JP7051145B1 - Optical ground station distributed placement evaluation system, evaluation device and optical ground station distributed placement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical ground station distributed arrangement evaluation system, an evaluation device and an optical ground station distributed arrangement method using satellite image data and ground observation data.
An optical ground station distributed arrangement evaluation system according to an embodiment of the present invention includes a low-rise cloud analysis device, a high-rise cloud analysis device, and an evaluation device. The low-level cloud analyzer extracts low-level cloud cover characteristics related to the amount of clouds at each of the plurality of ground observation points from past meteorological data groups observed at the plurality of ground observation points. The high cloud cover analyzer extracts high cloud cover characteristics related to the amount of clouds at the coordinates corresponding to each point of the plurality of ground observation points from the past meteorological data group observed by the meteorological satellite. The evaluation device selects a combination of points where the correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic at the plurality of ground observation points is low.
[Selection diagram] Fig. 3

Description

The present invention relates to an optical ground station distributed arrangement evaluation system, an evaluation device, and an optical ground station distributed arrangement method.

For ground equipment that is affected by the weather, a place with good weather conditions is generally selected as a candidate site for installation. In the field of radio wave communication, there are calculation of rainfall utilization rate according to rainfall, rainfall data of each region, and radio wave attenuation theory. If you want a service by radio communication between space and ground, these theories determine the line establishment and station distribution from the viewpoint of rainfall.

On the other hand, in the field of optical communication, the weather conditions are different from those of radio wave communication, and the place where weight is placed on cloud cover, wind speed, seeing, dust (yellow sand, volcanic ash, etc.), humidity, salt damage, etc. is determined. In optical communication, as with radio communication, ground infrastructure lines (power supply, existence of NW (network)) are taken into consideration, and instead of finding only one place as in astronomical observation, a combination of multiple ground stations is used. Search for a combination of places to increase the utilization rate.

In space-ground optical communication, clouds significantly attenuate free space optical communication (FSOC) signals. Therefore, if a cloud exists in the transmission section of the laser, the laser is blocked and communication is not established. For this reason, a station dispersion technology (site diversity) that disperses a plurality of optical ground stations in places where the annual cloud occupancy rate is uncorrelated is required. In other words, it is important to consider the spatial range that can be installed from a geographical point of view, and to achieve high utilization rate by a group of multiple optical ground stations for global satellite tracking operation instead of a single optical ground station. Is.

For example, Patent Document 1 discloses a renewable energy network optimization tool for finding an optimum ground station using a cloud of satellite images.
Further, Non-Patent Document 1 discloses a method of selecting a candidate site from the viewpoint of the average cloud cover based on past ground-based cloud cover data, obtaining a cloud cover correlation value between the selected candidate sites, and analyzing the combination of the candidate sites. Has been done.

US Patent Specification No. 9536021

Yuki Ueda, Tatsuya Mukai and Yoshihisa Takayama .: Studies on site diversity to mitigate cloud blockage in satellite-ground optical communications by long term ground meteorological observation data, Proc. 37h AIAA International Communications Satellite Systems Conference (ICSSC-2019), 29-31 Oct. 2019, Okinawa, Japan.

The optimum placement of optical ground stations needs to be determined from the statistics of past meteorological data. As meteorological data, there are satellite image data and ground observation data. However, cloud discrimination in satellite images has the problem that it is difficult to observe low-rise clouds in winter. On the other hand, in the ground observation data, there is a limit to the altitude at which clouds can be visually discriminated, and the higher the altitude, the more difficult it is to observe.

In view of the above circumstances, an object of the present invention is to provide an optical ground station distributed arrangement evaluation system, an evaluation device, and an optical ground station distributed arrangement method using satellite image data and ground observation data.

In order to achieve the above object, the optical ground station distributed arrangement evaluation system according to one embodiment of the present invention includes a low-rise cloud analyzer, a high-rise cloud analyzer, and an evaluation device.
The low-level cloud analyzer extracts low-level cloud cover characteristics related to the amount of clouds at each of the plurality of ground observation points from past meteorological data groups observed at the plurality of ground observation points.
The high cloud cover analyzer extracts high cloud cover characteristics related to the amount of clouds at the coordinates corresponding to each point of the plurality of ground observation points from the past meteorological data group observed by the meteorological satellite.
The evaluation device selects a combination of points where the correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic at the plurality of ground observation points is low.

The optical ground station dispersion evaluation system analyzes the cloud cover by combining the past data of low-rise observation (ground) and high-rise observation (satellite), and mutually evaluates the past data of low-rise clouds and high-rise clouds from both directions. It is possible to optimize the distributed arrangement of ground stations.

The evaluation device calculates the correlation coefficient of the cloud cover at an arbitrary distance between two points at the plurality of ground observation points based on the low cloud cover characteristic and the high cloud cover characteristic, and the correlation coefficient becomes 0 or less. It may be configured to extract a combination of a plurality of two points.

The low-rise cloud cover characteristic and the high-rise cloud cover characteristic may include the time rate of the designated cloud cover with respect to the total time of the designated years period at each point of the plurality of ground observation points.
In this case, the evaluation device is configured to select a set having a time rate of the designated cloud amount of a predetermined value or more from the combination of the plurality of extracted two points.

Alternatively, the low cloud cover characteristic and the high cloud cover characteristic include the time rate of the designated cloud cover with respect to the total time of the designated years period at each point of the plurality of ground stations, and the evaluation device includes the time ratio of the designated cloud cover of the plurality of extracted points. From the combination, a plurality of combinations of three or more optical ground stations having a time rate of the designated cloud amount of a predetermined value or more may be extracted.

The evaluation device may be configured to weight the low-rise cloud cover characteristic and the high-rise cloud cover characteristic at each of the points by environmental factors at each of the plurality of ground observation points.

The environmental factors may include parameters related to at least one of wind speed, seeing, yellow sand, volcanic ash, humidity, salt content, sulfuric acid concentration, freezing, dew condensation and snowfall.

The high cloud analyzer has an observation area processing unit that redefines the analysis space so that the meteorological data observed by the meteorological satellite becomes equivalent to the observed area of the meteorological data observed at the ground observation point. May be good.

The evaluation device according to one embodiment of the present invention includes a calculation unit.
The calculation unit was observed on a meteorological satellite with low-level cloud cover characteristics related to the amount of clouds at each point of the plurality of ground observation points extracted from the past meteorological data group observed at the plurality of ground observation points. Based on the high cloud cover characteristics related to the amount of clouds at the coordinates corresponding to each point of the plurality of ground observation points extracted from the past meteorological data group, the low cloud cover characteristics and the high layer at the plurality of ground observation points. Select a combination of points that have a low correlation with cloud cover characteristics.

The optical ground station distributed arrangement method according to one embodiment of the present invention is
The low-level cloud cover characteristics related to the cloud cover at each of the multiple ground stations were extracted from the past meteorological data groups observed at multiple ground stations.
From the past meteorological data group observed by the meteorological satellite, the high cloud cover characteristics related to the cloud cover at the coordinates corresponding to each point of the plurality of ground stations are extracted.
A combination of points having a low correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic at the plurality of ground observation points is selected.

In the step of selecting a combination of points having a low correlation between the low-level cloud cover characteristics and the high-level cloud cover characteristics at the plurality of ground observation points, wind speed, seeing, yellow sand, volcanic ash, and humidity at each point of the plurality of ground observation points, The low cloud cover and high cloud cover characteristics at each of the points may be weighted by environmental factors including parameters related to at least one of salt, seesight concentration, freezing, dew condensation and snowfall.

According to the present invention, since the combination of points having a low correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic is selected, it is possible to optimize the distributed arrangement of the optical ground stations.

It is explanatory drawing of the space optical communication system which performs optical communication (satellite communication) between an optical ground station and a spacecraft. It is a conceptual diagram explaining optical site diversity. It is a block diagram which shows the optical ground station distributed arrangement evaluation system which concerns on one Embodiment of this invention. It is a figure which shows an example of the correlation map of the cloud cover of the distance between two points. It is a figure explaining the redefinition method of a satellite observation area. It is a flowchart which shows an example of the processing procedure executed in the evaluation apparatus in the said optical ground station distributed arrangement evaluation system. It is a figure which shows an example of the list created in the said evaluation apparatus. It is a figure which shows an example of the installation condition and the requirement. It is a list which shows the group of the combination of the candidate values of a plurality of stations created in the said evaluation apparatus. It is explanatory drawing which shows the example of the distributed arrangement of the optical ground station to a plurality of candidate sites.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Optical ground station]
FIG. 1 is an explanatory diagram of a space optical communication system 100 that performs optical communication (satellite communication) between the optical ground station G and the spacecraft S.

The optical ground station G is a space optical communication device that performs optical space transmission with the spacecraft S. The optical ground station G includes a telescope 10. The telescope 10 constitutes a receiving unit that receives the downlink (second laser beam L2) transmitted from the spacecraft S. Further, the telescope 10 is configured as a transmission unit that transmits an uplink (first laser beam L1) for increasing the direction of the downlink (second laser beam L2) transmitted from the spacecraft S with respect to the optical ground station G. You may.

The first laser beam L1 functions as guided light for emitting the downlink of the spacecraft S toward the optical ground station G. The first laser beam L1 and the second laser beam L2 may be a continuous laser or a pulse laser. The first laser beam L1 and the second laser beam L2 are typically infrared light, and the wavelength thereof is, for example, the 1550 nm band or the 1064 nm band.

The telescope 10 is mounted on a base 11 installed on the ground. The base 11 has an adjustment mechanism 11a for adjusting the attitude of the telephoto station 10, and the telephoto station 10 is supported by the base 11 so as to be able to track the spacecraft S. The base 11 controls the direction and / or elevation angle of the optical axis of the telescope 10 so as to track the spacecraft S according to the forecast value. The predicted value is the space coordinate of the spacecraft S calculated from the orbit of the spacecraft S, and is the first laser beam L1 or the second laser beam L2 of the space transmission path from the installation location of the base 11 to the spacecraft S. The refractive index at the wavelength of the above may be taken into consideration.

The aperture of the telescope 10 is not particularly limited, and is, for example, 30 cm to 10 m. The opening of the telescope 10 is not limited to a single number, and may be a plurality of openings. The telescope 10 has a signal processing unit (not shown) that converts the focused second laser beam L2 into an electric signal and performs predetermined signal processing such as analysis of received information. Further, the optical ground station G has a signal generation unit (not shown) that modulates and amplifies a transmission signal for transmitting the first laser beam L1 from the transmission unit 20 described later.

The optical ground station G is not limited to the example of being fixedly installed on the ground, and may be mounted on a moving body such as a vehicle, a ship, or an aircraft. Further, the ground station G may be connected to a communication body such as a gateway, a ground communication network installed on the ground, a vehicle, a ship, an aircraft, or the like. In this case, the gateway, the terrestrial communication network, the communication body, and the like transmit and receive optical signals to and from the spacecraft S via the ground station G.

The spacecraft S typically means a structure having a communication function capable of moving in outer space, such as an artificial satellite or a space station. Artificial satellites include geostationary orbits (GEO: Geostationary Earth Orbit), as well as low earth orbit (LEO) and medium earth orbit (MEO), regardless of the rotation period of the earth. Furthermore, it includes artificial satellites that fly in deep space. That is, the altitude of the spacecraft S from the ground surface is not particularly limited. The artificial satellite is typically a meteorological satellite, a search satellite, a communication satellite, or the like, but may be launched for any purpose.

The optical ground station G further includes a transmission unit 20, a seeing monitor 31, a light receiving intensity monitor 32, a beam monitor 33, a control unit 40, and the like.
The transmission unit 20 emits the first laser beam L1 transmitted toward the spacecraft S. The seeing monitor 31 detects the state of the atmosphere on the propagation path of the second laser beam L2 based on the second laser beam L2 transmitted from the spacecraft S. The light receiving intensity monitor 32 detects the light receiving intensity of the second laser beam L2. The beam monitor 33 detects the emission direction of the first laser beam L1. The control unit 40 controls the direction and elevation angle of the optical axis of the telescope 10 so that the spacecraft S can be tracked according to the predicted value, and also controls the transmission unit 20 based on the outputs of the seeing monitor 31, the light receiving intensity monitor 32, and the beam monitor 33. Control.

By attaching the transmission unit 20 to the outer peripheral portion of the telescope 10, the transmission unit 20 is configured to be integrally movable with the telescope 10 with respect to the base 11. The optical axis of the first laser beam L1 in the transmission unit 20 is installed in parallel with the optical axis of the telescope 10.

(Distributed arrangement of optical ground stations)
In space-ground optical communication, clouds significantly attenuate free-space optical communication (FSOC) signals. Therefore, if a cloud exists in the transmission section of the laser, the laser is blocked and communication is not established. For this reason, a station dispersion technology (site diversity) that disperses a plurality of optical ground stations in places where the annual cloud occupancy rate is uncorrelated is required. In other words, it is important to consider the spatial range that can be installed from a geographical point of view, and to achieve high utilization rate by a group of multiple optical ground stations for global satellite tracking operation instead of a single optical ground station. Is.

FIG. 2 is a conceptual diagram of optical site diversity in Japan. The optical ground stations G as shown in FIG. 1 are installed at a plurality of points in Japan, and in the illustrated example, the first optical ground station G1 and the second optical ground station are located at predetermined points in Honshu, Hokkaido, and Kyushu. G2 and the third optical ground station G3 are installed respectively. Each optical ground station G1, G2, G3 has data storages D1, D2, D3 for storing data received from the spacecraft S, respectively, and the received data stored in the data storages D1 to D3 is sent to the management center DC. It is configured to be transmittable.

The management center DC is installed in any area in Japan or in any optical ground stations G1 to G3, and plans and executes the operation of each optical ground stations D1 to D3. The management center DC determines the optical ground station that communicates with the spacecraft S according to the amount of clouds above the observation points where the optical ground stations G1 to G3 are installed. For example, when the first optical ground station G1 is blocked from communicating with the spacecraft S (Pass-1) by the cloud C1, the second optical ground station G2 or the third optical ground station G3 communicates with the spacecraft S. Communicate (Pass-2 or Pass-3). In this way, by switching the optical ground station that communicates with the spacecraft S according to the change in the amount of clouds in the sky at each observation point, it is possible to continue the communication with the spacecraft S.

In order to construct a network with multiple optical ground stations and perform stable communication with the spacecraft S while avoiding communication interruption due to clouds as much as possible, it is necessary to optimize the distributed arrangement of each optical ground station. .. Typically, a place with good weather conditions is selected as a candidate site for each optical ground station. Statistics of past meteorological data are generally used as the judgment material. As meteorological data, there are satellite image data and ground observation data.

However, there is a problem that it is difficult to observe low-rise clouds in winter in the cloud discrimination of satellite images. On the other hand, in the ground observation data, there is a limit to the altitude at which clouds can be visually discriminated, and the higher the altitude, the more difficult it is to observe. Moreover, since the satellite image data and the ground observation data differ not only in the observation altitude but also in the observation area, the spatial resolution differs. Therefore, comprehensive analysis and evaluation of space is required (Problem 1: Comprehensive spatial analysis and evaluation).
In addition, a comprehensive analysis and evaluation of the amount of clouds covering the target area over multiple years is required, but the amount of data is extremely large, and automatic processing is required after matching the spatial resolution of both data as much as possible. Here, for a plurality of years, for example, 10 years or more is desirable (Problem 2: Multivariate information analysis).
Assuming long-term operation, installation conditions other than clouds will be subdivided more than conventional ground stations for radio communication. As described later, the installation conditions include environmental factors such as cloud cover, wind speed, seeing, yellow sand, volcanic ash, humidity, salinity, sulfuric acid gas concentration, freezing / condensation, and snowfall. For optical communication, a method of achieving an annual operating rate by arranging a network with a group of stations distributed over a wide area is important for satellite tracking. A device for clarifying the conditions necessary for this optical communication and determining the station arrangement by the weighting thereof has not been completed (Problem 3: Condition and weighting process).

(Outline of the invention)
In order to solve these problems, the optical ground station distributed arrangement evaluation system of the present embodiment combines the past data of low-rise observation (ground) and high-rise observation (satellite) at the time of cloud cover analysis. Since all upper clouds cannot be observed by ground observation and clouds near the surface of the earth cannot be discriminated by satellites such as in winter, these data will be evaluated comprehensively.
Specifically, the cloud cover at the candidate point is analyzed for about 10 years from both the low-rise observation and the high-rise observation, and the correlation coefficient of the cloud cover at the distance between each point is obtained. At this time, there is a difference in temporal resolution and spatial resolution between low-rise observations (eg, at an altitude of 18 km, 725858.7 km ² , every 3 hours) and high-rise observations (eg, 16 km ² , every hour), but time is required to grasp the tendency. In order to grasp the tendency of the amount of clouds at the same point from both low-rise observation and high-rise observation from the viewpoint of spatial resolution, the analysis space is re-analyzed so that the 4 km mesh of the satellite is equivalent to the ground observation area. Define and analyze.
Then, the items of other installation conditions (environmental factors) such as wind speed, seeing, dust (yellow sand, volcanic ash, etc.), humidity, salt damage, etc. are weighted and managed for the identified place, and the cloud cover is correlated with each other. Extract multiple places to be searched with priority given to the weighting of installation conditions (environmental factors). Furthermore, the combination is plotted in coordinates on a map, the total sunny time when the conditions are met, etc. are calculated, and the expected operating rate as a whole is evaluated.

Hereinafter, the details of the optical ground station distributed arrangement system of the present embodiment will be described.

[Optical ground station distributed placement evaluation system]
FIG. 3 is a block diagram showing an optical ground station distributed arrangement evaluation system 200 according to an embodiment of the present invention. The optical ground station distributed placement evaluation system 200 is composed of a single computer or a plurality of computers.
The optical ground station distributed arrangement evaluation system 200 of the present embodiment includes a low-rise cloud analysis device 210, a high-rise cloud analysis device 220, and an evaluation device 230.
The optical ground station distributed arrangement evaluation system 200 may be configured by a single device or may be configured by a plurality of devices.

(Low cloud analyzer)
The low-level cloud analyzer 210 extracts low-level cloud cover characteristics related to the amount of clouds at each of the plurality of ground observation points from the past meteorological data groups observed at the plurality of ground observation points.

For example, Japan consists of four large islands (ie Hokkaido, Honshu, Shikoku, Kyushu) and many other islands surrounded by territorial waters defined by the waters of Japan. These areas provide the basic geographical area where the optical ground station G is installed to form the domestic site diversity. Since these areas include undeveloped land of lifelines (transportation, power transmission lines, networks, etc.) and designated land used for defense, land that cannot be used from a geopolitical point of view is excluded. Will be done.

In the present embodiment, the low-level cloud analysis device 210 has a low-layer cloud amount capture processing unit 211, a low-layer cloud amount analysis unit 212, and a low-layer cloud correlation map creation unit 213.

The low-level cloud cover capture processing unit 211 acquires meteorological data groups of each ground-based observation point in Japan from the ground-based observation database 251. The ground-based observation database 251 stores meteorological data observed at a plurality of ground-based meteorological stations installed in various parts of the country. These meteorological data are observed, for example, every 3 hours, and the observation range is 72588.7 km ² at an altitude of 18 km, for example. The low-level cloud cover capture processing unit 211 acquires meteorological data for the past several years (for example, 10 years) of each ground observation point from the ground observation database 251.

The low-rise cloud cover analysis unit 212 analyzes the meteorological data at each ground-based observation point captured by the low-rise cloud cover capture processing unit 211, and extracts the low-rise cloud cover characteristics at each ground-based observation point. The low-level cloud cover characteristics are typically the average annual cloud cover, the time of the designated cloud cover, or the time of the designated cloud cover from the ground observation data observed at multiple candidate sites in the domestic area where the optical ground station G can be installed. Includes rates (the rate of sunny weather and the rate of designated cloud cover will be described later). The average cloud cover x _ave is calculated by, for example, the following equation (1).

式（１）において、ｎは、地上観測点のデータ数、ｘiは観測データである。

In equation (1), n is the number of data at the ground observation point, and xi is the observation data.

The low-rise cloud correlation map creation unit 213 creates a correlation map showing the correlation between the average cloud cover (of low-rise clouds) at each ground observation point extracted by the low-rise cloud cover analysis unit 212 and the distance at each location in a specific area. do.

FIG. 4 shows an example of the correlation map. As shown in FIG. 4, the correlation map shows the correlation coefficient r of each cloud amount at a distance between arbitrary two points (candidate positions) at a plurality of ground observation points. The correlation coefficient r is calculated by, for example, the following equation (2).

式（２）において、ｘとｙはそれぞれの候補位置、ｓ_xyはｘとｙの共分散、ｓ_xはｘの標準偏差、ｓ_yはｙの標準偏差、ｎはデータの総数、ｘ_iとｙ_iはそれぞれ候補地ｘとｙの雲量データ、ｘ_aveとｙ_aveはそれぞれ候補地ｘとｙの平均雲量である。

In equation (2), x and y are candidate positions, s _xy is the covariance of x and y, s _x is the standard deviation of x, sy is the standard deviation of _y , n is the total number of data, x _i and y _i is the cloud amount data of the candidate sites x and y, respectively, and x _ave and y _ave are the average cloud amounts of the candidate sites x and y, respectively.

The correlation coefficient r is a value in the range of -1 or more and 1 or less. The closer r is to 1, the higher the correlation (higher positive correlation), and the closer r is to -1, the lower the correlation (inverse correlation is). There is a high negative correlation). When r = 0, it means no correlation. In the example of FIG. 4, the points B to J indicate points that are distant from the point A in order. Typically, the correlation coefficient r of the cloud cover at the distance between two points shows a large value (positive value) as the distance between the two points is short, and a small value (negative value) as the distance between the two points is far. show.

(Altostratus cloud analyzer)
The altostratus cloud analyzer 220 extracts the cloud cover characteristics related to the cloud cover at the coordinates corresponding to each point of the plurality of ground observation points from the past meteorological data group observed by the meteorological satellite. In the present embodiment, the altostratus cloud analysis device 220 includes an altostratus cloud extraction processing unit 221, an observation area processing unit 222, an altostratus cloud cover amount analysis unit 223, and an altostratus cloud correlation map creation unit 224.

The altostratus cloud extraction processing unit 221 acquires a group of meteorological data (satellite data) at ground-based observation points in Japan from the satellite observation database 252. The satellite observation database 252 stores, for example, cloud image data observed by a geostationary meteorological satellite (GMS). These cloud image data are observed every hour, for example, and the data range determined from the spatial resolution is 16 km ² . Then, the altostratus cloud extraction processing unit 221 extracts altostratus cloud image data for the past several years (for example, 10 years) of each ground observation point from the satellite observation database 252.

Here, the high-rise cloud extraction processing unit 221 uses satellite data having the same coordinates as the cloud data of each ground-based observation point (coordinates matching each ground-based observation point) captured by the low-rise cloud cover amount acquisition processing unit 211. This is because there is a difference in cloud observation altitude between the cloud data at the ground observation point and the satellite data.

The observation area processing unit 222 uses the image data of the 4 km mesh extracted by the high-rise cloud extraction processing unit 221 in order to grasp the tendency of the cloud amount at the same point from the ground observation data and the satellite image data from the viewpoint of spatial resolution. Redefine the analysis space for image data so that it is equivalent to the ground-based observation area.

For example, as shown in Fig. 5, the radius of the earth is R [km], the observation altitude of clouds is h [km], and the radius and area of the circle (observation range) centered on the observation point on the ground surface (however, the bottom surface is Excludes) and latitudes are r ₀ [km], S [km ² ] and θ ₀ [deg], respectively.
The observation area processing unit 222 sets the observation area S corresponding to the observation altitude h on the ground as the cloud analysis range on the coordinates on the satellite side. As a result, the spatial resolution between the ground observation data and the satellite data becomes equivalent. The time axis is averaged in the designated target period according to the observation cycle of each data. As a result, the time resolution between the two data becomes equivalent.

ここで、Ｒ＝６４００ｋｍとすると、ｈ＝１８ｋｍの場合、θ_０＝１．４９５９ｒａｄ、ｒ_０＝４８０．３ｋｍ、Ｓ＝７２５８５８．７ｋｍ^２となる。 As shown in FIG. 5, R, r ₀ , h, S and θ ₀ satisfy the relationship of the following equations (3) to (5).

Here, assuming that R = 6400 km, when h = 18 km, θ ₀ = 1.4959 rad, r ₀ = 480.3 km, and S = 725858.7 km ² .

The high cloud cover analysis unit 223 analyzes the meteorological data on the coordinates corresponding to each ground observation point processed by the observation area processing unit 222, and extracts the high cloud cover characteristics on the coordinates. The high-rise cloud cover characteristic typically refers to the annual average cloud cover of high-rise clouds on the coordinates. The average cloud cover is calculated by the above equation (2).

The altostratus cloud correlation map creation unit 224 creates a correlation map showing the correlation between the average cloud cover (of altostratus clouds) on each coordinate extracted by the altostratus cloud cover analysis unit 223 and the distance at each location in a specific area. (See FIG. 4).

(Evaluation device)
The evaluation device 230 is an operation for selecting a combination of points having a low correlation between the low cloud cover characteristics at the plurality of ground observation points calculated by the low cloud analysis device 210 and the high cloud cover characteristics calculated by the high cloud cover 220. It has a unit 231.
As a result, while satellite observation data can supplement the weakness of high cloud observation difficulty, which is a problem in ground observation, ground observation data can supplement the weakness of low cloud observation difficulty in winter, which is a problem in satellite observation. Therefore, it is possible to comprehensively evaluate the amount of low-rise clouds and high-rise clouds at the same point on the ground.

FIG. 6 is a flowchart showing an example of a processing procedure executed by the evaluation device 230 (calculation unit 231). Hereinafter, the details of the evaluation device 230 will be described together with an operation example of the optical ground station distributed arrangement evaluation system 200.

(1) Geographical space definition The evaluation device 230 first designates a target geographical space (national land) and a position (coordinates), which are candidate sites for installing the optical ground station G (step 101).
Here, the city name or region name in Japan is specified as the target geographical space, and the latitude and longitude of the candidate site are specified as the coordinates indicating the position. The coordinates of each designated candidate site are instructed from the evaluation device 230 to the low cloud analyzer 210 and the high cloud analyzer 220, and the low cloud analyzer 210 and the high cloud analyzer 220 are the areas to which each designated candidate site belongs. The low-level cloud cover characteristics and high-level cloud cover characteristics of the above-ground observation points are extracted.

(2) Cloud cover / time rate analysis Next, the evaluation device 230 calculates the sunny time rate for the designated years period of the designated coordinates (candidate site), or the designated cloud cover and its time rate (step 102).

The designated number of years is 10 years here, but of course, it is not limited to this, and it may be a period shorter than 10 years or a period longer than 10 years. The longer the specified period, the more reliable cloud cover analysis becomes possible. In view of recent climate change, the analysis may be performed by weighting the meteorological data of the last few years.

The sunny time rate is the time rate of each point that is completely sunny with respect to the total time.
On the other hand, the designated cloud cover means a cloud cover designated from a multi-step cloud cover preset according to the cloud cover. The number of stages of cloud cover is not particularly limited, and for example, it can be evaluated in 11 stages from 0 (fine) to 10 (completely cloudy). The time rate of the designated cloud cover is the time rate of each point with respect to the total time of the designated cloud cover. For example, when the designated cloud cover is "3", the time rate is calculated using data with a cloud cover of 3 or less (data corresponding to cloud covers 0 to 3).

The evaluation device 230 instructs the low-rise cloud analyzer 210 and the high-rise cloud analyzer 220 to calculate the sunny time rate or the designated cloud amount and the time rate for the designated number of years. The low-rise cloud analyzer 210 and the high-rise cloud analyzer 220 calculate the sunny time rate or the time rate of the designated cloud amount for the specified number of years based on the instruction content from the evaluation device 230, and based on the calculation result, the low-rise cloud and the high-rise cloud analyzer 220. Create a correlation map for altostratus clouds (see Fig. 4).

(3) Correlation coefficient analysis Subsequently, the evaluation device 230 uses the low-rise cloud correlation map created by the low-rise cloud analyzer 210 and the high-rise cloud correlation map created by the high-rise cloud analyzer 220 to obtain low-rise clouds and high-rise clouds. The correlation coefficient (r) of the cloud amount at the distance between two arbitrary points including the cloud is calculated for the plurality of sets between the two points (step 103).

The plurality of two-point distances mean, for example, between two points between points A and B (A / B), between two points between points A and C (A / C), and the like (see FIG. 4). If there is a difference between the correlation coefficient on the low-rise cloud side and the correlation coefficient on the high-rise cloud side with respect to the correlation coefficient of the amount of clouds at a common distance between two points, the value with the lower correlation is adopted. When a value with a high correlation (positive value) appears in the low-rise or high-rise cloud cover, the place is excluded, and a combination of candidate sites having a low correlation (negative value) is always extracted.

That is, the evaluation device 230 mutually compares the correlation coefficient based on the low-rise cloud correlation map and the correlation coefficient based on the high-rise cloud correlation map between two specific points (for example, A / B), and these. Of these, the value with the lower correlation (the value with the smaller correlation coefficient) is adopted, and if both correlation coefficients have the same value, that value is adopted.
Perform the same operation for all other two points (A / C, A / D, ..., B / C, B / D, ..., etc.), and based on these, the distance between each two points. Create a new correlation map of cloud cover.

(4) Calculation of a set of cloud cover / time rate and correlation coefficient Next, the evaluation device 230 uses the low-rise cloud cover characteristics and the high-rise cloud cover characteristics to determine the phase relationship between the cloud cover at any distance between two points at a plurality of ground observation points. A combination of a plurality of two points whose number (r) is equal to or less than a predetermined threshold value is extracted (step 104).
The threshold value is preferably a value having a low correlation (a value with a small r), for example, in the vicinity of 0, more preferably a value less than 0 (negative value) of 0 to -1.
In the present embodiment, the threshold value is 0, and a combination of a plurality of two points having a correlation coefficient (r) of 0 or less (0 or a negative value) is extracted.

As a result, it is possible to list a set in which the correlation coefficient between the cloud cover condition (cloud cover, time rate) at each point and the cloud cover at the distance between each point is small, and it is possible to grasp the regional characteristics of the cloud cover. An example of the list is shown in FIG. In the list of FIG. 7, combinations between two points having a correlation coefficient (r) of 0 or less are listed. In the combination between the two points listed, the operating rates (Availability) X1, X2, ... When the optical ground station G is installed at the two points are described together as a percentage. The operating rate typically shows a larger value as the correlation coefficient becomes smaller.
The list shown in FIG. 7 is output from the evaluation device 230 to the output device 240. The output device 240 is not particularly limited, and examples thereof include an external device such as a display device, a printing device, and a computer.

Here, the operating rate is the ratio of the number of days satisfying the cloud cover condition to the specified period days required for the operation of the optical ground station.
(Number of days that satisfy the cloud cover condition / Number of specified period days) x 100 (%)
It is represented by.
In addition, the operating rate when operating at three points (for example, points A, B, and C) is
(Number of days that satisfy the cloud cover conditions at points A, B, and C / Number of designated period days) x 100 (%)
It is represented by.

(5) Judgment of reaching the target operating rate Next, the evaluation device 230 uses the evaluation device 230 to have a clear sky time rate or a designated cloud cover time rate of a predetermined value or more among the combinations between the two points having the correlation coefficient (r) of 0 or less. Search for pairs (step 105).
The above-mentioned sunny time rate or the time rate of the designated cloud cover is equivalent to the operating rate of the optical ground station. Therefore, as the predetermined value, for example, a value of 90% or more is adopted. As a result, it is possible to extract a combination of candidate sites for installing the optical ground station G that can realize the desired operating rate.

As described above, the purpose of establishing site diversity (distributed arrangement of optical ground stations) is to realize a high operating rate (for example, 99% or more) by a group of a plurality of optical ground stations. For that purpose, it is ideal to select a place with as many sunny days as possible as a candidate site for the optical ground station. On the other hand, the more candidate sites there are, the higher the occupancy rate will be, but the lower the economic efficiency. Therefore, in order to reduce the number of stations and improve economic efficiency, even if some cloud cover characteristics are recognized, the correlation coefficient (r) of the cloud cover in the distance between candidate sites is small, and the value is close to 0 or less. It is necessary to search for and configure the network. Therefore, when constructing a network with economic efficiency as the main viewpoint, it is preferable to search for candidate sites in the range where the value of the cloud cover correlation coefficient (r) between candidate sites is less than 0 (0 to -1). ..
If a combination of candidate sites satisfying the correlation coefficient (r) less than 0 cannot be extracted, for example, a candidate site whose correlation coefficient (r) value is in the vicinity of 0 within a range where economic efficiency is allowed to decrease. Combinations may also be listed as options. The “near 0” means, for example, a value in the range of −0.2 to +0.2 or −0.1 to +0.1.

(6) Derivation of the final set (filtering) by the weighting coefficient of the installation condition (environmental factor)
When there is a set whose determination is "Yes" in step 105, the evaluation device 230 is preset for the two candidate sites for the set between two points where the time rate of the sunny weather or the time rate of the designated cloud cover is equal to or more than a predetermined value. Weighting is weighted for each installation condition (environmental factor), and the set that satisfies the installation condition is derived as the final set (step 106).

Installation conditions (environmental factors) are determined according to the geographical conditions of each candidate site. FIG. 8 shows an example of the installation conditions and the requirements for each installation condition for the optical ground station. Installation conditions include Cloud amount, Wind speed, Seeing, Yellow sand, Volcanic ash, Humidity, Salinity, and Sulfuric acid gas. , Freezing, Condensation, Snow amount and other environmental factors. The evaluation device 230 uses parameters related to at least one of these environmental factors as installation conditions.

It is desirable that the amount of cloud cover is small because it causes a factor that blocks optical communication between space and the ground. The wind speed is closely related to seeing, so a smaller wind speed is desirable. Yellow sand and volcanic ash affect visibility, so less is desirable. Humidity, salt, sulfuric acid gas, freezing and dew condensation affect the durability of the equipment of the optical ground station, so it is desirable that they are all low or low. The amount of snowfall affects the accessibility to the optical ground station, so it is preferable that the amount of snowfall is small.

These installation conditions (environmental factors) are unique parameters related to the regional characteristics of each candidate site, and are stored in the database 250 in advance for each candidate site. The evaluation device 230 filters the set of the two candidate sites extracted in step 105 by individually weighting the above installation conditions, and derives a combination of candidate sites that satisfies the requirements of these installation conditions as the final set. do. The weighting coefficient weighted as an installation condition is not particularly limited, and an arbitrary coefficient that can exclude candidate sites that do not satisfy the requirements by filtering can be set.

(7) Search processing On the other hand, when the determination is "No" in step 105 (when there is no set of "Yes" for the determination), the evaluation device 230 has the correlation coefficient (r) of the cloud amount at the distance between each of the above two points. Is a set in which is 0 or less, the time rate of the same contact point is calculated, and a set that reaches the target operating rate at a plurality of stations is searched for (step 107). In the present embodiment, from a combination of a plurality of two points whose correlation coefficient (r) is 0 or less, a combination of three or more points of optical ground stations that reach the target operating rate (the time rate of the designated cloud amount is a predetermined value or more). A combination of three or more optical ground stations) is extracted.

This process is performed by adding more candidate sites and arranging three or more optical ground stations G when there is no set with a clear sky time rate or a specified cloud cover time rate of a predetermined value or more when there are only two candidate sites. The purpose is to achieve the target utilization rate. Here, while increasing the number of candidate sites one by one, a combination of three or more candidate sites that reach the target occupancy rate is searched for. “The same contact point” refers to a set in which any one of the candidate sites constituting the two points is common, and an example thereof is shown in FIG.

FIG. 9 is a list showing a group of combinations of candidate values of three or more stations having a correlation coefficient (r) of 0 or less. Here, a total of 10 groups are shown with the candidate sites (A / F / I, B / G / A, ...) Between the three points as one group. This forms a line or triangular topology connecting the three candidate sites, as shown in FIG. 10, when the three candidate sites A, F, and I are node A, node F, and node I, respectively. For example, each node represents a large coastal area and island on the Pacific side, is less cloudy throughout the year, tends to be sunny, and is rated to correspond to the small average cloud cover known from daytime data. ..

The evaluation device 230 searches again for a set of each group shown in FIG. 9 in which the time rate of fine weather or the time rate of the designated cloud cover is equal to or greater than a predetermined value. As a result, if the corresponding group exists, the above-mentioned filtering process is executed again, and the final set of the group satisfying the requirements of the installation conditions as the candidate site for the installation of the optical ground station G is derived (step 108).

As described above, according to the present embodiment, since the evaluation device 230 for selecting the combination of the points where the correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic at a plurality of ground observation points is low is provided, the low-rise observation (ground) By combining past data from high-rise observations (satellite) to analyze cloud cover, mutual evaluation of past data from low-rise clouds and high-rise clouds from both directions, and filtering by installation conditions (environmental factors), distributed arrangement of optical ground stations Can be optimized.

Further, according to the present embodiment, as a selection condition for the candidate site, not only the time rate of fine weather in the designated number of years at the candidate site but also the time rate of the designated cloud amount subdivided into a plurality of stages is adopted. , It becomes easier to search for a candidate site that matches the target occupancy rate according to the weather characteristics of the area. In particular, it is fully applicable to the distributed arrangement evaluation of optical ground stations in areas having cloud cover characteristics that do not apply to both sunny and cloudy weather.

Moreover, conventionally, for an operator who handles an optical system, it has been necessary to search from a huge amount of data where to arrange an optical ground station to realize efficient and economical operation, whereas in this embodiment. According to the report, it is possible to automatically select and evaluate a candidate site between two points with a low cloud cover correlation between the two points from a huge amount of meteorological data on low-rise clouds and high-rise clouds. It will be possible to significantly improve the efficiency of study work such as planning updates.

Further, according to the present embodiment, since it is possible to narrow down the candidate sites in consideration of the installation conditions (environmental factors) derived from the geographical characteristics of each candidate site, not only the cloud cover characteristics but also the operational efficiency and durability , Can evaluate candidate sites for optical ground stations comprehensively, including accessibility.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made.

For example, in the above embodiment, the distributed arrangement evaluation for newly installing the optical ground station has been described, but the present invention is not limited to this, and the existing optical ground station is modified or added to the existing optical ground station. The present invention can also be applied to the selection of candidate sites for newly installed optical ground stations.

Further, in the above embodiment, the optimum arrangement evaluation method of the optical ground station in the space optical communication system has been described, but the optical ground station is not limited to the optical communication with the spacecraft. For example, a system (satellite ranging network, space debris observation network) that measures the distance between a spacecraft and a ground station with the earth's atmosphere sandwiched between transmission lines, and between the spacecraft and power receiving equipment with the earth's atmosphere sandwiched between transmission lines. The present invention can also be applied to an optical ground station in a solar power generation satellite system (optical energy transmission) or the like that transmits energy by a laser. Further, the optical ground station is not limited to optical communication with a spacecraft and distance measurement, and may be a ground station equipped with a power receiving facility for photovoltaic power generation.

200 ... Optical ground station distributed arrangement system 210 ... Low-layer cloud analysis device 211 ... Low-layer cloud cover capture processing unit 212 ... Low-level cloud cover analysis unit 213 ... Low-level cloud correlation map creation unit 220 ... High-level cloud analysis device 221 ... High-level cloud extraction processing unit 222 … Observation area processing unit 223… High cloud cover analysis unit 224… High cloud correlation map creation unit 230… Evaluation device 231… Calculation unit G… Optical ground station S… Spacecraft

Claims (10)

Based on the low-level cloud cover analysis unit that extracts the low-level cloud cover characteristics related to the amount of clouds at each point of the multiple ground-based stations from the past meteorological data groups observed at multiple ground-based stations, and the low-level cloud cover characteristics. A low-rise cloud analyzer having a low-rise cloud correlation processing unit for creating a low-rise cloud correlation map showing the correlation of low-rise cloud cover between each of the plurality of ground observation points .
Based on the high-level cloud cover analysis unit that extracts the high-level cloud cover characteristics related to the amount of clouds at the coordinates corresponding to each point of the plurality of ground observation points from the past meteorological data group observed by the meteorological satellite, and the high-level cloud cover characteristics. A high-level cloud analyzer having a high-level cloud correlation processing unit for creating a high-level cloud correlation map showing the correlation of the high-level cloud cover between each point of the plurality of ground observation points .
Based on the low-rise cloud correlation map and the high-rise cloud correlation map, by selecting a combination of points where the correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic is low between each point of the plurality of ground observation points, light is applied. An optical ground station distributed placement evaluation system equipped with an evaluation device that evaluates the placement of ground stations. The optical ground station distributed arrangement evaluation system according to claim 1.
The low-rise cloud correlation processing unit and the high-rise cloud correlation processing unit calculate a cloud cover correlation coefficient between any two points at the plurality of ground observation points based on the low-rise cloud cover characteristics and the high-rise cloud cover characteristics. Then, the low cloud correlation map and the high cloud correlation map were created, respectively .
The evaluation device is an optical ground station distributed arrangement evaluation system that extracts a combination of a plurality of two points having a correlation coefficient of 0 or less based on the low cloud correlation map and the high cloud correlation map . The optical ground station distributed arrangement evaluation system according to claim 2.
The low-rise cloud cover characteristic and the high-rise cloud cover characteristic include the time rate of the designated cloud cover with respect to the total time of the designated year period at each point of the plurality of ground stations.
The evaluation device is an optical ground station distributed arrangement evaluation system that selects a set having a time rate of the designated cloud amount of a predetermined value or more from a combination of a plurality of extracted points. The optical ground station distributed arrangement evaluation system according to claim 2.
The low-rise cloud cover characteristic and the high-rise cloud cover characteristic include the time rate of the designated cloud cover with respect to the total time of the designated year period at each point of the plurality of ground stations.
The evaluation device is a set of three or more points in which the time rate of the designated cloud amount is a predetermined value or more and any one of the candidate sites constituting the two points is common from the combination of the plurality of two points extracted. Optical ground station distributed placement evaluation system that extracts multiple sets of ground station combinations. The optical ground station distributed arrangement evaluation system according to claim 3 or 4.
The evaluation device is an optical ground station distributed arrangement evaluation system that weights the low-level cloud cover characteristics and the high-level cloud cover characteristics at each point by environmental factors at each point of the plurality of ground observation points. The optical ground station distributed arrangement evaluation system according to claim 5.
The environmental factor is an optical ground station distributed placement evaluation system including parameters related to at least one of wind speed, seeing, yellow sand, volcanic ash, humidity, salt content, sulfuric acid concentration, freezing, dew condensation and snowfall. The optical ground station distributed arrangement evaluation system according to any one of claims 1 to 6.
The high cloud analyzer has an optical ground processing unit that redefines the analysis space so that the meteorological data observed by the meteorological satellite is equivalent to the observed area of the meteorological data observed at the ground observation point. Station distribution evaluation system. Of the plurality of ground stations created based on the low cloud cover characteristics related to the amount of clouds at each point of the multiple ground stations extracted from the past meteorological data group observed at the multiple ground stations. The low-rise cloud correlation map showing the correlation between the low-rise cloud cover between each point and the cloud cover at the coordinates corresponding to each point of the plurality of ground observation points extracted from the past meteorological data group observed by the meteorological satellite. The low layer between the points of the plurality of ground observation points based on the high cloud correlation map showing the correlation of the high cloud cover between the points of the plurality of ground observation points created based on the related high cloud cover characteristics. An evaluation device provided with a calculation unit that evaluates the arrangement of optical ground stations by selecting a combination of points where the correlation between the cloud cover characteristics and the high cloud cover characteristics is low. Low -level cloud cover between each point of the plurality of ground stations based on the low-level cloud cover characteristics related to the amount of clouds at each point of the plurality of ground stations from the past meteorological data group observed at the multiple ground stations. Create a low-level cloud correlation map that shows the correlation of
High-rise clouds between each point of the plurality of ground stations based on the cloud cover characteristics related to the amount of clouds at the coordinates corresponding to each point of the plurality of ground stations from the past meteorological data group observed by the meteorological satellite. Create a high-rise cloud correlation map that shows the cloud cover correlation,
Based on the low-rise cloud correlation map and the high-rise cloud correlation map, by selecting a combination of points where the correlation between the low-rise cloud cover characteristic and the high-rise cloud cover characteristic is low between each point of the plurality of ground observation points, light is applied. Optical ground station distributed placement evaluation method to evaluate the placement of ground stations. The method for evaluating distributed arrangement of optical ground stations according to claim 9.
In the step of selecting a combination of points having a low correlation between the low-level cloud cover characteristics and the high-level cloud cover characteristics at the plurality of ground observation points, wind speed, seeing, yellow sand, volcanic ash, and humidity at each point of the plurality of ground observation points, Optical ground station distribution assessment that weights the low cloud cover and high cloud cover characteristics at each point by environmental factors including parameters related to at least one of salt, seewater concentration, freezing, dew condensation and snowfall. Method.

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