Microwave radiometer data flow calibration method based on basic data support

Abstract

The invention discloses a microwave radiometer data flow calibration method based on basic data support, 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, defining coefficients for radiation brightness temperature and temperature conversion and cosmic background brightness temperature coefficients for a receiver to observe cold air; 2, antenna parameters used for completing antenna pattern and self-radiation correction are set; 3, setting receiver parameters used for completing two-point calibration of the receiver; 4, two-point calibration is carried out by using parameters of the antenna and the receiver, so that the atmospheric brightness temperature is obtained; and 5, correcting the atmospheric radiation brightness temperature obtained in the step 4 by using an antenna pattern and antenna self-radiation in a de-noising manner to obtain a corrected atmospheric radiation brightness temperature parameter which is used for iterative correction of an antenna and a receiver. The influence is eliminated through the correction technology, the radiation brightness temperature of the atmosphere can be accurately measured, and the method has good economic value.

Description

Technical Field

[0001] The invention relates to a microwave radiometer data stream calibration method based on basic data support, belongs to the technical field of microwave radiometer calibration, and is applied to the calibration of geostationary orbit microwave radiometers. Background Art

[0002] At present, microwave radiometers are usually divided into ground-based microwave radiometers and satellite-borne microwave radiometers; ground-based microwave radiometers are used in an environment with balanced surface thermal environment, and adopt a full-aperture two-point calibration method to carry out real-time data correction; satellite-borne microwave radiometers are used in a polar orbit environment 800km away from the earth, and can adopt a full-aperture or back-optical two-point calibration mode to carry out real-time data correction.

[0003] Since the geostationary microwave radiometer works in a geosynchronous orbit of 36,000 km, the daily temperature difference of the thermal environment can reach 200 degrees Celsius. The thermal environment is worse than that of ground-based microwave radiometers and polar-orbiting satellite microwave radiometers. At the same time, in order to achieve the same ground observation resolution, an ultra-large aperture antenna is used, and the impact of the thermal environment on the antenna pattern distortion and self-radiation needs to be considered.

[0004] Aiming at the problem of data accuracy error caused by the thermal environment of the antenna and receiver of the existing microwave radiometer, a calibration of microwave and millimeter wave bands applied to the geostationary orbit is proposed. However, in the calibration of the antenna and receiver in the geostationary orbit, the accuracy is not high due to the external thermal environment factors. Therefore, in the geostationary orbit environment, improving the accuracy of the correction model of the geostationary orbit microwave radiometer for calibration has become an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem of improving the accuracy of radiation brightness temperature data of a geostationary orbit microwave radiometer in a geostationary orbit environment, and to propose a microwave radiometer data stream calibration method based on basic data support.

[0006] The objective of the present invention is achieved through the following technical solutions:

[0007] A microwave radiometer data stream calibration method based on basic data support of the present invention comprises the following steps:

[0008] Step 1: Define the coefficients used for the conversion between radiation brightness temperature and temperature and the cosmic background brightness temperature coefficient used by the receiver to observe the cold sky;

[0009] Step 1.1: Define the Planck constant used for the conversion between radiation brightness and temperature as 6.6260755e-34, the Boltzmann constant as 1.380658e-23J / K, the first radiation constant as 1.191044e-05, and the second radiation constant as 1.438769;

[0010] Step 1.2: Define the cosmic background brightness temperature used by the receiver to observe the cold sky as 2.73K;

[0011] Step 2: Set the antenna parameters used to complete the antenna pattern and self-radiation correction;

[0012] Step 2.1: Set the channel center frequencies for the antenna operating frequencies to 23.8 GHz, 31.4 GHz, 89 GHz, 118 GHz, 183 GHz, 229 GHz, 380 GHz, 425 GHz and 50-57 GHz;

[0013] Step 2.2: Setting the antenna deformation parameters and antenna pattern efficiency for antenna pattern correction to 0.9 to 0.99;

[0014] Step 2.3: Set the antenna emissivity to 0.001~0.1 and the antenna temperature to 163K~400K for antenna self-radiation correction;

[0015] Step 3: Set the receiver parameters for completing the two-point calibration of the receiver;

[0016] Step 3.1: Obtain the blackbody radiation brightness temperature using the blackbody temperature of 293K and the blackbody emissivity of 0.9980 to 0.9999;

[0017] Step 3.2: Use the cold mirror emissivity of 0.001 to 0.1 and the cold mirror temperature of 163 K to 400 K to obtain the cold mirror self-radiation brightness temperature;

[0018] Step 3.3: Use the cold air temperature of 2.73K to 4.73K to obtain the cold air radiation brightness temperature;

[0019] Step 3.3: Use the probe point to obtain the temperature parameters of the receiver;

[0020] Step 3.4: Set the temperature range of the receiver used for calibration environment to 280-300K;

[0021] Step 3.5: Observe the heat source record and cold source record of the receiver respectively to obtain the heat source count value and cold source count value;

[0022] Step 4: Perform two-point calibration using the antenna and receiver parameters described in Steps 2 and 3 to obtain the atmospheric brightness temperature;

[0023] Step 4.1: Construct the blackbody nonlinear mapping end value using the blackbody radiation brightness temperature and heat source count value;

[0024] Step 4.2: Use the cold sky radiation brightness temperature and cold source count values ​​to construct the cold sky nonlinear mapping end value;

[0025] Step 4.3: Obtain the atmospheric radiation brightness temperature through two-point calibration;

[0026] Step 4.3.1: Use the receiver nonlinear coefficients obtained from ground testing to construct a quadratic nonlinear relationship between the target radiation brightness temperature observed by the receiver and the receiver count value;

[0027] Step 4.3.2: The receiver uses the quadratic nonlinear relationship including the blackbody nonlinear mapping end value and the cold sky nonlinear mapping end value to observe the atmospheric target and obtain the atmospheric radiation brightness temperature;

[0028] Step 5: The atmospheric radiation brightness temperature obtained in step 4 is corrected by removing noise using the antenna pattern and antenna self-radiation to obtain the corrected atmospheric radiation brightness temperature parameters, which are then used for iterative correction of the antenna and receiver.

[0029] The present invention discloses a microwave radiometer data stream calibration system based on basic data support, which is used to implement the above method. The present invention discloses a microwave radiometer data stream calibration system based on basic data support, which includes an antenna setting unit for executing step 2, a temperature measurement unit for executing step 3, a receiver setting unit for executing step 3, an execution unit for executing step 4, and a correction unit for executing step 5;

[0030] The antenna setting unit is used to set the antenna pattern and self-radiation parameters of the antenna. The antenna pattern is recorded by the monitoring instrument to record the antenna deformation and transmit it to the ground for real-time calculation. The self-radiation is obtained by combining the antenna temperature and the antenna emissivity. The set parameters are input into the execution unit.

[0031] The temperature measuring unit is used to obtain the temperature of the receiver, the antenna temperature and the black body temperature through the probe point; the temperature of the receiver is used for temperature interpolation during nonlinear correction; the antenna temperature is used as the input of the antenna self-radiation; the black body temperature is used to calculate the input of the black body radiation;

[0032] The receiver setting unit is used to set the temperature, black body and cold air parameters of the receiver; and input the set parameters into the execution unit;

[0033] The execution unit is used to obtain the atmospheric brightness temperature including the influence of antenna pattern distortion and antenna self-radiation;

[0034] The correction unit is used to revise the atmospheric brightness temperature by removing the antenna pattern and self-radiation effects to obtain accurate atmospheric radiation brightness temperature;

[0035] Beneficial effects:

[0036] Compared with the prior art, the present invention has the following beneficial effects in the calibration of microwave radiometers on geostationary orbit:

[0037] From a technical perspective, the influencing parameters caused by the geostationary orbit thermal environment were analyzed based on the physical model, and correction techniques were used to remove the impact in the later execution stage.

[0038] From an accuracy perspective, effective corrections can make it possible to more accurately measure the radiation brightness temperature of the atmosphere itself.

[0039] From the perspective of performance or economy, this method is a model algorithm that effectively organizes and designs environmental parameters measured by satellites while introducing as little hardware as possible, and has good economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural diagram of the present invention;

[0041] Figure 2 Schematic diagram of the antenna pattern structure. DETAILED DESCRIPTION

[0042] 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.

[0043] Example

[0044] like Figure 1 As shown, a microwave radiometer data stream calibration method based on basic data support in this embodiment has the following specific implementation steps:

[0045] Step 1: Define the coefficients used for the conversion between radiation brightness temperature and temperature and the cosmic background brightness temperature coefficient used by the receiver to observe the cold sky;

[0046] Step 1.1: Define the Planck constant used for the conversion between radiation brightness and temperature as 6.6260755e-34, the Boltzmann constant as 1.380658e-23J / K, the first radiation constant as 1.191044e-05, and the second radiation constant as 1.438769;

[0047] Step 1.2: Define the cosmic background brightness temperature used by the receiver to observe the cold sky as 2.73K;

[0048] In the embodiment, the 50.3, 53.596, 54.94, and 57.29 GHz channels of the receiver use the parameters in step 1 to calculate the conversion between the temperature T and the radiation brightness temperature B in the manner of formula (1).

[0049]

[0050] Where C1 is the first radiation constant, C2 is the second radiation constant, and F is the frequency.

[0051] Step 2: Set the antenna parameters used to complete the antenna pattern and self-radiation correction;

[0052] Step 2.1: Set the channel center frequencies for the antenna operating frequencies to 23.8 GHz, 31.4 GHz, 89 GHz, 118 GHz, 183 GHz, 229 GHz, 380 GHz, 425 GHz and 50-57 GHz;

[0053] Step 2.2: Setting the antenna deformation parameters and antenna pattern efficiency for antenna pattern correction to 0.9 to 0.99;

[0054] Step 2.3: Set the antenna emissivity to 0.001~0.1 and the antenna temperature to 163K~400K for antenna self-radiation correction;

[0055] In the embodiment, the 50.3, 53.596, 54.94, and 57.29 GHz channels of the receiver are tested using a 5-meter-diameter antenna, and the actual atmospheric radiation is obtained using the method of formula (2). The antenna pattern efficiency η F and η m are 0.95 and 0.93 respectively, the antenna emissivity ρ = 0.002, and the antenna temperature is 300K. Self-radiation R r , side lobe radiation R S , R Q is the total radiation output by the antenna, and A is the actual atmospheric radiation.

[0056]

[0057] Step 3: Set the receiver parameters for completing the two-point calibration of the receiver;

[0058] Step 3.1: Obtain the blackbody radiation brightness temperature using the blackbody temperature of 293K and the blackbody emissivity of 0.9980 to 0.9999;

[0059] Step 3.2: Use the cold mirror emissivity of 0.001 to 0.1 and the cold mirror temperature of 163 K to 400 K to obtain the cold mirror self-radiation brightness temperature;

[0060] Step 3.3: Use the cold air temperature of 2.73K to 4.73K to obtain the cold air radiation brightness temperature;

[0061] Step 3.3: Use the probe point to obtain the temperature parameters of the receiver;

[0062] Step 3.4: Set the temperature range of the receiver used for calibration environment to 280-300K;

[0063] Step 3.5: Observe the heat source record and cold source record of the receiver respectively to obtain the heat source count value and cold source count value;

[0064] In the embodiment, the counting values ​​of the cold and hot sources are obtained by using formula (3); the black body temperature is 293K, the black body occurrence rate is 0.9997, R W It is the product of the black body temperature and the black body emissivity. The reflectivity of the cold air reflector is 0.002, the temperature of the cold air reflector is 300K, R C is the cold air radiation, C S is the observed variable temperature source count value, C W is the observed heat source blackbody count value, C C is the observed cold air count value.

[0065]

[0066] Step 4: Perform two-point calibration using the antenna and receiver parameters described in Steps 2 and 3 to obtain the atmospheric brightness temperature;

[0067] Step 4.1: Construct the blackbody nonlinear mapping end value using the blackbody radiation brightness temperature and heat source count value;

[0068] Step 4.2: Use the cold sky radiation brightness temperature and cold source count values ​​to construct the cold sky nonlinear mapping end value;

[0069] Step 4.3: Obtain the atmospheric radiation brightness temperature through two-point calibration;

[0070] Step 4.3.1: Use the receiver nonlinear coefficients obtained from ground testing to construct a quadratic nonlinear relationship between the target radiation brightness temperature observed by the receiver and the receiver count value;

[0071] Step 4.3.2: The receiver uses the quadratic nonlinear relationship including the blackbody nonlinear mapping end value and the cold sky nonlinear mapping end value to observe the atmospheric target and obtain the atmospheric radiation brightness temperature;

[0072] In the embodiment, the atmospheric radiation brightness temperature=240+3.12×count value+0.97×count value 2, and the atmospheric radiation brightness temperature can be obtained.

[0073] Step 5: The atmospheric radiation brightness temperature obtained in step 4 is corrected by removing noise using the antenna pattern and antenna self-radiation to obtain the corrected atmospheric radiation brightness temperature parameters, which are then used for iterative correction of the antenna and receiver.

[0074] In the embodiment, Figure 2 The antenna pattern structure of the present invention is shown. In this structure, it is a display of the path for monitoring instruments to record and observe antenna deformation, where Z1 is the main antenna surface A of the monitoring device. ij Partial deformation, Z2 is to monitor the first secondary reflector B ijPart and second sub-reflection surface C ij The antenna pattern on the left is the main lobe and side lobe distribution caused by the original antenna deformation, and the antenna pattern on the right is the main lobe and side lobe distribution of the antenna after correction.

[0075] The present invention discloses a microwave radiometer data stream calibration system based on basic data support, which is used to implement the above method. The present invention discloses a microwave radiometer data stream calibration system based on basic data support, which includes an antenna setting unit for executing step 2, a temperature measurement unit for executing step 3, a receiver setting unit for executing step 3, an execution unit for executing step 4, and a correction unit for executing step 5;

[0076] The antenna setting unit is used to set the antenna pattern and self-radiation parameters of the antenna. The antenna pattern is recorded by the monitoring instrument to record the antenna deformation and transmit it to the ground for real-time calculation. The self-radiation is obtained by combining the antenna temperature and the antenna emissivity. The set parameters are input into the execution unit.

[0077] The temperature measuring unit is used to obtain the temperature of the receiver, the antenna temperature and the black body temperature through the probe point; the temperature of the receiver is used for temperature interpolation during nonlinear correction; the antenna temperature is used as the input of the antenna self-radiation; the black body temperature is used to calculate the input of the black body radiation;

[0078] The receiver setting unit is used to set the temperature, black body and cold air parameters of the receiver; and input the set parameters into the execution unit;

[0079] The execution unit is used to obtain the atmospheric brightness temperature including the influence of antenna pattern distortion and antenna self-radiation;

[0080] The correction unit is used to revise the atmospheric brightness temperature by removing the antenna pattern and self-radiation effects to obtain accurate atmospheric radiation brightness temperature;

[0081] In order to further demonstrate the superiority of the present invention, the following experiments are used in combination with experimental data for illustration. This embodiment is carried out under ground-based sky-observation atmospheric experiments and ground-based laboratory environmental conditions; a microwave radiometer, a black body, and a liquid nitrogen cold source device are used to set the radiometer target and environmental parameters, and a two-point calibration is used to remove the antenna self-radiation for calibration operations, thereby achieving a beneficial effect in improving the calibration accuracy.

[0082] Table 1 Calibration effect of microwave radiometer

[0083]

[0084]

[0085] As shown in Table 1, 50.3, 53.596, 54.94, and 57.29 GHz channels were selected for before-and-after comparison analysis. Through modeling and correction analysis, it can be seen that the accuracy of the 50.3 GHz channel is improved from 0.83 k to 0.78 k, the accuracy of the 53.596 GHz channel is improved from 0.65 k to 0.2 k, the accuracy of the 54.94 GHz channel is improved from 0.7 k to 0.56 k, and the accuracy of the 57.29 GHz channel is improved from 0.6 k to 0.46 k.

Claims

1. A microwave radiometer data stream calibration method based on basic data support, characterized in that: The following steps are included: Step 1: Define the coefficients used for the conversion between radiation brightness temperature and temperature and the cosmic background brightness temperature coefficient used by the receiver to observe the cold sky; Step 1.1: Define the Planck constant used for the conversion between radiation brightness and temperature as 6.6260755e-34, the Boltzmann constant as 1.380658e-23J / K, the first radiation constant as 1.191044e-05, and the second radiation constant as 1.438769; Step 1.2: Define the cosmic background brightness temperature used by the receiver to observe the cold sky as 2.73K; Step 2: Set the antenna parameters used to complete the antenna pattern and self-radiation correction; Step 2.1: Set the channel center frequencies for the antenna operating frequencies to 23.8 GHz, 31.4 GHz, 89 GHz, 118 GHz, 183 GHz, 229 GHz, 380 GHz, 425 GHz and 50-57 GHz; Step 2.2: Setting the antenna deformation parameters and antenna pattern efficiency for antenna pattern correction to 0.9 to 0.99; Step 2.3: Set the antenna emissivity to 0.001~0.1 and the antenna temperature to 163K~400K for antenna self-radiation correction; Step 3: Set the receiver parameters for completing the two-point calibration of the receiver; Step 3.1: Obtain the blackbody radiation brightness temperature using the blackbody temperature of 293K and the blackbody emissivity of 0.9980 to 0.9999; Step 3.2: Use the cold mirror emissivity of 0.001 to 0.1 and the cold mirror temperature of 163 K to 400 K to obtain the cold mirror self-radiation brightness temperature; Step 3.3: Use the cold air temperature of 2.73K to 4.73K to obtain the cold air radiation brightness temperature; Step 3.3: Use the probe point to obtain the temperature parameters of the receiver; Step 3.4: Set the temperature range of the receiver used for calibration environment to 280-300K; Step 3.5: Observe the heat source record and cold source record of the receiver respectively to obtain the heat source count value and cold source count value; Step 4: Perform two-point calibration using the antenna and receiver parameters described in Steps 2 and 3 to obtain the atmospheric brightness temperature; Step 4.1: Construct the blackbody nonlinear mapping end value using the blackbody radiation brightness temperature and heat source count value; Step 4.2: Use the cold sky radiation brightness temperature and cold source count values ​​to construct the cold sky nonlinear mapping end value; Step 4.3: Obtain the atmospheric radiation brightness temperature through two-point calibration; Step 4.3.1: Use the receiver nonlinear coefficients obtained from ground testing to construct a quadratic nonlinear relationship between the target radiation brightness temperature observed by the receiver and the receiver count value; Step 4.3.2: The receiver uses the quadratic nonlinear relationship including the blackbody nonlinear mapping end value and the cold sky nonlinear mapping end value to observe the atmospheric target and obtain the atmospheric radiation brightness temperature; Step 5: The atmospheric radiation brightness temperature obtained in step 4 is corrected by removing noise using the antenna pattern and antenna self-radiation to obtain the corrected atmospheric radiation brightness temperature parameters, which are then used for iterative correction of the antenna and receiver.

2. A microwave radiometer data stream calibration system based on basic data support to implement the method as claimed in claim 1, characterized in that: It includes an antenna setting unit for executing step 2, a temperature measuring unit for executing step 3, a receiver setting unit for executing step 3, an execution unit for executing step 4, and a correction unit for executing step 5; The antenna setting unit is used to set the antenna pattern and self-radiation parameters of the antenna. The antenna pattern is recorded by the monitoring instrument to record the antenna deformation and transmit it to the ground for real-time calculation. The self-radiation is obtained by combining the antenna temperature and the antenna emissivity. The set parameters are input into the execution unit. The temperature measuring unit is used to obtain the temperature of the receiver, the antenna temperature and the black body temperature through the probe point; the temperature of the receiver is used for temperature interpolation during nonlinear correction; Antenna temperature is used as input for antenna self-radiation; blackbody temperature is used as input for calculating blackbody radiation; The receiver setting unit is used to set the temperature, black body and cold air parameters of the receiver; and input the set parameters into the execution unit; The execution unit is used to obtain the atmospheric brightness temperature including the influence of antenna pattern distortion and antenna self-radiation; The correction unit is used to revise the atmospheric brightness temperature by removing the antenna pattern and the self-radiation influence to obtain the accurate atmospheric radiation brightness temperature.

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