Control device, control method, and program

Abstract

A control device according to the present disclosure controls a relay satellite of a satellite constellation that receives, via an optical communication link, observation data acquired by an observation satellite and that relays transmission of the observation data, said control device comprising at least one memory and at least one processor connected to the at least one memory. The at least one processor causes a communication device of the relay satellite to transmit a scanning light beam for searching for the observation satellite and causes the communication device of the relay satellite to receive a response light beam from a communication device of the observation satellite with respect to the scanning light beam.

Description

Control Device, Control Method, and Program

[0001] The present disclosure relates to a control device, a control method, and a program.

[0002] As a communication technology in space, there is satellite optical communication between a satellite and the ground (for example, Patent Document 1). In Patent Document 1, a technique related to supplementary tracking for establishing an optical communication link is proposed. In this supplementary tracking, a process of aligning the optical axes between the transmission side and the reception side of optical communication is performed.

[0003] In addition, a Low Earth Orbit (LEO) satellite constellation including a plurality of satellites has been proposed.

[0004] Japanese Patent Application Laid-Open No. 2003-218801

[0005] By the way, as a usage scenario of the LEO satellite constellation, it is considered that the LEO satellite constellation satellites relay a large amount of measurement data measured by an observation satellite. That is, the satellites of the LEO satellite constellation function as relay satellites.

[0006] The inventor has paid attention to the fact that the miniaturization of observation satellites is progressing and there is a need to reduce the power consumption of observation satellites.

[0007] An object of the present disclosure is to provide a control device, a control method, and a program capable of reducing the power consumption of an observation satellite. It should be noted that this object is only one of the plurality of objects that the plurality of embodiments disclosed in this specification attempt to achieve. Other objects or problems and novel features will be clarified from the description of this specification or the attached drawings.

[0008] The control device according to this disclosure is a control device for controlling a relay satellite of a satellite constellation that receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of the observation data, and comprises at least one memory and at least one processor coupled to the at least one memory, wherein the at least one processor causes a scanning light beam for searching the observation satellite to be transmitted to the communication device of the relay satellite, and causes the communication device of the relay satellite to receive a response light beam from the communication device of the observation satellite to the scanning light beam.

[0009] The control method relating to this disclosure is a control method by a control device that controls a relay satellite of a satellite constellation, which receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of the observation data, and includes transmitting a scanning light beam for searching for the observation satellite to the communication device of the relay satellite, and receiving a response light beam from the communication device of the observation satellite to the scanning light beam to the communication device of the relay satellite.

[0010] The program relating to this disclosure causes a control device that controls a relay satellite of a satellite constellation, which receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of said observation data, to execute a process that includes sending a scanning light beam for searching for the observation satellite to the communication device of the relay satellite, and having the communication device of the relay satellite receive a response light beam from the communication device of the observation satellite to the scanning light beam.

[0011] This disclosure provides a control device, a control method, and a program that can reduce the power consumption of an observation satellite.

[0012] This figure shows an example of the system of this disclosure. This block diagram shows an example of the control device of this disclosure. This block diagram shows an example of the control device on the relay satellite side of this disclosure. This figure illustrates the scanning of the scanning light beam. This figure illustrates the emission angle range when using the divergence angle of the data transmission light beam. This block diagram shows an example of the control device on the observation satellite side of this disclosure. This flowchart shows an example of the processing operation of the control device on the relay satellite side of this disclosure. This flowchart shows an example of the processing operation of the control device on the observation satellite side of this disclosure. This figure shows an example of the communication device on the relay satellite side and the communication device on the observation satellite side of this disclosure. This figure shows an example of the configuration of the control device.

[0013] The embodiments will be described below with reference to the drawings. In this disclosure, the drawings may be associated with one or more embodiments. Also, each element in the drawings may correspond to one or more embodiments. Furthermore, in the embodiments, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0014] <First Embodiment> <System Overview> Figure 1 shows an example of the system of the present disclosure. In Figure 1, System 1 includes a relay satellite 2 of a satellite constellation, an observation satellite 3, and a ground station 4. The satellite constellation includes multiple relay satellites 2.

[0015] After an optical communication link is established between relay satellite 2 and observation satellite 3, observation data is transmitted from observation satellite 3 to relay satellite 2 via the optical communication link.

[0016] For example, wireless communication takes place between the relay satellite 2 and the ground station 4. For instance, the relay satellite 2 wirelessly transmits observation data received from the observation satellite 3 to the ground station 4.

[0017] <Example of Control Device Configuration> Figure 2 is a block diagram showing an example of a control device according to the present disclosure. The control device 10 controls the communication device (not shown) of the relay satellite 2 of the satellite constellation. The control device 10 is installed, for example, on the relay satellite 2. The relay satellite 2 receives observation data obtained by the observation satellite via an optical communication link and relays the transmission of this observation data. In Figure 1, the control device 10 has a scanning control unit 11 and a receiving control unit 12.

[0018] The scanning control unit 11 transmits a scanning light beam to the communication device of the relay satellite 2 to search for the observation satellite 3. The scanning control unit 11 may also transmit the scanning light beam to the observation satellite 3 via the communication device of the relay satellite 2 at the beginning of the procedure for establishing an optical communication link between the observation satellite 3 and the relay satellite 2. The scanning control unit 11 may, for example, transmit the scanning light beam to the communication device of the relay satellite 2 towards the planned location where the observation satellite 3 is located. The planned location where the observation satellite 3 is located can be calculated, for example, based on the orbital information of the observation satellite 3 (for example, information that associates multiple passing positions with the planned time of passing each position). The scanning light beam is also used by the observation satellite 3 to align the optical axis of the communication device (not shown) of the observation satellite 3 with the optical axis of the communication device of the relay satellite 2.

[0019] The receiving control unit 12 causes the communication device of the observation satellite 3 to receive the response light beam from the communication device of the observation satellite 2 in response to the scanning light beam. This response light beam is used by the relay satellite 2 to align the optical axis of the communication device of the relay satellite 2 with the optical axis of the communication device of the observation satellite 3. This response light beam may also transmit a response signal containing information about the position of the observation satellite 3. This information about the position of the observation satellite 3 may be used to calculate the expected location of the observation satellite 3 when the next opportunity to search for the observation satellite 3 arises. In the following, the direction from the relay satellite 2 to the observation satellite 3 is sometimes referred to as the "forward direction," and the link from the relay satellite 2 to the observation satellite 3 is sometimes referred to as the forward link (FL). Also, the direction from the observation satellite 3 to the relay satellite 2 is sometimes referred to as the "return direction," and the link from the observation satellite 3 to the relay satellite 2 is sometimes referred to as the return link (RL).

[0020] As described above, according to the first embodiment, the scanning control unit 11 in the control device 10 transmits a scanning light beam for searching for the observation satellite 3 to the communication device of the relay satellite 2. The receiving control unit 12 receives the response light beam from the communication device of the observation satellite 3 to the scanning light beam at the communication device of the relay satellite 2.

[0021] This configuration of the control device 10 allows the relay satellite 2 to transmit a scanning light beam to search for the other device, instead of the observation satellite 3 transmitting large amounts of observation data via the optical communication link. Therefore, it is possible to avoid increasing the processing load of the observation satellite 3 that transmits large amounts of observation data, and to reduce the power consumption of the observation satellite 3.

[0022] <Second Embodiment> <Example of Configuration of Relay Satellite Side Control Device> Figure 3 is a block diagram showing an example of a relay satellite side control device according to the present disclosure. In Figure 3, the control device 20 includes a scanning control unit 21, an adjustment control unit 22, and a receiving control unit 23.

[0023] The scanning control unit 21, like the scanning control unit 11, transmits a scanning light beam for searching for the observation satellite 3 to the communication device (not shown) of the relay satellite 2. For example, the scanning control unit 21 transmits a scanning light beam to the communication device of the relay satellite 2 for each of the multiple "emission angle ranges" within the "search angle range". The search angle range is an angular range that extends over a predetermined angle from a straight line connecting the expected location of the observation satellite 3 and the location of the relay satellite 2 at the timing when the process of searching for the observation satellite 3 begins. The emission angle range is an angular range defined by the divergence angle of the light beam centered on one candidate emission direction of light within the search angle range.

[0024] The scanning control unit 21 may set the setting value for the scanning light beam divergence angle to a value greater than the divergence angle of the data transmission light beam used for transmitting observation data from the observation satellite 3 to the relay satellite 2.

[0025] Figure 4A is a diagram illustrating the scanning of the scanning light beam. Figure 4B is a diagram illustrating the emission angle range when using the divergence angle of the data transmission light beam. In Figures 4A and 4B, the large circles correspond to the search angle range. Also, in Figures 4A and 4B, each small circle corresponds to the emission angle range.

[0026] As shown in Figure 4A, when the divergence angle of the scanning beam is larger than that of the scanning beam in Figure 4B, the entire search angle range can be covered with fewer emission angle ranges compared to the case in Figure 4B. In other words, scanning within the search angle range can be completed with fewer scans (i.e., fewer changes in emission direction), thus reducing the scanning time (i.e., the time required for acquisition and optical axis adjustment).

[0027] Furthermore, the scanning control unit 21 may control the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite 3 and the relay satellite 2. For example, the scanning control unit 21 reduces the divergence angle of the scanning light beam and increases the transmission power of the scanning light beam as the distance between the observation satellite 3 and the relay satellite 2 increases. This makes it possible to accommodate a wide dynamic range communication distance between the observation satellite 3 and the relay satellite 2, ranging from 200 km to 2000 km. For example, the distance between the observation satellite 3 and the relay satellite 2 can be calculated using the positions of the observation satellite 3 and the relay satellite 2, provided that the response light beam contains a response signal that includes information about the position of the observation satellite 3.

[0028] The receiving control unit 23, similar to the receiving control unit 12, causes the communication device of the relay satellite 2 to receive the response light beam from the communication device (not shown) of the observation satellite 3 in response to the scanning light beam. For example, if the response light beam contains a response signal that includes information about the position of the observation satellite 3, the receiving control unit 23 may control the reception processing (including demodulation processing) of the response signal. The receiving control unit 23 determines whether or not it has received the response light beam from the communication device of the observation satellite 3 in response to the scanning light beam within a predetermined time from the transmission timing of the scanning light beam.

[0029] Furthermore, the receiving control unit 23 controls the reception processing of observation data after the optical communication link has been established.

[0030] If the adjustment control unit 22 determines that it has received a response light beam from the communication device of the observation satellite 3 to the scanning light beam within a predetermined time from the transmission timing of the scanning light beam, it adjusts the optical axis of the communication device of the relay satellite 2 based on that response light beam. For example, the technology disclosed in Patent Document 1 may be used for this optical axis adjustment.

[0031] <Example of configuration of the control device on the observation satellite side> Figure 5 is a block diagram showing an example of the control device on the observation satellite side of the present disclosure. In Figure 5, the control device 30 has a receiving control unit 31, an adjustment control unit 32, and a transmitting control unit 33.

[0032] The receiving control unit 31 determines whether or not it has received the scanning light beam transmitted from the communication device of the relay satellite 2.

[0033] The adjustment control unit 32 adjusts the optical axis of the communication device of the observation satellite 3 based on the received scanning light beam. This adjustment of the optical axis may be performed using, for example, the technology disclosed in Patent Document 1.

[0034] When the receiving control unit 31 determines that the scanning light beam has been received, the transmission control unit 33 transmits a response light beam from the communication device of the observation satellite 3. As described above, the transmission control unit 33 may also transmit a response signal containing information about the position of the observation satellite 3 to the observation satellite 3 using the response light beam. For example, the position of the observation satellite 3 may be measured by a GPS installed on the observation satellite 3.

[0035] Furthermore, once the optical axis adjustment of the communication device on observation satellite 3 is complete, the transmission control unit 33 instructs the communication device on observation satellite 3 to transmit observation data using the data transmission light beam. The transmission control unit 33 sets the divergence angle of the data transmission light beam to a value smaller than the divergence angle of the scanning light beam. This narrows the divergence angle of the data transmission light beam, suppressing energy loss and ensuring sufficient receiving power for high-capacity transmission at relay satellite 2.

[0036] <Example of operation of the control device on the relay satellite side> Figure 6 is a flowchart showing an example of the processing operation of the control device on the relay satellite side of this disclosure.

[0037] The scanning control unit 21 sets the search angle range (step S11). For example, at the timing of starting the process of searching for the observation satellite 3, the scanning control unit 21 sets the search angle range as an angle range that extends over a predetermined angle centered on a straight line connecting the planned location of the observation satellite 3 and the location of the relay satellite 2. The scanning control unit 21 may also set the search angle range at the timing of the planned connection time or when the relay satellite 2 reaches the planned connection location. The scanning control unit 21 may also pre-set the planned connection time and planned connection location based on the orbital information of the observation satellite 3.

[0038] The scanning control unit 21 selects one of a plurality of exit angle ranges of the search angle range (step S12). Hereinafter, this selected exit angle range may be referred to as the exit angle range to be used.

[0039] The scanning control unit 21 causes the communication device of the relay satellite 2 to emit a scanning light beam within the emission angle range of the target object (step S13).

[0040] The receiving control unit 23 determines whether or not it has received a response light beam from the communication device of the observation satellite 3 for the scanning light beam within a predetermined time from the transmission timing of the scanning light beam (step S14).

[0041] If it is determined that no response light beam from the observation satellite 3's communication device was received for the scanning light beam within a predetermined time from the transmission timing of the scanning light beam (step S14NO), the scanning control unit 21 determines whether all emission angle ranges have been selected (step S19). If there are emission angle ranges that have not yet been selected (step S19NO), the scanning control unit 21 selects one of the unselected emission angle ranges as the emission angle range to be used (step S12).

[0042] If it is determined that the response optical beam from the communication device of the observation satellite 3 to the scanning optical beam is received within a predetermined time from the light transmission timing of the scanning optical beam (step S14 YES), the adjustment control unit 22 adjusts the optical axis of the communication device of the relay satellite 2 based on the response optical beam (step S15).

[0043] The reception control unit 23 switches to the tracking / communication mode of the observation satellite 3 (step S16).

[0044] The reception control unit 23 causes the communication device of the relay satellite 2 to receive the data transmission optical beam transmitted from the communication device of the observation satellite 3 (step S17). The data transmission optical beam transmits observation data.

[0045] When the reception of the data transmission optical beam including the observation data is completed, the reception control unit 23 ends the tracking / communication mode of the observation satellite 3 (step S18). For example, the reception control unit 23 may determine that the reception of the data transmission optical beam is completed by receiving the observation data including the end flag.

[0046] <Example of the operation of the control device on the observation satellite side> FIG. 7 is a flowchart showing an example of the processing operation of the control device on the observation satellite side of the present disclosure.

[0047] The reception control unit 31 determines whether or not it has received the scanning optical beam transmitted from the communication device of the relay satellite 2 (step S21).

[0048] If it is determined that the scanning optical beam transmitted from the communication device of the relay satellite 2 is received (step S21 YES), the adjustment control unit 32 adjusts the optical axis of the communication device of the relay satellite 2 based on the received scanning optical beam (step S22).

[0049] The transmission control unit 33 transmits the response optical beam to the communication device of the observation satellite 3 (step S23).

[0050] The transmission control unit 33 switches to the tracking / communication mode of the relay satellite 2 (step S24).

[0051] The transmission control unit 33 transmits the observation data to the communication device of the observation satellite 3 using the data transmission optical beam (step S25).

[0052] Once the transmission of observation data is complete, the transmission control unit 33 terminates the tracking and communication mode of the relay satellite 2 (step S26). As described above, the end flag may be included at the end of the observation data to be transmitted.

[0053] As described above, according to the second embodiment, the scanning control unit 21 in the control device 20 sets the setting value for the divergence angle of the scanning light beam to a value greater than the divergence angle of the data transmission light beam used for transmitting observation data from the communication device of the observation satellite 3 to the communication device of the relay satellite 2.

[0054] The configuration of this control device 20 makes it possible to reduce the number of emission angle ranges within the search angle range. As a result, scanning within the search angle range can be completed with fewer scans (i.e., fewer changes in emission direction), thus shortening the scanning time (i.e., the time required for acquisition and optical axis adjustment).

[0055] Furthermore, the scanning control unit 21 controls the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite 3 and the relay satellite 2. Specifically, the scanning control unit 21 reduces the divergence angle of the scanning light beam and increases the transmission power of the scanning light beam as the distance between the observation satellite 3 and the relay satellite 2 increases.

[0056] This configuration of the control device 20 allows for a wide dynamic range and can accommodate the communication distance between the observation satellite 3 and the relay satellite 2.

[0057] Furthermore, the scanning control unit 21 specializes the forward link (FL) for transmitting the scanning light beam. As a result, the receiver (not shown) of the observation satellite 3 does not need to receive large amounts of data, and can be designed to primarily receive the scanning light beam and adjust the optical axis. Therefore, the need for precise alignment can be relaxed, and the degree of freedom in optical design is increased. Consequently, the number of optical components and modulation / demodulation components required for high-speed communication can be reduced.

[0058] The transmission control unit 33 sets the divergence angle of the data transmission light beam to a value smaller than the divergence angle of the scanning light beam. This narrows the divergence angle of the data transmission light beam, suppressing energy loss and ensuring the light receiving power necessary for high-capacity transmission at the relay satellite 2.

[0059] <Third Embodiment> The third embodiment mainly relates to communication equipment on the relay satellite side and communication equipment on the observation satellite side.

[0060] Figure 8 shows an example of the communication equipment on the relay satellite side and the communication equipment on the observation satellite side of this disclosure.

[0061] In Figure 8, the communication device 40 on the relay satellite side includes a transmitting unit 41, a transmitting optical system 42, a receiving optical system 43, and a receiving unit 44.

[0062] The transmitting unit 41 has a light source 41A. The light source 41A is, for example, a laser diode.

[0063] The transmitting optical system 42 includes a collimator 42A, an aberration correction mirror 42B, a beam splitter 42C, a precision tracking mirror drive mechanism 42D, and a telescope 42E.

[0064] The receiving optical system 43 includes a telescope 43A, a precision mirror drive mechanism 43B, a beam splitter 43C, a beam splitter 43D, a lens 43E, a coarse adjustment sensor 43F, a beam splitter 43G, a lens 43H, a fine adjustment sensor 43I, and a collimator 43J. The telescope 43A, precision mirror drive mechanism 43B, and beam splitter 43C of the receiving optical system 43 are the same as the telescope 42E, precision mirror drive mechanism 42D, and beam splitter 42C of the transmitting optical system 42. In other words, the telescope 43A (42E), precision mirror drive mechanism 43B (42D), and beam splitter 43C (42C) are shared between the transmitting optical system 42 and the receiving optical system 43.

[0065] The receiving unit 44 includes a light source 44A, a coherent receiver 44B, and a demodulation unit 44C.

[0066] In Figure 8, the communication device 50 on the observation satellite side includes a receiving optical system 51, a transmitting unit 52, and a transmitting optical system 53.

[0067] The receiving optical system 51 includes a telescope 51A, a precision tracking mirror drive mechanism 51B, a beam splitter 51C, a beam splitter 51D, a lens 51E, a coarse adjustment sensor 51F, a lens 51G, and a fine adjustment sensor 51H.

[0068] The transmitting unit 52 includes a modulation unit 52A and a light source 52B.

[0069] The transmitting optical system 53 includes a collimator 53A, an aberration correction mirror 53B, a beam splitter 53C, a precision mirror drive mechanism 53D, and a telescope 53E. The beam splitter 53C, the precision mirror drive mechanism 53D, and the telescope 53E are the same as the beam splitter 51C, the precision mirror drive mechanism 51B, and the telescope 51A of the receiving optical system 51. In other words, the beam splitter 53C (51C), the precision mirror drive mechanism 53D (51B), and the telescope 53E (51A) are shared between the transmitting optical system 53 and the receiving optical system 51.

[0070] (Sending and receiving of scanning light beam) At the communication device 40 of the relay satellite 2, the light source 41A outputs light corresponding to the scanning light beam. The light output from the light source 41A is emitted from the telescope 42E via the collimator 42A, the aberration correction mirror 42B, the beam splitter 42C, and the precision tracking mirror drive mechanism 42D.

[0071] The scanning light beam transmitted from the communication device 40 is received by the communication device 50 on the observation satellite 3. The light received by the communication device 50 reaches the beam splitter 51D via the telescope 51A, the precision mirror drive mechanism 51B, and the beam splitter 51C. A portion of the light that reaches the beam splitter 51D is reflected by the beam splitter 51D, and the remainder is transmitted through the beam splitter 51D.

[0072] Light reflected by the beam splitter 51D reaches the coarse adjustment sensor 51F via the lens 51E. The coarse adjustment sensor 51F detects the received light and outputs the detection result to the coarse adjustment control unit 32A. The detection result of the coarse adjustment sensor 51F is the optical axis error. The coarse adjustment control unit 32A is included in the adjustment control unit 32 described above. Based on the detection result of the coarse adjustment sensor 51F, the coarse adjustment control unit 32A controls the coarse adjustment gimbal (not shown) to adjust the attitude of the telescope 53E (51A). The detection result of the coarse adjustment sensor 51F may also be output to the transmission control unit 33 described above.

[0073] Light transmitted through the beam splitter 51D reaches the fine-tuning sensor 51H via the lens 51G. The fine-tuning sensor 51H detects the received light and outputs the detection result to the fine-tuning control unit 32B. The detection result of the fine-tuning sensor 51H is the optical axis error. The fine-tuning control unit 32B is included in the adjustment control unit 32 described above. The fine-tuning control unit 32B adjusts the optical aberration correction mirror 53B based on the detection result of the fine-tuning sensor 51H. The detection result of the fine-tuning sensor 51H may also be output to the transmission control unit 33 described above.

[0074] (Transmission and Reception of Response Light Beam) When the transmission control unit 33 detects a scanning light beam transmitted from the communication device 40 using at least one of the coarse adjustment sensor 51F or the fine adjustment sensor 51H, it causes the light source 52B to output light corresponding to the response light beam. The light output from the light source 52B is emitted from the telescope 53E via the collimator 53A, the aberration correction mirror 53B, the beam splitter 53C, and the precision tracking mirror drive mechanism 53D.

[0075] The response light beam transmitted from the communication device 50 of observation satellite 3 is received by the communication device 40 of relay satellite 2. The light received by the communication device 40 reaches the beam splitter 43D via the telescope 43A, the precision mirror drive mechanism 43B, and the beam splitter 43C. A portion of the light that reaches the beam splitter 43D is reflected by the beam splitter 43D, and the remainder is transmitted through the beam splitter 43D.

[0076] Light reflected by the beam splitter 43D reaches the coarse adjustment sensor 43F via the lens 43E. The coarse adjustment sensor 43F detects the received light and outputs the detection result to the coarse adjustment control unit 22A. The detection result of the coarse adjustment sensor 43F is the optical axis error. The coarse adjustment control unit 22A is included in the adjustment control unit 22 described above. Based on the detection result of the coarse adjustment sensor 43F, the coarse adjustment control unit 22A controls the coarse adjustment gimbal (not shown) to adjust the attitude of the telescope 43A (42E). The detection result of the coarse adjustment sensor 43F may also be output to the receiving control unit 23 described above.

[0077] Light that has passed through beam splitter 43D reaches beam splitter 43G. Of the light that reaches beam splitter 43G, a portion is reflected by beam splitter 43G, and the remainder passes through beam splitter 43G.

[0078] Light reflected by the beam splitter 43G reaches the fine-tuning sensor 43I via the lens 43H. The fine-tuning sensor 43I detects the received light and outputs the detection result to the fine-tuning control unit 22B. The detection result of the fine-tuning sensor 43I is the optical axis error. The fine-tuning control unit 22B is included in the adjustment control unit 22 described above. The fine-tuning control unit 22B adjusts the optical aberration correction mirror 42B based on the detection result of the fine-tuning sensor 43I. The detection result of the fine-tuning sensor 43I may also be output to the receiving control unit 23 described above.

[0079] (Transmission and Reception of Observation Data) The transmission control unit 33 modulates the observation data stored in the memory unit (not shown) of the observation satellite 3 with light from the light source 52B and the modulation unit 52A, causing them to output light corresponding to the data transmission light beam. The light output from the light source 52B and the modulation unit 52A is emitted from the telescope 53E via the collimator 53A, the optical aberration correction mirror 53B, the beam splitter 53C, and the precision tracking mirror drive mechanism 53D.

[0080] The data transmission light beam transmitted from the communication device 50 of observation satellite 3 is received by the communication device 40 of relay satellite 2. The light received by the communication device 40 reaches the coherent receiving unit 44B via the telescope 43A, the precision mirror drive mechanism 43B, the beam splitter 43C, the beam splitter 43D, the beam splitter 43G, and the collimator 43J. The light source 44A outputs light to the coherent receiving unit 44B.

[0081] The coherent receiver 44B performs coherent reception processing on the light received by the communication device 40 using the light output from the light source 44A. The coherent receiver 44B outputs the signal obtained by the coherent reception processing to the demodulation unit 44C. The demodulation unit 44C performs demodulation processing on the signal output from the coherent receiver 44B. This allows observation data transmitted from the communication device 50 of the observation satellite 3 to be obtained.

[0082] Furthermore, when information regarding the position of observation satellite 3 is transmitted using the response light beam, the response light beam may be transmitted and received in the same manner as the data transmission light beam described here.

[0083] Furthermore, while the above explanation assumes that data transmission is performed by digital coherent optical communication, this disclosure is not limited to this. For example, data transmission may be performed by pulsed optical communication.

[0084] <Other Embodiments> Figure 9 shows an example of the configuration of a control device. In Figure 9, the control device 100 has a processor 101 and a memory 102. The processor 101 may be, for example, a microprocessor, an MPU (Micro Processing Unit), or a CPU (Central Processing Unit). The processor 101 may include multiple processors. The memory 102 is composed of a combination of volatile memory and non-volatile memory. The memory 102 may include storage located away from the processor 101. In this case, the processor 101 may access the memory 102 via an I (Input) / O (Output) interface, which is not shown.

[0085] The control devices 10, 20, and 30 of the first to third embodiments can each have the configuration shown in Figure 9. The scanning control units 11 and 21, the receiving control units 12, 23, and 31, the adjustment control units 22 and 32, and the transmission control unit 33 of the control devices 10, 20, and 30 of the first to third embodiments may be implemented by the processor 101 reading and executing a program stored in the memory 102. In other words, the control devices 10, 20, and 30 of the first to third embodiments can be implemented in software. The program can be stored using various types of non-transitory computer-readable medium and supplied to the control devices 10, 20, and 30.

[0086] Alternatively, the scanning control units 11, 21, receiving control units 12, 23, 31, adjustment control units 22, 32, and transmission control unit 33 of the control devices 10, 20, 30 in the first to third embodiments may each be implemented with dedicated hardware. Furthermore, some or all of the components of each device may be implemented by general-purpose or dedicated circuits, processors, etc., or combinations thereof. These may be configured by a single chip or by multiple chips connected via a bus. Some or all of the components of each device may be implemented by a combination of the above-mentioned circuits, etc., and programs. Furthermore, a CPU (Central Processing Unit), GPU (Graphics Processing Unit), FPGA (field-programmable gate array), etc., can be used as the processor.

[0087] Although the present invention has been described above with reference to embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made within the scope of the invention as can be understood by those skilled in the art. Furthermore, each embodiment can be combined with other embodiments as appropriate.

[0088] Each drawing is merely illustrative to illustrate one or more embodiments. Each drawing may be associated with one or more other embodiments, rather than being associated with only one specific embodiment. As those skilled in the art will understand, various features or steps described with reference to any one drawing can be combined with features or steps shown in one or more other drawings, for example, to create embodiments not explicitly shown or described. Not all features or steps shown in any one drawing to illustrate an exemplary embodiment are necessarily required, and some features or steps may be omitted. The order of steps described in any of the drawings may be changed as appropriate.

[0089] Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) A control device for controlling a relay satellite of a satellite constellation that receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of the observation data, comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor causes the communication device of the relay satellite to transmit a scanning light beam for searching for the observation satellite; and causes the communication device of the relay satellite to receive a response light beam from the communication device of the observation satellite to the scanning light beam. (Note 2) The control device according to Note 1, wherein the at least one processor causes the communication device of the relay satellite to transmit a scanning light beam for each of a plurality of emission angle ranges within a search angle range; and sets the set value of the divergence angle of the scanning light beam to a value greater than the divergence angle of the data transmission light beam from the communication device of the observation satellite to the communication device of the relay satellite used for transmitting the observation data. (Note 3) The control device according to Note 1, wherein at least one processor causes the communication device of the relay satellite to transmit a scanning light beam to each of a plurality of emission angle ranges within the search angle range, and controls the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite and the relay satellite. (Note 4) The control device according to Note 3, wherein at least one processor reduces the divergence angle and increases the transmission power as the distance increases. (Note 5) The control device according to any one of Notes 1 to 4, wherein at least one processor transmits the scanning light beam to the communication device of the relay satellite at the beginning of the procedure for establishing an optical communication link between the communication device of the observation satellite and the communication device of the relay satellite. (Note 6) The control device according to any one of Notes 1 to 4, wherein the response signal transmitted by the response light beam includes information relating to the position of the observation satellite. (Note 7) A relay satellite comprising the control device according to any one of Notes 1 to 6.(Note 8) A control method by a control device that controls a relay satellite of a satellite constellation, which receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of the observation data, the control method comprising: transmitting a scanning light beam for searching for the observation satellite to the communication device of the relay satellite; and having the communication device of the relay satellite receive a response light beam from the communication device of the observation satellite to the scanning light beam. (Note 9) The control method according to Note 8, wherein transmitting the scanning light beam includes having the communication device of the relay satellite transmit a scanning light beam for each of a plurality of emission angle ranges within the search angle range, and the method further includes setting the divergence angle of the scanning light beam to a value greater than the divergence angle of the data transmission light beam from the communication device of the observation satellite to the communication device of the relay satellite used for transmitting the observation data. (Note 10) The control method according to Note 8, wherein transmitting the scanning light beam includes causing the communication device of the relay satellite to transmit the scanning light beam to each of a plurality of emission angle ranges within the search angle range, and the method includes controlling the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite and the relay satellite. (Note 11) The control method according to Note 10, wherein transmitting the scanning light beam includes decreasing the divergence angle and increasing the transmission power as the distance increases. (Note 12) The control method according to any one of Notes 8 to 11, wherein transmitting the scanning light beam includes causing the communication device of the relay satellite to transmit the scanning light beam at the beginning of the procedure for establishing an optical communication link between the communication device of the observation satellite and the communication device of the relay satellite. (Note 13) The control method according to any one of Notes 8 to 11, wherein the response signal transmitted by the response light beam includes information relating to the position of the observation satellite.(Note 14) A program that causes a control device for controlling a relay satellite of a satellite constellation, which receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of the observation data, to execute a process that includes: transmitting a scanning light beam for searching for the observation satellite to the communication device of the relay satellite; and causing the communication device of the relay satellite to receive a response light beam from the observation satellite to the scanning light beam. (Note 15) The program according to Note 14, wherein transmitting the scanning light beam includes causing the communication device of the relay satellite to transmit a scanning light beam for each of a plurality of emission angle ranges within the search angle range, and the method includes setting the divergence angle of the scanning light beam to a value greater than the divergence angle of the data transmission light beam used for transmitting the observation data from the communication device of the observation satellite to the communication device of the relay satellite. (Note 16) The program according to Note 14, wherein transmitting the scanning light beam includes causing the communication device of the relay satellite to transmit the scanning light beam to each of a plurality of emission angle ranges within the search angle range, and the method includes controlling the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite and the relay satellite. (Note 17) The program according to Note 16, wherein transmitting the scanning light beam includes decreasing the divergence angle and increasing the transmission power as the distance increases. (Note 18) The program according to any one of Notes 14 to 17, wherein transmitting the scanning light beam includes transmitting the scanning light beam to the communication device of the relay satellite at the beginning of the procedure for establishing an optical communication link between the communication device of the observation satellite and the communication device of the relay satellite. (Note 19) The response signal transmitted by the response light beam is a program according to any one of Notes 14 to 17, which includes information relating to the position of the observation satellite.

[0090] This application claims priority based on Japanese Patent Application No. 2024-168041, filed on 27 September 2024, and incorporates all of its disclosures herein.

[0091] 1 System 2 Relay satellite 3 Observation satellite 4 Ground station 10 Control unit 11 Scanning control unit 12 Receiving control unit 20 Control unit 21 Scanning control unit 22 Adjustment control unit 22A Coarse adjustment control unit 22B Fine adjustment control unit 23 Receiving control unit 30 Control unit 31 Receiving control unit 32 Adjustment control unit 32A Coarse adjustment control unit 32B Fine adjustment control unit 33 Transmitting control unit 40 Communication device 41 Transmitting unit 41A Light source 42 Transmitting optical system 42A Collimator 42B Aberration correction mirror 42C Beam splitter 42D Precision tracking mirror drive mechanism 42E Telescope 43 Receiving optical system 43A Telescope 43B Precision tracking mirror drive mechanism 43C Beam splitter 43D Beam splitter 43E Lens 43F Coarse adjustment sensor 43G Beam splitter 43H Lens 43I Fine adjustment sensor 43J Collimator 44 Receiver 44A Light source 44B Coherent receiver 44C Demodulator 50 Communication device 51 Receiver optics 51A Telescope 51B Precision tracking mirror drive mechanism 51C Beam splitter 51D Beam splitter 51E Lens 51F Coarse adjustment sensor 51G Lens 51H Fine adjustment sensor 52 Transmitter 52A Modulation unit 52B Light source 53 Transmitter optics 53A Collimator 53B Aberration correction mirror 53C Beam splitter 53D Precision tracking mirror drive mechanism 53E Telescope

Claims

1. A control device for controlling a relay satellite of a satellite constellation that receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of said observation data, comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor causes a scanning light beam for searching the observation satellite to be transmitted to the communication device of the relay satellite; and causes the communication device of the relay satellite to receive a response light beam from the communication device of the observation satellite to the scanning light beam.

2. The control device according to claim 1, wherein the at least one processor causes the communication device of the relay satellite to transmit a scanning light beam for each of a plurality of emission angle ranges within the search angle range, and sets the set value for the divergence angle of the scanning light beam to a value greater than the divergence angle of the data transmission light beam used for transmitting the observation data from the communication device of the observation satellite to the communication device of the relay satellite.

3. The control device according to claim 1, wherein the at least one processor causes the communication device of the relay satellite to transmit a scanning light beam for each of a plurality of emission angle ranges within the search angle range, and controls the divergence angle and transmission power of the scanning light beam according to the distance between the observation satellite and the relay satellite.

4. The control device according to claim 3, wherein the at least one processor reduces the divergence angle and increases the light transmission power as the distance increases.

5. The control device according to any one of claims 1 to 4, wherein at least one processor causes the communication device of the observation satellite to transmit the scanning light beam to the communication device of the relay satellite at the beginning of the procedure for establishing an optical communication link between the communication device of the observation satellite and the communication device of the relay satellite.

6. The control device according to any one of claims 1 to 4, wherein the response signal transmitted by the response light beam includes information relating to the position of the observation satellite.

7. A control method by a control device for controlling a relay satellite of a satellite constellation that receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of said observation data, the control method comprising: transmitting a scanning light beam for searching for the observation satellite to the communication device of the relay satellite; and receiving a response light beam from the communication device of the observation satellite to the scanning light beam at the communication device of the relay satellite.

8. A program that causes a control device for a relay satellite of a satellite constellation, which receives observation data obtained by an observation satellite via an optical communication link and relays the transmission of said observation data, to execute a process including: sending a scanning light beam for searching for the observation satellite to the communication device of the relay satellite; and having the communication device of the relay satellite receive a response light beam from the communication device of the observation satellite to the scanning light beam.

Images