Satellite-to-ground optical communication method and apparatus for reducing solar noise

Abstract

A satellite-to-ground optical communication method and apparatus for reducing solar noise are disclosed. A ground terminal apparatus for satellite-to-ground optical communication may include: an optical driving unit that controls the pointing angle of a telescope to track the trajectory of a satellite changing in real time, radiates a transmission beam to a satellite using the angle-controlled telescope, and receives a reception beam from the satellite; an optical modem that demodulates received communication data transmitted by a counterpart terminal from the reception beam; and a control unit that controls the optical driving unit to perform communication while tracking the trajectory of the satellite.

Description

Technology Field

[0001] The present invention relates to a satellite-to-ground optical communication method and apparatus, and more specifically, to a satellite-to-ground optical communication method and apparatus capable of reducing solar noise. Background Technology

[0002] Free-space optical communication (FSO) is a technology that wirelessly transmits data using light propagating in free space. Due to its advantages of easy lightweighting and low power consumption, high-speed and large-capacity data transmission, and high security, FSO is used in satellite-based optical communication methods.

[0003] In satellite-based optical communication, compared to satellite-to-satellite links, satellite-to-ground links are highly likely to experience a decrease in reception strength due to atmospheric disturbances such as rain, fog, dust, and clouds, or a deterioration in the signal-to-noise ratio (SNR) of the optical communication channel due to background noise caused by daytime sunlight scattering.

[0004] Therefore, conventional satellite-to-ground optical communication tended to avoid daytime hours, when the influence of solar noise is high, and utilize nighttime or early morning / evening hours.

[0005] Therefore, there is a demand for optical communication methods that mitigate the effects of solar noise and enable use during the day. The problem to be solved

[0006] The present invention provides a method and apparatus that enable laser communication even under solar noise by overcoming the effects of solar noise in a satellite-ground laser communication link through controlling a ground terminal for satellite-ground optical communication in different ways depending on the presence or absence of solar noise.

[0007] The present invention provides a method and apparatus for improving the availability and usability of a ground terminal device by reducing solar noise using a filter of a ground terminal for satellite-ground optical communication during the day, thereby enabling the use of daytime hours in satellite-ground laser communication. means of solving the problem

[0008] A ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention may include: an optical driving unit that controls the pointing angle of a telescope to track the trajectory of a satellite changing in real time, radiates a transmission beam to a satellite using the angle-controlled telescope, and receives a reception beam from the satellite; an optical modem that demodulates received communication data transmitted by a counterpart terminal from the reception beam; and a control unit that controls the optical driving unit to track the trajectory of the satellite and controls the optical modem to perform communication.

[0009] The control unit of the ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention can control the optical driving unit by selecting one of a first method including direction acquisition tracking or a second method using a beacon modulation frequency.

[0010] The control unit of the ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention may select one of a first method including direction acquisition tracking or a second method using a beacon modulation frequency depending on the current time or solar noise.

[0011] The optical modem of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention comprises: a laser that generates and outputs a laser beam of a preset wavelength band; a communication detector that converts the received beam into an electronic signal; and a modem that demodulates received communication data from the electronic signal, wherein the modem can generate and output a modulation signal corresponding to the transmitted communication data.

[0012] The optical driving unit of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention may include: a telescope that radiates the transmission beam to a satellite and receives the reception beam from the satellite; a gimbal that controls the pointing angle of the telescope so that the telescope tracks the trajectory of the satellite changing in real time; a transmitting optical system that generates the transmission beam based on the laser and the modulation signal and transmits it to the telescope; and a receiving optical system that adjusts the beam size of the reception beam received by the telescope and transmits it to the communication detector.

[0013] The transmitting optical system of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention may include: a communication modulator that modulates at least one of the intensity, frequency, and phase of the laser beam according to the modulation signal or polarizes the laser beam to output a first modulated beam; a beacon modulator that modulates the intensity of the first modulated beam at a beacon modulation frequency to output a second modulated beam; and an optical amplifier that amplifies the intensity of the second modulated beam to output the transmitting beam.

[0014] The light-transmitting optical system of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention may further include a collimator that corrects the divergence angle of the transmission beam so that the transmission beam is radiated in parallel; and a aiming mirror that controls the emission angle of the transmission beam.

[0015] The light receiving optical system of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention may include: a first beam splitter that divides the receiving beam into a first receiving beam and a second receiving beam and transmits them in different directions; a first sensor that receives the first receiving beam and detects the position of the received first receiving beam to generate position information of the first receiving beam; a second beam splitter that divides the second receiving beam into a third receiving beam and a fourth receiving beam and transmits them in different directions; a second sensor that receives the third receiving beam and detects the position of the received third receiving beam to generate position information of the third receiving beam; a third lens that adjusts the size of the fourth receiving beam and causes it to be incident on the communication detector; and a steering mirror that adjusts the angle of the second receiving beam incident on the second beam splitter so that the fourth receiving beam is incident on the communication detector.

[0016] The light receiving optical system of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention may further include: a first lens that adjusts the size of the first receiving beam and causes it to be incident on the first sensor; and a second lens that adjusts the size of the third receiving beam and causes it to be incident on the second sensor.

[0017] The optical driving unit of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention further includes a solar filter that filters the second receiving beam, and the solar filter may include at least one of a space filter that is manufactured in a pinhole shape to remove scattered light, a long wavelength transmission filter that blocks the 800 nm band of the solar spectrum and transmits only long wavelengths, and a narrow band wavelength filter that transmits only a narrow band with a laser wavelength as the center wavelength.

[0018] The light receiving optical system of a ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention further comprises: a first electronic filter that processes a first electronic signal in which the first receiving beam is converted into an electronic signal at the first sensor; and a second electronic filter that processes a second electronic signal in which the third receiving beam is converted into an electronic signal at the second sensor, wherein the first electronic filter and the second electronic filter may include at least one of a high-pass filter that blocks the solar DC band, a band-pass filter that passes only the beacon modulation frequency band, and a locking amplifier that extracts the beacon modulation frequency signal.

[0019] The control unit of a ground terminal device for satellite-ground optical communication according to one embodiment of the present invention includes a main controller that controls the operation procedure of the ground terminal device for satellite-ground optical communication according to a satellite optical communication standard or a pre-agreed operation procedure; and a solar radiation discriminator that determines whether solar radiation noise is incident, wherein the main controller can control the optical driving unit by selecting one of the first method or the second method according to the determination result of the solar radiation discriminator.

[0020] The solar energy discriminator of the ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention determines that solar energy noise is not incident when the solar energy noise is below a threshold value or when the current time is nighttime, and the main controller can control the optical driving unit by selecting the first method when it is determined that the solar energy noise is not incident.

[0021] The main controller of the ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention, when the first method is selected, modulates the laser beam output from the optical modem with the communication modulator of the optical drive unit to generate the transmission beam, calculates the orbit of the satellite based on the satellite's TLE (two line element) data, controls the telescope to orient the satellite direction in which the satellite is expected to be located at the current time according to the satellite's orbit, corrects the angle of the telescope by controlling the gimbal according to the position information of the first reception beam detected by the first sensor, corrects the angle of the second reception beam by controlling the steering mirror according to the position information of the third reception beam detected by the second sensor so that the fourth reception beam is incident on the communication detector, receives the reception beam using the angle-corrected telescope, and performs optical communication by radiating the transmission beam.

[0022] The solar energy discriminator of the ground terminal device for satellite-to-ground optical communication according to one embodiment of the present invention determines that solar energy noise is incident when the solar energy noise is greater than or equal to a threshold value or when the current time is daytime, and the main controller can control the optical driving unit by selecting the second method when it is determined that the solar energy noise is incident.

[0023] The main controller of the ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention, when the second method is selected, generates the transmission beam by modulating the laser beam output from the optical modem with the communication modulator of the optical drive unit, calculates the orbit of the satellite based on the satellite's TLE data, controls the telescope to orient the satellite direction in which the satellite is expected to be located at the current time according to the satellite's orbit, removes solar noise included in the first reception beam by filtering the first reception beam with a first electronic filter so that the beacon modulation frequency band passes from the first electronic signal converted by the first sensor, corrects the angle of the telescope by controlling the gimbal according to the position information of the first reception beam from which solar noise has been removed, removes solar noise included in the third reception beam by filtering the third reception beam with a second electronic filter so that the beacon modulation frequency band passes from the second electronic signal converted by the second sensor, and controls the steering mirror according to the position information of the third reception beam from which solar noise has been removed so that the fourth reception beam is incident on the communication detector. The angle of the second receiving beam is corrected, and the receiving beam is received using an angle-corrected telescope, and optical communication can be performed by radiating the transmitting beam.

[0024] A satellite-to-ground optical communication method according to an embodiment of the present invention comprises: a step of determining whether solar noise is incident on a ground terminal device for satellite-to-ground optical communication; a step of performing optical communication by controlling an optical driving unit according to a first method including direction acquisition tracking when solar noise is not incident; and a step of performing optical communication by controlling the optical driving unit according to a second method using a beacon modulation frequency when solar noise is incident, wherein the optical driving unit can perform optical communication by radiating a transmission beam to a satellite and receiving a reception beam from the satellite.

[0025] The determining step of the satellite-to-ground optical communication method according to one embodiment of the present invention may determine that solar noise is not incident if the solar noise is below a threshold value or if the current time is nighttime, and determine that solar noise is incident if the solar noise is above a threshold value or if the current time is daytime.

[0026] The optical driving unit of a satellite-to-ground optical communication method according to an embodiment of the present invention comprises: a telescope that radiates a transmission beam to a satellite and receives a reception beam from the satellite; a gimbal that controls the pointing angle of the telescope so that the telescope tracks the trajectory of the satellite changing in real time; a transmitting optical system that generates a transmission beam based on a laser and a modulation signal output from an optical modem and transmits it to the telescope; and a receiving optical system that adjusts the beam size of the reception beam received by the telescope and transmits it to a communication detector of the optical modem, wherein the receiving optical system comprises: a first beam splitter that divides the reception beam into a first reception beam and a second reception beam and transmits them in different directions; a first sensor that receives the first reception beam, detects the position of the received first reception beam, and generates position information of the first reception beam; and a second beam splitter that divides the second reception beam into a third reception beam and a fourth reception beam and transmits them in different directions. It may include a second sensor that receives the third receiving beam and detects the position of the received third receiving beam to generate position information of the third receiving beam; a third lens that adjusts the size of the fourth receiving beam and causes it to be incident on the communication detector; and a steering mirror that adjusts the angle of the second receiving beam incident on the second beam splitter so that the fourth receiving beam is incident on the communication detector.

[0027] The step of performing optical communication by controlling an optical drive unit according to the first method of a satellite-to-ground optical communication method according to an embodiment of the present invention may include: a step of generating the transmission beam by modulating a laser beam output from an optical modem with a communication modulator of the optical drive unit; a step of calculating the orbit of the satellite based on the satellite's TLE data and controlling the telescope of the optical drive unit to orient the satellite in the direction where the satellite is expected to be located at the current time according to the satellite's orbit; a step of correcting the angle of the telescope by controlling the gimbal of the optical drive unit according to the position information of the first reception beam; a step of correcting the angle of the second reception beam by controlling the steering mirror of the optical drive unit according to the position information of the third reception beam so that the fourth reception beam is incident on a communication detector; and a step of receiving the reception beam using the telescope with the corrected angle and performing optical communication by radiating the transmission beam.

[0028] The step of performing optical communication by controlling an optical drive unit according to the second method of a satellite-to-ground optical communication method according to an embodiment of the present invention comprises: a step of generating the transmission beam by modulating a laser beam output from an optical modem with a communication modulator of the optical drive unit when the second method is selected; a step of calculating the orbit of the satellite based on the satellite's TLE data and controlling the telescope of the optical drive unit to orient the satellite in the direction where the satellite is expected to be located at the current time according to the satellite's orbit; a step of removing solar noise included in the first receiving beam by filtering the first receiving beam with a first electronic filter so that the beacon modulation frequency band passes through the first electronic signal converted by the first sensor of the optical drive unit; a step of correcting the angle of the telescope by controlling the gimbal of the optical drive unit according to the position information of the first receiving beam from which solar noise has been removed; and a step of removing solar noise included in the third receiving beam by filtering the third receiving beam with a second electronic filter so that the beacon modulation frequency band passes through the second electronic signal converted by the second sensor of the optical drive unit. The method may include the step of correcting the angle of the second receiving beam by controlling the steering mirror of the optical drive unit according to the position information of the third receiving beam from which solar noise has been removed so that the fourth receiving beam is incident on the communication detector; and the step of receiving the receiving beam using the angle-corrected telescope and performing optical communication by radiating the transmitting beam. Effects of the invention

[0029] According to one embodiment of the present invention, by controlling a ground terminal for satellite-ground optical communication in different ways depending on the presence or absence of solar noise, the effect of solar noise in a satellite-ground laser communication link can be overcome, thereby enabling laser communication even under solar noise.

[0030] According to one embodiment of the present invention, by reducing solar noise using a filter of a ground terminal for satellite-ground optical communication during the day, the daytime can be utilized in satellite-ground laser communication, thereby improving the availability and usability of the ground terminal device. Brief explanation of the drawing

[0031] FIG. 1 is a drawing illustrating a ground terminal device for satellite-ground optical communication of a satellite-ground optical communication system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the detailed configuration of an optical modem of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention. FIG. 3 is a diagram illustrating the detailed configuration of an optical driving unit and a control unit of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a satellite-to-ground optical communication method according to an embodiment of the present invention. FIG. 5 is a diagram illustrating the process of communicating by tracking the direction of the phase of a satellite-to-ground optical communication method according to an embodiment of the present invention. FIG. 6 is a diagram illustrating the process of communicating using a beacon modulation frequency of a satellite-to-ground optical communication method according to an embodiment of the present invention. Specific details for implementing the invention

[0032] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0033] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0034] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0036] FIG. 1 is a drawing illustrating a ground terminal device for satellite-ground optical communication of a satellite-ground optical communication system according to an embodiment of the present invention.

[0037] A satellite-to-ground optical communication system according to one embodiment of the present invention may be composed of satellites and ground terminal devices (100) for satellite-to-ground optical communication.

[0038] A ground terminal device (100) for satellite-to-ground optical communication may include an optical modem (110), an optical driving unit (120), and a control unit (130) as shown in FIG. 1.

[0039] The optical drive unit (120) controls the pointing angle of the telescope to track the trajectory of the satellite changing in real time, and can radiate a transmission beam L1 to the satellite using the angle-controlled telescope. Additionally, the optical drive unit (120) can receive a reception beam L2 from the satellite using the telescope.

[0040] The optical modem (110) can demodulate received communication data transmitted by the counterpart terminal in the receiving beam. Additionally, the optical modem (110) can generate a laser for generating a transmitting beam and a modulation signal corresponding to the transmitted communication data and output them to the optical driving unit (120).

[0041] The control unit (130) can generate a signal to control the optical drive unit (120) to track the trajectory of the satellite, and a signal to control the optical modem (110) to perform communication. Additionally, the control unit (130) can control the optical drive unit (120) by selecting one of a first method including directional acquisition tracking or a second method using a beacon modulation frequency, depending on the current time or solar noise.

[0042] A satellite-to-ground optical communication system according to one embodiment of the present invention controls a ground terminal for satellite-to-ground optical communication in different ways depending on the presence or absence of solar noise, thereby overcoming the effect of solar noise in a satellite-to-ground laser communication link and enabling laser communication even under solar noise.

[0043] A satellite-to-ground optical communication system according to one embodiment of the present invention can improve the availability and usability of a ground terminal device by reducing solar noise using a filter of a ground terminal for satellite-to-ground optical communication during the day, thereby enabling the use of daytime hours in satellite-to-ground laser communication.

[0044] FIG. 2 is a diagram illustrating the detailed configuration of an optical modem of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention.

[0045] The optical modem (110) may include a laser (210), a communication detector (220), and a modem (230) as shown in FIG. 2.

[0046] The laser (210) can generate a laser beam of a preset wavelength band and output it to the communication modulator (331) of the optical drive unit (120). At this time, the laser beam may be light having a carrier frequency. For example, the laser beam may be a laser beam of a wavelength band of 1,550 nm with low solar noise.

[0047] The communication detector (220) can convert the received beam received from the third lens (329) of the optical drive unit (120) into an electronic signal and transmit it to the modem (230).

[0048] The modem (230) can demodulate received communication data transmitted by the counterpart terminal to the user terminal from the received electronic signal. Additionally, the modem (230) can be used to modulate a laser beam based on outgoing communication data generated by the user terminal to transmit to the counterpart terminal. Furthermore, the modem (230) can generate a modulation signal corresponding to the outgoing communication data and transmit it to the communication modulator (331). The modulation signal may be a signal containing one of the methods, processes, or conditions for modulating a laser beam to generate a transmission beam containing the content of the outgoing communication data.

[0049] FIG. 3 is a diagram illustrating the detailed configuration of an optical driving unit and a control unit of a ground terminal device for satellite-to-ground optical communication according to an embodiment of the present invention.

[0050] The optical drive unit (120) may include a telescope (310), a gimbal (315), a light receiving optical system (320), a light transmitting optical system (330), and a solar filter (340) as shown in FIG. 3.

[0051] The telescope (310) can radiate a transmission beam L1 output from the light receiving optical system (320) to the satellite. Additionally, the telescope (310) can receive a reception beam L2 from the satellite and transmit it to the light receiving optical system (320).

[0052] The gimbal (315) can control the pointing angle of the telescope (310) so that the telescope (310) tracks the trajectory of the satellite changing in real time according to the control of the control unit (130). The gimbal (315) is manufactured to be able to mount the telescope (310) and can rotate at least two axes of elevation and azimuth at a rotational speed that follows the movement of the satellite.

[0053] The receiving optical system (320) can adjust the beam size of the receiving beam L2 received by the telescope (310) and transmit it to the communication detector.

[0054] The light receiving optical system (320) may include a first beam splitter (321), a first lens (322), a first sensor (323), a first electronic filter (324), a steering mirror (325), a beam combiner (341), a second beam splitter (342), a second lens (326), a second sensor (327), a second electronic filter (328), and a third lens (329).

[0055] The first beam splitter (321) can split the receiving beam L2 into a first receiving beam and a second receiving beam and transmit them in different directions. At this time, the first receiving beam is a beam transmitted in the direction where the first sensor (323) is located among the beams split from the receiving beam L2, and the second receiving beam may be a beam transmitted to the second beam splitter (342) after passing through the steering mirror (325), the beam combiner (341), and the solar filter (340).

[0056] The first lens (322) can adjust the size of the first receiving beam so that it is incident on the first sensor (323).

[0057] The first sensor (323) can receive the first receiving beam that has passed through the first lens (322) and detect the position of the received first receiving beam to generate position information of the first receiving beam. For example, the first sensor (323) may be one of the position detection sensors such as a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, a CCD (Charge Coupled Device) sensor, a SWIR (Short-Wave Infrared) camera, or a quadrant detector. The counterpart terminal may generate a beacon beam to provide position information regarding its location. At this time, the beacon beam may be a beam in which the counterpart terminal intensity modulates a laser beam of a pre-set wavelength band to a beacon frequency according to a satellite optical communication standard. Then, the beacon beam transmitted by the counterpart terminal may be incident as a receiving beam L2 on a ground terminal device (100) for satellite-to-ground optical communication via a satellite. Accordingly, the first receiving beam split from the receiving beam L2 may include the same signal as the beacon beam transmitted by the counterpart terminal. And, the first sensor (323) may convert the received first receiving beam into an electronic signal and output a first electronic signal.

[0058] The first electronic filter (324) can process the first electronic signal converted from the first sensor (323). Specifically, the first electronic filter (324) can remove solar noise by filtering the first electronic signal so that the beacon frequency band passes through. As previously explained, since the beacon beam is a beam in which the counterpart terminal has intensity-modulated a laser beam to the beacon frequency according to the satellite optical communication standard, the position information of the counterpart terminal may be included in the portion intensity-modulated to the beacon frequency. And, since the first receiving beam contains the same signal as the beacon beam, the beacon frequency band of the first electronic signal, in which the first receiving beam is converted into an electronic signal, may include the position information of the counterpart terminal. Therefore, the first electronic filter (324) can remove the band (solar noise) that does not contain the position information of the counterpart terminal by filtering the first electronic signal so that the beacon frequency band passes through.

[0059] For example, the first electronic filter (324) may include at least one of a high-pass filter that blocks the solar DC band, a band-pass filter that passes only the beacon modulation frequency band, and a locking amplifier that extracts the beacon modulation frequency signal.

[0060] The steering mirror (325) can adjust the angle at which the second receiving beam, split from the first beam splitter (321), is transmitted to the second beam splitter (342). At this time, the steering mirror (325) can adjust the angle of the second receiving beam so that the third receiving beam and the fourth receiving beam, split from the second beam splitter (342), are incident on the second sensor (327) and the communication detector (220), respectively.

[0061] The beam combiner (341) can transmit the second receiving beam reflected from the steering mirror (325) to the solar filter (340). Also, the beam combiner (341) can transmit the transmitting beam L1 output from the transmitting optical system (330) so that it is incident on the steering mirror (325).

[0062] The second beam splitter (342) can split the second receiving beam incident from the solar filter (340) into a third receiving beam and a fourth receiving beam and transmit them in different directions. At this time, the third receiving beam is a beam transmitted in the direction where the second sensor (327) is located among the beams split from the second receiving beam, and the fourth receiving beam may be a beam transmitted to the communication detector (222) of the optical modem (110).

[0063] The second lens (326) can adjust the size of the third receiving beam and direct it to the second sensor (327).

[0064] The second sensor (327) can receive the third receiving beam that has passed through the second lens (326) and detect the position of the received third receiving beam to generate position information of the third receiving beam. For example, the second sensor (237) may be one of the position detection sensors such as a CMOS sensor, a CCD sensor, a SWIR camera, or a quadrant detector. The second sensor (327) is designed to have a narrower field of view (FOV) than the first sensor (323) so that it can display the position of the satellite more precisely than the first sensor (323) by using the third receiving beam that has passed through the second lens (326). Additionally, the third receiving beam split from the receiving beam L2 may contain the same signal as the beacon beam transmitted by the counterpart terminal. Furthermore, the second sensor (327) can convert the received third receiving beam into an electronic signal and output a second electronic signal.

[0065] The second electronic filter (328) can process the second electronic signal converted from the second sensor (327). Specifically, the second electronic filter (328) can remove solar noise by filtering the second electronic signal so that the beacon frequency band passes through. Since the third receiving beam contains the same signal as the beacon beam, the beacon frequency band of the second electronic signal, which is converted from the third receiving beam into an electronic signal, may contain location information of the counterpart terminal. Therefore, the second electronic filter (328) can remove the band (solar noise) that does not contain location information of the counterpart terminal by filtering the second electronic signal so that the beacon frequency band passes through. For example, the second electronic filter (328) may include at least one of a high-pass filter that blocks the solar DC band, a band-pass filter that passes only the beacon modulation frequency band, and a locking amplifier that extracts the beacon modulation frequency signal.

[0066] The third lens (329) can adjust the size of the fourth receiving beam so that it is incident on the communication detector (220).

[0067] The solar filter (340) can filter the second receiving beam. For example, the solar filter may include at least one of a space filter that removes scattered light by being made in the shape of a pinhole, a long wavelength transmission filter that blocks the 800 nm band of the solar spectrum and transmits only long wavelengths, and a narrow band wavelength filter that transmits only a narrow band with a laser wavelength as the center wavelength.

[0068] The transmitting optical system (330) can generate a transmitting beam L1 based on a laser and a modulation signal and transmit it to a telescope (310).

[0069] The transmitting optical system (330) may include a communication modulator (331), a beacon modulator (332), an optical amplifier (333), a collimator (334), and a aiming mirror (335).

[0070] The communication modulator (331) can output a first modulated beam by modulating the laser beam output by the laser (210) according to a modulation signal received from the modem (230). Specifically, the communication modulator (331) can output a first modulated beam by modulating at least one of the amplitude, phase, and frequency of the laser beam according to the modulation signal at a data rate of Gbps or higher, or by polarizing the laser beam.

[0071] The beacon modulator (332) can output a second modulated beam by intensity modulating the first modulated beam output from the communication modulator (331) with a beacon modulation frequency. Specifically, the beacon modulator (332) can output a second modulated beam by intensity modulating the amplitude of the first modulated beam with a beacon modulation frequency of several tens of kHz.

[0072] The optical amplifier (333) can amplify the intensity of the second modulation beam output from the beacon modulator (332) and output a transmission beam.

[0073] The collimator (334) can correct the divergence angle of the transmission beam so that the transmission beam output from the optical amplifier (333) is radiated in parallel. At this time, the transmission beam with the corrected divergence angle may be the transmission beam L1.

[0074] The aiming mirror (335) can control the firing angle of the transmitting beam L1. Specifically, the transmitting beam L1 can pass through the receiving optical system (320) as shown in FIG. 3 and be incident on the telescope (310). At this time, the aiming mirror (335) can control the angle of the transmitting beam L1 incident on the receiving optical system (320).

[0075] The control unit (130) may include a main controller (350) and a solar energy discriminator (360) as shown in FIG. 3.

[0076] The main controller (350) can control the operation procedure of the ground terminal device (100) for satellite-to-ground optical communication according to satellite optical communication standards such as the SDA (Space Development Agency) or CCSDS (Consultative Committee for Space Data Systems) standards or pre-agreed operation procedures. Specifically, the main controller (350) can control the optical modem (110) to demodulate received communication data transmitted by the counterpart terminal in the receiving beam, or to generate a laser and modulation signal. In addition, the main controller (350) can control the optical drive unit (120) by selecting either the first method or the second method according to the determination result of the solar energy discriminator (360).

[0077] The solar energy discriminator (360) can determine whether solar energy noise is incident on the ground terminal device (100) for satellite-to-ground optical communication. The solar energy discriminator (360) can measure solar energy noise included in the receiving beam L2 or identify the current time.

[0078] The solar noise detector (360) can determine that solar noise is not incident if the solar noise is below a threshold value or if the current time is nighttime. If it is determined that solar noise is not incident, the main controller (350) can select a first method to control the optical drive unit (120).

[0079] Specifically, the main controller (350) can generate a transmission beam L1 by modulating the laser beam output from the optical modem (110) with the communication modulator (331) of the optical drive unit (120). Additionally, the main controller (350) can calculate the satellite's orbit based on the satellite's TLE (two line element) data. Next, the main controller (350) can control the telescope (310) to orient the satellite in the direction where the satellite is expected to be located at the current time, according to the calculated satellite orbit. Next, the main controller (350) can correct the angle of the telescope (310) by controlling the gimbal (315) according to the position information of the first receiving beam detected by the first sensor (323). Next, the main controller (350) can correct the angle of the second receiving beam using the steering mirror (325) according to the position information of the third receiving beam detected by the second sensor (327) so that the fourth receiving beam is incident on the communication detector (220). Finally, the main controller (350) can receive the receiving beam L2 using the angle-corrected telescope (310) and radiate the transmitting beam L1 to perform optical communication.

[0080] The solar noise detector (360) can determine that solar noise is incident when the solar noise is above a threshold value or when the current time is daytime. When it is determined that solar noise is incident, the main controller (350) can select a second method to control the optical drive unit (120).

[0081] Specifically, the main controller (350) can generate a transmission beam L1 by modulating the laser beam output from the optical modem (110) with the communication modulator (331) of the optical drive unit (120). Additionally, the main controller (350) can calculate the satellite's orbit based on the satellite's TLE data. Next, the main controller (350) can control the telescope (310) to orient the satellite in the direction where the satellite is expected to be located at the current time according to the calculated satellite's orbit. Next, the main controller (350) can remove solar noise included in the first receiving beam by filtering the first electronic signal converted by the first sensor (323) with a first electronic filter (324) so ​​that the beacon modulation frequency band passes through, and correct the angle of the telescope (310) by controlling the gimbal (315) according to the position information of the first receiving beam from which the solar noise has been removed. Next, the main controller (350) can remove solar noise included in the third receiving beam by filtering it with a second electronic filter (328) so that the beacon modulation frequency band passes through the second electronic signal converted from the second sensor (327), and correct the angle of the second receiving beam with a steering mirror (325) according to the position information of the third receiving beam from which solar noise has been removed so that the fourth receiving beam is incident on the communication detector (220). Finally, the main controller (350) can perform optical communication by receiving the receiving beam L2 using the angle-corrected telescope (310) and radiating the transmitting beam L1.

[0082] FIG. 4 is a flowchart illustrating a satellite-to-ground optical communication method according to an embodiment of the present invention.

[0083] In step (410), the solar noise discriminator (360) measures the solar noise contained in the receiving beam L2 and can determine whether the measured solar noise is below a threshold. If the solar noise contained in the receiving beam L2 is below the threshold, the main controller (350) can perform step (420). If the solar noise contained in the receiving beam L2 is above the threshold, the main controller (350) can perform step (440).

[0084] In step (420), the solar discriminator (360) can determine whether the current time is nighttime. If the current time is nighttime, the main controller (350) can perform step (430). If the current time is daytime, the main controller (350) can perform step (440).

[0085] Step (410) and Step (420) may be performed as a single step according to the embodiment, or may be performed in the order of Step (420) -> Step (410).

[0086] In step (430), the main controller (350) can perform optical communication by controlling the optical drive unit (120) according to a first method including directional acquisition tracking.

[0087] In step (440), the main controller (350) can perform optical communication by controlling the optical drive unit (120) according to a second method using a beacon modulation frequency.

[0088] FIG. 5 is a diagram illustrating a process of communicating by tracking the direction of the phase of a satellite-to-ground optical communication method according to an embodiment of the present invention. Steps (510) to (560) of FIG. 5 may be included in step (430) of FIG. 4.

[0089] In step (510), the main controller (350) can generate a transmission beam L1 by modulating the laser beam output from the optical modem (110) with the communication modulator (331) of the optical drive unit (120).

[0090] In step (520), the main controller (350) can calculate the satellite's orbit based on the satellite's TLE data. Then, the main controller (350) can track the satellite's direction in which the satellite is expected to be located at the current time according to the calculated satellite's orbit.

[0091] In step (530), the main controller (350) can control the telescope (310) to orient the satellite direction tracked in step (520). At this time, the ground terminal device (100) for satellite-to-ground optical communication can receive a receiving beam L2 from the satellite through the telescope (310). Then, the receiving optical system (320) of the ground terminal device (100) for satellite-to-ground optical communication can split the receiving beam L2 into a first receiving beam and a second receiving beam, transmit the first receiving beam to the first sensor (323), pass the second receiving beam through a solar filter (340), split it into a third receiving beam and a fourth receiving beam, transmit the third receiving beam to the second sensor (327), and transmit the fourth receiving beam to the optical modem (110). At this time, the first sensor (323) can detect the position of the received first receiving beam and generate position information of the first receiving beam. Additionally, the second sensor (327) can detect the position of the received third receiving beam and generate position information of the third receiving beam.

[0092] In step (540), the main controller (350) can correct the angle of the telescope (310) by controlling the gimbal (315) according to the position information of the first receiving beam generated in step (530).

[0093] In step (550), the main controller (350) can correct the angle of the second receiving beam with the steering mirror (325) according to the position information of the third receiving beam generated in step (530) so that the fourth receiving beam is incident on the communication detector (220).

[0094] In step (560), the main controller (350) can receive the receiving beam L2 transmitted from the satellite after step (530) using the telescope (310) whose angle was corrected in step (540), and in step (550), transmit the fourth receiving beam to the communication detector (220) according to the corrected angle to perform optical communication.

[0095] FIG. 6 is a diagram illustrating the process of communicating using a beacon modulation frequency of a satellite-to-ground optical communication method according to an embodiment of the present invention. Steps (610) to (680) of FIG. 6 may be included in step (440) of FIG. 4.

[0096] In step (610), the main controller (350) can generate a transmission beam L1 by modulating the laser beam output from the optical modem (110) with the communication modulator (331) of the optical drive unit (120).

[0097] In step (620), the main controller (350) can calculate the satellite's orbit based on the satellite's TLE data. Then, the main controller (350) can track the satellite's direction in which the satellite is expected to be located at the current time according to the calculated satellite's orbit.

[0098] In step (630), the main controller (350) can control the telescope (310) to orient the satellite direction tracked in step (520). At this time, the ground terminal device (100) for satellite-to-ground optical communication can receive a receiving beam L2 from the satellite through the telescope (310). Then, the receiving optical system (320) of the ground terminal device (100) for satellite-to-ground optical communication can split the receiving beam L2 into a first receiving beam and a second receiving beam, transmit the first receiving beam to the first sensor (323), pass the second receiving beam through a solar filter (340), split it into a third receiving beam and a fourth receiving beam, transmit the third receiving beam to the second sensor (327), and transmit the fourth receiving beam to the optical modem (110).

[0099] In step (640), the main controller (350) can remove solar noise contained in the first receiving beam detected by the first sensor (323) by filtering the first receiving beam with a first electronic filter (324) so ​​that the beacon modulation frequency band passes through the first electronic signal converted by the first sensor (323).

[0100] In step (650), the main controller (350) can correct the angle of the telescope (310) by controlling the gimbal (315) according to the position information of the first receiving beam from which solar noise has been removed in step (640).

[0101] In step (660), the main controller (350) can remove solar noise contained in the third receiving beam detected by the second sensor (327) by filtering the third receiving beam with a second electronic filter (328) so that the beacon modulation frequency band passes through the second electronic signal converted by the second sensor (327).

[0102] In step (670), the main controller (350) can correct the angle of the second receiving beam with the steering mirror (325) according to the position information of the third receiving beam from which solar noise has been removed in step (660), so that the fourth receiving beam is incident on the communication detector (220).

[0103] In step (680), the main controller (350) can receive the receiving beam L2 transmitted from the satellite after step (630) using the angle-corrected telescope (310) in step (650), and perform optical communication by sending the fourth receiving beam to the communication detector (220) according to the angle corrected in step (670).

[0104] The present invention enables laser communication even under solar noise by overcoming the effects of solar noise in a satellite-ground laser communication link through controlling a ground terminal for satellite-ground optical communication in different ways depending on the presence or absence of solar noise.

[0105] The present invention can improve the availability and usability of a ground terminal device by reducing solar noise using a filter of a ground terminal for satellite-ground optical communication during the day, thereby enabling the use of daytime hours in satellite-ground laser communication.

[0107] Meanwhile, the satellite-to-ground optical communication device or satellite-to-ground optical communication method according to the present invention is written as a program that can be executed on a computer and can also be implemented on various recording media such as magnetic storage media, optical reading media, and digital storage media.

[0108] Implementations of the various technologies described herein may be implemented as digital electronic circuits, or as computer hardware, firmware, software, or combinations thereof. Implementations may be implemented as computer programs tangibly embodied in a computer program product, for example, a machine-readable storage device (computer-readable medium), for processing by the operation of a data processing device, e.g., a programmable processor, a computer, or a plurality of computers, or for controlling such operation. Computer programs such as the computer program(s) described above may be written in any form of programming language, including compiled or interpreted languages, and may be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. Computer programs may be deployed to be processed on one computer or a plurality of computers at one site, or distributed across a plurality of sites and interconnected by a communication network.

[0109] Processors suitable for processing computer programs include, for example, both general-purpose and special-purpose microprocessors, and any one or more processors of any type of digital computer. Generally, the processor will receive instructions and data from read-only memory or random access memory, or both. The elements of the computer may include at least one processor that executes instructions and one or more memory devices that store instructions and data. Generally, the computer may include one or more mass storage devices that store data, for example, magnetic, magneto-optical disks, or optical disks, or may be combined to receive data from these, transmit data to these, or both. Information carriers suitable for embodying computer program instructions and data include, for example, semiconductor memory devices, magnetic media such as hard disks, floppy disks, and magnetic tapes; optical media such as CD-ROMs (Compact Disk Read Only Memory) and DVDs (Digital Video Disks); magneto-optical media such as floptical disks; ROMs (Read Only Memory); RAMs (Random Access Memory); flash memory; EPROMs (Erasable Programmable ROM); EEPROMs (Electrically Erasable Programmable ROM); etc. Processors and memory may be supplemented by or included in special-purpose logic circuit organizations.

[0110] Additionally, a computer-readable medium may be any available medium accessible by a computer and may include all computer storage media.

[0111] Although this specification contains details of a number of specific embodiments, they should not be understood as limiting the scope of any invention or claimables, but rather as descriptions of features that may be characteristic of a specific embodiment of a specific invention. Specific features described in this specification in the context of individual embodiments may be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any appropriate sub-combination. Furthermore, while features may operate in a specific combination and be described as initially claimed, one or more features from the claimed combination may be excluded from the combination in some cases, and the claimed combination may be changed to a sub-combination or a variation of the sub-combination.

[0112] Likewise, although operations are depicted in the drawings in a specific order, this should not be understood as requiring that such operations be performed in that specific or sequential order depicted to obtain a desirable result, or that all depicted operations must be performed. In certain cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of the various device components of the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and devices can generally be integrated together into a single software product or packaged into multiple software products.

[0113] Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples provided to aid understanding and are not intended to limit the scope of the present invention. It is obvious to those skilled in the art that other variations based on the technical concept of the present invention are possible in addition to the embodiments disclosed herein.

Claims

Claim 1 An optical drive unit that controls the pointing angle of a telescope to track the trajectory of a satellite changing in real time, radiates a transmission beam to a satellite using the angle-controlled telescope, and receives a reception beam from said satellite; an optical modem that demodulates received communication data transmitted by a counterpart terminal in said reception beam; and a control unit that controls the optical drive unit to track the trajectory of a satellite and controls the optical modem to perform communication; wherein the optical drive unit comprises: a telescope that radiates the transmission beam to a satellite and receives a reception beam from said satellite; a gimbal that controls the pointing angle of said telescope to track the trajectory of a satellite changing in real time; and a transmitting optical system that generates a transmission beam based on a laser beam output from said optical modem and a modulation signal corresponding to the transmitted communication data and transmits it to said telescope. A ground terminal device for satellite-to-ground optical communication, comprising: a receiving optical system that adjusts the beam size of a receiving beam received by the telescope and transmits it to the optical modem; wherein the receiving optical system comprises: a first beam splitter that splits the receiving beam into a first receiving beam and a second receiving beam and transmits them in different directions; a first sensor that receives the first receiving beam and detects the position of the received first receiving beam to generate position information of the first receiving beam; a second beam splitter that splits the second receiving beam into a third receiving beam and a fourth receiving beam and transmits them in different directions; a second sensor that receives the third receiving beam and detects the position of the received third receiving beam to generate position information of the third receiving beam; a third lens that adjusts the size of the fourth receiving beam and transmits it to the optical modem; and a steering mirror that adjusts the angle of the second receiving beam transmitted to the second beam splitter so that the fourth receiving beam is transmitted to the optical modem. Claim 2 A ground terminal device for satellite-to-ground optical communication, wherein the control unit controls the optical drive unit by selecting one of a first method including direction acquisition tracking or a second method using a beacon modulation frequency. Claim 3 A ground terminal device for satellite-to-ground optical communication, wherein the control unit selects one of a first method including directional acquisition tracking or a second method using a beacon modulation frequency according to the current time or solar noise. Claim 4 In paragraph 2, the optical modem comprises: a laser that generates and outputs a laser beam of a preset wavelength band; a communication detector that converts the receiving beam into an electronic signal; and a modem that demodulates received communication data from the electronic signal, and the modem generates and outputs a modulation signal corresponding to the transmitted communication data, a ground terminal device for satellite-to-ground optical communication. Claim 5 delete Claim 6 A ground terminal device for satellite-to-ground optical communication according to claim 1, wherein the transmitting optical system comprises: a communication modulator that modulates at least one of the intensity, frequency, and phase of the laser beam according to the modulation signal or polarizes the laser beam to output a first modulated beam; a beacon modulator that modulates the intensity of the first modulated beam at a beacon modulation frequency to output a second modulated beam; and an optical amplifier that amplifies the intensity of the second modulated beam to output the transmitting beam. Claim 7 A ground terminal device for satellite-to-ground optical communication, wherein the transmitting optical system further comprises: a collimator that corrects the divergence angle of the transmitting beam so that the transmitting beam is radiated parallel to the ground; and a aiming mirror that controls the emission angle of the transmitting beam. Claim 8 delete Claim 9 A ground terminal device for satellite-to-ground optical communication, wherein the light receiving optical system further comprises: a first lens that adjusts the size of the first receiving beam and directs it to the first sensor; and a second lens that adjusts the size of the third receiving beam and directs it to the second sensor. Claim 10 A ground terminal device for satellite-to-ground optical communication according to claim 1, wherein the optical driving unit further includes a solar filter for filtering the second receiving beam, and the solar filter comprises at least one of a space filter fabricated in a pinhole shape to remove scattered light, a long wavelength transmission filter that blocks the 800 nm band of the solar spectrum and transmits only long wavelengths, and a narrow band wavelength filter that transmits only a narrow band with a laser wavelength as the center wavelength. Claim 11 A ground terminal device for satellite-to-ground optical communication according to claim 1, wherein the light receiving optical system further comprises: a first electronic filter that processes a first electronic signal in which the first receiving beam is converted into an electronic signal at the first sensor; and a second electronic filter that processes a second electronic signal in which the third receiving beam is converted into an electronic signal at the second sensor, wherein the first electronic filter and the second electronic filter each comprise at least one of a high-pass filter that blocks the solar DC band, a band-pass filter that passes only the beacon modulation frequency band, and a locking amplifier that extracts the beacon modulation frequency signal. Claim 12 In paragraph 2, the control unit comprises: a main controller that controls the operation procedure of a ground terminal device for satellite-ground optical communication according to a satellite optical communication standard or a pre-agreed operation procedure; and a solar radiation discriminator that determines whether solar radiation noise is incident, wherein the main controller controls the optical driving unit by selecting one of the first method or the second method according to the determination result of the solar radiation discriminator. Claim 13 A ground terminal device for satellite-to-ground optical communication, wherein, in claim 12, the solar photodetector determines that solar photodetector is not incident when the solar photodetector is below a threshold value or when the current time is nighttime, and the main controller controls the optical drive unit by selecting the first method when it is determined that the solar photodetector is not incident. Claim 14 In claim 13, the main controller, when the first method is selected, modulates the laser beam output from the optical modem with the communication modulator of the optical drive unit to generate the transmission beam, calculates the orbit of the satellite based on the satellite's TLE (two line element) data, controls the telescope to orient the satellite in the direction where the satellite is expected to be located at the current time according to the satellite's orbit, controls the gimbal according to the position information of the first receiving beam to correct the angle of the telescope, controls the steering mirror according to the position information of the third receiving beam to correct the angle of the second receiving beam so that the fourth receiving beam is incident on the optical modem, receives the receiving beam using the angle-corrected telescope, and performs optical communication by radiating the transmission beam, a ground terminal device for satellite-to-ground optical communication. Claim 15 A ground terminal device for satellite-to-ground optical communication, wherein, in claim 12, the solar photodetector determines that solar photodetector noise is incident when the solar photodetector noise is above a threshold value or when the current time is daytime, and the main controller controls the optical drive unit by selecting the second method when it is determined that the solar photodetector noise is incident. Claim 16 In paragraph 15, the main controller, when the second method is selected, modulates the laser beam output from the optical modem with the communication modulator of the optical drive unit to generate the transmission beam, calculates the orbit of the satellite based on the satellite's TLE data, controls the telescope to orient the satellite direction in which the satellite is expected to be located at the current time according to the satellite's orbit, filters the first receiving beam with a first electronic filter so that the beacon modulation frequency band passes through the first electronic signal converted by the first sensor to remove solar noise included in the first receiving beam, controls the gimbal according to the position information of the first receiving beam from which solar noise has been removed to correct the angle of the telescope, filters the third receiving beam with a second electronic filter so that the beacon modulation frequency band passes through the second electronic signal converted by the second sensor to remove solar noise included in the third receiving beam, controls the steering mirror according to the position information of the third receiving beam from which solar noise has been removed to correct the angle of the second receiving beam so that the fourth receiving beam is incident on the optical modem, and the angle A ground terminal device for satellite-to-ground optical communication that receives the receiving beam using a calibrated telescope and performs optical communication by radiating the transmitting beam. Claim 17 A satellite-to-ground optical communication method comprising: a step of determining whether solar noise is incident on a ground terminal device for satellite-to-ground optical communication; a step of performing optical communication by controlling an optical drive unit according to a first method including direction acquisition tracking when solar noise is not incident; and a step of performing optical communication by controlling the optical drive unit according to a second method using a beacon modulation frequency when solar noise is incident, wherein the optical drive unit radiates a transmission beam to a satellite and receives a reception beam from the satellite to perform optical communication. Claim 18 A satellite-to-ground optical communication method according to claim 17, wherein the determining step determines that solar noise is not incident if the solar noise is below a threshold value or if the current time is nighttime, and determines that solar noise is incident if the solar noise is above a threshold value or if the current time is daytime. Claim 19 In claim 17, the optical drive unit comprises: a telescope that radiates the transmission beam to a satellite and receives the reception beam from the satellite; a gimbal that controls the pointing angle of the telescope so that the telescope tracks the trajectory of the satellite changing in real time; a transmitting optical system that generates a transmission beam based on a laser and a modulation signal output from an optical modem and transmits it to the telescope; and a receiving optical system that adjusts the beam size of the reception beam received by the telescope and transmits it to a communication detector of the optical modem, wherein the receiving optical system comprises: a first beam splitter that splits the reception beam into a first reception beam and a second reception beam and transmits them in different directions; a first sensor that receives the first reception beam and detects the position of the received first reception beam to generate position information of the first reception beam; a second beam splitter that splits the second reception beam into a third reception beam and a fourth reception beam and transmits them in different directions; and a second sensor that receives the third reception beam and detects the position of the received third reception beam to generate position information of the third reception beam. A satellite-to-ground optical communication method comprising: a third lens that adjusts the size of the fourth receiving beam and causes it to be incident on the communication detector; and a steering mirror that adjusts the angle of the second receiving beam incident on the second beam splitter so that the fourth receiving beam is incident on the communication detector. Claim 20 In claim 19, the step of performing optical communication by controlling an optical drive unit according to the first method comprises: a step of generating the transmission beam by modulating a laser beam output from an optical modem with a communication modulator of the optical drive unit; a step of calculating the orbit of the satellite based on the satellite's TLE data and controlling the telescope of the optical drive unit to orient the satellite in the direction where the satellite is expected to be located at the current time according to the satellite's orbit; a step of correcting the angle of the telescope by controlling the gimbal of the optical drive unit according to the position information of the first receiving beam; a step of correcting the angle of the second receiving beam by controlling the steering mirror of the optical drive unit according to the position information of the third receiving beam so that the fourth receiving beam is incident on a communication detector; and a step of receiving the receiving beam using the angle-corrected telescope and performing optical communication by radiating the transmission beam. Claim 21 In claim 19, the step of performing optical communication by controlling the optical drive unit according to the second method comprises: when the second method is selected, the step of generating the transmission beam by modulating the laser beam output from the optical modem with the communication modulator of the optical drive unit; the step of calculating the orbit of the satellite based on the satellite's TLE data and controlling the telescope of the optical drive unit to orient the satellite direction in which the satellite is expected to be located at the current time according to the satellite's orbit; the step of removing solar noise included in the first reception beam detected by the first sensor by filtering the first reception beam with a first electronic filter so that the beacon modulation frequency band passes through the first electronic signal converted by the first sensor of the optical drive unit; the step of correcting the angle of the telescope by controlling the gimbal of the optical drive unit according to the position information of the first reception beam from which solar noise has been removed; the step of removing solar noise included in the third reception beam detected by the second sensor by filtering the third reception beam with a second electronic filter so that the beacon modulation frequency band passes through the second electronic signal converted by the second sensor of the optical drive unit; and the position information of the third reception beam from which solar noise has been removed A satellite-to-ground optical communication method comprising: a step of correcting the angle of the second receiving beam by controlling the steering mirror of the optical drive unit so that the fourth receiving beam is incident on the communication detector; and a step of receiving the receiving beam using the angle-corrected telescope and performing optical communication by radiating the transmitting beam.

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