Ground control system for distant space vehicle

When performing space missions to study deep space objects, the target task is to deliver a complex of scientific instruments as part of a spacecraft (SC) to a given area of outer space, conduct scientific research in this area and deliver the information received to Earth. area of outer space, in which scientific research is carried out, there may be the surface of the planet or its satellite, the orbit of the artificial satellite of the planet, the trajectory of the spacecraft flight, which ensures the flight at a given distance from the object under study.

Methods for studying the physical characteristics of deep space objects using scientific instruments installed on board a long range spacecraft (LRS) are called direct methods. Direct methods have provided valuable information about the planets of the solar system, as well as about cosmic plasma, ionized and neutral shells of planets, and some comets. In the future studies of solar system objects by direct methods will continue, for example, with the help of promising spacecraft, such as the planned launch of ExoMars, controlled by the multifunctional ground radio complexes (GRC) being created . GRC carry out trajectory measurements of the current navigation parameters of the spacecraft, by which the trajectory of its movement is determined, receive telemetric information from the board on the operation of service systems and scientific instruments of the spacecraft [1–5], with the help of control commands transmitted on board, ensure their normal operation, accept from on-board spacecraft systems information obtained in the course of scientific research [6; 7].

The main feature of the radio links of deep space communications is the need to carry out radio communications over gigantic distances – hundreds and thousands of millions of kilometers. The signal propagation time over these distances can reach several tens of minutes and when flying to distant planets, several hours. The specific features of deep space radio links impose additional requirements on GRC, which make them unique in terms of technical characteristics and significantly different. from ground tracking stations of other space systems [8–10].

The first generations of GRC, with the help of which long-range spacecraft (LRS) was controlled, were the Pluto complexes with antennas ADU 1000 и «Saturn -MSD» with the antennas P-400 and P200. From 1981 to 2000 to control the LRS, the Kvant-D MGREC installed at the checkpoints was used in Evpatoria and Ussuriysk. The Kvant-D complex, equipped with P-2500 antennas with a mirror diameter of 70 m and P-400 with a mirror diameter of 32 m, operated in two frequency bands – L and C. During this period, using the Kvant-D complex, space programs for the study of Venus, Mars, Halley's comet, as well as scientific research conducted with spacecraft in highly elliptical orbits (Astron, Granat, Interball) were successfully completed.

However, today the equipment of the Kvant-D complex is morally obsolete, has used up its technical resource and, most importantly, operates in frequency bands that do not comply with the regulations of the International Telecommunication Union where Russia is a member. Therefore, the newly developed spacecraft for deep space exploration and the corresponding GRC should operate in the frequency ranges allocated for this – X, S and Ka.

These circumstances were the basis for the development of the next generation of GRC to manage promising LRS and integrate them into regional and global network structures. Taking into account the high cost of creating antennas, as well as the long duration of their life cycle (up to 30–40 years), in the future, the ground control complex (GCC) LRS will use the existing P-2500 and TNA-1500 antennas that have undergone refurbishment and upgraded for operation in new ranges, and new complexes will be developed on the basis of antenna systems with mirror diameters of 32 and 12 m.

The practice of LRS full-scale tests shows that even with the simultaneous control of two spacecraft of various space programs, the time for using ground-based facilities at one point does not exceed 6–10 hours. The rest of the time, these expensive facilities are not used. Therefore, in order to increase the time of using ground facilities, it is necessary already when designing the complex to provide for the possibility of using it for other work, such as scientific research and participation in the management of foreign LRS.

Therefore, a comprehensive study of a promising GCC LRS is needed, which has great potential not only in managing the LRS, but also in conducting fundamental and applied radio astronomy research. Much attention is paid to the analysis requirements for the radio engineering complex, which must be met in order to realize the possibility of conducting several areas of scientific research with its help [11–14], and above all:

– planetary radar ;

– very long baseline interferometry ;

– radio translucence ;

– radio astronomy .

GRC LRS configuration

The existing means of the ground-based complex for remote spacecraft control are built according to a single-point scheme of a receiving-transmitting GRC, which solves the problems of controlling a certain distant spacecraft.

At present, the following GCC LRS facilities are used to control distant spacecraft :

– command and measuring system (CMS) "Cobalt-R" based on the antenna system (AS) TNA-1500 (Bear Lakes);

– CMS "Klen-D" based on AS P-2500 "Ussuriysk";

– GRC "Cobalt-M-FG" based on AS TNA-1500 (Bear Lakes);

– GRC " Phobos" on the basis of AS P-2500 "Ussuriysk";

• – ground station "Spektr-X" based on AS TNA-57 ;

• –    mission control center of spacecraft "Spektr-RG" (on the basis of MCC Central Research Institute of Mechanical Engineering);

• –    sector of the chief designer of spacecraft Spektr-RG (based on MCC-L);

• –    mission control center of the spacecraft "Spektr-R" (based on MCC-L );

• –    ballistic center Keldysh Institute of Applied Mathematics of Russian Academy of Sciences (abbreviation: KIAM RAS);

• –    ballistic center of the Central Research Institute of Mechanical Engineering;

• –    Means of communication and data transmission (based on the existing means of a multi-service communication and data transmission system from the ground-based automated control complex for spacecraft for scientific and socio-economic purposes and measurements, communication and data transmission facilities of the Special Design Bureau of the Moscow Power Engineering Institute, Scientific and Production Association named after S. A. Lavochkin, Central Research Institute of Mechanical Engineering, settlement of Ussuriysk, settlement of Baikonur.

However, the existing tools that provide spacecraft control in deep space have a number of significant drawbacks that do not allow to fully ensure continuous and stable control, communication and navigation of domestic and international deep spacecraft, for example:

• –    around the clock radio communication of LRS is not maintained;

• –    the technical life of large antenna systems included in the LRS control tools is ending and cannot be extended indefinitely ;

• –    there is no single standard for creating GCC LRS tools (each developer has his own school of development);

• –    a single-point GRC transceiver scheme is inefficient with an increase in the LRS constellation and does not provide the necessary energy potential for radio communication with promising LRS .

The upgraded GCC LRS facilities should ensure the control of spacecraft of lunar projects launched in the interests of the Roscosmos State Corporation, equipped with C-band onboard radio complexes (OE CMS type).

Due to the fact that the mass and power supply capabilities of the LRS are very limited, the power of the onboard transmitters and the size of the onboard antennas are small. To receive signals from the LRS on Earth, it is necessary to build large antennas with a parabolic mirror diameter of 30–70 m. Unusually high requirements are placed on the pointing accuracy of these antennas when tracking a spacecraft – fractions of arc minutes. The sensitivity of GRC receivers should be as high as the state of the art; the power of the transmitting devices is quite high (tens and hundreds of kilowatts of power in continuous mode); long-term stability of radiated and heterodyne frequencies of deep space communication complexes is very high (1 x 10^-13 - 1 x 10^-15).

It is necessary to ensure high reliability of the control commands issued to the LRS, and the issuance of commands, as well as the performance of other basic operations of deep space communication complexes in the implementation of LRS control, must be carried out in automatic mode.

The results of research conducted in deep space directly depend on the technical characteristics of the GRC controls used [15–19]. As the technical characteristics of these tools improve, the possibilities expand and the results of ongoing scientific experiments grow. Therefore, the improvement of the technical characteristics of terrestrial and onboard radio systems is ongoing, but mainly with a change in the generations of these systems. Specifications of the new generation of GRC control LRS must comply with the latest achievements of science, engineering and technology at the time of its creation [20–25].

The cost of creating such radio control complexes is very high; their service life can reach up to 20 years. Therefore, the development of equipment should be carried out in such a way as to provide flexibility in the modernization of the complex, which will allow upgrading individual systems during use without affecting the operation of the rest of the complex.

Methods for exploring the solar system

To obtain information from objects of the Solar System that are currently inaccessible to direct research methods, such as the solar corona, solar wind at small distances from the Sun, asteroids and comets, the atmospheres of some planets and their satellites, etc., indirect or remote sensing methods are used, based on the relationship between the physical properties of objects and the characteristics of radio signals propagating through the medium under study or reflected from the surface of the objects under study.

In radio astronomy research carried out with the help of GRC, natural sources of radiation - quasars and pulsars – or artificial sources of radio waves emitted by airborne or ground-based transmitters are used as probes.

Remote research methods include:

• –    radio translucence of planetary atmospheres (radio occultation research methods), solar plasma research ;

• –    radar research carried out with the help of a ground-based planetary radar and a radar located on a satellite of the planet (side-scan radar), as well as bistatic radar ;

• –    studies conducted using the Doppler frequency shift caused by the mutual movement of the object under study and the tracking station ;

• –    studies using radio interferometers with a very large base;

• –    radio astronomy research.

The sensitivity of remote sensing methods for space research depends on the relationship between the effects created by the medium under study on the propagation path of the radio wave and the in- strumental errors of the GRCs used, due to the noise of the receiving systems. The improvement of radio engineering complexes, dictated by the requirements of new space programs, increases the possibility of using the GRC as a tool for conducting remote radiophysical research. The technical characteristics of domestic GRC controls from the LRS GCC turned out to be adequate for conducting highly efficient radio engineering research conducted by remote methods, which provided unique and, in some cases, priority scientific information on various objects of the solar system.

Conclusion

The main task of the advanced GCC is the management of promising LRSs; therefore, ways to improve the technical capabilities of the complex in managing promising LRSs and methods for ensuring compatibility with space radio links of foreign LRSs are outlined. Creation of GCC is carried out step by step. At the first stage, the LRS GCC is created as part of the structure that ensures the implementation of space programs from the territory of Russia. At subsequent stages, the LRS GCC is being retrofitted and territorially expanded in order to improve its technical characteristics, which will make it possible to manage the grouping of promising LRS and manned missions. The use of promising technologies will make it possible to carry out this in a continuous radio communication mode.

At the moment JSC Special design bureau of the Moscow Power Engineering Institute (SDB MPEI), within the framework of the preliminary design "Development of the structure and systems of the ground control complex for deep space spacecraft", has approved the appearance of the global radio interferometric network GCC deep space spacecraft. The global network will make it possible to solve the problems of providing continuous and sustainable control, communication and navigation services for the Russian orbital constellation of manned and automatic spacecraft (including when implementing deep space exploration programs on flight trajectories to the Moon, Mars, and other celestial bodies of the solar system); international spacecraft; objects of planetary and interplanetary infrastructure, as well as to ensure the conduct of fundamental scientific research in deep space. The longterm program for the creation of such a LRS GCC network until 2035 was approved with the protection of the draft design by the Conclusion of the Roscosmos State Corporation. Created as a synthesized coherent spatio-temporal radio measuring system, the LRS GCC network can be used as a base platform for creating a spatio-temporal system of ground-space communication and navigation of the Russian Federation.

Acknowledgements . The work was prepared with the financial support of a grant from the President of Russia (Project NSH-1357.2022.6 “Models, methods and means of obtaining and processing information about space objects in a wide spectral range of electromagnetic waves”).