A method for evaluating the signal-to-noise ratio of stellar measurements

Abstract

The present invention belongs to the field of astronomical navigation, and specifically relates to a method for evaluating the signal-to-noise ratio of star measurement, comprising: determining the spectrum segments to be measured of the star to be measured and the detection background; dividing each spectrum segment to be measured into segments according to the accuracy requirement of signal-to-noise ratio calculation; and calculating the number of signal electrons corresponding to each segmented spectrum generated by the star to be measured; and calculating the number of signal electrons corresponding to each segmented spectrum. S Add them together as the final signal electron number generated by the star to be measured; calculate the signal electron number corresponding to each segment spectrum generated by the background respectively; and add the signal electron number N corresponding to each segment B The sum of these is used to determine the final number of signal electrons generated by the background. Based on this final number of signal electrons generated by the star under test and the background, the signal-to-noise ratio of the star under test is calculated to complete the evaluation. This invention proposes a piecewise integration method for calculating the number of signal electrons generated by the star and the background, which can significantly improve the analytical accuracy and reliability of the star sensor's star measurement capabilities.

Description

Technical Field

[0001] The present invention belongs to the field of celestial navigation, and more particularly, relates to a method for evaluating the signal-to-noise ratio of star measurement. Background Art

[0002] Astronomical navigation can comprehensively provide core navigation information such as position, heading, attitude and speed, and plays a unique and important role, especially in complex electromagnetic environments. It has many advantages such as high measurement accuracy, freedom from interference, no time drift and high reliability, making it an indispensable equipment in integrated navigation systems.

[0003] Star detection capability is one of the core indicators of astronomical navigation equipment. However, there are currently some problems in the analysis of star sensor star detection capability. The main problem is that the parameters related to the star detection capability of star sensors, such as atmospheric background, transmittance, and star point energy, are generally calculated using a single spectral wavelength point. These parameters are distributed with wavelength, which will cause certain errors and seriously affect the analysis accuracy and credibility of the star detection capability of star sensors. Summary of the Invention

[0004] In response to the defects of the existing technology and the need for improvement, the present invention provides a method for evaluating the signal-to-noise ratio of stellar measurement, which aims to improve the evaluation accuracy of the signal-to-noise ratio of stellar measurement and thus enhance the analysis accuracy and credibility of the star measurement capability of the star sensor.

[0005] To achieve the above object, according to one aspect of the present invention, a method for evaluating the signal-to-noise ratio of stellar measurements is provided, comprising:

[0006] Determine the first spectrum segment to be measured of the star to be measured, divide the first spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the star to be measured; calculate the number of signal electrons corresponding to each segment N S Add them together to form the final number of signal electrons produced by the star to be measured;

[0007] Determine the second spectrum segment to be measured for the detection background, divide the second spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the background; calculate the number of signal electrons N corresponding to each segment B Add together, the final signal electron number generated as the background;

[0008] Based on the final number of signal electrons generated by the star to be measured and the final number of signal electrons generated by the background, the measurement signal-to-noise ratio of the star to be measured is calculated to complete the evaluation.

[0009] Furthermore, the length of the segments ranges from 1 to 50 nanometers.

[0010] Furthermore, the celestial body to be measured is a star.

[0011] Further, for calculating N S The atmospheric transmittance is calculated as follows:

[0012] Using the improved Modtran / CART graphical interface software, combined with the configuration file of the Modtran / CART graphical interface software, the atmospheric transmittance τ is automatically generated. a (λ) distribution curve along the wavelength of the first spectral segment to be measured, wherein the improved Modtran / CART graphical interface software is configured with a configuration file generated by Matlab, which is used to automatically input the values ​​of the calculation parameters for the calculation of the atmospheric transmittance at each wavelength.

[0013] Further, for calculating N B The atmospheric radiation transmission background intensity is calculated in the following way:

[0014] The improved Modtran / CART graphical interface software is used in combination with the configuration file of the Modtran / CART graphical interface software to automatically generate the atmospheric radiation transmission background intensity I B (λ) distribution curve along the wavelength of the second spectral segment to be measured, wherein the improved Modtran / CART graphical interface software is configured with a configuration file generated by Matlab, which is used to automatically input the values ​​of the calculation parameters for the calculation of the atmospheric radiation transmission background intensity at each wavelength.

[0015] The present invention also provides a method for analyzing the star measurement capability of a star sensor, which uses the measurement signal-to-noise ratio of the star to be measured obtained by the star measurement signal-to-noise ratio evaluation method described above to analyze the star measurement capability of the star sensor.

[0016] The present invention also provides a computer-readable storage medium, which includes a stored computer program. When the computer program is executed by a processor, the processor controls the device where the storage medium is located to execute the above-mentioned method for evaluating the signal-to-noise ratio of star measurement and / or the above-mentioned method for analyzing the star measurement capability of a star sensor.

[0017] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0018] (1) The present invention proposes a segmented integration method to calculate the number of signal electrons generated by stars and background, which can significantly improve the analytical accuracy and credibility of the star sensor's star measurement capability. According to the star measurement capability calculation formula, the number of signal electrons generated by stars and background is related to the photon energy of the detection band. The energy of the wavelength photons of a single spectral point, that is, the center wavelength photon energy, is generally used. According to the spectral irradiance table of a zero-magnitude star, the center wavelength photon energy of the band to be measured (generally in the range of 400-1000nm) can be calculated. For example, the center wavelength of the visible light band is 550nm. In fact, the spectral irradiance of stars and background varies with wavelength distribution, and using the center wavelength photon energy will cause a certain error. In the spectral band to be measured (such as the 400-1000 band), the star target energy and background energy are equally divided (such as divided into 1-50 nanometers), and the segmented integration method will significantly improve the analytical accuracy and credibility.

[0019] (2) The present invention also proposes to combine Matlab to provide automated support for the calculation of atmospheric transmittance and atmospheric radiation transmission background intensity, significantly reducing the calculation time of parameters related to star measurement capabilities and improving calculation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A flowchart of a method for evaluating the signal-to-noise ratio of stellar measurements provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of factors influencing the photoelectric star measurement capability provided by an embodiment of the present invention;

[0022] Figure 3 A schematic diagram of a star sensor receiving star radiation provided by an embodiment of the present invention;

[0023] Figure 4 A schematic diagram of a star sensor receiving space background radiation provided by an embodiment of the present invention;

[0024] Figure 5 The atmospheric transmittance τ provided by the embodiment of the present invention a (λ)Automated calculation flow chart;

[0025] Figure 6 The transmittance τ generated by automatically generating a configuration file through Matlab provided in the embodiment of the present invention a (λ) distribution curve with wavelength;

[0026] Figure 7 A stellar spectrum distribution curve diagram of a G2 type 0-magnitude star provided in an embodiment of the present invention;

[0027] Figure 8The embodiment of the present invention provides a method for automatically generating a configuration file through Matlab to generate the atmospheric radiation transmission background intensity I B (λ) distribution curve with wavelength;

[0028] Figure 9 This is a graph of the daytime atmospheric background radiation in the 400-1000nm band at an altitude of 50km provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] Example 1

[0031] A method for evaluating the signal-to-noise ratio of stellar measurements, such as Figure 1 Shown, including:

[0032] Determine the first spectrum segment to be measured of the star to be measured, divide the first spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the star to be measured; calculate the number of signal electrons corresponding to each segment N S Add them together to form the final number of signal electrons produced by the star to be measured;

[0033] Determine the second spectrum segment to be measured for the detection background, divide the second spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the background; calculate the number of signal electrons N corresponding to each segment B Add together, the final signal electron number generated as the background;

[0034] Based on the final number of signal electrons generated by the star to be measured and the final number of signal electrons generated by the background, the measurement signal-to-noise ratio of the star to be measured is calculated to complete the evaluation.

[0035] like Figure 2 Figure 2 shows a schematic diagram of factors influencing photoelectric star measurement capability. Calculation of photoelectric channel star measurement capability involves complex parameters such as stellar radiation, sky background, atmospheric transmittance in the detection band, optical system transmittance, optical system relative aperture, optical system focal length, detector quantum efficiency, and noise. The signal-to-noise ratio of the photoelectric channel, which is related to star measurement capability, can be calculated using the following formula:

[0036]

[0037] Where Ke It is an additional factor for processing circuit, usually 0.8; N S is the number of signal electrons produced by the star; N B is the number of signal electrons generated by the background; σ T is the RMS value of the detector's dark current noise electron count, which is selected based on the relevant parameters in the detector manual; σ R To read the RMS value of the circuit noise electron number, select the relevant parameters according to the detector manual. Therefore, the key to calculating the star measurement capability is the number of signal electrons N generated by the star. S The number of signal electrons generated by the calculation and background N B Calculation.

[0038] The number of signal electrons N in each segment spectrum produced by the star to be measured S Calculation, such as Figure 3 The figure shows a schematic diagram of a star sensor receiving stellar radiation. The radiation angle of a star to the earth is generally less than 0.01". A star can be regarded as a point light source at infinite distance, and starlight can be regarded as parallel light. The number of electrons generated per second by the photoelectric effect of a star on a certain imaging pixel of the photoelectric detector is N. S The specific method is:

[0039]

[0040] Where D is the aperture of the star sensor optical system; λ is the wavelength, ranging from λ1 to λ2; E ph (λ) is the energy of a single photon at wavelength λ, E ph (λ)=hc / λ, where h is Planck's constant 6.6×10 -34 J / s, c is the speed of light 3×10 8 m / s; τ a (λ) is the atmospheric transmittance; τ0(λ) is the transmittance of the optical system, which is related to the characteristics of the optical system, varies with wavelength, and can be obtained through calculation formulas and test methods; QE(λ) is the detector quantum response efficiency, that is, the number of electrons converted by photons in a detection band in the photodetector, which can be queried through the typical detector quantum response efficiency curve; E m (λ) is the spectral irradiance of the star reaching the detection surface of the star sensor, in W·m -2 ·m -1 .

[0041] The number of signal electrons N generated by the background B Calculation, such as Figure 4The figure shows a schematic diagram of the star sensor receiving space background radiation. The sky background is simplified to a target with uniform radiance. The space background radiation is processed using an extended source target. Therefore, the atmospheric transmittance does not need to be considered when calculating the space background radiation. The number of electrons generated per second by the photoelectric effect of the space background on a certain imaging pixel of the photoelectric detector is N. B The calculation is as follows:

[0042]

[0043] Where λ is the wavelength, ranging from λ1 to λ2; Ω is the solid angle occupied by the unit pixel, in steradian, and its relationship with the field of view of the star sensor is: N is the number of pixels in this direction, Ω is inversely proportional to the square of the focal length f of the optical system; I B (λ) is the scattered radiation intensity of the space background light before it is transmitted to the star sensor optical system, and the unit is W·m -2 ·sr -1 ·m -1 ; D is the aperture of the optical system; E ph (λ) is the energy of a single photon at wavelength λ, E ph (λ)=hc / λ, where h is Planck's constant 6.6×10 -34 J / s, c is the speed of light 3×10 8 m / s; τ0(λ) is the transmittance of the optical system, which is related to the characteristics of the optical system, varies with wavelength, and can be obtained through calculation formulas and testing methods; QE(λ) is the detector quantum response efficiency, that is, the number of electrons converted by photons in a detection band in the photodetector, which can be queried using a typical detector quantum response efficiency curve.

[0044] Preferably, the length of the segments ranges from 1 to 50 nanometers.

[0045] Preferably, if Figure 5 is the atmospheric transmittance τ a (λ) Automated calculation process. In the traditional calculation process, the atmospheric transmittance τ a (λ) is usually calculated through the Modtran / CART graphical interface, but this method is complex, slow, and prone to errors. a (λ) Automated calculation technology generates atmospheric transmittance τ by automatically generating configuration files through Matlab a The distribution curve of (λ) with wavelength greatly shortens the calculation time and improves the reliability of the calculation results.

[0046] Specifically, the configuration file of Modtran / CART graphical interface software is automatically generated through Matlab;

[0047] Modtran / CART graphical interface software is used to generate the atmospheric transmittance τ in combination with the configuration file. a (λ) a distribution curve along the wavelength of the first spectral band to be measured, wherein the configuration file is used to automatically input the values ​​of calculation parameters for calculating the atmospheric transmittance at each wavelength.

[0048] like Figure 6 As shown, the transmittance τ is generated by automatically generating a configuration file through Matlab a The distribution curve of (λ) with wavelength is calculated under the atmospheric conditions of mid-latitude summer and the atmospheric transmission window at an altitude of 50 km observed vertically toward the zenith at noon in summer.

[0049] The spectral irradiance of a star reaching the detection surface of a star sensor is related to the type and magnitude of the star, and varies with the wavelength distribution. In the design of a star sensor, the magnitude is generally used as a concept to predict and estimate parameters such as the detection capability of the star sensor. In the process of analyzing the star measurement capability of a traditional star sensor, a single spectral wavelength point is generally used to calculate the spectral irradiance of a star, which will cause a large error. As described above, the present embodiment subdivides the stellar spectral irradiance into the full working spectrum segment according to 1-50 nanometers, and combines the atmospheric transmittance, the optical system transmittance, and the detector quantum response efficiency curve to perform a distributed energy integral calculation on the subdivided spectrum segment to calculate the parameter N related to the star measurement capability of the star sensor. S .

[0050] The calculation process of star target energy proposed in this embodiment is described by taking a G2 type 0 magnitude star as an example. Figure 7 The figure below shows the stellar spectrum distribution curve for a G2-type, zero-magnitude star. The optical system design of the star sensor should minimize reflection and dispersion, with the spectrum transmission range being between 400 and 1000 nm.

[0051] Its spectral irradiance E0(λ) is subdivided into the full working spectrum segment by 50 nanometers, as shown in Table 1.

[0052] Table 1 Spectral irradiance distribution of G2 type 0-magnitude stars

[0053]

[0054]

[0055] According to the spectral irradiance distribution table in Table 1, combined with the gas transmittance, optical system transmittance, and detector quantum efficiency curve, the number of electrons N generated per second by the photoelectric effect of a star on a certain imaging pixel of the photoelectric detector can be calculated by substituting it into formula (2): S .

[0056] Preferably, in the traditional calculation process, the atmospheric radiation transmission background intensity I B(λ) is usually calculated through the Modtran / CART graphical interface, but this method is complex, slow, and prone to errors. Figure 8 As shown in the figure, the atmospheric background radiation intensity automatic calculation technology generates the atmospheric radiation transmission background intensity I by automatically generating a configuration file through Matlab. B The distribution curve of (λ) with wavelength greatly shortens the calculation time and improves the reliability of the calculation results. Specifically, the configuration file of Modtran / CART graphical interface software is automatically generated by Matlab; Modtran / CART graphical interface software is used to generate the atmospheric radiation transmission background intensity I in combination with the configuration file. B (λ) a distribution curve along the wavelength of the second spectral segment to be measured, wherein the configuration file is used to automatically input the values ​​of calculation parameters for calculating the atmospheric radiation transmission background intensity at each wavelength.

[0057] like Figure 9 The following is a daytime atmospheric background radiation curve for the 400-1000 nm band at an altitude of 50 km, generated using automated atmospheric background radiation intensity calculation technology. The observed atmospheric model reflects average atmospheric conditions in Northwest China. The observation zenith angle ranged from 45° to 65° at 5° intervals, the solar zenith angle ranged from 0° to 70° at 10° intervals, and the observation azimuth angle relative to the solar azimuth ranged from 0° to 180° at 20° intervals. Calculations were iterated 1000 times.

[0058] The atmospheric radiation transmission background energy calculation method proposed in this embodiment divides the radiation intensity of the whole sky area pointing to the maximum background radiation of the daytime sky into the full working spectrum segment by 1-50 nanometers. Combined with the optical system transmittance and the detector quantum response efficiency curve, the energy distribution of the subdivided spectrum segment is integrated to calculate the star sensor's star detection capability related parameter N. B .

[0059] Its spectral radiation intensity is subdivided into the full working spectrum segment by 50 nanometers, as shown in Table 2.

[0060] Table 2 Background radiation intensity distribution

[0061] Wavelength μm <![CDATA[Background radiation intensity W / cm 2 / sr / μm]]> 1 4.17E-07 0.95 6.14E-07 0.9 8.45E-07 0.85 1.02E-06 0.8 1.31E-06 0.75 1.96E-06 0.7 2.78E-06 0.65 3.86E-06 0.6 6.44E-06 0.55 8.98E-06 0.5 1.34E-05 0.45 2.12E-05 0.4 2.55E-05

[0062] According to the background spectral radiation intensity distribution table in Table 2, combined with the optical system transmittance and the detector quantum efficiency curve, the number of electrons generated per second by the photoelectric effect of the space background on a certain imaging pixel of the photoelectric detector can be calculated by substituting it into formula (3): B .

[0063] Finally, the number of signal electrons generated by the star is N S and the number of signal electrons N generated by the background BSubstituting into formula (1) we can calculate the signal-to-noise ratio of the photoelectric star measurement channel that can provide feedback on the star measurement capability.

[0064] Example 2

[0065] A method for analyzing the star measurement capability of a star sensor is provided, which uses the measurement signal-to-noise ratio of a star to be measured obtained by the star measurement signal-to-noise ratio evaluation method described in the first embodiment to analyze the star measurement capability of the star sensor.

[0066] The relevant technical solutions are the same as those in Example 1 and will not be described again here.

[0067] Example 3

[0068] A computer-readable storage medium includes a stored computer program, wherein when the computer program is executed by a processor, the computer program controls the device where the storage medium is located to execute the above-mentioned method for evaluating the signal-to-noise ratio of stellar measurement and / or the above-mentioned method for analyzing the star measurement capability of a star sensor.

[0069] The relevant technical solutions are the same as those in Example 1 and Example 2 and will not be described in detail here.

[0070] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 method for evaluating the signal-to-noise ratio of stellar measurements, characterized in that: include: Determine the first spectrum segment to be measured of the star to be measured, divide the first spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the star to be measured; calculate the number of signal electrons corresponding to each segment N S Add them together to form the final number of signal electrons produced by the star to be measured; Determine the second spectrum segment to be measured for the detection background, divide the second spectrum segment to be measured into segments according to the signal-to-noise ratio calculation accuracy requirement, and calculate the number of signal electrons corresponding to each segment spectrum generated by the background; calculate the number of signal electrons N corresponding to each segment B Add together, the final signal electron number generated as the background; Based on the final number of signal electrons generated by the star to be measured and the final number of signal electrons generated by the background, the measurement signal-to-noise ratio of the star to be measured is calculated to complete the evaluation.

2. The evaluation method according to claim 1, wherein: The length of the segments ranges from 1 to 50 nanometers.

3. The evaluation method according to claim 1, wherein: The celestial body to be measured is a star.

4. The evaluation method according to claim 1, wherein: To calculate N S The atmospheric transmittance is calculated as follows: Using the improved Modtran / CART graphical interface software, combined with the configuration file of the Modtran / CART graphical interface software, the atmospheric transmittance τ is automatically generated. a (λ) distribution curve along the wavelength of the first spectral segment to be measured, wherein the improved Modtran / CART graphical interface software is configured with a configuration file generated by Matlab, which is used to automatically input the values ​​of the calculation parameters for the calculation of the atmospheric transmittance at each wavelength.

5. The evaluation method according to claim 1, wherein: To calculate N B The atmospheric radiation transmission background intensity is calculated in the following way: The improved Modtran / CART graphical interface software is used in combination with the configuration file of the Modtran / CART graphical interface software to automatically generate the atmospheric radiation transmission background intensity I B (λ) distribution curve along the wavelength of the second spectral segment to be measured, wherein the improved Modtran / CART graphical interface software is configured with a configuration file generated by Matlab, which is used to automatically input the values ​​of the calculation parameters for the calculation of the atmospheric radiation transmission background intensity at each wavelength.

6. A method for analyzing the star measurement capability of a star sensor, characterized in that: The star measurement capability of a star sensor is analyzed by using the measurement signal-to-noise ratio of the star to be measured obtained by the star measurement signal-to-noise ratio evaluation method according to any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that The computer-readable storage medium includes a stored computer program, wherein, when the computer program is executed by a processor, the processor controls the device where the storage medium is located to execute the method for evaluating the signal-to-noise ratio of stellar body measurement according to any one of claims 1 to 5 and / or the method for analyzing the star measurement capability of a star sensor according to claim 6.

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