JP3993178B2 - Ground beacon station and beacon wave transmission method - Google Patents

Description

  The present invention relates to a satellite and a ground beacon station. For example, it relates to control of beacon waves from a ground beacon station when two quasi-zenith satellites perform handover.

A technique is known in which three quasi-zenith satellites always fly over Japan by three quasi-zenith satellites turning around the earth while writing the figure of 8. At that time, two quasi-zenith satellites need to be handed over. In addition, since the quasi-zenith satellite has an 8-shaped orbit, the attitude of the satellite must be controlled while moving the orbit. In order to control the attitude, it is conceivable to control the attitude of the quasi-zenith satellite by sending a beacon wave from a ground beacon station and tracking the beacon wave.
JP 2004-062874 A JP 2004-028593 A JP 2004-015451 A

  When two quasi-zenith satellites are handed over, there has been a problem that a technical solution for how to hand over using one beacon wave has to be sought.

  An object of the present invention is to provide a method or a method capable of performing handover using one beacon wave when two satellites such as a quasi-zenith satellite are handed over.

  The terrestrial beacon station according to the present invention transmits a beacon wave between two satellites when the terrestrial beacon station transmits a beacon wave to the satellite and performs handover at the meeting point of the two satellites. It is characterized by doing.

  According to the present invention, when two satellites are handed over at the meeting point, the beacon wave is communicated between the two satellites, so that the handover can be performed using one ground beacon station. .

  In addition, since the satellite also includes a receiver that receives a beacon wave having the same frequency, the cost of the satellite can be reduced.

  First, details of the quasi-zenith satellite will be described below.

  1 is a diagram for explaining a difference in elevation angle between a quasi-zenith satellite and a geostationary satellite (FIG. 1 is a quotation from “www2.crl.go.jp/ka/control/efsat/index-j.html”). Is).

  As shown in FIG. 1, the quasi-zenith satellite is launched so that the elevation angle is 60 degrees or more. On the other hand, geostationary satellites cannot have an elevation angle higher than 48 degrees in Tokyo. Due to this difference in elevation angle, radio waves may not reach the buildings and mountains due to geostationary satellites. For example, as shown in FIG. 1, radio waves reach a vehicle behind a building from a quasi-zenith satellite with a high elevation angle, but do not reach a stationary satellite with a low elevation angle.

  FIG. 2 is a diagram for explaining a case where an inclined orbit is projected onto the equator plane. FIG. 3 is a diagram showing the locus of the quasi-zenith satellite Z on the map. (FIGS. 2 and 3 are quotes from “www2.crl.go.jp/ka/control/efsat/8n.html”). The quasi-zenith satellite has three satellites arranged as Z1, Z2 and Z3 in FIG. In FIG. 2, S1, S2, and S3 indicate the revolution of the geostationary satellite S, and Z1, Z2, and Z3 indicate the revolution of the quasi-zenith satellite Z.

  FIG. 4 will be explained with reference to the contents of “Quasi-Zenith Satellite 8-shaped satellite” by the Communications Research Laboratory, Ministry of Posts and Telecommunications.

  FIG. 4 is a diagram showing the orbit of the zenith satellite and the tilt angle with respect to the equatorial plane. As shown in FIG. 4, each of the three quasi-zenith satellites orbits one day a day in accordance with the rotation of the earth over 35800 km above the ground so that the inclination angle is about 45 degrees from the equator plane.

  In addition, each of the three quasi-zenith satellites is arranged 120 degrees apart at the intersection with the equator plane. For example, when attention is paid to one of the three quasi-zenith satellites Z1 (FIG. 2), the quasi-zenith satellite is shifted in longitude in the minus direction as compared to the geostationary satellite.

  For this reason, when the ground is fixed, the locus of the quasi-zenith satellite draws “8” as shown in FIG. The three quasi-zenith satellites have different orbital planes, but are located above Japan without interruption so that they change every eight hours.

  Moreover, the fact that there are always quasi-zenith satellites with an elevation angle of 60 degrees or more in the sky above Japan means that receivers of positioning information can receive radio waves from quasi-zenith satellites even in the shadows of buildings. Compared to the GPS used, there is no fear of blocking radio waves, so the time rate for positioning with the required positioning accuracy increases.

  As described above, FIG. 4 and the above description are the contents described in the document “Quasi-Zenith Satellite 8-shaped satellite”.

Embodiment 1 FIG.
FIG. 5 is a configuration diagram of the terrestrial beacon tracking system according to this embodiment. The ground beacon station 55 transmits a beacon wave 44. Three quasi-zenith satellites 99 are flying above.

  One of them is the active satellite 88 in the sky above Japan. Here, the ACTIVE satellite 88 is a satellite that is actually communicating. That is, the satellite in communication state.

  The remaining two are not in Japan, but are inactive satellites. Here, an inactive satellite is a satellite that is not communicating. That is, a satellite in a non-satellite communication state.

  In FIG. 5, the satellite flying in the orbit 43 on the right side from the meeting point 41 is the ACTIVE satellite 88. Two satellites on the left side of the meeting point 41 are inactive satellites.

  The terrestrial beacon station 55 transmits the beacon wave 44 toward the ACTIVE satellite 88. The active satellite 88 captures the beacon wave 44 and controls the beacon wave 44 to direct the attitude of the active satellite 88 so that the active satellite 88 can accurately communicate with other communication devices on the ground. it can.

  In FIG. 5, the case where the ACTIVE satellite 88 heads for the meeting point 41 is referred to as an OUT satellite 66. In FIG. 5, the case where the inactive satellite heads to the meeting point 41 is called an IN satellite 77. The OUT satellite 66 is an example of a first satellite. The IN satellite 77 is an example of a second satellite.

  The OUT satellite 66 and the IN satellite 77 intersect at the meeting point 41. At that time, handover is performed. That is, the OUT satellite 66 changes from an active satellite to an inactive satellite. Conversely, the IN satellite 77 changes from an inactive satellite to an active satellite.

  Along with this handover, the ground beacon station 55 needs to switch the beacon wave 44 from the OUT satellite 66 to the IN satellite 77. That is, the direction of the beacon wave 44 must be changed as indicated by the arrow C.

  The quasi-zenith satellite 99 is provided with, for example, 24 horn antennas. FIG. 6 is a diagram showing the arrangement of horn antennas of the quasi-zenith satellite 99. This arrangement is shaped to cover the Japanese archipelago. Four horns form one beam. That is, the center of the four horns is the center of the beam.

  In FIG. 6, A, B, C, and D indicate Osaka beam horns for Osaka.

  FIG. 7 is a diagram showing the beam arrangement. One beam is formed by four horns of the 24 horns shown in FIG. Then, as shown in FIG. 7, nine beams are irradiated so as to cover the Japanese archipelago. These multiple beams are called multi-beams.

  Communication is not possible unless this beam always irradiates a position as shown in FIG. However, since the quasi-zenith satellite 99 moves in the orbit 43, the attitude control of the quasi-zenith satellite 99 must be performed in order to irradiate the multi-beams accurately on the ground.

  Therefore, the quasi-zenith satellite 99 needs to perform RF (radio frequency) tracking. That is, high precision pointing by RF tracking is required. The beacon wave 44 transmitted from the ground beacon station 55 is used for RF tracking.

  The quasi-zenith satellite 99 receives the beacon wave 44 from the terrestrial beacon station 55, controls the attitude of the quasi-zenith satellite 99, and performs control so that the multi-beams are correctly irradiated to each place in the Japanese archipelago.

  FIG. 8 is a configuration diagram of the terrestrial beacon station 55.

  The ground beacon station 55 includes an antenna 51 that transmits a beacon wave 44. The antenna 51 receives radio waves from the quasi-zenith satellite 99.

  The transceiver 53 transmits or receives signals transmitted and received by the antenna 51. The communication system 54 is a circuit for processing signals transmitted and received by the transceiver 53. The transceiver 53 receives a signal from the quasi-zenith satellite 99 and outputs the reception level to the tracking device 57.

  The tracking device 57 inputs the orbit parameters of the quasi-zenith satellite 99 from the orbit parameter database 58 and determines the direction of the beacon wave 44 based on the orbit parameters. This operation of the tracking device 57 is performed by the tracking program 59.

  In addition, the tracking device 57 inputs the reception level and confirms that the reception from the quasi-zenith satellite 99 is being performed correctly. The tracking device 57 outputs a signal for controlling the direction of the antenna 51.

  The drive unit 56 receives the signal for controlling the direction of the antenna 51 output from the tracking device 57 and changes the direction of the antenna 51. The antenna 51 changes the direction of the antenna under the control of the driving unit 56, and consequently changes the direction of the beacon wave 44.

  FIG. 9 is a configuration diagram of the quasi-zenith satellite 99. The quasi-zenith satellite 99 is provided with 24 horn antennas 81. FIG. 9 shows four horn antennas 81 among them. The four horn antennas 81 are for the Osaka beam.

  The quasi-zenith satellite 99 is provided with a test coupler 83 and a bandpass filter 84 corresponding to the horn antenna 81. The output of the band pass filter 84 is input to the satellite communication system 86. The satellite communication system 86 performs communication control of the quasi-zenith satellite 99.

  The quasi-zenith satellite 99 is further provided with a directivity control unit 97. The pointing control unit 97 includes a program tracking unit 91, a beacon wave tracking unit 93, and a satellite control system 95, and controls the attitude of the quasi-zenith satellite 99.

  The beacon wave tracking unit 93 inputs a signal from the coupler 85 and performs RF tracking.

  The program tracking unit 91 controls the attitude of the quasi-zenith satellite 99 by a program.

  The monopulse comparator 87 outputs a sum pattern and a difference pattern from the signals A, B, C, and D from the Osaka beam horn.

  The tracking receiver 89 outputs a control signal to the satellite control system 95 from the sum pattern and the difference pattern. The satellite control system 95 controls the attitude of the satellite.

  FIG. 10 is a sequence of satellite antenna pointing control at the time of handover.

  FIG. 11 is a flowchart of the tracking program 59 of the ground beacon station 55.

  FIG. 12 is a flowchart of the pointing control unit 97 of the quasi-zenith satellite 99.

  In FIG. 10, the horizontal axis is time. The vertical axis shows the OUT satellite 66, the IN satellite 77, and the ground beacon station 55.

  The time for handover of communication signals between the OUT satellite 66 and the IN satellite 77 is 120 seconds. The time before and after the handover (H / O) is a time for stabilizing the attitude of the satellite. The time before and after this including HO is 23 minutes. This period of 23 minutes is called the meeting period.

  Since the OUT satellite 66 is the ACTIVE satellite 88, the RF tracking is performed toward the meeting point. That is, the attitude is controlled so as to face the direction of the ground beacon station 55. At the end of the meeting period, the OUT satellite 66 switches to program tracking. The program tracking is to control the attitude of the satellite so that it faces the center of the earth (hereinafter referred to as the earth's center).

  On the other hand, since the IN satellite 77 is an inactive satellite, control toward the center is performed by program tracking, and RF tracking is performed at the meeting period start time. Therefore, the attitude of the satellite is controlled so as to face the direction of the ground beacon station 55.

  The ground beacon station 55 controls the direction of the beacon wave 44 by the tracking program 59 and keeps emitting the beacon wave 44 in the direction based on the orbit parameters.

  When the meeting period start time is reached, the ground beacon station 55 fixes the beacon wave 44 between the OUT satellite 66 and the IN satellite 77, that is, at the meeting point. At the end of the meeting period, the ground beacon station 55 directs the beacon wave 44 to the IN satellite 77 and tracks the IN satellite 77.

  Based on FIG. 11, the operation of the tracking program 59 of the ground beacon station 55 will be described.

  The trajectory parameter database 58 stores parameters indicating trajectories over the Japanese archipelago, as shown in FIG. That is, the 8-hour satellite orbit shown in FIG. 13 is stored. This 8-hour orbit is that of an active satellite.

S61: First satellite tracking step First, the active satellite (OUT satellite 66) is tracked based on the orbit parameters stored in the orbit parameter database 58.

S63: Meeting start determination step The tracking program 59 determines whether or not the current time is the meeting period start time. If it is not the meeting period start time, S61 is continued. When the meeting period start time is reached, the following S64 is executed.

S64: Beam Change Step When the meeting period start time is reached, the tracking program 59 of the ground beacon station 55 changes the beam direction of the beacon wave 44 between the OUT satellite 66 and the IN satellite 77. That is, the beam is moved to the meeting point.

S65: Beacon wave fixing step The tracking program 59 fixes the beam of the beacon wave 44 to the meeting point. While this beam is fixed at the meeting point, the OUT satellite 66 and the IN satellite 77 exist in the range of the beacon wave 44 as shown in FIG. This time is about 23 minutes. The IN satellite 77 controls the attitude so that the satellite faces the direction of the ground beacon station 55 using the initial time of 23 minutes. Then, a handover for 120 seconds is performed.

S67: Meeting End Determination Step The tracking program 59 determines whether or not the current time has reached the meeting period end time. If not, the tracking program 59 continues to maintain the beam fixing in S65. When the meeting period end time is reached, the following S68 is executed.

S68: Tracking start process The tracking program 59 changes the beam of the beacon wave 44 to the IN satellite 77.

S69: Second satellite tracking step The tracking program 59 tracks the IN satellite 77. Thereafter, the tracking program 59 returns to S61 and continues to track the IN satellite 77 as an active satellite.

  Next, the operation of the pointing control unit 97 of the quasi-zenith satellite 99 will be described with reference to FIG. First, in S91, it is determined whether or not the meeting is in progress. If it is not during the meeting period, it is determined in S93 whether it is active or inactive. If it is inactive, program tracking is performed in S94. This program tracking is a tracking method that does not use a beacon wave at all. That is, it is a tracking process that ignores the beacon wave. In this program tracking, attitude control is performed so that the satellite is directed in the geocentric direction.

  FIG. 15 explains the direction of the satellite. There is a difference in angle θ between the direction of the ground beacon station 55 and the direction of the earth center seen from the quasi-zenith satellite 99. Program tracking controls the attitude of the satellite in the receiving direction. This angle θ varies depending on the orbital position of the satellite. For example, when the satellite is at the meeting point, the angle between the direction of the ground beacon station 55 and the geocentric direction is about 1.4 degrees.

  Next, when it is determined in S93 that the satellite is an active satellite, RF tracking is performed in S95. With this tracking, the attitude of the satellite is controlled in the direction of the ground beacon station 55.

  Next, if it is determined in S91 that the meeting is in progress, it is determined in S96 whether the satellite is the OUT satellite 66 or the IN satellite 77. If it is the IN satellite 77, RF tracking is started in S97. That is, as shown in FIG. 15, an operation of changing the posture from the geocentric direction to the direction of the ground beacon station 55 is performed. If the ground beacon station is located in the Osaka region, this angle is about 1.4 degrees. The location of the ground beacon station is not limited to Osaka, but can be any location. If it is determined in S96 that the satellite is an OUT satellite 66, RF tracking is continued in S98. In any of the tracking cases, the actual attitude control is performed by the satellite control system 95 in S99.

  FIG. 16 is a diagram showing the above-described operation.

  The left side of FIG. 16 shows before handover. The right side shows after handover. Times are indicated from T1 to T10.

  The handover is assumed to be performed at T6. The meeting period start time is T5. The meeting period end time is assumed to be T7.

  In FIG. 16, an arrow A indicates the moving direction of the IN satellite 77. An arrow B indicates the moving direction of the OUT satellite 66. A circle on the arrow A indicates the position of the IN satellite 77. A circle on the arrow B indicates the position of the OUT satellite 66.

  As shown on the left side of FIG. 16, the ground beacon station 55 tracks the OUT satellite 66 until time T4. At time T5, the direction of the beacon wave 44 is changed so that the two satellites enter the beam. During T6 and T7, the beacon wave 44 is fixed in the direction in which both satellites enter the beam. For example, it is desirable that the center of the beacon wave 44 is facing the meeting point. Alternatively, it is desirable that the center of the beacon wave 44 is directed to a point at an equal distance from both satellites. During this time T5, T6, T7, the attitude control of the satellite is performed, and the handover is performed. At time T8, the beacon wave 44 is directed to the IN satellite 77. Thereafter, the IN satellite 77 is tracked.

  17 to 20 are diagrams for explaining the operations of the monopulse comparator 87 and the tracking receiver 89 of the beacon wave tracking unit 93. The beacon wave tracking unit 93 performs monopulse tracking over four horn arrays.

  FIG. 17 shows the arrangement of four horns A, B, C, and D. The horizontal direction is the azimuth direction. The vertical direction is the elevation direction.

  FIG. 18 is an explanatory diagram of the operation of the monopulse comparator 87. The monopulse comparator 87 inputs signals from the four horns A, B, C, and D, and outputs a sum pattern Σ and a difference pattern Δ to the synthesis circuit by # 1 # 2, # 3, and # 4.

  FIG. 19 is a relationship diagram between the sum pattern and the difference pattern. The horizontal axis in FIG. 19 is the direction of the antenna. The unit is an angle. The vertical axis represents gain. The difference pattern (Δ) minus the sum pattern (Σ) is called a gain difference here. The tracking receiver 89 controls the attitude of the satellite so that the gain difference is maximized. That is, the tracking receiver 89 searches for a point where the gain difference approaches the maximum by swinging the antenna direction (the attitude of the satellite) left and right and up and down. The tracking receiver 89 swings the direction of the antenna left and right and up and down at regular time intervals to search for the posture direction.

  As described above, in this embodiment, the method of realizing the primary radiator of the multi-beam communication antenna with the four-element pyramid horn array configuration in consideration of monopulse tracking has been described.

  In the quasi-zenith satellite, an antenna having a diameter of 3.5 meters is used for Ku-band communication transmission / reception. And this antenna is used with the horn which comprises a multi-beam. Thus, by using the communication antenna and the monopulse tracking antenna, there are the following advantages.

  By making the antenna of the quasi-zenith satellite 99 have a high gain, the antenna 51 of the ground beacon station 55 can have a small diameter.

  Thus, by setting the antenna 51 of the ground beacon station 55 to have a small diameter (about 30 centimeters), the directivity direction of the beacon wave 44 becomes wide, and it becomes possible to cover two satellites at the same time during handover. . That is, it becomes possible to acquire two satellites simultaneously by one ground beacon station 55.

  Thus, there is no need to provide two ground beacon stations 55, and the cost of the ground station can be reduced. In addition, since only one ground beacon station 55 needs to be provided, it is possible to use a single beacon frequency signal for the two quasi-zenith satellites 99.

  On the other hand, in the quasi-zenith satellite 99, the three quasi-zenith satellites 99 need only be equipped with receivers having the same frequency, so that the manufacturing cost of the satellite can be reduced.

  In the above example, the RF tracking and the program tracking are individually operated. However, the program tracking is always backed up during the RF tracking, and even if the RF tracking fails, the program tracking may be performed immediately. Good. Conversely, the program tracking may be always corrected and maintained with high accuracy by the information of RF tracking.

It is a figure explaining the difference in the elevation angle of a quasi-zenith satellite and a geostationary satellite. It is a figure explaining the case where an inclined orbit is projected on an equatorial plane. It is a figure which shows the locus | trajectory of the quasi-zenith satellite Z on a map. It is a figure which shows the inclination angle with respect to the orbit of an zenith satellite and an equatorial plane. It is a figure which shows the ground beacon station 55, the OUT satellite 66, and the IN satellite 77. It is a figure which shows horn arrangement | positioning. It is a figure which shows beam arrangement | positioning. 2 is a configuration diagram of a ground beacon station 55. FIG. 2 is a configuration diagram of a quasi-zenith satellite 99. FIG. It is a sequence of satellite antenna pointing control at the time of handover. It is a flowchart of the tracking program 59 of the ground beacon station 55. 10 is a flowchart of the pointing control unit 97 of the quasi-zenith satellite 99. It is a figure which shows the orbit of the quasi-zenith satellite 99. It is a figure which shows the meeting state of OUT satellite 66 and IN satellite 77. FIG. It is a figure explaining the ground beacon station 55 and the angle of a center. It is a figure explaining RF tracking of a beacon wave. It is a figure which shows the arrangement | positioning relationship of a horn. 6 is an operation explanatory diagram of a monopulse comparator 87. FIG. It is a related figure of a sum pattern and a difference pattern.

Explanation of symbols

  41 meeting point, 43 orbit, 44 beacon wave, 51 antenna, 53 transceiver, 54 communication system, 55 ground beacon station, 56 drive unit, 57 tracking device, 58 orbit parameter database, 59 tracking program, 66 OUT satellite, 77 IN Satellite, 81 Horn antenna, 88 ACTIVE satellite, 99 Quasi-zenith satellite.

Claims (2)

In terrestrial beacon stations that transmit beacon waves to satellites,
The satellite to which the beacon wave is transmitted has a first loop orbit among a plurality of satellites moving on an orbit having an association point in which the first loop orbit and the second loop orbit are connected at one point. The first satellite to move,
The first satellite moving in the first loop orbit is handed over to the second satellite moving in the second loop orbit at the meeting point for a predetermined period and moves in the second loop orbit. The second satellite,
The second satellite that moves in the second loop orbit is a satellite that becomes the first satellite that moves in the first loop orbit by handover,
The above ground beacon station
An orbit parameter database for storing satellite orbits;
An antenna that transmits the beacon wave;
A driving unit that receives a signal for controlling the direction of the antenna and controls the direction of the antenna based on the received signal;
The satellite orbit stored in the orbit parameter database is inputted, the orbit of the first satellite is tracked based on the inputted satellite orbit, and the direction of the beacon wave transmitted from the antenna is changed to the first satellite. A signal to be controlled in the direction of
Find the meeting point based on the satellite orbit entered above,
Based on the input satellite orbit, the time at which the first satellite starts handover with the second satellite at the meeting point, the time to end handover, and a predetermined time before the handover start time. Find the meeting period start time and the meeting period end time after a predetermined time after the handover end time,
It is determined whether or not the current time is the meeting period start time. If the current time is the meeting period start time, the tracking of the first satellite is stopped and the direction of the beacon wave transmitted from the antenna is obtained. A signal to be controlled in the direction of the meeting point is output to the driving unit, and the direction of the beacon wave transmitted from the antenna by the driving unit is fixed to the direction of the meeting point until the current time reaches the meeting period end time, If the current time is the meeting period end time, moving from the second loop orbit to the first loop orbit starts tracking the satellite that has become the first satellite from the second satellite, A tracking device that outputs a signal for controlling the direction of the beacon wave transmitted from the antenna in the direction of the satellite that has become the first satellite from the second satellite to the driving unit. Characteristic ground Bacon stations. A beacon with respect to the first satellite moving in the first loop orbit among a plurality of satellites moving in the orbit having the meeting point obtained by connecting the first loop orbit and the second loop orbit at one point. In a beacon wave transmission method of a ground beacon station, comprising: an antenna that transmits a wave; a drive unit that controls the direction of the antenna; and a tracking device that outputs a signal that controls the direction of the antenna to the drive unit .
The first satellite moving in the first loop orbit is handed over to the second satellite moving in the second loop orbit at the meeting point for a predetermined period and moves in the second loop orbit. The second satellite,
The second satellite moving in the second loop orbit is a satellite that becomes the first satellite moving in the first loop orbit by handover,
The beacon wave transmission method is as follows:
The tracking device inputs the satellite orbit from the orbit parameter database storing the satellite orbit, tracks the first satellite orbit based on the input satellite orbit, and transmits the beacon wave transmitted from the antenna. A first satellite tracking step of outputting a signal for controlling the direction to the direction of the first satellite to the driving unit ;
The tracking device determines the meeting point based on the input satellite orbit,
Based on the satellite orbit input by the tracking device, the time when the first satellite starts handover with the second satellite at the meeting point, the time when handover ends, and the handover start time The meeting period start time before the predetermined time and the meeting period end time after the predetermined time after the handover end time,
A meeting start determination step for determining whether or not the current time is the meeting period start time by the tracking device;
When it is determined in the meeting start determination step that the current time is the meeting period start time, the tracking device stops tracking the first satellite in the first satellite tracking step and transmits a beacon wave transmitted from the antenna. A beam changing step for outputting a signal for controlling the direction to the direction of the determined meeting point to the drive unit,
The direction of the beacon wave transmitted from the antenna is fixed to the direction of the meeting point by the tracking device until the current time reaches the end time of the meeting period. A beacon wave fixing step for outputting a signal to be controlled to the drive unit ;
The meeting end determination step for determining whether or not the current time is the meeting period end time by the tracking device;
If it is determined in the meeting end determination step that the current time is the meeting period end time, the tracking device moves from the second loop orbit to the first loop orbit to move the first from the second satellite. The tracking of the satellite that has become the first satellite is started, and a signal for controlling the direction of the beacon wave transmitted from the antenna from the second satellite to the direction of the satellite that has become the first satellite is sent to the driving unit. A beacon wave transmission method comprising: a second satellite tracking step of outputting .

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