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

Abstract

The present application relates to the technical field of satellite infrared remote sensing sensor absolute radiation calibration, and provides a method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation, comprising the following steps: step one, selecting a specific satellite data file as an experimental sample; step two, extracting key temperature data from the selected data file; step three, performing data calculation according to the extracted data in step two; and step four, calculating the equivalent outgoing radiation of the blackbody by using the Planck function and the blackbody emissivity. The method can accurately calculate the equivalent outgoing radiation of the satellite infrared remote sensing calibration blackbody, thereby effectively improving the on-orbit blackbody absolute radiation calibration accuracy of the satellite infrared remote sensor, and can effectively overcome the shortcomings of large workload, low frequency and high threshold of cross calibration in field calibration, so as to realize high-frequency and automatic radiation calibration of the on-orbit infrared channel of the remote sensing satellite.

Description

Technical Field

[0001] This invention relates to the field of absolute radiometric calibration technology for satellite infrared remote sensing sensors, specifically a method for analyzing the sensitivity of blackbody emissivity to equivalent radiation in infrared remote sensing calibration. Background Technology

[0002] Absolute radiometric calibration of remote sensing sensors serves as a bridge between instrument counts and the actual surface parameters they reflect. It is the starting point for the quantification of remote sensing information and the foundation for quantitative inversion of surface biophysical parameters and the establishment of remote sensing models. From a technical perspective, satellite infrared sensor radiometric calibration includes pre-launch laboratory calibration, on-board blackbody calibration, and off-orbit calibration. A typical pre-launch calibration uses a temperature-controlled uniform blackbody source placed at the sensor's entrance pupil. The temperature of this blackbody source is continuously adjustable and covers the sensor's dynamic range. Laboratory calibration using blackbodies is generally performed in a simulated cryogenic space environment. A typical on-board blackbody calibration setup utilizes two blackbody sources. For oscillating sweep thermal infrared sensors, in the nonlinear region of each scan line, the emission radiance of two blackbody sources at different temperatures is directed to the focal plane to monitor changes in the detector and electronic circuit responsivity (e.g., ...). Figure 1 (As shown). This calibration is both a relative calibration, used to correct inconsistencies in response between different detectors and scan lines, and a primary means of absolute radiometric calibration for thermal infrared sensors. A typical method for on-orbit calibration after satellite launch is to use a rigorously validated ground field and atmospheric model to determine the radiance at the sensor's entrance pupil; another method is to use a calibrated radiometer to measure under similar geometric conditions and at the same time as the satellite sensor, and then perform atmospheric correction above the radiometer's altitude on the radiance measured by the onboard sensor. The three stages of satellite remote sensor calibration mentioned above are interconnected and complementary. Pre-launch laboratory calibration mainly determines the linearity of the sensor and establishes the relationship between the sensor output and the detected physical quantity. 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 for infrared remote sensors can also provide on-orbit absolute radiometric calibration during satellite operation. After satellite launch, changes in the working environment and status, as well as the aging of components over long-term operation, may alter the pre-launch calibration coefficients. Therefore, on-orbit calibration is necessary to ensure the reliability and accuracy of remote sensing data applications.

[0003] Before and after launch, all satellites and their onboard remote sensing sensors must undergo comprehensive and accurate absolute radiometric calibration of their outputs and acquired data to ensure maximum application of the acquired data. Satellite instruments undergo rigorous calibration and testing in laboratories, providing various parameters under laboratory conditions. However, during orbital insertion and operation, their performance will change due to environmental changes, particularly mechanical shock, weightlessness, vacuum, component aging, and space radiation. Especially after launch, due to inherent instrument limitations and external interference, sensor performance often deviates from pre-launch test results. Furthermore, during satellite operation, instrument sensitivity continuously decreases due to component aging. Therefore, post-launch blackbody calibration and on-orbit alternative calibration are crucial. However, on-orbit alternative calibration using site radiometric calibration is limited by the number of field visits and weather conditions, restricting it to the calibration of only a portion of remote sensors. Moreover, the available calibration methods are limited, and test site climate conditions are not ideal, falling far short of practical application needs. On-orbit alternative calibration using cross-calibration is not a safe and independent calibration method due to its high dependence on the calibration accuracy of the reference sensor itself. In-orbit blackbody calibration is hampered by the inability to accurately monitor the emissivity of a blackbody in orbit, which makes it impossible to accurately calculate the background radiation reflected by the blackbody. Consequently, the equivalent outgoing radiation of the blackbody cannot be accurately calculated, which directly affects the absolute radiometric calibration accuracy of the satellite's infrared remote sensing sensors. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to solve the problem of accurately calculating the equivalent emitted radiation of a blackbody in infrared calibration. On-orbit blackbody calibration of satellite infrared remote sensors is often affected by ambient background radiation. The equivalent emitted radiation of an infrared blackbody is directly influenced by its emissivity. By quantitatively analyzing the sensitivity of blackbody emissivity to the effect of blackbody emissivity on equivalent radiation, the equivalent emitted radiation of the blackbody can be accurately calculated, thereby improving the accuracy of absolute radiometric calibration of infrared remote sensors and promoting the quantitative application of satellite infrared remote sensing data.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation, comprising the following steps:

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

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

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

[0009] Step 4: Calculate the equivalent emitted radiation of the blackbody using Planck's function and blackbody emissivity;

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

[0011] Step 6: Using laboratory-measured blackbody emissivity data from the satellite, perform interpolation processing according to the satellite spectral channel settings to fill 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 at 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 two includes the onboard blackbody temperature, the interferometer component temperature, the head thermal control temperature, and the cold optics temperature.

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

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

[0017] Calculation of background radiation temperature: The temperature of the beam splitter support was selected as the main contributing component of background radiation, and the arithmetic mean was obtained as 287.2545K.

[0018] Preferably, the formula for calculating the equivalent emitted radiation of the blackbody in step four 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 It is the blackbody equivalent emitted radiation, T bb It is the blackbody temperature, T bs The background radiation contributes to the component temperature, 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, then the emissivity data is judged to have high accuracy and reliability.

[0023] This invention provides a method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation. It offers the following advantages:

[0024] This invention enables precise calculation of the equivalent emitted radiation of a blackbody in satellite infrared remote sensing calibration, thereby effectively improving the on-orbit absolute radiometric calibration accuracy of satellite infrared remote sensors. It overcomes the drawbacks of low-frequency, labor-intensive field calibration and high barriers to cross-calibration, achieving high-frequency, automated radiometric calibration of the on-orbit infrared channels of remote sensing satellites. This improves the calibration accuracy of satellite infrared remote sensing data and promotes the quantitative application of remote sensing. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a program example for reading a dataset in this invention;

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

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

[0028] Figure 4 This is a schematic diagram of the temperature difference between the equivalent emitted radiation and the brightness of the blackbody radiation in this invention (unit: K);

[0029] Figure 5 This is a schematic diagram of the laboratory-measured emissivity data obtained by the National Institute of Metrology in this invention.

[0030] Figure 6 This is a schematic diagram of the measured emissivity interpolated based on the HIRAS channel in this invention;

[0031] Figure 7 This is a schematic diagram illustrating the difference between blackbody equivalent radiation and blackbody radiation in this invention (unit: mW / (m^2νsr)).

[0032] Figure 8 This is a schematic diagram of the equivalent brightness temperature of the blackbody and the difference between the brightness temperature of the blackbody in this invention (unit: K). Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example:

[0035] Please see the appendix Figure 1 -Appendix Figure 8 This invention provides a method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation, comprising the following steps:

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

[0037] Step 2: Extract the onboard blackbody temperature, interferometer component temperature, head thermal control, and cold optics temperature data from the selected data file. Take the arithmetic average of the blackbody temperature readings from PRTs 2 to 6 to obtain a blackbody temperature of 282.6295 K; referencing the CrIS structure ( Figure 2 As shown, the beam splitter was selected as the component that contributes the most to the background radiation of the blackbody. The temperature of the first beam splitter support in the interferometer assembly was used to calculate the background radiation. The arithmetic mean of the temperature data read was 287.2545K.

[0038] Step 3: Based on the structure of the on-board calibration blackbody extracted in Step 2, calculate the equivalent emitted radiation of the blackbody using the following formula:

[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 It is the blackbody equivalent emitted radiation, T bb It is the blackbody temperature, T bs The background radiation contributes to the component temperature, R is the Planck function, and emis is the blackbody emissivity;

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

[0042] Step 5: To more intuitively reflect the effect of emissivity changes on the blackbody's equivalent brightness temperature, the radiance difference is converted into a brightness temperature difference. The results are as follows: Figure 4 As shown;

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

[0044] The theoretical analysis of the influence of blackbody emissivity on equivalent radiation is applied to measured emissivity data to conduct an analysis of the equivalent radiation brightness-temperature difference of existing blackbodies. Based on laboratory-measured emissivity data of on-board blackbodies obtained by the National Institute of Metrology, such as... Figure 5 As shown, we will conduct the analysis.

[0045] Step Six: Interpolate the acquired emissivity data according to the spectral channel settings of FY-3D HIRAS. Note that the measured data for the MW2 band is not covered. Figure 6 As shown;

[0046] Step 7: Using the same emissivity analysis method as described above, calculate the difference between the blackbody equivalent radiation obtained from the measured emissivity and the blackbody radiation, as follows: Figure 7 As shown;

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

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

Claims

1. A method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation, characterized in that, Includes the following steps: Step 1: Select a specific satellite data file as the experimental sample; Step 2: Extract key temperature data from the selected data file; Step 3: Perform calculations based on the data extracted in Step 2; Step 4: Calculate the equivalent emitted radiation of the blackbody using Planck's function and blackbody emissivity; Step 5: Calculate the difference between the blackbody equivalent emitted radiation and the blackbody radiation by varying the emissivity, and convert it into a brightness temperature difference; Step 6: Using laboratory-measured blackbody emissivity data from the satellite, perform interpolation processing according to the satellite spectral channel settings to fill data gaps; Step 7: Using the same method as the sensitivity analysis, calculate the difference between the blackbody equivalent radiation and the blackbody radiation at 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 method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1, characterized in that, The temperature data in step two includes the temperature of the onboard blackbody, the temperature of the interferometer components, and the temperature of the head thermal control and cold optics.

3. The method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1, characterized in that, The data calculation in step three includes: Calculate the blackbody temperature: Take the arithmetic mean of the readings from PRTs 2 to 6, and the blackbody temperature is 282.6295 K; Calculation of background radiation temperature: The temperature of the beam splitter support was selected as the main contributing component of background radiation, and the arithmetic mean was obtained as 287.2545K.

4. The method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1, characterized in that, The formula for calculating the equivalent emitted radiation of the blackbody in step four 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 It is the blackbody equivalent emitted radiation, T bb It is the blackbody temperature, T bs The temperature of the component is contributed by the background radiation, R is the Planck function, and emis is the blackbody emissivity.

5. The method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1, characterized in that, In step five, the blackbody emissivity changes from 0.99 to 0.999 in a step size of 0.

001.

6. The method for analyzing the sensitivity of infrared remote sensing calibration blackbody emissivity to equivalent radiation according to claim 1, 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, then the emissivity data is judged to have high accuracy and reliability.

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