CN114614884B - Method for continuously covering satellite wave beam of non-stationary orbit satellite on ground - Google Patents
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Abstract
The invention discloses a method for continuously covering a non-stationary orbit satellite constellation satellite beam on ground, which comprises the following steps: dividing the whole earth surface into a plurality of coverage blocks, wherein each coverage block is covered by one wave beam of one satellite in a constellation; each satellite in the constellation controls the on-board wave beam to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, calculates the on-board wave beam direction when each satellite moves in the visible range corresponding to the coverage block to be covered, and controls the on-board wave beam to always point to the area; when the previous satellite in the constellation moves out of the visible range of a certain coverage block, the next satellite continuously covers the coverage block; the satellites realize continuous coverage of a certain area in time in a mode that the coverage time of the front satellite and the rear satellite are connected end to end; satellites positioned in the same orbit and covered by covering blocks belonging to different covering groups are distributed in a crossed manner, sequentially cover the geographically connected ground areas, and spatially and continuously cover the surface of the earth in the above manner.
Description
Technical Field
The invention belongs to the technical field of satellite communication, and particularly relates to a method for continuously covering a satellite wave beam of a non-stationary orbit satellite constellation on the ground.
Background
During operation, satellites need to know their precise orbital position, which information is known as ephemeris. Satellites are typically periodically charged by a ground control center.
The angle between the line between the satellite and the ground target and the horizon is called the elevation angle of the ground target to the satellite. Since non-stationary orbiting satellites orbit the earth, ground targets can communicate with satellites in radio only over a limited range of elevation angles, referred to as the visible range of the satellite. The time corresponding to each turn of the visual range is called visual time.
Satellites typically interact with terrestrial objects by radio signals, which cover a continuous area, called a beam. This area is called the coverage block of this beam of this satellite. The range of the signal intensity above a certain threshold value in the area is the coverage area of the beam of the satellite. If the satellite has multiple beams, there may be multiple coverage blocks at the same time.
Non-stationary orbiting satellites vary in geographic location of their satellite beams over the earth coverage blocks due to relative movement over the earth. When a certain area of the earth's surface needs to be continuously covered, a constellation needs to be formed by a plurality of satellites, and the beam of each satellite covers the area in turn.
Existing non-stationary orbit satellite beam-to-ground coverage is generally achieved by a fixed on-satellite beam pointing method. The method is simple and feasible, but because the satellite movement can cause the single satellite to have short earth coverage time, the ground target needs to be frequently switched among the beams of a plurality of satellites, so that the signal transmission quality is possibly reduced, and the switching signaling overhead is increased. The existing non-stationary orbit satellite systems, such as ORBCOMM, starlink, adopt the method, and the ground targets of Starlink need to be switched once for 3 minutes on the maximum average.
Secondly, the initiator of the existing satellite system wave beam switching process is a ground target, and the most common method is that the ground target automatically detects satellite signal intensity and then selects a certain satellite according to a certain strategy. This brings about an increase in complexity of the ground target, and on the other hand, the handover strategies selected by different manufacturers are different, which may lead to mismatch with the handover strategy on the satellite, resulting in handover failure.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a method for continuously covering the satellite beams of a non-stationary orbit satellite constellation on the ground.
The aim of the invention is achieved by the following technical scheme:
a method for continuously covering a constellation satellite of a non-stationary orbit satellite with a beam to ground, the method comprising:
dividing the whole earth surface into a plurality of coverage blocks, wherein each coverage block is covered by a satellite wave beam in a constellation, and geographic position information of all the coverage blocks is represented in the form of an earth coverage table and is preset or injected into a satellite;
each satellite in the constellation controls the on-board wave beam to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, calculates the on-board wave beam direction when each satellite moves in the visible range corresponding to the coverage block to be covered, and controls the on-board wave beam to always point to the area;
when the previous satellite in the constellation moves out of the visible range of a certain coverage block, the next satellite continuously covers the coverage block; the next satellite controls the beam on the satellite to always point to the area within the visible range of the area, and the satellites realize continuous coverage of the area in time in an end-to-end mode of the coverage time of the front satellite and the rear satellite;
satellites positioned in the same orbit and covered by covering blocks belonging to different covering groups are arranged in a crossed manner, sequentially cover the geographically connected ground areas, and spatially and continuously cover the surface area of the earth in the above manner.
According to a preferred embodiment, each covering block corresponds to two numbers: a cover group number and a cover block number;
wherein the coverage group number represents a set of radio parameters used by the corresponding coverage block, comprising at least: the ground targets on the coverage blocks with the same coverage group number and the satellite being covered use the same radio parameter set;
the cover block number represents the sequential number of the corresponding cover block within the cover group;
and, the corresponding relation between the coverage group number and the radio parameter set is preset in the satellite and the ground targets in advance.
According to a preferred embodiment, the earth coverage table contains at least the following information: the geographic coordinate position of all the coverage blocks, the coverage group number of all the coverage blocks, the coverage block number of all the coverage blocks, which coverage blocks the satellite needs to cover, the size of the coverage block the satellite needs to cover, and the coverage time starting and stopping point of the coverage blocks the satellite needs to cover.
According to a preferred embodiment, the coverage time is: under the condition that the elevation angle of any place in the coverage block to the satellite is larger than or equal to the lowest elevation angle threshold, the visible time of the satellite; wherein the lowest elevation threshold is preset to 5 degrees to 15 degrees.
According to a preferred embodiment, the longest coverage time t of a satellite for a coverage block 1 The method comprises the following steps:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the cover block, β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction, and w is the angular velocity of the satellite around the earth.
According to a preferred embodiment, at the time of coverage t 1 The satellite controls and changes the direction of the beam on the satellite according to the geographic coordinate position of the coverage block and the ephemeris information of the satellite in the earth coverage table, so that the beam on the satellite always points to the coverage block; the initial value of the on-satellite beam width is set according to the size of a coverage block in the earth coverage table, and then the coverage is adjusted according to ephemeris within the coverage time, so that the coverage to the earth is kept unchanged all the time.
According to a preferred embodiment, the two satellites in the same orbit and covering the same covering block have an included angle with the earth center line of less than or equal to:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction.
According to a preferred embodiment, two geographically connected covering blocks belong to different covering groups, satellites of the same orbit covering the covering blocks belonging to the different covering groups are arranged crosswise, and the covering blocks of the geographically connected covering blocks belonging to the different covering groups are sequentially covered;
and, lie in the same orbit, cover two satellites belonging to different coverage groups and two covering blocks that link up geographically, the included angle with the geocenter is less than or equal to:
where r is the earth radius, h is the satellite orbit height, α1 is the lowest elevation threshold of the previous satellite coverage group satellite, β1 is the initial value of the beam width of the previous satellite beam along the satellite orbit direction, α2 is the lowest elevation threshold of the next satellite coverage group satellite, and β2 is the initial value of the beam width of the next satellite beam along the satellite orbit direction.
According to a preferred embodiment, the satellite, at the beginning of and during the coverage time of a certain coverage block, periodically broadcasts to the coverage block, according to the earth coverage table, a coverage broadcast message comprising at least: a cover group number to which the cover block belongs, a cover block number of the cover block, and a satellite number of the satellite; letting the ground target know the radio parameter set of the coverage block through the coverage group number, comprising: frequency, bandwidth, transmit power threshold, receive sensitivity threshold; the ground target knows the number of the coverage block through the number of the coverage block, and knows which satellite is in communication with the ground target through the satellite number.
According to a preferred embodiment, the satellite broadcast transmits a satellite handoff message to the corresponding coverage block before the coverage time in the earth coverage table expires, the satellite handoff message comprising at least: satellite number of the satellite and beam switching time of the satellite; after receiving the satellite switching message, the ground target pauses sending information to the satellite until receiving the coverage broadcast message; the value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message; if the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the delay threshold, the ground target loses the satellite signal and needs to search the satellite signal again for access.
The foregoing inventive concepts and various further alternatives thereof may be freely combined to form multiple concepts, all of which are contemplated and claimed herein. Various combinations will be apparent to those skilled in the art from a review of the present disclosure, and are not intended to be exhaustive or all of the present disclosure.
The invention has the beneficial effects that: the frequency of beam switching is reduced by the method; the signaling overhead during beam switching is reduced; the problems of transmission quality degradation and transmission interruption caused by beam switching are reduced; the switching main body is changed from a ground target to a satellite, so that the complexity of realizing switching of the ground target is reduced, and the switching success rate is improved.
Drawings
FIG. 1 is a schematic view of a satellite with satellite number A covering areas of coverage blocks 1 and 2 belonging to coverage group 1 according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of the location of the same satellite beginning and ending to cover the same coverage block in an embodiment of the present invention;
fig. 3 is a schematic diagram of a two satellite implementation of continuous coverage of the coverage block 1 in an embodiment of the invention;
FIG. 4 is a schematic diagram of beam switching performed by two satellites in an embodiment of the invention;
FIG. 5 is a schematic diagram of a coverage group arrangement for geographically coupled regions in an embodiment of the invention;
fig. 6 is a schematic diagram of the angle between two satellites belonging to different coverage groups and the earth center line in the same orbit according to the embodiment.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the following embodiments and features in the embodiments may be combined with each other without conflict.
It should be noted that, for the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments.
The invention discloses a method for continuously covering a constellation satellite wave beam of a non-stationary orbit satellite on the ground, which comprises the following steps: a time-continuous coverage to ground and a space-continuous coverage to ground.
First, the entire earth surface is divided into a number of cover blocks, each covered by one satellite beam in the constellation, and the geographical location information of all cover blocks is represented in the form of an earth cover table, preset or annotated to the satellites.
Further, each covering block corresponds to two numbers: a cover group number and a cover block number.
Wherein the coverage group number represents a set of radio parameters used by the corresponding coverage block, comprising at least: frequency, bandwidth, transmit power threshold, receive sensitivity threshold, terrestrial targets on coverage blocks with the same coverage group number and the satellite being covered use the same set of radio parameters. The cover block number represents the sequential number of the corresponding cover block within this cover group. And, the corresponding relation between the coverage group number and the radio parameter set is preset in the satellite and the ground targets in advance.
Further, the earth coverage table contains at least the following information: the geographic coordinate position of all the coverage blocks, the coverage group number of all the coverage blocks, the coverage block number of all the coverage blocks, which coverage blocks the satellite needs to cover, the size of the coverage block the satellite needs to cover, and the coverage time starting and stopping point of the coverage blocks the satellite needs to cover.
The earth coverage table is known to the satellite by presetting or uploading, and the satellite can only execute according to the earth coverage table and cannot modify the earth coverage table.
The geographical coordinate position information of the covering block is generally the coordinate of the center point of the covering block, and longitude and latitude coordinates, geodetic coordinates and the like can be used. The size information of the coverage blocks may take the form of the geographic radius of the coverage blocks or the initial value of the on-satellite beam width, etc.
The covering time is as follows: and under the condition that the elevation angle of any place in the coverage block to the satellite is larger than or equal to the lowest elevation angle threshold, the visible time of the satellite is ensured. Wherein the lowest elevation threshold is preset to 5 degrees to 15 degrees.
The longest coverage time t of a satellite for one coverage block 1 The method comprises the following steps:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the cover block, β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction, and w is the angular velocity of the satellite around the earth.
Then, each satellite in the constellation controls the on-board wave beam to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, and when each satellite moves in the visible range corresponding to the coverage block to be covered, the on-board wave beam direction is calculated, and the on-board wave beam is controlled to always point to the area.
When the previous satellite in the constellation moves out of the visible range of a certain coverage block, the next satellite continuously covers the coverage block; the next satellite controls the beam on the satellite to always point to the area within the visual range of the area, and the satellites realize continuous coverage of the area in time in an end-to-end mode of the coverage time of the front satellite and the rear satellite.
Specifically, at the coverage time t 1 The satellite controls and changes the direction of the beam on the satellite according to the geographic coordinate position of the coverage block and the ephemeris information of the satellite in the earth coverage table, so that the beam on the satellite always points to the coverage block; the initial value of the on-satellite beam width is set according to the size of a coverage block in the earth coverage table, and then the coverage is adjusted according to ephemeris within the coverage time, so that the coverage to the earth is kept unchanged all the time.
The constellation is positioned on the same orbit, and the included angle between the earth center connecting line and the front and rear satellites which cover the same covering block is smaller than or equal to:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction. Thereby ensuring that the front satellite and the rear satellite are connected end to the same covering block in covering time.
Finally, the satellites which are located in the same orbit and are covered by the covering blocks belonging to different covering groups are distributed in a crossing way, sequentially cover the geographically connected ground areas, and spatially continuous covering is carried out on the surface area of the earth in the above way.
In particular, two geographically connected coverage blocks belong to different coverage groups, with different frequency parameters. Satellites which are located in the same orbit and are covered by covering blocks belonging to different covering groups are distributed in a crossing manner, and the covering blocks which are connected in a geographic manner and belong to different covering groups are sequentially covered.
And, lie in the same orbit, cover two satellites belonging to different coverage groups and two covering blocks that link up geographically, the included angle with the geocenter is less than or equal to:
where r is the earth radius, h is the satellite orbit height, α1 is the lowest elevation threshold of the previous satellite coverage group satellite, β1 is the initial value of the beam width of the previous satellite beam along the satellite orbit direction, α2 is the lowest elevation threshold of the next satellite coverage group satellite, and β2 is the initial value of the beam width of the next satellite beam along the satellite orbit direction. Thereby ensuring continuous coverage of the earth's surface space by the satellite constellation.
Preferably, when a satellite starts to cover a certain coverage block and within the coverage time of the coverage block, periodically broadcasting and transmitting a coverage broadcast message to the coverage block according to the earth coverage table, wherein the coverage broadcast message at least comprises: a cover group number to which the cover block belongs, a cover block number of the cover block, and a satellite number of the satellite; letting the ground target know the radio parameter set of the coverage block through the coverage group number, comprising: frequency, bandwidth, transmit power threshold, receive sensitivity threshold; the ground target knows the number of the coverage block through the number of the coverage block, and knows which satellite is in communication with the ground target through the satellite number.
Further, the satellite number has a uniqueness throughout the non-stationary orbiting satellite constellation, as determined by a preset.
Preferably, before the coverage time in the earth coverage table expires, the satellite broadcasts and transmits a satellite switching message to the corresponding coverage block, wherein the satellite switching message at least comprises: satellite number of the satellite and switching beam time of the satellite. After receiving the satellite switching message, the ground target pauses sending information to the satellite until receiving the coverage broadcast message.
The value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message.
The maximum propagation delay of the coverage block, namely the maximum radio propagation delay from the satellite to any place in the coverage block, is defined as r as the earth radius, h as the satellite orbit height, alpha as the lowest elevation threshold of the coverage block to the satellite, c as the speed of light, and the maximum propagation delay of the coverage block is equal to
If the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the delay threshold, the ground target loses the satellite signal and needs to search the satellite signal again for access.
The switching delay threshold is equal to or more than 2 times of the maximum propagation delay of the coverage block minus 1 time of the minimum propagation delay of the coverage block
The maximum propagation delay of the coverage block and the minimum propagation delay of the coverage block are respectively the maximum and minimum radio propagation delays from the satellite to any place in the coverage block.
Therefore, the frequency of beam switching is reduced by the method; the signaling overhead during beam switching is reduced; the problems of transmission quality degradation and transmission interruption caused by beam switching are reduced; the switching main body is changed from a ground target to a satellite, so that the complexity of realizing switching of the ground target is reduced, and the switching success rate is improved.
Examples:
all areas of the earth's surface that need to be covered are pre-divided into a plurality of coverage blocks, the geographic location of each area, etc. are pre-determined. The information such as the geographic coordinate positions of all the covering blocks, the covering group numbers and the covering block numbers of the covering blocks which are required to be covered by the satellite, the sizes of the covering blocks which are required to be covered by the satellite, the covering time starting and stopping points of the covering blocks which are required to be covered by the satellite and the like is manufactured into an earth covering table, and the information is known to the satellite through a preset or uploading mode.
An expression of the earth coverage table is shown in table 1, and specific values in the table are only shown as schematic, and so on. The geographical coordinates of the coverage blocks in the table use longitude and latitude coordinates, the coverage group numbers and the coverage block numbers use numerical numbers, whether the satellite needs to be covered is indicated by English letters Y or N, the coverage block size is indicated by on-satellite beam width, and the coverage time are indicated by the format of 'year, month, day, hour, minute and second'.
The ground target in this embodiment refers to a ground or low-altitude stationary or slow-moving target that communicates with a satellite, and includes a handheld terminal, a vehicle-mounted terminal, an airborne terminal, a ship-mounted terminal, a ground station, and the like.
TABLE 1
As shown in fig. 1, a satellite with a satellite number a covers the areas of the cover blocks 1 and 2 belonging to the cover group 1. The triangle area under the satellite in the figure represents the satellite beam. The satellite with the satellite number A starts and ends to cover the covering block number 1 according to the covering time start and the covering time stop in the earth covering table, and the elevation angle of the covering block 1, which is farthest from the satellite along the satellite orbit direction, is exactly equal to the lowest elevation angle threshold.
During the coverage time of the coverage block 1, the satellite A always points to the coverage block 1 according to the ephemeris control beam direction of the satellite A. After the "coverage time stop" in the earth coverage table, the satellite adjusts the beam direction to the area with the coverage group number of 1 and the coverage block number of 2, i.e., the dotted line part in the figure, according to the earth coverage table. The elevation angle in the cover block 2 furthest from the satellite in the satellite orbit direction is also equal to the lowest elevation threshold.
The calculation of the coverage time is shown in fig. 2, in which satellites are the positions where the same satellite starts and ends to cover the same coverage block, the triangle area under the satellite is the satellite beam, the dotted line is the satellite orbit, and the dotted line is the connection line between the satellite and the earth center. In the figure, the point A and the point B are the elevation angles of the farthest point of the coverage area when the satellite starts and ends coverage respectively, and the lowest elevation angle threshold is the lowest elevation angle when the coverage area is circular. In the figure, the point C and the point D are the satellite points under the satellite when the satellite starts and ends to cover, and the time when the satellite passes through the included angles between the point C and the point D and the earth center is the satellite cover time.
Let r be the earth radius, h be the satellite orbit height, α be the lowest elevation threshold of the covering block to the satellite, β be the initial value of the beam width of the beam on the satellite, n be the angle between the satellite's point and the target point, θ1 be the angle between the point C and the point A relative to the earth center, and θ2 be the angle between the point C and the point B relative to the earth center. θ1 and θ2 are also equal to the angles between the point D and the point B and between the point D and the point A relative to the earth center respectively. The included angle of the relative earth center between the C point and the D point can be calculated as follows:
the coverage time is at most the longest when the satellite travels around the earth at an angular velocity w
Since the shape of the satellite beam is generally circular or elliptical, the shape of each coverage block is circular or elliptical. When the cover block is circular, the elevation angle furthest from the satellite in the satellite orbit direction is equal to the lowest elevation threshold. When the covering block is elliptical, if the covering block is elliptical long side along the satellite orbit direction, the elevation angle farthest from the satellite is equal to the lowest elevation angle threshold; if the satellite orbit direction is the shorter side of the ellipse, the elevation angle farthest from the satellite is larger than the lowest elevation angle threshold, so as to ensure that the elevation angle at any position in the whole coverage block is larger than or equal to the lowest elevation angle threshold.
As shown in fig. 3. When satellite number a adjusts the beam direction to cover block 2, satellite number B directs the beam to cover block 1 to ensure continuous coverage of cover block 1 over time. The satellite with the satellite number A and the satellite with the satellite number B use the same radio parameter sets such as frequency, bandwidth, transmitting power threshold, receiving sensitivity threshold and the like for the covering block 1 according to the earth covering table, so that the ground target does not need to change the radio parameters thereof in the satellite switching process, and the influence of satellite beam switching on the ground target is reduced to the greatest extent.
The end-to-end connection of the coverage time can be realized only when the included angle relation between the front satellite and the rear satellite which are positioned on the same orbit and the earth center line of the same coverage group meets certain requirements, specifically comprises the following steps: the latter satellite happens to be in the position where the former satellite starts to cover when the former satellite ends to cover. The included angle between the two satellites and the geocentric line, which meets the condition, is less than or equal to the included angle between the points C and D in FIG. 2 and the geocentric line, which is
In the process of switching between two satellites, the former satellite transmits a satellite switching message to the terrestrial broadcast, and the latter satellite transmits an overlay broadcast message. The satellite switching message at least comprises: satellite number of the satellite, time of beam switching of the satellite. The overlay broadcast message includes at least: the cover group number to which the cover block belongs, the cover block number of the cover block, and the satellite number of the satellite. After receiving the satellite switching message, the ground target pauses data transmission according to the satellite switching time point, and resumes data transmission after receiving the coverage broadcast message, so as to ensure that the ground target does not lose packets in the satellite switching process. The information interaction process related to the handover process is shown in fig. 4. In fig. 4, satellite i represents a satellite that covers a ground target before handover, and satellite i+1 represents a satellite that covers a ground target after handover.
Two geographically connected covering blocks must belong to different covering groups, different frequency parameters are adopted to realize frequency division multiplexing, and different satellites are used to realize spatially continuous covering. As shown in fig. 5, the 4 geographically connected areas belong to 3 coverage groups, respectively, wherein the first three coverage blocks belong to different coverage groups, and the 4 th coverage block multiplexes coverage group number 1.
The cover blocks belonging to the cover group numbers 1, 2, 3 and the cover block number 1 are respectively covered by satellites A, B, C located in the same orbit. When satellite a finishes covering the area of coverage group number 1 that covers block number 1, after decovering the area of coverage group number 1 that covers block number 2, coverage group number 1 covers block number 1 by the next satellite in the process described in fig. 3. Thus, satellites located in the same orbit, covering coverage blocks belonging to different coverage groups, must be laid crosswise and cover the geographically connected coverage blocks in turn.
Note that here it is emphasized that "geographically connected covering blocks" the same covering group number may also be used if two covering blocks are geographically adjacent but not connected, but spaced apart.
In practice, in one case, the frequency of the satellite-to-ground coverage beam is fixed. Thus covering only a number of satellites with the same satellite beam with the same coverage group number covering block, and covering another coverage group number covering block is another number of satellites with the same satellite beam with another frequency. These satellites with different frequency on-satellite beams are arranged crosswise at different positions of the same orbit, covering in turn the geographically connected covering blocks belonging to different covering groups.
When the included angle between two satellites belonging to different coverage groups and the earth center connection is smaller than a certain threshold value, the earth coverage blocks of the two satellites can be connected end to end in space, so that continuous coverage in space is realized, and no overlapping coverage is realized to the greatest extent. Let θ A For the angle between the most distant coverage point of the previous satellite and the point below the satellite and the earth center, theta B And the included angle between the point to the point under the satellite and the earth center is covered for the nearest satellite. Let r be the earth radius, h be the satellite orbit height, α1 be the lowest elevation threshold of the previous satellite coverage group satellite, β1 be the initial value of the beam width on the satellite, α2 be the lowest elevation threshold of the next satellite coverage group satellite, and β2 be the initial value of the beam width on the satellite. Bit of thenThe threshold value of the included angle between two satellites belonging to different coverage groups and the earth connection on the same orbit is shown as theta in figure 6 A -θ B Calculated to obtain
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. A method for continuously covering a satellite beam of a non-stationary orbit satellite constellation on earth, which is characterized by comprising the following steps:
dividing the whole earth surface into a plurality of coverage blocks, wherein each coverage block is covered by a satellite wave beam of a satellite in a constellation, and geographic position information of all the coverage blocks is represented by an earth coverage table and is preset or injected into the satellite;
each satellite in the constellation controls the on-board wave beam to cover the ground according to the earth coverage table and by combining with the ephemeris of the satellite, calculates the on-board wave beam direction when each satellite moves in the visible range corresponding to the coverage block to be covered, and controls the on-board wave beam to always point to the area;
when the previous satellite in the constellation moves out of the visible range of a certain coverage block, the next satellite continuously covers the coverage block; the next satellite controls the beam on the satellite to always point to the area within the visible range of the area, and the satellites realize continuous coverage of the area in time in an end-to-end mode of the coverage time of the front satellite and the rear satellite;
satellites positioned in the same orbit and covered by covering blocks belonging to different covering groups are arranged in a crossed manner, sequentially cover the geographically connected ground areas, and spatially and continuously cover the surface area of the earth in the above manner.
2. The method for continuous beam-to-ground coverage on a non-stationary orbiting satellite constellation according to claim 1, wherein each coverage block corresponds to two numbers: a cover group number and a cover block number;
wherein the coverage group number represents a set of radio parameters used by the corresponding coverage block, comprising at least: the ground targets on the coverage blocks with the same coverage group number and the satellite being covered use the same radio parameter set;
the cover block number represents the sequential number of the corresponding cover block within the cover group;
and, the corresponding relation between the coverage group number and the radio parameter set is preset in the satellite and the ground targets in advance.
3. The method for continuous beam-to-ground coverage on a non-stationary orbiting satellite constellation according to claim 1 wherein said earth coverage table contains at least the following information: the geographic coordinate position of all the coverage blocks, the coverage group number of all the coverage blocks, the coverage block number of all the coverage blocks, which coverage blocks the satellite needs to cover, the size of the coverage block the satellite needs to cover, and the coverage time starting and stopping point of the coverage blocks the satellite needs to cover.
4. A method for continuous coverage of beams on a non-stationary orbiting satellite constellation according to claim 3 wherein said coverage time is: under the condition that the elevation angle of any place in the coverage block to the satellite is larger than or equal to the lowest elevation angle threshold, the visible time of the satellite; wherein the lowest elevation threshold is preset to 5 degrees to 15 degrees.
5. The method for continuous beam-to-ground coverage on a non-stationary orbiting satellite constellation according to claim 4 wherein the longest coverage time t of the satellite for a coverage block 1 The method comprises the following steps:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the cover block, β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction, and w is the angular velocity of the satellite around the earth.
6. A non-stationary orbiting satellite constellation on-satellite beam to ground sequential coverage method according to claim 3, characterized by the fact that at the time of coverage t 1 In the inner part of the inner part,
the satellite controls and changes the direction of the beam on the satellite according to the geographic coordinate position of the coverage block in the earth coverage table and the ephemeris information of the satellite so that the beam on the satellite always points to the coverage block;
the initial value of the on-satellite beam width is set according to the size of a coverage block in the earth coverage table, and then the coverage is adjusted according to ephemeris within the coverage time, so that the coverage to the earth is kept unchanged all the time.
7. The method for continuously covering a satellite beam on a non-stationary orbit satellite constellation onto ground according to claim 1, wherein the two satellites in the constellation are located on the same orbit, and the included angle between the earth center line and the front and rear satellites covering the same covering block is smaller than or equal to:
where r is the earth radius, h is the satellite orbit height, α is the lowest elevation threshold of the coverage block to the satellite, and β is the initial value of the beam width of the beam on the satellite along the satellite orbit direction.
8. The method for continuously covering beams on a satellite constellation of non-stationary orbit satellites to ground according to claim 1 wherein two covering blocks which are geographically connected belong to different covering groups, satellites which are located in the same orbit and which are covered by covering blocks which are geographically connected and which are covered by different covering groups are arranged in a crossing manner;
and, lie in the same orbit, cover two satellites belonging to different coverage groups and two covering blocks that link up geographically, the included angle with the geocenter is less than or equal to:
where r is the earth radius, h is the satellite orbit height, α1 is the lowest elevation threshold of the previous satellite coverage group satellite, β1 is the initial value of the beam width of the previous satellite beam along the satellite orbit direction, α2 is the lowest elevation threshold of the next satellite coverage group satellite, and β2 is the initial value of the beam width of the next satellite beam along the satellite orbit direction.
9. The method for continuous beam-to-ground coverage on a non-stationary orbiting satellite constellation according to claim 1 wherein,
when a satellite starts to cover a certain coverage block and within the coverage time of the coverage block, periodically broadcasting and transmitting a coverage broadcast message to the coverage block according to an earth coverage table, wherein the coverage broadcast message at least comprises: a cover group number to which the cover block belongs, a cover block number of the cover block, and a satellite number of the satellite;
letting the ground target know the radio parameter set of the coverage block through the coverage group number, comprising: frequency, bandwidth, transmit power threshold, receive sensitivity threshold; the ground target knows the number of the coverage block through the number of the coverage block, and knows which satellite is in communication with the ground target through the satellite number.
10. The method for continuous beam-to-ground coverage on a non-stationary orbiting satellite constellation according to claim 9 wherein,
before the coverage time in the earth coverage table expires, the satellite broadcasts and transmits a satellite switching message to the corresponding coverage block, wherein the satellite switching message at least comprises: satellite number of the satellite and beam switching time of the satellite;
after receiving the satellite switching message, the ground target pauses sending information to the satellite until receiving the coverage broadcast message;
the value of the switching beam time of the satellite in the satellite switching message is at least 2 times of the maximum propagation delay of the coverage block after the actual sending time of the satellite switching message;
if the ground target does not receive the coverage broadcast message after receiving the satellite switching message and switching the delay threshold, the ground target loses the satellite signal, and then searches the satellite signal again for access.
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