Fizikai Szemle honlap


Fizikai Szemle 1999/5. 206.o.


Károly Szegő
Central Research Institute for Physics,

Space research is one of the few exceptions when the research field has a birthday: it was the launch of the first Sputnik on 4 October, 1957; this was the moment when in-situ investigation of the outer space started. Birth is preceded by conception, and space research had a long delivery period. It included the development of rocket technology, measurements from balloons and sounding rockets, reaching out to heavens using electromagnetic radiation, investigating events caused by various solar phenomena, etc. Hungarian researchers industriously contributed in these early years, the name of von Kármán, the founder of the Jet Propulsion Laboratory in Pasadena, California, the father of the jet engines, is one of the best known persons. Here in Hungary we associate the beginning of space research with the lunar radar experiment of Zoltan Bay (Tungsram Laboratory) who measured the distance between the Moon and Earth using a radar signal in the beginning of 1946. This was a pioneering experiment, done in parallel though totally independently from a group working in the U.S. Army Signals Laboratory, New Jersey; the key to his success was a novel method to inerease the signal to noise ratio.

A new phase started in 1957-58, during the International Geophysical Year when the Hungarian engineers designed a special sounding radar to study the ionosphere (this radar station was used later in large numbers in other: countries as well). The visual observation of the sputniks also began, leading to the derivation of many important physical characteristics of the upper atmosphere. Space research slowly proliferated: Hungary participated in the analysis of moon samples and provided micrometeorit traps to study interplanetary materials on Vertical-type Sounding Rockets and Intercosmos sputniks. Charged particle analyzers were flown on board of several probes to study the ionosphere, and experiments started to clarify wave propagation in the ionosphere, especially the role of whistler waves was studied.

The gate to space for Hungary was the Intercosmos cooperation, an international venture that brought together the efforts of the Soviet-Union and the Central and Eastern European countries in the early seventies. This framework provided the cradle for the exploration of the geospace, the Sun, comet Halley, and the nearest planets, Mars and Venus. The importance of space techniques in geophysics and geodesy was well recognized because it resulted in maps of higher accuracy, and it also paved the way to study the universe using very long based interferometry (VLBI). Applications gained importance; space technique became an every day tool both in meteorology and in telecommunication.

The space flight of the Hungarian cosmonaut, Bertalan Farkas, on 26 May 1980 initialized research in material sciences and in space biology. An especially successful development was a dosimeter for the cosmonauts, called "Pille" (butterfly), that allowed a quick and easy analysis of the radiation dose, it will be described later in detail. In space biology, the vestibular system of humans was investigated, and instrumentation was worked out to measure the psychic state of the cosmonauts. Works in the field of material sciences has lead to the development of a special space furnace; its advantage is that during the beating of the sample, the sample itself is at rest and only the surrounding beating environment changes in a preprogrammed manner. This furnace will be a facility device on board of the International Space Station.

International cooperation in space research not only grew, but has also been institutionalized. Cooperative agreement has been signed with the European Space Agency (ESA) in 1991, and nowadays Hungary considers accession, to be an ESA member in the future. Government-level agreement was signed with Russia, and a framework agreement with NASA is currently under preparation.

During the turbulent history of Hungary many scientists emigrated from this century, and several excelled in the field of space sciences, especially those who went to the United States. I name only two persons who deceased recently: Imre Izsak, and Victor Szebehely. They both worked in the field of celestial mechanics and contributed significantly to map the gravitation field of the Earth using the orbital perturbations of satellites, worked out numerical method to solve the three body problem, such as the motion of the Apollo modules in the gravity field of the Earth and Moon. Though the intensity of collaboration with Hungarian-born U.S. scientists changed in time, their open or tacit support advanced formal cooperation between NASA and the Hungarian researchers; and we have benefitted much while working together with them in various space missions. I think, this is a proper place to acknowledge their support.

Albeit it is not directly related to the Hungarian space research, I cannot resist temptation to copy here a few lines from the book of György Marx, entitled "The Voice of the Martians": There is a mount named Von Kármán Crater on the Red Planet. Hungarians left more traces on the Moon: a huge ring in the southern part of the far side of the Moon has been named Von Kármán Crater, honoring the pioneer of supersonic flight and rocketry. East of it is a tiny crater, honoring Imre Izsak, the HungarianAmerican expert of celestial mechanics of the Space Age. In the North-West, near the Terminator line, halfway between H.G. Wells and F. Joliot is the great Szilard Crater East of it astronauts may find the Von Neumann Crater. Further 19th century Hungarians who did not cross the Ocean, deserved place on the lunar map: in the southern part of the far side are János Bolyai (pioneer of non-Euclidean geometry), a bit east of it is Roland Eötvös (proving the equivalence of the inertial and gravitation mars). And this list is not complete!

In what follows, selected results will be presented from the field of Solar System exploration mostly, the results reported were obtained by spacecraft instrumentation built with Hungarian participation; the selection represents exclusively the personal bias of the author.

The Pille thermoluminescent dosimeter

Dosimetry is an important aspect of human safety around reactors; research in this field started in Hungary at the same time when our nuclear research reactor began to operate in the Central Research Institute for Physics (KFKI), Budapest. Solid state dosimeters were a novelty of the sixties, the thermoluminescent dosimeters use a special material that absorbs radiation, and when heated, the emitted light is proportional with the accumulated dose. At the same time, beating resets the material, and the measurement cycle may start again.

During the first space applications, in the seventies; the sensor and the evaluation module were separated, cosmonauts carried the solid state detector with them, and all the analysis was done on the ground, using huge and heavy instrumentation. However, for the flight of the first Hungarian cosmonaut in 1980 a "carry-on" version called "Pille" was completed, comprising both a pen-size sensor and the data processing electronics of about 2 kg. The test of the instrument was successful, and it served onboard of Mir space station for a few more years.

During the conference of the International Astronautical Federation, in 1983, in Budapest, a NASA delegation visited the Central Research Institute for Physics, and they proposed to fly Pille on board of the space shuttle. The acceptance of this proposal was not without complications. For unknown reasons, some high ranking Soviet military officers got convinced that Pille is sensitive enough to pinpoint nuclear submarines under water. When this claim turned out to be false, it was still demanded as a compromise that though Pille may fly on the shuttle, the event cannot be made public. At last, Pille got onboard of Challenger, and was operated successfully by NASA astronaut Sally Ride in October 1984.

As electronics developed, more and more feature was accommodated to facilitate data acquisition and processing, and Pille was used in many more missions. ESA astronaut T Reiter operated it for about half a year on board of the Mir station during the Euromir'95 cooperative activity. Later, in 1997, NASA astronaut J. Lineger operated it during the NASA4 flight in a novel way, he measured the amount of radiation they were exposed during extravehicular activity (space walk) together with his Russian partner cosmonaut ?'sibliev. This was the first time when dosimetry was done during extravehicular activity. It is of no surprise that Pille will continue its achievements, and it will be a standard component of the International Space Station.

Exploration of comet Halley

In the late seventies the big space agencies prepared missions to explore comet Halley during its perihelion passage in 1986. The Intercosmos also took advantage of this opportunity, and modified the orbit and objective of one of the missions dedicated originally to investigate Venus. The new mission, under the code name VEGA, united the objectives to balloon around Venus and to encounter comet Halley. In that time Hungarian engineers excelled already in preparing space electronics, therefore it was natural that the Soviet lead institute, IKI (Institute of Space Research, Moscow), approached us whether we were interested to participate in this challenging mission.

A major task was to image the cometary nucleus, first time in the history of mankind. We proposed to use a novel technique of that time, to use CCD to capture images, as we had already good experiences with it. Others, including even leading western authorities, considered it still risky and untested. We, however, argued for its merits, at last our arguments were accepted, and it was decided that the imaging device would be based on CCD technique. Institutes from the Soviet Union, France, and Hungary united forces to meet the technical challenge. Our task in the Central Research Institute for Physics was to design and manufacture all the electronics, and the software of television system, TVS. This system, however, grew fart to be much more than an imaging device, because the high relative speed (80 km/s) of the comet and the spacecraft during the encounter caused a special difficulty 'for flight operation. As the spacecraft was three axes stabilized, the TV system had to be mounted on a pointing platform, and the platform guidance soon became a task of the TVS. The comet nucleus could not be resolved by ground telescopes, so targeting the nucleus was added to the list of requirements. TVS developed to a full, autonomous space robot. Its task became even more sensitive when the European Space Agency and Intercosmos agreed that the VEGA probes would find the path to the cometary nucleus for the GIOTTO probe of ESA. GIOTTO assumed a 500 km closest approach distance, and at such a small distance ground technique for guidance was already inadequate.

The Hungarian participation in the VEGA mission grew fart in size and in ambition. Soon it became our task to provide the onboard data acquisition system (Technical University, Budapest), to participate in building the electronics of two plasma measuring instruments and a dust counter, and to provide computers and data distribution software for the ground segment (KFKI). One of the plasma measuring instruments, TUNDE, to measure suprathermal ions was designed and built fully in Hungary. Actually, one third of the total electronics was Hungarian product. VEGA was the first Intercosmos mission open to western participants, that lead to interesting security considerations on both sides of the Atlantic. Hungary somehow became a bridge and a channel for concerted actions in those years. As an example I can mention the dust detector made at the University of Chicago which was selected in the very late phase of the mission, and had to be completed quickly to avoid certain technology transfer problems associated with components.

The VEGA mission was really risky. When I was appointed to lead the works in Hungary, a person wished me good luck by saying he had decided not to run for the job because the risks overweighed the potential return of success. I am happy to state he proved to be wrong. The imaging system on board of the VEGA spacecraft provided the first image of a cometary nucleus (see back cover of this issue), and we were able to identify many physical parameters of the nucleus including the structure of the surface. The plasma instruments identified new acceleration mechanism for space plasmas, discovered new type of plasma boundaries, and many outstanding features of the cometary magnetosphere. In my opinion, it was the success of the VEGA mission that has made Hungarian space research mature, and internationally recognized.

Investigation of Venus and Mars

In the seventies Hungarian space physicist established good contacts with the group of the late Prof. Gringaus (who, among others, discovered the magnetopause of Earth), and we soon joined to the investigation of the nightside ionosphere of Venus. It was known that the ionosphere is the result of the solar UV ionizing radiation, but processes that can maintain the ionosphere on the nightside of Venus were a mystery; U.S. and Intercosmos teams suggested different explanations based on the measurements of respective missions. The explanation we favored proved to be right, and that made possible cooperation with NASA teams operating the Pioneer Venus Orbiter, and several joint action to explore the magnetospheres of Venus and Mars. We built space instruments to this end for the two Soviet Phobos orbiters and their (unsuccessful) landers, and also to the ill-fated Mars-96 missions.

The Phobos-2 spacecraft investigated the plasma regions around Mars for a period of almost two months in 1989, first on highly elliptical orbits, then on almost circular ones. Those orbits penetrated some domains never investigated before, and the on-board instruments represented much more advanced technology than those used in previous missions.

The HARP instrument (Hyperbolic Analyzer in Retarded Potential mode), constructed in a Hungarian-Soviet-U.S. collaboration, was the first to detect hot electrons in the deep plasma sheet of Mars. None of the earlier Mars orbiters were able to carry out measurements in the optical shadow of the planet, thus there had been no data from regions close to the axis of the magnetic tail. Heavy ions were measured by the combined electrostatic and magnetic spectrometer TAUS, prepared in a German-Soviet-Hungarian collaboration. It was shown that the heavy ions moving tailwards consisted mainly of singly ionized oxygen of Martian origin. The measured oxygen outflow was intense enough to significantly deplete the oxygen atmosphere of Mars in a few billion years, i.e. on a time scale comparable with the age of the Solar System. This indicate that plasma features of the Martian environment may have played a crucial role in shaping the history of the Martian atmosphere, and thus also of conditions for the creation and maintenance of life on that planet.

Another interesting problem is how energy is transferred from the Sun to planets. Most of the energy is irradiated in the form of electromagnetic waves in a broad range of the spectrum, but not negligible is the energy that the Sun emits/ejects in the form of fast moving particles. This stream of particles is known as the solar wind, moving with supersonic velocity in the interplanetary space (relative to the characteristic velocities of the interplanetary plasma, such as the ion sound velocity or the velocity of Alfven waves). The solar wind carries about 0.2 1 erg cm-2 s-1 energy flux at the Earth, the effective cross section where this stream can be captured is the cross section of the magnetosphere, it is more than 100 times bigger than the geometrical cross section of the planet. Planets are obstacles in the wind, brakes that slow down the wind, and it is natural that the brake is also got heated. The physics of that, however, is very much complex, because the free energy is transferred from the non-equilibrium distribution of the solar wind particles via complicated wave excitation mechanisms, and subsequently the waves are absorbed or interact otherwise with the planetary plasma population. In the case of Venus and Mars (both are non-magnetic), the solar wind comes to direct contact with the ionosphere, creating a special transition region, the dayside mantle, where both the solar wind and planetary plasma are present, and where most of the energy exchange takes place. Using data measured by instruments carried on board of the Pioneer Venus Orbiter of NASA, and the Phobos-2 probe of Intercosmos, Hungarian physicist contributed significantly to clarify the characteristics and the microphysical processes of the mantle region. Our results advanced knowledge how energv and momentum are transferred via these complicated plasma interactions from the solar wind, that is from the Sun.

Exploration of the interplanetary space

For a long period of time the in-situ Solar System exploration could be done only in the close vicinity of the ecliptic plane, because mankind for a long time did not have resources to break through the "angular momentum prison", to overcome the huge angular momentum due to the orbital motion of Earth, shared by all artificial satellites as well. The first space mission that provided a three dimensional view of the heliosphere was the ULYSSES mission of ESA; its orbit passed above both the northern and southern polar regions of the Sun. Hungarian space physicists have participated in the investigation of the three dimensional structure of the magnetic field in the heliosphere. The solar magnetic field plays a major role determining how cosmic rays can penetrate and propagate in the Solar System; and as in Hungary we have had a long experience in cosmic ray research, we could easily contribute to solve some of the special questions emerging. Certain type of solar eruptions were detected by a particle analyzer on board of the Solar and Heliospheric Observatory (SOHO) of the European Space Agency, this instrument was built with Hungarian participation. These observations are significant to clarify particle propagation in the interplanetary space.

Current and future activities in Solar System exploration

Space missions are long-term undertakings, the CASSINI mission of NASA to explore the Saturnian system began around 1990 and will not finish before 2008; the ROSETTA mission of ESA, to explore comet Wirtanen, started in the mid-nineties and will run well after 2011. Though the new trend is to reach research objectives "faster, cheaper, better", decade long work is still needed before the rocket is lifted to the sky. Evidently this requires long term planning, and many factors should be harmonized, especially for a small country with limited resources:

  1. Physicists need results and publications, therefore a team has to participate in a sequence of missions, each in a different phase (preparatory, manufacturing, post-launch commissioning, operational, and data analysis phases).
  2. Data comes exclusively in exchange of instruments, therefore the participation in mission sequence should correspond to the engineering expertise of the team(s), the work of physicists and engineers are strongly coupled.
  3. A small country can only moderately influence mission objectives, therefore one has to live with opportunities defined elsewhere; however, a good understanding of the future plans of the big agencies is necessary to use wisely both the human and the financial resources available.

Despite the most careful approach in these matters, double failures within one year, such as the rocket failure of the CLUSTER mission of ESA, and the loss of the MARS-96 spacecraft of the Russian Space Agency, have caused a tremendous setback for us (for space physicists working in KFKI-RMKI), and much hard work is needed to recover.

The space research team working in KFKI-RMKI has selected the interaction of the solar wind with solar system bodies as the major research field to study. As of today, they are involved in several space missions:

An important aspect of the exploration of the geospace is to study how waves can propagate in the near Earth environment. Researchers from the Roland Eötvös University and from the Roland Eötvös Geophysical Institute take part in these studies, they manufactured a dedicated instrument called SAS that flew in 1989 on board of the "Aktiv" Intercosmos satellite. There are several plans to re-fly an upgraded version in the near future, one of the opportunities under study is ALPSAT space probe, a joint satellite of Austrian and Swiss researchers.

Final remarks

Space research is an exciting field of science, it discovers unknown and unimaginable alien worlds in the Solar System, we can reach out in time when investigating comets, and we may even understand how life has spread around. Almost all space missions produced unexpected results, warning us that our knowledge of the complexity of the world is very much limited, warning that speculation never can substitute experiments. Space activity has changed the everyday life, we are really living in a new age, in the space age.

Having said so, other aspects of space research bring us back to the ground. It is an expensive venture, an expensive branch of science; and especially for a small nation it is not trivial to decide: in which way to contribute, and how to benefit from the achievements, especially from those reached in the field of high technology.

In this brief review overview I wanted to show that we in Hungary have used the opportunities, we have reached a good balance in cost, efforts, and benefits. I wonder whether the picture I presented is convincing to others as well.