JP2012074924A - Satellite transmission terminal and satellite transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve reduction in size and weight and low power consumption while ensuring time of communication with an SSO satellite.SOLUTION: A satellite transmission terminal 110 comprises: a satellite signal receiving part 162a receiving a GPS signal (satellite signal) transmitted by a GPS satellite (navigation satellite) 102; a satellite signal decoding part 162b deriving local time by decoding the received GPS signal; a time deriving part 172 deriving start time that is the time of starting data transmission to an SSO satellite and finish time that is the time of finishing data transmission to the SSO satellite based on descending node passing local time or ascending node passing local time, and satellite passing window width; a transmission part 154 transmitting data to the SSO satellite 104 while receiving the supply of a power source; and a power supply part 160 supplying the transmission part 154 with the power source while the derived local time is between the start time and the finish time.

Description

  The present invention relates to a satellite transmission terminal that transmits data to a satellite orbiting a solar synchronous quasi-return orbit and a satellite transmission method using the same.

  2. Description of the Related Art Conventionally, a communication system in which a transmission terminal derives a current position using a GPS satellite and directly transmits position information indicating the derived current position to a data aggregation device that aggregates data via wireless communication has become widespread. (For example, Patent Document 1). However, in such a communication system, if the distance between the transmission terminal and the data aggregation device is too long, the radio waves transmitted from the transmission terminal do not reach the data aggregation device, and the data aggregation device cannot acquire position information. Therefore, the transmission terminal can be used only within a certain narrow range centering on the data aggregation device.

  Conventionally, communication systems that use artificial satellites as repeaters have been used. For example, as a satellite used as a repeater, there has been proposed a communication system using an artificial satellite (hereinafter simply referred to as an SSO satellite) that orbits a sun-synchronous sub-recurrent orbit (SSO). Yes. Such communication systems using SSO satellites are used for animal tracking, ocean observation, and the like.

  For example, when used for animal tracking, a satellite transmission terminal is attached to an animal such as a bird or a mammal. The satellite transmission terminal receives a GPS signal transmitted from a GPS (Global Positioning System) satellite separate from the SSO satellite, derives a current position from the received GPS signal, and positional information indicating the derived current position And an identifier for identifying the other satellite transmission terminal and itself are transmitted to the SSO satellite. The SSO satellite transmits the position information and the identifier transmitted from the satellite transmission terminal to a data aggregation device in an arbitrary organization on the earth, for example, an animal protection center or a research institution.

  In addition, for example, when used for ocean observation, a satellite transmission terminal is attached to a buoy for ocean observation, and the satellite transmission terminal uses temperature information, an identifier, a temperature, humidity, atmospheric pressure, and wave measured by the ocean buoy. Measurement information indicating highness is transmitted via an SSO satellite to a data aggregating apparatus in an arbitrary organization on the earth such as the Japan Meteorological Agency.

Japanese Patent Laid-Open No. 08-180286

  The satellite transmission terminal receives, for example, a signal from a navigation satellite at a predetermined time interval such as every hour, for example, a GPS signal of a GPS (Global Positioning System) satellite, and position information generated based on the received GPS signal, Data such as an identifier and measurement information is burst transmitted to the SSO satellite at predetermined time intervals such as every minute. Here, the timing at which the satellite transmission terminal can communicate with one SSO satellite is, for example, 15 minutes × several times in one day (the number varies depending on the latitude, for example, 5-6 times near the equator) Limited to. In order to accurately communicate with the SSO satellite in such a limited time of 15 minutes, a signal including information on the orbit of the SSO satellite itself (hereinafter simply referred to as an orbit signal) transmitted by the SSO satellite is used. It receives and adjusts the timing of communication according to the orbit signal.

  However, for the purpose of small size and light weight, a receiving device for receiving an orbit signal transmitted by the SSO satellite is not intentionally mounted. When the receiving device is not installed in this way, the satellite transmitting terminal cannot receive the orbit signal transmitted from the SSO satellite, and therefore cannot accurately grasp the timing at which communication with the SSO satellite can be performed. Therefore, the satellite transmission terminal transmits data such as position information, identifiers, and measurement information to the SSO satellite reliably regardless of the orbit of the SSO satellite. Sending data. In this case, data is continuously transmitted even in a time zone in which communication with the SSO satellite cannot be surely performed, and unnecessary power for data transmission is consumed.

  In view of the above problems, an object of the present invention is to provide a satellite transmission terminal and a satellite transmission method capable of reducing power consumption while ensuring communication time with an SSO satellite. .

  In order to solve the above problems, a satellite transmission terminal according to the present invention includes a satellite signal receiving unit that receives a satellite signal transmitted from a navigation satellite, and decodes the received satellite signal to obtain longitude, latitude, and local time. The satellite signal decoding unit, the SSO satellite orbiting the sun-synchronous quasi-regressive orbit and the center of the earth passing through the descending point indicated by the local time at the longitude of the point where the equator passed from north to south Due to local time, or the local time at the ascending intersection indicated by the local time at the longitude of the point where the connection between the SSO satellite and the center of the earth passed from the south to the north on the equator, and due to restrictions based on the rotation of the earth Based on the satellite passage window width that is a period excluding the period during which communication with the SSO satellite cannot be performed, the start time that is the time at which data transmission to the SSO satellite is started and the transmission of data to the SSO satellite A time deriving unit for deriving an end time that is an end time, a transmitting unit for transmitting data to the SSO satellite while receiving power supply, and the derived local time from the start time to the end time A power supply unit that supplies power to the transmission unit while being included.

  You may further provide the window width calculation part which calculates a satellite passage window width based on the derived latitude.

  The satellite transmission terminal further includes a memory that holds in advance a window width table in which the latitude and the satellite passing window width are associated, and the window width calculating unit refers to the window width table and passes the satellite from the derived latitude. The window width may be calculated.

  In order to solve the above-described problem, a satellite transmission method using a satellite transmission terminal including a transmission unit that transmits data to an SSO satellite orbiting a solar synchronous quasi-regression orbit while receiving power supply according to the present invention is provided. The satellite signal transmitted from the navigation satellite is received, the received satellite signal is decoded to derive the longitude, latitude, and local time, and the connection between the SSO satellite and the center of the earth passes from the north to the south on the equator. Depending on the local time at the crossing local time indicated by the local time in the longitude of the point where the time passed, or the longitude of the point where the connection between the SSO satellite and the center of the earth passed from the south to the north on the equator Data transmission to the SSO satellite starts based on the local time shown at the rising intersection and the satellite passage window width that is the period excluding the period when communication with the SSO satellite cannot be performed due to restrictions based on the rotation of the earth. The start time that is the time to be transmitted and the end time that is the time to end the transmission of data to the SSO satellite are derived, and while the derived local time is included from the start time to the end time, to the transmission unit The power supply is performed.

  The above-described components based on the technical idea of the satellite transmission terminal and the description thereof can be applied to the satellite transmission method.

  According to the present invention, it is possible to reduce the power consumption while securing the communication time with the SSO satellite.

It is explanatory drawing for demonstrating the connection relation of a satellite communication system. It is explanatory drawing for demonstrating the communication operation | movement of the conventional satellite transmission terminal. It is the functional block diagram which showed the schematic function of the satellite transmission terminal. It is explanatory drawing for demonstrating the orbit of the SSO satellite which is a transmission partner of the data (position information and identifier) of a satellite transmission terminal. It is explanatory drawing for demonstrating the relative positional relationship in which an SSO satellite can communicate with a satellite transmission terminal. It is explanatory drawing for demonstrating a satellite passage window width. It is explanatory drawing for demonstrating the range in which a satellite transmission terminal can carry out radio wave observation of an SSO satellite. It is explanatory drawing for demonstrating the range in which a satellite transmission terminal can carry out radio wave observation of an SSO satellite. It is explanatory drawing for demonstrating the calculation method of meridian LT1E and meridian LT1W. It is explanatory drawing for demonstrating a window width table. It is a flowchart for demonstrating the specific process of a satellite transmission method.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

(Satellite communication system 100)
FIG. 1 is an explanatory diagram for explaining a connection relationship of the satellite communication system 100. As shown in FIG. 1, a satellite communication system 100 includes a satellite transmission terminal 110 (indicated by 110a and 110b in FIG. 1) and a navigation satellite such as a GPS satellite 102 (in FIG. 1, GPS satellites 102a, 102b, and 102c). And an SSO satellite 104 and a data aggregating apparatus 106.

  The satellite transmission terminal 110 according to the present embodiment is used for, for example, animal tracking, and is attached to animals such as birds and mammals. The satellite transmission terminal 110a receives satellite signals (hereinafter referred to as GPS signals) transmitted from three or more GPS satellites 102, derives the current position of the satellite transmission terminal 110a, and position information indicating the derived current position Is generated. Then, the satellite transmission terminal 110a transmits the generated position information and an identifier for identifying the satellite transmission terminal 110a that is the satellite transmission terminal 110a to the other satellite transmission terminal 110b to the SSO satellite 104.

  The SSO satellite 104 that has received the position information and identifier transmitted from the satellite transmission terminal 110 transmits the position information and identifier to the data aggregating apparatus 106 in any organization on the earth, for example, an animal protection center or a research institution. To do.

  FIG. 2 is an explanatory diagram for explaining a communication operation of a conventional satellite transmission terminal. In FIG. 2, the timing at which a GPS signal is received is indicated by a solid bar in which the timing at which one SSO satellite 104 can be seen from the position of the satellite transmission terminal (can communicate with the SSO satellite 104) is black, and the timing at which a GPS signal is received is a white bar. Shown with a line. As shown in FIG. 2, the timing at which the satellite transmission terminal can see the radio wave from the SSO satellite 104, that is, the timing at which the satellite transmission terminal can communicate with the SSO satellite 104 is, for example, 15 minutes × several times (the number of times varies depending on the latitude, for example, 5 to 6 times near the equator).

  Therefore, a conventional satellite transmission terminal includes a receiving device for receiving an orbit signal transmitted from the SSO satellite 104, and derives a timing at which communication with the SSO satellite 104 can be performed from the received orbit signal. , Data such as position information and identifiers were transmitted at the derived timing.

  However, the conventional satellite transmission terminal requires a receiving device for receiving the orbit signal transmitted from the SSO satellite 104, and the volume increases accordingly. In addition, since the receiving apparatus must maintain the reception state, power consumption increases. For this reason, reduction in size and weight is required, and it is difficult to provide a receiving device in a satellite transmission terminal that is attached to an animal and uses a battery as a power source.

  The satellite transmission terminal to be attached to such an animal uses a configuration in which no receiving device is provided for the purpose of reducing the size and weight. In a configuration in which no receiving device is provided, there is no way to grasp the timing at which communication with the SSO satellite 104 can be performed. Therefore, regardless of the orbit of the SSO satellite 104, data such as position information and identifiers can be reliably transmitted to the SSO satellite 104. In order to transmit, in order to ensure the maximum communication time, it will transmit continuously for 24 hours. In this case, even during a time zone in which communication with the SSO satellite 104 cannot be reliably performed, data transmission is continued, resulting in unnecessary power consumption for data transmission.

  Therefore, the satellite transmission terminal 110 according to the present embodiment is used for animal tracking, ocean observation, and the like, and aims to reduce power consumption while ensuring communication time with the SSO satellite 104. Hereinafter, a specific configuration of the satellite transmission terminal 110 will be described in detail, and then a satellite transmission method using the satellite transmission terminal 110 will be described.

(Satellite transmission terminal 110)
FIG. 3 is a functional block diagram showing a schematic function of the satellite transmission terminal 110. As shown in FIG. 3, the satellite transmission terminal 110 includes a navigation satellite unit 150, an RTC unit 152, a transmission unit 154, a memory 156, a central control unit 158, and a power supply unit 160. . In FIG. 3, the flow of power is indicated by solid arrows, and the flow of data is indicated by broken arrows.

  The navigation satellite unit 150 includes a satellite signal receiving unit 162a and a satellite signal decoding unit 162b. The satellite signal receiving unit 162 a receives a GPS signal (satellite signal) transmitted from the GPS satellite (navigation satellite) 102. In the present embodiment, the satellite signal receiving unit 162a receives GPS signals at predetermined time intervals (for example, every hour, every 30 minutes, every 15 minutes, etc.). The satellite signal decoding unit 162b decodes the received GPS signal, acquires the latitude and longitude of the position of itself (satellite transmission terminal 110), and acquires position information that is information indicating the latitude and longitude (current position). Generate and output to the transmission unit 154.

Further, in the present embodiment, the satellite signal decoding unit 162b decodes the received GPS signal to obtain Universal Time, Coordinated (UTC), and the position of the satellite signal decoding unit 162b together with the already acquired longitude. Deriving the local time of (longitude). Specifically, the satellite signal decoding unit 162b first derives the difference between the world coordinated time and the local time using the following equations (1) and (2) using the acquired longitude of the satellite. .
“Time” of the difference between the world time and the local time = INT (longitude / 15 degrees) (1)
“Minute” of the difference between the world time and the local time = [(longitude / 15 degrees) − {INT (longitude / 15 degrees)}] × 60 (2)
Here, INT (longitude / 15 degrees) means an integer part of (longitude / 15 degrees) (the decimal part is rounded down). Therefore, when the acquired longitude is, for example, 142.5 degrees, the satellite signal decoding unit 162b has a difference of 9 hours 30 minutes between the world coordinated time and the local time.

  Next, the satellite signal decoding unit 162b derives the local time by adding or subtracting the acquired world coordinated time to the difference between the world coordinated time and the local time derived by the above formulas (1) and (2). . For example, if the acquired longitude is east longitude and the world coordinated time is 1:00, the local time is 10:30, which is the difference between 9 hours and 30 minutes, which is the difference between the world coordinated time and the local time. . In addition, when the acquired longitude is west longitude and the universal time is 1:00, the local time is 15:30, which is the difference between 9 hours and 30 minutes, which is the difference between the global time and the local time. . In this embodiment, the value derived in this way is defined as local time. Hereinafter, the case where the longitude acquired by the satellite signal decoding unit 162b is east longitude will be described as an example.

  An RTC (Real Time Clock) unit 152 is composed of an RTC circuit and plays a role as a clock of the satellite transmission terminal 110 itself. The RTC unit 152 is calibrated by the central control unit 158 described later at a local time derived by the satellite signal decoding unit 162b at predetermined time intervals (for example, every hour). Here, when the satellite transmission terminal 110 is attached to an animal or the like that moves, the difference between the world time and the local time indicated by the RTC unit 152 changes due to the movement in the east-west direction, and the actual local time and the RTC. Since a difference occurs in the local time indicated by the unit 152, the RTC unit 152 needs to be calibrated.

  More specifically, if the absolute position (especially longitude) of the satellite transmission terminal 110 on the earth does not change, that is, if the satellite transmission terminal 110 has not moved in the east-west direction after receiving the GPS signal, the RTC unit 152 The local time indicated by is the same as the actual local time. However, when the satellite transmission terminal 110 moves in the east-west direction, the actual local time changes. For example, when the longitude change per hour when the satellite transmission terminal 110 moves in the east-west direction at a speed of 50 km at a position where the latitude is 60 degrees is converted into time, 50 (km) / [40000 (km) / 24 (hours) / {1 / sin (90-60)}] × 60 (minutes) = 3.6 (minutes). Therefore, in this case, when the satellite transmission terminal 110 derives the local time at an arbitrary longitude position and acquires the local time from the GPS signal at a longitude position separated by 50 km in the east-west direction after 1 hour, the local time indicated by the RTC unit 152 The time and the actual local time acquired from the GPS signal will have an error of about 4 minutes. In order to avoid such errors from accumulating, the RTC unit 152 is periodically calibrated. Since the power supply unit 160 to be described later supplies power to the transmission unit 154 for a long time of 6 hours or more, such an error of about 4 minutes does not affect the communication operation of this embodiment. .

  The transmission unit 154 transmits data (position information output from the satellite signal decoding unit 162b and an identifier for identifying itself) to the SSO satellite 104 while receiving power supply from the power supply unit 160 described later. In this embodiment, the transmission unit 154 performs burst transmission intermittently at a predetermined time interval (for example, every minute) for a predetermined time (for example, 1 second).

  When the satellite transmission terminal 110 is attached to a buoy for ocean observation for use in ocean observation, the satellite transmission terminal 110 acquires measured values such as temperature, water temperature, atmospheric pressure, and wave height, and the transmission unit 154 The information indicating the measurement value is transmitted to the SSO satellite 104 together with the position information or instead of the position information. In this case, the satellite transmission terminal 110 may include a measurement sensor that measures the temperature, water temperature, atmospheric pressure, wave height, and the like, or the buoy may include a measurement sensor. When the buoy includes a measurement sensor, the satellite transmission terminal 110 acquires a measurement value from the buoy measurement sensor.

  The memory 156 includes a nonvolatile storage medium capable of storing data, such as a ROM (Read Only Memory), an EEPROM (Electrically Erasable and Programmable ROM), a nonvolatile RAM (Random Access Memory), a flash memory, and an HDD.

  The central control unit 158 can use a semiconductor integrated circuit including a central processing unit (CPU), a signal processing unit (DSP: Digital Signal Processor), a ROM storing programs, a RAM as a work area, and the like. The control unit 158 manages and controls the entire satellite transmission terminal 110.

  In the present embodiment, the central control unit 158 also functions as a window width calculation unit 170 and a time derivation unit 172.

  The window width calculation unit 170 calculates the satellite passing window width based on the latitude derived by the satellite signal decoding unit 162b. Here, the satellite passing window width is a period excluding a period during which communication with the SSO satellite 104 is not possible due to restrictions based on the rotation of the earth. Hereinafter, a specific calculation method by which the window width calculation unit 170 calculates the satellite passing window width will be described.

  FIG. 4 is an explanatory diagram for explaining the orbit of the SSO satellite 104 that is the transmission partner of the data (position information and identifier) of the satellite transmission terminal 110. 4A is an explanatory diagram for explaining the relationship between the orbital plane 108a of the SSO satellite 104 and the sun 120, and FIG. 4B explains the orbit 108b of the SSO satellite 104 with respect to the earth. It is explanatory drawing for.

  The SSO satellite 104 orbits a sun-synchronous sub-recurrent orbit. The sun-synchronous quasi-regressive orbit is a kind of polar orbit that goes around with a period of about 100 minutes, for example. As shown in FIG. 4 (a), the sun-synchronous quasi-regressive orbit has an orbital plane 108a, which is a virtual plane including the orbit, and an angle Ω formed by the connection between the sun 120 and the earth 122 is substantially constant throughout the year. Orbit.

  Therefore, as shown in FIG. 4 (b), the connecting point R where the connection R between the SSO satellite 104 and the center point O of the earth 122 is the local time at the longitude of the passing point when passing through the equator from north to south. The time is the same local time at any position (longitude) on the earth 122, and the ascending intersection passing local time, which is the local time at the longitude of the point where the connection R passes through the equator from south to north, is also the time. The same local time is used at any position (longitude) on the earth 122. There is a 12-hour difference between local time at the descending intersection and local time at the ascending intersection. The descending intersection passing local time and the ascending intersection passing local time are predetermined for each SSO satellite 104.

  FIG. 5 is an explanatory diagram for explaining a relative positional relationship in which the SSO satellite 104 can communicate with the satellite transmission terminal 110. The SSO satellite 104 can receive only data transmitted from the satellite transmission terminal 110 within a predetermined range on the earth 122 (hereinafter referred to as a satellite radio wave forecast range). In other words, the satellite transmission terminal 110 can communicate with the SSO satellite 104 only when it is located within the satellite radio wave prospect range.

  For example, as shown in FIG. 5, it is assumed that the SSO satellite 104 orbits the vicinity of the equator from the back to the front of FIG. 5, and the satellite transmission terminal 110 moves from T0 to T4 according to the rotation of the earth 122 ( It is assumed that the satellite transmission terminal 110 does not move except according to the rotation of the earth 122, that is, the satellite transmission terminal 110 is stationary when viewed from the earth 122). That is, T0, T1, T2, T3, and T4 indicate local times at each position of the satellite transmission terminal 110, respectively.

  When the satellite transmission terminal 110 is located at T1, T2, T3 within the satellite radio wave prospect range 164 (indicated by hatching in FIG. 5) of the SSO satellite 104, the SSO satellite 104 receives the data transmitted by the satellite transmission terminal 110. However, the SSO satellite 104 cannot receive the data transmitted by the satellite transmission terminal 110 when located at T0, T4 outside the satellite radio wave prospect range 164. That is, the data transmitted by the satellite transmission terminal 110 can be received by the SSO satellite 104 only during a time period of several hours before and after the descending intersection passing local time or the rising intersection passing local time.

  Therefore, the window width calculation unit 170 uses the relative positional relationship between the SSO satellite 104 and the satellite transmission terminal 110 described above, and excludes a period during which communication with the SSO satellite 104 due to restrictions based on rotation of the earth 122 is not possible. The satellite passing window width is derived.

  FIG. 6 is an explanatory diagram for explaining the satellite passing window width. In FIG. 6, the timing at which one SSO satellite 104 can be seen from the position of the satellite transmitting terminal 110 (can communicate with the SSO satellite 104) is a black line with a black line, and the satellite passing window width is hatched with a square. It shows with.

  As described above, the satellite passing window width is a period excluding the period 180 (indicated by a white square in FIG. 6) during which communication with the SSO satellite 104 cannot be performed reliably. Here, during the period 180 during which communication with the SSO satellite 104 cannot be performed reliably, the position of the earth is separated in the direction perpendicular to the orbit of the SSO satellite 104 due to the rotation of the earth. This is the period during which the outlook is impossible. On the other hand, during the satellite passing window width, the satellite transmission terminal 110 can communicate with the SSO satellite 104 depending on the position of the SSO satellite 104 in the orbit. become.

  7 and 8 are explanatory diagrams for explaining a range in which the satellite transmission terminal 110 can see the SSO satellite 104 in the radio wave. As shown in FIG. 7, it is assumed that the SSO satellite 104 is orbiting at an altitude (height from sea level) h orbit 108b, and radio waves can be observed from an arbitrary position F2 on the earth 122 at an elevation angle θ (degrees). The positions on the orbit 108b of the SSO satellite 104 that passes right above F2 at an altitude h are S1 and S3, and the intersection (foot point) between the line connecting the position S1 and the center point O of the earth and the ground surface is F1. F3 is the intersection of the connection line connecting the position S3 and the center point O and the ground surface. Also, assuming that the angle α between the position F1, the center point O, and the position F2 is the range on the ground surface where the SSO satellite 104 at an altitude h from the position F2 can see the radio wave at an elevation angle θ or more (hereinafter simply referred to as the device). The radio wave prediction range) is a circle T1 on the ground surface when the connection between the center point O and the position F2 is a rotation axis and the connection between the center point O and the position F1 is rotated at an angle α (FIG. 8). Reference). Note that the positions F1 and F3 are intersections between the circumference of the circle T1 and the meridian passing through the position F2.

  Since the earth has a spherical shape, if the device radio wave prospect range is equal, the width of meridians located at the boundary of the device radio wave forecast range becomes wider at high latitude than at low latitude. This will be specifically described with reference to FIG. In FIG. 8, the meridians on the circumference of the circle T1 are indicated by LT1W and LT1E, and the meridians on the circumference of the circle T2 having a higher latitude than the circle T1 are indicated by LT2W and LT2E. Then, as shown in FIG. 8, the width of the meridian entering the device radio wave prospect range is wider in the circle T2 at a higher latitude than the circle T1.

  In addition, the longitude corresponds to the local time, and the earth rotates once in 24 hours. Therefore, if the longitude is different by 15 degrees, it is different for one hour in terms of the local time.

The satellite passing window width can be derived from the longitude difference of the boundary of the device radio wave forecast range obtained in this way by the following formula (3). Here, as an example, a case where the device radio wave prospect range is a circle T1 is given. Here, the case where the longitude is east longitude will be described as an example.
Satellite passing window width = Longitude difference / 15
= (LT1E-LT1W) ... Formula (3)

  That is, the satellite passing window width is the width of two meridian LT1E and meridian LT1W in contact with the circumference of the circle T1. Therefore, the window width calculation unit 170 can calculate the satellite passing window width by obtaining the meridian LT1E and the meridian LT1W. When the longitude is west longitude, the satellite passing window width = (LT1W−LT1E).

FIG. 9 is an explanatory diagram for explaining a method of calculating the meridian LT1E and the meridian LT1W. In FIG. 9, if the angle A is an angle that bisects the angle formed by the meridian LT1E and the meridian LT1W, the angle A can be calculated using the following equations (4) to (8). Here, Lat indicates the latitude of the position F2 where the satellite transmission terminal 110 is located, and α indicates the angle α in FIG. The angle formed by the intersection point Q of the position F1, the center point O, the circle T1 and the meridian LT1W is x, the north pole P, the center point O, the angle formed by the position F1 is y, the north pole point P, the center point O, and the intersection point Q are The resulting angle is indicated by z.
sin (A) = sin (x) / sin (y) (4)
sin (y) = sin (90−Lat) (5)
sin (x) = sin (α) (6)
sin (A) = sin (α) / sin (90−Lat) (7)
A = arcsin {sin (α) / sin (90−Lat)} (8)
Next, the window width calculation unit 170 calculates α shown in FIG. 7 using the following equations (9) to (14). Here, when the connection between the position F2 and the position S1 is a, the connection between the position S2 and the center point O is b, the connection between the position S1 and the center point O is c, and the radius of the earth is r, from the cosine theorem,
c / sin (γ) = b / sin (β) = a / sin (α) (9)
It is. Here, since c = r + h, γ = θ + 90, and b = r, when these are substituted into the equation (9),
(R + h) / sin (θ + 90) = r / sin (β) (10)
(R + h) × sin (β) = r × sin (θ + 90) (11)
sin (β) = {r / (r + h)} × sin (θ + 90) (12)
β = arcsin [{r / (r + h)} × sin (θ + 90)] (13)
It becomes. Here, since α = 180−γ−β,
α = 180−90−θ−arcsin [{r / (r + h)} × sin (θ + 90)]
= 90−θ−arcsin [{r / (r + h)} × sin (θ + 90)] (14)
It becomes.

  Here, the window width calculation unit 170 calculates and calculates the angle α by substituting the radius r of the earth 6371 km, the altitude h of the SSO satellite 104 850 km, and the elevation angle θ 6 ° into the equation (14). The angle α and the latitude Lat at the position F2 where the satellite transmission terminal 110 is located are substituted into the equation (8) to calculate the angle A, the angle A is doubled and substituted into the equation (3), and the satellite passing window width is calculated. Is calculated.

  Thus, when the satellite signal decoding unit 162b acquires the latitude, the window width calculation unit 170 calculates the satellite passing window width based on the current latitude of the satellite transmission terminal 110. Then, the window width calculation unit 170 outputs the calculated satellite passage window width to the time deriving unit 172.

  The time deriving unit 172 starts transmission of data to the SSO satellite 104 based on the descending intersection passing local time or the rising intersection passing local time and the satellite passing window width calculated by the window width calculating unit 170. The start time that is the time and the end time that is the time when the transmission unit 154 ends the transmission of data to the SSO satellite 104 are derived.

  Specifically, the time deriving unit 172 is centered on the descending intersection passing local time or the rising intersection passing local time, and the time before half the satellite passing window width is set as the start time, and the half of the satellite passing window width has elapsed. The later time is derived as the end time. For example, when the descending intersection passing local time is 10:30 and the satellite passing window width is 3 hours, the time deriving unit 172 derives the start time as 9:00 and the end time as 12:00.

  As described above, in the SSO satellite 104 that orbits the solar synchronous return orbit, the descending intersection passing local time and the ascending intersection passing local time are predetermined for each SSO satellite 104. The time deriving unit 172 determines the SSO satellite 104 and the satellite according to restrictions based on the rotation of the earth based on the predetermined time at the descending intersection passing local time and the rising intersection passing local time and the satellite passing window width calculated by the window width calculating unit 170. The time excluding the time when the transmission terminal 110 cannot communicate, that is, the start time and the end time when the SSO satellite 104 can be seen from the satellite transmission terminal 110 can be derived. Therefore, the time from the start time to the end time is a time during which data can be transmitted to the SSO satellite 104.

  The power supply unit 160 supplies power to the transmission unit 154 while the local time indicated by the RTC unit 152 is included from the start time to the end time derived by the time deriving unit 172. That is, the transmission unit 154 includes the SSO satellite only while the local time of the current position of the satellite transmission terminal 110 (local time indicated by the RTC unit 152) is included from the start time to the end time derived by the time deriving unit 172. Data is transmitted to 104.

  The power supply unit 160 supplies power to the transmission unit 154 only while the local time at the current position of the satellite transmission terminal 110 is included from the start time to the end time derived by the time deriving unit 172. Therefore, the transmission unit 154 transmits data to the SSO satellite 104 only for the satellite passing window width centered around the descending intersection passing local time or the ascending intersection passing local time.

  That is, the power supply unit 160 sends the data to the transmission unit 154 at a time other than the start time to the end time, that is, the time when the SSO satellite 104 cannot receive data even if data is transmitted due to the limitation due to the rotation of the earth. By turning off the power supply, wasteful power consumption can be reduced.

  As described above, the satellite transmission terminal 110 includes a satellite transmission terminal (hereinafter simply referred to as a terminal having a reception function) provided with a conventional reception device and a conventional satellite transmission terminal (hereinafter simply referred to as a terminal having a reception function) ( Hereinafter, the power consumption can be greatly reduced as compared with a continuous transmission terminal. For example, since a terminal with a reception function consumes a large amount of power, the satellite transmission terminal 110 can significantly reduce power consumption compared with a terminal with a reception function.

  For example, it is assumed that the power consumed by the receiving device is 0.8 W / h and the power consumed by the transmission unit is 0.08 W / h. In this case, since the terminal with the reception function supplies power to the reception device and the transmission unit during the time of communication with the SSO satellite 104 (for example, 15 minutes × 6 times), the total power consumption is {(0.8 W / h × 15 minutes) + (0.08 W / h × 15 minutes)} × 6 times = 1.32 W On the other hand, since the satellite transmission terminal 110 supplies power to the transmission unit 154 only during the satellite passing window width (3 hours × 2 times), the total power consumption is 0.08 W / h × 6 hours = The power consumption is 0.48 W, and the power consumption can be reduced to about 1/3 compared to a terminal with a reception function. Further, while the continuous transmission terminal supplies power to the transmission unit for 24 hours continuously, the satellite transmission terminal 110 supplies power to the transmission unit 154 only for the satellite passing window width. When the satellite passing window width is 3 hours (6 hours in total when the local time passing through the descending intersection and the local time passing through the ascending intersection is the center), it is approximately 1 / compared to the continuous transmission terminal. 4. Power consumption can be reduced.

  In addition, regarding the volume (size) of the device itself, the satellite transmission terminal 110 is equivalent to the continuous transmission terminal, but can be formed extremely small as compared with a terminal with a reception function.

  Further, regarding the reliability of the device, the terminal with the receiving function transmits data when an error occurs in the calculation of the orbit of the SSO satellite 104 due to a malfunction of the receiving device, and the communication possible time and the transmission time are temporarily shifted by 10 minutes. Although the time may become extremely short and normal communication may not be executed, even if the transmission time is shifted by 10 minutes, the satellite transmission terminal 110 performs communication sufficiently within the other satellite passing window width, Data can be reliably transmitted to the SSO satellite 104. Therefore, the satellite transmission terminal 110 is equivalent to the continuous transmission terminal in terms of reliability, but is higher than the terminal with a reception function.

  In addition, here, the configuration in which the window width calculation unit 170 calculates the satellite passage window width has been described, but a window width table in which the latitude and the satellite passage window width are associated is stored in the memory 156 of the satellite transmission terminal 110 in advance. The window width calculation unit 170 may calculate the satellite passing window width from the latitude derived by the satellite signal decoding unit 162b with reference to the window width table.

  FIG. 10 is an explanatory diagram for explaining the window width table 190. In particular, FIG. 10 (a) is an explanatory diagram for explaining the relationship between the latitude and the actually calculated satellite passing window width. FIG. 10B is a diagram showing the window width table 190, and FIG. 10C is an explanatory diagram for explaining the correspondence between the window width table 190 and the calculated satellite passage window width.

  As shown in FIG. 10A, it can be seen that the satellite passing window width becomes longer as the latitude becomes higher. When the latitude is 90-α (α is the numerical value portion of the angle α indicating the device prospect range in FIG. 7) or more, a pole point (north pole or south pole) enters the device radio wave forecast range. The passing window width is 24 hours.

  Then, as shown in FIG. 10B, in the window width table 190, the latitude and the satellite passing window width are associated with each other so that the calculated satellite passing window width is uniquely determined corresponding to each latitude. ing. For example, as shown in FIG. 10B, the window width table 190 indicates that the satellite passing window width is 3 hours when the latitude is 0 degree or more and less than 15, and 3.5 hours when the latitude is 15 degrees or more and less than 30 degrees. 4. 30 hours or more and less than 40 degrees, 4 hours, 40 degrees or more and less than 45 degrees, 4.5 hours, 45 degrees or more and less than 50 degrees, 5 hours, 50 degrees or more and less than 55 degrees. The latitude and the satellite passage window width are associated with each other, such as 5 hours, 7 hours when 55 degrees or more and less than 60 degrees, and 24 hours when 60 degrees or more. The window width table 190 shown in FIG. 10B is a table formed step by step using the relationship between the latitude and the calculated satellite passing window width shown in FIG. is there.

  Even if there are a plurality of SSO satellites 104 that transmit data, the satellite transmission terminal 110 stores one window width table 190 in the memory 156 if the heights h of the orbits around them are equal from the ground surface. However, if the height h from the ground surface of the orbit that circulates for each SSO satellite 104 is different, the window width table 190 is held in the memory 156 by the number of the SSO satellites 104.

  When the memory 156 of the satellite transmission terminal 110 holds the window width table 190 in advance, when the satellite signal decoding unit 162b acquires the latitude, the window width calculation unit 170 refers to the window width table 190 held in the memory 156. The satellite passage window width is calculated based on the current latitude of the satellite transmission terminal 110. Then, the window width calculation unit 170 outputs the calculated satellite passage window width to the time deriving unit 172.

  As described above, the memory 156 of the satellite transmission terminal 110 holds the window width table 190 in advance, so that the satellite transmission terminal 110 only refers to the window width table 190 that associates the latitude and the satellite passing window width. Since the transmission time with the SSO satellite 104 is derived by simple processing, the processing load can be reduced and the reliability can be improved.

  As described above, the satellite transmission terminal 110 according to the present embodiment has a volume equivalent to that of a continuous transmission terminal and can significantly reduce power consumption compared to a continuous transmission terminal or a terminal with a reception function. Since a battery for ocean observation or the like is used as a power source, it can be suitably used for applications where power supply is limited.

(Satellite transmission method)
A satellite transmission method using the above-described satellite transmission terminal 110 is also provided. FIG. 11 is a flowchart for explaining specific processing of the satellite transmission method.

  As shown in FIG. 11, the central control unit 158 refers to the RTC unit 152 to determine whether or not a predetermined time (for example, one hour) has elapsed since the last time the GPS signal (satellite signal) was received ( If a predetermined time has elapsed (S200), YES is output to satellite signal receiving section 162a. Then, the satellite signal receiving unit 162a receives the GPS signal (S202), and the satellite signal decoding unit 162b decodes the GPS signal received in the receiving step S202, and acquires the latitude, longitude, and world coordinated time (S204). . Then, the satellite signal decoding unit 162b derives the local time of the point where the satellite transmission terminal 110 is currently located (the point where the satellite signal receiving unit 162a received the GPS signal) from the acquired longitude and the world agreement time (S206), The central control unit 158 calibrates the RTC unit 152 in this local time (S208).

  Subsequently, the power supply unit 160 acquires the current local time from the RTC unit 152 (S210), and the window width calculation unit 170 calculates the satellite passing window width from the latitude acquired in the current position acquisition step S204 (S212). ). The time deriving unit 172 centers on the descending intersection passing local time or the ascending intersection passing local time, and uses the time before half the satellite passage window width as the start time, and the time after half the satellite passage window width has elapsed. Is derived as the end time (S214).

  Next, the power supply unit 160 determines whether or not the local time acquired in the local time acquisition step S210 is included between the start time and the end time calculated in the start / end time derivation step S214 (S216). . When the local time is included between the start time and the end time (YES in S216), the power supply unit 160 determines whether or not power is currently being supplied to the transmission unit 154 (S218), and the power is turned on. If not supplied (NO in S218), supply of power to the transmission unit 154 is started (S220).

  The transmission unit 154 supplied with power in the power supply step S220 burst-transmits data including position information, an identifier, and the like indicating the current position (latitude and longitude) acquired in the current position acquisition step S204 at predetermined time intervals (S222). ). Note that the transmission unit 154 intermittently transmits data in bursts at predetermined time intervals (for example, every minute), but is omitted here for convenience of explanation.

  On the other hand, in the local time determination step S216, when it is determined that the local time is not included between the start time and the end time (NO in S216), the power supply unit 160 currently supplies power to the transmission unit 154. If the power is supplied (YES in S224), the supply of power to the transmission unit 154 is stopped (S226).

  As described above, in the satellite transmission method using the satellite transmission terminal 110 according to the present embodiment, it is used for animal tracking, ocean observation, and the like, so that the communication time with the SSO satellite 104 is ensured and the size and weight are reduced. In addition, low power consumption can be achieved.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Is done.

  For example, in the above-described embodiment, the window width calculation unit 170 has been described with reference to the window width table in which the satellite passing window width differs depending on the latitude. However, the satellite passing window width is a fixed value at any latitude. (For example, 3 hours). As described above, the higher the latitude, the longer the satellite passing window width (3.02 hours at 0 degrees latitude but 6.72 hours at 60 degrees latitude). For example, when the cycle of the SSO satellite 104 is 100 minutes, even if the satellite passage window width is fixed to 3 hours, the satellite transmission terminal 110 is set to the SSO satellite 104 at a high latitude position once or twice within the satellite passage window width. Can communicate with.

  Therefore, by setting the satellite passage window width to a fixed value, not only can the processing load of the satellite transmission terminal 110 be reduced, but also the power consumed by the transmission unit 154 can be further reduced. In addition, when the satellite transmission terminal 110 is attached to a buoy that is fixedly installed for ocean observation, since the latitude hardly changes, the satellite passing window width may be a fixed value.

  In the above-described embodiment, the SSO satellite 104 that orbits the sun-synchronous quasi-regression orbit is cited as the transmission partner of the satellite transmission terminal 110. 110 can transmit data while reducing power consumption.

  Note that each step of the satellite transmission method of the present specification does not necessarily have to be processed in time series in the order described in the flowchart, and may include parallel or subroutine processing.

  INDUSTRIAL APPLICABILITY The present invention can be used for a satellite transmission terminal that transmits data to a satellite that orbits a solar synchronous quasi-return orbit and a satellite transmission method using the same.

104 ... SSO satellite 110 ... satellite transmission terminal 150 ... navigation satellite unit 152 ... RTC unit 154 ... transmission unit 156 ... memory 158 ... central control unit 160 ... power supply unit 162a ... satellite signal reception unit 162b ... satellite signal decoding unit 164 ... satellite Radio wave forecast range 170 ... window width calculation unit 172 ... time derivation unit 190 ... window width table

Claims (4)

A satellite signal receiver for receiving satellite signals transmitted from the navigation satellite;
A satellite signal decoding unit that decodes the received satellite signal to derive longitude, latitude, and local time;
The local time passing through the descending point indicated by the local time in the longitude of the point where the connection between the SSO satellite orbiting the sun-synchronous quasi-return orbit and the center of the earth passes through the equator from north to south, or the SSO satellite When the connection between the center of the earth and the center of the earth passes from the south to the north of the equator, the local time at the ascending point indicated by the local time at the longitude of the passing point, and the period during which communication with the SSO satellite is not possible due to restrictions based on the rotation of the earth On the basis of the satellite passing window width that is a period excluding the start time, a start time that is a time at which data transmission to the SSO satellite is started, and an end time that is a time at which data transmission to the SSO satellite is ended. A time deriving unit for deriving
A transmission unit for transmitting data to the SSO satellite while receiving power supply;
A satellite transmission terminal comprising: a power supply unit that supplies power to the transmission unit while the derived local time is included from the start time to the end time.   The satellite transmission terminal according to claim 1, further comprising a window width calculation unit that calculates the satellite passage window width based on the derived latitude. A memory for previously storing a window width table in which the latitude and the satellite passing window width are associated;
The satellite transmission terminal according to claim 2, wherein the window width calculation unit calculates the satellite passing window width from the derived latitude with reference to the window width table. A satellite transmission method using a satellite transmission terminal including a transmission unit that transmits data to an SSO satellite orbiting a solar synchronous quasi-return orbit while receiving power supply,
Receives satellite signals transmitted from navigation satellites,
Decode the received satellite signal to derive longitude, latitude, and local time,
When the connection between the SSO satellite and the center of the earth passes through the equator from north to south, the local time at the descending intersection point indicated by the local time at the longitude of the passing point, or the connection between the SSO satellite and the center of the earth The satellite is a period excluding the local time at the rising intersection passing local time indicated by the local time at the longitude of the passing point when passing through the equator from the south to the north, and the period during which communication with the SSO satellite cannot be performed due to restrictions based on the rotation of the earth Based on the passing window width, a start time that is a time for starting transmission of data to the SSO satellite and an end time that is a time for ending transmission of data to the SSO satellite are derived,
A satellite transmission method characterized in that power is supplied to the transmitter while the derived local time is included from the start time to the end time.

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