Satellite constellation, ground equipment, artificial satellite, mission satellite, communication satellite, control method, and control program

Abstract

To provide a LEO satellite constellation which achieves the purposes of various mission satellites at a high frequency or all times, and transmits satellite information to a ground facility in real time.SOLUTION: A satellite constellation 20 is composed of one or more mission satellites and one or more communication satellites. Each of the mission satellites includes a first communication device for communicating with satellites positioned from the front sides and the rear sides of each of the mission satellites, and a second communication device for communicating with a ground facility 90. Each of the communication satellites includes a first communication device and a second communication device. The one or more mission satellites and the one or more communication satellites form annular communication network. Each of the mission satellites transmits satellite information acquired by each of the mission satellites to the ground facility 90 through the annular communication network and a satellite 30 flying within such a range as to communicate with the ground facility 90.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a satellite constellation, a ground facility, an artificial satellite, a mission satellite, a communication satellite, a control method, and a control program. [Background technology]

[0002] Due to needs such as obtaining high-resolution images of the Earth's surface and obtaining information on ships in the ocean, there is hope for frequent observations by low-earth orbit satellites (hereinafter referred to as LEO satellites) equipped with optical observation equipment or radio observation equipment called synthetic aperture radar (SAR). In addition, with the emergence of flying objects that perform intermittent jet injection, it is expected that LEO satellites equipped with infrared observation devices will be used for constant monitoring in order to detect the launch of flying objects and to track the flying objects after injection. Patent Document 1 discloses a surveillance satellite for comprehensively monitoring an area at a specific latitude using a small number of satellites orbiting in low earth orbit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4946398 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a problem in that a huge number of LEO satellites are required to achieve various mission objectives frequently or constantly. Furthermore, there is a problem that a satellite communication network is necessary to transmit the satellite information acquired by various mission equipment equipped on the LEO satellites to ground facilities, and there is also a problem that a huge number of communication satellites is required to build a communication network that can transmit continuously by LEO satellites. The present disclosure aims to realize a LEO satellite constellation that achieves the objectives of various mission satellites frequently or constantly and transmits satellite information to ground facilities in real time. [Means for solving the problem]

[0005] The satellite constellation according to the present disclosure includes: It consists of one or more mission satellites and one or more communications satellites. each of the one or more mission satellites is an artificial satellite including a first communication device and a second communication device in communication with a ground facility; each of the one or more communication satellites is an artificial satellite including the first communication device and the second communication device; The one or more mission satellites and the one or more communications satellites fly in a symmetric orbital plane; the total number of said one or more mission satellites and said one or more communications satellites is six or more; the first communication device communicates with satellites located ahead and behind the satellite in the target orbital plane with respect to the direction of travel of the satellite having the first communication device; the one or more mission satellites and the one or more communications satellites form a circular communications network in the target orbital plane; When each of the one or more mission satellites is designated as a target mission satellite, the target mission satellite transmits satellite information acquired by the target mission satellite to the ground facility via the circular communication network and any one of the artificial satellites flying in the target orbital plane that is flying within a range capable of communicating with the ground facility. Effect of the Invention

[0006] In the present disclosure, the satellite constellation may be a LEO satellite constellation. The mission satellites may have various objectives. The mission satellites may be arranged so that the objectives of each mission satellite can be achieved frequently or constantly. In addition, satellite information acquired by the mission satellites is transmitted to the ground equipment via a circular communication network and an artificial satellite flying within a range where the ground equipment can communicate. Therefore, according to the present disclosure, it is possible to realize a LEO satellite constellation that achieves the objectives of various mission satellites frequently or constantly and transmits satellite information to the ground equipment in real time. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing an example of the configuration of a communications satellite system 10 according to a first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of a hardware configuration of a satellite 30 according to the first embodiment. [Diagram 3] 2 is a diagram showing an example of a hardware configuration of a ground facility 90 according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing an example of a satellite constellation 20 according to the first embodiment. [Diagram 5] FIG. 1 is a diagram explaining the problems of mesh communication networks. [Figure 6] FIG. 2 is a diagram for explaining communication in the vicinity of an intersection of orbital planes. [Figure 7] FIG. 2 is a diagram for explaining communication in the vicinity of an intersection of orbital planes. [Figure 8] FIG. 13 is a diagram showing an example of a hardware configuration of a ground facility 90 according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the description of the embodiments and the drawings, the same elements and corresponding elements are given the same reference numerals. Descriptions of elements given the same reference numerals are omitted or simplified as appropriate. Arrows in the drawings mainly indicate data flow or processing flow. Furthermore, "part" may be read as "circuit," "step," "procedure," "processing," or "circuitry" as appropriate. In this specification, an artificial satellite may be referred to simply as a satellite. In addition, in the description of the embodiments, directions or positions such as "upper", "lower", "left", "right", "front", "rear", "front", and "back" may be indicated. These notations are merely given for the convenience of explanation and do not limit the arrangement and orientation of components such as devices, equipment, or parts.

[0009] Embodiment 1 Hereinafter, the present embodiment will be described in detail with reference to the drawings.

[0010] ***Configuration Description*** FIG. 1 shows an overview of a communications satellite system 10 according to the present embodiment. As shown in the figure, the communications satellite system 10 comprises a satellite constellation 20 and ground equipment 90.

[0011] The satellite constellation 20 is composed of one or more mission satellites and one or more communication satellites, and is composed of one or more orbital planes. Each orbital plane may be either an orbital plane corresponding to an inclined orbit or an orbital plane corresponding to a sun-synchronous orbit. The satellite constellation 20 is typically a LEO (Low Earth Orbit) constellation. When the satellite constellation 20 is composed of a plurality of orbital planes, the azimuth components of the normal vectors to each of the plurality of orbital planes are dispersed in the longitude direction. In addition, a group of artificial satellites flies on each orbital plane. That is, the plurality of artificial satellite groups form a plurality of orbital planes in which the azimuth components of the normal vectors are dispersed in the longitude direction. Here, the group of artificial satellites is composed of a plurality of satellites 30. Each of the satellites 30 constituting each of the artificial satellite groups is either one or more mission satellites or one or more communication satellites. The satellites 30 are typically LEO satellites. Satellite constellation 20 may be comprised of one or more mission satellites flying at a target orbital altitude above the equator and one or more communications satellites flying at a target orbital altitude above the equator, each of which may fly in a region other than above the equator.

[0012] The mission satellite is a general term for an artificial satellite equipped with various mission devices, such as an optical satellite equipped with an optical observation device, a radio satellite equipped with a synthetic aperture radar, and an infrared satellite equipped with an infrared observation device. The mission satellite is a satellite 30 equipped with each of a first communication device and a second communication device, and acquires satellite information. The satellite information is information acquired by various mission devices equipped in the mission satellite. The mission satellite may not have a second communication device. The mission satellite may be equipped with an earth observation sensor. The various mission devices may be mission devices other than communication devices, such as observation devices, positioning devices, or information collection devices, and may be communication devices that communicate with various ground assets. The ground assets are, as specific examples, data relay devices or mobile bodies. The communication satellite is a satellite 30 including a first communication device, a second communication device, and a third communication device. The communication satellite does not have to include at least one of the second communication device and the third communication device. The first communication device communicates with a satellite 30 that flies in the same orbital plane as the target satellite, and that is located both ahead and behind the target satellite in the direction of flight. The second communication device communicates with ground equipment 90 installed on the ground. The third communication device communicates with a satellite 30 flying in another orbital plane near an intersection formed in a plan view by the orbital plane in which the target satellite flies and the other orbital plane that is different from the orbital plane in which the target satellite flies. The communication distance of the third communication device may be 1800 km or less. At least two of the first communication device, the second communication device, and the third communication device may be integrally configured as appropriate. Note that the vicinity of the intersection is a region surrounding the intersection including the intersection. The range of the vicinity of the intersection may be determined as appropriate. In addition, when each orbital plane is regarded as a target orbital plane, each satellite 30 flying in the target orbital plane communicates with an adjacent satellite 30 in the target orbital plane, thereby forming a circular communication network in the target orbital plane. Examples of the satellite constellation 20 are disclosed in [Reference 1] and [Reference 2]. The communications satellite system 10 may include the functions disclosed in these references. The satellite constellation 20 may also be a mega-constellation.

[0013] [Reference 1] Patent Publication No. 2021-054167 [Reference 2] JP 2021-070342 A

[0014] The ground facility 90 includes a ground-side communication device 810 and a satellite control device 91, and controls the satellite constellation 20 by communicating with each satellite 30. The ground facility 90 is a component of the ground system. The satellite control device 91 is a computer that generates various commands for controlling each satellite 30, and includes hardware such as a processing circuit and an input / output interface. The processing circuit generates the various commands. An input device and an output device are connected to the input / output interface. The satellite control device 91 is connected to the ground communication device 810 via the input / output interface. The ground communication device 810 communicates with each satellite 30. Specifically, the ground communication device 810 transmits various commands to each satellite 30.

[0015] Fig. 2 shows an example of the hardware configuration of the satellite 30. The hardware configuration of the satellite 30 will be described with reference to Fig. 2. 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. The satellite 30 may include components that realize various other functions, but FIG. 2 will explain the satellite control device 31, the communication device 32, the propulsion device 33, the attitude control device 34, and the power supply device 35.

[0016] 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 in accordance with various commands transmitted from the ground facility 90 and the like. The communication device 32 is a device that executes communication with the outside of the satellite 30. The communication device 32 is also a general term for the first communication device, the second communication device, and the third communication device. The propulsion device 33 is a device that provides thrust to the satellite 30 and changes the speed of the satellite 30. The attitude control device 34 is a device for controlling attitude elements such as the attitude of the satellite 30, the angular velocity of the satellite 30, and the line of sight (Line Of Sight). The attitude control device 34 changes each attitude element to a desired direction. Alternatively, the attitude control device 34 maintains each attitude element in a desired direction. The attitude control device 34 includes an attitude sensor, an actuator, and a controller. The attitude sensor is a device such as a gyroscope, an earth sensor, a sun sensor, a star tracker, a thruster, and a magnetic sensor. The actuator is a device such as an attitude control thruster, a momentum wheel, a reaction wheel, and a control moment gyro. The controller controls the actuator according to measurement data of the attitude sensor or various commands from the ground equipment 90 or the like. The power supply unit 35 includes devices such as solar cells, batteries, and a power control device, and supplies power to each device installed on the satellite 30.

[0017] The processing circuit provided in the satellite control device 31 will be described. The processing circuit may be dedicated hardware, or a processor that executes a program stored in a memory. In the processing circuit, some functions may be realized by dedicated hardware, and the remaining functions may be realized by software or firmware. In other words, the processing circuit can be realized by hardware, software, firmware, or a combination of these. Specifically, the dedicated hardware is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination of these.

[0018] 3 shows an example of a hardware configuration of the ground facility 90. The ground facility 90 may be configured from a general computer. The ground facility 90 communicates with the satellite 30. The ground facility 90 is connected to a ground-side communication device 810, and communicates with the satellite 30 via the ground-side communication device 810. The ground facility 90 may be a mobile terminal.

[0019] The ground equipment 90 includes a processor 710, as well as other hardware such as a main memory device 720, an auxiliary memory device 730, an input interface 740, an output interface 750, and a communication interface 760. In Fig. 3, the interfaces are denoted as IF. The processor 710 is connected to other hardware via a signal line 770 and controls the other hardware.

[0020] The processor 710 is an integrated circuit (IC) that performs arithmetic processing. Specific examples of the processor 710 include a central processing unit (CPU), a digital signal processor (DSP), and a graphics processing unit (GPU).

[0021] The primary storage device 720 is a storage device that temporarily stores data. Specific examples of the primary storage device 720 include a static random access memory (SRAM) and a dynamic random access memory (DRAM).

[0022] The auxiliary storage device 730 is a storage device that stores data. Specific examples of the auxiliary storage device 730 include a hard disk drive (HDD) and a solid state drive (SSD). The auxiliary storage device 730 stores a control program which is a program for realizing the functions of the ground equipment 90 .

[0023] The input interface 740 is a port connected to an input device such as a mouse, a keyboard, a touch panel, etc. Specific examples of the input interface 740 include a USB (Universal Serial Bus) terminal or a LAN (Local Area Network) port.

[0024] The output interface 750 is a port to which a cable of an output device such as a display is connected. Specific examples of the output interface 750 include a USB terminal or an HDMI (High Definition Multimedia Interface) (registered trademark) terminal. A specific example of the display is an LCD (Liquid Crystal Display).

[0025] The communication interface 760 has a receiver and a transmitter, and is, for example, a communication chip or a network interface card (NIC).

[0026] The ground equipment 90 includes a control unit 711 as a functional element. The function of the control unit 711 is realized by hardware or software. The control unit 711 executes processing according to instructions from a communications satellite program. The operation procedure of the ground equipment 90 corresponds to a control method. Also, the program that realizes the operation of the ground equipment 90 corresponds to a control program.

[0027] The control program may be recorded in a computer-readable non-volatile recording medium. Specific examples of the non-volatile recording medium include an optical disk and a flash memory. The control program may be provided as a program product.

[0028] ***Explanation of Operation*** <Operation Example 1 According to Embodiment 1> The configuration of the satellite constellation 20 according to this operation example will be described. The satellite constellation 20 is composed of one or more mission satellites and one or more communication satellites. Each of the one or more mission satellites includes a first communication device and a second communication device. Each of the one or more communication satellites includes a first communication device and a second communication device. The one or more mission satellites and the one or more communication satellites fly in a symmetric orbital plane. The total number of the one or more mission satellites and the one or more communication satellites is six or more. In the target orbital plane, one or more mission satellites and one or more communication satellites form a circular communication network. When each of the one or more mission satellites is designated as a target mission satellite, the target mission satellite transmits satellite information acquired by the target mission satellite to the ground facility 90 via the circular communication network and any one of the satellites 30 flying in the target orbital plane that is within a range where the ground facility 90 can communicate with the target mission satellite.

[0029] A conventional satellite constellation consists of multiple satellites with a common mission objective. In addition, there are satellite constellations such as the A-Train, which have a common mission objective of observing the Earth but each satellite has different observation instruments. However, there has been no satellite constellation that forms a circular communication network within the same orbital plane. In addition, some foreign countries have a concept of forming a circular communication network with mission satellites. However, in this concept, a mission satellite constellation, which is a satellite constellation formed by mission satellites, and a communication satellite constellation, which is a satellite constellation formed by communication satellites, are separately configured. Therefore, in order to transmit satellite information acquired by the mission satellites in real time, information needs to be exchanged between the mission satellite constellation and the communication satellite constellation. Therefore, this concept has a problem of complicated operation.

[0030] According to this operation example, if any one of the satellites 30 flying within the orbital plane is flying within the communication range of the ground facility 90, information on the mission equipment equipped on each of all the mission satellites flying in the same orbital plane can be transmitted in real time to the ground facility 90 via the circular communication network. Furthermore, according to this operational example, since the mission satellite and the communication satellite share a circular communication network, there is an advantage that satellite information can be transmitted relatively easily without complicated operations.

[0031] In addition, when both the first and second communication devices are optical communication devices, since acquisition and tracking are required to align the optical axes between the communication devices, high pointing accuracy and high pointing stability are required. Therefore, in this case, there is a problem that it is difficult for one satellite 30 to continue optical communication with many targets. Here, since the relative positions of the satellites 30 flying in formation are almost constant, it is relatively easy for a given satellite 30 to continue optical inter-satellite communication with two other satellites 30 flying in front of or behind the given satellite 30 in the orbital plane in which the given satellite 30 is flying, using the first communication device. However, when communication between a LEO satellite and ground equipment 90 is carried out using an optical communication device while continuing communication using the first communication device, the relative positional relationship between the LEO satellite and ground equipment 90 changes from moment to moment, which poses the problem that such communication is technically more difficult than communication using the first communication device. Here, in areas with a high cloud coverage rate, such as Japan, it is reasonable to use radio communication for communication between the LEO satellites and the ground equipment 90, since optical communication is interrupted by clouds. The communication range of radio communication is wider than that of optical communication. Therefore, it is possible for one satellite 30 to continue communication with three targets at the same time using radio communication. Therefore, by communicating with the ground equipment 90, if any of the satellites 30 flying in a circular pattern are within the field of view of the ground equipment 90, satellite information for each of the satellites 30 forming the circular communication network can be transmitted to the ground equipment 90 in real time. When radio communication is used for communication between the satellite 30 and the ground facility 90, high pointing accuracy and high pointing stability, as required for optical communication, are not required. In addition, by consolidating adjacent orbital communications, which have a high technical difficulty, into only the communications satellite, it is possible to level out the technical difficulty so that the technical difficulty of the mission satellite does not become too high. Therefore, according to this operation example, there is an effect that the feasibility of a satellite constellation is improved.

[0032] <Operation Example 2 According to Embodiment 1> The configuration of the satellite constellation 20 according to this operation example will be described. The satellite constellation 20 is composed of one or more mission satellites flying at a target orbital altitude and one or more communication satellites flying at a target orbital altitude. The satellite constellation 20 includes a plurality of satellite groups. Each of the plurality of satellite groups flies in a different orbital plane and is composed of a plurality of satellites 30. The plurality of satellite groups form a plurality of orbital planes in which the azimuth components of normal vectors are distributed in the longitude direction. Each of the satellites 30 constituting each of the plurality of satellite groups is one or more mission satellites or one or more communication satellites. Each of the one or more mission satellites includes a first communication device and a second communication device. Each of the one or more communication satellites includes a first communication device, a second communication device, and a third communication device. Each of the plurality of satellite groups forms a circular communication network in an orbital plane corresponding to each of the plurality of satellite groups. When each of one or more mission satellites is designated as a target mission satellite, satellite information acquired by the target mission satellite is transmitted from the target mission satellite to the ground facility 90 by performing communication in a circular communication network formed in a target orbital plane, which is the orbital plane in which the target mission satellite is flying, inter-orbital communication between a communication satellite flying in a first orbital plane and a communication satellite flying in the target orbital plane, communication in a circular communication network formed in the first orbital plane, and communication between the first artificial satellite and the ground facility 90. The first orbital plane is the orbital plane in which the first artificial satellite is flying. The first artificial satellite is a satellite 30 flying within a range in which it can communicate with the ground facility 90.

[0033] In the in-orbit communication using the first communication device, the relative positional relationship with the communication target is maintained almost constant. However, in the inter-orbit communication using the third communication device, the azimuth angle and the relative distance to the communication target vary greatly, which poses a problem that the technical difficulty of realizing inter-orbit communication is significantly increased. In particular, when the third communication device is an optical communication device, the technical difficulty of acquisition and tracking is high because this is inter-orbital communication in which the relative azimuth angle and relative distance fluctuate. Furthermore, in the conventional LEO communication satellite constellation plan to form a mesh-like communication network using adjacent orbital communication, adjacent orbits are switched left and right at the north and south ends of the orbital plane, which makes it very difficult to continue optical communication. In addition, in order for a certain satellite 30 to communicate with adjacent orbits located on the left and right, the certain satellite 30 simultaneously performs optical inter-satellite communication with four communication targets flying forward, backward, left and right with respect to the direction of travel of the certain satellite 30, and furthermore, the certain satellite 30 communicates with a ground facility 90. Here, there is a problem that it is very difficult to continue communication while maintaining communication with five communication targets at the same time. Furthermore, when communicating between orbits whose normal vectors are far apart in the longitude direction, there is a problem in that communication between adjacent orbits must be repeated like a bucket brigade.

[0034] According to this operation example, since the mission satellite does not include the third communication device, which is difficult to operate, the mission satellite can concentrate on accomplishing its original mission. Furthermore, each communication satellite equipped with a third communication device performs inter-orbital communication not in adjacent orbits located to the left and right of the orbit in which each communication satellite flies, but in the vicinity of an intersection point where multiple orbits intersect. Therefore, according to this operation example, while each communication satellite makes one revolution in an orbital plane, each communication satellite only needs to perform inter-orbital communication a maximum of two times with a communication target flying in another orbital plane. Therefore, according to this operation example, there is an effect that inter-orbital communication can be easily realized. Furthermore, according to this operation example, when communication is performed between orbits whose normal vectors are separated in the longitude direction, by executing the inter-orbit communication near the intersection of the orbits, it is possible to realize the inter-orbit communication by a single inter-orbit communication.

[0035] In order to deploy mission satellites and communication satellites globally to form individual mission satellite constellations and communication satellite constellations, a huge number of satellites 30 are required. However, according to this operation example, in the satellite constellation 20, the number of satellites 30 required for each of the various mission satellites is deployed, and satellites 30 that are insufficient for global coverage are supplemented with communication satellites. Therefore, according to this operation example, there is an effect that the total number of satellites 30 can be minimized and information transmission of various missions can be made globally.

[0036] <Operation Example 3 According to Embodiment 1> The configuration of the satellite constellation 20 according to this operation example will be described. The satellite constellation 20 is composed of one or more mission satellites flying at a target orbit altitude in the sky above the equator, and one or more communication satellites flying at a target orbit altitude in the sky above the equator. Each of the one or more mission satellites includes a first communication device. Each of the one or more communication satellites includes a first communication device and a third communication device. The artificial satellite group composed of the one or more mission satellites and the one or more communication satellites forms a circular communication network. When each of the one or more mission satellites is set as a target mission satellite, satellite information acquired by the target mission satellite is transmitted to the ground equipment 90 described in the operation example 2 according to the embodiment 1 via the satellite constellation 20 described in the operation example 2 according to the embodiment 1.

[0037] Equatorial orbit satellites are suitable for monitoring the mid-latitude sky using a method of observing the Earth's circumference called limb observation. However, there is a problem in determining how to transmit satellite information to ground facilities 90 located in the mid-latitude zone. Therefore, by having the hybrid constellation forming a circular communication network in the sky above the equator perform inter-orbital communication with the satellites constituting the satellite constellation described in the operation example 2 according to the first embodiment, it is possible to transmit satellite information acquired in the sky above the equator to the ground equipment 90 in the mid-latitude band. Here, the hybrid constellation is a satellite constellation that includes various mission satellites to form a circular communication network.

[0038] <Operation Example 4 According to Embodiment 1> The configuration of the ground equipment 90 according to this operation example will be described. Here, the ground equipment 90 is the ground equipment 90 described in any one of the operation examples 1 to 3 according to the first embodiment. In response to the satellite 30 flying within a range in which communication with the ground equipment 90 can be established changing over time from the second artificial satellite to the third artificial satellite, the control unit 711 generates information indicating the third artificial satellite as information indicating the satellite 30 flying within a range in which communication with the ground equipment 90 can be established, and transmits the generated information to the satellite 30 that constitutes the satellite constellation 20. In addition, in response to the orbital plane existing within the range in which communication with the ground equipment 90 is possible changing from the second orbital plane to the third orbital plane over time, the control unit 711 generates information indicating the third orbital plane as information indicating the orbital plane existing within the range in which communication with the ground equipment 90 is possible, and transmits the generated information to the satellites 30 that constitute the satellite constellation 20.

[0039] The orbital plane of the satellite 30 orbiting in low earth orbit is not synchronized with the rotation of the earth, so that the orbital plane that is hovering over a particular ground facility 90 is replaced with an orbital plane adjacent to the orbital plane that was hovering over the ground facility 90 over time. Furthermore, among the satellites 30 flying in a particular orbital plane, the satellite 30 flying above a particular ground facility 90 is replaced with a succeeding satellite 30 over time. Therefore, in order to transmit satellite information acquired by a mission satellite at a certain time in real time via a satellite 30 flying above the ground equipment 90, it is necessary to identify in advance the satellite 30 flying within the communication range of the ground equipment 90 at that certain time and share the identification information with the mission satellite. In addition, it is necessary to share between the satellites 30 identification information indicating the orbital plane in which the satellite 30 that is the communication path is flying and identification information indicating the orbital plane in which the mission satellite is flying, identify the position of the intersection point where the orbits intersect at the satellite orbit altitude on the intersection line of both orbital planes, and identify the satellites 30 in each of both orbital planes that are flying near the identified intersection point position at that given time. The ground equipment 90 involved in this operation derives in advance the positional relationship between the ground equipment 90, the orbital plane, and the flight position of the satellite 30 over time, and shares the information by transmitting information indicating the derived positional relationship to all mission satellites and communication satellites via the communication network formed by the satellite constellation 20.

[0040] <Operation Example 5 According to Embodiment 1> The satellite 30 according to this operation example includes a server that records orbit information indicating the orbit in which the satellite 30 is flying, and a computer. Here, the satellite 30 is the satellite 30 described in any one of the operation examples 1 to 3 according to the first embodiment. In response to the satellite 30 flying within a range in which it can communicate with the ground equipment 90 changing over time from the second artificial satellite to the third artificial satellite, the computer generates information indicating the third artificial satellite as information indicating the satellite 30 flying within a range in which it can communicate with the ground equipment 90, and transmits the generated information to the satellite 30 that constitutes the satellite constellation 20. In addition, in response to the orbital plane existing within the range in which communication with the ground facility 90 can be established changing from the second orbital plane to the third orbital plane over time, the computer generates information indicating the third orbital plane as information indicating the orbital plane existing within the range in which communication with the ground facility 90 can be established, and transmits the generated information to the satellites 30 that constitute the satellite constellation 20.

[0041] With the advancement of edge computing and artificial intelligence in space applications, the identification information derived by the ground equipment 90 in operation example 4 in embodiment 1, which indicates each of the orbital plane and the satellite 30, can also be autonomously derived by a computer in orbit.

[0042] <Operation Example 6 According to Embodiment 1> The mission satellite according to this operation example is equipped with an infrared observation device. The satellite information according to this operation example includes at least one of flying object launch detection information and flying object tracking information corresponding to the data acquired by the infrared observation device. Note that the information corresponding to the data acquired by each device or each sensor may be information acquired by each device or each sensor, or may be information obtained by processing the information acquired by each device or each sensor.

[0043] For a flying object that changes its orbit by repeating intermittent firing after launch, it is difficult to detect from geostationary orbit a flying object that has stopped firing. Therefore, it is expected that the LEO satellite constellation will be able to detect the launch and track the flying object. On the other hand, it is difficult to estimate the flight direction and impact position of a flying object at the launch stage. Therefore, it is necessary to share the information acquired by an infrared satellite that detects the launch of a flying object with a succeeding satellite of the infrared satellite as flying object information, and for the succeeding satellite to track and monitor the flying object as its position changes over time. In this case, a means for realizing the exchange of flying object information in real time is required. The satellite constellation 20 according to this operation has the advantage that the flying object information acquired by the infrared satellite can be transmitted in real time to the succeeding satellite via the circular communication network and inter-orbital communication.

[0044] <Operation Example 7 According to Embodiment 1> The mission satellite according to this operation example is equipped with an earth observation sensor and is also called an earth observation satellite. The satellite information according to this operation example includes at least one of visible image information corresponding to data acquired by an earth observation sensor and synthetic aperture radar information.

[0045] Continuous monitoring by satellite constellations observing the Earth is expected to be performed to monitor moving objects on land or the movements of ships sailing on the ocean, etc. In low-earth-orbit satellite constellations, the relative positional relationship between the monitored object and the satellite 30 changes over time, so multiple satellites 30 need to work together to perform continuous monitoring. The satellite constellation 20 according to this operation example has the advantage that satellite information acquired by an earth observation satellite can be transmitted to a subsequent satellite via a circular communication network and inter-orbital communication.

[0046] <Operation Example 8 According to Embodiment 1> Each orbital plane in this operation example is an orbital plane corresponding to an inclined orbit. Northern latitude θ deg The satellite 30 that communicates with the ground equipment 90 installed at is flying in an orbital plane with an orbital inclination angle of θ deg By selecting an orbital plane set in the vicinity of the ground facility 90, it is possible to ensure a long time for one satellite 30 flying in that orbital plane from the time it enters a range in which it can communicate with the ground facility 90 until it leaves the range in which it can communicate with the ground facility 90. Furthermore, when limb observation is performed using an infrared satellite that monitors flying objects, the adoption of an inclined orbit with a small orbital inclination angle is suitable for monitoring flying objects flying in the mid-latitudes. In addition, SAR satellites equipped with synthetic aperture radar perform a side look at an off-nadir angle, which allows them to monitor latitudes that correspond to angles larger than the orbital inclination angle. It is reasonable to configure a satellite constellation 20 having an optimal orbital inclination angle by including these multiple missions.

[0047] FIG. 4 is a diagram showing an embodiment of a satellite constellation 20 according to this operation example. 4, each of the IR and SAR satellites is depicted performing observations, each satellite 30 performing in-orbit communications, the communication satellites performing inter-orbit communications, and the communication satellites communicating with ground facilities 90. Here, IR satellites refer to infrared satellites.

[0048] <Operation Example 9 According to Embodiment 1> In this operational example, each orbital plane corresponds to a sun-synchronous orbit.

[0049] The time period during which a sun-synchronous satellite flies above the ground facility 90 is limited to a time called LST (Local Sun Time) and 12 hours after LST, which is the time on the other side of the Earth. Therefore, according to this operation example, there is an effect that it is possible to easily derive the orbital plane identification information for inter-orbit communication at any time.

[0050] <Operation Example 10 According to Embodiment 1> The communication distance of the third communication device according to this operation example is 1800 km or less. When implementing inter-orbit communication using optical communication, which is technically difficult, the smaller the relative distance is, the more relaxed the requirements for pointing accuracy and pointing stability can be, making it more feasible. Here, in the concept of forming a mesh-like communication network by implementing optical communication between adjacent orbits, the relative distance is maximum above the equator. Therefore, as a specific example, if a satellite constellation with 24 orbital planes is formed at an orbital altitude of 600 km, the communication distance above the equator will exceed 1,800 km. In addition, the number of orbital planes of the satellite constellations currently announced for development is fewer than 24, so the technical difficulty of inter-orbital communication is even higher. Therefore, the communication satellite according to this operation example realizes inter-orbital communication with a communication distance of 1800 km or less in the vicinity of the intersection of different orbits. Therefore, according to this operation example, there is an effect that the technical difficulty can be reduced and the feasibility of inter-orbital communication can be increased.

[0051] ***Additional information about the assignment*** <Challenges for low-earth orbit satellite constellations> In order to maintain constant communication lines using LEO satellites, a huge number of satellites are required. Furthermore, unlike geostationary satellites that appear almost fixed relative to an Earth-fixed coordinate system, LEO satellites constantly move their flight positions. Therefore, the configuration of communication satellites and the data transmission method are issues in low-earth orbit satellite constellations. In addition, in low-earth orbit satellite constellations, if there is only one orbital plane, the relative position between the orbital plane and ground equipment 90 changes with the rotation of the Earth, which makes constant communication impossible. Therefore, in this embodiment, the satellite constellation 20 has multiple orbital planes whose normal vectors are dispersed in the longitude direction, and is a satellite constellation composed of multiple orbital planes that form a hybrid constellation, thereby adopting a configuration that allows satellite information to be transmitted to the ground equipment 90 in real time.

[0052] <Challenges for mesh communication networks> In recent years, there has been a concept of forming a circular communication network for low-orbit satellite constellations by each satellite communicating with the satellites located in front and behind it in an orbital plane, and further forming a mesh communication network by each satellite flying in each orbital plane communicating with a satellite flying in an adjacent orbital plane. However, when communicating with a satellite flying in an adjacent orbital plane, communication is interrupted at least twice per orbit because the orbits switch sides at the north and south ends of the orbital plane. Therefore, mesh communication networks have the problem that they are complicated to operate because they require reconnection at the north and south ends of the orbital plane. Figure 5 shows a situation where a satellite flying in a first target orbital plane and a satellite flying in a second target orbital plane switch sides at the northernmost end of the orbital plane. In addition, the method of transmitting satellite information via a mesh communication network requires the selection of satellites on the route for sending and receiving information and the setting of the time for sending and receiving information, and has the problem that operation becomes complicated because it is necessary to search for the shortest communication route.

[0053] <Issues regarding low-earth orbit satellites> Geostationary orbit satellites have an orbital period synchronized with the Earth's rotation, allowing constant communication from ground systems installed at specific longitudes. On the other hand, low-orbit satellites have an orbital period asynchronous with the Earth's rotation, and each satellite passes over a ground system installed at a specific longitude in a short time. Therefore, low-orbit satellites have the challenge of requiring multiple satellites to work together to create an environment for constant communication.

[0054] <Issues regarding solar asynchronous orbits> The orbital period of a sun-synchronous satellite's orbital plane around the Earth is synchronized with the Earth's orbital period around the Sun. Therefore, the normal vector of a sun-synchronous satellite's orbital plane revolves around the Earth once a year in sync with the Earth. Therefore, a sun-synchronous satellite has the characteristic that the incidence angle of the Sun on the orbital plane remains almost constant throughout the year. A satellite orbiting in a sun-synchronous orbit, LST12:00, passes over the sky at 12:00 noon for ground systems installed in any country in the world. When a hybrid constellation is formed that forms a circular communication network on one orbital plane at 12:00 LST, it is possible to communicate with specific ground equipment twice a day, at 12:00 noon and at midnight, which corresponds to the other side of the Earth. However, this orbital plane has the problem that it is not possible to communicate at any other time. On the other hand, a problem with a solar-asynchronous orbital plane is that the angle of incidence of the sun relative to the orbital plane changes from moment to moment, meaning that the time at which the satellite flies above ground equipment installed in a specific location is not constant.

[0055] <Issues with inclined orbits> The rotation of the orbital plane of an inclined orbit satellite is not synchronized with either the rotation of the Earth or the revolution of the Earth around the Sun. Therefore, an inclined orbit has a problem in that the time period during which the satellite passes over the ground system is limited because the longitude component of the normal vector moves relatively as seen from the ground system installed at a specific latitude and longitude. Furthermore, an inclined orbit has the problem that even if the orbital plane corresponding to the inclined orbit is in a position that passes above the ground system, the satellite is not necessarily flying above the ground system. Another problem with inclined orbits is that even if the satellite happens to fly above the terrestrial system at the same time that the orbital plane passes above the terrestrial system, the orbital plane and the time period during which the satellite passes are not constant.

[0056] ***Additional Policy Information*** <Continuous communication environment with ground systems> In an inclined orbit satellite constellation, 15 or more satellites fly in the same orbital plane for the purpose of transmitting satellite information in quasi-real time to a ground system installed at a specific latitude and longitude. As a specific example, if the orbital altitude is about 1000 km, it takes about 100 minutes to make one revolution around the Earth, so when the orbital plane passes over the ground system, one satellite flies over the ground system for a few minutes, and then the succeeding satellite flies over the ground system. Therefore, a state is realized in which satellites flying in the same orbital plane are always flying within the communication field of view from the ground system. In addition, if a circular communication network is formed in the same orbital plane, a satellite communicating with a ground system can communicate with the ground system on behalf of other satellites flying in the same orbital plane. Furthermore, the inclined orbit satellite constellation has 12 or more orbital planes with the longitudinal components of the normal vectors dispersed. As a specific example, when the number of orbital planes is 12, the separation angle of the longitudinal components of the normal vectors of the orbital planes is 30 degrees. Here, the separation angle corresponds to 2 hours of the Earth's rotation. In this example, the time it takes for a satellite flying in the target orbital plane to make one revolution is about 100 minutes. Therefore, while 15 or more satellites flying in the target orbital plane communicate with the ground system in turn, the effect of the Earth's rotation ensures that the ground system has a communication field of view for satellites flying in the orbital plane adjacent to the east side of the target orbital plane. Therefore, if 15 or more satellites fly in each of the 12 or more orbital planes, the inclined orbit satellite constellation can constantly communicate with a ground system installed at a specific latitude and a specific longitude. Needless to say, the number of orbital planes required and the number of satellites flying in the same orbital plane will increase or decrease depending on the latitude at which the ground system is installed, the satellite altitude, the orbital inclination, the amount of communication, etc.

[0057] <Nearby communication at orbital intersection> Adjacent orbital communications require long-distance communication, such as above the equator. For this reason, a large-diameter antenna that requires a drive mechanism is required as a communications device. In addition, when optical communications are used, it is necessary to perform highly accurate optical axis alignment to establish a communication line. On the other hand, in the case of near-field communication, inter-orbit communication can be realized using omnidirectional antennas or fixed antennas, etc. Therefore, in the case of near-field communication, the cost of the system can be reduced and the complicated operation for establishing communication lines is not required. In addition, the satellite constellation 20 according to this embodiment executes inter-orbital communication by utilizing the characteristic that there are always two intersections between two orbits with different normal vectors, so that inter-orbital communication is sufficient only once. Therefore, according to this embodiment, there is no need to repeat adjacent orbital communication multiple times, and there is an effect that operation is simplified.

[0058] FIG. 6 shows how a satellite 30 flying in a target orbital plane communicates with a satellite 30 flying in another orbital plane in the vicinity of an orbital plane node.

[0059] FIG. 7 is a diagram illustrating a process of transmitting satellite information to the ground facility 90 using a specific example. In this example, first, intra-orbit communication is performed in the second target orbital plane. Next, inter-orbit communication is performed between the satellite 30 flying in the second target orbital plane and the satellite 30 flying in the first target orbital plane. Next, by performing intra-orbit communication in the first target orbital plane, the satellite 30 flying in the first target orbital plane within a range where it can communicate with the ground facility 90 receives the satellite information. Next, the satellite 30 that has received the satellite information transmits the received satellite information to the ground facility 90.

[0060] <Effects of hybrid constellations> Conventional communications satellite constellations have been formed using satellites dedicated to communications in order to create a constant communications environment. On the other hand, in this embodiment, the mission satellite contributes to the formation of a circular communication network, and by the mission satellite performing communication with the ground equipment 90, the number of communication-dedicated satellites required to create a constant communication environment can be reduced.

[0061] <Effects of communication near orbital intersections> In a conventional communication satellite constellation forming a mesh communication network, one satellite must simultaneously maintain communication between four satellites: one in front of and one behind the satellite in the direction of flight, and one flying in an adjacent orbital plane on the left and right of the direction of flight. Here, there is a problem that it is difficult to switch orbits between the left and right at the north and south ends of the orbital plane in adjacent orbital communication. There is also a problem that the communication distance becomes long near the equator. On the other hand, the proximity communication according to the present embodiment has the advantage that it is easy to realize inter-orbital communication because only one inter-orbital communication device is required. In addition, while a mesh communication network requires repeated inter-orbital communications, proximity communication at the intersection of orbital planes has the advantage that only one inter-orbital communication is required to transmit the satellite information acquired by the mission satellite to a specific ground facility 90.

[0062] ***Explanation of the Effects of the First Embodiment*** In a conventional communication satellite constellation forming a mesh-like communication network, each satellite needs to maintain communication with a total of five targets, including satellites in front, behind, left and right, and ground equipment. For this reason, there is a problem that high pointing accuracy and high pointing stability are required to maintain a mesh-like communication network in optical inter-satellite communication, as a specific example. It is also known that in conventional satellite constellations, the same orbital plane is configured with a group of satellites having the same mission purpose. On the other hand, in this embodiment, various mission satellites with different mission purposes fly on the same orbital plane, and each satellite 30 constituting the group of artificial satellites flying in formation at the same altitude on the same orbital plane communicates with the satellites 30 in front and behind to form a circular communication network. In this embodiment, the number of mission satellites included in a particular orbital plane is appropriately set according to requirements such as the performance of observation equipment for each mission purpose and the frequency of acquiring satellite information. In this embodiment, a satellite constellation 20 is formed that includes a hybrid constellation of multiple orbital planes whose normal vectors are distributed in the longitude direction, as a mechanism for transmitting satellite information acquired by a mission satellite to a specific ground facility 90 in real time. Furthermore, in this embodiment, as a method for realizing inter-orbital plane communication, a method is adopted in which satellites 30 passing near an intersection between orbital planes execute inter-satellite communication.

[0063] ***Other configurations*** <Variation 1> In this embodiment, the functions of the control unit 711 are realized by software. As a modified example, the functions of the control unit 711 may be realized by hardware. Figure 8 shows this modified example.

[0064] The ground equipment 90 includes an electronic circuit 780 in place of the processor 710 . The electronic circuit 780 is a dedicated electronic circuit that realizes the functions of the control unit 711 . Specifically, the electronic circuit 780 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a logic IC (Integrated Circuit), a GA (Gate Array), an ASIC, or an FPGA. The functions of the control unit 711 may be realized by one electronic circuit, or may be distributed across multiple electronic circuits. As another modification, some of the functions of the control unit 711 may be realized by the electronic circuit 780, and the remaining functions may be realized by software.

[0065] The processor 710, the electronic circuit 780, the main memory device 720, and the auxiliary memory device 730 are collectively referred to as a processing circuitry. That is, in the ground equipment 90, the function of the control unit 711 is realized by the processing circuitry.

[0066] ***Other embodiments*** Although the first embodiment has been described, it is possible to combine a plurality of parts of the present embodiment. Alternatively, it is possible to partially implement the present embodiment. In addition, the present embodiment may be modified in various ways as necessary, and may be implemented in any combination, either as a whole or in part. The above-described embodiment is essentially a preferred example, and is not intended to limit the scope of the present disclosure, its applications, and uses. The described procedure may be modified as appropriate.

[0067] Various aspects of the present disclosure are summarized below as appendices.

[0068] (Appendix 1) It consists of one or more mission satellites and one or more communications satellites. each of the one or more mission satellites is an artificial satellite including a first communication device and a second communication device in communication with a ground facility; each of the one or more communication satellites is an artificial satellite including the first communication device and the second communication device; The one or more mission satellites and the one or more communications satellites fly in a symmetric orbital plane; the total number of said one or more mission satellites and said one or more communications satellites is six or more; the first communication device communicates with satellites located ahead and behind the satellite in the target orbital plane with respect to the direction of travel of the satellite having the first communication device; the one or more mission satellites and the one or more communications satellites form a circular communications network in the target orbital plane; A satellite constellation in which, when each of the one or more mission satellites is designated as a target mission satellite, the target mission satellite transmits satellite information acquired by the target mission satellite to the ground facility via the circular communication network and any one of the artificial satellites flying in the target orbital plane that is flying within a range capable of communicating with the ground facility.

[0069] (Appendix 2) A satellite constellation consisting of one or more mission satellites flying at a target orbital altitude and one or more communication satellites flying at the target orbital altitude, the satellite constellation comprises a group of multiple artificial satellites; Each of the plurality of satellite groups flies in different orbital planes and is composed of a plurality of satellites, the plurality of artificial satellites form a plurality of orbital planes in which azimuth components of normal vectors are distributed in the longitude direction; Each of the satellites constituting each of the plurality of satellite constellations is one of the one or more mission satellites or one of the one or more communication satellites; each of the one or more mission satellites is an artificial satellite including a first communication device and a second communication device in communication with a ground facility; each of the one or more communication satellites is an artificial satellite including the first communication device, the second communication device, and a third communication device; When a satellite equipped with the first communication device is regarded as a target satellite, the first communication device communicates with satellites located ahead and behind the target satellite in a direction of travel in an orbital plane in which the target satellite is flying, and the third communication device communicates with a communication satellite flying in an orbital plane different from an orbital plane in which the communication satellite including the third communication device is flying; each of the plurality of satellite groups forms a circular communication network in an orbital plane corresponding to the satellite group; When each of the one or more mission satellites is a target mission satellite, satellite information acquired by the target mission satellite is transmitted from the target mission satellite to the ground facility by executing communication in a ring-shaped communication network formed on a target orbital plane which is the orbital plane in which the target mission satellite is flying, inter-orbital communication between a communication satellite flying in a first orbital plane which is the orbital plane in which a first artificial satellite which is a satellite flying within a range capable of communicating with the ground facility is flying and the communication satellite flying in the target orbital plane, communication in a ring-shaped communication network formed on the first orbital plane, and communication between the first artificial satellite and the ground facility.

[0070] (Appendix 3) A satellite constellation consisting of one or more mission satellites flying at a target orbital altitude above the equator, and one or more communication satellites flying at the target orbital altitude above the equator, each of the one or more mission satellites is a satellite including a first communication device; each of the one or more communication satellites is an artificial satellite including the first communication device and a third communication device; When a satellite equipped with the first communication device is regarded as a target satellite, the first communication device communicates with satellites located ahead and behind the target satellite in a direction of travel in an orbital plane in which the target satellite is flying, and the third communication device communicates with a communication satellite flying in an orbital plane different from an orbital plane in which a communication satellite including the third communication device is flying; a constellation of artificial satellites including the one or more mission satellites and the one or more communication satellites forms a circular communication network; A satellite constellation in which, when each of the one or more mission satellites is a target mission satellite, satellite information acquired by the target mission satellite is transmitted to the ground equipment described in Appendix 2 via the satellite constellation described in Appendix 2.

[0071] (Appendix 4) The ground equipment according to any one of Supplementary Note 1 to Supplementary Note 3, In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from the second artificial satellite to the third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; A control unit that generates information indicating the third orbital plane as information indicating the orbital plane present within a range capable of communicating with the ground facility in response to the change of the orbital plane present within a range capable of communicating with the ground facility over time from the second orbital plane to the third orbital plane, and transmits the generated information to the artificial satellites constituting the satellite constellation. Ground equipment equipped with:

[0072] (Appendix 5) 4. A satellite according to claim 1, A server that records orbital information indicating an orbit in which the artificial satellite is flying, and a computer, The computer includes: In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from the second artificial satellite to the third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; A satellite that, in response to an orbital plane existing within a range capable of communicating with the ground equipment changing over time from a second orbital plane to a third orbital plane, generates information indicating the third orbital plane as information indicating the orbital plane existing within a range capable of communicating with the ground equipment, and transmits the generated information to the satellites that constitute the satellite constellation.

[0073] (Appendix 6) each of the one or more mission satellites carrying an infrared observation device; 4. A satellite constellation as described in any one of appendices 1 to 3, wherein the satellite information includes at least one of airborne vehicle launch detection information and airborne vehicle tracking information corresponding to data acquired by the infrared observation device.

[0074] (Appendix 7) each of the one or more mission satellites carrying an Earth observation sensor; 3. The satellite constellation of claim 1, wherein the satellite information includes at least one of visible image information and synthetic aperture radar information corresponding to data acquired by the earth observation sensor.

[0075] (Appendix 8) 2. The satellite constellation of claim 1, wherein the target orbital plane is one of an orbital plane corresponding to an inclined orbit and an orbital plane corresponding to a sun-synchronous orbit.

[0076] (Appendix 9) 3. The satellite constellation of claim 2, wherein each of the plurality of orbital planes is one of an orbital plane corresponding to an inclined orbit and an orbital plane corresponding to a sun-synchronous orbit.

[0077] (Appendix 10) 1. A mission satellite as described in any one of Annexes 1 to 9.

[0078] (Appendix 11) 10. A communications satellite as described in any one of Appendix 1 to Appendix 9.

[0079] (Appendix 12) 4. The communications satellite of claim 2 or 3, wherein the communication range of the third communications device is 1800 km or less. [Explanation of symbols]

[0080] 10 communications satellite system, 20 satellite constellation, 30 satellite, 31 satellite control device, 32 communications device, 33 propulsion device, 34 attitude control device, 35 power supply device, 90 ground equipment, 91 satellite control device, 710 processor, 711 control unit, 720 main memory device, 730 auxiliary memory device, 740 input interface, 750 output interface, 760 communications interface, 770 signal line, 780 electronic circuit, 810 ground communications device.

Claims

1. A satellite constellation that is a hybrid constellation consisting of two or more mission satellites and one or more communications satellites, each of the two or more mission satellites is an artificial satellite including a first communication device and a second communication device that communicates with a ground facility; each of the one or more communication satellites is an artificial satellite including the first communication device and the second communication device; The two or more mission satellites and the one or more communications satellites fly in a symmetric orbital plane; a total number of the two or more mission satellites and the one or more communications satellites is six or more; the first communication device communicates with satellites located ahead and behind the satellite in the target orbital plane with respect to the direction of travel of the satellite having the first communication device; the two or more mission satellites and the one or more communications satellites form a circular communications network on the target orbital plane; When each of the two or more mission satellites is designated as a target mission satellite, the target mission satellite transmits satellite information acquired by the target mission satellite to the ground facility via the annular communication network and any one of the artificial satellites flying on the target orbital plane within a range capable of communicating with the ground facility, The two or more mission satellites are a satellite constellation including multiple types of mission satellites.

2. A satellite constellation including one or more mission satellites flying at a target orbital altitude and one or more communication satellites flying at the target orbital altitude, the satellite constellation comprises a group of multiple artificial satellites; Each of the plurality of satellite groups flies in different orbital planes and is composed of a plurality of satellites, the plurality of artificial satellites form a plurality of orbital planes in which azimuth components of normal vectors are distributed in the longitude direction; Each of the satellites constituting each of the plurality of satellite constellations is any one of the one or more mission satellites or any one of the one or more communication satellites, each of the one or more mission satellites is an artificial satellite including a first communication device and a second communication device in communication with a ground facility; each of the one or more communication satellites is an artificial satellite including the first communication device, the second communication device, and a third communication device; When a satellite equipped with the first communication device is regarded as a target satellite, the first communication device communicates with satellites located ahead and behind the target satellite in a direction of travel on an orbital plane in which the target satellite is flying, and the third communication device communicates with a communication satellite flying in an orbital plane different from an orbital plane in which a communication satellite including the third communication device is flying; each of the plurality of satellite groups forms a circular communication network in an orbital plane corresponding to the satellite group; When each of the one or more mission satellites is a target mission satellite, satellite information acquired by the target mission satellite is transmitted from the target mission satellite to the ground facility by executing communication in a ring-shaped communication network formed on a target orbital plane which is the orbital plane in which the target mission satellite is flying, inter-orbital communication between a communication satellite flying in a first orbital plane which is the orbital plane in which a first artificial satellite which is a satellite flying within a range capable of communicating with the ground facility is flying and the communication satellite flying in the target orbital plane, communication in a ring-shaped communication network formed on the first orbital plane, and communication between the first artificial satellite and the ground facility.

3. One or more mission satellites flying at a target orbital altitude above the equator and A satellite constellation consisting of one or more communication satellites flying at the target orbit altitude in the sky, each of the one or more mission satellites is a satellite having a first communication device; each of the one or more communication satellites is an artificial satellite including the first communication device and a third communication device; When a satellite equipped with the first communication device is regarded as a target satellite, the first communication device communicates with satellites located ahead and behind the target satellite in a direction of travel on an orbital plane in which the target satellite is flying, and the third communication device communicates with a communication satellite flying in an orbital plane different from an orbital plane in which a communication satellite including the third communication device is flying; a constellation of artificial satellites including the one or more mission satellites and the one or more communication satellites forms a circular communication network; A satellite constellation in which, when each of the one or more mission satellites is designated as a target mission satellite, satellite information acquired by the target mission satellite is transmitted to the ground equipment described in claim 2 via the satellite constellation described in claim 2.

4. The ground equipment according to claim 2 or 3, In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from a second artificial satellite to a third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; A control unit that generates information indicating the third orbital plane as information indicating the orbital plane present within a range capable of communicating with the ground facility in response to the change of the orbital plane present within a range capable of communicating with the ground facility over time from the second orbital plane to the third orbital plane, and transmits the generated information to the artificial satellites constituting the satellite constellation. Ground equipment equipped with:

5. The satellite according to claim 2 or 3, A server that records orbital information indicating an orbit in which the artificial satellite is flying, and a computer, The computer includes: In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from a second artificial satellite to a third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; An artificial satellite that, in response to an orbital plane existing within a range capable of communicating with the ground equipment changing over time from a second orbital plane to a third orbital plane, generates information indicating the third orbital plane as information indicating the orbital plane existing within a range capable of communicating with the ground equipment, and transmits the generated information to artificial satellites that constitute the satellite constellation.

6. Each mission satellite is equipped with an infrared observation device, 4. The satellite constellation according to claim 1, wherein the satellite information includes at least one of airborne vehicle launch detection information and airborne vehicle tracking information corresponding to data acquired by the infrared observation device.

7. Each mission satellite is equipped with an Earth observation sensor, 3. The satellite constellation according to claim 1, wherein the satellite information includes at least one of visible image information and synthetic aperture radar information corresponding to data acquired by the earth observation sensor.

8. 2. The satellite constellation of claim 1, wherein the target orbital plane is one of an orbital plane corresponding to an inclined orbit and an orbital plane corresponding to a sun-synchronous orbit.

9. 3. The satellite constellation of claim 2, wherein each of the plurality of orbital planes is one of an orbital plane corresponding to an inclined orbit and an orbital plane corresponding to a sun-synchronous orbit.

10. A mission satellite according to any one of claims 1 to 3.

11. A communications satellite according to any one of claims 1 to 3.

12. 4. The communications satellite according to claim 2 or 3, wherein the communication range of said third communications device is 1800 km or less.

13. The computer provided in the ground equipment according to claim 2 or 3 is In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from a second artificial satellite to a third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; A control method for generating information indicating the third orbital plane as information indicating an orbital plane present within a range capable of communicating with the ground equipment in response to the orbital plane present within a range capable of communicating with the ground equipment changing from a second orbital plane to a third orbital plane over time, and transmitting the generated information to an artificial satellite constellation.

14. A control program executed by a computer included in the ground equipment according to claim 2 or 3, In response to the change over time of the artificial satellite flying within a range capable of communicating with the ground facility from a second artificial satellite to a third artificial satellite, generate information indicating the third artificial satellite as information indicating the artificial satellite flying within a range capable of communicating with the ground facility, and transmit the generated information to the artificial satellites constellation; A control process for generating information indicating the third orbital plane as information indicating the orbital plane present within a range capable of communicating with the ground facility in response to the change of the orbital plane present within a range capable of communicating with the ground facility over time from the second orbital plane to the third orbital plane, and transmitting the generated information to the artificial satellites constituting the satellite constellation. A control program that causes the computer to execute the above.

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