Patent Publication Number: US-2022234764-A1

Title: Imaging method of satellite system, and transmission device

Description:
TECHNICAL FIELD 
     The present technology relates to an imaging method of a satellite system and a transmission device, and particularly relates to an imaging method of a satellite system and a transmission device that enable to perform imaging of an artificial satellite in accordance with an event having occurred on the ground, in remote sensing by the artificial satellite. 
     BACKGROUND ART 
     There is a technology called satellite remote sensing for observing a situation of a target region or a target object and detecting a situation change from an image of a predetermined region on the earth captured by an artificial satellite (see, for example, Patent Documents 1 and 2). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: International Publication No. 2010/097921 
         Patent Document 2: Japanese Patent Application Laid-Open No. 2004-15451 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, in remote sensing by an artificial satellite, it may be currently difficult for the artificial satellite to perform imaging in accordance with an event having occurred on the ground in some cases. 
     The present technology has been made in view of such a situation, and an object is to enable an artificial satellite to perform imaging in accordance with an event having occurred on the ground, in remote sensing by the artificial satellite. 
     Solutions to Problems 
     An imaging method of a satellite system according to a first aspect of the present technology includes: transmitting, by a transmission device of a satellite system including the transmission device installed on the earth and an artificial satellite having an imaging device, an imaging instruction to the artificial satellite passing in the sky, in accordance with a predetermined event detected by a sensor installed on the earth; and imaging, by the artificial satellite, an occurrence region of the event on the basis of the imaging instruction. 
     In the first aspect of the present technology, an imaging instruction is transmitted from the transmission device to the artificial satellite passing in the sky, in accordance with a predetermined event detected by a sensor installed on the earth, and the artificial satellite performs imaging of an event occurrence region on the basis of the imaging instruction. 
     A transmission device according to a second aspect of the present technology includes a transmission unit configured to transmit an imaging instruction to an artificial satellite passing in the sky, in accordance with a predetermined event detected by a sensor installed on the earth. 
     In the second aspect of the present technology, the imaging instruction is transmitted to the artificial satellite passing in the sky, in accordance with a predetermined event detected by the sensor installed on the earth. 
     The transmission device may be an independent device, or may be an internal block that forms one device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration example of a first embodiment of a satellite image processing system to which the present technology is applied. 
         FIG. 2  is a diagram for explaining formation flight. 
         FIG. 3  is a diagram for explaining formation flight. 
         FIG. 4  is a block diagram illustrating a configuration example of a satellite. 
         FIG. 5  is a block diagram illustrating a configuration example of a satellite group management device, a communication device, and an image analysis server. 
         FIG. 6  is a flowchart illustrating an imaging sequence focusing on one satellite. 
         FIG. 7  is a detailed flowchart of imaging preparation processing in step S 33  in  FIG. 6 . 
         FIG. 8  is a view for explaining determination of a remaining battery amount. 
         FIG. 9  is a flowchart of the satellite image processing system that performs formation flight. 
         FIG. 10  is a view for explaining information given as metadata. 
         FIG. 11  is a view illustrating a configuration example of a second embodiment of a satellite image processing system to which the present technology is applied. 
         FIG. 12  is a block diagram illustrating a configuration example of a transmission device in the second embodiment. 
         FIG. 13  is a flowchart illustrating a first event imaging sequence by the satellite image processing system of the second embodiment. 
         FIG. 14  is a flowchart for explaining a second event imaging sequence by the satellite image processing system according to the second embodiment. 
         FIG. 15  is a flowchart illustrating a third event imaging sequence by the satellite image processing system according to the second embodiment. 
         FIG. 16  is a block diagram illustrating another configuration example of the transmission device in the second embodiment. 
         FIG. 17  is a block diagram illustrating a configuration example of an embodiment of a computer to which the present technology is applied. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, embodiments for implementing the present technology (hereinafter, referred to as embodiments) will be described. Note that the description will be given in the following order. 
     1. Configuration example of satellite image processing system 
     2. Imaging sequence of single device 
     3. Imaging preparation processing 
     4. Flowchart of formation flight 
     5. Example of image processing 
     6. Details of metadata 
     7. Details of distribution management processing 
     8. Application example of formation flight 
     9. Second embodiment of satellite image processing system 
     10. First event imaging sequence of second embodiment 
     11. Second event imaging sequence of second embodiment 
     12. Third event imaging sequence of second embodiment 
     13. Another configuration example of transmission device 
     14. Application example of satellite image processing system using event detection sensor 
     15. Computer configuration example 
     &lt;1. Configuration Example of Satellite Image Processing System&gt; 
       FIG. 1  is a block diagram illustrating a configuration example of a first embodiment of a satellite image processing system to which the present technology is applied. 
     A satellite image processing system  1  of  FIG. 1  is a system that observes a situation of a target region or a target object on the earth by using a captured image captured by a plurality of artificial satellites (hereinafter, simply referred to as satellites), and performs satellite remote sensing for detecting a situation change. In the present embodiment, the satellite is mounted with an imaging device and has at least a function of imaging on the ground. 
     A satellite operation company includes a satellite group management device  11  that manages a plurality of satellites  21  and a plurality of communication devices  13  that communicates with the satellites  21 . Note that the satellite group management device  11  and some of the plurality of communication devices  13  may be devices owned by other than the satellite operation company. The satellite group management device  11  and the plurality of communication devices  13  are connected via a predetermined network  12 . The communication devices  13  are arranged at a ground station (base station on the ground)  15 . Note that  FIG. 1  illustrates an example in which the number of communication devices  13  is three of communication devices  13 A to  13 C, but any number of communication devices  13  may be adopted. 
     The satellite group management device  11  manages the plurality of satellites  21  owned by the satellite operation company. Specifically, the satellite group management device  11  acquires related information from one or more information providing servers  41  of an external organization as necessary, and determines an operation plan for the plurality of satellites  21  owned by the self. Then, the satellite group management device  11  gives an imaging instruction to the predetermined satellite  21  via the communication device  13  in response to a request of a customer, to cause the predetermined satellite  21  to perform imaging. Furthermore, the satellite group management device  11  acquires and stores a captured image transmitted from the satellite  21  via the communication device  13 . The acquired captured image is subjected to predetermined image processing as necessary, and provided (transmitted) to the customer. Alternatively, the acquired captured image is provided (transmitted) to an image analysis server  42  of an image analysis company, subjected to predetermined image processing, and then provided to the customer. 
     The information providing server  41  installed in an external organization supplies predetermined related information to the satellite group management device  11 , in response to a requirement from the satellite group management device  11  or periodically via a predetermined network. The related information provided from the information providing server  41  includes, for example, the following. For example, orbit information of a satellite described in a two-line elements (TLE) format can be acquired as related information from North American Air and Space Defense Command (NORAD) as an external organization. Furthermore, for example, it is possible to acquire weather information such as weather and cloud cover at a predetermined point on the earth, from a weather information providing company as an external organization. 
     The image analysis server  42  performs predetermined image processing on a captured image obtained by the satellite  21 , supplied from the satellite group management device  11  via a predetermined network. The processed image is provided to a customer of the image analysis company or supplied to the satellite group management device  11  of the satellite operation company. For example, the image analysis server  42  performs metadata generation processing of adding predetermined metadata to an image captured by the satellite  21 , correction processing such as distortion correction of the captured image, image synthesis processing such as color synthesis processing, and the like. The image processing on the captured image may be performed by the satellite operation company, and in this case, the satellite operation company and the image analysis company are the same. Furthermore, the satellite group management device  11  and the image analysis server  42  may be implemented by one device. 
     The communication device  13  communicates with a predetermined satellite  21  designated by the satellite group management device  11  via an antenna  14 , under the control of the satellite group management device  11 . For example, the communication device  13  transmits an imaging instruction for performing imaging of a predetermined region on the ground at a predetermined time and position, to the predetermined satellite  21 . Furthermore, the communication device  13  receives the captured image transmitted from the satellite  21 , and supplies to the satellite group management device  11  via the network  12 . Transmission from the communication device  13  of the ground station  15  to the satellite  21  is also referred to as uplink, and transmission from the satellite  21  to the communication device  13  is also referred to as downlink. The communication device  13  can perform direct communication with the satellite  21 , and can also perform communication via a relay satellite  22 . As the relay satellite  22 , for example, a geostationary satellite is used. 
     The network  12  and a network between the information providing server  41  or the image analysis server  42  and the satellite group management device  11  are any communication network, and may be a wired communication network or a wireless communication network, or may be configured with both of them. Furthermore, the network  12  and the network between the information providing server  41  or the image analysis server  42  and the satellite group management device  11  may be configured by one communication network or may be configured by a plurality of communication networks. These networks may be a communication network or a communication path of any communication standard such as, for example, the Internet, a public telephone network, a wide-area communication network for a wireless mobile body such as a so-called 4G line or 5G line, a wide area network (WAN), a local area network (LAN), a wireless communication network that performs communication conforming to the Bluetooth (registered trademark) standard, a communication path for short-range wireless communication such as near field communication (NFC), a communication path for infrared communication, and a communication network of wired communication conforming to a standard such as high-definition multimedia interface (HDMI (registered trademark)) or universal serial bus (USB). 
     A plurality of the individual satellites  21  constitutes a satellite group  31 . In  FIG. 1 , a satellite  21 A and a satellite  21 B are included in a first satellite group  31 A, and a satellite  21 C and a satellite  21 D are included in a second satellite group  31 B. Note that, in the example of  FIG. 1 , for the sake of simplicity, an example is illustrated in which one satellite group  31  includes two satellites  21 , but the number of satellites  21  included in one satellite group  31  is not limited to two. 
     In a case where the communication device  13  communicates with each of the satellites  21  included in the satellite group  31 , there are a method of individually communicating with each satellite  21  as in the first satellite group  31 A of  FIG. 1 , and a method in which, as in the second satellite group  31 B, only one satellite  21 C (hereinafter, also referred to as a representative satellite  21 C) representing the satellite group  31  communicates with the communication device  13  while another satellite  21 D indirectly communicates with the communication device  13  through inter-satellite communication with the representative satellite  21 C. Which method is to be used for communicating with (the communication device  13  of) the ground station  15  may be determined in advance by the satellite group  31 , or may be appropriately selected in accordance with contents of communication. 
     In the satellite image processing system  1  configured as described above, the plurality of satellites  21  included in one satellite group  31  may be operated by an operation method called formation flight. 
     As illustrated in  FIG. 2 , the formation flight is an operation method in which the plurality of satellites  21  included in one satellite group  31  flies while maintaining a relative positional relationship in a narrow range of about several hundred meters to several kilometers, and the plurality of satellites  21  operates in cooperation, which can provide a service that cannot be achieved by a single satellite. In  FIG. 2 , three satellites  21 X to  21 Z are included in one satellite group  31 , and each of the satellites  21 X to  21 Z communicates with the ground station  15 . On the uplink, by designating a group ID (satellite group ID) that is an identifier for identifying the satellite group  31  and an individual ID (satellite ID) that is an identifier for identifying each of the satellites  21  included in the satellite group  31 , a command or data is transmitted to the desired satellite  21 . 
     In the formation flight, since functions can be shared by the plurality of satellites  21  instead of a single satellite, there is an advantage that each satellite  21  can be downsized. For example, in the imaging function, even if a performance (for example, a resolution) of the imaging device mounted on each satellite  21  is lowered, a high resolution can be achieved by image synthesis or the like on captured images captured by the plurality of satellites  21 . 
     For example, as illustrated in A of  FIG. 3 , two satellites  21 E and  21 F can simultaneously image (simultaneously perform imaging of) one region  52  from different imaging points (satellite positions). Imaging results of the same ground surface from different imaging points can be used to generate a numerical altitude model (digital elevation model, DEM) indicating a height necessary for three-dimensional measurement. Furthermore, a parallax image is obtained from captured images of the two satellites  21 E and  21 F, and three-dimensional measurement can be performed. 
     Furthermore, as illustrated in B of  FIG. 3 , the plurality of satellites  21 E and  21 F can perform imaging (differential imaging) on one region  52  with a time difference at the same imaging point and imaging angle. For example, in a case where the satellite  21  moves at a speed of 7 km per second and a distance between the satellites  21  in convoy flight is 100 m, imaging can be performed every 1.4×10 −2  seconds. As described above, in the formation flight, imaging can be performed at short time intervals. Therefore, for example, it is possible to extract a change (displacement) of an object on the earth such as a passenger car on a road or a buoy on the sea, and measure a speed of a moving object. 
     For operating the plurality of satellites  21 , there is a constellation as a system. However, the constellation is a “a system that develops services mainly uniformly over the entire sphere by putting a large number of satellites into a single or a plurality of orbital planes”, and is a concept different from the formation flight. 
       FIG. 4  is a block diagram illustrating a configuration example of the satellite  21 . 
     The satellite  21  includes a management unit  101 , a bus  102 , an imaging control unit  103 , a heat control unit  104 , an attitude control system control unit  105 , an orbit control system control unit  106 , a propulsion system control unit  107 , a sensor control unit  108 , a power supply control unit  109 , and a communication control unit  110 . Furthermore, the satellite  21  also includes an imaging device  111 , a cooling device  112 , an attitude control device  113 , a propulsion device  114 , a sensor group  115 , a battery  116 , a solar cell panel  117 , and a communication device  118 . The management unit  101 , and the imaging control unit  103 , the heat control unit  104 , the attitude control system control unit  105 , the orbit control system control unit  106 , the propulsion system control unit  107 , the sensor control unit  108 , the power supply control unit  109 , and the communication control unit  110 , which are control units of the respective devices, are connected via the bus  102 . 
     The management unit  101  acquires a state of each device from the control unit of each device via the bus  102  and outputs an operation command to the control unit of each device, to control an operation of the entire satellite  21 . 
     The imaging control unit  103  controls an operation of the imaging device  111  in response to an operation command from the management unit  101 . The imaging device  111  includes, for example, a camera module including an image sensor, and performs imaging of a target object. In a case where the satellite  21  is a synthetic aperture radar (SAR) satellite, the imaging device  111  includes a radar device. 
     The heat control unit  104  acquires sensor values of temperature sensors included in the sensor group  115 , monitors a temperature change in the satellite  21 , and controls the entire satellite  21  to have a temperature within a prescribed temperature range. Basically, the temperature change is controlled by characteristics of a structure and a material, but dynamic cooling using the cooling device  112  may be performed as necessary in some cases. The cooling device  112  performs cooling using a cryogen such as liquid helium, for example. 
     The attitude control system control unit  105  controls the attitude control device  113  in response to an operation command from the management unit  101 , to perform control to direct the satellite  21  toward a target direction. For example, the attitude control system control unit  105  performs control to direct the antenna  14  toward the ground station  15 , direct the solar cell panel  117  toward a direction of the sun, and direct an observation sensor such as the imaging device  111  toward an observation target direction. The attitude control device  113  includes, for example, a wheel such as a three-axis gyro or a control moment gyro, a magnetic torquer, and the like. The attitude control system control unit  105  may use not only the attitude control device  113  but also the propulsion device  114  for attitude control application, in some cases. When performing attitude control, the attitude control system control unit  105  acquires sensor values of various sensors of the sensor group  115  as necessary. Examples of the sensor used for the attitude control application include, for example, a sun sensor, an earth sensor, a star sensor, a magnetic sensor, a gyro, and the like. 
     The orbit control system control unit  106  performs control related to maintenance of an orbital altitude and to a change of the orbit. The orbit control system control unit  106  performs control in cooperation with the propulsion system control unit  107  and the propulsion device  114 . 
     The propulsion system control unit  107  controls the propulsion device  114  in response to an operation command from the management unit  101 . The propulsion device  114  includes, for example, a solid motor, an ion engine, an apogee engine, and the like. The propulsion system control unit  107  acquires sensor values of various sensors of the sensor group  115 , and operates the propulsion device  114  in cooperation with the attitude control device  113  as necessary, to perform attitude control and attitude control of the satellite  21 . In a case where the satellite  21  is a small satellite, a chemical propulsion thruster or the like may not be mounted for attitude control purposes. 
     The sensor control unit  108  controls various sensors included in the sensor group  115 , and supplies sensor values to the management unit  101  or to another control unit. The various sensors are sensors to monitor a state in the satellite  21 , and include, for example, a GPS receiver, a star tracker (attitude sensor), an acceleration sensor, a gyro sensor, a magnetic sensor, a temperature sensor, a sun sensor, an earth sensor, a star sensor, and the like. 
     The power supply control unit  109  controls the battery  116  and the solar cell panel  117 . Power generated by the solar cell panel  117  is stored in the battery  116  under the control of the power supply control unit  109 . Power of the battery  116  may be directly distributed to each device in the satellite  21  or may be distributed via the bus  102 . 
     The communication control unit  110  controls the communication device  118  in response to an operation command from the management unit  101 . The communication device  118  includes an antenna, and communicates with the communication device  13  of the ground station  15  under the control of the communication control unit  110 . Furthermore, the communication device  118  can also communicate with other satellites  21  included the same satellite group  31  and the relay satellite  22 . Furthermore, in some cases, the communication control unit  110  and the communication device  118  may have a configuration in which systems are divided for transmission and reception of commands and telemetry, which involves small data amounts, and transmission and reception of mission system data (imaging data and the like), which involves large data amounts. 
     The individual control units of the imaging control unit  103  to the communication control unit  110  may be further divided into two or more or may be integrated with the management unit  101 , or any two or more may be integrated. Calculation resources such as a central processing unit (CPU) and a memory are basically mounted on the management unit  101 , but may also be mounted on each control unit. Each control unit may be implemented in a common hardware module. 
     The imaging devices  111  of the respective satellites  21  may have the same performance or different performances between the plurality of satellites  21  included in one satellite group  31 . 
     For example, in a case where the imaging devices  111  of the same model number are adopted as the imaging devices  111  mounted on the respective satellites  21  and the satellites  21  have the same performance, there are the following advantages. For example, images having the same performance can be acquired with a short time difference, and a difference can be easily detected. Furthermore, it is possible to generate a highly accurate (high-resolution) image by synthesizing images captured in a shared manner. Furthermore, since redundancy can be provided, even if a malfunction occurs in one device, it is allowable. 
     Whereas, in a case where the imaging devices  111  mounted on the respective satellites  21  have different performances, for example, it is possible to cause imaging of different roles to be performed, such as sharing between high-sensitivity monochrome imaging and low-sensitivity color imaging. Note that a case of the different performances includes not only a case where the mounted hardware configuration is different but also a case where the mounted hardware configuration is the same but the performance is made different by performing different control. For example, for image sensors of the same model number, an example is assumed in which one satellite  21  acquires a low-resolution image with high sensitivity by increasing a shutter speed, and another satellite  21  acquires a high-resolution image with low sensitivity on the contrary. 
     As a sharing example in a case where the performance is made different among the imaging devices  111  of the plurality of satellites  21 , for example, there may be control to individually make a difference in any one of sensitivity/shutter speed, a resolution, monochrome/color/polarization, and a band (wavelength range), or a combination thereof. Furthermore, the plurality of satellites  21  may have different battery performances and communication performances. 
       FIG. 5  is a block diagram illustrating a configuration example of the satellite group management device  11 , the communication device  13 , and the image analysis server  42 . 
     The satellite group management device  11  includes a control unit  211 , a communication unit  212 , an operation unit  213 , and a display unit  214 . 
     The control unit  211  manages the plurality of satellites  21  owned by the satellite operation company, by executing a satellite management application program stored in a storage unit (not illustrated). For example, the control unit  211  determines an operation plan of the plurality of satellites  21  by using related information acquired from the information providing server  41  as necessary, and instructs each satellite  21  to control an attitude and perform imaging, via the communication device  13 . Furthermore, the control unit  211  performs processing of generating metadata of a captured image transmitted from the satellite  21  via the communication device  13  and adding to the captured image. 
     In accordance with an instruction from the control unit  211 , the communication unit  212  performs predetermined communication with the communication device  13  via the network  12 , and also performs predetermined communication with the image analysis server  42 . 
     The operation unit  213  includes, for example, a keyboard, a mouse, a touch panel, or the like, receives a command or data input based on a user (operator) operation, and supplies to the control unit  211 . 
     The display unit  214  includes, for example, a liquid crystal display (LCD) or an organic electro luminescence (EL) display, and displays a screen of a satellite management application program, or displays a captured image captured by the satellite  21 , a processed image obtained by performing predetermined image processing on the captured image, and the like. 
     The communication device  13  includes a satellite communication unit  221 , a control unit  222 , and a communication unit  223 . 
     The satellite communication unit  221  communicates with each satellite  21  of the target satellite group  31  via the antenna  14  on the basis of the control of the control unit  222 . 
     The control unit  222  causes the satellite communication unit  221  to communicate with the satellite  21  under the control from the satellite group management device  11 . Furthermore, the control unit  222  transmits data such as a captured image acquired from the satellite  21 , to the satellite group management device  11  via the communication unit  223 . 
     The communication unit  223  performs predetermined communication with the satellite group management device  11  on the basis of the control of the control unit  222 . 
     The image analysis server  42  includes a control unit  231 , a communication unit  232 , an operation unit  233 , and a display unit  234 . 
     The control unit  231  executes an image analysis application program stored in a storage unit (not illustrated) to execute predetermined image processing on the captured image supplied from the satellite group management device  11 , such as, for example, metadata generation processing of adding predetermined metadata to the captured image, correction processing such as distortion correction of the captured image, and image synthesis processing such as color synthesis processing. 
     The communication unit  232  performs predetermined communication with the satellite group management device  11  or another device under the control from the control unit  231 . For example, the communication unit  232  receives a captured image captured by the satellite  21  from the satellite group management device  11 , supplies the captured image to the control unit  231 , and transmits a processed image after image processing to the satellite group management device  11 . 
     The operation unit  233  includes, for example, a keyboard, a mouse, a touch panel, or the like, receives a command or data input based on a user (operator) operation, and supplies to the control unit  231 . 
     The display unit  214  includes, for example, an LCD or an organic EL display, and displays a screen of an image analysis application program or displays an image before image processing or after image processing, and the like. 
     The satellite  21  and other devices included in the satellite image processing system  1  are configured as described above. 
     Note that the satellite group management device  11  selects an optimum communication device  13  from among the plurality of communication devices  13  in accordance with an orbit of the satellite  21  that performs communication, and causes the selected communication device  13  to transmit a predetermined command such as an imaging instruction or receives data such as a captured image via the communication device  13 . The satellite group management device  11  performs predetermined communication integrally with the communication device  13  that is freely selected in accordance with the target satellite  21 . Therefore, in the following description, the satellite group management device  11  and the communication device  13  will be collectively referred to as a management system. 
     &lt;2. Imaging Sequence of Single Device&gt; 
     Next, an imaging sequence focusing on one predetermined satellite  21  of the satellite group  31  that performs formation flight will be described with reference to a flowchart of  FIG. 6 . 
     First, in step S 11 , the management system determines imaging requirements by the satellite  21  on the basis of a request of a customer. 
     Specifically, the management system determines, as the imaging requirements, an imaging date and time, an imaging point, environmental conditions for imaging, camera setting values, and the like. The environmental conditions for imaging include, for example, weather conditions such as cloud cover at the imaging date and time, and the camera setting values include, for example, a resolution (resolving power), zoom, a shutter speed, sensitivity, an aperture, and the like. 
     In step S 12 , the management system determines (the communication device  13  of) the satellite  21  that meets the imaging requirements, and the ground station  15 . 
     Specifically, the management system selects the satellite  21  that meets the determined imaging requirements. For example, the satellite  21  is determined by determining whether the satellite  21  passes in the sky above an imaging target position at the determined imaging date and time, whether the imaging target position is within a range of an observation width of the satellite  21 , whether the imaging device  111  mounted on the satellite  21  satisfies the determined requirement for the resolving power and the camera setting values, and the like. Then, the ground station  15  suitable for communicating with the selected satellite  21  is determined. 
     Furthermore, the management system can select the satellite  21  in consideration of an expected remaining amount of a battery of the satellite  21  at the imaging date and time, power consumption of imaging, and the like. For example, in a case where the selected satellite  21  is planned to perform another imaging immediately before the imaging date and time, it is also assumed that power is consumed by the imaging, and by attitude control, data communication, heat control, and the like accompanying the imaging, and the next imaging cannot be performed. Therefore, the satellite  21  is selected by setting the priority of the satellite  21  in accordance with the expected remaining amount of the battery and the power consumption of imaging. 
     In step S 13 , the management system directs the antenna  14  of the selected ground station  15  to an expected orbit. The satellite group management device  11  transmits orbit information of the selected satellite  21  to the communication device  13 , and the communication device  13  directs the antenna  14  to the expected orbit. 
     In step S 14 , the management system transmits (uplinks) an imaging instruction to the selected satellite  21 . That is, the satellite group management device  11  transmits a command for transmitting an imaging instruction to the communication device  13  of the selected ground station  15 , and the communication device  13  having received the command transmits the imaging instruction to the selected satellite  21  via the antenna  14 . The imaging instruction includes an imaging date and time, an imaging point, camera setting values, and the like. 
     The satellite  21  receives the imaging instruction from the ground station  15  in step S 31 , and transmits reception completion to the ground station  15  in step S 32 . 
     In step S 15 , the management system receives the reception completion from the satellite  21 , and stops transmitting the imaging instruction. The transmission of the imaging instruction from the ground station  15  is repeatedly executed until there is a response of the reception completion from the satellite  21 . 
     In step S 33 , the satellite  21  performs imaging preparation processing based on the received imaging instruction. For example, the satellite  21  controls an attitude of the satellite  21  or an orientation of the imaging device  111  (pointing) such that the imaging device  111  faces the imaging target position, as necessary. Furthermore, for example, the imaging control unit  103  sets zoom, a shutter speed, sensitivity, an aperture, and the like of the image sensor. Moreover, the power supply control unit  109  performs charging in advance so as to obtain sufficient power for the imaging date and time. 
     When the imaging date and time designated by the imaging instruction comes, the satellite  21  performs imaging of the imaging target position in step S 34 . 
     In step S 35 , the satellite  21  generates metadata that is information to be associated with the captured image obtained as a result of the imaging, and adds to the captured image. Although details of the metadata will be described later, for example, information such as a group ID for identifying the satellite group  31 , an individual ID for identifying each satellite  21 , an imaging target position (subject position), and an imaging time can be generated as the metadata. 
     In step S 36 , the satellite  21  transmits (downlinks) the captured image added with the metadata, to the ground station  15 . The downlink may be performed immediately after generation of the captured image and the metadata, or may be performed when the satellite  21  reaches within a predetermined range of the predetermined ground station  15 . Furthermore, the captured image may be transmitted via the relay satellite  22 . 
     In step S 16 , the management system receives the captured image from the satellite  21 . Specifically, the communication device  13  receives the captured image via the antenna  14 , and supplies to the satellite group management device  11 . 
     In step S 17 , the satellite group management device  11  analyzes the metadata of the captured image. At this time, the satellite group management device  11  may newly generate metadata on the basis of the analysis result, and add the metadata. For example, the satellite group management device  11  calculates a satellite position at the time of imaging on the basis of the group ID and the individual ID of the captured image and on the basis of orbit information of the satellite  21 , and adds the satellite position as metadata. 
     In step S 18 , the satellite group management device  11  performs predetermined image processing on the captured image captured by the satellite  21 . The satellite group management device  11  performs, for example, correction processing such as distortion correction, image synthesis processing such as color synthesis processing, and the like. Details of the image processing will be described later. 
     In step S 19 , the satellite group management device  11  executes distribution management processing on the captured image and the processed image, and causes a predetermined storage unit to store. Details of the distribution management processing will also be described later. 
     Thus, a series of sequence in which one satellite  21  performs imaging is ended. Note that the image processing by the image analysis server  42  can be appropriately performed as necessary, and can be performed in a shared manner with the image processing of the satellite group management device  11  or instead of being performed by the satellite group management device  11 . The distribution management processing may also be performed by the image analysis server  42 . 
     Note that, in the example described above, the metadata is added to the captured image to be transmitted, but the metadata may be transmitted as a stream different from the captured image. At this time, only the metadata may be transmitted prior to the captured image. 
     &lt;3. Imaging Preparation Processing&gt; 
     Meanwhile, resources are limited particularly in a small satellite  21 . Therefore, it is necessary to particularly pay attention to a remaining battery amount, and imaging control corresponding thereto is important. 
       FIG. 7  is a detailed flowchart of the imaging preparation processing in step S 33  of  FIG. 6 . Here, it is assumed that the imaging instruction received in step S 31  before step S 33  has instructed imaging at an imaging time t 1 . 
     In the imaging preparation processing, first, in step S 51 , the management unit  101  of the satellite  21  estimates a remaining battery amount at the imaging time t 1 . Specifically, the management unit  101  estimates the remaining battery amount at the imaging time t 1  from (an estimated value of) a charge amount to be accumulated by solar power generation by the imaging time t 1  with respect to a current remaining battery amount. 
     In step S 52 , the management unit  101  determines whether there is a sufficient remaining battery amount on the basis of the estimated remaining battery amount. 
     Specifically, the management unit  101  determines whether the estimated remaining battery amount is a sufficient remaining battery amount, from a power consumption element related to imaging and a power consumption element for other than imaging. The power consumption element related to imaging includes imaging processing of the imaging device  111 , attitude control (pointing) of the satellite  21 , heat control associated therewith, and the like. In the imaging processing of the imaging device  111 , consideration is given to how many images are captured at the imaging time t 1  and with what degree of accuracy (resolving power, a shutter speed, necessity of zooming, and the like). The attitude control of the satellite  21  includes a change in an attitude of the satellite itself and a change in an attitude of the antenna. Furthermore, in a case where a camera module itself as the imaging device  111  can change an attitude toward an imaging direction, the attitude change of the camera module is also included in the attitude control of the satellite  21 . The power consumption elements other than imaging include communication (uplink and downlink) performed by the imaging time t 1 . 
     For example, as illustrated in A of  FIG. 8 , based on the premise that a charge amount of 70% with respect to a full charge amount of the battery  116  is always maintained, assuming that the current remaining battery amount is 90%, the charge amount until the time t 1  is 5%, the power consumption by the imaging processing at the time t 1  is 3%, the power consumption by the attitude control is 10%, and the power consumption by communication performed until the imaging time t 1  is 2%, 90%+5%−3%−10%−2%=80% is obtained. Since the charge amount of 70% can be secured even after imaging at the time t 1 , the satellite  21  can be determined to have a sufficient remaining battery amount. 
     Note that the management unit  101  may determine whether the remaining battery amount is sufficient on the basis of the remaining battery amount to be left after the imaging time t 1 , also in consideration of imaging to be performed at a next timing of the imaging time t 1 . 
     For example, as illustrated in B of  FIG. 8 , assuming that imaging is scheduled at a time t 2  after the imaging time t 1 , the charge amount from the time t 1  to the time t 2  is 2%, the power consumption by the imaging processing at the time t 2  is 3%, the power consumption by the attitude control is 10%, and the power consumption by the communication performed until the imaging time t 2  is 2%, since the remaining battery amount of 83% is required after the imaging at the time t 1 , it is determined that the estimated remaining battery amount of 80% at the imaging time t 1  is not a sufficient remaining battery amount. 
     Note that, in the example described above, the power consumption related to imaging has been mainly described, but other power consumption, for example, power consumption due to heat control associated with attitude control, periodic communication, and the like is also considered. 
     As described above, in a case where it is determined whether or not there is sufficient remaining battery amount and it is determined in step S 52  of  FIG. 7  that there is not a sufficient remaining battery amount, the process proceeds to step S 53 , and the satellite  21  determines whether an expected downlink timing can be changed by the imaging time t 1 . Changing the downlink timing makes it possible to save the amount of power required therefor. 
     In a case where it is determined in step S 53  that the downlink timing cannot be changed, the process in step S 53  is skipped, and the process proceeds to step S 55 . 
     Whereas, in a case where it is determined in step S 53  that the downlink timing can be changed, the process proceeds to step S 54 , and the management unit  101  changes the downlink timing and determines whether this change allows a sufficient remaining battery amount to be secured. Also in step S 54 , in a case where it is determined that there is not a sufficient remaining battery amount, the process proceeds to step S 55 . Whereas, in a case where it is determined in step S 54  that there is a sufficient remaining battery amount, the process proceeds to step S 57 . 
     In step S 55 , the management unit  101  changes accuracy of attitude control. In the attitude control, for example, in repeatedly applying a moment toward a target attitude with use of two types of a wheel and an ion engine and applying a reverse moment when the target attitude is exceeded, in a case where a swing speed becomes equal to or less than a certain value, it is determined that the attitude is changed to the target attitude. For example, the management unit  101  changes a range of a swing speed that is used for determining that the target attitude is obtained, as the change of the accuracy of the attitude control. By changing into a direction to increase the range of the swing speed and reducing a control amount of the attitude control, power consumption can be saved. 
     In step S 56 , the management unit  101  changes the imaging condition in accordance with the accuracy of the attitude control. When the range of the swing speed becomes large, the attitude of the satellite  21  is not stabilized to cause wobble, so that subject blurring may occur. Furthermore, since the pointing is insufficient, it is conceivable that sufficient zooming cannot be performed. Therefore, the management unit  101  compensates for an adverse effect due to the reduction in the control amount of the attitude control, by changing the imaging condition. 
     For example, the management unit  101  changes the imaging condition as follows. 
     The management unit  101  responds to subject blurring by increasing a shutter speed of the image sensor. Furthermore, since the captured image becomes dark when the shutter speed is increased, the management unit  101  may further perform control to increase sensitivity (gain). 
     Furthermore, for example, the management unit  101  can reduce resolving power (resolution) of the captured image for the purpose of improving sensitivity per unit pixel. As a result, the shutter speed can be improved, the influence of the reduction in the accuracy of the attitude control is unlikely to be received, and an amount of data at the time of downlink can be reduced. Furthermore, the management unit  101  selects a setting value with which optical zooming is not performed. This configuration makes it possible to increase tolerance for image blurring (wobble). 
     Furthermore, in a case where the camera module includes a mechanical blur correction mechanism (space blur correction), the mechanical blur correction mechanism may be performed instead of reducing the accuracy of the attitude control. 
     Furthermore, instead of reducing the resolving power (resolution) of the captured image, the management unit  101  may perform imaging setting so as to perform continuous capturing of a plurality of images. When a high-resolution captured image generated by synthesizing the captured images by the continuous capturing is generated and transmitted (downlinked) to the ground station  15 , reduction in resolving power (resolution) of the captured image can be compensated. Note that the high-resolution image generation by the image synthesis may be performed by the satellite group management device  11  or the image analysis server  42  after the down-ring. The satellite group management device  11  or the image analysis server  42  can also perform synthesis with a captured image in the past such as a base image, and with a captured image captured by another satellite  21 . 
     After step S 56 , or in a case where it is determined in step S 52  or step S 54  that there is a sufficient remaining battery amount, the process proceeds to step S 57 . 
     In step S 57 , the management unit  101  controls the attitude (performs pointing) of the satellite  21  or the imaging device  111  in accordance with the setting of the attitude control determined in the processing of step S 55 . 
     In step S 58 , the management unit  101  sets the imaging conditions determined in the process in step S 56 . 
     As described above, when the imaging preparation processing in step S 33  in  FIG. 6  ends and the imaging date and time designated by the imaging instruction comes, the process in step S 34  in  FIG. 6 , that is, imaging on the imaging target position is performed. 
     According to the imaging preparation processing, by lowering the stable accuracy of attitude control greatly affecting the power consumption, and changing the imaging condition and the image processing in the subsequent stage in a case where the remaining battery amount is small, it is possible to ensure the quality of the captured image while suppressing battery consumption. 
     &lt;4. Flowchart of Formation Flight&gt; 
     Next, the formation flight executed by a plurality of satellites  21  included in one satellite group  31  will be described. 
       FIG. 9  is a flowchart of the satellite image processing system  1  in which one satellite group  31  performs formation flight. 
     First, relative position checking processing in steps S 101 , S 121 , S 122 , and S 102  is performed between the management system and each satellite  21  of the satellite group  31  that performs formation flight. That is, in step S 101 , the management system inquires, about a relative position, of each satellite  21  of the satellite group  31  that performs the formation flight. In step S 121 , each of the satellites  21  included in the satellite group  31  performs processing of checking the relative position in response to the inquiry from the management system. Then, in step S 122 , each satellite  21  transmits the relative position, and in step S 102 , the management system receives the relative position from each satellite  21 . Here, the relative position is an arrangement order of the individual satellites  21  included in the satellite group  31  and a distance between the satellites. The arrangement order of the individual satellites  21  is, for example, an order in which a traveling direction of the satellite  21  is set as a head (No. 1). This relative position checking processing may be performed every time imaging is performed, or may be periodically performed, for example, once a day or once a week. 
     The management system has orbit information of the satellite group  31  acquired from NORAD as an external organization, but may not be able to discriminate orbit information of each satellite  21  included in the satellite group  31  in some cases. Alternatively, even if individual pieces of orbit information can be discriminated by observation from the ground, it may not be possible to discriminate the order of airframes in some cases. In the formation flight, there is a case where the satellite  21  is arranged in a range in which the orbit information cannot be individually allocated, and it is not possible to discriminate what number a certain satellite is from the head in the satellite group  31 . Therefore, it is necessary to measure a relative positional relationship. 
     Methods for controlling the relative position are roughly classified into two types: an open-loop method and a closed-loop method. 
     The open-loop method is a method in which there is no communication between satellites included in the satellite group  31  and the relative position is controlled by an instruction from the ground side. An error is likely to occur in a distance between the satellites. 
     On the other hand, the closed-loop method is a method of controlling the relative position by performing communication between satellites included in the satellite group  31 . The closed-loop method has higher accuracy in relative position than that of the open-loop method. The closed-loop method includes a centralized management type (centralized type) and a decentralized management type (decentralized type). In the central management type, there are a mode in which a satellite  21  serving as a leader is present and other satellites  21  follow the leader satellite, and a mode in which the leader satellite gives an instruction to other satellites  21 . The decentralized management type is a mode in which each satellite  21  included in the satellite group  31  autonomously communicates with other surrounding satellites  21  and controls its own position. 
     For the processing of checking the relative position in step S 121 , there is a method in which, in the open-loop method, for example, individual satellites  21  simultaneously perform imaging of a predetermined point on the ground, and the satellite group management device  11  on the ground side checks the arrangement order of the satellites  21  on the basis of captured images and attitude (pointing angle) information of the satellites  21 . Furthermore, for example, there is a method in which individual satellites  21  simultaneously perform communication with a predetermined point on the ground, and the communication device  13  on the ground side checks the arrangement order from a radio wave at that time. The communication for checking the arrangement order may be downlink of a predetermined captured image, or may be a signal for calibration or the like. Whereas, in the closed-loop method, each satellite  21  executes processing of measuring the relative position, and a measurement result is downlinked. As a method of measuring the relative position of each satellite  21 , there are a method of measuring a position (direction) through communication between satellites, a method of irradiating a laser by the satellite  21  to measure a distance from reflected light thereof, and the like. 
     In the closed-loop method and the open-loop method, only the arrangement order of the individual satellites  21  may be detected, while the distance between the satellites may be calculated by observation from the ground. 
     In step S 103 , the management system calculates imaging conditions of each satellite  21  on the basis of the relative position of each satellite  21 . The imaging conditions here include attitude control of the satellite  21  at the time of imaging, an imaging timing, and the like, in addition to set values of the image sensor. For example, in a case where three-dimensional measurement of the ground is performed, an imaging condition for causing each of the satellites  21  to have an attitude to achieve the same imaging target position is calculated using an inter-satellite distance as a baseline length. In a case where imaging with a time difference (differential imaging) is performed by the plurality of satellites  21  included in the satellite group  31 , a timing (imaging position) at which the preceding satellite  21  and the subsequent satellite  21  perform imaging and an attitude at the time of imaging are calculated. The timing at which each satellite  21  performs imaging is calculated on the basis of an inter-satellite distance. 
     In step S 104 , the management system transmits an imaging instruction to each satellite  21  on the basis of the calculated imaging conditions. The imaging instruction is transmitted (multicast) to all the satellites  21  of the satellite group  31 , but each satellite  21  can select the instruction addressed to the self by the individual ID as destination information included in the imaging instruction. 
     In step S 123 , the satellite  21  receives an imaging instruction from the ground station  15 , performs imaging preparation processing in step S 124 , and performs imaging in step S 125 . Moreover, the satellite  21  generates and adds metadata to the captured image in step S 126 , and transmits (downlinks) the captured image added with the metadata to the ground station  15  in step S 127 . 
     The processes of steps S 123  to S 127  are basically similar to the processes of steps S 31  to S 36  performed by the individual satellites  21  described with reference to  FIG. 6 . Note that, in the transmission of the captured image in step S 127 , each satellite  21  may individually transmit its own captured image, or the captured images may be collected in the leader satellite through inter-satellite communication and collectively transmitted by the leader satellite. 
     In step S 105 , the management system receives the captured image from each satellite  21 , and analyzes the metadata of the captured image in step S 106 . Moreover, in step S 107 , the management system performs predetermined image processing on the captured image, and in step S 108 , the management system executes the distribution management processing on the captured image and the processed image, and causes a predetermined storage unit to store. 
     The processes of steps S 105  to S 108  are basically similar to the processes of steps S 16  to S 19  performed by the management system described with reference to  FIG. 6 . However, in the image processing in step S 107 , not only image processing on a captured image obtained by one satellite  21  but also image processing using a plurality of captured images captured in cooperation by a plurality of satellites  21  of the satellite group  31  can be performed. 
     &lt;5. Example of Image Processing&gt; 
     A processing example of image processing executed by the satellite group management device  11  or the image analysis server  42  in step S 18  in  FIG. 6  or step S 107  in  FIG. 9  will be described. 
     The satellite group management device  11  or the image analysis server  42  can perform the following image processing on one captured image captured by each satellite  21 . 
     (1) Generation of Metadata 
     Metadata can be generated on the basis of information transmitted from the satellite  21  or information on the satellite  21  that has performed imaging. For example, information on latitude and longitude of an imaging target position, information on attitude control and acceleration at the time of imaging by the satellite  21 , and the like can be generated as metadata. 
     (2) Correction Processing of Captured Image 
     Correction processing can be performed, such as radiometric correction regarding sensitivity characteristics, geometric correction of an orbital position, an attitude error, and the like of the satellite  21 , ortho-correction for correcting geometric distortion caused by a height difference of terrain, and map projection of performing image projection onto a map projection surface. 
     (3) Color Synthesis Processing 
     Color synthesis processing can be performed, such as pan-sharpening processing, true-color synthesis processing, false color synthesis processing, natural color synthesis processing, SAR image synthesis processing, and processing of adding a color to a captured image for each band. 
     (4) Other Image Synthesis 
     It is also possible to perform synthesis with a captured image captured by itself (satellite  21 ) in the past, a captured image captured by another satellite  21 , or some base image, synthesis of captured images captured in different bands, synthesis with map information, and the like. 
     (5) Information Extraction 
     It is possible to calculate vegetation detection information such as normalized difference vegetation index (NDVI) and water detection information such as normalized difference water index (NDWI), with different bands such as red (R) and infrared (IR). It is possible to perform highlight processing of a specific subject such as a vehicle, a moving object, or a fish group, extraction of information on a specific band, a change point from previous imaging, and the like. 
     In particular, in a case of using a plurality of captured images captured by a plurality of satellites  21  that performs formation flight, the satellite group management device  11  or the image analysis server  42  can more effectively perform the following image processing. 
     (1) Resolution Enhancement or Quality Enhancement Processing 
     By superimposing a plurality of captured images, a captured image with improved resolving power can be generated. Furthermore, it is possible to generate a pansharped image obtained by combining a monochrome image and a color image, and a high-resolution captured image by synthesizing captured images with different imaging conditions such as, for example, different dynamic ranges or shutter speeds, different bands (wavelength bands), or different resolutions. 
     (2) Function Sharing 
     An index such as a normalized difference vegetation index (NDVI) can be calculated with different bands such as red (R) and infrared (IR). 
     (3) Three-Dimensional Measurement 
     Three-dimensional information can be obtained from a parallax image. Furthermore, accuracy of object recognition on the ground can be enhanced by the three-dimensional information. For example, it is possible to discriminate whether or not an object is a vehicle (even if it is not immediately recognized as a vehicle from the image in terms of resolving power, it can be estimated as a vehicle if the object on the road is not a pattern and is recognized as a three-dimensional object). 
     (4) Difference Measurement 
     A change between a first time and a second time can be extracted using a plurality of captured images captured from the same position with a time difference. Furthermore, imaging may be performed such that only a changed target is extracted and colored. Furthermore, for example, a moving speed of a ship or a vehicle can be calculated using a plurality of captured images, or a wind speed can be calculated from a movement of cloud or the like. 
     (5) Other Image Synthesis 
     It is also possible to perform synthesis with a captured image in the past or a captured image captured by another satellite  21 , synthesis of captured images captured in different bands, synthesis with map information, and the like. 
     The satellite group management device  11  and the image analysis server  42  as the image processing device perform the above-described image processing on the basis of satellite specification information that specifies a satellite and is associated as metadata with a captured image captured by the satellite  21 . In other words, since the satellite specification information is associated as metadata with the captured image, it is possible to perform image processing on a plurality of pieces by using a relative positional relationship among the plurality of satellites  21  in the formation flight. The satellite specification information includes at least a group ID for identifying the satellite group  31 , an individual ID for identifying each of the satellites  21  included in the satellite group  31 , and relative position information of each of the satellites  21  that perform formation flight. 
     Note that the image processing using the plurality of captured images captured by the formation flight has been described, but the above-described image processing may be performed on a plurality of captured images captured by a constellation instead of the formation flight. For example, image processing such as (1) resolution enhancement or quality enhancement processing, (3) three-dimensional measurement, and (5) other image synthesis may be performed on a plurality of captured images captured by a constellation. 
     (Image Format) 
     The processed image after the image processing and the captured image are stored in the storage unit and provided to the customer or the like by using, for example, the following image formats. 
     (1) CEOS 
     CEOS is a format standardized by the Committee on Earth Observation Satellites. CEOS includes “CEOS-BSQ” in which a file is divided for every band and “CEOS-BIL” in which a plurality of bands is multiplexed. 
     (2) HDF 
     HDF is a format developed at the National Center for Supercomputing Applications (NCSA) of the University of Illinois. A plurality of bands is grouped into one file so that data can be easily subjected to mutual exchange in various computer environments. 
     (3) Geo TIFF 
     Geo TIFF is a format in which information for remote sensing is added to a tagged image file format (TIFF). Since the format is the TIFF, Geo TIFF can be opened with a general image viewer or the like. 
     (4) JPEG2000 
     JPEG 2000 is an image format standardized by the Joint Photographic Experts Group. JPEG 2000 not only simply increases a compression rate, but also adopts a technique of improving an image of a region of interest and a copyright protection technique such as an electronic watermark. 
     As a method of presenting the processed image and the captured image, there are (1) a method of providing an image in a browsable manner and (2) a method of presenting only information based on analysis of an image. 
     Moreover, (1) the method of providing an image in a browsable manner includes: (1A) a method of providing (transmitting) an image itself; (1B) a method of allowing access on a platform, such as a data server, and allowing a user to browse an image for data on the platform; and (1C) a method of providing a user with dedicated software for browsing an image and allowing the user to browse only on the dedicated software. 
     (2) The method of presenting only information based on analysis of an image is, for example, a method of presenting the number of vehicles or moving objects for every time or presenting an area of a fish group, which are obtained by performing the above-described information extraction processing. 
     &lt;6. Details of Metadata&gt; 
       FIG. 10  illustrates an example of information to be given as metadata to a captured image or a processed image. 
     The information to be given as metadata includes, depending on a type of information, each piece of: information that can be added by the satellite  21 ; information that can be added by the satellite group management device  11 ; and information that can be added by the image analysis server  42  of the analysis company. In  FIG. 10 , each piece of information is arranged in a table format, and a circle (∘) is given to a device that can add each piece of information. Note that, in a case where the satellite group management device  11  also has an image processing function, it goes without saying that the satellite group management device  11  itself can also add information that can be added by the image analysis server  42 . 
     As the metadata, for example, information (satellite specification information) for specifying a satellite can be added. The information for specifying a satellite can include, for example, a group ID for identifying the satellite group  31 , an individual ID for identifying individual satellites  21 , relative position information of the individual satellites  21  included in the satellite group  31  that performs formation flight, angle information of the self (satellite  21 ) at the time of imaging, a satellite type, and the like. The relative position information includes, for example, information such as an order of the plurality of satellites  21  included in the satellite group  31  and a distance between the satellites. The relative position information may be information serving as a material for estimating a relative position. The angle information of the self at the time of imaging represents, for example, an angle of the self with respect to a ground surface at the time of imaging. The satellite type includes, for example, whether to be an optical satellite or an SAR satellite, classification by categorization such as application and a size of the satellite, and the like. 
     Furthermore, the information for specifying a satellite can include, for example, orbit information (TLE information) in the TLE format of the satellite  21 , position information (GPS information) based on a GPS signal, orbital position/orbital altitude information calculated from at least one of TLE information or GPS information, speed information of the satellite  21 , sensor information such as an earth sensor, a sun sensor, and a star tracker of the satellite  21 , and the like. 
     Furthermore, information regarding imaging contents can be added to the metadata. The information regarding the imaging contents can include, for example, imaging target position information indicating a location on the earth as an imaging target, imaging conditions such as a resolution (resolving power), zoom, a shutter speed, sensitivity, and an aperture (f-number), a sensor type such as a model number of the image sensor, an imaging time, a satellite position at the time of imaging, weather information such as a cloud cover and a sunshine amount, and the like. 
     As the imaging target position information, for example, information on latitude and longitude of a location on the earth as an imaging target is given. The satellite position at the time of imaging is added on the ground side on the basis of orbit information of the satellite  21 . The satellite position at the time of imaging may be the orbit information of the satellite  21  itself. Furthermore, in the above-described imaging preparation processing, there is a case where accuracy of attitude control is changed in accordance with a remaining battery amount. Therefore, the satellite position at the time of imaging may further include accuracy information of attitude control of the satellite  21  at the time of imaging, three-dimensional acceleration information indicating a movement of the satellite itself at the time of imaging, and the like. This information regarding the attitude control can be used as a reference for processing in high-resolution processing or the like on the captured image performed on the ground side. 
     Moreover, information regarding an image type can be added to the metadata. The information regarding the image type can include band information and image processing information. 
     The band information includes: wavelength information related to a wavelength band; color information indicating whether to be RGB (TrueColor), IR (infrared light), or monochrome, coloring information indicating that a specification target such as a plant is colored (False Color), analysis information indicating that the image indicates a normalized vegetation index (normalized difference vegetation index: NDVI) or a normalized difference water index (NDWI); and the like. 
     The image processing information includes a processing time, a processing level, a processing method, and the like of the image processing. The processing time indicates a time when the image processing has been performed. The processing level is divided into six stages from L0 to L5. L0 is a level indicating an uncorrected state where correction processing is not performed, L1 is a level where radiometric correction regarding sensitivity characteristics is performed, and L2 is a level where geometric correction of an orbital position, an attitude error, and the like of the satellite  21  is performed. In addition, there are a level where an image projection is performed on a map projection surface, a level where ortho-correction for correcting geometric distortion is performed, and the like. In the processing method, processing names such as pan-sharpening processing, true-color synthesis processing, and SAR image synthesis processing are described. In a processed image of the three-dimensional measurement, distinction between an L image (image for the left eye) and an R image (image for the right eye) may be described. 
     Moreover, to the metadata, related person information that is information regarding a related person of the captured image or the processed image can be added. The information regarding the related person includes, for example, information such as an owner of the satellite  21 , a service operator operating a satellite remote sensing service, and a right holder of the captured image or the processed image. By adding the related person information as metadata to the captured image or the processed image, a related person of the captured image or the processed image can be managed by referring to or collating the related person of the captured image or the processed image, and authenticity of the image can be ensured. 
     &lt;7. Details of Distribution Management Processing&gt; 
     Next, a description is given to the distribution management processing of a captured image or a processed image executed by the satellite group management device  11  or the image analysis server  42  in step S 19  in  FIG. 6  and step S 108  in  FIG. 9 . 
     The captured image and the processed image can be subjected to the following processing for managing distribution of data. 
     (1) Usage Limitation Processing 
     It is possible to perform processing so that the captured image and the processed image cannot be downloaded or displayed without permission, or perform processing for disabling downloading or displaying of the captured image and the processed image in a case where predetermined conditions such as an expiration date, the number of times of copying, and the number of times of display are satisfied. Furthermore, processing can be performed on the captured image and the processed image so that secondary processing such as image synthesis cannot be performed. 
     (2) Watermark 
     Processing of adding a watermark (electronic watermark) indicating that there is a copyright can be performed on the captured image and the processed image. Furthermore, it is possible to perform processing of adding, as a watermark, information that enables discrimination of an outflow path. 
     By performing the distribution management processing as described above, the authenticity of the image can be ensured, and leakage and inappropriate use of the captured image and the processed image can be prevented. At this time, a method for managing each piece of data and a usage mode of the data by using a blockchain may be adopted. 
     (Processing Example of Image Protection) 
     In a case where there is a user&#39;s request for privacy protection on the captured image and the processed image, or on an image showing an area whose disclosure is restricted (disclosure restriction area) or prohibited (prohibited area) by a law or the like of each country, such as a military facility or a public facility, the satellite group management device  11  or the image analysis server  42  can perform processing for protecting an image by a predetermined protection method. It suffices that whether or not the area is the protection target area is determined using the imaging target position information of the metadata. 
     Examples of the method for protecting the image include, for example, performing processing on an image of the protection target area such that a person other than an end user or a permitted user cannot perform resolution enhancement processing more than necessary. Alternatively, the resolution of the image of the protection target area may be lowered, or blurring may be applied. Furthermore, updating of the image of the protection target area may be stopped, and the image may be replaced with an image in the past to be displayed, or an image indicating protection may be superimposed. 
     In addition to a case where the image protection is executed in advance before the image is first provided to the user, processing can be performed later in a case where a privacy protection request is made, in a case where distribution of an unauthorized image is detected, or the like. In a case where distribution of an unauthorized image is detected, means to delete the captured image and the processed image that have been illicitly leaked can also be employed. 
     Since the satellite group management device  11  and the image analysis server  42  can handle the image protection processing as described above, it is possible to respond to a request for privacy protection and disclosure restriction of the user. 
     &lt;8. Application Example of Formation Flight&gt; 
     Hereinafter, an example of an image analysis processing using captured images captured by the plurality of satellites  21  included in the satellite group  31  by formation flight will be described. 
     (1) Germination Confirmation of Crops by Resolution Enhancement (Remote Sensing for Agriculture) 
     A resolution of several cm is required for observation for germination confirmation of crops. By synthesizing captured images of a plurality of satellites by formation flight, resolving power exceeding resolving power in a single machine can be achieved, and germination can be detected. 
     The satellite group  31  performs imaging with the same point of farmland as an imaging target position. Individual satellites  21  may simultaneously capture images from different positions, or may capture images from the same position with a time difference. In order to direct the imaging target position of each satellite  21  to the same point, it is necessary to grasp a satellite position in advance. 
     In the image synthesis processing, it is not necessary to be able to grasp which satellite  21  has captured each captured image. However, if it is possible to grasp which satellite  21  has performed the imaging, an angle and a time at the time of imaging can be discriminated, so that more efficient image synthesis can be performed. 
     For example, the Geo TIFF format can be used as a format of the processed image after synthesis, and the fact that it is a synthesized image by formation flight, and an imaging position, an imaging time, an imaging condition, and the like of each of the captured images as a synthesis source can be added as metadata. As the imaging position information, imaging position information of any captured image (representative captured image) as a synthesis source can be used. 
     (2) Confirmation of Growth Status of Crops by Three-Dimensional Measurement (Remote Sensing for Agriculture) 
     A growth status of crops is confirmed by an index such as NDVI, but can also be acquired by accurately acquiring height information with three-dimensional measurement. 
     The individual satellites  21  of the satellite group  31  simultaneously perform imaging with the same point, which is farmland, as an imaging target position, to obtain a parallax image. In order to obtain a distance between the satellites, which is a base length, relative position information of the satellite  21  is required. This relative position information may also be obtained simultaneously with downlink of the captured image instead of being obtained in advance. 
     In the image synthesis processing, it is not necessary to be able to grasp which satellite  21  has captured each captured image. However, if it is possible to grasp which satellite  21  has performed the imaging, an angle and a time at the time of imaging can be discriminated, so that more efficient image synthesis can be performed. 
     For the processed image after synthesis, for example, a format of a three-dimensional image including a set of an L image and an R image can be used, and the fact that it is a synthesized image by formation flight, and an imaging position, an imaging time, an imaging condition, and the like of each of the captured images as a synthesis source can be added as metadata. As the imaging position information, imaging position information of any captured image (representative captured image) as a synthesis source can be used. In addition to information of the three-dimensional measurement, a vegetation index such as NDVI or other information may be further added. 
     (3) Other Remote Sensing for Agriculture 
     For example, it is possible to accurately acquire height information for horizontal confirmation after tilling of farmland by three-dimensional measurement. 
     (4) Movement Detection of Fish Group (Marine Observation Remote Sensing) 
     Information regarding detection of a fish group and a moving direction and a moving speed of the fish group can be obtained. 
     The satellite group  31  performs imaging with the same point in the ocean as an imaging target position. Individual satellites  21  capture images from the same position with a time difference. In order to direct the imaging target position of each satellite  21  to the same point, it is necessary to grasp a satellite position in advance. In particular, in imaging in which the ocean having no target as a reference is set as the imaging target position, it is necessary to precisely align captured images of the respective satellites  21 . Therefore, it is important to grasp a relative position and moving speed information of each satellite  21  in advance. 
     In the analysis processing of the captured image, alignment of the captured images of the individual satellites  21  and comparison processing of the fish group are performed on the basis of an imaging position (including angle information) and an imaging time. By the comparison processing, a moving speed of the fish group can be calculated from a time difference between imaging times of the two or more satellites  21  and a moving distance of the fish group. 
     As the image presented as an analysis processing image, for example, it is possible to adopt an image in which information indicating a moving direction and a moving speed of the fish group is displayed in a superimposed manner on a captured image (captured image of the predetermined satellite  21 ), as a base, of the fish group. Various pieces of information on the captured image as a base are added to the metadata. 
     As a result of the analysis processing, information may be presented describing a calculation method at a time of calculating a moving direction and a moving speed of the fish group, for example, a plurality of captured images capturing the fish group, and information such as an imaging time and a position of the fish group. 
     (5) Other Marine Observation Remote Sensing 
     For example, it is also possible to obtain information regarding a moving direction and a moving speed of a ship and observation information of an ocean current. 
     (6) Counting of Number of Vehicles (Economic Index Estimation) 
     An economic index (economic trend or sales prediction of a specific store) is calculated by examining a number of vehicles in a parking lot and a number of traveling vehicles on a road. By synthesizing captured images of a plurality of satellites by formation flight, it is possible to generate a high resolution captured image and to more accurately detect the number of vehicles or the number of traveling vehicles. 
     The satellite group  31  simultaneously performs imaging with the same point as an imaging target position. In order to direct the imaging target position of each satellite  21  to the same point, it is necessary to grasp a satellite position in advance. A plurality of captured images captured at the same time enables resolution enhancement of an image and acquisition of three-dimensional information based on a parallax image. 
     In the image synthesis processing, it is not necessary to be able to grasp which satellite  21  has captured each captured image. However, if it is possible to grasp which satellite  21  has performed the imaging, an angle and a time at the time of imaging can be discriminated, so that more efficient image synthesis can be performed. In synthesis of two or more captured images, a target object serving as a reference may be extracted from a road or a building in the image, and the two or more images may be aligned on the basis of the target object. The target object serving as a reference may be selected on the basis of height information. 
     In the image analysis processing, the number of vehicles or the number of traveling vehicles are calculated on the basis of a high-resolution captured image. The number of vehicles or the number of traveling vehicles may be efficiently calculated by increasing a resolution only in a specific region in the captured image. In a case where it is not possible to discriminate whether or not to be a vehicle in the two-dimensional image, it may be discriminated whether or not to be a vehicle on the basis of three-dimensional information including the height. 
     As the image presented as an analysis processing image, for example, an image can be adopted in which a captured image as a base (a captured image of a predetermined satellite  21 ) is colored with a color changed for every detection target area or every count target (a vehicle or a person), and the number of counts is displayed in a superimposed manner. Various pieces of information on the image as a base are given to the metadata. 
     As a result of the analysis processing, information such as imaging conditions of the image and a method of calculating the detection target object may be presented to the user. 
     Note that, while the example described above is an example of resolution enhancement by simultaneous imaging, a moving speed of the vehicle may be measured on the basis of captured images captured with a time difference, and traffic volume information before and after the imaging time may be estimated and presented. 
     (7) Other 
     By synthesizing captured images of a plurality of satellites by formation flight, three-dimensional information based on a parallax image can be acquired, and a three-dimensional map of a construction site or a residence can be created. 
     (8) Modified Example 
     A constellation of formation flight may also be adopted. That is, by putting the satellite group  31  that performs formation flight into a single or a plurality of orbital planes, it is possible to perform an operation of uniformly developing a service mainly over the entire sphere. 
     Image synthesis of a captured image by formation flight or a captured image of another satellite may be performed. For example, it is possible to perform image processing of superimposing and displaying moving-object information obtained in formation flight on a high-resolution image captured by a geostationary satellite. 
     &lt;9. Second Embodiment of Satellite Image Processing System&gt; 
       FIG. 11  illustrates a configuration example of the second embodiment of a satellite image processing system to which the present technology is applied. 
     In the first embodiment described above, the satellite group  31  that performs formation flight has a configuration to perform simultaneous imaging or time difference imaging at an imaging point and an imaging time instructed in advance on the basis of orbit information or the like of the satellite  21 . Therefore, for example, it is not possible to detect a predetermined event having occurred on the ground and perform real-time imaging at the time of the event occurrence. 
     In a second embodiment described below, a description is given to a configuration in which one or more satellites  21  perform real-time imaging in accordance with an event having occurred on the ground. In a case where a satellite group  31  including a plurality of satellites  21  performs real-time imaging in accordance with an event having occurred on the ground, the satellite group  31  may be operated by either a constellation or formation flight. 
     As illustrated in  FIG. 11 , to the configuration of a satellite image processing system  1  of the second embodiment, a plurality of transmission devices  251  including a sensor that detects a predetermined event on the ground is newly added. In the example of  FIG. 11 , four transmission devices  251 A to  251 D are installed in an event detection region  250 , but any number of transmission devices  251  may be adopted. Note that three satellites  21 X to  21 Z of the second embodiment illustrated in  FIG. 11  may be operated by either a constellation or formation flight. Furthermore, the three satellites  21 X to  21 Z may be the satellites  21  each operated independently. 
     The four transmission devices  251 A to  251 D each share the event detection region  250  to detect an event. A fan-shaped region indicated by a broken line in  FIG. 11  indicates an event detection range of one transmission device  251 . The event detection region  250  is farmland, for example, and a sensor included in the transmission device  251  monitors a temperature and the like of the farmland or monitors a growth status of crops. 
     The transmission device  251  detects a predetermined event in the event detection region  250 , and transmits an imaging instruction to one or more satellites  21 . The satellites  21 X to  21 Z perform imaging of the event occurrence region in accordance with the imaging instruction transmitted from the transmission device  251 . 
       FIG. 12  is a block diagram illustrating a configuration example of the transmission device  251 . 
     The transmission device  251  includes a transmission unit  271 , a control unit  272 , a sensor unit  273 , and a power supply unit  274 . 
     Under the control of the control unit  272 , the transmission unit  271  transmits an imaging instruction to the satellite  21  passing through the vicinity of the transmission device  251 . 
     The transmission unit  271  is nondirectional, for example, and can transmit an imaging instruction to all the satellites  21  passing through a certain range of the transmission device  251 . The transmission unit  271  includes, for example, a communication device capable of performing long-distance communication of 100 km or more for a high-speed moving object of 100 km/h, and having low power consumption. 
     The transmission unit  271  may have directivity. In this case, the transmission unit  271  directs an antenna (not illustrated) to the satellite  21  passing through the vicinity of the transmission device  251  on the basis of orbit information of the satellite  21 , and transmits an imaging instruction to the target satellite  21 . The orbit information of the satellite  21  is stored in advance. 
     The control unit  272  controls the entire operation of the transmission device  251 . In a case where a predetermined event has been detected by the sensor unit  273 , the control unit  272  controls the transmission unit  271  to transmit an imaging instruction to the satellite  21 . 
     The sensor unit  273  includes one or more types of predetermined sensors according to a purpose of event detection. For example, the sensor unit  273  includes an odor sensor, an atmospheric pressure sensor, a temperature sensor, and the like. Furthermore, for example, the sensor unit  273  may include an image sensor (an RGB sensor, an IR sensor, or the like) that performs imaging of the event detection region  250 . For example, when a detection value becomes a predetermined threshold value or more, the sensor unit  273  detects an occurrence of an event and notifies the control unit  272  of the occurrence of the event. 
     Note that the sensor unit  273  and the transmission unit  271  may be arranged in proximity, for example, or may be arranged apart from each other such that, for example, the transmission unit  271  is at a high place closest to the satellite  21 , and the sensor unit  273  is arranged at a low place close to the ground. 
     To one transmission device  251 , a plurality of sensors of different types may be mounted, or a plurality of sensors of the same type may be mounted. In a case where a plurality of sensors is mounted to the transmission device  251 , there is a case where it is necessary to add, as transmission information, sensor information such as a sensor detection range as an imaging target position and a sensor detection type, and to transmit a sensor detection result. 
     The power supply unit  274  includes, for example, a battery or the like charged by solar power generation or the like, and supplies power to each unit of the transmission device  251 . 
     The transmission device  251  is a communication device that is configured as described above and is capable of only one-way communication from the transmission device  251  to the satellite  21 , but may also be a communication device capable of bidirectional communication including a direction from the satellite  21  to the transmission device  251 . 
     In both unidirectional communication and bidirectional communication, in a case of nondirectional, since a transmission side does not need to direct the antenna toward the satellite  21  or a ground station  15  that is to be a reception side, it is particularly preferable in a case of transmitting from the ground to the satellite  21  in the sky. In the present embodiment, it is assumed that the transmission unit  271  of the transmission device  251  is nondirectional and the transmission device  251  is a device that performs unidirectional communication. However, needless to say that the transmission device  251  may be a device that is directional and performs bidirectional communication. 
     &lt;10. First Event Imaging Sequence of Second Embodiment&gt; 
     Next, a first event imaging sequence performed by the satellite image processing system  1  according to the second embodiment will be described with reference to a flowchart in  FIG. 13 . 
     First, in step S 141 , the control unit  272  of the transmission device  251  determines whether an event has been detected by the sensor unit  273 . When the sensor unit  273  detects a predetermined event and notifies the control unit  272  of the occurrence of the event, the control unit  272  determines that an event has been detected. Therefore, in step S 141 , the control unit  272  waits until there is notification of an event occurrence from the sensor unit  273 , and the process proceeds from step S 141  to step S 142  in a case where it is determined that an event has been detected. 
     In response to the occurrence of the event, in step S 142 , the control unit  272  controls the transmission unit  271  to transmit an imaging instruction to the satellite  21  passing through the vicinity of the transmission device  251 . The transmission unit  271  transmits an imaging instruction in response to a command from the control unit  272 . 
     Since the communication between the transmission device  251  and the satellite  21  is unidirectional communication only from the ground side to the satellite  21 , the transmission device  251  cannot check whether or not the satellite  21  has received the imaging instruction. Therefore, for example, the transmission device  251  continues to transmit the imaging instruction for a certain period of time such as 30 minutes or 1 hour, or repeatedly transmits the imaging instruction intermittently at certain time intervals. In a case where the transmission device  251  and the satellite  21  can perform bidirectional communication, as in the imaging sequence described with reference to  FIG. 6 , it suffices that reception completion is received from the satellite  21 , and the transmission of the imaging instruction is stopped. The reception completion from the satellite  21  to the transmission device  251  may include a fact that the satellite  21  performs imaging, to be transmitted. 
     Furthermore, in this imaging sequence, when detecting an occurrence of an event, the transmission device  251  transmits an imaging instruction without selecting the satellite  21 . However, in a case where orbit information and imaging capability of the satellite  21  passing over the sky are known, the imaging instruction may be transmitted by designating, with a group ID or an individual ID, a satellite group  31  or a satellite  21  that satisfies required imaging conditions. 
     The imaging instruction from the transmission device  251  to the satellite  21  is added with, for example, imaging-related information such as a required imaging condition, a required imaging target position, a sensor ID, an event occurrence time, and a detected event type as a parameter, to be transmitted. The required imaging conditions include, for example, a resolution, a wavelength band (RGB, IR, and the like), and the like. The required imaging target position represents a region on the ground of the imaging target, and is a position corresponding to an event occurrence region of the sensor unit  273 . As the required imaging target position, an installation position of the transmission device  251  or the sensor unit  273  may be stored. The sensor ID is sensor identification information for identifying the sensor unit  273  that has detected the event. The event occurrence time is a time at which the sensor unit  273  has detected the event, and corresponds to a time at which a requirement for an imaging instruction has occurred. The detected event type represents, for example, a type of an event detected by the sensor unit  273 , such as detection of an abnormal temperature. As the detected event type, a sensor type may be stored instead of a specific detected event type. 
     In step S 161 , the satellite  21  receives the imaging instruction from the transmission device  251 , and determines whether imaging by the self is possible in step S 162 . The satellite  21  checks whether or not the required imaging condition added to the imaging instruction is satisfied, and determines whether or not imaging by the self is possible. In a case where it is determined in step S 162  that imaging by the self is not possible, the satellite  21  ends the process. 
     Whereas, in a case where it is determined in step S 162  that imaging by the self is possible, the process proceeds to step S 163 , and the satellite  21  performs imaging preparation processing based on the received imaging instruction. Subsequently, the satellite  21  performs imaging in step S 164 , and generates metadata and adds to the captured image in step S 165 . Since individual processes of steps S 163  to S 165  are basically similar to individual processes of steps S 33  to S 35  of  FIG. 6  described above, the details thereof will be omitted. The metadata can include a part or all of information received from the transmission device  251 . For example, information such as a sensor ID representing the sensor unit  273  and an event occurrence time can be included as the metadata. 
     In step S 166 , it is determined whether the satellite  21  has reached a downlink point, in other words, whether the satellite  21  has reached within a range that allows communication with the communication device  13  of the ground station  15 . The satellite  21  repeats the process of step S 166  until it is determined that the downlink point has been reached, and the process proceeds to step S 167  in a case where it is determined that the downlink point has been reached. 
     In step S 167 , the satellite  21  transmits (downlinks) the captured image added with the metadata, to the ground station  15 . The downlink may be performed via a relay satellite  22 . 
     In step S 181 , a management system receives a captured image from the satellite  21 . That is, the communication device  13  receives the captured image via an antenna  14 , and supplies to a satellite group management device  11 . After receiving the captured image, the management system performs processing similar to steps S 17  to S 19  in  FIG. 6 , but the description thereof will be omitted because the description will be redundant. 
     &lt;11. Second Event Imaging Sequence According to Second Embodiment&gt; 
     Next, a second event imaging sequence performed by the satellite image processing system  1  according to the second embodiment will be described with reference to a flowchart in  FIG. 14 . 
     In the first event imaging sequence described above, each satellite  21  individually determines whether or not imaging is possible, and transmits a captured image to the communication device  13  on the ground in a case where imaging is performed. 
     In the second event imaging sequence in  FIG. 14 , processing is added in which a subsequent satellite  21  takes over the imaging instruction in a case where the satellite  21  having received the imaging instruction determines that imaging by the self is not possible. The subsequent satellite  21  is, for example, a satellite  21  belonging to the same satellite group  31  operated in a constellation or formation flight. In the following second event imaging sequence, the satellite  21  that receives an imaging instruction is referred to as a first satellite  21 , and the subsequent satellite  21  that takes over the imaging instruction is referred to as a second satellite  21 , to be distinguished. 
     Detection of an event occurrence and transmission of the imaging instruction by the transmission device  251  in steps S 141  and S 142  are the same as those in the first event imaging sequence described above. 
     In step S 201 , the first satellite  21  receives the imaging instruction from the transmission device  251 , and determines whether imaging by the self is possible in step S 202 . In a case where it is determined in step S 202  that imaging by the self is possible, the process proceeds to step S 203 , the first satellite  21  performs imaging based on the imaging instruction and transmission, and the process ends. Since the imaging sequence in a case where it is determined that imaging by the self is possible is the same as that of the first event imaging sequence described above, the description thereof will be omitted. 
     Whereas, in a case where it is determined in step S 202  that imaging by the self is not possible, the process proceeds to step S 204 , and the first satellite  21  determines whether imaging by the subsequent second satellite  21  belonging to its own satellite group  31  is possible. In a case where it is determined in step S 204  that imaging by the second satellite  21  is not possible, the process ends. 
     In a case where it is determined in step S 204  that imaging by the second satellite  21  is possible, the process proceeds to step S 205 , and the first satellite  21  transmits an imaging instruction to the subsequent second satellite  21  through inter-satellite communication. 
     Then, in step S 206 , the first satellite  21  determines whether the downlink point has been reached, and repeats the process of step S 206  until it is determined that the downlink point has been reached. 
     Then, in a case where it is determined in step S 206  that the downlink point has been reached, the process proceeds to step S 207 , and the first satellite  21  transmits (downlinks) event detection data included in the imaging instruction received from the transmission device  251 , to the ground station  15 . The event detection data includes a part or all of the imaging-related information included in the imaging instruction, information indicating that the imaging instruction has been transferred to the subsequent satellite, and information indicating the subsequent second satellite  21  to which the imaging instruction has been transferred. The downlink may be performed via the relay satellite  22  similarly to other processing described above. The processing of the first satellite  21  ends as described above. 
     The subsequent second satellite  21  to which the imaging instruction has been transmitted from the first satellite  21  through inter-satellite communication receives the imaging instruction in step S 221 , and performs the imaging preparation processing based on the received imaging instruction in step S 222 . 
     The processes in steps S 223  to S 226  are similar to the processes in steps S 164  to S 167  in  FIG. 13 . By the processes of steps S 223  to S 226 , a captured image and metadata are generated by performing imaging, and the captured image to which the metadata is added is transmitted to the ground station  15  at the time when the downlink point is reached. 
     Whereas, the management system receives event detection data in step S 241  in response to transmission of the event detection data by the first satellite  21 . Furthermore, in response to transmission of the captured image by the second satellite  21 , the captured image is received in step S 242 . After receiving the captured image, the management system performs processing similar to steps S 17  to S 19  in  FIG. 6 , but the description thereof will be omitted because the description will be redundant. 
     &lt;12. Third Event Imaging Sequence According to Second Embodiment&gt; 
     Next, a third event imaging sequence performed by the satellite image processing system  1  according to the second embodiment will be described with reference to a flowchart in  FIG. 15 . 
     In the second event imaging sequence described above, the imaging instruction is transferred from the first satellite  21  to the second satellite  21  by using inter-satellite communication. The third event imaging sequence is an example in which an imaging instruction is transferred from the first satellite  21  to the second satellite  21  through communication via the ground station  15 . 
     Detection of an event occurrence and transmission of the imaging instruction by the transmission device  251  in steps S 141  and S 142  are the same as those in the first event imaging sequence described above. 
     In step S 301 , the first satellite  21  receives the imaging instruction from the transmission device  251 , and determines whether imaging by the self is possible in step S 302 . In a case where it is determined in step S 302  that imaging by the self is possible, the process proceeds to step S 303 , the first satellite  21  performs imaging based on the imaging instruction and transmission, and the process ends. Since the imaging sequence in a case where it is determined that imaging by the self is possible is the same as that of the first event imaging sequence described above, the description thereof will be omitted. 
     Whereas, in a case where it is determined in step S 302  that imaging by the self is not possible, the process proceeds to step S 304 , and the first satellite  21  determines whether imaging by the subsequent satellite  21  belonging to its own satellite group  31  is possible. In a case where it is determined in step S 304  that imaging by the subsequent satellite  21  is possible, the process proceeds to step S 305 , imaging by the subsequent satellite  21  and transmission are performed, and the process ends. Since the imaging sequence in a case where it is determined that imaging by the subsequent satellite  21  is possible is the same as that of the second event imaging sequence described above, the description thereof will be omitted. 
     In a case where it is determined in step S 304  that imaging by the subsequent satellite  21  is not possible, the process proceeds to step S 306 , and the first satellite  21  determines whether the downlink point has been reached, and repeats the process of step S 306  until it is determined that the downlink point has been reached. 
     Then, in a case where it is determined in step S 306  that the downlink point has been reached, the process proceeds to step S 307 , and the first satellite  21  transmits (downlinks) the imaging instruction received from the transmission device  251 , to the ground station  15 . The downlink may be performed via the relay satellite  22  similarly to other processing described above. The processing of the first satellite  21  ends as described above. 
     In response to the transmission of the imaging instruction by the first satellite  21 , the management system receives the imaging instruction in step S 321 . Then, in step S 322 , the management system specifies another satellite  21  that satisfies the imaging requirements, on the basis of the required imaging condition, the required imaging target position, and the like included in the imaging-related information of the imaging instruction. Here, the second satellite  21  is specified as the another satellite  21 . 
     In step S 323 , the management system transmits an imaging instruction to the specified second satellite  21 . Note that (the communication device  13  of) the ground station  15  that receives the imaging instruction from the first satellite  21  may be the same as or different from (the communication device  13  of) the ground station  15  that transmits the imaging instruction to the second satellite  21 . 
     In step S 341 , the second satellite  21  receives the imaging instruction from the ground station  15 . The subsequent processes in steps S 342  to S 346  are similar to the processes in steps S 222  to S 226  in  FIG. 14 , and thus description thereof will be omitted. In step S 346 , the captured image is transmitted from the second satellite  21  to the management system. 
     In step S 324 , the management system receives the captured image, and the third event imaging sequence ends. 
     In the third event imaging sequence described above, the first satellite  21  transmits an imaging instruction to the ground station  15  in a case where it is determined that imaging by the subsequent satellite  21  is not possible. However, the imaging instruction may be transmitted to the ground station  15  in a case where it is determined that imaging by the self is not possible without determination as to whether or not imaging by the subsequent satellite  21  is possible. 
     According to the third event imaging sequence, even if the required imaging target position is a location where connection to a network is not possible, such as on the sea, an imaging instruction can be transferred to the management system via the first satellite  21 , and imaging can be performed by the second satellite  21 . 
     &lt;13. Another Configuration Example of Transmission Device&gt; 
     The transmission device  251  illustrated in  FIG. 12  has incorporated a sensor that detects an occurrence of an event, and has been integrated with the transmission unit that transmits an imaging instruction. However, the sensor that detects an occurrence of an event and the transmission device that transmits an imaging instruction can be configured as separate devices. 
       FIG. 16  is a block diagram illustrating another configuration example of the transmission device in the second embodiment. 
     In the event detection region  250  ( FIG. 11 ), a transmission device  291 , a control device  292 , and one or more sensors  293  are installed.  FIG. 16  illustrates an example in which a number of sensors  293  is three, that is, sensors  293 A to  293 C, but any number of sensors  293  may be adopted. Furthermore, a plurality of sets of the transmission device  291 , the control device  292 , and one or more sensors  293  may be installed in the event detection region  250 . 
     Under the control of the control device  292 , the transmission device  291  transmits an imaging instruction to the satellite  21  passing through the vicinity of the transmission device  291 . 
     In a case where a predetermined event has been detected by any of the plurality of sensors  293  ( 293 A to  293 C), the control device  292  performs control to acquire an event detection result from the sensor  293 , generate an imaging instruction, and cause the transmission device  291  to transmit the imaging instruction. To this imaging instruction, imaging-related information is added as a parameter similarly to the example described above. 
     Each of the plurality of sensors  293  ( 293 A to  293 C) corresponds to the sensor unit  273  described above, detects an occurrence of an event, and notifies the control device  292  of the occurrence of the event. The plurality of sensors  293  may include different types of sensors or the same type of sensors. The plurality of sensors  293  may be arranged close to each other or may be arranged apart from each other. Furthermore, the plurality of sensors  293  may be arranged close to or apart from the transmission device  291  and the control device  292 . To the notification of the event occurrence from the sensor  293  to the control device  292 , the above-described sensor information is added as necessary. 
     In the satellite image processing system  1  of the second embodiment, even in a case where the transmission device  291  and the sensor  293  are configured as separate devices as described above, the first to third event imaging sequences described above are similarly executable. 
     &lt;14. Application Example of Satellite Image Processing System Using Event Detection Sensor&gt; 
     Hereinafter, an application example of a satellite image processing system using an event detection sensor of the second embodiment will be described. 
     (1) Event Detection in Farmland 
     A plurality of sensors (the transmission device  251  including the sensor unit  273  or the sensor  293 ) is installed at regular intervals in a predetermined observation region of farmland, and each of the plurality of sensors detects abnormality such as pest generation and disease generation. The transmission device  251  or  291  transmits an imaging instruction to the satellite  21  in accordance with a detection result of the abnormality of the farmland as an event. The satellite  21  performs, for example, imaging of RGB, imaging of red (R) and infrared (IR) for a vegetation index such as NDVI, and the like. To a required imaging target position added to the imaging instruction, a sensor detection range of the sensor having detected the abnormality is assigned. In the observation region in which the plurality of sensors is arranged, the satellite  21  having received the imaging instruction may perform imaging of only the sensor detection range of the sensor in which the abnormality has occurred, or may to perform wide-area imaging of the entire observation region. Furthermore, by changing an imaging condition such as zooming, it is possible to perform both imaging of the sensor detection range of the sensor having detected the abnormality and wide-area imaging of the entire observation region. 
     Instead of detection of an abnormality, an imaging instruction can also be given to the satellite  21  by using, as a trigger, an occurrence of a predetermined situation for checking a growth status such as, for example, a fact that a ground surface is in a predetermined environmental state (for example, a temperature of the ground surface has reached a predetermined temperature), a fact that a photosynthesis amount or a growth situation of the plant is in a predetermined state, and a fact that germination is detected. 
     (2) Event Detection in Ocean 
     For example, a buoy incorporating the transmission device  251  including the sensor unit  273  is released to a marine investigation target sea region. The sensor unit  273  detects a predetermined condition such as detection of a fish group, a sea water temperature, an ocean current speed, or a wind speed. Then, the transmission device  251  transmits an imaging instruction to the satellite  21  on the basis of a detection result of the event. Imaging-related information of the imaging instruction includes a required imaging condition, a required imaging target position, an event occurrence time, and the like. Since the satellite  21  capable of imaging a nighttime state is limited, the satellite  21  is selected on the basis of the required imaging condition, and a situation of the imaging target sea region is analyzed on the basis of a captured image. 
     (3) Observation of Unmanned Zone 
     A sensor (the transmission device  251  including the sensor unit  273  or the sensor  293 ) is installed in an unmanned zone such as a forest, a mountain, or a desert, to detect a change in climatic conditions, detection of organisms to be observed, and an abnormality such as forest fire. The satellite  21  performs imaging on the basis of an imaging instruction from the transmission device  251  or  291 . A situation of the unmanned zone is analyzed on the basis of a captured image. 
     (4) Accident Observation 
     For example, the transmission device  251  is mounted on a black box of an airplane or a ship, and the transmission device  251  transmits an imaging instruction in an event of an emergency such as an airplane crash, ship stranding, or an oil tanker leakage. The satellite  21  promptly captures an image of an emergency occurrence location and transmits the image to the ground station  15 . 
     (5) Climber Distress 
     A climber or the like carries the transmission device  251 , and, at the time of distress, an imaging instruction including a rescue signal as a detected event type and added with imaging-related information including a distress occurrence location as a required imaging target position is transmitted from the transmission device  251  to the satellite  21 . The satellite  21  captures an image of the distress occurrence location on the basis of the imaging instruction, and transmits the image to the ground station  15 . 
     (6) Pipeline Emission Control 
     Sensors are attached to a pipeline at predetermined intervals, and an occurrence of leakage is monitored. In a case where leakage is detected, an imaging instruction is transmitted to the satellite  21 . As a required imaging condition, for example, an imaging instruction added with imaging-related information designating a satellite  21  capable of leakage detection, such as the satellite  21  capable of heat detection by an IR band, is transmitted, and a satellite  21  that satisfies the requirement performs imaging. It is possible to promptly observe the leakage situation in the leakage area on the basis of the captured image. In particular, in a case where an outflow from the pipeline is caused by a human cause, prompt observation after the event occurrence is effective. 
     (7) Other 
     A captured image triggered by the sensor  293  arranged on the ground may be made as only primary information, and image analysis or the like may be performed by combining the captured image and another image. For example, a captured image with a trigger from the sensor  293  is promptly captured by the low-performance satellite  21  with priority given to an imaging timing. Thereafter, the satellite group management device  11  schedules the satellite  21  having a higher imaging capability, and performs high-resolution and high-accuracy imaging. The satellite group management device  11  performs analysis by using a first captured image captured by a low-performance satellite  21  and a second captured image captured by a satellite  21  having a high imaging capability. For example, the satellite group management device  11  may perform resolution enhancement on the first captured image on the basis of difference information, or may perform synthesis processing on the first captured image and the second captured image. 
     As described above, according to satellite remote sensing using a sensor, an event having occurred on the ground can be detected by the sensor, and an imaging instruction can be directly given to the satellite  21  in the sky. In particular, even from a sensor installed in a zone without connection to the Internet such as the ocean, an imaging instruction can be directly given to a satellite, or an imaging instruction can be given to another satellite via the satellite. For example, since it is possible to immediately detect an event occurring at a specific location in a vast zone and cause imaging to be performed, efforts can be greatly reduced. 
     &lt;15. Computer Configuration Example&gt; 
     The series of processes described above can be executed by hardware or also executed by software. In a case where the series of processes are performed by software, a program that configures the software is installed in a computer. Here, examples of the computer include, for example, a microcomputer that is built in dedicated hardware, a general-purpose personal computer that can perform various functions by being installed with various programs, and the like. 
       FIG. 17  is a block diagram illustrating a configuration example of hardware of a computer that executes the series of processes described above in accordance with a program. 
     In a computer, a central processing unit (CPU)  301 , a read only memory (ROM)  302 , and a random access memory (RAM)  303  are mutually connected by a bus  304 . 
     The bus  304  is further connected with an input/output interface  305 . To the input/output interface  305 , an input unit  306 , an output unit  307 , a storage unit  308 , a communication unit  309 , and a drive  310  are connected. 
     The input unit  306  includes a keyboard, a mouse, a microphone, a touch panel, an input terminal, and the like. The output unit  307  includes a display, a speaker, an output terminal, and the like. The storage unit  308  includes a hard disk, a RAM disk, a nonvolatile memory, and the like. The communication unit  309  includes a network interface or the like. The drive  310  drives a removable recording medium  311  such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory. 
     In the computer configured as described above, the series of processes described above are performed, for example, by the CPU  301  loading a program recorded in the storage unit  308  into the RAM  303  via the input/output interface  305  and the bus  304 , and executing. The RAM  303  also appropriately stores data necessary for the CPU  301  to execute various processes, for example. 
     The program executed by the computer (CPU  301 ) can be provided by being recorded on, for example, the removable recording medium  311  as a package medium or the like. Furthermore, the program can be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting. 
     In the computer, by attaching the removable recording medium  311  to the drive  310 , the program can be installed in the storage unit  308  via the input/output interface  305 . Furthermore, the program can be received by the communication unit  309  via a wired or wireless transmission medium, and installed in the storage unit  308 . Besides, the program can be installed in advance in the ROM  302  and the storage unit  308 . 
     In this specification, the steps described in the flowcharts can be performed in time series according to the described order as a matter of course, but are not necessarily performed in time series, and may be performed in parallel or at necessary timing such as when a call is made. 
     Furthermore, in this specification, the system means a set of a plurality of components (a device, a module (a part), and the like), and it does not matter whether or not all the components are in the same housing. Therefore, a plurality of devices housed in separate housings and connected via a network, and a single device with a plurality of modules housed in one housing are both systems. 
     The embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present technology. 
     For example, a form in which all or some of the plurality of embodiments described above are combined can be adopted. 
     For example, the present technology can have a cloud computing configuration in which one function is shared and processed in cooperation by a plurality of devices via a network. 
     Furthermore, each step described in the above-described flowchart can be executed by one device, and also shared and executed by a plurality of devices. 
     Moreover, in a case where one step includes a plurality of processes, the plurality of processes included in the one step can be executed by one device, and also shared and executed by a plurality of devices. 
     Note that the effects described in this specification are merely examples and are not limited, and effects other than those described in this specification may be present. 
     Note that the present technology can have the following configurations. 
     (1) 
     An imaging method of a satellite system, the satellite system including: a transmission device installed on the earth; and an artificial satellite having an imaging device, the imaging method including: 
     transmitting, by the transmission device, an imaging instruction to the artificial satellite passing in sky, in accordance with a predetermined event detected by a sensor installed on the earth; and 
     imaging, by the artificial satellite, an occurrence region of the predetermined event on the basis of the imaging instruction. 
     (2) 
     The imaging method of the satellite system according to (1) described above, in which 
     the artificial satellite transmits the imaging instruction to another artificial satellite in a case where imaging by self is not possible. 
     (3) 
     The imaging method of the satellite system according to (2) described above, in which 
     in a case where the artificial satellite transmits the imaging instruction to the another artificial satellite, the artificial satellite transmits, to a ground station, data indicating that the imaging instruction has been transmitted to the another artificial satellite. 
     (4) 
     The imaging method of the satellite system according to (2) described above, in which 
     in a case where imaging by self is not possible, the artificial satellite determines whether or not the another artificial satellite is able to perform imaging, and transmits the imaging instruction to the another artificial satellite. 
     (5) 
     The imaging method of the satellite system according to (4) described above, in which 
     the artificial satellite transmits the imaging instruction to a ground station in a case where the another artificial satellite is not able to perform imaging. 
     (6) 
     The imaging method of the satellite system according to (1) described above, in which 
     the artificial satellite transmits the imaging instruction to a ground station in a case where imaging by self is not possible. 
     (7) 
     The imaging method of the satellite system according to any one of (1) to (6) described above, in which 
     to the imaging instruction, imaging-related information including a required imaging condition is added. 
     (8) 
     The imaging method of the satellite system according to (1) or (7) described above, in which 
     the artificial satellite transmits a captured image captured on the basis of the imaging instruction to a ground station, in a case of reaching a downlink point. 
     (9) 
     The imaging method of the satellite system according to (1), (7), or (8) described above, in which 
     the artificial satellite adds metadata to a captured image obtained by imaging, and transmits the captured image to a ground station. 
     (10) 
     The imaging method of a satellite system according to (9) described above, in which the metadata includes a satellite group identifier to identify a satellite group including the artificial satellite, a satellite identifier to identify the artificial satellite, and relative position information of each artificial satellite included in the satellite group. 
     (11) 
     A transmission device including: 
     a transmission unit configured to transmit an imaging instruction to an artificial satellite passing in sky, in accordance with a predetermined event detected by a sensor installed on the earth. 
     (12) 
     The transmission device according to (11) described above, further including: 
     the sensor configured to detect the predetermined event. 
     (13) 
     The transmission device according to (11) described above, further including: 
     a control unit configured to acquire a detection result of the predetermined event from a plurality of the sensors installed on the earth at predetermined intervals, and configured to cause the transmission unit to transmit the imaging instruction. 
     REFERENCE SIGNS LIST 
     
         
           1  Satellite image processing system 
           11  Satellite group management device 
           13  Communication device 
           14  Antenna 
           15  Ground station (base station) 
           21  Satellite 
           31  Satellite group 
           41  Information providing server 
           42  Image analysis server 
           101  Management unit 
           111  Imaging device 
           211  Control unit 
           222  Control unit 
           231  Control unit 
           250  Event detection region 
           251  Transmission device 
           271  Transmission unit 
           272  Control unit 
           273  Sensor unit 
           291  Transmission device 
           292  Control device 
           293  Sensor 
           301  CPU 
           302  ROM 
           303  RAM 
           306  Input unit 
           307  Output unit 
           308  Storage unit 
           309  Communication unit 
           310  Drive