Yuri Gagarin public astronomical observatory – the first in Bulgaria: 60 years later

The report presents an analysis of the history of the Public Astronomical Observatory (NAO) "Yuri Gagarin", the city of Stara Zagora, which was officially opened on February 26, 1961. The initiative to open it belongs to a group of enthusiasts, among which the figure of Boncho Bonev is of particular importance. With financial and material assistance from the municipality of Stara Zagora, the first premises were equipped and the first astronomical instruments and equipment were purchased. The observatory bears the name of the world's first pilot - cosmonaut Yuri Gagarin. The natural evolution of the development of the Observatory is presented, as well as the need of creation an observational base outside the city, in the area of the Ayazmo Park (opened in 1968). The supply with amateur telescopes is shown, as well as of a large optical instrument for professional astronomical work – a refractor (200/3000 mm), the Kude system, the production of the Carl Zeiss, Jena (former East Germany). The acquired ZKP-2 planetarium at the Carl Zeiss factory in Jena expands the NAO's capabilities in the education and promotion of astronomy and space science.The evolution of extracurricular astronomy training and the mass popularization of the achievements of astronomy, aeronautics, physics and human technology in PAOP are analyzed, as well as scientific observations of artificial Earth satellites. In this connection, in 1979 a specialized out-of-town observation base was built in the area of the Stara Zagora Mineral Baths, equipped with one of the most modern devices of its time – the AFU-75 satellite camera. An attempt was made to periodize the history of PAOP «Yu. Gagarin», the main stages being arranged in time according to significant historical, technological, organizational or other events.

General relativistic effects acting on the orbits of Galileo satellites

The first pair of satellites belonging to the European Global Navigation Satellite System (GNSS)—Galileo—has been accidentally launched into highly eccentric, instead of circular, orbits. The final height of these two satellites varies between 17,180 and 26,020 km, making these satellites very suitable for the verification of the effects emerging from general relativity. We employ the post-Newtonian parameterization (PPN) for describing the perturbations acting on Keplerian orbit parameters of artificial Earth satellites caused by the Schwarzschild, Lense–Thirring, and de Sitter general relativity effects. The values emerging from PPN numerical simulations are compared with the approximations based on the Gaussian perturbations for the temporal variations of the Keplerian elements of Galileo satellites in nominal, near-circular orbits, as well as in the highly elliptical orbits. We discuss what kinds of perturbations are detectable using the current accuracy of precise orbit determination of artificial Earth satellites, including the expected secular and periodic variations, as well as the constant offsets of Keplerian parameters. We found that not only secular but also periodic variations of orbit parameters caused by general relativity effects exceed the value of 1 cm within 24 h; thus, they should be fully detectable using the current GNSS precise orbit determination methods. Many of the 1-PPN effects are detectable using the Galileo satellite system, but the Lense–Thirring effect is not.

Holding Geostationary Satellite at Given Standing Point, Taking into Account Additional Phase Restrictions

The active lifetime of orbital facilities in the geostationary orbit (GSO), which include stationary artificial earth satellites (SAES) for various purposes, can be more than 15 years. At the same time, in modern conditions of orbital grouping increment, the number of space debris, including those on the GSO, also increases: SAES, which have finished its active lifetime and were not transferred to disposal orbit for some reasons, shards of SAES appeared from collision with meteors or accidents. This leads to the increase of probability of collisions with active SAESs. The listed factors determine the need of considering not only the problem of keeping SAESs in vicinities of position, but also the task of avoiding collisions with space debris objects (SDO), while the costs of the working fluid should not increase. A great attention is being paid to rational power units placing during the projection of new space shuttles, especially those with long useful lifetime. In this article, it is assumed that SESs are equipped with several correction motors, which make it possible to create control accelerations in only several directions, without changing the orientation of the SES itself. In other words, in this task it is assumed that the corrections of the parameters of the AES orbit do not affect the orientation of the SAES itself. This condition is a severe limitation in the synthesis of the SES’s control system. In the considered methodological approach, the costs of the working fluid are set as a functionality from control, which are necessary to perform the next correction, after which the SAES will not have dangerous distances and approaching in projection horizon’s interval. This makes it possible to avoid situations when the decision on control is being made after the SES leaves the vicinity of the station point, and first of all, the approach to the SDO at a distance less than a liminal one. This article provides the results of modeling, which indicate the effectiveness of the proposed solutions. An important advantage compared with the existing methods is the consideration of the movement of the SAES relatively not only to the stationary point, but also to several other objects located in its vicinity, both controlled and uncontrolled. Moreover, there can be any given number of objects.

Conversations about Science Fiction: The Category of “Fantastic” in The Bibliographic Discourse of the 1960s and 1970s

In the 1950s and 1970s, bibliographers made attempts to define the genre of fiction and offer a systematization of the available fiction literature. The purpose of the article is to trace the development of the category of “fantastic” in the recommendation indexes of Z. P. Shalashova “Adventures. Journeys. Science Fiction”, “Artificial Earth satellites. Interplanetary flights”, “Adventures and travel”. The problems faced by bibliographers were related both to the sharp increase in publications of fantastic literature, and to the weak development of the theoretical apparatus in literary studies and bibliography. The concept of “fantastic” has evolved from an adventure-related type of scientific and educational literature to a metaphorical “dream world” devoid of terminological clarity. The material of bibliographic indexes, de- spite its limited functionality, nevertheless demonstrates that the processes that took place in the field of recommendation bibliography of children’s books reflect the significant difficulties that bibliographers experienced in finding a language for describing fiction.

Vitaly Grigorevsky’s Contribution to the Development of International Cooperation in Photometric Studies of Artificial Earth Satellites

This article highlights the participation of the Ukrainian scientist, Professor Vitaly Mikhailovich Grigorevsky, doctor of physical and mathematical sciences, and representative of the scientific school of Vladimir Platonovich Tsesevich, in the organization and development of international cooperative partnership in the field of satellite astronomy and photometric studies of artificial satellites of the Earth. The activity of the scientist in the coordination of scientific research of the countries of Eastern Europe in 1965–1973 under the SPIN program, carried out under the auspices of the Astronomical Council of the USSR Academy of Sciences, is discussed. The article explores the main forms of Grigorevsky’s scientific cooperation with the world’s leading experts in the field of satellite astronomy—the British scientist Desmond King-Hele, the Czech astronomer František Link, Hungarian researchers Iván Almár and D. Toth, and others. Also, the achievements of the Latvian researchers Māris Ābele and Kasimirs Lapushka in the creation of photographic cameras of surveillance of satellites are analysed.

«Space Kamikazes» Will Help Defence the Earth

The article provides a justification for the possibility of using some artificial earth satellites and spacecraft that are being prepared for launch to exert a kinetic impact on asteroids and comet nucleus in order to destroy them. This will prevent catastrophic collisions with the Earth of celestial bodies ranging in size from tens to hundreds of meters. Suggestions are given on how to prepare for the use of this method.