Multi-dimensional formation spacecraft security situation assessment method

Abstract

The invention relates to a multi-dimensional formation spacecraft safety situation assessment method. According to the method, various elements for evaluating threats in a threat event are calculated, and the means strength, the time urgency degree, the space urgency degree and the scale urgency degree under the condition that multiple threat targets are combined are obtained through weighting, so that the situation intensity of the whole formation spacecraft is calculated. The specific calculation method comprises the following steps: step 1, forecasting target orbits of both threat parties; step 2, element layer index calculation; 3, calculating indexes of a measurement layer; and 4, calculating the situation intensity. The method has the advantage of wide applicability, can be applied to a multi-target threat formation spacecraft scene, and solves the problem that the security situation of the formation spacecraft is not easy to quantify.

Description

Technical Field

[0001] The present invention relates to a multi-dimensional security situation assessment method for formation spacecraft. The method calculates various elements of threat assessment in a threat event, and weightedly obtains the means strength, time urgency, space urgency, and scale urgency under the composite situation of multiple threat targets, so as to calculate the overall situation intensity of the formation spacecraft, and belongs to the field of aerospace technology. Background Art

[0002] In recent years, the number of satellites in orbit has increased dramatically, and strategic competition between countries in space has also intensified. It is not uncommon for satellites in orbit to be actively approached by non-cooperative targets. At the same time, depending on the payload, satellites with approaching intentions may have different non-cooperative means, posing different degrees of threats to the approached satellite. At this time, it is necessary to evaluate the situation of satellites being threatened by non-cooperative threats, in order to determine the safety situation of the satellite and make possible disposal countermeasures.

[0003] In addition, the technology of multiple satellites operating in formation is becoming more mature. Compared with the traditional "single large satellite" form, formation spacecraft has the advantages of multi-satellite coordination, greater flexibility, and diverse mission capabilities. However, traditional situation assessment research focuses on single satellites, and there is still a certain gap in related research on formation spacecraft as a whole. Therefore, it is necessary to propose a set of situation assessment indicator systems that can adapt to multiple objects in order to comprehensively and accurately evaluate the on-orbit approach threat events faced by formation spacecraft. Summary of the invention

[0004] 1. Purpose

[0005] The present invention focuses on the threat events faced by formation spacecraft in orbit. By calculating the various elements of threat evaluation in a threat event, the weighted means strength, time urgency, space urgency, and scale urgency in the case of multiple threat targets are obtained to calculate the overall situation intensity of the formation spacecraft, thereby achieving a quantitative assessment of the safety situation of the formation spacecraft.

[0006] 2. Technical solution

[0007] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions.

[0008] A multi-dimensional safety situation assessment index system for formation spacecraft includes three levels of indicators, namely, situation level, measurement level, and factor level, from top to bottom. Figure 1As shown in the figure. Among them, the situation layer indicator is the situation intensity, which is used to quantitatively evaluate the safety situation of formation spacecraft under multi-target threats, and its value is between 0 and 1. The measurement layer reflects the degree of threat from multiple evaluation dimensions of a threat event, including means urgency, space urgency, time urgency and scale urgency. The element layer is the bottom-level indicator, including the basic elements composed of both threat parties in the threat scenario, with clear physical meanings, including accompanying flight time, approach distance, approach time, etc.

[0009] Based on the above indicator system, a multi-dimensional formation spacecraft safety situation assessment method includes the following steps:

[0010] Step 1: Prediction of target orbits of both threat parties

[0011] The threat parties include our formation satellites and enemy threat targets. First, the orbital elements of the threat targets are determined according to the space situational awareness system. For the average orbital elements such as the two-row orbital elements, a semi-analytical predictor such as SGP4 is used. For the instantaneous orbital elements, an integral predictor is used to predict the position vector of the spacecraft within the simulation start and end time range.

[0012] Step 2: Calculation of factor layer indicators

[0013] The element layer indicators are the bottom-level indicators of the evaluation system, including the basic elements composed of both threat parties in the threat scenario, and have clear physical meanings. Based on the orbit forecast, the element layer indicators corresponding to each indicator of the measurement layer are calculated respectively:

[0014] (1) Calculation of indicators at the means intensity factor level:

[0015] The indicators of the means strength factor layer include payload strength, minimum approach distance, effective reconnaissance time and accompanying flight time. Payload strength refers to the weight assigned according to the payload type carried by the threat target, reflecting the threat capability of the threat target; minimum approach distance refers to the closest distance of the threat target relative to the formation satellite within the simulation time range; effective reconnaissance time refers to the total time that the threat target meets the reconnaissance constraint condition relative to the formation satellite within the simulation time range; accompanying flight time refers to the total time that the threat target meets the accompanying flight distance constraint relative to the formation satellite within the simulation time range.

[0016] (2) Calculation of spatial urgency factor layer indicators:

[0017] The spatial urgency factor layer indicators include the maneuverable reachable domain of the formation satellite and the maneuverable reachable domain of the threat target. The maneuverable reachable domain refers to the set of all positions that the spacecraft can reach under the given initial orbit and fuel constraints.

[0018] (3) Calculation of indicators at the time urgency factor level:

[0019] The time urgency factor layer indicator is the approach time, which refers to the earliest time when the threat target is closest to the formation satellite within the simulation time range.

[0020] (4) Calculation of indicators at the scale urgency factor level:

[0021] The scale urgency factor layer indicators include the number of threatened member satellites, the importance of member satellites and the number of threat targets. The present invention defines that a threat constitutes a threat when a threat target enters a certain distance range of a formation member satellite within the simulation time range, and the number of threatened member satellites and the number of threat targets can be calculated based on the relative distance relationship; the importance of member satellites refers to a weight vector determined according to the status of member satellites in the formation.

[0022] Step 3: Calculation of metrics at the measurement layer

[0023] The metrics layer indicators include means strength, spatial urgency, time urgency and scale urgency, which are calculated by different weighting methods according to the element layer indicators. Means strength is calculated according to the load strength and simulation parameters, reflecting the threat capability of the target. Spatial urgency is defined as the proportion of the composite maneuverable reachable domain of the threat target to the maneuverable reachable domain of the formation satellite. Time urgency is calculated according to the approach time. Scale urgency is obtained by weighting the number of threatened member satellites and the number of threat targets in the formation. Spatial urgency, time urgency and scale urgency reflect the urgency of the threat event from the three dimensions of space, time and scale respectively.

[0024] Step 4: Situation Intensity Calculation

[0025] The situation intensity reflects the overall threat level of the formation spacecraft, and is calculated through the hierarchical analysis method based on the calculation results of means intensity, space urgency, time urgency and scale urgency in step three.

[0026] 3. Advantages and effects

[0027] The present invention proposes a multi-dimensional security situation assessment method for formation spacecraft, which conducts assessment from multiple dimensions such as means strength, space urgency, time urgency, and scale urgency, and comprehensively quantifies the security situation. The present invention has wide applicability and can be applied to scenarios where multiple targets threaten formation spacecraft, solving the problem that the security situation of formation spacecraft is difficult to quantify. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is an indicator system for assessing the safety situation of spacecraft in a formation.

[0029] Figure 2 It is a flowchart of the safety situation assessment method for formation spacecraft. DETAILED DESCRIPTION

[0030] The present invention is further described below in conjunction with the accompanying drawings and a multi-target threat formation spacecraft scenario embodiment, but this embodiment is not intended to limit the present invention. All similar methods and similar variations of the present invention are included in the protection scope of the present invention.

[0031] Depend on Figure 2 It can be seen that the present invention provides a multi-dimensional formation spacecraft safety situation assessment method, which mainly includes the following steps:

[0032] Step 1: Prediction of target orbits of both threat parties

[0033] The threatening parties include our formation satellites and enemy threatening targets. Firstly, the orbital elements of the threatening parties are determined according to the space situation awareness system.

[0034] In this embodiment, the formation satellites adopt a wheel formation configuration of "1 main + 4 auxiliary", and the number of orbital elements is as follows:

[0035] Table 1 Number of track elements in wheel formation

[0036]

[0037]

[0038] In this embodiment, there are 2 threat targets, and the number of orbital elements is as follows:

[0039] Table 2 Number of threat target orbit elements

[0040]

[0041] This embodiment uses the SGP4 predictor to perform orbit prediction, selects 3 days after the epoch time as the simulation time range, and obtains the position vector of the spacecraft through orbit prediction.

[0042] Step 2: Calculation of factor layer indicators

[0043] The element layer indicators are the bottom-level indicators of the evaluation system, including the basic elements composed of both threat parties in the threat scenario, and have clear physical meanings. Based on the orbit forecast, the element layer indicators corresponding to each indicator of the measurement layer are calculated respectively:

[0044] (1) Calculation of indicators at the means intensity factor level:

[0045] The indicators at the means strength element layer include load strength, minimum approach distance, effective reconnaissance time and escort time.

[0046] The load strength refers to the weight assigned according to the type of load carried by the threat target, reflecting the threat capability of the threat target. The load strength value can be referred to the following table. In this embodiment, the target carries an optical reconnaissance device, and the load strength is 0.4.

[0047] Table 3 Load strength values

[0048]

[0049] The minimum approach distance refers to the closest distance between the threat target and the formation satellite within the simulation time range. The relative distance between the threat target j and the member satellite i in the formation at the kth discrete moment is defined as:

[0050]

[0051] in, and is the position vector of satellite i and threat target j at time t. The closest distance of threat target j to member satellite i in the formation can be expressed as:

[0052]

[0053] Among them, n t is the number of discrete moments. The approaching moment corresponding to the approaching distance is The minimum approach distance can be expressed as:

[0054]

[0055] Among them, n formation and n threat are the number of satellites in the formation and the number of threat targets respectively. In this embodiment, the minimum approach distance calculation result is 0.50 km.

[0056] The effective reconnaissance duration refers to the total duration that the threat target meets the reconnaissance constraint conditions relative to the formation satellite within the simulation time range. Consider the two reconnaissance constraints of reconnaissance distance and illumination angle:

[0057]

[0058] in, is the angle between the line connecting the member satellite i and the threat target j in the formation at the kth discrete moment relative to the direction of the sun, R spy and θ spy is the maximum detection distance and illumination angle constraint. The total detection time can be expressed as:

[0059]

[0060] in, is the surveillance time of threat target j relative to member satellite i in the formation. In this embodiment, the total surveillance time is calculated to be 53.2h.

[0061] The duration of the accompanying flight refers to the time within which the threat target meets the accompanying flight distance constraint relative to the formation satellite within the simulation time range. The total duration of acc is the maximum escort distance. The total escort duration can be expressed as:

[0062]

[0063] in, is the duration of the escort of the threat target j relative to the member satellite i in the formation. In this embodiment, the total escort duration is calculated to be 261.9h.

[0064] (2) Calculation of spatial urgency factor layer indicators:

[0065] The spatial urgency factor layer indicators include the maneuverable reachable domain of the formation satellite and the maneuverable reachable domain of the threat target. The maneuverable reachable domain refers to the set of all positions that the spacecraft can reach under the given initial orbit and fuel constraints. The present invention adopts a reachable domain with free maneuvering time. The detailed calculation method has been introduced in relevant papers (Wen C, Zhao Y, Shi P. Precise determination of reachable domain for spacecraft with single impulse [J]. Journal of Guidance, Control, and Dynamics, 2014, 37 (6): 1767-1779.), which will not be repeated here.

[0066] (3) Calculation of indicators at the time urgency factor level:

[0067] The time urgency factor layer indicator is the approach time. The approach time refers to the earliest time when the threat target is closest to the formation satellite within the simulation time range, which can be expressed as:

[0068]

[0069] Among them, the approaching time corresponding to the approaching distance is In this embodiment, the calculated approach time is 10.3h.

[0070] (4) Calculation of indicators at the scale urgency factor level:

[0071] The scale urgency factor layer indicators include the number of threatened member satellites, the importance of member satellites and the number of threat targets. The present invention defines that a threat constitutes a threat when a threat target enters a certain distance range of a formation member satellite within the simulation time range, and the number of threatened member satellites and the number of threat targets can be calculated based on the relative distance relationship.

[0072] The importance of a member satellite refers to a weight vector determined according to the position of the member satellite in the formation. In this embodiment, the importance of the main satellite of the wheel formation is higher than that of the sub-satellite (auxiliary satellite), and the importance vector is taken as:

[0073] I f =[10.60.60.60.6] T

[0074] Step 3: Calculation of metrics at the measurement layer

[0075] The measurement layer indicators include means intensity, spatial urgency, time urgency and scale urgency, which are calculated by different weighting methods according to the factor layer indicators.

[0076] The means strength is calculated based on the load strength P and simulation parameters, reflecting the threat posed by the target. First, the element layer indicators are normalized, and linear normalization is used to map the indicators to the range of [0,1]. The means strength evaluation index vector can be expressed as:

[0077]

[0078] in, are the normalized upper limits of the corresponding indicators. tech It can be expressed as:

[0079]

[0080] Among them, w tech is the means strength weight vector, which can be set according to different load types to meet the following requirements:

[0081]

[0082] In this embodiment, w tech Take [0.30.50.2] T , the calculated result of the means strength is 0.354.

[0083] The spatial urgency is defined as the ratio of the composite maneuverable reachable domain of the threat target to the maneuverable reachable domain of the formation satellite. Since the distance between formation satellites is generally close, their reachable domains are approximately the same. The composite threat domain refers to the part of the intersection of the union of the threat target reachable domain and the formation satellite reachable domain to the reachable domain of the formation satellite, which can be expressed as:

[0084]

[0085] in, and are the maneuverable domains of threat targets and formation satellites respectively. The spatial urgency can be expressed as:

[0086]

[0087] In this embodiment, the calculation result of the space urgency is 0.925.

[0088] Time urgency is defined as the time approaching t min The simulation time range t max The ratio reflects the urgency of the threat event from the time dimension and can be expressed as:

[0089]

[0090] In this embodiment, the calculation result of the time urgency is 0.860.

[0091] The scale urgency is obtained by weighting the number of threatened member satellites and the number of threat targets in the formation. According to the threat situation of satellites in the formation, the threat vector is defined:

[0092]

[0093] The threatened formation member satellites are weighted according to their importance and normalized to the range of [0,1]. The scale urgency evaluation index vector can be expressed as:

[0094]

[0095] in, is the normalized upper limit of the number of threat targets, and the scale urgency can be expressed as:

[0096] S scale =w scale E scale

[0097] Among them, w scale is the scale urgency weight vector, satisfying:

[0098]

[0099] In this embodiment, w scale Take [0.30.7] T , the calculation result of scale urgency is 0.777.

[0100] Step 4: Situation Intensity Calculation

[0101] The situation intensity reflects the overall threat level of the formation spacecraft, and is calculated through the hierarchical analysis method based on the calculation results of means intensity, space urgency, time urgency and scale urgency in step three.

[0102] When the weight coefficient is determined by using the hierarchical analysis method, it is necessary to construct a pairwise comparison matrix. In this embodiment, the comparison matrix is ​​shown in the following table.

[0103] Table 4 Comparison matrix

[0104]

[0105] After determining the comparison matrix, calculate the eigenvector corresponding to the largest eigenvalue of the comparison matrix, normalize it (make the sum of the elements in the vector equal to 1) and get the weight vector w intensity In this embodiment, the calculation result of the situation intensity weight vector is:

[0106] w intensity =[0.55960.09550.09550.2495] T

[0107] The situation intensity can be expressed as:

[0108]

[0109] In this embodiment, the calculated result of the situation intensity is 0.562. The spacecraft in the formation as a whole are under a strong approaching threat, and the actual situation should be taken into consideration and dealt with accordingly.

[0110] The embodiments described above are only used as illustrations of the technical solutions of the present invention and do not limit the protection scope of the present invention. It should be understood by ordinary technicians in the field of applying the present invention that they can make appropriate modifications to the technical solutions or make equivalent replacements for some technical details, but the technical solutions after these operations do not deviate from the scope of protection of this patent.

Claims

1. A multi-dimensional formation spacecraft safety situation assessment method, characterized in that: The following steps are involved: Step 1: Prediction of target orbits of both threat parties The threatening parties include our formation satellites and enemy threatening targets; firstly, the orbital elements of the threatening parties' targets are determined according to the space situation awareness system; Step 2: Calculation of factor layer indicators The element layer indicators are the bottom-level indicators of the evaluation system, including the basic elements composed of both threat parties in the threat scenario. On the basis of orbit forecast, the element layer indicators corresponding to each indicator of the measurement layer are calculated respectively: Step 3: Calculation of metrics at the measurement layer The measurement layer indicators include means strength, space urgency, time urgency and scale urgency, which are calculated by different weighting methods according to the element layer indicators; the means strength is calculated according to the load strength and simulation parameters, reflecting the threat capability of the target; the space urgency is defined as the proportion of the composite maneuverable reachable domain of the threat target to the maneuverable reachable domain of the formation satellite, the time urgency is calculated according to the approach time, and the scale urgency is obtained by weighting the number of threatened member satellites and the number of threat targets in the formation. The space urgency, time urgency and scale urgency reflect the urgency of the threat event from the three dimensions of space, time and scale respectively; Step 4: Situation Intensity Calculation The situation intensity reflects the overall threat level of the formation spacecraft, and is calculated through the hierarchical analysis method based on the calculation results of means intensity, space urgency, time urgency and scale urgency in step three.

2. The multi-dimensional formation spacecraft safety situation assessment method according to claim 1, characterized in that: In step 1, for the average orbital elements such as the two-row orbital elements, a semi-analytical predictor such as SGP4 is used, and for the instantaneous orbital elements, an integral predictor is used to predict the position vector of the spacecraft within the simulation start and end time range.

3. The multi-dimensional formation spacecraft safety situation assessment method according to claim 1, characterized in that: In step 2, it specifically includes: (1) Calculation of indicators at the means intensity factor level: The indicators of the means strength factor layer include payload strength, minimum approach distance, effective reconnaissance time and accompanying flight time; payload strength refers to the weight assigned according to the payload type carried by the threat target, reflecting the threat capability of the threat target; minimum approach distance refers to the closest distance of the threat target relative to the formation satellite within the simulation time range; effective reconnaissance time refers to the total time that the threat target meets the reconnaissance constraint condition relative to the formation satellite within the simulation time range; accompanying flight time refers to the total time that the threat target meets the accompanying flight distance constraint relative to the formation satellite within the simulation time range; (2) Calculation of spatial urgency factor layer indicators: The spatial urgency factor layer indicators include the maneuverable reachable domain of the formation satellite and the maneuverable reachable domain of the threat target; the maneuverable reachable domain refers to the set of all positions that the spacecraft can reach under the given initial orbit and fuel constraints; (3) Calculation of indicators at the time urgency factor level: The time urgency factor layer indicator is the approach time; the approach time refers to the earliest time corresponding to the threat target being closest to the formation satellite within the simulation time range; (4) Calculation of indicators at the scale urgency factor level: The scale urgency factor layer indicators include the number of threatened member satellites, the importance of member satellites and the number of threat targets; it is defined that a threat constitutes a threat when a threat target enters the distance range of a formation member satellite within the simulation time range, and the number of threatened member satellites and the number of threat targets are calculated based on the relative distance relationship; the importance of a member satellite refers to a weight vector determined according to the position of the member satellite in the formation.

4. The multi-dimensional formation spacecraft safety situation assessment method according to claim 3 is characterized by: In step 2, the relative distance of threat target j to member satellite i in the formation at the kth discrete moment is defined as: in, and is the position vector of satellite i and threat target j at time t; the closest distance of threat target j to member satellite i in the formation is expressed as: Among them, n t is the number of discrete moments; the approaching moment corresponding to the approaching distance is The minimum approach distance is expressed as: Among them, n formation and n threat They are the number of satellites in the formation and the number of threat targets; Consider two detection constraints: detection distance and illumination angle: in, is the angle between the line connecting the member satellite i and the threat target j in the formation at the kth discrete moment relative to the direction of the sun, R spy and θ spy is the maximum detection distance and illumination angle constraint; the total detection time is expressed as: in, is the detection time of threat target j relative to member satellite i in the formation; The threat target meets the accompanying distance constraint relative to the formation satellite The total duration of acc is the maximum escort distance; the total escort duration is expressed as: in, is the duration of escort of threat target j relative to member satellite i in the formation.

5. The multi-dimensional formation spacecraft safety situation assessment method according to claim 3, characterized in that: In step 2, the approach time is expressed as: Among them, the approaching time corresponding to the approaching distance is 6. The multi-dimensional formation spacecraft safety situation assessment method according to claim 1, characterized in that: In step three, the means strength is calculated based on the load strength P and simulation parameters, reflecting the threat posed by the target. The element layer indicators are normalized and linear normalization is used to map the indicators to the range of [0,1]. The means strength evaluation index vector is expressed as: in, are the normalized upper limits of the corresponding indicators respectively; the strength of the means S tech It is expressed as: Among them, w tech is the means strength weight vector, which is set according to different load types and satisfies:

7. The multi-dimensional formation spacecraft safety situation assessment method according to claim 6, characterized in that: In step three, the composite threat domain is represented as: in, and are the maneuverable domains of threat targets and formation satellites respectively; the spatial urgency is expressed as:

8. The multi-dimensional formation spacecraft safety situation assessment method according to claim 7, characterized in that: In step 3, time urgency is defined as the time approaching t min The simulation time range t max The ratio reflects the urgency of the threat event from the time dimension, which is expressed as:

9. The multi-dimensional formation spacecraft safety situation assessment method according to claim 8, characterized in that: In step 3, the scale urgency is obtained by weighting the number of threatened member satellites and the number of threat targets in the formation. According to the threat situation of satellites in the formation, the threat vector is defined: The threatened formation member satellites are weighted according to their importance and normalized to the range of [0,1]. The scale urgency evaluation index vector is expressed as: in, is the normalized upper limit of the number of threat targets, and the scale urgency is expressed as: S scale =w scale E scale Among them, w scale is the scale urgency weight vector, satisfying:

10. The multi-dimensional formation spacecraft safety situation assessment method according to claim 1, characterized in that: In step 4, when using the hierarchical analysis method to determine the weight coefficient, it is necessary to construct a pairwise comparison matrix. After determining the comparison matrix, the eigenvector corresponding to the maximum eigenvalue of the comparison matrix is ​​calculated and normalized to obtain the weight vector w intensity ; The situation intensity is expressed as:

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