Signal processing circuit and signal processing method

Abstract

To provide a technique for achieving inter-satellite optical communication for satellites having limited calculation capability.SOLUTION: One aspect of the present disclosure relates to an earth station, including: a data acquisition unit that acquires from the earth station a predicted orbit data sequence indicative of a predictive ephemeris of a satellite; and a communication unit that transmits the acquired predicted orbit data sequence to a relay satellite.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to an earth station, a satellite relay, a satellite system, and a communication method. [Background technology]

[0002] An earth station and a user satellite (e.g., an observation satellite, a communication satellite, etc.) can communicate with each other via a relay satellite. In such communication between an earth station and a user satellite via a relay satellite, the user satellite and the relay satellite exchange data with each other through inter-satellite communication.

[0003] For example, Japanese Patent Application Laid-Open No. 2013-70226 discloses a satellite system that enables satellite communications over the entire orbit by performing short-wave communications between a ground station and a communication relay satellite in a low orbit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-70226 A Summary of the Invention [Problem to be solved by the invention]

[0005] In inter-satellite communications, the use of inter-satellite optical communications, in which a user satellite and a relay satellite communicate with each other by optical communications, is being considered. To start inter-satellite optical communications, a source satellite needs to predict the position information of a destination satellite with high accuracy. For example, the source satellite may calculate the orbit of the destination satellite based on the six elements of Kepler's orbit, which are the semi-major axis, eccentricity, orbital inclination, ascending node longitude, argument of perigee, and mean anomaly of the destination satellite. Typically, the source satellite calculates orbit data of the destination satellite based on the six elements of the orbit of the destination satellite that are held in advance or obtained from an earth station, and determines the relative position with respect to the destination satellite and the attitude of the source satellite based on the calculated orbit data, thereby controlling the pointing direction of the optical signal.

[0006] However, satellites typically have limited computing power, so for a relay satellite that is required to communicate with a large number of destination satellites, calculating the orbital data of the destination satellites imposes an excessive computational burden.

[0007] In view of the above problems, one objective of the present disclosure is to provide a technique for realizing inter-satellite optical communications for satellites with limited computing capabilities. [Means for solving the problem]

[0008] One aspect of the present disclosure relates to an earth station having a data acquisition unit that acquires a predicted orbit data sequence indicating a predicted orbital ephemeris of a satellite from an earth station, and a communication unit that transmits the acquired predicted orbit data sequence to a relay satellite. Effect of the Invention

[0009] The present disclosure can provide a technique for enabling inter-satellite optical communications, which requires highly accurate orbit prediction, to be realized by satellites with limited computing capabilities. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram illustrating a satellite system according to one embodiment of the present disclosure. [Diagram 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. [Diagram 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. 2 is a schematic diagram illustrating a communication establishment procedure according to an embodiment of the present disclosure. [Diagram 5] FIG. 2 is a block diagram showing a hardware configuration of an earth station according to an embodiment of the present disclosure. [Figure 6] FIG. 2 is a block diagram showing a hardware configuration of a user satellite and a relay satellite according to an embodiment of the present disclosure. [Figure 7]FIG. 2 is a block diagram showing a functional configuration of an earth station according to an embodiment of the present disclosure. [Figure 8] FIG. 2 illustrates a predicted orbit position sequence according to one embodiment of the present disclosure. [Figure 9] FIG. 2 illustrates a predicted orbit position sequence according to one embodiment of the present disclosure. [Figure 10] FIG. 2 illustrates a predicted orbit position sequence according to one embodiment of the present disclosure. [Figure 11] FIG. 2 illustrates a predicted orbit position sequence according to one embodiment of the present disclosure. [Figure 12] FIG. 2 is a block diagram showing a functional configuration of a relay satellite according to an embodiment of the present disclosure. [Figure 13] FIG. 11 is a sequence diagram showing a communication process according to an embodiment of the present disclosure. [Figure 14A] FIG. 2 is a block diagram illustrating a communication process between an earth station and a satellite relay according to one embodiment of the present disclosure. [Figure 14B] FIG. 2 is a block diagram illustrating a communication process between an earth station and a satellite relay according to one embodiment of the present disclosure. [Figure 14C] FIG. 2 is a block diagram illustrating a communication process between an earth station and a satellite relay according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0012] In the embodiments described below, a satellite system is disclosed that includes an earth station, a relay satellite, and a user satellite. The following embodiments are described with respect to inter-satellite optical communication between a relay satellite and a user satellite in the satellite system, but the present disclosure is not necessarily limited thereto and is applicable to inter-satellite optical communication between any two satellites.

[0013] [Summary of the Disclosure] In the following embodiment, in order to reduce the calculation load of the relay satellite, the earth station calculates a data sequence (e.g., predicted ephemeris data) indicating the predicted orbital ephemeris of the satellite and transmits the calculated data sequence to the relay satellite. Here, the predicted orbital ephemeris data sequence can be calculated not only based on Kepler's six orbital elements, but also taking into consideration perturbation factors such as the non-spherical component of the earth's gravity, the gravitational forces of the sun and the moon, atmospheric resistance, solar radiation pressure, and earth's gravitational distortion due to tides. Therefore, it is possible to realize a more accurate orbit prediction than a satellite orbit calculated in the relay satellite based on Kepler's six orbital elements. Furthermore, the earth station may provide the relay satellite with a predicted orbital ephemeris data sequence required to realize satellite communication with a user satellite via the relay satellite with an appropriate granularity or resolution.

[0014] Conventionally, a relay satellite holds or acquires six orbital elements (for example, in the case of Kepler's six orbital elements, the semi-major axis, eccentricity, orbital inclination, ascending node longitude, argument of perigee, and mean anomaly) of each user satellite to be communicated with, and calculates orbital data of each user satellite from the six orbital elements to realize inter-satellite optical communication with each user satellite at the relay satellite. Therefore, the relay satellite needs to calculate orbital data according to the number of user satellites, and when the relay satellite covers a large number of user satellites, the relay satellite needs to have high computing power. Typically, in order to obtain a calculation result with sufficient accuracy, it may take several tens of minutes to calculate one day's worth of orbital data of one user satellite even when a general personal computer on the ground is used. Meanwhile, the calculation of the orbital data is typically performed using an on-board computer having radiation resistance provided on the relay satellite. For this reason, it is not easy to improve the computing power required to obtain a calculation result with sufficient accuracy, and the manufacturing cost and operational risk of the relay satellite may increase.

[0015] In addition, in orbit calculations based on Kepler's six orbital elements, the further into the future the satellite's orbit, the more calculation errors accumulate, and the lower the accuracy of orbit prediction becomes. On the other hand, if the amount of data and calculations required to reduce the calculation errors is increased, it becomes difficult for the relay satellite to process the data. In addition, in orbit calculations based on Kepler's six orbital elements, it is difficult to calculate orbits with high accuracy by taking into account perturbations (deviations from Kepler's laws in the motion of planets, asteroids, etc.). The main perturbation factors for satellites orbiting the Earth are known to be the non-spherical component of the Earth's gravity, the gravitational forces of the Sun and Moon, atmospheric resistance, solar radiation pressure, and Earth's gravitational distortion due to tides.

[0016] In order to perform highly directional optical communication between satellites, highly accurate orbit prediction is required for the transmitting and receiving satellites. That is, in order for two satellites (a relay satellite and a user satellite) equipped with optical communication equipment to perform optical communication by laser light, they need to calculate the position and speed of the satellite itself and the other satellite, and point their optical telescopes toward the other satellite. The current position of the satellite itself can be obtained from the Global Positioning System (GPS), while the positions of the satellite itself and the communication partner satellite at a certain time in the future can be calculated based on the predicted value of the satellite orbit. In addition to the relay satellite predicting (calculating) the orbit (future position) of the communication partner user satellite, the communication partner user satellite also needs to point its optical communication equipment toward the position of the relay satellite, so it is required to predict (calculate) the orbit (future position) of the relay satellite with higher accuracy than before.

[0017] Calculating the position and velocity of a satellite moving at a certain time at a certain time at a certain time is called "orbit propagation". In the case of an artificial satellite moving under the influence of the gravity of a celestial body such as the Earth, the orbit can be calculated analytically (using simple formulas), but more complex orbit propagation requires more complex numerical calculations. The main orbit propagation models (orbit propagators) are analytical propagators, semi-analytical propagators, and numerical integration propagators. Orbit propagation calculation models are divided into analytical methods and numerical integration methods. Analytical methods require less calculation because they perform approximate calculations, but the error from the satellite's actual orbit becomes larger. On the other hand, numerical integration methods increase accuracy, but the number of parameters and the amount of calculations increase.

[0018] Two-Line Elements (TLE) are used as a data format for indicating values ​​of Keplerian orbital elements that represent the orbit of a satellite (especially an artificial satellite at a low altitude) orbiting the Earth. When calculating a predicted orbital almanac of a user satellite, an earth station according to the following embodiment creates a predicted orbital ephemeris data series with improved accuracy by various corrections for perturbations and the like in addition to using the six Keplerian orbital elements. The predicted orbital ephemeris data series of a satellite can be calculated in two ways: (1) from the TLE, or (2) from GPS positioning information of the satellite transmitted in downlink from the satellite. The predicted orbital ephemeris data can be composed of time series data of each orbital element, namely, epoch (reference time), position (X, Y, Z), velocity (X_DOT, Y_DOT, Z_DOT), and (optional) acceleration (X_DDOT, Y_DDOT, Z_DDOT).

[0019] In an embodiment of the present disclosure, the predicted ephemeris data series of the user satellite is calculated on the ground, not on the relay satellite, by correcting the influence of perturbations in addition to the six orbital elements of Kepler. The earth station transmits the predicted ephemeris data series calculated with higher accuracy to the relay satellite. The Orbit Ephemeris Message (OEM) of the CCSDS (Consultative Committee for Space Data System) 502.0-B-2 ORBIT DATA MESSAGE (ODM) may be used for the predicted ephemeris data series transmitted in uplink. The relay satellite performs inter-satellite optical communication with the user satellite based on the predicted ephemeris data series acquired from the earth station by GPS. Furthermore, position data series with different time resolutions may be calculated on the ground, and the earth station may transmit the predicted ephemeris data series with a time resolution appropriately selected according to a predetermined selection criterion to the relay satellite.

[0020] For example, the predetermined selection criteria may relate to the distance between the user satellite and the relay satellite, the communication state between the earth station and the relay satellite, the capability of the relay satellite, the computational margin of the relay satellite, etc. For example, when the communication state between the earth station and the relay satellite is good, it is expected that a relatively large amount of data can be transmitted from the earth station to the relay satellite. Therefore, the earth station may transmit a position data sequence with a relatively high time resolution to the relay satellite. On the other hand, when the communication state between the earth station and the relay satellite is not good, it is expected that only a relatively small amount of data can be transmitted from the earth station to the relay satellite. Therefore, the earth station may transmit a position data sequence with a relatively low time resolution to the relay satellite.

[0021] The relay satellite can utilize the predicted orbital ephemeris data series of the user satellite selected in this manner to satisfactorily realize inter-satellite optical communications with the user satellite. Note that, in the following embodiment, attention is focused on the predicted orbital ephemeris data series of the user satellite, but the data transmitted from the earth station to the relay satellite according to the present disclosure is not limited to this, and may be any other type of data for realizing inter-satellite optical communications.

[0022] [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 the multiple user satellites 100.

[0023] The user satellite 100 is an artificial satellite having 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.

[0024] Without limitation, 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 data transmission and reception between the earth station 50 on the Earth and the user satellites 100. Typically, the relay satellite 200 covers multiple user satellites 100 and communicates with a desired user satellite 100.

[0025] The earth station 50 is a communication station that communicates with the relay satellite 200. The earth station 50 can communicate with the user satellite 100 via the relay satellite 200. In addition, if the earth station 50 can communicate with the user satellite 100 without the relay satellite 200, it may directly communicate with the user satellite 100. 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) 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 acquired 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 network 20.

[0026] 2, the communication range of the earth station 50 with respect to a satellite is defined 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 exists in a communication coverage area, but cannot communicate with a user satellite 100_1 that exists in a non-communication area.

[0027] In this case, 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.

[0028] According to the inter-satellite optical communication in the satellite system 10, the relay satellite 200 first transmits a beacon light onto the orbit around which the user satellite 100 revolves, based on the position data sequence of the user satellite 100. 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 communication partner user satellite 100 are encoded. When the user satellite 100 determines 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 transmitted the beacon light, and starts communication with the relay satellite 200.

[0029] For example, as shown in Fig. 4, in order to start inter-satellite optical communication with the user satellite 100_3, the relay satellite 200 transmits a beacon light for detecting the user satellite 100_3 onto the orbit of the user satellite 100_3. For example, the beacon light is transmitted toward the position of the user satellite 100_3 predicted from the position data sequence of the user satellite 100_3 possessed by the relay satellite 200, and is composed of light with relatively low directivity so as to cover a wide range including the predicted position. For example, the beacon light may be composed of a pulse signal in which the identifier of the relay satellite 200 and the identifier of the user satellite 100_3 requested as a communication partner are encoded.

[0030] When the user satellite 100_3 detects the beacon light from the relay satellite 200, it extracts the identifier of the relay satellite 200 encoded in the beacon light and the identifier of the requested communication partner. The user satellite 100_3 determines whether the extracted identifier of the communication partner matches its own identifier. In this example, since the identifier of the user satellite 100_3 is included in the beacon light, the user satellite 100_3 determines that it is requested as a communication partner according to a predetermined communication establishment procedure, and proceeds to a communication establishment procedure with the relay satellite 200. When 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 by a communication light with relatively high directivity. This enables the earth station 50 to communicate with the user satellite 100_3 via the relay satellite 200.

[0031] Here, the earth station 50 may have, for example, a hardware configuration as shown in Fig. 5. As shown in Fig. 5, the earth station 50 has a storage device 501, a processing device 502, and a communication device 503.

[0032] The storage device 501 stores various data and programs for inter-satellite optical communication between the user satellite 100 and the earth station 50 via the relay satellite 200. For example, the data and programs may be held in advance, may be acquired via the network 20, or may be input by an operator of the earth station 50, etc. The storage device 501 may be realized by, for example, a non-transitory storage medium such as a memory or storage.

[0033] The processing device 502 executes the programs loaded from the storage device 501, controls each component of the earth station 50, and executes various processes for inter-satellite optical communications. The processing device 502 may be realized by, for example, a processor, a signal processing circuit, or the like.

[0034] The communication device 503 is controlled by the processing device 502 to transmit and receive data. The communication device 503 may be realized by, for example, a communication interface, a communication circuit, an antenna, etc. For example, the communication device 503 transmits and receives data via the network 20, or transmits and receives data to and from the user satellite 100 and / or the relay satellite 200 via an antenna.

[0035] Next, the user satellite 100 may have, for example, a hardware configuration as shown in Fig. 6. 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 / thermal structure system 104, an attitude control system 105, and a power supply system 106.

[0036] The command and data handling system 101 processes received commands, as well as status data, mission data, etc. of the satellite. For example, the command and data handling system 101 has a processing circuit for data processing, and realizes various functional units described below by using the processing circuit.

[0037] 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 various sensors such as an image sensor and a data processing device. Also, if the satellite is a communication satellite, the mission system 102 may be composed of an antenna for data relay, communication equipment, etc.

[0038] The communication system 103 may be composed of a communication device, an antenna, and the like, which receives commands from the earth station 50 and transmits the satellite's status, observation data (telemetry), and the like to the earth station 50. The communication system 103 also has an optical communication system 103A for communicating with the user satellite 100 by inter-satellite optical communication. The optical communication system 103A has a camera that captures images of the surroundings of the satellite, 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 & data handling system 101, etc. The camera may also have a spherical lens, such as a circular fisheye lens, so as to capture a wider range.

[0039] The mechanical and thermal structure system 104 is composed of the satellite body, movable deployable parts such as solar panels, and mechanisms for stabilizing the temperature inside the satellite and dissipating heat.

[0040] 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, etc., and controls the position and / or attitude of the satellite in orbit.

[0041] 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 a solar cell, and supplies the power required by each system in the satellite.

[0042] The relay satellite 200 may also have the hardware configuration shown in FIG. 6. However, the above-mentioned hardware configuration is merely an example, and the earth station 50, the user satellite 100, and the relay satellite 200 according to the present disclosure may be realized by any other appropriate hardware configuration. In addition, the above-mentioned grouping into each system is merely an example, and the hardware configurations of the earth station 50, the user satellite 100, and the 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 mission of the satellite. For example, since the relay satellite 200 has a main mission of data relay by inter-satellite optical communication, the optical communication device 103A (e.g., a camera, an optical telescope, an optical transmission device, etc.) may be classified into the mission system 102. On the other hand, since the user satellite 100 has a mission such as earth observation, the optical communication device (e.g., a camera, an optical telescope, an optical transmission device, etc.) with the relay satellite 200 may be classified into the communication system 103.

[0043] [Earth station] Next, the earth station 50 according to an embodiment of the present disclosure will be described with reference to Fig. 7. Fig. 7 is a block diagram showing the functional configuration of the earth station 50 according to an embodiment of the present disclosure.

[0044] 7, the earth station 50 has a data acquisition unit 51 and a communication unit 52. Each functional unit can be realized by any one or a combination of the hardware devices described above.

[0045] The data acquisition unit 51 acquires a data series indicating a predicted orbital ephemeris of a satellite. For example, the data series may be predicted orbital ephemeris data of the user satellite 100 and / or the relay satellite 200. The data acquisition unit 51 may calculate the predicted orbital ephemeris data according to either (1) a method of calculating from the TLE or (2) a method of obtaining from GPS positioning information downlinked from the satellite. Specifically, the predicted orbital ephemeris data series may be configured as time series data of the position and velocity of the satellite at each time point. Alternatively, the predicted orbital ephemeris data series may be configured as time series data of the position, velocity and acceleration of the satellite at each time point.

[0046] The data series may be calculated taking into account perturbation factors. Specific examples of perturbation factors include the non-spherical component of the Earth's gravity, the gravitational forces of the Sun and the Moon, atmospheric resistance, solar radiation pressure, and Earth's gravitational distortion due to tides, which are major perturbation factors of a satellite orbiting the Earth. The data acquisition unit 51 may calculate the predicted orbital ephemeris data series taking into account the perturbation factors by using an analytical method or a numerical integration method.

[0047] In one embodiment, the data acquisition unit 51 acquires a first data series having a first time resolution and a second data series having a second time resolution lower than the first time resolution. For example, these data series may be predicted ephemeris data series of the user satellite 100 and / or the relay satellite 200. Specifically, the first data series and the second data series may be composed of vector data of the same dimension or size, such as a predicted ephemeris data series. In this case, the first data series may be a data series composed of a pieces of data, and the second data series may be a data series composed of b pieces of data (a>b).

[0048] In one embodiment, the first data series may be a first predicted ephemeris data series of the user satellite 100 with a first time resolution (e.g., a predicted ephemeris data series with a high time resolution), and the second data series may be a second predicted ephemeris data series of the user satellite 100 with a second time resolution lower than the first time resolution (e.g., a predicted ephemeris data series with a low time resolution). For example, the first predicted ephemeris data series may be time series data of 60 pieces of position data indicating the position of the user satellite 100 in units of 1 minute in a specific time period having a time length of 1 hour, and the second predicted ephemeris data series may be time series data of 6 pieces of position data indicating the position of the user satellite 100 in units of 10 minutes in the time period. Here, the position of the user satellite 100 may be represented by any appropriate method known in the art, such as a position on a predetermined coordinate axis or a relative position with respect to the relay satellite 200. However, the data series according to the present disclosure are not necessarily limited to predicted ephemeris data series, but may be any other suitable type of time series data that may be indicative of the orbit of user satellite 100, such as an orientation data series that indicates the orientation of user satellite 100 relative to relay satellite 200.

[0049] For example, the relay satellite 200 can predict the position of the user satellite 100 at any point in the time period by interpolating the predicted ephemeris data series, which is such discrete time series data. In this case, the orbit of the user satellite 100 acquired by interpolating the first predicted ephemeris data series having a relatively high time resolution (e.g., predicted ephemeris data series having a high time resolution) is considered to have higher accuracy than the orbit of the user satellite 100 acquired by interpolating the second predicted ephemeris data series having a relatively low time resolution (e.g., predicted ephemeris data series having a low time resolution). On the other hand, the calculation load involved in the interpolation of the first predicted ephemeris data series is considered to be smaller than the calculation load involved in the interpolation of the second predicted ephemeris data series. In addition, when the predicted ephemeris data for a predetermined period is transmitted from the earth station 50 to the relay satellite 200, the amount of data required to transmit the first predicted ephemeris data series from the earth station 50 to the relay satellite 200 is considered to be larger than the amount of data required to transmit the second predicted ephemeris data series, resulting in a longer communication time.

[0050] The communication unit 52 transmits the acquired data sequence to the relay satellite 200. Specifically, the communication unit 52 transmits the predicted ephemeris data sequence to the user satellite 100 and / or the relay satellite 200. The transmission data rate from the earth station 50 to the user satellite 100 and / or the relay satellite 200 has conventionally been about several kbps to several hundreds of kbps, but in the future, it is expected that a transmission data rate faster than several Mbps will be realized. The predicted ephemeris data sequence transmitted from the earth station 50 to the user satellite and / or the relay satellite 200 may be of the following four types: Type I: The communication unit 52 may transmit the predicted orbital ephemeris data sequence of the relay satellite 200 to the relay satellite 200. The relay satellite 200 can predict its own orbit with higher accuracy by using the predicted orbital ephemeris data sequence. The relay satellite 200 may calculate the position and velocity of the relay satellite 200 based on GPS positioning information. Type II: The communication unit 52 may transmit the predicted orbital ephemeris data sequence of the user satellite 100 to the relay satellite 200. The relay satellite 200 can predict the orbit of the user satellite 100 with higher accuracy by using the predicted orbital ephemeris data sequence. Type III: The communication unit 52 may transmit the predicted orbital ephemeris data sequence of the relay satellite 200 to the user satellite 100. The user satellite 100 can predict the orbit of the relay satellite 200 with higher accuracy by using the predicted orbital ephemeris data sequence. Type IV: The communication unit 52 may transmit a predicted orbital ephemeris data sequence of the user satellite 100 to the user satellite 100. The user satellite 100 may use the predicted orbital ephemeris data sequence to predict its own orbit with higher accuracy. The user satellite 100 may calculate the position and velocity of the user satellite 100 based on GPS positioning information.

[0051] The communication unit 52 may transmit a data sequence selected from the first data sequence and the second data sequence according to a predetermined selection criterion to the relay satellite 200 as orbit information of the user satellite 100. For example, the communication unit 52 may select either the first data sequence or the second data sequence by itself according to the predetermined selection criterion, and transmit the selected data sequence to the relay satellite 200. Alternatively, the communication unit 52 may receive a selection instruction based on the predetermined selection criterion from the network 20 or the like, and transmit the instructed data sequence from the first data sequence or the second data sequence to the relay satellite 200. That is, the communication unit 52 switches between transmitting the first data sequence and transmitting the second data sequence according to the predetermined selection criterion.

[0052] For example, the communication unit 52 may switch between transmitting the first data sequence and transmitting the second data sequence depending on the magnitude of the allowable range of the prediction error of the position of the user satellite 100 seen from the relay satellite 200. Specifically, when the allowable range of the prediction error is equal to or greater than a predetermined threshold, the communication unit 52 may transmit the second data sequence (e.g., a predicted orbital ephemeris data sequence with a low time resolution) to the relay satellite 200. On the other hand, when the allowable range of the prediction error is less than the predetermined threshold, the communication unit 52 may transmit the first data sequence (e.g., a predicted orbital ephemeris data sequence with a high time resolution) to the relay satellite 200.

[0053] In one embodiment, the predetermined selection criterion may be related to the distance between the user satellite 100 and the relay satellite 200. The communication unit 52 may transmit the first data sequence to the relay satellite 200 as orbit information when the distance is less than a predetermined distance threshold, and may transmit the second data sequence to the relay satellite 200 as orbit information when the distance is equal to or greater than the predetermined distance threshold. That is, the communication unit 52 may switch the data sequence to be transmitted to the relay satellite 200 based on the distance between the user satellite 100 and the relay satellite 200.

[0054] For example, in the example shown in FIG. 8, two curves indicate a predicted orbital ephemeris data sequence with low time resolution and a predicted orbital ephemeris data sequence with high time resolution obtained in high-precision orbit prediction. The black circle indicates the position of the user satellite 100, the circle indicates the estimated position of the user satellite 100 interpolated based on the predicted orbital ephemeris data sequence obtained from the earth station 50, and the area surrounded by a circular dashed line indicates the prediction error of the estimated position. The prediction error of the estimated position may become larger as time passes from the point indicated by the black circle. For example, the prediction error at time Pt1-5 is larger than the prediction error at time Pt1-1. As can be seen from FIG. 8, the estimated position of the user satellite 100 interpolated based on the predicted orbital ephemeris data sequence with high time resolution can limit the prediction error (the range in which the user satellite 100 may exist) to a smaller radius.

[0055] In Fig. 9, two lines extending from the relay satellite 200 indicate the range in which the user satellite 100 can be captured and tracked. When the distance between the relay satellite 200 and the user satellite 100 is large, the range in which the user satellite 100 may exist may be included in the capture and trackable range even with a predicted ephemeris data sequence with low time resolution. On the other hand, when the distance between the relay satellite 200 and the user satellite 100 is small, the range in which the user satellite 100 may exist may be larger than the capture and trackable range with a predicted ephemeris data sequence with low time resolution, and as shown in Fig. 10, the relay satellite 200 may not be able to capture and track the user satellite 100. In this case, as shown in Fig. 11, by using a predicted ephemeris data sequence with high time resolution, the range in which the user satellite 100 may exist may be smaller, and the prediction error of the position of the user satellite 100 may be included in the capture and trackable range.

[0056] According to this embodiment, the data sequence to be transmitted to the relay satellite 200 can be appropriately switched based on the distance between the user satellite 100 and the relay satellite 200.

[0057] In one embodiment, the predetermined selection criterion may be related to a communication state between the earth station 50 and the relay satellite 200. The communication unit 52 may transmit the second data series to the relay satellite 200 as orbit information when the communication state is below a predetermined quality threshold, and may transmit the first data series to the relay satellite 200 as orbit information when the communication state is equal to or higher than the predetermined quality threshold. That is, the communication unit 52 may switch the data series to be transmitted to the relay satellite 200 based on the communication state between the earth station 50 and the relay satellite 200.

[0058] Specifically, when the communication state between the earth station 50 and the relay satellite 200 is not good, a data sequence with a large amount of data may not be successfully transmitted. For this reason, the communication unit 52 may transmit (e.g., repeatedly transmit) a second data sequence, which is a predicted orbital ephemeris data sequence with a relatively low time resolution, to the relay satellite 200 so that the data sequence reaches the relay satellite 200 more reliably. On the other hand, when the communication state between the earth station 50 and the relay satellite 200 is good, it is expected that even a data sequence with a large amount of data will be successfully transmitted. For this reason, the communication unit 52 may transmit a first data sequence, which is a predicted orbital ephemeris data sequence with a relatively high time resolution, to the relay satellite 200, and have the relay satellite 200 perform an interpolation calculation based on the first data sequence to estimate the orbit of the user satellite 100 with high accuracy.

[0059] According to this embodiment, the data sequence to be transmitted to the relay satellite 200 can be appropriately switched based on the communication state between the earth station 50 and the relay satellite 200.

[0060] In one embodiment, the predetermined selection criterion may be related to the capability of the relay satellite 200. The communication unit 52 may transmit the second data sequence to the relay satellite 200 as orbit information when the capability is less than a predetermined capability level threshold, and may transmit the first data sequence to the relay satellite 200 as orbit information when the capability is equal to or greater than the predetermined capability level threshold. Here, the capability of the relay satellite 200 may be, for example, the computation capability, memory capacity, communication capability with the earth station 50, and capability of the optical communication system 103A that communicates with the user satellite 100 of the relay satellite 200. That is, the communication unit 52 may switch the data sequence to be transmitted to the relay satellite 200 based on the capability of the relay satellite 200.

[0061] Specifically, when the capability of the relay satellite 200 is relatively low, the relay satellite 200 may not be able to process or utilize a predicted orbital ephemeris data sequence with a low time resolution. For this reason, the communication unit 52 may transmit a first data sequence with a relatively high time resolution to the relay satellite 200, and cause the relay satellite 200 to estimate the orbit of the user satellite 100 based on the first data sequence without using the relatively high capability. On the other hand, when the capability of the relay satellite 200 is relatively high, the relay satellite 200 may be able to process or utilize a predicted orbital ephemeris data sequence with a low time resolution. For this reason, the communication unit 52 may transmit a second data sequence with a relatively low time resolution to the relay satellite 200, and cause the relay satellite 200 to estimate the orbit of the user satellite 100 with high accuracy based on the second data sequence by using the relatively high capability.

[0062] According to this embodiment, the data sequence to be transmitted to the relay satellite 200 can be appropriately switched based on the capability of the relay satellite 200 .

[0063] Also, in one embodiment, the predetermined selection criterion may be related to the computational margin of the relay satellite 200. The communication unit 52 may transmit the second data sequence to the relay satellite 200 as orbit information when the computational margin is less than a predetermined threshold, and may transmit the first data sequence to the relay satellite 200 as orbit information when the computational margin is equal to or greater than the predetermined threshold. That is, the communication unit 52 may switch the data sequence to be transmitted to the relay satellite 200 based on the computational margin of the relay satellite 200.

[0064] Specifically, when the computational margin of the relay satellite 200 is relatively low, the relay satellite 200 may not be able to perform an interpolation calculation for a predicted orbital ephemeris data sequence with a low time resolution. For this reason, the communication unit 52 may transmit a first position data sequence with a relatively high time resolution to the relay satellite 200, and cause the relay satellite 200 to estimate the orbit of the user satellite 100 based on the first data sequence without requiring a relatively high computational load. On the other hand, when the computational margin of the relay satellite 200 is relatively high, it is considered that the relay satellite 200 can process a predicted orbital ephemeris data sequence with a low time resolution. For this reason, the communication unit 52 may transmit a second data sequence with a relatively low time resolution to the relay satellite 200, and cause the relay satellite 200 to estimate the orbit of the user satellite 100 with high accuracy based on the second data sequence by utilizing the relatively high computational margin.

[0065] According to this embodiment, the data sequence to be transmitted to the relay satellite 200 can be appropriately switched based on the computational capacity of the relay satellite 200.

[0066] [Relay satellite] Next, a relay satellite 200 according to an embodiment of the present disclosure will be described with reference to Fig. 12. Fig. 12 is a block diagram showing a functional configuration of the relay satellite 200 according to an embodiment of the present disclosure.

[0067] 12, the relay satellite 200 has a control unit 210, a processing unit 220, and an optical communication unit 230. Each functional unit can be realized by any one or a combination of the hardware devices described above.

[0068] The control unit 210 acquires a data series indicating a predicted ephemeris of the satellite. For example, the data series may be predicted ephemeris data (Ephemeris) of the user satellite 100 and / or the relay satellite 200. Specifically, the predicted ephemeris data may be configured as time series data of the position and velocity of the satellite at each time point. Alternatively, the predicted ephemeris data may be configured as time series data of the position, velocity, and acceleration of the satellite at each time point.

[0069] The predicted ephemeris data series may be calculated taking into account perturbation factors. For example, the predicted ephemeris data series may be calculated by the earth station 50 taking into account the perturbation factors using an analytical method or a numerical integration method. Specific examples of perturbation factors include the non-spherical component of the earth's gravity, the gravitational forces of the sun and the moon, atmospheric resistance, solar radiation pressure, and earth's gravitational distortion due to tides, which are major perturbation factors of a satellite orbiting the earth. This makes it possible for the control unit 210 to realize a more accurate orbit prediction with fewer computational resources than a conventional approach in which the control unit 210 receives Kepler's six orbital elements from the earth station 50 and calculates the predicted ephemeris data of the user satellite 100 based on the received six orbital elements without taking into account the perturbation factors.

[0070] The processing unit 220 performs an interpolation calculation of the predicted orbit of the user satellite 100 based on the acquired predicted orbital ephemeris data sequence. The processing unit 220 acquires the position and velocity of the relay satellite 200 from the GPS positioning result, and acquires the attitude angle and angular velocity as the attitude data of the relay satellite 200 from the attitude sensor. The processing unit 220 then calculates the distance and direction of the user satellite 100 relative to the relay satellite 200 based on the positional relationship between the destination user satellite 100 on the predicted orbit and the relay satellite 200. The predicted orbital ephemeris data acquisition and calculation may be performed, for example, every N seconds (e.g., every second), or may be performed according to the time resolution of the acquired predicted orbital ephemeris data sequence. The processing unit 220 calculates the rotation angle at which the optical telescope (e.g., capable of rotating on two axes) of the optical communication device is directed toward the user satellite 100 based on the direction of the user satellite 100 and the attitude angle of the relay satellite 200.

[0071] The optical communication unit 230 performs inter-satellite optical communication with the user satellite 100 based on the predicted orbit predicted by the interpolation calculation. The optical communication unit 230 rotates the optical telescope by the calculated rotation angle to transmit and receive laser light. Here, the optical communication unit 230 may control the direction of the optical communication device at a predetermined time, such as every 0.1 second. For this reason, the predicted orbit may be interpolated every M seconds (M≦0.1) by an interpolation calculation based on the predicted orbital ephemeris data series, based on the speed and angular velocity of the user satellite 100 and the relay satellite 200. The distance between the user satellite 100 and the relay satellite 200 may be used in a calculation for correcting the light receiving direction and the light output direction, taking into account the arrival time of the laser light. For example, when the distance between the user satellite 100 and the relay satellite 200 is L km, the light arriving from the user satellite 100 reaches a wavelength of (L / 3×10 5 ) seconds ago. 5 ) seconds later, the optical communication unit 230 needs to output the laser light taking into consideration the amount of movement of the user satellite 100 and the relay satellite 200 during that time.

[0072] In one embodiment, the control unit 210 acquires a data series selected from the first data series and the second data series according to a predetermined selection criterion from the earth station 50. Here, the first data series has a first time resolution, and the second data series has a second time resolution lower than the first data amount. Specifically, the first data series and the second data series may be composed of vector data of the same dimension, such as time series data of predicted orbital ephemeris data indicating the orbit of the user satellite 100. In the case of time series data of predicted orbital ephemeris data of the user satellite 100 in a predetermined period, the first data series may be a data series composed of a pieces of data, and the second data series may be a data series composed of b pieces of data (a>b).

[0073] In one embodiment, the first data series may be a first predicted ephemeris data series of the user satellite 100 with a first time resolution (e.g., a predicted ephemeris data series with a high time resolution), and the second data series may be a second predicted ephemeris data series of the user satellite 100 with a second time resolution lower than the first time resolution (e.g., a predicted ephemeris data series with a low time resolution). For example, the first predicted ephemeris data series may be time series data of 60 pieces of position data indicating a predicted position of the user satellite 100 in units of 1 minute in a specific time period having a time length of 1 hour, and the second predicted ephemeris data series may be time series data of 6 pieces of position data indicating a predicted position of the user satellite 100 in units of 10 minutes in the time period. Here, the position of the user satellite 100 may be represented by any appropriate method known in the art, such as a position in a predetermined coordinate system or a relative position with respect to the relay satellite 200. However, the data series according to the present disclosure is not necessarily limited to a predicted ephemeris data series, but may be any other suitable type of time series data indicative of the orbit of the user satellite 100, such as an orientation data series indicative of the orientation of the user satellite 100 relative to the relay satellite 200.

[0074] In one embodiment, the predetermined selection criterion may be related to the distance between the user satellite 100 and the relay satellite 200. The controller 210 may obtain the first data series if the distance is less than the predetermined distance threshold, and may obtain the second data series if the distance is equal to or greater than the predetermined distance threshold. That is, the controller 210 may obtain the data series selected from the earth station 50 based on the distance between the user satellite 100 and the relay satellite 200.

[0075] Specifically, when the user satellite 100 is close to the relay satellite 200, the earth station 50 may transmit a first predicted ephemeris data sequence having a relatively high time resolution to the relay satellite 200, and the control unit 210 may interpolate the first predicted ephemeris data sequence to estimate the orbit of the user satellite 100. On the other hand, when the user satellite 100 is far from the relay satellite 200, the communication unit 52 may transmit a second predicted ephemeris data sequence having a relatively low time resolution to the relay satellite 200, and the control unit 210 may interpolate the second predicted ephemeris data sequence to estimate the orbit of the user satellite 100 with high accuracy.

[0076] According to this embodiment, a data sequence that is appropriately switched based on the distance between the user satellite 100 and the relay satellite 200 can be obtained.

[0077] In one embodiment, the predetermined selection criterion may be related to a communication state between the earth station 50 and the relay satellite 200. The control unit 210 may acquire the second data series when the communication state is below a predetermined quality threshold, and may acquire the first data series when the communication state is equal to or above the predetermined quality threshold. That is, the control unit 210 may acquire the data series selected based on the communication state between the earth station 50 and the relay satellite 200.

[0078] Specifically, when the communication state between the earth station 50 and the relay satellite 200 is not good, a data sequence with a large amount of data may not be successfully transmitted. Therefore, the earth station 50 may transmit (e.g., repeatedly transmit) a second predicted ephemeris data sequence with a relatively low time resolution to the relay satellite 200, so that the control unit 210 may more reliably acquire the data sequence. On the other hand, when the communication state between the earth station 50 and the relay satellite 200 is good, it is considered that even a data sequence with a large amount of data may be successfully transmitted. Therefore, the earth station 50 may transmit a first predicted ephemeris data sequence with a relatively high time resolution to the relay satellite 200, so that the control unit 210 may interpolate the first predicted ephemeris data sequence to estimate the orbit of the user satellite 100 with high accuracy.

[0079] According to this embodiment, a predicted ephemeris data series that is appropriately switched based on the communication state between the earth station 50 and the relay satellite 200 can be acquired.

[0080] In one embodiment, the predetermined selection criterion may be related to the capability of the relay satellite 200. The control unit 210 may acquire the first predicted ephemeris data sequence when the capability is less than a predetermined computational capability level threshold, and may acquire the second predicted ephemeris data sequence when the capability is equal to or greater than the predetermined capability level threshold. Here, the capability of the relay satellite 200 may be, for example, the computational capability, memory capacity, communication capability with the earth station 50, and capability of the optical communication system 103A communicating with the user satellite 100 of the relay satellite 200. That is, the control unit 210 may acquire the predicted ephemeris data sequence selected based on the capability of the relay satellite 200.

[0081] Specifically, when the computational capability of the relay satellite 200 is relatively low, the relay satellite 200 may not be able to process or utilize a predicted ephemeris data sequence with a low time resolution. For this reason, the earth station 50 may transmit a first predicted ephemeris data sequence with a relatively high time resolution to the relay satellite 200, and the control unit 210 may estimate the orbit of the user satellite 100 based on the first predicted ephemeris data sequence without utilizing the relatively high capability. On the other hand, when the capability of the relay satellite 200 is relatively high, the relay satellite 200 may be able to process or utilize a predicted ephemeris data sequence with a low time resolution. For this reason, the earth station 50 may transmit a second predicted ephemeris data sequence with a relatively low time resolution to the relay satellite 200, and the control unit 210 may estimate the orbit of the user satellite 100 with high accuracy based on the second predicted ephemeris data sequence by utilizing the relatively high capability.

[0082] According to this embodiment, a data sequence that is appropriately switched based on the capabilities of the relay satellite 200 can be acquired.

[0083] In one embodiment, the predetermined selection criterion may be related to the computational margin of the relay satellite 200. The control unit 210 may acquire the first predicted ephemeris data sequence when the computational margin is less than a predetermined threshold, and may acquire the second predicted ephemeris data sequence when the computational margin is equal to or greater than the predetermined threshold. That is, the control unit 210 may acquire the predicted ephemeris data sequence selected based on the computational margin of the relay satellite 200.

[0084] Specifically, when the computational margin of the relay satellite 200 is relatively low, the relay satellite 200 may not be able to perform an interpolation calculation for a predicted ephemeris data sequence with a low time resolution. Therefore, the earth station 50 may transmit a first predicted ephemeris data sequence with a relatively high time resolution to the relay satellite 200, and the control unit 210 may estimate the orbit of the user satellite 100 based on the first predicted ephemeris data sequence without using a relatively high computational load. On the other hand, when the computational margin of the relay satellite 200 is relatively high, it is considered that the relay satellite 200 can process a predicted ephemeris data sequence with a low time resolution. Therefore, the earth station 50 may transmit a second predicted ephemeris data sequence with a relatively low time resolution to the relay satellite 200, and the control unit 210 may estimate the orbit of the user satellite 100 with high accuracy based on the second predicted ephemeris data sequence by utilizing the relatively high computational margin.

[0085] According to this embodiment, a data sequence that is appropriately switched based on the computational margin of the relay satellite 200 can be acquired.

[0086] [Communication processing] Next, a communication process according to an embodiment of the present disclosure will be described with reference to Fig. 13. The communication process can be executed by the earth station 50 and the relay satellite 200. Fig. 13 is a sequence diagram showing the communication process according to an embodiment of the present disclosure.

[0087] 13, in step S100, the earth station 50 calculates a predicted orbital ephemeris data series of the user satellite 100 and / or the relay satellite 200 by correcting the influence of perturbation factors in addition to the information of the six Kepler orbital elements included in the TLE, thereby generating orbit predicted ephemeris data with higher accuracy than before. Also, the relay satellite operator 30 or the user satellite operator 40 may calculate and generate the predicted orbital ephemeris data series.

[0088] 14A to 14C are block diagrams showing communication processing between an earth station 50 and a relay satellite 200 according to an embodiment of the present disclosure. As shown in FIG. 14A, the earth station 50 and the relay satellite 200 perform wireless communication by radio waves or the like. For example, as shown in FIG. 14B, the earth station 50 may calculate predicted orbital ephemeris data of the user satellite 100 based on the six orbital elements or TLE of the user satellite 100 and GPS positioning information, and may calculate predicted orbital ephemeris data of the relay satellite 200 based on the six orbital elements or TLE of the relay satellite 200 and GPS positioning information. Note that the earth station 50 according to the present disclosure is not limited thereto, and may obtain predicted orbital ephemeris data of the relay satellite 200 and / or the user satellite 100 calculated by the relay satellite operator 30 and / or the user satellite operator 40, or the like. Then, the earth station 50 transmits the calculated predicted orbital ephemeris data of the relay satellite 200 and / or the user satellite 100 to the relay satellite 200.

[0089] Upon receiving the predicted orbital ephemeris data of the relay satellite 200 and / or the user satellite 100 from the earth station 50, the relay satellite 200 determines the position and velocity of the relay satellite 200 and / or the user satellite 100 at the target time based on the received predicted orbital ephemeris data, as shown in Fig. 14C, and calculates the direction and distance to the user satellite 100 by performing data interpolation. In parallel with this, the relay satellite 200 measures the attitude angle and / or angular velocity of the relay satellite 200 by an attitude sensor or the like, and calculates the attitude angle and angular velocity to the user satellite 100 by performing data interpolation. Then, the relay satellite 200 adjusts the direction of the optical communication device 103A based on the calculated direction, distance, attitude angle and / or angular velocity to the user satellite 100, and transmits an optical signal.

[0090] In step S101, the earth station 50 acquires a data sequence indicating a predicted orbital ephemeris of the user satellite 100 and / or the relay satellite 200. Specifically, the earth station 50 may calculate a more accurate predicted orbital ephemeris data sequence of the user satellite 100 (or the relay satellite 200) based on the six Kepler orbital elements (the Kepler orbital elements may be derived from information included in the TLE) or the GPS positioning information received by the user satellite 100 (or the relay satellite 200) and downlink transmitted from the user satellite 100 (or the relay satellite 200) and taking into account perturbation factors. In addition, the generation of the predicted orbital ephemeris data sequence may be executed by the relay satellite operator 30 or the user satellite operator 40, and the earth station 50 may acquire the predicted orbital ephemeris data sequence from the relay satellite operator 30 or the user satellite operator 40 via the network 20 such as the Internet. In addition, the earth station 50 may acquire a first predicted orbital ephemeris data sequence having a first data amount and a second predicted orbital ephemeris data sequence having a second data amount less than the first data amount. In one embodiment, the first predicted ephemeris data sequence may be a first predicted ephemeris data sequence of the user satellite 100 with a first time resolution, and the second predicted ephemeris data sequence may be a second predicted ephemeris data sequence of the user satellite 100 with a second time resolution lower than the first time resolution. The earth station 50 may acquire one of the first predicted ephemeris data sequence and the second predicted ephemeris data sequence selected according to a predetermined selection criterion, instead of acquiring both the first predicted ephemeris data sequence and the second predicted ephemeris data sequence. The first predicted ephemeris data sequence or the second predicted ephemeris data sequence selected by the relay satellite operator 30 or the user satellite operator 40 may be transmitted to the earth station 50 via a network 20 such as the Internet.

[0091] In step S102, the earth station 50 transmits the predicted ephemeris data sequence to the relay satellite 200. In addition, when the earth station 50 acquires the first predicted ephemeris data sequence and the second predicted ephemeris data sequence, the earth station 50 may transmit a data sequence selected from the first predicted ephemeris data sequence and the second predicted ephemeris data sequence according to a predetermined selection criterion to the relay satellite 200 as orbit information of the user satellite 100. For example, the earth station 50 may identify a selected data sequence for each user satellite 100 covered by the relay satellite 200, and transmit a group of data sequences identified as transmission targets to the relay satellite 200. In addition, the earth station 50 may transmit the predicted ephemeris data of the user satellite 100 to the user satellite 100 in step S102. In addition, in step S102, the earth station 50 may transmit to the user satellite 100 a predicted orbital ephemeris data sequence for the user satellite 100 selected from the first predicted orbital ephemeris data sequence and the second predicted orbital ephemeris data sequence in accordance with a predetermined selection criterion as orbit information of the relay satellite 200.

[0092] In one embodiment, the predetermined selection criteria may relate to the distance between the user satellite 100 and the satellite relay 200, the communication conditions between the earth station 50 and the satellite relay 200, the capabilities of the satellite relay 200, and / or the computational margin of the satellite relay 200. These selection criteria may also be combined. The selection of the data series may be performed by the earth station 50, or a selection instruction may be received from another entity, such as the satellite relay operator 30 or the user satellite operator 40.

[0093] In step S103, the relay satellite 200 acquires a predicted ephemeris data sequence. Specifically, the relay satellite 200 may receive the predicted ephemeris data sequence of the user satellite 100 and / or the relay satellite 200 from the earth station 50. The relay satellite 200 may also acquire a data sequence selected from the first predicted ephemeris data sequence and the second predicted ephemeris data sequence according to a predetermined selection criterion from the earth station 50. For example, when the relay satellite 200 covers a plurality of user satellites 100, the relay satellite 200 may acquire a predicted ephemeris data sequence of each user device 100 covered by the relay satellite 200. In step S103, the user satellite 100 may also acquire a predicted ephemeris data sequence of the relay satellite 200 and / or the user satellite 100 from the earth station 50.

[0094] In step S104, the relay satellite 200 executes inter-satellite optical communication with the user satellite 100 based on the acquired predicted orbital ephemeris data sequence. Specifically, the relay satellite 200 may estimate the orbit of the user satellite 100 based on the acquired predicted orbital ephemeris data sequence of the user satellite 100, and transmit a beacon light toward the estimated position of the user satellite 100. Upon receiving the beacon light, the user satellite 100 establishes a communication connection with the relay satellite 200, and exchanges data by transmitting and receiving communication light.

[0095] According to the above-mentioned embodiment, instead of the relay satellite 200 receiving the six orbital elements of Kepler according to the conventional technology calculating the predicted orbit of the user satellite 100, the earth station 50, the relay satellite operator 30, or the user satellite operator 40 can calculate more accurate predicted orbital ephemeris data required for inter-satellite optical communication with the user satellite 100 and provide the derived predicted orbital ephemeris data to the relay satellite 200. This makes it possible for the relay satellite 200 to appropriately perform inter-satellite optical communication with the user satellite 100 by using the orbit data acquired from the earth station 50, even if the relay satellite 200 has only limited computing power. Also, it becomes possible to provide the relay satellite 200 with a data series of an appropriate amount of data based on the distance between the user satellite 100 and the relay satellite 200, the communication state between the earth station 50 and the relay satellite 200, the capability of the relay satellite 200, and / or the computing capacity of the relay satellite 200.

[0096] Although the above-mentioned embodiment has been described with respect to two predicted ephemeris data series with different data amounts or different time resolutions, namely, the first predicted ephemeris data series and the second predicted ephemeris data series, the present disclosure is not limited thereto and may be applied to three or more predicted ephemeris data series with different data amounts or different time resolutions. Also, while the predicted ephemeris data series focuses on the predicted position data series of the user satellite 100, the present disclosure is not limited thereto and may be applied to any other data transmitted from the earth station 50 to the relay satellite 200 or the user satellite 100.

[0097] In addition, the following supplementary notes are provided in relation to the above description. (Appendix 1) a data acquisition unit that acquires a predicted orbit data sequence indicating a predicted orbital ephemeris of the satellite from an earth station; a communication unit that transmits the acquired predicted orbit data series to a relay satellite; An earth station having (Appendix 2) 2. The earth station of claim 1, wherein the predicted orbit data sequence is calculated taking into account perturbation factors. (Appendix 3) the data acquisition unit acquires a first data sequence which is the predicted trajectory data sequence having a first data amount, and a second data sequence which is the predicted trajectory data sequence having a second data amount which is less than the first data amount, 3. The earth station according to claim 2, wherein the communication unit transmits the first data sequence or the second data sequence selected according to a predetermined selection criterion to a relay satellite as satellite orbit information. (Appendix 4) the data acquisition unit acquires a first data series, which is the predicted orbit data series having a first time resolution, and a second data series, which is the predicted orbit data series having a second time resolution lower than the first time resolution; 3. The earth station according to claim 2, wherein the communication unit transmits a data sequence selected from the first data sequence and the second data sequence in accordance with a predetermined selection criterion to a relay satellite as satellite orbit information. (Appendix 5) the predetermined selection criterion relates to a distance between the satellite and the relay satellite; 5. The earth station according to claim 3, wherein the communication unit transmits the first data series to the relay satellite as the orbit information when the distance is less than a predetermined distance threshold, and transmits the second data series to the relay satellite as the orbit information when the distance is equal to or greater than the predetermined distance threshold. (Appendix 6) the predetermined selection criterion relates to a communication condition between the earth station and the relay satellite; 5. The earth station according to claim 3, wherein the communication unit transmits the second data series to the relay satellite as the orbit information when the communication state is below a predetermined quality threshold, and transmits the first data series to the relay satellite as the orbit information when the communication state is equal to or greater than the predetermined quality threshold. (Appendix 7) the predetermined selection criteria relate to capabilities of the satellite relay; 5. The earth station according to claim 3, wherein the communication unit transmits the second data series to the relay satellite as the orbit information when the capability is less than a predetermined capability level threshold, and transmits the first data series to the relay satellite as the orbit information when the capability is equal to or greater than the predetermined capability level threshold. (Appendix 8) the predetermined selection criterion relates to a computational margin of the relay satellite; 5. The earth station according to claim 3, wherein the communication unit transmits the second data series to the relay satellite as the orbit information when the computational capacity is less than a predetermined threshold, and transmits the first data series to the relay satellite as the orbit information when the computational capacity is equal to or greater than the predetermined threshold. (Appendix 9) obtaining from an earth station a predicted orbit data sequence indicative of a predicted orbital ephemeris of the satellite; Transmitting the obtained predicted orbit data series to a relay satellite; A communication method implemented by an earth station having the (Appendix 10) 10. The communication method of claim 9, wherein the predicted orbit data sequence is calculated taking into account perturbation factors. (Appendix 11) A control unit that acquires a predicted orbit data sequence indicating a predicted orbital ephemeris of the satellite from an earth station; an optical communication unit that performs inter-satellite optical communication with the satellite based on the acquired predicted orbit data sequence; A relay satellite having (Appendix 12) 12. The relay satellite of claim 11, wherein the predicted orbit data sequence is calculated taking into account perturbation factors. (Appendix 13) the control unit acquires from the earth station a data sequence selected from a first data sequence and a second data sequence according to a predetermined selection criterion; 13. The relay satellite of claim 12, wherein the first data sequence is the predicted orbit data sequence having a first amount of data, and the second data sequence is the predicted orbit data sequence having a second amount of data less than the first amount of data. (Appendix 14) the control unit acquires from the earth station a data sequence selected from a first data sequence and a second data sequence according to a predetermined selection criterion; 13. The relay satellite of claim 12, wherein the first data sequence is the predicted orbit data sequence having a first temporal resolution, and the second data sequence is the predicted orbit data sequence having a second temporal resolution lower than the first temporal resolution. (Appendix 15) the predetermined selection criterion relates to a distance between the satellite and the relay satellite; 15. The relay satellite described in claim 13 or 14, wherein the control unit acquires the first data series when the distance is less than a predetermined distance threshold, and acquires the second data series when the distance is equal to or greater than the predetermined distance threshold. (Appendix 16) the predetermined selection criterion relates to a communication condition between the earth station and the relay satellite; 15. The relay satellite described in claim 13 or 14, wherein the control unit acquires the second data sequence when the communication state is below a predetermined quality threshold, and acquires the first data sequence when the communication state is equal to or greater than the predetermined quality threshold. (Appendix 17) the predetermined selection criteria relate to capabilities of the satellite relay; 15. The relay satellite described in claim 13 or 14, wherein the control unit acquires the second data sequence when the capability is less than a predetermined capability level threshold, and acquires the first data sequence when the capability is equal to or greater than the predetermined capability level threshold. (Appendix 18) the predetermined selection criterion relates to a computational margin of the relay satellite; The relay satellite described in Appendix 13 or 14, wherein the control unit acquires the second data series when the computational capacity is less than a predetermined threshold, and acquires the first data series when the computational capacity is equal to or greater than the predetermined threshold. (Appendix 19) obtaining from an earth station a predicted orbit data sequence indicative of a predicted orbital ephemeris of the satellite; performing inter-satellite optical communication with the satellite based on the obtained predicted orbit data sequence; A communication method implemented by a relay satellite having the following components: (Appendix 20) An earth station; Satellites and a relay satellite for relaying between the earth station and the satellite; having The earth station includes: obtaining a predicted orbit data series indicative of a predicted orbital ephemeris of the satellite; Transmitting the obtained predicted orbit data series to a relay satellite; Satellite system.

[0098] 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 described in the claims. [Explanation of symbols]

[0099] 10 Satellite Systems 50 earth station 51 Data Acquisition Section 52 Communications Department 100 user satellites 200 relay satellites 210 Control section 220 Processing section 230 Optical Communications Department

Claims

1. A data acquisition unit that acquires a series of predicted orbit ephemeris data indicating the predicted orbit ephemeris of a satellite during a predetermined period, a communication unit that transmits the acquired series of predicted orbit ephemeris data to a relay satellite, and has, the data acquisition unit acquires a first series of predicted orbit ephemeris data of a first data amount during the predetermined period and a second series of predicted orbit ephemeris data of a second data amount less than the first data amount during the predetermined period, the communication unit transmits the first series of predicted orbit ephemeris data or the second series of predicted orbit ephemeris data selected according to a predetermined selection criterion to the relay satellite as orbit information of the satellite, a signal processing circuit.

2. The data acquisition unit acquires the first series of predicted orbit ephemeris data having a first time resolution and a second series of data having a second time resolution lower than the first time resolution. The signal processing circuit according to claim 1.

3. The first series of predicted orbit ephemeris data or the second series of predicted orbit ephemeris data is calculated in consideration of perturbation factors. The signal processing circuit according to claim 1.

4. The communication unit is compatible with communication at a plurality of transmission data rates for transmitting the series of predicted orbit ephemeris data to the relay satellite. The signal processing circuit according to claim 1.

5. The predetermined selection criterion is related to the distance between the satellite and the relay satellite, the communication unit transmits the first series of predicted orbit ephemeris data to the relay satellite as the orbit information when the distance is less than a predetermined distance threshold, and transmits the second series of predicted orbit ephemeris data to the relay satellite as the orbit information when the distance is greater than or equal to the predetermined distance threshold. The signal processing circuit according to claim 1.

6. The predetermined selection criterion is related to the communication state between the earth station and the relay satellite, the communication unit transmits the second series of predicted orbit ephemeris data to the relay satellite as the orbit information when the communication state is less than a predetermined quality threshold, and transmits the first series of predicted orbit ephemeris data to the relay satellite as the orbit information when the communication state is greater than or equal to the predetermined quality threshold. The signal processing circuit according to claim 1.

7. The predetermined selection criterion is related to the capability of the relay satellite, When the capability is less than a predetermined capability level threshold, the communication unit transmits the second predicted orbit ephemeris data series to the relay satellite as the orbit information, and when the capability is equal to or greater than the predetermined capability level threshold, the communication unit transmits the first predicted orbit ephemeris data series to the relay satellite as the orbit information. The signal processing circuit according to claim 1.

8. The predetermined selection criterion is related to the computing power of the relay satellite. When the computing power is less than a predetermined threshold, the communication unit transmits the second predicted orbit ephemeris data series to the relay satellite as the orbit information, and when the computing power is equal to or greater than the predetermined threshold, the communication unit transmits the first predicted orbit ephemeris data series to the relay satellite as the orbit information. The signal processing circuit according to claim 1.

9. Obtain a first predicted orbit ephemeris data series of a first data amount indicating the predicted orbit ephemeris of a satellite over a predetermined period, and a second predicted orbit ephemeris data series of a second data amount less than the first data amount over the predetermined period. Transmit the first predicted orbit ephemeris data series or the second predicted orbit ephemeris data series selected according to a predetermined selection criterion to a relay satellite. A signal processing method executed by an earth station.

10. The first predicted orbit ephemeris data series is a predicted orbit ephemeris data series having a first time resolution. The second predicted orbit ephemeris data series is the predicted orbit ephemeris data series having a second time resolution lower than the first time resolution. The signal processing method according to claim 9.

11. The first predicted orbit ephemeris data series or the second predicted orbit ephemeris data series is calculated considering perturbation factors. The signal processing method according to claim 9.

12. Corresponding to communication at a plurality of transmission data rates for transmitting the first predicted orbit ephemeris data series or the second predicted orbit ephemeris data series to the relay satellite. The signal processing method according to claim 9.

13. A control unit that obtains a predicted orbit ephemeris data series indicating the predicted orbit ephemeris of a satellite over a predetermined period from an earth station. An optical communication unit that performs inter-satellite optical communication based on the obtained predicted orbit ephemeris data series. And has The control unit obtains, from the earth station, the first predicted orbit ephemeris data series during the predetermined period or the second predicted orbit ephemeris data series during the predetermined period, which are selected according to a predetermined selection criterion. The first predicted orbit ephemeris data series has a first data volume, and the second predicted orbit ephemeris data series has a second data volume that is less than the first data volume. Signal processing circuit.

14. The first predicted orbit ephemeris data series has a first time resolution, and the second predicted orbit ephemeris data series has a second time resolution that is lower than the first time resolution. The signal processing circuit according to claim 13.

15. The first predicted orbit ephemeris data series or the second predicted orbit ephemeris data series is calculated in consideration of perturbation factors. The signal processing circuit according to claim 13.

16. The predetermined selection criterion is related to the distance between the satellite and the relay satellite. When the distance is less than a predetermined distance threshold, the control unit acquires the first predicted orbit ephemeris data series, and when the distance is greater than or equal to the predetermined distance threshold, the control unit acquires the second predicted orbit ephemeris data series. The signal processing circuit according to claim 13.

17. The predetermined selection criterion is related to the communication state between the earth station and the relay satellite. When the communication state is less than a predetermined quality threshold, the control unit acquires the second predicted orbit ephemeris data series, and when the communication state is greater than or equal to the predetermined quality threshold, the control unit acquires the first predicted orbit ephemeris data series. The signal processing circuit according to claim 13.

18. The predetermined selection criterion is related to the ability of the relay satellite. When the ability is less than a predetermined ability level threshold, the control unit acquires the second predicted orbit ephemeris data series, and when the ability is greater than or equal to the predetermined ability level threshold, the control unit acquires the first predicted orbit ephemeris data series. The signal processing circuit according to claim 13.

19. The predetermined selection criterion is related to the computational spare capacity of the relay satellite. When the computational spare capacity is less than a predetermined threshold, the control unit acquires the second predicted orbit ephemeris data series, and when the computational spare capacity is greater than or equal to the predetermined threshold, the control unit acquires the first predicted orbit ephemeris data series. The signal processing circuit according to claim 13.

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