A fast calculation method for constellation coverage of ground target area

Abstract

The present invention discloses a method for quickly calculating the coverage of a constellation to a target area on the ground. This method addresses the problems of a large number of satellites, a large amount of coverage calculation, and low calculation accuracy, and designs a calculation method that can quickly locate relevant satellites, quickly calculate coverage, and maintain high accuracy. First, satellite orbit recursion is performed, and satellites related to the target area are quickly located based on a dichotomy method. Secondly, the satellite's beam coverage area to the ground is calculated based on the satellite payload type. Finally, the beam coverage area is abstracted into a planar polygon, and the intersection of the satellite's beam coverage strip polygon to the ground and the ground target area polygon is calculated to quickly calculate the satellite's coverage of the ground target area. Addressing the problems of a large number of satellites, a large amount of coverage calculation, and low calculation accuracy, the present invention can quickly locate relevant satellites, quickly calculate coverage, and maintain high accuracy.

Description

Technical Field

[0001] The present invention belongs to the field of aerospace reconnaissance technology, and in particular, provides a method for quickly calculating the coverage rate of a constellation-oriented ground target area. Background Art

[0002] Space reconnaissance technology typically integrates multiple sensors, combining optical, radar, and electronic reconnaissance techniques to conduct all-weather detection of ground targets, providing more comprehensive and accurate intelligence information. The key to this technology lies in ground coverage analysis, with all information derived from the observable area. In practical applications, developing efficient and rapid methods for calculating constellation ground coverage is crucial for evaluating constellation coverage effectiveness.

[0003] Existing methods for calculating satellite coverage of a target area on Earth are suitable for calculating coverage of a single satellite. However, as the number of satellites increases, the number of passes through the ground grid increases dramatically, severely impacting calculation speed. Furthermore, to improve calculation accuracy, a finer grid division of the target area is required, which exponentially increases the impact on calculation speed.

[0004] Patent publication number CN116975504A discloses a method for quickly calculating targets in satellite reconnaissance coverage areas. Although this method can quickly calculate satellite reconnaissance coverage areas, it has not been applied to constellations. Patent publication number CN116975501A discloses a method for optimizing satellite payload coverage calculations for ground targets. Although this method can solve the problem of long time and interval calculation time for satellite payload coverage of ground targets, it does not quickly calculate the coverage rate of the coverage area. Patent publication number CN117493796A discloses a method for calculating satellite beam coverage multiplicity based on the grid point method. This method can be used to calculate satellite beam coverage multiplicity, but the calculation efficiency of using the grid method is relatively low. Summary of the Invention

[0005] The purpose of the present invention is to propose a fast calculation method for the coverage rate of a constellation to a ground target area to address the problems of a large number of satellites, diversified ground target areas, and time-consuming coverage calculation. The method can efficiently and accurately calculate the coverage rate of a constellation to a ground target area.

[0006] The technical solution to achieve the purpose of the present invention is: a method for quickly calculating the coverage rate of a constellation over a target area on the ground. The specific implementation steps are as follows:

[0007] Step (1): Perform rough orbit recursion on the constellation satellites to obtain satellite orbit data and calculate the coverage relationship of all satellites to all ground target areas;

[0008] Step (2): Based on the coverage relationship between the satellite and the ground target area, a dynamic step size is used to quickly locate the sub-satellite position of the satellite before and after entering and exiting the ground target area;

[0009] Step (3): Calculate all beam coverage areas of the same satellite relative to the same ground target area and merge all beam coverage areas into one beam coverage strip;

[0010] Step (4): Calculate the intersection of the beam coverage strip of the same satellite relative to the same ground target area and the target area. This area is the area of the ground target area covered by a single satellite.

[0011] Step (5): Count the parts of the same ground target area covered by each relevant satellite, calculate their union, and then calculate the coverage rate of the constellation to the ground target area based on the ratio of the union to the ground target area.

[0012] Compared with the existing technology, the present invention has the following significant advantages: (1) The calculation speed of the coverage problem of a single satellite is fast and the accuracy is high. The present invention uses a dynamic step size to recursively infer the satellite orbit, which greatly reduces the calculation time of the satellite orbit. At the same time, by judging whether the maximum beam profile of the satellite and the maximum profile of the ground area intersect, the satellite related to the ground target area is screened, and the calculation efficiency is higher. For the calculation of the satellite coverage area, the coverage area is abstracted into a polygon in the geodetic coordinate system, and the polygon intersection operation rule is used for fast calculation. This calculation method is fast and accurate. Compared with the traditional grid method, the calculation efficiency is not affected by the accuracy. (2) For the ground coverage problem of the constellation, the relevant satellite can be quickly located. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a flow chart of a method for quickly calculating the coverage rate of a constellation over a ground target area according to the present invention. DETAILED DESCRIPTION

[0014] The present invention will be further described below with reference to the accompanying drawings.

[0015] like Figure 1 As shown, the present invention is a method for quickly calculating the coverage of a constellation to a target area on the ground, comprising the following steps:

[0016] Step (1): Perform rough orbit recursion on the constellation satellites to obtain satellite orbit data and calculate the matching relationship between all satellites and all target areas. The specific description is as follows:

[0017] Perform a large-step recursion on all satellites in the constellation according to the orbital model. Based on the distance between the satellite sub-satellite trajectory and the center of the target area, mark all satellites that may have coverage with the target area, satisfying the following constraints:

[0018] dis(sat i R +area j r ) <dis(sat i ,area j ) (1)

[0019] Among them, sat i R is the maximum radius of the beam coverage of satellite i, area j r is the maximum contour radius of the target area j, dis(sat i R +area j r ) is the sum of the maximum radius of satellite i and target area j, dis(sat i ,area j ) is the distance between the subsatellite point of satellite i and the center of target area j.

[0020] Step (2): Based on the matching relationship between the satellite and the target area, a dynamic step size is used to quickly locate the sub-satellite position of the satellite before and after entering and exiting the ground area. The specific process is as follows:

[0021] For the satellites and ground areas that may have coverage in step (1), at the moment of coverage,

[0022] The satellite orbit is dynamically recursively calculated with a step length of 1 second and a maximum preset step length of n seconds. A binary selection is performed, and formula (1) is used as the binary judgment criterion. If it is true, the step length is increased, and if it is false, the step length is reduced. The orbit recursion is stopped when there is no intersection between the satellite and the target area and the step length is the minimum value. At this time, the sub-satellite position of the satellite before and after entering and exiting the ground area can be quickly located, as described below:

[0023] Ω temp =Ω sat ∩Ω area (2)

[0024] Among them, Ω temp The set of satellite sub-satellite points representing the entry and exit times, Ω sat represents the set of all recursive satellite sub-satellite points, Ω area Represents the input ground target area set.

[0025] Step (3): Calculate all beam coverage areas of the same satellite relative to the same ground target area and merge all areas into one beam coverage strip, as described below:

[0026] For the satellites and ground areas that may have a coverage relationship in step (2), calculate the beam coverage range around the sub-satellite point when the satellite has a coverage event. The coverage range is expressed as a polygon in the geodetic coordinate system. Calculate the union of all beam coverage polygons around the sub-satellite point. This set is the beam coverage strip of the same satellite relative to the same ground target area, which is described as follows:

[0027]

[0028] Among them, Ω band is the satellite beam coverage strip, It is the intersection of the satellite instantaneous beam coverage area and the ground target area.

[0029] Step (4): Calculate the intersection of the beam coverage strip of the same satellite relative to the same ground target area and the ground target area. This area is the area of the ground target area covered by a single satellite. The specific process is as follows:

[0030] For the beam coverage strip of the same satellite relative to the same ground target area calculated in step (3), the strip is also expressed in the form of a polygon in the geodetic coordinate system, and the ground target area is also expressed in the form of a polygon. By calculating the intersection of these two polygons, the coverage area of the same satellite relative to the same ground target area can be obtained. This area is the area of the target area covered by the satellite, which is described as follows:

[0031] Ω out =Ω band ∩Ω area (4)

[0032] Among them, Ω out It is the portion of the ground target area covered by the satellite beam coverage strip.

[0033] Step (5): Count the parts of the same ground target area covered by each relevant satellite, calculate their union, and then calculate the ratio of the union to the area of the ground target area to obtain the coverage rate of the constellation to the ground target area. The specific process is as follows:

[0034] For the intersection of the beam coverage strip and the target area of the same satellite relative to the same ground target area calculated in step (4), the coverage area of each satellite in the entire constellation relative to the same ground target area is counted, and the polygons of all coverage areas are unioned. Finally, the ratio of the area of the union polygon to the area of the ground target area is calculated to obtain the coverage rate of the constellation over the ground target area.

[0035]

[0036] Among them, F areais the coverage rate of the entire constellation to the ground target area, is the area of the same ground target area covered by all satellites, f(Ω area ) is the area of the ground target area.

[0037] The present invention will be further described below with reference to the embodiments.

[0038] In order to illustrate the effectiveness of the method of the present invention and fully demonstrate that the method has the function of quickly calculating the coverage rate of the constellation to the ground target area, the following experiments were completed:

[0039] (1) Experimental initial conditions and parameter settings

[0040] This simulation setup includes a constellation of 24 satellites and five ground target areas, including two circular areas and three polygonal areas. The coverage of these five ground areas is calculated over a single day. The experiment primarily demonstrates the speed of the proposed method by comparing the time required for the algorithm before and after the improvement. Using STK's coverage as a reference value, the accuracy of the proposed method is demonstrated by comparing the absolute error between the coverage calculated before and after the improvement and the reference value.

[0041] The experimental hardware platform is as follows:

[0042] Processor: Intel(R) Core(TM) i9-14900HX; Memory: 32.0GB; Operating system: Windows 11; Development tools: Visual Studio 2022.

[0043] Take some satellites in the constellation as an example, and their orbital parameters are as follows:

[0044] Table 1 Some satellite orbit experiment parameters

[0045]

[0046] Take some satellites in the constellation as an example, and their payload parameters are as follows:

[0047] Table 2 Experimental parameters of some satellite payloads

[0048]

[0049]

[0050] The ground target area parameters are as follows:

[0051] Table 3 Experimental parameters of ground target area

[0052]

[0053] (2) Analysis of experimental results

[0054] In one day, the coverage of the preset constellation for five target areas on the ground is as follows:

[0055] Table 4 Ground target area coverage

[0056]

[0057] The absolute errors before and after the improvement and the present invention relative to STK are shown in the following table:

[0058] Table 5 Absolute error table with STK coverage

[0059]

[0060] The time consumption of the algorithm of the present invention and the time consumption of the algorithm before improvement are as follows:

[0061] Table 6 Algorithm time consumption

[0062]

[0063] From the analysis of the above table, we can see that the average absolute error of the present invention is 0.027, while the average absolute error of the algorithm before improvement is 0.133. The coverage error calculated by the present invention is only 20.3% of that before improvement, and the time consumption is only 20.2% of that before improvement.

[0064] In summary, the present invention can quickly and accurately calculate the coverage rate of a constellation over a ground target area.

[0065] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for quickly calculating the coverage of a constellation-based target area, characterized in that: The steps include: Step (1): Perform rough orbit recursion on the constellation satellites to obtain satellite orbit data and calculate the coverage relationship of all satellites to all ground target areas; Step (2): Based on the coverage relationship between the satellite and the ground target area, use a dynamic step size to locate the sub-satellite position of the satellite before and after entering and exiting the ground target area; Step (3): Calculate all beam coverage areas of the same satellite relative to the same ground target area and merge all areas into one beam coverage strip; the specific implementation method is as follows: For the coverage relationship between the satellite and the ground target area in step (2), the beam coverage range around the sub-satellite point of the satellite is calculated when a coverage event occurs. The coverage range is expressed as a polygon in the geodetic coordinate system. The union of the beam coverage polygons around all sub-satellite points is calculated. This set is the beam coverage strip of the same satellite relative to the same ground target area, which is described as follows: Among them, Ω band is the satellite beam coverage strip, It is the intersection of the satellite instantaneous beam coverage area and the ground target area; Step (4): Calculate the intersection of the beam coverage strip of the same satellite relative to the same ground target area and the ground target area. This area is the area of the ground target area covered by a single satellite. Step (5): Count the parts of the same ground target area covered by each relevant satellite, calculate their union, and calculate the ratio of the area of the union area to the area of the ground target area to obtain the coverage rate of the constellation on the ground target area.

2. The method for rapidly calculating the coverage of a constellation-oriented ground target area according to claim 1, characterized in that: The specific implementation method of step (1) is as follows: Perform a large-step recursion on all satellites in the constellation according to the orbital model. Based on the distance between the satellite sub-satellite point trajectory and the center of the target area, mark all satellites that may have coverage with the target area, as follows: dis(sat i R +area j r )<dis(sat i ,area j ) (1) Among them, sat i R is the maximum radius of the beam coverage of satellite i, area j r is the maximum contour radius of the target area j, dis(sat i R +area j r ) is the sum of the maximum radius of satellite i and target area j, dis(sat i , area j ) is the distance between the subsatellite point of satellite i and the center of target area j.

3. The method for rapidly calculating the coverage of a constellation-oriented ground target area according to claim 2, characterized in that: The specific implementation method of step (2) is as follows: In view of the coverage relationship between the satellite and the ground target area in step (1), at the moment of coverage, the satellite orbit is dynamically recursively stepped, and a binary selection is made between the minimum step size of 1 second and the maximum preset step size of n seconds. Formula (1) is used as the binary judgment standard. If it is true, the step size is increased, and if it is false, the step size is reduced. The orbit recursion is stopped until there is no intersection between the satellite and the target area and the step size is the minimum value. At this time, the sub-satellite point position of the satellite before and after entering and exiting the ground target area can be located, which is described as follows: Oh temp =Oh sat ∩Oh area (2) Among them, Ω temp The set of satellite sub-satellite points representing the entry and exit times, Ω sat represents the set of all recursive satellite sub-satellite points, Ω area Represents the input ground target area set.

4. The method for rapidly calculating the coverage of a constellation-oriented ground target area according to claim 1, characterized in that: The specific implementation method of step (4) is as follows: For the beam coverage strip of the same satellite relative to the same ground target area calculated in step (3), the strip is also expressed as a polygon in the geodetic coordinate system, and the ground target area is also expressed as a polygon. By finding the intersection of these two polygons, the coverage area of the same satellite relative to the same ground target area can be calculated. This area is the area of the target area covered by the satellite, which is described as follows: Oh out =Oh band ∩Oh area (4) Among them, Ω out is the portion of the ground target area covered by the satellite beam coverage strip, Ω band is the satellite beam coverage strip, Ω area Represents the input ground target area set.

5. The method for rapidly calculating the coverage of a constellation-oriented ground target area according to claim 1, characterized in that: The specific implementation method of step (5) is as follows: For the intersection of the beam coverage strip and the target area of the same satellite relative to the same target area calculated in step (4), the coverage area of each satellite in the entire constellation for the same ground target area is counted, and the union of all coverage area polygons is calculated. The union is the coverage area of all satellites covering the same ground area. Finally, the ratio of the area of the union polygon to the area of the ground target area is calculated to obtain the coverage rate of the constellation for the ground target area, which is described as follows: Among them, F area is the coverage rate of the entire constellation to the ground target area, is the area of the same ground target area covered by all satellites, f(Ω area )The area of the ground target area.

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