JP2023018714A - Positioning satellite constellation, and ground system - Google Patents

Abstract

To realize a positioning satellite system which can be achieved by covering an entire sphere using a small number of positioning satellite instruments and loading an inexpensive timepiece on each satellite.SOLUTION: A positioning satellite constellation 201 is constituted of a plurality of satellites 30. Each of the plurality of satellites 30 is equipped with: a communication device 32a for communicating with satellites forward and rearward in a traveling direction on the same orbital plane; and a positioning signal transmitting device 36 for transmitting a positioning signal. The plurality of satellites 30 form a toric-shape communication network 702 and exchange a signal 41 for time management among the satellites via the toric-shape communication network 702.SELECTED DRAWING: Figure 9

Description

The present disclosure relates to positioning satellite constellations and terrestrial systems.

Global Navigation Satellite Systems (GNSS), such as GPS, Galileo, BeiDou, Glonass, and Regional Navigation Satellite Systems (RNSS), such as the Quasi-Zenith Navigation Satellite System, are active as positioning satellite systems. GNSS is an abbreviation for Global Navigation Satellite System. RNSS is an abbreviation for Regional Navigation Satellite System. GPS is an abbreviation for Global Positioning System.

On the other hand, the formation of a satellite communication network using a constellation of low-orbit satellites called a mega-constellation is being promoted these days, and a positioning satellite system that transmits positioning signals from the constellation of low-orbit orbit satellites is eagerly awaited.

Patent Literature 1 discloses a technique for highly accurate positioning using positioning signals transmitted from quasi-zenith satellites and geostationary satellites.

JP 2010-266390 A

In the GNSS and RNSS currently in operation, each satellite is equipped with a high-precision reference clock such as an atomic clock, thereby adopting a means of transmitting positioning signals without synchronous control between the satellites. However, since the high-precision reference clock is expensive, there is a problem that the positioning satellite system becomes expensive.

In addition, in general, a huge number of low-orbit satellites are required to irradiate global positioning signals comprehensively. Therefore, there is a problem that the positioning satellite system formed by the group of satellites in low earth orbit is expensive.

An object of the present disclosure is to realize a positioning satellite system that can cover the entire globe with a small number of positioning satellites and that each satellite can be equipped with an inexpensive clock.

A positioning satellite constellation according to the present disclosure includes:
A plurality of satellites equipped with a communication device that communicates with satellites before and after the same orbital plane in the direction of travel, and a positioning signal transmission device that transmits a positioning signal,
forming a circular communication network,
Time management signals are exchanged between satellites via the annular communication network.

According to the satellite constellation according to the present disclosure, there is an effect that it is possible to realize a positioning satellite system that can cover the entire globe with a small number of positioning satellites and that each satellite can be equipped with an inexpensive clock. .

An example of a satellite constellation with multiple orbital planes that intersect outside the polar regions. 1 is a configuration example of a satellite constellation forming system according to Embodiment 1; 1 shows an example of a configuration of satellites in a satellite constellation according to Embodiment 1. FIG. 4 is another example of the satellite configuration of the satellite constellation according to the first embodiment; 4 is a configuration example of ground equipment included in the satellite constellation forming system according to Embodiment 1; 2 is an example of functional configuration of the satellite constellation forming system according to Embodiment 1; 2 is a diagram showing Example 1 of a positioning satellite constellation according to Embodiment 1; FIG. FIG. 5 is a diagram showing Example 2 of a positioning satellite constellation according to Embodiment 1; FIG. 10 is a diagram showing Example 3 of a positioning satellite constellation according to Embodiment 1; FIG. 5 is a diagram showing Example 4 of a positioning satellite constellation according to Embodiment 1; FIG. 5 is a diagram showing Example 5 of a positioning satellite constellation according to Embodiment 1; FIG. 8 is a diagram showing the arrangement of a plurality of positioning satellites A in a positioning satellite constellation according to Embodiment 2; FIG. 8 is a diagram showing the arrangement of a plurality of positioning satellites B in a positioning satellite constellation according to Embodiment 2; FIG. 8 is a diagram showing the arrangement of a plurality of positioning satellites C in a positioning satellite constellation according to Embodiment 2; FIG. 8 is a diagram showing the arrangement of a plurality of positioning satellites D in a positioning satellite constellation according to Embodiment 2; FIG. 4 is a diagram showing an example of a synchronous control method according to Embodiment 1; FIG. FIG. 5 is a diagram showing another example of the synchronous control method according to Embodiment 1; FIG.

Embodiments of the present disclosure will be described below with reference to the drawings. In each figure, the same reference numerals are given to the same or corresponding parts. In the description of the embodiments, the description of the same or corresponding parts will be omitted or simplified as appropriate. In addition, in the following drawings, the size relationship of each component may differ from the actual one. In addition, in the description of the embodiments, directions or positions such as "top", "bottom", "left", "right", "front", "back", "front", and "back" are indicated. There is These notations are provided as such for convenience of explanation only and are not intended to limit the arrangement and orientation of structures such as devices, instruments or components.

Embodiment 1.
An example of a satellite constellation 20 according to the following embodiment will be described.

*** Configuration description ***
FIG. 1 is an example of a satellite constellation 20 having multiple orbital planes 21 that intersect outside the polar regions.
In the satellite constellation 20 of FIG. 1, a plurality of satellites 30 fly at the same altitude in the same orbital plane. The satellite 30 is also called an artificial satellite.
In the satellite constellation 20 of FIG. 1, the orbital inclination angles of the orbital planes 21 of the plurality of orbital planes are not approximately 90 degrees, and the orbital planes 21 of the plurality of orbital planes are on different planes. In the satellite constellation 20 of FIG. 1, any two orbital planes intersect at points other than the polar regions. As shown in FIG. 1, the intersection of a plurality of orbital planes with an orbital inclination angle of more than 90 degrees moves away from the polar regions according to the orbital inclination angle. In addition, there is a possibility that the orbital planes intersect at various positions including near the equator depending on the combination of the orbital planes.
In addition to the satellite constellation 20 of FIG. 1, there is also a satellite constellation configured such that each of the orbital planes has an orbital inclination of about 90 degrees and the orbital planes intersect near the polar regions. .

An example of satellites 30 and ground facilities 700 in a satellite constellation forming system 600 forming the satellite constellation 20 will be described with reference to FIGS. 2 to 6. FIG. Satellite constellation forming system 600 is sometimes referred to simply as a satellite constellation, a communications constellation, or a positioning satellite constellation.

FIG. 2 is an example configuration of a satellite constellation forming system 600 .
Satellite constellation forming system 600 comprises a computer. Although FIG. 2 shows the configuration of one computer, in reality, each satellite 30 of the plurality of satellites forming the satellite constellation 20 and each of the ground facilities 700 communicating with the satellites 30 are equipped with computers. be done. The satellites 30 of the plurality of satellites and the computers provided in each of the ground facilities 700 communicating with the satellites 30 cooperate to implement the functions of the satellite constellation forming system 600 . An example of the configuration of a computer that implements the functions of satellite constellation forming system 600 will be described below.

Satellite constellation forming system 600 comprises satellites 30 and ground equipment 700 . Satellite 30 comprises a communication device 32 that communicates with communication device 950 of ground facility 700 . In FIG. 2, the communication device 32 is illustrated among the components provided in the satellite 30. As shown in FIG.

Satellite constellation forming system 600 comprises processor 910 and other hardware such as memory 921 , secondary storage 922 , input interface 930 , output interface 940 and communication device 950 . The processor 910 is connected to other hardware via signal lines and controls these other hardware.

The satellite constellation forming system 600 includes a satellite constellation forming section 11 as a functional element. Functions of the satellite constellation forming unit 11 are realized by hardware or software.
The satellite constellation formation unit 11 controls formation of the satellite constellation 20 while communicating with the satellites 30 .

FIG. 3 is an example configuration of satellites 30 of satellite constellation forming system 600 .
The satellite 30 includes a satellite control device 31 , a communication device 32 , a propulsion device 33 , an attitude control device 34 and a power supply device 35 . In addition, the satellite control device 31, the communication device 32, the propulsion device 33, the attitude control device 34, and the power supply device 35 will be described with reference to FIG.

The satellite control device 31 is a computer that controls the propulsion device 33 and the attitude control device 34, and includes a processing circuit. Specifically, the satellite control device 31 controls the propulsion device 33 and the attitude control device 34 according to various commands transmitted from the ground equipment 700 .
The communication device 32 is a device that communicates with the ground facility 700 . Alternatively, the communication device 32 is a device that communicates with satellites 30 before and after in the same orbital plane, or with satellites 30 in adjacent orbital planes. Specifically, the communication device 32 transmits various data related to its own satellite to the ground equipment 700 or other satellites 30 . The communication device 32 also receives various commands transmitted from the ground equipment 700 .
The propulsion device 33 is a device that gives propulsion force to the satellite 30 and changes the speed of the satellite 30 .
The attitude control device 34 controls the attitude of the satellite 30, the angular velocity of the satellite 30, and the line-of-sight direction (Line Of
Sight) is a device for controlling attitude elements. The attitude control device 34 changes each attitude element in a desired direction. Alternatively, attitude controller 34 maintains each attitude element in the desired orientation. The attitude control device 34 includes an attitude sensor, an actuator, and a controller. Attitude sensors are devices such as gyroscopes, earth sensors, sun sensors, star trackers, thrusters and magnetic sensors. Actuators are devices such as attitude control thrusters, momentum wheels, reaction wheels and control moment gyros. The controller controls the actuators according to measurement data from the attitude sensor or various commands from the ground equipment 700 .
The power supply device 35 includes devices such as a solar cell, a battery, and a power control device, and supplies power to each device mounted on the satellite 30 .

A processing circuit provided in the satellite control device 31 will be described.
The processing circuitry may be dedicated hardware or a processor executing a program stored in memory.
In the processing circuit, some functions may be implemented in dedicated hardware and the remaining functions may be implemented in software or firmware. That is, processing circuitry can be implemented in hardware, software, firmware, or a combination thereof.
Dedicated hardware is specifically a single circuit, multiple circuits, programmed processors, parallel programmed processors, ASICs, FPGAs, or combinations thereof.
ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

FIG. 4 is another example configuration of satellites 30 of satellite constellation forming system 600 .
FIG. 4 shows a configuration example in which the satellite 30 is a positioning satellite 301. As shown in FIG.
The positioning satellite 301 is an artificial satellite for satellite positioning. Specifically, positioning satellite 301 is an artificial satellite that transmits a positioning signal that is a signal for satellite positioning.
The satellite 30 of FIG. 4 includes a positioning signal transmitter 36 in addition to the configuration of FIG.
The positioning signal transmitter 36 is a device that transmits a positioning signal.

FIG. 5 is a configuration example of a ground facility 700 included in the satellite constellation forming system 600. As shown in FIG.
Ground facility 700 programs multiple satellites in all orbital planes. Ground facility 700 is also referred to as ground equipment or ground system. The ground equipment consists of a ground station such as a ground antenna device, a communication device connected to the ground antenna device, or a computer, and ground equipment as a server or a terminal connected to the ground station via a network. The ground equipment may also include a communication device mounted on a moving object such as an aircraft, a self-propelled vehicle, or a mobile terminal.

The positioning satellite constellation 201 according to the present embodiment realizes a positioning satellite system that can cover the entire globe with a small number of positioning satellites and that each satellite can be equipped with an inexpensive clock.
The ground facility 700 operates and controls a positioning satellite constellation 201, which is one of the satellite constellations 20, performs high-precision orbit determination processing for the positioning satellites, and calibrates time management signals exchanged between satellites to improve accuracy. It is a ground system that maintains and manages

Ground facility 700 forms satellite constellation 20 by communicating with each satellite 30 . Ground facility 700 includes processor 910 and other hardware such as memory 921 , secondary storage 922 , input interface 930 , output interface 940 and communication device 950 . The processor 910 is connected to other hardware via signal lines and controls these other hardware.

The ground facility 700 includes a trajectory control command generation unit 510 and an analysis prediction unit 520 as functional elements. The functions of the trajectory control command generation unit 510 and the analysis prediction unit 520 are realized by hardware or software.

Communication device 950 transmits and receives signals that track and control each satellite 30 of the constellation of satellites 20 . The communication device 950 also transmits orbit control commands 55 to each satellite 30 .
The analytical prediction unit 520 analyzes and predicts the orbit of the satellite 30 .
The orbit control command generator 510 generates an orbit control command 55 to be transmitted to the satellite 30 .
The orbit control command generation unit 510 and analysis prediction unit 520 realize the function of the satellite constellation formation unit 11 . That is, the orbit control command generation unit 510 and the analysis prediction unit 520 are examples of the satellite constellation formation unit 11 .

FIG. 6 is a diagram showing a functional configuration example of a satellite constellation forming system 600. As shown in FIG.
The satellite 30 further comprises a satellite constellation forming part 11 b forming the satellite constellation 20 . The satellite constellation forming unit 11b of each satellite 30 of the plurality of satellites cooperates with the satellite constellation forming unit 11 provided in each of the ground facilities 700 to realize the functions of the satellite constellation forming system 600. . Note that the satellite constellation forming unit 11 b of the satellite 30 may be provided in the satellite control device 31 .

***Explanation of configuration example and effect of positioning satellite constellation 201***
Next, an example of positioning satellite constellation 201 according to this embodiment will be described.
The positioning satellite constellation 201 is formed by a satellite constellation forming system 600, for example.

A positioning satellite constellation 201 is composed of a plurality of satellites 30 .
The plurality of satellites 30 includes a positioning satellite 301 that transmits positioning signals while orbiting a specific orbit in synchronization with other satellites 30 by controlling the propulsion device 33 according to control commands from the ground equipment 700. .
Ground facility 700 sends control commands to each satellite 30 to cause each satellite 30 to orbit a particular orbit in synchronization with other satellites 30 .

<Example 1 of positioning satellite constellation 201>
FIG. 7 is a diagram showing Example 1 of positioning satellite constellation 201 according to the present embodiment.
A positioning satellite constellation 201 is composed of a plurality of satellites 30 .
The satellite 30 includes a communication device that communicates with satellites in the same orbital plane in the direction of travel, and a positioning signal transmission device that transmits a positioning signal.
A plurality of satellites 30 form an annular communication network 702 and exchange time management signals 41 between satellites via the annular communication network 702 .
The time management signal 41 is a signal for managing the time of each satellite of the plurality of satellites 30 .
A communication device is a device that transmits information between satellites.
A positioning signal transmitter, as known from GPS or a quasi-zenith positioning system, is a device that emits radio waves (positioning signals) to the ground and transmits positioning signals for users on the ground to perform positioning (position coordinate measurement). be.

<Example 2 of positioning satellite constellation 201>
FIG. 8 is a diagram showing Example 2 of positioning satellite constellation 201 according to the present embodiment.
A positioning satellite constellation 201 is composed of a plurality of satellites 30 .
The satellite 30 includes a communication device that communicates with satellites in the same orbital plane in the same orbital plane in the direction of travel, a communication device that communicates with satellites in adjacent orbits, and a positioning signal transmission device that transmits a positioning signal.
A plurality of satellites 30 form an annular communication network 702, communicate with satellites in adjacent orbits to form a mesh communication network 703, and exchange time management signals 41 between satellites via the mesh communication network 703. .

<Example 3 of positioning satellite constellation 201>
FIG. 9 is a diagram showing Example 3 of the positioning satellite constellation 201 according to this embodiment.
The positioning satellite constellation 201 of Example 1 or Example 2 includes positioning satellites 301a equipped with high-precision master clocks 37, and exchanges time management signals 41 between the satellites.
FIG. 9 shows an aspect in which Example 1 of the positioning satellite constellation 201 includes a positioning satellite 301a. Also, the satellite 30 in FIG. 9 has the configuration explained in FIG. 3 or 4, but only the configuration necessary for explanation is shown here.
The positioning satellite 301a includes a communication device 32a, a high-precision master clock 37, and a positioning signal transmission device .
The communication device 32a is a communication device that communicates with satellites before and after the same orbital plane in the traveling direction.
The high precision master clock 37 is a high precision clock such as an atomic clock or an optical lattice clock.
The positioning signal transmitter 36 transmits positioning signals.
Also, the time management signal 41 may be a synchronous control signal or a time information signal.

FIG. 16 is a diagram showing an example of a synchronous control method according to this embodiment.
FIG. 17 is a diagram showing another example of the synchronization control method according to this embodiment.

As shown in FIG. 16, there is a method of simultaneously transmitting a synchronization signal A for coarse adjustment and a synchronization signal B for fine adjustment of a clock whose accuracy is not as high as that of an atomic clock, for example, as synchronization control signals.
Also, as shown in FIG. 17, a method of adding time information to the timing signal is effective.

For example, as shown in FIG. 17, a case where positioning satellite A and positioning satellite B are provided with two-way optical communication devices will be described.
Clocks of positioning satellite A and positioning satellite B provide time stamp information of the time when the synchronization control signal is transmitted and the time when the synchronization control signal is received. Assuming that the relative distance L is constant, the time difference between the time A sent and the time B received, and the time difference between the time B sent and the time A received, are supposed to match. , it is possible to derive the relative error of the clocks they both have.
Needless to say, even if the communication terminal is a radio wave communication device, the same time management can be performed in consideration of delay error, Doppler effect, or the like.

According to Example 3 of the positioning satellite constellation 201, even if the individual satellites 30 do not have high-precision clocks, the time management signals transmitted from the positioning satellites that have high-precision master clocks enable high-precision There is an effect that time management becomes possible. A positioning satellite equipped with a high precision master clock is also called a master clock satellite.
For example, if the mission device is a positioning mission, using the time management signal transmitted by the master clock satellite has the effect of enabling distribution of a highly accurate positioning signal from a positioning satellite that does not have an atomic clock.

The positioning mission will be described below.
If a satellite equipped with a high-precision clock such as an atomic clock or an optical lattice clock and a positioning signal transmission device as a mission device distributes a positioning signal including the precise orbital information of its own satellite, it can be used as a GPS or a quasi-zenith positioning satellite. Like GNSS, it functions as a positioning satellite.
However, since a high-precision clock that serves as a master clock is expensive, there is a problem that a system in which all satellites are equipped with a master clock is expensive.
Clocks such as quartz clocks, which are standard equipment on satellites, are inferior to atomic clocks in long-term stability.
Therefore, while maintaining the desired time accuracy, by referring to the synchronization signal from the master clock and calibrating the standard clock, accurate time can be maintained without having a high-precision master clock. It becomes possible to function as a positioning satellite.

<Example 4 of positioning satellite constellation 201>
FIG. 10 is a diagram showing Example 4 of positioning satellite constellation 201 according to the present embodiment.
The positioning satellite constellation 201 of Example 1 or Example 2 includes positioning satellites 301b having positioning signal receivers 38 for receiving positioning signals. The positioning satellite 301b calculates the correct time based on the signal received by the positioning signal receiver 38 and calibrates its own satellite clock. The positioning satellite constellation 201 exchanges the time management signal 41 among a plurality of satellites.
FIG. 10 shows an aspect in which Example 1 of the positioning satellite constellation 201 includes a positioning satellite 301b. Also, the satellite in FIG. 10 has the configuration explained in FIG. 3 or FIG. 4, but the configuration necessary for the explanation is shown here.
The positioning satellite 301 b includes a communication device 32 a , a communication device 32 b , a positioning signal receiver 38 and a positioning signal transmitter 36 .
The communication device 32b is a communication device that communicates with satellites in adjacent orbits.
The positioning signal receiver 38 receives the positioning signal, calculates the correct time based on the received signal, and calibrates the clock of its own satellite.
The positioning signal receiver on the satellite constellation side is, for example, a so-called GPS receiver similar to a device such as car navigation. It receives radio waves (positioning signals) from positioning signal transmitters provided in GPS satellites or quasi-zenith positioning satellites. Since the GPS receiver can derive the correct time using the received positioning signals, this time information is used as the master clock.
In FIG. 10, the positioning satellite 301c is a positioning satellite such as a GPS satellite or a quasi-zenith positioning satellite.

The positioning signal receiver of the satellite constellation in low earth orbit is the positioning signal transmitter of the quasi-zenith positioning satellite flying in the geostationary orbit or quasi-zenith orbit, or the positioning signal transmitter of the GPS satellite flying in the MEO orbit at an altitude of about 20000 km. receive a signal. MEO is an abbreviation for Medium Earth Orbit.
A positioning signal receiver that receives a GNSS positioning signal such as a GPS satellite or a quasi-zenith positioning satellite can calculate not only the position but also the accurate time by receiving the positioning signal. Therefore, even a satellite that does not have a master clock can calibrate and synchronize its own satellite's clock with the GNSS as a master clock if it has a positioning signal receiver.
A standard clock calibrated by a master clock is hereinafter referred to as a slave clock.
A method called GPS time synchronization is known as a slave clock synchronization control method. The synchronous control method has been described with reference to FIGS. 16 and 17. FIG.

<Example 5 of positioning satellite constellation 201>
FIG. 11 is a diagram showing Example 5 of positioning satellite constellation 201 according to the present embodiment.
In each of the positioning satellite constellations 201 of Examples 1 to 4, each satellite of the plurality of satellites 30 is equipped with a ranging device 39 to measure the distance between the satellites.
FIG. 11 shows how each satellite of Example 2 of the positioning satellite constellation 201 is equipped with a ranging device 39 . Also, the satellite in FIG. 11 has the configuration explained in FIG. 3 or FIG. 4, but the configuration necessary for the explanation is shown here.

Refinement of orbital information, including positioning satellite position information, helps improve the accuracy of positioning service signals for positioning missions.
In a constellation in which the orbital period is managed and the satellites fly synchronously in the same orbital plane, the distances to the preceding and succeeding satellites are accurately measured, and highly accurate orbit determination processing is performed on the orbital information on the ground. This has the effect of eliminating systematic errors and increasing the accuracy of orbit information.

Range finder is a means of distance measurement between satellites. For example, a satellite equipped with a laser range finder receives reflected laser from a laser reflector provided on a satellite flying ahead, and performs double-pass ranging. good too. Alternatively, a signal of an optical communication terminal may be transmitted and received between time-synchronized satellites for single-path ranging.
It is also possible to use the optical communication terminal as a distance measuring device.
Further, there is an effect that the flight positions of satellites in different orbital planes can be accurately measured by inter-satellite ranging between adjacent orbits.

<Example 6 of positioning satellite constellation 201>
In each of the positioning satellite constellations 201 of Examples 1 to 5, satellites forming an annular communication network and flying in the same orbital plane perform forward time management and backward time management.
Forward time management is a method of transmitting time management signals in the direction of flight of the satellite.
Reverse direction time management is a method of transmitting a time management signal in the direction opposite to the traveling direction.

Since the satellite moves in orbit at a speed exceeding 4 km/s, it lags behind the clock on the ground relatively according to special relativity theory.
In addition, since the effect of gravity is weaker in orbit at an altitude of 20,000 km than on the earth's surface, the general theory of relativity makes clocks advance faster than clocks on the ground.
Combining the two effects, the atomic clocks onboard GPS satellites advance 28.6 microseconds per day faster than the clocks on the ground.
Light travels about 11 km in 28.6 microseconds, so if you leave this deviation alone for a day, the GPS will have an error of 11 km.

In GNSS, atomic clock corrections are made to counteract these relativistic effects.
When a positioning mission is realized using a positioning satellite constellation, clock correction is also required to cancel the effect of relativity. Correction of the slave clock of satellites without a master clock requires the elimination of systematic errors that occur during the process of synchronous control. By comparing and evaluating forward time management and backward time management time and orbital information on the ground in a group of satellites forming an annular communication network, systematic errors can be eliminated.

***Description of the effects of the first embodiment***
According to this embodiment, when a constellation of low earth orbit satellites constructs an inter-satellite communication network, it is not necessary for all satellites to have a high-precision reference clock. A low-cost positioning satellite system can be constructed by synchronously controlling other satellites using a high-precision reference clock provided by some satellites as a master clock.
Moreover, even a satellite that does not have a high-precision master clock can calibrate and synchronize its own satellite's clock with GNSS as a master clock if it has a positioning signal receiver.
As described above, according to the present embodiment, high-precision time control essential for positioning satellites can be achieved at low cost.

Here, the hardware provided in the computer of each device such as satellite constellation forming system 600 forming positioning satellite constellation 201, ground facilities 700 and 800, and each satellite 30 will be described.

Processor 910 is a device that executes a program that implements the functions of each device.
The processor 910 is an IC (Integrated Circuit) that performs arithmetic processing. Specific examples of the processor 910 are a CPU (Central Processing Unit), a DSP (Digital Signal Processor), and a GPU (Graphics Processing Unit).

The memory 921 is a storage device that temporarily stores data. A specific example of the memory 921 is SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory).
Auxiliary storage device 922 is a storage device that stores data. A specific example of the auxiliary storage device 922 is an HDD. The auxiliary storage device 922 may be a portable storage medium such as an SD (registered trademark) memory card, CF, NAND flash, flexible disk, optical disk, compact disk, Blu-ray (registered trademark) disk, or DVD. Note that HDD is an abbreviation for Hard Disk Drive. SD® is an abbreviation for Secure Digital. CF is an abbreviation for CompactFlash®. DVD is an abbreviation for Digital Versatile Disk.

The input interface 930 is a port connected to an input device such as a mouse, keyboard, or touch panel. The input interface 930 is specifically a USB (Universal Serial Bus) terminal. The input interface 930 may be a port connected to a LAN (Local Area Network).
The output interface 940 is a port to which a cable of a display device 941 such as a display is connected. The output interface 940 is specifically a USB terminal or an HDMI (registered trademark) (High Definition Multimedia Interface) terminal. The display is specifically an LCD (Liquid Crystal Display).

Communication device 950 has a receiver and a transmitter. The communication device 950 is specifically a communication chip or a NIC (Network Interface Card).

A program that implements the function of each device is read into processor 910 and executed by processor 910 . The memory 921 stores not only programs but also an OS (Operating System). The processor 910 executes programs while executing the OS. The program and OS may be stored in the auxiliary storage device 922 . The programs and OS stored in the auxiliary storage device 922 are loaded into the memory 921 and executed by the processor 910 . Note that part or all of the program that implements the functions of each device may be incorporated in the OS.

Each device may include multiple processors in place of processor 910 . These multiple processors share program execution. Each processor, like processor 910, is a device that executes a program.

The data, information, signal values and variable values used, processed or output by the programs may be stored in memory 921 , secondary storage 922 , registers or cache memory within processor 910 .

You may read "the part" of each part of each apparatus as a "process", a "procedure", a "means", a "step", a "circuitry", or a "process." In addition, "part" of each part of each device may be read as "program", "program product" or "computer-readable recording medium recording the program". "Process", "procedure", "means", "step", "circuitry" or "process" can be read interchangeably.

Embodiment 2.
In the present embodiment, points different from the first embodiment and points added to the first embodiment will be mainly described.
In the present embodiment, the same reference numerals are assigned to components having the same functions as those of the first embodiment, and the description thereof will be omitted.

In the present embodiment, in the positioning satellite constellation 201 described in the first embodiment, a mode will be described in which the number of positioning satellites 301 within the field of view is insufficient and satellite positioning cannot be performed.

In the present embodiment, in the positioning satellite constellation 201 described in the first embodiment, the plurality of positioning satellites are 12 or more, which is a multiple of 6.
Each positioning satellite orbits an oblique circular orbit multiple times a day.
A plurality of orbital planes corresponding to a plurality of positioning satellites have their normals shifted by an equal angle in the azimuth direction. The plurality of orbital planes constitutes two or more orbital plane sets of six orbital planes each, and the six orbital planes of each orbital plane set are synchronized in the timing of orbiting by the six orbiting satellites.

More specific description will be given below.
The plurality of positioning satellites is composed of a plurality of positioning satellites 301 whose number is a multiple of 6 which is 12 or more.
Each positioning satellite 301 orbits an oblique circular orbit multiple times a day. An inclined circular orbit is an inclined orbit and a circular orbit.

A plurality of positioning satellites 301 form a plurality of orbital planes.
The normals of the plurality of orbital surfaces are shifted by an equal angle in the azimuth direction. The azimuth direction is a direction corresponding to the traveling direction of the positioning satellite 301 .
When the plurality of positioning satellites is 12 positioning satellites 301, the 12 positioning satellites 301 form 12 orbital planes. The normals of the 12 orbital planes are shifted by 30 degrees in the azimuth direction.
When the plurality of positioning satellites is 18 positioning satellites 301, the 18 positioning satellites 301 form 18 orbital planes. The normals of the 18 orbital planes are shifted by 20 degrees in the azimuth direction.

A plurality of positioning satellites constitute two or more positioning satellite sets each consisting of six positioning satellites 301 . The 12 positioning satellites 301 constitute two positioning satellite sets, and the 18 positioning satellites 301 constitute three positioning satellite sets.
The plurality of raceway surfaces constitute two or more raceway surface sets of six raceway surfaces each. The 12 raceway surfaces constitute two raceway surface sets, and the 18 raceway surfaces constitute three raceway surface sets.
Timings at which the six positioning satellites 301 orbit in six orbital planes are synchronized for each orbital plane set.

The positioning satellite 301 is also called an orbiting satellite.

In the positioning satellite constellation 201 according to the present embodiment, the timing at which the first orbiting satellite, which is an orbiting satellite that orbits in the first orbital plane of each orbital plane set, passes through the northernmost end of the first orbital plane is , the timing at which the orbiting satellite orbiting in the third orbital plane of each orbital plane pair passes through a point whose in-plane phase is shifted by 120 degrees from the northernmost end of the third orbital plane; It is synchronized with the timing when the orbiting satellite orbiting in the orbital plane passes through a point that is 240 degrees out of phase with the northernmost point of the fifth orbital plane.
In addition, the timing at which the fourth orbiting satellite, which is an orbiting satellite orbiting in the fourth orbital plane of each orbital plane set, passes through each in-plane phase point on the fourth orbital plane is 6 of each orbital plane set. the timing at which the circulating satellite orbiting in the 6th orbital plane passes through a point on the 6th orbital plane whose in-plane phase is shifted by 120 degrees from the point corresponding to the in-plane phase of the 4th orbital plane; and each orbital plane. the timing at which the orbiting satellite orbiting in the second orbital plane of the pair passes through a point in the second orbital plane whose in-plane phase is shifted by 240 degrees from the point corresponding to the in-plane phase of the fourth orbiting satellite; Synchronized.
In each orbital plane pair, the fourth orbital satellite is placed in the fourth orbital plane at a timing half the orbital period after the first orbital satellite passes the northernmost end of the first orbital plane. passes through the northernmost point of the orbital plane of

FIG. 12 is a diagram showing the arrangement of a plurality of positioning satellites A in positioning satellite constellation 201 according to this embodiment.
A plurality of positioning satellites A is an example of a plurality of positioning satellites, and is composed of 12 positioning satellites 301 .
A circle marked with m represents the m-th positioning satellite 301 . “m” is an integer of 1 or more and 12 or less. The m-th positioning satellite 301 is called an orbiting satellite (m). The orbital plane of the orbiting satellite (m) is called the orbital plane (m).

Solid-line waveforms represent the orbits of the odd-numbered positioning satellites 301 . A dashed waveform represents the orbit of the even-numbered positioning satellite 301 .
The vertical direction represents latitude. The horizontal direction represents longitude.
The top of each track corresponds to the northernmost point of the track, and the bottom of each track corresponds to the southernmost point of the track.
Each track number is attached to the top of each track.

In the following description, "n" is 0 and 1.
The timing at which the orbiting satellite (6n+1) passes the northernmost point of the orbital plane (6n+1) is referred to as timing (1).
Timing (1) is synchronized with timings (3) and (5) below.
Timing (3) is the timing at which the orbiting satellite (6n+3) passes through a point whose in-plane phase is shifted by plus 120 degrees from the northernmost end of the orbital plane (6n+3).
Timing (5) is the timing when the orbiting satellite (6n+5) passes through a point whose in-plane phase is shifted by plus 240 degrees from the northernmost end of the orbital plane (6n+5).

The timing at which the orbital satellite (6n+4) passes through each in-plane phase point in the orbital plane (6n+4) is called timing (4).
Timing (4) is synchronized with timing (6)(2) below.
Timing (6) is the timing when the orbital satellite (6n+6) passes through a point on the orbital plane (6n+6) whose in-plane phase is shifted by +120 degrees from the point corresponding to the in-plane phase of the orbital satellite (6n+4).
Timing (2) is the timing at which the orbital satellite (6n+2) passes through a point on the orbital plane (6n+2) whose in-plane phase is shifted by +240 degrees from the point corresponding to the in-plane phase of the orbital satellite (6n+4).

The orbiting satellite (6n+4) passes the northernmost point of the orbital plane (6n+4) at a timing T/2 after the orbital satellite (6n+1) passes the northernmost point of the orbital plane (6n+1).
“T” means the orbital period of each positioning satellite 301 . The orbit period is the time required for each positioning satellite 301 to make one round of the oblique circular orbit.
“T/2” means a half period of the orbital period of each positioning satellite 301 .

FIG. 13 is a diagram showing the arrangement of a plurality of positioning satellites B in positioning satellite constellation 201 according to this embodiment.
A plurality of positioning satellites B is an example of a plurality of positioning satellites, and is composed of 12 positioning satellites 301 .

The timing at which the orbiting satellite (6n+1) passes the northernmost point of the orbital plane (6n+1) is referred to as timing (1).
Timing (1) is synchronized with timings (3) and (5) below.
Timing (3) is the timing when the orbiting satellite (6n+3) passes through a point whose in-plane phase deviates from the northernmost end of the orbital plane (6n+3) by minus 120 degrees.
Timing (5) is the timing when the orbiting satellite (6n+5) passes through a point whose in-plane phase is shifted by -240 degrees from the northernmost end of the orbital plane (6n+5).

The timing at which the orbital satellite (6n+4) passes through each in-plane phase point in the orbital plane (6n+4) is called timing (4).
Timing (4) is synchronized with timing (6)(2) below.
Timing (6) is the timing when the orbital satellite (6n+6) passes through a point whose in-plane phase is shifted by minus 120 degrees from the point corresponding to the in-plane phase of the orbital plane (6n+6) of the orbital plane (6n+4).
Timing (2) is the timing when the orbital satellite (6n+2) passes through a point whose in-plane phase is shifted by -240 degrees from the point corresponding to the in-plane phase of the orbital plane (6n+2) of the orbital plane (6n+4).

The orbiting satellite (6n+4) passes the northernmost point of the orbital plane (6n+4) at a timing T/2 after the orbital satellite (6n+1) passes the northernmost point of the orbital plane (6n+1).

FIG. 14 is a diagram showing the arrangement of a plurality of positioning satellites C in positioning satellite constellation 201 according to this embodiment.
A plurality of positioning satellites C is an example of a plurality of positioning satellites, and is composed of 18 positioning satellites 301 .

In the following description, "n" is an integer of 0 or more and 2 or less.
The timing at which the orbiting satellite (6n+1) passes through the orbital plane (6n+1) is called timing (1).
Timing (1) is synchronized with timings (3) and (5) below.
Timing (3) is the timing at which the orbiting satellite (6n+3) passes through a point whose in-plane phase is shifted by plus 120 degrees from the northernmost end of the orbital plane (6n+3).
Timing (5) is the timing when the orbiting satellite (6n+5) passes through a point whose in-plane phase is shifted by plus 240 degrees from the northernmost end of the orbital plane (6n+5).
Timing (1) is also synchronized with timings (4), (6), and (2) below.
Timing (4) is the timing when the orbiting satellite (6n+4) passes through the southernmost point of the orbital plane (6n+4).
Timing (6) is the timing when the orbiting satellite (6n+6) passes through a point whose in-plane phase is shifted by plus 120 degrees from the southernmost end of the orbital plane (6n+6).
Timing (2) is the timing when the orbiting satellite (6n+2) passes through a point whose in-plane phase is shifted by plus 240 degrees from the southernmost end of the orbital plane (6n+2).

FIG. 15 is a diagram showing the arrangement of a plurality of positioning satellites D in positioning satellite constellation 201 according to this embodiment.
A plurality of positioning satellites C is an example of a plurality of positioning satellites, and is composed of 18 positioning satellites 301 .

The timing at which the orbiting satellite (6n+1) passes through the orbital plane (6n+1) is called timing (1).
Timing (1) is synchronized with timings (3) and (5) below.
Timing (3) is the timing when the orbiting satellite (6n+3) passes through a point whose in-plane phase deviates from the northernmost end of the orbital plane (6n+3) by minus 120 degrees.
Timing (5) is the timing when the orbiting satellite (6n+5) passes through a point whose in-plane phase is shifted by -240 degrees from the northernmost end of the orbital plane (6n+5).
Timing (1) is also synchronized with timings (4), (6), and (2) below.
Timing (4) is the timing when the orbiting satellite (6n+4) passes through the southernmost point of the orbital plane (6n+4).
Timing (6) is the timing when the orbiting satellite (6n+6) passes through a point whose in-plane phase deviates from the southernmost end of the orbital plane (6n+6) by minus 120 degrees.
Timing (2) is the timing when the orbiting satellite (6n+2) passes through a point whose in-plane phase deviates from the southernmost end of the orbital plane (6n+2) by -240 degrees.

The ground system sets the orbital inclination angle and orbital altitude of each positioning satellite 301 and controls a plurality of positioning satellites. As a result, positioning signals can be constantly emitted while the plurality of positioning satellites 301 take turns in the latitude band where the target area (for example, Japan) is located. Therefore, it is possible to increase the number of positioning satellites within the field of view in the target area by one.
The ground system can increase the orbital altitude of each positioning satellite 301 . If the orbit altitude of each positioning satellite 301 rises, a plurality of positioning satellites 301 can irradiate positioning signals to the same point on the ground. Thereby, the positioning accuracy can be improved.
Since a group of geostationary satellites fly over the equator, the elevation angle of each geostationary satellite with respect to a positioning terminal on the ground is limited. However, each positioning satellite 301 can pass over the target area at a high elevation angle. Therefore, the positioning signal from each positioning satellite 301 to the positioning terminal on the ground is less likely to be adversely affected by multipath. As a result, positioning accuracy can be improved.

A plurality of portions of the first and second embodiments described above may be combined for implementation. Alternatively, one portion of these embodiments may be implemented. In addition, these embodiments may be implemented in any combination as a whole or in part.
That is, in Embodiments 1 and 2, it is possible to freely combine any part of Embodiments 1 and 2, modify any component, or omit any component in Embodiments 1 and 2. is.

The above-described embodiments are essentially preferable examples, and are not intended to limit the scope of the present disclosure, the scope of application of the present disclosure, and the range of applications of the present disclosure. Various modifications can be made to the above-described embodiments as required.

11, 11b satellite constellation forming unit, 20 satellite constellation, 201 positioning satellite constellation, 21 orbital plane, 30 satellite, 301, 301a, 301b, 301c positioning satellite, 31 satellite control device, 32, 32a, 32b communication device, 33 propulsion device, 34 attitude control device, 35 power supply device, 36 positioning signal transmitter, 37 high-precision master clock, 38 positioning signal receiver, 39 ranging device, 41 time management signal, 55 orbit control command, 510 orbit control command Generation Unit 520 Analysis Prediction Unit 600 Satellite Constellation Formation System 700 Ground Equipment 702 Annular Communication Network 703 Mesh Communication Network 910 Processor 921 Memory 922 Auxiliary Storage Device 930 Input Interface 940 Output Interface 941 display equipment, 950 communication equipment;

Claims (9)

A plurality of satellites equipped with a communication device that communicates with satellites before and after the same orbital plane in the direction of travel, and a positioning signal transmission device that transmits a positioning signal,
forming a circular communication network,
A positioning satellite constellation for exchanging time management signals between satellites via the annular communication network. A plurality of satellites equipped with a communication device for communicating with satellites in the same orbital plane before and after the traveling direction, a communication device for communicating with satellites in adjacent orbits, and a positioning signal transmission device for transmitting a positioning signal,
While forming an annular communication network, it communicates with satellites in adjacent orbits to form a mesh communication network,
A positioning satellite constellation for exchanging time management signals between satellites via the mesh communication network. including a positioning satellite with a high-precision master clock;
3. The positioning satellite constellation according to claim 1, wherein time management signals are exchanged between satellites. including a positioning satellite equipped with a positioning signal receiver for receiving a positioning signal;
Calibrate the clock of the own satellite by calculating the correct time from the signal received by the positioning signal receiver,
3. The positioning satellite constellation according to claim 1, wherein a time management signal is exchanged between said plurality of satellites. 5. The positioning satellite constellation according to any one of claims 1 to 4, comprising a range finder for measuring distances between satellites. satellites forming the annular communication network and flying in the same orbital plane,
6. Any one of claims 1 to 5, wherein forward time management in which the time management signal is transmitted in the traveling direction of the satellite and backward time management in which the time management signal is transmitted in the direction opposite to the traveling direction of the satellite are performed. A positioning satellite constellation as described in paragraph 1 above. A positioning satellite constellation according to any one of claims 1 to 5,
The plurality of satellites are positioning satellites, the number of which is a multiple of 12 or more and 6;
Each positioning satellite makes multiple orbits in an oblique circular orbit a day,
the normals of the plurality of orbital planes corresponding to the plurality of satellites are shifted by an equal angle in the azimuth direction;
The plurality of orbital planes constitute two or more orbital plane sets each consisting of six orbital planes, and six positioning satellites are synchronized in the timing of orbiting the six orbital planes of each orbital plane set. satellite constellation. Using the positioning satellite as an orbiting satellite,
The timing at which the first orbiting satellite, which is an orbiting satellite orbiting in the first orbital plane of each orbital plane pair, passes through the northernmost end of the first orbital plane is
a timing at which an orbiting satellite orbiting in the third orbital plane of each orbital plane set passes through a point whose in-plane phase is shifted by 120 degrees from the northernmost end of the third orbital plane;
Synchronized with the timing when the orbiting satellite orbiting in the fifth orbital plane of each orbital plane set passes through a point whose in-plane phase is shifted by 240 degrees from the northernmost end of the fifth orbital plane,
The timing at which the fourth orbiting satellite, which is an orbiting satellite orbiting on the fourth orbital plane of each orbital plane set, passes through each in-plane phase point on the fourth orbital plane,
An orbiting satellite orbiting on the sixth orbital plane of each orbital plane set passes through a point on the sixth orbital plane whose in-plane phase is shifted by 120 degrees from the point corresponding to the in-plane phase of the fourth orbiting satellite. timing and
The orbiting satellite orbiting in the second orbital plane of each orbital plane pair passes through a point on the second orbital plane whose in-plane phase is shifted by 240 degrees from the point corresponding to the in-plane phase of the fourth orbital satellite. timing and synchronized
In each orbital plane set, the fourth orbital satellite is placed in the fourth orbital plane at a timing half the orbit period after the first orbital satellite passes the northernmost end of the first orbital plane. 8. The positioning satellite constellation of claim 7 passing through the northernmost point of the orbital plane of . Operationally controlling the positioning satellite constellation according to any one of claims 1 to 8, performing high-precision orbit determination processing of the positioning satellites, and calibrating time management signals exchanged between satellites to improve accuracy Ground system for maintenance.

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