JPH1065620A - Data optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a data optical communication system which precisely and inexpensively transmit large quantity of observed data which an observation satellite obtains to ground in short time without being affected by weather and the like. SOLUTION: Reception stations 2A and 2B are installed in a plurality of places for receiving observed data from the observation satellite 1. A center station 3 refers to weather information and the like in the respective reception station installation points and designates the reception station which can execute optical communication without clouds for long time for a communication station with the satellite 1. The reception station designated for the communication station emits laser from a laser transmitter 21A to the satellite. The satellite detects the arriving direction of laser light and transmits observed data to the direction by light. The communication station receives it and transmits to the center station 3. When optical communication is interrupted by the cloud, a data reception level drops and therefore the effect is informed to the center station 3. The center station designates one of the reception stations which can perform optical communication, executes the similar processing again and transmits/receives following data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a data optical communication system, and more particularly to a data optical communication system for transmitting and receiving observation data between an observation satellite and a ground station by an optical communication system.

[0002]

2. Description of the Related Art Data obtained by an earth observation satellite or the like is recorded in a storage device mounted on the satellite, and is collectively transmitted to the ground when the satellite comes within a range where communication with a receiving station on the ground is possible. The range in which a satellite can communicate with a receiving station on the ground does not always exist for each orbit of the satellite, and is limited only when the satellite passes near the sky above the ground station.

A satellite launched at an angle inclined with respect to the equator shifts by a fixed amount every time the satellite passes near the ground station, and after several orbits, it passes through unreachable places. After lapping for a while, it returns to the communication range again. While in communication range, all data recorded until the return must be sent to the ground, or in a recoverable satellite, all data until recovery must be stored inside the satellite.

[0004] Radio waves have a limited usable frequency bandwidth, so that a large amount of data cannot be transmitted to the ground, and there is a limit even if data compression or the like is performed. Therefore, even if a large amount of data can be collected by the sensor of the observation satellite, the amount of data that can be used is limited due to the limitation of the transmission capacity.

The current observation satellites are only passive (passive), and are basically limited to planar data. Therefore, while having the above-mentioned problems, unsatisfactory and practical data can be obtained. Was possible.

However, active in the future
When observing the distribution of snow and the distribution of aerosol three-dimensionally (by adding height information) with a laser radar (rider), which is expected as a sensor, the data amount increases dramatically, but the transmission capacity increases. Due to restrictions, it is almost impossible to drop all of them on the ground even if data compression is performed.

Optical communication, which is expected to be used as a large-capacity communication, has been put to practical use for optical communication on the ground through an optical fiber, and has been widely used. However, communication using spatial propagation is restricted by weather (visibility etc.). As a result, the laser was intensively researched shortly after its invention, but is currently only used for short-distance communication.

[0008] As an idea of optical communication from a satellite, as shown in Japanese Patent Application Laid-Open No. 5-227069, optical communication is performed between a flying object flying on a cloud and the satellite, and the received data is transmitted to the ground by radio waves. There is something to try, but this is intended for receiving signals from geostationary satellites,
It is not always appropriate for tracking rapidly changing observation satellites. In addition, it is uneconomical to fly an aircraft etc. every time a satellite returns, and there are restrictions on the use of radio waves (although considering the intended use of the present invention, all It is also possible to accumulate and transfer the data to a device on the ground after landing, so the use of radio waves is not an essential problem).

The essential problem may be limited to the economics of flying a projectile and the tracking of fast-moving observation satellites.

[0010] Since the density of the atmosphere above the sky is low and there is no aerosol or the like that is thicker than a certain degree that deteriorates the visibility, even if the visibility on the ground is deteriorated, the decay in the case of communication with the satellite is compared. Although it is very few, communication cannot be performed at all when clouds are applied.

Therefore, light is avoided as an auxiliary means in communication between the satellite and the ground, but is avoided as a main communication means from the viewpoint of line reliability.

[0012]

The first problem is that communication using radio waves that can transmit and receive data without being affected by the presence of clouds or the like has a limited transmission capacity and limits the amount of acquired data. is there.

[0013] The reason is that the transmission band is determined according to the frequency, and the transmission band is limited in radio waves having a low frequency, and that there is a restriction on the simultaneous use of the same frequency due to the limitation in directivity. In addition, many users want to use radio waves, and thus cannot secure a frequency band necessary for data transmission.

[0014] The second problem is that in optical communication in which a sufficient transmission band can be obtained, communication becomes impossible due to snow or other obstructions. The reason is that light is absorbed or scattered by snow droplets or aerosols, making communication impossible, and a high-quality line cannot be maintained in relation to the frequency of cloud formation.

[0015] The third problem is the feasibility of tracking a satellite when it is assumed that the flying object is to fly in a high altitude not affected by snow. The reason is that tracking can be performed using only satellite position data if the position of the device does not change and the attitude of the device does not change as in the case of ground installation, but the tracking mounted on the flying object The device is constantly changing its position and attitude, and it is necessary to calculate the relative relationship with the satellite while detecting this, and perform tracking.This is not technically impossible, but high-speed response and stable operation are possible. It has to be expensive because it is required. If a large window is to be opened in order to receive light from a wide range, a structural problem of the body occurs.

The fourth problem relates to economical or safe operation of the flying object. The reason is that it takes a lot of money to fly a flying object every time the satellite returns and data can be received, and due to the time it takes to return, night flight and takeoff and landing in stormy weather This is because it may be necessary to perform

An object of the present invention is to convert a large amount of observation data acquired by an observation satellite in a short time without being influenced by weather or the like.
An object of the present invention is to provide a data optical communication system capable of transmitting data accurately and inexpensively to the ground.

[0018]

SUMMARY OF THE INVENTION A data optical communication system according to the present invention has an observation satellite, a tracking function for tracking the observation satellite, receives observation data from the satellite, and is installed at different points from each other. A plurality of receiving stations, and a central station respectively connected to the plurality of receiving stations by a data link and receiving and processing data transmitted from the respective receiving stations via the data link. The station has control means for alternately specifying and controlling a station to be a communication station with the observation satellite among the plurality of receiving stations,
Each of the receiving stations has laser oscillation means for irradiating a laser beam toward the observation satellite in response to designation of a communication station from the central station, and the observation satellite detects the laser beam. It is characterized by having tracking means for controlling pointing in the direction of arrival, and transmitting means for transmitting the observation data after the pointing control.

The control means of the central station is configured to selectively designate a station to be the communication station in accordance with weather information of a receiving station installation point notified from each of the receiving stations. Wherein the receiving station, which is the communication station, further includes a unit that detects a data reception state from the observation satellite and notifies the central station, and the control unit of the central station includes the control unit, It is characterized in that it is configured to change and control the designation of the communication station according to the data reception state.

Still further, the tracking means of the observation satellite executes the pointing control again when the arrival direction of the laser beam changes, and the transmission means of the observation satellite is After the pointing control is re-executed, the transmission data is partially overlapped and retransmitted.

Receiving stations installed in various parts of the country are mounted on a tracking device with the field of view of the receiving telescope matched with the direction of the laser, and constantly track the satellite based on orbit data under computer control.

A station with the longest communication time with the satellite is selected based on weather information and visual observation at the site, and only that station emits a laser.

The satellite that receives the laser directs the optical axis of the device for performing optical communication in the direction of arrival and transmits the data to the ground. The selected receiving station that emits the laser becomes a communication station with the satellite and receives data from the satellite. The received data is transferred to the central office via the data link.

[0024] All data is 1
There is no problem as long as the station can receive the signal, but if communication becomes impossible on the way, another station at a position where communication with the satellite is possible at that time will emit a laser and take over the communication.

The satellite detects the change in the direction of arrival of the laser, redirects the axis of the transmission optical system, and partially renews the data transmitted to the ground. Send in the direction. The receiving station that has taken over the communication transfers the received data to the central office. The central office processes the data transferred from each receiving station, removes the duplicated parts, and restores the original data.

The selection and replacement of the station to be communicated with is performed by the central station in the following manner.

From each receiving station, information such as whether or not there is a cloud in the direction in which the satellite passes is transmitted to the central station.

The central station selects, in principle, the station that can communicate first among the receiving stations that are considered to be communicable, but it may also determine it in consideration of the quality and reliability of the data link line on the way. One station always selects the second and third candidates even during communication, and updates the second and third candidates according to a positional relationship that changes with time.

When the reception level of the receiving station that is communicating decreases, the receiving station that is the second candidate takes over the communication.

The method of transmitting this to the satellite and changing the pointing direction is as follows. That is, the station in communication stops laser emission. The new station fires a laser at the satellite. Then, the satellite enters the search mode when the laser beam from the communicating station stops arriving, and performs the work of detecting the laser beam that will arrive from another direction.

When a laser beam from another direction is detected, the axis of the transmission optical system is directed in that direction, and the remaining data is transmitted. At this time, some data may not be received by the first receiving station, so that a certain amount of data is redundantly transmitted.

[0032] Even if all data including the duplicated transmission has been transmitted, if communication with any of the receiving stations is possible, the reliability may be increased by retransmitting the data.

In particular, when the weather conditions are bad, it is conceivable that not all data can be transmitted within a communicable range. Therefore, it is necessary to take measures such as changing the transmission order according to the importance of the data.

An instruction to transmit data to the satellite, an instruction to transmit only important data, and the like can be made by changing the interval of emission of the high-output pulse laser from the receiving station. There is no problem with communication using radio waves without using light

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a system block diagram conceptually showing the whole system of the present invention. Referring to FIG. 1, a large number of receiving stations 2A and 2B (in the figure, only two receiving stations are shown for the sake of simplicity) installed in various parts of the country (including overseas in some cases) Tracking devices 23A and 23A that always track the satellite based on the orbit data of the satellite 1
3B, telescopes 22A and 22B attached to the tracking devices 23A and 23B, respectively,
Data links 4A and 4B are formed together with photodetectors 24A and 24B for receiving optical transmission data from the satellite 1 by A and 22B, and laser oscillators 21A and 21B for irradiating the satellite 1 with laser light. I have.

A common central station 3 is installed in the receiving stations 2A and 2B, and the central station 3 and each receiving station 2
A and 2B are connected via data links 4A and 4B, respectively, and all data received by each of the receiving stations 2A and 2B is transmitted to the central office 3.

FIG. 2 is a block diagram showing a communication-related configuration of the observation satellite 1. Referring to FIG. 2, a laser oscillator 11 for optical communication, a transmitting optical system 12, and receiving stations 2A and 2B
A tracking device 13 for detecting laser beams from the laser oscillators 21A and 21B and controlling the direction of the optical axis of the transmission optical system 12 in the direction of arrival, and receives laser beams from a receiving station for the tracking control. A four-quadrant detection type light receiving element 14a to 14d (see FIG. 8, details will be described later), an arrival direction identification circuit 15 for identifying an arrival direction of laser light based on the output of these light receiving elements 14a to 14d,
An optical modulator 16, a signal processing unit 17, a storage device 18,
And an observation sensor 19.

Next, the operation of the embodiment of the present invention will be described in detail with reference to the operation flowchart of the satellite 1 in FIG. 3 and the operation flowchart of the receiving station and the central station in FIG.

Each of the receiving stations 2A to 2C performs an operation of always pointing the device toward the observation satellite 1 based on the satellite orbit data (step S201: hereinafter, "step" is omitted). Each receiving station determines the presence or absence of a cloud in the direction of the satellite 1 by weather data or visual observation at the site (S20).
2), the central office makes a communication to the effect that a station that cannot communicate with the cloud cannot be a communication station (S203). In addition, the stations that can communicate are notified of this to the central station 3, and the central station 3 determines the receiving stations 2 that can communicate, taking into account conditions such as that they can communicate for a long time. Is determined as the communication station (S20).
4).

The specific criterion for the decision is a station which is unlikely to be interrupted by a cloud or the like, a station which can communicate with a satellite earliest, a station which is connected to a central station by a high speed and high quality data link, and the like. A station that has more superiority. Various conditions are comprehensively determined, and the most suitable station at that time is set as the communication station.

Each station determines whether or not it has been designated as a communication station (S205), and the unspecified station waits (S2).
06), the receiving station 2 determined as the communication station (the n-th station, temporarily assumed to be station A) emits a laser from the laser oscillator 21 before the observation satellite 1 enters the line of sight (S2).
07).

The divergence angle of the laser beam is widened in consideration of the error in the trajectory calculation, the tracking accuracy, and the like. Therefore, a laser with a high laser output (such as a pulse laser) is used. Since this is used for tracking on the satellite side, oscillation repetition may be slow.

The observation satellite 1 completes communication preparation before entering the line of sight (S101), determines whether or not laser light has entered the light receiving element 14 (S102). Is checked (S103). If light is received, the optical axis of the transmission optical system 12 is directed in the direction of arrival of the laser beam (S104).

One example of this method is as follows.
If d (at least three units are required or a two-dimensional position detecting element) is appropriately arranged, the ratio of the amount of light incident on each element differs depending on the direction of arrival. This utilizes the fact that the direction of arrival can be detected (calculated), and the details will be described later.

Using the tracking device 13, the optical axis of the transmission optical system 12 is kept pointing in the detected direction of arrival, and the data obtained by the sensor 19 stored in the storage device 18 is emitted as a laser beam. The data is sequentially transmitted to the light receiving station 2 (A) (S105).

In order to transmit data using the light emitted from the laser oscillator 11, the laser light is modulated using the modulator 16, but the modulator 16 is not necessarily an external modulator, and the semiconductor laser may be used. In such a case, the drive current may be modulated. Further, the modulation is not limited to analog modulation, but it is preferable that the modulation is strong against noise such as PCM and matches the type of accumulated data.

The laser beam modulated by the observation data from the satellite 1 is condensed by the telescope 22 at the receiving station 2 (A) and received by the photodetector 24 (S 208).

The received data (naturally performing demodulation etc.)
The data is transferred to the central office 3 by the data link 4 (the transfer timing is not constant as described below, so that it is omitted in the flowchart).

The transfer does not have to be performed at a high speed because real-time transfer is not always required. However, as described later, when communication becomes impossible, it is necessary to change the communication to another station, so it is necessary to transmit information on whether data has been received reliably or not in real time (S212).

There is no problem if all data can be received by the receiving station 2A. However, it is conceivable that a cloud will cover a part of the sky and communication will be impossible before all data is received. The main object of the present invention is to acquire data in such a case.

FIG. 5 is a timing chart in the case where all data can be obtained (taken off the satellite) only by the receiving station 2A. The observation satellite 1 having received the laser beam from the receiving station 2A changes the optical axis of the transmission optical system 12 by the arrival direction discriminating circuit 15 and the tracking device 13 so that the arrival direction of the laser beam, that is, the receiving station 2
It points in the direction of A and transmits observation data a to z after the tracking is locked on. If there is enough time, data is transmitted again as a spare. The receiving station 2A transfers the received data to the central office 3.

FIG. 6 shows that the receiving station 2A alone cannot completely receive the signal.
FIG. 7 is a timing chart when another station takes over reception. It is assumed that, after the receiving station 2A has reliably acquired the data up to j, the reception level has been reduced due to being blocked by clouds or the like (S20).
9).

When the reception level reduction information is sent to the central station 3, the central station 3 instructs the receiving station 2A to stop laser emission, and the receiving station 2B scheduled as the next communication station.
To laser emission. The receiving station 2A may stop emitting the laser beam by its own judgment without waiting for the instruction of the central station 3 (S212, S213).

The observation satellite 1 detects the interruption of the laser beam from the receiving station 2A and detects the arrival of the laser beam from another direction, that is, the direction of the receiving station 2B, and stops data transmission. Data is sent up to n due to the time delay during that time.

Several laser beams are received until the observation satellite 1 is directed toward the receiving station 2B and locked on. After the lock-on, the observation data is transmitted to the reception station 2B. In consideration of a reception error during switching, the transmission is performed from g, which is the data before the data j completely received by the reception station 2A (S106). To S112).

The reason why the data completely received by the receiving station 2A is determined to be j may be after the data processing in some cases, and at this time, the switching is performed only based on the decrease in the reception level as a criterion. .

It suffices if the receiving station 2B can receive all of the subsequent data. However, if the reception level decreases after receiving the data until t, the receiving station 2B emits the laser beam in accordance with the instruction of the central station 3 as before. Is stopped, and the receiving station 2C, which is the next communication station, emits a laser (in step S113, it is determined that the data transmission is completed. The receiving station performs steps S213 to S213).
220 is performed).

The observation satellite 1 similarly transmits observation data from q after locking on the receiving station 2C. If communication is possible even after the last data z has been transmitted, the same data is transmitted again as a spare. Central station 3 is each receiving station 2
A, 2B, 2C,... Process the transferred data and restore the original data.

In the above example, the data a is received from the receiving station 2A.
To j, data g to t from the receiving station 2B, and data q to z and retransmitted data from the receiving station 2C.
The original data a to z are restored from this data except for the overlapping part.

The results of detailed evaluation of specific feasibility will be described. One of the factors that can be expensive in the system of the present invention is the problem of installing a large number of receiving stations. The telescope mounted on the precision tracking device is expensive, and it is not appropriate to arrange many of them.However, even a telescope that is easily available as a commercial product keeps tracking a specific star by computer control. Since it is sufficiently possible to add the orbit data of the observation satellite to the satellite within the field of view and track it, this is used.

However, since there is a problem in tracking with extremely high precision, it is necessary to emit a laser beam at a large divergence angle. Therefore, a high-power pulse laser is used.

By spreading and emitting a high-power laser beam, the laser beam surely hits the observation satellite, and there is no problem in detecting the arrival direction of the satellite and directing the optical axis. The adoption of a method in which the satellite is captured within the beam by expanding the laser beam makes it impossible to match the center of the field of view of the telescope with the satellite direction. In order to solve this, it is necessary to increase the field stop, and a large amount of sunlight is scattered, which is disadvantageous for daytime communication. Also, the photodetector must be large according to the uncertainty of the visual field.

As a means for solving this problem,
It is conceivable to equip the observation satellite side with a light reflector such as a corner cube, and use the laser beam that has returned upon hitting it to also use precise tracking by light.

There is no particular problem because precision tracking by light can be easily performed using a four-divided photodetector called a four-quadrant detector as described later. Regarding the direction-of-arrival identification circuit 15 mounted on a satellite, a device for detecting the direction of arrival of laser light has been put to practical use in another field, and there is no particular problem except for carefully selecting components for use in outer space. There is no.

An example of a method for identifying the direction of arrival of light will be described with reference to FIGS. FIG. 7 is a diagram illustrating where the light arriving from the θ direction is collected by the lens. Assuming that the focal length of the lens is f, the focal point X is separated from the focal point O of light arriving from the axial direction by f · θ. Therefore, in order to detect a small change in the direction of arrival with high sensitivity, it is advantageous to use a lens having a focal length as long as possible. Conversely, when detecting a wide range of incoming light, a lens with a short focal length is convenient.

FIG. 8 shows a case where a "quadrant of four light detecting elements 14a to 14d as one detector", which is called a four-quadrant detector, is placed at the position of the focal point shown in FIG. The state of is shown. When O is located at the center, the light spots hitting the small detection elements 14a to 14d have the same area respectively, so that the outputs from the respective small elements are equal.

When light arrives from the θ direction and the center of the spot is at the position of X, light impinges on the small elements 14a and 14d but does not impinge on the elements 14b and 14c.
That is, only the elements 14a and 14d have outputs.
When θ is small, the light slightly hits the elements 14b and 14c, and an output is obtained although it is small. Therefore, by comparing the output of each of the small elements 14a to 14d,
The position where the light spot is located can be calculated, and the arrival direction θ can be obtained from this.

In the arrival direction discriminating circuit 15, the tracking device 13 is moved to change the position of the focused spot.
If the outputs of the small elements 14a to 14d are made equal, this optical axis is oriented in the direction of arrival of light.

Although a four-quadrant detector is used for the sake of convenience of description, a single element called a two-dimensional position detecting element may be used to indicate the position of a spot as X and Y coordinates, and a four-quadrant detector is inevitable. It is also possible to compensate for defects such as the absence of the "cross-shaped insensitive portion" and the "small spot, in which only one element is irradiated with light and the position cannot be practically detected".

Since the two-dimensional position detecting element generally has a problem that it takes a longer response time than the four-quadrant detector, each item is compared in consideration of the time response to the laser pulse that arrives only for a short time. What is necessary is just to select a suitable detection element. Considering further higher speed and higher sensitivity, it is advantageous to use a single light receiving element (photodetector). The light is split into four directions using a pyramid-shaped (polygonal pyramid) mirror, and the light is divided into four directions. Is detected by a single light receiving element, an effect similar to that of a four-quadrant detector can be obtained, and it may be used.

Due to the limitation of the size of the photodetector and the limitation of the resolution, etc., when focusing is performed with a lens having a long focal length f and an attempt is made to increase the accuracy, the tracking range is narrowed. There is also a problem that sufficient tracking accuracy cannot be obtained when trying to perform tracking over a wider range.Therefore, instead of using only a single lens and detection element combination, a tracking range using a lens with a short focal length is used. It is also necessary to take measures such as tracking the approximate position with a wide object and then using a lens with a long focal length to accurately direct the beam toward the receiving station 2.

The data links 4A and 4B have no problem if a high-speed optical fiber line is constructed, but it is difficult to request all the receiving stations located in various parts of the country. However, it is not necessary to collect the data once dropped on the ground at a high speed, and it is only necessary to be able to transmit and receive the information of the decrease in the reception level and the command of the laser emission and the stop. In addition, since it is sufficient that this information can be transmitted before the next laser emission, no particularly high speed is required.

It is desirable that the receiving station be installed in a place that is not blocked by buildings or mountains, and that a large site is also a necessary condition. The use of data from observation satellites equipped with laser radar that require three-dimensional data is based on the fact that the field of meteorology is the mainstream and that people other than those directly involved are always observing clouds. It may be good to install at weather stations.

If the amount of data acquired by the observation satellite 1 increases, it is conceivable that not all data can be transmitted at the time of passing over the sky even if the method of the present invention is used depending on weather conditions. It is also conceivable to take measures such as assigning priority to important data and transmitting the data first, or reducing the overlapping part of data with a low priority.

[0076]

The first effect is that a large amount of measurement data acquired by the observation satellite can be transmitted to the ground in a short time.
The reason is that, unlike radio waves, optical communication having a wide transmission band is used.

The second effect is that data can be received without being affected by the weather despite optical communication, and the reliability of the line is high. The reason is that if there is no cloud in the line of sight with any satellite above any of the receiving stations installed all over the country, data can be received using that station, and communication is not necessarily performed while all data is acquired. That is, there is no need to continue.

The third effect is that the operation cost can be reduced as compared with the method of receiving data on a cloud by appropriately flying an aircraft or the like. The reason is that the receiving station can be constructed relatively inexpensively and uses a conventional observing facility such as a weather station as an installation location. As a result of the low cost, a large number of stations can be installed, and data can be received at any point.

[Brief description of the drawings]

FIG. 1 is a diagram conceptually showing a system of the present invention.

FIG. 2 is a block diagram showing a configuration of an optical communication related portion of the observation satellite.

FIG. 3 is a flowchart showing the operation of the observation satellite.

FIG. 4 is a flowchart showing operations of the receiving station and the central station.

FIG. 5 is a timing chart showing data transmission / reception of the system of the present invention in time, and is a timing chart when one station can receive all data.

FIG. 6 is a timing chart showing data transmission / reception of the system of the present invention in time, in a case where communication stations cannot be received by one station and communication stations are successively changed.

FIG. 7 is a diagram simply illustrating a principle of identifying a direction of arrival of light, and is a diagram illustrating a position where light having a different incident direction is collected when collected by a lens;

FIG. 8 shows a light beam collected on a light receiving surface of a four-quadrant photodetector.
FIG. 4 is a diagram illustrating a positional relationship of a converging spot according to an arrival direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Observation satellite 2A, 2B Receiving station 3 Central station 4A, 4B Delink 11, 21, A, 21B Laser oscillator 12 Transmission optical system 13, 23A, 23B Tracking device 14a-14d Light receiving element 15 Arrival direction discriminating circuit 16 Modulator 17 Signal processing Unit 18 Storage device 19 Sensor 22A, 22B Telescope 24A, 24B Photodetector

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[Procedure amendment]

[Submission date] August 26, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

However, active in the future
When the distribution of clouds and the distribution of aerosols are observed three-dimensionally (by adding height information) with a laser radar (lider) expected as a sensor, the data amount increases dramatically, but the transmission capacity increases. Dropping all this on the ground from restrictions
Even if data compression is performed, it becomes almost impossible.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

A second problem, in the optical communication transmission band can take enough, is to become impossible to communicate with clouds or other obstructions. The reason for this is that light is absorbed or scattered by water droplets or aerosol of clouds , making communication impossible, and a high-quality line cannot be maintained in relation to the frequency of occurrence of clouds.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

[0015] The third problem is the feasibility of tracking the satellite when the flying object is assumed to fly in a high sky unaffected by clouds . The reason is that tracking can be performed using only satellite position data if the position of the device does not change and the attitude of the device does not change as in the case of ground installation, but the tracking mounted on the flying object The device is constantly changing its position and attitude, and it is necessary to calculate the relative relationship with the satellite while detecting this, and perform tracking.This is not technically impossible, but high-speed response and stable operation are possible. It has to be expensive because it is required. If a large window is to be opened in order to receive light from a wide range, a structural problem of the body occurs.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04B 10/26 10/14 10/04 10/06 17/00

Claims (5)

[Claims] 1. An observation satellite, a plurality of receiving stations having a tracking function for tracking the observation satellite, receiving observation data from the satellite, and installed at different points from each other, and a plurality of these receiving stations And a central station respectively connected by a data link and receiving and processing data transmitted from the respective receiving stations via the data link, wherein the central station is the observation satellite among a plurality of the receiving stations. Control means for alternatively designating a station to be a communication station with, and each of the receiving stations emits laser light toward the observation satellite in response to designation of a communication station from the central station. The observation satellite has a laser oscillation unit for irradiating, and the observation satellite has a tracking unit for detecting the laser beam and performing pointing control in an arrival direction thereof, and a transmission unit for transmitting the observation data after the pointing control. Characteristic data optical communication system. 2. The control means of the central station is configured to selectively designate a station to be the communication station in accordance with weather information of a receiving station installation point notified from each of the receiving stations. The data optical communication system according to claim 1, wherein: 3. The receiving station, which is the communication station, further includes a unit that detects a data reception state from the observation satellite and notifies the central station of the data reception state. 3. The data optical communication system according to claim 2, wherein a designation of a communication station is changed and controlled according to a reception state. 4. The data optical communication system according to claim 3, wherein the tracking means of the observation satellite executes the pointing control again when the arrival direction of the laser beam changes. 5. The data optical communication system according to claim 4, wherein said transmission means of said observation satellite retransmits data after partially re-executing said pointing control by partially overlapping transmission data. .