Microwave radiometer full-aperture calibration method based on cold and heat source modeling

Abstract

The invention discloses a microwave radiometer full-aperture calibration method based on cold and heat source modeling, belongs to the technical field of microwave radiometer calibration, and is applied to stationary orbit microwave radiometer calibration. The method comprises the steps that 1, a receiver obtains cold air target energy through observation of a cold air reflector in a full-aperture mode; 2, a receiver observes a heat source blackbody in a full-aperture manner to obtain heat source total radiation energy; 3, determining a nonlinear coefficient of a quadratic curve of receiver gain in a receiver gain mode by using cold air target energy and heat source total radiation energy in the full caliber of the receiver; and 4, the receiver observes the atmospheric target by using the quadratic nonlinear relation mu between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment, and then the brightness temperature of the atmospheric target is obtained. In order to realize full-aperture cold air observation of the microwave radiometer in a satellite narrow space, cold air modeling is adopted to carry out self radiation and leakage radiation on a cold air target and a cold air reflector, and the problem that a large-aperture antenna microwave radiometer is difficult to calibrate can be solved.

Description

Technical Field

[0001] The invention relates to a full-aperture calibration method for a microwave radiometer based on cold and hot source modeling, 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, the microwave radiometer carried by the satellite needs to be calibrated in real time in order to observe high-precision targets. Therefore, the conventional method is to perform two-point calibration by full-aperture observation of cold sources and black bodies. However, the inaccuracy of the cold source and black body models leads to calibration errors, especially when the cold source mode is observed with the help of cold space reflectors, which increases the complexity of the cold source model.

[0003] Therefore, how to improve the accuracy of microwave radiometers after the interference introduced by the existing cold air reflector becomes an urgent problem to be solved. Summary of the invention

[0004] The purpose of the present invention is to improve the calibration accuracy of a microwave radiometer after the interference introduced by the existing cold air reflector is solved, and a full-aperture calibration method for a microwave radiometer based on cold and hot source modeling is proposed.

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

[0006] A full-aperture calibration method for a microwave radiometer based on cold and hot source modeling of the present invention comprises the following steps:

[0007] Step 1: The receiver obtains the cold-air target energy through the cold-air reflector observation at full aperture;

[0008] Step 1.1: The receiver obtains the spatial efficiency η of observing the cold source through the cold space reflector using the method shown in formula (1): c ;

[0009]

[0010] Where Ωc is the spatial solid angle facing the cold space reflector; the antenna pattern is

[0011] Step 1.2: The receiver uses the spatial efficiency η of the observed cold source c The observed cold air total radiation energy including the cold air radiation energy, the cold air reflector self-radiation energy and the cold air reflector leakage energy is obtained by the method shown in formula (2);

[0012]

[0013] Among them, ρ c is the cold air reflector emissivity, is the self-radiation spectrum power density of the cold air reflector surface, is the backward leakage spectral power density of the cold air reflector, is the cold air radiation spectrum power density;

[0014] Step 1.3: Synchronously record the real-time cold space observation count values ​​obtained by the receiver to obtain the average value of the cold space observation count value

[0015] Step 2: The receiver observes the heat source blackbody with full aperture to obtain the total radiation energy of the heat source;

[0016] Step 2.1: The receiver obtains the spatial efficiency η of the observed heat source using the method shown in formula (3): w ;

[0017]

[0018] Where Ωc is the spatial solid angle facing the cold space reflector, and the antenna pattern is

[0019] Step 2.2: Receiver utilizes the spatial efficiency η of the observed heat source w The observed total radiation energy of the heat source including the radiation energy of the heat source, the radiation energy from the heat source and the leakage energy of the heat source is obtained by the method shown in formula (4);

[0020]

[0021] where e is the heat source emissivity, is the self-radiation spectrum power density of the heat source surface, is the back leakage spectral power density of the heat source, is the spectral power density of the heat source radiation;

[0022] Step 2.3: Synchronously record the real-time heat source observation count value obtained by the receiver to obtain the average heat source observation count value

[0023] Step 3: The receiver uses the cold air target energy and the total radiation energy of the heat source to determine the nonlinear coefficient of the quadratic curve of the receiver gain using the receiver gain method;

[0024] Step 3.1: The cold air target energy and the total radiation energy of the heat source are used to obtain the receiver gain G as shown in formula (5);

[0025]

[0026] Step 3.2: Determine the nonlinear coefficient of the quadratic curve of the receiver using the receiver gain described in step 3.1 using the method shown in equations (6) to (8);

[0027]

[0028] 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;

[0029] Step 4: The receiver uses the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment to observe the atmospheric target, and then obtain the atmospheric target brightness temperature.

[0030]

[0031] Among them, c s is the target receiver count value, is the brightness temperature of the atmospheric target.

[0032] To achieve the purpose of the present invention, according to the above method, the present invention further proposes a full-aperture calibration system for a microwave radiometer based on cold and hot source modeling, including a cold source acquisition module, a hot source acquisition module, and a correction module;

[0033] In the cold source acquisition module, the receiver observes the cold sky through a cold sky reflector to obtain the low temperature source radiation brightness temperature for two-point calibration processing; the processed cold sky reflector self-radiation and leakage are used for correction; and they are used as input of the correction module;

[0034] In the heat source acquisition module, the receiver obtains the high temperature source radiation brightness temperature by observing the black body for two-point calibration processing; the processed black body self-radiation and leakage are used for correction; and they are used as the input of the correction module;

[0035] The correction module obtains the gain of the receiver by observing the black body and the cold sky respectively, and establishes the relationship between the target brightness temperature and the receiver count value in combination with the quadratic nonlinear relationship obtained by ground testing, thereby completing the full-aperture calibration of the microwave radiometer.

[0036] Beneficial effects:

[0037] Compared with the prior art, the present invention has the following effects:

[0038] In order to realize the full-aperture observation of cold sky by microwave radiometer in the narrow space of satellite body, it is necessary to observe cold sky through cold sky reflector, and adopt cold sky modeling to comprehensively model cold sky target, cold sky reflector self-radiation and leakage according to the spatial geometric efficiency of cold sky to obtain accurate cold sky observation model; at the same time, observe heat source target, establish accurate heat source model including heat source radiation, heat source radiation and leakage, and obtain accurate heat source observation model. This method has the advantages of high accuracy, can solve the difficulty of calibration of large-aperture antenna microwave radiometer, and is suitable for a full-aperture calibration method of microwave radiometer based on cold and heat source modeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the process of the present invention;

[0040] Figure 2 This is a schematic diagram of the microwave radiometer of the present invention observing a cold source and a heat source. DETAILED DESCRIPTION

[0041] 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.

[0042] Example

[0043] like Figure 1 As shown, a full-aperture calibration method of a microwave radiometer based on cold and hot source modeling in this embodiment is specifically implemented in the following steps:

[0044] Step 1: The receiver obtains the cold-air target energy through the cold-air reflector observation at full aperture;

[0045] Step 1.1: The receiver obtains the spatial efficiency η of observing the cold source through the cold space reflector using the method shown in formula (1): c ;

[0046]

[0047] Where Ωc is the spatial solid angle facing the cold space reflector; the antenna pattern is

[0048] Step 1.2: The receiver uses the spatial efficiency η of the observed cold source c The observed cold air total radiation energy including the cold air radiation energy, the cold air reflector self-radiation energy and the cold air reflector leakage energy is obtained by the method shown in formula (2);

[0049]

[0050] Among them, ρ c is the cold air reflector emissivity, is the self-radiation spectrum power density of the cold air reflector surface, is the backward leakage spectral power density of the cold air reflector, is the cold air radiation spectrum power density;

[0051] Step 1.3: Synchronously record the real-time cold space observation count values ​​obtained by the receiver to obtain the average value of the cold space observation count value

[0052] In the embodiment, the space efficiency of the cold source is observed to be 0.95, the total radiation energy of the cold space is observed to be 3.56k, and the average value of the count value when observing the cold space is 36.75.

[0053] Step 2: The receiver observes the heat source blackbody with full aperture to obtain the total radiation energy of the heat source;

[0054] Step 2.1: The receiver obtains the spatial efficiency η of the observed heat source using the method shown in formula (3): w ;

[0055]

[0056] Where Ωc is the spatial solid angle facing the cold space reflector, and the antenna pattern is

[0057] Step 2.2: Receiver utilizes the spatial efficiency η of the observed heat source w The observed total radiation energy of the heat source including the radiation energy of the heat source, the radiation energy from the heat source and the leakage energy of the heat source is obtained by the method shown in formula (4);

[0058]

[0059] where e is the heat source emissivity, is the self-radiation spectrum power density of the heat source surface, is the back leakage spectral power density of the heat source, is the spectral power density of the heat source radiation;

[0060] Step 2.3: Synchronously record the real-time heat source observation count value obtained by the receiver to obtain the average heat source observation count value

[0061] In the embodiment, the space efficiency of the observed heat source is 0.96, the total radiation energy of the observed heat source is 293k, and the average value of the count value when observing the cold space is 136.55.

[0062] Step 3: The receiver uses the cold air target energy and the total radiation energy of the heat source to determine the nonlinear coefficient of the quadratic curve of the receiver gain using the receiver gain method;

[0063] Step 3.1: The cold air target energy and the total radiation energy of the heat source are used to obtain the receiver gain G as shown in formula (5);

[0064]

[0065] Step 3.2: Determine the nonlinear coefficient of the quadratic curve of the receiver using the receiver gain described in step 3.1 using the method shown in equations (6) to (8);

[0066]

[0067] 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;

[0068] In the embodiment, the receiver gain is 0.34, a0=240, a1=3.12, a2=0.97.

[0069] Step 4: The receiver uses the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment to observe the atmospheric target, and then obtain the atmospheric target brightness temperature.

[0070]

[0071] Among them, C s is the target receiver count value, is the brightness temperature of the atmospheric target.

[0072] In the embodiment, the received atmospheric target brightness temperature of 297 K is obtained.

[0073] To achieve the purpose of the present invention, according to the above method, the present invention further proposes a full-aperture calibration system for a microwave radiometer based on cold and hot source modeling, including a cold source acquisition module, a hot source acquisition module, and a correction module;

[0074] In the cold source acquisition module, the receiver observes the cold sky through a cold sky reflector to obtain the low temperature source radiation brightness temperature for two-point calibration processing; the processed cold sky reflector self-radiation and leakage are used for correction; and they are used as input of the correction module;

[0075] In the heat source acquisition module, the receiver obtains the high temperature source radiation brightness temperature by observing the black body for two-point calibration processing; the processed black body self-radiation and leakage are used for correction; and they are used as the input of the correction module;

[0076] The correction module obtains the gain of the receiver by observing the black body and the cold sky respectively, and establishes the relationship between the target brightness temperature and the receiver count value in combination with the quadratic nonlinear relationship obtained by ground testing, thereby completing the full-aperture calibration of the microwave radiometer.

[0077] In the embodiment, Figure 2 The microwave radiometer observes the cold source and the hot source, and the microwave radiometer antenna pattern can be seen. The emissivity of the heat source blackbody target is e, the nonlinear calibration coefficients a0, a1, a2 of the microwave radiometer; the count value C of the microwave radiometer observing the atmosphere and other targets s , the receiver observes the spatial efficiency of the heat source, the receiver observes the spatial efficiency of the cold space reflector, establishes the heat source and cold source models, and carries out two-point calibration work.

[0078] Table 1 Brightness temperatures obtained by microwave radiometer full-aperture cold and hot sources

[0079]

[0080] As shown in Table 1, the brightness temperature of the atmospheric target is obtained by taking the cold source and the heat source as examples. After the 50.3 GHz receiver observes the heat source and the cold sky, the nonlinear coefficient of the receiver determined on the ground is combined with the counting value of the receiver to effectively solve the brightness temperature of the atmospheric target.

[0081] 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. A full-aperture calibration method for a microwave radiometer based on cold and hot source modeling, characterized in that: The following steps are included: Step 1: The receiver obtains the cold-air target energy through the cold-air reflector observation at full aperture; Step 1.1: The receiver obtains the spatial efficiency η of observing the cold source through the cold space reflector using the method shown in formula (1): c ; Where Ωc is the spatial solid angle facing the cold space reflector; the antenna pattern is Step 1.2: The receiver uses the spatial efficiency η of the observed cold source c The observed cold air total radiation energy including the cold air radiation energy, the cold air reflector self-radiation energy and the cold air reflector leakage energy is obtained by the method shown in formula (2); Among them, ρ c is the cold air reflector emissivity, is the self-radiation spectrum power density of the cold air reflector surface, is the backward leakage spectral power density of the cold air reflector, is the cold air radiation spectrum power density; Step 1.3: Synchronously record the real-time cold space observation count values ​​obtained by the receiver to obtain the average value of the cold space observation count value Step 2: The receiver observes the heat source blackbody with full aperture to obtain the total radiation energy of the heat source; Step 2.1: The receiver obtains the spatial efficiency η of the observed heat source using the method shown in formula (3): w ; Where Ωc is the spatial solid angle facing the cold space reflector, and the antenna pattern is Step 2.2: Receiver utilizes the spatial efficiency η of the observed heat source w The observed total radiation energy of the heat source including the radiation energy of the heat source, the radiation energy from the heat source and the leakage energy of the heat source is obtained by the method shown in formula (4); where e is the heat source emissivity, is the self-radiation spectrum power density of the heat source surface, is the back leakage spectral power density of the heat source, is the spectral power density of the heat source radiation; Step 2.3: Synchronously record the real-time heat source observation count value obtained by the receiver to obtain the average heat source observation count value Step 3: The receiver uses the cold air target energy and the total radiation energy of the heat source to determine the nonlinear coefficient of the quadratic curve of the receiver gain using the receiver gain method; Step 3.1: The cold air target energy and the total radiation energy of the heat source are used to obtain the receiver gain G as shown in formula (5); Step 3.2: Determine the nonlinear coefficient of the quadratic curve of the receiver using the receiver gain described in step 3.1 using the method shown in equations (6) to (8); 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 4: The receiver uses the quadratic nonlinear relationship μ between the receiver radiation brightness temperature and the receiver count value determined by the ground vacuum tank experiment to observe the atmospheric target, and then obtain the atmospheric target brightness temperature. Among them, C s is the target receiver count value, is the brightness temperature of the atmospheric target.

2. A microwave radiometer full-aperture calibration system based on cold and hot source modeling that implements the method as claimed in claim 1, characterized in that: It includes a cold source acquisition module, a heat source acquisition module, and a correction module; The cold source acquisition module, the receiver observes the cold sky through the cold sky reflector to obtain the low temperature source radiation brightness temperature for two-point calibration processing; The processed cold space reflector self-radiation and leakage are used for correction; they will be used as the input of the correction module; The heat source acquisition module, the receiver obtains the high temperature source radiation brightness temperature by observing the black body for two-point calibration processing; The processed blackbody self-radiation and leakage are used for correction; they will be used as the input of the correction module; The correction module obtains the gain of the receiver by observing the black body and the cold sky respectively, and establishes the relationship between the target brightness temperature and the receiver count value in combination with the quadratic nonlinear relationship obtained by ground testing, thereby completing the full-aperture calibration of the microwave radiometer.

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