Satellite-borne synthetic aperture radiometer antenna radiation target determination method, device and equipment

Abstract

The invention discloses a method, a device and equipment for determining an antenna radiation target of a satellite-borne synthetic aperture radiometer, relates to the technical field of microwave remote sensing, and is used for solving the problems of antenna omnidirectional radiation beam pointing and pointing target determination when a load is in a cold air calibration mode in the prior art. Comprising the following steps: determining a unit vector of an antenna omnidirectional radiation beam under an antenna coordinate system, and converting the unit vector from the antenna coordinate system to an inertial coordinate system; determining the category of a space target pointed by an omnidirectional radiation beam of the antenna, and performing coordinate system conversion of the space target; and carrying out brightness temperature matching on the space target category after the space target coordinate system conversion to obtain the brightness temperature of the space target category. According to the method provided by the invention, the accurate pointing of the omnidirectional radiation beam of the antenna in the space and the brightness temperature values of targets such as the ocean and the land on the cold air and the earth can be obtained; the calculated wave beam precise space pointing is an important component of satellite in-orbit cold air calibration work, and in-orbit calibration and calibration of satellite loads are facilitated.

Description

Technical Field

[0001] The present invention relates to the field of microwave remote sensing technology, and in particular to a method, device and equipment for determining radiation targets of a satellite-borne synthetic aperture radiometer antenna. Background Art

[0002] A microwave radiometer is a highly sensitive receiver used to measure the microwave radiation energy of matter. Aperture Synthetic Radiometer (ASR) uses a small-aperture antenna array to synthesize a large observation aperture, solving the problem that traditional microwave radiometers require a single antenna with a large enough physical aperture to obtain the desired spatial resolution at lower frequencies. However, in practical applications, ASR systems need to face complex space environments and multiple sources of error. Therefore, accurate determination of the antenna's omnidirectional radiation target is the key to achieving high-precision remote sensing measurements.

[0003] The calibration of the on-orbit equipment of the spaceborne synthetic aperture radiometer requires cold-space calibration, which mainly involves turning the satellite platform maneuverably to convert the payload's conventional earth observation into cold-space observation. During the cold-space calibration process, the direction of the antenna in all directions in space and the determination of the pointing target become particularly important, which will directly affect the accuracy of the cold-space calibration.

[0004] At present, no satellite or payload has carried out such work in China, so there is an urgent need to provide a solution for determining the omnidirectional radiation target of a satellite-borne synthetic aperture radiometer antenna. Summary of the invention

[0005] The purpose of the present invention is to provide a method, device and equipment for determining the radiation target of a satellite-borne synthetic aperture radiometer antenna, which is used to solve the problem of determining the omnidirectional radiation beam pointing of the antenna and the pointing target when the payload is in a cold space calibration mode in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect, the present invention provides a method for determining a radiation target of a spaceborne synthetic aperture radiometer antenna, the method comprising: Determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; Converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; Determine the space target category that the antenna omnidirectional radiation beam is pointing to; the space target category includes cold space targets and earth targets; Performing space target coordinate system conversion according to the space target category; Brightness temperature matching is performed on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category.

[0007] Optionally, determining a unit vector of an omnidirectional radiation beam of an antenna in an antenna coordinate system includes: Using the formula: ; Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; in, The unit vector representing the omnidirectional radiation beam of the antenna in the antenna coordinate system, is the beam vector and the antenna coordinate system - The angle of the axis, is the beam vector Projection of plane and + The angle of the axis.

[0008] Optionally, converting the unit vector in the antenna coordinate system from the antenna coordinate system to an inertial coordinate system includes: Obtaining geolocation data; parsing the geopositioning data and determining the geo-orientation parameter closest to the satellite epoch time in the parsed geopositioning data; The satellite orbit data is converted from the Earth-centered Earth-fixed coordinate system to the inertial coordinate system based on the Earth orientation parameter, and the unit vector in the antenna coordinate system is converted from the antenna coordinate system to the inertial coordinate system.

[0009] Optionally, the converting the satellite orbit data from the Earth-centered Earth-fixed coordinate system to the inertial coordinate system based on the Earth orientation parameter, and converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system, includes: Based on the installation matrix, the beam pointing unit vector corresponding to the satellite orbit data is converted from the antenna coordinate system to the satellite body coordinate system; The beam pointing unit vector is converted from the satellite body coordinate system to the satellite flight coordinate system using the satellite attitude angle; Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system; Based on the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system, the transformation matrix from the satellite flight coordinate system to the inertial coordinate system is determined, and the beam pointing unit vector in the satellite flight coordinate system is transformed to the inertial coordinate system.

[0010] Optionally, the step of converting the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system by using the satellite attitude angle includes: Using the formula: ; The rotation matrix is ​​calculated to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system; in, represents the rotation matrix, is the yaw angle, is the rolling angle, is the pitch angle.

[0011] Optionally, based on the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system, a transformation matrix from the satellite flight coordinate system to the inertial coordinate system is determined, and the beam pointing unit vector in the satellite flight coordinate system is transformed to the inertial coordinate system, including: Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system to obtain the coordinate transformation matrix; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system; Based on the formula: Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system; in, and is the position vector of the satellite in the inertial coordinate system and the modulus of the vector, and is the velocity vector and the magnitude of the vector of the satellite in the inertial coordinate system, is the beam pointing unit vector in the inertial coordinate system.

[0012] Optionally, determining the category of the space target to which the omnidirectional radiation beam of the antenna is pointed includes: Using the satellite position vector and beam pointing vector in the coordinate system, a model is established, and the category of the space target is determined based on the model; The model is: ; ; in, is the satellite position vector, is the distance from the satellite to the space target along the beam pointing direction, is the beam pointing unit vector, is the position vector of the space target; , and are the position coordinates of the space target in the three coordinate axis directions, is the semi-major axis of the Earth, is the eccentricity of the Earth; Determine the equation expression based on the model characterization: ; If the equation expression has no solution or the solution is a negative value, the beam points to the cold sky, and the position of the cold sky target pointed to by the beam vector in the inertial coordinate system is obtained; If the equation expression has a solution and the solution is positive, the beam points to the earth and has an intersection with the earth; the position of the earth target pointed by the beam vector in the inertial coordinate system is obtained; In the equation expression: ; ; ; in, , and is the coordinate of the beam pointing unit vector, , and is the coordinate of the satellite position vector, is the coefficient of the quadratic term of the quadratic equation, is the coefficient of the first-order term, is a constant term.

[0013] Optionally, performing space target coordinate system conversion according to the space target category includes: Convert the cold sky target in the inertial coordinate system to the galactic coordinate system; Convert the earth target in the inertial coordinate system to the geodetic coordinate system; The cold sky targets in the galactic coordinate system and the earth targets in the geodetic coordinate system are matched with the cold sky brightness temperature dataset and the ocean simulation brightness temperature dataset respectively to obtain the brightness temperature corresponding to the space targets.

[0014] Compared with the prior art, the present invention provides a method for determining the radiation target of a satellite-borne synthetic aperture radiometer antenna. By determining the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; determining the category of the space target to which the antenna's omnidirectional radiation beam points; the space target category includes cold sky targets and earth targets; performing a space target coordinate system conversion according to the space target category; performing brightness temperature matching on the space target category after the space target coordinate system conversion to obtain the brightness temperature corresponding to the space target category. The method proposed in the present invention can obtain the precise pointing of the antenna's omnidirectional radiation beam in space and the brightness temperature values ​​of the cold sky, oceans and land targets on the earth; the calculated precise spatial pointing of the beam is an important part of the satellite's on-orbit cold sky calibration work, and is helpful for the on-orbit calibration and calibration of satellite payloads.

[0015] In a second aspect, the present invention provides a device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, the device comprising: A unit vector determination module, used to determine the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system; A first coordinate system conversion module, used to convert the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; A space target category determination module, used to determine the space target category to which the antenna omnidirectional radiation beam is pointed; the space target category includes cold air targets and earth targets; A second coordinate system conversion module, used for performing space target coordinate system conversion according to the space target category; The brightness temperature matching module is used to perform brightness temperature matching on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category.

[0016] In a third aspect, the present invention provides a device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, the device comprising: A memory, a processor and a communication interface coupled to the processor; the memory stores a computer program that can be run by the processor; when the processor runs the computer program, the above-mentioned method for determining the radiation target of the space-borne synthetic aperture radiometer antenna is executed.

[0017] The technical effects achieved by the device-type solutions provided in the second aspect and the equipment-type solutions provided in the third aspect are the same as those of the method-type solutions provided in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 This is a flow chart of the method for determining the radiation target of the antenna of a spaceborne synthetic aperture radiometer; Figure 2 It is a flow chart of the overall implementation scheme of the antenna omnidirectional radiation target determination method; Figure 3 A schematic diagram of the antenna coordinate system and angle definition; Figure 4 Determine the model schematic for the space object category; Figure 5 This is a schematic diagram of the structure of the device for determining the radiation target of the antenna of the spaceborne synthetic aperture radiometer; Figure 6 Schematic diagram of the structure of the equipment for determining the radiation target of the satellite-borne synthetic aperture radiometer antenna. DETAILED DESCRIPTION

[0019] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0020] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0021] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

[0022] Next, the solution provided by the embodiments of this specification is described in conjunction with the accompanying drawings: like Figure 1 As shown, the process may include the following steps: Step 110: Determine the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system.

[0023] The antenna coordinate system is a coordinate system established with the antenna as the center, which is used to describe the direction and intensity of the antenna radiation field. This coordinate system is usually associated with other coordinate systems such as the satellite coordinate system and the carrier coordinate system to facilitate coordinate transformation and navigation positioning.

[0024] The omnidirectional radiation beam of an antenna means that the antenna can radiate or receive signals evenly in all directions in the horizontal direction, forming a spherical radiation pattern. The antenna radiates 360 degrees evenly in the horizontal direction, and the signal strength in all directions is relatively consistent.

[0025] Step 120: Convert the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system.

[0026] In practical applications, the antenna coordinate system needs to be transformed with other coordinate systems. The inertial coordinate system is a non-rotating, fixed reference system that provides a unified and stable reference to describe the position and velocity of an object. In contrast, the antenna coordinate system is established relative to the antenna or carrier and may change with the movement of the carrier. Therefore, converting the unit vectors in the antenna coordinate system to the inertial coordinate system allows these vectors to be compared and analyzed in a unified, time-invariant reference frame. In navigation and positioning systems, it is crucial to accurately know the pointing and radiation characteristics of the antenna. By converting the unit vectors in the antenna coordinate system to the inertial coordinate system, it is easier to fuse and compare with other navigation data (such as GPS signals, inertial navigation sensor data, etc.), thereby improving the accuracy of navigation and positioning.

[0027] Step 130: Determine the category of the space target to which the antenna's omnidirectional radiation beam is directed; the space target category includes cold sky targets and earth targets.

[0028] Using the satellite position vector and beam pointing vector in the J2000 coordinate system, a model is established to determine the category of space targets. Space targets are mainly divided into cold sky targets and earth targets.

[0029] Cold air targets usually refer to targets that exist in a colder or lower temperature environment, or targets that present a lower temperature relative to the background temperature during detection. Earth targets refer to targets located on the surface of the earth or within the earth's atmosphere.

[0030] Step 140: Perform space target coordinate system conversion according to the space target category.

[0031] The space target coordinate system conversion is to convert the coordinate systems of the two types of targets pointed by the beam vector, converting the cold sky targets in the J2000 inertial coordinate system to the Galactic coordinate system, and converting the earth targets in the J2000 inertial coordinate system to the geodetic coordinate system.

[0032] Step 150: performing brightness temperature matching on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category.

[0033] The brightness temperature matching of space targets is to match the cold sky targets and the earth targets with the cold sky brightness temperature dataset and the ocean simulation brightness temperature dataset respectively to obtain the brightness temperature corresponding to the space targets.

[0034] Figure 1 The method in the invention is to determine the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system; convert the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; determine the category of the space target pointed by the antenna omnidirectional radiation beam; the space target category includes cold sky targets and earth targets; perform space target coordinate system conversion according to the space target category; perform brightness temperature matching on the space target category after the space target coordinate system conversion to obtain the brightness temperature corresponding to the space target category. The method proposed in the invention can obtain the precise pointing of the antenna omnidirectional radiation beam in space and the brightness temperature values ​​of the cold sky, oceans and land targets pointed to; the calculated precise spatial pointing of the beam is an important part of the satellite on-orbit cold sky calibration work, which is helpful for the on-orbit calibration and calibration of satellite payloads.

[0035] based on Figure 1 The method for determining the radiation target of the satellite-borne synthetic aperture radiometer antenna provided by the present invention, when implemented specifically, the overall process is as follows Figure 2 As shown, it mainly includes the determination of the antenna omnidirectional radiation beam pointing, the coordinate system conversion of the beam pointing, the determination of the space target category, the space target coordinate system conversion and the space target brightness temperature matching. Among them, the coordinate system conversion of the beam pointing can include the earth positioning data matching, the satellite orbit data coordinate system conversion and the beam pointing unit vector coordinate system conversion; the space target coordinate system conversion mainly includes the cold sky target coordinate system conversion and the earth target coordinate system conversion. Next, for Figure 2 The specific implementation method of the steps in the above is described below.

[0036] In step 110, when determining the direction of the antenna omnidirectional radiation beam, the antenna coordinate system and angle are as follows: Figure 3 As shown, the omnidirectional radiation beam of the antenna is determined by calculating the unit vector of the omnidirectional radiation beam of the antenna in the antenna coordinate system. and To calculate the unit vector , is the beam vector and the antenna coordinate system - The angle of the axis, is the beam vector in Projection of plane and + The angle between the axes. The calculation formula is as follows: (1) In step 120, the coordinate system conversion of the beam pointing is to convert the unit vector of the antenna omnidirectional radiation beam calculated in the antenna coordinate system into a coordinate system, which mainly includes: Earth positioning data matching (obtaining earth positioning data; parsing the earth positioning data, and determining the earth orientation parameter closest to the satellite epoch time in the parsed earth positioning data), satellite orbit data coordinate system conversion (converting the satellite orbit data from the earth-centered earth-fixed coordinate system to the J2000 inertial coordinate system based on the earth orientation parameter), beam pointing unit vector coordinate system conversion (converting the unit vector under the antenna coordinate system from the antenna coordinate system to the J2000 inertial coordinate system). Next, each implementation step in 120 is described separately: (1) Earth positioning data matching Read and parse the earth positioning data, search for the earth orientation parameter dut1 that is closest to the satellite epoch time, and dut1 is the difference between Universal Time 1 (UT1) and Coordinated Time (UTC). and is the second component of polar motion.

[0037] (2) Satellite orbit data coordinate system conversion The coordinate frame of satellite orbit data is the Earth-centered, Earth-fixed coordinate system (ecef). To facilitate subsequent calculations, the satellite orbit data needs to be converted from the Earth-centered, Earth-fixed coordinate system to the J2000 inertial coordinate system (eci). The conversion of these two coordinate systems involves four rotation matrices, namely the polar shift matrix 、Earth rotation matrix , nutation matrix and the precession matrix The polar motion matrix is ​​calculated using the two components of the polar motion, the Earth rotation matrix is ​​calculated using Greenwich true sidereal time, the nutation matrix is ​​calculated using the 1980 nutation model of the International Astronomical Union (IAU), and the precession matrix is ​​calculated using the 1976 precession model of the IAU. The coordinate system conversion formula from ecef to eci is as follows: ( ) The satellite position vector in the J2000 inertial coordinate system is: ( ) Where: is the satellite position vector in the J2000 inertial coordinate system, is the satellite position vector in the Earth-centered, Earth-fixed coordinate system.

[0038] (3) Beam pointing unit vector coordinate system conversion The coordinate system conversion of the beam pointing unit vector mainly involves converting the vector from the antenna coordinate system to the J2000 inertial coordinate system, which involves the continuous conversion of multiple coordinate systems. The conversion methods include: 1) Conversion from antenna coordinate system to satellite coordinate system The conversion from the antenna coordinate system to the satellite body coordinate system requires the use of the installation matrix The installation matrix requires accurate measurement of the relative relationship between the three coordinate axes of the antenna coordinate system and the three coordinate axes of the satellite body coordinate system, which is obtained through complex calculations. This matrix can be used to transform the beam pointing unit vector from the antenna coordinate system to the satellite body coordinate system.

[0039] 2) Conversion from satellite body coordinate system to satellite flight coordinate system The transformation from the satellite body coordinate system to the satellite flight coordinate system requires the use of the satellite attitude angles, namely the pitch angle (pitch), roll angle (roll) and yaw angle (yaw) to calculate the rotation matrix , the calculation formula is as follows: ( ) Where: is the yaw angle, is the rolling angle, is the pitch angle.

[0040] 3) Conversion from satellite flight coordinate system to J2000 inertial coordinate system The conversion of the satellite flight coordinate system to the J2000 inertial coordinate system requires calculating the unit vectors of the three coordinate axes of the satellite flight coordinate system in the J2000 inertial coordinate system, and then obtaining the coordinate transformation matrix .

[0041] Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system: ( ) Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system: ( ) Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system: ( ) Where: and is the position vector of the satellite in the J2000 inertial coordinate system and the magnitude of the vector, and is the velocity vector and the magnitude of the vector in the inertial coordinate system of the satellite J2000.

[0042] Therefore, the transformation matrix from the satellite flight coordinate system to the J2000 inertial coordinate system is: ( ) 4) Beam pointing unit vector calculation After a series of coordinate system conversions, the beam pointing unit vector in the antenna coordinate system can be converted to the J2000 inertial coordinate system. The conversion formula is: ( ) Where: is the beam pointing unit vector in the J2000 inertial coordinate system.

[0043] For step 130, when determining the category of the space target that the antenna omnidirectional radiation beam is pointing to, a model is established using the satellite position vector and the beam pointing vector in the J2000 coordinate system to determine the category of the space target. The space targets are mainly divided into cold space and the earth. The schematic diagram of the model principle is shown in the figure below. Figure 4 As shown, according to Figure 4 , the model formula is as follows: ( ) ( ) Where: is the satellite position vector, is the distance from the satellite to the space target along the beam pointing direction, is the beam pointing unit vector, is the position vector of the space target. , and is the position coordinate of the space target, is the semi-major axis of the Earth, is the eccentricity of the Earth.

[0044] Substituting equation (10) into equation (11), we get the following equation: ( ) in: ; ; ; Where: , and is the coordinate of the beam pointing unit vector, , and is the coordinate of the satellite position vector, is the coefficient of the quadratic term of the quadratic equation, is the coefficient of the first-order term, is a constant term.

[0045] Solve the quadratic polynomial in formula (12). If the equation has no solution or the solution is negative, the beam points to the cold sky, and the position of the cold sky target pointed by the beam vector in the J2000 inertial coordinate system can be obtained; if the equation has a solution and the solution is positive, the beam points to the earth and there is an intersection with the earth. Substituting the positive solution into formula (10), the position of the earth target pointed by the beam vector in the J2000 inertial coordinate system can be obtained.

[0046] In step 140, when the space target coordinate system conversion is performed according to the space target category, the space target coordinate system conversion is to convert the coordinate systems of the two types of targets pointed by the beam vector, convert the cold sky targets in the J2000 inertial coordinate system to the Galactic coordinate system, and convert the earth targets in the J2000 inertial coordinate system to the geodetic coordinate system.

[0047] 1) Cold air target coordinate system conversion To convert a cold sky target from the J2000 inertial coordinate system to the Galactic coordinate system, first convert the J2000 inertial coordinate system to the International Celestial Reference System (ICRS), and then convert from the International Celestial Reference System to the Galactic coordinate system.

[0048] Both the J2000 inertial coordinate system and the International Celestial Reference System are inertial coordinate systems. The difference between the two is relatively small. The J2000 inertial coordinate system can be first converted to the Earth-centered Earth-fixed coordinate system, and then the Earth-centered Earth-fixed coordinate system can be converted to the International Celestial Coordinate System.

[0049] The conversion matrix calculation formula from the International Celestial Reference System to the Galactic Coordinate System is as follows: ; Where: is the right ascension of the Galactic North Pole in the International Celestial Reference System, is the declination of the Galactic North Pole in the International Celestial Reference System, It is the galactic longitude of the ascending node of the galactic equator on the equator of the International Celestial Reference System.

[0050] By converting the rectangular coordinates of the cold sky target's galactic coordinate system into spherical coordinates, we can get the galactic longitude and latitude.

[0051] 2) Earth target coordinate system conversion The transformation matrix from the J2000 inertial coordinate system to the Earth-centered Earth-fixed coordinate system is as follows: ; Where: , , and They are the precession matrix, nutation matrix, Earth rotation matrix and polar motion matrix respectively.

[0052] The conversion from the Earth-centered Earth-fixed coordinate system to the Earth coordinate system uses a method that does not require iteration, which is faster. The calculation formula is as follows: ; ; ; ; ; ; Where: is the geodetic longitude, is the geodetic latitude, For the earth is high, is the Earth's semi-major axis, is the Earth's oblateness, is the eccentricity of the Earth.

[0053] In step 150, brightness temperature matching is performed on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category. Specifically, the space target brightness temperature matching is to match the cold sky target and the earth target with the cold sky brightness temperature dataset and the ocean simulation brightness temperature dataset respectively to obtain the brightness temperature corresponding to the space target.

[0054] The cold sky target brightness temperature matching uses the minimum distance method to match the closest point in the cold sky brightness temperature dataset as the cold sky target brightness temperature value pointed by the beam.

[0055] The brightness temperature matching of the earth target requires the sea and land masking of the earth target pointed by the beam. The ocean target is marked as 1 and the earth target is marked as 0. Then the minimum distance method is used to match the brightness temperature value of the ocean target.

[0056] Based on the above embodiments, the method calculates the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system through the antenna omnidirectional radiation beam pointing determination module, converts the beam pointing unit vector in the antenna coordinate system to the J2000 inertial coordinate system using the beam pointing coordinate system conversion module, and then obtains the category of the space target pointed by the antenna omnidirectional beam through the space target category determination module. The space target category is mainly divided into cold sky and earth. The space target coordinate system is converted according to the space target category, and the cold sky target is converted from the J2000 inertial coordinate system to the galactic coordinate system, and the earth target is converted from the J2000 inertial coordinate system to the earth-centered earth-fixed coordinate system; finally, the brightness temperature of the space target pointed by the antenna beam is matched to obtain the target brightness temperature. The method proposed in the present invention can quickly calculate the space target pointed by the omnidirectional radiation of the synthetic aperture radiometer antenna. The method has high calculation accuracy and can be applied to the cold sky calibration algorithm of the ocean salinity detection satellite.

[0057] The method for determining the radiation target of the satellite-borne synthetic aperture radiometer antenna proposed in the present invention solves the problem of determining the omnidirectional beam pointing of the antenna and the pointing target of the payload in the cold space calibration mode. This method can be used to obtain the precise pointing of the antenna omnidirectional beam in space and the brightness temperature values ​​of the cold space, oceans and land targets on the earth, which are used for the cold space calibration of the satellite-borne synthetic aperture radiometer. The precise spatial pointing of the beam calculated by this method is an important component of the satellite's on-orbit cold space calibration work, and is helpful for the on-orbit calibration and calibration of satellite payloads. The present invention has a wide range of applications in space observation and cold space calibration of satellite-borne passive microwave payloads.

[0058] Based on the same idea, the present invention also provides a device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, such as Figure 5 As shown, the device may include: A unit vector determination module 510 is used to determine the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system; A first coordinate system conversion module 520, configured to convert the unit vector in the antenna coordinate system from the antenna coordinate system to an inertial coordinate system; A space target category determination module 530 is used to determine the category of the space target to which the antenna omnidirectional radiation beam is pointed; the space target category includes cold air targets and earth targets; A second coordinate system conversion module 540, configured to perform space target coordinate system conversion according to the space target category; The brightness temperature matching module 550 is used to perform brightness temperature matching on the space target category after the space target coordinate system is converted, so as to obtain the brightness temperature corresponding to the space target category.

[0059] based on Figure 5 The device in the embodiment may further include some specific implementation units: Optionally, the unit vector determination module 510 may include: Using the formula: ; Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; in, The unit vector representing the omnidirectional radiation beam of the antenna in the antenna coordinate system, is the beam vector and the antenna coordinate system - The angle of the axis, is the beam vector Projection of plane and + The angle of the axis.

[0060] Optionally, the first coordinate system conversion module 520 may include: A geo-positioning data acquisition unit, used for acquiring geo-positioning data; an earth orientation parameter determination unit, configured to parse the earth positioning data and determine the earth orientation parameter closest to the satellite epoch time in the parsed earth positioning data; The coordinate system conversion unit is used to convert the satellite orbit data from the Earth-centered Earth-fixed coordinate system to the J2000 inertial coordinate system based on the earth orientation parameters, and to convert the unit vector under the antenna coordinate system from the antenna coordinate system to the J2000 inertial coordinate system.

[0061] Optionally, the coordinate system conversion unit may include: A satellite body coordinate system conversion unit, used for converting a beam pointing unit vector corresponding to the satellite orbit data from an antenna coordinate system to a satellite body coordinate system based on an installation matrix; A satellite flight coordinate system conversion unit, used to convert a beam pointing unit vector from a satellite body coordinate system to a satellite flight coordinate system using a satellite attitude angle; Coordinate axis unit vector calculation unit, used to calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the J2000 inertial coordinate system; The conversion matrix determination unit is used to determine the conversion matrix from the satellite flight coordinate system to the J2000 inertial coordinate system based on the unit vectors of the three coordinate axes of the satellite flight coordinate system in the J2000 inertial coordinate system, and convert the beam pointing unit vector in the satellite flight coordinate system to the J2000 inertial coordinate system.

[0062] Optionally, the satellite flight coordinate system conversion unit can be used to: Using the formula: ; The rotation matrix is ​​calculated to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system; in, represents the rotation matrix, is the yaw angle, is the rolling angle, is the pitch angle.

[0063] Optionally, a transformation matrix determination unit may be used to: Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the J2000 inertial coordinate system to obtain the coordinate transformation matrix; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system; Based on the formula: Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system; in, and is the position vector of the satellite in the inertial coordinate system and the modulus of the vector, and is the velocity vector and the magnitude of the vector of the satellite in the inertial coordinate system, is the beam pointing unit vector in the inertial coordinate system.

[0064] Optionally, the space target category determination module 530 may be used to: Using the satellite position vector and beam pointing vector in the J2000 coordinate system, a model is established, and the space target category is determined based on the model; The model is: ; ; in, is the satellite position vector, is the distance from the satellite to the space target along the beam pointing direction, is the beam pointing unit vector, is the position vector of the space target; , and are the position coordinates of the space target in the three coordinate axis directions, is the semi-major axis of the Earth, is the eccentricity of the Earth; Determine the equation expression based on the model characterization: ; If the equation has no solution or the solution is negative, the beam points to the cold sky, and the position of the cold sky target pointed by the beam vector in the J2000 inertial coordinate system is obtained; If the equation expression has a solution and the solution is positive, the beam points to the earth and has an intersection with the earth; the position of the earth target pointed by the beam vector in the J2000 inertial coordinate system is obtained; In the equation expression: ; ; ; in, , and is the coordinate of the beam pointing unit vector, , and is the coordinate of the satellite position vector, is the coefficient of the quadratic term of the quadratic equation, is the coefficient of the first-order term, is a constant term.

[0065] Optionally, the second coordinate system conversion module 540 may include: Galactic coordinate system conversion unit, used to convert cold air targets in the J2000 inertial coordinate system to the Galactic coordinate system; The earth coordinate system conversion unit is used to convert the earth target in the J2000 inertial coordinate system to the earth coordinate system; The brightness temperature matching unit is used to match the cold sky target in the galactic coordinate system and the earth target in the geodetic coordinate system with the cold sky brightness temperature dataset and the ocean simulation brightness temperature dataset respectively to obtain the brightness temperature corresponding to the space target.

[0066] Based on the same idea, the embodiments of this specification also provide a device for determining the radiation target of a spaceborne synthetic aperture radiometer antenna. Figure 6 As shown, the device includes: A memory, a processor, and a communication interface coupled to the processor; the memory stores a computer program that can be run by the processor; when the processor runs the computer program, the aforementioned method for determining the radiation target of the space-borne synthetic aperture radiometer antenna is executed.

[0067] like Figure 6 As shown, the processor may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of the program of the present invention. The communication interface may be one or more. The communication interface may use any transceiver or other device for communicating with other devices or communication networks.

[0068] like Figure 6 As shown, the terminal device may further include a communication line. The communication line may include a path to transmit information between the components.

[0069] Optional, such as Figure 6 As shown, the terminal device may further include a memory. The memory stores a computer program that can be executed by the processor; when the processor executes the computer program, the method provided by the embodiment of the present invention is implemented.

[0070] like Figure 6 As shown, the memory may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory may exist independently and be connected to the processor through a communication line. The memory may also be integrated with the processor.

[0071] Optionally, the computer-executable instructions in the embodiment of the present invention may also be referred to as application program codes, which is not specifically limited in the embodiment of the present invention.

[0072] In a specific implementation, as an example, Figure 6 As shown, the processor may include one or more CPUs, such as Figure 6 CPU0 and CPU1 in.

[0073] In a specific implementation, as an example, Figure 6 As shown, the terminal device may include multiple processors, such as Figure 6 Each of these processors can be a single-core processor or a multi-core processor.

[0074] The above mainly introduces the solution provided by the embodiment of the present invention from the perspective of the interaction between the various modules. It is understandable that, in order to realize the above functions, each module includes a hardware structure and / or software unit corresponding to the execution of each function. It should be easily appreciated by those skilled in the art that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the present invention can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0075] The embodiment of the present invention can divide the functional modules according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated module can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0076] The processor in this specification may also have the function of a memory. The memory is used to store computer-executable instructions for executing the solution of the present invention, and the execution is controlled by the processor. The processor is used to execute the computer-executable instructions stored in the memory, thereby implementing the method provided by the embodiment of the present invention.

[0077] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0078] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, characterized in that: Methods include: Determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; Converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; Determine the category of space target that the antenna's omnidirectional radiation beam is pointing to; The space target categories include cold space targets and earth targets; Performing space target coordinate system conversion according to the space target category; Brightness temperature matching is performed on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category.

2. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The step of determining a unit vector of an omnidirectional radiation beam of an antenna in an antenna coordinate system includes: Using the formula: ； Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; in, The unit vector representing the omnidirectional radiation beam of the antenna in the antenna coordinate system, is the beam vector and the antenna coordinate system - The angle of the axis, is the beam vector Projection of plane and + The angle of the axis.

3. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system includes: Obtaining geolocation data; parsing the geopositioning data and determining the geo-orientation parameter closest to the satellite epoch time in the parsed geopositioning data; The satellite orbit data is converted from the Earth-centered Earth-fixed coordinate system to the inertial coordinate system based on the Earth orientation parameter, and the unit vector in the antenna coordinate system is converted from the antenna coordinate system to the inertial coordinate system.

4. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 3, characterized in that: The method of converting the satellite orbit data from the Earth-centered Earth-fixed coordinate system to the inertial coordinate system based on the Earth orientation parameter, and converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system, comprises: Based on the installation matrix, the beam pointing unit vector corresponding to the satellite orbit data is converted from the antenna coordinate system to the satellite body coordinate system; The beam pointing unit vector is converted from the satellite body coordinate system to the satellite flight coordinate system using the satellite attitude angle; Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system; Based on the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system, the transformation matrix from the satellite flight coordinate system to the inertial coordinate system is determined. Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system.

5. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 4, characterized in that: The method of using the satellite attitude angle to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system includes: Using the formula: ； The rotation matrix is ​​calculated to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system; in, represents the rotation matrix, is the yaw angle, is the rolling angle, is the pitch angle.

6. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 4, characterized in that: Based on the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system, the transformation matrix from the satellite flight coordinate system to the inertial coordinate system is determined, and the beam pointing unit vector in the satellite flight coordinate system is transformed to the inertial coordinate system, including: Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system to obtain the coordinate transformation matrix; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system; Based on the formula: Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system; Based on the formula: Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system; in, and is the position vector of the satellite in the inertial coordinate system and the magnitude of the vector, and is the velocity vector and the magnitude of the vector of the satellite in the inertial coordinate system, is the beam pointing unit vector in the inertial coordinate system.

7. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The determination of the space target category to which the antenna omnidirectional radiation beam is pointed includes: Using the satellite position vector and beam pointing vector in the coordinate system, a model is established, and the category of the space target is determined based on the model; The model is: ； ； in, is the satellite position vector, is the distance from the satellite to the space target along the beam pointing direction, is the beam pointing unit vector, is the position vector of the space target; , and are the position coordinates of the space target in the three coordinate axis directions, is the semi-major axis of the Earth, is the eccentricity of the Earth; Determine the equation expression based on the model characterization: ； If the equation expression has no solution or the solution is a negative value, the beam points to the cold sky, and the position of the cold sky target pointed to by the beam vector in the inertial coordinate system is obtained; If the equation expression has a solution and the solution is positive, the beam points to the earth and has an intersection with the earth; the position of the earth target pointed by the beam vector in the inertial coordinate system is obtained; In the equation expression: ； ； ； in, , and is the coordinate of the beam pointing unit vector, , and is the coordinate of the satellite position vector, is the coefficient of the quadratic term of the quadratic equation, is the coefficient of the first-order term, is a constant term.

8. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The converting of the space target coordinate system according to the space target category includes: Convert the cold sky target in the inertial coordinate system to the galactic coordinate system; Convert the earth target in the inertial coordinate system to the geodetic coordinate system; The cold sky targets in the galactic coordinate system and the earth targets in the geodetic coordinate system are matched with the cold sky brightness temperature dataset and the ocean simulation brightness temperature dataset respectively to obtain the brightness temperature corresponding to the space targets.

9. A device for determining radiation targets of a satellite-borne synthetic aperture radiometer antenna, characterized in that: The device includes: A unit vector determination module, used to determine the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system; A first coordinate system conversion module, used to convert the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; A space target category determination module, used to determine the category of the space target to which the antenna omnidirectional radiation beam is pointing; The space target categories include cold space targets and earth targets; A second coordinate system conversion module, used for performing space target coordinate system conversion according to the space target category; The brightness temperature matching module is used to perform brightness temperature matching on the space target category after the space target coordinate system is converted to obtain the brightness temperature corresponding to the space target category.

10. A device for determining radiation targets of a satellite-borne synthetic aperture radiometer antenna, characterized in that: include: A memory, a processor, and a communication interface coupled to the processor; The memory stores a computer program executable by the processor; When the processor runs the computer program, it executes the method for determining the radiation target of the space-borne synthetic aperture radiometer antenna as described in any one of claims 1 to 8.

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