear interpolation and linear function fitting. The Milky Way region is located by brightness temperature threshold, and the center line of the Milky Way band is fitted by weighted least squares. The upper and lower boundaries of the band are fitted with the center line as the reference to obtain the Milky Way brightness temperature band model. The geographic latitude and longitude coordinate set is classified into land and sea by the land surface segmentation model to obtain a formatted land surface brightness temperature data table. After interpolation and fitting of a continuous surface, a standardized land surface brightness temperature background database is obtained. Determine the spatial pointing of each beam in the radiation pattern of the satellite radiometer antenna. For beams pointing to the ground, use a standardized ground brightness temperature background database to match the brightness temperature value. Otherwise, use a cold air brightness temperature radiation background database to match the brightness temperature value and iterate to obtain the spatial brightness temperature radiation value in the direction of each beam. This forms a vector of radiation values ​​received by the satellite antenna in the current satellite state. The numerical solution of the effect of the final spatial brightness temperature radiation background on the antenna brightness temperature integral is obtained by using the brightness temperature integral formula, thus completing the construction of the spatial brightness temperature radiation model.

2. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 1, characterized in that: Transformation of the antenna pattern of a spaceborne radiometer between different coordinate systems, including: First, generate the nominal direction map pointing set. Mapping radiation pattern using a spaceborne radiometer antenna Based on the nominal direction chart pointing set Perform formatted calibration to generate a formatted power radiation pattern. ; In Cartesian coordinates, the formatted power pattern is determined using the load installation matrix. Representation in the spacecraft's body coordinate system, i.e. And it is transformed to the reference inertial frame using the spacecraft attitude rotation matrix. Reference inertial frame The formatted antenna pattern under the celestial sphere is denoted as... .

3. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 2, characterized in that: The nominal radiation pattern beam pointing is generated based on the antenna coordinate system, and the specified resolution scale is . Take the lower azimuth angle of the antenna coordinate system polar angle ,by For the distance of the walk, for the first Discretizing the azimuth angles yields: ； Polar angle discretization yields: ； The coordinates of each grid point are the azimuth angle. and polar angle The combination is represented as the set pointed to by the nominal coordinates. : ； The total number of grid points is: ; Based on the direction of the calibration coordinates, the power radiation pattern is... Perform the following matching: Assume that the measured L-band power pattern of a certain radiometer antenna is as follows: Regarding the power pattern No. Each direction is represented in spherical coordinates: ； in, This represents the highest resolution scale actually measured. for Beam power corresponding to angular coordinates; to obtain the calibrated beam angular coordinates Corresponding beam power ,right Zhongyu Matching is performed using the beam coordinates with the minimum angular distance. Defined as: ； For each calibrated beam angle coordinate Find the actual measurement Make distance The smallest point is denoted as: ； in, These are the indices that satisfy the minimum angular distance condition; The matched angular coordinate data is used for beam power allocation mapping, and the measured radiation pattern data table is indexed. Beam power in angular coordinates Mapped to the nearest beam coordinates ,get That is to say, it is believed = And form a formatted power pattern function: ； The relative rotation relationship between the known antenna coordinate system and the spacecraft body coordinate system is established using the spaceborne antenna installation mode; Let the antenna coordinate system be... The spacecraft's body coordinate system is The coordinate bases of both consist of two sets of vector arrays, each containing three orthogonal unit vectors. and composition: ； Relative installation relationship matrix of antenna relative to satellite body Defined by the following formula: ； Formatted power pattern function In the antenna coordinate system, beam vectors are defined using spherical coordinates. In the spacecraft body coordinate system, the beam vectors are transformed from the antenna coordinate system to the body coordinate system, given a beam coordinate system in the antenna coordinate system. It has a corresponding power in the beam direction. Its beam coordinates in the antenna coordinate system can be expressed in Cartesian coordinates as follows: The calculation is as follows: ； Using rotation matrix , In the spacecraft's body coordinate system, it is represented as: ； Known current Transformation matrix from spacecraft body coordinate system to reference inertial frame at any given time This allows the formatted power directional beam to be represented as a vector in the reference inertial frame. : 。 4. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 1, characterized in that: Preprocessing of cold air brightness temperature mapping data includes: firstly, generating a set of nominal right ascension and declination coordinates. Data table of brightness and temperature measurement of cold air Based on the nominal right ascension and declination coordinates, a formatted calibration is performed to generate a formatted cold air brightness temperature data table. Subsequently, a piecewise bivariate linear interpolation method was used to obtain high-resolution interpolated cold air brightness temperature data, and a two-dimensional convolutional smoothing window was used to smooth the periodic data to obtain high-resolution smoothed cold air brightness temperature data. Next, piecewise bivariate linear fitting was performed on this data. While preserving the integrity of the original data, the discrete data coordinates were fitted into a continuous surface, resulting in a cold air brightness temperature radiation background database in the form of a piecewise bivariate linear fitting function. .

5. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 4, characterized in that: Construct a nominal right ascension and declination grid coordinate system, format the original cold air brightness temperature radiation mapping data, and set the specified resolution scale as [missing information]. Right ascension in the celestial coordinate system declination by For the distance from the walking distance, the right ascension discretization is as follows: ； Declination discretization yields: ； The discretized coordinates of the nominal celestial right ascension and declination are: ； The total number of grid points is: ; Match the cold air brightness temperature radiation background data; and convert the original cold air brightness temperature data table. Represented as: ； in, This represents the highest resolution scale actually measured. for The cold air brightness temperature radiation corresponding to the coordinates; To obtain the nominal right ascension and declination coordinates Corresponding cold air brightness temperature radiation ,right Zhongyu Matching is performed using the celestial coordinates with the smallest angular distance. Defined as: ； For each formatted celestial grid coordinate Find the actual measurement Make distance The smallest point is denoted as: ； in, These are the indices that satisfy the minimum angular distance condition; The matched angular coordinate data is used for the allocation and mapping of cold air brightness temperature radiation background values, and the measured cold air brightness temperature radiation data is used for this purpose. Map to the nearest grid point ,get And generate a formatted cold air brightness temperature radiation background data table. : ； A cold air brightness temperature radiation background database is obtained by piecewise fitting based on linear interpolation and boundary data smoothing methods; the method is designed as follows: The known formatted cold air brightness temperature radiation background database consists of discretized data points represented by right ascension and declination. These data points can be represented as... ,in It has a periodicity, with a period of 1 / 2. ; It does not have a periodicity; Constructing a periodic bivariate interpolation function The function satisfies: exist The direction satisfies the periodic boundary condition: ； Linear interpolation is used for each segment, while the overall process is smooth and the boundaries are continuous. To achieve Periodic boundary conditions in the direction will cause discrete data points to... The direction is periodically expanded, and the expansion rule is as follows: right Directional expansion: ； in For the extended width; The expanded data points are represented as That is, the expanded brightness temperature data points are composed of the expanded right ascension coordinates and the original declination coordinates; For the expanded data point set In each two-dimensional matrix unit Construct a linear fitting function. : ； in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries; After interpolation, perform a two-dimensional sliding window smoothing operation on the result; define the two-dimensional smoothing kernel. : ； in They are respectively The window width set in the direction; Smoothed result Achieved through two-dimensional convolution: ； Ultimately, the cold air brightness temperature radiation background fitting database is represented as a piecewise bivariate linear fitting function, in each It contains: ； in, Indicates that in the number A linear fitting function for cold air brightness temperature within a two-dimensional matrix unit; the boundaries of each two-dimensional matrix unit are continuous, forming a continuous fitting function. This refers to the cold air brightness temperature radiation background fitting database. Given any right ascension and declination coordinates, the brightness temperature radiation data corresponding to those coordinates can be calculated.

6. The method for constructing a space brightness-temperature radiation model for on-orbit satellite antennas according to claim 5, characterized in that: The construction of the galactic brightness temperature band model includes: Set the threshold for abnormal brightness temperature detection. The cold air brightness temperature measurement data table that exceeds this threshold The brightness temperature coordinates are considered to be abnormal brightness temperature coordinates; For the anomalous brightness temperature coordinates under the Mercator projection, weighted least squares regression was used to obtain the centerline that best represents the galactic brightness temperature band. ; with the center line To reference the upper and lower boundaries of the fitted brightness temperature bands .

7. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 6, characterized in that: Based on a weighted least squares curve fitting method, the distribution of outlier bands in cold space data is fitted. Through outlier identification and weighted polynomial fitting, the center curve and its boundary that best represent the distribution of brightness temperature outlier bands caused by the Milky Way in the cold space database are determined. First, set the threshold for abnormal brightness temperature points in the cold air brightness temperature radiation background database. The anomalous brightness temperature data set in the cold air brightness temperature radiation background database is represented as: ； Use weighted least squares regression to regress the center line of its strips, let Let the center line of the Milky Way band on the Mercator projection be given, and set... Represented by a polynomial expansion, the highest order is : ； set up For each Constructing a matrix superscript Used to indicate the first One abnormal coordinate: ； remember For each The vector formed This is a column vector of polynomial coefficients; brightness temperature As weights, the weight matrix is: ； The objective function of weighted least squares is: ； Its closed-form solution is: ; Obtain the centerline function of the Milky Way band Its polynomial coefficients are derived from Decision; to define the Milky Way bands in the Mercator projection coordinates of the celestial sphere, and to identify each anomaly point. The value given by the center line is , and The difference is ;like The indication point is above the center line, if Then it lies below the center line; regressing on the upper boundary, for all and Let the deviations of the sampling coordinate points relative to the center line satisfy the polynomials: ； Similarly, using weighted least squares, the weight matrix is ​​changed to an exponentially decaying form to suppress excessive expansion of the boundary by extreme brightness temperature points: ； in This is the exponential decay factor that needs to be set; The upper and lower boundaries were obtained through fitting: 。 8. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 5, characterized in that: Construct a nominal geographic latitude and longitude grid coordinate system, and set the specified resolution scale as . Take the longitude in the geographic latitude and longitude coordinate system ,latitude by For the distance from the walk, longitude discretization yields: ； Latitude discretization includes: ； The coordinates of the discretized geographic latitude and longitude grid points are: ； The total number of grid points is: ; The brightness temperature values ​​are assigned using a land-sea separation model, with the brightness temperature radiation value corresponding to the ocean coordinate point being... Land brightness temperature value set to This forms a formatted database of Earth's surface brightness temperature radiation background. ； in, , These represent the sets of ocean latitude and longitude coordinates in the land-sea separation model; For the data point set of the formatted surface brightness temperature radiation background database In each two-dimensional matrix unit Construct a linear fitting function. : ； in: The interpolation results are defined independently within each rectangular cell, and due to the periodicity of the extended dataset, the interpolation results are continuous at the boundaries; Ultimately, the surface brightness temperature radiation background fitting database was represented as a piecewise bivariate linear fitting function, in each It contains: ； in, Indicates that in the number The linear fitting function of surface brightness temperature within a two-dimensional matrix cell; the boundaries of each two-dimensional matrix cell are continuous, thus forming a continuous fitting function. This refers to the Earth's surface brightness temperature radiation background fitting database. Given any geographic latitude and longitude coordinates, the brightness temperature radiation data corresponding to those coordinates can be calculated; resulting in a brightness temperature radiation background fitting model for the Earth's surface with land and sea separation.

9. The method for constructing a space brightness temperature radiation model for on-orbit satellite antennas according to claim 1, characterized in that: Based on current satellite telemetry information, including the position of the reference inertial frame, the attitude relative to the inertial frame, and the latitude and longitude coordinates of the current satellite nadir point, the spatial brightness temperature radiation values ​​pointing upwards for each beam are calculated using a formatted onboard antenna pattern and a fitted database. First, the pattern beam pointing is formatted and determined based on the current spacecraft attitude under the actual orbital space environment; assuming the nominal orbit is... At any given moment, a satellite celestial coordinate system exists, and at that moment, the satellite under the celestial sphere receives spatial brightness and temperature radiation from all directions, contributed by the visible area of ​​the Earth's surface and cold air. In the satellite celestial coordinate system, the origin of the spherical coordinate system is the satellite center, and the spherical coordinate angles are described as follows: Meanwhile, the origin of the spherical coordinate system for surface brightness temperature is the Earth's center, and the spherical coordinate angle is described as follows: Let the celestial coordinate system be a celestial coordinate system with the satellite center as the origin. Its coordinate axes Orientation and J2000 reference inertial frame parallel; set up The angular coordinate system of the next point is It has its Cartesian coordinate system vector: ； To determine whether it points to a cold space region or an area on the Earth's surface, let the satellite's current orbital position vector be... ,like If the following equation is satisfied, the angular coordinates point to the Earth's surface region; otherwise, they point to the cold air region: ； in, The semi-cone angle of the visible area on the Earth's surface relative to the satellite is given by the Earth's radius. Atmospheric thickness is , It is expressed as follows: ； When angular coordinates When pointing to the cold air region, the brightness temperature gain corresponding to that angular coordinate system is calculated directly using the fitted cold air database function. ; When angular coordinates When pointing towards a region on the Earth's surface, calculate the latitude and longitude of the angular coordinates pointing towards the Earth's surface; angular coordinate vector. There are two intersections with the Earth's surface Select intersection point Obtain its latitude and longitude The brightness temperature gain corresponding to this angular coordinate system is calculated using the fitted surface brightness temperature database function. The direction of each formatted beam is determined, and the brightness temperature value is calculated using a brightness temperature background fitting database to obtain the brightness temperature radiation value vector. This vector contains the brightness temperature radiation values ​​of the spatial background at the current moment, pointing towards the N beams of the formatted antenna pattern. The numerical solution of the effect of the final spatial brightness temperature radiation background on the antenna brightness temperature integral is performed using the brightness temperature integral formula. Given the original antenna power pattern, the formula for calculating the brightness temperature integral of its spatial brightness temperature radiation background effect is as follows: ； in, The power pattern after conversion to an inertial frame is shown. and Completed with The matching correspondence, Represents a surface in the celestial coordinate system. ; set up It can be used as a constant for preliminary calculations, for formatted radiation patterns and their solved radiation matrix. The integral formula, discretized into a summative form, can be represented using matrix multiplication as follows: ； in, The element in the i-th row is .

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