RU2149507C1 - Satellite regional communication system using elliptical orbits - Google Patents

Abstract

FIELD: satellite communications engineering. SUBSTANCE: system has at least three artificial Earth satellites placed in their respective elliptical orbits and net of ground stations. Orbits of all satellites have similar orbital period T found from equation T = t/N, where t is day-and-night period; N is total number of satellites in system, and similar inclination of orbit plane to equator plane which is, in effect, equal to critical value; pericenter of each orbit is in hemisphere opposite to service area. Actually proposed system has six artificial Earth satellites; orbital period is chosen from mentioned equation; inclination of orbit plane of each satellite to equator plane is, in effect, about 63.4 deg (i ≈ 63,4^o); artificial satellites placed in adjacent orbits are arranged so that all of them reach orbital pericenter point at shift of half or one third of orbital period relative to each other. EFFECT: improved stability of communications among ground stations in chosen region including Russian territory; reduced cost. 3 cl, 9 dwg, 4 tbl

Description

 The invention relates to satellite communication systems, and more particularly relates to a satellite system of regional communication using elliptical orbits and is intended to provide various types of communication for vast regions of the globe.

 Currently, the interest in personal satellite communications has significantly increased in the telecommunications market. A fundamentally new stage in the development of personal mobile satellite communications began after the advent of satellite communications systems using artificial satellites (IS) in low and medium altitude orbits, which allows us to expand the range of telecommunications services and provide users with reliable and high-quality personal communications, regardless of the location of the subscriber using fixed and / or portable subscriber terminals, comparable in size to cellular.

 A number of satellite communication systems for continuous viewing are known, in which artificial satellites are placed in elliptical orbits (US Pat. N 4,804,935, CL 244/158. R; N 4854527, CL 244 / 158.R, articles: Draim, John E., "Three- and four- satellite continuous-coverage constellations," Journal of Guidance, Control, and Dynamics, 1985, Vol. 8, pp. 725-730; Draim, John E., "A common-period four-satellite continuous global coverage constellation, "Journal of Guidance, Control, and Dynamics, 1987, Vol. 10, pp. 492-499), which, in particular, can be used to provide regional communication in any of the hemispheres. Orbital inclinations that are significantly different from critical are used for these systems; therefore, they require significant fuel costs on artificial satellites to maintain the required satellite system structure (see, for example, Chao, S. S. "Long-term orbit perturbations of the Draim four-satellite constellations, "Journal of Guidance, Control, and Dynamics, 1992, Vol. 15, N. 6, pp. 1406-1410).

Satellite communication systems using elliptical solar-synchronous orbits are known (US patents N 5582367, class 244 / 158.R; N 5669585, class 244 / 158.R) with a critical inclination of orbit i of about 116.6 ^o . The orbital parameters of these orbits are selected by providing a special condition for the precession of the longitude of the ascending node and the rate of change of the position of the pericenter of the orbit. For such systems, orbital inclinations typical of solar-synchronous orbits (115-118 ^o ) are used, which is more expensive when deploying the system, compared with systems with orbital inclinations less than 90 ^o . These satellite communication systems are oriented mainly to global communications. That is, if it is necessary to cover a specific region, for example, the territory of the Russian Federation, other regions are covered, which significantly increases the cost of the system and makes its use for regional communication economically disadvantageous.

 A known satellite communication system using elliptical orbits (RF patent N 2032988, CL H 04 B 7/185), we have chosen for the prototype. A method of constructing said satellite communication system is to use artificial satellites placed in elliptical orbits lying in planes other than the equator. The parameters of the orbits in this system are selected from such conditions that, at the apogee sections of the orbit in the zones between the lines of intersection of the planes of the orbits, the average value of the absolute values of the angular velocities of the satellites relative to the axis of rotation of the Earth for a certain period of time equal to t = 24 hours / N, where N is the total number of artificial satellites in the system coincided with the absolute value of the angular velocity of the Earth, and the change in azimuth and elevation relative to the subscribers did not exceed the angle of the main lobe of the radiation pattern.

 The indicated choice of orbit parameters determines the necessity of using antenna systems with a wide radiation pattern, which increases the cost of the communication system as a whole, worsens the quality of communication and limits the ability to use other types of antennas.

 The basis of the invention is the task of developing a satellite system of regional communication using elliptical orbits, in which, by choosing the parameters of the orbits of artificial satellites, a stable regional satellite communication of latitudinal zones would be provided, for example, in the northern hemisphere, including in the Russian Federation, or in the southern hemisphere that would allow providing a wide range of consumers with satellite communications services at minimal cost.

 The problem is solved in that in a satellite system of regional communication using elliptical orbits, including at least three artificial satellites located in elliptical orbits and equipped with communication equipment with a network of ground points located in the service area and providing communication through these artificial satellites, according to According to the invention, each artificial satellite is placed in its own elliptical orbit and the orbits of all artificial satellites have the same orbital period, calculated from the relation T = t / N, where T is the orbital period of each artificial satellite, t is the daily duration, N is the total number of artificial satellites in the system, and the orbits of all artificial satellites have the same inclination of the orbit plane of each artificial satellite to the equator plane, which is essentially critical, and the pericenter of each orbit is located in the hemisphere opposite the service area.

Thanks to the use in the claimed invention of elliptical orbits at medium altitudes, the inclination of which is close to critical, the costs of deploying and maintaining the operability of a satellite communication system are significantly reduced. In addition, such orbits provide the ability to work with large elevation angles when positioning ground stations at high latitudes, the presence of satellite communications in which is a very urgent problem, in particular, for the polar regions of the Russian Federation. The service area in which the sustainable energy of the radio lines is provided is the territory of the Russian Federation and the adjacent areas from 40 to 90 ^o N (north latitude).

 The use of the same orbital period for all orbits ensures the continuity of communication and the invariance of the communication conditions with respect to any artificial satellite when working with it from the territory of the service area. In addition, the repeatability of radio link parameters between the satellite and the ground station is achieved.

It is advisable that the inclination of the plane of each orbit to the plane of the equator is about i ≈ 63.4 ^o . Such inclination of the orbits ensures the stability of the position of the pericenter of each orbit, increases the active life of the system as a whole and significantly reduces the cost of maintaining the nominal parameters of the system.

 It is useful that the orbit planes are evenly spaced along the longitude of the ascending node in the equatorial plane, which allows for continuous radio visibility of at least one satellite from the territory of the service area.

 It is reasonable that in the satellite system artificial satellites would be placed so that each of the artificial satellites would reach the point of the orbital pericenter with a shift of 1/2 of the orbital period with respect to the satellites in adjacent planes.

 It is also useful that artificial satellites are placed in a satellite system so that each of the artificial satellites reaches a point of the orbital pericenter with a 2 / N shift of the orbital period with respect to satellites in adjacent planes.

This construction of a satellite communications system provides radio visibility from the territory of the Russian Federation with an elevation angle of at least 30 ^o .

 It is preferable that the height of the perigee of each orbit is at least 500 km, which reduces the level of atmospheric disturbances of the orbit when passing through the pericenter region.

The pericenter argument of each orbit is chosen close to minus 90 ^o , which ensures stable communication in the Northern Hemisphere.

The problem is also solved by the fact that in a satellite system of regional communication using elliptical orbits, including artificial satellites placed in elliptical orbits and equipped with communication equipment with a network of ground points located in the service area and providing communication through these artificial satellites, according to the invention, the system contains six artificial satellites placed on their own elliptical orbits, which have the same orbital period, the same inclination the orbits of the orbit to the equatorial plane and the pericenter of each orbit located in the hemisphere opposite the service area, the orbital period being selected from the relation T = t / N, where T is the orbital period of each artificial satellite, t is the daily duration, N = 6, inclination the orbit plane of each artificial satellite to the equator plane is essentially i ≈ 63.4 ^o , and the artificial satellites located in adjacent orbits are located so that each of the artificial satellites reaches the point of the orbital pericenter with 1/2 or 1/3 of the orbital period with respect to one another.

The use of six artificial satellites in the communication system provides stable communication in vast regions, in particular in the territory of the Russian Federation and adjacent areas from 40 to 72 ^o N (northern latitude) with relatively low costs, and in essence is the optimal system for these regions.

The invention is further explained in the description of specific options for its implementation and the accompanying drawings and graphs, on which:
FIG. 1 shows a satellite communication system with six artificial satellites in elliptical orbits (first embodiment), according to the invention;
FIG. 2 - a sequence diagram of the radio visibility intervals of artificial satellites by a subscriber in Moscow;
FIG. 3 - statistical characteristics of the radio visibility of artificial satellites at various elevation angles (first option);
figure 4 - the same as in figure 3 (second option);
FIG. 5 - characteristics of the limiting durations of radio visibility zones from the latitude of ground points;
FIG. 6 - instant radio-visibility zones for an artificial satellite located at a latitude of 63.4 ^o N;
Fig.7 - the same as in Fig.6, at a latitude of 40 ^o N .;
FIG. 8 - path of one artificial satellite and envelopes formed by the field of view;
FIG. 9 - minimum and maximum communication ranges from the latitude of ground points.

 The inventive satellite communication system using elliptical orbits may contain at least three artificial satellites. Figure 1 presents the proposed satellite communication system using elliptical orbits, containing six artificial satellites 1, equipped with communication equipment with a network of ground stations 2, providing communication in the service area through these artificial satellites 1. Moreover, each artificial satellite 1 is placed on its own elliptical the orbit and orbits of all artificial satellites have the same orbital period T (sec), selected from the relation T = t / N, where t ≈ 86164 s is the daily duration, N is the total number of usstvennyh 1 satellites in the system. Given the various requirements for communications, the proposed system can provide high-quality communications using a small number of satellites, mainly from 3 to 8.

To increase the stability of the system and reduce operating costs, a critical inclination i of each orbit of about 63.4 ^o (or about 116.6 ^o ) was chosen. The pericenter argument ω _{π was} chosen close to minus 90 ^o for the system providing communications in the Northern Hemisphere, and close to plus 90 ^o for the system providing communications in the Southern Hemisphere, and the pericenter of each orbit is located in the hemisphere opposite the service area. In order to reduce the level of atmospheric perturbations of the orbit during the passage of the pericenter region, its altitude is chosen at least 400 km.

 The main characteristics of the elliptical orbits of the proposed satellite communications system with a different number of satellites in the system are presented in table. 1.

 As follows from the table. 1, for a communication system containing from three to eight artificial satellites, each satellite makes three to eight orbits around the Earth per day, respectively.

 Possible options for the systems of six satellites and their main characteristics will be considered in more detail below. In addition to the above-mentioned parameters of satellite systems, the mutual position of satellites in adjacent planes is very important.

 In the table. Figure 2 presents some of the possible system configurations (longitudes of ascending nodes and time shifts from the pericenter are indicated for all satellites from 1 to 6).

 As an example in FIG. Figure 1 shows the first version of a system of six satellites (from Table 2). Tracks 3 of all satellites 1 and their instantaneous positions at a particular point in time, as well as examples of ground points 2 (subscriber, earth station, etc.) are presented. Ground stations 2 are connected by direct lines to satellites 1, with which radio communication is possible at this moment (indicated satellites are conventionally marked with squares).

 The choice of the service area of the system is largely related to the statistical characteristics of the radio visibility of satellites. They, in turn, depend on the structure of the system and the minimum elevation angle of the satellites over the horizon α, at which the required communication technical characteristics are provided.

Examples of cyclograms of satellite radio visibility intervals for a subscriber in the city of Moscow on a daily interval for the first embodiment are shown in FIG. 2 (α = 30 ^o ), where the current time (hour) is plotted on the abscissa axis, and the number of the artificial satellite is plotted on the ordinate axis.

The statistical characteristics of the radio visibility of satellites at various elevation angles (α = 20 ^o ; 25 ^o ; 30 ^o — highlighted in bold; 35 ^o ) for the first and second options are shown in FIG. 3, 4, where latitude (degrees) is plotted on the abscissa axis, and the proportion of continuous visibility (%) on the ordinate axis. Latitudinal ranges for Russia, the USA (without Alaska), Central Europe and Canada with Alaska are also shown there. The numerical data on the statistics of the review for these options are given in table. 3, 4.

As can be seen from the results, the first option (Fig. 3, Table 3) is preferable for moderately high latitudes, in particular, to ensure continuous communication in Russia. In this case, for minimum elevation angles α = 30 ^o , a continuous 100% radio visibility of satellites is provided in the latitude range φ ≈ 40 ^o N ... 72 ^o N

The second option (figure 4, table 4), on the contrary, is preferable to provide communication in the polar and polar regions. In particular, at α = 30 ^{o the} satellite communication system provides continuous radio visibility for all latitudes φ ≥ ~ 60 ^o N, and at α = 20 ^{o it} covers the entire territory of Russia in addition to the polar regions.

 In FIG. 5 shows the characteristics of the limiting durations of radio visibility zones from the latitude of a subscriber or an earth station.

For the territory of Russia, the maximum duration of the radio visibility zone can exceed 2 hours. For latitudes φ ≥ ~ 75 ^o N on each turn of each satellite there is always a radio visibility zone with a duration of at least a certain value (Fig. 6). For the Northern Belt, the duration of the radio visibility zone always has the same value, equal to ~ 94 min.

Examples of instantaneous positions of radio-visibility zones for a satellite located in the apocenter (latitude φ = 63.4 ^o N) and a satellite at latitude φ = 40 ^o s. w. shown respectively in FIG. 6, 7 (for α = 30 ^o ), where the artificial satellite 1, located on the flight path 3, and the radio visibility zone 4 of this satellite 1 are conventionally depicted. In the first case, the instantaneous position of the viewing zone covers all the polar regions with latitudes φ ≥ ~ 75 ^o N, and in the second - all of Europe, North Africa and the Middle East.

The field of view of a satellite in an elliptical orbit during the passage of one turn covers a significant part of the Earth's surface. In FIG. 8 shows the flight path 3 of one satellite 1 and the envelopes 5 formed by the field of view (α = 30 ^o ). The transverse curves are plotted in increments of 3 minutes and show a significant non-uniformity of flight times over different regions.

 Elliptical orbits are also characterized by a significant range of radio visibility ranges of satellites from the Earth. Figure 9 shows the minimum and maximum ranges of radio links depending on the latitude of the subscriber and / or earth station. With increasing latitude, this range narrows. For the territory of Russia, the maximum ranges will be ~ 7000 ... 12500 km.

 Communication between subscribers located in the radio visibility zone of one satellite is carried out directly through this satellite.

 Communication of remote subscribers, i.e. located in the radio visibility zone of different satellites, is carried out using ground-based relay stations and / or communication lines between artificial satellites.

 Thus, the claimed satellite communications system, as a regional system, provides stable operation with high elevation angles when locating ground stations primarily in the Russian Federation and, in particular, at high latitudes.

 In addition, the use of the proposed system makes it possible to significantly reduce the cost of deployment and maintenance of the satellite communications system.

Claims (4)

 1. A satellite system of regional communication using elliptical orbits, comprising at least three artificial satellites equipped with communication equipment with a network of ground stations located in the service area and providing communication through these artificial satellites that are placed in elliptical orbits having the same plane inclination each orbit to the equatorial plane and the same orbital period, characterized in that each artificial satellite is placed in its own elliptical orbit, ne the center of which is located in the hemisphere opposite the service area, the inclination of its plane to the equatorial plane is essentially critical and the orbits of all artificial satellites have an orbital period selected from the relation T = t / N, where T is the orbital period of each artificial satellite, t is the daily duration, N is the total number of artificial satellites in the system, while in adjacent orbits artificial satellites are placed so that each of the artificial satellites reaches a point of the orbital pericenter with a shift 1/2 or 2 / N of the orbital period.  2. The satellite system according to claim 1, characterized in that the planes of the orbits are evenly spaced along the longitude of the ascending node in the plane of the equator. 3. The satellite system according to claim 1, characterized in that the pericenter argument of each orbit is about minus 90 ^o . 4. A satellite system of regional communication using elliptical orbits, including artificial satellites located in elliptical orbits and equipped with communication equipment with a network of ground points located in the service area and providing communication through these artificial satellites, characterized in that the system contains six artificial satellites, placed on their own elliptical orbits, which have the same orbital period, the same inclination of the orbit plane to the plane of the equator and peri The center of each orbit, located in the hemisphere opposite the service area, the orbital period is selected from the relation T = t / N, where T is the orbital period of each artificial satellite, t is the daily duration, N = 6, the inclination of the orbit plane of each artificial satellite to the equatorial plane is essentially equal to i ≈ 63.4 ^o , and artificial satellites located in adjacent orbits are located so that each of the artificial satellites reaches a point of the orbital pericenter with a shift of 1/2 or 1/3 of the orbital period one relative relative to another.

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