by Georgi YEFREMOV, Cand. Sc. (Tech.), Chief Designer and General Director, R&D Engineering Amalgamation

Satellite communications take pride of place among other areas of space research. This includes their level, scale and rate of development and the future of these services is really impressive, including the transmission of digital and video data, TV and radio traffic, telephone and fax communications, access to Internet and so on and so forth. And last, but not least, in the present state of affairs this is about the only area of our space program which brings in commercial returns.

Having said that, one has to bear in mind, however, that the use of big and heavy communication satellites (of about 2 tons) equipped with a large number of transponders (sets of radio-technical devices which pick up traffic from transmissions on the ground, alter their frequency, amplify radio signals and transmit them to users) for such applications is unprofitable and often costs more than the potential users are ready to offer. An attractive alternative to communication satellites of this kind is offered by communication equipment installed on smaller satellites with limited rates of transmission which can be placed into orbit by medium and light carrier rockets.

All of these tendencies are fully taken into account by a program called Pragmatic Cosmos on which our R&D Center is working now. The project rests on the principle of making the maximum use of this country's material, technical, technological and research potential available today. Everything we do fully meets international standards and we choose our partners only when we have full confidence in their ability to do the job which we want them to do. And everything is being done to bring down production costs by taking full advantage of what we call multipurpose, or general-purpose, technical solutions and unified basic modules as well as of the already available technical designs ^* .

Work is now in progress on a new satellite communication system, codenamed RUSLAN-RS - a project spearheaded by our Center. We plan using small satellites, called RUSLAN-1, 2 and 3, which will be

^* See: V. Buglak, "Space Communication for Russia", Science in Russia, No. 2, 1993.- Ed.

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placed into three positions on a geostationary orbit (on the plane of equator with the satellite moving at the speed of rotation of the Earth, and as if "hanging" in one and the same position) with the coordinates of 61.0 ⁰ , 88.1 ⁰ and 138.5 ⁰ E. These were assigned to the former Soviet Union in accordance with the World Plan of fixed satellite service adopted by the world conference of the International Union of Electro-communication in 1988. The satellites are codenamed URS 00001, URS 00002 and URS 00003. It should be pointed out that the advantage of such an approach consists in the autonomous, or indepen-

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dent functioning of the respective Russian satellites which does not require coordination with the satellite networks of other countries.

The RUSLANs will be performing two tasks. Operating in what is known as the C-band (4-6 GHz) it will take care of data transmission both within the regions of Russia and CIS countries and also between them. Their second task is to organize what we call low-level communication between local zones (primarily the most remote ones) within the regions. This will be conducted in the KU-band (11-13 GHz). The project has already been given "clearance" by the State Commission for Radio Frequencies at the RF Ministry of Communications. By a decision of the Bureau for Radio Communication of the International

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Union of Electrocommunication the aforesaid frequencies were registered in the Attachment S30B to the Regiment of Radiocommunication.

A small-size satellite with a general title RUSLAN-MM which is being developed within this program will have a mass of not more than 550 kg while in orbit and a payload of 125 kg. Its position can be stabilized along three axes and the accuracy of its orbital parameters by latitude and longitude will be within +/-0.1 ⁰ . The service life of such satellites is expected to be within 10 to 12 years.

The satellites will be placed into orbit by STRELA light-weight carrier rockets launched from the Svobodny cosmodrome (Amur Territory). Thanks to that the satellites will be positioned in orbits which offer the best advantages in terms of energy parameters with inclinations in the ranges of 51-63 ⁰ and 90- 98 ⁰ , including solar synchronous ones.

Placing small communication satellites into a geostationary orbit (where they are meant to operate from) is a rather long process of many stages. In the beginning a satellite is placed by a booster into a circular orbit at 170 km and inclination of 52 ⁰ . Then comes the stage of a stabilized passive flight until crossing the equatorial plane. After that a solid-fuel booster takes the satellite to a transitional high-ellipsoid orbit (apogee - 100,000 km, perigee - 170 km). After that an electric booster of the satellite itself brings the perigee up to 1,000 km within a span of two orbits to a position where there is no aerodynamic deceleration. During the next 29 revolutions the plane of its orbit is rotated to match the equatorial. Finally, using the satellite's own electric plasma thrusters, it is switched into its operational geostationary orbit at an altitude of 36,000 km. The whole placing procedure takes 147 days.

The proposed version of forming the space segment of satellite communication systems and broadcasting offers considerable advantages as compared with the traditional launchings of full-size geostationary satellites with the help of heavy boosters like the PROTON. The main advantage consists in the fact that it will be possible to offer satellite communication services on regional markets, build infrastructures of the ground segment of such systems and make use of the unoccupied radio frequencies. And all of these things will be geared to the changing requirements of the local users.

Incidentally, utilizing the spare bands makes the suggested approach especially attractive in view of the growing complexity of international coordination of satellite networks over the past few years. Using our version it will be possible to offer satellite communication and broadcasting services even within the relatively narrow "conflict-free" frequency bands. This will also make it possible to increase the volume of transmission in any, occupied by another satellite, orbital position (if there is a spare frequency margin) by launching additional apparatuses in step with a growing traffic volume and the need for additional capacity.

A stage-by-stage expansion of the frequency "capacity" of an orbital position will make it possible to optimize the composition and characteristics of the "payload" of each successive small-size satellite in the interests of the user companies. This is especially important now in view of the constantly changing user requirements spurred by the rapid progress of information technologies.

Apart from the above benefits, the development of small, or compact communication satellites offers quite a few other advantages. They can be placed into orbit, for example, by heavy carrier rockets as some "additional payload". And we shall have a greater choice of medium and light carrier rockets which will make it possible to have more flexible launch schedules and reduce the operating costs of the proposed system.

And one more thing. Commercial production of such satellites and easy access to their launchers will make it possible to have a stock of standard and ready-for-use platforms (structures with all of the auxiliary service systems) and what we call payload modules (be it a communication satellite or a probe for Earth studies) which can be brought into action at a moment's notice in cases of emergencies or unexpected market requirements. Compact satellites can also be used as an "orbital reserve" which can be moved without delay into practically any point of a geostationary orbit.

And last, but no least, there is the important factor of data safety and protection. The future users of our system will be assured absolute independence so that no outside interference (bar cataclysm) will be able to put the established space communication system out of order.

The list of advantages offered by our RUSLAN-RS system - one of the few of Russia's high-tech offers on the world market today - includes low cost, dependability, efficiency and stability, to name but a few.

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