Patent Publication Number: US-2022219841-A1

Title: Debris retrieval control apparatus, debris retrieval satellite, capture interface instrument, connection device, and debris retrieval system

Description:
TECHNICAL FIELD 
     The present invention relates to a debris retrieval control apparatus, a debris retrieval satellite, a capture interface instrument, a connection device, a debris retrieval system, a debris retrieval method, and a debris retrieval program. 
     BACKGROUND ART 
     In recent years, space debris such as an artificial satellite that has become uncontrollable due to a failure or rocket debris has been increasing, and retrieval of space debris has become a problem. 
     In addition to the increase in space debris, large-scale satellite constellations including hundreds to thousands of satellites have started to be constructed, and the risk of collision accidents in orbit is increasing. Thus, in order to avoid collisions, there has been an appeal for the need for deorbit after completion of a mission in orbit (PMD), or ADR that causes debris such as a failed satellite or an upper stage of a rocket that is floating to deorbit by external means such as a debris retrieval satellite. International discussions have begun as STM on the need for such ADR. PMD is an abbreviation for Post Mission Disposal. ADR is an abbreviation for Active Debris Removal. STM is an abbreviation for Space Traffic Management. 
     Patent Literature 1 discloses a technology to capture space debris that is tumbling or rotating. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2012-236591 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In the technology of Patent Literature 1, debris is captured with a rope-shaped object, so that a problem is that it is difficult to determine a center-of-gravity position when debris such as rocket debris or a failed satellite is to be retrieved. 
     In particular, in order to carry out an active control operation during orbital descent by a debris retrieval satellite connected with debris, it is necessary to place propulsion devices in a plurality of directions so as to sandwich the center-of-gravity position of the debris retrieval satellite connected with the debris. Therefore, for debris such as rocket debris or a failed satellite, it is difficult to place the propulsion devices at appropriate positions. For example, an instrument such as a robot arm that is long enough to wrap around the debris and has a great deal of freedom is required. 
     An object of the present invention is mainly to provide a debris retrieval control apparatus that can retrieve debris unerringly. 
     Solution to Problem 
     A debris retrieval control apparatus according to the present invention includes 
     an apparatus communication device to communicate with at least one of a first satellite and a second satellite; and 
     a control unit to generate a control command to capture debris by sandwiching the debris between the first satellite and the second satellite and carry out an active control operation during orbital descent on a flying object which is the first satellite, the debris, and the second satellite being connected together, and transmit the control command to at least one of the first satellite and the second satellite via the apparatus communication device. 
     Advantageous Effects of Invention 
     In a debris retrieval control apparatus according to the present invention, a control unit generates a control command to capture debris by sandwiching the debris between a first satellite and a second satellite and carry out an active control operation during orbital descent on a flying object which is the first satellite, the debris, and the second satellite being connected together. Then, the control unit transmits the control command to at least one of the first satellite and the second satellite via an apparatus communication device. Therefore, with the debris retrieval control apparatus according to this embodiment, there is an effect that debris can be retrieved unerringly. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a configuration diagram of a debris retrieval system according to Embodiment 1; 
         FIG. 2  is a configuration diagram of a debris retrieval satellite according to Embodiment 1; 
         FIG. 3  is a comparison example to be compared with Embodiment 1; 
         FIG. 4  is a flowchart illustrating operation of the debris retrieval system according to Embodiment 1; 
         FIG. 5  is a diagram illustrating an example of capture of debris and orbit control by debris retrieval satellites according to Embodiment 1; 
         FIG. 6  is a diagram illustrating an example of capture of debris and orbit control by debris retrieval satellites according to Embodiment 1; 
         FIG. 7  is a diagram illustrating an example of capture of debris and orbit control by debris retrieval satellites according to a variation of Embodiment 1; 
         FIG. 8  is a diagram illustrating an example of capture of debris and orbit control by debris retrieval satellites according to a variation of Embodiment 1; 
         FIG. 9  is a configuration diagram of the debris retrieval system according to a variation of Embodiment 1; 
         FIG. 10  is a diagram illustrating an example of capture of debris by debris retrieval satellites according to Embodiment 2; 
         FIG. 11  is a diagram illustrating an example of capture of debris by debris retrieval satellites according to Embodiment 3; and 
         FIG. 12  is a diagram illustrating an example of a connection device according to Embodiment 3. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described hereinafter with reference to the drawings. Throughout the drawings, the same or corresponding parts are denoted by the same reference signs. In the description of the embodiments, description of the same or corresponding parts will be suitably omitted or simplified. In the drawings hereinafter, the relative sizes of components may be different from actual ones. In the description of the embodiments, directions or positions such as “up”, “down”, “left”, “right”, “front”, “rear”, “top side”, and “back side” may be indicated. These terms are used only for convenience of description, and are not intended to limit the placement and orientation of components such as devices, equipment, or parts. 
     The background to the following embodiments will now be described. 
     If a mega-constellation satellite or a debris retrieval satellite passes a congested low orbit or the polar region in the process of deorbiting, the risk of a collision becomes disproportionately high. The congested low orbit is, for example, in the vicinity of local standard time (LST) 10:30 or at altitudes of about 500 km to 800 km. For such deorbit in which the risk of a collision is disproportionately high, the rules for deorbit actions such as PMD or ADR currently being discussed are insufficient. In the deorbit process before entry into the atmosphere, it is necessary to carry out an active control operation during orbital descent which causes a descent by avoiding areas with disproportionately high risks. Such an active control operation during orbital descent will be referred to as an active deorbit operation. It is possible to avoid a collision by operation control in the deorbit process so as to control the orbital plane, altitude, timing for changing the orbital plane or altitude, and so on. 
     If only a deorbit action is simply to be performed, the purpose will be achieved by, for example, capturing debris by a debris retrieval satellite using net-like or rope-like capture means and applying deceleration force in a direction opposite to a flying direction. 
     However, in order to carry out active operation control in the deorbit process, orbit control and attitude control need to be performed on the mass characteristics of two bodies coupled together which are the debris retrieval satellite and the captured debris. Therefore, capture means that is not capable of restraining six degrees of freedom, such as net-like or rope-like capture means, is insufficient. 
     Even with capture means that is capable of restraining six degrees of freedom, desired orbit control and attitude control cannot be performed unless an injection vector of a propulsion device can be directed appropriately for the mass characteristics of the two bodies coupled together. 
     When carrying out such an active deorbit operation for debris, the debris retrieval satellite performs orbit control and attitude control with the mass characteristics in the state of being connected with the debris. For such orbit control and attitude control, the propulsion device needs to apply an injection that is vectored to pass through a center-of-gravity position. 
     In the following embodiments, aspects according to which debris retrieval satellites realize accurate orbit control and attitude control with the mass characteristics in the state of being connected with debris will be described. 
     Embodiment 1 
     DESCRIPTION OF CONFIGURATIONS 
       FIG. 1  a diagram illustrating a configuration of a debris retrieval system  500  according to this embodiment. 
       FIG. 2  is a diagram illustrating a configuration of a debris retrieval satellite  300  according to this embodiment. 
     The debris retrieval system  500  includes a debris retrieval control apparatus  100  and the debris retrieval satellite  300 . The debris retrieval system  500  captures debris  200  by sandwiching it between a parent satellite  310  and a child satellite  320 , and carries out an active control operation during orbital descent, that is, an active deorbit operation on a flying object which is the parent satellite  310 , the debris  200 , and the child satellite  320  being connected together. 
     Specifically, the debris  200  is an object such as an artificial satellite that has become uncontrollable due to a failure or rocket debris. That is, the debris  200  is a relatively large object. For example, the debris  200  floats at altitudes of 100 km to 2000 km in an elliptical orbit. 
     The debris retrieval satellite  300  includes the parent satellite  310  and the child satellite  320 . The parent satellite  310  is an example of a first satellite  31 . The child satellite  320  is an example of a second satellite  32 . The debris retrieval control apparatus  100  communicates with each of the parent satellite  310  and the child satellite  320 . The debris retrieval control apparatus  100  communicates with the debris retrieval satellite  300  via an apparatus communication device  950  of the debris retrieval control apparatus  100  and a satellite communication device  131  of each of the parent satellite  310  and the child satellite  320 . 
     In the following description, both or each of the parent satellite  310  and the child satellite  320  may be referred to as the debris retrieval satellite  300 . 
     The debris retrieval control apparatus  100  is a facility located on the ground. The debris retrieval control apparatus  100  controls the parent satellite  310  and the child satellite  320 . For example, the debris retrieval control apparatus  100  is composed of a ground station, such as a ground antenna device, a communication device connected to a ground antenna device, or an electronic computer, and a ground facility as a server or terminal connected with the ground station via a network. The debris retrieval control apparatus  100  may include a communication device installed in a mobile object such as an airplane, a self-driving vehicle, or a mobile terminal. The debris retrieval control apparatus  100  is an apparatus that controls the parent satellite  310  and the child satellite  320  to retrieve debris such as rocket debris or a failed satellite. The debris retrieval control apparatus  100  is referred to also as a ground device or a ground facility. 
     The debris retrieval control apparatus  100  includes a computer. The debris retrieval control apparatus  100  includes a processor  910 , and also includes other hardware components such as a memory  921 , an auxiliary storage device  922 , an input interface  930 , an output interface  940 , and the apparatus communication device  950 . The processor  910  is connected with other hardware components via signal lines and controls these other hardware components. 
     The debris retrieval control apparatus  100  includes a control unit  110  as a functional element. The functions of the control unit  110  are realized by hardware or software. 
     The processor  910  is a device that executes a debris retrieval program. The debris retrieval program is a program to realize the functions of the control unit  110 . 
     The processor  910  is an integrated circuit (IC) that performs operational processing. Specific examples of the processor  910  are a central processing unit (CPU), a digital signal processor (DSP), and a graphics processing unit (GPU). 
     The memory  921  is a storage device to temporarily store data. Specific examples of the memory  921  are a static random access memory (SRAM) and a dynamic random access memory (DRAM). 
     The auxiliary storage device  922  is a storage device to store data. A specific example of the auxiliary storage device  922  is an HDD. Alternatively, the auxiliary storage device  922  may be a portable storage medium, such as an SD (registered trademark) memory card, CF, a NAND flash, a flexible disk, an optical disc, a compact disc, a Blu-ray (registered trademark) disc, or a DVD. HDD is an abbreviation for Hard Disk Drive. SD (registered trademark) is an abbreviation for Secure Digital. CF is an abbreviation for CompactFlash (registered trademark). DVD is an abbreviation for Digital Versatile Disk. 
     The input interface  930  is a port to be connected with an input device, such as a mouse, a keyboard, or a touch panel. Specifically, the input interface  930  is a Universal Serial Bus (USB) terminal. The input interface  930  may be a port to be connected with a local area network (LAN). 
     The output interface  940  is a port to which a cable of an output device, such as a display, is to be connected. Specifically, the output interface  940  is a USB terminal or a High Definition Multimedia Interface (HDMI, registered trademark) terminal. Specifically, the display is a liquid crystal display (LCD). 
     The apparatus communication device  950  has a receiver and a transmitter. Specifically, the apparatus communication device  950  is a communication chip or a network interface card (NIC). The debris retrieval control apparatus  100  communicates with the debris retrieval satellite  300  or other devices via the apparatus communication device  950 . 
     The debris retrieval program is read into the processor  910  and executed by the processor  910 . The memory  921  stores not only the debris retrieval program but also an operating system (OS). The processor  910  executes the debris retrieval program while executing the OS. The debris retrieval program and the OS may be stored in the auxiliary storage device  922 . The debris retrieval program and the OS that are stored in the auxiliary storage device  922  are loaded into the memory  921  and executed by the processor  910 . Part or the entirety of the debris retrieval program may be embedded in the OS. 
     The debris retrieval control apparatus  100  may include a plurality of processors as an alternative to the processor  910 . These processors share the execution of the debris retrieval program. Each of the processors is, like the processor  910 , a device that executes the debris retrieval program. 
     Data, information, signal values, and variable values that are used, processed, or output by the debris retrieval program are stored in the memory  921  or the auxiliary storage device  922 , or stored in a register or a cache memory in the processor  910 . 
     “Unit” of the control unit  110  may be interpreted as “process”, “procedure”, or “step”. “Process” of the control process may be interpreted as “program”, “program product”, or “computer readable storage medium recording a program”. 
     The debris retrieval program causes a computer to execute each process, each procedure, or each step, where “unit” of the above control unit  110  is interpreted as “process”, “procedure”, or “step”. A debris retrieval method is a method performed by execution of the debris retrieval program by the debris retrieval control apparatus  100 . 
     The debris retrieval program may be stored and provided in a computer readable recording medium or storage medium. Alternatively, the debris retrieval program may be provided as a program product. 
     Referring to  FIG. 2 , a configuration of the parent satellite  310  and the child satellite  320  according to this embodiment will be described. Each satellite of the parent satellite  310  and the child satellite  320  will be described as the debris retrieval satellite  300  here. 
     The debris retrieval satellite  300  is an artificial satellite. The debris retrieval satellite  300  may be an observation satellite or a communications satellite, or may be a satellite produced for the purpose of debris retrieval. The debris retrieval satellite  300  includes devices such as the satellite communication device  131 , a command data processing device  132 , an attitude and orbit control device  133 , a propulsion device  134 , a capture device  135 , and a mission data processing device  136 . 
     The capture device  135  is a device to capture the debris  200  by sandwiching it between the parent satellite  310  and the child satellite  320 . The capture device  135  may transmit capture data indicating a capture state of the debris  200  to the other debris retrieval satellite  300  or the debris retrieval control apparatus  100 . 
     The propulsion device  134  is a device to change the velocity of the debris retrieval satellite  300 . Specifically, the propulsion device  134  is a chemical thruster or an electric propulsion thruster. For example, the propulsion device  134  is a hydrazine thruster, an ion engine, or a Hall thruster. 
     The satellite communication device  131  is a device to receive a command and transmit capture data. The command is a signal transmitted from the ground and transferred, as data or a control signal, to the attitude and orbit control device  133  or the capture device  135  via the command data processing device  132 . The capture data is data that indicates a capture operation performed by the capture device  135  and is transmitted, using the satellite communication device  131 , to the ground or a data relay satellite via the mission data processing device  136 . For example, the capture data indicates a capture state of the debris  200 . 
     The attitude and orbit control device  133  is a device to control attitude elements such as the attitude and angular velocity of the debris retrieval satellite  300  and the orientation of the capture device  135  and to control orbital elements of the debris retrieval satellite  300 . The attitude and orbit control device  133  changes the orientation of each attitude element to a desired orientation. Alternatively, the attitude and orbit control device  133  maintains each attitude element in a desired orientation. The attitude and orbit control device  133  includes an attitude sensor, an actuator, and a controller. Specifically, the attitude sensor is a sensor such as a gyroscope, an Earth sensor, a sun sensor, a star tracker, or a magnetic sensor. The actuator is an instrument such as a momentum wheel, a reaction wheel, or a control moment gyroscope. The controller controls the actuator by executing a control program based on measurement data of the attitude sensor or a control command from Earth. 
     The attitude and orbit control device  133  includes a Global Positioning System receiver (GPSR) and a controller. Specifically, the actuator is an attitude and orbit control thruster. The controller executes a control program based on measurement data of the attitude sensor and the GPSR or a control command from Earth, and performs orbit control by controlling the attitude and the propulsion device  134 . 
     Specifically, the power supply device  137  includes equipment such as a solar cell, a battery, and an electric power control device. The power supply device  137  provides electric power to each piece of equipment installed in the debris retrieval satellite  300 . 
     A processing circuit of the controller included in the attitude and orbit control device  133  will now be described. 
     The processing circuit may be dedicated hardware, or may be a processor that executes control programs stored in a memory. 
     In the processing circuit, some functions may be realized by hardware, and the remaining functions may be realized by software or firmware. That is, the processing circuit can be realized by hardware, software, firmware, or a combination of these. 
     Specifically, the dedicated hardware is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, an ASIC, an FPGA, or a combination of these. 
     ASIC is an abbreviation for Application Specific Integrated Circuit. 
     FPGA is an abbreviation for Field Programmable Gate Array. 
       FIG. 3  is a diagram illustrating a comparison example to be compared with this embodiment. 
     As illustrated in  FIG. 3 , a debris retrieval satellite  91  of the comparison example retrieves debris  92  such as an artificial satellite that has lost an orbit control function due to a failure or rocket debris. In  FIG. 3 , the debris retrieval satellite  91  of the comparison example captures the debris  92  with a capture device, and carries out an active deorbit operation in a state in which the debris retrieval satellite  91  and the debris  92  are connected. In this case, propulsion devices in a plurality of directions need to be placed so as to sandwich a center-of-gravity position C of the debris retrieval satellite  91  and the debris  92  being connected together. However, it is difficult with only the debris retrieval satellite  91  to place the propulsion devices in the above arrangement. 
     DESCRIPTION OF OPERATION 
     Referring to  FIG. 4 , operation of the debris retrieval system  500  according to this embodiment will be described. 
     A procedure for the operation of the debris retrieval system  500  is equivalent to the debris retrieval method. A program that realizes the operation of the debris retrieval system  500  is equivalent to the debris retrieval program. 
     In step S 101 , the control unit  110  of the debris retrieval control apparatus  100  generates a control command  51  to be transmitted to at least one of the parent satellite  310  and the child satellite  320 . The control command  51  includes a capture command  511  and an orbit control command  512 . 
     The control unit  110  generates the capture command  511  to capture the debris  200  by sandwiching it between the parent satellite  310  and the child satellite  320 . 
       FIG. 5  is a diagram illustrating an example of capture of the debris  200  and orbit control by the debris retrieval satellites  300  according to this embodiment. As illustrated in  FIG. 5 , an object which is the parent satellite  310 , the debris  200 , and the child satellite  320  being connected together will be referred to as a flying object  400 . The control unit  110  generates the capture command  511  to place the parent satellite  310  and the child satellite  320  so that a center-of-gravity position C of the flying object  400  is on a straight line of a traveling direction vector V of the propulsion device. 
     The control unit  110  generates the orbit control command  512  to carry out an active deorbit operation on the flying object  400  which is the parent satellite  310 , the debris  200 , and the child satellite  320  being connected together. 
     In step S 102 , the control unit  110  transmits the control command  51  including the capture command  511  and the orbit control command  512  to at least one of the parent satellite  310  and the child satellite  320  via the apparatus communication device  950 . 
     The control command  51  may be received by the parent satellite  310  as a single recipient. Alternatively, the debris retrieval control apparatus  100  may generate a control command  51  individually for each of the parent satellite  310  and the child satellite  320  and transmit the control command  51  to each. 
     Mutual communication between the parent satellite  310  and the child satellite  320  may be performed by non-directional short-range communication. The parent satellite  310  and the child satellite  320  may be connected at the time of launch and launched simultaneously. Alternatively, the parent satellite  310  and the child satellite  320  may approach the debris  200  after being connected with each other. 
     In step S 103 , the debris retrieval satellites  300  capture the debris  200  based on the control command  51  by sandwiching it between the parent satellite  310  and the child satellite  320 , and carry out the active deorbit operation on the flying object  400 . Specifically, the capture devices  135  of the parent satellite  310  and the child satellite  320  capture the debris  200  by sandwiching it based on the control command  51 . Then, the propulsion devices  134  of the parent satellite  310  and the child satellite  320  carry out the active deorbit operation on the flying object  400  based on the control command  51 . 
     As illustrated in  FIG. 5 , each of the parent satellite  310  and the child satellite  320  is placed so that the center-of-gravity position C of the flying object  400  is on a straight line of the traveling direction vector V of the propulsion device. 
     For example, when rocket debris is to be retrieved, the debris retrieval satellites  300  capture the upper end in an axial direction with the parent satellite  310  and capture the lower end with the child satellite  320 . Then, orbit control and attitude control are performed as the integrated flying object  400 . 
     When it is assumed that the upper end of the debris  200  faces toward the traveling direction, an injection in a direction opposite to the traveling direction by the propulsion device of the parent satellite  310  causes the flying object  400  to decelerate and descend in altitude. By continuing to descend in altitude, the flying object  400  will eventually descend to the atmosphere due to the gravity of Earth and burn up as a result of friction with the atmosphere, thereby completing the purpose of debris removal. 
       FIG. 6  is a diagram illustrating an example of capture of the debris  200  and orbit control by the debris retrieval satellites  300  according to this embodiment. 
     If there is a risk of intrusion into a congested orbit during a descent in altitude, an injection in the traveling direction by the child satellite  320  generates an acceleration effect, so that the falling velocity of the flying object  400  is reduced. 
     As illustrated in  FIGS. 5 and 6 , in the debris retrieval system  500 , the velocity of the flying object  400  can be increased or decreased by appropriately controlling the operation amount and timing of the propulsion devices  134  of the parent satellite  310  and the child satellite  320 . Specifically, the debris retrieval system  500  can speed up the descent before the flying object  400  intrudes into the congested orbit so as to cause it to fall before intruding into the congested orbit. Alternatively, the debris retrieval system  500  may slow down the descent, and then speed up the descent for falling after the congested orbital plane has rotated and passed away to an orbital plane different from that of the flying object  400 . In this way, the debris retrieval system  500  carries out the active deorbit operation on the flying object  400 . 
     Other Configurations 
     &lt;Variation 1&gt; 
       FIGS. 7 and 8  are diagrams illustrating examples of capture of the debris  200  and orbit control by the debris retrieval satellites  300  according to a variation of this embodiment. 
     Orbit control and attitude control of the flying object  400  requires not only increasing or decreasing the velocity in the traveling direction but also a movement of the propulsion device  134  in a direction orthogonal to the traveling direction, that is, a traveling-direction orthogonal direction, or a movement in a rotation direction. 
     As illustrated in  FIG. 7 , the flying object  400  can accelerate in the traveling-direction orthogonal direction. Specifically, each of the parent satellite  310  and the child satellite  320  operates the propulsion device  134  in the traveling-direction orthogonal direction and in the same direction and with thrust that is inversely proportional to the ratio of the distance from the center of gravity of the flying object  400  to each of the propulsion devices  134 . 
     As illustrated in  FIG. 8 , a movement in the rotation direction can be made by causing the propulsion device  134  of each of the parent satellite  310  and the child satellite  320  to make an injection in a direction opposite to each other or to operate with thrust that generates a moment corresponding to the distance from the center of gravity of the flying object  400 . 
     &lt;Variation 2&gt; 
     In this embodiment, the functions of the control unit  110  are realized by software. As a variation, the functions of the control unit  110  may be realized by hardware. 
       FIG. 9  is a diagram illustrating a configuration of the debris retrieval system  500  according to a variation of this embodiment. 
     The debris retrieval control apparatus  100  includes an electronic circuit  909  in place of the processor  910 . 
     The electronic circuit  909  is a dedicated electronic circuit that realizes the functions of the control unit  110 . 
     Specifically, the electronic circuit  909  is a single circuit, a composite circuit, a programmed processor, a parallel-programmed processor, a logic IC, a GA, an ASIC or an FPGA. GA is an abbreviation for Gate Array. 
     The functions of the control unit  110  may be realized by one electronic circuit, or may be distributed among and realized by a plurality of electronic circuits. 
     As another variation, some of the functions of the control unit  110  may be realized by the electronic circuit, and the rest of the functions may be realized by software. 
     Each of the processor and the electronic circuit is referred to also as processing circuitry. That is, in the debris retrieval control apparatus  100 , the functions of the control unit  110  are realized by the processing circuitry. 
     DESCRIPTION OF EFFECTS OF THIS EMBODIMENT 
     For debris such as rocket debris or a large satellite that has failed, the center-of-gravity position of a flying object which is a debris retrieval satellite being connected with the captured debris is located far, making it difficult to place propulsion devices. In the debris retrieval system according to this embodiment, even for debris for which it is difficult to place propulsion devices because the center-of-gravity position of a flying object which is a debris retrieval satellite being connected with the captured debris is far, an active deorbit operation can be easily carried out and the debris can be retrieved unerringly. 
     In the debris retrieval system according to this embodiment, the center-of-gravity position as the flying object after the parent satellite and the child satellite have captured debris is positioned to be on the straight line of the traveling direction vector of the propulsion devices of the parent satellite and the child satellite. Therefore, the debris retrieval system according to this embodiment can accurately perform orbit control and attitude control of the flying object. 
     The debris retrieval system according to this embodiment can realize the active deorbit operation whose capability has not been explicitly defined in PMD or ADR for performing a deorbit action. That is, the capability for operation control in the deorbit process is provided, and the active deorbit operation can be realized by capturing a non-cooperative target without a dedicated attachment and restraining the six degrees of freedom of the target, and arranging an injection environment for the propulsion devices necessary for performing orbit control and attitude control. 
     Embodiment 2 
     In this embodiment, additions to Embodiment 1 will be mainly described. Components that are substantially the same as those in Embodiment 1 are denoted by the same reference signs, and description thereof will be omitted. 
       FIG. 10  is a diagram illustrating an example of capture of the debris  200  by the debris retrieval satellites  300  according to this embodiment. 
     In this embodiment, a capture interface instrument  60  is provided in each of the debris retrieval satellites  300  and the debris  200 . 
     The capture interface instrument  60  is placed so that the center-of-gravity position C of the flying object  400  is on the straight line of the traveling direction vector V of the propulsion device  134 . 
     Each of the parent satellite  310  and the child satellite  320  is provided with the capture interface instrument  60  for capturing the debris  200 . The debris  200  is also provided with a capture interface instrument  60  at a position such that the center-of-gravity position C of the flying object  400  is on the straight line of the traveling direction vector V of the propulsion device  134  when connected with the parent satellite  310  and the child satellite  320 . The capture interface instrument  60  is preferably provided in advance in each of the parent satellite  310  and the child satellite  320  and in objects that may become debris  200  in the future. Specifically, the capture interface instrument  60  is preferably provided in advance in each satellite of the parent satellite  310  and the child satellite  320 , rockets for launching, observation satellites, and communications satellites. 
     The debris retrieval system according to this embodiment facilitates retrieval of debris such as an artificial satellite or rocket that has completed a mission and a failed artificial satellite. 
     Embodiment 3 
     In this embodiment, additions to Embodiments 1 and 2 will be mainly described. Components that are substantially the same as those in Embodiments 1 and 2 are denoted by the same reference signs, and description thereof will be omitted. 
       FIG. 11  is a diagram illustrating an example of capture of the debris  200  by the debris retrieval satellites  300  according to this embodiment. 
     In this embodiment, the debris retrieval satellite  300  includes a connection device  700 . 
     The connection device  700  is included in each of the parent satellite  310  and the child satellite  320 . The connection device  700  includes an arm part  71  and a connection part  70 . 
     The arm part  71  extends from a body portion of each the parent satellite  310  and the child satellite  320  toward the other satellite with which the debris  200  is sandwiched. That is, the arm part  71  extending from the parent satellite  310  extends toward the child satellite  320 , which is the other satellite. The arm part  71  extending from the child satellite  320  extends toward the parent satellite  310 , which is the other satellite. 
     The connection part  70  is provided at an end portion of the arm part  71  and connects with an end portion of the arm part  71  of the other satellite. Specifically, the connection part  70  is a holding mechanism or a magnet. That is, the connection part  70  of the parent satellite  310  connects with the connection part  70  provided at the end portion of the arm part  71  of the child satellite  320 . The connection part  70  of the child satellite  320  connects with the connection part  70  provided at the end portion of the arm part  71  of the parent satellite  310 . That is, the connection devices  700  mechanically connect the parent satellite  310  and the child satellite  320  that are flying with the debris  200  being sandwiched between them. 
     The arm part  71  may be provided, for example, in the parent satellite  310  so as to wrap around the debris  200  and reach the child satellite  320 . In this case, the child satellite  320  may include only the connection part  70 . Alternatively, the configurations of the parent satellite  310  and the child satellite  320  may be interchanged. 
       FIG. 12  is a diagram illustrating an example of the connection device  700  according to this embodiment. 
     As illustrated in  FIG. 12 , three or more connection devices  700  may be provided. In  FIG. 12 , three connection devices  700  are illustrated. Three or more connection devices  700  can be placed to surround a large structure such as a rocket. 
     The arm part  71  may be provided only in the parent satellite  310  or may be provided in each of the parent satellite  310  and the child satellite  320 . The connection device  700  may be utilized as a capture device for a large structure such as a rocket by contracting the connection device  700  or pulling the child satellite  320  from the parent satellite  310  as a robot arm after enclosing the large structure. 
     The debris retrieval system according to this embodiment facilitates capture of debris that is not provided with a structure such as a protrusion suitable for capture. It is also possible to avoid a risk of pushing away and losing debris as a result of failing to capture the debris in orbit. 
     In Embodiments 1 to 3 above, each unit of the debris retrieval control apparatus has been described as an independent functional block. However, the configuration of the debris retrieval control apparatus may be different from the configuration in the embodiments described above. The functional blocks of the debris retrieval control apparatus may be arranged in any configuration, provided that the functions described in the above embodiments can be realized. The debris retrieval control apparatus may be one device or may be a system composed of a plurality of devices. 
     A plurality of portions of Embodiments 1 to 3 may be implemented in combination. Alternatively, one portion of these embodiments may be implemented. These embodiments may be implemented as a whole or partially in any combination. 
     That is, in Embodiments 1 to 3, each of the embodiments may be freely combined, or any constituent element of each of the embodiments may be modified, or any constituent element may be omitted in each of the embodiments. 
     The above embodiments are essentially preferable examples, and are not intended to limit the scope of the present invention, the scope of applications of the present invention, and the scope of uses of the present invention. Various modifications can be made to the above embodiments as necessary. 
     REFERENCE SIGNS LIST 
       31 : first satellite;  32 : second satellite;  51 : control command;  60 : capture interface instrument;  70 : connection part;  71 : arm part;  100 : debris retrieval control apparatus;  110 : control unit;  131 : satellite communication device;  132 : command data processing device;  133 : attitude and orbit control device;  134 : propulsion device;  135 : capture device;  136 : mission data processing device;  137 : power supply device;  92 ,  200 : debris;  91 ,  300 : debris retrieval satellite;  310 : parent satellite;  320 : child satellite;  400 : flying object;  500 : debris retrieval system;  511 : capture command;  512 : orbit control command;  700 : connection device;  909 : electronic circuit;  910 : processor;  921 : memory;  922 : auxiliary storage device;  930 : input interface;  940 : output interface;  950 : communication device.