LEO SATELLITE, LEO SATELLITE SYSTEM, AND CONTROL METHOD

an LEO satellite includes a light projecting element that emits emission light to another LEO satellite, an optical telescope, an optical phased array, a light receiving element that receives incident light from the other LEO satellite, a distance measurement unit that measures a distance to the other LEO satellite based on at least one of the emission light and the incident light, and a control unit. The control unit captures the other LEO satellites by scanning emission light using the optical telescope and receives incident light from the other LEO satellites for the other LEO satellites on the same orbital plane, and captures the other LEO satellites by scanning emission light using the optical phased array and receives incident light from the other LEO satellites for the other LEO satellites on different orbital planes.

TECHNICAL FIELD

The present disclosure relates to a low earth orbit (LEO) satellite, an LEO satellite system, and a control method.

BACKGROUND ART

In recent years, application technologies related to LEO satellites configuring an LEO satellite constellation have been developed. For example, Patent Literature 1 discloses a technology for measuring a distance between LEO satellites by wirelessly transmitting and receiving a distance measurement signal between the LEO satellites.

CITATION LIST

Patent Literature

Patent Literature 1: International Patent Publication No. 2013/036328

SUMMARY OF INVENTION

Technical Problem

However, the technology disclosed in Patent Literature 1 has a problem that it is necessary to add a distance measuring device to the LEO satellite because a distance measuring signal is wirelessly transmitted and received between the LEO satellites.

Therefore, an object of the present disclosure is to solve the above-described problems and to provide an LEO satellite, an LEO satellite system, and a control method capable of measuring a distance between LEO satellites without adding a distance measuring device to the LEO satellite.

Solution to Problem

A low earth orbit (LEO) satellite according to an aspect is an LEO satellite that configures an LEO satellite constellation, the LEO satellite including:a light projecting element that emits laser light as emission light to another LEO satellite configuring the LEO satellite constellation;an optical telescope;an optical phased array;a light receiving element that receives laser light from the other LEO satellite as incident light;a distance measurement unit that measures a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control unit that controls the light projecting element and the light receiving element, in whichthe control unitcauses the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andcauses the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

A low earth orbit (LEO) satellite system according to an aspect is an LEO satellite includinga plurality of LEO satellites that configures an LEO satellite constellation, in whicheach of the plurality of LEO satellites includes:a light projecting element that emits laser light as emission light to another LEO satellite configuring the LEO satellite constellation;an optical telescope;an optical phased array;a light receiving element that receives laser light from the other LEO satellite as incident light;a distance measurement unit that measures a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control unit that controls the light projecting element and the light receiving element, andthe control unitcauses the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andcauses the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

A control method according to an aspect is a method of controlling a low earth orbit (LEO) satellite that configures an LEO satellite constellation, the method including:a step of emitting laser light as emission light to another LEO satellite configuring the LEO satellite constellation by a light projecting element;a step of receiving laser light from the other LEO satellite as incident light by a light receiving element;a step of measuring a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control step of controlling the light projecting element and the light receiving element, in whichin the control step,the light receiving element is caused to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andthe light receiving element is caused to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

Advantageous Effects of Invention

According to the above aspect, it is possible to provide the LEO satellite, the LEO satellite system, and the control method capable of measuring the distance between the LEO satellites without adding a distance measuring device to the LEO satellite.

EXAMPLE EMBODIMENT

Example embodiments of the present disclosure are described below with reference to the drawings. Note that in the description and drawings described below, omission and simplification are made as appropriate, for clarity of description. Furthermore, in each of the drawings described below, the same elements are denoted by the same reference signs, and a duplicate description is omitted as necessary.

EXAMPLE EMBODIMENTS

<Configuration of Example Embodiment>

First, an overall configuration example of an LEO satellite system according to the present example embodiment will be described with reference toFIG.1. As illustrated inFIG.1, the LEO satellite system according to the present example embodiment includes LEO satellites10-1to10-5configuring an LEO satellite constellation. Note that, inFIG.1, it is assumed that the LEO satellites10-1to10-4move on the same orbital plane, and the LEO satellite10-5moves on an orbital plane different from the orbital planes of the LEO satellites10-1to10-4.

Hereinafter, in a case where the LEO satellites10-1to10-5are referred to without particular distinction, they may be simply referred to as the “LEO satellite10”.

Furthermore, inFIG.1, five LEO satellites10-1to10-5are provided, but the number of LEO satellites10may be two or more.

In the present example embodiment, as will be described later, distributed multiple input multiple output (MIMO) can be realized by utilizing antennas (not illustrated) provided in the LEO satellites10-1to10-5. Therefore, each of the LEO satellites10-1to10-5can perform distributed MIMO communication with a terminal21, an aircraft22, a parabolic antenna23, and the like.

Next, a configuration example of the LEO satellite10according to the present example embodiment will be described with reference toFIG.2. Note thatFIG.2illustrates a configuration example of the LEO satellite10-1, but the other LEO satellites10-2to10-5also have the same configuration as the LEO satellite10-1.

As illustrated inFIG.2, the LEO satellite10-1according to the present example embodiment includes a light projecting element11, an optical telescope12, an optical phased array13, a light receiving element14, a distance measurement unit15, and a control unit16. Note that, inFIG.2, only components related to distance measurement in the LEO satellite10-1are illustrated, and other components are not illustrated.

The light projecting element11emits laser light as emission light to the other LEO satellites10configuring the LEO satellite constellation.

The optical telescope12is used to capture other LEO satellites10on the same orbital plane as LEO satellites10-1.

The optical phased array13is used to capture other LEO satellites10on a different orbital plane than from that of the LEO satellites10-1.

The control unit16controls the light projecting element11and the light receiving element14, and captures another LEO satellite10using the optical telescope12or the optical phased array13.

Note that details of the optical telescope12, the optical phased array13, and the control unit16will be described later.

The light receiving element14receives laser light from another LEO satellite10as incident light. The incident light is, for example, laser light (reflected light) obtained by reflecting emission light emitted from the light projecting element11by another LEO satellite10, laser light emitted from the light projecting element11of another LEO satellite10, or the like.

The distance measurement unit15measures a distance from the LEO satellite10-1to another LEO satellite10based on at least one of the emission light emitted from the light projecting element11and the incident light received by the light receiving element14.

<Operation of Example Embodiment>

Next, the operation of the LEO satellite system according to the present example embodiment will be described.

First, an example of a distance measurement method in the distance measurement unit15will be described. The distance measurement unit15may measure the distance using an arbitrary distance measurement method among the distance measurement methods described below. Hereinafter, a case where the distance measurement unit15of the LEO satellite10-1measures the distance to the LEO satellite10-2on the same orbital plane will be described as an example. However, the distance measurement method described below is also applicable to a case where the distance measurement unit15of the LEO satellite10-1measures the distance to the LEO satellite10-5of a different orbital plane.

(1) Reflective Type Distance Measurement Method

First, a reflective type distance measurement method will be described.

In the reflective type distance measurement method, as illustrated inFIG.3, the LEO satellite10-1emits emission light to the LEO satellite10-2, and receives reflected light of the emission light reflected by the LEO satellite10-2. Then, the distance measurement unit15of the LEO satellite10-1measures the distance from the LEO satellite10-1to the LEO satellite10-2based on at least one of the emission light and the reflected light.

Examples of the reflective type distance measurement method include a pulse propagation method, a phase difference distance method, and a triangular distance measurement method. Each distance measurement method will be described below.

(1-1) Pulse Propagation Method

First, a pulse propagation method will be described with reference toFIG.4.

As illustrated inFIG.4, in the pulse propagation method, the emission light is a rectangular wave with a constant pulse width. The distance measurement unit15of the LEO satellite10-1measures a time t since the pulse is emitted as the emission light and then the pulse is received as the reflected light. Then, the distance measurement unit15of the LEO satellite10-1calculates a distance L from the LEO satellite10-1to the LEO satellite10-2by the following mathematical formula using a light speed c.

Therefore, in the pulse propagation method, the LEO satellite10-1needs a clock for measuring the time t. A highly accurate atomic clock is suitable as the clock of the LEO satellite10-1.

(1-2) Phase Difference Distance Method

Next, the phase difference distance method will be described with reference toFIG.5.

As illustrated inFIG.5, in the phase difference distance method, the emission light is a sine wave. The phase difference between the emission light and the reflected light changes according to the distance L from the LEO satellite10-1to the LEO satellite10-2. Therefore, the distance measurement unit15of the LEO satellite10-1calculates the distance L based on the phase difference between the emission light and the reflected light.

(1-3) Triangular Distance Measurement Method

Next, a triangular distance measurement method will be described with reference toFIG.6.

As illustrated inFIG.6, the reflected light reflected by the LEO satellite10-2is received by the light receiving element14of the LEO satellite10-1. At this time, the position on the light receiving element14where the reflected light is received changes according to the distance L from the LEO satellite10-1to the LEO satellite10-2. In the example ofFIG.5, the distance L is different between when the LEO satellite10-2is at a position A and when it is at a position B, and as a result, the position on the light receiving element14where the reflected light is received also changes. Therefore, the distance measurement unit15of the LEO satellite10-1calculates the distance L based on the position on the light receiving element14at which the reflected light is received.

(2) Bidirectional Transmission/Reception Type Distance Measurement Method

Next, a bidirectional transmission/reception type distance measurement method will be described.

In the bidirectional transmission/reception type distance measurement method, as illustrated inFIG.7, the light projecting element11of the LEO satellite10-1emits emission light, and the light receiving element14of the LEO satellite10-2receives the emission light. In addition, the light projecting element11of the LEO satellite10-2also emits the emission light, and the light receiving element14of the LEO satellite10-1receives the emission light.

At this time, the emission time is included in the emission light emitted by the light projecting element11of the LEO satellite10-2. Then, the distance measurement unit15of the LEO satellite10-1calculates the distance L from the LEO satellite10-1to the LEO satellite10-2based on the emission time at which the light projecting element11of the LEO satellite10-2emits emission light and the reception time at which the light receiving element14of the LEO satellite10-1receives the emission light.

Similarly, the emission time is also included in the emission light emitted by the light projecting element11of the LEO satellite10-1. Then, the distance measurement unit15of the LEO satellite10-2calculates the distance L based on the emission time at which the light projecting element11of the LEO satellite10-1emits the emission light and the light receiving time at which the light receiving element14of the LEO satellite10-2receives the emission light.

Therefore, in the bidirectional transmission/reception type distance measurement method, the LEO satellites10-1and10-2need clocks. A highly accurate atomic clock is suitable as the clock of the LEO satellites10-1and10-2.

As described above, the distance measurement unit15of the LEO satellite10-1measures the distance from the LEO satellite10-1to another LEO satellite using any of the above-described distance measurement methods. The same applies to the distance measurement units15of the other LEO satellites10-2to10-5.

However, in any of the above-described distance measurement methods, in order for the distance measurement unit15to perform distance measurement, it is necessary to capture another LEO satellite10.

Here, as illustrated inFIG.8, for example, in a case where the distance measurement unit15of the LEO satellite10-1measures the distance to the LEO satellite10-2on the same orbital plane, the relative velocity of the LEO satellite10-2with respect to the LEO satellite10-1decreases. Therefore, the control unit16of the LEO satellite10-1can capture the LEO satellite10-2by scanning the mechanical emission light. Therefore, in this case, the control unit16of the LEO satellite10-1captures the LEO satellite10-2by scanning the emission light emitted from the light projecting element11using the optical telescope12, and causes the light receiving element14to receive the incident light from the LEO satellite10-2.

On the other hand, as illustrated inFIG.9, for example, in a case where the distance measurement unit15of the LEO satellite10-1measures the distance to the LEO satellite10-5on a different orbital plane, the relative velocity of the LEO satellite10-5with respect to the LEO satellite10-1increases. Therefore, even if the control unit16of the LEO satellite10-1uses the optical telescope12, the optical telescope12has a problem in tracking speed, and thus, cannot capture the LEO satellite10-5. For this reason, in order to capture the LEO satellite10-5, scanning with electronic emission light is required. Therefore, in this case, the control unit16of the LEO satellite10-1captures the LEO satellite10-5by scanning the emission light using the optical phased array13, and causes the light receiving element14to receive the incident light from the LEO satellite10-5.

Note that, in a case where the control unit16captures another LEO satellite10using the optical phased array13, it is preferable to capture another LEO satellite10in the vicinity of the intersection of the orbital plane. This makes it possible to compensate for the low gain of the antenna included in the LEO satellite10.

In addition, in a case where the control unit16captures another LEO satellite10using the optical phased array13, it is preferable to capture another LEO satellite10on an orbital plane having different altitudes in an orbit having an altitude of 300 km to 2000 km.

In addition, the optical phased array13is preferably realized using an electro-optic polymer.

In addition, the optical phased array13is preferably realized using an optical waveguide based on a silicon microfabrication technology.

Next, with reference toFIG.10, an example of an operation flow in a case where the distance to another LEO satellite10is measured in the LEO satellite10according to the present example embodiment will be described. Here, a case where the LEO satellite10-1measures a distance to another LEO satellite10will be described as an example.

As illustrated inFIG.10, the control unit16of the LEO satellite10-1captures the other LEO satellite10by scanning the emission light emitted from the light projecting element11(step S101), and causes the light receiving element14to receive the captured incident light from the other LEO satellite10(Step S102). At this time, in a case where the other LEO satellite10is the LEO satellite10on the same orbital plane, the control unit16performs capture using the optical telescope12, and in a case where the other LEO satellite10is the LEO satellite10on a different orbital plane, the control unit performs capture using the optical phased array13.

Thereafter, the distance measurement unit15of the LEO satellite10-1measures the distance from the LEO satellite10-1to another LEO satellite10based on at least one of the emission light and the incident light (step S103). Note that, as the distance measurement method in the distance measurement unit15, any distance measurement method may be used from among the reflection type distance measurement method and the bidirectional transmission/reception type distance measurement method described above.

<Effects of Example Embodiment>

As described above, according to the present example embodiment, the control unit16captures the other LEO satellites10by scanning the emission light emitted from the light projecting element11, and causes the light receiving element14to receive the incident light from the other LEO satellites10. At this time, in a case where the other LEO satellite10is the LEO satellite10on the same orbital plane, the control unit16performs capture using the optical telescope12, and in a case where the other LEO satellite10is the LEO satellite on a different orbital plane, the control unit performs capture using the optical phased array13. Then, the distance measurement unit15measures a distance to another LEO satellite10based on at least one of the emission light and the incident light.

Furthermore, in order to implement distributed MIMO by utilizing the antennas included in the plurality of LEO satellites10configuring the LEO satellite constellation, for example, in order to combine signals received by different antennas, it is necessary to know the distance between these antennas. In this regard, according to the present example embodiment, since the distance between the LEO satellites10can be measured, the distance between the antennas provided in the different LEO satellites10can be measured as the distance between the LEO satellites10. Thus, distributed MIMO can be implemented by utilizing antennas included in the plurality of LEO satellites10.

<Hardware Configuration of LEO Satellite According to Example Embodiment>

Next, a hardware configuration example of a computer90that implements processing of a part or all of the LEO satellites10according to the above-described example embodiment will be described with reference toFIG.11. The computer90illustrated inFIG.11includes a processor91and a memory92.

The processor91may be, for example a microprocessor, a micro processing unit (MPU), or a central processing unit (CPU). The processor91may include a plurality of processors.

The memory92is constituted by a combination of a volatile memory and a nonvolatile memory. The memory92may include a storage located away from the processor91. In this case, the processor91may access the memory92through an input/output (I/O) interface (not illustrated).

In addition, some components (for example, the distance measurement unit15, the control unit16, and the like) in the LEO satellite10according to the above-described example embodiments may be implemented by the processor91reading and executing a program stored in the memory92.

In addition, the program described above may be stored by using various types of non-transitory computer readable media to be supplied to a computer. The non-transitory computer-readable media include various types of tangible storage media. Examples of the non-transitory computer readable medium include a magnetic recording medium (for example, a flexible disk, a magnetic tape, or a hard disk drive), a magneto-optical recording medium (for example, a magneto-optical disk), a compact disc-ROM (CD-ROM), a CD-recordable (CD-R), a CD-rewritable (CD-R/W), and a semiconductor memory (for example, a mask ROM, a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, or a RAM. Furthermore, the programs may be supplied to the computer by various types of transitory computer readable media. Examples of the transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line such as electric wires and optical fibers or a radio communication line.

Although the present disclosure has been described with reference to the example embodiments, the present disclosure is not limited to the example embodiments described above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure.

For example, the LEO satellite10generally includes an encoder. Therefore, the LEO satellite10may detect the angle of the emission light using an encoder and measure the altitude of the LEO satellite10based on the angle of the emission light. Furthermore, the LEO satellite10may utilize the measured altitude for correction of the orbit or the like.

Furthermore, the LEO satellite10may include a millimeter wave sensor in a band of 30 GHz to 300 GHz as the distance measurement unit15. Here, a configuration example of the millimeter wave sensor17in the LEO satellite10according to another example embodiment will be described with reference toFIG.12. Note thatFIG.12illustrates a configuration example of the millimeter wave sensor17in the LEO satellite10-1, but the millimeter wave sensors17in the other LEO satellites10-2to10-5have a similar configuration. The millimeter wave sensor17illustrated inFIG.12is a millimeter wave sensor in a band of 30 GHz to 300 GHz including a synthesizer171, a TX antenna172, an RX antenna173, a mixer174, and a calculation unit175. The calculation unit175is realized by, for example, a processor such as a CPU. In a case of measuring the distance from LEO satellite10-1to LEO satellite10-2, the millimeter wave sensor17operates as follows. That is, the TX antenna172transmits a transmission wave to the LEO satellite10-2, and the RX antenna173receives a reflected wave of the transmission wave reflected by the LEO satellite10-2. The mixer174mixes the transmission wave and the reception wave to generate an intermediate frequency (IF) signal. The calculation unit175measures the distance from the LEO satellite10-1to the LEO satellite10-2based on the IF signal. Note that the millimeter wave sensor17is preferably realized by using a 300 GHz band antenna. As a result, since the millimeter wave sensor17can be reduced in size and weight, the price of the LEO satellite10can be reduced.

Furthermore, part or the entirety of the example embodiments described above can also be described as described in the following supplementary notes, but is not limited to the following.

A low earth orbit (LEO) satellite that configures an LEO satellite constellation, the LEO satellite comprising:a light projecting element configured to emit laser light as emission light to another LEO satellite configuring the LEO satellite constellation;an optical telescope;an optical phased array;a light receiving element configured to receive laser light from the other LEO satellite as incident light;a distance measurement unit configured to measure a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control unit configured to control the light projecting element and the light receiving element, whereinthe control unit is configured tocause the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andcause the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

The LEO satellite according to Supplementary Note 1, further comprising: an atomic clock, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a time from emission of the emission light to reception of the incident light by a pulse propagation method.

The LEO satellite according to Supplementary Note 1, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a phase difference between the emission light and the incident light by a phase difference distance method.

The LEO satellite according to Supplementary Note 1, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a position on the light receiving element at which the incident light is received by a triangular distance measurement method.

The LEO satellite according to Supplementary Note 1, further comprising an atomic clock, whereinthe incident light is laser light emitted from the other LEO satellite and including emission time information, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a time from when the incident light is emitted from the other LEO satellite to when the incident light is received.

The LEO satellite according to any one of Supplementary Notes 1 to 5, wherein in a case of capturing the other LEO satellite using the optical phased array, the control unit is configured to capture the other LEO satellite on an orbital plane at an altitude different from that of the LEO satellite in an orbit at an altitude of 300 km to 2000 km.

The LEO satellite according to any one of Supplementary Notes 1 to 5, wherein in a case of capturing the other LEO satellite using the optical phased array, the control unit is configured to capture the other LEO satellite near an intersection of an orbital plane.

The LEO satellite according to any one of Supplementary Notes 1 to 7, wherein the optical phased array is realized by using an electro-optic polymer.

The LEO satellite according to any one of Supplementary Notes 1 to 7, wherein the optical phased array is realized by using an optical waveguide based on a silicon microfabrication technology.

The LEO satellite according to any one of Supplementary Notes 1 to 9, further comprising an encoder configured to detect an angle of the emission light,wherein an altitude of the LEO satellite is measured based on the angle of the emission light.

A low earth orbit (LEO) satellite system comprisinga plurality of LEO satellites that configures an LEO satellite constellation, whereineach of the plurality of the LEO satellites includes:a light projecting element configured to emit laser light as emission light to another LEO satellite configuring the LEO satellite constellation;an optical telescope;an optical phased array;a light receiving element configured to receive laser light from the other LEO satellite as incident light;a distance measurement unit configured to measure a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control unit configured to control the light projecting element and the light receiving element, andthe control unit is configured tocause the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andcause the light receiving element to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

The LEO satellite system according to Supplementary Note 11, further comprising an atomic clock, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a time from emission of the emission light to reception of the incident light by a pulse propagation method.

The LEO satellite system according to Supplementary Note 11, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a phase difference between the emission light and the incident light by a phase difference distance method.

The LEO satellite system according to Supplementary Note 11, whereinthe incident light is laser light that is the emission light reflected by the other LEO satellite, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a position on the light receiving element at which the incident light is received by a triangular distance measurement method.

The LEO satellite system according to Supplementary Note 11, further comprising an atomic clock, whereinthe incident light is laser light emitted from the other LEO satellite and including emission time information, andthe distance measurement unit is configured to measure a distance from the LEO satellite to the other LEO satellite based on a time from when the incident light is emitted from the other LEO satellite to when the incident light is received.

The LEO satellite system according to any one of Supplementary Notes 11 to 15, wherein in a case of capturing the other LEO satellite using the optical phased array, the control unit is configured to capture the other LEO satellite on an orbital plane at an altitude different from that of the LEO satellite in an orbit at an altitude of 300 km to 2000 km.

The LEO satellite system according to any one of Supplementary Notes 11 to 15, wherein in a case of capturing the other LEO satellite using the optical phased array, the control unit is configured to capture the other LEO satellite near an intersection of an orbital plane.

The LEO satellite system according to any one of Supplementary Notes 11 to 17, wherein the optical phased array is realized by using an electro-optic polymer.

The LEO satellite system according to any one of Supplementary Notes 11 to 17, wherein the optical phased array is realized by using an optical waveguide based on a silicon microfabrication technology.

The LEO satellite system according to any one of Supplementary Notes 11 to 19, further comprising an encoder configured to detect an angle of the emission light,wherein an altitude of the LEO satellite is measured based on the angle of the emission light.

A method of controlling a low earth orbit (LEO) satellite that configures an LEO satellite constellation, the method comprising:a step of emitting laser light as emission light to another LEO satellite configuring the LEO satellite constellation by a light projecting element;a step of receiving laser light from the other LEO satellite as incident light by a light receiving element;a step of measuring a distance from the LEO satellite to the other LEO satellite based on at least one of the emission light and the incident light; anda control step of controlling the light projecting element and the light receiving element, whereinin the control step,the light receiving element is caused to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical telescope for the other LEO satellite on the same orbital plane as the LEO satellite, andthe light receiving element is caused to receive the incident light from the other LEO satellite by capturing the other LEO satellite by scanning the emission light emitted from the light projecting element using the optical phased array for the other LEO satellite on an orbital plane different from the LEO satellite.

This application claims priority based on Japanese Patent Application No. 2021-053786 filed on Mar. 26, 2021, the entire disclosure of which is incorporated herein.

REFERENCE SIGNS LIST