Monitoring and control equipment, satellites, and ground equipment

Abstract

To continuously monitor an object region by one artificial satellite.SOLUTION: A monitoring control device 110 is mounted on an artificial satellite 101 going around an orbit. The orbit is an elliptic orbit and an inclined orbit. The artificial satellite 101 includes a monitoring device 102 for monitoring a monitoring object, and a propulsion device 103 for changing speed of the artificial satellite 101. The monitoring control device 110 controls the propulsion device 103 while the artificial satellite 101 goes around the orbit, and thereby allows the artificial satellite 101 to fly in the sky over the monitoring object at a far point of the orbit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a system for monitoring objects on Earth or in outer space from space. [Background technology]

[0002] Systems are known in which regions of interest on Earth are monitored by satellites orbiting the Earth. Patent Document 1 discloses a system for observing a target area using a constellation of observation satellites orbiting the Earth. The cost of building a system increases as the number of satellites used increases. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-126876 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure aims to enable continuous monitoring of a target area using a single satellite. [Means for solving the problem]

[0005] The monitoring control device of the present disclosure includes: A monitoring and control device mounted on an orbiting artificial satellite, the orbit is an elliptical orbit and an inclined orbit, The artificial satellite a monitoring device for monitoring a monitoring target; a propulsion device for varying the velocity of the satellite; The monitoring and control device includes: The propulsion device is controlled while the satellite is orbiting the orbit, causing the satellite to fly over the monitored object at the apogee of the orbit. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to continuously monitor a target area using a single satellite. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a configuration diagram of a monitoring system 100 and a ground facility 140 according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing an orbit 122 according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing the relationship between satellite velocity and satellite altitude in the first embodiment. [Figure 4] FIG. 3 is a diagram showing the relationship between an orbit 122 and a monitoring time according to the first embodiment. [Figure 5] FIG. 3 is a diagram showing changes in satellite altitude in the first embodiment. [Figure 6] FIG. 11 is a diagram showing the relationship between the orbit 122 and the monitoring time in the second embodiment. [Figure 7] FIG. 10 is a diagram showing changes in satellite altitude in the second embodiment. [Figure 8] FIG. 11 is a diagram showing the relationship between the orbit 122 and the monitoring time in the third embodiment. [Figure 9] FIG. 11 is a diagram showing changes in satellite altitude in the third embodiment. [Figure 10] FIG. 11 is a diagram showing the relationship between the orbit 122 and the monitoring time in the fourth embodiment. [Figure 11] FIG. 11 is a diagram showing changes in satellite altitude in the fourth embodiment. [Figure 12] FIG. 13 is a diagram showing the relationship between the orbit 122 and the monitoring time in the fifth embodiment. [Figure 13] FIG. 12 is a diagram showing the relationship between an orbit 122, an artificial satellite 101, and the sun 123 in the fifth embodiment. [Figure 14] FIG. 13 is a diagram showing the relationship between the orbit 122 and the monitoring time in the fifth embodiment. [Figure 15] FIG. 20 is a diagram showing the configuration of a satellite constellation 130 according to a seventh embodiment. [Figure 16]FIG. 20 is a diagram showing the configuration of a satellite constellation 130 according to a seventh embodiment. [Figure 17] FIG. 20 is a diagram showing the movement of a satellite constellation 130 in the seventh embodiment. [Figure 18] FIG. 20 is a diagram showing the movement of a satellite constellation 130 in the seventh embodiment. [Figure 19] FIG. 20 is a diagram showing the movement of a satellite constellation 130 in the seventh embodiment. [Figure 20] 13 is a graph showing the relationship between orbital altitude and latitude in the seventh embodiment. [Figure 21] FIG. 20 is a diagram showing an orbit 122 according to the eighth embodiment. [Figure 22] FIG. 20 is a diagram showing an orbit 122 according to the ninth embodiment. [Figure 23] FIG. 22 is a diagram showing an orbit 122 in the tenth embodiment. [Figure 24] FIG. 22 is a diagram showing an orbit 122 in the eleventh embodiment. [Figure 25] FIG. 22 is a diagram showing an orbit 122 in the eleventh embodiment. [Figure 26] FIG. 22 is a diagram showing an orbit 122 in the eleventh embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the embodiments and drawings, the same or corresponding elements are denoted by the same reference numerals, and the description of elements denoted by the same reference numerals as elements already described will be omitted or simplified as appropriate.

[0009] Embodiment 1 The monitoring system 100 will be described with reference to FIGS. The monitoring system 100 is a system for monitoring targets such as terrestrial features or objects in outer space from space, with a high degree of freedom in the monitoring time period and under favorable observation conditions.

[0010] In the first embodiment, values ​​such as time, altitude, distance, and number of laps are approximate values.

[0011] ***Configuration Description*** The configuration of a monitoring system 100 will be described with reference to FIG. The monitoring system 100 is realized by an artificial satellite 101. The number of artificial satellites 101 may be plural. The artificial satellite 101 includes a monitoring device 102, a propulsion device 103, a communication device 104, an attitude control device 105, a power supply device 106, and the like. The monitoring device 102 is mounted on the artificial satellite 101 and monitors the monitoring target. Specifically, the monitoring device 102 is a visible optical sensor or an infrared optical sensor. However, the monitoring device 102 may also be a synthetic aperture radar (SAR) or other device. "Monitoring" may also be read as "observation" or "photography." The propulsion device 103 is mounted on the satellite 101 and changes the speed of the satellite 101. Specifically, the propulsion device 103 is an electric propulsion device. For example, the propulsion device 103 is an ion engine or a Hall thruster. The communication device 104 is mounted on the artificial satellite 101 and communicates monitoring data and the like. The monitoring data is data obtained by monitoring performed by the monitoring device 102. The monitoring data corresponds to an image showing a monitoring target. The attitude control device 105 is installed on the satellite 101 and controls attitude elements such as the attitude of the satellite 101, the angular velocity of the satellite 101, and the line of sight of the monitoring device 102. The attitude control device 105 changes each attitude element to a desired direction. Alternatively, the attitude control device 105 maintains each attitude element in a desired direction. The attitude control device 105 includes an attitude sensor, an actuator, and a controller. For example, the attitude sensor is a gyroscope, an earth sensor, a sun sensor, a star tracker, a thruster, a magnetic sensor, etc. For example, the actuator is an attitude control thruster, a momentum wheel, a reaction wheel, a control moment gyro, etc. For example, the controller controls the actuator by executing a control program based on measurement data from the attitude sensor or a control command from the ground equipment 140. The power supply device 106 includes a solar cell, a battery, a power control device, and the like, and supplies power to each device mounted on the artificial satellite 101 .

[0012] The satellite 101 further includes a monitor and control device 110 . The monitoring and control device 110 is mounted on the artificial satellite 101. The monitoring and control device 110 controls the propulsion device 103, the monitoring device 102, and the attitude control device 105 so that the monitoring device 102 can monitor the target under favorable monitoring conditions for as long as possible. For example, the monitoring and control device 110 performs various controls by executing a control program based on control commands from the ground equipment 140. For example, the monitoring and control device 110 is a computer.

[0013] The monitoring and control device 110 includes a processing circuit 111 . The processing circuitry 111 may be dedicated hardware or a processor that executes a program stored in a memory. The processing circuitry 111 functions as a monitoring control unit that controls the propulsion device 103. In the processing circuit 111, some functions may be realized by dedicated hardware and the remaining functions may be realized by software or firmware, i.e., the processing circuit 111 may be realized by hardware, software, firmware, or a combination thereof. Dedicated hardware may be, for example, a single circuit, a complex circuit, 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.

[0014] The pointing function of the satellite 101 will now be described. The artificial satellite 101 has a pointing function for directing the monitoring direction of the monitoring device 102 toward a monitoring target. The pointing function is a function for changing the monitoring direction. For example, the satellite 101 is equipped with a reaction wheel. The reaction wheel is a device for controlling the attitude of the satellite 101. By controlling the attitude of the satellite 101 with the reaction wheel, body pointing is realized. For example, the monitoring device 102 includes a pointing mechanism. The pointing mechanism is a mechanism for changing the monitoring direction. For example, a drive mirror or the like is used for the pointing mechanism.

[0015] The monitoring function of the monitoring device 102 will now be described. The monitoring device 102 has a variable resolution function and an autofocus function. The variable resolution function is a function for changing the resolution. The autofocus function is a function for adjusting the focus.

[0016] The configuration of the ground facility 140 will be described with reference to FIG. The ground facility 140 includes a communication device 141 and a satellite control device 142, and controls the satellite 101 by communicating with the satellite 101. For example, the ground facility 140 controls the monitor and control device 110 of the satellite 101. The satellite control device 142 is a computer that generates various commands for controlling the artificial satellite 101, and includes hardware such as a processing circuit and an input / output interface. The processing circuit generates the various commands. An input device and an output device are connected to the input / output interface. The satellite control device 142 is connected to the communication device 141 via the input / output interface. The communication device 141 communicates with the artificial satellite 101. Specifically, the communication device 141 transmits various commands to the artificial satellite 101. The communication device 141 also receives monitoring data transmitted from the artificial satellite 101. The satellite control device 142 processes the monitoring data.

[0017] ***Explanation of Operation*** The operation of the satellite 101 and the operation of the monitor and control device 110 will be described with reference to FIG. Satellite 101 orbits Earth 120 . The orbit in which the artificial satellite 101 goes around the Earth 120 is called an orbit 122. The orbit 122 will be described later.

[0018] A case will be described where the monitoring target is an object present in the target area 121. Monitoring the target area 121 corresponds to monitoring the monitoring target. However, the monitoring target may also be an object present in outer space. The monitor and control device 110 adjusts the relative position of the satellite 101 with respect to the target area 121 during the target time period so that the time during which the satellite 101 flies above the target area 121 is extended. The target area 121 is an area to be monitored. For example, the target area 121 is Japan. The target time period is a time period during which the target area 121 is monitored. For example, the target time period is daytime.

[0019] Specifically, the monitor and control device 110 controls the propulsion device 103 while the satellite 101 orbits the Earth 120 . For example, the monitor and control device 110 instructs the propulsion device 103 to increase or decrease the thrust, and the propulsion device 103 increases or decreases the thrust in accordance with the instruction, resulting in the satellite 101 speeding up or slowing down. For example, the monitoring and control device 110 executes a monitoring and control program to input predetermined control signals to the propulsion device 103 and the like at predetermined times. Alternatively, the monitoring and control device 110 receives control data from ground equipment via the communication device 104 and inputs control signals to the propulsion device 103 and the like in accordance with the control data from the ground equipment. For example, the monitor and control device 110 controls the direction, amount, and duration of propellant injection by the propulsion device 103.

[0020] Various parameters of the artificial satellite 101 are changed under the control of the monitor and control device 110. For example, parameters such as the satellite altitude or the increase / decrease of thrust are changed.

[0021] The relationship between satellite velocity and satellite altitude will be explained based on Figure 3. The black circle inside the Earth 120 represents the North Pole. When the flight speed of the artificial satellite 101 increases, the altitude of the artificial satellite 101 increases. When the altitude of the artificial satellite 101 increases, the speed of the artificial satellite 101 relative to the ground decreases. When the flight speed of the artificial satellite 101 decreases, the altitude of the artificial satellite 101 decreases. When the altitude of the artificial satellite 101 decreases, the speed of the artificial satellite 101 above the ground increases.

[0022] The orbit 122 and the monitoring will be described with reference to FIG. The times indicated on Earth 120 are Japan Standard Time (JST). The time stamped on the orbit 122 is JST when the satellite 101 passes by. The dotted arrow indicates the flight range of Satellite 101 during the time period when Japan is visible.

[0023] The orbit 122 is a circular orbit above the equator. For example, the artificial satellite 101 flies in the orbit 122 in a phase where the artificial satellite 101 crosses directly below the sun at noon. The altitude of orbit 122 is 20,000 kilometers. The revolution period of the orbit 122 is half a day, or 12 hours. The artificial satellite 101 makes two revolutions around the orbit 122 per day.

[0024] The monitoring device 102 continuously monitors Japan from 9:00 to 15:00, ie, for six daytime hours. Based on current technological advances, it is expected that telescopes with a geostationary orbit nadir resolution (GSD) of around 5 meters will be realized in the future. Furthermore, by imaging the same monitored object multiple times and applying super-resolution technology, it is expected that the resolution will be improved to around 3 meters. If this is done, and the GSD improvement effect due to differences in orbital altitude is considered, the GSD will be between 2.8 meters and 10 meters, and the resolution will be 1.7 meters or higher.

[0025] The relationship between satellite altitude and time will be explained based on FIG. The shading represents the sunshine or shade conditions of the target area 121. The dashed lines indicate the altitude of the artificial satellite 101 at each time.

[0026] The speed of the satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, so that the satellite 101 completes two revolutions around the orbit 122 per day. The average satellite altitude is high during the day, and after sunset, the satellite 101 decelerates and the satellite altitude decreases. Before sunrise, the satellite 101 accelerates, and the satellite altitude increases by sunrise. The higher the satellite altitude, the slower the ground speed, so the daytime monitoring time is extended.

[0027] ***Supplement to the first embodiment*** A supplementary explanation about the monitoring and controlling device 110 is as follows: "Ground speed" is the orbital speed of the artificial satellite 101 relative to the rotation speed of the Earth 120. The monitor and control device 110 controls the propulsion device 103 so that the satellite 101 decelerates. The orbital altitude of the satellite 101 decreases as the satellite 101 decelerates. The ground speed of the satellite 101 increases as the orbital altitude decreases. The satellite 101 moves eastward relative to the monitored object due to its increased ground speed. The monitoring control device 110 operates the monitoring device 102 after the artificial satellite 101 starts to move eastward relative to the monitored object.

[0028] The monitor and control device 110 controls the propulsion device 103 so that the satellite 101 accelerates. The orbital altitude of the satellite 101 increases as the satellite 101 accelerates. The ground speed of the satellite 101 decreases as the orbital altitude increases. The satellite 101 moves westward relative to the target due to its reduced ground speed. The monitoring control device 110 operates the monitoring device 102 after the artificial satellite 101 starts to move westward relative to the monitored object.

[0029] The monitor and control device 110 adjusts the orbital period of the satellite 101 by decelerating the satellite 101 and accelerating the satellite 101 . The monitoring device 102 operates at an arbitrary timing during the eastward movement of the artificial satellite 101 and at an arbitrary timing during the westward movement of the artificial satellite 101. Then, the average orbital period of the artificial satellite 101 is adjusted.

[0030] The monitoring and control device 110 maintains the average relative position of the satellite 101 with respect to the monitored object by decelerating the satellite 101 and accelerating the satellite 101 . The monitoring device 102 operates at any timing during the eastward movement of the artificial satellite 101 and at any timing during the westward movement of the artificial satellite 101. The average relative position of the artificial satellite 101 with respect to the monitored object is maintained.

[0031] The monitoring and control device 110 controls the propulsion device 103 to adjust the relative position of the satellite 101 with respect to the monitored object. The time period during which the monitoring device 102 monitors the monitoring target (monitoring time period) is changed by adjusting the relative position. The time (monitoring time) that the artificial satellite 101 flies over the monitoring target is extended by adjusting the relative position.

[0032] ***Effects of the First Embodiment*** Even if electric propulsion is not used, if the satellite 101 flies in a phase where it crosses directly below the sun at noon, it will be possible to monitor the target area 121 from 9:00 to 15:00, i.e., for six daytime hours. The first embodiment enables a further extension of the monitoring time. In addition, since the altitude of the artificial satellite 101 above the ground is 0.6 times that of a geostationary orbit satellite, the resolution of the monitoring device 102 is improved by 1.8 times compared to the resolution of a monitoring device for a geostationary orbit satellite.

[0033] The line of sight vector, i.e., the monitoring direction, can be changed by controlling the pointing function of the artificial satellite 101. Therefore, the target area 121 can be gazed at or the target area 121 can be changed.

[0034] As seen from the target area 121, the distance (ground distance) from the artificial satellite 101 to the target area 121 changes as the artificial satellite 101 rises above the horizon, passes over the sky, and sets below the horizon. When the artificial satellite 101 flies near the horizon, the ground distance is short and the skew angle is shallow. When the artificial satellite 101 passes over the sky, the ground distance is long and the skew angle is deep. By controlling the monitoring function of the monitoring device 102 according to the ground distance, monitoring can be performed under optimal monitoring conditions according to the ground distance.

[0035] ***Summary of the first embodiment*** The monitor and control device 110 is mounted on the artificial satellite 101 . The satellite 101 includes a monitoring device 102 for monitoring a target area 121 and a propulsion device 103 for varying the speed of the satellite 101 . The monitoring control device 110 adjusts the relative position of the satellite 101 with respect to the target area 121 during the target time period by controlling the propulsion device 103 while the satellite 101 is orbiting the circular orbit 122. The monitoring time during which the satellite 101 flies above the target area 121 is extended by adjusting the relative position.

[0036] Orbit 122 is a circular orbit above the equator at an altitude of 20,000 kilometers. The artificial satellite 101 makes two revolutions around the earth's orbit 122 per day.

[0037] The monitor and control device 110 accelerates the satellite 101 before the target time period, thereby increasing the altitude of the satellite 101 during the target time period. The monitoring time is extended by the speed (ground speed) of the satellite 101 relative to the target area 121 decreasing as the altitude of the satellite 101 increases.

[0038] The satellite 101 has a pointing function. The monitoring control device 110 controls the pointing function to direct the monitoring direction of the monitoring device 102 toward the target area 121 .

[0039] The monitoring device 102 has a variable resolution function. The monitoring control device 110 adjusts the resolution of the monitoring device 102 by controlling the monitoring device 102 in accordance with changes in the distance from the artificial satellite 101 to the target area 121 .

[0040] Embodiment 2 The monitoring system 100 will be described with reference to FIGS. 6 and 7, focusing mainly on the differences from the first embodiment.

[0041] In the second embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0042] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0043] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0044] The orbit 122 and the monitoring will be described with reference to Fig. 6. Fig. 6 can be viewed in the same way as Fig. 4. The orbit 122 is a circular orbit above the equator. For example, the artificial satellite 101 flies in the orbit 122 in a phase where the artificial satellite 101 crosses directly below the sun at noon. Orbit 122 is at an altitude of 14,000 kilometers. The revolution period of the orbit 122 is eight hours. The artificial satellite 101 makes three revolutions around the orbit 122 per day.

[0045] The monitoring device 102 continuously monitors Japan from 10:00 to 14:00, ie, for four daytime hours. When converted based on the GSD improvement effect due to differences in orbital altitude, the GSD will be between 1.9 meters and 7 meters, and the resolution will be 1.2 meters or more.

[0046] The relationship between satellite altitude and time will be explained based on Figure 7. The way to read Figure 7 is the same as that for Figure 5. The speed of the satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, so that the satellite 101 completes three revolutions around the orbit 122 per day. The average satellite altitude is high during the day, and after sunset, the satellite 101 decelerates and the satellite altitude decreases. Before sunrise, the satellite 101 accelerates, and the satellite altitude increases by sunrise. The higher the satellite altitude, the slower the ground speed, so the daytime monitoring time is extended.

[0047] ***Effects of the Second Embodiment*** Even if electric propulsion is not used, if the satellite 101 flies in a phase where it crosses directly below the sun at noon, it will be possible to monitor the target area 121 from 10:00 to 14:00, i.e., for four hours during the day. The second embodiment enables a further extension of the monitoring time. In addition, since the altitude of the artificial satellite 101 above the ground is 0.4 times that of a geostationary orbit satellite, the resolution of the monitoring device 102 is improved by 2.6 times compared to the resolution of a monitoring device for a geostationary orbit satellite.

[0048] ***Features of the Second Embodiment*** Orbit 122 is a circular orbit above the equator at an altitude of 14,000 kilometers. The artificial satellite 101 orbits the earth's orbit 122 three times a day.

[0049] Embodiment 3 The monitoring system 100 will be described with reference to FIGS. 8 and 9, focusing mainly on the differences from the first embodiment.

[0050] In the third embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0051] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0052] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0053] The orbit 122 and the monitoring will be described with reference to Fig. 8. Fig. 8 can be viewed in the same way as Fig. 4. The orbit 122 is a circular orbit above the equator. The artificial satellite 101 flies in the orbit 122 in a phase where the artificial satellite 101 crosses directly below the sun at noon. The altitude of orbit 122 is 10,000 kilometers. The revolution period of the orbit 122 is six hours. The artificial satellite 101 makes four revolutions around the orbit 122 per day.

[0054] The monitoring device 102 continuously monitors Japan from 10:30 to 13:30, ie, for three daytime hours. When converted based on the GSD improvement effect due to differences in orbital altitude, the GSD will be between 1.5 meters and 5 meters, and the resolution will be 0.9 meters or more.

[0055] The relationship between satellite altitude and time will be explained based on Figure 9. The way to read Figure 9 is the same as that for Figure 5. The speed of the satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, so that the satellite 101 completes four orbits per day. The average satellite altitude is high during the day, and after sunset, the satellite 101 decelerates and the satellite altitude decreases. Before sunrise, the satellite 101 accelerates, and the satellite altitude increases by sunrise. The higher the satellite altitude, the slower the ground speed, so the daytime monitoring time is extended.

[0056] ***Effects of the Third Embodiment*** Even if electric propulsion is not used, if the satellite 101 flies in a phase where it crosses directly below the sun at noon, it will be possible to monitor the target area 121 from 10:30 to 13:30, i.e., for three daytime hours. The third embodiment enables a further extension of the monitoring time. In addition, since the altitude of the artificial satellite 101 above the ground is 0.3 times that of a geostationary orbit satellite, the resolution of the monitoring device 102 is improved by 3.6 times compared to the resolution of a monitoring device for a geostationary orbit satellite.

[0057] ***Features of the Third Embodiment*** Orbit 122 is a circular orbit above the equator at an altitude of 10,000 kilometers. The artificial satellite 101 flies in a phase where it crosses directly below the sun at noon, and makes four orbits in a circular orbit 122 per day.

[0058] Embodiment 4 The monitoring system 100 will be described with reference to FIGS. 10 and 11, focusing mainly on the differences from the first embodiment.

[0059] In the fourth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0060] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0061] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0062] The orbit 122 and the monitoring will be described with reference to Fig. 10. Fig. 10 can be viewed in the same way as Fig. 4. The orbit 122 is a circular orbit above the equator. The artificial satellite 101 flies in the orbit 122 in a phase where the artificial satellite 101 crosses directly behind the Earth 120 at noon. The altitude of orbit 122 is 10,000 kilometers. The revolution period of the orbit 122 is six hours, which means that the artificial satellite 101 completes four revolutions around the orbit 122 per day.

[0063] The monitoring device 102 continuously monitors Japan from 7:30 to 9:30 and from 14:30 to 16:30. In other words, the monitoring device 102 performs two consecutive two-hour periods of monitoring during the day. When converted based on the GSD improvement effect due to differences in orbital altitude, the GSD will be between 1.5 meters and 5 meters, and the resolution will be 0.9 meters or more.

[0064] The relationship between satellite altitude and time will be explained based on Figure 11. The way to read Figure 11 is the same as that for Figure 5. The speed of the satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, so that the satellite 101 completes four orbits per day. The average satellite altitude during the day is low, and after sunset, the satellite 101 accelerates and the satellite altitude rises. Before sunrise, the satellite 101 decelerates, and the satellite altitude drops by sunrise. The lower the satellite altitude, the higher the ground speed, so monitoring is possible with two orbits during the day. The (total) daytime monitoring time is extended. Even if the sun 123 is shining on the target area 121, the target area 121 cannot be monitored from the artificial satellite 101 while the artificial satellite 101 is positioned below the horizon. Therefore, the continuous monitoring time per session is shorter than the continuous monitoring time in the third embodiment.

[0065] ***Effects of the Fourth Embodiment*** Even assuming that electric propulsion is not used, if the satellite 101 flies in a phase where it crosses directly behind the Earth 120 at noon, it will be possible to monitor it twice: for two hours from 7:30 to 9:30 and for two hours from 14:30 to 16:30. The fourth embodiment enables monitoring twice in two time periods close to noon. In addition, since the altitude of the artificial satellite 101 above the ground is 0.3 times that of a geostationary orbit satellite, the resolution of the monitoring device 102 is improved by 3.6 times compared to the resolution of a monitoring device for a geostationary orbit satellite.

[0066] ***Features of the Fourth Embodiment*** Orbit 122 is a circular orbit above the equator at an altitude of 10,000 kilometers. The artificial satellite 101 flies in a phase that crosses directly behind the Earth 120 at noon, and makes four orbits in a circular orbit 122 per day.

[0067] The monitor and control device 110 decelerates the satellite 101 before the target time slot, thereby lowering the altitude of the satellite 101 during the target time slot. The number of revolutions of the artificial satellite 101 during the target time period will be two or more because the ground speed of the artificial satellite 101 increases as the altitude of the artificial satellite 101 decreases. The monitoring time is extended by making two or more orbits of the satellite during the target time period.

[0068] Embodiment 5. The monitoring system 100 will be described with reference to FIGS. 12 to 14, focusing mainly on the differences from the first embodiment.

[0069] In the fifth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0070] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0071] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0072] The orbit 122 and the monitoring will be described below. The orbit 122 is a sun-synchronous, inclined, circular orbit. That is, the orbit 122 is a sun-synchronous, inclined, and circular orbit. The artificial satellite 101 is a satellite that flies in a sun-synchronous orbit (a sun-synchronous satellite). The orbital inclination angle of the circular orbit 122 is equal to or greater than 30 degrees and equal to or less than 60 degrees. Orbit 122 is an orbit at 12:00 LST, where LST stands for Local Standard Time. The artificial satellite 101 flies at the northernmost point of the circular orbit 122 at the timing when the local time in the target area 121 is 12 o'clock. The number of revolutions of the artificial satellite 101 per day is an integral number. The monitoring control device 110 controls the pointing function, thereby satisfying the condition that the target area 121 is visible for 10 minutes or more.

[0073] A specific example of an orbit 122 will be described with reference to Fig. 12. Fig. 12 can be viewed in the same way as Fig. 4. However, each time shown in Fig. 12 is local standard time (LST) in the target area 121. The orbital altitude is 5,144 kilometers. The orbital inclination is 141.6 degrees. The orbital period is 3.4 hours. The artificial satellite 101 makes seven revolutions around the circular orbit 122 per day. The monitoring area extends from plus 38 degrees north latitude to minus 38 degrees north latitude. The monitoring device 102 continuously monitors the target area 121 for 0.75 hours from 7:45 to 8:30, 1.5 hours from 11:15 to 12:45, and 0.75 hours from 15:30 to 16:15. In other words, the monitoring device 102 performs continuous monitoring for 10 minutes or more about three times during the day, and monitors the target area 121 for about three hours during the day. However, when the target area 121 is Japan, it is not necessarily the case that the artificial satellite 101 in the orbital plane happens to be flying over Japan. Therefore, the time period during which Japan can be monitored may be earlier or later than the time mentioned above.

[0074] If the phase position of the satellite 101 in the orbital plane is far from the target area 121, the monitoring conditions for the target area 121 are poor even if the sunshine conditions of the orbital plane are maintained. Therefore, the monitoring control device 110 controls the thrust of the propulsion device 103 to bring the phase position of the satellite 101 closer to the target area 121, in order to enable monitoring of the target area 121 under favorable conditions. Thereafter, the monitoring control device 110 controls the thrust of the propulsion device 103 in the direction opposite to the controlled thrust direction. This maintains average orbital conditions, thereby maintaining sun-synchronous conditions. This allows monitoring to continue.

[0075] A supplementary explanation about the orbit 122 will be provided. The number of revolutions of the artificial satellite 101 depends on the satellite altitude, so once the number of revolutions is determined, the satellite altitude is uniquely determined. For example, if the satellite 101 orbits seven times per day, the satellite altitude is 5,144 kilometers. The sun-synchronous condition is caused by the uneven distribution of gravity due to the flat shape of the Earth 120, and is uniquely determined based on the correlation between the satellite altitude and the orbital inclination. If the satellite altitude is 5,144 km, an orbit with an inclination of 141.6 degrees is a sun-synchronous orbit. When the orbital inclination angle is 141.6 degrees, the orbital plane is inclined 38.4 degrees (=180-141.6) from the equator, so the artificial satellite 101 flies in a latitude range from plus 38 degrees to minus 38 degrees relative to the Earth 120. The monitoring control device 110 controls the monitoring direction in the latitudinal direction, which enables the monitoring device 102 to monitor the Earth 120 within the latitude range from plus 60 degrees to minus 60 degrees. If the orbit 122 has a solar incidence angle of 12:00 LST, the northern hemisphere is always illuminated in the orbital plane of the orbit 122. The artificial satellite 101 flies above 38 degrees north latitude at the northernmost end of the orbit 122.

[0076] Based on Figure 13, we will provide additional information about monitoring. Monitoring can be performed under optimal conditions if the target area 121 on Earth 120 is in sunlight, the latitude of the northernmost point in orbit 122 is close to the latitude of the target area 121, and the artificial satellite 101 passes over the target area 121.

[0077] The orbit 122 may be an elliptical orbit having an eccentricity, instead of a circular orbit. Even if the orbit 122 is an elliptical orbit, it is possible to realize the artificial satellite 101 that satisfies the sun-synchronous condition.

[0078] ***Effects of the Fifth Embodiment*** In a sun-synchronous orbit, the angle of incidence of sunlight with respect to the orbital plane is maintained approximately constant regardless of time or season. For example, if the purpose is to monitor an area around 40 degrees latitude, if the orbital plane is set so that the artificial satellite 101 flies directly above the target area 121 at 12 o'clock, it will be possible to maintain an orbit in which the artificial satellite 101 stays near 40 degrees north latitude during sunshine. Since the altitude of the artificial satellite 101 above the ground is 0.14 times that of the geostationary orbit satellite, the resolution of the monitoring device 102 is improved by 7 times compared to the resolution of the monitoring device for the geostationary orbit satellite. The monitoring devices of geostationary orbit satellites monitor the area around 40 degrees north latitude with a diagonal view, resulting in a decrease in resolution. However, the monitoring device 102 can view the area around 40 degrees north latitude directly below, so the resolution does not decrease.

[0079] ***Description of Example*** An example of the orbit 122 will be described with reference to FIG. Orbit 122 is at an altitude of 4,163 kilometers. The inclination of the circular orbit 122 is 125 degrees. The artificial satellite 101 orbits the earth's orbit 122 eight times a day. This allows the satellite 101 to fly in an orbital plane ranging from plus 55 degrees north latitude to minus 55 degrees north latitude. It is then possible to continuously monitor the target area 121 for 0.75 hours from 8:15 to 9:00, 1.5 hours from 11:15 to 12:45, and 0.75 hours from 15:00 to 15:45. In other words, it is possible to perform continuous monitoring for 10 minutes or more three times during the day, for a total of about three hours of monitoring.

[0080] If it is not necessary that the number of revolutions per day be an integer, the orbit 122, which is a sun-synchronous orbit, can be realized by the following combination. Note that it is assumed that the orbit 122 is a circular orbit. (1) The orbital altitude is 4,000 kilometers. The orbital inclination is 123 degrees. Artificial satellite 101 flies between latitudes of plus 57 degrees and minus 57 degrees. Artificial satellite 101 orbits 122 eight times a day. Artificial satellite 101 orbits 122 once every three hours. (2) The orbital altitude is 4,500 kilometers. The orbital inclination is 130 degrees. The artificial satellite 101 flies within a range of latitude from plus 50 degrees to minus 50 degrees. The artificial satellite 101 makes seven to eight orbits in the orbit 122 per day. The artificial satellite 101 makes one orbit in the orbit 122 every three to four hours. (3) The orbital altitude is 5,000 kilometers. The orbital inclination is 139 degrees. The artificial satellite 101 flies between latitudes of plus 41 degrees and minus 41 degrees. The artificial satellite 101 makes seven to eight orbits in the orbit 122 per day. The artificial satellite 101 makes one orbit in the orbit 122 every three to four hours. (4) The orbital altitude is 5,500 kilometers. The orbital inclination is 151 degrees. Artificial satellite 101 flies between latitudes of plus 29 degrees and minus 29 degrees. Artificial satellite 101 orbits 122 seven times a day. Artificial satellite 101 orbits 122 once every four hours. The orbital plane of the orbit 122 of (1) to (4) is the orbital plane at 12:00 LST, and its northernmost point is noon. However, since the artificial satellite 101 is not necessarily flying at the northernmost point at 12:00, the times when the artificial satellite 101 passes the northernmost point of the orbital plane will be around the same time.

[0081] ***Features of the Fifth Embodiment*** The monitoring system 100 includes an artificial satellite 101 that orbits an orbital orbit 122 an integer number of times per day. The orbit 122 is a sun-synchronous orbit, an inclined orbit, and a circular orbit. The artificial satellite 101 flies at the northernmost point of the circular orbit 122 at the timing when the local time in the target area 121 is 12 o'clock.

[0082] Embodiment 6 The monitoring system 100 will be described mainly focusing on the differences from the first embodiment.

[0083] In the sixth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0084] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0085] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0086] The circular orbit 122 will be described. The orbit 122 is a sun-synchronous inclined elliptical orbit. That is, the orbit 122 is both a sun-synchronous and inclined orbit. Furthermore, the orbit 122 is an elliptical orbit with a high eccentricity. The orbital altitude is 5,100 kilometers. The semi-major axis of its orbit is 11,478 kilometers. The eccentricity is 0.418. The orbital inclination is 121.88 degrees. The apogee altitude is 9,898 kilometers. The perigee altitude is 302 kilometers.

[0087] The orbit 122 is an orbit at 12:00 LST. The artificial satellite 101 flies at the perigee of the orbit 122 when the local time in the target region 121 is 12:00. The perigee of the orbit 122 is the northernmost point of the orbit 122.

[0088] ***Effects of the Sixth Embodiment*** When the artificial satellite 101 flies in the circular orbit 122, the condition that the target area 121 is visible for 10 minutes or more is met.

[0089] ***Features of the Sixth Embodiment*** The orbit 122 is a sun-synchronous orbit, an inclined orbit, and an elliptical orbit. The artificial satellite 101 flies through the perigee of the circular orbit 122 at the timing when the local time in the target area 121 is 12 o'clock.

[0090] Embodiment 7 The satellite constellation 130 will be described with reference to FIGS. 15 to 20, focusing mainly on the differences from the first embodiment.

[0091] In the seventh embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0092] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0093] The configuration of the satellite constellation 130 will be described with reference to FIGS. FIG. 15 shows the satellite constellation 130 as viewed normal to the orbital plane. Figure 16 shows the satellite constellation 130 as viewed from the orbital plane. For example, Figure 16 shows the satellite constellation 130 as viewed from above the equator. 17, 18 and 19 show how the major axis of the elliptical orbit of each of the artificial satellites (101A to 101C) rotates around the earth 120 in the orbital plane. Each of the artificial satellites (101A to 101C) is of the same type as the artificial satellite 101.

[0094] Each of the artificial satellites (101A to 101C) orbits in a sun-synchronous inclined elliptical orbit. Three satellites (101A-101C) maintain surveillance of the Northern Hemisphere during the day.

[0095] The orbits of the satellites (101A to 101C) are unfrozen orbits. That is, the orbit of each of the artificial satellites (101A to 101C) is not a frozen orbit, but rather the major axis rotates around the Earth 120 over time.

[0096] Three satellites (101A-101C) monitor a region of interest 121 on Earth 120, alternating from perigee, apogee, or midpoint. The midpoint is a point located between perigee and apogee. At perigee, short-term but high-resolution monitoring is possible. At apogee, long-term monitoring is possible, albeit at lower resolution.

[0097] The major axes of the three orbits are tilted at 120 degrees from each other in the circumferential direction around the Earth 120, i.e., in the latitudinal direction. In other words, the major axes of the three orbits are evenly spaced apart in the latitudinal direction. The major axis of each orbit rotates relative to the Sun 123, but the relative relationships between the three orbits are maintained.

[0098] The relative relationship between the normal direction and the solar incidence angle is maintained in all three orbits.

[0099] At 12 noon, the phase of each satellite (101A-101C) does not correlate with the latitude of the target area 121 on Earth 120.

[0100] One of the three satellites (101A to 101C) is capable of monitoring a target area 121 on the Earth 120. The three satellites can continuously monitor the target area 121.

[0101] When each of the artificial satellites (101A to 101C) passes over the target area 121 of the Earth 120 on the apogee side, each artificial satellite can monitor the target area 121 of the Earth 120 for a long period of time, although with low resolution. When each satellite passes over the target area 121 of the Earth 120 on the perigee side, each satellite can monitor the target area 121 of the Earth 120 for a short period of time but with high resolution.

[0102] Specific examples of the orbits of the satellites (101A to 101C) are as follows: The altitude of the circular orbit that forms the basis of the elliptical orbit is 5,100 kilometers. The eccentricity of the elliptical orbit is 0.418. The orbital inclination is 122 degrees. The apogee altitude is 9,898 kilometers. The perigee altitude is 302 kilometers.

[0103] Based on FIG. 20, the relationship between altitude and latitude for the orbit of each of the artificial satellites (101A to 101C) will be explained. The dotted line represents the orbit of the artificial satellite 101A, the dashed line represents the orbit of the artificial satellite 101B, and the broken line represents the orbit of the artificial satellite 101C.

[0104] "Ha" is the perigee altitude, and "Hc" is the normal perigee utilization altitude. The normal perigee utilization altitude is the altitude at which the target area 121 can be monitored from the perigee side by at least one of the three artificial satellites (101A to 101C). "Hb" is the apogee altitude, and "Hd" is the normal apogee utilization altitude. The normal apogee utilization altitude is the altitude at which the target area 121 can be monitored from the apogee side by at least one of the three artificial satellites (101A to 101C). Each utilization altitude (Hd, Hc) corresponds to the altitude of the intersection of the two orbits in the graph of FIG.

[0105] The length of time that each of the artificial satellites (101A to 101C) stays in the sky above the target area 121 is called the staying time of the artificial satellite. On the apogee side, each satellite stays for a long time and has a wide field of view. The utilization altitude Hb and the viewing angle of the monitoring device 102 are determined so that the target area 121 falls within the viewing range when each of the artificial satellites (101A to 101C) is flying at an altitude higher than the utilization altitude Hd. This allows the target area 121 to be monitored at all times. Since the time spent by each of the satellites (101A to 101C) on the perigee side is short, monitoring on the perigee side is not constant. However, no matter what latitude the target area 121 is located at, at least one of the satellites can monitor the target area 121 from an altitude lower than the utilization altitude Hc.

[0106] The resolution of the monitoring device 102 is determined so that a desired resolution is achieved at the utilization altitude Hc, which makes it possible to monitor the target area 121 with high resolution.

[0107] ***Effects of the Seventh Embodiment*** Three satellites (101A to 101C) alternately stay near the apogee for long periods of time, making constant monitoring possible. Of the three satellites, the one passing near the perigee will enable high-resolution observations.

[0108] ***Features of the Seventh Embodiment*** The satellite constellation 130 includes three artificial satellites (101A to 101C). The orbit 122 of each satellite is a sun-synchronous, inclined, and elliptical orbit. The three orbits 122 of the three satellites are arranged so that the major axes of the orbits are tilted at an angle of 120 degrees in the latitudinal direction.

[0109] Embodiment 8 The monitoring system 100 will be described with reference to FIG. 21, focusing mainly on the differences from the first embodiment.

[0110] In the eighth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0111] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0112] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0113] A specific example of the orbit 122 will be described with reference to Figure 21. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 7,000 km. The apogee altitude is 34,000 km. The orbital inclination ranges from 20 to 60 degrees. The orbital period is 12 hours. The artificial satellite 101 completes two revolutions around the earth's orbit 122 per day. In monitoring using apogee, the monitoring device 102 can monitor Japan for six hours from 9:00 to 15:00. The GSD is between 5 metres and 17 metres long.

[0114] ***Effects of the eighth embodiment*** It can continuously monitor the skies above target area 121 for six hours during the day. From an apogee at an altitude of 34,000 kilometers, it will be possible to view the target area 121 directly below. On the way from the horizon to the apogee and on the way from the apogee to the horizon, the farther the satellite 101 is from the apogee, the smaller the distance to the ground becomes, making high-resolution monitoring possible. It will be possible to continue monitoring the target area 121 with only one satellite 101 for six hours from 9:00 a.m. to 3:00 p.m., which is the time period often used for monitoring using visible light telescopes.

[0115] An orbital inclination of around 35 to 40 degrees is suitable for monitoring all of Japan, China, the Korean Peninsula, etc. On the other hand, an orbital inclination of around 50 degrees is suitable for monitoring major European countries, an orbital inclination of around 60 degrees is suitable for monitoring Northern Europe, and an orbital inclination of around 20 to 30 degrees is suitable for monitoring northern Africa, the Middle East, India, etc.

[0116] ***Features of the Eighth Embodiment*** The monitor and control device 110 is mounted on an artificial satellite 101 that orbits in an orbit 122 . The orbit 122 is an elliptical and inclined orbit. The monitoring and control device 110 controls the propulsion device 103 while the satellite 101 is orbiting the circular orbit 122 , thereby causing the satellite 101 to fly over the target area 121 at the apogee of the circular orbit 122 .

[0117] The perigee altitude of Orbit 122 is 7,000 kilometers. The apogee altitude of Orbit 122 is 34,000 kilometers. The artificial satellite 101 makes two revolutions around the earth's orbit 122 per day.

[0118] Embodiment 9 The monitoring system 100 will be described with reference to FIG. 22, focusing mainly on the differences from the first embodiment.

[0119] In the ninth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0120] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0121] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0122] A specific example of the orbit 122 will be described with reference to Fig. 22. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 4000 km. The apogee altitude is 25,000 kilometers. The orbital inclination ranges from 20 to 60 degrees. The orbital period is eight hours. The artificial satellite 101 makes three revolutions around the earth's orbit 122 per day. In monitoring using apogee, the monitoring device 102 can monitor Japan for four hours from 10:00 to 14:00. The GSD is between 3.4 metres and 12 metres.

[0123] ***Effects of the 9th embodiment*** It can continuously monitor the sky above target area 121 for four hours during the day. From an apogee at an altitude of 25,000 kilometers, it will be possible to view the target area 121 directly below. On the way from the horizon to the apogee and on the way from the apogee to the horizon, the farther the satellite 101 is from the apogee, the smaller the distance to the ground becomes, making high-resolution monitoring possible. The two satellites 101 will be able to continue monitoring the target area 121 for six hours, from 9:00 a.m. to 3:00 p.m., which is the time most often used for monitoring using visible light telescopes.

[0124] ***Features of the 9th embodiment*** The perigee altitude of Orbit 122 is 4,000 kilometers. The apogee altitude of orbit 122 is 25,000 kilometers. The artificial satellite 101 makes three revolutions around the earth's orbit 122 per day.

[0125] Embodiment 10 The monitoring system 100 will be described with reference to FIG. 23, focusing mainly on the differences from the first embodiment.

[0126] In the tenth embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0127] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0128] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0129] A specific example of the orbit 122 will be described with reference to Fig. 23. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 1,700 kilometers. The apogee altitude is 17,000 km. The orbital inclination ranges from 20 to 60 degrees. The orbital period is six hours. The artificial satellite 101 completes four revolutions around the circular orbit 122 per day. In monitoring using apogee, the monitoring device 102 can monitor Japan for two hours from 11:00 to 13:00. GSDs are between 2.6 metres and 9 metres tall.

[0130] ***Effects of the 10th embodiment*** It will be able to continuously monitor the skies above target area 121 for two hours during the day. From an apogee at an altitude of 17,000 kilometers, it will be possible to view the target area 121 directly below. On the way from the horizon to the apogee and on the way from the apogee to the horizon, the farther the satellite 101 is from the apogee, the smaller the distance to the ground becomes, making high-resolution monitoring possible. The three satellites 101 will be able to continue monitoring the target area 121 for six hours, from 9:00 a.m. to 3:00 p.m., which is the time most often used for monitoring using visible light telescopes.

[0131] ***Features of the 10th embodiment*** The perigee altitude of Orbit 122 is 1,700 kilometers. The apogee altitude of Orbit 122 is 17,000 kilometers. The artificial satellite 101 makes four revolutions around the earth's orbit 122 per day.

[0132] Embodiment 11 The monitoring system 100 will be described mainly with reference to FIGS. 24 to 26, focusing on the differences from the first embodiment.

[0133] In the eleventh embodiment, values ​​such as time, altitude, distance, or number of laps are approximate values.

[0134] ***Configuration Description*** The configuration of the monitoring system 100 is the same as the configuration in the first embodiment (see FIG. 1).

[0135] ***Explanation of Operation*** The basic operations of the satellite 101 and the monitor control device 110 are the same as those in the first embodiment (see FIGS. 2 and 3).

[0136] A specific example of the orbit 122 will be described with reference to Fig. 24. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 2000 km. The apogee altitude is 19,000 kilometers. The orbital period is six hours. The artificial satellite 101 completes four revolutions around the circular orbit 122 per day. In monitoring using perigee, the monitoring device 102 can monitor Japan for one hour from 11:30 to 12:30. The GSD is between 0.3 and 1.1 meters. The resolution is 0.2 meters or better.

[0137] A specific example of the orbit 122 will be described with reference to Figure 25. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 4000 km. The apogee altitude is 25,000 kilometers. The orbital period is eight hours. The artificial satellite 101 makes three revolutions around the earth's orbit 122 per day. In monitoring using perigee, the monitoring device 102 can monitor Japan for one hour from 11:30 to 12:30. The GSD is between 0.6 meters and 2.1 meters. The resolution is between 0.6 meters and 2.1 meters.

[0138] A specific example of the orbit 122 will be described with reference to Fig. 26. The solid curve drawn on the map represents the orbit 122. The orbit 122 is an inclined elliptical orbit. The perigee altitude is 7,000 km. The apogee altitude is 34,000 km. The orbital period is 12 hours. The artificial satellite 101 completes two revolutions around the earth's orbit 122 per day. In monitoring using perigee, the monitoring device 102 can monitor Japan for two hours from 11:00 to 13:00. The GSD is between 1 and 4 meters. The resolution is 0.6 meters or better.

[0139] ***Effects of Embodiment 11*** By having the monitoring device 102 monitor the target area 121 at perigee, monitoring with significantly higher resolution than stationary observation is possible. Satellite 101 will fly across the skies of Asia, including Japan and China, and will have the opportunity to visit Asia more than once during the day.

[0140] ***Features of the 11th embodiment*** The monitor and control device 110 is mounted on an artificial satellite 101 that orbits in an orbit 122 . The orbit 122 is an elliptical and inclined orbit. The monitoring and control device 110 controls the propulsion device 103 while the satellite 101 is orbiting the circular orbit 122 , thereby causing the satellite 101 to fly over the target area 121 at the perigee of the circular orbit 122 .

[0141] ***Supplementary explanation of implementation form*** Each embodiment is an example of a preferred embodiment and is not intended to limit the technical scope of the present disclosure. Each embodiment may be implemented in part or in combination with other embodiments. [Explanation of symbols]

[0142] 100 Monitoring system, 101 Satellite, 102 Monitoring equipment, 103 Propulsion unit, 104 Communication equipment, 105 Attitude control unit, 106 Power supply unit, 110 Monitoring control unit, 111 Processing circuit, 120 Earth, 121 Target area, 122 Orbit, 123 Sun, 130 Satellite constellation, 140 Ground equipment, 141 Communication equipment, 142 Satellite control equipment.

Claims

1. A monitoring and control device mounted on an orbiting artificial satellite, the orbit is an elliptical orbit and an inclined orbit, The orbit has a perigee altitude of about 7,000 kilometers, an apogee altitude of about 34,000 kilometers, an inclination angle of 20 degrees to 60 degrees, an orbital period of 12 hours, and the satellite completes two revolutions per day in the orbit; The satellite, surveillance equipment for monitoring targets including Japan; a propulsion device for varying the velocity of the satellite; It has a pointing function, The monitoring and control device includes: controlling the propulsion device while the satellite is orbiting the orbit to cause the satellite to fly over the monitored object at an apogee of the orbit; By controlling the pointing function, the monitoring direction of the monitoring device is directed toward the monitoring target, and the monitoring device is made to look directly down at the monitoring target; By making the monitoring device perform monitoring using the apogee, the monitoring target is continuously monitored for six hours from 9:00 AM to 3:00 PM with a nadir resolution of 5 meters or more and 17 meters or less from the apogee altitude. Monitoring and control equipment.

2. A monitoring and control device mounted on an orbiting artificial satellite, the orbit is an elliptical orbit and an inclined orbit, The perigee altitude of the orbit is about 7,000 kilometers, the apogee altitude of the orbit is about 34,000 kilometers, the orbital period is 12 hours, and the artificial satellite completes the orbit twice per day; The satellite, A surveillance device for monitoring Japan, which is the target of surveillance; a propulsion device for varying the velocity of the satellite; It has a pointing function, The monitoring and control device includes: controlling the propulsion device while the satellite is orbiting the orbit to fly the satellite across Asian skies during the day and over Japan at the perigee of the orbit; By controlling the pointing function, the monitoring direction of the monitoring device is directed toward Japan, By making the monitoring device perform monitoring using perigee, Japan is monitored for two hours from 11:00 to 13:00 with a nadir resolution of 1 meter to 4 meters from the perigee altitude. Monitoring and control equipment.

3. An artificial satellite comprising the monitoring and control device according to claim 1 or 2.

4. a ground facility that generates a control command for causing the monitoring and control device according to claim 1 or 2 to control the propulsion device, the pointing function, and the monitoring device, and transmits the control command to the artificial satellite; a satellite control device that generates the control commands; a communication device that transmits the control command to the satellite; Ground equipment equipped with:

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