Multi-source data-based lunar surface sampling area site selection method

Abstract

The invention relates to a lunar surface sampling area site selection method based on multi-source data, and belongs to the technical field of deep space exploration. Determining the site selection constraint of the lunar surface sampling area; integrating site selection constraints, and carding available data sources; determining an analysis model and an analysis chart corresponding to each data source; establishing a site selection constraint analysis method; dividing a site selection constraint analysis stage into a sampling area rapid progressive analysis stage and a fine analysis stage; carrying out analysis stage classification and distribution on each site selection constraint analysis method, sorting each site selection constraint analysis method, and formulating a screening process of a sampling region; carrying out rapid progressive analysis on the sampling area to obtain an optional range covering the final sampling area; carrying out fine analysis on the selectable range covering the final sampling area to obtain several alternative sampling areas; optimal conditions are set for the alternative sampling areas, and a final sampling area is confirmed; according to the method, the site selection efficiency can be improved, the credibility of a data source is enhanced, and balanced optimization selection of rapid asymptotic and refined analysis of the sampling area is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of deep space exploration and relates to a lunar surface sampling area site selection method based on multi-source data. Background Art

[0002] Sampling return is one of the most important forms of lunar exploration at present. The site selection of the lunar probe's sampling area is crucial to achieving the mission objectives and may directly affect the probe's landing / takeoff safety, lunar surface work, sample value, etc. The selection of the sampling area needs to be combined with the mission objectives, probe design capabilities, and existing lunar remote sensing or in-situ detection data to conduct a comprehensive evaluation of the lunar surface characteristics, thereby supporting the site selection of the sampling area.

[0003] The landing / sampling area site selection work has been carried out for the multiple landing / sampling missions completed at home and abroad, and a certain technical foundation has been formed in the field of constraint identification, terrain analysis and other site selection related technologies. The existing lunar landing / sampling area site selection methods usually consider the constraints step by step according to the mission relevance, use a single data source to screen a certain constraint threshold, analyze a certain terrain condition of the lunar surface sampling area, and then screen or normalize it step by step for scoring and evaluation.

[0004] With the diversification and complexity of lunar exploration forms and exploration areas, and the increasing requirements of scientific and engineering goals, the constraints involved in the site selection of lunar sampling areas have gradually increased and are coupled with each other, and the need to shorten the site selection cycle has become more urgent; and with the successful implementation of lunar remote sensing mapping and landing exploration missions in various countries, as well as the widespread application of machine learning methods, the categories of lunar-related data sources and the resolution types of similar data have increased significantly. The use of multi-data source fusion analysis will significantly increase the credibility of site selection results, and at the same time, the efficiency of site selection can be improved through the optimal use of multi-source data. Therefore, a site selection method is urgently needed to identify the necessity, coupling, and screening efficiency of various constraints, fully combine the existing multi-source data, integrate and sort the multiple constraints, and establish a multi-source data analysis and evaluation method to achieve a balanced optimization selection of sampling areas with rapid asymptotic and refined analysis. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and propose a lunar surface sampling area site selection method based on multi-source data, which can improve the site selection efficiency, enhance the credibility of the data source, and achieve balanced optimization selection of rapid asymptotic and refined analysis of the sampling area.

[0006] The solution of the present invention is:

[0007] A lunar surface sampling area site selection method based on multi-source data, comprising:

[0008] Confirm the site selection constraints of the lunar surface sampling area;

[0009] Integrate site selection constraints and sort out available data sources; determine the analysis model and analysis diagram corresponding to each data source;

[0010] Establish a site selection constraint analysis method; divide the site selection constraint analysis stage into a rapid and progressive analysis stage of the sampling area and a refined analysis stage; classify and allocate the analysis stages of each site selection constraint analysis method, rank each site selection constraint analysis method, and formulate a screening process for the sampling area;

[0011] Conduct rapid progressive analysis of the sampling area to obtain optional ranges covering the final sampling area;

[0012] Conduct detailed analysis on the optional range covering the final sampling area and obtain several candidate sampling areas;

[0013] Set preferred conditions for the alternative sampling areas and confirm the final sampling area.

[0014] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the site selection constraints include scientific constraints and engineering constraints;

[0015] The scientific constraints are: the sampling area is selected on the far side of the moon to obtain samples from the far side of the moon; at the same time, the sampling area is selected in the SPA area to obtain samples from this body of land; areas of different geological years are selected for landing and sampling;

[0016] Engineering constraints include terrain slope, track elevation safety, rocks, impact craters, and terrain obstruction;

[0017] Terrain slope: According to the design status of the lander, select an area with a sufficiently gentle slope to carry out landing to ensure the landing stability of the lander;

[0018] Track elevation safety: The terrain on the back side of the moon is very undulating. During the powered descent of the lander, the lander introduces the ranging information of the navigation sensor at a predetermined height to ensure that the track elevation fluctuation after the ranging information is introduced is as small as possible to ensure landing safety; during the takeoff and ascent process of the return, ensure that the ascender does not interfere with the mountains on its ascent track;

[0019] Stones: Avoid areas with stones.

[0020] Impact craters: Avoid areas with small and medium-sized impact craters;

[0021] Terrain occlusion: The sampling area should avoid occlusion caused by the surrounding terrain to prevent it from affecting measurement, control and lighting conditions.

[0022] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the analysis of terrain slope, track elevation safety, terrain shielding and crater depth in the engineering constraints is performed using a digital elevation model, which is the DEM; the analysis of rocks and crater morphology in the engineering constraints is performed using an orthophoto model and a stone abundance map; wherein the orthophoto model is the DOM; and the analysis of lunar geology in the scientific constraints is performed using a lunar geological map.

[0023] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the site selection constraint analysis method includes a scientific constraint analysis method and an engineering constraint analysis method;

[0024] The scientific constraint analysis method uses existing analysis models and analysis diagrams to quickly narrow the landing range to the SPA area. It does not use complex calculations, but makes basic judgments based on existing scientific results, with a small amount of calculations.

[0025] Engineering constraint analysis methods include terrain slope analysis method, track elevation safety analysis method, stone analysis method, crater analysis method and terrain obstruction analysis method.

[0026] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the terrain slope analysis method is:

[0027] Different slope calculation methods are used for different terrain data sources, including the third-order inverse distance square weighted slope algorithm and the simple differential comparison algorithm of the slope between the detector legs;

[0028] The third-order inverse distance square weighted slope algorithm is:

[0029] Divide the terrain data source into grids; pre-set a threshold, calculate the terrain slope value according to the third-order inverse distance square weighted slope algorithm, and when the terrain slope value is less than the threshold, judge that the grid meets the slope requirement; otherwise, judge that the grid does not meet the slope requirement;

[0030] The simple differential comparison algorithm for the slope between the detector legs and feet is:

[0031] Divide the terrain data source into grids; when there are multiple data grids between the two legs of the probe, consider the slope α1 between the farthest two landing legs at the same time slope (i, j), the slope between the two nearest landing legs α2 slope (i, j), relative height z of the area below the lander down (i,j) three constraints; when the slope α1 slope (i,j) and α2 slope (i,j) is lower than the preset slope threshold θ thr , and the relative terrain elevation z under the detector down(i,j) is lower than the height z of the lower end of the thruster relative to the lunar surface down-thr , it is judged that the grid meets the slope requirement; otherwise, it is judged that the grid does not meet the slope requirement;

[0032] When the resolution of the terrain data object is lower than the detector envelope size, the third-order inverse distance square weighted slope algorithm is used, which has a small amount of calculation and can achieve fast progressive analysis of the sampling area;

[0033] When the resolution of the terrain data object is comparable to the size of the detector envelope, a third-order inverse distance square weighted slope algorithm is used with moderate computational effort to characterize and evaluate the overall landing slope trend of the detector.

[0034] When the resolution of the terrain data object is significantly higher than the size of the detector envelope, a simple differential comparison algorithm of the slope between the detector legs is used to finely consider the elevation difference between the leg landing points and analyze whether the relative elevation of the lunar surface below the detector will interfere with the thruster equipment below the detector and affect the landing stability.

[0035] The terrain slope safety layer is formed by using data sources with different resolutions, and different layers are superimposed according to the resolution to form a total slope safety layer:

[0036] α slope_sgn (i,j)=α slope_sgn (i,j,1)⊙...⊙α slope_sgn (i,j,k)...⊙α slope_sgn (i,j,kmax)

[0037] In the formula, α slope_sgn Mark the matrix for total slope safety;

[0038] (i, j) is the grid coordinate of terrain data source;

[0039] ⊙ is the matrix dot multiplication operation;

[0040] k is the number of markers for the slope calculation method;

[0041] Based on the slope safety master map, the comprehensive evaluation results of terrain slope analysis are obtained.

[0042] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the track elevation analysis method is:

[0043] For different planned landing points on the lunar surface, the nominal and error tracks are fitted according to the orbit and GNC strategies, and the elevation values ​​on the DEM are read under the track;

[0044] The stone analysis method is:

[0045] Different rock analysis methods were used for different data sources; rocks affect the safe landing and sampling process;

[0046] In the rapid progressive analysis stage, the rock abundance map data is used for coarse screening; the resolution of the rock abundance map data is less than 100m / pixel;

[0047] The screening method is: pre-set the stone abundance threshold A rock_thr ; When the stone abundance in the analyzed area is less than the stone abundance threshold, the stone distribution requirements of the grid are determined;

[0048] In the detailed analysis stage, DOM data with a resolution of 1m is used to complete the analysis of stone abundance and stone size; multi-dimensional stone analysis is carried out on the planned sampling areas, and stone safety is confirmed in the proposed sampling areas.

[0049] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the impact crater analysis method is:

[0050] Through image and terrain recognition, DOM data with a resolution of 1m is used to identify the shape of the impact crater and obtain the distribution of its diameter and density. Then, a DEM with a resolution of 1m is used to analyze the depth of the impact crater and obtain the depth-to-diameter ratio analysis results. Based on the depth-to-diameter ratio analysis results, the safety of the impact crater in the proposed sampling area is confirmed.

[0051] The depth-to-diameter ratio of the impact crater should meet the following ratio requirements:

[0052] Y=H crater / D crater

[0053] H crater ≈a×D crater b

[0054] Ratio crater (Y>Y crater_thr )<Ratio crater_thr

[0055] Where Y is the depth-to-diameter ratio of the impact crater;

[0056] H crater is the depth of the impact crater;

[0057] D crater is the diameter of the impact crater;

[0058] a and b are constants;

[0059] Y crater_thr Setting a threshold for the crater depth-to-diameter ratio;

[0060] Ratio crater (Y>Ycrater_thr ) is the aspect ratio greater than Y crater_thr The proportion of impact craters;

[0061] Ratio crater_thr is the corresponding proportion threshold;

[0062] The terrain occlusion analysis method is:

[0063] A large-scale comparative analysis of the terrain in the proposed sampling area and its surroundings is carried out. The main method is to radiate rays 360° outward from the analyzed point, calculate the terrain occlusion angles in different directions along the rays, and compare them with the illumination angle threshold α illum And the measurement and control angle threshold α con By comparison, when the terrain occlusion angle is less than the illumination angle threshold α illum And the measurement and control angle threshold α con When the terrain of the analyzed point is judged to have no influence on the illumination and measurement and control requirements of the detector on the lunar surface; otherwise, the terrain of the analyzed point is judged to have influence on the illumination and measurement and control requirements of the detector on the lunar surface.

[0064] In the above-mentioned method of selecting the lunar surface sampling area based on multi-source data, the scientific constraint analysis method, the terrain slope analysis method using the third-order inverse distance square weighted slope algorithm, and the stone analysis method using the stone abundance map data are classified into the rapid progressive analysis stage of the sampling area;

[0065] The terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the probe, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the impact crater analysis method and the terrain shielding analysis method are classified as the refined analysis stage;

[0066] The screening process of the sampling area is as follows:

[0067] Scientific constraint analysis method, terrain slope analysis method using third-order inverse distance square weighted slope algorithm, stone analysis method using stone abundance map data, terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, track elevation safety analysis method, stone analysis method using DOM data with a resolution of 1m, crater analysis method, and terrain occlusion analysis method.

[0068] In the above-mentioned method for selecting lunar surface sampling areas based on multi-source data, the contents of the rapid progressive analysis of the sampling areas are as follows:

[0069] The optional range covering the final sampling area was obtained by sequentially using the scientific constraint analysis method, the terrain slope analysis method using the third-order inverse distance square weighted slope algorithm, and the stone analysis method using stone abundance map data;

[0070] The content of the detailed analysis of the optional range covering the final sampling area is:

[0071] Several candidate sampling areas were obtained by screening step by step through the terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the crater analysis method and the terrain obstruction analysis method.

[0072] In the above-mentioned method for selecting a lunar surface sampling area based on multi-source data, the preferred conditions include:

[0073] Larger safe sampling area: The sampling area for the lunar backside sampling return mission is no less than 15km×6km. Considering the improvement of landing safety, an area with a larger safe sampling area is selected;

[0074] Gentle terrain slope: The slope of the landing site for the lunar backside sample return mission is constrained to be less than 8°. In order to improve landing stability, an area that meets the lower slope requirement is selected.

[0075] More landing opportunities: To make the entire mission more reliable, the lunar backside sample return mission will select associated areas with the ability to land at the nominal time and delay landing, taking into account the impact of on-orbit failures or other factors.

[0076] Higher scientific value: The sampling on the far side of the moon contains rich geological age distribution of lunar samples;

[0077] Fewer rocks and crater distribution: Through high-resolution DEM maps or DOM, impact craters and rocks can be identified, and sampling areas can be selected while avoiding obstacles as much as possible.

[0078] The beneficial effects of the present invention compared with the prior art are:

[0079] (1) The present invention proposes a method for screening site selection constraints using multi-source data, which can increase the credibility of site selection results and improve site selection efficiency by optimizing the use of multi-source data;

[0080] (2) The present invention integrates and sorts multiple constraints, designs a screening method that combines rapid sampling area rapid asymptotics with refined analysis, and achieves high-efficiency and high-quality site selection;

[0081] (3) The present invention takes the approach of first asymptotically approaching the sampling area and then performing fine fusion analysis to focus on the final sampling area, and designs a fusion analysis method of multi-source data and multiple influencing factors, which can improve the site selection efficiency, enhance the credibility of the data source, and achieve a balanced optimization selection of rapid asymptotic and fine analysis of the sampling area. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 This is a flowchart for site selection of lunar surface sampling areas based on multi-source data in the present invention.

[0083] Figure 2 It is a schematic diagram of the screening process of the sampling area of ​​the present invention;

[0084] Figure 3 Schematic diagram of the grid for calculating the slope using the third-order inverse distance square weight of the present invention DETAILED DESCRIPTION

[0085] The present invention will be further described below in conjunction with the embodiments.

[0086] The present invention provides a lunar surface sampling area site selection method based on multi-source data, which can improve site selection efficiency, enhance the credibility of data sources, and achieve balanced optimization selection of sampling areas for rapid asymptotic and refined analysis.

[0087] The site selection method of lunar surface sampling area based on multi-source data, such as Figure 1 As shown, the specific steps include:

[0088] Confirm the site selection constraints of the lunar surface sampling area.

[0089] Site selection constraints include scientific constraints and engineering constraints;

[0090] The scientific constraints are: the sampling area is selected on the back side of the moon to obtain samples from the back side of the moon; at the same time, the sampling area is selected in the SPA area to obtain samples from the land body; areas of different geological years are selected for landing and sampling.

[0091] Engineering constraints include terrain slope, track elevation safety, rocks, impact craters, and terrain obstruction.

[0092] Terrain slope: Based on the design status of the lander, select an area with a sufficiently gentle slope for landing to ensure the landing stability of the lander.

[0093] Track elevation safety: The terrain on the back side of the moon is very undulating. During the lander's powered descent, the lander introduces the ranging information of the navigation sensor at a predetermined altitude to ensure that the track elevation fluctuation after the introduction of the ranging information is as small as possible to ensure landing safety; during the return takeoff and ascent process, it is ensured that the ascender's ascent track does not interfere with the mountains.

[0094] Stones: Avoid areas with stones.

[0095] Impact craters: Avoid areas with small and medium-sized impact craters.

[0096] Terrain occlusion: The sampling area should avoid occlusion caused by the surrounding terrain to prevent it from affecting measurement, control and lighting conditions.

[0097] Integrate the site selection constraints, sort out the available data sources; determine the analysis models and analysis diagrams corresponding to each data source. The analysis of terrain slope, track elevation safety, terrain shielding and impact crater depth in the engineering constraints is analyzed using a digital elevation model, which is a DEM; the analysis of rocks and impact crater morphology in the engineering constraints is analyzed using an orthophoto model and a rock abundance map, where the orthophoto model is a DOM; the analysis of lunar geology in the scientific constraints is analyzed using a lunar geological map.

[0098] Combined with the above constraints on data source requirements, there are a variety of available data sources, which differ mainly in detection tasks, sensors, data product categories, product resolution, etc.:

[0099] The existing data on the far side of the moon mainly come from the lunar remote sensing exploration missions that have been carried out. The original data mainly include stereo images, laser ranging data, orthophotos, multispectral camera data, etc.

[0100] Different types of data products were then generated by different research institutions, including digital elevation models (DEMs), orthophoto models (DOMs), lunar geological maps, rock abundance maps, etc.

[0101] Data sources of the same category also include different resolutions. Taking DEM as an example, the official product resolutions of various exploration missions range from 7m to 7.6km / pixel. In addition, near the sampling area, the resolution of the DEM generated by fusion reconstruction can reach about 1m / pixel.

[0102] Establish a site selection constraint analysis method; divide the site selection constraint analysis stage into a rapid and progressive analysis stage of the sampling area and a refined analysis stage; classify and allocate each site selection constraint analysis method into analysis stages, rank each site selection constraint analysis method, and develop a screening process for the sampling area.

[0103] Site selection constraint analysis methods include scientific constraint analysis methods and engineering constraint analysis methods;

[0104] The scientific constraint analysis method uses existing analysis models and analysis diagrams to quickly narrow the landing range to the SPA area. It does not use complex calculations, but makes basic judgments based on existing scientific results, with a small amount of calculations.

[0105] Engineering constraint analysis methods include terrain slope analysis method, track elevation safety analysis method, stone analysis method, crater analysis method and terrain obstruction analysis method.

[0106] The terrain slope analysis method is:

[0107] Different slope calculation methods are used for different terrain data sources, including the third-order inverse distance square weighted slope algorithm and the simple differential comparison algorithm of the slope between the detector legs.

[0108] The third-order inverse distance square weighted slope algorithm is:

[0109] The terrain data source is divided into grids; a threshold is set in advance, and the terrain slope value is calculated according to the third-order inverse distance square weighted slope algorithm. When the terrain slope value is less than the threshold, it is judged that the grid meets the slope requirement; otherwise, it is judged that the grid does not meet the slope requirement.

[0110] The third-order inverse distance square weighted slope algorithm is shown in formulas (1) to (4). When the slope α0 slope (i,j) is lower than the preset threshold θ thr (In this example, this threshold is defined as 8°), the grid is considered to meet the slope requirements, and the slope safety marking matrix grid α is defined slope_sgn (i,j,k)=1, otherwise 0.

[0111]

[0112] f x =(z i+1,j+1 -z i+1,j-1 +2(z i,j+1 -z i,j-1 )+z i-1,j+1 -z i-1,j-1 ) / (8×cellsize)(2)

[0113] f y =(z i+1,j-1 -z i-1,j-1 +2(z i+1,j -z i-1,j )+z i+1,j+1 -z i-1,j+1 ) / (8×cellsize)(3)

[0114]

[0115] Where: z i,j is the elevation value of the current analyzed point; i±1,j±1 is the elevation value of the adjacent points of the analyzed point; cellsize is the grid size; k is the number of markers of the slope calculation method, representing the layer of this slope calculation method; the position relationship between each grid is shown in Figure 3 .

[0116] The simple differential comparison algorithm for the slope between the detector legs and feet is:

[0117] Divide the terrain data source into grids; when there are multiple data grids between the two legs of the probe, consider the slope α1 between the farthest two landing legs at the same time slope (i, j), the slope between the two nearest landing legs α2 slope(i, j), relative height z of the area below the lander down (i,j) three constraints; when the slope α1 slope (i,j) and α2 slope (i,j) is lower than the preset slope threshold θ thr , and the relative terrain elevation z under the detector down (i,j) is lower than the height z of the lower end of the thruster relative to the lunar surface down-thr , it is judged that the grid meets the slope requirement; otherwise, it is judged that the grid does not meet the slope requirement.

[0118] When the resolution of the terrain data object is lower than the detector envelope size, the third-order inverse distance square weighted slope algorithm is used, which has a small amount of calculation and can achieve fast progressive analysis of the sampling area.

[0119] When the resolution of the terrain data object is comparable to the size of the detector envelope, a third-order inverse distance square weighted slope algorithm is used with moderate computational effort to characterize and evaluate the landing slope trend of the entire detector.

[0120] When the resolution of the terrain data object is significantly higher than the size of the probe envelope, a simple differential comparison algorithm of the slopes between the probe legs is used to refine the elevation difference between the leg landing points and analyze whether the relative elevation of the lunar surface under the probe will interfere with the thruster equipment under the probe and affect the landing stability.

[0121] The basis is that there will be multiple data grids covering the bottom of the probe, so it is necessary to carefully consider the elevation difference between the landing points of the legs and feet, and whether the relative elevation of the lunar surface under the probe will interfere with the thrusters and other equipment under the probe, affecting landing stability.

[0122] The terrain slope safety layer is formed by using data sources with different resolutions, and different layers are superimposed according to the resolution to form a total slope safety layer:

[0123] α slope_sgn (i,j)=α slope_sgn (i,j,1)⊙...⊙α slope_sgn (i,j,k)...⊙α slope_sgn (i,j,kmax)

[0124] In the formula, α slope_sgn Mark the matrix for total slope safety;

[0125] (i, j) is the grid coordinate of terrain data source;

[0126] ⊙ is the matrix dot multiplication operation;

[0127] k is the number of markers for the slope calculation method;

[0128] Based on the slope safety master map, the comprehensive evaluation results of terrain slope analysis are obtained.

[0129] The track elevation analysis method is:

[0130] For different planned landing points on the lunar surface, the nominal and error tracks are fitted according to the orbit and GNC strategies, and the elevation values ​​on the DEM are read under the tracks. Usually, for a certain sampling area, multiple landing tracks and ascent tracks will be simulated. If all tracks meet the requirements, the track of the sampling area is considered safe.

[0131] The stone analysis method is:

[0132] Different rock analysis methods were used for different data sources; rocks affect safe landing and sampling processes.

[0133] In the rapid progressive analysis stage, the rock abundance map data is used for coarse screening; the resolution of the rock abundance map data is less than 100m / pixel.

[0134] The screening method is: pre-set the stone abundance threshold A rock_thr ; When the stone abundance in the analyzed area is less than the stone abundance threshold, the stone distribution requirements of the grid are determined.

[0135] In the detailed analysis stage, DOM data with a resolution of 1m is used to complete the analysis of stone abundance and stone size; multi-dimensional stone analysis is carried out on the planned sampling areas, and stone safety is confirmed in the proposed sampling areas.

[0136] Stone abundance meets threshold requirements:

[0137] A rock (i,j)<A rock_thr (10)

[0138] The proportion of stones larger than a certain diameter (usually 5m) is less than a certain threshold (about 15% in previous models):

[0139] Ratio rock (D>D rock_thr )<Ratio rock_thr (11)

[0140] Among them, A rock (i,j) is the rock abundance at the analysis grid, Ratio rock (D>D thr ) is the proportion of rocks larger than a certain diameter (usually 5m), Ratio rock_thr It is the threshold value of the proportion of stones larger than a certain diameter (usually 5m).

[0141] The impact crater analysis method is:

[0142] Through image and terrain recognition, DOM data with a resolution of 1m is used to identify the shape of the impact crater and obtain the distribution of its diameter and density. Then, a DEM with a resolution of 1m is used to analyze the depth of the impact crater and obtain the depth-to-diameter ratio analysis results. Based on the depth-to-diameter ratio analysis results, the safety of the impact crater in the proposed sampling area is confirmed.

[0143] The depth-to-diameter ratio of the impact crater should meet the following ratio requirements:

[0144] Y=H crater / D crater

[0145] H crater ≈a×D crater b

[0146] Ratio crater (Y>Y crater_thr )<Ratio crater_thr

[0147] Where Y is the depth-to-diameter ratio of the impact crater;

[0148] H crater is the depth of the impact crater;

[0149] D crater is the diameter of the impact crater;

[0150] a and b are constants;

[0151] Y crater_thr Setting a threshold for the crater depth-to-diameter ratio;

[0152] Ratio crater (Y>Y crater_thr ) is the aspect ratio greater than Y crater_thr The proportion of impact craters;

[0153] Ratio crater_thr is the corresponding proportion threshold;

[0154] The terrain occlusion analysis method is:

[0155] A large-scale comparative analysis of the terrain in the proposed sampling area and its surroundings is carried out. The main method is to radiate rays 360° outward from the analyzed point, calculate the terrain occlusion angles in different directions along the rays, and compare them with the illumination angle threshold α illum And the measurement and control angle threshold α con By comparison, when the terrain occlusion angle is less than the illumination angle threshold α illum And the measurement and control angle threshold α conWhen the terrain of the analyzed point is judged to have no influence on the illumination and measurement and control requirements of the detector on the lunar surface; otherwise, the terrain of the analyzed point is judged to have influence on the illumination and measurement and control requirements of the detector on the lunar surface.

[0156] The present invention classifies the scientific constraint analysis method, the terrain slope analysis method using the third-order inverse distance square weighted slope algorithm, and the stone analysis method using stone abundance map data into the rapid progressive analysis stage of the sampling area.

[0157] The terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the probe, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the crater analysis method and the terrain obstruction analysis method are classified as the refined analysis stage.

[0158] like Figure 2 As shown in the figure, the screening process of the sampling area is as follows:

[0159] Scientific constraint analysis method, terrain slope analysis method using third-order inverse distance square weighted slope algorithm, stone analysis method using stone abundance map data, terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, track elevation safety analysis method, stone analysis method using DOM data with a resolution of 1m, crater analysis method, and terrain occlusion analysis method.

[0160] Conduct a rapid progressive analysis of the sampling area to obtain selectable ranges covering the final sampling area.

[0161] The contents of the rapid progressive analysis of the sampling area are as follows:

[0162] The optional range covering the final sampling area was obtained by successively using a scientific constraint analysis method, a terrain slope analysis method using a third-order inverse distance square weighted slope algorithm, and a rock analysis method using rock abundance map data.

[0163] Conduct a detailed analysis of the optional range covering the final sampling area to obtain several alternative sampling areas.

[0164] The content of the detailed analysis of the optional range covering the final sampling area is:

[0165] Several candidate sampling areas were obtained by screening step by step through the terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the crater analysis method and the terrain obstruction analysis method.

[0166] Set preferred conditions for the alternative sampling areas and confirm the final sampling area.

[0167] Preferred conditions include:

[0168] Larger safe sampling area: The sampling area for the lunar backside sampling return mission is no less than 15km×6km. Considering the improvement of landing safety, an area with a larger safe sampling area is selected; for example, 20km×6km, 30km×6km, etc.

[0169] Gentler terrain slope: The slope of the landing point for the sample return mission on the far side of the moon is constrained to be less than 8°. In order to improve the stability of the landing, an area with a lower slope requirement is selected; for example, less than 7° or 6°.

[0170] More landing opportunities: To make the entire mission more reliable and taking into account the impact of on-orbit failures or other factors, the lunar back side sample return mission selects associated areas with the ability to land at the nominal time and delay landing.

[0171] Higher scientific value: Sampling on the far side of the moon contains rich geological age distribution of lunar samples.

[0172] Fewer rocks and crater distribution: Through high-resolution DEM maps or DOM, impact craters and rocks can be identified, and sampling areas can be selected while avoiding obstacles as much as possible.

[0173] The present invention provides a lunar surface sampling area site selection method based on multi-source data, and its proposed protection points are mainly: ① A method for site selection constraint screening using multi-source data is proposed, which can increase the credibility of the site selection results, and at the same time, the site selection efficiency can be improved by optimizing the use of multi-source data; ② Multiple constraints are integrated and sorted, and a screening method combining rapid sampling area rapid approximation with refined analysis is designed to achieve high-efficiency and high-quality site selection.

[0174] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for selecting a lunar surface sampling area based on multi-source data, characterized in that: include: Confirm the site selection constraints of the lunar surface sampling area; Integrate site selection constraints and sort out available data sources; Determine the analysis model and analysis diagram corresponding to each data source; Establish a site selection constraint analysis method; divide the site selection constraint analysis stage into a rapid and progressive analysis stage of the sampling area and a refined analysis stage; classify and allocate the analysis stages of each site selection constraint analysis method, rank each site selection constraint analysis method, and formulate a screening process for the sampling area; Conduct rapid progressive analysis of the sampling area to obtain optional ranges covering the final sampling area; Conduct detailed analysis on the optional range covering the final sampling area and obtain several candidate sampling areas; Set preferred conditions for the alternative sampling areas and confirm the final sampling area.

2. The method for selecting a lunar surface sampling area based on multi-source data according to claim 1, characterized in that: The site selection constraints include scientific constraints and engineering constraints; The scientific constraints are: the sampling area is selected on the far side of the moon to obtain samples from the far side of the moon; at the same time, the sampling area is selected in the SPA area to obtain samples from this body of land; areas of different geological years are selected for landing and sampling; Engineering constraints include terrain slope, track elevation safety, rocks, impact craters, and terrain obstruction; Terrain slope: According to the design status of the lander, select an area with a sufficiently gentle slope to carry out landing to ensure the landing stability of the lander; Track elevation safety: The terrain on the back side of the moon is very undulating. During the powered descent of the lander, the lander introduces the ranging information of the navigation sensor at a predetermined height to ensure that the track elevation fluctuation after the ranging information is introduced is as small as possible to ensure landing safety; during the takeoff and ascent process of the return, ensure that the ascender does not interfere with the mountains on its ascent track; Stones: Avoid areas with stones. Impact craters: Avoid areas with small and medium-sized impact craters; Terrain occlusion: The sampling area should avoid occlusion caused by the surrounding terrain to prevent it from affecting measurement, control and lighting conditions.

3. The method for selecting a lunar surface sampling area based on multi-source data according to claim 1, characterized in that: The analysis of terrain slope, track elevation safety, terrain shielding and crater depth in the engineering constraints is performed using a digital elevation model, which is the DEM; the analysis of rocks and crater morphology in the engineering constraints is performed using an orthophoto model and a rock abundance map, where the orthophoto model is the DOM; the analysis of lunar geology in the scientific constraints is performed using a lunar geological map.

4. The method for selecting a lunar surface sampling area based on multi-source data according to claim 1, characterized in that: The site selection constraint analysis method includes a scientific constraint analysis method and an engineering constraint analysis method; The scientific constraint analysis method uses existing analysis models and analysis diagrams to quickly narrow the landing range to the SPA area. It does not use complex calculations, but makes basic judgments based on existing scientific results, with a small amount of calculations. Engineering constraint analysis methods include terrain slope analysis method, track elevation safety analysis method, stone analysis method, crater analysis method and terrain obstruction analysis method.

5. The method for selecting a lunar surface sampling area based on multi-source data according to claim 4 is characterized in that: The terrain slope analysis method is: Different slope calculation methods are used for different terrain data sources, including the third-order inverse distance square weighted slope algorithm and the simple differential comparison algorithm of the slope between the detector legs; The third-order inverse distance square weighted slope algorithm is: Gridding terrain data sources; A threshold is set in advance, and the terrain slope value is calculated according to the third-order inverse distance square weighted slope algorithm. When the terrain slope value is less than the threshold, the grid is judged to meet the slope requirement; otherwise, the grid is judged to not meet the slope requirement; The simple differential comparison algorithm for the slope between the detector legs and feet is: Divide the terrain data source into grids; when there are multiple data grids between the two legs of the probe, consider the slope α1 between the farthest two landing legs at the same time slope (i, j), the slope between the two nearest landing legs α2 slope (i, j), relative height z of the area below the lander down (i,j) three constraints; when the slope α1 slope (i,j) and α2 slope (i,j) is lower than the preset slope threshold θ thr , and the relative terrain elevation z under the detector down (i,j) is lower than the height z of the lower end of the thruster relative to the lunar surface down-thr , it is judged that the grid meets the slope requirement; otherwise, it is judged that the grid does not meet the slope requirement; When the resolution of the terrain data object is lower than the detector envelope size, the third-order inverse distance square weighted slope algorithm is used, which has a small amount of calculation and can achieve fast progressive analysis of the sampling area; When the resolution of the terrain data object is comparable to the size of the detector envelope, a third-order inverse distance square weighted slope algorithm is used with moderate computational effort to characterize and evaluate the overall landing slope trend of the detector. When the resolution of the terrain data object is significantly higher than the size of the detector envelope, a simple differential comparison algorithm of the slope between the detector legs is used to finely consider the elevation difference between the leg landing points and analyze whether the relative elevation of the lunar surface below the detector will interfere with the thruster equipment below the detector and affect the landing stability. The terrain slope safety layer is formed by using data sources with different resolutions, and different layers are superimposed according to the resolution to form a total slope safety layer: a slope_sgn (i,j)=a slope_sgn (i,j,1)⊙...⊙a slope_sgn (i,j,k)...⊙a slope_sgn (i,j,kmax) In the formula, α slope_sgn Mark the matrix for total slope safety; (i, j) is the grid coordinate of terrain data source; ⊙ is the matrix dot multiplication operation; k is the number of markers for the slope calculation method; Based on the slope safety master map, the comprehensive evaluation results of terrain slope analysis are obtained.

6. The method for selecting a lunar surface sampling area based on multi-source data according to claim 5, characterized in that: The track elevation analysis method is: For different planned landing points on the lunar surface, the nominal and error tracks are fitted according to the orbit and GNC strategies, and the elevation values ​​on the DEM are read under the track; The stone analysis method is: Different rock analysis methods were used for different data sources; rocks affect the safe landing and sampling process; In the rapid progressive analysis stage, the rock abundance map data is used for coarse screening; the resolution of the rock abundance map data is less than 100m / pixel; The screening method is: pre-set the stone abundance threshold A rockthr ; When the stone abundance in the analyzed area is less than the stone abundance threshold, the stone distribution requirements of the grid are determined; In the detailed analysis stage, DOM data with a resolution of 1m is used to complete the analysis of stone abundance and stone size; multi-dimensional stone analysis is carried out on the planned sampling areas, and stone safety is confirmed in the proposed sampling areas.

7. The method for selecting a lunar surface sampling area based on multi-source data according to claim 4 is characterized in that: The impact crater analysis method is: Through image and terrain recognition, DOM data with a resolution of 1m is used to identify the shape of the impact crater and obtain the distribution of its diameter and density. Then, a DEM with a resolution of 1m is used to analyze the depth of the impact crater and obtain the depth-to-diameter ratio analysis results. Based on the depth-to-diameter ratio analysis results, the safety of the impact crater in the proposed sampling area is confirmed. The depth-to-diameter ratio of the impact crater should meet the following ratio requirements: Y=H crater / D crater H crater ≈a×D crater b Ratio crater (Y>Y crater_thr )<Ratio crater_thr Where Y is the depth-to-diameter ratio of the impact crater; H crater is the depth of the impact crater; D crater is the diameter of the impact crater; a and b are constants; Y crater_thr Setting a threshold for the crater depth-to-diameter ratio; Ratio crater (Y>Y crater_thr ) is the aspect ratio greater than Y crater_thr The proportion of impact craters; Ratio crater_thr is the corresponding proportion threshold; The terrain occlusion analysis method is: A large-scale comparative analysis of the terrain in the proposed sampling area and its surroundings is carried out. The main method is to radiate rays 360° outward from the analyzed point, calculate the terrain occlusion angles in different directions along the rays, and compare them with the illumination angle threshold α illum And the measurement and control angle threshold α con By comparison, when the terrain occlusion angle is less than the illumination angle threshold α illum And the measurement and control angle threshold α con When the terrain of the analyzed point is judged to have no influence on the illumination and measurement and control requirements of the detector on the lunar surface; otherwise, the terrain of the analyzed point is judged to have influence on the illumination and measurement and control requirements of the detector on the lunar surface.

8. The method for selecting a lunar surface sampling area based on multi-source data according to claim 5 is characterized in that: The scientific constraint analysis method, the terrain slope analysis method using the third-order inverse distance square weighted slope algorithm, and the rock analysis method using rock abundance map data were classified into the rapid progressive analysis stage of the sampling area; The terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the probe, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the impact crater analysis method and the terrain shielding analysis method are classified as the refined analysis stage; The screening process of the sampling area is as follows: Scientific constraint analysis method, terrain slope analysis method using third-order inverse distance square weighted slope algorithm, stone analysis method using stone abundance map data, terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, track elevation safety analysis method, stone analysis method using DOM data with a resolution of 1m, crater analysis method, and terrain occlusion analysis method.

9. The method for selecting a lunar surface sampling area based on multi-source data according to claim 8, characterized in that: The contents of the rapid progressive analysis of the sampling area are as follows: The optional range covering the final sampling area was obtained by sequentially using the scientific constraint analysis method, the terrain slope analysis method using the third-order inverse distance square weighted slope algorithm, and the stone analysis method using stone abundance map data; The content of the detailed analysis of the optional range covering the final sampling area is: Several candidate sampling areas were obtained by screening step by step through the terrain slope analysis method using a simple differential comparison algorithm of the slope between the legs of the detector, the track elevation safety analysis method, the stone analysis method using DOM data with a resolution of 1m, the crater analysis method and the terrain obstruction analysis method.

10. The method for selecting a lunar surface sampling area based on multi-source data according to claim 1, characterized in that: The preferred conditions include: Larger safe sampling area: The sampling area for the lunar backside sampling return mission is no less than 15km×6km. Considering the improvement of landing safety, an area with a larger safe sampling area is selected; Gentle terrain slope: The slope of the landing site for the lunar backside sample return mission is constrained to be less than 8°. In order to improve the stability of landing, an area with a lower slope requirement is selected; More landing opportunities: To make the entire mission more reliable, the lunar backside sample return mission will select associated areas with the ability to land at the nominal time and delay landing, taking into account the impact of on-orbit failures or other factors. Higher scientific value: The sampling on the far side of the moon contains rich geological age distribution of lunar samples; Fewer rocks and crater distribution: Identify craters and rocks through high-resolution DEM or DOM, and select sampling areas while avoiding obstacles as much as possible.

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