Radio wave monitoring system, ground equipment, satellite constellation, and radio wave monitoring method

Abstract

The aim is to suppress the increase in resources and costs that would result from an increase in the number of satellites by reliably observing directional radio waves, which have uncertainty, using a small number of satellites. [Solution] The radio wave monitoring system includes a satellite constellation forming unit that forms a satellite constellation that flies within a pointing change range at an orbital altitude H where directional radio waves may be emitted. The satellite constellation forms a satellite formation that includes a first group of satellites that have the same azimuth angle value and have the same zenith angle difference between adjacent satellites in a tangential plane coordinate system with the monitored object 10 as the origin, at the time when the position coordinates of the monitored object 10 pass through the common range of the observation ranges of each satellite formed when the observation field of view θsat of each satellite reaches the Earth's surface.

Description

[Technical Field]

[0001] The present disclosure relates to a radio wave monitoring system, a ground facility, a satellite constellation, and a radio wave monitoring method, and more particularly to a radio wave monitoring system, a ground facility, a satellite constellation, and a radio wave monitoring method for observing directional radio waves emitted by a radio wave radiation source. [Background technology]

[0002] One technology for radio wave monitoring systems using satellites is to observe radio waves emitted from the same radio wave source using multiple mobile objects and locate the radio wave source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-250865 Summary of the Invention [Problem to be solved by the invention]

[0004] Even if one tries to apply the technology of Patent Document 1 to the observation of directional radio waves with uncertainty, it is not possible to reliably observe such directional radio waves with uncertainty using the technology of Patent Document 1. Directional radio waves with uncertainty are radio waves (beams) that have directionality and where they will be emitted is uncertain. In order to reliably observe directional radio waves, which have uncertainty, it is necessary to comprehensively deploy radio monitoring satellites within the range in which radio waves may be emitted. For example, within the range D of the directionality change of directional radio waves emitted by a radio wave emission source, satellites must be deployed comprehensively so that any satellite can observe a directional radio wave with an effective beam width θt wherever it occurs. Therefore, an increase in the number of satellites increases the challenges of increased resources and costs.

[0005] The present disclosure aims to suppress increases in resources and costs due to an increase in the number of satellites by efficiently observing directional radio waves with uncertainty using a small number of satellites. [Means for solving the problem]

[0006] The radio wave monitoring system according to the present disclosure monitors directional radio waves emitted by a monitoring target, The satellite constellation is made up of a plurality of satellites each equipped with a radio wave detection device that detects directional radio waves emitted by the monitored object, and flies within a direction change range at an orbital altitude H where the directional radio waves may be emitted, wherein each of the plurality of satellites has an observation field of view angle θsat, and the satellite constellation forming unit forms a satellite formation having a first group of satellites that have the same azimuth angle value in a tangential plane coordinate system with the monitored object as the origin, and in which the zenith angle difference between adjacent satellites is equal, at the time when the position coordinates of the monitored object pass through a common range of the observation ranges of each of the plurality of satellites formed when the observation field of view angle θsat of each of the plurality of satellites reaches the Earth's surface. [Effects of the Invention]

[0007] In a radio wave monitoring system according to the present disclosure, a satellite constellation is formed in a tangential plane coordinate system with the monitoring target as the origin, the satellite constellation including a first group of satellites having the same azimuth angle value and having the same difference in zenith angle between adjacent satellites. With this first group of satellites, the radio wave monitoring system according to the present disclosure can efficiently observe directional radio waves with uncertainty using a small number of satellites, thereby suppressing increases in resources and costs due to an increase in the number of satellites. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram showing an example of the configuration of a radio wave monitoring system according to a first embodiment; [Figure 2] FIG. 1 is a diagram for explaining the premise of a radio wave monitoring system according to a first embodiment. [Figure 3]FIG. 2 is a diagram showing an overview of a satellite formation of a satellite constellation according to the first embodiment. [Figure 4] FIG. 2 is a diagram showing an example of positional representation of each satellite in a satellite constellation according to the first embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the positional relationship of satellites in satellite formation example 1 according to embodiment 1. [Figure 6] FIG. 2 is a diagram showing an example of a method for generating satellite formation example 1 according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing an example of an orbit analysis result in satellite formation example 1 according to embodiment 1. [Figure 8] FIG. 10 is a diagram showing an example of the configuration of a radio wave monitoring system according to a modification of the first embodiment. [Figure 9] FIG. 10 is a diagram showing an example of the positional relationship of satellites in satellite formation example 2 according to embodiment 2. [Figure 10] FIG. 10 is a diagram showing an example of the positional relationship of each satellite in satellite formation example 3 according to embodiment 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present embodiment will be described below with reference to the drawings. In each drawing, identical or corresponding parts are designated by the same reference numerals. In the description of the embodiment, the description of identical or corresponding parts will be omitted or simplified as appropriate. Arrows in the drawings mainly indicate the flow of data or the flow of processing. Furthermore, the sized relationships between components in the following drawings may differ from the actual relationships. Furthermore, in the description of the embodiment, directions or positions such as up, down, left, right, front, rear, front and back may be indicated. These notations are used for convenience of explanation and do not limit the placement, direction or orientation of devices, instruments, parts, etc.

[0010] Embodiment 1 ***Configuration Description*** FIG. 1 is a diagram showing an example of the configuration of a radio wave monitoring system 500 according to this embodiment. The radio wave monitoring system 500 includes a satellite 30 and a ground facility 700 . Each of the satellites 30 and the ground facilities 700 is equipped with a computer. While Fig. 1 shows the configuration of one computer, in reality, a computer is provided for each of the multiple satellites 30 constituting the satellite constellation 300 and for each of the ground facilities 700 that communicate with the satellites 30. The computers provided for each of the multiple satellites 30 and for each of the ground facilities 700 that communicate with the satellites 30 work together to realize the functions of the radio wave monitoring system 500.

[0011] The ground equipment 700 controls the programs of the multiple satellites that make up the satellite constellation 300. The ground equipment 700 is an example of ground equipment. The ground equipment is composed of a ground station such as a ground antenna device, a communication device connected to the ground antenna device, or a computer, and ground equipment as a server or terminal connected to the ground station via a network. The ground equipment may also include a communication device mounted on a moving object such as an aircraft, a self-propelled vehicle, or a mobile terminal.

[0012] The ground equipment 700 forms the satellite constellation 300 by communicating with each satellite 30. The ground equipment 700 includes a processor 910 as well as other hardware such as a memory 921, an auxiliary storage device 922, an input interface 930, an output interface 940, and a communication device 950. The processor 910 is connected to the other hardware via signal lines and controls the other hardware.

[0013] The ground equipment 700 includes, as a functional element, a satellite constellation forming unit 11 that forms the satellite constellation 300. The satellite constellation forming unit 11 controls the formation of the satellite constellation 300 while communicating with the satellites 30. The functions of the satellite constellation forming unit 11 are realized by hardware or software.

[0014] The communication device 950 transmits and receives signals for tracking and controlling each satellite 30 constituting the satellite constellation 300. The communication device 950 also transmits orbit control commands 55 to each satellite 30 for controlling the orbit of the satellite 30.

[0015] The satellite 30 comprises a satellite control device 31, a satellite communication device 32, a propulsion device 33, an attitude control device 34, a power supply device 35, and a radio wave detection device 36. In addition, the satellite 30 comprises components that realize various functions.

[0016] The satellite control device 31 is a computer that controls the propulsion devices 33 and the attitude control device 34, and includes a processing circuit. Specifically, the satellite control device 31 controls the propulsion devices 33 and the attitude control device 34 in accordance with various commands transmitted from the ground facility 700. The satellite communication device 32 is a device that communicates with the ground facility 700. Specifically, the satellite communication device 32 transmits various data related to its own satellite to the ground facility 700. In addition, the satellite communication device 32 receives various commands transmitted from the ground facility 700. The propulsion device 33 is a device that provides thrust to the satellite 30 . The attitude control device 34 controls the attitude of the satellite 30, the angular velocity of the satellite 30, and the line of sight (Line Of Sight) direction. The attitude control device 34 controls each attitude element such as the aircraft's flight control system (AF) and the aircraft's sight. 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 power supply unit 35 includes devices such as solar cells, batteries, and a power control device, and supplies power to each device mounted on the satellite 30. The radio wave detection device 36 detects directional radio waves emitted from the monitored object 10 .

[0017] The satellite 30 further includes a satellite constellation forming unit 11b that forms a satellite constellation 300. The satellite constellation forming unit 11b of each of the multiple satellites 30 and the satellite constellation forming unit 11 provided in each of the ground facilities 700 work together to realize the functions of the radio wave monitoring system 500. The satellite constellation forming unit 11b of the satellite 30 may be provided in the satellite control device 31.

[0018] *** Functional overview of the Radio Monitoring System 500 *** FIG. 2 is a diagram illustrating the premise of the radio wave monitoring system 500 according to this embodiment. The radio wave monitoring system 500 includes a plurality of satellites 30 and ground equipment 700 . The satellite 30 is equipped with a radio wave detection device 36 that detects directional radio waves emitted by the monitored object 10. The plurality of satellites 30 and the ground facility 700 communicate with each other. Furthermore, it is preferable that the total range of radio wave detection by the radio wave detection device 36 provided on each of the multiple satellites 30 is approximately the same as the range of directionality change of the directional radio waves emitted from the monitored object 10. Alternatively, it is preferable that the total range of radio wave detection by the radio wave detection device 36 provided on each of the multiple satellites 30 is slightly larger than the range of directionality change of the directional radio waves emitted from the monitored object 10. The radio wave detection range is the range that can be observed by the satellite, and is also called the coverage area of ​​the satellite.

[0019] The monitored object 10 is a radio wave radiation source that radiates directional radio waves. The monitored object 10 radiates directional radio waves with uncertainty within a direction change range 80 at an orbital altitude H where the directional radio waves may be radiated. The monitored object 10 is also referred to as an observation object. Figure 2 shows satellites that can observe radio waves in the state of Figure 2, and satellites that cannot observe radio waves in the state of Figure 2. The satellites that cannot observe radio waves in the state of Figure 2 are satellites that are provided so that observation can be made by the satellite constellation 300 even if the monitored object 10 changes the direction of the radio waves. It should be noted that all satellites 30 must carry out observations when passing over the monitored location, since it is not known which beam will be illuminated.

[0020] FIG. 3 is a diagram showing an outline of the satellite formation of a satellite constellation 300 according to this embodiment. The ground equipment 700 forms a satellite constellation 300 that flies within a pointing change range 80 at an orbital altitude H where directional radio waves may be emitted. In the satellite constellation 300, the distance between each satellite of the multiple satellites 30 and its adjacent satellites is used as an estimate of the beam width of the directional radio waves. The estimated value of the beam width of the directional radio waves may include the relative position fluctuation of the satellite formation and the relative position control error of the satellite formation. The ground equipment 700 also includes a database 71 that records estimated values ​​of the position coordinates of the monitored object 10, estimated values ​​of the frequency band of the directional radio waves, estimated values ​​of the beam width of the directional radio waves, and estimated values ​​of the direction change range of the directional radio waves.

[0021] Figure 3 shows a satellite formation formed by the first to Mth satellites in a tangential plane coordinate system with the monitored object 10 as the origin. In Figure 3, M=9. The tangential plane coordinate system is a coordinate system with the position coordinates of the monitored object 10 as the origin, the direction normal to the Earth's surface at the position coordinates of the monitored object 10 as the Z axis, the Earth's surface projection in the east direction at the position coordinates of the monitored object 10 as the X axis, and the Earth's surface projection in the north direction at the position coordinates of the monitored object 10 as the Y axis. FIG. 3 shows satellite formation example 1, satellite formation example 2, and satellite formation example 3. In this embodiment, satellite formation example 1 will be described.

[0022] The shape of the beam width of the radio waves emitted from the monitored object 10 is defined by an azimuth angle range and a zenith angle range (elevation angle range). Therefore, we propose a satellite formation in which the azimuth angle interval between adjacent satellites is constant and the zenith angle interval is also constant. However, the azimuth angle interval and the zenith angle interval do not have to be approximately the same. As shown in the left diagram of Figure 3, when the beam width shape is defined by the azimuth angle range and the zenith angle range, the optimal formation is, for example, satellite formation example 1, in which the azimuth angle interval between adjacent satellites is constant and the zenith angle interval is also constant. In this case, it is preferable that the total radio wave detection range of the multiple satellites 30 constituting the satellite constellation 300 at orbital altitude H is approximately the same as the irradiation range of the directional radio wave beam at orbital altitude H. Alternatively, it is preferable that the total radio wave detection range of the multiple satellites 30 constituting the satellite constellation 300 at orbital altitude H is slightly larger than the irradiation range of the directional radio wave beam at orbital altitude H.

[0023] <About Satellite Formation Example 1> FIG. 4 is a diagram showing an example of position representation of each satellite in a satellite constellation 300 according to this embodiment. In Fig. 4, each of the multiple satellites 30 has an observation field of view angle θsat. Fig. 4 shows a state in which the position coordinates of the monitored object 10 pass through a common range of the observation ranges of the multiple satellites 30, which is formed when the observation field of view angle θsat of each of the multiple satellites 30 reaches the Earth's surface. 4, the multiple satellites 30 are four satellites 1-1, 1-2, 2-1, and 2-2. If the zenith angle is Zn and the azimuth angle is Az, the position of each satellite can be expressed as follows: Note that the position of each satellite is also called the azimuth of each satellite. Position representation of satellite 1-1: (Az11,Zn11) Position representation of satellite 1-2: (Az12,Zn12) Position representation of satellite 2-1: (Az21,Zn21) Position representation of satellite 2-2: (Az22,Zn22)

[0024] FIG. 5 is a diagram showing an example of position representation of each satellite in satellite formation example 1 according to the present embodiment. 5 shows a satellite formation example 1 formed by the first to M-th satellites in a tangential plane coordinate system with the origin at the monitored object 10. In FIG. 5, M=9. The satellite constellation 300 includes a first group of satellites 301 that have the same azimuth angle value and have the same zenith angle difference between adjacent satellites in a tangential plane coordinate system with the monitored object 10 as the origin. The satellite constellation 300 includes the first group of satellites 301 at the time when the position coordinates of the monitored object 10 pass through a common range of the observation ranges of the multiple satellites 30 that is formed when the observation field of view angle θsat of each of the multiple satellites 30 reaches the Earth's surface. In the left diagram of FIG. 5, satellites 1-1, 1-2, and 1-3 are an example of a first satellite group 301.

[0025] Furthermore, satellite constellation 300 forms satellite formation example 1 in which a first group of satellites 301 are aligned evenly in the azimuth direction. In the left diagram of FIG. 5, a first group of satellites 301 forms a satellite formation example 1 in which three satellites are arranged evenly in the azimuth direction.

[0026] The satellite constellation 300 also has a second group of satellites 302 that have the same zenith angle value and have the same azimuth angle difference between adjacent satellites in a tangential plane coordinate system with the monitored object 10 as the origin. The satellite constellation 300 has the second group of satellites 302 at the time when the position coordinates of the monitored object 10 pass through a common range of the observation ranges of the multiple satellites 30 that is formed when the observation field of view angle θsat of each of the multiple satellites 30 reaches the Earth's surface. In the left diagram of FIG. 5, satellites 1-1, 2-1, and 3-1 are an example of the second satellite group 302.

[0027] The satellite constellation 300 also includes a second group of satellites 302 arranged in a satellite formation evenly spaced in the zenith angle direction. In the left diagram of FIG. 5, the second group of satellites 302 forms a satellite formation with three satellites evenly spaced in the zenith angle direction.

[0028] The left diagram in FIG. 5 shows the positions of the first satellite to the Mth satellite (M=9). The position of satellite 1-1 is expressed as (Az11,Zn11), the position of satellite 1-2 as (Az11,Zn11+dZ), the position of satellite 2-1 as (Az11+dA,Zn11), and the position of satellite KN as (Az11+(K-1)×dA,Zn11+(N-1)×dZ). dA and dZ are stored in a database in the ground equipment 700. The ground equipment 700 maintains the satellite formation by referring to dA and dZ stored in the database.

[0029] As described above, the shape of the beam width of radio waves emitted from a radio wave emission source is defined by the azimuth angle range and the zenith angle range (elevation angle range). Therefore, we propose a satellite formation in which the azimuth angle interval between adjacent satellites is constant and the zenith angle interval is also constant. However, the azimuth angle interval and the zenith angle interval do not have to be approximately the same. When the beam width shape is defined by the azimuth angle range and the zenith angle range, as shown in the left diagram of Figure 3, the optimal satellite formation is satellite formation example 1, in which the azimuth angle interval between adjacent satellites is constant and the zenith angle interval is also constant. Satellite formation example 1 is also called a formation with uniform distribution of azimuth angles and zenith angles.

[0030] The right diagram of FIG. 5 illustrates an example of defining the position of the satellite constellation 300 relative to the pointing range 80. The position of the minimum point of the azimuth angle and zenith angle of the directional radio wave change range is expressed as (Azbase, Znbase). In this case, the position of satellite 1-1 is expressed as (Az11, Zn11) = (Azbase + dAabs, Znbase + dZabs). The dAabs and dZabs are stored in a database in the ground equipment 700. The ground equipment 700 maintains the satellite formation by referring to the dAabs and dZabs stored in the database.

[0031] <Example of how to generate the orbit for satellite formation example 1> FIG. 6 is a diagram showing an example of a method for generating an orbit of satellite formation example 1 according to the present embodiment. The following methods can be used to realize satellite formation example 1. The orbit of each satellite in the satellite constellation 300 is defined as (orbital inclination, right ascension of ascending node, semi-major axis, orbital eccentricity, argument of perigee, argument of latitude). Satellite 1-1 in the satellite constellation 300 is defined as the reference satellite. In this case, the orbits of the other satellites are expressed by relative orbital elements that differ from the orbit of the reference satellite only in the right ascension of ascending node and argument of latitude, and the attitudes of the other satellites are expressed as target attitudes in which the antenna boresight pointing direction points to the same point as the reference satellite. However, the attitudes of the other satellites may also be target attitudes in which the same point as the reference satellite is included in the observation field of view θsat of the satellite.

[0032] Specifically, we propose a method for setting relative orbital elements for other satellites that provides differences (ΔΩ and Δη) only in the right ascension of the ascending node and the argument of latitude with respect to the orbit of the reference satellite, and a method for setting a target attitude such that the same point as the reference satellite falls within the observation field of view θsat of the satellite. The orbit of the reference satellite is assumed to be an inclined near-circular orbit (a special example is a solar non-orbital subrecurrent inclined frozen orbit). Furthermore, orbital analysis has confirmed that it is possible to form a formation that distributes azimuth and zenith angles using only ΔΩ and Δη based on an inclined near-circular orbit (excluding high latitudes).

[0033] Here is an example of a specific method for generating a reference orbit. First, the position of the observation target in the Earth-fixed coordinate system is determined, and the azimuth and elevation angles of the reference satellite when observing the observation target are calculated using the above method. The desired time for observing the observation target with the reference satellite, the object distance when observing the observation target with the reference satellite, the orbital inclination of the reference orbit, the orbital eccentricity of the reference orbit, and the argument of perigee of the reference orbit are determined. From this, the position and velocity of the reference satellite in a tangential coordinate system based on the observation target are calculated. Using the position of the observation target in the Earth-fixed coordinate system, a transformation from the tangential coordinate system to the Earth-fixed coordinate system is calculated, and this transformation calculates the position and velocity of the reference satellite in the Earth-fixed coordinate system. Using the desired time for observing the observation target with the reference satellite, a transformation from the Earth-fixed coordinate system to an inertial coordinate system is calculated, and this transformation calculates the position and velocity of the reference satellite in the inertial coordinate system (called Cartesian orbital elements). Finally, by performing a general conversion between Cartesian and Keplerian orbital elements, the inclination, right ascension of the ascending node, semi-major axis, orbital eccentricity, argument of perigee, and argument of latitude of the reference orbit are calculated.

[0034] The advantage of only setting differences in the right ascension of the ascending node and the argument of latitude (ΔΩ and Δη) is that when only ΔΩ and Δη are used, the difference in the perturbation forces experienced by each satellite in the formation is small, so the amount of orbital control required to maintain the formation is small.

[0035] In FIG. 6, the orbital expression (orbital inclination, right ascension of ascending node, semi-major axis, orbital eccentricity, argument of perigee, argument of latitude) of satellite 1-1, which is the reference satellite, is (i11, Ω11, a11, e11, ω11, η11). In this case, the orbital expression of satellite KN (orbital inclination, right ascension of ascending node, semi-major axis of orbit, orbital eccentricity, argument of perigee, argument of latitude) is (i11,Ω11+dΩkn,a11,e11,ω11,η11+dηkn).

[0036] The relative positional relationship between satellites at the moment when directional radio waves emitted by a radio wave source are observed at a single point that can be observed with a small number of satellites can be realized using only the difference in longitude ascension of the ascending node and the difference in latitude argument between the orbits of each satellite, which has the following effects. All satellites in the formation receive equal forces from the Earth and the Sun, making it easier to maintain the formation (requiring less propellant and fuel). When the target radio wave source is located near the equator (including mid- and low-latitude regions), moving the satellites in the direction of their flight from the source to establish a new monitoring point does not significantly change the relative positions of all satellites in the formation as seen from the new monitoring point, allowing observations of the new monitoring point with a configuration close to optimal. This allows a formation designed for a representative target near the equator (including mid- and low-latitude regions) to be used to observe other targets near the equator (including mid- and low-latitude regions) (with the same estimated directional radio wave beam width and the same estimated directional radio wave redirection range as the representative target). Note that due to the sparse population distribution near the North and South Poles, targets are often located in the mid- and low-latitude regions.

[0037] FIG. 7 is a diagram showing an example of an orbit analysis result in satellite formation example 1 according to the present embodiment. Figure 7 shows a satellite constellation 300 in a formation arrangement in which azimuth and zenith angles are distributed using only ΔΩ and Δη, based on an inclined near-circular orbit. This figure shows an example of orbit analysis results when the satellites in the satellite constellation 300 observe a monitored object 10a located near the equator (including mid-latitude and low-latitude bands), and then move forward while keeping their attitudes fixed relative to the orbital coordinate system, and observe monitored object b. It can be seen that near the equator (including mid-latitude and low-latitude bands), there is little fluctuation in the relative positions of all the satellites making up the formation, and the formation arrangement is relatively well maintained. In addition, by only setting the differences in the right ascension of the ascending node and the argument of latitude (ΔΩ and Δη), it is easier to maintain over the long term and there is less disruption. In addition, there is an advantage that the flight positions of the satellites that make up the satellite formation can be appropriately controlled simply by focusing on the minimum evaluation indexes, namely the right ascension Ω of the ascending node and the latitude argument η.

[0038] <Example of how to correct satellite formation example 1> Next, an example of a method for correcting the satellite constellation 300 forming satellite formation example 1 by the ground equipment 700 will be described. The ground equipment 700 has a database 71 that records estimated values ​​(xt, yt, zt) of the position coordinates of the monitored object 10 in the Earth-fixed coordinate system, an estimated value ω1 of the frequency band of the directional radio waves, an estimated value Φ1 of the beam width of the directional radio waves, and an estimated value of the direction change range of the directional radio waves. The ground facility 700 forms the satellite constellation 300 as follows, when the satellite constellation 300 includes a first satellite and a second satellite. The first satellite flies in an orbit with the ascending node right ascension Ω1 and latitude argument η1. The first satellite passes through the radio wave irradiation area formed by the directional radio waves at the orbital altitude H. The second satellite flies in an orbit with an ascending node right ascension of Ω2 and latitude argument of η2. At time t1 when the first satellite receives the directional radio waves, the first satellite is at a flight position (t1, xs1, ys1, zs1), while the second satellite is at a flight position (t1, xs2, ys2, zs2). The relative direction of the second satellite from the first satellite is (xs2-xs1, ys2-ys1, zs2-zs1), and the relative distance between the first and second satellites is ΔL.

[0039] The ground equipment 700 records in advance in database 71 estimated values ​​for radio waves emitted by monitored objects for which functional or performance information is unavailable due to security reasons, etc. This satellite constellation 300 has the advantage that, when a first satellite and a second satellite simultaneously detect directional beams, it is possible to verify that the beam width of the directional beam in the relative direction of the second satellite as seen from the first satellite (xs2-xs1, ys2-ys1, zs2-zs1) is greater than or equal to ΔL, and that the relative distance between the first satellite and the second satellite is greater than or equal to ΔL. Also, when only the first satellite or the second satellite detects a directional beam, it is possible to verify that the beam width of the directional beam in the relative direction of the second satellite as seen from the first satellite (xs2-xs1, ys2-ys1, zs2-zs1) is less than ΔL.

[0040] Furthermore, if a first satellite can detect directional radio waves even once through multiple observations of the same observation target at different times, it is possible to verify that the position of the first satellite is within the range in which the directional radio waves can be changed.Similarly, if a second satellite can detect directional radio waves even once through multiple observations of the same observation target at different times, it is possible to verify that the position of the second satellite is within the range in which the directional radio waves can be changed. When the satellite constellation 300 includes more than two satellites 30, there is an advantage that the beam widths in multiple directions and the beam direction change range can be verified according to the relative positions of the satellites 30. The satellite constellation 300 can actively control the orbit of the satellite formation relative to the beam emitted to the monitored object, which has the effect of enabling accurate verification of the beam width in the direction to be verified.

[0041] The method of correcting satellite formation example 1 is just one example, and satellite formation example 1 may be corrected using other methods.

[0042] The satellite monitoring system may also have the following functions: If the time at which the satellite constellation 300 receives the directional radio waves emitted from the monitored object 10 differs from the expected time, the ground equipment 700 generates an updated value for the position coordinates of the monitored object 10 recorded in the database 71. This has the effect of enabling the estimated values ​​to be updated with high precision for a monitoring target whose exact position coordinates are unknown.

[0043] In addition, the ground equipment 700 generates updated values ​​for the estimated beam width of the directional radio waves and the estimated direction change range of the directional radio waves using the above-mentioned method, depending on whether or not directional radio waves are detected from each satellite 30 that makes up the satellite constellation 300. This has the effect of enabling the estimated values ​​to be updated with high precision for a monitored object for which the exact beam width and the exact pointing change range are unknown.

[0044] In addition, if the satellite constellation 300 cannot detect radio waves in the frequency band ω1 recorded in the database 71 but can detect radio waves in the frequency band ω2, the ground equipment 700 generates an updated value for the frequency band recorded in the database 71. This has the effect of enabling the estimated value to be updated with high precision for a monitored object for which the exact frequency band of the irradiated beam is unknown.

[0045] ***Other Configurations*** In this embodiment, the functions of the radio wave monitoring system 500 are realized by software. As a modification, the functions of the radio wave monitoring system 500 may be realized by hardware.

[0046] FIG. 8 is a diagram showing the configuration of a radio wave monitoring system 500 according to a modification of this embodiment. The ground equipment 700 includes an electronic circuit 909 instead of a processor 910 . The electronic circuit 909 is a dedicated electronic circuit that realizes the functions of the ground equipment 700 . The electronic circuit 909 is specifically a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, a logic IC, a GA, an ASIC, or an FPGA, where GA is an abbreviation for Gate Array. The functions of the ground equipment 700 may be realized by a single electronic circuit, or may be realized by distributing them among multiple electronic circuits. As another variation, some of the functions of the ground equipment 700 may be realized by electronic circuits, and the remaining functions may be realized by software.

[0047] Each of the processor and the electronic circuit is also called a processing circuitry. That is, the functions of the radio wave monitoring system 500 are realized by the processing circuitry.

[0048] In this embodiment, the satellite constellation forming unit 11 is provided in the ground facility 700. As a modification, the satellite constellation forming unit 11 may be provided in a satellite 30 that constitutes the satellite constellation 300, or in a relay satellite in outer space that can communicate with the satellite 30 that constitutes the satellite constellation 300.

[0049] In this embodiment, a satellite constellation 300 constituting one satellite formation example 1 is formed for the direction change range of the directional radio waves emitted from the monitored object 10, but if the shape of the direction change range of the directional radio waves emitted from the monitored object 10 is a special shape, multiple satellite formation examples 1 may be combined. In addition, in this embodiment, the directional radio waves emitted from the monitored object 10 are observed by at least one satellite. However, if it is required to observe the directional radio waves emitted from the monitored object 10 by multiple satellites, multiple satellite formation example 1 may be combined. FIG. 3 shows an example in which three satellite formation example 1s are combined to observe the same directional radio waves by at least three satellites. By combining multiple satellite formation example 1s, it is possible to reliably observe directional radio waves with uncertainty using as few satellites as possible. Furthermore, it is possible to suppress increases in resources and costs due to an increase in the number of satellites. Observing the directional radio waves emitted from the monitored object 10 by multiple satellites has the advantage of being able to estimate the position and speed of the monitored object 10 by radio wave source positioning processing such as TDOA processing or FDOA processing. TDOA is an abbreviation for Time Difference of Arrival. FDOA is an abbreviation for Frequency Difference of Arrival. This effect also applies to satellite formation example 2 and example 3, which will be described later.

[0050] ***Explanation of the effect of this embodiment*** As described above, the radio wave monitoring system according to the present embodiment forms a satellite constellation in which satellites fly in a satellite formation in which the distance between each satellite and its neighboring satellite is an estimated value of the beam width of the directional radio waves within the pointing change range in which directional radio waves may be emitted. Therefore, the radio wave monitoring system according to the present disclosure can reliably observe directional radio waves, which have uncertainty, with as few satellites as possible, and can suppress increases in resources and costs due to an increase in the number of satellites. Furthermore, the radio wave monitoring system according to this embodiment has the advantage of being able to observe directional radio waves emitted by a monitored object for which information on the direction of direction cannot be obtained due to security reasons or the like, with a small number of units. Furthermore, in the radio wave monitoring system according to this embodiment, the estimated value of the beam width of a directional radio wave can be defined using two variables: azimuth angle width and zenith angle width (elevation angle width). This has the effect of reducing the amount of data that needs to be managed as estimated values ​​of the beam width. The azimuth angle width is also called the azimuth angle range, the zenith angle width is also called the zenith angle range, and the elevation angle width is also called the elevation angle range.

[0051] According to the radio wave monitoring system of this embodiment, for each target orbit of each satellite constituting the satellite formation, the semi-major axis, orbital inclination, eccentricity, and argument of perigee are the same for all satellites, and only the right ascension of the ascending node and argument of latitude differ. In this way, by realizing the satellite relative constellation conditions using only the differences in the right ascension of the ascending node and argument of latitude, all satellites constituting the formation receive the same forces from the Earth and the Sun, which reduces the amount of disruption of the satellite relative constellation and saves on the propellant required to maintain the satellite relative constellation. Furthermore, if the radio wave radiation source to be monitored is located near the equator (including mid-latitude and low-latitude bands), and a new monitoring point is set by moving the satellite from the point where the radio wave radiation source is located in the direction of its movement, the relative positions of all satellites that make up the formation as seen from the new monitoring point will not change significantly, and the new monitoring point can also be observed in a configuration that is close to optimal. In addition, by only setting the differences in the right ascension of the ascending node and the argument of latitude (ΔΩ and Δη), it is easier to maintain over the long term and there is less disruption.

[0052] 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. The configuration, premise, and satellite position representation of the radio wave monitoring system 500 according to this embodiment are the same as those of the first embodiment.

[0053] In this embodiment, satellite formation example 2 in FIG. 3 will be described. In this embodiment, satellite constellation 300 forms satellite formation example 2 in which a first group of satellites 301 are arranged uniformly in the azimuth angle direction and offset in the zenith angle direction. As shown in FIG. 3, satellite formation example 2 is a satellite formation in which a first group of satellites 301 aligned in the azimuth angle direction is shifted in the zenith angle direction.

[0054] <About Satellite Formation Example 2> FIG. 9 is a diagram showing an example of the positional relationship of satellites in satellite formation example 2 according to the present embodiment. 9 shows a second example of a satellite formation formed by the first to M-th satellites in a tangential plane coordinate system with the origin at the monitored object 10. In FIG. 9, M=9. The satellite constellation 300 includes a first group of satellites 301 arranged uniformly in the azimuth direction and offset in the zenith direction. In the left diagram of Figure 9, first satellite group 301a consisting of satellites 1-1, 1-2, and 1-3, first satellite group 301b consisting of satellites 2-1, 2-2, and 2-3, and first satellite group 301c consisting of satellites 3-1, 3-2, and 3-3 are arranged with a zenith angle offset of Lz. Satellites 3-1, 3-2, and 3-3 are not shown. Note that the zenith angle offset Lz(2) between first satellite group 301a and first satellite group 301b and the zenith angle offset Lz(3) between first satellite group 301a and first satellite group 301c do not have to be approximately the same.

[0055] At this time, the positional relationship between the first satellite to the Mth satellite (M=9) is as shown in the left diagram of FIG. The position of satellite 1-1 is expressed as (Az11,Zn11), the position of satellite 1-2 as (Az11,Zn11+dZ), the position of satellite 2-1 as (Az11+dA,Zn11+Lz(2)), and the position of satellite KN as (Az11+(K-1)×dA,Zn11+(N-1)×dZ+Lz(K)). In the ground equipment 700, dA and dZ are stored in a database. Lz(K) is a value according to K and is also stored in the database. The ground equipment 700 maintains the satellite formation by referring to dA, dZ, and Lz(K) stored in the database. Note that Lz(1)=0.

[0056] The right diagram of FIG. 9 illustrates an example of defining the position of the satellite constellation 300 relative to the pointing change range 80. The position of the minimum point of the azimuth angle and zenith angle of the directional radio wave change range is expressed as (Azbase, Znbase). In this case, the position of the reference satellite 1-1 is expressed as (Az11, Zn11) = (Azbase + dAabs, Znbase + dZabs). The dAabs and dZabs are stored in a database in the ground equipment 700. The ground equipment 700 maintains the satellite formation by referring to the dAabs and dZabs stored in the database.

[0057] As described above, by adopting satellite formation example 2 in which the first group of satellites 301 arranged in the azimuth direction are shifted in the zenith angle direction, it becomes possible to arrange the multiple satellites 30 that make up the satellite constellation 300 in a relative position in polar coordinates (distance from the origin = zenith angle, declination = azimuth angle) that is not limited to a fan-shaped grid arrangement, as shown in the right diagram of Figure 3. The range in which directional radio waves can be changed is determined by the beam width of the directional radio waves being observed and the operating range of the antenna that emits the directional radio waves being observed, so it is not necessarily a fan-shaped range in polar coordinates (distance from the origin = zenith angle, declination = azimuth angle). In formation example 2, by setting the zenith angle direction deviation amount Lz according to the shape of the direction change range of the directional radio waves, it is possible to adopt a relative arrangement of the multiple satellites 30 that make up the satellite constellation 300 that corresponds to the shape of the direction change range of the directional radio waves.This makes it possible to bring the total radio wave detection range of the multiple satellites 30 that make up the satellite constellation 300 closer to the direction change range of the directional radio waves, which has the effect of reducing the number of satellites 30 required to reliably observe directional radio waves.

[0058] <Example of how to generate the orbit for satellite formation example 2> The method for generating the orbit of satellite formation example 2 is the same as the method for generating the orbit of satellite formation example 1 described in the first embodiment. For example, for a satellite constellation 300 generated using the generation method of satellite formation example 1, satellite formation example 2 may be formed by shifting multiple first satellite groups 301 arranged evenly in the azimuth angle direction by Lz in the zenith angle direction.

[0059] <Example of how to correct satellite formation example 2> The correction method for satellite formation example 2 is the same as the correction method for satellite formation example 1 described in the first embodiment.

[0060] ***Explanation of the effect of this embodiment*** As described above, in the radio wave monitoring system of this embodiment, by generating satellite formation example 2 in which the first group of satellites aligned in the azimuth angle direction is shifted in the zenith angle direction, it is possible to apply the optimal satellite formation depending on the shape of the pointing change range.

[0061] Embodiment 3 In this embodiment, differences from the first and second embodiments and additional features to the first and second embodiments 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. The configuration, premise, and satellite position representation of the radio wave monitoring system 500 according to this embodiment are the same as those of the first embodiment.

[0062] In this embodiment, satellite formation example 3 in FIG. 3 will be described. In this embodiment, satellite constellation 300 forms satellite formation example 3 in which second satellite group 302 is arranged uniformly in the zenith angle direction and offset in the azimuth angle direction. As shown in FIG. 3, satellite formation example 3 is a satellite formation in which a second group of satellites 302 aligned in the zenith angle direction is shifted in the azimuth angle direction.

[0063] <About Satellite Formation Example 3> FIG. 10 is a diagram showing an example of the positional relationship of satellites in satellite formation example 3 according to the present embodiment. 10 shows a satellite formation example 3 formed by the first to M-th satellites in a tangential plane coordinate system with the origin at the monitored object 10. In FIG. 10, M=9. The satellite constellation 300 includes a second group of satellites 302 arranged uniformly in the zenith angle direction and offset in the azimuth angle direction. In the left diagram of Figure 10, second satellite group 302a consisting of satellites 1-1, 2-1, and 3-1, second satellite group 302b consisting of satellites 1-2, 2-2, and 3-2, and second satellite group 302c consisting of satellites 1-3, 2-3, and 3-3 are arranged with an offset of La in the zenith angle direction. Satellites 1-3, 2-3, and 3-3 are not shown. Note that the azimuth angle offset La(2) between second satellite group 302a and second satellite group 302b and the azimuth angle offset La(3) between second satellite group 302a and second satellite group 302c do not have to be approximately the same.

[0064] At this time, the positional relationship between the first satellite to the Mth satellite (M=9) is as shown in the left diagram of FIG. The position of satellite 1-1 is expressed as (Az11,Zn11), the position of satellite 1-2 as (Az11+La(2),Zn11+dZ), the position of satellite 2-1 as (Az11+dA,Zn11), and the position of satellite KN as (Az11+(K-1)×dA+La(N),Zn11+(N-1)×dZ). In the ground equipment 700, dA and dZ are stored in a database. La(N) is a value according to N and is also stored in the database. The ground equipment 700 maintains the satellite formation by referring to dA, dZ, and La(N) stored in the database. Note that La(1)=0.

[0065] The right diagram of FIG. 10 illustrates an example of defining the position of the satellite constellation 300 relative to the pointing range 80. The position of the minimum point of the azimuth angle and zenith angle of the directional radio wave change range is expressed as (Azbase, Znbase). In this case, the position of the reference satellite 1-1 is expressed as (Az11, Zn11) = (Azbase + dAabs, Znbase + dZabs). The dAabs and dZabs are stored in a database in the ground equipment 700. The ground equipment 700 maintains the satellite formation by referring to the dAabs and dZabs stored in the database.

[0066] As described above, by adopting satellite formation example 3 in which the second group of satellites 302 aligned in the zenith angle direction are shifted in the azimuth angle direction, it becomes possible to arrange the multiple satellites 30 that make up the satellite constellation 300 in a relative position in polar coordinates (distance from the origin = zenith angle, declination = azimuth angle) that is not limited to a fan-shaped grid arrangement, as shown in the right diagram of Figure 3. The range in which directional radio waves can be changed is determined by the beam width of the directional radio waves being observed and the operating range of the antenna that emits the directional radio waves being observed, so it is not necessarily a fan-shaped range in polar coordinates (distance from the origin = zenith angle, declination = azimuth angle). In formation example 3, by setting the azimuth angle direction deviation amount La according to the shape of the direction change range of the directional radio waves, it is possible to adopt a relative arrangement of the multiple satellites 30 that make up the satellite constellation 300 that corresponds to the shape of the direction change range of the directional radio waves.This makes it possible to bring the total radio wave detection range of the multiple satellites 30 that make up the satellite constellation 300 closer to the direction change range of the directional radio waves, which has the effect of reducing the number of satellites 30 required to reliably observe the directional radio waves.

[0067] <Example of how to generate the orbit for satellite formation example 3> The method for generating the orbit of satellite formation example 3 is the same as the method for generating the orbit of satellite formation example 1 described in the first embodiment. For example, for a satellite constellation 300 generated using the generation method of satellite formation example 1, satellite formation example 3 may be formed by shifting multiple second satellite groups 302 that are evenly arranged in the zenith angle direction by La in the azimuth angle direction.

[0068] <Example of how to correct satellite formation example 3> The correction method for satellite formation example 3 is the same as the correction method for satellite formation example 1 described in the first embodiment.

[0069] ***Explanation of the effect of this embodiment*** As described above, in the radio wave monitoring system of this embodiment, by generating satellite formation example 3 in which the second group of satellites aligned in the zenith angle direction is shifted in the azimuth angle direction, it is possible to apply the optimal satellite formation depending on the shape of the pointing change range.

[0070] In the above first to third embodiments, each part of the radio wave monitoring system has been described as an independent functional block. However, the configuration of the radio wave monitoring system does not have to be as in the above-described embodiments. The functional blocks of the radio wave monitoring system may have any configuration as long as they can realize the functions described in the above-described embodiments. Furthermore, it is possible to combine multiple parts of the first to third embodiments. Alternatively, it is possible to implement only one part of these embodiments. In addition, it is possible to implement any combination of these embodiments, either as a whole or in part. That is, in the first to third embodiments, the embodiments can be freely combined, or any of the components in each embodiment can be modified, or any of the components in each embodiment can be omitted.

[0071] The above-described embodiments are essentially preferred examples and are not intended to limit the scope of the present disclosure, the scope of application 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. For example, the procedures described using flow charts or sequence diagrams may be modified as appropriate.

[0072] Various aspects of the present disclosure are summarized below as appendices.

[0073] (Appendix 1) In a radio wave monitoring system that monitors directional radio waves emitted by a monitored object, A radio wave monitoring system comprising a satellite constellation consisting of a plurality of satellites equipped with radio wave detection devices that detect directional radio waves emitted by the monitored object, and flying within a direction change range at an orbital altitude H where the directional radio waves may be emitted, wherein each of the plurality of satellites has an observation field of view angle θsat, and wherein, at the time when the position coordinates of the monitored object pass through a common range of the observation ranges of each of the plurality of satellites formed when the observation field of view angle θsat of each of the plurality of satellites reaches the Earth's surface, the radio wave monitoring system comprises a satellite constellation forming unit that forms a satellite formation including a first group of satellites that have the same azimuth angle value in a tangential plane coordinate system with the monitored object as the origin, and in which the zenith angle difference between adjacent satellites is equal. (Appendix 2) The satellite constellation A radio wave monitoring system as described in Appendix 1, wherein the first group of satellites forms a satellite formation in which multiple satellites are evenly arranged in the azimuth direction without being shifted in the zenith angle direction. (Appendix 3) The satellite constellation 2. The radio wave monitoring system according to claim 1, wherein the first group of satellites forms a satellite formation in which multiple satellites are arranged evenly in the azimuth direction and offset in the zenith angle direction. (Appendix 4) In a radio wave monitoring system that monitors directional radio waves emitted by a monitored object, A radio wave monitoring system comprising a satellite constellation consisting of a plurality of satellites equipped with radio wave detection devices that detect directional radio waves emitted by the monitored object, and flying within a direction change range at an orbital altitude H where the directional radio waves may be emitted, wherein each of the plurality of satellites has an observation field of view angle θsat, and the radio wave monitoring system further comprises a satellite constellation forming unit that forms a satellite formation with a second group of satellites that have the same zenith angle value in a tangential plane coordinate system with the monitored object as the origin, and in which the azimuth angle difference between adjacent satellites is equal, at the time when the position coordinates of the monitored object pass through a common range of the observation ranges of each of the plurality of satellites, which is formed when the observation field of view angle θsat of each of the plurality of satellites reaches the Earth's surface. (Appendix 5) The satellite constellation 5. The radio wave monitoring system of claim 4, wherein the second group of satellites forms a satellite formation in which multiple satellites are evenly arranged in the zenith angle direction without being shifted in the azimuth angle direction. (Appendix 6) The satellite constellation 5. The radio wave monitoring system according to claim 4, wherein the second group of satellites forms a satellite formation in which multiple satellites are arranged evenly in the zenith angle direction and offset in the azimuth angle direction. (Appendix 7) The satellite constellation 7. A radio wave monitoring system according to any one of claims 1 to 6, wherein a satellite formation is formed between each satellite of the plurality of satellites and an adjacent satellite, and the beam width of the directional radio waves is an estimated value. (Appendix 8) The radio wave monitoring system includes: a ground facility communicating with the plurality of satellites; 7. The radio wave monitoring system according to claim 1, wherein the ground equipment includes the satellite constellation forming unit. (Appendix 9) The satellite constellation The radio wave monitoring system according to any one of Supplementary Note 1 to Supplementary Note 6, wherein, when the orbit of each satellite is (orbital inclination, right ascension of ascending node, semi-major axis of orbit, orbital eccentricity, argument of perigee, argument of latitude), one satellite of the satellite constellation is used as a reference satellite, and the orbits of the other satellites are expressed by relative orbital elements that differ from the orbit of the reference satellite only in right ascension of ascending node and argument of latitude. (Supplementary Note 10) The satellite constellation 10. A radio wave monitoring system as described in Appendix 9, wherein a satellite formation is formed between each satellite of the plurality of satellites and an adjacent satellite, and the beam width of the directional radio waves is an estimated value. (Appendix 11) The radio wave monitoring system includes: a ground facility communicating with the plurality of satellites; 11. The radio wave monitoring system according to claim 10, wherein the ground equipment comprises the satellite constellation forming unit. (Appendix 12) The radio wave monitoring system includes: A radio wave monitoring system as described in Appendix 10, comprising a database that records at least one of an estimated value of the position coordinates of the monitored object, an estimated value of the frequency band of the directional radio waves, an estimated value of the beam width of the directional radio waves, and a direction change range of the directional radio waves. (Appendix 13) The ground equipment includes: A radio wave monitoring system as described in Appendix 11, comprising a database that records at least one of an estimated value of the position coordinates of the monitored object, an estimated value of the frequency band of the directional radio waves, an estimated value of the beam width of the directional radio waves, and a direction change range of the directional radio waves. (Appendix 14) The ground equipment includes: A radio wave monitoring system as described in Appendix 13, comprising a database that records estimated values ​​of the beam width of the directional radio waves of the monitored object, and generates an updated value of the beam width of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation. (Appendix 15) The ground equipment includes: A radio wave monitoring system as described in Appendix 13, which includes a database that records the directionality change range of the directional radio waves of the monitored object, and generates the directionality change range of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation. (Appendix 16) The ground equipment includes: A radio wave monitoring system as described in Appendix 13, which generates updated values ​​of the position coordinates of the monitored object recorded in the database if the time at which the satellite receives directional radio waves emitted from the monitored object differs from the planned time. (Appendix 17) The ground equipment includes: A radio wave monitoring system as described in Appendix 13, which generates an updated value of the frequency band recorded in the database when it cannot detect radio waves in the frequency band ω1 recorded in the database but can detect radio waves in the frequency band ω2. (Appendix 18) The radio wave monitoring system includes: A radio wave monitoring system according to any one of Supplementary Note 1 to Supplementary Note 6, comprising a database that records at least one of estimated values ​​of the position coordinates of the monitored object, estimated values ​​of the frequency band of the directional radio waves, estimated values ​​of the beam width of the directional radio waves, and the directionality change range of the directional radio waves. (Appendix 19) The radio wave monitoring system includes: 7. A radio wave monitoring system as described in any one of Supplementary Note 1 to Supplementary Note 6, comprising a database that records estimated values ​​of the beam width of the directional radio waves of the monitored object, and generates an updated value of the beam width of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation. (Appendix 20) The radio wave monitoring system includes: A radio wave monitoring system as described in any one of Supplementary Note 1 to Supplementary Note 6, which includes a database that records the directionality change range of the directional radio waves of the monitored object, and generates the directionality change range of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation. (Appendix 21) The radio wave monitoring system includes: 7. A radio wave monitoring system according to any one of claims 1 to 6, comprising a database for recording the position coordinates of the monitored object, and generating updated values ​​of the position coordinates of the monitored object recorded in the database if the time at which the satellite receives directional radio waves emitted from the monitored object differs from that planned. (Appendix 22) The radio wave monitoring system includes: 7. A radio wave monitoring system according to any one of claims 1 to 6, comprising a database for recording the frequency bands to be monitored, wherein if radio waves in the frequency band ω1 recorded in the database cannot be detected but radio waves in the frequency band ω2 can be detected, an updated value of the frequency band recorded in the database is generated. (Appendix 23) A ground facility provided in the radio wave monitoring system described in Supplementary Note 8, the ground facility controlling each satellite constellation so that the satellite constellation flying within the pointing change range forms the satellite formation. (Appendix 24) A radio wave monitoring method used in the radio wave monitoring system according to Supplementary Note 8, comprising: A radio wave monitoring method in which the ground equipment controls each satellite constellation so that the satellite constellation flying within the pointing change range forms the satellite formation. (Appendix 25) A satellite constellation formed by a radio wave monitoring system according to any one of Supplementary Note 1 to Supplementary Note 6, wherein the satellite constellation flies to form the satellite formation within the pointing change range. (Appendix 26) A radio wave monitoring method used in the radio wave monitoring system described in any one of Supplementary Note 1 to Supplementary Note 6, wherein the satellite constellation flies to form the satellite formation. [Explanation of symbols]

[0074] 10 Monitoring target, 11,11b Satellite constellation formation unit, 30 Satellite, 31 Satellite control device, 32 Satellite communication device, 33 Propulsion device, 34 Attitude control device, 35 Power supply device, 36 Radio wave detection device, 71 Database, 80 Pointing change range, 300 Satellite constellation, 301 First satellite group, 302 Second satellite group, 500 Radio wave monitoring system, 700 Ground equipment, 909 Electronic circuit, 910 Processor, 921 Memory, 922 Auxiliary storage device, 930 Input interface, 940 Output interface, 950 Communication device.

Claims

1. In a radio wave monitoring system that monitors directional radio waves emitted by a monitored object, A radio wave monitoring system comprising a satellite constellation consisting of a plurality of satellites each equipped with a radio wave detection device that detects directional radio waves emitted by the monitored object, and flying within a directionality change range at an orbital altitude H where the directional radio waves may be emitted, wherein each of the plurality of satellites has an observation field of view angle θsat, and wherein, at the time when the position coordinates of the monitored object pass through a common range of the observation ranges of each of the plurality of satellites formed when the observation field of view angle θsat of each of the plurality of satellites reaches the Earth's surface, the radio wave monitoring system comprises a satellite constellation forming unit that forms a satellite formation including a first group of satellites having the same azimuth angle value in a tangential plane coordinate system with the monitored object as the origin, and wherein the zenith angle difference between adjacent satellites is equal.

2. The satellite constellation 2. The radio wave monitoring system according to claim 1, wherein the first group of satellites forms the satellite formation in which the plurality of satellites are aligned evenly in the azimuth direction without being shifted in the zenith angle direction.

3. The satellite constellation 2. The radio wave monitoring system according to claim 1, wherein the first group of satellites forms the satellite formation by arranging a plurality of satellites uniformly in the azimuth direction and offset in the zenith angle direction.

4. In a radio wave monitoring system that monitors directional radio waves emitted by a monitored object, A radio wave monitoring system comprising a satellite constellation consisting of a plurality of satellites each equipped with a radio wave detection device for detecting directional radio waves emitted by the monitored object, the satellite constellation flying within a direction change range at an orbital altitude H where the directional radio waves may be emitted, wherein each of the plurality of satellites has an observation field of view angle θsat, and the radio wave monitoring system further comprises a satellite constellation forming unit that forms a satellite formation including a second group of satellites having the same zenith angle value in a tangential plane coordinate system with the monitored object as the origin, the second group of satellites having the same azimuth angle difference between adjacent satellites, at the time when the position coordinates of the monitored object pass through a common range of the observation ranges of each of the plurality of satellites formed when the observation field of view angle θsat of each of the plurality of satellites reaches the earth's surface.

5. The satellite constellation 5. The radio wave monitoring system according to claim 4, wherein the second group of satellites forms the satellite formation in which a plurality of satellites are aligned evenly in the zenith angle direction without being shifted in the azimuth angle direction.

6. The satellite constellation 5. The radio wave monitoring system according to claim 4, wherein the second group of satellites forms the satellite formation by arranging a plurality of satellites uniformly in the zenith angle direction and offset in the azimuth angle direction.

7. The satellite constellation 7. The radio wave monitoring system according to claim 1, wherein each of the plurality of satellites forms a satellite formation with an adjacent satellite, which serves as an estimate of the beam width of the directional radio waves.

8. The radio wave monitoring system includes: a ground facility communicating with the plurality of satellites; The radio wave monitoring system according to claim 1 , wherein the ground facility includes the satellite constellation forming unit.

9. The satellite constellation 7. The radio wave monitoring system according to claim 1, wherein, when the orbit of each satellite is (orbital inclination, right ascension of ascending node, semi-major axis of orbit, orbital eccentricity, argument of perigee, argument of latitude), one satellite of the satellite constellation is used as a reference satellite, and the orbits of the other satellites are expressed by relative orbital elements that differ from the orbit of the reference satellite only in right ascension of ascending node and argument of latitude.

10. The satellite constellation 10. The radio wave monitoring system according to claim 9, wherein each of said plurality of satellites forms a satellite formation with an adjacent satellite, which serves as an estimate of the beam width of said directional radio waves.

11. The radio wave monitoring system includes: a ground facility communicating with the plurality of satellites; The radio wave monitoring system according to claim 10 , wherein the ground facility comprises the satellite constellation forming unit.

12. The radio wave monitoring system includes: The radio wave monitoring system according to claim 10, further comprising a database that records at least one of an estimated value of the position coordinates of the monitored object, an estimated value of the frequency band of the directional radio waves, an estimated value of the beam width of the directional radio waves, and a direction change range of the directional radio waves.

13. The ground equipment includes: The radio wave monitoring system according to claim 11, further comprising a database that records at least one of an estimated value of the position coordinates of the monitored object, an estimated value of the frequency band of the directional radio waves, an estimated value of the beam width of the directional radio waves, and a direction change range of the directional radio waves.

14. The ground equipment includes:

14. The radio wave monitoring system according to claim 13, further comprising a database that records estimated values ​​of the beam width of the directional radio waves of the monitored object, and generates an updated value of the beam width of the directional radio waves of the monitored object recorded in the database in accordance with detection information of the directional radio waves of the satellite constellation.

15. The ground equipment includes:

14. The radio wave monitoring system according to claim 13, further comprising a database that records the range of directionality change of the directional radio waves of the monitored object, and generates the range of directionality change of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation.

16. The ground equipment includes:

14. The radio wave monitoring system according to claim 13, wherein if the time at which the satellite receives the directional radio waves emitted from the monitored object differs from the planned time, updated values ​​of the position coordinates of the monitored object recorded in the database are generated.

17. The ground equipment includes: The radio wave monitoring system of claim 13, wherein when radio waves in the frequency band ω1 recorded in the database cannot be detected but radio waves in the frequency band ω2 can be detected, an updated value of the frequency band recorded in the database is generated.

18. The radio wave monitoring system includes: A radio wave monitoring system as described in any one of claims 1 to 6, comprising a database that records at least one of an estimated value of the position coordinates of the monitored object, an estimated value of the frequency band of the directional radio waves, an estimated value of the beam width of the directional radio waves, and a direction change range of the directional radio waves.

19. The radio wave monitoring system includes:

7. A radio wave monitoring system as described in any one of claims 1 to 6, comprising a database that records estimated values ​​of the beam width of the directional radio waves of the monitored object, and generates an updated value of the beam width of the directional radio waves of the monitored object recorded in the database in accordance with detection information of directional radio waves of the satellite constellation.

20. The radio wave monitoring system includes: A radio wave monitoring system as described in any one of claims 1 to 6, comprising a database that records the directionality change range of the directional radio waves of the monitored object, and generates the directionality change range of the directional radio waves of the monitored object recorded in the database in accordance with directional radio wave detection information of the satellite constellation.

21. The radio wave monitoring system includes:

7. A radio wave monitoring system according to claim 1, further comprising a database for recording the position coordinates of the monitored object, and if the time at which the satellite receives the directional radio waves emitted from the monitored object differs from the planned time, an updated value of the position coordinates of the monitored object recorded in the database is generated.

22. The radio wave monitoring system includes:

7. A radio wave monitoring system according to claim 1, further comprising a database for recording the frequency bands to be monitored, wherein if radio waves in the frequency band ω1 recorded in the database cannot be detected but radio waves in the frequency band ω2 can be detected, an updated value for the frequency band recorded in the database is generated.

23. 9. A ground facility provided in the radio wave monitoring system according to claim 8, which controls each satellite constellation so that the satellite constellation flying within the pointing change range forms the satellite formation.

24. A radio wave monitoring method used in the radio wave monitoring system according to claim 8, A radio wave monitoring method in which the ground equipment controls each satellite constellation so that the satellite constellation flying within the pointing change range forms the satellite formation.

25. 7. A satellite constellation formed by the radio wave monitoring system according to claim 1, wherein the satellite constellation flies so as to form the satellite formation within the pointing change range.

26. 7. A radio wave monitoring method used in the radio wave monitoring system according to claim 1, wherein the satellite constellation flies to form the satellite formation.

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