Preface and Summary

In the late fifties of the last century, a revolutionary change happened in the investigation of our cosmic environment by launching the first artificial satellites of the Earth. Already in October 1957, it proved to be a challenge to track optically the fast motion of the first Sputnik on an orbit of several hundred kilometers altitude in the barely known upper-atmosphere. As long as the radio transmitter of the satellite was active, the task of calculation of its orbit was solvable based on radio tracking. However, as the radio connection ended, less accurate data were only available: observations of the newly established visual satellite tracking stations, operated by untrained staff. (Actually, the optical tracking observed just the empty but bright last rocket stage of Sputnik-1 from the very first moment). Telegrams with predicted positions of the next transits of new satellites arrived from the Cosmos center (Moscow). In the very beginning, the inaccuracy of these forecasts caused severe difficulties in every country that joined this unique astronomical activity. Of course, it was the same in our country because the determination of the celestial position of a transiting artificial satellite was rather difficult.

The participants did know that even artificial satellites should follow the precisely calculated orbital equations. Therefore, experts started to focus on the orbital perturbation effects acting on relatively low orbits (up to several hundred km heights). Of course, these are not acting on our natural satellite, the Moon, so they had not been studied before. One of these perturbations is caused by the not perfectly spherical form of the Earth, which can be taken into account relatively easily by methods of geodesy. The other effect is the drag of the then yet unknown neutral upper-atmosphere. The latter influence could not be predicted precisely, because of the lack of any usable model of the upper-atmosphere.  (This region also named as thermosphere or exosphere sometimes).

The meteorological measurements (on board of aircraft or balloons) reached only the stratosphere. So, we had practically no information on atmospheric layers above it. However, it became clear rather quickly that although the density of the neutral upper-atmosphere is very low, nevertheless it can slow down considerably the motion of satellites.  Due to this, the orbital altitude decreases and the vehicle is annihilated finally in the dense lower atmosphere. Researchers have even discovered that the atmospheric decay is not constant but varies very strongly in connection with solar activity. The observed deviations of satellite orbits provided the basis for that conclusion that different effects and previously unknown peculiarities have to exist in the solar-terrestrial relations.

Hence, the simple orbital tracking of the first artificial satellites, using astronomical methods, gave two immediate results. First, it became possible to determine the exact form of the Earth using geodetic methods, and secondly, to construct a model of the upper-atmosphere based on the observations. The deduced density and temperature changes contained the direct effects of solar activity on the atmosphere using methods of geophysics and solar physics. These results had immediate practical value as well since exact atmospheric models needed, for example, to determine the probable lifetime of artificial satellites. The better knowledge of the shape of the Earth could help the cartography and geodesy.

How did Hungary participate in these quickly evolving researches? After 60 years it can be said as a fact, that taking into account the size and financial possibilities of the country we were able to join quickly and successfully into the international cooperation in both fields, even enriching them by several new ideas and methods. In early 1958, the optical satellite tracking service has been started in the Astronomical Institute (Konkoly Observatory) of the Hungarian Academy of Sciences, Budapest, and somewhat later in the Baja Observatory at the initiative of the Academy of Sciences of the USSR. Then the local observatories of Szombathely and Miskolc joined the Hungarian network. The small telescopes and the required time service have been developed rapidly to reduce the necessary number of observers and to carry out the task more effectively and precisely.

In 1961 a very crucial turning point was the INTEROBS program, a new initiative proposed by Márton Ill to use our satellite observations in upper-atmospheric research through orbital calculations of the satellites. This proposal, after several changes and modifications, led to outstanding and internationally acknowledged results during the following decades both at Budapest and Baja. The project, led by Márton Ill, was the main program of the Baja Observatory until 1990. Among his numerous co-workers, Károly Sütő, Előd Both and Sándor Nagy contributed significantly to the results.

The astronomers of Baja worked in close collaboration with the French working group led by Professor Francois Barlier, and took part in the successful improvement of upper-atmospheric models by adding their own and independent research results. In the Konkoly Observatory, Budapest, the research group worked in the same direction but used different methods. Its members were Erzsébet Illés (from 1959 until 2010!), Iván Almár and, for a shorter period, András Horváth. A close collaboration of the group with the geophysicist Pál Bencze from the Geophysical and Geodetic Institute in Sopron lasted for decades.

In the beginning, the research in Budapest concentrated mostly on the density increase of the neutral upper-atmosphere during geomagnetic storms but then extended to the investigation of other phenomena as well, such as atmospheric waves and the ring current heating. Later on, both groups started to use microaccelerometer measurements as well to improve the accuracy of their models. These in-situ measurements originated from onboard instruments of French and Italian satellites. The Hungarian astronomers have published their results at national and international conferences regularly. The three Ph.D. and two D.Sc dissertations prepared in this field are worth mentioning.

Now, sixty years after launching this field of research parallel to the space era, it is high time to collect and display on one webpage a more or less complete summary of our results.

In 2008 Márton Ill immigrated to Canada, where he passed away in 2015. The Baja Observatory under the leadership of Tibor Hegedüs turned toward other, mostly astrophysical topics. The Konkoly Observatory in Budapest (its present name is Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós Astronomical Institute of the Hungarian Academy of Sciences) finished the traditional investigation of the upper-atmosphere around 2010.  Meanwhile, the cutting edge and fast developing space astronomy  plays an increasingly crucial role in the life of the Institute.

In 2016 we organized a successful memorial conference in Baja, honoring Márton Ill which also provided an opportunity to survey our investigations of the upper-atmosphere. This webpage aims to put into context and preserve on the internet the primary materials of this research, compiled from mostly dispersed and difficult to access but irreplaceable sources.

The structure of the webpage is simple. On the right side, one can find the research activity at Baja, with particular emphasis on the work of Márton Ill. It includes the text of the last interview with Márton Ill in the book "Tudomány születik" (A science is born) published and edited by László Elek, as well as the recorded videos of the memorial conference in 2016  in Baja. On the left side, you can find English, Hungarian, and some Russian, German and Italian publications of the Konkoly Observatory group. The dissertations related to upper-atmospheric research together with several Hungarian comprehensive essays (Fizikai Szemle, Magyar Tudomány) were included for interested Hungarian readers. We have received all the permissions needed for the use of  the documents on the webpage.

The material on this website cannot be complete but some overlaps might be observed  among the publications. Our goal is to present and archive the significant and lasting research results from this very early and successful segment of Hungarian space research to both Hungarian and foreign readers at different levels of interest. The majority of publications written in Hungarian have been taken from the issues of the annual Seminars on Ionospheric and Magnetospheric Physics, organized by the predecessor of the Hungarian Astronautical Society, which are almost inaccessible nowadays. These seminars have played a crucial role in the regular discussions and cooperation of experts accomplishing different, but connected research in astronomy and Earth sciences. At the same time, these seminars helped to accept a common Hungarian terminology in this entirely new field. In our English publications, the fixed page limit was a frequent difficulty but was no similar problem in the Hungarian issues. Therefore we are convinced that their preservation for future investigations might be relevant.

We hope that our readers will find pleasure browsing these materials. Feel free to go straight  for the texts or figures you are interesting in most! The importance and place of this complex research field within the Hungarian scientific scene of the 20th century can only be judged by  future historians of science.  

The Editors
January, 2019