JP3172736B2 - Geostationary satellite orbit determination method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a geostationary satellite orbit determination method for accurately controlling a geostationary satellite orbit.

[0002]

2. Description of the Related Art In order to determine the orbit of a geostationary satellite, the following techniques have been implemented. First, orbit determination consists of two stages. The first is to acquire tracking data using satellite tracking equipment (hereinafter referred to as "tracking"), and the second is to analyze satellite tracking data. Processing by software to determine the orbital element of the geostationary satellite (hereinafter referred to as "data processing"). Here, the orbital element is a set of six numerical values that determine the orbital motion of the geostationary satellite.

[0003] As a configuration of a tracking facility for a geostationary satellite, the following is used. In each of the two earth stations, a geostationary satellite is measured (measurement of the distance to the satellite). One earth station performs ranging and angle measurement (measurement of azimuth and elevation) of the geostationary satellite. One earth station measures the angle of a geostationary satellite. In any of the above configurations, the acquisition of the measurement data is performed in units of one day when the geostationary satellite makes one orbit, but the measurement does not necessarily need to be always continuous, and after a certain period of time. It is usually repeated intermittently. Among the above configurations, the angle measurement by one station is used particularly when monitoring the satellite position based only on the reception of satellite radio waves.

Next, in data processing, a model representing the orbital motion of the geostationary satellite is provided in the analysis software. The model contains six unknowns, the orbital elements of the geostationary satellite. Comparing the distance, azimuth / elevation angle output from this model with the actually acquired satellite tracking data, and determining unknown values so that the values of those data coincide with each other is performed in orbit 6. It is indispensable for element determination, that is, orbit determination.

[0005]

The trajectory determination according to the prior art has the following problems. Ranging is performed by measuring the time required for a signal to reciprocate between an earth station and a geostationary satellite. Here, the true distance is the distance between the center point of the earth station antenna and the center of gravity of the satellite, whereas the signal is actually delayed by equipment and cables in the earth station and inside the geostationary satellite. Therefore, the distance indicated by the distance measurement data includes an extra distance. There is a technical difficulty in completely and correctly removing the surplus, and an error occurs in distance measurement depending on the degree of incompleteness of the removal. As a result, the resulting error is constant in value, and thus the error with a constant value is referred to as a bias error, or simply bias.

[0006] Next, the angle measurement is to read the angle at which the antenna for automatically tracking the geostationary satellite points. Specifically, the angle encoders attached to the azimuth and elevation angles of the antenna read the angle measurement data. There is technical difficulty in setting the zero point of the angle encoder completely correctly, and a bias is generated in the angle measurement according to the error of the zero point setting.

[0007] For the reasons described above, no matter what kind of tracking equipment is used, tracking data usually contains some kind of bias. In this tracking data processing, assuming that the bias of the tracking data is an unknown number, if it is possible to determine the bias together with the orbital 6 element which is the original unknown, it is necessary to prevent the influence of the tracking bias from affecting the orbit determination. Or it can be reduced. However, it is known that it is impossible to determine the tracking bias as an unknown in orbit determination for a geostationary satellite. For the reasons described above, it has been generally assumed that an orbit determination of a geostationary satellite includes an unknown error due to an unknown tracking bias.

In order to calibrate the tracking bias, it is necessary to perform tracking by another satellite tracking facility or to perform comparative verification with precise optical observation. However, the problem of bias error also accompanies "other satellite tracking equipment", and optical observation is severely restricted by weather conditions and the like. At present, there is no reliable and constantly operable bias calibration means.

A geosynchronous orbit is a limited orbit that makes only one round at a certain altitude above the equator. If the number of geosynchronous satellites arranged in this orbit increases, geosynchronous satellites belonging to different countries and business entities may be operated adjacent to each other. Different countries and entities use different tracking equipment and therefore different tracking bias errors. In such a case, if the geostationary satellite is operated based on the conventional orbit determination method, the orbit determination of each satellite involves an unknown error, and as a result, the satellites approach each other to a dangerous state. There was fear.

[0010] As the number of satellites operating in geosynchronous orbit increases and the traffic in orbit increases, the possibility of satellites approaching dangerous states has become a concern. In order to avoid such danger in advance, it is important to accurately determine the position of each satellite based on the orbit determination. However, in the conventional orbit determination technology, there is a problem that a bias error unavoidably included in the tracking data of the satellite hinders an improvement in the accuracy of the orbit determination.

The present invention provides a technique for enabling a bias error included in tracking data to be removed in trajectory determination, and for enabling accurate trajectory determination while avoiding the influence of a bias error. The purpose is to:
Also, according to the present invention, while one satellite is targeted for tracking in the conventional orbit determination method, two satellites are simultaneously targeted for tracking, thereby increasing the number of relational expressions to be satisfied by the unknown representing the bias. And, as a result, it is possible to determine the value of the bias unknown.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is a method for determining the orbit of a geostationary satellite using a tracking facility comprising two ranging stations. equipment internal delay is equal Ri position near different on geostationary orbit
Or two orbital motion models representing orbital motions corresponding to the two satellites, respectively, are included in analysis software for tracking two satellites whose internal delay differences are known and processing the tracking data of both satellites. And a total of 14 unknowns representing the orbital elements of the two satellites and two unknowns representing the bias error of the two ranging stations, or a total of 14 unknowns including the unknowns. By determining the value of the unknown number, accurate orbit determination is performed based on removing the ranging bias error between the two ranging stations.

Further, the present invention is a method for determining the orbit of a geostationary satellite using a tracking facility comprising one tracking station for measuring distance, azimuth and elevation, wherein the tracking facility comprises a geostationary orbit. or location near the different Ri internal delay above equal Wakashi Ku
Tracks two geostationary satellites with known internal delay differences ,
Some of the analysis software that processes the tracking data includes
Total 2 representing orbital motion corresponding to two geostationary satellites respectively
There are a total of 15 unknowns that are obtained by adding two orbital motion models and a total of 12 unknowns representing orbital elements of two geostationary satellites and three unknowns representing measurement bias errors of distance, azimuth, and elevation. Or determining the value of a greater number of unknowns, including the unknown, to eliminate the measurement bias errors of distance, azimuth, and elevation,
It is characterized by performing accurate trajectory determination.

Further, the present invention is a method for determining the orbit of a geosynchronous satellite using a tracking facility comprising one tracking station for measuring azimuth and elevation, wherein the tracking facility is located at different positions on a geosynchronous orbit. The internal delay is equal or the difference
In the analysis software that tracks two known geostationary satellites and processes the tracking data, a total of two orbital motion models corresponding to the two geostationary satellites and representing orbital motion are provided, and two more geostationary motion models are provided. A total of 12 unknowns representing the satellite's orbital elements and two unknowns representing the azimuth and elevation measurement bias errors are determined, for a total of 14 unknowns or a greater number of unknowns including the unknowns. This is characterized in that an accurate trajectory determination is performed based on removing measurement bias errors of the azimuth angle and the elevation angle.

According to the present invention, even if the tracking equipment has a measurement bias, accurate trajectory determination can be performed while avoiding the influence of the measurement bias. Therefore,
In geosynchronous orbit, even when a large number of satellites are operated adjacent to each other, it is possible to prevent the satellites from approaching a dangerous situation.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. (First Embodiment) FIG. 1 is a schematic diagram showing a positional relationship between two geostationary satellites and the earth. In FIG. 1, ranging stations R ₁ and R ₂ located at two places on the earth form a tracking facility,
This tracking equipment tracks the geostationary satellites S ₁ and S ₂ . The geostationary satellites S ₁ and S ₂ are at different positions on the geosynchronous orbit G. In tracking, the ranging station R ₁ alternately measures the distance between the satellites S ₁ and S _2, and the ranging station R ₂ alternately measures the distance between the geostationary satellites S ₁ and S _2. The time zone of ranging between two stations is adjusted so that only one ranging station accesses one satellite.

The majority of satellites that are increasing in geosynchronous orbit are communication satellites. In the communication satellite business, 1
Since it is common for one operator to operate two or more satellites, it is actually possible for one tracking facility to track two satellites. In order to process the ranging data obtained for the satellites S ₁ and S ₂ , the analysis software provides two models representing the orbital motion of the satellite, one of which describes the motion of the geostationary satellite S ₁ . one Matabetsu will express the motion of geostationary satellites S _2. Since the orbital elements of the two satellites are unknown, the total number of orbital elements is twelve. At the same time, unknown u ranging bias ranging station R _1
1, and since the unknown u ₂ ranging bias of the distance measuring station R _2, unknowns to determine the value is 14 total.
That is, by tracking the satellites S ₁ and S ₂ using the ranging stations R ₁ and R ₂ , the orbit determination of S ₁ and S _{2 and} the determination of the biases u ₁ and u ₂ are performed simultaneously and collectively. .

The principle by which the orbit determination method configured as described above can determine the bias as an unknown number will be described below. In the description, attention is paid only to the relationship that is established between the three components, that is, the actually occurring ranging bias, the value obtained by solving it as an unknown, and the determination error of the satellite position. The distance measurement range finding station R ₁ and R ₂ are performed, and the bias B ₁ and B ₂ has occurred, respectively.
Here, regardless of whether the ranging station R ₁ measures the distance between the satellites S _{1 and} S ₂ , the bias B ₁ is the same, and the ranging station R ₂ measures the distance between the satellites S _{1 and} S _2. But bias B ₂
Are the same. This need is met if the internal delays of the two satellites are equal, especially if the two satellites are of the same standard. If the above conditions are not met, know the difference between the internal delays of the two satellites in advance,
By correcting the difference, it is possible to satisfy the above-mentioned need.

In the data processing, the ranging biases of the two ranging stations are determined as unknowns u ₁ and u ₂ , and the ranging bias is corrected based on the determined results. The biases after the correction are B ₁ -u ₁ and B ₂ -u _{2. If} the values of these biases become zero, the satellite position is correctly determined. If B ₁ -u ₁ and B ₂ -u ₂ do not become zero, an error will occur in the determination of the satellite position. The process is as follows.

In FIG. 1, let S ₁ and S ₂ represent the correct positions of the two satellites in geosynchronous orbit G, respectively. First, assuming that the position of the satellite S ₁ is displaced along the geosynchronous orbit G to a position different by x, the distance from S ₁ to R ₁ changes by c ₁ x in proportion to the displacement. Here, c ₁ is a proportional coefficient determined by the arrangement of S ₁ and R ₁ . Similarly, the distance from S ₁ to R ₂ changes by c ₂ x. Here, c ₂ is a proportional coefficient determined by the arrangement of S ₁ and R ₂ . Next, the position of the satellite S ₂ is determined by the geosynchronous orbit G
, And the distance from S ₂ to R ₁ or R ₂ in proportion to the displacement is
Each changes by d ₁ y or d ₂ y. Where d ₁ and d
₂ is a proportional coefficient, d ₁ is determined by the arrangement of S ₂ and R _1, and d ₂ is determined by the arrangement of S ₂ and R ₂ .

Since the change in distance caused as described above due to the satellite position errors x and y should be equal to the remaining distance measurement bias after correction, c ₁ x = B ₁ -u _{1 c 2 x = B 2 -u 2} d 1 y = B 1 -u 1 d 2 y = B 2 -u 2 relational expression is established that. In the above formula, x is
A unknowns corresponding to one of the orbital six elements of the satellite S _1,
The y also unknown which corresponds to one track 6 elements of the satellite S _2. The above four relational expressions represent a total of 14
Of the four unknowns, x, y, u ₁ , and u ₂
Represents the relationship to be satisfied. A set of unknowns that simultaneously satisfies these four relational expressions is x = y = 0, u ₁ =
Only B ₁ and u ₂ = B ₂ . Where d ₁ / c ₁ =
If d ₂ / c ₂ , the set of unknowns would not be fixed to one, but as long as the satellites S ₁ and S ₂ are at different positions in geosynchronous orbit, with one exception, the unknowns There is no danger that a set will not be fixed. The One exception, the longitude to be the midpoint of the longitude of the satellite S ₁ and S _2, a case where two distance measuring stations are arranged along the north-south, such an arrangement of said, as to avoid I do. In this case, in the orbit determination, the two ranging biases are correctly corrected, and thus the positions of the two satellites are also correctly determined.

In determining the orbit of a satellite, it may be necessary to determine an orbital element and a tracking bias together with unknowns. One example is the magnitude of the force generated by the sun's light exerting pressure on the satellite, which is unknown.
Therefore, if that combined supplementary unknowns in this way,
The total number of unknowns whose values are to be determined is increased from the above 14 values. However, even in such a case, the relationship that holds between the tracking bias and the satellite position determination error is the same as that described above.

Next, in contrast to the above description,
The reason why the bias cannot be determined as an unknown by the conventional trajectory determination method will be described. In the conventional method, since only one satellite is tracked at a time, the satellite S shown in FIG.
Considering only the portion of the _1, unknowns related displacement x along the track G of the satellite S _1, the distance measuring station R _1, or bias u ₁ of R _2, or a u _2, to be satisfied by these unknowns There are the following two relational expressions. c ₁ x = B ₁ −u ₁ c ₂ x = B ₂ −u ₂ An infinite number of sets of unknowns (x, u ₁ , and u ₂ ) satisfying these two relations exist, and one of them is set. Can not be specified. The infinite number of sets of unknowns is the reason that it was impossible to obtain a bias as an unknown using the conventional trajectory determination method. In other words, since there is only one satellite, the number of relational expressions to be satisfied by the unknown is insufficient. Therefore, it is the method of the first embodiment according to the present invention that increases the number of relational expressions by increasing the number of satellites to be tracked, thereby enabling the value of the bias unknown to be determined . The means of increasing the number of relational expressions by increasing the number of satellites is common to the second and third embodiments described below.

(Second Embodiment) FIG. 2 is a schematic diagram showing the positional relationship between two geostationary satellites and the earth. In FIG. 2, a tracking station T on the earth is:
Distance measurement and angle measurement are performed on the _two satellites S ₁ and S ₂ . Distance measurement and angle measurement are performed alternately for two geostationary satellites. The configuration of the analysis software for data processing is the same as that of the first embodiment. However, the number of unknowns related to the orbit determination includes a distance bias u _R , an azimuth bias u _A , and a twelve orbital element. A total of 15 elevation biases u _E are combined, and the values of these unknowns are determined . According to the first embodiment, a principle that enables the bias to be determined as an unknown value according to the orbit determination method configured as described above will be described below.

Suppose biases B _R , B _A , and B _E occur in the distance, azimuth, and elevation measurements at the tracking station, respectively. Here, it is assumed that the distance the bias B _R also tracking station T is then ranging either satellite S ₁ and S ₂ are the same.
This need is met if the internal delays of the two geostationary satellites are equal, especially if the two geostationary satellites are of the same standard. When the above condition is not satisfied, the above-mentioned necessity can be satisfied by knowing in advance the difference between the internal delays of the two geostationary satellites and correcting the difference.

Furthermore, azimuth bias B _A be angle measurement either of the tracking station T satellite S ₁ and S ₂ are the same, also tracking station T is hidden measuring either the satellite S ₁ and S ₂ However, it is assumed that the elevation bias _BE is the same. This need can be satisfied if the angle measurement of two geostationary satellites is performed with the same characteristics by the same angle measurement antenna.
In the data processing, biases for distance, azimuth, and elevation are obtained as unknowns u _R , u _A , and u _E , respectively, and the measurement bias is corrected based on the obtained results. The biases B _R -u _R , B _A -u _A ,
If B _E -B _E and B _E -u _E do not become zero, an error will occur in the determination of the satellite position.

The position of satellite S ₁ is x along geosynchronous orbit G
, The distances, azimuths, and elevations measured in accordance therewith are displacement values c _R x, c _A.
x, and c _E x is generated each. Here, c _R , c _A , and c _E are proportional coefficients determined by the arrangement of T and S ₁ .
If the position of the satellite S ₂ is displaced along the geosynchronous orbit G to a position different by y, displacements d _R y and d _A y are included in the distance, azimuth, and elevation measured accordingly. ,
And d _E y respectively. Note that d _R , d _A , and d
_E is a proportional coefficient determined by the arrangement of T and S ₂ .

[0028] With the errors x and y of the satellite position, the change occurring in the tracking measurements as described above, after performing the correction, because should be equal to the still remaining measurement _{bias, c R x = B R -u} R holds relational expression _{c A x = B A -u A} c E x = B E -u E d R y = B R -u R d A y = B A -u A d E y = B E -u E . A set of unknowns that simultaneously satisfies the above six relational expressions is x = y = 0, u _R = _BR , u _A =
B _A and u _E = B _E only. However, d _R / c _R =
If d _A / c _A = d _E / c _E , the set of unknowns is not fixed, but as long as the geosynchronous satellites S ₁ and S ₂ are at different positions in geosynchronous orbit, such a situation is assumed. Never be. Therefore, as a result of the orbit determination, the three measurement biases are correctly corrected, and thus the positions of the two geostationary satellites are also correctly determined.

[0029] Incidentally, the first as described in the embodiments, especially with sunlight Ru combined supplemental unknowns to one example of the magnitude of the force generated by exerting pressure on the satellite,
Even when the total number of unknowns whose values are to be determined is greater than 15 described above, the relationship that holds between the tracking bias and the satellite position determination error is the same as that described in the second embodiment. is there.

(Third Embodiment) In FIG. 2, a tracking station T on the earth measures angles for _two geostationary satellites S ₁ and S ₂ . Angle measurement is performed alternately for two geostationary satellites. The configuration of the analysis software for data processing is the same as in the first embodiment or the second embodiment, but the number of unknowns related to the trajectory determination is
In addition to the 12 orbital elements, a total of 14 azimuth biases u _A and elevation biases u _E are determined , and their unknown values are determined . The principle by which the bias can be determined as an unknown value according to the orbit determination method configured as described above will be described below according to the second embodiment.

For measurement of azimuth and elevation at a tracking station,
It is assumed that biases B _A and _BE have occurred, respectively. Here, no matter which tracking station T measures the angle of the geostationary satellites S ₁ and S ₂ ,
The azimuthal bias B _A is the same, and the tracking station T
It is assumed that the elevation bias B _E is the same regardless of which of the angles ₁ and S ₂ is measured. This need can be met if two geostationary satellites are angle-measured with the same characteristics using the same angle-measuring antenna.

In the data processing, the biases of the azimuth and the elevation are obtained as unknowns u _A and u _E , respectively, and the measurement bias is corrected based on the obtained results. The biases B _A -u _A and B _E -u _E after the correction are
If it does not become zero, it will cause an error in the determination of the satellite position, but the process is as follows.

The position of satellite S ₁ is x along geosynchronous orbit G
When displaced by different positions, the displacement value c _A x and c _E x is generated each in azimuth and elevation is measured accordingly. Here, c _A and c _E are proportional coefficients determined by the arrangement of T and S ₁ . The position of the satellite S ₂ is, when displaced by different positions y along the geostationary orbit G, resulting displacement value d _A y and d _E y are each in azimuth and elevation is measured accordingly. Note that d _A and d _E are
It is a proportional coefficient determined by the placement of the T and S _2.

[0034] With the errors x and y of the satellite position, the change occurring in the tracking measurements as described above, after performing the correction, because should be equal to the still remaining measurement _{bias, c A x = B A -u} A _{c E x = B E -u E} d A y = B A -u A d E y = B E -u relational expression _E holds.

The set of unknowns that simultaneously satisfy the above four relational expressions is only x = y = 0, u _A = B _A , and u _E = B _E. However, if d _A / c _A = d _E / c _E , the set of unknowns is not fixed to one, but as long as the geostationary satellites S ₁ and S ₂ are at different positions in orbit, such a set is unknown. There is no state. Therefore, as a result of the orbit determination, the two measurement biases are correctly corrected, and thus the positions of the two geostationary satellites are also correctly determined.

As described in the first and second embodiments, supplementary unknowns, for example, the magnitude of the force generated by the solar light exerting pressure on the satellite are combined. especially with, even if the total number of unknowns to determine the value increases more than 14 described above, the relationship established between the tracking bias and satellite positioning errors, described in the third embodiment that Is equivalent to

[0037]

According to the method of the present invention, even if the tracking equipment has a measurement bias, it is possible to determine an accurate trajectory while avoiding the influence of the measurement bias. Furthermore, since the method according to the present invention does not need to rely on external means such as tracking by other tracking equipment or optical observation, it is possible to determine the trajectory at any time. Thus, the method of the present invention prevents a large number of geosynchronous satellites from approaching dangerous situations, especially if they are forced to operate adjacent to each other in geosynchronous orbit. It becomes possible to do.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a positional relationship between two geostationary satellites and the earth according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a positional relationship between two geostationary satellites and the earth according to another embodiment of the present invention.

[Explanation of symbols]

R ₁ ranging station R ₂ ranging station S ₁ geostationary satellite S ₂ geostationary satellite G geostationary orbit x displacement on G orbit y displacement on G orbit T tracking station

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B64G 3/00

Claims (3)

(57) [Claims] 1. A method of performing orbit determination of geostationary satellites with a tracking facility consisting of two distance measuring station, tracking equipment Wakashi Ku or internal delay Ri position near different on geostationary orbit are equal
In the analysis software that tracks two satellites having a known internal delay difference and processes the tracking data of both satellites, a total of 2 representing the orbital motion corresponding to each of the two satellites is included.
One orbit motion model is provided, and a total of 12 unknowns representing the orbital elements of the two satellites and two unknowns representing the bias errors of the two ranging stations are added up to a total of 14 unknowns.
Determining an orbit based on removing the ranging bias error of the two ranging stations by determining the value of the unknowns or a greater number of unknowns including the unknowns. How to determine the orbit of a satellite. 2. A method for determining the orbit of a geosynchronous satellite using a tracking facility comprising one tracking station for measuring distance, azimuth and elevation, wherein the tracking facility comprises different positions on a geosynchronous orbit. near Ri difference to or internal delay internal delay is equal to
In the analysis software that tracks two geostationary satellites for which the satellites are known and processes the tracking data, a total of two orbital motion models representing orbital motions corresponding to each of the two geostationary satellites are provided. A total of 12 unknowns representing the orbital elements of the geostationary satellite and three unknowns representing the measurement bias errors of distance, azimuth, and elevation are added up to a total of 15 unknowns.
Determining the value of the unknowns or a greater number of unknowns including the unknowns, thereby making an accurate trajectory determination based on removing measurement bias errors of distance, azimuth, and elevation. Orbit determination method for geostationary satellites. 3. A method of performing orbit determination of geostationary satellites with a tracking facility consisting of track 1 station to measure the azimuth and elevation, internal tracking facility Ri position near different on geostationary orbit
Analysis software that tracks two geostationary satellites with equal delays or a known difference in internal delay and processes the tracking data includes a total of two geostationary satellites corresponding to the two geostationary satellites, each representing an orbital motion. An orbital motion model is provided, and a total of 14 unknowns or a total of 12 unknowns representing the orbital elements of the two geosynchronous satellites and two unknowns representing the measurement bias errors of the azimuth and elevation are calculated. A method for determining an orbit of a geostationary satellite, comprising determining an azimuth and elevation angle measurement bias error by determining a larger number of unknown values, including an unknown value.