Calculation method for solving sky radiance and atmospheric transmittance of Mars sand and dust environment

Abstract

The invention relates to a calculation method for solving the sky radiance and the atmospheric transmittance of a Mars sand and dust environment, and belongs to the technical field of Mars exploration. Comprising the following steps: Mars atmosphere characteristic modeling: combining data, dust rules and normal distribution characteristics to construct a layered atmosphere particle input model; based on the Mie scattering theory and the Mars atmospheric parameters, the scattering characteristics and radiation transmission of particles are calculated; solving atmospheric radiation transmission; and performing multi-parameter coupling spectral response analysis, transmittance calculation and radiance calculation. Based on the Mie theory and the Monte Carlo method, key factors such as scattering and absorption of sand and dust particles, the solar elevation angle and the atmospheric structure are completely considered, the radiation characteristics in the Mars sand and dust environment can be relatively truly reflected, the simulation precision of the Mars complex atmospheric environment is remarkably improved, and the landing precision requirement is met.

Description

TECHNICAL FIELD

[0001] The application relates to a calculation method for solving sky radiance and atmospheric transmittance in a dust environment, and belongs to the technical field of Mars exploration. BACKGROUND

[0002] Mars dust particles interact with solar radiation and thermal infrared radiation, affecting the structure, dynamics and thermal balance process of the Martian atmosphere by scattering and absorbing solar radiation and thermal radiation, and are key factors in the change of the Martian atmospheric environment. Therefore, accurate detection and correct understanding of the Martian dust environment are crucial for planning Mars exploration missions.

[0003] Although existing Earth atmospheric radiation transfer software (such as MODTRAN and LOWTRAN) performs well in the Earth environment, it has significant limitations in the Martian environment. The core database lacks parameters for the composition of the unique atmospheric dust particle distribution characteristics of Mars. Due to the special conditions of Martian dust, traditional aerosol modeling uses the assumption of homogenization height, without considering the vertical gradient characteristics of the change of the Martian dust particle size distribution with altitude. The sand weather laser radar point cloud data enhancement method based on multi-scale physical simulation of the application with the publication number CN117872316B and the application name Multi-scale physical simulation of sand weather laser radar point cloud data enhancement method classifies sand particles based on multi-scale physical simulation, simulates extinction and scattering effects, simulates radar data in sand weather, enhances training data, and improves the robustness of the model in the sand environment. The existing verification system relies too much on single-point measurement data from the probe, lacks a systematic confidence evaluation framework for multi-spectral and multi-observation geometry, and does not consider the vertical gradient characteristics of the change of the Martian dust particle size distribution with altitude, resulting in distortion of the atmospheric stratified radiation characteristics simulation, making it difficult for the model to meet the accuracy requirements of the landing navigation optical system.

[0004] Therefore, it is urgent to propose a calculation method for solving the sky radiance and atmospheric transmittance in the Martian dust environment to solve the above technical problems. SUMMARY

[0005] To solve the above problems, a calculation method for solving the sky radiance and atmospheric transmittance in the Martian dust environment is provided. In the following, a brief summary of the application is given to provide a basic understanding of some aspects of the application. It should be understood that this summary is not an exhaustive summary of the application. It is not intended to determine the key or important parts of the application, nor to limit the scope of the application.

[0006] The technical scheme of the application is as follows: The calculation method for solving the sky radiance and atmospheric transmittance in the Martian dust environment comprises the following steps: Step 1, modeling of the Martian atmospheric characteristics, including: Step 1.1: Combine data, sand dust law, normal distribution characteristics to build a layered atmospheric particle input model; Step 1.2: Based on Mie scattering theory and Mars atmospheric parameters, calculate the scattering characteristics and radiation transfer of particles; Step 2, atmospheric radiation transfer solution; Step 3, multi-parameter coupled spectral response analysis, including: Step 3.1: transmittance calculation; Step 3.2: calculation of radiance.

[0007] Preferred: In step 1.1, use Mars probe data and Mars sand dust equivalent particle diameter and height distribution law, describe the particle size distribution according to the lognormal distribution, and according to the effective particle radius and effective width distribution relationship given by MCD, so that the particle input of each atmospheric layer conforms to the normal distribution: (1) Wherein, r 0 is the geometric mean diameter; σ is the standard deviation; n(r) is the particle size probability distribution function; ; r is the sand particle size; (2) (3) Wherein, r eff is the effective particle radius; v eff is the effective variance.

[0008] Preferred: In step 1.2, combine the complex refractive index of Martian-like sand dust minerals, calculate the single-particle scattering characteristic parameters based on Mie theory, including extinction coefficient, scattering phase function, and asymmetric factor; According to the Mars atmospheric database, set the vertical profile of Mars atmospheric temperature, pressure and composition, consider the absorption and Rayleigh scattering of radiation by each layer of gas; (4) (5) (6) Wherein, Q ext is the extinction efficiency factor, Q sca is the scattering efficiency factor, Q abs is the absorption efficiency factor, a n , b n is the Mie scattering coefficient; n is the number of terms in the series expansion; characterizing the relative size of the particle size to the wavelength of the incident light; R e is an operator taking the real part.

[0009] Preferred: In step 2, the Mars atmosphere is vertically divided into several layers of the same height, and the Monte Carlo algorithm is used to solve the radiative transfer integral equation to track the light path from the sun to the detection point, including multiple scattering and ground reflection paths.

[0010] Preferred: In step 2, the atmospheric parameter information input in step 1 is used to model the layers 120 km away from the surface of Mars, and the optical parameters of the sand dust in each layer are calculated independently, wherein the Mars solar constant takes an average value of 589 W / m 2 ; The Mie scattering calculation formulas (4)-(6) are used to calculate the extinction efficiency factor and scattering phase function of the Mars sand dust particles; The transmittance is calculated according to the line-by-line integral calculation of the transmittance according to formula (7); In the process of solving the sky radiance, the radiation flux contributed by the direct radiation of the sun, the atmospheric gas thermal radiation, the multiple scattering of the sand dust particles and the ground reflection is considered; The path tracking algorithm based on the Monte Carlo integral strategy is used to simulate the radiation transfer behavior of different incident paths; Each light path calculates the radiation transfer according to the medium properties and interaction behaviors (such as scattering, absorption, reflection) it passes through, and performs multi-path statistics to obtain the sky radiance distribution within a unit solid angle and the total transmittance from the sun direction to the ground.

[0011] Preferred: In step 3.1, the transmittance calculation includes the following steps: Strict line-by-line integration according to the wave number can obtain the average transmittance within the wave number interval v . The expression is: (7) Where, S l is the absorption intensity of the spectral line per unit path length; is the spectral line half-width; v 0,l is the spectral line center wave number;△ v is the wave number integral interval width;T v (7) u is the transmittance at the wave number v ; u is the absorption path length; The optical thickness of Zhurong, Curiosity and Opportunity obtained from the MCD database in the visible light band is used to verify the accuracy of the model application.

[0012] Preferred 3.2, the radiance calculation includes the following steps: The amount of solar radiation received by any horizontal surface on Mars includes three parts: direct solar radiation, scattered solar radiation, and albedo. The different levels of atmospheric transparency affect the proportion of these three components. (8) in, I Riback Atmospheric background radiance, I Sun The received direct solar radiance. I Sca The received solar diffuse radiance, I Ground The received ground reflected radiance; The atmospheric path radiation received at a certain point is the superposition of infrared radiation from each layer of the atmosphere in the direction observed by the detector, mainly the thermal radiation of atmospheric and aerosol components in the atmosphere; a highly layered strategy was adopted from the Martian surface, and the vertical spatial division achieved a precise correspondence with the vertical distribution of atmospheric components. The mathematical formula for calculating the atmospheric path radiance received at the observation point is: (9) in, T j For the first j Temperature of the layer of atmosphere; τ α ( j The first is caused by the presence of atmospheric absorption. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ β ( j The first is caused by the presence of atmospheric scattering. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ b This represents the total atmospheric transmittance from the radiative transfer boundary layer to the observation point. L b ( λ , T b () represents the radiance of the target infrared radiation transmission boundary layer; m The total number of atmospheric layers; T b This refers to the surface temperature of Mars. λ The wavelength of the electromagnetic wave.

[0013] The present invention has the following beneficial effects: 1. The application is based on Mie theory and Monte Carlo method, and fully considers key factors such as scattering, absorption, solar elevation angle, and atmospheric structure of dust particles, can relatively truly reflect the radiation characteristics in the Martian dust environment, significantly improve the simulation accuracy of the complex Martian atmospheric environment, and meet the landing accuracy requirement.

[0014] 2. The application constructs a dynamic layered atmospheric model based on the MCD database, divides the upper surface of Mars into 120 vertical levels, realizes the fine vertical representation of atmospheric parameters, and describes the aerosol particle profile by using normal distribution for each independent level, and through dynamic coupling of the evolution law of the seasonal dust storm of Mars, establishes a radiation transfer model adaptable to the change of solar azimuth angle and observation geometry condition. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The flow chart for solving the sky radiance and atmospheric transmittance in the Martian dust environment.

[0016] Figure 2 The overall block diagram for solving the sky radiance and atmospheric transmittance in the Martian dust environment. Figure 2 In the figure, 1 is atmospheric molecular absorption and scattering, 2 is dust particle scattering, 3 is direct solar radiation, and 4 is ground reflection.

[0017] Figure 3 The modeling diagram of the sun and observation angle.

[0018] Figure 4 The result comparison diagram of the atmospheric transmittance in the Martian dust environment.

[0019] Figure 5 The result simulation diagram of the atmospheric sky radiance in the Martian dust environment. Figure 5 In the figure, (a) is the integral value in the visible light band varying with the observation angle and azimuth angle under the fixed solar elevation angle, (b) is the integral value in the near-infrared band varying with the observation angle and azimuth angle under the fixed solar elevation angle, (c) is the integral value in the visible light band varying with the observation angle and azimuth angle under the fixed observation angle, and (d) is the integral value in the near-infrared band varying with the observation angle and azimuth angle under the fixed observation angle. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the application more clear and obvious, the application will be described below by specific embodiments shown in the drawings. However, it should be understood that these descriptions are only exemplary and are not intended to limit the scope of the application. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the application.

[0021] Specific implementation one: combined with Figures 1-5To illustrate the embodiment, the calculation method for solving the sky radiance and atmospheric transmittance in the Mars dust environment of the embodiment includes the following steps: Step 1, modeling of the characteristics of the Mars atmosphere, including: Step 1.1: combining the measured data, dust rules, and normal distribution characteristics to realize model fusion and construct a layered atmospheric particle input model; In step 1.1, according to the information of the dust particles in the Mars atmosphere measured by the Phobos 2 Mars probe, the corresponding relationship between the particle number concentration and the effective radius of the Mars dust particles and the height is obtained as the basic particle input information of the dust. The surface albedo of Mars is obtained from the multi-band spectral data (0.4~5.65 μm) of the Ophir Planum and Margaritifer Terra regions in the literature, and the interpolation of the dark and bright area surface reflectivity is used in the radiation modeling calculation. Using the Mars probe data and the equivalent particle diameter and height distribution rule of the Mars dust given in the existing literature, the particle size distribution can be described according to the logarithmic normal distribution, and the effective particle radius and effective width distribution relationship given by MCD (mass median diameter) is used to make the particle input of each atmospheric layer conform to the normal distribution: (1) wherein, r 0 is the geometric mean diameter; σ is the standard deviation; n(r) is the particle size probability distribution function; ; r is the dust particle size; (2) (3) wherein, r eff is the effective particle radius; v eff is the effective variance, used to measure the effective width; Step 1.2: based on the Mie scattering theory and the Mars atmospheric parameters, the scattering characteristics and radiation transmission of a single dust particle are calculated. The radiation transmission can include absorption and scattering; In step 1.2, the complex refractive index (the real and imaginary parts vary with wavelength) of the Mars-like dust mineral is combined, and the single-particle scattering characteristic parameters are calculated based on the Mie theory, including the extinction coefficient, the scattering phase function, the asymmetry factor, etc. According to the Mars atmospheric database, the vertical profile of the temperature, pressure and composition of the Mars atmosphere is set, and the absorption and Rayleigh scattering of the radiation by the gas in each layer (mainly CO2) are considered; (4) (5) (6) in, Q ext Extinction efficiency factor Q sca Is it the scattering efficiency factor? Q abs This is the absorption efficiency factor. a n , b n denoted as Mie scattering coefficient; n is the number of terms in the series expansion; This characterizes the relative size of the particle to the wavelength of the incident light; R e is the operator for extracting the real part; Step 2: Solve the atmospheric radiation transfer problem. Divide the Martian atmosphere vertically into 120 layers (0-120 km, 1 km per layer). Use the Monte Carlo algorithm to solve the radiation transfer integral equation and trace the light path from the sun to the probe point (multiple perspectives), including multiple scattering and surface reflection paths. In step 2, using the atmospheric parameter information input in step 1, a layered model is constructed at a distance of 120 km from the Martian surface. The optical parameters of the dust are calculated independently for each layer, with the Martian solar constant taken as an average value of 589 W / m. 2 The extinction efficiency factor and scattering phase function of Martian dust particles are calculated using the Mie scattering calculation formulas (4)-(6) respectively; the atmospheric transmittance is calculated by integrating the transmittance line by line according to formula (7); in the process of solving the sky radiance, the radiation flux contributed by direct solar radiation, atmospheric gas thermal radiation, multiple scattering of dust particles and surface reflection is considered. A path-tracing algorithm based on the Monte Carlo integration strategy is used to simulate the radiative transfer behavior of different incident paths. Specifically, the path is discretized into segments according to the number of atmospheric layers, starting from the observed back-emitted light (reverse path tracing). In the multiple scattering path tracing, the energy contribution is calculated along the discrete directions, and the weights are accumulated. , w j This represents the integral weight in the j-th direction. N d The discrete number of the sphere; the radiative transmission of each ray path is calculated based on the properties of the medium it passes through and the interaction behavior (such as scattering, absorption, and reflection), and multipath statistics are performed to obtain the sky radiance distribution within a unit solid angle and the total transmittance incident from the direction of the sun to the earth's surface; Step 3, multi-parameter coupled spectral response analysis, multi-parameter coupled spectral response analysis, explore its in different sand particle characteristics, solar elevation angle (0-90 °), ground albedo, Mars orbit position (solar longitude angle Ls ∈ [0 °, 360 °], corresponding to the heliocentric distance change 1.38-1.66 AU) and observation conditions (angle, altitude) under the spectral variation law, and compare the visible light band and near-infrared band radiance distribution, including: Step 3.1: transmittance calculation includes the following steps: According to the strict line-by-line integration of the wave number, the average transmittance in the wave number interval △ v The expression is: (7) Wherein, S l The absorption intensity of the spectral line per unit path length; The spectral line half-width; v 0,l The spectral line center wave number; △ v The wave number integral interval width; T v u The transmittance at the wave number v u The absorption path length; In addition, the optical thickness of Zhurong, Curiosity and Opportunity in the visible light band obtained by using the MCD database verifies the accuracy of the model application; the present application constructs a dynamic layered atmosphere model based on the MCD database, divides the space above the surface of Mars into 120 vertical levels, and realizes the fine vertical representation of the atmospheric parameters; each independent level uses a normal distribution to describe the aerosol particle profile, and by dynamically coupling the evolution law of the seasonal dust storm on Mars, a radiation transfer model adaptable to the changes of solar azimuth angle and observation geometry is established. Step 3.2: the transmission process of solar radiation in the atmosphere is solved to obtain the solar radiation and thermal radiation on the surface of Mars; the radiation transmission in the atmosphere is related to the optical properties of the ground, sand and cloud layer; after passing through the atmosphere, the size, spectrum and directional distribution of solar radiation are changed, which is caused by the absorption, scattering and reflection of the atmospheric medium to the radiation; the calculation of radiance includes the following steps: The amount of solar radiation received by any horizontal surface on Mars includes three parts of direct solar radiation, solar scattered radiation and reflected radiation, and the different transparency of the atmosphere affects the proportion of the three; (8) Wherein, I Riback The atmospheric background radiance, I Sun ​​​The received direct solar radiance. I Sca The received solar diffuse radiance, I Ground The received ground reflected radiance; The atmospheric path radiation received at a certain point is the superposition of infrared radiation from each layer of the atmosphere in the direction observed by the detector, mainly the thermal radiation of atmospheric and aerosol components in the atmosphere; a highly layered strategy was adopted from the Martian surface, dividing the vertical space from 0 to 120 km into 120 layers, each layer with a thickness of 1 km, to achieve a precise correspondence with the vertical distribution of atmospheric components. The mathematical formula for calculating the atmospheric path radiance received at the observation point is: (9) in, T j For the first j Temperature of the layer of atmosphere; τ α ( j The first is caused by the presence of atmospheric absorption. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ β ( j The first is caused by the presence of atmospheric scattering. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ b This represents the total atmospheric transmittance from the radiative transfer boundary layer to the observation point. L b ( λ , T b () represents the radiance of the target infrared radiation transmission boundary layer; m The total number of atmospheric layers; T b This refers to the surface temperature of Mars. λ The wavelength of an electromagnetic wave; Based on Mie theory and Monte Carlo method, this invention fully considers key factors such as dust particle scattering and absorption, solar altitude angle, and atmospheric structure, and can relatively realistically reflect the radiation characteristics of Martian dust environment, significantly improving the simulation accuracy of complex Martian atmospheric environment.

[0022] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0023] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment, characterized by: Includes the following steps: Step 1: Modeling the characteristics of the Martian atmosphere, including: Step 1.1: Combine data, dust patterns, and normal distribution characteristics to construct a hierarchical atmospheric particle input model; Step 1.2: Based on Mie scattering theory and Martian atmospheric parameters, calculate the scattering characteristics and radiative transfer of particles; Step 2: Solve for atmospheric radiation transfer; Step 3, multi-parameter coupled spectral response analysis, including: Step 3.1: Transmittance calculation; Step 3.2: Radiance calculation.

2. The method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment according to claim 1, characterized in that: In step 1.1, using data from the Mars probe and the equivalent particle size and height distribution patterns of Martian dust, the particle size distribution is described according to the log-normal distribution. Based on the effective particle radius and effective width distribution relationship given by the MCD, the particle input for each atmospheric layer is ensured to conform to a normal distribution. （1） in, r 0 is the geometric mean diameter; σ It is the standard deviation; n(r) It is the particle size probability distribution function; r represents the particle size of the sand and dust. （2） （3） in, r eff It is the effective particle radius; v eff It is the effective variance.

3. The method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment according to claim 2, characterized in that: In step 1.2, the complex refractive index of Martian dust minerals is combined with the Mie theory to calculate single-particle scattering characteristic parameters, including extinction coefficient, scattering phase function, and asymmetry factor; and a vertical profile of Martian atmospheric temperature, pressure, and composition is set according to the Martian atmospheric database, taking into account the absorption of radiation and Rayleigh scattering by each layer of gas. （4） （5） （6） in, Q ext Extinction efficiency factor Q sca Is it the scattering efficiency factor? Q abs This is the absorption efficiency factor. a n , b n denoted as Mie scattering coefficient; n is the number of terms in the series expansion; This characterizes the relative size of the particle to the wavelength of the incident light; R e is the operator for extracting the real part.

4. The method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment according to claim 3, characterized in that: In step 2, the Martian atmosphere is vertically divided into several layers of equal height. The Monte Carlo algorithm is used to solve the radiative transfer integral equation and trace the light path from the sun's incident point to the probe point, including multiple scattering and surface reflection paths.

5. The method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment according to claim 4, characterized in that: Step 3.1, the transmittance calculation includes the following steps: By performing a rigorous line-by-line integration based on the wavenumber, the wavenumber interval Δ can be obtained. v Average transmittance within The expression is: （7） in, S l The absorption intensity of the spectral line per unit path length; The half-width of the spectral line; v 0,l △ is the center wavenumber of the spectral line; v T is the width of the wavenumber integration interval; v ( u ) represents the wave number v Transmittance at that location; u This represents the absorption path length. The optical thicknesses of the Zhurong, Curiosity, and Opportunity rover in the visible light band, obtained from the MCD database, were used to verify the accuracy of the model application.

6. The method for calculating the sky radiance and atmospheric transmittance of a Martian dust environment according to claim 7, characterized in that: Step 3.2, the radiance calculation includes the following steps: The amount of solar radiation received by any horizontal surface on Mars includes three parts: direct solar radiation, scattered solar radiation, and albedo. The different levels of atmospheric transparency affect the proportion of these three components. （8） in, I Riback Atmospheric background radiance, I Sun The received direct solar radiance. I Sca The received solar diffuse radiance, I Ground The received ground reflected radiance; The atmospheric path radiation received at a certain point is the superposition of infrared radiation from each layer of the atmosphere in the direction observed by the detector, mainly the thermal radiation of atmospheric and aerosol components in the atmosphere; a highly layered strategy was adopted from the Martian surface, and the vertical spatial division achieved a precise correspondence with the vertical distribution of atmospheric components. The mathematical formula for calculating the atmospheric path radiance received at the observation point is: （9） in, T j For the first j Temperature of the layer of atmosphere; τ α ( j The first is caused by the presence of atmospheric absorption. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ β ( j The first is caused by the presence of atmospheric scattering. j Atmospheric transmittance from the first layer of atmosphere to the observation point; τ b This represents the total atmospheric transmittance from the radiative transfer boundary layer to the observation point. L b ( λ , T b () represents the radiance of the target infrared radiation transmission boundary layer; m The total number of atmospheric layers; T b This refers to the surface temperature of Mars. λ The wavelength of the electromagnetic wave.

7. The method for calculating the sky radiance and atmospheric transmittance in a Martian dust environment according to claim 5, characterized in that: In step 2, using the atmospheric parameter information input in step 1, a layered model is constructed at a distance of 120 km from the Martian surface. The optical parameters of the dust are calculated independently for each layer, with the Martian solar constant taken as an average value of 589 W / m. 2 The extinction efficiency factor and scattering phase function of Martian dust particles are calculated using the Mie scattering calculation formulas (4)-(6); the atmospheric transmittance is calculated by integral of the transmittance line by line according to formula (7); In the process of solving for sky radiance, the radiation flux contributed by direct solar radiation, atmospheric gas thermal radiation, multiple scattering by dust particles, and surface reflection is considered. A path tracing algorithm based on the Monte Carlo integration strategy is used to simulate the radiative transfer behavior of different incident paths; The radiative transmission of each ray path is calculated based on the properties of the medium it passes through and its interaction behavior. Multipath statistics are then performed to obtain the sky radiance distribution per unit solid angle and the total transmittance from the direction of the sun to the Earth's surface.

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