the pushchino radio astronomy observatory: origin and first decade's history

Astron. Nachr. / AN 328, No. 5, 395 – 404 (2007) / DOI 10.1002/asna.200710765

The Pushchino Radio Astronomy Observatory: origin and first decade’shistory

R.D. Dagkesamanskii�

Pushchino Radio Astronomy Observatory, Pushchino, 142290, Russia

Received 2007 Mar 21, accepted 2007 Mar 21Published online 2007 May 15

Key words history and philosophy of astronomy – obituaries, biographies

The first radio astronomical investigations in the Lebedev Physical Institute are described. Some details of the largeradio telescopes construction in Pushchino Radio Astronomy Observatory as well as the most significant scientific resultsobtained with them are quoted in the paper,too.

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1 LPI as a cradle of Soviet radio astronomy

In 2006 the Pushchino Radio Astronomy Observatory(PRAO) of the P.N. Lebedev Physical Institute (LPI) cel-ebrated the 50th anniversary. The birthday of the Obser-vatory is April 11, 1956 when the Council of Ministersof the USSR has accepted the Decision that permitted theAcademy of Sciences to construct in the Serpukhov area abuilding and a radio telescope of the Radio Astronomy Sta-tion of the LPI.

This important decision was preceded with famousdecade of origin and becoming of the Soviet radio astron-omy, which cradle was LPI. In 1946 the young scientist Vi-taly L. Ginzburg from LPI has predicted that the radio di-ameter of the Sun at meter wavelengths should surpass itsoptical diameter noticeably. And in 1947 under the initia-tive of academician Nikolai D. Papaleksi, the head of theLaboratory of Fluctuations of LPI, an expedition was orga-nized to Brazil coast for observations of a total solar eclipse.Papaleksi carefully prepared the expedition but suddenlydied shortly before departure of the steam-ship “Griboedov”with optical astronomers, radiophysicists and experts on anionosphere. In N.D. Papaleksi’s absence Prof. Semyon E.Khaikin – the remarkable scientist who really possessed anencyclopedic knowledge in physics – has headed the radio-physics and ionosphere groups. Among the participants ofthe expedition there were many talented scientists, some ofwhich (V.L. Ginzburg, B.M. Chihachev, I.S. Shklovsky aswell as S.E. Khaikin) had played subsequently a great rolein the development of radio astronomy in the USSR (seeFig. 1).

Radioastronomical observations of the solar eclipsewere very successful and confirmed the calculations madeby V.L. Ginzburg. During total phase of the eclipse theflux density of the Sun at 1.5 m had fallen only up to 40%

� Corresponding author: [email protected]

Fig. 1 Participants of the expedition to Brazil for observations ofthe total solar eclipse of 1947. From right to the left: S.E. Khaikin(first in the first row), B.M. Chikhachev and V.L.Ginzburg (sixthand eleventh in the second row), I.S. Shklovsky (second in the thirdrow).

(Fig. 2) that confirmed the significant contribution of the so-lar corona to the integral radiation of the Sun at this wave-length (Khaikin & Chikhachev 1947). Inspired by the firstsuccess, radiophysicists of LPI organized a constantly op-erating expedition (and subsequently a radio astronomy sta-tion) in several sites of Crimea where they constructed thefirst domestic radio telescopes and obtained the first out-standing scientific results. This work had been begun un-der the initiative and was headed by S.E. Khajkin. How-ever, from 1955, when S.E. Khaikin finally left LPI (for thePulkovo Observatory), the work had been headed by VictorV. Vitkevich. Later, V.V. Vitkevich recollected these years:

“In 1948 when I have started to work in LPI, the groupof radioastronomers consisted of scientists S.E. Khajkin,B.M. Chikhachev, J.I. Lihter and radio engineer M.V. Ko-marov. In the next 2–3 years T.I. Gavrilenko, S.A. Zajtsev,P.D. Kalachev, M.T. Levchenko and G.V. Rybakov joined

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396 R.D. Dagkesamanskii: The Pushchino Radio Astronomy Observatory

Fig. 2 Decrease of the solar flux density at 1.5 m during the totaleclipse of the Sun (May 1947).

this group. All these people (led by S.E. Khajkin) formedthe radio astronomy part of the Laboratory of Fluctuations,headed by academician M.A. Leontovich. At that time themain radio astronomy objects were the Sun and the Galaxy(as the whole). The large number of small sources werenot suspected yet. All the basic observations were made inCrimea (in Alushta and at the mountains Koshka and Aj-Petri). There the radar antennas were used (the first domes-tic radio telescopes were only just developed that time). Agreat role had played the “Big Wurzburg” – trophy radar an-tenna (of 8 m diameter) – mounted by P.D. Kalachev. It wasused in the first important works on researches of the Sun,the Moon and studying of radio waves propagation throughthe Earth’s atmosphere.”

“In 1951 the first observations in our country of a dis-crete radio source, namely Crab nebula, have been made.These observations have strongly suffered from the power-ful solar radio emission. Then it has been decided to use this“neighbourhood” for researches of circumsolar space by ra-dio occultation technique.”

“The largest experimental base in Crimea was the scien-tific station in Katsiveli. But even in 1953 there was no sci-entific tool at the station site. However, in 3–4 years at ourmechanical workshop many of modern radio telescopes hadbeen constructed by M.M. Tyaptin and other qualified me-chanical workers headed by general engineer P.D. Kalachev.They were earthen dishes (with diameters of 30 m) for meterwavelengths, and wooden nonmovable antennas for study-ing the solar super corona and an ionosphere of the Earth,the interferometers with variable baselines for centimeterand decimeter wavelengths, the spectrograph antenna and,finally, a large earthen dish (of 32 m diameter) for centime-ter wavelengths . . . ... ”.

Here V.V. Vitkevich mentions only casually the radiooccultation technique that has been suggested and usedby him (and independently in the same year by AnthonyHewish in Cambridge, Great Britain) for researches of cir-cumsolar space. This remarkable competition of two groupsheaded by A. Hewish and V.V. Vitkevich has led to the dis-covery of the solar supercorona and to the determination ofits basic parameters (Vitkevich 1955).

Among the other significant results obtained at Crimeanstations, it should be recognized the first measurements oflinear polarization of the Crab nebula radio emission byA.D. Kuzmin and V.A. Udaltsov at 6 cm using the 32-meter earthen dish (Kuzmin & Udaltsov 1957). Their ob-servations had confirmed I.S. Shklovsky’s hypothesis on thesynchrotron mechanism of the Crab nebula radio emission.More details of this work can be found in A.D. Kuzmin’spaper (this volume). It should be noted also that the firstspectral radio line observations in USSR were made at Kat-siveli station by R.L. Sorochenko with his group. Usinga 18 m × 8 m parabolic segment they investigated severalgalactic nebulae in the 21 cm hydrogen line.

Besides the results listed above and also others of ba-sic nature obtained during this Crimean period, the LPIradioastronomers had fulfilled also a set of applied re-searches. There are not only numerous studies of the ra-dio waves propagation through the Earth’s troposphere andionosphere, but also such work as measurements of coordi-nates of the landings to the Moon of Soviet space vehicles,made by using a radio interferometer technique (see Fig. 3).

Fig. 3 Interferometer fringes and the landing place of the Sovietspace vehicle “Luna-2”.

Thus, in a little bit more than ten years many verygood – for those times – tools had been constructed atCrimean stations of the LPI, well-known and new meth-ods were developed, and excellent scientific results wereobtained. There has grown also the first generation of So-viet radio astronomers (Yu.I. Alekseev, P.D. Kalachev, J.L.Kokurin, A.D. Kuzmin, L.I. Matveenko, R.L. Sorochenko,V.A. Udaltsov and others). At the same time, around themiddle of the 1950s, it became clear, as V.V. Vitkevich testi-fies in already quoted note, “. . . that the further developmentof radio astronomy cannot proceed in Crimea; first, becauseit was impossible to construct the large high sensitive radiotelescopes at rather small sites of the Crimean stations and,secondly, because of the presence of high-level manmadeinterferences. Therefore, it has been decided to create a bigexperimental base of radio astronomy at the right bank ofthe Oka river, near Serpukhov city”.

2 The first steps at the Pushchino site

The Order of the Soviet Government mentioned above wasfollowed soon by the lower level decisions of the Moscowand the Serpukhov regions’ directing bodies. As a result,already in the same year 1956 the first group of LPI radio

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Astron. Nachr. / AN (2007) 397

astronomers has landed in the area of the villages Kharinoand Pushchino that were approximately 15 km from Ser-pukhov downstream of the Oka river. Despite lacking anycomfortable habitation, necessary infrastructure and goodroads even to the nearest Serpukhov city, fast work hadstarted. Already by the end of 1956 the laying of the largeradio telescope foundation had been made and the construc-tion of the fully steerable 22-m parabolic dish (RT-22) formillimeter wavelengths was begun (Fig. 4). In the followingyear 1957 construction of the other tool – the giant cross-type meter wavelength radio telescope was started.

Fig. 4 Transportation of the main tower of RT-22.

Simultaneously with the construction of the two largeradio telescopes and the corresponding receivers, the sci-entific observations with the rather small installations werealso made. In particular, the investigations of the solarsupercorona by observations of Crab nebula radio emis-sion started in Crimea were continued in Pushchino. Atthe same time the staff of the radio observatory was alsoformed. By the end of the 1950s several now well-knownbut at that time rather young astronomers (Yu.P. Ilyasov,V.I. Slysh, A.A. Korchak, M.V. Konjukov) had alreadylived and worked in Pushchino. However, those years thegeneral rhythm of work was set by the first generationof the Soviet radio astronomers, i.e. by V.V. Vitkevich,P.D. Kalachev, D.V. Kovalevsky, A.D. Kuzmin, A.E. Sa-lomonovich. Their experience and enthusiasm were pickedup by the younger scientists and engineers. In 1960–62 the staff of the Pushchino Observatory has replen-ished with the new young astronomers graduated from theMoscow and Leningrad universities (R.D. Dagkesaman-skii, B.Ya. Losovsky, V.I. Shishov and T.D. Antonova (laterShishova)) and also with some skilled experts from Crimea(V.A. Udaltsov, R.L. Sorochenko, B. Evstafev, V.I. Ariskin,Yu.I. Alekseev). By this time already all radio astronom-ical researches fulfilled in LPI had been concentrated inPushchino.

Here it would be pertinent to tell a little bit more aboutone of the enthusiasts and pioneers of Soviet radio astron-omy.

3 The founder and the first head of PRAO

Victor Vitoldovich Vitkevich was born on July 2nd, 1917 inKlin town, Moscow region. In 1933, after the termination ofseven-form school and the first rate of radiotechnical school,he started learning at the radio faculty of the Moscow In-stitute of Communication Engineers and finished it in 1939with “excellent” mark for his degree project led by professorS.E. Khaikin. In 1940 V.V. Vitkevich continued postgradu-ate study at the same Institute.

Fig. 5 V.V. Vitkevich in the end of 1960s.

V.V. Vitkevich began his scientific work when he wasstill a student, and in spring of 1941, when he prepared thedocuments for the Stalin grant they contained already themanuscripts of 12 scientific papers. But soon he has beenmobilized to Soviet Pacific Navy Fleet. In 1942 V.V. Vitke-vich was sent to work in the Scientific Institute of Commu-nication and Telemechanics of the Naval Forces. Here heperformed work on tests of new radio equipment. Under hisinitiative the experiments on the antenna beam patterns onmodel studying were started for what he took special en-couragements of the Navy Ministry. At the same time hecontinued and in absentia completed in 1944 his postgrad-uate study under the direction of S.E. Khaikin. The subjectof his candidate dissertation is synchronization of explosiveauto-oscillating systems.

In 1947 V.V. Vitkevich was demobilized from NavalForces and started to work in the Section of Radio Engi-neering of the Academy of Sciences. In the beginning of1948 he had come to work in the LPI. From those days upto his death V.V. Vitkevich worked in LPI: first as a memberof Prof. Khaikin’s team of radio astronomers, then as headof the team, and finally as head of the Radio AstronomyLaboratory of the LPI and Radio Astronomy Station (nowObservatory) in Pushchino. In 1951 he has suggested a newmethod of research of external layers of a solar corona –the radio occultation technique. After the discovery of thesolar super corona V.V. Vitkevich has found (together withB.N. Panovkin) that the magnetic fields in the super coronaare radially elongated. The discovery and the subsequent re-searches of the solar super corona have made the basis of his

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thesis for a second (doctor’s) degree successfully defendedat the academic council of the Physical faculty of MoscowState University in 1964.

From 1968 V.V. Vitkevich’s scientific activity is almostentirely devoted to research of a new class objects – pulsars.Just after the first publication of the discovery of pulsarsby A. Hewish’ team the corresponding observations werestarted at PRAO. Some important results of these investiga-tions will be described below in one of the following sec-tions of the paper. Here it should be noted that V.V. Vitke-vich has died early when he was not even 55, in the primeof creative power (Fig. 5). However, for 25 years of workin LPI he has got not only many important scientific results,but he also was the main person in the process of creationof the many radio astronomical tools at the Crimean andPushchino radio astronomy stations. Finally, V.V. Vitkevichhas brought up many pupils who nowadays make the basisof PRAO staff.

4 First scientific results obtained with22-meter dish

Unique radio telescope. The base of radio telescope RT-22 has been completed right at the end of 1956 and in 2years of work, which were carried out under the directionof principal scientist A.E. Salomonovich and main designerP.D. Kalachev, construction of the radio telescope was closeto the end. In November 1958 a multi-ton 22-meter reflec-tor, with root-mean-square surface accuracy of 0.3 mm hasbeen set up on the mount (Fig. 6). Adjustment of the ra-dio telescope was also made in a short time, and alreadyright at the beginning of May 1959 the first scientific obser-vations have been made with the new radio telescope. Thebeam-width of the radio telescope at shortest wavelengths(8 mm) was less than 2 minutes of arc, so it was the radiotelescope with the best angular resolution among all othersingle dishes. The matter is that the original principle ofloadings distribution of the main reflector offered and re-alized in practice by P.D. Kalachev has reduced to a mini-mum, both thermal deformations of a design of a telescopeand the deformations caused by change of its orientation. In1966, under Kalachev’s drawings, another 22-meter radiotelescope with slightly improved parameters has been builtat Crimean Astrophysical Observatory.

Observations of the Sun and the Moon The first ob-jects of researches with the Pushchino RT-22 were the Sunand the Moon. Mapping of these sources of a radio emis-sion, even with the angular resolution of 2 minutes of arcwas of interest that time for studying of active areas at so-lar disk, definition of physical parameters of lunar regolithas well as for some applied (in particular navigation) tasks.Measurements of polarization of the local radio sourcesat solar disk, identification of these sources with the solarspots, floccules and some other optical details were tasksof special interest. All these researches of the Sun and the

Fig. 6 RT-22 radio telescope.

Moon were made under the direct supervision of principalscientist A.E. Salomonovich.

Considerable progress in sensitivity of the receivers atcentimeter wavelengths in the 1950–60s has allowed start-ing rather quickly the observations with RT-22 of weakerobjects, namely the planets of Solar system and discrete ra-dio sources.

Researches of the planets The first measurements of ra-dio emission of Venus at Pushchino RT-22 made in Septem-ber 1959 have given unexpected results. It was revealed thatat millimeter wavelengths Venus brightness temperature is1.5 times less than at centimeter wavelengths, so the spec-trum of the radio emission of the planet is not thermal. A.D.Kuzmin and A.E. Salomonovich have assumed that radioemission at millimeter wavelengths comes from the planet’satmosphere, which is colder than a surface. But in 1961D. Jones offered an alternative, the so-called ionosphericmodel. According to his model, the radiation observed atcentimeter wavelengths arises in the optically thick iono-sphere with electron temperature close to 600 K, but radioemission observed at millimeter range is caused by a sur-face of the planet, being colder with a temperature of about400 K.

In the beginning of the 1960s the USSR and USAplanned the flights of space vehicles to Venus with theprobes landing on the planet surface. These projects re-quired more exact values of temperature, density and pres-sure in an atmosphere and on a surface of the planet. Fora choice of the planet model some critical experiment wasneeded. In 1964 A.D. Kuzmin has suggested such an exper-iment based on measurement of polarization of radio emis-sion of the planet in a decimeter range. The suitable tool forsuch measurements was the interferometer of the CaltechOwens Valley Observatory, and the corresponding experi-ment has been made by A.D. Kuzmin together with BarryClark. The experiment has revealed the planet surface tem-perature (700±50K), radius (6057±55km) and atmosphere



Fig. 7 First USA-USSR meeting on radio astronomy (USA, GB,1962) 1st row: G. Getmantsev, F. Haddock, M. Wide, Mrs. X (in-terpreter), R. Minkowski, V. Vitkevich, O. Struve, R. Sorochenko,J. Firor, G. Keller, A. Kuzmin, R. Bracewell, F. Drake; 2d row: C.Wade, E. McClain, V. Sanamyan, P. Kalachev, G. Stanley, A. Bar-rett, H. Weawer, G. Swenson, C. Mayer, D. Heeschen, J. Kraus;3d row: G. Field, T. Menon, C. Seeger, L. Woltjer, A. Sandage, A.Lilley, A. Blaum, F. Kahn, B. Burke.

pressure near the surface (80 ± 50 atm) (Kuzmin & Clark1965). All these results have been confirmed later by spacevehicles “Venus 4, 7 and 8”.

This very fruitful scientific cooperation became possibleonly due to so-called Khrushchev’s thawing weather. Thefirst contacts between the radio astronomers of two coun-tries were during the USA-USSR symposium on radio as-tronomy, organized in 1962 by the National Academy ofSciences of the USA in Washington. The Soviet side wasrepresented by V.V. Vitkevich, P.D. Kalachev, A.D. Kuzmin,R.L. Sorochenko (all from LPI), G.G. Getmantsev (NIRFI,Gor’ky city) and V.A. Sanamyan (Burakan Observatory).From the other side there were many famous American as-tronomers who can be seen in Fig. 7. After intensive study-ing of Venus the planet program at RT-22 radio telescopeincludes the studies of physical conditions in atmospheresand on surfaces of Mercury, Mars, Jupiter, Saturn, Uraniumand the Jupiter satellite Callisto. All planetary researcheswere carried out by A.D. Kuzmin and members of his group(B.Ya. Losovsky, Yu.N. Vetuhnovskaja, A.G. Solovev).

Observations of the discrete radio sources In the be-ginning of the 1960s A.D. Kuzmin has made many obser-vations of galactic and extragalactic objects with the RT-22and compiled one of the first catalogues of the discrete radiosources at centimeter wavelengths. The catalogue containscoordinates, flux densities and estimates of angular sizesfor several tens of the galactic gaseous nebulae, supernovaeremnants and radio galaxies. Using these data and results ofmeasurements of other authors, the spectra of radio emis-sion have been constructed and estimates of the emissionmeasure, electronic density and temperature in a numberof galactic gaseous nebulae were obtained. The same datahave allowed to establish reliably the presence of a high-frequency break in a spectrum of a radio emission of the

Cygnus A radio galaxy that has been used for getting thefirst experimental estimate of its age.

In the 1960s several skilled radio astronomers fromCrimea have joined the Pushchino team in radio astro-nomical observations with the RT-22 radio telescope. V.A.Udaltsov has continued his successful work on Crab neb-ula started in Crimea and made with the RT-22 the mea-surements of polarized radio emission of the source at sev-eral centimeter and decimeter wavelengths. Together withLeonid I. Matveenko he organized also investigation ofCrab nebula brightness distribution by observations of theradio source at several frequencies during its occultationby the Moon. In 1964 a new program – the observationsof extragalactic radio sources with unusual high-frequencyexcesses – was started at RT-22. This program was initi-ated by USA radio astronomer Allan Barrett during his visitto Pushchino RAO. In 1965–69 L.I. Matveenko and V.I.Kostenko continued these researches at 5.2, 3.3 and 0.8 cm.They have concluded that the flux densities of 3C279,3C345 are definitely variable, and about the variability ofsome others (3C84, 3C273) it was possible to speak witha rather high probability. Careful studying of these radiogalaxies and quasars has shown that their unusual spectraare caused by synchrotron reabsorption effect in extremelycompact details located in the central areas of these galax-ies. Interpretation of observable variations of their flux den-sities in the frame of the adiabatically extending plasmoidmodel has led to a conclusion about very young age of theseformations.

More detailed researches of very compact radio sourcesbecame possible only with use of very-long-baseline inter-ferometers. Here it will be pertinent to notice that the op-portunity to create interferometers with independent regis-tration of signals has been shown for the first time by L.I.Matveenko in autumn 1962, when he reported about thisat a scientific seminar of Pushchino Radio Astronomy Sta-tion (now PRAO). The first publication concerning this sub-ject was late and published by Matveenko et al. (1965).Nevertheless, one of the first intercontinental interferom-eter observations was made by V.V. Vitkevich (LPI) andK.I. Kellermann (NRAO) with the members of their teams(Broderick et al. 1970).

Discovery of the radio recombination lines In 1959,just when the RT-22 had become operational, the young sci-entist N.S. Kardashev from Sternberg Astronomical Insti-tute (Moscow) has predicted the existence in space of highlyexcited atoms and the observable corresponding radio re-combination lines in spectra of ionized gaseous nebulas. Atthat time the RT-22 radio telescope was the most adequatetool to search for expected spectral radio lines. The specialhigh-sensitivity radiospectrometer has been developed for3 cm wavelength and has been installed at RT-22. In April1964, during the first series of observations of the Omeganebula, the radio line of the excited hydrogen has been reg-istered at frequency ν = 8872 MHz (λ = 3.38 cm). This



Fig. 8 Spectrogram of the observed radio recombination line,corresponding base line, difference between the both, and depen-dence of observed radial velocity from seasons.

line was caused by transitions between 91 and 90 levels ofthe hydrogen atoms (Sorochenko & Borodzich 1964). Inthree months the frequency of an observed line was changedcorresponding to change of the Doppler shift due to orbitalrotation of the Earth. This fact proved the cosmic origin ofthe observed radio line (see Fig. 8).

Practically simultaneously with observations of the firstradio recombination line in Pushchino the searching of radiorecombination line corresponding to 105–104 transition ofthe hydrogen atom had been undertaken in a spectrum ofthe same Omega nebula by scientists couple A.F. and Z.V.Dravskikh. In May 1964 they have managed to register thisline. The presentations about the discoveries of both groupshave been made on August 31, 1964 at the IAU GeneralAssembly in Hamburg, where they were met by colleagueswith great attention and interest.

During the following decades many observations of theradio recombination lines of hydrogen, helium and carbon– the most abundant in space chemical element – have beenmade by radio astronomers at different radio observatoriesin the world. Measurements of the key parameters of theradio recombination lines corresponding to the higher andhigher excitation levels of the cosmic atoms became pow-erful means for the determination of the physical condi-tions in the interstellar environment, definitions of a rela-tive abundance of chemical elements in space, estimationsof density of energy of soft cosmic rays. Many results inthe fields mentioned above have been obtained from obser-vations made by Pushchino radio astronomers at the RT-22radio telescope.

5 DKR-1000 and first researches with thistool

Construction of DKR-1000 From the first days of thePushchino Observatory formation the investigations of so-lar super corona were made. Up to the mid-1960s the smallphased meter-wavelengths arrays were used for this pur-pose. By result of these observations V.V. Vitkevich andB.N. Panovkin found the anisotropy of the scattering of theCrab nebula radio emission and came to the conclusion onmainly radial elongation of the electronic inhomogeneitiesas well as the magnetic fields in the super corona of the Sun(Vitkevich & Panovkin 1959).

Construction of the second large radio telescope of thePRAO – the wide-band cross-type radio telescope DKR-

Fig. 9 East-West arm of the DKR-1000 radio telescope.

1000 – has begun in 1957, only a year later than RT-22.However, the first observations with the East-West (E-W)arm of this radio telescope have been made only in 1964.This meridian tool consists structurally of two paraboliccylinders of 40 m×1000 m in size (Fig. 9). The beam orien-tation in declination of the E-W arm of the radio telescope iscarried out by synchronous mechanical turn of 37 parabolicforms supporting a cylindrical reflector of the aerial. Changeof the North-South arm beam position was implemented byelectric phase shifts.

Originally, V.V. Vitkevich and B.M. Chihachev, whosuggested this giant cross-type radio telescope, haveplanned to construct it as a narrow-band system workingat 86 MHz, mainly to check the results of the Australiansky survey made by B. Mills at the same frequency. How-ever, during the development of the radio telescope feed sys-tem that was made by very young engineer Yu.P. Ilyasovand A.D. Kuzmin, the idea arose to use broadband Aizen-berg dipoles as a basic element of the feed system. Yu.P.Ilyasov has shown that some losses of sensitivity of the ra-dio telescope due to the use of broadband dipoles will quitepay back with the new opportunities. As a result, the fre-quency range 30–120 MHz was chosen. This quality of theradio telescope in combination with its large collective areaprovides unique possibilities for investigations of differenttypes of astrophysical objects.

Interplanetary scattering and scintillations Amongthe first projects fulfilled with the E-W arm of DKR-1000 inthe 1960s, were researches of the solar super corona of theSun. However, using the new radio telescope V.V. Vitkevichand the people from his team observed not only Crab neb-ula, but also other, weaker radio sources simultaneously attwo frequencies. But the main result was the beginning ofscientific observations with the E-W arm of DKR-1000 thatpractically coincided with the discovery (by A. Hewish) ofinterplanetary scintillations of compact radio sources. Thisdiscovery has marked the beginning of the new period inresearches of circumsolar and interplanetary plasma.

The first observations of interplanetary scintillationswith the E-W arm of DKR-1000 have been made by V.V.



Vitkevich, T.D. Antonova and V.I. Vlasov. It was immedi-ately obvious that observable fluctuations are directly con-nected with a solar wind, i.e. with the outflow of inhomoge-neous plasma from the Sun, which was discovered shortlybefore from the measurements executed by space vehicles.To measure the velocity of the solar wind V.V. Vitkevichhas organized the construction of two additional radio tele-scopes of around 1000 square meters in effective area andlocated about 300 km to the North-East and North-Westfrom Pushchino.

Measurements of solar wind velocity have been begunby Vitkevich & Vlasov (1966). It has been found that thevelocity in average is about 400 km/s and directed out ofthe Sun at all helio latitudes. It is necessary to note that atthat time, and also long time later, measurements of the solarwind velocity by space vehicles were made only in the eclip-tic plane, so radio astronomical measurements have givenessentially new information.

Spectra of extragalactic radio sources As was men-tioned above, one of the main motives for the constructionof the giant cross-type radio telescope DKR-1000 was thedesire to make careful counts of discrete sources and tosolve the discrepancies between the conclusions made byM. Ryle and B.Y. Mills. Such radio source counts could giveus the answer: do we live in a stationary or in an evolvingUniverse? However, by the mid-1960s, when the E- arm ofDKR-1000 started to work, the situation with counts of rela-tively bright radio sources had cleared up, and observationsof weaker objects using only the E-W arm (without N-Sone) were not possible due to high-level “confusion” effect.Therefore, the decision was made to use the new opportu-nity of making multi-frequency flux density measurementswith the E-W arm of DKR-1000 and to concentrate effortson studying the spectral characteristics of several hundredsof the brightest radio sources at meter wavelengths. Accord-ing to this decision, in 1965–1968 the flux density mea-surements were made at 38, 60 and 86 MHz for most radiosources from the 3C and 3CR catalogues. For more than twohundred radio sources observations at such low frequencieshave been made for the first time. But the main advantageof the measurements was a careful calibration of the datain one of the existing flux scales. It has allowed studyinglow-frequency spectra of the number of radio sources, andalso making a careful statistical analysis of the distributionof radiation sources on spectral indexes. The most signifi-cant result of this analysis was the detection of correlationbetween spectral indices of extragalactic radio sources andtheir flux densities, namely spectra of weaker sources fromthe low-frequency sample were on average steeper. It hasbeen shown that the result obtained is statistically signifi-cant and cannot be caused by K0- or selection effects.

Though in the 1960s the available optical identificationswere not complete even for several hundreds of the brightestradio sources, it was shown that the correlation mentionedabove is much stronger for quasars than for radio galaxies,

Fig. 10 Distribution of quasars from the 3C and 3CR cataloguesin “spectral index-redshift” plane.

and that unidentified radio sources show intermediate corre-lation. Moreover, it was found (Dagkesamanskii 1970) thatall identified by then quasars from the 3C and 3CR cata-logues with z > 1.0 have steep spectra, while among closer(z < 1) quasars there are also objects with flat spectra (seeFig. 10). It became clear that the distribution of quasars andradio galaxies on spectral indices varies with cosmologicalepoch, and this evolution is much better seen at more dis-tant quasars. The radio sources not identified by then shouldbe in majority radio galaxies, in average more distant thanthose already identified. At last, radio galaxies and quasars,despite the essential differences in their morphology, repre-sent the uniform class of objects with similar character oftheir spectral indices cosmological evolution. The conclu-sions listed above are almost obvious now. However, onlyin 1982 Gopal-Krishna and Steppe and then Kapahi andKulkarni have confirmed the mentioned spectral index–fluxdensity relation for relatively strong radio sources and havetraced its changes with decreasing flux densities of the radiosources.

Structure of radio galaxies and quasars If the firststage of researches of extragalactic radio sources at me-ter wavelengths in Pushchino concerned mainly to studyingtheir spectra, the following second stage of the researcheswas connected with the investigation of their structure. But,let’s return to one decade ago for a moment. From the endof the 1950s V.V. Vitkevich bore the idea of a radio linkinterferometer with baselines of tens kilometers, sufficient,as it seemed then, for the investigation of the extragalacticradio source structure at meter wavelengths. However, allattempts at that time were unsuccessful – lack of experi-ence in construction and work with the relaying equipmentas well as high requirements to its phase stability were af-fected. The situation has changed noticeably when at theend of the 1960s V.V.Vitkevich has involved in this workG.I. Dobysh, the engineer with a wide experience of workwith the equipment of radio relay stations. In a rather shorttime the prototype of the interferometer on a wavelengthof about 8 m with relaying a signal from remote station



to Pushchino has been constructed under the direction ofG.I. Dobysh. In 1971 the working complex of the equip-ment for observations at 3.5 m (86 MHz) was finished. Thisequipment and a transportable Yagi-array developed underIlyasov’s direction have provided an opportunity to carryout an extensive cycle of observations with variable baselineinterferometer of about 150 radio sources from the 3C and3CR catalogues. The E-W arm of DKR-1000 had been usedas the main element of the interferometer. Within severalyears the observations of the radio sources have been madewith 10 different locations of the remote antenna. The inter-ferometer baseline has been changed from 600 up to a littlebit more than 5000 wavelengths (from 2 km up to 18 km).Most of the baselines were close to the East-West direction.In few cases the measured values of visibility function am-plitudes have appeared enough for tracing of the changeswith wavelength of the source?s brightness distribution pa-rameters or even for allocation a new component in it.

However, the data obtained in observations had muchmore interest for the statistical analysis of structural fea-tures of radio galaxies and quasars (Volodin, Gubanov &Dagkesamanskii 1989). It has been shown that in meter-wavelengths morphology of 3C quasars there are the sameextended components as in radio galaxies. Extensions andluminosities of these components are very similar in theboth classes of objects. Relative contribution of rather com-pact structure (<10 kpc), i.e. central component of a radioemission of the active galaxies including of the core and jet-like details of the brightness distribution, at 3.5 m is about70% of the total flux density in quasars and only 20% forradio galaxies. New confirmation was also received for theconclusion made earlier from spectral index statistics thatthe majority of unidentified (at that time) radio sources ofthe 3C and 3CR catalogues are the more distant radio galax-ies. Really, angular structure of not identified sources hasappeared to similar angular structure of radio galaxies, butshifted to the smaller angular scales. At last, it has beenshown that the radio luminosity of extended components ofradio galaxies and quasars, Lext, is roughly proportional tothe luminosity of their compact structure, Lcomp. It meansthat in the analyzed sample of 140 sources there is not oneobject with rather developed compact structure and withoutrather high luminosity extended component, and otherwise,there is no source with high luminosity extended componentwithout bright compact structure. So it could be concludedthat the relative duration of the extended structure formationas well as the lifetime of the extended structure after its ad-ditional charging by the “central machine” stops are smallin comparison with time of the machine’s action.

The use of the North-South arm of DKR-1000 was con-siderably more limited. The reason consisted in difficultiesof maintenance of reliable work of its complex phasing sys-tem, especially since it works in a wide frequency range.But for the tasks demanding large integration time, the useof this antenna with wide beam in right ascension appearedfavorable enough. For this reason the N-S arm of DKR-1000

Fig. 11 First record of CP1919 pulses obtained with the E-Warm of DKR-1000.

was used by R. Sorochenko and his team for the detection oflow-frequency carbon absorption radio recombination linesin a spectrum of the supernova remnant Cassiopea A. Theyobserved not α-, but β-transition lines and registered ex-tremely high excited carbon atoms, corresponding to a mainquantum number of around 750. These quantum numbersare close to the possible upper limit determined by interac-tion of the atoms with background radiation of the Galaxy.

Pulsar observations Regular observations of pulsarswith the E-W arm of DKR-1000 had been begun on March1968, right after the messages on the discovery of the newclass of astronomical objects (Fig. 11). The initiative group(Ju.I. Alekseev, V.F. Zhuravlev, N.S. Solomin, Ju.P. Shi-tov, and some very young scientists) has been organizedby V.V. Vitkevich, and in a very short time new receiversand data-acquisition equipment necessary for pulsar obser-vations were developed. These observations were made atlow frequencies, so they were a good supplement to the pul-sar observations that were made in most other observatoriesover the world. Low-frequency observations of pulsars werevery important for investigations of the outer pulsar magne-tospheres, where the linear rotation speed of the magneticpower lines approaches the speed of light. Moreover, suchobservations are most effective for researches of the inter-stellar medium in our Galaxy.

In mid-1968 the first Pushchino pulsar PP 0943 hadbeen found (Alekseev et al. 1969). It was the first peculiarpulsar that showed the deep nullings as well as some otherunusual properties. A few first years of pulsar investigationswith the E-W arm of the DKR-1000 radio telescope havealready given many bright results in research of the spectraof individual and average pulses of pulsars, of changes ofaverage pulse profiles with frequency, of frequency depen-dence of pulsar polarization properties. A little bit later theover-dispersion low-frequency delays of pulses caused bydeformation of magnetic power lines near the light cylin-der area were revealed (Shitov 1983). Many of the resultsmentioned above were obtained due to fruitful cooperationof the Pushchino pulsar research team with colleagues fromAustralia, Germany, Great Britain and USA. Simultaneousmulti-frequency observations of pulsars with precise bind-ing of the different observatories time scales were extremelyuseful for the modeling of the pulsar magnetospheres.



6 The BSA radio telescope and the firstresults obtained with it

The detection of interplanetary scintillations of the compactradio sources and the discovery of pulsars have shown thatconfusion effect caused by limited angular resolution of theradio telescope does not play an essential role in some of thevery important observational tasks. For such observations itis quite possible to use a giant filled-aperture radio telescopeand there is no necessity to construct cross-type antennas orother tools of similar type. Therefore, right by the end ofthe 1960s V.V. Vitkevich convinced the management of theAcademy of Sciences of the USSR to construct at PRAOone more radio telescope of meter wavelengths – the largephased array BSA. This giant array has been constructedin rather short time and for a small cost. The total collect-ing area of the radio telescope is 7.2 hectares and the cen-tral operational frequency was originally 102.5 MHz. Con-sisting of more than 16 thousands dipoles, this array is themost sensitive meter wavelength radio telescope until today(Fig. 12). Observations with this radio telescope have beenstarted in 1974. The large effective area (around 30 000 m2)has allowed opening new pages in investigations of inter-planetary and interstellar media, as well as in pulsars study-ing.

Fig. 12 Large phased array BSA.

The first scientific program at BSA concerned the mea-surement of the interplanetary scintillation spectra of com-pact radio sources. It is known that the structure of the scin-tillation spectrum is determined by both the spectrum of tur-bulence and the initial brightness distribution over a source.The complex analysis of data has allowed to separate theseeffects and to measure a spectrum of turbulence. It has beenshown that the spectrum of fluctuations of electronic con-centration in a wide range of scales is a power-law exponentof a three-dimensional spectrum n = 3.6. This result corre-sponds to distances of 70–200 solar radii (i.e. 0.3–1 AU).

The high sensitivity of the BSA has provided the oppor-tunity to carry out daily observations of interplanetary scin-tillations of about one hundred fifty compact radio sources.

This monitoring of the interplanetary environment allowswatching the dynamics of the perturbations extending fromthe Sun to the external borders of the Solar system and, ashas been shown, can be used for short-term predictions ofvarious kinds of geomagnetic disturbances. Regular map-ping of the interplanetary plasma structure already duringseveral decades has revealed the dependence of the solarwind key parameters on a phase of the solar activity cycle.

However, the observations of interplanetary scintilla-tions of the compact radio source not only carry the in-formation on a condition in interplanetary plasma, but alsoabout the angular structure of the source. High sensitiveobservations of interplanetary scintillations made with theBSA radio telescope for several hundreds of compact extra-galactic radio sources had revealed the degree of their com-pactness, some physical parameters of their compact struc-tures, as well as the distribution of the compact sources inthe Universe.

The BSA radio telescope was also used for observationsof the radio halo of the Andromeda Nebula, for investiga-tions of the rich (and especially X-ray) clusters of galax-ies and in some other scientific programs. But still, as onewould expect, the great bulk of interesting results obtainedfrom observations with the BSA concerns pulsar investiga-tions. The very high sensitivity of the radio telescope pro-vides observations of practically all known pulsars of thenorthern sky. Average profiles of pulses for more than 150pulsars were constructed from observations with the BSA.For the most powerful pulsars it is possible to register in-dividual pulses of radiation and investigate their sub-pulsesand microstructure investigated with very high time resolu-tion. Sub-pulse drifting phenomena found in such observa-tions are shown in Fig. 13.

Amongst the most interesting results obtained with theBSA the detections of radio emission of the well-known X-ray pulsar Geminga, magnetar SGR 1900+14 and severalother AXPs should be mentioned. The following observa-tions of their very week radio emission at lower frequencieswith the E-W arm of DKR-1000 provide useful informationabout their spectra and pulse profiles.

Another fruitful field of pulsar investigations at the BSAis pulsar timing made with this radio telescope for a num-ber of pulsars during several decades. The rare glitches inperiodicity of pulses observed for some pulsars represent aunique tool to study the internal structure of these neutronstars. On the other hand, some slow variations of the resid-ual differences between predicted and observed pulse arrivaltimes can be used to testify the presence of some kind ofpulsar satellite, in particular planets, or precession of theirrotation axes.

It is well known that if the pulsar doesn’t display anyglitches, it could be used as a source of extremely high sta-ble periodical process. Based on this, Yu. Ilyasov and A.Kuzmin together with other scientists from their teams havesuggested in 1974 a new Pulsar Time Scale. This idea hasbeen approved by the IAU Commission, and now such scale



Fig. 13 Drifting sub-pulses and the integral profile of PSR0809+74 observed with the BSA radio telescope.

is kept not only in PRAO, but also in several other obser-vatories in the world. The accuracy of the new astronomi-cal time scale has essentially increased after the discoveryof so-called “millisecond” pulsars, and is now comparablewith the accuracy of the best atomic standards.

In spite of the fact that the main radio telescopes of thePRAO have been constructed many years ago, their scien-tific potential continues to grow up to today. It is promotedby active work of all scientists and engineers of the observa-tory on maintenance and development of the unique exper-imental tools. Perfection of the radio telescopes’ feed sys-tems, beam-forming systems, development and manufactur-ing of the new amplifiers, radiometers and spectra analyz-ers, automation of process of observations, creation of thelocal computer network and a rather good computer com-munication with the external world – all this continuouslyincreases the overall efficiency of investigations in PRAOand provides high-level scientific results.

7 As a part of Astro Space Center

Before 1990 the Pushchino Radio Astronomy Observatory(at that time called Radio Astronomy Station) was the ba-sic part of the Radio Astronomy Department of the Lebe-dev Physical Institute. However, in 1990 the Observatorywas joined with a former Department of Astrophysics ofthe Space Research Institute of the Russian Academy ofScience led by N.S. Kardashev, so the Astro Space Center(ASC) – the new scientific division of the LPI was formed.Without any doubts, this association has appeared useful

Fig. 14 “RADIOASTRON” 10-m radio dish during its test atPRAO.

to both scientific groups. In particular, the scientific pro-grams of the Observatory (already PRAO ASC LPI) wereenriched with researches of compact radio sources withVLBI and Space VLBI technique. The test-shop for the fu-ture space radio telescopes was built at PRAO and had beenused already for testing of the 10-meter space radio tele-scope that will be installed onboard a space vehicle “RA-DIOASTRON” (Fig. 14). Many scientists and engineersfrom PRAO are now involved in this space project. To-day the Pushchino Observatory has many fruitful scientificcontacts with astronomical institutions inside Russia andabroad. Usually three or four astronomical schools, meet-ings and conferences are taking place annually in Puschinoon the basis of PRAO.

Today Pushchino Radio Astronomy Observatory of theASC LPI is the big astronomical institution having not onlyunique radio astronomical tools, but also the qualified staffof scientists and engineers, capable to solve many actual andcomplex tasks of observational radio astronomy.

References

Alekseev, Yu.I., Vitkevich, V.V., Zhuravlev, V.F., Shitov Yu.P.:1969, Doklady AN SSSR 187, 1019

Broderick, D.D., Vitkevich, V.V., Jancey, D.L., et al.: 1970, AZh47, 784

Dagkesamanskii, R.D.: 1970, Nature 226, 432Khaikin, S.E., Chikhachev, B.M.: 1947, Doklady AN SSSR 58,

1923Kuzmin, A.D., Clark, B.G.: 1965, AZh 43, 595Kuzmin, A.D., Udaltsov, V.A.: 1957, Astron. Cirk. 187, 14Matveenko, L.I., Kardashev, N.S., Sholomitskii, G.B.: 1965, Ra-

diofizika, Izv. VUZ 8, 651Shitov, Yu.P.: 1983, AZh 60, 541Sorochenko, R.L., Borodzich, E.V.: 1964, Trans. IAU 12, 360Vitkevich, V.V.: 1955, AZh 32, 106Vitkevich, V.V., Panovkin, B.N.: 1959, AZh 36, 544Vitkevich, V.V., Vlasov, V.I.: 1966, Astron. Cirk. 396, 1Volodin, Yu.V., Gubanov, A.G., Dagkesamanskii, R.D.: 1989,

Proc. Lebedev Physical Institute Ac. Sci. USSR 189, 229


the pushchino radio astronomy observatory: origin and first decade's history

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