Method for analyzing sensitivity of infrared remote sensing calibration black body emissivity to equivalent radiation

Abstract

The invention relates to the technical field of absolute radiometric calibration of satellite infrared remote sensing sensors, and provides a method for analyzing sensitivity of infrared remote sensing calibration black body emissivity to equivalent radiation, which comprises the following steps of: 1, selecting a specific satellite data file as an experimental sample; step 2, extracting key temperature data from the selected data file; 3, performing data calculation according to the data extracted in the step 2; and 4, calculating the equivalent emergent radiation of the black body by using a Planck function and the emissivity of the black body. According to the method, the equivalent emergent radiation of the satellite infrared remote sensing calibration black body is accurately calculated, so that the absolute radiation calibration precision of the satellite infrared remote sensor on the on-satellite black body is effectively improved, and the defects of large workload and low frequency of site calibration, high implementation threshold of cross calibration and the like can be effectively overcome; therefore, high-frequency and automatic radiometric calibration of the on-orbit infrared channel of the remote sensing satellite is realized.

Description

Technical Field

[0001] The invention relates to the technical field of absolute radiation calibration of satellite infrared remote sensing sensors, in particular to a sensitivity analysis method of infrared remote sensing calibration black body emissivity to equivalent radiation. Background Art

[0002] The absolute radiation calibration of remote sensing sensors is a bridge between the instrument count value and the real surface parameters it reflects. It is the beginning of the quantification of remote sensing information and the basis for quantitative inversion of surface biophysical parameters and the establishment of remote sensing models. From the perspective of technical means, satellite infrared sensor radiation calibration includes pre-launch laboratory calibration, on-board blackbody calibration, and off-orbit calibration. A typical pre-launch calibration is to place a temperature-controlled uniform blackbody source at the entrance pupil of the sensor. The temperature of this blackbody source is continuously adjustable and can cover the dynamic range of the sensor. Laboratory calibration using a blackbody is generally performed in a simulated deep-cold space environment. The typical device for on-board blackbody calibration is to use two blackbody sources for calibration. For the nonlinear region of each scanning line of the swing-scanning thermal infrared sensor, the emission radiance of two blackbody sources of different temperatures is respectively directed to the focal plane to monitor the changes in the response rate of the detector and electronic circuit (such as Figure 1 (as shown). This calibration is both a relative calibration, used to correct the response inconsistency between different detectors and scan lines; and the main means of absolute radiometric calibration of thermal infrared band sensors. A typical method of off-orbit calibration after satellite launch is to use a well-qualified ground field and atmospheric model to determine the radiance at the sensor entrance pupil; another method is to use a calibrated radiometer to measure at the same time and under similar geometric conditions as the satellite sensor, and then make atmospheric corrections for the radiance measured by the onboard sensor above the height of the radiometer. The three working links of satellite remote sensor calibration mentioned above are interrelated and complementary. The laboratory calibration before launch mainly determines the linearity of the sensor and establishes the relationship between the sensor output and the physical quantity being detected; the on-board blackbody calibration can determine or monitor the changes in the remote sensor relative to the pre-launch calibration. The on-board blackbody calibration system of infrared band remote sensor can also provide on-orbit absolute radiation calibration during satellite operation; after the satellite is launched, the calibration coefficients before launch may change due to changes in the working environment and status, and aging of components due to long-term operation. Therefore, on-orbit calibration is required to ensure the reliability and accuracy of remote sensing data applications.

[0003] Before and after the launch of any satellite and its remote sensing sensors, the output and data of the instruments must be fully and accurately calibrated with absolute radiation to ensure the maximum application of the acquired data. Satellite instruments are strictly calibrated and tested in the laboratory, and various parameters under laboratory conditions are given. However, during the process of entering orbit and on-orbit operation, due to changes in the environment, especially mechanical shock, weightlessness, vacuum, device aging, space radiation, etc., their performance will change. Especially after the satellite is launched, due to the interference of the instrument itself and external factors, there is often a certain deviation between the performance of the sensor and the test results before the launch. In addition, during the operation of the satellite, due to the aging of the instrument components, the sensitivity of the instrument will continue to decrease. Therefore, after the satellite is launched, it is very important to perform blackbody calibration on the orbiting satellite and on-orbit replacement calibration. However, in terms of field radiation calibration of on-orbit replacement calibration, due to the restrictions on the number of approaches and weather conditions, it is limited to the calibration of some remote sensors, and the calibration methods used are relatively few, and the climatic conditions of the test site are not ideal, which is far from meeting the needs of practical applications; in terms of cross calibration of on-orbit replacement calibration, due to the high dependence on the calibration accuracy of the reference sensor itself, it is not a safe and independent calibration method. Blackbody calibration on orbiting satellites cannot accurately monitor the blackbody emissivity on orbit, resulting in the inability to accurately calculate the environmental background radiation reflected by the blackbody, which in turn leads to the inability to accurately calculate the blackbody equivalent outgoing radiation, which directly affects the absolute radiation calibration accuracy of satellite infrared remote sensing sensors. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention aims to solve the problem of accurate calculation of infrared calibration blackbody equivalent outgoing radiation. The on-orbit blackbody calibration of satellite infrared remote sensors is often affected by the environmental background radiation. The equivalent outgoing radiation of infrared blackbodies is directly affected by the blackbody emissivity. By quantitatively analyzing the sensitivity of the blackbody emissivity to the blackbody equivalent radiation, the equivalent outgoing radiation of blackbodies can be accurately calculated, the accuracy of absolute radiation calibration of infrared remote sensors can be improved, and the quantitative application of satellite infrared remote sensing data can be promoted.

[0005] To achieve the above purpose, the present invention is implemented by the following technical scheme: a sensitivity analysis method of infrared remote sensing calibration black body emissivity to equivalent radiation, comprising the following steps:

[0006] Step 1: Select a specific satellite data file as an experimental sample;

[0007] Step 2: extract key temperature data from the selected data file;

[0008] Step 3: Perform data calculation based on the data extracted in step 2;

[0009] Step 4: Calculate the equivalent outgoing radiation of the black body using the Planck function and the black body emissivity;

[0010] Step 5: Calculate the difference between the blackbody equivalent outgoing radiation and the blackbody radiation by changing the emissivity, and convert it into brightness temperature difference;

[0011] Step 6: Use the on-board blackbody emissivity data measured in the laboratory to perform interpolation processing according to the satellite spectral channel settings to fill in the data gaps;

[0012] Step 7: Using the same method as the sensitivity analysis, calculate the difference between the blackbody equivalent radiation and the blackbody radiation under the measured emissivity and convert it into brightness temperature difference;

[0013] Step 8: Based on the measured emissivity data, use the difference between the blackbody equivalent brightness temperature and the blackbody temperature to determine the measured emissivity data.

[0014] Preferably, the temperature data in step 2 includes on-board blackbody temperature, interferometer component temperature, head thermal control and cold optical temperature.

[0015] Preferably, the data calculation in step three includes:

[0016] Calculate the blackbody temperature: Take the arithmetic mean of the readings of PRTs 2 to 6 and obtain a blackbody temperature of 282.6295K.

[0017] Calculate the background radiation temperature: Select the beam splitter bracket temperature as the main contributor to the background radiation, and take the arithmetic average to get 287.2545K.

[0018] Preferably, the calculation formula for the equivalent emitted radiation of the black body in step 4 is as follows:

[0019] R eff_bb (v)=emis·R(T bb ,v)+(1-emis)·R(T bs ,v)

[0020] Where v is the wave number, R eff_bb is the blackbody equivalent outgoing radiation, T bb is the blackbody temperature, T bs is the temperature of the background radiation contribution component, R is the Planck function, and emis is the blackbody emissivity.

[0021] Preferably, in step five, the blackbody emissivity changes from 0.99 to 0.999 in a step size of 0.001.

[0022] Preferably, in step eight, when the blackbody temperature is 282.6295K, the difference between the blackbody equivalent brightness temperature and the blackbody temperature is less than 16mK, and less than 7mK in the long-wave band, the emissivity data is judged to have high accuracy and reliability.

[0023] The present invention provides a sensitivity analysis method for infrared remote sensing calibration black body emissivity to equivalent radiation. It has the following beneficial effects:

[0024] The present invention uses this method to accurately calculate the equivalent emitted radiation of the satellite infrared remote sensing calibration blackbody, thereby effectively improving the calibration accuracy of the satellite infrared remote sensor on-orbit blackbody absolute radiation, and can effectively overcome the shortcomings of large workload and low frequency of field calibration, high threshold for cross calibration, etc., thereby realizing high-frequency and automatic radiation calibration of the on-orbit infrared channel of the remote sensing satellite. Thereby improving the calibration accuracy of satellite infrared remote sensing data and promoting the quantitative application of remote sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a program example for reading a data set in the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of the on-star calibration blackbody in the present invention;

[0027] Figure 3 Schematic diagram of the radiance difference between the blackbody equivalent emitted radiation and the blackbody radiation in the present invention (unit: mW / (m^2νsr));

[0028] Figure 4 Schematic diagram of the blackbody equivalent emitted radiation and the blackbody radiation brightness temperature difference in the present invention (unit: K);

[0029] Figure 5 A schematic diagram of the laboratory measured emissivity data obtained by the Institute of Metrology in the present invention;

[0030] Figure 6 is a schematic diagram of the measured emissivity interpolated according to the HIRAS channel in the present invention;

[0031] Figure 7 Schematic diagram of the difference between the blackbody equivalent radiation and the blackbody radiation in the present invention (unit: mW / (m^2νsr));

[0032] Figure 8 Schematic diagram of the blackbody equivalent brightness temperature and the blackbody brightness temperature difference in the present invention (unit: K). DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example:

[0035] Please see attached Figure 1 -Attached Figure 8 The embodiment of the present invention provides a sensitivity analysis method of infrared remote sensing calibration black body emissivity to equivalent radiation, comprising the following steps:

[0036] Step 1. Select FY3D_HIRAS_GBAL_L1_20180501_1310_OBCXX_MS.HDF file as the specific satellite data file as the experimental sample ( Figure 1 shown);

[0037] Step 2: Extract the onboard blackbody temperature, interferometer component temperature, head thermal control and cold optical temperature data from the selected data file. Take the arithmetic average of the readings of PRT No. 2 to 6 to get the blackbody temperature: 282.6295K; refer to the structure of CrIS ( Figure 2 As shown in the figure, the beam splitter is selected as the component that contributes the most to the background radiation of the black body. The temperature of the first beam splitter bracket in the interferometer component temperature is used to calculate the background radiation. The arithmetic average of the read temperature data is: 287.2545K;

[0038] Step 3: According to the structure of the on-board calibration black body extracted in step 2, the equivalent outgoing radiation of the black body is calculated by the formula, and the calculation formula is as follows:

[0039] R eff_bb (v)=emis·R(T bb ,v)+(1-emis)·R(T bs ,v)

[0040] Where v is the wave number, R eff_bb is the blackbody equivalent outgoing radiation, T bb is the blackbody temperature, T bs is the temperature of the background radiation contribution component, R is the Planck function, and emis is the blackbody emissivity;

[0041] Step 4: In order to analyze the effect of blackbody emissivity change on equivalent radiation, the emissivity was increased from 0.99 to 0.999 in steps of 0.001 in the experiment; the effect of emissivity was analyzed by calculating the difference between the blackbody equivalent outgoing radiation and the blackbody radiation. The results are as follows: Figure 3 As shown;

[0042] Step 5: In order to more intuitively reflect the effect of the change in emissivity on the blackbody equivalent brightness temperature, the radiance difference is converted into brightness temperature difference. The result is as follows: Figure 4 As shown;

[0043] Through the above experimental analysis, we can conclude that when the black body temperature is 282.6295K, the black body emissivity changes from 0.99 to 0.999, and considering the contribution of background radiation (287.2545K), the difference between the black body equivalent brightness temperature and the black body temperature is reduced from about 50mK to about 5mK;

[0044] The above theoretical analysis of the effect of blackbody emissivity on equivalent radiation is applied to the measured emissivity data to carry out the analysis of the brightness temperature difference of equivalent radiation of existing blackbody. According to the laboratory measured emissivity data of on-star blackbody obtained by the Institute of Metrology, such as Figure 5 As shown, to carry out the analysis;

[0045] Step 6: Interpolate the acquired emissivity data according to the spectral channel settings of FY-3D HIRAS, where the measured data of MW2 band is not covered, such as Figure 6 As shown;

[0046] Step 7: Using the same emissivity analysis method as the previous analysis, calculate the difference between the blackbody equivalent radiation obtained by using the measured emissivity and the blackbody radiation. Figure 7 As shown;

[0047] Step 8: Convert the radiation difference into brightness temperature difference, such as Figure 8 It can be concluded that according to the measured emissivity, when the black body temperature is 282.6295K, considering the contribution of background radiation (287.2545K), the difference between the black body equivalent brightness temperature and the black body temperature is less than 16mK, and less than 7mK in the long wave band.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A sensitivity analysis method for infrared remote sensing calibration blackbody emissivity to equivalent radiation, characterized in that: The following steps are involved: Step 1: Select a specific satellite data file as an experimental sample; Step 2: extract key temperature data from the selected data file; Step 3: Calculate based on the data extracted in step 2; Step 4: Calculate the equivalent outgoing radiation of the black body using the Planck function and the black body emissivity; Step 5: Calculate the difference between the blackbody equivalent outgoing radiation and the blackbody radiation by changing the emissivity, and convert it into brightness temperature difference; Step 6: Use the on-board blackbody emissivity data measured in the laboratory to perform interpolation processing according to the satellite spectral channel settings to fill in the data gaps; Step 7: Using the same method as the sensitivity analysis, calculate the difference between the blackbody equivalent radiation and the blackbody radiation under the measured emissivity and convert it into brightness temperature difference; Step 8: Based on the measured emissivity data, use the difference between the blackbody equivalent brightness temperature and the blackbody temperature to determine the measured emissivity data.

2. The sensitivity analysis method of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1 is characterized in that: The temperature data in step 2 include the on-board blackbody temperature, interferometer component temperature, head thermal control and cold optical temperature.

3. The sensitivity analysis method of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1 is characterized in that: The data calculation in step 3 includes: Calculate the blackbody temperature: Take the arithmetic mean of the readings of PRTs 2 to 6 and obtain a blackbody temperature of 282.6295K. Calculate the background radiation temperature: Select the beam splitter bracket temperature as the main contributor to the background radiation, and take the arithmetic average to get 287.2545K.

4. The sensitivity analysis method of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1 is characterized in that: The calculation formula for the equivalent emitted radiation of the black body in step 4 is as follows: R eff_bb (v)=emis·R(T bb, v)+(1-emis)·R(T bs, v) Where v is the wave number, R eff_bb is the blackbody equivalent outgoing radiation, T bb is the blackbody temperature, T bs is the temperature of the background radiation contribution component, R is the Planck function, and emis is the blackbody emissivity.

5. The sensitivity analysis method of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1 is characterized in that: In step 5, the blackbody emissivity changes from 0.99 to 0.999 with a step length of 0.

001.

6. The sensitivity analysis method of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1 is characterized in that: In step eight, when the blackbody temperature is 282.6295K, the difference between the blackbody equivalent brightness temperature and the blackbody temperature is less than 16mK, and less than 7mK in the long-wave band, the emissivity data is judged to have high accuracy and reliability.

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