Inter-satellite link sun-sun avoidance method for huge satellite base satellite network

Abstract

The invention provides an inter-satellite link sun-sun avoidance method for a giant satellite base satellite network. The method comprises the following steps: initializing the giant satellite base satellite network; calculating the date of the inter-satellite link influenced by the sun; calculating the included angle between each inter-satellite link and the sun position vector in the date influenced by the sun; and avoiding the sun. According to the method, on the basis of the uniform distribution characteristic of a Walker constellation, the dates of the same-orbit link and the different-orbit link influenced by the sun-sun are calculated under a J2000 geocentric inertial coordinate system, the dates of the inter-satellite links influenced by the sun-sun are calculated according to the motion law of the sun and the characteristics of the different types of inter-satellite links, and the data of the inter-satellite links influenced by the sun-sun are calculated within the dates influenced by the sun-sun. According to the relative position relation of the satellites, the included angle between the inter-satellite link and the sun is calculated in real time, whether the inter-satellite link is affected by the sun or not is judged, the optical axis direction of the laser terminal does not need to be obtained in real time, the included angle between the inter-satellite link and the sun does not need to be calculated in real time on the date without the sun influence, and invalid calculation expenses are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite communication, and relates to a method for avoiding sun outage of inter-satellite links in a mega-constellation satellite network. Background Art

[0002] In recent years, the deployment of mega-constellation communication satellite constellations represented by Starlink and OneWeb has marked the rapid development stage of mega-constellation satellite network technology. A mega-constellation usually consists of thousands to tens of thousands of low-earth orbit satellites, and mostly adopts the Walker constellation configuration. Its core feature is that all satellites maintain the same orbital altitude and inclination, and are evenly distributed in each orbital plane. Such a system can achieve wide-area communication coverage with low latency and high reliability by equipping with inter-satellite laser link technology, and is considered an important infrastructure for the future space-air-ground integrated network. However, in the space environment, inter-satellite laser links face multiple challenges: in addition to conventional risks such as space debris impact and thermal radiation disturbance, the sun outage effect is particularly prominent - when the sun forms a collinear interference with the inter-satellite communication link, it will not only cause the interruption of laser signals, but may also cause permanent damage to sensitive optical devices inside the laser terminal.

[0003] The core principle of avoiding sun outage of inter-satellite links is based on real-time monitoring and dynamic control of space geometry: by continuously predicting the spatial geometric relationship between the sun vector and the communication link through the on-board attitude and orbit control system, when the included angle between the two is lower than a preset threshold, the device pointing adjustment or link interruption is triggered autonomously, so as to avoid the interference of solar radiation on laser signals and optical devices. For example, the patent application with the application publication number CN119402063A and the name "A method and system for avoiding sun outage of inter-satellite laser communication against direct sunlight" adopts the strategy of calculating the included angle between the sun vector and the optical axis pointing on the satellite in real time, autonomously switches the avoidance mode according to the threshold judgment, and determines the azimuth / pitch adjustment direction through coordinate transformation to achieve efficient avoidance at the single-link level. However, in a mega-constellation network with N nodes, this scheme needs to maintain a vector calculation scale of O(N) in real time, and the communication overhead and computing resource occupation increase exponentially with the network scale, making it difficult to meet the engineering implementation requirements of a constellation with tens of thousands of satellites. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art, and propose a method for avoiding sun outage of inter-satellite links in a mega-constellation satellite network, aiming to reduce the calculation overhead.

[0005] To achieve the above purpose, the technical solution of the present invention includes the following steps:

[0006] (1) Initialize the mega-constellation satellite network:

[0007] Initialize the giant constellation satellite network \(W = \{w\}\) with a total of \(N = P\times S\) satellites, where each of the \(P\) orbits has \(S\) satellites distributed, p,s \(|1\leq p\leq P, 1\leq s\leq S\}\). The \(s\)-th satellite \(w\) on the \(p\)-th orbit p,s forms an in-orbit laser communication link with the 2 adjacent satellites in the same orbit and an out-of-orbit laser communication link with the 2 adjacent satellites in the adjacent orbit, where \(P\geq5\) and \(S\geq10\);

[0008] (2) Calculate the dates when the inter-satellite links are affected by solar eclipse:

[0009] In the J2000 geocentric inertial coordinate system, calculate the date \(D\) when the in-orbit link is affected by solar eclipse through the normal vector of the \(p\)-th orbital plane and the position vector of the sun on the \(d\)-th day. intra At the same time, calculate the date \(D\) when the out-of-orbit link is affected by solar eclipse through the declination \(\chi\) d of the sun on the \(d\)-th day and the maximum angle \(\omega\) between each out-of-orbit link and the equatorial plane, where \(d\) represents the number of days from January 1 of the current year to the calculated date, and \(d\in[1,365]\); intra

[0010] (3) Calculate the angle between each inter-satellite link and the sun position vector during the dates affected by solar eclipse:

[0011] In the J2000 geocentric inertial coordinate system, calculate the angle \(\theta\) intra between the direction vector of each in-orbit link at time \(t\) and the sun position vector during the date \(D\) n when the in-orbit link is affected by solar eclipse. At the same time, calculate the angle inter between the direction vector of each out-of-orbit link at time \(t\) and the sun position vector during the date \(D\) when the out-of-orbit link is affected by solar eclipse, where \(n\in[1,N]\), \(t\in[1,T]\), and \(T\) is the total number of seconds in a day;

[0012] (4) Avoid solar eclipse:

[0013] According to the current date \(d\), the dates \(D\) intra and \(D\) inter affected by solar eclipse, and the angles \(\theta\) n (t) between each in-orbit and out-of-orbit inter-satellite link and the sun position vector during \(D\) and

[0014] turn off the in-orbit or out-of-orbit inter-satellite link to achieve the avoidance of solar eclipse.

[0015] Compared with the prior art, the present invention has the following advantages:Based on the uniform distribution characteristics of the Walker constellation, the present invention calculates the dates affected by solar eclipse for in-orbit and cross-orbit links respectively in the J2000 geocentric inertial coordinate system, and calculates the dates when the inter-satellite link is affected by solar eclipse according to the movement law of the sun and the characteristics of different types of inter-satellite links. During the dates affected by solar eclipse, according to the relative position relationship of the satellites, the included angle between the inter-satellite link and the sun is calculated in real time, and it is judged whether it is affected by solar eclipse, without the need to obtain the pointing of the optical axis of the laser terminal in real time. During the dates without solar eclipse, there is no need to calculate the included angle between the inter-satellite link and the sun in real time. Compared with the prior art, the repeated operations are effectively reduced, and the ineffective computational overhead is reduced. Description of the Drawings

[0016] Figure 1 It is a flowchart for the implementation of the present invention. Detailed Embodiments

[0017] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0018] Refer to Figure 1 , the present invention includes the following steps:

[0019] Step 1) Initialize the giant constellation satellite network:

[0020] In the J2000 geocentric inertial coordinate system, initialize a Walker-type giant constellation satellite network W = {w p,s | 1 ≤ p ≤ P, 1 ≤ s ≤ S} with a total of N = P × S satellites, where each of the P orbits has S satellites. The s-th satellite w p,s on the p-th orbit forms an in-orbit laser communication link with 2 adjacent satellites on the same orbit, and forms a cross-orbit laser communication link with 2 adjacent satellites on the adjacent orbits, where P ≥ 5 and S ≥ 10;

[0021] In this embodiment, the coordinate description and vector calculation are based on the J2000 geocentric inertial coordinate system, which takes the geocenter as the origin, the x-axis points to the vernal equinox at 12:00 on January 1, 2000, the z-axis points to the north pole of the earth's rotation axis, and the y-axis is perpendicular to the x-axis and z-axis and conforms to the right-hand rule. To ensure the stability of the laser link, each satellite establishes 1 in-orbit link with the adjacent forward and backward satellites in the moving direction on the same orbit respectively. For example, the satellite w 1,5 establishes 1 in-orbit link with w 1,4 and w 1,6 respectively. The entire satellite network has N in-orbit links. At the same time, each satellite establishes 1 cross-orbit link with the satellites with the same number on the left and right adjacent orbits in the moving direction respectively. For example, the satellite w 2,5 establishes 1 cross-orbit link with w 1,5 and w 3,5One off-plane link is established respectively. There are N off-plane links in the whole satellite network. In the mega-constellation of this embodiment, the number of orbits P = 60, the number of satellites in each orbit S = 60, and the total number of satellites N = 3600. There are 3600 in-plane links and 3600 off-plane links in the whole satellite network;

[0022] Step 2) Calculate the dates when the inter-satellite links are affected by solar eclipse:

[0023] In the J2000 geocentric inertial coordinate system, through the normal vector of the p-th orbital plane and the position vector of the sun on the d-th day Calculate the date D when the in-plane link is affected by solar eclipse intra , and the calculation method is:

[0024] Calculate the normal vector of the p-th orbital plane and the position vector of the sun on the d-th day The included angle β between them p,d , and let β p,d Satisfy β with the preset threshold μ p,d ∈[90°-μ,90°], and the date is taken as the date D when the in-plane link is affected by solar eclipse intra , where:

[0025]

[0026] χ d =23.5sinδ d

[0027] Among them, d represents the number of days between January 1 of the current year and the calculated date, d∈[1,365], arccos(·) represents the inverse cosine function, [·] represents the coordinates of the vector in the J2000 geocentric inertial coordinate system, Ω p Represents the right ascension of the ascending node of the p-th orbit, γ represents the orbital inclination, γ∈[0°,90°], mod(·) represents the modulo operation, δ d Represents the right ascension of the sun on the d-th day;

[0028] All the satellite orbits described in the present invention are circular orbits with an eccentricity of 0. The right ascension of the ascending node of the p-th orbit represents the angular distance from the position where the satellite in this orbit flies from south to north across the equatorial plane to the positive direction of the x-axis from west to east. The orbital inclination represents the angle between each orbital plane and the equatorial plane. The orbital inclinations of each orbit in the Walker constellation are the same. In this embodiment, γ = 45°. The right ascension of the sun represents the angular distance from the projection point of the sun on the equatorial plane to the positive direction of the x-axis from west to east. The declination of the sun represents the angle between the position vector of the sun and the equatorial plane. When the sun is in the northern part of the equatorial plane, the declination of the sun is positive, and vice versa;

[0029] Normal vector of the p-th orbital plane Represents a unit vector starting from the coordinate origin and along the direction perpendicular to the p-th orbital plane. The position vector of the sun represents a unit vector starting from the coordinate origin and pointing to the position where the sun is located. The threshold μ is a preset value, indicating that when the angle between the inter-satellite link and the sun is less than this value, the link is affected by solar eclipse. When the angle β between the normal vector of the p-th orbital plane and the position vector of the sun on the d-th day p,d Satisfies β p,d ∈[90° - μ, 90°], it means that the angle between the position vector of the sun and the p-th orbital plane is less than the threshold μ, that is, there will be a moment when the angle between the sun and all the in-orbit links of the satellites on this orbit is less than μ. Therefore, whether all the in-orbit links on the same orbit are affected by solar eclipse only depends on the orbital plane where they are located and the position of the sun. That is, as long as the angles between the normal vectors of all orbital planes and the sun at different dates are calculated, the dates when the in-orbit links are affected by solar eclipse can be determined. In this example, let the threshold μ = 1°, starting from January 1, 2025 as the starting date, through model calculation, the date D when the in-orbit links are affected by solar eclipse intra A total of 100 elements are included, indicating that there are 100 days from January 1, 2025 to January 1, 2026 when the in-orbit links are affected by solar eclipse;

[0030] Through the declination χ of the sun on the d-th day d And the maximum angle ω between each cross-orbit link and the equatorial plane to calculate the date D when the cross-orbit link is affected by solar eclipse intra , the calculation method is:

[0031] Calculate the maximum angle ω between each cross-orbit link and the equatorial plane, and take the date when |ω - χ d | satisfies the set threshold μ, that is, |ω - χ d | < μ as the date D when the cross-orbit link is affected by solar eclipse inter , where:

[0032]

[0033] Among them, |·| represents the absolute value operation, arcsin(·) represents the arcsine operation, F represents the phase factor, and Θ represents the angle between the line connecting the satellite and the earth's center when the angle between all cross-orbit links and the equatorial plane is the largest;

[0034] The phase factor represents the phase relationship between the satellites in adjacent orbits, that is, mapping the satellites between two adjacent orbits of the satellite to the same orbit. The angle between the lines connecting the satellites with the same number and the earth's center, and this angle is For example, satellite w 1,1 When mapped to the 2nd orbit and satellite w 2,1The included angle with the line connecting to the earth's center;

[0035] Under the Walker constellation and the off-orbit link connection strategy described in the present invention, the included angle range of each off-orbit link with the equatorial plane is [0, ω], where ω is a fixed value. When the solar declination on the d-th day satisfies |χ d - ω| < μ, the included angle between the solar position vector and the off-orbit link is less than the threshold value. It can be considered that within the current date, there is an off-orbit link collinear with the sun and affected by solar eclipse. In this example, through model calculation, the date D inter in which there are off-orbit links affected by solar eclipse contains 2 elements, indicating that there are 2 days from January 1, 2025 to January 1, 2026 when off-orbit links are affected by solar eclipse;

[0036] Step 3) Calculate the included angle between each inter-satellite link and the solar position vector during the date affected by solar eclipse:

[0037] Calculate the direction vector of each in-orbit link at time t during the date D intra in the J2000 geocentric inertial coordinate system when there is an in-orbit link affected by solar eclipse and the included angle θ n (t) with the solar position vector. The calculation formulas are as follows:

[0038]

[0039] where n ∈ [1, N], T is the total number of seconds in a day, t ∈ [1, T], respectively represent the position vectors of satellite w p,s 、w p,s+1 at time t, represents the true anomaly of satellite w p,s at time t, The true anomaly represents the angle that the satellite has traveled from the ascending node of the orbit it is in to the current position;

[0040] Calculate the direction vector of each off-orbit link at time t during the date D inter when there is an off-orbit link affected by solar eclipse and the included angle with the solar position vector. The calculation formulas are as follows:

[0041]

[0042] where, represents the position vector of satellite w p+1,s at time t.

[0043] Step 4) Avoid solar eclipse:

[0044] According to the current date d and the date D affected by solar eclipseintra and D inter The included angle θ between each in-orbit and cross-orbit inter-satellite link and the solar position vector within D n (t), Turn off the in-orbit or cross-orbit inter-satellite link to avoid sun transit. The specific implementation steps are as follows:

[0045] (4a) Determine whether d ∈ D intra ∩D inter holds, where ∩ represents the intersection operation of two sets, that is, whether d exists in both D intra and D inter simultaneously. If so, execute step (4d); otherwise, execute step (4b);

[0046] (4b) Determine whether d ∈ D intra -D intra ∩D inter holds, that is, whether d only exists in D intra simultaneously. If so, execute step (4e); otherwise, execute step (4c);

[0047] (4c) Determine whether d ∈ D inter -D intra ∩D inter , that is, whether d only exists in D inter simultaneously. If so, execute step (4f); otherwise, sun transit avoidance is not required;

[0048] (4d) Respectively determine whether θ n (t), satisfies the pre-set threshold μ, that is, θ n (t) ≤ μ, If so, turn off the laser communication terminal of the nth in-orbit and cross-orbit inter-satellite link to avoid sun transit, and continuously observe θ n (t), When θ n (t) > μ, is satisfied, restart the corresponding laser terminal and establish the link;

[0049] (4e) Determine whether θ n (t) satisfies the pre-set threshold μ, that is, θ n (t) ≤ μ. If so, turn off the laser communication terminal of the corresponding in-orbit inter-satellite link and continuously observe θ n (t). When θ n (t) > μ is satisfied, restart the corresponding laser terminal and establish the link;

[0050] (4f) Determine whether it satisfies the pre-set threshold μ, that is, If so, turn off the laser communication terminal corresponding to the inter-orbit inter-satellite link and continuously observe When it meets re-open the corresponding laser terminal and establish the link

[0051] In the sun outage avoidance of the inter-satellite link of the giant constellation satellite network, due to the large number of inter-satellite links and the frequent impact of sun outage on the giant constellation, it is necessary to continuously monitor the status of the links, resulting in a large consumption of resources of the giant constellation system. Through classifying and modeling the inter-satellite links and combining with the movement law of the sun, the present invention directly calculates the dates when the inter-satellite links are affected by sun outage, effectively reducing repeated calculations and thus reducing resource consumption. In this embodiment, the number of calculations required by the traditional real-time calculation scheme is: 2×3600×86400×365 = 227059200000 times. The present invention first calculates that the number of days when only the same-orbit links are affected by sun outage, only the inter-orbit links are affected by sun outage, and both the same-orbit links and the inter-orbit links are affected by sun outage are 100, 2, and 0 respectively. Then, the total number of calculations required for sun outage avoidance is 3600×86400×100 + 2×3600×2 = 31104014400, which is 86% lower than that of the traditional real-time calculation scheme in terms of the number of calculations. This shows that using the present invention can significantly reduce the resource consumption of the giant constellation in sun outage avoidance.

Claims

1. An inter-satellite link solar eclipse avoidance method for a giant constellation satellite network, characterized in that Including the following steps: (1) Initialize the constellation satellite network: Initialize the giant constellation satellite network \(W = \{w\) with a total of \(N = P\times S\) satellites, where each of the \(P\) orbits is distributed with \(S\) satellites p,s \(|1\leq p\leq P, 1\leq s\leq S\}\), and the \(s\)-th satellite \(w\) on the \(p\)-th orbit p,s forms an in-orbit laser communication link with the 2 adjacent satellites in the same orbit, and forms a cross-orbit laser communication link with the 2 adjacent satellites in the adjacent orbits, where \(P\geq5\) and \(S\geq10\); (2) Calculate the dates when the inter-satellite links are affected by solar eclipse: In the J2000 geocentric inertial coordinate system, through the normal vector of the p-th orbital plane and the position vector of the sun on the d-th day Calculate the date D when the co-orbit link is affected by solar eclipse intra , and at the same time, through the declination χ of the sun on the d-th day d And the maximum angle ω between each cross-orbit link and the equatorial plane are used to calculate the date D when the cross-orbit link is affected by solar eclipse intra , where d represents the number of days between January 1 of the current year and the calculated date, and d ∈ [1, 365]; (3) Calculate the angle between each inter-satellite link and the solar position vector within the dates affected by solar eclipse: Calculate the date D when the same-orbit link is affected by solar eclipse in the J2000 geocentric inertial coordinate system intra The direction vector of each same-orbit link at time t The angle θ with the solar position vector n (t), and at the same time calculate the date D when the cross-orbit link is affected by solar eclipse inter The direction vector of each cross-orbit link at time t The angle with the solar position vector where n ∈ [1, N], t ∈ [1, T], and T is the total number of seconds in a day; (4) Avoid solar eclipse: According to the current date d and the date D affected by solar interference intra and D inter the included angle θ between each in-orbit and cross-orbit inter-satellite link and the solar position vector n (t), Turn off the in-orbit or cross-orbit inter-satellite link to avoid solar interference.

2. The method according to claim 1, wherein The date D when the co-orbit link is affected by the sun outage as described in step (2) intar , and the calculation method is as follows: Calculate the normal vector of the p-th orbital plane and the position vector of the sun on the d-th day to obtain the angle β p,d between them. Then, when β p,d satisfies β p,d ∈[90° - μ, 90°], the date is taken as the date D when there is damage to the same-orbit link intra where: χ d = 23.5sinδ d where arccos() represents the inverse cosine function, [] represents the coordinates of the vector in the J2000 geocentric inertial coordinate system, and Ω p represents the right ascension of the ascending node of the p-th orbit, and Ω p ∈ [0°, 360°], γ represents the orbital inclination, mod() represents the modulo operation, and δ d represents the right ascension of the sun on the d-th day.

3. The method according to claim 2, wherein The date D when the off-track link is affected by solar eclipse in step (2) inter , and the calculation method is as follows: Calculate the maximum angle ω between each cross-track link and the equatorial plane, and use the date when |ω - χ d | satisfies |ω - χ d | < μ with the set threshold μ as the date D when the cross-track link is damaged inter , where: where, |·| represents the absolute value operation, arcsin(·) represents the arcsine operation, F represents the phase factor, and Θ represents the angle between the connecting line between the satellite corresponding to the maximum angle between all non-synchronous links and the equatorial plane and the center of the earth.

4. The method according to claim 2, wherein The direction vector of each in-orbit link at time t in step (3) and the included angle θ intra between each inter-satellite in-orbit link and the solar position vector on the current date d n (t), and the calculation formulas are respectively as follows: Among them, respectively represent the position vectors of satellite w p,s and w p,s+1 at time t, represents the true anomaly of satellite w p,s at time t, 5. The method according to claim 4, wherein The direction vector of each off-track link at time t in step (3) and the included angle between each inter-satellite off-track link and the solar position vector inter within the current date d are calculated by the following formulas respectively: Calculation formulas are as follows: Among them, represents the position vector of satellite w p+1,s at time t.

6. The method according to claim 1, wherein The specific implementation steps for avoiding solar eclipse described in step (4) are as follows: (4a) Determine whether d ∈ D intra ∩D inter holds. If so, execute step (4d); otherwise, execute step (4b). (4b) Determine whether d ∈ D intra -D intra ∩D inter If it holds, execute step (4e); otherwise, execute step (4c). (4c) Determine whether d ∈ D inter -D intra ∩D inter , if it holds, execute step (4f); otherwise, no sun outage avoidance is required; (4d) Determine θ n (t), and whether it satisfies θ n (t) ≤ μ with the preset threshold μ, if so, turn off the laser communication terminals of the nth in-orbit and cross-orbit inter-satellite links to avoid solar eclipse, and continuously observe θ n (t), when θ n (t) > μ is satisfied, restart the corresponding laser terminal and establish the link; (4e) Judge θ n (t) and a preset threshold μ to check if θ n (t) ≤ μ. If so, turn off the laser communication terminal of the corresponding inter-satellite link on the same orbit and continuously observe θ n (t). When θ n (t) > μ, restart the corresponding laser terminal and establish the link; (4f) Judgment Whether it meets the pre-set threshold μ If so, turn off the laser communication terminal of the corresponding off-track inter-satellite link and continuously observe When it meets Re-open the corresponding laser terminal and establish a link.

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