Large-aperture antenna microwave radiometer on-orbit calibration method based on cold air analysis

Abstract

The invention discloses a large-aperture antenna microwave radiometer on-orbit calibration method based on cold air analysis, belongs to the technical field of microwave radiometer calibration, and is applied to stationary orbit microwave radiometer calibration. The implementation method comprises the following steps: 1, observing an atmospheric target by using an antenna to obtain atmospheric radiation energy; 2, the receiver determines the gain of the receiver in a gain mode; 3, the microwave radiometer observes cold air through the receiver to obtain cold air radiation energy; 4, the microwave radiometer observes the cold air through the antenna to obtain cold air radiation energy; and 5, observing the atmosphere target and the antenna error by using the antenna to obtain the atmosphere target brightness temperature. In order to correct the deformation and self-radiation influence of the main reflecting surface and the auxiliary reflecting surface of the external antenna, a receiver can directly observe the cold air and can also observe the cold air through the antenna surface, and the overall influence of the real-time antenna is obtained through an offset modeling mode, so that the correction on the overall influence of the antenna in the calibration process is realized. And the problem that the large-aperture antenna microwave radiometer is difficult to calibrate can be solved.

Description

Technical Field

[0001] The invention relates to an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold-space analysis, belongs to the technical field of microwave radiometer calibration, and is applied to the calibration of a geostationary orbit microwave radiometer. Background Art

[0002] In the microwave and millimeter wave bands, in order to improve the spatial resolution to observe the earth, the microwave radiometers carried by satellites have to use large-aperture antennas to reduce the antenna beam width. The antenna aperture is often several meters or even tens of meters. It is difficult for the satellite body to carry a black body of sufficient size to calibrate the entire radiometer. It can only rely on carrying a small black body and only perform two-point calibration on the receiver at the rear end of the antenna. The deformation and self-radiation of the exposed main and secondary reflective surfaces of the antenna cannot be accurately calibrated.

[0003] The deformation of the reflecting surface and self-radiation of the external antenna lead to distortion of the antenna pattern and self-radiation interference, which results in inaccurate accuracy of the receiver's observation of the atmospheric radiation brightness temperature through the external antenna. Therefore, how to achieve high-precision calibration that comprehensively removes the influence of the antenna pattern and self-radiation has become an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to realize high-precision calibration by integrally removing the influence of antenna pattern and self-radiation under the deformation and self-radiation correction of large-aperture antenna microwave radiometer based on cold space field analysis, and a method for on-orbit calibration of large-aperture antenna microwave radiometer based on cold space analysis is proposed.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] The invention discloses an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold-air analysis, comprising the following steps:

[0007] Step 1: Use the antenna to observe the atmospheric target and obtain the atmospheric radiation energy;

[0008] Step 2: The receiver determines the receiver gain using the gain method shown in equation (1);

[0009]

[0010] Step 2.1: The receiver obtains the total radiation energy of the heat source by observing the heat source The average count value corresponding to the receiver

[0011] Step 2.2: The receiver obtains the total radiation energy of the heat source by observing the cold source The average count value corresponding to the receiver

[0012] Step 2.3: The receiver observes the atmospheric target using the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment;

[0013] Step 2.4 uses equations (2) to (4) to obtain the receiver nonlinear coefficient;

[0014]

[0015] Wherein, μ is the quadratic nonlinear relationship between the receiver radiation brightness temperature and the receiver count value; a0, a1 and a2 are the nonlinear coefficients of the quadratic curve of the receiver;

[0016] Step 3: The microwave radiometer observes the cold sky through the receiver to obtain the cold sky radiation energy

[0017] Step 3.1: Using the atmospheric radiation brightness temperature The output count value C obtained from the ground vacuum tank experiment s Determine the quadratic nonlinear relationship coefficients a0, a1 and a2;

[0018] Step 3.2: The receiver observes the cold air and obtains the cold air radiation energy by the method shown in equation (5):

[0019]

[0020] Among them, the receiver count value C s , a0, a1 and a2 are quadratic nonlinear relationship coefficients;

[0021] Step 4: The microwave radiometer observes the cold air through the antenna to obtain the cold air radiation energy

[0022] Step 4.1: Introduce the errors of antenna self-radiation and leakage

[0023] Step 4.2: The antenna observes the cold air and obtains the cold air radiation energy by the method shown in equation (6).

[0024]

[0025] Among them, the receiver count value C sA ;

[0026] Step 5: Use the antenna to observe the atmospheric target and the antenna error to obtain the brightness temperature of the atmospheric target in the manner shown in formula (7);

[0027]

[0028] The invention discloses an on-orbit calibration device for a large-aperture antenna microwave radiometer based on cold air analysis, which is used to implement the above method. The invention discloses an on-orbit calibration device for a large-aperture antenna microwave radiometer based on cold air analysis, which comprises an antenna device, a receiver device, a communication processing device, and a storage device.

[0029] The antenna device is used to obtain the radiation brightness temperature of the cold sky observed by the receiver through the antenna, including the radiation brightness temperature of the cold sky and the antenna interference;

[0030] The receiver device is used to obtain the radiation brightness temperature of the cold sky directly observed by the receiver (including the radiation brightness temperature of the cold sky);

[0031] The communication processing device is used to perform upload and download processing of antenna and receiver data parameters, and trigger the device to perform an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold space analysis when the calibration of the geostationary orbit microwave radiometer is corrected;

[0032] The storage device is used to store setting data parameters of the antenna and the receiver, and the setting data parameters can be executed by the communication processing device to implement an on-orbit calibration method of a large-aperture antenna microwave radiometer based on cold air analysis;

[0033] Beneficial effects:

[0034] Compared with the prior art, it has the following beneficial effects:

[0035] In order to correct the deformation and self-radiation influence of the main reflector and sub-reflector of the external antenna, the microwave radiometer receiver can directly observe the cold sky, or observe the cold sky through the antenna surface. By offsetting the modeling method, the overall influence of the real-time antenna can be obtained, thereby realizing the correction of the overall influence of the antenna during the calibration process. This method has the advantages of high accuracy and the ability to solve the difficulty in calibrating large-aperture antenna microwave radiometers. It is suitable for an on-orbit calibration method for large-aperture antenna microwave radiometers based on cold sky analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the process of the present invention;

[0037] Figure 2 It is a structural schematic diagram of the method of the present invention;

[0038] Figure 3 This is the antenna pattern and self-radiation correction result diagram. DETAILED DESCRIPTION

[0039] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below in conjunction with the accompanying drawings and examples. It should be noted that the implementation of the present invention is not limited to the following embodiments, and any form of modification or change made to the present invention will fall within the protection scope of the present invention.

[0040] Example

[0041] like Figure 1 As shown, the on-orbit calibration method of a large-aperture antenna microwave radiometer based on cold air analysis of the present invention is specifically implemented in the following steps:

[0042] Step 1: Use the antenna to observe the atmospheric target and obtain the atmospheric radiation energy;

[0043] Step 2: The receiver determines the receiver gain using the gain method shown in equation (1);

[0044]

[0045] Step 2.1: The receiver obtains the total radiation energy of the heat source by observing the heat source The average count value corresponding to the receiver

[0046] Step 2.2: The receiver obtains the total radiation energy of the heat source by observing the cold source The average count value corresponding to the receiver

[0047] Step 2.3: The receiver observes the atmospheric target using the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment;

[0048] Step 2.4 uses equations (2) to (4) to obtain the receiver nonlinear coefficient;

[0049]

[0050] Wherein, μ is the quadratic nonlinear relationship between the receiver radiation brightness temperature and the receiver count value; a0, a1 and a2 are the nonlinear coefficients of the quadratic curve of the receiver;

[0051] Step 3: The microwave radiometer observes the cold sky through the receiver to obtain the cold sky radiation energy

[0052] Step 3.1: Using the atmospheric radiation brightness temperature The output count value C obtained from the ground vacuum tank experiment s Determine the quadratic nonlinear relationship coefficients a0, a1 and a2;

[0053] Step 3.2: The receiver observes the cold air and obtains the cold air radiation energy by the method shown in equation (5):

[0054]

[0055] Among them, the receiver count value C s , a0, a1 and a2 are quadratic nonlinear relationship coefficients;

[0056] Step 4: The microwave radiometer observes the cold air through the antenna to obtain the cold air radiation energy

[0057] Step 4.1: Introduce the errors of antenna self-radiation and leakage

[0058] Step 4.2: The antenna observes the cold air and obtains the cold air radiation energy by the method shown in equation (6).

[0059]

[0060] Among them, the receiver count value C sA ;

[0061] Step 5: Use the antenna to observe the atmospheric target and the antenna error to obtain the brightness temperature of the atmospheric target in the manner shown in formula (7);

[0062]

[0063] The invention discloses an on-orbit calibration device for a large-aperture antenna microwave radiometer based on cold air analysis, which is used to implement the above method. The invention discloses an on-orbit calibration device for a large-aperture antenna microwave radiometer based on cold air analysis, which comprises an antenna device, a receiver device, a communication processing device, and a storage device.

[0064] The antenna device is used to obtain the radiation brightness temperature of the cold sky observed by the receiver through the antenna, including the radiation brightness temperature of the cold sky and the antenna interference;

[0065] The receiver device is used to obtain the radiation brightness temperature of the cold sky directly observed by the receiver (including the radiation brightness temperature of the cold sky);

[0066] The communication processing device is used to perform upload and download processing of antenna and receiver data parameters, and trigger the device to perform an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold space analysis when the calibration of the geostationary orbit microwave radiometer is corrected;

[0067] The storage device is used to store setting data parameters of the antenna and the receiver, and the setting data parameters can be executed by the communication processing device to implement an on-orbit calibration method of a large-aperture antenna microwave radiometer based on cold air analysis;

[0068] In the embodiment, Figure 2 As shown in the figure, the microwave radiometer receiver observes the cold space target through the second secondary reflector of the antenna, the first secondary reflector of the antenna and the main reflector of the antenna At this time, the receiver's count output is C s ; At the same time, the microwave radiometer receiver observes the cold space target through the cold space reflector At this time, the receiver's count output is C sA ; Antenna surface structure and self-radiation introduce antenna error, and the antenna error is obtained by analyzing the cold air field through two observations. Carry out calibration work.

[0069] To further illustrate the superiority of the present invention, the simulated data is tested in the form of annual analysis, such as Figure 3 As shown in the figure, the red line graph shows that the data accuracy is 1.5k when the receiver observes the cold sky data through the antenna, and the green line graph shows that the data accuracy is 0.5k when the receiver directly observes the cold sky data. It can be seen that the overall antenna pattern and self-radiation correction can effectively remove the error factors caused by the external antenna group and effectively improve the calibration accuracy.

[0070] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold-air analysis, characterized in that: The following steps are included: Step 1: Use the antenna to observe the atmospheric target and obtain the atmospheric radiation energy; Step 2: The receiver determines the receiver gain using the gain method shown in equation (1); Step 2.1: The receiver obtains the total radiation energy of the heat source by observing the heat source The average count value corresponding to the receiver Step 2.2: The receiver obtains the total radiation energy of the heat source by observing the cold source The average count value corresponding to the receiver Step 2.3: The receiver observes the atmospheric target using the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment; Step 2.4 uses equations (2) to (4) to obtain the receiver nonlinear coefficient; Wherein, μ is the quadratic nonlinear relationship between the receiver radiation brightness temperature and the receiver count value; a0, a1 and a2 are the nonlinear coefficients of the quadratic curve of the receiver; Step 3: The microwave radiometer observes the cold sky through the receiver to obtain the cold sky radiation energy Step 3.1: Using the atmospheric radiation brightness temperature The output count value C obtained from the ground vacuum tank experiment s Determine the quadratic nonlinear relationship coefficients a0, a1 and a2; Step 3.2: The receiver observes the cold air and obtains the cold air radiation energy by the method shown in equation (5): Among them, the receiver count value C s , a0, a1 and a2 are quadratic nonlinear relationship coefficients; Step 4: The microwave radiometer observes the cold air through the antenna to obtain the cold air radiation energy Step 4.1: Introduce the errors of antenna self-radiation and leakage Step 4.2: The antenna observes the cold air and obtains the cold air radiation energy by the method shown in equation (6). Among them, the receiver count value C sA ; Step 5: Use the antenna to observe the atmospheric target and the antenna error to obtain the brightness temperature of the atmospheric target using the method shown in equation (7).

2. An on-orbit calibration device for a large-aperture antenna microwave radiometer based on cold air analysis that implements the method as claimed in claim 1, characterized in that: It includes an antenna device, a receiver device, a communication processing device, and a storage device; The antenna device is used to obtain the radiation brightness temperature of the cold sky observed by the receiver through the antenna, including the radiation brightness temperature of the cold sky and the antenna interference; The receiver device is used to obtain the radiation brightness temperature of the cold sky directly observed by the receiver (including the radiation brightness temperature of the cold sky); The communication processing device is used to perform upload and download processing of antenna and receiver data parameters, and trigger the device to perform an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold space analysis when the calibration of the geostationary orbit microwave radiometer is corrected; The storage device is used to store the setting data parameters of the antenna and the receiver, and the setting data parameters can be executed by the communication processing device to implement an on-orbit calibration method for a large-aperture antenna microwave radiometer based on cold space analysis.

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