Method, device and equipment for determining radiation target of spaceborne synthetic aperture radiometer antenna

Abstract

The present invention discloses a method, device and equipment for determining the radiation target of a satellite-borne synthetic aperture radiometer antenna, which relates to the field of microwave remote sensing technology and is used to solve the problem of determining the pointing direction of the antenna omnidirectional radiation beam and the pointing target of the payload in the cold space calibration mode in the prior art. It includes: determining the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system, and converting it from the antenna coordinate system to the inertial coordinate system; determining the category of the space target to which the antenna omnidirectional radiation beam points, and performing a space target coordinate system conversion; performing brightness temperature matching on the space target category after the space target coordinate system conversion, and obtaining the brightness temperature of the space target category. The method proposed in the present invention can obtain the precise pointing direction of the antenna omnidirectional radiation beam in space and the brightness temperature value of the cold sky, ocean and land on the earth; the calculated precise spatial pointing of the beam is an important part of the satellite's on-orbit cold space calibration work, which is helpful for the on-orbit calibration and calibration of the satellite payload.

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 spaceborne synthetic aperture radiometer antenna. Background Art

[0002] A microwave radiometer is a highly sensitive receiver used to measure the microwave energy emitted by matter. Aperture Synthetic Radiometers (ASRs) utilize an array of small antennas to create a large observation aperture. This solves the problem of traditional microwave radiometers requiring a single antenna with a sufficiently large physical aperture to achieve the desired spatial resolution at lower frequencies. However, in practical applications, ASR systems must contend with complex spatial environments and multiple sources of error. Therefore, accurately determining the antenna's omnidirectional radiation target is crucial for achieving high-precision remote sensing measurements.

[0003] The on-orbit calibration of the Spaceborne Synthetic Aperture Radiometer requires cold-space calibration, which primarily involves maneuvering the satellite platform to transition the payload's conventional Earth observations to cold-space observations. During this cold-space calibration, the antenna's orientation in all directions and the determination of its target become crucial, directly impacting its accuracy.

[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 space-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 space-borne synthetic aperture radiometer antenna, which is used to solve the problem of determining the omnidirectional radiation beam pointing and the pointing target of the antenna in the cold space calibration mode in the prior art.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] 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:

[0008] Determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system;

[0009] Converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system;

[0010] Determining the category of the space target that the antenna's omnidirectional radiation beam is directed toward; the space target category includes cold space targets and earth targets;

[0011] Performing space target coordinate system conversion according to the space target category;

[0012] 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.

[0013] Optionally, determining a unit vector of an omnidirectional radiation beam of the antenna in an antenna coordinate system includes:

[0014] Using the formula:

[0015] ;

[0016] Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system;

[0017] 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 between the axes, is the beam vector in Projection of plane and + The angle between the axes.

[0018] Optionally, converting the unit vector in the antenna coordinate system from the antenna coordinate system to an inertial coordinate system includes:

[0019] Obtaining geolocation data;

[0020] parsing the geopositioning data and determining a geoorientation parameter closest to the satellite epoch time in the parsed geopositioning data;

[0021] 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.

[0022] Optionally, the converting of satellite orbit data from an Earth-centered Earth-fixed coordinate system to an inertial coordinate system based on Earth orientation parameters, and converting the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system, includes:

[0023] 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;

[0024] The satellite attitude angle is used to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system;

[0025] Calculate the unit vectors of the three coordinate axes of the satellite flight coordinate system in the inertial coordinate system;

[0026] 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.

[0027] Optionally, the step of converting the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system using the satellite attitude angle includes:

[0028] Using the formula:

[0029] ;

[0030] The rotation matrix is calculated to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system;

[0031] in, represents the rotation matrix, is the yaw angle, is the roll angle, is the pitch angle.

[0032] 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:

[0033] 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;

[0034] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0035] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0036] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0037] Based on the formula: Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system;

[0038] Based on the formula: Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system;

[0039] 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 modulus of the vector of the satellite in the inertial coordinate system, is the beam pointing unit vector in the inertial coordinate system.

[0040] Optionally, determining the category of the space target to which the antenna's omnidirectional radiation beam is directed includes:

[0041] Using the satellite position vector and beam pointing vector in the coordinate system, a model is established, and the space target category is determined based on the model;

[0042] The model is:

[0043] ;

[0044] ;

[0045] in, is the satellite's 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 in the three coordinate axis directions, is the Earth's semi-major axis, is the Earth's eccentricity;

[0046] Determine the equation expression based on the model characterization:

[0047] ;

[0048] 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 to by the beam vector in the inertial coordinate system is obtained;

[0049] If the equation 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;

[0050] In the equation expression:

[0051] ;

[0052] ;

[0053] ;

[0054] 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.

[0055] Optionally, performing space target coordinate system conversion according to the space target category includes:

[0056] Convert the cold sky target in the inertial coordinate system to the galactic coordinate system;

[0057] Convert the earth target in the inertial coordinate system to the geodetic coordinate system;

[0058] 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.

[0059] 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 category of the space target includes cold sky targets and earth targets; performing a space target coordinate system conversion according to the category of the space target; 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 it points to; 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.

[0060] In a second aspect, the present invention provides a device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, the device comprising:

[0061] A unit vector determination module, used to determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system;

[0062] A first coordinate system conversion module, configured to convert the unit vector in the antenna coordinate system from the antenna coordinate system to an inertial coordinate system;

[0063] A space target category determination module, configured to determine the category of the space target to which the antenna's omnidirectional radiation beam is directed; the space target categories include cold sky targets and earth targets;

[0064] A second coordinate system conversion module, configured to perform space target coordinate system conversion according to the space target category;

[0065] 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.

[0066] In a third aspect, the present invention provides a device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, the device comprising:

[0067] 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, it executes the above-mentioned method for determining the radiation target of the space-borne synthetic aperture radiometer antenna.

[0068] 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 achieved by the method-type solutions provided in the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] 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:

[0070] Figure 1 This is a flow chart of the method for determining the radiation target of the spaceborne synthetic aperture radiometer antenna;

[0071] Figure 2 This is a flow chart of the overall implementation scheme of the antenna omnidirectional radiation target determination method;

[0072] Figure 3 Schematic diagram of antenna coordinate system and angle definition;

[0073] Figure 4 Determine the model diagram for the space object category;

[0074] Figure 5 This is a schematic diagram of the structure of the device for determining the radiation target of the spaceborne synthetic aperture radiometer antenna;

[0075] Figure 6 Schematic diagram of the structure of the equipment for determining the radiation target of the space-borne synthetic aperture radiometer antenna. DETAILED DESCRIPTION

[0076] To facilitate a clear description of the technical solutions of the embodiments of the present invention, the words "first" and "second" are used in the embodiments of the present invention to distinguish between identical or similar items with substantially the same functions and effects. For example, the first threshold and the second threshold are merely used to distinguish between different thresholds and do not limit their order. Those skilled in the art will understand that the words "first" and "second" do not limit the quantity or execution order, and the words "first" and "second" do not necessarily mean different.

[0077] 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 construed as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0078] In the present invention, "at least one" means one or more, and "more" 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: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following items" 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 plural.

[0079] Next, the solutions provided in the embodiments of this specification are described with reference to the accompanying drawings:

[0080] like Figure 1 As shown, the process may include the following steps:

[0081] Step 110: Determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system.

[0082] The antenna coordinate system is a coordinate system centered on the antenna, used to describe the direction and intensity of the antenna's radiation field. This coordinate system is often associated with other coordinate systems, such as the satellite coordinate system and the carrier coordinate system, to facilitate coordinate transformation and navigation positioning.

[0083] An antenna's omnidirectional radiation beam means that the antenna radiates or receives signals evenly in all directions horizontally, forming a spherical radiation pattern. The antenna radiates uniformly 360 degrees horizontally, and the signal strength in all directions is relatively consistent.

[0084] Step 120: Convert the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system.

[0085] 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 benchmark 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 integrate and compare with other navigation data (such as GPS signals, inertial navigation sensor data, etc.), thereby improving the accuracy of navigation and positioning.

[0086] Step 130: Determine the category of the space target to which the antenna's omnidirectional radiation beam is directed; the category of the space target includes cold-sky targets and earth targets.

[0087] 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.

[0088] Cold air targets generally refer to targets that exist in a relatively cold or low-temperature environment, or targets that appear to be lower in temperature relative to the background temperature during detection. Earth targets refer to targets located on the Earth's surface or within the Earth's atmosphere.

[0089] Step 140: Perform space target coordinate system conversion according to the space target category.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] Figure 1The method in the invention determines the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system; converts the unit vector in the antenna coordinate system from the antenna coordinate system to the inertial coordinate system; determines the category of the space target pointed by the antenna omnidirectional radiation beam; the category of the space target includes cold sky targets and earth targets; converts the space target coordinate system according to the category of the space target; performs 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 omnidirectional radiation beam in space and the brightness temperature value of the cold sky, ocean 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 the satellite payload.

[0094] based on Figure 1 The method of determining the radiation target of the spaceborne synthetic aperture radiometer antenna provided by the present invention is implemented as follows: Figure 2 As shown, it mainly includes the determination of antenna omnidirectional radiation beam pointing, coordinate system conversion of beam pointing, determination of space target category, space target coordinate system conversion and space target brightness temperature matching. Among them, the coordinate system conversion of beam pointing can include earth positioning data matching, satellite orbit data coordinate system conversion and beam pointing unit vector coordinate system conversion; space target coordinate system conversion mainly includes cold sky target coordinate system conversion and earth target coordinate system conversion. Next, for Figure 2 The specific implementation method of the steps in the following is described.

[0095] 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 antenna omnidirectional radiation beam pointing direction is determined by calculating the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system. and To calculate the unit vector , is the beam vector and the antenna coordinate system - The angle between the axes, is the beam vector in Projection of plane and + The angle between the axes. The calculation formula is as follows:

[0096] (1)

[0097] 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:

[0098] 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), and beam pointing unit vector coordinate system conversion (converting the unit vector in the antenna coordinate system from the antenna coordinate system to the J2000 inertial coordinate system). Next, each implementation step in 120 is explained separately:

[0099] (1) Earth positioning data matching

[0100] Read and parse the Earth positioning data, search for the Earth orientation parameter dut1 that matches the satellite epoch time closest to it, and dut1 is the difference between Universal Time 1 (UT1) and Coordinated Time (UTC). and is the second component of polar motion.

[0101] (2) Satellite orbit data coordinate system conversion

[0102] 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 between 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 polar motion, the Earth's 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:

[0103] ( )

[0104] The satellite position vector in the J2000 inertial coordinate system is:

[0105] ( )

[0106] 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.

[0107] (3) Beam pointing unit vector coordinate system conversion

[0108] The coordinate system conversion of the beam pointing unit vector mainly converts 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:

[0109] 1) Conversion from antenna coordinate system to satellite coordinate system

[0110] The conversion from the antenna coordinate system to the satellite body coordinate system requires the use of the installation matrix The installation matrix requires precise measurement of the relative relationship between the three coordinate axes of the antenna coordinate system and the three coordinate axes of the satellite coordinate system, and 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 coordinate system.

[0111] 2) Conversion from satellite body coordinate system to satellite flight coordinate system

[0112] 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:

[0113] ( )

[0114] Where: is the yaw angle, is the roll angle, is the pitch angle.

[0115] 3) Conversion from satellite flight coordinate system to J2000 inertial coordinate system

[0116] 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 conversion matrix .

[0117] Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system:

[0118] ( )

[0119] Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system:

[0120] ( )

[0121] Satellite flight coordinate system Unit vector of the axis in the J2000 inertial coordinate system:

[0122] ( )

[0123] Where: and is the position vector of the satellite in the J2000 inertial coordinate system and the modulus of the vector, and is the velocity vector and the modulus of the vector in the inertial coordinate system of satellite J2000.

[0124] Therefore, the transformation matrix from the satellite flight coordinate system to the J2000 inertial coordinate system is:

[0125] ( )

[0126] 4) Calculation of beam pointing unit vector

[0127] 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:

[0128] ( )

[0129] Where: is the beam pointing unit vector in the J2000 inertial coordinate system.

[0130] Regarding step 130, when determining the space target category that the antenna omnidirectional radiation beam is pointing to, a model is established using the satellite position vector and beam pointing vector in the J2000 coordinate system to determine the space target category. Space targets are mainly divided into cold space and the Earth. The schematic diagram of the model principle is shown below. Figure 4 As shown, according to Figure 4 , the model formula is as follows:

[0131] ( )

[0132] ( )

[0133] Where: is the satellite's 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 Earth's semi-major axis, is the eccentricity of the Earth.

[0134] Substituting formula (10) into formula (11), we get the following formula:

[0135] ( )

[0136] in:

[0137] ;

[0138] ;

[0139] ;

[0140] 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.

[0141] Solve the quadratic polynomial in formula (12). If the equation has no solution or the solution is negative, then the beam is pointing toward cold space, and the position of the cold space 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, then the beam is pointing toward the Earth and has an intersection with the Earth. Substituting this positive solution into formula (10) yields the position of the Earth target pointed by the beam vector in the J2000 inertial coordinate system.

[0142] In step 140, when performing space target coordinate system conversion 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.

[0143] 1) Cold air target coordinate system conversion

[0144] 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 ICRS to the Galactic coordinate system.

[0145] The J2000 inertial coordinate system and the International Celestial Reference System are both inertial coordinate systems. The difference between the two is relatively small. You can first convert the J2000 inertial coordinate system to the Earth-centered Earth-fixed coordinate system, and then convert the Earth-centered Earth-fixed coordinate system to the International Celestial Coordinate System.

[0146] The calculation formula of the transformation matrix from the International Celestial Reference System to the Galactic Coordinate System is as follows:

[0147] ;

[0148] 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 Milky Way equator on the equator of the International Celestial Reference System.

[0149] By converting the rectangular coordinates of the cold sky target's galactic coordinate system into spherical coordinates, we can obtain the galactic longitude and latitude.

[0150] 2) Earth target coordinate system conversion

[0151] The transformation matrix from the J2000 inertial coordinate system to the Earth-centered Earth-fixed coordinate system is as follows:

[0152] ;

[0153] Where: , , and They are the precession matrix, nutation matrix, Earth rotation matrix and polar motion matrix respectively.

[0154] The conversion from the Earth-centered Earth-fixed coordinate system to the geodetic coordinate system uses a method that does not require iteration, which is faster. The calculation formula is as follows:

[0155] ;

[0156] ;

[0157] ;

[0158] ;

[0159] ;

[0160] ;

[0161] Where: is the geodetic longitude, is the geodetic latitude, For the height of the earth, is the Earth's semi-major axis, is the Earth's oblateness, is the eccentricity of the Earth.

[0162] 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.

[0163] 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.

[0164] The brightness temperature matching of the earth target requires a land and sea mask for 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.

[0165] Based on the above embodiment, 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.

[0166] The method for determining the radiation target of a spaceborne 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 when the payload is in cold-space calibration mode. This method can be used to obtain the precise pointing of the antenna's omnidirectional beam in space and the brightness temperature values of the targets it points to, such as the cold sky, oceans, and land on Earth, for cold-space calibration of the spaceborne 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 facilitates 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 spaceborne passive microwave payloads.

[0167] Based on the same idea, the present invention also provides a device for determining the radiation target of a spaceborne synthetic aperture radiometer antenna, such as Figure 5 As shown, the device may include:

[0168] A unit vector determination module 510 is configured to determine a unit vector of an antenna's omnidirectional radiation beam in an antenna coordinate system;

[0169] A first coordinate system conversion module 520 is configured to convert the unit vector in the antenna coordinate system from the antenna coordinate system to an inertial coordinate system;

[0170] A space target category determination module 530 is configured to determine the category of the space target to which the antenna's omnidirectional radiation beam is directed; the space target categories include cold sky targets and earth targets;

[0171] A second coordinate system conversion module 540 is configured to perform space target coordinate system conversion according to the space target category;

[0172] 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, and obtain the brightness temperature corresponding to the space target category.

[0173] based on Figure 5 The device may further include some specific implementation units:

[0174] Optionally, the unit vector determination module 510 may include:

[0175] Using the formula:

[0176] ;

[0177] Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system;

[0178] 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 between the axes, is the beam vector in Projection of plane and + The angle between the axes.

[0179] Optionally, the first coordinate system conversion module 520 may include:

[0180] A geopositioning data acquisition unit, configured to acquire geopositioning data;

[0181] an earth orientation parameter determination unit, configured to parse the earth positioning data and determine an earth orientation parameter closest to the satellite epoch time in the parsed earth positioning data;

[0182] 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 in the antenna coordinate system from the antenna coordinate system to the J2000 inertial coordinate system.

[0183] Optionally, the coordinate system conversion unit may include:

[0184] A satellite body coordinate system conversion unit is used to convert the beam pointing unit vector corresponding to the satellite orbit data from the antenna coordinate system to the satellite body coordinate system based on the installation matrix;

[0185] A satellite flight coordinate system conversion unit is used to convert the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system using the satellite attitude angle;

[0186] 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;

[0187] 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.

[0188] Optionally, the satellite flight coordinate system conversion unit can be used to:

[0189] Using the formula:

[0190] ;

[0191] The rotation matrix is calculated to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system;

[0192] in, represents the rotation matrix, is the yaw angle, is the roll angle, is the pitch angle.

[0193] Optionally, a conversion matrix determination unit may be used to:

[0194] 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;

[0195] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0196] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0197] Based on the formula: Determine the satellite flight coordinate system The unit vector of the axis in the inertial coordinate system;

[0198] Based on the formula: Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system;

[0199] Based on the formula: Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system;

[0200] 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 modulus of the vector of the satellite in the inertial coordinate system, is the beam pointing unit vector in the inertial coordinate system.

[0201] Optionally, the space object category determination module 530 may be used to:

[0202] 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;

[0203] The model is:

[0204] ;

[0205] ;

[0206] in, is the satellite's 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 in the three coordinate axis directions, is the Earth's semi-major axis, is the Earth's eccentricity;

[0207] Determine the equation expression based on the model characterization:

[0208] ;

[0209] 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;

[0210] If the equation 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;

[0211] In the equation expression:

[0212] ;

[0213] ;

[0214] ;

[0215] 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.

[0216] Optionally, the second coordinate system conversion module 540 may include:

[0217] Galactic coordinate system conversion unit, used to convert cold air targets in the J2000 inertial coordinate system to the Galactic coordinate system;

[0218] The earth coordinate system conversion unit is used to convert the earth target in the J2000 inertial coordinate system to the earth coordinate system;

[0219] The brightness temperature matching unit is used to match the cold sky targets in the Galactic coordinate system and the earth targets 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 targets.

[0220] 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:

[0221] 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, it executes the aforementioned method for determining the radiation target of the space-borne synthetic aperture radiometer antenna.

[0222] like Figure 6 As shown, the processor can be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling program execution of the present invention. The communication interface can be one or more. The communication interface can use any device, such as a transceiver, for communicating with other devices or a communication network.

[0223] like Figure 6 As shown, the terminal device may further include a communication line. The communication line may include a path for transmitting information between the components.

[0224] Optional, such as Figure 6 As shown, the terminal device may further include a memory. The memory stores a computer program executable by the processor; when the processor executes the computer program, the method provided by the embodiment of the present invention is implemented.

[0225] like Figure 6As shown, the memory may be, but is not limited to, read-only memory (ROM) or other types of static storage devices capable of storing static information and instructions, random access memory (RAM) or other types of dynamic storage devices capable of storing information and instructions, electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer. The memory may be independent and connected to the processor via a communication link. Alternatively, the memory may be integrated with the processor.

[0226] 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.

[0227] In a specific implementation, as an embodiment, Figure 6 As shown, the processor may include one or more CPUs, such as Figure 6 CPU0 and CPU1 in.

[0228] In a specific implementation, as an embodiment, 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.

[0229] 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 can be understood 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 easy for those skilled in the art to realize 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.

[0230] The embodiments of the present invention can be divided into functional modules according to the above-mentioned method examples. For example, each functional module can be divided according to each function, or two or more functions can be integrated into a single processing module. The above-mentioned integrated modules can be implemented in the form of hardware or software functional modules. It should be noted that the division of modules in the embodiments of the present invention is illustrative and is only a logical functional division. In actual implementation, other division methods may be used.

[0231] The processor in this specification may also function as a memory. The memory is used to store computer-executable instructions for implementing the solutions of the present invention, and the processor controls the execution of the instructions. The processor is used to execute the computer-executable instructions stored in the memory, thereby implementing the methods provided in the embodiments of the present invention.

[0232] Although the present invention has been 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 reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" 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.

[0233] Although the present invention has been described with reference to specific features and embodiments thereof, it will be apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the 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 invention. It will be apparent that various modifications and variations may be made to the present invention by those skilled in the art without departing from the spirit and scope of the invention. Thus, the present invention is intended to include such modifications and variations as 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 targets 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; 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; The determination of the space target category to which the antenna omnidirectional radiation beam is directed includes: Using the satellite position vector and beam pointing vector in the inertial coordinate system, a model is established, and the space target category is determined based on the model; Determine the equation expression based on the model characterization: C1*S 2 +2C2*S+C3=0; 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 to by the beam vector in the inertial coordinate system is obtained; If the equation 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: C2=R x *In x +R y *In y +R z *In z / (1-e 2 ); Among them, V x 、V y and V z is the coordinate of the beam pointing unit vector, R x 、R y and R z is the coordinate of the satellite position vector, C1 is the coefficient of the quadratic term of the quadratic equation, C2 is the coefficient of the linear term, C3 is the constant term, S is the distance from the satellite to the space target along the beam pointing, a is the semi-major axis of the Earth, and e is the eccentricity of the Earth; 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 a geoorientation 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; The converting of satellite orbit data from an Earth-centered Earth-fixed coordinate system to an 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 satellite attitude angle is used to transform the beam pointing unit vector from the satellite body coordinate system to the satellite flight coordinate system; 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; The method 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; Among them, T orb / scb Represents the rotation matrix, y is the yaw angle, r is the roll angle, and p is the pitch angle; 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: orb =-r eci / |r eci |Determine the satellite flight coordinate system Z orb The unit vector of the axis in the inertial coordinate system; Based on the formula: orb =z orb ×v eci / |v eci |Determine the satellite flight coordinate system Y orb The unit vector of the axis in the inertial coordinate system; Based on the formula: orb =y orb ×z orb Determine the satellite flight coordinate system X orb The unit vector of the axis in the inertial coordinate system; Based on the formula: T eci / orb =[x orb y orb z orb ]Determine the transformation matrix from the satellite flight coordinate system to the inertial coordinate system; Based on the formula: V eci =T eci / orb T orb / scb T scb / ant V a Convert the beam pointing unit vector in the satellite flight coordinate system to the inertial coordinate system; Among them, r eci and |r eci | is the position vector of the satellite in the inertial coordinate system and the modulus of the vector, v eci and|v eci | is the velocity vector and the modulus of the vector of the satellite in the inertial coordinate system, V eci is the beam pointing unit vector in the inertial coordinate system.

2. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The determining of the unit vector of the antenna omnidirectional radiation beam in the antenna coordinate system includes: Using the formula: Calculate the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; Among them, V a Represents the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system, and θ is the difference between the beam vector and -Z in the antenna coordinate system. a The angle between the axes, is the beam vector in X a Y a Projection of a plane and +X a The angle between the axes.

3. The method for determining radiation targets of a spaceborne synthetic aperture radiometer antenna according to claim 1, characterized in that: The model is: R eci +S*V eci =P eci ; where R eci is the satellite position vector, V eci is the beam pointing unit vector, P eci is the position vector of the space target; P x 、P y and P z It is the position coordinate of the space target in the three coordinate axis directions.

4. 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.

5. A device for determining radiation targets of a spaceborne synthetic aperture radiometer antenna, characterized in that: The device includes: A unit vector determination module, used to determine the unit vector of the antenna's omnidirectional radiation beam in the antenna coordinate system; A first coordinate system conversion module, 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, used to determine the category of the space target that the antenna's omnidirectional radiation beam is pointing to; The space target categories include cold space targets and earth targets; A second coordinate system conversion module, configured to perform 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.

6. Satellite-borne synthetic aperture radiometer antenna radiation target determination device, characterized in that the device 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 a spaceborne synthetic aperture radiometer antenna according to any one of claims 1 to 4.

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