JP7724695B2 - Satellite information transmission system and geostationary satellite - Google Patents

Description

This disclosure relates to satellite information transmission systems, geostationary satellites, and ground facilities.

In geostationary orbit, the orbital locations where communication with the ground is permitted, the frequency bands available for communication, and the transmission capacity available for communication are limited. As a result, the locations where surveillance satellites near geostationary orbit can directly communicate with the ground and the communication performance are limited, which may make it impossible to respond to emergencies.

Patent document 1 discloses a method for observing space debris in geostationary satellite orbit.

JP 2011-218834 A

Patent Document 1 addresses the issue that with respect to monitoring satellites that monitor space objects on geostationary satellites, the area in which communication between the monitoring satellite and ground equipment is permitted may be limited.

This disclosure aims to enable a monitoring satellite near a geostationary orbit to transmit satellite information to the ground via a geostationary satellite that is permitted to communicate with ground facilities. This enables constant communication between the monitoring satellite and the ground.

The satellite information transmission system according to the present disclosure includes:
a monitoring satellite that monitors the Earth or space objects while moving in the longitude direction near a geostationary orbit;
a ground facility for transmitting and receiving satellite information to and from the monitoring satellite;
A satellite information transmission system comprising a plurality of geostationary satellites that fly in geostationary orbits and relay communication of satellite information between the monitoring satellite and the ground equipment,
optical communication in the 1.0 μm band between the plurality of geostationary satellites;
optical communication in the 1.5 μm band between the monitoring satellite and each of the plurality of geostationary satellites;
Radio wave communication is performed between each of the plurality of geostationary satellites and the ground facility.

In the satellite information transmission system disclosed herein, a monitoring satellite near geostationary orbit transmits satellite information to the ground via a geostationary satellite that is permitted to communicate with ground equipment. Furthermore, communication between multiple geostationary satellites is optical communication in the 1.0 μm band, and communication between the monitoring satellite and each geostationary satellite is optical communication in the 1.5 μm band. Therefore, the satellite information transmission system disclosed herein has the effect of enabling constant communication between the monitoring satellite and ground equipment at low cost.

FIG. 1 is a diagram showing an example of the configuration of a satellite information transmission system according to a first embodiment. FIG. 1 is a diagram showing an example of the configuration of a monitoring satellite according to a first embodiment. FIG. 2 is a diagram showing an example of the hardware configuration of ground equipment according to the first embodiment. FIG. 1 is a diagram showing a configuration example of Example 1 of a satellite information transmission system according to a first embodiment; FIG. 10 is a diagram showing monitoring from a high altitude while moving westward in Example 1 of the satellite information transmission system according to the first embodiment. FIG. 10 is a diagram showing monitoring from a low altitude during eastward movement in Example 1 of the satellite information transmission system according to the first embodiment. FIG. 2 is a diagram showing an example of the configuration of a data relay satellite, which is a geostationary satellite, according to the first embodiment. FIG. 10 is a diagram showing monitoring from a high altitude while moving westward in Example 2 of the satellite information transmission system according to the first embodiment. FIG. 10 is a diagram showing monitoring from a low altitude during eastward movement in Example 2 of the satellite information transmission system according to the first embodiment. 2 is a diagram showing an example of a communication field of view of a monitoring satellite in the satellite information transmission system according to the first embodiment; FIG. 2 is a diagram showing an example of communication in the satellite information transmission system according to the first embodiment. FIG. 2 is a diagram showing an example of communication in the satellite information transmission system according to the first embodiment. 2 is a diagram showing an example of a communication field of view of a geostationary satellite in the satellite information transmission system according to the first embodiment; FIG. 10 is a diagram showing a configuration example of an optical communication device according to a second embodiment. 10 is a diagram showing the optical axis of communication light transmitted and received from the aperture of an optical antenna in a communication satellite that is an example of a geostationary satellite according to the second embodiment. FIG. FIG. 10 is a diagram showing a first example of the configuration of a geostationary satellite according to a second embodiment. FIG. 10 is a diagram showing a second example of the configuration of a geostationary satellite according to the second embodiment.

Embodiments of the present disclosure will be described below using the figures. Note that in each figure, identical or corresponding parts are designated by the same reference numerals. In describing the embodiments, descriptions of identical or corresponding parts will be omitted or simplified as appropriate. Furthermore, the size relationships between components in the following drawings may differ from the actual size. Furthermore, in describing the embodiments, directions or positions such as "up," "down," "left," "right," "front," "rear," "front," and "back" may be indicated. These notations are used merely for convenience of description and do not limit the placement or orientation of components such as devices, instruments, or parts.

Embodiment 1.
***Configuration Description***
FIG. 1 is a diagram showing an example of the configuration of a satellite information transmission system 500 according to this embodiment.

The satellite information transmission system 500 comprises a monitoring satellite 300, multiple geostationary satellites 400, and ground equipment 700.

The monitoring satellite 300 monitors the Earth or space objects while moving longitude-wise near the geostationary orbit.
The ground facility 700 is a facility provided on the ground. The ground facility 700 exchanges satellite information 200 with the monitoring satellite 300.
The geostationary satellite 400 flies in a geostationary orbit and relays communication of the satellite information 200 between the monitoring satellite 300 and the ground facility 700 .
The satellite information 200 is information exchanged between the monitoring satellite 300 and the ground facility 700 .

FIG. 2 is a diagram showing an example of the configuration of a monitoring satellite 300 according to this embodiment.
The monitoring satellite 300 monitors a target such as the Earth or a space object.
1, the monitoring target monitored by the monitoring satellite 300 may include a geostationary satellite 400 in a geostationary orbit or a positioning satellite in a quasi-zenith orbit (QZO). QZO is an abbreviation for Quasi-Zenith Satellite Orbit.

The monitoring satellite 300 comprises a satellite communication device 31, a monitoring device 32, a propulsion device 33, an attitude control device 34, a satellite control device 35, and a power supply device 36.

The satellite communication device 31 is a communication device for communicating with the ground facility 700. For example, the satellite communication device 31 receives various commands from the ground facility 700. The satellite communication device 31 also transmits monitoring data obtained by the monitoring device 32 to the ground facility 700.
The various commands and monitoring data are examples of satellite information 200 .

The monitoring device 32 is a device for monitoring a monitoring target such as the Earth or a space object, and generates monitoring data. In this embodiment, the monitoring target may be referred to as a flying object. The monitoring device 32 is an infrared monitoring device that uses infrared rays. For example, the monitoring device 32 is an infrared monitoring device that is directed toward the edge of the Earth.
The monitoring satellite 300 has a pointing function for directing the line of sight toward the flying object.

The monitoring data is data corresponding to an image of a flying object, and indicates the position of the flying object within the field of view (monitoring range) of the monitoring device 32.
The monitoring data may include time information, position information, line-of-sight information, field-of-view information, etc. The time information indicates the time when monitoring was performed (monitoring time). The position information indicates the coordinate values of the monitoring satellite 300. The line-of-sight information indicates the line-of-sight direction of the monitoring device 32. The field-of-view information indicates the field of view of the monitoring device 32.

The propulsion device 33 is a device that provides thrust to the monitoring satellite 300 and changes the speed of the monitoring satellite 300. Specifically, the propulsion device 33 is an electric propulsion device. For example, the propulsion device 33 is an ion engine or a Hall thruster.

The attitude control device 34 is a device for controlling the attitude elements such as the attitude of the monitoring satellite 300 and the angular velocity of the monitoring satellite 300 .
The attitude control device 34 changes each attitude element in 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 includes a gyroscope, an earth sensor, a sun sensor, a star tracker, a thruster, a magnetic sensor, etc. The actuator includes an attitude control thruster, a momentum wheel, a reaction wheel, and a control moment gyro. The controller controls the actuator according to measurement data from the attitude sensor or various commands from the ground facility 700.
The attitude control device 34 can be used as a device (field of view changing device) for changing the field of view of the monitoring device 32. The field of view of the monitoring device 32 corresponds to the line of sight of the monitoring device 32. The range (field of view) centered on the line of sight of the monitoring device 32 becomes the monitoring range.

The satellite control device 35 is a computer that controls each device on the monitoring satellite 300 and is equipped with processing circuits. For example, the satellite control device 35 controls each device in accordance with various commands transmitted from the ground equipment 700.

The power supply unit 36 includes a solar cell, a battery, a power control device, etc., and supplies power to each device on the monitoring satellite 300.

As shown in FIG. 1, geostationary satellites 400 flying in geostationary orbits are specifically satellites such as a communication satellite 401, a positioning satellite 402, a data relay satellite 403, a meteorological satellite 404, and an observation satellite 405.
These geostationary satellites 400 are similar in configuration to the monitoring satellites 300 described above, but each includes mission equipment for carrying out its own mission instead of the monitoring device 32. For example, a meteorological satellite 404 includes a satellite communication device 31, a propulsion device 33, an attitude control device 34, a satellite control device 35, and a power supply device 36, as well as meteorological observation equipment for observing the Earth's weather.

FIG. 3 is a diagram showing an example of the hardware configuration of the ground equipment 700 according to this embodiment.
The hardware included in the computer will be described using the ground equipment 700 as an example.

The processor 910 is a device that executes a program that realizes the functions of the ground equipment 700 .
The processor 910 is an IC that performs arithmetic processing. Specific examples of the processor 910 are a CPU, a DSP, and a GPU. IC is an abbreviation for Integrated Circuit. CPU is an abbreviation for Central Processing Unit. DSP is an abbreviation for Digital Signal Processor. GPU is an abbreviation for Graphics Processing Unit.

Memory 921 is a storage device that temporarily stores data. Specific examples of memory 921 are SRAM and DRAM. SRAM is an abbreviation for Static Random Access Memory. DRAM is an abbreviation for Dynamic Random Access Memory.

The 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 also 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. HDD is an abbreviation for Hard Disk Drive. SD (registered trademark) is an abbreviation for Secure Digital. CF is an abbreviation for CompactFlash (registered trademark). 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. Specifically, the input interface 930 is a USB terminal. The input interface 930 may also be a port connected to a LAN. USB is an abbreviation for Universal Serial Bus. LAN is an abbreviation for 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. Specifically, the output interface 940 is a USB terminal or an HDMI (registered trademark) terminal. Specifically, the display is an LCD. HDMI (registered trademark) is an abbreviation for High Definition Multimedia Interface. LCD is an abbreviation for Liquid Crystal Display.

The communication device 950 has a receiver and a transmitter. Specifically, the communication device 950 is a communication chip or NIC. NIC is an abbreviation for Network Interface Card.

The program that realizes the functions of the ground equipment 700 is loaded into the processor 910 and executed by the processor 910. In addition to the program, the OS is also stored in the memory 921. OS is an abbreviation for Operating System. The processor 910 executes the program while running the OS. The program and OS may be stored in the auxiliary storage device 922. The program and OS stored in the auxiliary storage device 922 are loaded into the memory 921 and executed by the processor 910. Note that some or all of the program that realizes the functions of the ground equipment 700 may be incorporated into the OS.

The ground equipment 700 may be equipped with multiple processors that replace processor 910. These multiple processors share the task of executing the program. Each processor is a device that executes a program, just like processor 910.

Data, information, signal values, and variable values used, processed, or output by the program are stored in memory 921, auxiliary storage device 922, or registers or cache memory within processor 910.

The "parts" of the ground equipment 700 may be read as "processing," "procedure," "means," "steps," "circuitry," or "steps." Furthermore, the "parts" of the ground equipment 700 may be read as "program," "program product," or "computer-readable recording medium on which a program is recorded." "Processing," "procedure," "means," "steps," "circuitry," or "steps" may be read as interchangeable with each other.

For example, the ground facility 700 generates various commands for each monitoring satellite 300 in order to control each monitoring satellite 300. The ground facility 700 also analyzes the monitoring data obtained from each monitoring satellite 300 and generates information (e.g., location information) about the flying object being monitored.
The communication device 950 communicates with each monitoring satellite 300. Specifically, the communication device 950 transmits various commands to each monitoring satellite 300. The communication device 950 also receives monitoring data transmitted from each monitoring satellite 300.
In this embodiment, the communication device 950 communicates with each monitoring satellite 300 via the geostationary satellite 400 .

The processing circuits provided in the ground equipment 700 and the satellite control device 35 will now be described.
The processing circuitry may be dedicated hardware or may be a processor that executes a program stored in a memory as described above.
In the processing circuit, some functions may be realized by dedicated hardware and the remaining functions may be realized by software or firmware, i.e., the processing circuit may be realized by hardware, software, firmware, or a combination thereof.
Dedicated hardware may be, for example, a single circuit, multiple circuits, a programmed processor, parallel programmed processors, an ASIC, an FPGA, or a combination thereof.
ASIC is an abbreviation for Application Specific Integrated Circuit.
FPGA is an abbreviation for Field Programmable Gate Array.

The adjustment of satellite altitude and orbital inclination will be explained.
The relative angle of the normal to the orbital plane of the monitoring satellite 300 as viewed from the north pole side is determined by the correlation between the satellite altitude and the orbital inclination angle.
By fine-tuning the orbital inclination angle appropriately under altitude conditions that maintain the number of satellite orbits per day, it becomes possible to operate the satellite constellation while maintaining the relative angle between the orbital planes.
The ground facility 700 generates commands for controlling the altitude of each monitoring satellite 300. The ground facility 700 also generates commands for controlling the orbital inclination of each monitoring satellite 300. The ground facility 700 then transmits these commands to each monitoring satellite 300.
In each monitoring satellite 300, the satellite control device 35 adjusts the satellite altitude and orbital inclination angle in accordance with these commands. Specifically, the satellite control device 35 controls the propulsion device 33 in accordance with these commands. The propulsion device 33 can change the satellite speed, thereby adjusting the satellite altitude and orbital inclination angle.
When the flight speed of the monitoring satellite 300 increases, the altitude of the monitoring satellite 300 increases. When the altitude of the monitoring satellite 300 increases, the ground speed of the monitoring satellite 300 decreases.
When the flight speed of the monitoring satellite 300 decreases, the altitude of the monitoring satellite 300 decreases. When the altitude of the monitoring satellite 300 decreases, the ground speed of the monitoring satellite 300 increases.
If the propulsion device 33 generates thrust in a direction perpendicular to the orbital plane at the point where the monitoring satellite 300 crosses the equator (the equinox), the orbital inclination angle can be effectively fine-tuned.

***Functions of the satellite information transmission system 500***
In Fig. 1, the communication represented by the solid lines is optical communication, and the communication represented by the dotted lines is radio communication.
Information is exchanged between the geostationary satellites 400 of the plurality of geostationary satellites by optical communication in the 1.0 μm band.
Information is exchanged between the monitoring satellite 300 and each of the plurality of geostationary satellites 400 by optical communication in the 1.5 μm band.
Information is exchanged between each of the geostationary satellites 400 and the ground facility 700 by radio wave communication.

The monitoring satellite 300 moves in the longitude direction to monitor the Earth or space objects. At this time, the area in which the monitoring satellite 300 is permitted to communicate with the ground facility 700 is limited.
1, in this embodiment, the monitoring satellite 300 always transmits the satellite information 200 via the geostationary satellite 400 that is permitted to communicate with the ground facility 700. This has the effect of enabling communication between the monitoring satellite 300 and the ground facility 700 at all times.

Optical communication and radio communication can be selected as the means of communication between satellites.
Optical communications have the advantages of being able to transmit large volumes of data and of enabling secure communications. However, because optical communications require the optical axes of the transmitter and receiver to be aligned with high precision, it is necessary to achieve high-precision pointing control and high-precision pointing stability for the satellite carrying the communications equipment. Furthermore, suppression of disturbances, which can cause misalignment of the optical axis, is essential for optical communications.
When a single satellite communicates optically with multiple communication partners simultaneously, it is necessary to perform high-precision pointing direction control with all of the communication partners. Furthermore, since it is necessary to maintain high-precision pointing stability during communication, there are issues such as the technical difficulty and high cost of maintaining and operating the satellite. Furthermore, if the optical axis shifts, communication will be interrupted, and since it will be necessary to realign the optical axis, there is a risk of communication being interrupted and it will take time to restore communication.

In communications between multiple geostationary satellites, the relative positions of the geostationary satellites are maintained, making it easy to perform high-precision pointing control and maintain a high degree of pointing stability.
On the other hand, in communications between a monitoring satellite and a geostationary satellite, which are moving relative to each other, it is necessary to change the pointing direction while keeping the optical axis aligned.
Furthermore, when optical communications are used between geostationary satellites and ground equipment, there is the issue that communications may be cut off if there are clouds, and there is a high risk of communications being cut off in areas where ground equipment is installed with a high cloud cover rate.

<First embodiment of satellite information transmission system 500>
FIG. 4 is a diagram showing an example of the configuration of a satellite information transmission system 500 according to a first embodiment of the present invention.
As shown in Fig. 4, information is exchanged between multiple geostationary satellites 400 using optical communication in the 1.0 μm band. For example, in Fig. 4, the communication between the data relay satellite and meteorological satellite A, and between meteorological satellite A and meteorological satellite B, is optical communication in the 1.0 μm band.

Information is exchanged between the monitoring satellite 300 and the geostationary satellite 400 using optical communication in the 1.5 μm band. For example, in Figure 4, the communications between the monitoring satellite and the data relay satellite, between the monitoring satellite and the weather satellite A, and between the monitoring satellite and the weather satellite B are all optical communications in the 1.5 μm band.

The communication between each geostationary satellite 400 of the multiple geostationary satellites and each ground facility 700 is radio wave communication.
FIG. 4 illustrates ground facilities 700 such as mobile units, fixed ground stations, monitoring information centers, and weather information centers.
Geostationary satellites 400 such as data relay satellites and ground facilities 700 such as mobile bodies, fixed ground stations, and monitoring information centers exchange satellite information by radio wave communication.
Geostationary satellites 400 such as meteorological satellites A and B and ground facilities 700 such as a monitoring information center exchange satellite information 200 via radio wave communication. Also, geostationary satellites 400 such as meteorological satellites A and B and ground facilities 700 such as a weather information center exchange weather information via radio wave communication.

The geostationary satellite 400 is equipped with a radio communication device 41 that exchanges information with the ground equipment 700, and an optical communication device 42 that exchanges information between multiple geostationary satellites and with the monitoring satellite 300.

The notation "optical communication device (monitoring satellite-GEO)" for the optical communication device 42 in Fig. 4 indicates that it is an optical communication device used between a monitoring satellite and a geostationary satellite. Also, the notation "optical communication device (GEO-monitoring satellite, GEO-GEO)" indicates that it is an optical communication device used between a monitoring satellite and a geostationary satellite, and between geostationary satellites flying in geostationary orbits (GEO). GEO is an abbreviation for Geostationary Orbit.
4 includes radio wave communication device 41 (GEO-terrestrial) and radio wave communication device (terrestrial-GEO). Radio wave communication device (GEO-terrestrial) and radio wave communication device (terrestrial-GEO) are communication devices used for radio wave communication between geostationary satellites and ground facilities.

The monitoring satellite 300 is equipped with an optical communication device (monitoring satellite-GEO) for optically communicating with the geostationary satellite 400 .
The data relay satellite 403 is equipped with an optical communication device (GEO-monitoring satellite, GEO-GEO) for optical communication with the monitoring satellite 300 and the geostationary satellite 400, and a radio communication device (GEO-terrestrial) for radio communication with the ground facility 700.
The meteorological satellite 404 comprises meteorological mission equipment such as optical communication equipment (GEO-to-surveillance satellite, GEO-to-GEO), radio communication equipment (GEO-to-terrestrial), and meteorological observation equipment.
The ground facility 700 includes a radio wave communication device (terrestrial-GEO) that communicates with the geostationary satellite 400 via radio waves.

The ground facilities 700 include ground facilities such as fixed base stations, a monitoring information center, and a weather information center.
The ground equipment 700 may also include a mobile body 600 .
In the communication between the geostationary satellite 400 and the ground facility 700, the ground facility 700 may be a mobile body 600. For example, the ground facility 700 is a mobile body that takes direct action when an emergency response is required. If the ground facility 700 is such a mobile body 600, when the monitoring satellite 300 transmits information requiring an emergency response, the information can be transmitted to the mobile body 600 in real time without any delay.
This will have the effect of enabling rapid response actions, such as launching a rapid-response debris removal satellite, in the event of an emergency. An example of an emergency situation would be a situation in which a suspicious object, such as debris, approaches a domestic satellite.

FIG. 5 is a diagram showing monitoring from a high altitude while moving westward in Example 1 of the satellite information transmission system 500 according to the present embodiment.
FIG. 6 is a diagram showing monitoring from a low altitude while moving eastward in Example 1 of the satellite information transmission system 500 according to this embodiment.

In Example 1 of the satellite information transmission system 500, the multiple geostationary satellites 400 consist of two meteorological satellites and two data relay satellites.

In Example 1 of the satellite information transmission system 500, optical communication between the geostationary satellite 400 and the monitoring satellite 300 and optical communication between the geostationary satellites 400 and 400 are performed alternately in a time-division manner. Furthermore, communication between the geostationary satellite 400 and the ground equipment 700 is performed by radio wave communication. This limits the number of targets for which high-precision pointing control can be achieved simultaneously to one set.

Furthermore, by equipping geostationary satellite 400 with a 1.0 μm band transceiver and a 1.5 μm band transceiver, satellite information transmission system 500 becomes a system with international compatibility. The 1.0 μm band transceiver ensures compatibility with 1.0 μm band geostationary data relay satellites. The 1.5 μm band transceiver ensures compatibility with 1.5 μm band earth observation satellites.
The development of geostationary data relay satellites in the 1.0 μm band is progressing in Europe, and the development of earth observation satellites in the 1.5 μm band is progressing in Japan.

In the first embodiment of the satellite information transmission system 500, optical communication in the 1.0 μm band is limited to communication means between geostationary satellites 400.
For example, in FIG. 5, the communications between data relay satellite A and meteorological satellite B, between meteorological satellite A and meteorological satellite B, and between meteorological satellite B and data relay satellite A are optical communications in the 1.0 μm band.
In addition, in FIG. 6, the communications between data relay satellite A and data relay satellite B, between meteorological satellite A and meteorological satellite B, and between meteorological satellite B and data relay satellite A are optical communications in the 1.0 μm band.

Optical communication between the monitoring satellite 300 and the geostationary satellite 400 is performed in the 1.5 μm band.
For example, in FIG. 5, the communications between data relay satellite A and monitoring satellite 300, between meteorological satellite A and monitoring satellite 300, between meteorological satellite B and monitoring satellite 300, and between data relay satellite B and monitoring satellite 300 are optical communications in the 1.5 μm band.
In addition, in FIG. 6, the communications between data relay satellite A and monitoring satellite 300, between meteorological satellite A and monitoring satellite 300, between meteorological satellite B and monitoring satellite 300, and between data relay satellite B and monitoring satellite 300 are optical communications in the 1.5 μm band.

Radio wave communication is used between the geostationary satellite 400 and the ground facility 700.
For example, in FIG. 5, the communications between the data relay satellite A and the ground facility 700 and between the data relay satellite B and the ground facility 700 are radio wave communications.
In FIG. 6, the communications between the data relay satellite A and the ground facility 700, between the meteorological observation A and the ground facility 700, and between the data relay satellite B and the ground facility 700 are radio wave communications.
The communication between each of the meteorological satellites A and B and the ground facility 700, which is the weather information center, is radio wave communication for sending and receiving weather information.

Figure 7 is a diagram showing an example configuration of a data relay satellite 403, which is a geostationary satellite 400 according to this embodiment.

The geostationary satellite 400 is equipped with optical communication equipment.
The optical communication device of the geostationary satellite 400 includes a 1.0 μm band transceiver with a transmission/reception switch, a 1.5 μm band transceiver with a transmission/reception switch, and a shared optical antenna. The optical communication device of the geostationary satellite 400 also includes a coarse-precision two-axis pointing change device, a fine-precision two-axis pointing change device, and a switch for switching between the 1.0 μm band and the 1.5 μm band.
After performing optical communication in the 1.5 μm band with the monitoring satellite 300, the geostationary satellite 400 operates a switching device to switch between the 1.0 μm band and the 1.5 μm band transceiver, and performs optical communication in the 1.0 μm band with the geostationary satellite 400.

FIG. 8 is a diagram showing monitoring from a high altitude while moving westward in Example 2 of the satellite information transmission system 500 according to this embodiment.
FIG. 9 is a diagram showing monitoring from a low altitude while moving eastward in Example 2 of the satellite information transmission system 500 according to this embodiment.

9, a monitoring satellite 300 monitors a space object in geostationary orbit while moving eastward from a low altitude relative to the geostationary orbit. At this time, the monitoring satellite 300 flies on the earth-pointing side of the geostationary satellite 400. Therefore, a communication device between the monitoring satellite 300 and the geostationary satellite 400 must ensure a communication field of view on the earth-pointing side of the geostationary satellite 400.
8, the monitoring satellite 300 monitors space objects in geostationary orbit or the sunlit Earth surface while moving westward from a high altitude relative to the geostationary orbit. At this time, the monitoring satellite 300 flies on the side opposite to the Earth-pointing plane of the geostationary satellite 400, so the communication device between the monitoring satellite 300 and the geostationary satellite 400 must ensure a communication field of view on the side opposite to the Earth-pointing plane of the geostationary satellite 400.
Furthermore, it is necessary to be able to communicate in both cases where the monitoring satellite 300 flies to the east of the geostationary satellite 400 and where the monitoring satellite 300 flies to the west of the geostationary satellite 400 .

In optical communications, communication is interrupted if there is an obstruction such as the structure, solar paddles, or antenna of the geostationary satellite 400. Therefore, in order to ensure optical communications visibility at high altitudes, low altitudes, eastward, and westward, four or more optical communications devices must be installed, which poses a problem of extremely high costs.
The number of optical communication devices can be reduced by placing them at the end of a long boom and providing a function for changing the field of view over a large angle. However, there is a problem in that it is difficult to achieve high-precision pointing accuracy and stability at the end of a long boom.

To address the above-mentioned challenges in optical communications, two optical communications devices are placed, one on each of the east and west faces of the geostationary satellite 400. The coarse pointing change devices provided in each optical communications device are capable of changing the pointing direction by a large angle around the north-south axis, thereby enabling the pointing direction to be changed in the altitude direction.
Furthermore, the optical antenna, coarse pointing change device, and fine pointing change device, which are technically difficult and expensive to manufacture, are shared and can be used by switching between the 1.0 μm band and the 1.5 μm band, which has the advantage of reducing the cost of the satellite information transmission system 500.

FIG. 10 is a diagram showing an example of the communication field of view of a monitoring satellite 300 in a satellite information transmission system 500 according to this embodiment.
FIG. 11 is a diagram showing an example of communication in the satellite information transmission system 500 according to this embodiment.

The monitoring satellite 300 includes a monitoring device 32 .
The monitoring satellite 300 is also equipped with an optical communication device that has a communication field of view of ±80 degrees around the north-south axis (Y axis) from the east when the monitoring device 32 is flying with its line of sight vector pointing toward the center of the earth.
The monitoring satellite 300 also has an optical communication device with a communication field of view of ±80 degrees around the north-south axis (Y axis) from the west.

In Figure 11, the monitoring satellite 300 communicates with the ground equipment 700 via the geostationary satellite 400 while moving eastward and operating the monitoring device 32.

FIG. 12 is a diagram showing an example of communication in the satellite information transmission system 500 according to this embodiment.
In FIG. 12, monitoring satellite 300 communicates with ground facility 700 via geostationary satellite 400 while operating monitoring equipment 32 while moving westward.
11 and 12, the communication satellite is a geostationary satellite 400 as an example.

The monitoring satellite 300 is equipped with a 1.5 μm band transmitting/receiving device equipped with a transmission/reception switching device, and an optical communication device equipped with a coarse precision two-axis pointing change device and a fine precision two-axis pointing change device.
The monitoring satellite 300 performs optical communication with the geostationary satellite 400 in the 1.5 μm band.

Figure 13 is a diagram showing an example of the communication field of view of a geostationary satellite 400 in the satellite information transmission system 500 according to this embodiment.

The geostationary satellite 400 is equipped with a radio wave communication device for communicating with the ground equipment 700 .
In addition, the geostationary satellite 400 is equipped with an optical communication device having a communication field of view of ±80 degrees around the north-south axis (Y axis) from the east direction, and an optical communication device having a communication field of view of ±80 degrees around the north-south axis (Y axis) from the west direction.

Embodiment 2.
In this embodiment, differences from and additions to the first embodiment will be mainly described.
In this embodiment, components having the same functions as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

FIG. 14 is a diagram showing an example of the configuration of an optical communication device according to this embodiment.
The optical communication device includes a 1.0 μm band transceiver with a transmit/receive switch, a 1.5 μm band transceiver with a transmit/receive switch, a shared optical antenna, a coarse-precision two-axis pointing changer, a fine-precision two-axis pointing changer, and a switch between the 1.0 μm band and the 1.5 μm band.

FIG. 15 is a diagram showing the optical axis of communication light transmitted and received from the aperture of an optical antenna in a communication satellite, which is an example of a geostationary satellite 400 according to this embodiment.
The optical axis of the communication light transmitted and received from the aperture of the optical antenna can be changed by a large angle using a coarse-precision two-axis pointing change device, and the two-axis configuration may be two-axis rotation around azimuth and elevation, or two-axis rotation around the X axis and Y axis.

FIG. 16 is a diagram showing a first example of the configuration of a geostationary satellite 400 according to this embodiment.
The altitude of a monitoring satellite changes between high and low altitudes. Therefore, by providing a pointing direction changing device that changes the direction of a geostationary satellite at a large angle around the north-south axis, as in Configuration Example 1 of the geostationary satellite 400, communication is possible at any altitude using a single optical communication device.

FIG. 17 is a diagram showing a second configuration example of a geostationary satellite 400 according to this embodiment.
There are cases where a monitoring satellite flies in an orbit with an inclination angle relative to a geostationary satellite flying above the equator. Or, conversely, there are cases where a geostationary satellite flies in an orbit with an inclination angle relative to a monitoring satellite flying above the equator. In such cases, as in configuration example 2 of geostationary satellite 400, a pointing direction changing device with a large angle around the Earth-pointing axis is provided. This makes it possible to communicate with a single optical communication device even when the orbital inclination angle differs in the positive or negative direction.

After the optical axis is roughly oriented toward the target by the coarse-precision two-axis pointing change device, the optical axis is fine-tuned by the fine-precision two-axis pointing change device to achieve axis alignment that enables optical communication.
A device for switching between 1.0 μm and 1.5 μm can be realized by changing the angle of a switching mirror relative to the communication light.
Each of the 1.0 μm and 1.5 μm transmitter/receivers includes a transmitter that emits a laser beam and a receiver equipped with a photodetector. Each of the 1.0 μm and 1.5 μm transmitter/receivers alternately transmits and receives in a time-division manner using a transmission/reception switching device.

The optical communication device between the monitoring satellite and the geostationary satellite operates the transmission/reception switching device by synchronizing the timing at which the geostationary satellite starts transmitting commands to the monitoring satellite with the timing at which the monitoring satellite starts transmitting monitoring information and telemetry to the geostationary satellite.
It is also possible to distinguish between the polarization of the transmitted and received signals.

In this embodiment, optical communications between geostationary satellites and monitoring satellites and between geostationary satellites are alternately performed in a time-division manner, and radio communications are used for communications between geostationary satellites and ground equipment, thereby limiting the number of targets for which high-precision pointing control can be achieved simultaneously to one set. Therefore, this embodiment has the advantage of reducing costs by keeping the technical difficulty within a feasible range.

In this embodiment, the optical communication device is equipped with a 1.0 μm band transceiver that ensures compatibility with 1.0 μm band geostationary data relay satellites currently being developed in Europe, and a 1.5 μm band transceiver that ensures compatibility with 1.5 μm band earth observation satellites currently being developed in Japan. This has the effect of ensuring international compatibility.
Furthermore, according to this embodiment, there is an advantage that communication is possible even when the monitoring satellite employs an optical communication device in the 1.0 μm band.

In the first and second embodiments, the configurations of the systems and devices, such as the satellite information transmission system and the satellites, do not have to be as in the above-described embodiments. The configurations of the systems and devices may be any configuration as long as they can realize the functions described in the above-described embodiments.
Furthermore, it is possible to combine multiple parts or examples of the first and second embodiments. Alternatively, it is possible to implement only one part or example of these embodiments. Furthermore, it is possible to implement any combination of these embodiments, either as a whole or in part.
That is, in the first and second embodiments, the respective embodiments can be freely combined, or any of the components in the respective embodiments can be modified, or any of the components in the respective embodiments can be omitted.

The above-described embodiments are essentially preferred examples and are not intended to limit the scope of the present disclosure, the scope of applications of the present disclosure, or the scope of use of the present disclosure. The above-described embodiments can be modified in various ways as needed.

200 Satellite information, 300 Monitoring satellite, 31 Satellite communication equipment, 32 Monitoring equipment, 33 Propulsion unit, 34 Attitude control unit, 35 Satellite control unit, 36 Power supply unit, 400 Geostationary satellite, 401 Communication satellite, 402 Positioning satellite, 403 Data relay satellite, 404 Meteorological satellite, 405 Observation satellite, 41 Radio communication equipment, 42 Optical communication equipment, 500 Satellite information transmission system, 600 Mobile object, 700 Ground equipment, 910 Processor, 921 Memory, 922 Auxiliary storage device, 930 Input interface, 940 Output interface, 941 Display device, 950 Communication equipment.

Claims (5)

a monitoring satellite that monitors the Earth or space objects while moving in the longitude direction near a geostationary orbit;
a ground facility for transmitting and receiving satellite information to and from the monitoring satellite;
A satellite information transmission system comprising a plurality of geostationary satellites that fly in geostationary orbits and relay communication of satellite information between the monitoring satellite and the ground equipment,
optical communication in the 1.0 μm band between the plurality of geostationary satellites;
optical communication in the 1.5 μm band between the monitoring satellite and each of the plurality of geostationary satellites;
radio wave communication between each of the plurality of geostationary satellites and the ground facility;
Each geostationary satellite of the plurality of geostationary satellites
a 1.0 μm band transceiver having a transmission/reception switching device;
a 1.5 μm band transceiver having a transmission/reception switching device;
a shared optical antenna;
a coarse-precision two-axis pointing change device;
A precision two-axis pointing change device;
an optical communication device including a switching device for switching between the 1.0 μm band and the 1.5 μm band;
After optical communication in the 1.5 μm band with the monitoring satellite, the switching device is operated to switch between the 1.0 μm band and the 1.5 μm band transceiver, and the satellite information transmission system performs optical communication in the 1.0 μm band with the geostationary satellite. The monitoring satellite is equipped with a monitoring device, and the line-of-sight vector of the monitoring device is directed toward the center of the earth,
an optical communication device having a communication field of view of ±80° around a north-south axis (Y axis) from the east direction;
2. The satellite information transmission system according to claim 1, further comprising an optical communication device having a communication field of view of ±80° around the north-south axis (Y-axis) from the west direction, and communicating with the ground equipment via the geostationary satellite while the monitoring device is operating while moving eastward. The monitoring satellite is equipped with a monitoring device, and the line-of-sight vector of the monitoring device is directed toward the center of the earth,
an optical communication device having a communication field of view of ±80° around a north-south axis (Y axis) from the east direction;
2. The satellite information transmission system according to claim 1, further comprising an optical communication device having a communication field of view of ±80° around the north-south axis (Y-axis) from the west direction, and communicating with the ground equipment via the geostationary satellite while the monitoring device is operating while moving westward. The geostationary satellite
a radio wave communication device that communicates with the ground equipment;
an optical communication device having a communication field of view of ±80° around a north-south axis (Y axis) from the east direction;
2. A satellite information transmission system according to claim 1, further comprising an optical communication device having a communication field of view of ±80 degrees around a north-south axis (Y axis) from the west direction. A geostationary satellite constituting the satellite information transmission system described in claim 1.