Atmospheric transmittance measuring method based on single-photon detector

Abstract

The invention discloses an atmospheric transmittance measuring method based on a single-photon detector, and belongs to the technical field of atmospheric detection. The atmospheric transmittance measuring method has the core advantages that accurate photon flow measurement is carried out on the calibrated fixed star by utilizing high sensitivity of the single-photon detector, and the atmospheric extinction coefficient is obtained through data fitting direct inversion, so that high-precision and direct measurement of the atmospheric transmittance of the whole layer is realized; errors caused by indirect calculation depending on a physical model or aerosol parameters are effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of atmospheric sounding technology, and in particular relates to a method for measuring atmospheric transmittance based on a single-photon detector. Background Technology

[0002] Atmospheric transmittance is a crucial parameter in ground-based optical observations, reflecting the properties of atmospheric radiative transfer. It holds significant reference value in applications such as atmospheric radiation, remote sensing of Earth resources, environmental monitoring, and space target monitoring. Atmospheric transmittance is closely related to environmental parameters such as temperature, humidity, atmospheric pressure, visibility, and aerosols, but these parameters are difficult to obtain through conventional methods.

[0003] In the prior art, for example, the invention patent with authorization number CN102565007B discloses a method for inverting the transmittance of the entire atmospheric layer. It uses a multi-band solar radiometer combined with relevant atmospheric models or local atmospheric measurement data and related software to realize the inversion of the transmittance of the entire atmospheric layer. However, this invention requires the use of solar radiation to achieve measurement and cannot achieve nighttime measurement. Another example is the patent application with publication number CN120296947A, which discloses a method for obtaining atmospheric transmittance under haze weather. It obtains parameters such as the mixing composition ratio, particle size, and complex refractive index of haze particles and calculates atmospheric transmittance based on a calculation function. Its method indirectly calculates atmospheric transmittance based on particle parameters.

[0004] Therefore, there is a need for a method for measuring atmospheric transmittance based on a single-photon detector, which obtains atmospheric transmittance by measuring the calibrated star using a single-photon detector. Summary of the Invention

[0005] To address the need for measuring atmospheric transmittance, a method for measuring atmospheric transmittance based on a single-photon detector is provided.

[0006] This invention provides a method for measuring atmospheric transmittance based on a single-photon detector. The method uses a single-photon detector and a telescope to measure the photon flux of a calibrated star, calculate the theoretical photon flux value of the calibrated star, and then calculate the atmospheric transmittance by fitting the data with an algorithm.

[0007] This invention provides a method for measuring atmospheric transmittance based on a single-photon detector, comprising: S1. Select at least one calibrated star and obtain its nominal brightness value; S2. Based on the nominal brightness value, calculate the theoretical photon flux of the calibrated star at the measurement system; S3. Measure the calibrated star using a combination system of a single-photon detector and a telescope to obtain the actual photon flux and the corresponding telescope zenith angle; S4. Based on the theoretical photon flux, measured actual photon flux, and zenith angle of each calibrated star, data fitting is performed to obtain the fitting coefficient characterizing the atmospheric extinction characteristics. S5. Calculate the atmospheric transmittance in different zenith angle directions based on the fitting coefficients.

[0008] Furthermore, the step of selecting at least one calibrated star and obtaining its nominal brightness value specifically includes: Based on the geographical coordinates of the measurement point and the measurement time, select stars from the star catalog that are above the horizon of the measurement point at the measurement time as calibration stars, and obtain their nominal brightness values.

[0009] Specifically, based on the latitude and longitude of the measurement point and the measurement time, the star catalog is selected from those points that are above the horizon during the measurement time and at the location of the measurement point. These stars are used as identification stars, and their star numbers are as follows: , ... The nominal brightness values ​​are respectively , ... (Unit: Wm) -2 μm -1 ).

[0010] Furthermore, the theoretical photon flux The calculation formula is:

[0011] in, This is the nominal brightness value, in Wm. -2 μm -1 , To assign star numbers, The aperture of the telescope is in meters (m). The measurement system uses a filter bandwidth, measured in μm. For the measured band, This represents Planck's constant. It represents the speed of light.

[0012] Furthermore, in the step of measuring using a combination system of a single-photon detector and a telescope, the telescope and the single-photon detector are used to measure the calibration star, obtaining the photon flux per second of the calibration star as measured by the single-photon detector. The telescope zenith angle for measuring the calibrated star. .

[0013] Furthermore, the step of performing data fitting to obtain fitting coefficients includes: Constructing linear equations ,in , ,Right now:

[0014]

[0015] in, Corresponding zenith angle The atmospheric mass is calculated using the following piecewise function:

[0016] The coefficients of the linear equation are obtained by performing a linear fit on the measured data. and The coefficient The fitting coefficients characterize atmospheric extinction properties.

[0017] It represents "air mass," which is the zenith angle. A function. The essence of this function is: to describe the multiple of the path length of starlight through the atmosphere relative to the path length in the zenith direction.

[0018] When fitting the linear equation, the least squares method is used for linear regression to obtain the slope coefficient. With intercept coefficient .

[0019] Furthermore, the formula for calculating atmospheric transmittance in different zenith angle directions is as follows:

[0020] in, Atmospheric transmittance at different zenith angles.

[0021] The single-photon detector used in this invention is a single-photon avalanche diode, a superconducting nanowire single-photon detector, or a microchannel plate photomultiplier tube, etc.

[0022] The atmospheric transmittance measurement method described in this invention has the core advantage of using the high sensitivity of a single-photon detector to accurately measure the photon flux of a calibrated star, and directly inverting the atmospheric extinction coefficient through data fitting, thereby achieving high-precision and direct measurement of the transmittance of the entire atmospheric layer, effectively avoiding the errors caused by indirect calculations relying on physical models or aerosol parameters. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the atmospheric transmittance measurement method based on a single-photon detector according to the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments. The present invention provides a method for measuring atmospheric transmittance based on a single-photon detector. By measuring the photon flux of a calibrated star using a single-photon detector and linearly fitting it to its theoretical photon flux, atmospheric transmittance at different zenith angles can be obtained.

[0025] like Figure 1 As shown, the present invention provides an atmospheric transmittance measurement method based on a single-photon detector. The method consists of five steps: selecting a calibration star and calculating its nominal brightness value, calculating the theoretical photon flux of the calibration star, measuring the actual photon flux of the calibration star, data algorithm fitting, and calculating the atmospheric transmittance in different zenith angle directions.

[0026] Step S1, Select calibration stars: The measurement point is located at latitude and longitude (22.273734, 113.5721327), and the measurement time is the evening of July 14, 2023. Eighteen stars were selected from the star catalog as calibration stars, and their numbers and nominal brightness values ​​are shown in Table 1 below.

[0027] Table 1

[0028] Step S2, calculate the theoretical photon flux of the calibrated star: based on the nominal brightness value of the calibrated star in step S1. Telescope aperture =1.2m, the bandwidth of the filter used in the system The theoretical photon flux of each calibrated star is calculated using the following formula, given a wavelength of 0.2 μm. :

[0029] in, The measured wavelength is 1.064 × 10⁻⁶. -9 m, This represents Planck's constant. It represents the speed of light.

[0030] The theoretical photon flux values ​​for each calibrated star are shown in Table 2 below.

[0031] Table 2

[0032] Step S3, Measure the actual photon flux of the calibration star: Using a telescope and a single-photon detector, measure the photon flux per second of the calibration star obtained from the single-photon detector. The telescope zenith angle for measuring the calibrated star. The results are shown in Table 3 below.

[0033] Table 3

[0034] Step S4, Data Algorithm Fitting: Theoretical Photon Flux Based on Calibrated Stars and measured photon flux and the zenith angle for calibrating stars. For linear equations Perform least squares fitting, where , The linear equation is as follows:

[0035]

[0036] in,

[0037] After fitting, the coefficients of the linear equation can be obtained. =−0.1887.

[0038] Step S5, calculate atmospheric transmittance at different zenith angles: based on the coefficients of the linear equation. and The atmospheric transmittance at different zenith angles is calculated using the following formula:

[0039] The calculated atmospheric transmittance results for each zenith angle direction are shown in Table 4 below.

[0040] Table 4

[0041] The atmospheric transmittance measurement method of the present invention utilizes the high sensitivity of a single-photon detector to accurately measure the photon flux of a calibrated star, and directly inverts the atmospheric extinction coefficient through data fitting, thereby achieving high-precision and direct measurement of the transmittance of the entire atmospheric layer, effectively avoiding errors caused by indirect calculation.

Claims

1. A method for measuring atmospheric transmittance based on a single-photon detector, characterized in that, include: S1. Select at least one calibrated star and obtain its nominal brightness value; S2. Based on the nominal brightness value, calculate the theoretical photon flux of the calibrated star at the measurement system; S3. Measure the calibrated star using a combination system of a single-photon detector and a telescope to obtain the actual photon flux and the corresponding telescope zenith angle; S4. Based on the theoretical photon flux, measured actual photon flux, and zenith angle of each calibrated star, data fitting is performed to obtain the fitting coefficient characterizing the atmospheric extinction characteristics. S5. Calculate the atmospheric transmittance in different zenith angle directions based on the fitting coefficients.

2. The atmospheric transmittance measurement method based on a single-photon detector according to claim 1, characterized in that, The step of selecting at least one calibrated star and obtaining its nominal brightness value specifically includes: Based on the geographical coordinates of the measurement point and the measurement time, select stars from the star catalog that are above the horizon of the measurement point at the measurement time as calibration stars, and obtain their nominal brightness values.

3. The atmospheric transmittance measurement method based on a single-photon detector according to claim 1 or 2, characterized in that, The theoretical photon flux The calculation formula is: in, This is the nominal brightness value, in Wm. -2 μm -1 , The star is designated by its number, and the telescope aperture is in meters (m). The measurement system uses a filter bandwidth, measured in μm. For the measured band, This represents Planck's constant. It represents the speed of light.

4. The atmospheric transmittance measurement method based on a single-photon detector according to claim 3, characterized in that, In the step of measuring using a combination system of a single-photon detector and a telescope, the single-photon detector is used to measure the number of photons per second from the calibrated star to obtain the actual photon flux. Simultaneously record the zenith angle pointed to by the telescope during the measurement. .

5. The atmospheric transmittance measurement method based on a single-photon detector according to claim 4, characterized in that, The step of performing data fitting to obtain fitting coefficients includes: Constructing linear equations ,in , ,Right now: in, Corresponding zenith angle The atmospheric mass is calculated using the following piecewise function: The coefficients of the linear equation are obtained by performing a linear fit on the measured data. , which is the fitting coefficient characterizing the atmospheric extinction properties.

6. The atmospheric transmittance measurement method based on a single-photon detector according to claim 5, characterized in that, The formula for calculating atmospheric transmittance at different zenith angles is as follows: in, Atmospheric transmittance at different zenith angles.

7. The atmospheric transmittance measurement method based on a single-photon detector according to claim 5, characterized in that, When fitting the linear equation, the least squares method is used for linear regression to obtain the coefficients. .

8. The atmospheric transmittance measurement method based on a single-photon detector according to claim 1, characterized in that, The single-photon detector is a single-photon avalanche diode, a superconducting nanowire single-photon detector, or a microchannel plate photomultiplier tube.

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