JP2987443B1 - Geostationary satellite position monitoring method - Google Patents

Abstract

A geostationary satellite position monitoring method for monitoring the orbital position of a geostationary satellite is provided. SOLUTION: First and second movable reflectors 2a, 2b are installed at both ends of a rotating arm 1; first and second fixed reflectors 4a, 4b are provided on the ground; Second
The reflection directions of the first and second movable reflectors 2a and 2b and the first and second fixed reflectors 4a and 4b so that the antennas 5a and 5b always receive the radio waves of the geostationary satellite S even when the arm 1 rotates. Is changed, and the radio signals received by the antennas 5a and 5b are correlated to obtain the time difference T 'required for the signal emitted by the geostationary satellite S to reach the antennas 5a and 5b, respectively. As the rotation angle of the arm 1 increases from 0 to 360 degrees, the elevation and azimuth of the geostationary satellite S are determined by reading the amplitude and phase based on a sinusoidal curve drawn by the measured value of the time difference. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a technology for monitoring a geosynchronous orbit, and more particularly to a technology for accurately monitoring the orbital position of a geosynchronous satellite.

[0002]

2. Description of the Related Art With the development of satellite communication, a large number of geosynchronous satellites have been placed in geosynchronous orbit. When launching a new geosynchronous satellite into geosynchronous orbit, it is essential to adjust the orbital position and frequency to prevent radio interference with existing geosynchronous satellites. In order to make such adjustments appropriately as the number of geostationary satellites increases, the orbital position and frequency of an unspecified number of geostationary satellites launched in and outside Japan must be accurately determined at any time. It is important to monitor the situation.

As means for measuring the position of the geostationary satellite, there are two methods of measuring the distance from the earth station to the geostationary satellite or measuring the direction in which the geostationary satellite can be seen (elevation angle and azimuth angle). These are called distance measurement and angle measurement, respectively.

[0004] For operators operating geostationary satellites, etc.,
Usually, these are used together with distance measurement as a main and angle measurement as a sub. However, since ranging is to measure the delay time by reciprocating the radio signal between the earth station and the geostationary satellite, the earth station equipment must be designed for the geostationary satellite for its implementation. .

On the other hand, angle measurement can be performed only by receiving satellite radio waves. Therefore, in order to monitor an unspecified number of geostationary satellites, angle measurement is used instead of distance measurement.

In order to monitor the satellite position based on the angle measurement, the following techniques have been conventionally implemented. That is, the monitoring station is equipped with a parabolic antenna having a sufficiently large diameter. Then, the beam of the antenna is directed to a geosynchronous orbit visible from the monitoring station to monitor satellite radio waves.

Specifically, the antenna beam is directed to a certain point on the orbit, and the direction of the antenna is driven so that the one point is gradually moved along the orbit. It measures. If an elevation angle and an azimuth at which the strength of the radio wave is maximized for a certain geostationary satellite are found, the orbital position of the geostationary satellite is determined by converting the angle.

At this time, the reason for using a large-diameter antenna is as follows.
This is because the smaller the beam width of the antenna, the higher the accuracy of the angle measurement, and therefore the more accurate the position monitoring can be performed. However, when monitoring the orbital position of the geostationary satellite based on the angle measurement,
The prior art has the following problems.

[0009]

The beam width of the antenna, which is a factor determining the angle measurement accuracy, is determined by the ratio of the wavelength of the radio wave to the antenna aperture. Therefore, in order to obtain a certain angle measurement accuracy, when the frequency of the satellite radio wave to be monitored is low, the aperture of the antenna must be very large, which is difficult to implement.

The beam width of the antenna is determined by theoretical angle measurement accuracy. Actually, there is a limit to the mechanical rigidity of the antenna. In particular, when the elevation angle of the antenna is changed, the manner in which deflection occurs due to its own weight changes. Further, a device (angle encoder) for reading the directivity direction of the antenna as the rotation angle of the shaft also has an inherent error. For these reasons, the angle measurement accuracy actually achieved is lower than the theoretical angle measurement accuracy, and as a result, it has hindered the realization of accurate position monitoring.

[0011] It is assumed that interference occurs when an earth station performing satellite communication receives radio waves from a certain geostationary satellite and simultaneously receives another satellite radio wave. In order to cope with the occurrence of such interference, it is important to know the orbital position of the geostationary satellite causing the interference, and in such a case, accurate monitoring is required.

However, in the prior art, when the radio waves of two geosynchronous satellites interfere with each other, it is impossible, or even possible, to perform angle measurement for each geosynchronous satellite individually. There is a problem that the accuracy is considerably reduced as compared with the angle measurement accuracy when there is no interference.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and has an arm which rotates at a constant speed in a certain direction about a center of a circle as a rotation axis, such as a diameter of a circle in a horizontal plane. One moving reflector at one end of the arm, and one moving reflector at the other end, and a pair of antennas fixed on the ground are connected to a pair of antennas on the arm. The direction of reflection of each movable reflector and each fixed reflector is changed so as to always receive the radio wave of the geostationary satellite via the movable reflector and a pair of fixed reflectors fixed on the ground, and the pair of antennas receive the radio waves. By performing correlation processing on the obtained radio signal via the correlation processing means, a time difference required for the signal emitted by the geostationary satellite to reach each of the pair of antennas is obtained, and the radio wave reflected by one of the movable reflectors is obtained. From the moment of the reflection The time required to reach one antenna via one fixed reflector and the radio wave reflected by the other moving reflector are calculated from the moment of the reflection and reach the other antenna via the other fixed reflector. A correction method for the time difference is performed by adding a correction to the time difference based on a difference between the time difference and the time required for calculating the time difference curve, and a correction time difference curve is derived from the correction time difference. To provide.

According to the present invention, there is further provided an arm which rotates at a constant speed in a fixed direction about a center of the circle as a rotation axis, such as a diameter of the circle in a horizontal plane, and one end of the arm is provided with one movement. A reflector is installed, and one movable reflector is also installed at the other end, and a pair of antennas fixed on the ground are used as a pair of movable reflectors on the arm and a pair of fixed reflectors fixed on the ground. The reflection direction of each movable reflector and each fixed reflector is changed so as to always receive the radio wave of the geostationary satellite via the plate, and the radio signals received by the pair of antennas are subjected to correlation processing via correlation processing means. By calculating the time difference required for the signals emitted by the geostationary satellites to reach the pair of antennas, the radio wave reflected by one of the movable reflectors is counted from the moment of the reflection, and one of the fixed reflectors is calculated. Through one of Anne The difference between the time required to reach the antenna and the time required for the radio wave reflected by the other moving reflector to reach the other antenna via the other fixed reflector from the moment of reflection is corrected to the above time difference Is added to the corrected time difference, a corrected time difference curve is derived from the corrected time difference, and when the direction of the arm is perpendicular to the incident direction of the satellite radio wave, the time difference curve intersects the zero axis of the graph, and Provided is a geostationary satellite position monitoring method for determining the azimuth of the geostationary satellite by reading the phase of the time difference curve based on the fact that the time difference curve reaches the maximum of positive and negative when the direction of the arm follows the incident direction of the satellite radio wave. Is what you do.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the present invention will be described with reference to FIG.

An arm 1 that rotates at a constant speed about the center of the circle as a rotation axis, such as the diameter of a circle in a horizontal plane, is provided. A first movable reflection plate 2a is provided at one end of the arm 1 and the other is provided. At the end, a second movable reflection plate 2b is provided. First and second fixed reflectors 4a and 4b are installed as a pair of fixed reflectors outside the range where the arm 1 rotates and fixed, and first and second antennas 5a and 5b are installed as two receiving antennas. . The first and second movable reflectors 2a and 2b and the first and second fixed reflectors 4a and 4b are all planar reflectors, the pointing directions thereof are variable, and the reflected radio waves are incident on the receiving antenna without loss. Have the necessary area.

When the arm 1 rotates, the reflection directions of the first and second movable reflecting plates 2a and 2b and the first and second fixed reflecting plates 4
By adjusting the reflection directions of the first and second fixed reflectors 4a and 4b, the radio waves of the satellite S are constantly adjusted.
And then received by the first antenna 5a, and the radio waves of the satellite S are reflected by the second movable reflector 2b and the second fixed reflector 4b before being received by the second antenna 5b. That is, the first and second movable reflection plates 2
a, 2b and the first and second fixed reflecting plates 4a, 4b are provided with driving mechanisms capable of appropriately changing the direction of the reflecting surface, and these driving mechanisms are controlled by a control device (not shown). Radio waves are always first and second without loss
The first and second directions are set so as to be incident on the antennas 5a and 5b.
The movable reflectors 2a, 2b and the first and second fixed reflectors 4a,
4b.

It should be noted that the radio wave path from the first and second movable reflectors 2a and 2b to the first and second antennas 5a and 5b via the first and second fixed reflectors 4a and 4b is not blocked. The first and second antennas 5a and 5b are positioned below the plane on which the arm 1 rotates.

The radio signals received by the first and second antennas 5a and 5b are subjected to correlation processing using the correlation processing means 3, so that the signal emitted by the geostationary satellite S is transmitted to the first and second antennas 5a and 5b, respectively. The time difference T 'required to reach is measured. Here, the first delay time Ta required for the radio wave reflected by the first movable reflector 2a to reach the first antenna 5a via the first fixed reflector 4a starting from the moment of the reflection.
The second delay time Tb required for the radio wave reflected by the second movable reflector 2b to reach the second antenna 5b via the second fixed reflector 4b from the moment of the reflection is the rotation angle of the arm 1. It can be known as a function of θ. The difference between the measured time difference T ′ and the corrected time difference T ′ by Ta−Tb is referred to as T, and this is called a corrected time difference. That is, the corrected time difference T means that the first and second antennas 5a and 5b are respectively assumed to be the first and second movable reflectors 2a and 2a, respectively.
Assuming that it is at the position 2b, it is nothing but a time difference that should be obtained when measured by the correlation processing means 3.

That is, by measuring the corrected time difference T, it is possible to perform a measurement equivalent to receiving the radio wave from the satellite S with the first and second antennas 5a and 5b positioned at both ends of the arm 1, respectively. It becomes. In addition, Ta-
Since Tb changes sequentially with the rotation of the arm 1,
A function of detecting a rotational position of the arm 1 and calculating a distance between the first and second movable reflecting plates 2a and 2b and the first and second fixed reflecting plates 4a and 4b from the rotational position; 1
A function for obtaining the delay time Ta and the second delay time Tb is required. These functions may be provided in the correlation processing means 3 or provided separately with a correction time difference calculation means or the like.
The second delay times Ta and Tb may be calculated.

The measured value of the corrected time difference T obtained from the time difference T 'as described above draws a sinusoidal curve as the rotation angle θ of the arm 1 goes from 0 ° to 360 ° (hereinafter, referred to as “sinusoidal curve”). This is called a modified time difference curve G).

Assuming that the geostationary satellite S is on the horizon, the amplitude of the modified time difference curve G is maximized, which is equal to the arm length divided by the speed of light. If the geostationary satellite S is at the zenith, the modified time difference curve G becomes flat and always shows zero. Based on this relationship, the elevation angle of the geostationary satellite S is determined by reading the amplitude of the corrected time difference curve G.

On the other hand, when the direction of the arm 1 is perpendicular to the incident direction of the satellite radio wave, the corrected time difference curve G intersects the zero axis of the graph, and when the arm direction is along the incident direction of the satellite radio wave, the corrected time difference curve G is obtained. Curve G reaches a positive and negative maximum.

Based on this relationship, the azimuth of the geostationary satellite S is determined by reading the phase of the corrected time difference curve G.

The principle described above is based on the first moving reflector 2a.
In addition, the way in which radio waves travel to the first antenna 5a via the first fixed reflector 4a and the way in which radio waves travel to the second antenna 5b via the second movable reflector 2b and the second fixed reflector 4b are both geometric. We assume that we follow optics. This assumption is a good approximation if the arrangement of each reflector and the antenna is in the near field. That is, assuming that the diameter of the reflector and the antenna is d and the wavelength of the radio wave is λ, a good approximation is established if the reflector and the antenna are placed within a distance smaller than d ² / λ.

As the arm 1 rotates, the radio wave path from the first movable reflector 2a to the first fixed reflector 4a is interrupted by the second movable reflector 2b, In some cases, the path of the radio wave toward the second fixed reflector 4b may be interrupted by the first moving reflector 2a. In those cases, the measured corrected time difference curve G
Is partially interrupted. However, since the modified time difference curve is known in advance to be a sine curve, it is possible to determine the elevation angle and the azimuth angle of the geostationary satellite S by estimating and restoring a continuous curve shape.

It is also assumed that the two geostationary satellites S and S 'respectively emit radio signals in frequency bands overlapping each other, and that they are received together, that is, satellite radio interference occurs.

At this time, since there is no cross-correlation between the radio signals emitted by the different geostationary satellites, in the correlation processing, the arrival time difference of the signal from the geostationary satellite S and the geostationary satellite S '
Can be configured such that each time difference of arrival for the signal from is individually detected and measured.

When the measured two time differences are plotted in a graph with respect to the arm rotation angle, two corrected time difference curves G and G 'are obtained as shown in FIG. Can be determined separately. That is, even when the radio waves of the two geostationary satellites S and S 'interfere with each other, the angle measurement can be performed with the same accuracy as in the case where there is no interference.

Here, adjacent to the first and second antennas 5a and 5b, which are a pair of receiving antennas, the third and fourth antennas 5a 'and 5b which are a pair of receiving antennas having different reception frequencies from the first and second antennas 5a and 5b. '(See FIG. 1). In this case, by adjusting the directions of the first and second fixed reflecting plates 4a and 4b, the first and second antennas 5a and 5b or the third and fourth antennas 5a 'and 5 which are a pair of receiving antennas are adjusted.
It is possible to select which one of b 'to receive the radio wave. That is, it is possible to switch the frequency band to be monitored. This has the effect that it is easy to increase the frequency band to be monitored as needed.

Moreover, the first to fourth antennas 5a, 5b,
5a 'and 5b' are all fixed and the direction is invariant, so that it is not necessary to pass the received signal to the correlation processing means 3 through a rotary coupler. That is, according to the above-described measurement principle, it is possible to perform a measurement equivalent to receiving radio waves from the satellite S with the antennas located at both ends of the arm 1 and to actually rotate the antenna on the arm. It is not necessary to take out the received signal via the rotary coupler as in the case of causing the rotation. This has the effect of ensuring measurement stability.

Note that the position of the geostationary satellite S is not completely unchanged. One geosynchronous satellite S is:
International regulations stipulate that one point P of the geosynchronous orbit is assigned as a nominal position and that it is allowed to move around a certain range around it. That is, the geostationary satellite S
Is the combination of the nominal position P and the allowable position range Z around it.

In response to this, the monitoring of the orbital position refers to checking whether a certain geostationary satellite S complies with its assigned orbital position, and the geostationary satellite S using a certain orbital position. To see if it is or not.

FIG. 3 shows an embodiment of the present invention. In this embodiment, it is assumed that monitoring is performed on a nominal position P and a geostationary satellite S near the nominal position P.
Is a geostationary satellite S whose nominal position is assumed to be P. First, the first movable reflector 2a and the first fixed reflector 4 are so arranged that the beams 2a "and 2b" produced by the first and second antennas 5a and 5b, respectively, are directed to the point P.
a and the directions of the second movable reflection plate 2b and the second fixed reflection plate 4b are adjusted.

Since the first and second antennas 5a and 5b do not have a large diameter, the beams 2a "and 2b" produced by the first and second antennas 5a and 5b have an allowable position range Z around the nominal position P. It will cover with enough margin.
Therefore, even if the geostationary satellite S deviates from the allowable position range Z, monitoring will not be disabled.

When the arm 1 is rotated, the first and second movable reflectors 2a and 2b and the first and second movable reflectors 2a and 2b are so arranged that the beams of the first and second antennas 5a and 5b always point at the point P. The direction of the second fixed reflectors 4a, 4b is adjusted. At this time, it is necessary to change the direction of each reflector as the arm 1 rotates. In particular, the first and second movable reflectors 2a, 2b
Support columns 2a 'and 2b' make a turn close to a reverse turn with respect to the rotation of the arm.

If the rotation center of the arm 1 is to be supported by a single bearing, it is difficult to design a machine to withstand the entire load. Therefore, if the support load is dispersed by using both the circular rail 1 'and the support by the wheels, a stable arm rotation can be realized. Alternatively, the same applies to the case where support by an annular bearing is used.

The effective arm length for drawing the modified time difference curve G is the distance between the electrical center points of the first and second movable reflectors 2a and 2b, but the electrical center point on the reflectors. Is not always clear. However, the first and second fixed reflectors 4a, 4a, 5b are so arranged that the shape center points of the first and second antennas 5a, 5b are always projected on the shape center of the reflector.
If the direction of 4b is adjusted, the effective arm length is simply
It may be the distance between the rotation axes of the two reflector supports 2a ', 2b'.

The rotational movement of the arm needs to be in a horizontal plane, but in practice, it is inevitable that a vertical movement of the arm end is caused by a slight inclination of the rotation axis from the vertical. However, the only thing that affects the angle measurement is that
Only when a difference in height between both ends of the arm occurs as the arm 1 rotates. Therefore, this problem can be solved by preparing data obtained by level-measuring the height difference between both ends of the arm over one round, and performing a necessary correction on the corrected time difference curve G each time the curve G is obtained.

When measuring the time difference while rotating the arm 1, if the geostationary satellite S is ideally kept at the point P, the shape of the corrected time difference curve G can be predicted in advance. . On the other hand, since the time difference actually measured for the geostationary satellite S should be different from the predicted time difference, if the difference between the actually measured time difference and the predicted time difference is drawn as a corrected time difference curve G, the range of the time difference to be handled is small. Therefore, the correlation processing becomes easy.

While the arm 1 makes one revolution, the geostationary satellite S generally moves within the allowable position range Z. Alternatively, the position may deviate from the allowable position range Z as a possibility. When the geostationary satellite S moves in such a manner, a distortion from the sinusoidal curve appears in the modified time difference curve G. At this time, if the elevation angle and the azimuth angle are determined by regarding the modified time difference curve G approximately as a sine curve, the average satellite position over one round of the arm 1 has been monitored.

In order to perform more strict monitoring, the distortion component appearing in the modified time difference curve G is extracted while considering the law of the orbital motion of the geostationary satellite S. If this is performed while the number of rounds of the arm 1 is repeated, it is possible to determine the orbital element of the geostationary satellite S, whereby all information relating to monitoring of the orbital position is obtained.

Further, if an angle encoder for measuring the rotation angle of the arm 1 causes an error in reading the rotation angle of the shaft, it appears as an error in reading the arm rotation angle in the time difference graph. In determining the elevation and azimuth angles, a large number of readings ranging from 0 to 360 degrees of arm rotation are processed. Along with that, a large number of values of the error of the angle encoder are also smoothed, and the influence on the determination of the elevation angle and the azimuth angle is reduced.

[0044]

As is clear from the above description, the equivalent beam width for determining the elevation angle and the azimuth angle of the geosynchronous satellite of the present invention is determined by the ratio of the wavelength of the radio wave to the arm length. Angle measurement accuracy is determined. If the satellite radio wave is received with the intensity required for the correlation processing, by increasing the arm length even if the frequency of the satellite radio wave is low,
That is, required angle measurement accuracy can be obtained without having to increase the antenna aperture. Therefore, accurate position monitoring for the geostationary satellite can be performed.

Further, in order to obtain a corrected time difference curve based on the relative change in the distance from each end of the arm to the satellite due to the rotational movement of the arm, it is not necessary to actually provide an antenna on the arm and perform the rotational movement. Therefore, there is no need to extract the received signal via the rotary coupler, and the stability of the measurement can be improved.

In addition, since the antenna may be provided at a position where it can be guided by the movable reflector on the arm and the fixed reflector fixed on the ground, the degree of freedom of antenna installation is increased, and a plurality of antennas are set in advance. Is provided, and usage such as switching the antenna to be used according to the measurement frequency becomes possible.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating the principle of the present invention.

FIG. 2 is a conceptual diagram showing radio waves emitted from two geostationary satellites as modified time difference curves.

FIG. 3 is a configuration diagram showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Arm 1 'Circular rail 2a, 2b 1st, 2nd moving reflection plate 2a', 2b 'Reflection plate support 2a ", 2b" Antenna beam 3 Correlation processing means 4a, 4b 1st, 2nd fixed reflection plate 5a, 5b First and second antennas 5a ', 5b' Third and fourth antennas G, G 'Modified time difference curve S, S' Stationary satellite T Time difference P Nominal position of geostationary satellite Z Allowable position range

Claims (2)

(57) [Claims] 1. An arm that rotates at a constant speed in a fixed direction about a center of a circle as a rotation axis, such as a diameter of a circle in a horizontal plane, and one movable reflection plate is installed at one end of the arm. Also, one movable reflector is installed at the other end, and a pair of antennas fixed on the ground are connected via a pair of movable reflectors on the arm and a pair of fixed reflectors fixed on the ground. By changing the reflection direction of each movable reflector and each fixed reflector so as to always receive the radio wave of the geostationary satellite, and correlating the radio signals received by the pair of antennas via the correlation processing means, The time difference required for the signal emitted by the geostationary satellite to reach each of the pair of antennas is determined, and the radio wave reflected by one moving reflector is counted from the moment of the reflection, and the signal is transmitted through one fixed reflector to the other. Required to reach the antenna And the time required for the radio wave reflected by the other moving reflector to reach the other antenna via the other fixed reflector from the moment of the reflection and to correct the above time difference. A method for monitoring the position of a geostationary satellite, wherein a time difference is obtained, a corrected time difference curve is derived from the corrected time difference, and an elevation angle of the geostationary satellite is obtained from an amplitude value of the time difference curve. 2. An arm that rotates at a constant speed in a certain direction about a center of a circle as a rotation axis, such as a diameter of a circle in a horizontal plane, and one movable reflection plate is provided at one end of the arm. Also, one movable reflector is installed at the other end, and a pair of antennas fixed on the ground are connected via a pair of movable reflectors on the arm and a pair of fixed reflectors fixed on the ground. By changing the reflection direction of each movable reflector and each fixed reflector so as to always receive the radio wave of the geostationary satellite, and correlating the radio signals received by the pair of antennas via the correlation processing means, The time difference required for the signal emitted by the geostationary satellite to reach each of the pair of antennas is determined, and the radio wave reflected by one moving reflector is counted from the moment of the reflection, and the signal is transmitted through one fixed reflector to the other. Required to reach the antenna And the time required for the radio wave reflected by the other moving reflector to reach the other antenna via the other fixed reflector from the moment of the reflection and to correct the above time difference. A time difference is derived, and a corrected time difference curve is derived from the corrected time difference. When the direction of the arm is perpendicular to the incident direction of the satellite radio wave, the time difference curve intersects the zero axis of the graph, and the direction of the arm. A stationary satellite position monitoring method characterized in that the azimuth angle of the geostationary satellite is obtained by reading the phase of the time difference curve based on the fact that the time difference curve reaches the positive / negative maximum when is along the incident direction of the satellite radio wave.