Surveillance systems, satellites, and ground facilities

Abstract

To enable monitoring of a monitoring object from an artificial satellite.SOLUTION: A monitoring system 100 includes an artificial satellite 101 that revolves along an orbit an integer number of times per day. The orbit is a sun synchronous orbit, an inclined orbit, and a circular orbit. The artificial satellite 101 flies over a northernmost point of the orbit at a timing when a local time of a monitoring object is 12 o'clock. The artificial satellite 101 includes: a monitoring device 102 for monitoring the monitoring object; a pointing function for changing a monitoring direction of the monitoring device; and a monitoring control device 110 that directs the monitoring direction toward the monitoring object by controlling the pointing function.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A system for monitoring a target area on the Earth by an artificial satellite orbiting the Earth is known. Patent Document 1 discloses a system for observing an observation target area using a plurality of groups of observation satellites orbiting the Earth. The construction cost of the system increases as the number of artificial satellites used increases.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to enable monitoring of a monitoring target from an artificial satellite.

Means for Solving the Problems

[0006] The monitoring system of the present disclosure includes an artificial satellite that orbits the Earth an integer number of times per day. The aforementioned orbit is a sun-synchronous orbit, an inclined orbit, and a circular orbit. The aforementioned satellite flies to the northernmost point of its orbit at the moment when the local time of the monitored area becomes 12:00. The aforementioned artificial satellite, A monitoring device for monitoring the aforementioned target, A pointing function for changing the monitoring direction of the aforementioned monitoring device, The system includes a monitoring control device that directs the monitoring direction toward the object being monitored by controlling the pointing function. [Effects of the Invention]

[0007] According to this disclosure, it will be possible to monitor targets from satellites. [Brief explanation of the drawing]

[0008] [Figure 1] Configuration diagram of the monitoring system 100 and ground equipment 140 in reference form 1. [Figure 2] A diagram showing the orbital 122 in reference form 1. [Figure 3] A diagram showing the relationship between satellite velocity and satellite altitude in reference form 1. [Figure 4] A diagram showing the relationship between orbit 122 and monitoring time in reference form 1. [Figure 5] A diagram showing the change in satellite altitude in reference form 1. [Figure 6] A diagram showing the relationship between orbit 122 and monitoring time in reference form 2. [Figure 7] A diagram showing the change in satellite altitude in reference form 2. [Figure 8] A diagram showing the relationship between orbit 122 and monitoring time in reference form 3. [Figure 9] A diagram showing the change in satellite altitude in reference form 3. [Figure 10] A diagram showing the relationship between orbit 122 and monitoring time in reference form 4. [Figure 11] A diagram showing the change in satellite altitude in reference form 4. [Figure 12] Relationship diagram between the circular orbit 122 and the monitoring time in Embodiment 1. [Figure 13] Relationship diagram between the circular orbit 122, the artificial satellite 101, and the sun 123 in Embodiment 1. [Figure 14] Relationship diagram between the circular orbit 122 and the monitoring time in Embodiment 1. [Figure 15] Configuration diagram of the satellite constellation 130 in Reference Embodiment 6. [Figure 16] Configuration diagram of the satellite constellation 130 in Reference Embodiment 6. [Figure 17] Diagram showing the movement of the satellite constellation 130 in Reference Embodiment 6. [Figure 18] Diagram showing the movement of the satellite constellation 130 in Reference Embodiment 6. [Figure 19] Diagram showing the movement of the satellite constellation 130 in Reference Embodiment 6. [Figure 20] Graph showing the relationship between the orbital altitude and the latitude in Reference Embodiment 6. [Figure 21] Diagram showing the circular orbit 122 in Reference Embodiment 7. [Figure 22] Diagram showing the circular orbit 122 in Reference Embodiment 8. [Figure 23] Diagram showing the circular orbit 122 in Reference Embodiment 9. [Figure 24] Diagram showing the circular orbit 122 in Reference Embodiment 10. [Figure 25] Diagram showing the circular orbit 122 in Reference Embodiment 10. [Figure 26] Diagram showing the circular orbit 122 in Reference Embodiment 10. [[ID=S46]]

Mode for Carrying Out the Invention

[0009] Embodiment Reference form In the description and the drawings, the same elements or corresponding elements are denoted by the same reference numerals. The description of the elements denoted by the same reference numerals as those already described will be omitted or simplified as appropriate.

[0010] Reference Form 1 . The monitoring system 100 will be explained based on Figures 1 to 5. The monitoring system 100 is a system for monitoring targets such as Earth's geographical features or objects in outer space from space, with a high degree of flexibility in the monitoring time period and under favorable observation conditions.

[0011] Reference Form 1 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0012] ***Explanation of the structure*** The configuration of the monitoring system 100 will be explained based on Figure 1. The monitoring system 100 is implemented by artificial satellites 101. There may be multiple artificial satellites 101. The artificial satellite 101 is equipped with a monitoring device 102, a propulsion device 103, a communication device 104, an attitude control device 105, and a power supply device 106, among other things. The monitoring device 102 is mounted on the artificial satellite 101 and monitors the target of monitoring. Specifically, the monitoring device 102 is a visible optical sensor or an infrared optical sensor. However, the monitoring device 102 may be a synthetic aperture radar (SAR) or other device. "Monitoring" may be read as "observation" or "photography". The propulsion system 103 is mounted on the satellite 101 and changes the satellite's speed. Specifically, the propulsion system 103 is an electric propulsion system. For example, the propulsion system 103 is an ion engine or a Hall thruster. The communication device 104 is mounted on the artificial satellite 101 and transmits monitoring data, etc. The monitoring data is data obtained through monitoring performed by the monitoring device 102. The monitoring data corresponds to images of the monitored object. The attitude control device 105 is mounted on the satellite 101 and controls attitude elements such as the attitude of the satellite 101, its angular velocity, and the line of sight of the monitoring device 102. The attitude control device 105 changes each attitude element in a desired direction, or maintains each attitude element in a desired direction. The attitude control device 105 comprises attitude sensors, actuators, and a controller. For example, attitude sensors include gyroscopes, Earth sensors, solar sensors, star trackers, thrusters, and magnetic sensors. For example, actuators include attitude control thrusters, momentum wheels, reaction wheels, and control moment gyros. For example, the controller controls the actuators by executing a control program based on measurement data from the attitude sensors or control commands from ground equipment 140. The power supply unit 106 includes solar cells, a battery, and a power control device, and supplies power to each of the devices mounted on the artificial satellite 101.

[0013] The artificial satellite 101 is further equipped with a monitoring 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 system 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.

[0014] The monitoring and control device 110 includes a processing circuit 111. The processing circuit 111 may be dedicated hardware or a processor that executes a program stored in memory. The processing circuit 111 functions as a monitoring and control unit that controls the propulsion device 103. In the processing circuit 111, some functions may be implemented by dedicated hardware, while the remaining functions may be implemented by software or firmware. In other words, the processing circuit 111 can be implemented using hardware, software, firmware, or a combination thereof. Dedicated hardware includes, for example, single circuits, complex circuits, programmed processors, parallel programmed processors, ASICs, FPGAs, or combinations thereof. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array.

[0015] This section explains the pointing function of satellite 101. The satellite 101 is equipped with a pointing function for directing the monitoring direction of the monitoring device 102 toward the object being monitored. The pointing function is a function for changing the monitoring direction. For example, satellite 101 is equipped with reaction wheels. Reaction wheels are devices for controlling the attitude of satellite 101. Body pointing is achieved by controlling the attitude of satellite 101 with reaction wheels. For example, the monitoring device 102 includes a pointing mechanism. The pointing mechanism is a mechanism for changing the direction of monitoring. For example, a drive mirror or the like may be used for the pointing mechanism.

[0016] The monitoring function of the monitoring device 102 will now be explained. The monitoring device 102 has a variable resolution function and an autofocus function. The variable resolution function is a function that changes the resolution. Autofocus is a function that adjusts the focus.

[0017] Based on Figure 1, the configuration of the ground equipment 140 will be explained. Ground equipment 140 includes a communication device 141 and a satellite control device 142, and controls the artificial satellite 101 by communicating with it. For example, ground equipment 140 controls the monitoring and control device 110 of the artificial satellite 101. The satellite control system 142 is a computer that generates various commands for controlling the artificial satellite 101, and includes hardware such as processing circuits and input / output interfaces. The processing circuits generate various commands. Input devices and output devices are connected to the input / output interfaces. The satellite control system 142 is connected to the communication device 141 via the input / output interfaces. The communication device 141 communicates with the satellite 101. Specifically, the communication device 141 transmits various commands to the satellite 101. The communication device 141 also receives monitoring data transmitted from the satellite 101. The satellite control device 142 processes the monitoring data.

[0018] ***Explanation of operation*** Based on Figure 2, the operation of the artificial satellite 101 and the operation of the monitoring and control device 110 will be explained. Satellite 101 orbits the Earth at a 120-degree angle. The orbit in which artificial satellite 101 revolves around Earth 120 is called orbit 122. Orbit 122 will be described later.

[0019] This section describes the case where an object located in area 121 becomes the target of surveillance. Surveillance of area 121 is equivalent to surveillance of the target of surveillance. However, the target of surveillance may also be an object located in outer space. The monitoring and control device 110 adjusts the relative position of the artificial satellite 101 with respect to the target area 121 during the target time period so that the time the artificial satellite 101 is flying over the target area 121 is extended. Target region 121 is the region to be monitored. For example, target region 121 is Japan. The target time period is the time period during which the target area 121 is monitored. For example, the target time period is daytime.

[0020] Specifically, the monitoring and control device 110 controls the propulsion system 103 while the satellite 101 is orbiting the Earth 120. For example, the monitoring and control device 110 instructs the propulsion device 103 to increase or decrease thrust, and the propulsion device 103 increases or decreases thrust according to the instruction. As a result, the satellite 101 accelerates or decelerates. For example, the monitoring and control device 110 inputs a predetermined control signal to the propulsion device 103, etc., at a predetermined time by executing a monitoring and control program. 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, etc., according to the control data from the ground equipment. For example, the monitoring and control device 110 controls the direction, amount, and duration of propellant injection by the propulsion device 103.

[0021] The monitoring and control device 110 controls various parameters of the artificial satellite 101. For example, parameters such as satellite altitude or thrust acceleration / deceleration are changed.

[0022] Based on Figure 3, the relationship between satellite velocity and satellite altitude is explained. The black circle within the Earth 120 represents the North Pole. As the flight speed of satellite 101 increases, the altitude of satellite 101 increases. And as the altitude of satellite 101 increases, the speed of satellite 101 relative to the ground decreases. As the flight speed of satellite 101 decreases, the altitude of satellite 101 decreases. And as the altitude of satellite 101 decreases, the speed of satellite 101 above ground increases.

[0023] Based on Figure 4, we will explain the orbit 122 and the monitoring system. Each time displayed on Earth 120 is Japan Standard Time (JST). The time assigned to orbit 122 is JST (Japan Standard Time) when artificial satellite 101 passes over it. The dotted arrows indicate the flight range of satellite 101 during the time period when Japan is in its field of view.

[0024] Orbit 122 is a circular orbit above the equator. For example, when satellite 101 crosses directly beneath the sun at noon, satellite 101 is in orbit 122. The altitude of orbit 122 is 20,000 kilometers. The orbital period of orbit 122 is half a day, or 12 hours. Satellite 101 completes two orbits of orbit 122 per day.

[0025] The monitoring device 102 continuously monitors Japan for six hours during the daytime, from 9:00 to 15:00. Based on current technological advancements, it is anticipated that telescopes with a geostationary resolution (GSD) of approximately 5 meters will be realized in the future. Furthermore, it is anticipated that the resolution can be improved to approximately 3 meters by imaging the same target multiple times and applying super-resolution technology. In this case, when adjusted for the GSD improvement effect due to differences in orbital altitude, the GSD will be between 2.8 and 10 meters, and the resolution will be 1.7 meters or higher.

[0026] Based on Figure 5, the relationship between satellite altitude and time will be explained. The shaded areas represent the sunlight or shade conditions for the 121 target areas. The dashed line indicates the altitude of satellite 101 at each time point.

[0027] The speed of satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, allowing satellite 101 to orbit orbit 122 twice a day. During the day, the average satellite altitude is high, and after sunset, satellite 101 decelerates and its altitude decreases. Before sunrise, satellite 101 accelerates, and its altitude rises by sunrise. The higher the satellite altitude, the lower the ground velocity, so the daytime monitoring time is extended.

[0028] *** Reference Form 1 Supplement *** To elaborate on the monitoring and control device 110, "ground speed" is the orbital speed of the satellite 101 relative to the rotation speed of the Earth 120. The monitoring and control device 110 controls the propulsion system 103 so that the artificial satellite 101 decelerates. The orbital altitude of satellite 101 will decrease due to the deceleration of satellite 101. The ground velocity of satellite 101 increases as its orbital altitude decreases. As its ground speed increases, satellite 101 moves eastward relative to its target. The monitoring control device 110 activates the monitoring device 102 after the artificial satellite 101 begins to move eastward relative to the target being monitored.

[0029] The monitoring and control device 110 controls the propulsion system 103 so that the artificial satellite 101 increases its speed. The orbital altitude of satellite 101 increases as satellite 101's velocity increases. The ground velocity of satellite 101 decreases as its orbital altitude increases. Satellite 101 moves westward relative to its target as its ground velocity decreases. The monitoring control device 110 activates the monitoring device 102 after the artificial satellite 101 begins to move westward relative to the target being monitored.

[0030] The monitoring and control device 110 adjusts the orbital period of the artificial satellite 101 by decelerating and accelerating the artificial satellite 101. The monitoring device 102 operates at any time during the eastward movement of the satellite 101 and at any time during the westward movement of the satellite 101. This adjusts the average orbital period of the satellite 101.

[0031] The monitoring and control device 110 maintains the average relative position of the satellite 101 with respect to the monitored object by decelerating and accelerating the satellite 101. The monitoring device 102 operates at any time during the eastward movement of the satellite 101 and at any time during the westward movement of the satellite 101. The average relative position of the satellite 101 with respect to the monitored object is maintained.

[0032] The monitoring and control device 110 adjusts the relative position of the artificial satellite 101 with respect to the object being monitored by controlling the propulsion device 103. The time period during which the monitoring device 102 monitors the target object (monitoring time period) is changed by adjusting the relative position. The time that satellite 101 flies over the target area (monitoring time) is extended by adjusting its relative position.

[0033] *** Reference Form 1 The effect*** Even without electric propulsion, if satellite 101 is flying in a phase where it crosses directly beneath the sun at noon, it will be possible to monitor the target area 121 for six hours during the day, from 9 am to 3 pm. Reference Form 1 This enables a further extension of the monitoring time. Also, since the altitude of the artificial satellite 101 above ground is 0.6 times that of the geostationary satellite above ground, the resolution of the monitoring device 102 is improved by 1.8 times compared to the resolution of the monitoring device of the geostationary satellite.

[0034] By controlling the pointing function of satellite 101, the line-of-sight vector, i.e., the direction of observation, can be changed. Therefore, it is possible to focus on the target area 121 or to change the target area 121.

[0035] As viewed from the target area 121, the distance from satellite 101 to the target area 121 (ground distance) changes from when satellite 101 rises above the horizon, passes overhead, and sets below the horizon. When satellite 101 is flying near the horizon, the ground distance is short and the oblique angle is shallow. When satellite 101 is passing overhead, the ground distance is long and the oblique angle is deep. By controlling the monitoring function of the monitoring device 102 according to the distance from the ground, monitoring can be performed under optimal monitoring conditions according to the distance from the ground.

[0036] *** Reference Form 1 Summary*** The monitoring and control device 110 is mounted on the artificial satellite 101. The artificial satellite 101 includes a monitoring device 102 for monitoring the target area 121 and a propulsion device 103 for changing the speed of the artificial satellite 101. The monitoring and 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 in orbit 122. The monitoring time during which the satellite 101 flies over the target area 121 is extended by adjusting the relative position.

[0037] Orbit 122 is a circular orbit at an altitude of 20,000 kilometers above the equator. Satellite 101 orbits orbit 122 twice a day.

[0038] The monitoring and control device 110 increases the altitude of the artificial satellite 101 during the target time period by accelerating the satellite 101 before the target time period. The monitoring time is extended as the altitude of the satellite 101 increases, causing the speed of the satellite 101 relative to the target area 121 (speed relative to the ground) to decrease.

[0039] Satellite 101 is equipped with a pointing function. The monitoring control device 110 directs the monitoring direction of the monitoring device 102 toward the target area 121 by controlling the pointing function.

[0040] 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 the change in distance from the artificial satellite 101 to the target area 121.

[0041] Reference Form 2 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figures 6 and 7.

[0042] Reference Form 2 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0043] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0044] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0045] Based on Figure 6, we will explain both orbit 122 and monitoring. The way to interpret Figure 6 is the same as the way to interpret Figure 4. Orbit 122 is a circular orbit above the equator. For example, when satellite 101 crosses directly beneath the sun at noon, satellite 101 is in orbit 122. The altitude of orbit 122 is 14,000 kilometers. The orbital period of orbit 122 is 8 hours. Satellite 101 completes three orbits of orbit 122 per day.

[0046] The monitoring device 102 continuously monitors Japan during the four hours of daytime, from 10:00 to 14:00. When adjusted for the GSD improvement effect due to differences in orbital altitude, the GSD becomes between 1.9 meters and 7 meters, and the resolution becomes 1.2 meters or higher.

[0047] Based on Figure 7, the relationship between satellite altitude and time will be explained. The interpretation of Figure 7 is the same as that of Figure 5. The speed of satellite 101 is controlled by electric propulsion, and its orbital period is maintained by a combination of acceleration and deceleration, allowing satellite 101 to orbit orbit 122 three times a day. During the day, the average satellite altitude is high, and after sunset, satellite 101 decelerates and its altitude decreases. Before sunrise, satellite 101 accelerates, and its altitude rises by sunrise. The higher the satellite altitude, the lower the ground velocity, so the daytime monitoring time is extended.

[0048] *** Reference Form 2 The effect*** Even without electric propulsion, if satellite 101 is flying in a phase where it crosses directly beneath the sun at noon, it will be possible to monitor the target area 121 for four hours during the daytime, from 10:00 to 14:00. Reference Form 2 This allows for a further extension of the monitoring time. Also, since the altitude of the artificial satellite 101 above ground is 0.4 times that of the geostationary satellite above ground, the resolution of the monitoring device 102 is improved by 2.6 times compared to the resolution of the monitoring device of the geostationary satellite.

[0049] *** Reference Form 2 Features *** Orbit 122 is a circular orbit at an altitude of 14,000 kilometers above the equator. Satellite 101 orbits orbit 122 three times a day.

[0050] Reference Form 3 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figures 8 and 9.

[0051] Reference Form 3 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0052] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0053] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0054] Based on Figure 8, we will explain both orbit 122 and monitoring. The interpretation of Figure 8 is the same as that of Figure 4. Orbit 122 is a circular orbit above the equator. When satellite 101 crosses directly beneath the sun at noon, satellite 101 is in orbit 122. The altitude of orbit 122 is 10,000 kilometers. The orbital period of orbit 122 is 6 hours. Satellite 101 completes four orbits of orbit 122 per day.

[0055] The monitoring device 102 continuously monitors Japan for three hours during the daytime, from 10:30 to 13:30. When adjusted for the GSD improvement effect due to differences in orbital altitude, the GSD becomes between 1.5 meters and 5 meters, and the resolution becomes 0.9 meters or higher.

[0056] Based on Figure 9, the relationship between satellite altitude and time will be explained. The interpretation of Figure 9 is the same as that of Figure 5. The speed of satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, allowing satellite 101 to orbit four times a day. During the day, the average satellite altitude is high, and after sunset, satellite 101 decelerates and its altitude decreases. Before sunrise, satellite 101 accelerates, and its altitude rises by sunrise. The higher the satellite altitude, the lower the ground velocity, so the daytime monitoring time is extended.

[0057] *** Reference Form 3 The effect*** Even without electric propulsion, if satellite 101 is flying in a phase where it crosses directly beneath the sun at noon, it will be possible to monitor the target area 121 for three hours during the day, from 10:30 to 13:30. Reference Form 3 This allows for a further extension of the monitoring time. Also, since the altitude of the artificial satellite 101 above ground is 0.3 times that of the geostationary satellite above ground, the resolution of the monitoring device 102 is improved by 3.6 times compared to the resolution of the monitoring device of the geostationary satellite.

[0058] *** Reference Form 3 Features *** Orbit 122 is a circular orbit at an altitude of 10,000 kilometers above the equator. Satellite 101 flies in a phase that crosses directly beneath the sun at noon and completes four orbits of orbit 122 per day.

[0059] Reference Form 4 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figures 10 and 11.

[0060] Reference Form 4 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0061] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0062] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0063] Based on Figure 10, we will explain both the orbit 122 and the monitoring system. The way to interpret Figure 10 is the same as the way to interpret Figure 4. Orbit 122 is a circular orbit above the equator. Satellite 101 is in orbit 122 when it crosses directly opposite Earth 120 at noon. The altitude of orbit 122 is 10,000 kilometers. The orbital period of orbit 122 is 6 hours. This means that satellite 101 completes four orbits of orbit 122 per day.

[0064] 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 2-hour continuous monitoring periods during the daytime. When adjusted for the GSD improvement effect due to differences in orbital altitude, the GSD becomes between 1.5 meters and 5 meters, and the resolution becomes 0.9 meters or higher.

[0065] Based on Figure 11, the relationship between satellite altitude and time will be explained. The interpretation of Figure 11 is the same as that of Figure 5. The speed of satellite 101 is controlled by electric propulsion, and the orbital period is maintained by a combination of acceleration and deceleration, allowing satellite 101 to orbit four times a day. During the day, the average satellite altitude is low, and after sunset, satellite 101 accelerates, causing its altitude to rise. Before sunrise, satellite 101 decelerates, and its altitude decreases by sunrise. The lower the satellite altitude, the higher its speed relative to the ground, making monitoring possible with just two orbits during the day. This extends the total monitoring time during the day. Furthermore, even if the sun 123 is illuminating the target area 121, satellite 101 cannot monitor the target area 121 while it is below the horizon. Therefore, the continuous monitoring time per session is: Reference Form 3 This will be shorter than the continuous monitoring time in the previous scenario.

[0066] *** Reference Form 4 The effect*** Even without electric propulsion, if satellite 101 is flying in a phase where it crosses directly opposite Earth 120 at noon, it will be possible to conduct two monitoring periods: two 2-hour periods from 7:30 to 9:30 and another 2-hour period from 14:30 to 16:30. Reference Form 4 This enables two monitoring sessions at two time periods close to noon. In addition, since the altitude of artificial satellite 101 above ground is 0.3 times that of the geostationary satellite above ground, the resolution of monitoring device 102 is improved by 3.6 times compared to the resolution of the geostationary satellite's monitoring device.

[0067] *** Reference Form 4 Features *** Orbit 122 is a circular orbit at an altitude of 10,000 kilometers above the equator. Satellite 101 will orbit directly opposite Earth 120 at noon, completing four orbits of orbit 122 per day.

[0068] The monitoring and control device 110 lowers the altitude of the satellite 101 during the target time period by slowing down the satellite 101 before the target time period. During the time period in question, the number of orbits of artificial satellite 101 will be two or more as the altitude of artificial satellite 101 decreases and the velocity of artificial satellite 101 relative to the star increases. The monitoring time is extended when the number of orbits by the satellite during the target time period exceeds two.

[0069] Embodiment 1 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figures 12 to 14.

[0070] Embodiment 1 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0071] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0072] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0073] We will now explain both orbit 122 and the monitoring system. Orbit 122 is a sun-synchronous inclined circular orbit. In other words, orbit 122 is a sun-synchronous orbit, an inclined orbit, and a circular orbit. Satellite 101 is a satellite that flies in a sun-synchronous orbit (a sun-synchronous satellite). The orbital inclination of orbit 122 is between 30 and 60 degrees. Orbit 122 is the orbit with LST 12:00. LST stands for Local Standard Time. Satellite 101 will fly to the northernmost point of its orbit 122 at the moment when the local time in the target region 121 becomes 12:00. The number of orbits performed by artificial satellite 101 per day is an integer. The monitoring and control device 110 controls the pointing function. This satisfies the condition that the target area 121 remains visible for 10 minutes or more.

[0074] A specific example of the orbit 122 will be explained based on Figure 12. The interpretation of Figure 12 is the same as that of Figure 4. However, all times indicated in Figure 12 are local standard time (LST) for the target region 121. The orbital altitude is 5144 kilometers. The orbital inclination is 141.6 degrees. The orbital period is 3.4 hours. Satellite 101 completes 7 orbits of orbit 122 per day. The monitoring range is from +38 degrees North latitude to -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, monitoring the target area 121 for about 3 hours during the day. However, if the target region 121 is Japan, it is not guaranteed that satellite 101 in orbit will happen to be flying over Japan. Therefore, the time period during which Japan can be monitored may differ from the time mentioned above.

[0075] 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 will be poor, even if the sunlight conditions in 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. Subsequently, the monitoring control device 110 controls the thrust of the propulsion device 103 in the opposite direction to the controlled thrust direction. This maintains average orbital conditions, thus maintaining sun-synchronous conditions. As a result, monitoring can be continued.

[0076] I will add some information about orbit 122. Since the number of orbits of satellite 101 depends on its altitude, the altitude can be uniquely determined once the number of orbits is known. For example, if satellite 101 orbits the Earth 7 times per day, its altitude is 5144 kilometers. Sun-synchronous conditions are due to the uneven distribution of gravity associated with the flattened shape of Earth-120 and are uniquely determined based on the correlation between satellite altitude and orbital inclination. If the satellite altitude is 5144 kilometers, an orbit with an orbital inclination of 141.6 degrees is a sun-synchronous orbit. If the orbital inclination is 141.6 degrees, the orbital plane is tilted 38.4 degrees (=180-141.6) from the equator. Therefore, satellite 101 will fly within a latitude range of +38 degrees to -38 degrees relative to Earth 120. The monitoring control device 110 controls the monitoring direction in the latitudinal direction. This allows the monitoring device 102 to monitor the Earth 120 within a latitude range of +60 degrees to -60 degrees. If orbit 122 has a solar incidence angle of LST 12:00, then the Northern Hemisphere will always receive sunlight within the orbital plane of orbit 122. Then, at the northernmost point of orbit 122, satellite 101 will be flying above 38 degrees North latitude.

[0077] Based on Figure 13, let's add some details about monitoring. If the target area 121 on Earth 120 is under sunlight, the latitude of the northernmost point in orbit 122 is near the latitude of the target area 121, and the artificial satellite 101 passes over the target area 121, then monitoring can be performed under favorable conditions.

[0078] The orbit 122 may not be a circular orbit, but an elliptical orbit with eccentricity. Even if the orbit 122 is an elliptical orbit, it is still possible to realize a satellite 101 that satisfies the sun-synchronous conditions.

[0079] *** Embodiment 1 The effect*** In a sun-synchronous orbit, the angle of incidence of sunlight on the orbital plane remains largely constant regardless of the passage of time or season. For example, if the purpose is to monitor the area around 40 degrees latitude, setting the orbital plane so that satellite 101 flies directly over the target area 121 at 12:00 would allow satellite 101 to maintain an orbit that keeps it near 40 degrees north latitude during daylight hours. Since the altitude of artificial satellite 101 above ground is 0.14 times that of the geostationary satellite above ground, the resolution of the monitoring device 102 is improved by 7 times compared to the resolution of the monitoring device of the geostationary satellite. The monitoring equipment of a geostationary satellite monitors the area around 40 degrees north latitude at an oblique angle, which reduces its resolution. However, monitoring equipment 102 can directly monitor the area around 40 degrees north latitude, so its resolution does not decrease.

[0080] ***Description of the Example*** An example of orbit 122 will be explained based on Figure 14. The altitude of orbit 122 is 4,163 kilometers. The orbital inclination of orbit 122 is 125 degrees. Satellite 101 orbits orbit 122 eight times a day. This will enable satellite 101 to fly in an orbital plane ranging from +55 degrees North latitude to -55 degrees North latitude. Furthermore, it becomes possible to continuously monitor the target area 121 during 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 becomes possible to perform approximately three continuous monitoring sessions of 10 minutes or more during the day, and to perform a total of approximately 3 hours of monitoring.

[0081] If we are not concerned with the number of orbits per day being an integer, then orbit 122, which is a sun-synchronous orbit, can be realized by the following combinations. Note that we assume orbit 122 is a circular orbit. (1) The orbital altitude is 4000 kilometers. The orbital inclination is 123 degrees. Satellite 101 flies within the range of latitude +57 degrees to latitude -57 degrees. Satellite 101 orbits orbit 122 8 times a day. Satellite 101 orbits orbit 122 once every 3 hours. (2) The orbital altitude is 4500 kilometers. The orbital inclination is 130 degrees. Satellite 101 flies in the range of latitude +50 degrees to latitude -50 degrees. Satellite 101 orbits orbit 122 7 to 8 times a day. Satellite 101 orbits orbit 122 once every 3 to 4 hours. (3) The orbital altitude is 5,000 kilometers. The orbital inclination is 139 degrees. Satellite 101 flies within the range of latitude +41 degrees to latitude -41 degrees. Satellite 101 orbits orbit 122 7 to 8 times per day. Satellite 101 orbits orbit 122 once every 3 to 4 hours. (4) The orbital altitude is 5500 kilometers. The orbital inclination is 151 degrees. Satellite 101 flies within the range of latitude +29 degrees to latitude -29 degrees. Satellite 101 orbits orbit 122 seven times a day. Satellite 101 orbits orbit 122 once every four hours. The orbital plane of orbit 122 in (1) to (4) is the orbital plane at LST 12:00, with the northernmost point being noon. However, since satellite 101 is not necessarily flying at the northernmost point at 12:00, the time when satellite 101 passes the northernmost point of the orbital plane will be around the same time.

[0082] *** Embodiment 1 Features *** The monitoring system 100 includes an artificial satellite 101 that orbits the orbit 122 an integer number of times per day. Orbit 122 is a sun-synchronous orbit, an inclined orbit, and a circular orbit. Satellite 101 will fly to the northernmost point of its orbit 122 at the moment when the local time in the target region 121 becomes 12:00.

[0083] Reference Form 5 . Regarding the monitoring system 100, mainly Reference Form 1 Let's explain the differences.

[0084] Reference Form 5 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0085] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0086] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0087] Let's explain orbit 122. Orbit 122 is a sun-synchronous, inclined elliptical orbit. In other words, orbit 122 is both a sun-synchronous and inclined orbit. Furthermore, orbit 122 is an elliptical orbit with a high eccentricity. The orbital altitude is 5,100 kilometers. The semi-major axis of the orbit is 11,478 kilometers. The eccentricity is 0.418. The orbital inclination is 121.88 degrees. The apogee altitude is 9898 kilometers. The perigee altitude is 302 kilometers.

[0088] Orbit 122 is the LST 12:00 orbit. Satellite 101 will fly to the perigee of orbit 122 at the moment when the local time in the target region 121 becomes 12:00. The perigee of orbit 122 is the northernmost point of orbit 122.

[0089] *** Reference Form 5 The effect*** As artificial satellite 101 flies in orbit 122, the condition for the target area 121 to be visible for more than 10 minutes is met.

[0090] *** Reference Form 5 Features *** Orbit 122 is a sun-synchronous orbit, an inclined orbit, and an elliptical orbit. Satellite 101 will pass the perigee of its orbit 122 at the moment when the local time in the target region 121 becomes 12:00.

[0091] Reference Form 6 . Regarding the satellite constellation 130, mainly Reference Form 1 The differences will be explained based on Figures 15 to 20.

[0092] Reference Form 6 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0093] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0094] The configuration of satellite constellation 130 will be explained based on Figures 15 to 19. Figure 15 shows satellite constellation 130 as viewed from the direction normal to the orbital plane. Figure 16 shows the satellite constellation 130 as seen from the orbital plane. For example, Figure 16 shows the satellite constellation 130 as seen from above the equator. Figures 17, 18, and 19 show how the major axis of the elliptical orbit of each satellite (101A-101C) rotates around the Earth at 120 degrees in the orbital plane. Each of the satellites (101A to 101C) is the same type of satellite as satellite 101.

[0095] Each satellite (101A-101C) orbits in a sun-synchronous, inclined elliptical orbit. Three satellites (101A-101C) maintain monitoring of the Northern Hemisphere during the daytime.

[0096] The orbits of each satellite (101A to 101C) are non-frozen orbits. In other words, the orbits of each satellite (101A-101C) are not frozen orbits, but rather their major axes rotate around the Earth at 120 degrees over time.

[0097] The three satellites (101A-101C) alternately monitor the target area 121 on Earth 120 from their perigee, apogee, or midpoint. The midpoint is a point located between the perigee and apogee. At perigee, monitoring can be performed with high resolution, albeit for a short period of time. At afar, long-term monitoring is possible, albeit with low resolution.

[0098] The major axes of the three orbits are tilted at a ratio of 120 degrees relative to each other in the circumferential direction, or latitudinal direction, with Earth at 120 degrees. In other words, the three orbital major axes are spaced equally apart in the latitudinal direction. The major axis of each orbit rotates relative to the sun (123), but the relative relationship between the three orbits is maintained.

[0099] In the three orbits, the relative relationship between the normal direction and the angle of incidence to the sun is maintained.

[0100] At noon (12:00), the phase of each satellite (101A-101C) does not correlate with the latitude of the target region 121 on Earth 120.

[0101] One of the three satellites (101A-101C) is capable of monitoring the target region 121 on Earth. Furthermore, all three satellites can continuously monitor the target region 121.

[0102] When each satellite (101A to 101C) passes over the target area 121 of Earth 120 at its apogee, each satellite can monitor the target area 121 of Earth 120 for an extended period, albeit with low resolution. When each satellite passes over the target region 121 of Earth 120 at its perigee, each satellite can monitor the target region 121 of Earth 120 with high resolution, albeit for a short period of time.

[0103] Specific examples of the orbits of each satellite (101A-101C) are as follows: The altitude of the circular orbit that forms the basis of the elliptical orbit is 5100 kilometers. The eccentricity of an elliptical orbit is 0.418. The orbital inclination is 122 degrees. The apogee altitude is 9898 kilometers. The perigee altitude is 302 kilometers.

[0104] Based on Figure 20, the relationship between altitude and latitude for the orbits of each satellite (101A to 101C) will be explained. The dotted line represents the orbit of satellite 101A. The dashed line represents the orbit of satellite 101B. The dashed line represents the orbit of satellite 101C.

[0105] "Ha" is the perigee altitude, and "Hc" is the constant perigee access altitude. The constant perigee access altitude is the altitude at which the target area 121 can be monitored from the perigee side by at least one of the three satellites (101A to 101C). "Hb" is the apogee altitude, and "Hd" is the constant apogee access altitude. The constant apogee access altitude is the altitude at which the target area 121 can be monitored from the apogee side by at least one of the three satellites (101A to 101C). Each of the utilization altitudes (Hd, Hc) corresponds to the altitude at the intersection of the two orbits in the graph in Figure 20.

[0106] The length of time each artificial satellite (101A-101C) stays above the target region 121 is referred to as the satellite's stay time. At the apogee, each satellite stays in the area for a longer period, and its field of view is wider. The operating altitude Hb and the field of view of the monitoring device 102 are determined so that the target area 121 is within the field of view when each satellite (101A to 101C) is flying at an altitude higher than the operating altitude Hd. This enables continuous monitoring of the target area 121. Because the time spent by each satellite (101A-101C) is short at the perigee, monitoring at the perigee is not continuous. However, regardless of the latitude at which the target area 121 is located, at least one satellite can monitor the target area 121 from an altitude lower than the utilization altitude Hc.

[0107] The resolution of the monitoring device 102 is determined so that the desired resolution is achieved at the utilization altitude Hc. This makes it possible to monitor the target area 121 with high resolution.

[0108] *** Reference Form 6 The effect*** Since the three satellites (101A-101C) will alternately stay near the apogee for extended periods, continuous monitoring will be possible. Of the three satellites, the one that passes near the perigee will enable high-resolution observations.

[0109] *** Reference Form 6 Features *** Satellite constellation 130 consists of three artificial satellites (101A to 101C). The orbits of each artificial satellite 122 are sun-synchronous, inclined, and elliptical. The three satellites' three orbits 122 are positioned so that their major orbital axes are tilted and offset by 120 degrees in the latitudinal direction.

[0110] Reference Form 7 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figure 21.

[0111] Reference Form 7 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0112] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0113] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0114] A specific example of orbit 122 will be explained based on Figure 21. The actual curve shown on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 7,000 kilometers. The apogee altitude is 34,000 kilometers. The orbital inclination angle ranges from 20 to 60 degrees. The orbital period is 12 hours. Satellite 101 orbits orbit 122 twice a day. In far-point monitoring, the monitoring device 102 can monitor Japan for six hours, from 9:00 to 15:00. The GSD is between 5 meters and 17 meters.

[0115] *** Reference Form 7 The effect*** It can continuously monitor the airspace above the 121 target areas for six hours during the daytime. From an apogee at an altitude of 34,000 kilometers, the target area 121 can be viewed directly below. As satellite 101 moves away from the apogee, both during its journey from the horizon to the apogee and from the apogee to the horizon, its distance from the Earth decreases, enabling high-resolution monitoring. During the six-hour period from 9 a.m. to 3 p.m., which is frequently used for monitoring with visible telescopes, it will be possible to continuously monitor the target area 121 with just one satellite, 101.

[0116] An orbital inclination of approximately 35 to 40 degrees is suitable for monitoring all of Japan, China, and the Korean Peninsula. On the other hand, an orbital inclination of approximately 50 degrees is suitable for monitoring major European countries, and an orbital inclination of approximately 60 degrees is suitable for monitoring Northern Europe. Furthermore, an orbital inclination of approximately 20 to 30 degrees is suitable for monitoring North Africa, the Middle East, and India.

[0117] *** Reference Form 7 Features *** The monitoring and control device 110 is mounted on the artificial satellite 101, which is orbiting in orbit 122. Orbit 122 is both an elliptical and inclined orbit. The monitoring and control device 110 controls the propulsion system 103 while the satellite 101 is orbiting in orbit 122, thereby causing the satellite 101 to fly over the target area 121 at the apogee of orbit 122.

[0118] The perigee altitude of orbit 122 is 7,000 kilometers. The apogee altitude of orbit 122 is 34,000 kilometers. Satellite 101 orbits orbit 122 twice a day.

[0119] Reference Form 8 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figure 22.

[0120] Reference Form 8 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0121] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0122] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0123] A specific example of orbit 122 will be explained based on Figure 22. The actual curve shown on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 4000 kilometers. The apogee altitude is 25,000 kilometers. The orbital inclination angle ranges from 20 to 60 degrees. The orbital period is 8 hours. Satellite 101 completes three orbits of orbit 122 per day. In monitoring using apogee technology, the monitoring device 102 can monitor Japan for four hours, from 10:00 to 14:00. The GSD is between 3.4 meters and 12 meters.

[0124] *** Reference Form 8 The effect*** It can continuously monitor the airspace above the 121 target areas for four hours during the daytime. From an apogee at an altitude of 25,000 kilometers, the target area 121 can be viewed directly below. As satellite 101 moves away from the apogee, both during its journey from the horizon to the apogee and from the apogee to the horizon, its distance from the Earth decreases, enabling high-resolution monitoring. During the six-hour period from 9 a.m. to 3 p.m., which is frequently used for monitoring with visible telescopes, it will be possible to continuously monitor the target area 121 using two satellites 101.

[0125] *** Reference Form 8 Features *** The perigee altitude of orbit 122 is 4,000 kilometers. The apogee altitude of orbit 122 is 25,000 kilometers. Satellite 101 orbits orbit 122 three times a day.

[0126] Reference Form 9 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figure 23.

[0127] Reference Form 9 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0128] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0129] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0130] A specific example of orbit 122 will be explained based on Figure 23. The actual curve shown on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 1700 kilometers. The apogee altitude is 17,000 kilometers. The orbital inclination angle ranges from 20 to 60 degrees. The orbital period is 6 hours. Satellite 101 completes four orbits of orbit 122 per day. In apogee monitoring, the monitoring device 102 can monitor Japan for two hours, from 11:00 to 13:00. The GSD (Ground Score Distance) is between 2.6 meters and 9 meters.

[0131] *** Reference Form 9 The effect*** It can continuously monitor the airspace above the target area of ​​121 for two hours during the daytime. From an apogee at an altitude of 17,000 kilometers, the target area 121 can be viewed directly below. As satellite 101 moves away from the apogee, both during its journey from the horizon to the apogee and from the apogee to the horizon, its distance from the Earth decreases, enabling high-resolution monitoring. During the six-hour period from 9 a.m. to 3 p.m., which is frequently used for monitoring with visible telescopes, it will be possible to continuously monitor the target area 121 using three satellites 101.

[0132] *** Reference Form 9 Features *** The perigee altitude of orbit 122 is 1700 kilometers. The apogee altitude of orbit 122 is 17,000 kilometers. Satellite 101 orbits orbit 122 four times a day.

[0133] Reference Form 10 . Regarding the monitoring system 100, mainly Reference Form 1 The differences will be explained based on Figures 24 to 26.

[0134] Reference Form 10 In this context, values ​​such as time, altitude, distance, or number of laps are approximate.

[0135] ***Explanation of the structure*** The configuration of the monitoring system 100 is: Reference Form 1 The configuration is the same as in (see Figure 1).

[0136] ***Explanation of operation*** The basic operations of the artificial satellite 101 and the monitoring and control device 110 are as follows: Reference Form 1 This is the same operation as in (see Figures 2 and 3).

[0137] A specific example of orbit 122 will be explained based on Figure 24. The actual curve shown on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 2000 kilometers. The apogee altitude is 19,000 kilometers. The orbital period is 6 hours. Satellite 101 completes four orbits of orbit 122 per day. In monitoring perigee usage, the monitoring device 102 can monitor Japan for one hour, from 11:30 to 12:30. The GSD is between 0.3 meters and 1.1 meters. The resolution is 0.2 meters or higher.

[0138] A specific example of orbit 122 will be explained based on Figure 25. The actual curve drawn on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 4000 kilometers. The apogee altitude is 25,000 kilometers. The orbital period is 8 hours. Satellite 101 completes three orbits of orbit 122 per day. In monitoring perigee usage, 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.

[0139] A specific example of orbit 122 will be explained based on Figure 26. The actual curve shown on the map represents orbit 122. Orbit 122 is an inclined elliptical orbit. The perigee altitude is 7,000 kilometers. The apogee altitude is 34,000 kilometers. The orbital period is 12 hours. Satellite 101 orbits orbit 122 twice a day. In monitoring perigee usage, the monitoring device 102 can monitor Japan for two hours, from 11:00 to 13:00. The GSD is between 1 meter and 4 meters. The resolution is 0.6 meters or higher.

[0140] *** Reference Form 10 The effect*** By having the monitoring device 102 monitor the target area 121 at perigee, monitoring with significantly higher resolution becomes possible compared to static observation. Satellite 101 will fly across Asian airspace, including Japan and China. This will give satellite 101 at least two opportunities to visit Asian airspace during the daytime.

[0141] *** Reference Form 10 Features *** The monitoring and control device 110 is mounted on the artificial satellite 101, which is orbiting in orbit 122. Orbit 122 is both an elliptical and inclined orbit. The monitoring and control device 110 controls the propulsion system 103 while the satellite 101 is orbiting in orbit 122, thereby causing the satellite 101 to fly over the target area 121 at the perigee of orbit 122.

[0142] ***Supplementary Information on the Embodiment*** Each embodiment is an example of a preferred form and is not intended to limit the technical scope of this disclosure. Each embodiment may be implemented in part or in combination with other embodiments. [Explanation of symbols]

[0143] 100 Monitoring system, 101 Satellite, 102 Monitoring device, 103 Propulsion device, 104 Communication device, 105 Attitude control device, 106 Power supply device, 110 Monitoring and control device, 111 Processing circuit, 120 Earth, 121 Target area, 122 Orbit, 123 Sun, 130 Satellite constellation, 140 Ground equipment, 141 Communication device, 142 Satellite control device.

Claims

1. A monitoring system that monitors a target object under the condition that the target area where the target object exists is receiving sunlight, The system includes an artificial satellite that orbits the area an integer number of times per day and passes over the aforementioned target area. The aforementioned orbit is a sun-synchronous orbit, an inclined orbit, and a circular orbit. The latitude of the northernmost point of the aforementioned orbit is near the latitude of the aforementioned target area. The aforementioned satellite flies to the northernmost point of its orbit at the moment when the local time of the monitored object becomes 12:

00. The aforementioned artificial satellite, Propulsion system and A monitoring device for monitoring the aforementioned target, A pointing function for changing the monitoring direction of the aforementioned monitoring device, The monitoring control device includes a device that directs the monitoring direction toward the object being monitored by controlling the pointing function, The monitoring and control device controls the thrust of the propulsion system to bring the phase position of the satellite closer to the monitored object, and after controlling the thrust of the propulsion system, maintains the sun-synchronization condition by controlling the thrust of the propulsion system in the opposite direction to the controlled thrust direction. A monitoring system.

2. The target area is a region around 40 degrees north latitude, By maintaining the aforementioned sun-synchronization conditions, the orbit in which the satellite remains near 40 degrees north latitude during daylight hours is maintained, and the monitoring device views directly below 40 degrees north latitude, avoiding a decrease in resolution due to the oblique angle effect. The monitoring system according to claim 1.

3. The aforementioned monitoring device performs continuous monitoring for 10 minutes or more three times during the day, for a total of approximately three hours of monitoring. The monitoring system according to claim 1.

4. The aforementioned monitoring device performs continuous monitoring for 10 minutes or more three times during the day, for a total of approximately three hours of monitoring. The monitoring system according to claim 2.

5. An artificial satellite constituting the monitoring system according to any one of claims 1 to 4.

6. Ground equipment for controlling the monitoring system according to any one of claims 1 to 4, A satellite control system that generates control commands for controlling the propulsion device, the monitoring device, and the monitoring control device that controls the pointing function, A communication device that transmits the control command to the artificial satellite, Ground facilities equipped with these features.

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