Low earth orbit satellite constellation array antenna common view method and system

Abstract

A kind of low-orbit satellite constellation array antenna common view method and system, first, low-orbit satellite constellation each satellite is configured with the same frequency band, the array antenna with equivalent space domain coverage capability;Low-orbit satellite constellation each satellite on-board time synchronization, i.e. work in the same time system state;According to the orbit of low-orbit satellite constellation each satellite, configuration and array antenna space domain coverage capability, calculate the angle value that each satellite array antenna pointing angle needs to be corrected when satellite is in different orbit section, different antenna pointing angle, to make constellation maximum coverage common view range, and be noted to satellite through measurement and control link;Finally, the beam control module of each satellite according to the optimized pointing angle of array antenna after correction, set each array element signal delay and attenuation, realize antenna pointing adjustment, realize maximum common view range.The present application can increase the common view range of low-orbit satellite constellation coverage, improve the efficiency of low-orbit satellite constellation multi-star cooperative work.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of satellite remote sensing, and particularly relates to a low-orbit satellite constellation array antenna common-view method and system. TECHNICAL BACKGROUND

[0002] A low-orbit satellite constellation is composed of multiple remote sensing satellites distributed at the same orbital altitude, densely distributed on the orbital plane, and capable of rapid and wide-range remote sensing observation on the ground. The satellites work cooperatively to achieve satellite networking observation and play an important role in the field of ground observation. As a high-precision ground observation platform, low-orbit satellites are widely used in network communication, ocean height measurement, gravity field inversion, atmospheric monitoring and many other engineering and scientific fields, and have played a huge role in meeting the spatial data needs of daily environmental detection. In recent years, with the rapid increase in global communication and scientific research needs, many low-orbit satellite constellation programs have emerged, such as Oneweb, Iridium, SpaceX in the United States, Hongyan, Hongyun and CentiSpace in China, and Samsung in South Korea. At present, large low-orbit Internet constellations have become the forefront and focus of development at home and abroad.

[0003] Traditional panel antennas have a narrow working bandwidth and are difficult to control. Flat panel antennas and helical antennas have low gain coefficients and cannot adaptively adjust the directional pattern. Single antenna directional patterns are difficult to control, have low gain, and often cannot meet the development needs of remote sensing satellites in terms of polarization characteristics and bandwidth characteristics. Array antennas refer to an antenna system composed of multiple single antennas arranged in a certain pattern in a certain environment. Compared with traditional antenna structures, array antennas can obtain greater signal gain, more effectively control the main lobe direction of transmitted signals, suppress interference and noise, and achieve specific directional patterns, polarization characteristics and bandwidth characteristics by adjusting the feeding method of each antenna element. Therefore, array antennas have been widely applied and rapidly developed in radar, radio communication, navigation and other fields, and have gradually been applied in the field of remote sensing satellites.

[0004] Array antennas have high gain but small beam width, and limited instantaneous coverage on the ground. For a low-orbit satellite constellation, the problem of multi-satellite array antenna common-view directly affects the efficiency of inter-satellite cooperative work. There is little research on this issue at home and abroad.

[0005] Most existing low-orbit satellite constellations do not provide solutions to the problem of multi-satellite antenna common-view. On the one hand, the antennas configured on the satellites are mostly single antennas, which have a large instantaneous coverage range and can even cover the entire airspace, so there is no antenna common-view problem. On the other hand, low-orbit satellite constellations do not further process the antenna common-view problem, which makes it impossible to perform multi-satellite cooperative tasks in non-common-view areas, increases the airspace scanning time, and reduces the efficiency of multi-satellite cooperative work. SUMMARY

[0006] The technical problem solved by the present application is that, aiming at the problems of limited instantaneous spatial coverage and low inter-satellite common view efficiency of satellite array antennas in a low-orbit satellite constellation, a low-orbit satellite constellation array antenna common view method is provided, the angle value that needs to be corrected for the pointing angle of each satellite array antenna is calculated in advance so that the common view range of the constellation array antenna is maximum when the satellite is in different orbital segments, and the beam pointing correction is realized through a beam control module, thereby improving the multi-satellite cooperative working efficiency in the low-orbit satellite constellation.

[0007] The technical solution of the present application is a low-orbit satellite constellation array antenna common view method, comprising:

[0008] (1) configuring an array antenna with the same frequency band and the same spatial coverage capability for each satellite in the low-orbit satellite constellation, and designating one of the satellites as a reference satellite;

[0009] (2) time synchronizing each satellite in the low-orbit satellite constellation so that each satellite works in the same time system;

[0010] (3) for the reference satellite in the low-orbit satellite constellation, dividing the running track of the reference satellite in an orbital period into different orbital segments, setting a satellite remote sensing area on the ground according to the task requirement, determining the initial pointing angle of the array antenna of each satellite in the low-orbit satellite constellation, and setting the array antenna of the reference satellite to keep the initial pointing angle unchanged;

[0011] (4) determining a reference time T0 and acquiring the on-satellite time T utc of each satellite in the low-orbit satellite constellation in real time, determining the orbital position of each satellite according to the on-satellite time T utc and the reference time T0;

[0012] (5) for each satellite in the low-orbit satellite constellation except the reference satellite, according to the satellite configuration, the working frequency band of the array antenna and the initial pointing angle, taking the maximum array antenna ground common view area of the array antenna of the satellite when the array antenna of the satellite and the reference satellite are in different orbital segments as the target, and solving the optimized pointing angle of the array antenna of the satellite when the satellite is in different orbital positions;

[0013] (6) for each satellite in the low-orbit satellite constellation except the reference satellite, adjusting the pointing of the array antenna carried by the satellite according to the orbital segment of the reference satellite, so that the pointing of the array antenna is the optimized pointing angle.

[0014] Further, in step (3), the operation orbit of the reference satellite in the low-orbit satellite constellation is divided into different orbit segments in one orbit period, which includes: first, the satellite orbit is divided into multiple segments according to the satellite ascending or descending orbit and the satellite ground projection subsatellite point latitude, the satellite orbit period is determined according to the orbit of the reference satellite, and then the time interval of each orbit segment of the satellite in one orbit period is determined, and then the corresponding time of the satellite entering and exiting each segment is determined according to the time interval.

[0015] Further, in step (4), the orbit position of each satellite is determined according to the satellite time T utc and the reference time T0, specifically:

[0016] For the reference satellite orbit period R, any satellite time T utc is normalized to the time t in one orbit period, expressed as

[0017] T utc ≥T0, t=(T utc -T0)%R;

[0018] T utc <T0, t=|T utc +k*R-T0|%R, where k=(T0-T utc ) / R is rounded up;

[0019] The normalized time t is located in the mth orbit segment, that is, t m,s <t<t m,e , t m,s represents the satellite time entering the mth orbit segment, and t m,e represents the satellite time exiting the mth orbit segment.

[0020] Further, in step (5), the optimized pointing angle of the array antenna of the satellite at different orbit positions is obtained, specifically:

[0021] The initial pointing angle of the satellite to be corrected is set to be the same as the initial pointing angle of the reference satellite, and the common view area at this time is taken as the storage value;

[0022] The search range of the array antenna pointing correction angle is traversed with a specified search step, the common view area corresponding to a certain antenna pointing correction angle is calculated, which is compared with the storage value, and the larger one of the two is taken as the new storage value. After the traversal is completed, the pointing correction angle corresponding to the latest storage value is summed with the initial pointing angle of the satellite to be corrected to obtain the corrected array antenna optimized pointing angle.

[0023] Further, in step (1), one satellite in the specified low-orbit satellite constellation is designated as a reference satellite, specifically: a satellite at the center of the low-orbit satellite constellation layout is selected as the reference satellite.

[0024] Further, in step (6), the pointing direction of the array antenna carried by each satellite is adjusted, specifically:

[0025] According to the optimized pointing angle of the array antenna, the delay and attenuation of the signals of each array element of the array antenna are set according to the beam synthesis control table, and the optimized array antenna directional diagram is obtained by weighted summation of the field strength radiation patterns of the signals of each array element of the antenna, so that the antenna pointing adjustment is realized.

[0026] A low-orbit satellite constellation array antenna common view system, comprising: a low-orbit satellite constellation, a low-orbit satellite constellation task management module, a satellite array antenna optimized pointing angle determination module, and a satellite array antenna pointing angle correction module; wherein,

[0027] Each satellite of the low-orbit satellite constellation has an array antenna with the same frequency band and the same spatial coverage capability; the on-board time of each satellite of the constellation is synchronized, and the satellites work in the same time system; one of the satellites is a reference satellite;

[0028] The low-orbit satellite constellation task management module divides the orbit of the reference satellite within one orbit period into different orbit segments; sets the satellite remote sensing area on the ground according to the task requirements, determines the initial pointing angle of the array antenna of each satellite, and sets the reference satellite to keep the initial pointing angle of the array antenna unchanged;

[0029] The satellite array antenna optimized pointing angle determination module determines a reference time T0, and obtains the on-board time T utc of each satellite in the low-orbit satellite constellation in real time; according to the on-board time T utc and the reference time T0, the orbit position of each satellite is determined; for each satellite in the low-orbit satellite constellation except the reference satellite, the optimized pointing angle of the array antenna of the satellite at different orbit positions is obtained, with the maximum array antenna common view area of the array antenna of the satellite and the reference satellite at different orbit segments as the target, according to the satellite configuration, the working frequency band of the array antenna, and the initial pointing angle.

[0030] The satellite array antenna pointing angle correction module adjusts the pointing direction of the array antenna carried by each satellite in the low-orbit satellite constellation except the reference satellite according to the orbit segment of the reference satellite, so that the pointing direction of the array antenna is the optimized pointing angle.

[0031] Further, the satellite array antenna optimized pointing angle determination module determines the orbit position of each satellite according to the on-board time T utc and the reference time T0, comprising:

[0032] For the reference star orbital period R, any on-board time T utc is normalized to the time t within one orbital period, expressed as

[0033] T utc When ≥ T0, t = (T utc - T0) % R;

[0034] T utc When < T0, t = |T utc + k * R - T0| % R, where k = (T0 - T utc ) / R rounded up;

[0035] The normalized time t is in the m-th orbital segment, that is, t m,s < t < t m,e , t m,s represents the on-board time when entering the m-th orbital segment, and t m,e represents the on-board time when exiting the m-th orbital segment.

[0036] Furthermore, the satellite array antenna optimized pointing angle determination module obtains the optimized pointing angles of the array antennas of the satellites in the low-earth orbit satellite constellation except the reference star at different orbital positions. It further includes:

[0037] Set the initial pointing angle of the currently to-be-corrected satellite to be the same as that of the reference star, and take the co-visibility area at this time as the stored value;

[0038] Traverse the value range of the array antenna pointing correction angle with a specified search step, calculate the co-visibility area corresponding to a certain antenna pointing correction angle, compare it with the stored value, and take the larger value of the two as the new stored value; after the traversal, sum the pointing correction angle corresponding to the latest stored value and the initial pointing angle of the currently to-be-corrected satellite to obtain the corrected optimized pointing angle of the array antenna.

[0039] Furthermore, the satellite array antenna pointing angle correction module adjusts the pointing of the array antennas carried by each satellite in the low-earth orbit satellite constellation except the reference star respectively. It further includes:

[0040] According to the optimized pointing angle of the array antenna and the beam synthesis control table, set the delay and attenuation of the signals of each array element of the array antenna, and obtain the optimized array antenna pattern by weighted summation of the field strength radiation patterns of the signals of each array element of the antenna, so as to realize the adjustment of the antenna pointing.

[0041] The advantages of the present invention compared with the prior art are:

[0042] 1. The low-orbit satellite constellation array antenna common view method can increase the low-orbit satellite constellation ground scanning common view range, reduce the scanning times required for full coverage, and effectively improve the multi-satellite cooperative working efficiency of the low-orbit satellite constellation.

[0043] 2. The low-orbit satellite constellation array antenna common view method can pre-calculate the array antenna correction angle table and send it to the satellite through the uplink, which is saved on the satellite and has relatively low requirements for satellite on-orbit operation processing capacity, high timeliness, small research and development difficulty, and low development cost.

[0044] 3. The low-orbit satellite constellation array antenna common view method can re-calculate the array antenna correction angle table of each satellite according to the change of the satellite orbit and constellation configuration, and update it through the satellite uplink, which has good robustness and can flexibly adapt to changes during on-orbit period. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The figure is a low-orbit satellite constellation ground coverage area calculation schematic diagram.

[0046] Figure 2 The figure is a low-orbit satellite constellation array antenna pointing correction flowchart.

[0047] Figure 3 The figure is a low-orbit satellite constellation array antenna pointing correction schematic diagram.

[0048] Figure 4 The figure is a low-orbit satellite constellation reference star selection schematic diagram with five satellite constellations as an example. DETAILED DESCRIPTION

[0049] The present application provides a low-orbit satellite constellation array antenna common view method and system.

[0050] A low-orbit satellite constellation array antenna common view method, the specific steps are as follows:

[0051] S1, each satellite of the low-orbit satellite constellation is configured with an array antenna with the same frequency band and the same spatial coverage capability.

[0052] Due to the need to perform tasks, the low-orbit satellite constellation requires each satellite to work cooperatively, process the same target or signal interception, and requires the array antenna to have the same frequency band and the same spatial coverage capability.

[0053] S2, the on-orbit time of each satellite of the low-orbit satellite constellation is synchronized, i.e., working in the same time system.

[0054] In order to realize constellation measurement and control, inter-satellite cooperation and array antenna common view correction angle calculation, the on-orbit time of each satellite of the constellation is synchronized, i.e., working in the time system.

[0055] S3, a satellite in the low earth orbit satellite constellation is designated as a reference satellite, the running track of the reference satellite in one orbit period is divided into different orbit segments, and the initial pointing angle of each satellite in the low earth orbit satellite constellation is determined according to the task requirement and the satellite-to-ground remote sensing area, and the initial pointing angle of the reference satellite is kept unchanged. The ground calculates the satellite-to-ground scanning situation when the satellite is in different orbit segments according to the orbit, configuration and array antenna space coverage capability of the reference satellite in the low earth orbit satellite constellation; further, the maximum satellite-to-ground common view area coverage range is obtained by recursively making the maximum common view area of the current satellite and the reference satellite in the constellation as a constraint condition when the satellite is in different orbit segments and different antenna pointing angles, the angle value of the pointing angle of each satellite in the low earth orbit satellite constellation except the reference satellite needs to be corrected when the satellite is in different orbit segments is calculated as the array antenna pointing correction angle, and the array antenna pointing correction angle is uploaded to the satellite through the measurement and control link. The reference satellite does not need to be pointed and corrected, and works according to the initial pointing angle. The reference satellite is arbitrarily selected from the constellation, and when there are many satellites in the constellation, the satellite at the center of the constellation layout is selected as the reference satellite as much as possible to avoid the situation that the antenna pointing angle of other satellites is large.

[0056] Firstly, the satellite orbit is divided into n segments, i.e. orbit segments, according to the flight direction of the satellite from south to north / north to south, i.e. ascending orbit / descending orbit and the latitude of the subsatellite point of the satellite-to-ground projection. The latitude interval of the orbit segment can be expressed as (L i,s , L i,e ), i = 0, 1, 2,..., n-1, wherein i represents the sequence number of the current orbit segment, L i,s represents the latitude at which the satellite enters the i th orbit segment, and L i,e represents the latitude at which the satellite exits the i th orbit segment. Obviously, L i,e = L i+1,s and L 0,s = L n-1,e . According to the actual orbit and configuration of each satellite in orbit, the satellite orbit period is R, the time interval of each orbit segment within one orbit period is calculated, which is expressed as (t i,s , t i,e ), i = 0, 1, 2,..., n-1, wherein t i,s represents the satellite time at which the satellite enters the i th orbit segment, and t i,e represents the satellite time at which the satellite exits the i th orbit segment, i.e. the satellite time at which the satellite enters the i+1 th orbit segment. There is a time difference in the time at which each satellite in the low earth orbit satellite constellation enters the orbit segment, and one of the satellites can be selected as a reference. For example, according to the English alphabet, the reference satellite is A, and the other satellites B, C, D... in the constellation need to be corrected. Wherein, n and i are natural numbers.

[0057] A reference time T0 is determined, and an on-board time T of each satellite in the constellation of low-orbit satellites is acquired in real time utc . According to the on-board time T utc and the reference time T0, an orbit segment in which each satellite is located is determined. The satellite's sub-satellite point latitude repeats periodically every orbit period R for the reference satellite, so for any on-board time T utc , a normalized time t within one orbit period can be calculated and expressed as

[0058] T utc ≥ T0, t = (T utc -T0) % R;

[0059] T utc <T0, t = |T utc +k*R-T0| % R, where k = (T0-T utc ) / R and is rounded up.

[0060] According to the orbit division table, the normalized time t is located in the mth orbit segment (m is a natural number), that is, t m,s <t<t m,e . The current array antenna operating frequency band is represented as f, and the pointing angles include the azimuth angle and the elevation angle. According to the requirements of the task to be performed, the current pointing angles of the reference satellite A, that is, the azimuth angle and the elevation angle, are represented as (α A0 , β A0 ), the initial pointing angles of the satellite B are (α B0 , β B0 )=(α A0 , β A0 ), the azimuth angle pointing correction angle is represented as Δα B , and the elevation angle pointing correction angle is represented as Δβ B . According to the satellite orbit, configuration, and current operating frequency band (which can indicate the array antenna space coverage capability), as well as the current orbit segment in which the satellite is located and the current pointing angles, the optimized pointing angles of each satellite array antenna can be calculated in the following manner to achieve the maximum constellation common view area range .

[0061] The initial pointing angles of the satellite to be corrected are the same as those of the reference satellite. A specified search step traverses the search range of the array antenna pointing correction angle, calculates the current common view area of the reference satellite and the satellite to be corrected corresponding to a certain array antenna pointing correction angle, compares it with a register value, takes the larger one as the maximum common view area and a new register value, and outputs the pointing correction angle corresponding thereto at this time.

[0062] Repeat the above process until the end of the traversal, get the final pointing correction angle, sum the initial pointing angle of each satellite and the pointing correction angle to get the modified array antenna optimization pointing angle, and correct the array antenna pointing angle of each satellite in the low earth orbit satellite constellation.

[0063] The specific implementation method is:

[0064]

[0065] Among them, the common view area calculation method has the following two kinds:

[0066] (1) STK scene simulation

[0067] According to the input satellite orbit, antenna coverage range and other information, the STK scene is generated. Add satellite and antenna sensor, set the sensor instantaneous beam width and pointing angle, generate "Footprint Area" report to read each T utc Instant satellite coverage area.

[0068] Add constellation "constellation" containing all satellite antenna sensors, set all satellite sensors to be visible, and add coverage analysis "coverage definition", set the grid resolution of the earth coverage area to 0.1°. Generate "Periods of Global Coverage" report to calculate the grid proportion of each T utc Instant constellation common view area in fixed latitude and longitude interval.

[0069] Loop to calculate the common view area of each modified angle constellation, until the maximum common view area is determined.

[0070] (2) Mathematical theory calculation

[0071] As shown in the accompanying Figure 1 , a coordinate system is established, and the satellite coverage area can be expressed as

[0072]

[0073] Where Σ is the approximate spherical surface of the earth x 2 +y 2 +z 2 =r 2 , which is constrained by the antenna pointing angle β and the antenna instantaneous coverage width, corresponding to the curved surface defined by the central angle γ, then

[0074]

[0075] Where D is the area r 2 sin(σ-γ)2 ≤x 2 +y 2 ≤r 2 sinσ 2 .

[0076] The pointing correction table formed by the pointing correction angle calculation results of the satellite antennas is uploaded to the satellite through a measurement and control link.

[0077] S4, the beam control module of each satellite sets the signal delay and attenuation of each array element according to the array antenna correction angle, so as to realize the antenna pointing adjustment.

[0078] Each satellite sums the optimized angle calculated by S3 and the initial beam pointing to obtain a corrected pointing angle (α B , β B ), (α C , β C ),..., and sends the corrected pointing angle to the beam control module of the array antenna.

[0079] The antenna pattern of the array antenna is obtained by weighted summation of the field intensity radiation patterns of each array element. Figure 2 , 3 As shown in the figures, the beam control module of the array antenna reads the optimized pointing angle, queries the delay code and attenuation code corresponding to the angle in the beam synthesis control table, corrects the delay and attenuation of the signal of each array element, realizes the adjustment of the antenna pattern, and thus adjusts the antenna pointing.

[0080] Further description of the technical solution is as follows: the low-orbit satellite constellation refers to a constellation composed of two or more satellites with consistent orbit height, dense distribution, and common view to a certain area on the ground.

[0081] The array antenna refers to an antenna system composed of multiple identical array elements arranged in a certain rule, including linear array or planar array. By controlling the delay and attenuation of the signal of each array element, the maximum pointing of the array antenna can be electrically scanned.

[0082] The low-orbit satellite constellation orbit is divided into n segments according to the sub-satellite point latitude, and the number of divided orbit segments is related to the orbit inclination of the low-orbit satellite, the beam width, and the pointing correction accuracy.

[0083] The pointing correction table calculated by the ground according to the orbit configuration and the characteristics of the array antenna is related to the form of the array antenna characteristics, such as one-dimensional scanning array antenna only correcting a direction, and the correction table is one-dimensional, and the pointing correction table of two-dimensional scanning array antenna is extended to two-dimensional.

[0084] The application also provides a low-orbit satellite constellation array antenna common view system, which comprises:

[0085] Low-Earth orbit (LEO) satellite constellation, LEO satellite constellation mission management module, satellite array antenna pointing angle optimization and determination module, and satellite array antenna pointing angle correction module, among which;

[0086] Each satellite in the low-Earth orbit (LEO) satellite constellation has an array antenna with the same frequency band and the same airspace coverage capability; the onboard time synchronization of each satellite in the LEO satellite constellation operates under the same time system.

[0087] The low-Earth orbit satellite constellation mission management module divides the operating orbit of the reference satellite within one orbital cycle into different orbital segments; and sets the satellite's Earth remote sensing area according to mission requirements, and determines the initial pointing angle of each satellite array antenna.

[0088] The satellite array antenna optimization pointing angle determination module determines the optimal pointing angle of the array antenna for each satellite in the low-Earth orbit constellation, excluding the reference satellite, based on the satellite configuration, the operating frequency band of the array antenna, and the initial pointing angle, with the goal of maximizing the shared ground area between the array antenna of the satellite and the array antenna of the reference satellite.

[0089] Determine the reference time T0 and acquire the onboard time T of each satellite in the low-Earth orbit satellite constellation in real time. utc According to the on-board time T utc And the reference time T0, determine the orbital segment of each satellite, and thus determine the optimal pointing angle of the array antenna for each satellite at this time.

[0090] The satellite's array antenna pointing angle correction module adjusts the pointing of the array antenna on each satellite in the low-Earth orbit satellite constellation, except for the reference satellite, so that the pointing angle of the array antenna is optimized.

[0091] First, the low-Earth orbit satellite constellation orbits are arbitrarily divided into multiple orbital segments according to whether the satellites ascend or descend and the latitude of the nadir point of the satellite's projection onto the Earth. The satellite orbital period is determined based on the orbit and configuration of each satellite. Then, the time interval of each orbital segment within one orbital period is determined, starting from the reference satellite time. Based on this time interval, the corresponding time for the satellite to enter and exit each orbital segment is determined, and a reference satellite is selected.

[0092] The satellite array antenna pointing angle optimization determination module further includes: normalizing the current satellite time of any satellite to time t within one orbital period, determining its corresponding orbital segment, and determining the current satellite array antenna pointing correction angle based on the current satellite array antenna operating frequency band, pointing angle, orbital segment, and the pointing angle of the reference satellite, with the condition of maximizing the common viewing area between the current satellite and the reference satellite.

[0093] The satellite array antenna optimization pointing angle determination module determines the optimal pointing angle of the current satellite array antenna when the shared viewing area between the current satellite and the reference satellite is maximized, including:

[0094] An initial value is set as the maximum common viewing area registered value between the reference star and the current satellite; the initial pointing angle of the current satellite to be corrected is the same as the initial pointing angle of the reference star;

[0095] For the current array antenna pointing correction angle

[0096] Traverse the range of values ​​for the pointing correction angle of the search array antenna with a specified search step size, calculate the current common viewing area of ​​the reference satellite and the satellite to be corrected corresponding to a certain pointing correction angle, compare it with a registered value, take the larger of the two as the maximum common viewing area and the new registered value, record and output the corresponding pointing correction angle at this time.

[0097] Repeat the above process until the traversal is complete, obtaining the final pointing correction angle. Summing the initial pointing angle of each satellite with the pointing correction angle yields the corrected optimized pointing angle of the array antenna. This optimized pointing angle is then used to correct the pointing angle of the array antennas of each satellite in the low-Earth orbit satellite constellation. The specific process for determining the current optimized pointing angle of the satellite array antenna includes:

[0098] Normalize the current satellite time of any satellite to time t within one orbital period and determine its corresponding orbital segment m. Based on the current satellite array antenna operating frequency band f, pointing angle, orbital segment, and the pointing angle of the reference satellite, determine the pointing correction angle of the current satellite array antenna, taking the maximum common viewing area between the current satellite and the reference satellite as the condition. This includes:

[0099] The reference satellite is designated as A-star, and its pointing angle (α) is determined according to the mission requirements. A0 ,β A0 ), α A0 Indicates azimuth angle, β A0 Indicates the elevation angle.

[0100] Let the current satellite to be corrected be denoted as satellite B, and its array antenna be pointed at the correction angle (Δα). B , αβ B );

[0101] Set the maximum common viewing area register value.

[0102] For Δα B From Δα B，min Begin by iterating through the search every α_step until Δα is reached. B，max ; where Δα B ∈(Δα B，min ,Δα B，max), and alpha_step is a corresponding search step;

[0103] For Δβ B From Δβ B，min Start every beta_step traversal search to Δβ B，max ; wherein Δβ B ∈(Δβ B，min , Δβ B，max ), beta_step is a corresponding search step;

[0104] Calculate the current common view area of A-star and B-star at this time And compare it with the stored value Compare the current common view area with the stored value, and take the larger one as the maximum common view area and the new stored value

[0105] Record and output the pointing correction angle when the common view area Is maximum, that is

[0106]

[0107] The satellite array antenna pointing angle correction module realizes antenna pointing adjustment according to the corrected angle, which comprises: based on the corrected angle, setting the delay and attenuation of each array element signal of the array antenna according to the beam synthesis control table, and obtaining the array antenna directional diagram by weighted summation of the field intensity radiation pattern of each array element signal, so as to realize antenna pointing adjustment according to the array antenna directional diagram.

[0108] The low-orbit satellite constellation array antenna common view method can significantly improve the multi-satellite cooperative coordination detection capability, and the specific implementation process is as shown in Figure 2 And Figure 3 .

[0109] 1. The low-orbit satellite constellation orbit is divided into n segments, i.e. orbit segments, according to the flight direction of the satellite from south to north / north to south, i.e. the ascending orbit / descending orbit and the subsatellite point latitude of the satellite projection on the earth. According to the actual orbit and configuration of each satellite in orbit, it is known that the satellite orbit period is R, and the time interval of each orbit segment within one orbit period of the satellite starting from the reference star time T0 is represented as (t i,s , t i,e ), i=0,1,2,.....,n-1, wherein t i,s represents the star time of entering the i-th orbit segment, and t i,e represents the star time of exiting the i-th orbit segment, i.e. the star time of entering the i+1-th orbit segment. There is a time difference in the time of each satellite of the low-orbit satellite constellation entering the orbit segment, and one satellite can be selected as a reference, and the other satellites in the constellation need to be optimized for pointing calculation.

[0110] According to the orbit, configuration and array antenna space coverage capability of the satellite, the optimized pointing angle of each frequency band and wave position of the array antenna of each satellite is obtained through STK scene simulation or mathematical calculation to realize maximum constellation common view range. The calculation result of the optimized pointing angle of each satellite antenna is formed into a pointing correction table and is uploaded to the satellite through the TT&C link.

[0111] 2. For any on-board time T utc , the corresponding normalized time t within one orbit period is calculated and expressed as

[0112] T utc ≥T0, t=(T utc -T0)%R;

[0113] T utc <T0, t=|T utc +k*R-T0|%R, where k is the upward integer of (T0-T utc ) / R.

[0114] 3. According to the orbit segment division table, the normalized time t is located in the mth orbit segment, i.e. t m,s <t<t m,e , and the optimized pointing angle of the antenna array beam corresponding to the orbit segment.

[0115] 4. The antenna pattern of the array antenna is obtained by weighted summation of the field strength radiation patterns of each array element. The optimized pointing angle of each satellite is summed with the initial beam pointing to obtain the corrected pointing angle, which is sent to the beam control module of the array antenna. The delay code and attenuation code corresponding to the angle in the beam synthesis control table are queried to correct the delay and attenuation of the signals of each array element, so that the antenna pattern adjustment and thus the antenna pointing adjustment can be realized.

[0116] Embodiment

[0117] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0118] The simulation experiment model of the present application is a low-orbit double-satellite constellation, and the two satellites are represented as S1 satellite and S2 satellite. The orbit height of S1 satellite and S2 satellite is 1000 km, the eccentricity is 0, the orbit inclination is 70°, the perigee amplitude and the ascending node right ascension are both 0°, the true anomaly of S1 satellite is 0°, and the true anomaly of S2 satellite is 3°.

[0119] S1 and S2 stars are configured with array antennas of the same frequency band and equivalent space coverage capability. When the array antenna works at 1 GHz, the 3dB beam width is 20°, and the beam pointing is 60° in azimuth and 40° in elevation in the simulation experiment. S1 and S2 stars work under the same time system, and the beam pointing is consistent at the same time before correction.

[0120] When the satellite is near the equator, the common view area of the array antennas of the two satellites is small, and the two satellites cannot carry out cooperative tasks in the non-common view area, so increasing the common view area of the array antennas of the low-orbit satellite constellation has become a key concern.

[0121] In the simulation experiment, S1 satellite is the reference star, that is, the orbit segment is divided according to S1 star, and the initial pointing angle is used without correcting the array antenna pointing angle. On July 8, 2022, 04:00:00 (UTC time), the subsatellite point of S1 satellite rises over the equator, and the latitude changes from negative to positive at this time, that is, 0°, which is taken as the reference star time T0. The orbit period R of S1 and S2 satellites is 105 minutes (6300 seconds). According to the above orbit parameters of S1 and S2 satellites, the satellite can cover the area within ±70° latitude, and the rising and falling orbits and the subsatellite point latitude of S1 satellite are divided into 20 segments, as shown in the following table. The southern latitude is represented by a negative angle, and the northern latitude is represented by a positive angle.

[0122] Table 1 shows the orbit segment division table

[0123]

[0124]

[0125] For any star time T utc On July 8, 2022, 06:39:50 (UTC time), according to the following formula, it can be known that the corresponding normalized time t in one orbit period is 3290s.

[0126] T utc ≥T0, t=(T utc -T0)%R;

[0127] T utc <T0, t=|T utc +k*R-T0|%R, where k=(T0-T utc ) / R is rounded up.

[0128] From Table 1, the normalized time t is located in the 11th orbit segment, that is, 3148(t 11,s )<3290(t)<3409(t 11,s ), at this time the satellite is in the south latitude of 0°-14°, which is a falling orbit.

[0129] According to the satellite orbit configuration and array antenna parameters, the ground can obtain the beam pointing correction angle required for realizing the maximum common view range when the satellite is in the orbit segment 11 through STK simulation software or mathematical calculation analysis. The following table shows the results (except for the first row which is the actual simulation result, the other values are examples).

[0130] Table 2 Antenna beam pointing correction represents intention

[0131]

[0132]

[0133] S2 satellite obtains the pointing correction angle from the table according to the current working frequency and the initial beam pointing, sums the initial beam pointing to obtain the corrected pointing angle, and sends it to the beam control module. The beam control module queries the delay code and attenuation code corresponding to the angle in the beam synthesis control table, and corrects the delay and attenuation of each array element signal to realize antenna pointing adjustment. After the array antenna beam pointing correction, the common view range of S1 and S2 satellites is effectively increased. Table 3 shows the coverage area of S1 and S2 satellites and the constellation common view area before and after the beam pointing correction. It can be seen that the constellation common view area increases from 45.01% to 80.69% before and after the array antenna pointing correction, which significantly improves the efficiency of multi-satellite cooperation in the low-orbit satellite constellation.

[0134] Table 3 Comparison before and after beam pointing correction

[0135]

[0136] The reference star is an arbitrarily selected satellite in the constellation, but when there are many satellites in the constellation, the satellite at the center of the constellation layout should be selected as the reference star as much as possible to avoid the case of large antenna pointing angle of other satellites. For example, when a low-orbit satellite constellation is composed of five satellites and arranged as shown in Figure 4 , the satellite at the center of the constellation layout is selected as the reference star A, and the antennas of satellites B-E are relatively centered, avoiding the case of large antenna pointing angle.

[0137] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A method for low earth orbit satellite constellation array antenna common view, characterized in that, The method comprises the following steps: (1) configuring the same array antenna with the same frequency band and the same space coverage capability for each satellite in the low-orbit satellite constellation, and designating one satellite as a reference satellite; (2) time synchronizing each satellite in the low-orbit satellite constellation so that each satellite operates under the same time system; (3) for the reference satellite in the low-orbit satellite constellation, dividing the running track of the reference satellite in one orbit period into different orbit segments, setting the satellite remote sensing area according to the task requirement, determining the initial pointing angle of the array antenna of each satellite in the low-orbit satellite constellation, and setting the initial pointing angle of the array antenna of the reference satellite unchanged; (4) determining a reference time T0, and acquiring in real time an on-board time T of each satellite in the low-orbit satellite constellation utc , determining an orbit position of each satellite according to the on-board time T utc and the reference time T0; (5) for each satellite in the low-orbit satellite constellation except the reference satellite, according to the satellite configuration, the working frequency band of the array antenna and the initial pointing angle, the optimized pointing angle of the array antenna of the satellite at different orbit positions is obtained, with the maximum array antenna earth common view area of the array antenna of the satellite at different orbit segments as the target; (6) for each satellite in the low-orbit satellite constellation except the reference satellite, the pointing of the array antenna carried by the satellite is adjusted according to the orbit segment of the reference satellite, so that the pointing of the array antenna is the optimized pointing angle.

2. The LEO satellite constellation array antenna common view method of claim 1, wherein: In step (3), the running track of the reference satellite in one orbit period is divided into different orbit segments, which comprises the following steps: firstly, the satellite orbit is divided into multiple segments according to the satellite orbit rising or falling and the satellite projection on the ground, the satellite orbit period is determined according to the orbit of the reference satellite, then the time interval of each orbit segment in one orbit period of the satellite is determined, and finally the corresponding time when the satellite enters and exits each segment is determined according to the time interval.

3. The LEO satellite constellation array antenna common view method of claim 2, wherein: In step (4), the orbit position of each satellite is determined according to the on-board time T utc and the reference time T0, specifically as follows: For a reference star orbit period R, any star time T utc Normalized to one orbit period, t, is expressed as T utc ≥ T0, t = (T utc - T0) % R; T utc <T0, t = |T utc + k * R - T0| % R, where k = (T0- T utc ) / R rounded up; The normalized time t lies in the mth orbital segment, i.e. t m,s t < t m,e , t m,s denotes the on-board time of entering the mth orbital segment, t m,e denotes the on-board time of exiting the mth orbital segment.

4. The LEO satellite constellation array antenna common view method of claim 3, wherein: In step (5), the optimized pointing angle of the array antenna of the satellite at different orbit positions is obtained, which comprises the following steps: The initial pointing angle of the satellite to be corrected is set to be the same as the initial pointing angle of the reference satellite, and the common view area at this time is taken as the register value; The search range of the array antenna pointing correction angle is searched with a specified search step, the common view area corresponding to a certain array antenna pointing correction angle is calculated, and the larger one of the two is taken as the new register value; after the traversal is completed, the pointing correction angle corresponding to the latest register value is summed with the initial pointing angle of the satellite to be corrected to obtain the optimized pointing angle of the array antenna after correction.

5. The LEO satellite constellation array antenna common view method of claim 4, wherein: In step (1), the satellite in the low-orbit satellite constellation is designated as the reference satellite, which comprises the following steps: selecting the satellite at the center of the low-orbit satellite constellation as the reference satellite.

6. The LEO satellite constellation array antenna common view method of claim 5, wherein: In step (6), the pointing of the array antenna carried by the satellite is adjusted, which comprises the following steps: The delay and attenuation of the signals of each array element of the array antenna are set according to the optimized pointing angle of the array antenna and the beam synthesis control table, the optimized array antenna directional diagram is obtained by weighted summation of the field strength radiation pattern of each array element signal, so as to realize the adjustment of the antenna pointing.

7. A low earth orbit satellite constellation array antenna common view system, characterized by, The method comprises the following steps: The low-orbit satellite constellation, the low-orbit satellite constellation task management module, the satellite array antenna optimized pointing angle determination module and the satellite array antenna pointing angle correction module are provided. Each satellite of the low-orbit satellite constellation has an array antenna with the same frequency band and the same space coverage capacity; the on-board time of each satellite of the constellation is synchronized, and the satellites work in the same time system; one of the satellites is a reference satellite; The low-orbit satellite constellation task management module divides the orbit of the reference satellite in one orbit period into different orbit segments; and sets a satellite remote sensing area on the ground according to a task requirement, determines an initial pointing angle of the array antenna of each satellite, and sets the reference satellite to keep the initial pointing angle of the array antenna unchanged; The satellite array antenna optimization pointing angle determination module determines a reference time T0, and obtains an on-satellite time T of each satellite in a low-orbit satellite constellation in real time utc , determines an orbit position of each satellite according to the on-satellite time T utc and the reference time T0; for each satellite in the low-orbit satellite constellation except the reference satellite, according to a satellite configuration, a working frequency band of the array antenna and an initial pointing angle, an optimized pointing angle of the array antenna of the satellite when the satellite is located at different orbit positions is obtained, with the target of maximum array antenna earth-viewing area of the satellite when the array antenna of the satellite and the reference satellite are located at different orbit segments. The satellite array antenna pointing angle correction module adjusts the pointing of the array antenna carried by each satellite in the low-orbit satellite constellation except the reference satellite according to the orbit segment in which the reference satellite is located, so that the pointing of the array antenna is an optimized pointing angle.

8. The LEO satellite constellation array antenna synergetic system of claim 7, wherein, The satellite array antenna optimization pointing angle determination module determines the orbit position of each satellite according to the on-board time T utc and the reference time T0, and comprises: For a reference star orbit period R, any star time T utc Normalized to one orbit period, time t, is expressed as T utc ≥ T0, t = (T utc - T0) % R; T utc <T0, t = |T utc +k*R-T0| %R, where k = (T0-T utc ) / R rounded up; The normalized time t lies in the mth orbital segment, i.e. t m,s t < t m,e , t m,s denotes the on-board time of entering the mth orbital segment, t m,e denotes the on-board time of exiting the mth orbital segment.

9. The LEO satellite constellation array antenna synergetic system of claim 8, wherein, The satellite array antenna optimized pointing angle determination module determines the optimized pointing angle of the array antenna of the satellite in the low-orbit satellite constellation except the reference satellite when the satellite is located at different orbit positions, and further includes: The initial pointing angle of the current satellite to be corrected is set to be the same as the initial pointing angle of the reference satellite, and the common view area at this time is set as a register value; The value range of the array antenna pointing correction angle is searched with a specified search step, the common view area corresponding to a certain antenna pointing correction angle is calculated, the calculated common view area is compared with the register value, and the larger one of the two is taken as a new register value; after the traversal ends, the pointing correction angle corresponding to the latest register value is summed with the initial pointing angle of the current satellite to be corrected to obtain the corrected optimized pointing angle of the array antenna.

10. The low-orbit satellite constellation array antenna common view system of claim 9, wherein: The satellite array antenna pointing angle correction module adjusts the pointing of the array antenna carried by each satellite in the low-orbit satellite constellation except the reference satellite, and further includes: The delay and attenuation of the signals of each array element of the array antenna are set according to the optimized pointing angle of the array antenna and the beam synthesis control table, the optimized array antenna directional diagram is obtained by weighted summation of the field intensity radiation patterns of the signals of each array element of the antenna, so that the antenna pointing adjustment is realized.

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