A method and system for evaluating coverage of target area of ​​low-orbit communication constellation

Abstract

The present invention discloses a method and system for evaluating the coverage of a target area of ​​a low-orbit communication constellation, the method comprising: S1. dividing the target area of ​​a low-orbit communication constellation into quadrilateral grids based on longitude and latitude; S2. calculating the time series of single-satellite coverage of a single-point target under consideration of the earth's curvature; S3. calculating the coverage time of the constellation to the target area by counting the coverage time of the single-satellite to the target; S4. comprehensively evaluating the coverage performance of the communication constellation to the target area through coverage indicators. The method and system can quickly calculate the coverage indicators of the constellation to the target area, improve the accuracy of the constellation coverage evaluation, and have simple calculation and high real-time performance.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and is directed to communication coverage assessment of a low-orbit constellation, and in particular to a method and system for assessing coverage of a target area of ​​a low-orbit communication constellation. Background Art

[0002] Satellite ground coverage analysis usually refers to the effective area on the earth's surface that can be observed by aerospace instruments or antennas at a certain moment or over a long period of time. The coverage capability of a satellite is an important indicator for measuring the effectiveness of satellite applications. The rapidity of the evaluation of coverage performance indicators is of great significance to the optimization design of constellations. How to use coverage to quantify coverage quality is a very important issue. At present, the evaluation of satellite coverage performance mainly focuses on a single satellite, and there is little research on the coverage evaluation of constellations. Compared with the coverage calculation of remote sensing satellites for a region, the coverage of communication satellites mainly focuses on the coverage statistics of ground point targets. The coverage evaluation of satellite communication areas is relatively complex and less studied. The current coverage evaluation method is relatively complex and not very real-time. Therefore, there is an urgent need for a constellation coverage evaluation method that is simple to calculate and has high accuracy. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method and system for evaluating the coverage of a target area of ​​a low-orbit communication constellation, which can quickly calculate the coverage index of the constellation for the target area, improve the accuracy of the constellation coverage evaluation, and has simple calculation and high real-time performance.

[0004] To achieve the above object, the present invention provides a method for evaluating the coverage of a target area of ​​a low-orbit communication constellation, the method comprising the following steps:

[0005] S1. Divide the low-orbit communication constellation target area into quadrilateral grids based on longitude and latitude lines;

[0006] S2. Calculate the coverage time series of a single satellite to a single point target taking into account the curvature of the earth;

[0007] S3. Calculate the coverage time of the constellation over the target area by counting the coverage time of a single satellite over the target;

[0008] S4. Comprehensively evaluate the coverage performance of the communication constellation for the target area through coverage indicators.

[0009] Furthermore, in step S1, the target area is divided into quadrilateral grids based on longitude and latitude lines. The specific implementation method is as follows:

[0010] S1.1 Input area latitude and longitude range and latitude and longitude resolution;

[0011] S1.2 divide the regional grid by resolution to obtain grid points;

[0012] S1.3 Output grid point coordinates.

[0013] Further, in step S1.1, the resolution is set to , the target area coordinate range is: ; Number of pixels in latitude , the number of pixels in longitude As shown in the formula:

[0014] (1).

[0015] Further, in step S1.2, at a resolution of Under the condition of , the target area is divided into grids using longitude and latitude lines. The final grid coordinates are shown in the following formula:

[0016] (2)

[0017] in, Indicates the latitude pixels, Indicates the first pixels.

[0018] Further, in step S2, the specific method of calculating the coverage time of a single satellite to a single point target is as follows:

[0019] When the six elements of the satellite orbit and the geographical location of the ground target are known, the process of calculating the satellite's entry and exit of the coverage area includes the following steps:

[0020] S2.1 Input six orbit elements, orbit pitch angle, and ground target position; the six orbit elements include the orbit semi-major axis , eccentricity , orbital inclination , right ascension of ascending node , Argument of perigee , Really close ;

[0021] S2.2 Calculate the satellite's right ascension according to the following formula and declination ;

[0022]

[0023] in, represents the orbital pitch angle, represents the orbital inclination, Represents the right ascension of the ascending node.

[0024] Further, in step S3, for the multi-point target, the multi-point target is taken as a whole; The target points are ; For this Apply the single satellite processing method for a single target described in step S1 to each target, and obtain the coverage time matrix of each target point and .

[0025] Furthermore, in step S3, the constellation coverage calculation is to regard the center coordinate point of the divided grid area as the target point, and to obtain the coverage characteristics of the entire constellation by counting the coverage characteristic values ​​of the center target of each grid through a single satellite. The constellation coverage characteristic calculation steps are as follows:

[0026] S3.1 Collect constellation parameters, obtain the location of the target area, set visibility constraints, and determine the start and end times;

[0027] S3.2 Calculate the coverage time of a single row for each grid center point in the target area using the above-mentioned single-star-to-single-point target coverage time calculation method based on the six orbital elements of the constellation parameters, the location of the target area, the half-field viewing angle of the visibility constraint, and the solar altitude angle;

[0028] S3.3 Count the coverage time of each grid center point coordinate and store it in the coverage time matrix and ;

[0029] S3.4 outputs the coverage time matrix.

[0030] Furthermore, in step S3.2, GPU is used to perform parallel computing.

[0031] Further, in step S4, the comprehensive evaluation of constellation coverage performance is specifically implemented as follows:

[0032] Get the coverage performance index quality factor:

[0033] S4.1 Calculate the inverse of the coverage time percentage:

[0034] The coverage time interval of each grid point in the region by the constellation satellite is recorded as , take the union of each coverage interval to get the time interval of the area covered , the total coverage time of the statistical area , divided by the total simulation time The coverage time percentage of the constellation to the area is obtained. The inverse of the coverage time percentage is shown in the following formula:

[0035] (10)

[0036] S4.2 Calculate the maximum coverage gap:

[0037] The maximum coverage gap of a constellation for a single grid point is equal to the longest time that the constellation does not cover the grid point. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , the maximum coverage gap is obtained as shown in the following formula:

[0038] (11)

[0039] S4.3 Calculate the average coverage gap:

[0040] Take the union of the coverage time intervals of the constellation satellites for each grid point in the region to obtain the regional coverage time interval. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , this The average of the coverage gap durations is taken to obtain the average coverage gap of the constellation to the area as shown in the following formula:

[0041] (12)

[0042] S4.4 Calculate the time average gap:

[0043] The time average interval is equal to The sum of the squares of the coverage gap durations divided by the simulation time , which measures the average gap length; as shown in the following formula:

[0044] (13)

[0045] S4.5 calculates the average response time:

[0046] The average response time is equal to half of the time average interval, as shown in the following formula:

[0047] (14)

[0048] The quality factor of coverage performance index gives the satellite's coverage performance of the ground from different levels. The coverage score of the target area of ​​the low-orbit communication constellation is shown in the following formula:

[0049] (15)

[0050] in, Indicates the weight of each indicator.

[0051] On the other hand, the present invention provides a low-orbit communication constellation target area coverage assessment system, which is used to implement the low-orbit communication constellation target area coverage assessment method according to the present invention, the system comprises a satellite parameter configuration module, a target area configuration module, a satellite coverage performance calculation module, and a coverage result display module; wherein:

[0052] A satellite parameter configuration module is used to set the parameter configuration of the low-orbit communication constellation, wherein the parameters include the number of constellation satellites, the current satellite number, the six elements of the orbit, the beam size, and the communication rate;

[0053] The ground scene configuration module is used to realize the target area selection function and specify the size type and area resolution of the target area;

[0054] The satellite coverage performance calculation module is used to call the coverage performance evaluation method of the target area of ​​the low-orbit communication constellation to calculate the coverage time of the constellation for the specified target area;

[0055] The coverage result display module converts the coverage time results received from the satellite coverage calculation module into the inverse of the coverage time percentage, the maximum coverage gap, the average coverage gap, the average response time, and the time average gap, and finally displays the results on the interface.

[0056] Beneficial effects:

[0057] 1. This method meets the needs of low-orbit communication constellation coverage characteristics analysis of the target area and has fast calculation.

[0058] 2. This method calculates the satellite's coverage of the ground with sufficient accuracy when considering non-circular orbits, the rotation of the earth, or the overlapping coverage areas of several satellites.

[0059] 3. This method realizes the coverage performance calculation of a single satellite to a single point target and a single satellite to multiple point targets, and on this basis, it realizes the coverage evaluation of multiple satellites to a region. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is a flow chart of a method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to the present invention;

[0061] Figure 2 A flow chart of the method for dividing a target area based on longitude and latitude lines according to the present invention;

[0062] Figure 3 A geometric relationship diagram of the positions of photographic points formed by the star according to the present invention;

[0063] Figure 4 A satellite coverage time slot statistics flow chart according to the present invention;

[0064] Figure 5 A schematic diagram of a time series of coverage of multiple targets according to the present invention;

[0065] Figure 6 A schematic diagram of a parallel calculation process of constellation coverage characteristics according to the present invention;

[0066] Figure 7 Schematic diagram of the architecture of a low-orbit communication constellation target area coverage assessment system according to the present invention. DETAILED DESCRIPTION

[0067] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0068] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0069] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0070] The following combination Figure 1-Figure 7 The specific embodiments of the present invention are described in detail. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0071] The present invention discloses a method for evaluating the coverage of a target area of ​​a low-orbit communication constellation. A low-orbit satellite refers to a satellite operating in a low earth orbit, and its orbital altitude is generally between 500 and 2000 kilometers. The flow chart is as follows: Figure 1 As shown, the specific steps include:

[0072] S1. Divide the target area into quadrilateral grids based on longitude and latitude lines; the target area is a regional space, and multiple single point targets are covered in the area;

[0073] S2. Calculate the coverage time series of a single satellite to a single point target taking into account the curvature of the earth;

[0074] S3. Calculate the coverage time series of the constellation over the target area by counting the coverage time of a single satellite over a single point target;

[0075] S4. Comprehensively evaluate the coverage performance of the communication constellation for the target area through coverage indicators.

[0076] This method can quickly calculate the coverage index of the constellation to the target area, and can provide a basis for the evaluation of the constellation coverage performance. A single point target is mainly a point location, and a regional target is a regional space covering multiple point targets.

[0077] Specifically, in step S1, the target area is divided into quadrilateral grids based on longitude and latitude lines. The specific implementation method is as follows:

[0078] The sphere is divided into quadrilateral grids using longitude and latitude lines. The grid system formed by dividing the sphere by latitude circles has the characteristics of clear directionality, simple division method, and clear division levels. It can divide key areas in detail and is widely used in surveying and mapping, earth geography, meteorological science and other fields. The division process is as follows Figure 2 As shown, the following steps are included:

[0079] S1.1 Input the latitude and longitude range and latitude and longitude resolution of the area. Assume the resolution is , the target area coordinate range is: The number of pixels in latitude , the number of pixels in longitude As shown in the formula.

[0080] (1)

[0081] S1.2 Divide the regional grid by resolution to obtain grid points. Under the condition of , the target area is divided into grids using longitude and latitude lines. The final grid coordinates are shown in the following formula:

[0082] (2)

[0083] in, Indicates the latitude pixels, Indicates the first pixels.

[0084] S1.3 Output grid point coordinates.

[0085] In step S2, the specific method for calculating the coverage time of a single satellite to a single point target is as follows:

[0086] The coverage area of ​​the satellite on the earth's surface is the spherical part of a spherical cap. Considering that the satellite's observation of ground targets or satellite-to-ground communication is affected by factors such as ground thermal radiation, atmospheric propagation, and topography, in order to ensure the effective implementation of satellite applications, in actual work, it is required that the line of sight direction vector from the ground point to the satellite should be higher than the local horizontal plane where the ground point is located by a certain angle to ensure good satellite-to-ground visibility conditions, such as Figure 3 As shown, is the half field of view, is the minimum sun altitude angle.

[0087] Known geographic latitude ,longitude , right ascension , Declination , Satellite location , taking into account the curvature of the earth, we get the geocentric latitude As shown in the following formula:

[0088] (3)

[0089] in, Represents the Earth's flattening.

[0090] Taking into account the curvature of the earth, the local earth radius of the ground station target is given by the following formula:

[0091] (4)

[0092] in, represents the mean radius.

[0093] Geocentric-Satellite Unit Vector As shown in the following formula:

[0094] (5)

[0095] The unit vector of the ground station target-satellite direction is as follows:

[0096] (6)

[0097] (7)

[0098] The longitude , right ascension , Declination , Satellite location ,

[0099] Unit vector of the direction from the center of the earth to the ground station target As shown in the following formula:

[0100] (8)

[0101] The final satellite coverage of a single satellite to a single point at any time As shown in the following formula, the case where the inequality is satisfied by comparison is marked as 1, and the case where it is not satisfied is marked as 0.

[0102] (9)

[0103] in, is the half field of view, is the minimum sun altitude angle, the final coverage area is 1, and the outside of the coverage area is 0.

[0104] When the six elements of the satellite orbit and the geographical location of the ground target are known, the process of calculating the satellite entering and leaving the coverage area is as follows: Figure 4 As shown, the specific steps include:

[0105] S2.1 Input six orbit elements, orbit pitch angle, and ground target position; the six orbit elements include the orbit semi-major axis , eccentricity , orbital inclination , right ascension of ascending node , Argument of perigee , Really close ;

[0106] S2.2 Calculate the satellite's right ascension according to the following formula and declination ;

[0107]

[0108] in, represents the orbital pitch angle, represents the orbital inclination, Represents the right ascension of the ascending node.

[0109] S2.3 Calculate the satellite coverage according to the above formula (3) to formula (9);

[0110] Using the while loop, first select the step size (The step length accuracy can reach 0.1 second). Based on the previous analysis of the coverage situation, analyze the entry and exit of all satellites in the coverage area within a day, and count the entry and exit situation and time into the entry coverage area matrix and exit footprint matrix (The coverage mark is 0 at the previous moment and 1 at the next moment, indicating that the satellite has entered the coverage area, and vice versa.) Finally, the coverage time series statistical matrix of a single satellite to a single point is obtained.

[0111] In step S3, the coverage performance of multiple satellites in the area is calculated as follows:

[0112] For multi-point targets, treat the multi-point targets as a whole. The target points are For this Apply the single satellite processing method for a single target described in step S1 to each target. Obtain the coverage time matrix of each target point and .

[0113] exist Figure 5 In the specific embodiment shown, there are 7 target points, and the coverage time series of the satellite constellation for the 7 target points are respectively represented by Figure 5 The first vertical dotted line indicates the start of the first coverage, and the second vertical dotted line indicates the end of the first coverage and the start of the second coverage. Only when all target points are covered by the satellite once can the coverage mission be considered completed.

[0114] exist Figure 5 In the calculation of constellation coverage, the center coordinate point of the divided grid area is regarded as the target point, and the coverage characteristic value of the target in the center of each grid is counted by a single star to obtain the coverage characteristic of the entire constellation. The calculation steps of constellation coverage characteristic are as follows:

[0115] S3.1 Collect constellation parameters, obtain the location of the target area, set visibility constraints, and determine the start and end times;

[0116] S3.2 calculates the coverage time of a single row for each grid center point in the target area using the above-mentioned single-star-to-single-point target coverage time calculation method based on the six orbital elements of the constellation parameters, the location of the target area, the half-field viewing angle of the visibility constraint, and the solar altitude angle, and uses the GPU to complete parallel calculations.

[0117] S3.3 Count the coverage time of each grid center point coordinate and store it in the coverage time matrix and .

[0118] S3.4 outputs the coverage time matrix.

[0119] In step S4, the comprehensive evaluation of constellation coverage performance is specifically implemented as follows:

[0120] Get the following five coverage performance index quality factors:

[0121] S4.1 Calculate the inverse of the coverage time percentage ( )

[0122] The coverage time interval of each grid point in the region by the constellation satellite is recorded as , take the union of each coverage interval to get the time interval of the area covered , the total coverage time of the statistical area , divided by the total simulation time The coverage time percentage of the constellation to the area is obtained, and the inverse of the coverage time percentage is shown in the formula:

[0123] (10)

[0124] S4.2 Calculate the maximum coverage gap (maximum revisit time) ( )

[0125] The maximum coverage gap of a constellation for a single grid point is equal to the longest time that the constellation does not cover the grid point. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , the maximum coverage gap is obtained as shown in the following formula

[0126] (11)

[0127] S4.3 Calculate the average coverage gap (average revisit time) ( )

[0128] First, the coverage time interval of each grid point in the region by the constellation satellite is taken as the union, and the regional coverage time interval is obtained. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , this The average of the coverage gap durations is taken to obtain the average coverage gap of the constellation for the area.

[0129] (12)

[0130] S4.4 Calculate the time average gap ( )

[0131] The time average interval is equal to The sum of the squares of the coverage gap durations divided by the simulation time , measures the average gap length, which represents the size of the coverage gap that is expected to fall if a random time point is chosen.

[0132] (13)

[0133] S4.5 Calculate the average response time ( )

[0134] The response time refers to the time from a random time point (current time) to the time when the next coverage starts, and the average response time is the average value of the response time. If the current time is in coverage, the response time is 0. If the current time is at the end of coverage, the response time is equal to the coverage gap. If the current time is at the beginning of coverage, the response time is 0. The numerical value is equal to half of the average time gap.

[0135] (14)

[0136] The five coverage performance index quality factors give the satellite's coverage performance of the ground from different levels. The smaller the performance index requirement, the better. The coverage score of the target area of ​​the low-orbit communication constellation is shown in the following formula:

[0137] (15)

[0138] in, Indicates the weight of each indicator. The lower the score, the better the coverage performance of the constellation for the target area.

[0139] On the other hand, the present invention also provides a low-orbit communication constellation target area coverage assessment system for implementing the above method.

[0140] The architecture of the low-orbit communication constellation target area coverage assessment system is as follows: Figure 7 As shown, the system includes a satellite parameter configuration module, a target area configuration module, a satellite coverage performance calculation module, and a coverage result display module. Among them:

[0141] The satellite parameter configuration module is mainly used to set the parameter configuration of the low-orbit communication constellation, such as the number of constellation satellites, the current satellite number, the six elements of the orbit, the beam size, the communication rate, etc.

[0142] The ground scene configuration module is mainly used to realize the target area selection function and specify the size type and area resolution of the target area.

[0143] The satellite coverage performance calculation module is mainly used to call the coverage performance evaluation method of the target area of ​​the low-orbit communication constellation to calculate the coverage time of the constellation for the specified target area.

[0144] The coverage result display module converts the coverage time results received from the satellite coverage calculation module into the inverse of the coverage time percentage, the maximum coverage gap, the average coverage gap, the average response time, and the time average gap, and finally displays the results on the interface.

[0145] The technical emphasis of the present invention is:

[0146] 1. When dividing the sphere, the target area division method based on longitude and latitude is used to divide the sphere into quadrilateral grids.

[0147] 2. Based on the coverage time statistics of satellites to single-point targets and single-satellite to multi-point targets, the coverage time series statistics of multiple satellites to the area are realized.

[0148] 3. This method comprehensively evaluates the coverage performance of the low-orbit communication constellation over the target area from five dimensions: the inverse of the coverage time percentage, the maximum coverage gap, the average coverage gap, the time average gap, and the average response time.

[0149] Any process or method description in the flowchart of the present invention or described in other ways herein can be understood as a module, segment or part of a code including one or more executable instructions for implementing the steps of a specific logical function or process, which can be implemented in any computer-readable medium for use by an instruction execution system, device or equipment, and the computer-readable medium can be any medium containing storage, communication, propagation or transmission programs for use by execution systems, devices or equipment, including read-only memories, magnetic disks or optical disks, etc.

[0150] In the description of this specification, the description with reference to the terms "embodiment", "example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, those skilled in the art can combine or combine different embodiments or examples described in this specification and the features therein without causing any contradiction.

[0151] Although the above content has shown and described the embodiments of the present invention, it can be understood that the above embodiments are exemplary and cannot be understood as limitations of the present invention. Ordinary technicians in the field can change, modify, replace, modify and other update operations on the above embodiments within the scope of the present invention.

Claims

1. A method for evaluating the coverage of a target area of ​​a low-orbit communication constellation, characterized in that: The method comprises the following steps: S1. Divide the low-orbit communication constellation target area into quadrilateral grids based on longitude and latitude lines; S2. Calculate the coverage time series of a single satellite to a single point target while taking into account the curvature of the earth; S3. Calculate the coverage time of the constellation over the target area by counting the coverage time of a single satellite over the target; S4. Comprehensively evaluate the coverage performance of the communication constellation over the target area through coverage indicators; In step S4, the comprehensive evaluation of constellation coverage performance is specifically implemented as follows: Get the coverage performance index quality factor: S4.1 Calculate the inverse of the coverage time percentage: The coverage time interval of each grid point in the region by the constellation satellite is recorded as , take the union of each coverage interval to get the time interval of the area covered , the total coverage time of the statistical area , divided by the total simulation time The coverage time percentage of the constellation to the area is obtained. The inverse of the coverage time percentage is shown in the following formula: （10） S4.2 Calculate the maximum coverage gap: The maximum coverage gap of a constellation for a single grid point is equal to the longest time that the constellation does not cover the grid point. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , the maximum coverage gap is obtained as shown in the following formula: （11） S4.3 Calculate the average coverage gap: Take the union of the coverage time intervals of the constellation satellites for each grid point in the region to obtain the regional coverage time interval. The time of the first access minus the The time when the visit ends is Secondary coverage gap duration , this The average of the coverage gap durations is taken to obtain the average coverage gap of the constellation to the area as shown in the following formula: （12） S4.4 Calculate the time average gap: The time average interval is equal to The sum of the squares of the coverage gap durations divided by the simulation time , which measures the average gap length; as shown in the following formula: （13） S4.5 calculates the average response time: The average response time is equal to half of the time average interval, as shown in the following formula: （14） The above five coverage performance index quality factors give the satellite's coverage performance of the ground from different levels. The coverage score of the target area of ​​the low-orbit communication constellation is shown in the following formula: （15） in, Indicates the weight of each indicator. The lower the score, the better the coverage performance of the constellation for the target area.

2. The method for evaluating the coverage of a target area of ​​a low-orbit communication constellation according to claim 1, characterized in that: In step S1, the target area is divided into quadrilateral grids based on longitude and latitude lines. The specific implementation method is as follows: S1.1 Input area latitude and longitude range and latitude and longitude resolution; S1.2 divide the regional grid by resolution to obtain grid points; S1.3 Output grid point coordinates.

3. The method for evaluating the coverage of a target area of ​​a low-orbit communication constellation according to claim 2, characterized in that: In step S1.1, the resolution is set to , the target area coordinate range is: ; Number of pixels in latitude , the number of pixels in longitude As shown in the formula: （1）。 4. The method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to claim 2, characterized in that: In step S1.2, at a resolution of Under the condition of , the target area is divided into grids using longitude and latitude lines. The final grid coordinates are shown in the following formula: （2） in, Indicates the latitude pixels, Indicates the first pixels.

5. The method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to claim 1, characterized in that: In step S2, the specific method for calculating the coverage time of a single satellite to a single point target is as follows: When the six elements of the satellite orbit and the geographical location of the ground target are known, the process of calculating the satellite's entry and exit of the coverage area includes the following steps: S2.1 Input six orbit elements, orbit pitch angle, and ground target position; the six orbit elements include the orbit semi-major axis , eccentricity , orbital inclination , right ascension of ascending node , Argument of perigee , Really close ; S2.2 Calculate the satellite's right ascension according to the following formula and declination ; in, represents the orbital pitch angle, represents the orbital inclination, represents the right ascension of the ascending node; S2.3 Calculate the satellite coverage.

6. The method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to claim 5, characterized in that: In step S3, for the multi-point target, the multi-point target is taken as a whole; The goals are ; For this The processing method for calculating the coverage time of a single satellite to a single point target described in step S2 is applied to each target to obtain the coverage time matrix of each target point. and .

7. The method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to claim 6, characterized in that: In step S3, the constellation coverage calculation is to regard the center coordinate point of the divided grid area as the target point, and to obtain the coverage characteristics of the entire constellation by counting the coverage characteristic values ​​of the center target of each grid through a single star. The constellation coverage characteristic calculation steps are as follows: S3.1 Collect constellation parameters, obtain the location of the target area, set visibility constraints, and determine the start and end times; S3.2 Calculate the coverage time of a single satellite for each grid center point in the target area using the above-mentioned single satellite to single point target coverage time calculation method based on the six orbital elements of the constellation parameters, the location of the target area, the half-field viewing angle of the visibility constraint, and the solar altitude angle; S3.3 Count the coverage time of each grid center point coordinate and store it in the coverage time matrix and ; S3.4 outputs the coverage time matrix.

8. The method for evaluating coverage of a target area of ​​a low-orbit communication constellation according to claim 7, characterized in that: In step S3.2, GPU is used to perform parallel computing.

9. A low-orbit communication constellation target area coverage assessment system, characterized in that: The system is used to implement the low-orbit communication constellation target area coverage assessment method according to any one of claims 1 to 8, and the system comprises a satellite parameter configuration module, a target area configuration module, a satellite coverage performance calculation module, and a coverage result display module; wherein: A satellite parameter configuration module is used to set the parameter configuration of the low-orbit communication constellation, wherein the parameters include the number of constellation satellites, the current satellite number, the six elements of the orbit, the beam size, and the communication rate; The target area configuration module is used to realize the target area selection function and specify the size type and area resolution of the target area; The satellite coverage performance calculation module is used to call the coverage performance evaluation method of the target area of ​​the low-orbit communication constellation to calculate the coverage time of the constellation for the specified target area; The coverage result display module converts the coverage time results received from the satellite coverage performance calculation module into the inverse of the coverage time percentage, the maximum coverage gap, the average coverage gap, the average response time, and the time average gap, and finally displays the results on the interface.

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