A method for designing a constellation of extremely low earth orbit dual satellites for spot continuous dual coverage

Abstract

The application discloses a design method of a fixed-point continuous double-coverage extremely low orbit dual-satellite constellation, which comprises the following steps: calculating the latitude argument and the ascending node right ascension of the first satellite of an extremely low orbit single-satellite constellation; determining the orbit semi-major axis of the orbit where the given extremely low orbit single-satellite constellation is located; calculating the ascending node right ascension difference of the first satellites of two groups of extremely low orbit sub-satellite constellations relative to the corresponding ascending node right ascension of the single extremely low orbit single-satellite constellation, and determining the corresponding ascending node right ascensions of the first satellites of the two extremely low orbit sub-satellite constellations; determining the number of satellites of the extremely low orbit single-satellite constellation based on the continuous communication requirement time length of a target site; and sequentially determining the ascending node right ascensions and the latitude arguments of all the satellites in the two groups of extremely low orbit sub-satellite constellations. The application introduces two groups of fixed-point continuous coverage sub-satellite constellations with different ascending node right ascensions. The subsatellite point trajectories of the two groups of sub-satellite constellations are respectively located on the east side and the west side of the target site, so that the two sub-satellite constellations can pass through the upper air of the target in a "side-by-side" manner, and form double coverage of the target.

Description

Technical Field

[0001] This invention relates to the field of very low Earth orbit (VLEO) constellation technology, and more specifically to a method for designing a VLEO dual constellation with fixed-point continuous double coverage. Background Technology

[0002] Most current very low Earth orbit (EEO) constellations can achieve continuous communication coverage of the target area once or twice a day. However, in the highest-level emergency communication and critical facility monitoring scenarios, not only is uninterrupted communication required, but also extremely high reliability. This means that disaster recovery capabilities are needed to withstand risks such as single-satellite failures and momentary link interruptions.

[0003] However, the current very low Earth orbit (VLEO) constellations have the following drawbacks: at any given time, only one satellite typically covers the target. If that satellite malfunctions, service will be immediately interrupted until the next satellite enters the coverage area, posing a risk of momentary link disruption. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-constellation design method for fixed-point continuous dual coverage in Very Low Earth Orbit (ELEO) to solve the technical problem that in existing technologies, usually only one satellite covers the target at any given time. If the satellite malfunctions, it will immediately cause service interruption until the next satellite enters the coverage area, posing a risk of momentary link interruption.

[0005] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0006] A method for designing a dual-constellation VLEO with fixed-point continuous double coverage includes the following steps:

[0007] Step 100: Given the orbital inclination i of only one set of extremely low orbit constellations, determine the desired time when the first star of the extremely low orbit constellation appears directly above the target location. Determine the first satellite at the expected time. Corresponding right ascension and declination And based on the first star at the expected time Corresponding declination and right ascension Determine the latitude and argument of the first star. Right ascension of ascending node ;

[0008] Step 200: Determine the semi-major axis of the orbit of the given ultra-low orbit constellation. ;

[0009] Step 300: Calculate the coverage radius r of the satellite sensor. When using two sets of very low Earth orbit (VLEO) sub-constellations, calculate the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation based on the coverage radius r. The difference in right ascension of the ascending nodes is Determine the right ascension of the ascending nodes corresponding to the first stars of the two extremely low orbit sub-constellations. ;

[0010] Step 400: Determine the number of satellites in the ultra-low orbit constellation based on the continuous communication demand duration at the target location;

[0011] Step 500: Based on the first star in the two sets of extremely low orbit sub-constellations at the desired time... Corresponding latitudinal argument Right ascension of ascending node The right ascension and argument of the ascending node of all satellites in the two sets of extremely low Earth orbit (EEO) sub-constellations are determined sequentially, based on the orbital inclination of the two sets of EEO sub-constellations. The distribution pattern of the two sets of ultra-low orbit sub-constellations is determined by the latitude argument, right ascension of the ascending node, semi-major axis of the orbit, and number of satellites.

[0012] Furthermore, in step 100, the horizontal angle between the orbit of the ultra-low orbit constellation and the equator is taken as the orbital inclination i of the ultra-low orbit constellation, which is between 0 and 180°, and only one set of ultra-low orbit constellations is given the orbital inclination i.

[0013] Based on the right ascension corresponding to the 0° meridian of the aforementioned very low orbit single constellation. And the expected time t when the first star of a single constellation in a very low Earth orbit appears directly above the target location, to determine the position of the first star in the single constellation in a very low Earth orbit. Right ascension of time and declination ;

[0014] Here, we assume the longitude of the target location is... Latitude is The right ascension of the first star of the extremely low orbit constellation when it is directly overhead at the target location at the desired time t. = + Declination is ;

[0015] Based on the right ascension and declination of the first satellite in a very low Earth orbit constellation at the desired time t, determine the latitudinal argument of the first satellite. Right ascension of ascending node ;in:

[0016] ;

[0017] is the latitude of the target location; i is the orbital inclination of the orbit containing the aforementioned low Earth orbit constellation; The right ascension is the right ascension of the first star of the aforementioned low Earth orbit constellation when it is directly overhead at the target location at the desired time t.

[0018] Furthermore, in step 200, the semi-major axis of the track The semi-major axis of the orbit containing the aforementioned ultra-low Earth orbit constellation is determined by the sum of the Earth's radius and its orbital altitude. The calculation formula is:

[0019] ;

[0020] Where μ is the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶ 9 m³ / s²; For the Earth's radius, =6378.1km, J2 is the first-order nonspherical perturbation coefficient of the Earth, which is 1.08 × 10⁻⁶. -3 , This is the Earth's rotational angular velocity. =7.292×10^-5 rad / s;

[0021] i is the orbital inclination angle of the very low Earth orbit constellation, which is a known selected value;

[0022] N is the number of times a near-Earth orbit satellite orbits the Earth in one day; N is set to 16.

[0023] The initial semi-major axis of the orbit of the aforementioned ultra-low orbit constellation The initial value is input into the calculation formula for the semi-major axis of the orbit of the aforementioned ultra-low orbit single constellation, and the calculation is performed iteratively. ;

[0024] Until the accuracy requirements are met Stop iteration, where the precision satisfies 1e -3 Stop iteration when the time is right;

[0025] Will n As the semi-major axis of the track The calculation results.

[0026] Furthermore, in step 300, the right ascension of the ascending node of the first star in each of the two sets of extremely low orbit sub-constellations is calculated. The implementation method is as follows:

[0027] Half-cone angle based on satellite sensor field of view Determine the coverage radius of satellite sensors Coverage radius The calculation formula is:

[0028] ;

[0029] in, The semi-major axis of the track calculated in step 200, For the Earth's radius, =6378.1km;

[0030] When using two sets of very low Earth orbit (VLEO) sub-constellations, the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation is calculated based on the coverage radius r of the satellite sensors. The difference in right ascension of the ascending nodes is :

[0031] ;

[0032] in, For the Earth's radius, =6378.1km, The coverage radius of the satellite sensor. The latitude of the target location;

[0033] Right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations They are respectively and .

[0034] Furthermore, in step 400, the half-cone angle of the satellite sensor's field of view is denoted as... Field of view radius:

[0035] ;

[0036] in, For the Earth's radius, =6378.1km, To obtain the semi-major axis of the orbit;

[0037] according to Sure ,in, For the semi-major axis of the track; Let r be the difference in latitudinal argument between two adjacent satellites in a certain group of very low Earth orbit sub-constellations corresponding to the desired time t, and r be the field of view radius of the satellite sensor.

[0038] Assume that the actual duration of continuous communication at the target location is not less than the required duration t of continuous communication. c The number of satellites n in the constellation is determined according to the following formula;

[0039] ;

[0040] in, Indicates rounding up;

[0041] The continuous communication duration is defined as the time required from the first satellite of a certain low Earth orbit sub-constellation entering the coverage area to the last satellite leaving the coverage area.

[0042] Furthermore, the orbital inclinations of the two groups of extremely low orbit sub-constellations... The same orbital inclination i as that of a single constellation in very low Earth orbit;

[0043] The semi-major axis of the orbits corresponding to the two sets of very low orbit sub-constellations is the same as the semi-major axis of the orbits corresponding to the single very low orbit constellation.

[0044] The number of satellites corresponding to the two groups of very low Earth orbit sub-constellations is the same as the number of satellites corresponding to a single very low Earth orbit constellation;

[0045] Right ascension of the ascending node of the first star in the two groups of extremely low orbit sub-constellations Specifically, it is based on the right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations. They are respectively and Assume that the two sets of extremely low orbit sub-constellations are merely the right ascension of the ascending node of the first star. Unlike the other two groups of extremely low orbit sub-constellations, all other parameters are the same.

[0046] Furthermore, in step 500, the method for sequentially determining the right ascension of the ascending node and the argument of latitude of all satellites in a certain group of very low Earth orbit sub-constellations is as follows:

[0047] Determine the orbital period of satellites in a specific group of very low Earth orbit sub-constellations;

[0048] ;

[0049] in, Let μ be the semi-major axis of the orbit, and μ be the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶. 9 m³ / s²;

[0050] Based on the orbital period of the satellites in the aforementioned Very Low Earth Orbit (VLEO) constellation, the time difference between the successive passage of two adjacent satellites through the ascending node in the VLEO constellation is determined as follows: ;

[0051] in, p represents the difference in latitudinal argument between two adjacent satellites in the aforementioned ultra-low orbit constellation corresponding to the desired time t. nod The orbital period of the satellites in a certain group of very low Earth orbit sub-constellations;

[0052] Based on the time difference between the successive passage of two adjacent satellites through the ascending node in a certain group of very low Earth orbit (VLEO) subconstellations, the right ascension of the ascending node of all satellites in the certain VLEO subconstellation at the desired time t is determined. And determine the latitudinal argument of all satellites at the desired time t. .

[0053] Furthermore, the right ascension of the ascending node of all satellites in the aforementioned very low Earth orbit sub-constellation at the desired time t. The calculation formula is:

[0054] ;

[0055] in, The right ascension of the ascending node of the first star in the aforementioned low-orbit sub-constellation. The difference in latitudinal argument between two adjacent satellites in the aforementioned low Earth orbit sub-constellation corresponding to the desired time t. p is the Earth's rotational angular velocity. nod Let n be the orbital period of the satellite, and n be the number of satellites.

[0056] Furthermore, the latitude argument of all satellites in the aforementioned very low Earth orbit sub-constellation at the desired time t. The calculation formula is:

[0057] ;

[0058] in, This refers to the latitudinal argument of the first satellite in the aforementioned very low Earth orbit (VLEO) sub-constellation, specifically the latitudinal argument of the first satellite in a single VLEO constellation. Let n be the difference in latitudinal argument between adjacent satellites in the ultra-low orbit sub-constellation corresponding to the desired time t, and n be the number of satellites.

[0059] Compared with the prior art, the present invention has the following advantages:

[0060] This invention introduces two sets of fixed-point continuous coverage sub-constellations with different right ascensions of their ascending nodes. Their nadir trajectories are located to the east and west of the target location, respectively, allowing the two sub-constellations to pass "side by" over the target, forming a double coverage of the target. Attached Figure Description

[0061] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0062] Figure 1 This is a schematic diagram of the overall structure of the ultra-low orbit dual constellation design method according to an embodiment of the present invention;

[0063] Figure 2 This is a schematic diagram of the parameters of a single-constellation ultra-low orbit orbit according to an embodiment of the present invention; Detailed Implementation

[0064] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] like Figure 1 As shown, this invention provides a method for designing a dual-constellation ULE with fixed-point continuous double coverage, characterized by the following steps:

[0066] Step 100: Given the orbital inclination i of only one set of extremely low orbit constellations, determine the desired time when the first star of the extremely low orbit constellation appears directly above the target location. Determine the first satellite at the expected time. Corresponding right ascension and declination And based on the first star at the expected time Corresponding declination and right ascension Determine the latitude and argument of the first star. Right ascension of ascending node A schematic diagram of the parameters of a single constellation in Very Low Earth Orbit is shown below. Figure 2 As shown.

[0067] In step 100, the horizontal angle between the orbit of the ultra-low orbit constellation and the equator is taken as the orbital inclination i of the ultra-low orbit constellation, which is between 0 and 180°. Only one set of ultra-low orbit constellations is given the orbital inclination i.

[0068] Based on the right ascension corresponding to the 0° meridian of the aforementioned very low orbit single constellation. And the expected time t when the first star of a single constellation in a very low Earth orbit appears directly above the target location, to determine the position of the first star in the single constellation in a very low Earth orbit. Right ascension of time and declination ;

[0069] Here, we assume the longitude of the target location is... Latitude is The right ascension of the first star of the extremely low orbit constellation when it is directly overhead at the target location at the desired time t. = + Declination is ;

[0070] Based on the right ascension and declination of the first satellite in a very low Earth orbit constellation at the desired time t, determine the latitudinal argument of the first satellite. Right ascension of ascending node ;in:

[0071] ;

[0072] is the latitude of the target location; i is the orbital inclination of the orbit containing the aforementioned low Earth orbit constellation; The right ascension is the right ascension of the first star of the aforementioned low Earth orbit constellation when it is directly overhead at the target location at the desired time t.

[0073] like Figure 2 As shown, the first satellite in the VLEO constellation needs to appear at point K directly above the target location T at the desired time t. The longitude of the target location T is... Latitude is Latitude Argument Right ascension of ascending node The meaning is as follows Figure 2 As shown.

[0074] Step 200: Determine the semi-major axis of the orbit of the extremely low Earth orbit constellation. .

[0075] In step 200, the semi-major axis of the track The semi-major axis of the orbit containing the aforementioned ultra-low Earth orbit constellation is determined by the sum of the Earth's radius and its orbital altitude. The calculation formula is:

[0076] ;

[0077] Where μ is the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶ 9 m³ / s²; For the Earth's radius, =6378.1km, J2 is the first-order nonspherical perturbation coefficient of the Earth, which is 1.08 × 10⁻⁶. -3 , This is the Earth's rotational angular velocity. =7.292×10^-5 rad / s;

[0078] i is the orbital inclination angle of the very low Earth orbit constellation, which is a known selected value;

[0079] N is the number of times a near-Earth orbit satellite orbits the Earth in one day; N is set to 16.

[0080] The initial semi-major axis of the orbit of the aforementioned ultra-low orbit constellation The initial value is input into the calculation formula for the semi-major axis of the orbit of the aforementioned ultra-low orbit single constellation, and the calculation is performed iteratively. ;

[0081] Until the accuracy requirements are met Stop iteration, where the precision satisfies 1e -3 Stop iteration when the time is right;

[0082] Will n As the semi-major axis of the track The calculation results.

[0083] Step 300: Calculate the coverage radius r of the satellite sensor. When using two sets of very low Earth orbit (VLEO) sub-constellations, calculate the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation based on the coverage radius r. The difference in right ascension of the ascending nodes is Determine the right ascension of the ascending nodes corresponding to the first stars of the two extremely low orbit sub-constellations. .

[0084] The latitude argument of the first star of a single group of ultra-low orbit constellations calculated in steps 100 and 200. The latitude argument corresponding to the first star of each of the two sets of extremely low orbit sub-constellations. The orbital inclination i corresponding to a given single group of PLEAST constellations is taken as the orbital inclination i corresponding to two groups of PLEAST sub-constellations. The semi-major axis of the orbit containing the PLEAST constellation is taken as... As the semi-major axis of the orbits corresponding to the two sets of extremely low orbit sub-constellations.

[0085] In step 300, the right ascension of the ascending node of the first star in each of the two sets of extremely low orbit sub-constellations is calculated. The implementation method is as follows:

[0086] Half-cone angle based on satellite sensor field of view Determine the coverage radius of satellite sensors Coverage radius The calculation formula is:

[0087] ;

[0088] in, The semi-major axis of the track calculated in step 200, For the Earth's radius, =6378.1km.

[0089] When using two sets of very low Earth orbit (VLEO) sub-constellations, the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation is calculated based on the coverage radius r of the satellite sensors. The difference in right ascension of the ascending nodes is :

[0090] ;

[0091] in, For the Earth's radius, =6378.1km, The coverage radius of the satellite sensor. The latitude of the target location;

[0092] Right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations They are respectively and .

[0093] Step 400: Determine the number of satellites in the ultra-low orbit constellation based on the duration of continuous communication requirements at the target location.

[0094] Let the half-cone angle of the satellite sensor's field of view be . Field of view radius:

[0095] ;

[0096] in, For the Earth's radius, =6378.1km, To obtain the semi-major axis of the orbit;

[0097] according to Sure ,in, For the semi-major axis of the track; Let r be the difference in latitudinal argument between two adjacent satellites in a certain group of very low Earth orbit sub-constellations corresponding to the desired time t, and r be the field of view radius of the satellite sensor.

[0098] Assume that the actual duration of continuous communication at the target location is not less than the required duration t of continuous communication. c The number of satellites n in the constellation is determined according to the following formula;

[0099] ;

[0100] in, Indicates rounding up;

[0101] The continuous communication duration is defined as the time required from the first satellite of a certain low Earth orbit sub-constellation entering the coverage area to the last satellite leaving the coverage area.

[0102] This implementation method can be based on satellite sensor parameters (field of view radius r) and the minimum continuous communication duration required. The minimum number of satellites n for the constellation configuration is determined, and the duration of continuous communication requirements that change in real time is based on flexibly adjusting the number of satellites n for the constellation configuration.

[0103] The orbital inclination of the two groups of extremely low orbit sub-constellations Similar to the given orbital inclination *i* of a single VLEO constellation, the semi-major axes of the orbits corresponding to the two VLEO sub-constellations are the same as those corresponding to the single VLEO constellation. The number of satellites in the two VLEO sub-constellations is also the same as the number of satellites in the single VLEO constellation. Therefore, the two VLEO sub-constellations are merely the right ascension of the ascending node of the first satellite. Unlike the other two groups of extremely low orbit sub-constellations, all other parameters are the same.

[0104] Right ascension of the ascending node of the first star in the two groups of extremely low orbit sub-constellations Specifically, it is based on the right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations. They are respectively and The latitude argument of the first star in each of the two sets of extremely low orbit sub-constellations is set. It has the same latitude argument as the first star in a single constellation in a very low orbit.

[0105] Step 500: Based on the first star in the two sets of extremely low orbit sub-constellations at the desired time... Corresponding latitudinal argument Right ascension of ascending node The right ascension and argument of the ascending node of all satellites in the two sets of extremely low Earth orbit (EEO) sub-constellations are determined sequentially, based on the orbital inclination of the two sets of EEO sub-constellations. The distribution pattern of the two sets of ultra-low orbit sub-constellations is determined by the latitude argument, right ascension of the ascending node, semi-major axis of the orbit, and number of satellites.

[0106] In step 500, the method for sequentially determining the right ascension of the ascending node and the argument of latitude of all satellites in a certain group of very low Earth orbit sub-constellations is as follows:

[0107] Determine the orbital period of satellites in a specific group of very low Earth orbit sub-constellations;

[0108] ;

[0109] in, Let μ be the semi-major axis of the orbit, and μ be the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶. 9 m³ / s²;

[0110] Based on the orbital period of the satellites in the aforementioned Very Low Earth Orbit (VLEO) constellation, the time difference between the successive passage of two adjacent satellites through the ascending node in the VLEO constellation is determined as follows: ;

[0111] in, p represents the difference in latitudinal argument between two adjacent satellites in the aforementioned ultra-low orbit constellation corresponding to the desired time t. nod The orbital period of the satellites in a certain group of very low Earth orbit sub-constellations;

[0112] Based on the time difference between the successive passage of two adjacent satellites through the ascending node in a certain group of very low Earth orbit (VLEO) subconstellations, the right ascension of the ascending node of all satellites in the certain VLEO subconstellation at the desired time t is determined. And determine the latitudinal argument of all satellites at the desired time t. .

[0113] The right ascension of the ascending node of all satellites in the very low Earth orbit subconstellation at the desired time t. The calculation formula is:

[0114] ;

[0115] in, The right ascension of the ascending node of the first star in the aforementioned low-orbit sub-constellation. The difference in latitudinal argument between two adjacent satellites in the aforementioned low Earth orbit sub-constellation corresponding to the desired time t. p is the Earth's rotational angular velocity. nod Let n be the orbital period of the satellite, and n be the number of satellites.

[0116] The latitude argument of all satellites in the very low Earth orbit subconstellation at the desired time t. The calculation formula is:

[0117] ;

[0118] in, This refers to the latitudinal argument of the first satellite in the aforementioned very low Earth orbit (VLEO) sub-constellation, specifically the latitudinal argument of the first satellite in a single VLEO constellation. Let n be the difference in latitudinal argument between adjacent satellites in the ultra-low orbit sub-constellation corresponding to the desired time t, and n be the number of satellites.

[0119] Therefore, the parameters of the very low orbit sub-constellations are calculated in the same way except for the right ascension of the ascending node of the first star, which is equivalent to the two constellations passing over the target location "simultaneously" from the left and right.

[0120] For the first satellite in a very low Earth orbit sub-constellation, its right ascension of the ascending node and its latitudinal argument are... and For the second satellite, these are Ω1 and u1, and so on. The orbital semi-major axis, orbital inclination, and other parameters determined through this implementation method can be used to determine the unique position of a satellite in inertial space.

[0121] For all satellites in the very low Earth orbit sub-constellation designed by this method, all parameters are the same except for the right ascension of the ascending node and the argument of latitude corresponding to the desired time t. The sorting rule can be regarded as the satellite that passes over the target location first having the sequence number 0, and the satellite that passes over the target location last having the sequence number n-1.

[0122] Therefore, the sub-satellite points of the constellation designed according to this implementation method naturally coincide. As long as the orbital inclination, the semi-major axis of the orbit, the right ascension of the ascending node and the argument of latitude at a given desired time are calculated, the satellite will have a unique position in inertial space. It is not necessary to focus on parameters such as the position of its orbital plane and the number of planes to express the position of the satellite.

[0123] Since the two extremely low orbit sub-constellations are identical in all parameters except for the right ascension of the ascending node of their first star, the orbit of the second sub-constellation can be considered as the orbit of the first sub-constellation rotated around the Z-axis in the diagram above by a certain angle.

[0124] This implementation introduces two sets of fixed-point continuous coverage sub-constellations with different right ascensions of their ascending nodes. Their nadir trajectories are located to the east and west of the target location, respectively, allowing the two sub-constellations to pass "side by" over the target, forming a double coverage of the target.

[0125] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A method for designing a dual-constellation VLEO with fixed-point continuous double coverage, characterized in that, Includes the following steps: Step 100: Given the orbital inclination i of only one set of extremely low orbit constellations, determine the desired time when the first star of the extremely low orbit constellation appears directly above the target location. Determine the first satellite at the desired time. Corresponding right ascension and declination And based on the first star at the expected time Corresponding declination and right ascension Determine the latitude and argument of the first star. Right ascension of ascending node ; Step 200: Determine the semi-major axis of the orbit of the given ultra-low orbit constellation. ; Step 300: Calculate the coverage radius r of the satellite sensor. When using two sets of very low Earth orbit (VLEO) sub-constellations, calculate the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation based on the coverage radius r. The difference in right ascension of the ascending nodes is Determine the right ascension of the ascending nodes corresponding to the first stars of the two extremely low orbit sub-constellations. ; Step 400: Determine the number of satellites in the ultra-low orbit constellation based on the continuous communication demand duration at the target location; Step 500: Based on the first star in the two sets of extremely low orbit sub-constellations at the desired time... Corresponding latitudinal argument Right ascension of ascending node The right ascension and argument of the ascending node of all satellites in the two sets of extremely low Earth orbit (EEO) sub-constellations are determined sequentially, based on the orbital inclination of the two sets of EEO sub-constellations. The distribution pattern of the two sets of ultra-low orbit sub-constellations is determined by the latitude argument, right ascension of the ascending node, semi-major axis of the orbit, and number of satellites.

2. The method for designing a fixed-point continuous dual-coverage VLEO dual-constellation according to claim 1, characterized in that, In step 100, the horizontal angle between the orbit of the ultra-low orbit constellation and the equator is taken as the orbital inclination i of the ultra-low orbit constellation, which is between 0 and 180°. Only one set of ultra-low orbit constellations is given the orbital inclination i. Based on the right ascension corresponding to the 0° meridian of the aforementioned very low orbit single constellation. And the expected time t when the first star of a single constellation in a very low Earth orbit appears directly above the target location, to determine the position of the first star in the single constellation in a very low Earth orbit. Right ascension of time and declination ; Here, we assume the longitude of the target location is... Latitude is The right ascension of the first star of the extremely low orbit constellation when it is directly overhead at the target location at the desired time t. = + Declination is ; Based on the right ascension and declination of the first satellite in a very low Earth orbit constellation at the desired time t, determine the latitudinal argument of the first satellite. Right ascension of ascending node ;in: ； is the latitude of the target location; i is the orbital inclination of the orbit containing the aforementioned low Earth orbit constellation; The right ascension is the right ascension of the first star of the aforementioned low Earth orbit constellation when it is directly overhead at the target location at the desired time t.

3. The method for designing a fixed-point continuous dual-coverage VLEO dual-constellation according to claim 2, characterized in that, In step 200, the semi-major axis of the track The semi-major axis of the orbit containing the aforementioned ultra-low Earth orbit constellation is determined by the sum of the Earth's radius and its orbital altitude. The calculation formula is: ； Where μ is the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶ 9 m³ / s²; For the Earth's radius, =6378.1km, J2 is the first-order nonspherical perturbation coefficient of the Earth, which is 1.08 × 10⁻⁶. -3 , This is the Earth's rotational angular velocity. =7.292×10^-5 rad / s; i is the orbital inclination angle of the very low Earth orbit constellation, which is a known selected value; N is the number of times a near-Earth orbit satellite orbits the Earth in one day; N is set to 16. The initial semi-major axis of the orbit of the aforementioned ultra-low orbit constellation The initial value is input into the calculation formula for the semi-major axis of the orbit of the aforementioned ultra-low orbit single constellation, and the calculation is performed iteratively. ; Until the accuracy requirements are met Stop iteration, where the precision satisfies 1e -3 Stop iteration when the time is right; Will n As the semi-major axis of the track The calculation results.

4. The method for designing a fixed-point continuous dual-coverage VLEO dual-constellation according to claim 3, characterized in that, In step 300, the right ascension of the ascending node of the first star in each of the two sets of extremely low orbit sub-constellations is calculated. The implementation method is as follows: Half-cone angle based on satellite sensor field of view Determine the coverage radius of satellite sensors Coverage radius The calculation formula is: ;in, The semi-major axis of the track calculated in step 200, For the Earth's radius, =6378.1km; When using two sets of very low Earth orbit (VLEO) sub-constellations, the right ascension of the first satellite of each VLEO sub-constellation relative to the ascending node of a single VLEO constellation is calculated based on the coverage radius r of the satellite sensors. The difference in right ascension of the ascending nodes is : ； in, For the Earth's radius, =6378.1km, The coverage radius of the satellite sensor. The latitude of the target location; Right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations They are respectively and .

5. The method for designing a fixed-point continuous dual-coverage VLTO dual-constellation according to claim 1, characterized in that, In step 400, the half-cone angle of the satellite sensor's field of view is denoted as... Field of view radius: ； in, For the Earth's radius, =6378.1km, To obtain the semi-major axis of the orbit; according to Sure ,in, For the semi-major axis of the track; Let r be the difference in latitudinal argument between two adjacent satellites in a certain group of very low Earth orbit sub-constellations corresponding to the desired time t, and r be the field of view radius of the satellite sensor. Assume that the actual duration of continuous communication at the target location is not less than the required duration t of continuous communication. c The number of satellites n in the constellation is determined according to the following formula; ； in, Indicates rounding up; The continuous communication duration is defined as the time required from the first satellite of a certain low Earth orbit sub-constellation entering the coverage area to the last satellite leaving the coverage area.

6. The method for designing a fixed-point continuous coverage ultra-low orbit constellation according to claim 5, characterized in that, The orbital inclination of the two groups of extremely low orbit sub-constellations The same orbital inclination i as that of a single constellation in very low Earth orbit; The semi-major axis of the orbits corresponding to the two sets of very low orbit sub-constellations is the same as the semi-major axis of the orbits corresponding to the single very low orbit constellation. The number of satellites corresponding to the two groups of very low Earth orbit sub-constellations is the same as the number of satellites corresponding to a single very low Earth orbit constellation; Right ascension of the ascending node of the first star in the two groups of extremely low orbit sub-constellations Specifically, it is based on the right ascension of the ascending node of the first star of the two sets of extremely low orbit sub-constellations. They are respectively and Assume that the two sets of extremely low orbit sub-constellations are merely the right ascension of the ascending node of the first star. Unlike the other two groups of extremely low orbit sub-constellations, all other parameters are the same.

7. The method for designing a fixed-point continuous dual-coverage VLTO dual-constellation according to claim 1, characterized in that, In step 500, the method for sequentially determining the right ascension of the ascending node and the argument of latitude of all satellites in a certain group of very low Earth orbit sub-constellations is as follows: Determine the orbital period of satellites in a specific group of very low Earth orbit sub-constellations; ； in, Let μ be the semi-major axis of the orbit, and μ be the Earth's gravitational constant, μ = 398600.4418 × 10⁻⁶. 9 m³ / s²; Based on the orbital period of the satellites in the aforementioned Very Low Earth Orbit (VLEO) constellation, the time difference between the successive passage of two adjacent satellites through the ascending node in the VLEO constellation is determined as follows: ; in, p represents the difference in latitudinal argument between two adjacent satellites in the aforementioned ultra-low orbit constellation corresponding to the desired time t. nod The orbital period of the satellites in a certain group of very low Earth orbit sub-constellations; Based on the time difference between the successive passage of two adjacent satellites through the ascending node in a certain group of very low Earth orbit (VLEO) subconstellations, the right ascension of the ascending node of all satellites in the certain VLEO subconstellation at the desired time t is determined. And determine the latitudinal argument of all satellites at the desired time t. .

8. The method for designing a fixed-point continuous dual-coverage VLEO dual-constellation according to claim 6, characterized in that, The right ascension of the ascending node of all satellites in the very low Earth orbit subconstellation at the desired time t. The calculation formula is: ； in, The right ascension of the ascending node of the first star in the aforementioned low-orbit sub-constellation. The difference in latitudinal argument between two adjacent satellites in the aforementioned low Earth orbit sub-constellation corresponding to the desired time t. p is the Earth's rotational angular velocity. nod Let n be the orbital period of the satellite, and n be the number of satellites.

9. A method for designing a fixed-point continuous coverage ultra-low orbit constellation according to claim 6, characterized in that, The latitude argument of all satellites in the very low Earth orbit subconstellation at the desired time t. The calculation formula is: ； in, This refers to the latitudinal argument of the first satellite in the aforementioned very low Earth orbit (VLEO) sub-constellation, specifically the latitudinal argument of the first satellite in a single VLEO constellation. Let n be the difference in latitudinal argument between adjacent satellites in the ultra-low orbit sub-constellation corresponding to the desired time t, and n be the number of satellites.

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