Intersatellite optical communication control method, intersatellite optical communication control apparatus, relay satellite, and optical communication control circuit

Abstract

To provide a technology for realizing flexible and quick response communication by setting a communication opportunity not included in a communication plan scheduled in advance in inter-satellite optical communication on demand.SOLUTION: An aspect of the present disclosure relates to a satellite including an optical signal acquisition unit that captures an image of beacon light transmitted from a relay satellite in response to a communication request received from an earth station, an image processing unit that extracts a bright spot in a captured image frame, a beacon light detection unit that detects the beacon light on the basis of a blinking state of the extracted bright spot, and an optical communication unit that establishes inter-satellite optical communication with the relay satellite on the basis of the detected beacon light.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present disclosure relates to an inter-satellite optical communication control method, an inter-satellite optical communication control device, a relay satellite, and an optical communication control circuit. [Background technology]

[0002] An earth station and a user satellite (e.g., an observation satellite, a communication satellite, etc.) can communicate via a relay satellite. In such communications between an earth station and a user satellite via a relay satellite, the user satellite and the relay satellite exchange data via inter-satellite communications. In such inter-satellite communications, the use of inter-satellite optical communications, in which the user satellite and the relay satellite communicate via optical communications, is being considered.

[0003] In inter-satellite optical communications that have been studied so far, communications between a relay satellite and a user satellite are performed according to a schedule that is set in advance based on the relative positions of the relay satellite and the user satellite, which orbit different satellites. In typical inter-satellite optical communications, the relay satellite establishes a communications connection with a specific user satellite during a predetermined time period according to a pre-planned schedule, and transmits and receives data to and from the user satellite. Specifically, at the beginning of a time period determined by the schedule, the relay satellite first transmits a beacon light addressed to the user satellite with which it is communicating. When the user satellite receives the beacon light, the user satellite with which it is communicating establishes a communications connection with the relay satellite that transmitted the beacon light. After the communications connection is established, the relay satellite and the user satellite transmit and receive data using optical communications. When there is no more data to be transmitted or received, or when the time period determined by the schedule ends, the relay satellite and the user satellite release the communications connection and terminate the communications.

[0004] Free-space optical communication technology can be applied to inter-satellite optical communication. For example, Japanese Patent Application Laid-Open No. 2001-203641 discloses a free-space optical transmission device capable of tracking and pointing in free-space optical communication. Also, Japanese Patent Application Laid-Open No. 2016-100855 discloses a transceiver that transmits data and control information superimposed on each other in free-space optical communication. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-203641 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-100855 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in conventional inter-satellite communications, relay satellites and user satellites such as Earth observation satellites can only communicate during pre-set time periods according to a communication plan (hereinafter referred to as a communication schedule or scheduling) established in advance by the operators of the respective satellites, resulting in a lack of flexibility in communication opportunities. Therefore, for example, when a specific event occurs, such as a disaster such as an earthquake, the operator of the user satellite wants to respond to the event and quickly obtain observation data from the user satellite, but there is a problem in that communication with the desired user satellite can only be performed within a pre-set schedule.

[0007] In view of the above problems, one objective of the present disclosure is to provide a technology for realizing flexible communication in inter-satellite optical communications by setting, on demand, communication opportunities that are not included in a predetermined communication plan. [Means for solving the problem]

[0008] One aspect of the present disclosure relates to an inter-satellite optical communication control method that controls execution of inter-satellite optical communication with another satellite based on a predetermined communication schedule, receives a request for communication with another satellite from an earth station, and, upon receiving the communication request, establishes inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and controls to perform prompt communication.

[0009] Another aspect of the present disclosure relates to an inter-satellite optical communication control device that controls execution of inter-satellite optical communication with another satellite based on a predetermined communication schedule, receives a request for communication with another satellite from an earth station, and, upon receiving the communication request, establishes inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and controls to perform prompt communication.

[0010] Another aspect of the present disclosure relates to a relay satellite that controls execution of inter-satellite optical communications with other satellites based on a predetermined communication schedule, receives a request for communication with other satellites from an earth station, and, upon receiving the communication request, establishes inter-satellite optical communications with the other satellite, giving priority to the communication schedule, and controls to perform prompt communication.

[0011] Another aspect of the present disclosure relates to an optical communication control circuit that controls the execution of inter-satellite optical communication with another satellite based on a predetermined communication schedule, receives a request for communication with another satellite from an earth station, and, upon receiving the communication request, establishes inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and controls to perform prompt communication. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a technology for realizing flexible and responsive communication in inter-satellite optical communications by setting communication opportunities on demand for which no communication plan has been set up in advance. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 2 is a schematic diagram illustrating a user satellite and a relay satellite according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating communication coverage between an earth station and a satellite according to one embodiment of the present disclosure. [Figure 3] FIG. 2 is a schematic diagram illustrating communication between an earth station and a user satellite via a relay satellite according to one embodiment of the present disclosure. [Figure 4] FIG. 1 is a schematic diagram illustrating a communication establishment procedure according to an embodiment of the present disclosure. [Figure 5] FIG. 2 is a block diagram illustrating a hardware configuration of a user satellite and a relay satellite according to an embodiment of the present disclosure. [Figure 6] FIG. 2 is a block diagram illustrating a functional configuration of a user satellite according to an embodiment of the present disclosure. [Figure 7] FIG. 10 illustrates a table storing information about bright points according to an embodiment of the present disclosure. [Figure 8] FIG. 10 illustrates a table storing information about bright points according to an embodiment of the present disclosure. [Figure 9] FIG. 10 illustrates a table storing information about bright points according to an embodiment of the present disclosure. [Figure 10] FIG. 1 is a schematic diagram illustrating the identification of bright points according to an embodiment of the present disclosure. [Figure 11] FIG. 10 illustrates a table storing information about bright points according to an embodiment of the present disclosure. [Figure 12] FIG. 1 is a schematic diagram illustrating allocation of slots for responsive communication according to one embodiment of the present disclosure. [Figure 13] FIG. 1 is a schematic diagram illustrating allocation of slots for responsive communication according to one embodiment of the present disclosure. [Figure 14] FIG. 2 is a block diagram illustrating a functional configuration of a relay satellite according to an embodiment of the present disclosure. [Figure 15] 10 is a flowchart illustrating an on-demand communication process according to an embodiment of the present disclosure. [Figure 16] 10 is a flowchart illustrating a bright point extraction process according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0015] In the embodiments described below, a satellite system is disclosed that includes an earth station, a relay satellite, and a user satellite. Although the following embodiments are described with respect to inter-satellite optical communications between a relay satellite and a user satellite in the satellite system, the present disclosure is not necessarily limited thereto and can be applied to inter-satellite optical communications between any two satellites.

[0016] [Satellite System] 1, the satellite system 10 includes an earth station 50, a user satellite 100, and a relay satellite 200. The user satellite 100 and the relay satellite 200 orbit the Earth on different orbits. For example, if the user satellite 100 is an observation satellite, the user satellites 100 may orbit the Earth in a predetermined arrangement (satellite constellation) so that a target observation area on the Earth can be observed using multiple user satellites 100.

[0017] The user satellite 100 is an artificial satellite with a predetermined function that orbits the Earth in an orbit at a predetermined altitude, such as an observation satellite or a communication satellite, without being limited thereto.

[0018] The relay satellite 200 orbits the Earth in an orbit at a higher altitude than the user satellites 100, and functions as a relay station for transmitting and receiving data between the earth stations 50 on Earth and the user satellites 100, without limitation. Typically, the relay satellite 200 covers multiple user satellites 100 and communicates with a desired user satellite 100. For example, the user satellites orbit in a low Earth orbit (LEO) at an altitude of, for example, 20 km to 2,000 km above the Earth's surface. For example, the relay satellite 200 orbits in a medium Earth orbit (MEO) at an altitude of, for example, 1,000 km to approximately 36,0000 km above the Earth's surface.

[0019] The earth station 50 is a communication station that communicates with the relay satellite 200. In the illustrated example, the earth station 50 is installed on the ground, but the earth station 50 according to the present disclosure is not limited to this and may be, for example, a communication station of a non-terrestrial network (NTN: Non-Terrestrial Network) constructed in the stratosphere or the like. The earth station 50 may be communicatively connected to, for example, the relay satellite operator 30 and the user satellite operator 40 via a network 20 such as the Internet. Information obtained from the user satellite 100 via the relay satellite 200 is passed to the relay satellite operator 30 and / or the user satellite operator 40 via the Internet.

[0020] 2, the communication range of the earth station 50 with respect to a user satellite is determined by the visible range of the earth station 50. In the illustrated example, the earth station 50 can communicate with a user satellite 100_2 that is in a communication coverage area, but cannot communicate with a user satellite 100_1 that is in a non-communication area.

[0021] On the other hand, as shown in FIG. 3, the earth station 50 can use the relay satellite 200 present in the communication coverage area to communicate with the user satellite 100_1 present in the communication unavailable area via the relay satellite 200.

[0022] [Summary of the Disclosure] Communication between the earth station 50 and the user satellite 100 via the relay satellite 200 has been performed based on a predetermined schedule. For example, the scheduling information is determined in advance for 24 hours starting from a specific time in the reference time of the relay satellite system. The operators 30 and 40 of the relay satellite 200 and the user satellite 100 transmit the scheduling information to the relay satellite 200 and the user satellite 100, respectively, in advance. However, the user satellite operator 40 may wish to communicate with the user satellite 100 outside of the communication time slots assigned to the user satellite 100 by the prior scheduling. For example, in the event of a specific event that is difficult to predict, such as a disaster such as an earthquake or tsunami occurring anywhere in the world or a terrorist attack, the user satellite operator 40 may want to respond to the event and acquire observation data from the user satellite 100 in a shorter time than the usual observation data acquisition timing. The following embodiment discloses a technology for realizing responsive communication between the user satellite 100 and the earth station 50 via the relay satellite 200 using an on-demand method at any timing not included in the pre-scheduled communication plan.

[0023] Specifically, when a user satellite operator 40 desires to communicate with a user satellite 100 during a time period other than a pre-scheduled communication time, the relay satellite operator 30, upon receiving a communication request from the user satellite operator 40, transmits a communication request to the user satellite 100 via the earth station 50 to a relay satellite 200 located in a position where communication with the user satellite 100 is possible. Upon receiving the communication request from the earth station 50, the relay satellite 200 transmits a beacon light onto the orbit around which the user satellite 100 orbits. The beacon light may be, for example, a pulsed optical signal in which the identifier of the relay satellite 200 and the identifier of the user satellite 100 with which it is communicating are encoded. As will be described in detail below, the user satellite 100, which captures images of space using an imaging device such as a camera, detects the beacon light from the captured image frame and analyzes the blinking pattern of the detected beacon light. Then, if the user satellite 100 determines based on the analysis results that it has been requested by the relay satellite 200 as a communication partner, it establishes a communication connection with the relay satellite 200 that sent the beacon light and begins communication with the relay satellite 200, even if it is outside the pre-scheduled communication time.

[0024] For example, as shown in Fig. 4, the earth station 50 desires to communicate with the user satellite 100_3 and transmits a communication request for communication with the user satellite 100_3 to the relay satellite 200. The relay satellite 200 transmits beacon light to the orbits of the user satellites 100_1 to 100_4 (hereinafter collectively referred to as the user satellite 100) to detect the user satellite 100_3. For example, the beacon light is transmitted toward the position of the user satellite 100 predicted from orbit prediction data of the user satellite 100 held by the relay satellite 200, and is composed of light with relatively low directionality so as to cover a wide range including the predicted position. For example, the beacon light may be configured as a pulse signal in which the identifier of the relay satellite 200 and the identifier of the user satellite 100_3 requested as the communication partner are encoded.

[0025] When the user satellite 100_3 detects the beacon light from the relay satellite 200, it extracts the identifier of the relay satellite 200 and the identifier of the requested communication partner encoded in the beacon light. The user satellite 100_3 determines whether the extracted identifier of the communication partner matches its own identifier. In this example, because the identifier of the user satellite 100_3 is included in the beacon light, the user satellite 100_3 determines that it is the requested communication partner and proceeds to a communication establishment procedure with the relay satellite 200. Once a communication connection between the user satellite 100_3 and the relay satellite 200 is established according to a predetermined communication establishment procedure, the user satellite 100_3 and the relay satellite 200 transmit and receive data using communication light with relatively high directionality. The beacon light may also have a specific blinking pattern that does not include the identifier of the relay satellite 200. In this case, the user satellite 100 that detects the beacon light may determine from the blinking pattern that the beacon light was transmitted from a predetermined relay satellite.

[0026] This enables the earth station 50 to communicate with the desired user satellite 100 via the relay satellite 200 at the desired timing, realizing more flexible and responsive communications compared to the conventional technology which only allows communications during preset time periods.

[0027] Here, the user satellite 100 and the relay satellite 200 may have, for example, a hardware configuration as shown in Fig. 5. That is, the user satellite 100 and the relay satellite 200 each have a command and data handling system 101, a mission system 102, a communication system 103, a mechanical and thermal structure system 104, an attitude control system 105, and a power supply system 106.

[0028] The command and data handling system 101 processes received commands, as well as status data, mission data, etc. For example, the command and data handling system 101 has a processing circuit for data processing, and uses this processing circuit to realize various functional units described below.

[0029] The mission system 102 realizes a function (mission) specific to each satellite. For example, if the satellite is an earth observation satellite, the mission system 102 may be composed of a sensor, a data processing device, etc. If the satellite is a communications satellite, the mission system 102 may be composed of a data relay antenna, communications equipment, etc.

[0030] The communication system 103 may be composed of communication equipment, an antenna, and the like, which receives commands from the earth station 50 and transmits the satellite's status, satellite observation data, telemetry, and the like to the earth station 50. The communication system 103 of the user satellite 100 also has a camera that captures images of the satellite's surroundings, captures images of non-terrestrial areas such as outer space, and receives beacon light and communication light for inter-satellite optical communication. For example, the camera constantly captures images of the non-terrestrial areas around the satellite at a predetermined frame rate (e.g., 30 fps) and passes the captured image frames of the non-terrestrial areas to the command and data handling system 101, etc. The camera may also be equipped with a spherical lens such as a circular fisheye lens to capture a wider range.

[0031] The mechanism and thermal structure system 104 consists of the satellite body, movable deployable parts such as solar panels, and mechanisms for stabilizing the temperature inside the satellite and dissipating heat.

[0032] The attitude control system 105 is composed of sensors that measure the position and / or attitude of the satellite, thrusters that change the altitude and / or attitude of the satellite, and the like, and controls the position and / or attitude of the satellite in orbit.

[0033] The power supply system 106 controls and manages the power used in the satellite. For example, the power supply system 106 charges the battery with power generated by solar cells and supplies the power required by each system in the satellite.

[0034] However, the above-described hardware configuration is merely an example, and the user satellite 100 and relay satellite 200 according to the present disclosure may be realized by any other appropriate hardware configuration. Furthermore, the above-described grouping into each system is merely an example, and the hardware configurations of the user satellite 100 and relay satellite 200 may be described by other groupings. For example, the same equipment and mechanisms may be classified into different systems depending on the satellite's mission. For example, since the relay satellite 200's main mission is to relay data via optical communications, the optical communication equipment (e.g., cameras, optical transmission devices, etc.) and data relay equipment may be classified into the mission system 102. On the other hand, since the user satellite 100's mission is Earth observation, etc., various observation sensors and data processing devices may be classified into the mission system 102, and the optical communication equipment (e.g., cameras, optical transmission devices, etc.) for communication with the relay satellite 200 may be classified into the communication system 103.

[0035] [User satellite] Next, a user satellite 100 according to an embodiment of the present disclosure will be described with reference to Fig. 6. Fig. 6 is a block diagram showing the functional configuration of a user satellite 100 according to an embodiment of the present disclosure.

[0036] 6, the user satellite 100 includes an optical signal acquisition unit 110, an image processing unit 120, a beacon light detection unit 130, and an optical communication unit 140. Each functional unit can be realized by any one of the above-mentioned systems or a combination thereof.

[0037] The optical signal acquirer 110 captures an image of a beacon light transmitted by the relay satellite 200 in response to a communication request received from the earth station 50. In this embodiment, in response to the communication request from the earth station 50, the relay satellite 200 transmits a beacon light onto the orbit of the user satellite 100 requested by the earth station 50. The optical signal acquirer 110 observes an optical signal arriving at the user satellite 100 and acquires the observed optical signal. For example, when the user satellite 100 orbits in a low earth orbit (LEO) at a low altitude above the Earth and the relay satellite 200 orbits at a relatively higher altitude, the optical signal acquirer 110 captures an image including an optical signal transmitted through a non-terrestrial region such as outer space. Outer space here may be defined as a region of space not belonging to the Earth or other celestial bodies, and may represent a region of space outside the atmosphere. For example, the lens of the camera of the user satellite 100 is controlled to be pointed toward the relay satellite 200 that has jurisdiction over that user satellite 100, and the optical signal acquirer 110 captures images of the non-terrestrial area at a predetermined frame rate. In this embodiment, the optical signal acquirer 110 may constantly capture images of the non-terrestrial area and observe the arrival of beacon light from the relay satellite 200 so that the earth station 50 can communicate with the user satellite 100 at any time. The optical signal acquirer 110 transfers the captured image frames of the non-terrestrial area to the image processor 120.

[0038] The image processing unit 120 extracts bright spots in the captured image frames. Specifically, the image processing unit 120 performs preprocessing such as noise reduction and contrast adjustment on each image frame acquired from the optical signal acquisition unit 110.

[0039] High-sensitivity satellite cameras are prone to background noise, which may be mistaken for star or beacon light. For example, the image processor 120 may perform time averaging and / or spatial averaging on the image frames to reduce noise. The image processor 120 may also perform contrast (offset / gain) adjustment to adjust the brightness of the image frames to an appropriate level so that the background and the bright spot of the detected object can be clearly separated.

[0040] After performing the preprocessing as described above, the image processing unit 120 extracts bright spots as beacon light candidates from each preprocessed image frame. For example, the image processing unit 120 may perform binarization on each image frame and convert the image frame into a binary image of background pixels and pixels with a luminance higher than the background. The threshold for binarization is set to a luminance level that can appropriately separate bright spots such as stars and beacon lights from the background. Thereafter, the image processing unit 120 extracts clusters of high-luminance pixels (bright spots) in the binary image and labels the extracted bright spots as beacon light candidates. The labeled bright spots are held in association with various feature amounts such as, for example, its area (number of pixels), vertical and horizontal sizes, centroid image, circularity, and the like. For example, each extracted bright spot and the feature amounts may be held in a table format as shown in FIG. 7. In the table shown in FIG. 7, N bright spots are extracted in the image frame. Each bright spot that is a beacon light candidate is assigned a unique label number (1 to N).

[0041] Next, the image processing unit 120 performs filtering based on feature amounts on each of the extracted bright spots. For example, the extracted bright spots may include the sun, moon, satellite structures, ghosts, and the like. Since these bright spots have a significantly large area, the image processing unit 120 may remove bright spots having an area greater than or equal to a threshold value. Also, bright spots other than those considered to be beacon light areas may be removed. If beacon light can be detected as having a predetermined number of pixels or more, bright spots having less than the number of pixels are likely to be determined as noise and may be removed. Also, since the bright spots of beacon light are considered to take a circular or nearly circular shape, bright spots having a circularity less than a predetermined threshold value may be removed. By such filtering, the image processing unit 120 can extract beacon light candidates from the bright spots of high-luminance pixels extracted from the binary image. The extracted beacon light candidates may be held, for example, in a table format as shown in FIG. 8. In the table shown in FIG. 8, M particles (M < N) remain as beacon light candidates as a result of the filtering.

[0042] Next, the image processing unit 120 removes stars from the beacon light candidates. That is, the beacon light candidates extracted as described above may include not only beacon lights but also stars observed from the user satellite 100. The beacon light transmitted from the relay satellite 200 has a predetermined blinking pattern, and bright points corresponding to the blinking pattern may blink in the captured image frame sequence. On the other hand, stars are unlikely to blink in a specific blinking pattern, and bright points corresponding to stars are considered to exist across each image frame. For this reason, the image processing unit 120 extracts bright points that blink in the filtered image frame sequence as beacon light candidates and distinguishes them from bright points that exist in each image frame and are considered to be stars.

[0043] For example, the image processing unit 120 may distinguish between bright spots that are beacon light candidates and bright spots that are stars according to the following procedure. First, the image processing unit 120 converts the table shown in FIG. 8 into a bright spot tracking table as shown in FIG. 9. Here, the label numbers in FIG. 8 are replaced with tracking numbers in the bright spot tracking table. Then, a state indicating the tracking status of the bright spot and a type indicating the particle discrimination status (star, beacon light candidate, etc.) are added to the bright spot tracking table. Here, the state is initially set to undetermined.

[0044] The image processing unit 120 may then refer to the bright spot tracking table for the image frame at time t and the image frame at time (t-1) of the satellite system 10's reference time, and determine that bright spots with close centroid coordinates, for example, bright spots whose distance between centroid coordinates is less than a predetermined threshold, are the same bright spot. The centroid coordinates at time t of the bright spot assigned tracking number i (i=1 to N) are calculated as P i(t) Then, for example, the image processing unit 120 compares the image frame at time t with the image frame at time (t-1) to determine the bright spot P 1(t) and the bright spot P in the image frame at time (t-1). 1(t-1) When determining the identity of the bright point P 1(t) and P 1(t-1) When the positional relationship shown in FIG. 10A is satisfied, that is, when the bright point P1(t-1) A bright spot P is located within a radius R from 1(t) If there are two bright spots P 1(t) ,P 1(t-1) are determined to be the same bright spot. Here, the radius R is set to an appropriate value that allows the bright spot to be considered to be the same bright spot based on the frame rate for image acquisition set in the imaging unit 110. The radius R may also be set to a different value depending on the type of bright spot (for example, a star, a beacon light candidate, etc.).

[0045] Furthermore, the image processing unit 120 compares the image frame at time t with the image frame at time (t-1) to determine the brightness points P 2(t) ,P 3(t) and the bright spot P in the image frame at time (t-1). 2(t-1) ,P 3(t-1) The positional relationship between the bright spot P and the bright spot P is as shown in FIG. 3(t-1) Within the radius R from 3(t) While only bright spots exist, 2(t-1) Within the radius R from 2(t) ,P 3(t) In this case, the image processor 120 first calculates the brightness point P 3(t-1) Bright spot P within the radius R from 3(t) Bright spot P 3(t-1) It is judged to be the same bright point as bright point P 2(t-1) The other bright spot P within the radius R from 2(t) Bright spot P 2(t-1) However, the determination of the identity of the bright point in the present disclosure is not necessarily limited to this. For example, the image processing unit 120 may determine that the bright point P is the same as the bright point P from the tendency of the movement direction of the neighboring particles. 2(t-1) ,P 2(t) may be judged to be the same bright spot.

[0046] Furthermore, the image processing unit 120 may maintain the type of a bright spot whose type has been determined in the immediately preceding image frame. Furthermore, the image processing unit 120 may determine that a bright spot detected in the current image frame that cannot be associated with any bright spot in the immediately preceding image frame is a newly appeared bright spot. However, it should be noted that the image processing unit 120 cannot determine the type of the bright spot at this point.

[0047] Once the image processing unit 120 has extracted bright spots that are beacon light candidates in this manner, the extracted bright spots are processed by the beacon light detection unit 130 .

[0048] The beacon light detection unit 130 detects beacon light transmitted from the relay satellite 200 that received a communication request from the earth station 50 based on the blinking state of the extracted bright spot. In this embodiment, the relay satellite 200 responds to the communication request from the earth station 50 and transmits a beacon light along the orbit of the user satellite 100 requested by the earth station 50. The beacon light detection unit 130 determines whether a bright spot extracted as a beacon light candidate by the image processing unit 120 is a beacon light destined for the user satellite 100. For example, a bright spot that was not present in the previous image frame but is present in the current image frame can be classified as a blinking beacon light, a new beacon light, a change in light intensity due to reflection from debris, a newly visible star, or noise. The beacon light detection unit 130 determines whether the bright spot was detected in a previous image frame and corresponds to a bright spot being tracked. If the bright point does not correspond to such a bright point, the beacon light detection unit 130 may classify the bright point as a newly appeared bright point (beacon light candidate).

[0049] Specifically, the beacon light detection unit 130 first performs beacon light candidate appearance detection. For example, the beacon light detection unit 130 references the bright spot tracking table of the immediately preceding image frame to determine whether the extracted bright spot is a blinking bright spot being tracked or a newly appeared bright spot. The beacon light detection unit 130 may store a bright spot tracking table such as that shown in FIG. 11. For each bright spot, this bright spot tracking table includes a bright spot presence / absence indicating the presence or absence of the bright spot in the current image frame and a bright spot confirmation time indicating the time when the presence of the particle was confirmed. For data on bright spots that do not have a tracking number in the bright spot tracking table, the distance between the bright spots between different image frames is calculated, similar to the detection of the appearance of a new bright spot. If the distance is within the movement range estimated from the elapsed time, the bright spot is determined to be the same bright spot as the bright spot with the existing tracking number, and the bright spot tracking table is updated. The beacon light detection unit 130 then determines that a bright spot that does not match the bright spot tracking table is a new beacon light candidate.

[0050] Next, the beacon light detection unit 130 monitors the blinking of the beacon light candidates. For example, the beacon light detection unit 130 monitors whether or not the bright spots of the beacon light candidates blink, and determines the type of the bright spots based on the monitoring results. That is, the beacon light detection unit 130 determines that bright spots that blink in a certain pattern are beacon lights, and excludes other bright spots from the beacon light candidates.

[0051] Specifically, the beacon light detection unit 130 determines that a bright spot that does not disappear for a certain period of time is a star and excludes it from the beacon light candidates. The beacon light detection unit 130 also determines that a bright spot that disappears for a certain period of time and does not reappear has ceased to exist and deletes the bright spot from the bright spot tracking table. The beacon light detection unit 130 also performs beacon light determination, as described below, on a bright spot whose brightness level changes at regular intervals. If the brightness level changes at different intervals or randomly, the beacon light detection unit 130 may reset the type of the bright spot to unknown without deleting it from the bright spot tracking table.

[0052] Next, the beacon light detection unit 130 performs a beacon light determination. Specifically, the beacon light detection unit 130 decodes and reads the blinking pattern of a bright spot whose brightness level changes at regular intervals, and extracts the identifier of the relay satellite 200 and the identifier of the user satellite 100 that is requested to be the communication partner, both of which are encoded as the blinking pattern. If the two extracted identifiers match the identifier of the relay satellite 200 that has jurisdiction over the user satellite 100 and the identifier of the user satellite 100, the beacon light detection unit 130 determines that the beacon light candidate is beacon light intended for the user satellite and instructs the optical communication unit 140 to establish a communication connection with the relay satellite 200. On the other hand, if the two extracted identifiers do not match the identifier of the relay satellite 200 that has jurisdiction over the user satellite 100 and / or the identifier of the user satellite 100, the beacon light detection unit 130 determines that the beacon light candidate is not beacon light intended for the user satellite.

[0053] The beacon light detection unit 130 may further monitor for beacon light disappearance. Specifically, the beacon light detection unit 130 continues tracking the bright spot after determining that the beacon light is present, and terminates the tracking when it detects that the bright spot has disappeared for a certain period of time. For example, similar to the beacon light blinking monitoring described above, the beacon light detection unit 130 deletes from the bright spot tracking table any beacon light that has disappeared for a certain period of time and has not reappeared.

[0054] Based on the detected beacon light, the optical communication unit 140 establishes inter-satellite optical communication with the relay satellite 200 that transmitted the beacon light. Specifically, when the beacon light detection unit 130 detects that the detected beacon light is a communication request for the relay satellite itself, the optical communication unit 140 initiates a procedure for establishing communication with the relay satellite 200. For example, the optical communication unit 140 transmits an optical signal indicating a response to the received communication request to the relay satellite 200 according to a predetermined communication establishment procedure, and establishes a communication connection between the relay satellite 200 and the user satellite 100. Once the communication connection is established, the optical communication unit 140 performs inter-satellite optical communication with the relay satellite 200 using the communication light. Note that if communication cannot be established for some reason, a predetermined number of retries are performed, and the status is transmitted from the relay satellite 200 to the earth station 50 and monitored by the relay satellite operator 30. If communication establishment fails after the predetermined number of retries, the optical communication unit 140 takes action, such as notifying the user satellite operator 40 of the failure.

[0055] For example, the relay satellite 200 schedules communications in predetermined slot units, with a fixed communication time allocated to each slot. This fixed communication time may be, for example, 10 minutes, or a fixed time shorter or longer than 10 minutes. Upon receiving a communication request from the earth station 50, the relay satellite 200 reserves N slots for on-demand communications with the user satellite 100 specified in the received communication request. Here, the number of reserved slots N may be included in the communication request from the earth station 50. Then, when transmitting a beacon beam to the specified user satellite 100, the relay satellite 200 encodes information indicating the number of slots N, along with the identifier of the user satellite 100, into the beacon beam. Alternatively, the number of slots N for on-demand communications may be set as a default in the satellite system 10 (e.g., N = 1). In this case, the communication request from the earth station 50 to the relay satellite 200 and the beacon beam from the relay satellite 200 to the user satellite 100 do not need to include the number of reserved slots N.

[0056] When the designated user satellite 100 receives, detects, and decodes the beacon light, it recognizes the number of slots N for prompt communication based on the decoded beacon light, and becomes able to communicate promptly with the relay satellite 200 within the time period corresponding to this number of slots N. Note that the end timing of prompt communication within the N slot period may be notified by the user satellite 100 transmitting a predetermined communication end sequence (end sequence) to the relay satellite 200.

[0057] Here, when the relay satellite 200 receives a communication request from the earth station 50 and executes prompt communication, it needs to adjust the communication schedule instructed in advance. The relay satellite 200 may adjust the communication schedule, for example, by the following method. 1) If there are available slots within the pre-specified communication schedule, the relay satellite 200 may perform prompt communication in the earliest available available slot. However, N available slots are required for prompt communication of N slots. For example, as shown in FIG. 12A, the relay satellite 200 may start prompt communication using the earliest available slot among the available slots. 2) Free slots for ready communication may be reserved in advance in a communication schedule, and the relay satellite 200 may execute ready communication in the earliest available slot among the reserved free slots. Here, the number of slots N for ready communication available for one communication request is limited to be equal to or less than the number of reserved free slots. For example, as shown in FIG. 12B, a communication schedule may be set in advance so that free slots for ready communication are reserved, and the relay satellite 200 may start ready communication using the earliest available slot among the reserved free slots. 3) The relay satellite 200 cancels communications in slots in which other communications have been scheduled in advance, and executes prompt communications with the specified user satellite 100. Here, the number of slots to be canceled depends on the number of slots N included in the communication request. For example, if the communications schedule is as shown in FIG. 13A, the relay satellite 200 may cancel communications in some of the slots in which other communications have been scheduled in advance (two slots in this example), reallocate them to slots for prompt communications, and start prompt communications, as shown in FIG. 13B.

[0058] It should be noted that the processing from bright spot extraction to beacon light determination by the image processing unit 120 and the beacon light detection unit 130 as described above is not necessarily limited to that described above, and may be realized by any other appropriate processing.

[0059] For example, in detecting the appearance of a bright spot, if the image of the bright spot hardly moves between image frames, extracting the difference between the current image frame and the previous image frame can cancel out reflections from stars or satellite structures with small image changes, while a newly appeared or disappeared bright spot will appear in the image. Therefore, if the bright spot does not exist in the linear image frame but exists in the current image frame, it can be determined that a new bright spot has appeared or a blinking bright spot has re-lit. Also, if the bright spot does not exist in the previous image frame but exists in the current image frame, it can be determined that the bright spot has disappeared or a blinking bright spot has gone out.

[0060] Specifically, the image processor 120 performs an image-to-image operation on the current image frame and the immediately preceding image frame to obtain a difference image between these image frames. The difference image represents the difference in brightness level of each pixel. If the difference in brightness level is zero, the image processor 120 may convert the pixel to an intermediate brightness, converting the brightness of the pixel so that a bright spot that has appeared is brighter and a bright spot that has disappeared is darker. Alternatively, the absolute value may be converted into a brightness level. In this case, it is not possible to distinguish between a bright spot that has appeared and a bright spot that has disappeared, but since the bright spot that has disappeared has already been tracked, such a distinction is possible. By binarizing the difference image, the process of excluding stars and satellite structures can be omitted.

[0061] Alternatively, beacon lights may be detected by utilizing the difference in the speed of movement of stars and beacon lights in a sequence of image frames, in which case beacon light candidates can be extracted even if the first appearance of a bright point cannot be extracted.

[0062] Alternatively, a region where the relay satellite 200 may exist may be set as a Region of Interest (ROI) based on the orbital information of the relay satellite 200 and the position and attitude of the user satellite 100, and the beacon light detection unit 130 may detect beacon light candidates only within the ROI. For example, when the beacon light detection unit 130 detects the appearance of a new bright spot, if the position of the bright spot is within the ROI, the beacon light detection unit 130 may determine the bright spot as a beacon light candidate from the relay satellite 200. Therefore, when the image processing unit 120 detects the appearance of a new bright spot, the beacon light detection unit 130 calculates the ROI region where the relay satellite 200 may exist, and if the position of the bright spot is included in the ROI, determines the bright spot as a beacon light candidate. Alternatively, the image processing unit 120 may calculate the ROI region in advance and extract bright spots only within the ROI region.

[0063] [Relay satellite] Next, a relay satellite 200 according to an embodiment of the present disclosure will be described with reference to Fig. 14. Fig. 14 is a block diagram showing the functional configuration of the relay satellite 200 according to an embodiment of the present disclosure.

[0064] 14, the relay satellite 200 has a communication unit 210, an optical signal transmission / reception unit 220, an optical communication unit 230, and a communication control unit 240. Each functional unit can be realized by any one or a combination of the above-mentioned systems.

[0065] The communication unit 210 communicates with the earth station 50. For example, while the relay satellite 200 is within the coverage area of ​​the earth station 50, the communication unit 210 exchanges signals with the earth station 50. For example, the communication unit 210 receives a communication schedule for relaying with the user satellite 100 from the earth station 50, and also receives a communication request for on-demand communication with the user satellite 100.

[0066] The optical signal transceiver 220 transmits beacon light to the user satellite 100 in response to a communication request with the user satellite 100 received from the earth station 50, and receives a response signal from the user satellite 100 that detects the beacon light. Specifically, when the communication unit 210 receives a communication request for rapid communication with the user satellite 100 from the earth station 50, the optical signal transceiver 220 transmits beacon light to the user satellite 100. For example, the beacon light may be an optical signal with lower directionality than the communication light transmitted after a communication connection is established. This allows the beacon light to be transmitted over a relatively wider area than the communication light, making it easier for the user satellite 100 to receive the beacon light. Furthermore, if the user satellite 100 has a camera with a spherical lens, it can more easily receive the beacon light transmitted from the relay satellite 200.

[0067] Alternatively, the optical signal transceiver 220 may encode the identifier of the user satellite 100 and the identifier of the relay satellite 200 specified in the communication request into a beacon beam and transmit the beacon beam indicating these identifiers to the user satellite 100. For example, the optical signal transceiver 220 may transmit a beacon beam having a predetermined blinking pattern indicating the encoded information. Upon receiving the beacon beam, the user satellite 100 determines whether the received beacon beam is addressed to the user satellite 100, and if the beacon beam is addressed to the user satellite 100, transmits a response signal to the relay satellite 200. The identifier of the user satellite 100 and the identifier of the relay satellite 200 are encoded in this response signal, and the relay satellite 200 can determine whether the received response signal is addressed to the user satellite.

[0068] Furthermore, when transmitting a beacon beam to a designated user satellite 100, the optical signal transceiver 220 may further encode information indicating the slot number N into the beacon beam. For example, the communication schedule of the relay satellite 200 is performed in predetermined slot units, and a fixed communication time is assigned to each slot. This fixed communication time may be, for example, 10 minutes, or a fixed time shorter or longer than 10 minutes.

[0069] Based on the reception of the response signal, the optical communication unit 230 establishes inter-satellite optical communications with the user satellite 100. Specifically, upon receiving a response signal in response to the beacon light from the user satellite 100, the optical communication unit 230 establishes a communications connection between the relay satellite 200 and the user satellite 100 in accordance with a predetermined communications establishment procedure. Once the communications connection is established, the optical communication unit 230 performs inter-satellite optical communications with the user satellite 100 using the communications light.

[0070] Upon receiving a communication request from the earth station 50, the optical communication unit 230 reserves N slots for on-demand communication with the user satellite 100 specified in the received communication request, as described above. Here, the number of slots N to be reserved may be included in the communication request from the earth station 50. Alternatively, the number of slots N for on-demand communication may be set as a default in the satellite system 10 (e.g., N=1). In this case, the communication request does not need to include the number of slots N to be reserved.

[0071] When performing prompt communication, the optical communication unit 230 needs to adjust the communication schedule instructed in advance. The optical communication unit 230 may adjust the communication schedule by the method described above. 1) If there is a free slot in the pre-specified communication schedule, the optical communication unit 230 may execute a prompt communication in the available free slot at the earliest timing. 2) A free slot for prompt communication may be reserved in advance in the designated communication schedule, and the optical communication unit 230 may execute prompt communication in the earliest available slot among the reserved free slots. 3) The optical communication unit 230 cancels communication in the scheduled slot and executes prompt communication in that slot.

[0072] The communication control unit 240 relays data received from the user satellite 100 via inter-satellite optical communications to the earth station 50 using the communication unit 210. Specifically, when the optical communication unit 230 receives data from the user satellite 100, the communication control unit 240 instructs the communication unit 210 to transmit the received data to the earth station 50. Here, the timing of transmission to the earth station 50 may be immediately after receiving the data from the user satellite 100. Alternatively, the data received from the user satellite 100 may be temporarily buffered, and the communication control unit 240 may instruct the communication unit 210 to transmit the buffered data to the earth station 50 at an appropriate subsequent time.

[0073] [Beacon light detection processing] Next, an on-demand communication process according to an embodiment of the present disclosure will be described with reference to Figure 15. The on-demand communication process is performed by the user satellite 100 described above.

[0074] FIG. 15 is a flowchart illustrating an on-demand communication process according to an embodiment of the present disclosure.

[0075] 15, in step S101, the user satellite 100 captures the beacon light transmitted from the relay satellite 200 in response to a communication request received from the earth station 50. Specifically, the user satellite 100 captures images of a non-terrestrial region, such as outer space, around the user satellite 100 at a predetermined frame rate to obtain a series of image frames. Here, the user satellite 100 may capture images of the non-terrestrial region using a celestial sphere lens so that the beacon light from the relay satellite 200 can be extracted from a wide imaging range.

[0076] In step S102, the user satellite 100 extracts bright spots in the captured image frames. Specifically, the user satellite 100 performs preprocessing such as noise reduction and filtering on each image frame to extract bright spots that are beacon light candidates in the image frames. At this time, the user satellite 100 may calculate various characteristic quantities of the extracted bright spots, such as their area, centroid coordinates, size, and circularity.

[0077] More specifically, the user satellite 100 may perform a bright spot extraction process as shown in FIG. 16. As shown in FIG. 16, the user satellite 100 preprocesses the image frames in step S201. Specifically, the user satellite 100 may perform preprocessing such as noise reduction and contrast adjustment on each acquired image frame to remove background noise, etc. For example, the user satellite 100 may perform a time averaging process and / or a spatial averaging process on the image frames. The user satellite 100 may also perform contrast (offset / gain) adjustment to adjust the brightness of the image frames to an appropriate level so that the background and the detected bright spots can be well separated.

[0078] In step S202, the user satellite 100 extracts bright spots as beacon light candidates and stores the features of the extracted bright spots. For example, the user satellite 100 may perform binarization on each image frame, converting the image frame into a binary image consisting of background pixels and pixels with higher brightness than the background. The binarization threshold is set to a brightness level that allows bright spots such as stars and beacon lights to be properly separated from the background. Furthermore, the user satellite 100 extracts bright spots from the binary image and labels the extracted bright spots as beacon light candidates. The labeled bright spots may be associated with various features, such as their area (number of pixels), vertical and horizontal sizes, center of gravity, and circularity, and stored in a table format such as that shown in FIG. 7.

[0079] In step S203, the user satellite 100 performs feature-based filtering on each extracted bright spot. For example, the extracted bright spots may include the sun, the moon, satellite structures, ghosts, and the like. Because these bright spots have significantly large areas, the user satellite 100 may remove bright spots with areas equal to or greater than a threshold. It may also remove bright spots with areas other than those considered to be beacon lights. If a beacon light can be detected as having a predetermined number of pixels or more, bright spots with less than that number of pixels may be determined to be noise and removed. Furthermore, because beacon light bright spots are considered to have a circular or nearly circular shape, bright spots with a circularity less than a predetermined threshold may be removed. Through this filtering, the user satellite 100 can extract beacon light candidates from the bright spots of high-brightness pixels extracted from the binary image. The extracted beacon light candidates may be stored in a table format, such as that shown in FIG. 8.

[0080] In step S204, the user satellite 100 removes stars from the beacon light candidates. For example, the user satellite 100 may remove stars from the beacon light candidates by extracting bright spots that blink in the filtered image frame sequence as beacon light candidates and distinguishing them from bright spots that exist in each image frame and are considered to be stars. After extracting beacon light candidates in this way, the user satellite 100 proceeds to step S103 and extracts beacon lights from the beacon light candidates based on the blinking state of the extracted bright spots.

[0081] In step S103, the user satellite 100 detects the beacon light transmitted from the relay satellite 200 in response to receiving a communication request from the earth station 50, based on the blinking state of the extracted bright point. In this embodiment, for example, when the earth station 50 desires to communicate with the user satellite 100 during a time period other than a pre-scheduled time period, the earth station 50 transmits a communication request for the user satellite 100 to the relay satellite 200. Upon receiving the communication request from the earth station 50, the relay satellite 200 transmits a beacon light onto the orbit of the specified user satellite 100 to establish a communication connection with that user satellite 100. For example, the beacon light may be a blinking pulse signal indicating the identifiers of the relay satellite 200 and the user satellite 100. The user satellite 100 extracts blinking bright spots from the preprocessed image frame sequence as beacon light candidates, and if the identifier contained in the blinking pattern of the extracted bright spot matches the identifier of the user satellite 100, it determines that the blinking bright spot is a beacon light for the user satellite 100.

[0082] In step S104, based on the detected beacon light, the user satellite 100 establishes inter-satellite optical communications with the relay satellite 200 that transmitted the beacon light. Specifically, the user satellite 100 establishes a communications connection with the relay satellite 200 in accordance with a communications establishment procedure defined in advance in the satellite system 10, and performs inter-satellite optical communications by transmitting and receiving communications light via the established communications connection.

[0083] According to the above-described embodiment, the user satellite 100 and the relay satellite 200 can perform inter-satellite optical communications not only during pre-scheduled communication time slots but also during any time slot. In other words, in response to a communication request received from the earth station 50 at any time, data acquired by the desired user satellite 100 can be transferred to the earth station 50 via the relay satellite 200.

[0084] In addition, the following supplementary notes are provided in relation to the above description. (Appendix 1) an optical signal acquisition unit that captures an image of a beacon light transmitted from a relay satellite in response to a communication request received from an earth station; an image processing unit that extracts bright spots in the captured image frame; a beacon light detection unit that detects the beacon light based on the blinking state of the extracted bright point; an optical communication unit that establishes inter-satellite optical communication with the relay satellite based on the detected beacon light; A satellite having (Appendix 2) 2. The satellite of claim 1, wherein the optical signal acquisition unit includes a camera equipped with a spherical lens. (Appendix 3) 3. The satellite described in claim 1 or 2, wherein the beacon light has a predetermined blinking pattern including identification information of the relay satellite and identification information of the satellite. (Appendix 4) A satellite described in any one of appendix 1 to 3, wherein the beacon light detection unit determines that the extracted bright spot is beacon light from the relay satellite when it determines that the extracted bright spot has a predetermined blinking pattern. (Appendix 5) An earth station, Satellites and a relay satellite that relays between the ground station and the satellite; and The satellite an optical signal acquisition unit that captures an image of the beacon light transmitted from the relay satellite in response to a communication request received from the earth station; an image processing unit that extracts bright spots in the captured image frame; a beacon light detection unit that detects the beacon light based on the blinking state of the extracted bright point; an optical communication unit that establishes inter-satellite optical communication with the relay satellite based on the detected beacon light; A satellite system having: (Appendix 6) capturing an image of a beacon light transmitted from a relay satellite in response to a communication request received from an earth station; Extracting bright points in the captured image frame; detecting the beacon light based on the blinking state of the extracted bright point; establishing inter-satellite optical communication with the relay satellite based on the detected beacon light; A satellite-implemented beacon light detection method, including: (Appendix 7) a communication unit for communicating with an earth station; an optical signal transmitting / receiving unit that transmits a beacon light to the satellite in response to a request for communication with the satellite received from the earth station, and receives a response signal from the satellite upon detecting the beacon light; an optical communication unit that establishes inter-satellite optical communication with the satellite based on reception of the response signal; a communication control unit that relays data received from the satellite through the inter-satellite optical communication to the earth station using the communication unit; A relay satellite having (Appendix 8) 8. The relay satellite of claim 7, wherein the beacon light has a predetermined blinking pattern including identification information of the relay satellite and identification information of the satellite. (Appendix 9) 9. The relay satellite according to claim 7, wherein the optical signal transmitting and receiving unit transmits a beacon light having a predetermined blinking pattern. (Appendix 10) 8. The relay satellite according to claim 7, wherein the optical communication unit performs inter-satellite optical communications based on a predetermined communication schedule, and, when a request for communication with a satellite is received from the earth station, establishes inter-satellite optical communications with the satellite by utilizing a free time in the communication schedule. (Appendix 11) 8. The relay satellite according to claim 7, wherein the optical communication unit performs inter-satellite optical communications based on a predetermined communication schedule, and, when a request for communication with a satellite is received from the earth station, establishes inter-satellite optical communications with the satellite, giving priority to the communication schedule. (Appendix 12) transmitting a beacon light to the satellite in response to a request for communication with the satellite received from an earth station; receiving a response signal from the satellite that detected the beacon light; establishing inter-satellite optical communication with the satellite based on receipt of the response signal; relaying data received from the satellite via the inter-satellite optical communication to the earth station; A data relay method performed by a relay satellite, including: (Appendix 13) performing inter-satellite optical communications based on a predetermined communications schedule; when a request for communication with the satellite is received from an earth station, allocating a ready communication time to respond to the communication request; transmitting a beacon light to the satellite in response to the communication request; receiving a response signal from the satellite that detected the beacon light; establishing inter-satellite optical communication with the satellite based on receiving the response signal; receiving data from the satellite via the inter-satellite optical communication within the ready communication time; relaying said data to said earth station; A data relay method performed by a relay satellite, including:

[0085] Although the examples of the present disclosure have been described in detail above, the present disclosure is not limited to the specific embodiments described above, and various modifications and variations are possible within the scope of the gist of the present disclosure as set forth in the claims. [Explanation of symbols]

[0086] 10 Satellite Systems 50 earth station 100 user satellites 110 Optical signal acquisition unit 120 Image processing unit 130 Beacon light detector 140 Optical Communications Department 200 relay satellites 210 Communications Department 220 Optical signal transmitter / receiver 230 Optical Communications Department 240 Communication Control Unit

Claims

1. Controlling the execution of inter-satellite optical communications with other satellites based on a predetermined communication schedule; receive requests from earth stations to communicate with other satellites; When the communication request is received, control is performed to establish inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and to perform prompt communication. Inter-satellite optical communication control method.

2. Controlling the execution of inter-satellite optical communications with other satellites based on a predetermined communication schedule; receive requests from earth stations to communicate with other satellites; When the communication request is received, control is performed to establish inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and to perform prompt communication. Inter-satellite optical communication control device.

3. Controlling the execution of inter-satellite optical communications with other satellites based on a predetermined communication schedule; receive requests from earth stations to communicate with other satellites; When the communication request is received, control is performed to establish inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and to perform prompt communication. Relay satellite.

4. Controlling the execution of inter-satellite optical communications with other satellites based on a predetermined communication schedule; receive requests from earth stations to communicate with other satellites; When the communication request is received, control is performed to establish inter-satellite optical communication with the other satellite, giving priority to the communication schedule, and to perform prompt communication. Optical communication control circuit.

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