Patent Publication Number: US-2022230266-A1

Title: Image management method and data structure of metadata

Description:
TECHNICAL FIELD 
     The present technology relates to an image management method and a data structure of metadata, and more particularly, to an image management method and a data structure of metadata that allow for management of an image captured by an artificial satellite. 
     BACKGROUND ART 
     There is a technology called satellite remote sensing for observing a situation of a target area or a target object or detecting a change in situation from an image of a predetermined area on the earth captured by an artificial satellite (see, for example, Patent Documents 1 and 2). 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: WO 2010/097921 A 
         Patent Document 2: Japanese Patent Application Laid-Open No. 2004-15451 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In recent years, research and development of low-cost small satellites by private sectors have progressed. It is expected that images will be captured by many artificial satellites in the future, and a system for management of an image captured by an artificial satellite is desired. 
     The present technology has been made in view of such a situation, and allows for management of an image captured by an artificial satellite. 
     Solutions to Problems 
     An image management method according to a first aspect of the present technology includes adding, by a management device that manages a captured image captured by a satellite, metadata that includes at least information regarding a person related to the captured image, to the captured image. 
     In the first aspect of the present technology, the metadata that includes at least the information regarding the person related to the captured image captured by the satellite is added to the captured image. 
     A data structure of metadata according to a second aspect of the present technology is a data structure of metadata of a captured image captured by a satellite, in which the metadata includes at least information regarding a person related to the captured image, and a management device that manages the captured image is used for processing of collating the person related to the captured image. 
     In the second aspect of the present technology, the metadata that includes at least the information regarding the person related to the captured image captured by the satellite is used for the processing of collating the person related to the captured image. 
    
    
     
       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 illustrating a formation flight. 
         FIG. 3  is a diagram illustrating a 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 cluster 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 diagram illustrating determination of a remaining battery level. 
         FIG. 9  is a flowchart of the satellite image processing system in which a formation flight is performed. 
         FIG. 10  is a diagram illustrating information attached as metadata. 
         FIG. 11  is a diagram 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 according to 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 illustrating a second event imaging sequence by the satellite image processing system of the second embodiment. 
         FIG. 15  is a flowchart illustrating a third event imaging sequence by the satellite image processing system of the second embodiment. 
         FIG. 16  is a block diagram illustrating another configuration example of the transmission device according to the second embodiment. 
         FIG. 17  is a block diagram illustrating a configuration example of one embodiment of a computer to which the present technology is applied. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Modes for carrying out the present technology (hereinafter referred to as “embodiments”) will be described below. Note that the description will be made in the order below. 
     1. Configuration example of satellite image processing system 
     2. Imaging sequence by 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 examples of satellite image processing system using event detection sensor 
     15. Configuration example of computer 
     1. Configuration Example of Satellite Image Processing System 
       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  in  FIG. 1  is a system that uses captured images captured by a plurality of artificial satellites (hereinafter simply referred to as satellites) to perform satellite remote sensing in which a situation of a target area or a target object on the earth is observed or a change in situation is detected. In the present embodiment, a satellite is mounted with an imaging device, and has at least a function of imaging the ground. 
     A satellite operation company has a satellite cluster management device  11  that manages a plurality of satellites  21  and a plurality of communication devices  13  that communicate with the satellites  21 . Note that the satellite cluster management device  11  and some of the plurality of communication devices  13  may be devices owned by a company other than the satellite operation company. The satellite cluster management device  11  and the plurality of communication devices  13  are connected via a predetermined network  12 . The communication devices  13  are disposed at ground stations (base stations on the ground)  15 . Note that  FIG. 1  illustrates an example in which the number of the communication devices  13  is three, which are communication devices  13 A to  13 C, but the number of the communication devices  13  is optional. 
     The satellite cluster management device  11  manages the plurality of satellites  21  owned by the satellite operation company. Specifically, the satellite cluster management device  11  acquires related information from one or more information provision servers  41  of an external institution as necessary, and determines an operation plan for the plurality of satellites  21  owned by the satellite cluster management device  11  itself. Then, the satellite cluster management device  11  instructs a predetermined satellite  21  to capture an image via a communication device  13  in response to a request from a customer, thereby causing the predetermined satellite  21  to capture an image. Furthermore, the satellite cluster management device  11  acquires and stores the 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 provision server  41  installed in the external institution supplies predetermined related information to the satellite cluster management device  11  via a predetermined network in response to a request from the satellite cluster management device  11  or on a periodic basis. The related information provided from the information provision 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 Aerospace Defense Command (NORAD) as an external institution. 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 institution. 
     The image analysis server  42  performs predetermined image processing on the image captured by the satellite  21  supplied from the satellite cluster 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 cluster management device  11  of the satellite operation company. For example, the image analysis server  42  performs metadata generation processing for adding predetermined metadata to an image captured by the satellite  21 , correction processing such as distortion correction of the captured image, image composition processing such as color composition processing, and the like. The image processing of the captured image may be performed by a satellite operation company, and in this case, the satellite operation company and the image analysis company are the same. Furthermore, the satellite cluster management device  11  and the image analysis server  42  may be constituted by one device. 
     In accordance with the control of the satellite cluster management device  11 , the communication device  13  communicates with a predetermined satellite  21  designated by the satellite cluster management device  11  via an antenna  14 . For example, the communication device  13  transmits, to a predetermined satellite  21 , an imaging instruction for imaging a predetermined region on the ground at a predetermined time and position. Furthermore, the communication device  13  receives the captured image transmitted from the satellite  21 , and supplies the captured image to the satellite cluster 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 communication directly 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  or a network between the information provision server  41  or the image analysis server  42  and the satellite cluster management device  11  is an optional communication network, and may be a wired communication network, may be a wireless communication network, or may be constituted by both of them. Furthermore, the network  12  and the network between the information provision server  41  or the image analysis server  42  and the satellite cluster management device  11  may be constituted by one communication network, or may be constituted by a plurality of communication networks. These networks can be a communication network or a communication path compliant with an optional communication standard, for example, the Internet, a public telephone line network, a wide area communication network for a wireless moving object such as a so-called 4G line or 5G line, a wide area network (WAN), a local area network (LAN), a wireless communication network for communication that meets a Bluetooth (registered trademark) standard, a communication path for short-range wireless communication such as near field communication (NFC), a communication path for infrared communication, or a communication network for wired communication that meets a standard such as high-definition multimedia interface (HDMI (registered trademark)) or universal serial bus (USB). 
     A plurality of the satellites  21  constitutes a satellite cluster  31 . In  FIG. 1 , a satellite  21 A and a satellite  21 B constitute a first satellite cluster  31 A, and a satellite  21 C and a satellite  21 D constitute a second satellite cluster  31 B. Note that the example in  FIG. 1  illustrates, for the sake of simplicity, an example in which one satellite cluster  31  is constituted by two satellites  21 , but the number of satellites  21  constituting one satellite cluster  31  is not limited to two. 
     In a case where the communication device  13  communicates with the satellites  21  constituting the satellite cluster  31 , there are a method in which communication is performed individually with the satellites  21  as in the first satellite cluster  31 A in  FIG. 1 , and a method in which only one satellite  21 C (hereinafter also referred to as the representative satellite  21 C) representing the satellite cluster  31  communicates with the communication device  13  and the other satellite  21 D indirectly communicates with the communication device  13  by inter-satellite communication with the representative satellite  21 C as in the second satellite cluster  31 B. By which method communication with the ground station  15  (the communication device  13  thereof) is to be performed may be determined in advance by the satellite cluster  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  constituting one satellite cluster  31  may be operated by an operation method called formation flight. 
     The formation flight is an operation method in which, as illustrated in  FIG. 2 , a plurality of satellites  21  constituting one satellite cluster  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 a coordinated manner, so that a service that cannot be provided by a single satellite can be provided. In  FIG. 2 , three satellites  21 X to  21 Z constitute one satellite cluster  31 , and each of the satellites  21 X to  21 Z communicates with the ground station  15 . In the uplink, a cluster ID (satellite cluster ID), which is an identifier for identifying the satellite cluster  31 , and an individual ID (satellite ID), which is an identifier for identifying each satellite  21  constituting the satellite cluster  31 , are designated, so that a command or data is transmitted to a desired satellite  21 . 
     The formation flight allows functions to be assigned to a plurality of satellites  21  instead of a single satellite, and therefore has an advantage that the satellites  21  can be downsized. For example, as for imaging functions, even in a case where a performance (e.g., the resolution) of the imaging device mounted on each satellite  21  is lowered, high resolution can be achieved by image composition or the like of 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 one region  52  (simultaneous imaging) from different imaging points (satellite positions). A result of imaging the same ground surface from different imaging points can be used for generation of a digital elevation model (DEM) indicating a height necessary for three-dimensional measurement. Furthermore, a parallax image is obtained from the captured images from the two satellites  21 E and  21 F, and three-dimensional measurement can be performed. 
     Furthermore, as illustrated in B of  FIG. 3 , a plurality of satellites  21 E and  21 F can image one region  52  with a time difference (differential imaging) at the same imaging point and imaging angle. For example, in a case where the satellites  21  are moving at a speed of 7 km per second and flying in formation with a distance of 100 m between the satellites  21 , imaging can be performed every 1.4×10 −2  seconds. As described above, a formation flight allows for imaging at a short time interval, and thus, for example, it is possible to extract a change (displacement) in an object on the earth such as a passenger car on a road or a buoy on the sea, and to measure the speed of a moving object. 
     There is a constellation as a system for operating a plurality of satellites  21 , but the constellation is “a system that mainly deploys a uniform global service by putting a large number of satellites into a single or a plurality of orbital planes”, which is a concept different from that of the formation flight. 
       FIG. 4  is a block diagram illustrating a configuration example of a 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 panel  117 , and a communication device  118 . The management unit  101  and control units for devices are connected via the bus  102 , the control units including 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 . 
     The management unit  101  acquires states of the devices from the corresponding control units for the devices via the bus  102 , and outputs an operation command to the control units for the devices, thereby controlling an operation of the entire satellite  21 . 
     The imaging control unit  103  controls an operation of the imaging device  111  in accordance with the operation command from the management unit  101 . The imaging device  111  is constituted by, for example, a camera module including an image sensor, and images a target object. In a case where the satellite  21  is a synthetic aperture radar (SAR) satellite, the imaging device  111  is constituted by a radar device. 
     The heat control unit  104  acquires a sensor value of a temperature sensor included in the sensor group  115 , monitors a temperature change in the satellite  21 , and performs control to cause the entire satellite  21  to be within a prescribed temperature range. Basically, the temperature change is controlled by a structure or a characteristic of a material, but dynamic cooling using the cooling device  112  may be performed as necessary. The cooling device  112  performs cooling by using a cryogen such as liquid helium, for example. 
     The attitude control system control unit  105  controls the attitude control device  113  in accordance with an operation command from the management unit  101  to perform control to turn the satellite  21  in an intended direction. For example, the attitude control system control unit  105  performs control to turn the antenna  14  toward the ground station  15 , turn the solar panel  117  toward the sun, or turn an observation sensor of the imaging device  111  or the like in the direction of an observation target. The attitude control device  113  is constituted by, for example, a wheel such as a three-axis gyroscope or a control moment gyroscope, 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. 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 sensors used for the attitude control include a sun sensor, an earth sensor, a star sensor, a magnetic sensor, and a gyroscope. 
     The orbit control system control unit  106  performs control related to maintaining an orbit altitude and changing 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 accordance with an operation command from the management unit  101 . The propulsion device  114  is constituted by, for example, a solid motor, an ion engine, or an apogee engine. The propulsion system control unit  107  acquires sensor values of the various sensors of the sensor group  115  and operates the propulsion device  114  in cooperation with the attitude control device  113  as necessary, thereby performing attitude control and attitude control for 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 the purpose of attitude control. 
     The sensor control unit  108  controls the 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 for monitoring the state in the satellite  21 , and include, for example, a GPS receiver, a star tracker (attitude sensor), an acceleration sensor, a gyroscope sensor, a magnetic sensor, a temperature sensor, a sun sensor, an earth sensor, and a star sensor. 
     The power supply control unit  109  controls the battery  116  and the solar panel  117 . Power generated by the solar panel  117  is stored in the battery  116  under the control of the power supply control unit  109 . The power in the battery  116  may be directly distributed to the devices in the satellite  21 , or may be distributed via the bus  102 . 
     The communication control unit  110  controls the communication device  118  in accordance with an operation command from the management unit  101 . The communication device  118  has an antenna, and communicates with the communication device  13  of the ground station  15  in accordance with the control of the communication control unit  110 . Furthermore, the communication device  118  can also communicate with another satellite  21  constituting the same satellite cluster  31  and with the relay satellite  22 . Furthermore, the communication control unit  110  and the communication device  118  may have separate systems, one for transmission and reception of commands and telemetry, which are small in data amount, and one for mission-related data (imaging data and the like), which is large in data amount. 
     The control units from the imaging control unit  103  to the communication control unit  110  may be further divided into two or more, any two or more of the control units may be integrated, or the control units may be integrated with the management unit  101 . Computational resource such as a central processing unit (CPU) and a memory are basically mounted on the management unit  101 , but may also be mounted on the control units. The control units may be implemented in a common hardware module. 
     The imaging devices  111  of a plurality of the satellites  21  constituting one satellite cluster  31  may have the same performance, or may have different performances. 
     For example, in a case where imaging devices  111  of the same model number are adopted as the imaging devices  111  mounted on the satellites  21  so that the satellites  21  have the same performance, there are the following advantages. For example, images of the same performance can be acquired with a short time difference, and the difference can be easily detected. Furthermore, it is possible to generate a highly accurate (high-resolution) image by, for example, compositing images captured in accordance with an assignment. Furthermore, this allows for a redundancy, which makes a malfunction in one device tolerable. 
     On the other hand, in a case where the imaging devices  111  mounted on the satellites  21  have different performances, it is possible to assign different roles in imaging, for example, one for high-sensitivity monochrome imaging and one for low-sensitivity color imaging. Note that the different performances includes not only a case where the mounted hardware configurations are different but also a case where the mounted hardware configurations are the same but the performances are different due to a difference in control. For example, an example is assumed in which, in a case where the image sensors are of the same model number, one satellite  21  acquires a high-sensitivity low-resolution image with a faster shutter speed, and another satellite  21  acquires a low-sensitivity high-resolution image in an opposite way. 
     As an assignment example in a case where the imaging devices  111  of the plurality of satellites  21  have different performances, there may be, for example, control to make any one of sensitivity/shutter speed, resolution, monochrome/color/polarization, or band (wavelength region), or a combination thereof, different. Furthermore, the plurality of satellites  21  may be different in battery performance or communication performance. 
       FIG. 5  is a block diagram illustrating a configuration example of the satellite cluster management device  11 , the communication device  13 , and the image analysis server  42 . 
     The satellite cluster 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 for the plurality of satellites  21  by using related information acquired from the information provision server  41  as necessary, and instructs the satellites  21  to control the attitude or capture an image via the communication device  13 . Furthermore, the control unit  211  performs, for example, processing of generating metadata of a captured image transmitted from a satellite  21  via the communication device  13  and adding the metadata to the captured image. 
     In accordance with an instruction from the control unit  211 , the communication unit  212  performs a predetermined communication with the communication device  13  via the network  12 , and also performs a predetermined communication with the image analysis server  42 . 
     The operation unit  213  is constituted by, for example, a keyboard, a mouse, and a touch panel, receives an input of a command or data based on a user (operator) operation, and supplies the command or data to the control unit  211 . 
     The display unit  214  is constituted by, for example, a liquid crystal display (LCD) or an organic electro luminescence (EL) display, and displays a screen of the 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, or 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 the satellites  21  of a target satellite cluster  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 a satellite  21  in accordance with the control from the satellite cluster management device  11 . Furthermore, the control unit  222  transmits data such as a captured image acquired from the satellite  21  to the satellite cluster management device  11  via the communication unit  223 . 
     The communication unit  223  performs a predetermined communication with the satellite cluster 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 . 
     By executing an image analysis application program stored in a storage unit (not illustrated), the control unit  231  performs, on a captured image supplied from the satellite cluster management device  11 , predetermined image processing such as metadata generation processing for adding predetermined metadata to the captured image, correction processing for distortion correction or the like of the captured image, or image composition processing such as color composition processing. 
     The communication unit  232  performs a predetermined communication with the satellite cluster management device  11  or another device in accordance with 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 cluster management device  11  and supplies the captured image to the control unit  231 , or transmits a processed image after image processing to the satellite cluster management device  11 . 
     The operation unit  233  is constituted by, for example, a keyboard, a mouse, and a touch panel, receives an input of a command or data based on a user (operator) operation, and supplies the command or data to the control unit  231 . 
     The display unit  214  is constituted by, for example, an LCD or an organic EL display, and displays a screen of the image analysis application program or displays an image before or after image processing. 
     The satellites  21  and other devices constituting the satellite image processing system  1  are configured as described above. 
     Note that the satellite cluster management device  11  selects an optimal communication device  13  from among the plurality of communication devices  13  in accordance with the orbit of a satellite  21  with which communication is to be performed, and causes the selected communication device  13  to transmit a predetermined command such as an imaging instruction or receive data such as a captured image via the communication device  13 . Since the satellite cluster management device  11  performs a predetermined communication integrally with the communication device  13  optionally selected in accordance with the target satellite  21 , the satellite cluster management device  11  and the communication device  13  will be collectively referred to as a management system in the following description. 
     2. Imaging Sequence by Single Device 
     Next, an imaging sequence focusing on one predetermined satellite  21  of the satellite cluster  31  that performs a formation flight will be described with reference to a flowchart in  FIG. 6 . 
     First, in step S 11 , a management system determines requirements for imaging by the satellite  21  on the basis of a request from a customer. 
     Specifically, the management system determines, as the imaging requirements, an imaging date and time, an imaging point, an environmental condition for imaging, a camera setting value, and the like. The environmental condition for imaging includes, for example, a weather condition such as cloud cover at the imaging date and time, and the camera setting value includes, for example, the resolution (resolving power), zoom, shutter speed, sensitivity, and aperture. 
     In step S 12 , the management system determines the satellite  21  and the ground station  15  (the communication device  13  thereof) that meet the imaging requirements. 
     Specifically, the management system selects the satellite  21  that meets the determined imaging requirements. For example, the satellite  21  is determined on the basis of determinations on whether the satellite  21  passes over an imaging target position at the determined imaging date and time, whether the imaging target position is within the range of observation width of the satellite  21 , whether the imaging device  111  mounted on the satellite  21  satisfies requirements such as the resolving power and the determined camera setting value, 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 battery level of the satellite  21  at the imaging date and time, a power consumption for 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, power is consumed by the imaging, attitude control, data communication, heat control, and the like associated with the imaging, and it is assumed that the next imaging may not be able to be performed. Thus, a degree of priority of the satellite  21  is set in accordance with the expected remaining battery level and the power consumption for the imaging, and the satellite  21  is selected. 
     In step S 13 , the management system directs the antenna  14  of the selected ground station  15  toward an assumed orbit. The satellite cluster 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  toward the assumed orbit. 
     In step S 14 , the management system transmits (uplinks) an imaging instruction to the selected satellite  21 . That is, the satellite cluster 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  that has 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, a camera setting value, and the like. 
     In step S 31 , the satellite  21  receives the imaging instruction from the ground station  15 , and in step S 32 , transmits a reception completion to the ground station  15 . 
     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 repeated until the satellite  21  returns the reception completion. 
     In step S 33 , the satellite  21  performs imaging preparation processing based on the received imaging instruction. For example, the satellite  21  controls the attitude of the satellite  21  or an orientation of the imaging device  111  (pointing) such that the imaging device  111  turns toward the imaging target position as necessary. Furthermore, for example, the imaging control unit  103  sets zoom, shutter speed, sensitivity, aperture, and the like of the image sensor. Moreover, the power supply control unit  109  performs charging in advance so that sufficient power is obtained at the imaging date and time. 
     At the imaging date and time designated by the imaging instruction, the satellite  21  images the imaging target position in step S 34 . 
     In step S 35 , the satellite  21  generates metadata, which is information to be associated with a captured image obtained as a result of the imaging, and adds the metadata to the captured image. Although details of the metadata will be described later, for example, information such as a cluster ID for identifying the satellite cluster  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 to which the metadata has been added to the ground station  15 . The downlink may be performed immediately after generation of the captured image and the metadata, or may be performed at the time of arrival within a predetermined range in a 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 the captured image to the satellite cluster management device  11 . 
     In step S 17 , the satellite cluster management device  11  analyzes the metadata of the captured image. At this time, the satellite cluster management device  11  may newly generate metadata on the basis of a result of the analysis, and add this metadata. For example, the satellite cluster management device  11  calculates a satellite position at the time of imaging on the basis of the cluster ID and the individual ID of the captured image and the orbit information of the satellite  21 , and adds the satellite position as metadata. 
     In step S 18 , the satellite cluster management device  11  performs predetermined image processing on the captured image captured by the satellite  21 . The satellite cluster management device  11  performs, for example, correction processing such as distortion correction and image composition processing such as color composition processing. Details of the image processing will be described later. 
     In step S 19 , the satellite cluster management device  11  executes distribution management processing on the captured image and the processed image, and stores the captured image and the processed image in a predetermined storage unit. Details of the distribution management processing will also be described later. 
     Thus, a series of sequences for imaging by one satellite  21  ends. 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 by the satellite cluster management device  11  or performed instead of being performed by the satellite cluster management device  11 . In a similar manner, the distribution management processing may be performed by the image analysis server  42 . 
     Note that, in the above-described example, the metadata is added to the captured image and 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. 
     3. Imaging Preparation Processing 
     Incidentally, resources are limited particularly in a small satellite  21 , and thus, it is necessary to pay particular attention to the remaining battery level, and it is important to control imaging in accordance with this. 
       FIG. 7  is a detailed flowchart of the imaging preparation processing in step S 33  in  FIG. 6 . Here, it is assumed that the imaging instruction received in step S 31  before step S 33  is an instruction to capture an image at imaging time t 1 . 
     In the imaging preparation processing, first, in step S 51 , the management unit  101  of the satellite  21  estimates the remaining battery level at the imaging time t 1 . Specifically, the management unit  101  estimates the remaining battery level at the imaging time t 1  from (an estimated value of) a charge capacity accumulated by solar power generation by the imaging time t 1  with respect to the current remaining battery level. 
     In step S 52 , the management unit  101  determines whether the remaining battery level is sufficient on the basis of the estimated remaining battery level. 
     Specifically, the management unit  101  determines whether the estimated remaining battery level is sufficient from factors of power consumption related to imaging and factors of power consumption that are not for imaging. The factors of power consumption related to imaging include imaging processing by the imaging device  111 , attitude control (pointing) for the satellite  21 , and heat control associated therewith. The imaging processing by the imaging device  111  takes into consideration how many images are to be captured with what degree of accuracy (resolving power, shutter speed, necessity of zoom, and the like) at the imaging time t 1 . The attitude control for the satellite  21  includes a change in the attitude of the satellite itself and a change in the attitude of the antenna. Furthermore, in a case where the camera module itself as the imaging device  111  can change the attitude in the direction of imaging, a change in the attitude of the camera module is also included in the attitude control for the satellite  21 . The factors of power consumption that are not for imaging include communication (uplink and downlink) performed by the imaging time t 1 . 
     For example, as illustrated in A of  FIG. 8 , on the premise that a charge capacity of 70% of a full charge capacity of the battery  116  is to be maintained at all times, assuming that the current remaining battery level is 90%, the charge capacity by 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 the communication performed until the imaging time t 1  is 2%, 90%+5%−3%−10%−2%=80% is obtained. The charge capacity of 70% is ensured even after the imaging at the time t 1 , and the satellite  21  is determined to have a sufficient remaining battery level. 
     Note that the management unit  101  may determine whether the remaining battery level is sufficient on the basis of the remaining battery level to be kept after the imaging time t 1  also in consideration of imaging performed at a timing subsequent to the imaging time t 1 . 
     For example, as illustrated in B of  FIG. 8 , assuming that imaging is scheduled at time t 2  subsequent to the imaging time t 1 , the charge capacity 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%, the remaining battery level of 83% is required after the imaging at the time t 1 . Thus, it is determined that the estimated remaining battery level 80% at the imaging time t 1  is not a sufficient remaining battery level. 
     Note that the above-described example mainly describes power consumption related to imaging, but power consumption for others such as power consumption by heat control associated with attitude control, periodic communication, and the like is also taken into consideration. 
     As described above, whether or not the remaining battery level is sufficient is determined. If it is determined in step S 52  in  FIG. 7  that the remaining battery level is not sufficient, the processing proceeds to step S 53 , and the satellite  21  determines whether an assumed downlink timing before the imaging time t 1  can be changed. By changing the downlink timing, it is possible to save the amount of power required for the downlink. 
     If it is determined in step S 53  that the downlink timing cannot be changed, the processing in step S 53  is skipped, and the processing proceeds to step S 55 . 
     On the other hand, if it is determined in step S 53  that the downlink timing can be changed, the processing proceeds to step S 54 . The management unit  101  changes the downlink timing, and determines whether the remaining battery level is sufficient after the change. If it is determined also in step S 54  that the remaining battery level is not sufficient, the processing proceeds to step S 55 . On the other hand, if it is determined in step S 54  that the remaining battery level is sufficient, the processing proceeds to step S 57 . 
     In step S 55 , the management unit  101  changes an accuracy of the attitude control. In the attitude control, for example, two types, that is, a wheel and an ion engine, are used to repeat applying a moment toward a target attitude and then applying a reverse moment when the attitude has passed through the target attitude. When a swing speed has become equal to or less than a certain value, it is determined that the attitude has been changed to the target attitude. To change the accuracy of the attitude control, the management unit  101  changes, for example, the range of the swing speed used to determine that the target attitude has been obtained. An electricity consumption can be saved by changing the range of the swing speed to increase and reducing the control amount of the attitude control. 
     In step S 56 , the management unit  101  changes an imaging condition in accordance with the accuracy of the attitude control. When the range of the swing speed increases, the attitude of the satellite  21  is not stabilized and wobble occurs, which may cause subject blurring. Furthermore, the pointing is insufficient, and it is conceivable that sufficient zoom cannot be achieved. Thus, the management unit  101  changes an imaging condition to compensate for the adverse effects caused by the reduction in the control amount of the attitude control. 
     For example, the management unit  101  changes an imaging condition as follows. 
     The management unit  101  increases the shutter speed of the image sensor to cope with subject blurring. Furthermore, moreover, since the captured image becomes dark when the shutter speed is increased, the management unit  101  may perform control to increase the sensitivity (gain). 
     Furthermore, for example, the management unit  101  can reduce the resolving power (resolution) of the captured image for the purpose of improving the sensitivity per unit pixel. With this arrangement, the shutter speed can be improved, an influence of the decrease in the accuracy of the attitude control is reduced, and the amount of data at the time of downlink can be reduced. Furthermore, the management unit  101  selects a setting value for not using optical zoom. With this arrangement, a tolerance for image blurring (wobble) can be increased. 
     Furthermore, in a case where the camera module has a mechanical blur correction mechanism (spatial blurring 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 configure an imaging setting for continuously capturing a plurality of images. A high-resolution captured image composited and generated from the continuously captured images is generated and transmitted (downlinked) to the ground station  15 , so that a decrease in resolving power (resolution) of the captured image can be compensated. Note that generation of the high-resolution image by image composition may be performed by the satellite cluster management device  11  or the image analysis server  42  after downlink. The satellite cluster management device  11  or the image analysis server  42  can also perform composition by using a past captured image such as a base image or a captured image captured by another satellite  21 . 
     After step S 56 , or if it is determined in step S 52  or step S 54  that the remaining battery level is sufficient, the processing proceeds to step S 57 . 
     In step S 57 , the management unit  101  controls the attitude of the satellite  21  or the imaging device  111  (performs pointing) in accordance with the setting of the attitude control determined in the processing in step S 55 . 
     In step S 58 , the management unit  101  sets the imaging condition determined in the processing in step S 56 . 
     Thus, the imaging preparation processing in step S 33  in  FIG. 6  ends. At the imaging date and time designated by the imaging instruction, the processing in step S 34  in  FIG. 6 , that is, imaging of the imaging target position is performed. 
     According to the imaging preparation processing, in a case where the remaining battery level is low, the accuracy of stabilization in the attitude control that greatly affects the electricity consumption is lowered, and an imaging condition or the image processing in the subsequent stage is changed. This makes it possible to secure a quality of the captured image while suppressing a battery consumption. 
     4. Flowchart of Formation Flight 
     Next, a formation flight executed by the plurality of satellites  21  constituting one satellite cluster  31  will be described. 
       FIG. 9  is a flowchart of the satellite image processing system  1  in which one satellite cluster  31  performs a 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 the satellites  21  of the satellite cluster  31  that performs a formation flight. That is, in step S 101 , the management system inquires, about the relative position, of the satellites  21  of the satellite cluster  31  performing the formation flight. In step S 121 , the satellites  21  constituting the satellite cluster  31  perform processing of checking the relative position in response to the inquiry from the management system. Then, in step S 122 , the satellites  21  transmit the relative position. In step S 102 , the management system receives the relative position from each satellite  21 . Here, the relative position indicates an arrangement sequence of the satellites  21  constituting the satellite cluster  31  and distances between the satellites. The arrangement sequence of the satellites  21  is, for example, an order in which the top (No. 1) is in the traveling direction of the satellites  21 . The relative position checking processing may be performed every time an image is captured, or may be performed on a periodic basis, for example, once a day or once a week. 
     The management system has orbit information of the satellite cluster  31  acquired from NORAD as an external institution, but it may not be possible to determine orbit information of each satellite  21  constituting the satellite cluster  31 . Alternatively, even in a case where individual orbit information can be determined by observation from the ground, it may not be possible to determine the order of airframes. In the formation flight, there is a case where the satellites  21  are disposed in a range in which the orbit information cannot be individually allocated, and it is not possible to determine the position a certain satellite is placed from the top in the satellite cluster  31 . It is therefore necessary to measure the relative positional relationship. 
     Methods for controlling a 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 constituting the satellite cluster  31  and the relative position is controlled by an instruction from the ground side. An error is likely to occur in the distances between the satellites. 
     On the other hand, the closed-loop method is a method of controlling the relative position by performing communication between satellites constituting the satellite cluster  31 . The closed-loop method has higher accuracy in relative position than the open-loop method. The closed-loop method includes a centralized type and a decentralized type. In the centralized type, there are a mode in which a satellite  21  serves as a leader and other satellites  21  follow the leader satellite, and a mode in which the leader satellite gives an instruction to the other satellites  21 . The decentralized type is a mode in which each of the satellites  21  constituting the satellite cluster  31  autonomously communicates with other surrounding satellites  21  and controls its own position. 
     In the processing of checking the relative position in step S 121 , in a case of the open-loop method, for example, there is a method in which the satellites  21  simultaneously image a predetermined point on the ground, and the satellite cluster management device  11  on the ground side checks the arrangement sequence of the satellites  21  on the basis of the captured images and information regarding the attitude (pointing angle) of each satellite  21 . Furthermore, for example, there is a method in which the satellites  21  perform communication simultaneously with a predetermined point on the ground, and the communication device  13  on the ground side checks the arrangement sequence from the radio waves at that time. The communication for checking the arrangement sequence may be a downlink of a predetermined captured image, a signal for calibration, or the like. On the other hand, in a case of the closed-loop method, the satellites  21  execute processing of measuring the relative position, and the measurement result is downlinked. The satellites  21  measure the relative position by a method such as a method of measuring the position (direction) by communication between satellites, or a method of radiating laser from the satellites  21  and measuring the distances on the basis of its reflected light. 
     In the closed-loop method and the open-loop method, only the arrangement sequence of the satellites  21  may be detected, and the distances 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, in addition to a setting value of the image sensor, attitude control for the satellite  21  at the time of imaging, imaging timing, and the like. For example, in a case where three-dimensional measurement of the ground is performed, an imaging condition for causing the satellites  21  to be in attitudes in which the imaging target positions are the same is calculated with an inter-satellite distance as a baseline length. In a case where images are captured with a time difference (differential imaging) by the plurality of satellites  21  constituting the satellite cluster  31 , the timings (imaging positions) at which a preceding satellite  21  and a subsequent satellite  21  capture images and the attitude at the time of imaging are calculated. The timings at which the satellites  21  capture images are calculated on the basis of the 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 to all the satellites  21  of the satellite cluster  31  (multicast), and each satellite  21  can select an instruction addressed to itself by the individual ID as destination information included in the imaging instruction. 
     In step S 123 , the satellites  21  receive an imaging instruction from the ground station  15 , perform imaging preparation processing in step S 124 , and capture images in step S 125 . Moreover, the satellites  21  generate and add metadata to the captured images in step S 126 , and transmit (downlink) the captured images to which the metadata has been added to the ground station  15  in step S 127 . 
     The processing in steps S 123  to S 127  is basically similar to the processing in steps S 31  to S 36  performed by each satellite  21  described with reference to  FIG. 6 . Note that, when the captured images are transmitted in step S 127 , each satellite  21  may individually transmit an image captured by the satellite  21 , or the captured images may be collected in the leader satellite by inter-satellite communication and then 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. In step S 108 , the management system executes distribution management processing on the captured image and the processed image, and stores the captured image and the processed image in a predetermined storage unit. 
     The processing in steps S 105  to S 108  is basically similar to the processing in 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 the plurality of satellites  21  of the satellite cluster  31  can be performed. 
     5. Example of Image Processing 
     A processing example of image processing executed by the satellite cluster 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 cluster 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 regarding the satellite  21  that has captured the image. For example, information regarding latitude and longitude of an imaging target position, and information regarding attitude control and acceleration at the time of imaging by the satellite  21  can be generated as metadata. 
     (2) Correction Processing of Captured Image 
     It is possible to perform correction processing such as radiometric correction related to a sensitivity characteristic, geometric correction of an orbit position, an attitude error, or the like of the satellite  21 , ortho-correction for correcting geometric distortion caused by a height difference of terrain, and map projection for projecting an image on a map projection surface. 
     (3) Color Composition Processing 
     It is possible to perform color composition processing such as pan-sharpening processing, true color composition processing, false color composition processing, natural color composition processing, SAR image composition processing, and processing of adding color to a captured image for each band. 
     (4) Other Image Compositions 
     It is also possible to perform composition using a captured image captured by the satellite  21  itself in the past, a captured image captured by another satellite  21 , or a base image of some kind, composition using captured images captured in different bands, composition using map information, and the like. 
     (5) Extraction of Information 
     It is possible to calculate vegetation detection information such as a normalized difference vegetation index (NDVI) and water detection information such as a normalized difference water index (NDWI) by 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 group of fish, extraction of information regarding a specific band or a change from the previous imaging, and the like. 
     In particular, in a case of using a plurality of captured images captured by the plurality of satellites  21  that performs a formation flight, the satellite cluster management device  11  or the image analysis server  42  can more effectively perform the following image processing. 
     (1) Higher Resolution or High Quality Processing 
     By superimposing a plurality of captured images, it is possible to generate a captured image with improved resolving power. Furthermore, it is possible to generate a pan-sharpened image obtained by compositing a monochrome image and a color image, or a captured image in which the resolution has been increased obtained by compositing captured images with different imaging conditions such as different dynamic ranges or shutter speeds, different bands (wavelength bands), or different resolutions, for example. 
     (2) Function Assignment 
     An index such as a normalized difference vegetation index (NDVI) can be calculated by different bands such as red (R) and infrared (IR). 
     (3) Three-Dimensional Measurement 
     Three-dimensional information can be obtained from a parallax image. Furthermore, the accuracy of recognizing an object on the ground can be enhanced by the three-dimensional information. For example, it is possible to determine whether or not the object is a vehicle (even in a case where it is not possible to immediately recognize the object as a vehicle from the image in terms of resolving power, if it is determined that the object on the road is not a pattern but a three-dimensional object, it is possible to estimate that the object is a vehicle). 
     (4) Differential Measurement 
     By using a plurality of captured images captured from the same position with a time difference, it is possible to extract a change between a first time and a second time. Furthermore, imaging may be performed such that only a target that has changed is extracted and colored. Furthermore, for example, a moving speed of a ship or a vehicle can be calculated from a plurality of captured images, or a wind speed can be calculated from a movement of cloud or the like. 
     (5) Other Image Compositions 
     It is also possible to perform composition using a past captured image or a captured image captured by another satellite  21 , composition using captured images captured in different bands, composition using map information, and the like. 
     The satellite cluster management device  11  and the image analysis server  42  as image processing apparatuses perform the above-described image processing on the basis of satellite specification information for specifying a satellite 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 process a plurality of images by using a relative positional relationship among the plurality of satellites  21  in a formation flight. The satellite specification information includes at least a cluster ID for identifying the satellite cluster  31 , an individual ID for identifying each satellite  21  constituting the satellite cluster  31 , and information regarding the relative position of each satellite  21  that performs the formation flight. 
     Note that, although image processing using a plurality of captured images captured by a formation flight has been described, the above-described image processing may be performed on a plurality of captured images captured by a constellation instead of a formation flight. For example, image processing such as (1) higher resolution or high quality processing, (3) three-dimensional measurement, or (5) other image compositions may be performed on a plurality of captured images captured by a constellation. 
     (Image Format) 
     Processed images after image processing and captured images are stored in a storage unit and provided to a 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 each band and “CEOS-BIL” in which a plurality of bands is multiplexed. 
     (2) HDF 
     This is a format developed by the National Center for Supercomputing Applications (NCSA) at the University of Illinois. A plurality of bands is grouped into one file so that data can be easily exchanged in a wide variety of computer environments. 
     (3) Geo TIFF 
     This is a format in which information for remote sensing is added to a tagged image file format (TIFF). This is in the TIFF format, and can be opened with a general image viewer or the like. 
     (4) JPEG2000 
     This is an image format standardized by Joint Photographic Experts Group. JPEG 2000 not only simply increases a compression rate, but also adopts a technology for improving an image in a region of interest and a copyright protection technology such as an electronic watermark. 
     Methods for presenting processed images and captured images include (1) a method of providing an image in a manner such that the image can be viewed and (2) a method of presenting only information based on analysis of the image. 
     Moreover, examples of (1) the method of providing an image in a manner such that the image can be viewed include (1A) a method of providing (transmitting) the image itself, (1B) a method of allowing access to a platform such as a data server and allowing a user to view an image of data on the platform, and (1C) a method of providing dedicated software for viewing images to a user and allowing the user to view the images only with the dedicated software. 
     (2) The method of presenting only information based on analysis of the image is, for example, a method of presenting the number of vehicles or moving objects in each time zone or presenting an area of a group of fish obtained by the processing of information extraction described above. 
     6. Details of Metadata 
       FIG. 10  illustrates an example of information attached as metadata to a captured image or a processed image. 
     The information attached as metadata includes, depending on the type of information, information that can be added by a satellite  21 , information that can be added by the satellite cluster management device  11 , and information that can be added by the image analysis server  42  of the analysis company. In  FIG. 10 , the types of information are disposed in a table format, and a circle (∘) is attached to a device that can add the corresponding type of information. Note that, in a case where the satellite cluster management device  11  also has an image processing function, it goes without saying that information that can be added by the image analysis server  42  can also be added by the satellite cluster management device  11  itself. 
     As the metadata, for example, information for specifying a satellite (satellite specification information) can be added. The information for specifying a satellite may include, for example, a cluster ID for identifying the satellite cluster  31 , an individual ID for identifying each satellite  21 , information regarding the relative position of each satellite  21  constituting the satellite cluster  31  that performs a formation flight, angle information of itself (the satellite  21 ) at the time of imaging, and a satellite type. The information regarding the relative position includes, for example, information such as the order of the plurality of satellites  21  constituting the satellite cluster  31  and the distances between the satellites. The information regarding the relative position may be information that can be used for estimation of the relative position. The angle information of itself at the time of imaging indicates, for example, the angle of itself with respect to the ground surface at the time of imaging. The satellite type includes, for example, whether the satellite is an optical satellite or a SAR satellite, or a division by classification based on usage and size of the satellite. 
     Furthermore, the information for specifying a satellite may include, for example, orbit information (TLE information) in the TLE format of the satellite  21 , position information (GPS information) by a GPS signal, orbit position/orbit altitude information calculated from at least one of the TLE information or the GPS information, speed information of the satellite  21 , and sensor information of an earth sensor, a sun sensor, a star tracker, or the like of the satellite  21 . 
     Furthermore, information regarding imaging contents can be added to the metadata. The information regarding imaging contents may include, for example, imaging target position information indicating a place on the earth as an imaging target, imaging conditions such as the resolution (resolving power), zoom, shutter speed, sensitivity, and aperture (f-number), a sensor type such as the model number of an image sensor, the imaging time, the satellite position at the time of imaging, and weather information such as the cloud cover and amount of sunlight. 
     As the imaging target position information, for example, information regarding latitude and longitude of a place 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 imaging preparation processing described above, since there is a case where the accuracy of the attitude control is changed in accordance with the remaining battery level, the satellite position at the time of imaging may further include information regarding the accuracy of the attitude control for 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. The information regarding the attitude control can be used as a reference for processing in, for example, high resolution processing on a 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 may include band information and image processing information. 
     The band information includes wavelength information related to a wavelength band, color information indicating RGB (true color), IR (infrared light), or monochrome, coloring information indicating that a specific target such as a plant has been colored (false color), and analysis information indicating that the image indicates a normalized difference vegetation index (NDVI) or a normalized difference water index (NDWI). 
     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 the time when the image processing has been performed. The processing level is divided into six levels from L 0  to L 5 . L 0  is a level indicating an uncorrected state where correction processing has not been performed, L 1  is a level where a radiometric correction related to the sensitivity characteristic has been performed, and L 2  is a level where a geometric correction for the orbit position, attitude error, or the like of the satellite  21  has been performed. In addition, there are a level where an image has been projected on a map projection surface, a level where an ortho-correction for correcting geometric distortion has been performed, and the like. Processing methods are described by processing names such as pan-sharpening processing, true color composition processing, and SAR image composition processing. A processed image of the three-dimensional measurement may include a description of distinction between an L image (image for a left eye) and an R image (image for a right eye). 
     Moreover, related person information, which is information regarding a person related to a captured image or a processed image, can be added to the metadata. The information regarding the related person includes, for example, information regarding an owner of the satellite  21 , a service operator who operates a satellite remote sensing service, or a person who has a right to the captured image or the processed image. By adding the related person information as metadata to the captured image or the processed image, it is possible to manage the person related to the captured image or the processed image by referring to or collating the person related to the captured image or the processed image, and authenticity of the image can be secured. 
     7. Details of Distribution Management Processing 
     Next, the distribution management processing on a captured image or a processed image executed by the satellite cluster management device  11  or the image analysis server  42  in step S 19  in  FIG. 6  and step S 108  in  FIG. 9  will be described. 
     Captured images and processed images can be subjected to the following processing for managing distribution of data. 
     (1) Use Limitation Processing 
     It is possible to perform processing such that captured images and processed images cannot be downloaded or displayed without permission, or perform processing such that captured images and processed images cannot be downloaded or displayed in a case where a predetermined condition such as an expiration period, the number of times of copying, or the number of times of displays is satisfied. Furthermore, it is possible to perform the processing such that secondary processing such as image composition cannot be performed on captured images and processed images. 
     (2) Watermark 
     Processing of putting a watermark (electronic watermark) indicating copyright can be performed on captured images and processed images. Furthermore, it is possible to perform processing of putting, as a watermark, information that enables determination of a route of leakage. 
     By performing the distribution management processing as described above, it is possible to secure authenticity of images, and prevent leakage and inappropriate use of captured images and processed images. At this time, a method of using a blockchain to manage each piece of data and a mode of use of the data may be adopted. 
     (Processing Example of Image Protection) 
     In a case where a user has requested for privacy protection of captured images and processed images, or in a case of images including an area (disclosure-restricted area) disclosure of which is restricted or an area (prohibited area) disclosure of which is prohibited by a law or the like of each country, such as a military facility or a public facility, the satellite cluster management device  11  or the image analysis server  42  can perform processing of protecting the images by a predetermined protection method. Whether or not the area is a protected area may be determined with the use of imaging target position information of metadata. 
     Examples of a method of protecting an image include performing processing on an image of a protected area such that persons other than end users and permitted users cannot perform processing for increasing the resolution more than necessary. Alternatively, an image of a protected area may be decreased in resolution or blurred. Furthermore, updating of an image of a protected area may be stopped, and the image may be replaced with a past image and displayed, or an image indicating protection may be superimposed. 
     As for image protection, in addition to a case where the image protection is executed in advance before an image is first provided to a user, the processing can be performed later in a case where a privacy protection request has been made, in a case where distribution of an illegal image has been detected, or the like. In a case where distribution of an illegal image has been detected, it is possible to take measures to delete captured images and processed images that have been illegally leaked. 
     Allowing the satellite cluster management device  11  and the image analysis server  42  to perform the image protection processing as described above makes it possible to respond to a user&#39;s request for privacy protection and disclosure restriction. 
     8. Application Example of Formation Flight 
     Hereinafter, an example of image analysis processing using captured images captured by the plurality of satellites  21  constituting the satellite cluster  31  by a formation flight will be described. 
     (1) Checking Germination of Crops by Higher Resolution (Remote Sensing for Agriculture) 
     Observation for checking germination of crops requires a resolution of several centimeters. Compositing images captured by a plurality of satellites by a formation flight allows for achieving a resolving power exceeding a resolving power achieved by a single device, and this allows for detection of germination. 
     The satellite cluster  31  captures images with the same point in farmland as an imaging target position. The satellites  21  may simultaneously capture images from different positions, or may capture images from the same position with a time difference. In order to turn the imaging target position of each satellite  21  toward the same point, it is necessary to grasp the satellite position in advance. 
     In image composition processing, it is not required to grasp, for each captured image, which satellite  21  has captured the image. However, grasping which satellite  21  has captured the image makes it possible to determine the angle at the time of imaging and the time, and image composition can be performed more efficiently. 
     For example, a Geo TIFF format can be used as a format of a processed image after composition, and information that the processed image is a composite image by a formation flight, and the imaging position, the imaging time, the imaging conditions, and the like of each captured image used for the composition can be attached as metadata. As the information regarding the imaging position, information regarding the imaging position of any of the captured images (a representative captured image) used for the composition can be used. 
     (2) Checking Growth Situation of Crops by Three-Dimensional Measurement (Remote Sensing for Agriculture) 
     A growth situation of crops is checked on the basis of an index such as the NDVI, or can also be checked by accurately acquiring height information by three-dimensional measurement. 
     The satellites  21  of the satellite cluster  31  simultaneously capture images with the same point, which is farmland, as an imaging target position, and obtain a parallax image. In order to obtain the distances between the satellites, which is the baseline length, information regarding the relative position of the satellites  21  is required. This information regarding the relative position may not be obtained in advance, but may be obtained simultaneously with the downlink of the captured images. 
     In image composition processing, it is not required to grasp, for each captured image, which satellite  21  has captured the image. However, grasping which satellite  21  has captured the image makes it possible to determine the angle at the time of imaging and the time, and image composition can be performed more efficiently. 
     For a processed image after the composition, for example, a format of a three-dimensional image constituted by a set of an L image and an R image can be used, and information that the processed image is a composite image by a formation flight, and the imaging position, the imaging time, the imaging conditions, and the like of each captured image used for the composition can be attached as metadata. As the information regarding the imaging position, information regarding the imaging position of any of the captured images (a representative captured image) used for the composition can be used. In addition to information regarding the three-dimensional measurement, a vegetation index such as the NDVI or another piece of information may be further added. 
     (3) Other Types of Remote Sensing for Agriculture 
     For example, it is possible to accurately acquire height information for levelness check after tilling of farmland by three-dimensional measurement. 
     4) Detection of Movement of Group of Fish (Ocean Observation Remote Sensing) 
     A group of fish can be detected, and information regarding a moving direction and a moving speed of the group of fish can be obtained. 
     The satellite cluster  31  captures images with the same point in the ocean as an imaging target position. The satellites  21  capture images from the same position with a time difference. In order to turn the imaging target position of each satellite  21  toward the same point, it is necessary to grasp the satellite position in advance. Particularly in a case of imaging in which the ocean where there is no target that serves as a reference is set as an imaging target position, it is necessary to precisely align images captured by the satellites  21 , and thus, it is important to grasp in advance information regarding the relative position and the moving speed of the satellites  21 . 
     In processing of analyzing the captured images, alignment of the images captured by the satellites  21  and group of fish comparison processing are performed on the basis of the imaging positions (including angle information) and the imaging times. By performing the comparison processing, it is possible to calculate the moving speed of the group of fish from a time difference between the imaging times of the two or more satellites  21  and the moving distance of the group of fish. 
     As an image to be presented as an analyzed image, for example, an image can be adopted in which information indicating the moving direction and the moving speed of the group of fish is superimposed and displayed on a captured image of the group of fish serving as a base (an image captured by a predetermined satellite  21 ). Various types of information of the captured image serving as a base are added to the metadata. 
     As a result of the analysis processing, information describing a calculation method used to calculate the moving direction and the moving speed of the group of fish may be presented. Examples of this information include a plurality of captured images showing the group of fish, and information such as the imaging times of the captured images and the position of the group of fish. 
     (5) Other Types of Ocean Observation Remote Sensing 
     For example, it is also possible to obtain information regarding the moving direction and the moving speed of a ship and ocean current observation information. 
     (6) Counting the Number of Vehicles (Estimation of Economic Index) 
     An economic index (business trends or sales prediction of a specific store) is calculated by examining the number of vehicles in a parking lot and the number of vehicles running on a road. It is possible to generate a high-resolution captured image by compositing images captured by a plurality of satellites by a formation flight and more accurately detect the number of vehicles or the number of running vehicles. 
     The satellite cluster  31  simultaneously captures images with the same point as an imaging target position. In order to turn the imaging target position of each satellite  21  toward the same point, it is necessary to grasp the satellite position in advance. By using a plurality of captured images that have been captured simultaneously, it is possible to increase the resolution of an image and acquire three-dimensional information based on a parallax image. 
     In image composition processing, it is not required to grasp, for each captured image, which satellite  21  has captured the image. However, grasping which satellite  21  has captured the image makes it possible to determine the angle at the time of imaging and the time, and image composition can be performed more efficiently. In a case of composition from two or more captured images, a target object that serves as a reference may be extracted from a road or a building in the images, and the two or more images may be aligned on the basis of the extracted target object. The target object that serves as a reference may be selected on the basis of height information. 
     In image analysis processing, the number of vehicles or the number of running vehicles is calculated on the basis of a captured image in which the resolution has been increased. The number of vehicles or the number of running vehicles may be efficiently calculated by increasing the resolution only in a specific region in the captured image. In a case where it is not possible to determine whether or not a target object is a vehicle from a two-dimensional image, the determination of whether or not the target object is a vehicle may be made on the basis of three-dimensional information including the height. 
     As an image to be presented as an analyzed image, for example, it is possible to adopt an image in which a captured image serving as a base (an image captured by a predetermined satellite  21 ) is colored in different colors for each detection target area or each count target (vehicles or persons), and the number of counts is superimposed and displayed. Various types of information of the image serving as a base are given to the metadata. 
     As a result of the analysis processing, information such as an imaging condition of the image or a calculation method for the object to be detected may be presented to a user. 
     Note that the above-described example is an example of increasing the resolution by simultaneous imaging, and it is also possible to measure the moving speed of a vehicle on the basis of captured images captured with a time difference, and estimate and present traffic volume information before and after the imaging time. 
     (7) Others 
     By compositing images captured by a plurality of satellites by a formation flight, it is possible to acquire three-dimensional information based on a parallax image, and create a three-dimensional map of a construction site or a house. 
     (8) Modified Example 
     A constellation of a formation flight may be used. That is, by putting the satellite cluster  31  that performs a formation flight into a single or a plurality of orbital planes, it is possible to perform an operation of mainly deploying a uniform global service. 
     Image composition of an image captured by the formation flight and an image captured by another satellite may be performed. For example, it is possible to perform image processing in which moving object information obtained by the formation flight is superimposed and displayed on a high-resolution image captured by a geostationary satellite. 
     9. Second Embodiment of Satellite Image Processing System 
       FIG. 11  illustrates a configuration example of a second embodiment of a satellite image processing system to which the present technology is applied. 
     In the first embodiment described above, the satellite cluster  31  that performs a formation flight is configured to perform simultaneous imaging or imaging with a time difference at an imaging point or 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 that has occurred on the ground and perform real-time imaging at the time of occurrence of the event. 
     In the second embodiment described below, a configuration in which one or more satellites  21  perform real-time imaging in accordance with an event that has occurred on the ground will be described. In a case where a satellite cluster  31  including a plurality of the satellites  21  performs real-time imaging in accordance with an event that has occurred on the ground, the satellite cluster  31  may be operated by either a constellation or a formation flight. 
     In the configuration of a satellite image processing system  1  of the second embodiment, as illustrated in  FIG. 11 , a plurality of transmission devices  251  including a sensor that detects a predetermined event on the ground is newly added. In the example in  FIG. 11 , four transmission devices  251 A to  251 D are installed in an event detection region  250 , but the number of transmission devices  251  is optional. 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 a formation flight. Furthermore, the three satellites  21 X to  21 Z may be independently operated satellites  21 . 
     The event detection region  250  is divided and assigned to each of the four transmission devices  251 A to  251 D for event detection. 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, for example, farmland, and the sensors included in the transmission devices  251  monitor the temperature and the like of the farmland, or monitor a growth situation of crops. 
     The transmission devices  251  detect a predetermined event in the event detection region  250 , and transmit an imaging instruction to one or more satellites  21 . The satellites  21 X to  21 Z image an occurrence region of the event in accordance with the imaging instruction transmitted from the transmission devices  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 . 
     In accordance with the control of the control unit  272 , the transmission unit  271  transmits an imaging instruction to a satellite  21  passing through the vicinity of the transmission device  251 . 
     The transmission unit  271  is, for example, omnidirectional, 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  is constituted by, for example, a communication device that can communicate with an object moving at a high speed of 100 km/h over a long distance of 100 km or more, and consumes less power. 
     The transmission unit  271  may be directional. In this case, the transmission unit  271  directs an antenna (not illustrated) toward a 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  performs control to cause the transmission unit  271  to transmit an imaging instruction to the satellite  21 . 
     The sensor unit  273  is constituted by one or more types of predetermined sensors in accordance with the purpose of event detection. For example, the sensor unit  273  is constituted by an odor sensor, an atmospheric pressure sensor, a temperature sensor, and the like. Furthermore, for example, the sensor unit  273  may be constituted by an image sensor (RGB sensor, IR sensor, or the like) that images the event detection region  250 . For example, when a detection value is equal to or more than a predetermined threshold, the sensor unit  273  detects occurrence of an event, and notifies the control unit  272  of the occurrence of the event. 
     Note that the sensor unit  273  may be disposed close to the transmission unit  271 , or may be disposed away from the transmission unit  271  in such a way that, for example, the transmission unit  271  is disposed at a high place closest to the satellite  21 , and the sensor unit  273  is disposed at a low place close to the ground. 
     A plurality of sensors of different types may be mounted on one transmission device  251 , or a plurality of sensors of the same type may be mounted. In a case where a plurality of sensors is mounted on the transmission device  251 , there is a case where it is necessary to transmit a sensor detection result with sensor information such as a sensor detection range as an imaging target position or a sensor detection type as transmission information added. 
     The power supply unit  274  is constituted by, for example, a battery 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 has a configuration as described above and allows for only unidirectional communication from the transmission device  251  to the satellite  21 , but may also be a communication device that allows for bidirectional communication including a direction from the satellite  21  to the transmission device  251 . 
     In both the one-way communication and the bidirectional communication, in a case where the communication is omnidirectional, it is not necessary for a transmission side to direct an antenna toward the satellite  21  or a ground station  15 , which is a reception side, and thus such communication is preferable particularly in a case of transmission from the ground to the satellite  21  overhead. In the present embodiment, it is assumed that the transmission unit  271  of the transmission device  251  is omnidirectional and the transmission device  251  is a device that performs one-way communication. However, as a matter of course, the transmission device  251  may be a directional device that performs bidirectional communication. 
     10. First Event Imaging Sequence of Second Embodiment 
     Next, a first event imaging sequence performed by the satellite image processing system  1  of 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 occurrence of the event, the control unit  272  determines that an event has been detected. Thus, in step S 141 , the control unit  272  waits until a notification of occurrence of an event is received from the sensor unit  273 . If it is determined that an event has been detected, the processing proceeds from step S 141  to step S 142 . 
     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 a satellite  21  passing through the vicinity of the transmission device  251 . The transmission unit  271  transmits the 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 one-way 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, the transmission device  251  continues to transmit the imaging instruction for a certain period of time such as thirty minutes or one hour, or repeatedly transmits the imaging instruction intermittently at a certain time interval. 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 , a reception completion may be received from the satellite  21 , and then the transmission of the imaging instruction may be stopped. The reception completion from the satellite  21  to the transmission device  251  may include information that the satellite  21  will capture an image. 
     Furthermore, in the present imaging sequence, when occurrence of an event has been detected, the transmission device  251  transmits an imaging instruction without selecting a satellite  21 . Alternatively, in a case where orbit information and an imaging capability of a satellite  21  passing overhead are known, the transmission device  251  may transmit an imaging instruction in which the satellite cluster  31  or the satellite  21  that satisfies requested imaging conditions is designated by the cluster ID or the individual ID. 
     The imaging instruction from the transmission device  251  to the satellite  21  is transmitted with imaging-related information such as requested imaging conditions, a requested imaging target position, a sensor ID, an event occurrence time, and a detected event type added as parameters. The requested imaging conditions include, for example, resolution and a wavelength band (RGB, IR, or the like). The requested imaging target position represents a region on the ground to be imaged, and corresponds to an occurrence region of the event of the sensor unit  273 . An installation position of the transmission device  251  or the sensor unit  273  may be stored as the requested imaging target position. 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 request has been made as the imaging instruction. The detected event type indicates, for example, the type of event detected by the sensor unit  273 , such as detection of an abnormal temperature. The detected event type may store the sensor type instead of a specific type of the detected event. 
     In step S 161 , the satellite  21  receives the imaging instruction from the transmission device  251 , and in step S 162 , determines whether imaging by itself is possible. The satellite  21  checks whether or not the requested imaging conditions added to the imaging instruction are satisfied, and determines whether imaging by itself is possible. If it is determined in step S 162  that imaging by itself is not possible, the satellite  21  ends the processing. 
     On the other hand, if it is determined in step S 162  that imaging by itself is possible, the processing proceeds to step S 163 , and the satellite  21  performs imaging preparation processing based on the received imaging instruction. Subsequently, the satellite  21  captures an image in step S 164 , and generates metadata and adds the metadata to the captured image in step S 165 . Since each piece of processing in steps S 163  to S 165  is basically similar to each piece of processing in steps S 33  to S 35  in  FIG. 6  described above, the details thereof will be omitted. The metadata can include a part or all of the information received from the transmission device  251 . For example, information such as the sensor ID indicating the sensor unit  273  or the event occurrence time can be included as the metadata. 
     In step S 166 , the satellite  21  determines whether the satellite  21  has arrived at a downlink point, in other words, whether the satellite  21  has arrived within a range in which communicate with a communication device  13  of the ground station  15  is possible. The satellite  21  repeats the processing in step S 166  until it is determined that the satellite  21  has arrived at the downlink point. If it is determined that the satellite  21  has arrived at the downlink point, the processing proceeds to step S 167 . 
     In step S 167 , the satellite  21  transmits (downlinks) the captured image to which the metadata has been added to the ground station  15 . The downlink may be performed via a relay satellite  22 . 
     In step S 181 , a management system receives the captured image from the satellite  21 . That is, the communication device  13  receives the captured image via an antenna  14 , and supplies the captured image to a satellite cluster management device  11 . After receiving the captured image, the management system performs processing similar to that in steps S 17  to S 19  in  FIG. 6 , and the description thereof will not be repeated. 
     11. Second Event Imaging Sequence of Second Embodiment 
     Next, a second event imaging sequence performed by the satellite image processing system  1  of 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 has been added in which, in a case where a satellite  21  that has received an imaging instruction determines that imaging by itself is not possible, a subsequent satellite  21  takes over the imaging instruction. The subsequent satellite  21  is, for example, a satellite  21  belonging to the same satellite cluster  31  operated in a constellation or a formation flight. In the second event imaging sequence described below, the satellite  21  that receives the imaging instruction is referred to as the first satellite  21 , and the subsequent satellite  21  that takes over the imaging instruction is referred to as the second satellite  21  for distinction. 
     Detection of occurrence of an event in steps S 141  and S 142  and transmission of an imaging instruction by the transmission device  251  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 in step S 202 , determines whether imaging by itself is possible. if it is determined in step S 202  that imaging by itself is possible, the processing proceeds to step S 203 , and the first satellite  21  performs imaging based on the imaging instruction and transmission, and the processing ends. The imaging sequence in a case where it is determined that imaging by itself is possible is the same as that in the first event imaging sequence described above, and thus, description thereof will be omitted. 
     On the other hand, if it is determined in step S 202  that imaging by itself is not possible, the processing proceeds to step S 204 , and the first satellite  21  determines whether imaging by the subsequent second satellite  21  belonging to the satellite cluster  31  of the first satellite  21  is possible. If it is determined in step S 204  that imaging by the second satellite  21  is not possible, the processing ends. 
     If it is determined in step S 204  that imaging by the second satellite  21  is possible, the processing proceeds to step S 205 , and the first satellite  21  transmits the imaging instruction to the subsequent second satellite  21  by inter-satellite communication. 
     Then, in step S 206 , the first satellite  21  determines whether the first satellite  21  has arrived at the downlink point, and repeats the processing in step S 206  until it is determined that the first satellite  21  has arrived at the downlink point. 
     Then, if it is determined in step S 206  that the first satellite  21  has arrived at the downlink point, the processing proceeds to step S 207 , and the first satellite  21  transmits (downlinks), to the ground station  15 , event detection data included in the imaging instruction received from the transmission device  251 . The event detection data includes a part or all of imaging-related information included in the imaging instruction, information 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  in a similar manner to another piece of processing described above. Thus, the processing by the first satellite  21  ends. 
     The subsequent second satellite  21  to which the imaging instruction has been transmitted from the first satellite  21  by inter-satellite communication receives the imaging instruction in step S 221 , and performs imaging preparation processing based on the received imaging instruction in step S 222 . 
     The processing in steps S 223  to S 226  is similar to the processing in steps S 164  to S 167  in  FIG. 13 . By the processing in steps S 223  to S 226 , imaging is performed, a captured image and metadata are generated, and the captured image to which the metadata has been added is transmitted to the ground station  15  at the time of arrival at the downlink point. 
     On the other hand, in response to the transmission of the event detection data by the first satellite  21 , the management system receives the event detection data in step S 241 . Furthermore, in response to the 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 that in steps S 17  to S 19  in  FIG. 6 , and the description thereof will not be repeated. 
     12. Third Event Imaging Sequence of Second Embodiment 
     Next, a third event imaging sequence performed by the satellite image processing system  1  of the second embodiment will be described with reference to a flowchart in  FIG. 15 . 
     In the second event imaging sequence described above, inter-satellite communication is used for transfer of an imaging instruction from the first satellite  21  to the second satellite  21 . The third event imaging sequence is an example in which communication via the ground station  15  is used for transfer of an imaging instruction from the first satellite  21  to the second satellite  21 . 
     Detection of occurrence of an event in steps S 141  and S 142  and transmission of an imaging instruction by the transmission device  251  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 in step S 302 , determines whether imaging by itself is possible. If it is determined in step S 302  that imaging by itself is possible, the processing proceeds to step S 303 , and the first satellite  21  performs imaging based on the imaging instruction and transmission, and the processing ends. The imaging sequence in a case where it is determined that imaging by itself is possible is the same as that in the first event imaging sequence described above, and thus, description thereof will be omitted. 
     On the other hand, if it is determined in step S 302  that imaging by itself is not possible, the processing proceeds to step S 304 , and the first satellite  21  determines whether imaging by the subsequent satellite  21  belonging to the satellite cluster  31  of the first satellite  21  is possible. If it is determined in step S 304  that imaging by the subsequent satellite  21  is possible, the processing proceeds to step S 305 , imaging and transmission by the subsequent satellite  21  are performed, and the processing ends. An imaging sequence in a case where it is determined that imaging by the subsequent satellite  21  is possible is the same as that in the above-described second event imaging sequence, and thus, description thereof will be omitted. 
     If it is determined in step S 304  that imaging by the subsequent satellite  21  is not possible, the processing proceeds to step S 306 , and the first satellite  21  determines whether the first satellite  21  has arrived at the downlink point, and repeats the processing in step S 306  until it is determined that the first satellite  21  has arrived at the downlink point. 
     Then, if it is determined in step S 306  that the first satellite  21  has arrived at the downlink point, the processing proceeds to step S 307 , and the first satellite  21  transmits (downlinks), to the ground station  15 , the imaging instruction received from the transmission device  251 . The downlink may be performed via the relay satellite  22  in a similar manner to another piece of processing described above. Thus, the processing by the first satellite  21  ends. 
     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 requirements for imaging on the basis of the requested imaging conditions, the requested 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 other satellite  21 . 
     In step S 323 , the management system transmits the imaging instruction to the specified second satellite  21 . Note that the ground station  15  (the communication device  13  thereof) that receives the imaging instruction from the first satellite  21  and the ground station  15  (the communication device  13  thereof) that transmits the imaging instruction to the second satellite  21  may be the same, or may be different. 
     In step S 341 , the second satellite  21  receives the imaging instruction from the ground station  15 . The processing in the following steps S 342  to S 346  is similar to the processing 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 the imaging instruction to the ground station  15  if it is determined that imaging by the subsequent satellite  21  is not possible. Alternatively, the first satellite  21  may transmit the imaging instruction to the ground station  15  if it is determined that imaging by itself is not possible, without determining whether or not imaging by the subsequent satellite  21  is possible. 
     According to the third event imaging sequence, even in a case where the requested imaging target position is a place where connection to a network is not available, such as on the sea, an imaging instruction can be transmitted to the management system via the first satellite  21 , and imaging can be performed by the second satellite  21 . 
     13. Another Configuration Example of Transmission Device 
     The transmission device  251  illustrated in  FIG. 12  has the built-in sensor that detects occurrence of an event, and is configured integrally with the transmission unit that transmits an imaging instruction. However, the sensor that detects occurrence of an event and the transmission device that transmits an imaging instruction can be constituted by separate devices. 
       FIG. 16  is a block diagram illustrating another configuration example of the transmission device according to 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 the number of the sensors  293  is three, which is constituted by sensors  293 A to  293 C, but the number of sensors  293  is optional. 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 . 
     In accordance with the control of the control device  292 , the transmission device  291  transmits an imaging instruction to a satellite  21  passing through the vicinity of the transmission device  291 . 
     In a case where a predetermined event has been detected by any one of a plurality of sensors  293  ( 293 A to  293 C), the control device  292  acquires an event detection result from the sensor  293 , generates an imaging instruction, and performs control to cause the transmission device  291  to transmit the imaging instruction. In a similar manner to the above-described example, imaging-related information is added to the imaging instruction as parameters. 
     Each one of the plurality of sensors  293  ( 293 A to  293 C) corresponds to the sensor unit  273  described above, detects occurrence of an event, and notifies the control device  292  of the occurrence of the event. The plurality of sensors  293  may be constituted by different types of sensors, or may be sensors of the same type. The plurality of sensors  293  may be disposed close to or away from each other. Furthermore, the plurality of sensors  293  may be disposed close to or away from the transmission device  291  and the control device  292 . The above-described sensor information is added to a notification of occurrence of an event from the sensors  293  to the control device  292  as necessary. 
     In the satellite image processing system  1  of the second embodiment, even in a case where the transmission device  291  and the sensors  293  are configured as separate devices as described above, the first to third event imaging sequences described above can be executed in a similar manner. 
     14. Application Examples of Satellite Image Processing System Using Event Detection Sensor 
     Hereinafter, application examples of the satellite image processing system using the 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 sensors  293 ) is installed at a certain interval in a predetermined observation region in farmland, and each one of the plurality of sensors detects an abnormality such as vermination or occurrence of a disease. The transmission device  251  or  291  transmits an imaging instruction to the satellite  21  in accordance with a result of detection of an abnormality in 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 the NDVI, or the like. The sensor detection range of the sensor that has detected the abnormality is assigned to the requested imaging target position added to the imaging instruction. The satellite  21  that has received the imaging instruction may image only the sensor detection range of the sensor in which the abnormality has occurred, in the observation region in which the plurality of sensors is disposed, or may perform wide-area imaging of the entire observation region. Furthermore, an imaging condition such as zoom may be changed so that both imaging of the sensor detection range of the sensor that has detected the abnormality and wide-area imaging of the entire observation region may be performed. 
     It is also possible to give an imaging instruction to the satellite  21  by using, as a trigger, occurrence of a predetermined situation for checking a growing situation, such as the ground surface having got into a predetermined environmental state (e.g., the temperature of the ground surface having reached a predetermined temperature), an amount of photosynthesis or a growth situation of a plant having got into a predetermined state, or germination having been detected, instead of detection of an abnormality. 
     (2) Event Detection in Ocean 
     For example, a buoy incorporating the transmission device  251  including the sensor unit  273  is released into a sea area to be investigated in the ocean. The sensor unit  273  detects a group of fish, or detects a predetermined condition such as a sea water temperature, an ocean current speed, or a wind speed. On the basis of a result of the event detection, the transmission device  251  transmits an imaging instruction to the satellite  21 . Imaging-related information of the imaging instruction includes requested imaging conditions, a requested imaging target position, an event occurrence time, and the like. Since satellites  21  that can image a state during the night are limited, a satellite  21  is selected on the basis of the requested imaging conditions, and a situation of an imaging target sea area is analyzed on the basis of a captured image. 
     (3) Observation of Uninhabited Zone 
     A sensor (the transmission device  251  including the sensor unit  273 , or the sensor  293 ) is installed in an uninhabited zone such as a forest, a mountain, or a desert, and an abnormality such as a change in climatic condition, detection of an organism to be observed, or a forest fire is detected. The satellite  21  captures an image on the basis of an imaging instruction from the transmission device  251  or  291 . On the basis of the captured image, the situation of the uninhabited zone is analyzed. 
     (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 the event of an emergency such as a crash of the airplane, ship grounding, or a leak from an oil tanker. The satellite  21  promptly captures an image of the place where the emergency has occurred, and transmits the image to the ground station  15 . 
     (5) Stranded Mountain Climber 
     When a mountain climber or the like carrying the transmission device  251  is stranded, the transmission device  251  transmits, to the satellite  21 , an imaging instruction to which imaging-related information including a distress signal as a detected event type and including the place where the stranding has occurred as a requested imaging target position is added. The satellite  21  captures an image of the place where the stranding has occurred 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 a predetermined interval, and occurrence of a leak is monitored. In a case where a leak has been detected, an imaging instruction is transmitted to the satellite  21 . An imaging instruction is transmitted with imaging-related information designating a satellite  21  capable of detecting a leak, such as a satellite  21  capable of detecting heat by an IR band, added as requested imaging conditions, and a satellite  21  that satisfies requirements captures an image. It is possible to promptly observe the situation of the leak in the area of the leak on the basis of the captured image. In particular, in a case where the leakage from the pipeline is human-caused, prompt observation after occurrence of the event is effective. 
     (7) Others 
     A captured image triggered by the sensor  293  disposed on the ground may be used only as primary information, and the captured image may be combined with another image for image analysis or the like. For example, a captured image triggered by the sensor  293  is promptly captured by a low-performance satellite  21  with priority given to the timing of imaging. Thereafter, the satellite cluster management device  11  sets a schedule of a satellite  21  having a higher imaging capability for high-resolution and high-accuracy imaging. The satellite cluster management device  11  performs analysis by using the first captured image captured by the low-performance satellite  21  and the second captured image captured by the satellite  21  having a higher imaging capability. For example, the satellite cluster management device  11  may increase the resolution of the first captured image on the basis of differential information, or may perform processing of compositing the first captured image and the second captured image. 
     As described above, according to satellite remote sensing using a sensor, an event that has occurred on the ground can be detected by the sensor, and an imaging instruction can be directly given to a satellite  21  overhead. In particular, even from a sensor installed in an area that is not connected to the Internet such as the ocean, an imaging instruction can be directly given to a satellite, or an imaging instruction can be given via a satellite to another satellite. For example, since it is possible to instantly detect an event that has occurred at a specific place in a vast area and cause imaging to be performed, labor can be greatly reduced. 
     15. Configuration Example of Computer 
     The series of pieces of processing described above can be executed not only by hardware but also by software. In a case where the series of pieces of processing is executed by software, a program constituting the software is installed on a computer. Here, the computer includes a microcomputer incorporated in dedicated hardware, or a general-purpose personal computer capable of executing various functions with various programs installed therein, for example. 
       FIG. 17  is a block diagram illustrating a configuration example of hardware of a computer that executes the series of pieces of processing described above in accordance with a program. 
     In the computer, a central processing unit (CPU)  301 , a read only memory (ROM)  302 , and a random access memory (RAM)  303  are connected to each other by a bus  304 . 
     The bus  304  is further connected with an input/output interface  305 . The input/output interface  305  is connected with an input unit  306 , an output unit  307 , a storage unit  308 , a communication unit  309 , and a drive  310 . 
     The input unit  306  includes a keyboard, a mouse, a microphone, a touch panel, an input terminal, or the like. The output unit  307  includes a display, a speaker, an output terminal, or the like. The storage unit  308  includes a hard disk, a RAM disk, a nonvolatile memory, or 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. 
     To perform the series of pieces of processing described above, the computer configured as described above causes the CPU  301  to, for example, load a program stored in the storage unit  308  into the RAM  303  via the input/output interface  305  and the bus  304  and then execute the program. The RAM  303  also stores, as appropriate, data or the like necessary for the CPU  301  to execute various types of processing. 
     The program to be executed by the computer (CPU  301 ) can be provided by, for example, being recorded on 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. 
     Inserting the removable recording medium  311  into the drive  310  allows the computer to install the program into 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 into the storage unit  308 . In addition, the program can be installed in advance in the ROM  302  or the storage unit  308 . 
     In the present specification, the steps described in the flowcharts may be of course performed in chronological order in the order described, or may not necessarily be processed in chronological order. The steps may be executed in parallel, or at a necessary timing such as in a case where called. 
     Furthermore, in the present specification, a system means a set of a plurality of components (devices, modules (parts), and the like), and it does not matter whether or not all components are in the same housing. Thus, a plurality of devices housed in separate housings and connected via a network, and one device having a plurality of modules housed in one housing are both systems. 
     Embodiments of the present technology are not limited to the embodiments described above but can be modified in various ways within a scope of the present technology. 
     For example, it is possible to adopt a mode in which all or some of the plurality of embodiments described above are combined. 
     For example, the present technology can have a cloud computing configuration in which a plurality of devices shares one function and collaborates in processing via a network. 
     Furthermore, each step described in the flowcharts described above can be executed by one device or can be shared by a plurality of devices. 
     Moreover, in a case where a plurality of pieces of processing is included in one step, the plurality of pieces of processing included in that step can be executed by one device or can be shared by a plurality of devices. 
     Note that the effects described in the present specification are merely examples and are not restrictive, and effects other than those described in the present specification may be obtained. 
     Note that the present technology can be configured as described below. 
     (1) 
     An image management method including: 
     adding, 
     by a management device that manages a captured image captured by a satellite, 
     metadata that includes at least information regarding a person related to the captured image, to the captured image. 
     (2) 
     The image management method according to (1), in which 
     the related person information includes information regarding any of an owner of the satellite, a service operator using the satellite, or a person who has a right to the captured image. 
     (3) 
     The image management method according to (1) or (2), in which 
     the management device performs use limitation processing on the captured image. 
     (4) 
     The image management method according to (1) or (2), in which 
     the management device performs watermark processing on the captured image. 
     (5) 
     The image management method according to any one of (1) to (4), in which 
     the management device receives, from the satellite, the captured image to which the metadata is added. 
     (6) 
     The image management method according to any one of (1) to (4), in which 
     the management device receives the metadata from the satellite as a stream different from the captured image. 
     (7) 
     The image management method according to any one of (1) to (6), in which 
     the metadata includes a satellite identifier for identifying the satellite and a satellite cluster identifier for identifying a satellite cluster that includes the satellite. 
     (8) 
     The image management method according to any one of (1) to (7), in which 
     the metadata includes information regarding a relative position with respect to each satellite constituting a satellite cluster. 
     (9) 
     The image management method according to (8), in which 
     the information regarding the relative position includes an arrangement sequence of each satellite constituting the satellite cluster and distances between the satellites. 
     (10) 
     The image management method according to any one of (1) to (9), in which 
     the metadata includes information regarding imaging contents of imaging by the satellite. 
     (11) 
     The image management method according to (10), in which 
     the information regarding the imaging contents includes at least any one of imaging target position information, an imaging condition, an image sensor type, an imaging time, or a satellite position at time of imaging. 
     (12) 
     The image management method according to any one of (1) to (11), in which 
     the metadata includes information regarding an image type of the captured image. 
     (13) 
     The image management method according to (12), in which 
     the information regarding the image type of the captured image includes image processing information. 
     (14) 
     A data structure of metadata of a captured image captured by a satellite, 
     in which the metadata includes at least information regarding a person related to the captured image, and 
     a management device that manages the captured image is used for processing of collating the person related to the captured image. 
     (15) 
     The data structure of metadata according to (14), in which 
     the metadata is attached to the captured image. 
     REFERENCE SIGNS LIST 
     
         
           1  Satellite image processing system 
           11  Satellite cluster management device 
           13  Communication device 
           14  Antenna 
           15  Ground station (base station) 
           21  Satellite 
           31  Satellite cluster 
           41  Information provision 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