A method for total dose analysis of satellites based on ray tracing technology

Abstract

The present invention provides a total dose analysis method for satellites based on ray tracing technology, belonging to the technical field of satellite space environment analysis. The method includes: S1, constructing a geometric body corresponding to the satellite, adding material properties and detection points; S2, setting relevant parameters in a ray tracing program based on GEANT4, performing sector division of the spatial solid angle according to the range of polar angle, azimuth angle and the number of divisions, then performing random ray emission and ray tracing calculation based on logarithmic mean summation to obtain depth data of each of the detection points and each of the sector regions; S3, obtaining a depth-dose curve; S4, performing dose calculation for multiple detection points with multiple depth-dose curves to obtain the total dose of a specified detection point. S5, performing various dose analyses that are visual and interactive. The present invention can achieve the emission of random rays and the averaging of results, improve the representativeness of data within the sector region, and is conducive to enhancing interactivity and user experience.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite space environment analysis, and particularly to a method for analyzing the total dose of a satellite based on ray tracing technology. Background Art

[0002] During the on-orbit operation of a satellite, it faces complex space radiation environment factors and will be affected by space ionizing radiation for a long time. High-energy charged particles are the main radiation environment directly affecting the on-orbit service life and reliability of radiation-sensitive devices in the satellite. Among them, the electrons in the Earth's radiation belts, the protons in the Earth's radiation belts, and solar protons are the main radiation sources. The long-term accumulation of electrons and protons in the space radiation environment in sensitive devices will produce the total ionization dose effect and displacement damage effect, which will further cause changes in the electrical performance parameters of sensitive components and lead to abnormal operation of satellite equipment. Therefore, in order to ensure that the satellite will not be damaged or fail due to space radiation effects during its on-orbit operation, during the satellite development process, it is necessary to analyze the total ionization dose effect of some key devices or components on the satellite surface and inside that are sensitive to space radiation according to the charged particle radiation environment of the actual operating orbit of the satellite.

[0003] A satellite has a three-dimensional complex structure, and the absorbed dose at a certain point or a sensitive component in its cabin is generally calculated through two methods. One is the fan-shaped analysis method based on ray tracing, and the other is the Monte Carlo method. Among them, the Monte Carlo method has high calculation accuracy, but slow calculation speed and does not provide information related to direction, making it difficult to guide radiation hardening. The fan-shaped analysis method has a fast calculation speed, is suitable for rapid estimation in the design stage, can provide information related to azimuth, and is suitable for guiding radiation hardening technology. However, the existing radiation analysis tools based on the fan-shaped analysis method have the following problems: First, the operation of adding detection points is cumbersome and difficult to use. Second, the calculation process is fixed, and the shielding depth data is not fully utilized. Third, the sampling of the fan-shaped area depends on the division density, and the data representativeness of a single fan-shaped area is poor. Fourth, it is not suitable for analyzing a continuously changing space environment. Fifth, the interactivity is poor. Therefore, it is necessary to improve the process and algorithm of the fan-shaped analysis method in the above aspects. Summary of the Invention

[0004] In view of the above problems in the prior art, the present invention provides a method for analyzing the total dose of a satellite based on ray tracing technology.

[0005] To achieve the above object, the present invention is specifically realized through the following technologies:

[0006] The present invention provides a method for analyzing the total dose of a satellite based on ray tracing technology, including the following steps:

[0007] S1. Construct a geometric body, add material properties and detection points;

[0008] S2. Set relevant parameters in the ray tracing program based on GEANT4, and perform sector division of the solid angle in space according to the ranges of the polar angle, azimuth angle, and the number of divisions. Subsequently, perform random ray emission and ray tracing calculations based on logarithmic mean accumulation to obtain the depth data of each of the detection points and each of the sector regions.

[0009] S3. Obtain the depth-dose curve.

[0010] S4. Perform dose calculations for multiple detection points against multiple depth-dose curves to obtain the total dose of the specified detection points.

[0011] Further, in step S1, the specific operation of constructing the geometric body is: use a program based on Gmsh and Qt to import the CAD file of the satellite to construct the geometric body.

[0012] The specific operation of adding the material properties is: based on the material data provided by the GEANT4 program, add the material properties to the geometric body.

[0013] The specific operation of adding the detection points is: perform grid processing on the geometric body to which the material properties are added, calculate the rectangular bounding box of each geometric body, and then add the detection points.

[0014] Further, the adding method of the detection points is:

[0015] By the user inputting a space coordinate system, and then adding the detection points according to the space coordinate system.

[0016] Or, by the user selecting the geometric body, and then adding the detection points according to the center or centroid of the selected geometric body.

[0017] Or, by the user selecting the geometric body and setting the number of detection points, and the GEANT4 program automatically adds the detection points evenly on the selected geometric body according to the bounding box of the geometric body.

[0018] Further, in step S1, the material properties include at least one of density, composition, chemical formula, and atomic number.

[0019] Further, in step S2, the parameter settings include: the user respectively sets the sizes of the polar angle and azimuth angle and the number of divisions, the specific options of ray transport, and the mode of the ray path according to the desired solid angle size.

[0020] For each of the detection points, calculate the size of the solid angle according to the first formula, and the first formula includes:

[0021]

[0022] Among them, are the minimum and maximum values of the azimuth angle of the sector region, and θ L , θ u are the minimum and maximum values of the polar angle of the sector region.

[0023] Furthermore, in step S2, the ray tracing calculation method based on logarithmic mean accumulation is as follows:

[0024] The original shielding depth results in each sector region are logarithmically averaged according to the second formula to obtain the depth data, and the second formula includes:

[0025]

[0026] Among them, b is the offset to avoid too small logarithm values, N is the number of data for averaging, and x Logmean is the result of logarithmic averaging.

[0027] Furthermore, in step S3, the depth-dose curve is obtained by: importing user files, calculating through the energy spectrum imported by the user, or importing the environmental energy spectrum file, determining the start and end time and the step size, and performing batch calculations.

[0028] Furthermore, the specific operation of step S4 is:

[0029] First, perform data pre-calculation: for the given dose-depth curve, calculate the logarithm of its depth data and dose;

[0030] Secondly, perform interpolation weighted accumulation: between each group of dose-depth curves and the depth data of each detection point, use the binary search method to find the interval that meets the x range, satisfying x≥x i , x≤x i+1 , and the corresponding dose value interval boundaries are y i , y i+1 , calculate the interpolation result of the dose-depth curve according to the third formula and the method of slope prediction and calculate the solid angle size according to the first formula, divide by the total solid angle 4π of the spherical surface to obtain the weight of each sector region, and perform weighted accumulation to obtain the total dose of the specified detection point;

[0031]

[0032] Among them, is the interpolation result, corresponding to the dose; x represents the depth data participating in the interpolation.

[0033] Furthermore, after step S4, the following steps are also included:

[0034] S5. Perform visual and interactive multiple-dose analysis.

[0035] Furthermore, the specific operation of performing the total dose analysis is as follows: By the user inputting the lower limit ratio and upper limit ratio of the shielding depth, selecting the depth unit, sorting the depth data of each of the detection points in an increasing order of depth, calculating the corresponding upper limit and lower limit of the shielding depth value, and cumulatively calculating the corresponding solid angle proportion, dose proportion, and dose within the depth interval.

[0036] The present invention overcomes the drawbacks of the existing fan-shaped analysis method based on the ray tracing method, can flexibly add detection points to sensitive components in a three-dimensional complex structure, can automatically add detection points relying on the center of a geometric body, and has improved the calculation process, can perform multi-environment analysis on a continuously changing spatial environment, and simultaneously realizes the corresponding data analysis and processing functions. In addition, improvements have been made in the ray tracing technology, which can realize the emission of random rays and the averaging of results, improve the representativeness of data in the fan-shaped area, is conducive to enhancing the interactivity and user experience, and realizes an appropriate graphical user interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is the interface diagram of constructing a geometric body by importing the CAD file of a satellite in Embodiment 1 of the present invention;

[0039] Figure 2 It is the distribution diagram of the shielding depth in Embodiment 1 of the present invention;

[0040] Figure 3 It is the interface diagram of obtaining the depth-dose curve by inputting the energy spectrum file in Embodiment 1 of the present invention;

[0041] Figure 4 It is the interface diagram of obtaining the depth-dose curve by importing the environmental energy spectrum file in Embodiment 1 of the present invention;

[0042] Figure 5 It is the flowchart of the slope prediction method in Embodiment 1 of the present invention;

[0043] Figure 6 It is the single-point multi-environment interaction view of selecting the time period mode in Embodiment 1 of the present invention;

[0044] Figure 7 A single-point multi-environment interactive view in the accumulation mode is selected for embodiment 1 of the present invention;

[0045] Figure 8 This is a total dose analysis view of Example 1 of the present invention. DETAILED DESCRIPTION

[0046] It should be noted that, unless otherwise specified, the embodiments and features within the embodiments of the present invention may be combined with one another. Furthermore, the terms "comprising," "containing," and "having" are non-restrictive and may include other steps and components that do not affect the results. Unless otherwise specified, materials, equipment, and reagents were all commercially available.

[0047] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0048] An embodiment of the present invention provides a satellite total dose analysis method based on ray tracing technology, comprising the following steps:

[0049] S1. Construct the geometry corresponding to the satellite, add material properties and detection points;

[0050] For example, see Figure 1 ( Figure 1 The satellite's CAD file is imported using a Gmsh- and Qt-based program to construct the geometry. Based on the rich material data provided by GEANT4, material properties are added to the geometry. The geometry is then meshed and the rectangular bounding box of each geometry is calculated, allowing for the subsequent automatic addition of detection points based on the geometry's center.

[0051] Compared to the single, cumbersome coordinate adding method used in similar software, this invention implements an interactive point selection operation based on the VTK framework, providing a variety of detection point addition methods. The interactive point selection method is simpler than similar software. There is no need to view and enter coordinates for each geometric body. Users can manually add detection points one by one according to their wishes. By entering coordinates or geometric body names, users can repeatedly add detection points. In step S1, the detection points only need to be converted into coordinates relative to the specific geometry.

[0052] Specifically, there are three ways to add detection points. The first is for the user to input the spatial coordinate system, and then add detection points based on the spatial coordinate system; the second is for the user to select the geometric body, and then add detection points based on the center or centroid of the selected geometric body; the third is for the user to select the geometric body and set the number of detection points. According to the bounding box of the geometric body, the program automatically adds detection points evenly on the selected geometric body.

[0053] In step S1, the material properties include density, composition, chemical formula, atomic number, etc.

[0054] S2. Set relevant parameters in the ray tracing program based on GEANT4. Perform fan-shaped division of the solid angle according to the ranges of polar angle, azimuth angle, and the number of divisions, and then perform random ray emission and ray tracing calculation based on logarithmic mean accumulation to obtain the depth data for each detection point and each fan-shaped region.

[0055] Compared with the common single ray emission based on the center of the fan-shaped region and the ordinary averaging method, the random ray emission and logarithmic mean method improve the representativeness of the cumulative value in each fan-shaped region, can effectively reflect the weak parts, and help to reflect the true dose level in the region.

[0056] The parameter settings include: the user sets the polar angle, azimuth angle, and the number of divisions respectively according to the desired solid angle size, the specific options for ray transport, and the mode of the ray path. For each of the detection points, calculate the size of the solid angle according to the first formula, and the first formula includes:

[0057]

[0058] where are the minimum and maximum values of the azimuth angle of the fan-shaped region, and θ L , θ u are the minimum and maximum values of the polar angle of the fan-shaped region.

[0059] According to the above parameter settings, see Figure 2 , based on the division of azimuth angle and polar angle, within the given solid angle range, perform random sampling of azimuth to achieve the emission of random rays, calculate the intersection length of each ray with the material, accumulate the shielding depth according to the product of this length and the material density value, perform logarithmic mean on the original shielding depth results in each obtained fan-shaped region according to the second formula to obtain the depth data for each fan-shaped region, and write the results into a data file. The second formula includes:

[0060]

[0061] where b is the offset to avoid too small logarithmic values, N is the number of data for averaging, and x Logmean is the result of logarithmic mean.

[0062] S3. Obtain the depth-dose curve; there are three ways to obtain the depth-dose curve: import the user file, calculate by importing the energy spectrum by the user, or import the environmental energy spectrum file, determine the start and end time and step size, and perform batch calculation.

[0063] The first way to import user files means that the user directly imports the dose-depth curve. The second way, which calculates by importing the energy spectrum by the user, means that the user imports the differential energy spectrum of captured electrons, protons or solar protons and sets the mission life, and the program automatically calculates the corresponding depth-dose curve, as shown in Figure 3 The third way, which imports the environmental energy spectrum file by the user, means that the user selects the environmental energy spectrum file, sets the specific start and end time and step size, and obtains multiple dose-depth curves according to the method of averaging the energy spectrum within the window used by the user, as shown in Figure 4 .

[0064] S4. Perform dose calculations for multiple detection points on multiple depth-dose curves to obtain the total dose of the specified detection point;

[0065] In the dose calculation part of the present invention, the logarithmic interpolation method is adopted. For some depth data beyond the range of the dose-depth curve, reasonable slope prediction can be carried out. The specific process is shown in Figure 5 , where the X value in the figure represents the shielding depth data participating in the interpolation, and Y represents the dose value. Those that do not meet the slope prediction conditions are calculated according to the end point of the curve, and those that meet the slope prediction conditions are calculated according to the normal process. Performing slope prediction processing on the depth-dose curve can improve the calculation efficiency. Compared with the common process of integrating shielding depth and dose calculation, the method of the present invention decomposes the process. After calculating the shielding depth data once, subsequent analysis can be carried out multiple times.

[0066] The specific operation of step S4 is as follows:

[0067] First, perform data pre-calculation: For the given dose-depth curve, first calculate the logarithm of its depth data and dose; for the dose-depth curve representing a time period, perform accumulation between curves to obtain the total dose-depth curve, and then calculate the logarithm of its depth and dose.

[0068] Secondly, perform interpolation weighted accumulation: Between each group of the dose-depth curves and the depth data of each detection point, use the binary search method to find the interval that meets the x range, satisfying x≥x i , x≤x i+1 , and the corresponding dose value interval boundaries are y i , y i+1 , calculate the interpolation result of the dose-depth curve according to the third formula (logarithmic interpolation calculation formula) and the method of slope prediction (see Figure 5 ) and calculate the solid angle size according to the first formula, divide it by the total solid angle 4π of the spherical surface to obtain the weight value of each sector area, and perform weighted accumulation to obtain the total dose of the specified detection point. The third formula includes:

[0069]

[0070] Among them, is the interpolation result, corresponding to the dose; x represents the depth data value participating in the interpolation, and the interval of its corresponding dose-depth curve satisfies x≥x i , x≤x i+1 , and the corresponding curve dose value is y i , y i+1 .

[0071] To visually observe the total dose analysis result, preferably, after step S4, step S5 is further included.

[0072] S5. Perform visual and interactive multiple-dose analyses. Process the data after interpolation calculation into an analysis view to achieve visualization for intuitively observing the data. The multiple-dose analysis modes are as follows:

[0073] Single-point multi-environment interactive view analysis: The user selects a detection point and a mode, and the mode is divided into accumulation and time period. Use this detection point to draw a line graph of the dose calculation results of each depth-dose curve, and the effect is shown in Figure 6 and Figure 7 .

[0074] Multi-point single-environment interactive view analysis: Give the maximum, minimum, average value of the dose for each time period of each detection point, and the corresponding time period of the maximum time period dose.

[0075] Total dose analysis: The user inputs the lower limit ratio and upper limit ratio of the shielding depth, selects the depth unit, sorts the depth data of each detection point in ascending order of depth, calculates the corresponding upper and lower limits of the shielding depth value, accumulatively calculates the corresponding solid angle ratio, dose ratio, and dose within the depth interval, and gives a table feedback. See Figure 8 .

[0076] The intuitive and interactive interface, as well as the method of window averaging and multiple-dose curve calculations in step S3, make the present invention suitable for multi-environment and multi-detection point analyses, and can give analysis data such as the instantaneous and cumulative change trends of the dose at each detection point, and the dose ratio corresponding to the depth ratio.

[0077] The present invention overcomes the drawbacks of the existing fan-shaped analysis method based on the ray tracing method, can flexibly add detection points for sensitive components in a three-dimensional complex structure, can automatically add detection points relying on the center of a certain geometric body, and has improved the calculation process, can perform multi-environment analyses on a continuously changing space environment, and simultaneously realizes the corresponding data analysis and processing functions. In addition, improvements have been made in the ray tracing technology, which can realize the emission of random rays and the averaging of results, improve the representativeness of data in the fan-shaped region, is beneficial to enhancing interactivity and user experience, and realizes an appropriate graphical user interface.

[0078] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out according to the conditions recommended by the manufacturers.

[0079] Embodiment 1

[0080] A satellite total dose analysis method based on ray tracing technology includes the following steps:

[0081] S1. As shown in Figure 1 , import the satellite geometry structure, obtain the geometry list, display it on the program interface, select the geometry to be analyzed, and based on the geometry bounding box, add a batch of detection points;

[0082] S2. Set the required solid angle division parameters. The polar angle is divided into 30 parts from 0° to 180°, and the azimuth angle is divided into 60 parts from 0° to 360°. Use the ray tracing method to calculate the shielding depth based on logarithmic mean accumulation, obtain the depth data of each detection point and each sector area, and the calculation results are as shown in Figure 2 ;

[0083] Taking a sector area as an example: the range of the polar angle is from 78° to 84°, and the range of the azimuth angle is from 48° to 54°. According to the first formula, calculate the size of the solid angle: (54° - 48°) × (cos78° - cos84°) ≈ 0.6203. Divide it by 4π as the dose weight of this sector area, and perform ray tracing calculations in random directions within this area; for example, a set of emission angles are: polar angle 80.73°, azimuth angle 50.42°; obtain the following shielding depth data: 8.205, 8.138, 8.252, 13.977, 13.679, with the unit of g / cm^2. According to the second formula, take the b value as 0.001, and calculate to get about 2.313, and correspondingly, x Logmean is about 10.107, with the unit of g / cm^2.

[0084] S3. Select to calculate the dose-depth curve based on the input of the energy spectrum file, as shown in Figure 3 , fill in the mission duration (15 years in this embodiment) and the particle type (captured belt electrons in this embodiment); it is also possible to import the environmental energy spectrum file, as shown in Figure 4 , fill in the date range (January 1, 2017 - January 10, 2017 in this embodiment) and the step size (4 hours in this embodiment), and calculate multiple dose-depth curves.

[0085] S4. Perform dose calculation on the shielding depth data and dose-depth curve obtained in step S3. The slope prediction is carried out according to the Figure 5 process shown.

[0086] Taking the data in step S2 as an example, from the depth data value of 10.107, the corresponding part of the dose-depth curve can be obtained by the binary search method: depth 10.00 g / cm^2, dose 5.380e+1 rad; depth 10.59 g / cm^2, dose 5.020e+1 rad, without exceeding the data range of the dose-depth curve. According to the third formula, the logarithmic interpolation result of the dose can be obtained as 5.313e+1 rad. Using the weight obtained in step S2, the dose value of this region can be obtained as 2.623 rad. By analogy, the total dose is obtained by accumulating all the fan-shaped regions.

[0087] S5. Taking the dose analysis of a single point in multiple environments as an example, the user first selects the detection point, and then selects the view mode of period (see Figure 6 shown) or accumulation (see Figure 7 shown). Taking the environment as the abscissa and the dose results obtained by performing dose calculation on all dose-depth curves as the ordinate, a line chart is drawn.

[0088] For the total dose analysis, the user inputs the upper and lower limits of the depth ratio (in this embodiment, the lower limit is 0% and the upper limit is 10%), selects the depth unit (in this embodiment, it is mmAl), and the program sorts, accumulates, and converts the shielding data of the fan-shaped region calculated in step S4 to obtain a table feedback. See Figure 8 , and the table provides analysis results such as the proportion and magnitude of the dose within the depth interval.

Claims

1. A method for satellite total dose analysis based on ray tracing technology, characterized in that, It includes the following steps: S1. Construct a geometric body corresponding to the satellite, and add material properties and detection points; S2. Set relevant parameters in the ray tracing program based on GEANT4. According to the ranges of polar angle, azimuth angle and the number of divisions, conduct sector division of the solid angle of space, and then conduct random ray emission and ray tracing calculation based on logarithmic mean accumulation to obtain the depth data of each of the detection points and each sector area; S3. Obtain the depth-dose curve; S4. Conduct dose calculation for multiple detection points against multiple depth-dose curves to obtain the total dose of the specified detection points.

2. The satellite total dose analysis method according to claim 1, wherein In step S1, the specific operation of constructing the geometric body is: use the program based on Gmsh and Qt to import the CAD file of the satellite to construct the geometric body; The specific operation of adding the material properties is: based on the material data provided by the GEANT4 program, add the material properties to the geometric body; The specific operation of adding the detection points is: conduct grid processing on the geometric body to which the material properties are added, calculate the rectangular bounding box of each geometric body, and then add the detection points.

3. The satellite total dose analysis method according to claim 2, wherein The adding method of the detection points is: By the user inputting a space coordinate system, and then adding the detection points according to the space coordinate system; Or, by the user selecting the geometric body, and then adding the detection points according to the center or centroid of the selected geometric body; Or, by the user selecting the geometric body and setting the number of detection points, and according to the geometric body bounding box, the GEANT4 program automatically adds the detection points evenly on the selected geometric body.

4. The satellite total dose analysis method according to claim 1, characterized in that In step S1, the material properties include at least one of density, composition, chemical formula and atomic number.

5. The satellite total dose analysis method according to claim 1, characterized in that, In step S2, the parameter setting includes: the user respectively sets the magnitudes of the polar angle and the azimuth angle and the number of divisions, the specific options of ray transport and the mode of ray path according to the desired solid angle size of space; For each of the detection points, calculate the size of the solid angle of space according to the first formula, and the first formula includes: ； wherein, are the minimum and maximum values of the azimuth angle of the sector area, are the minimum and maximum values of the polar angle of the sector area.

6. The satellite total dose analysis method according to claim 1, wherein In step S2, the ray tracing calculation method based on logarithmic mean accumulation is: conduct logarithmic mean on the original shielding depth results in each sector area according to the second formula to obtain the depth data, and the second formula includes: ； where b is an offset to avoid too small values, and N is the number of data for averaging, which is the result of logarithmic averaging.

7. The total dose analysis method of a satellite according to claim 1, wherein In step S3, the obtaining method of the depth-dose curve is: import the user file, conduct calculation by the user importing the energy spectrum or import the environmental energy spectrum file, determine the start and end time and the step size, and conduct batch calculation.

8. The total dose analysis method of a satellite according to any one of claims 1-7, characterized in that The specific operation of step S4 is: First, for the given depth-dose curve, calculate the logarithm of its depth data and dose; Secondly, between each group of said depth-dose curves and the depth data of each said detection point, the binary search method is used to find an interval that meets the range and satisfies , and the corresponding dose value interval boundary is . The interpolation result of the depth-dose curve is calculated according to the third formula and the slope prediction method , and the size of the solid angle in space is calculated according to the first formula, and divided by the total solid angle of the spherical surface to obtain the weight of each said sector area, and weighted accumulation is performed to obtain the total dose of the specified said detection point. The third formula includes: ； Among them, is the interpolation result, corresponding to the dose; represents the depth data participating in the interpolation.

9. The satellite total dose analysis method according to claim 1, characterized in that After step S4, the following steps are further included: S5. Conduct various dose analyses of visualization and interaction.

10. The satellite total dose analysis method according to claim 9, wherein In step S5, the specific operation for performing the total dose analysis is as follows: By inputting the lower limit ratio and upper limit ratio of the shielding depth by the user, selecting the depth unit, sorting the depth data of each of the detection points in ascending order of depth, calculating the corresponding upper and lower limits of the shielding depth value, and cumulatively calculating the corresponding spatial solid angle ratio, dose ratio, and dose within the depth interval.

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