International Conference on Antenna Theoq and Techniques, 9-12 September, 2003, Sevastopol, Ukraine pp. 57-62

RADIO TELESCOPE RT-70 IN EVPATORU AND SPACE 1NVESTIGATIONS

A. A. Konovalenko I , L. N. Lytvynenko I , C. G. M. van ‘t Klooster

’ Institute of RadioAstronomy of the National Ukrainian Academy of Sciences 4 Krasnoznamennaja St., 61002 Kharkov, Ukraine

Phone: C380-572471I34; E-mail: cakonov@ira.kharkov.ua> ESA - Estec, TOS-EEA

P.O. Box 299, 2200 AG Noordwijk, the Netherlands Phone: +3 1-71-5653940; E-mail: <kvtkloos@estec.esa.nl>

Abstract The current situation with the Evpatoria 70-m antenna is described. This unique

70-meter radio-telescope antenna (RT-70) was realised between 1973 and 1978 and was an important element in different missions as antenna in transmit-receive mode for instance for the missions like Venera, Granat, Interbol, etc. It was and is used in other modes like radar for planetary and asteroid investigations as well as radio tele- scope. Its current state is such that after and with the necessary maintenance the tasks can be continued and expanded. Technical activities are carried out today with in- volvement of the first author for the technical management on behalf of the Ukrainian Space Agency, in panicular today the “Interferometer” - project be mentioned. The potential for future use is briefly indicated.

1. INTRODUCTION In this paper we concentrate on the situation with

the Radio-Telescope (RT-70) in Evpatoria. The main nlan W R C ronwivrd in th? late sixtiec. earlv seventies

~~~~~i ~I .._I ~ ~~~ .~~ Several ground-station antennas with a large diameter have been, or were planned to be constructed in Rus- sia, Ukraine, Uzbekistan, Armenia and Baltic coun- tries. A number o f 32 meter antennas was realised, examples are the antennas in Ussurijsk (Russia), Evpatoria, Simferopol (both Ukraine), as well as the

with strong support of prof, L~~ Davidovich Bak- hrakh, ~~i~ designers ofthe ~ ~ - 7 0 were v . B. T ~ ~ - sov and A. N. K O ~ I O V . Details are found (the reader is

recommended to learn some Russian .... ) in the journal sh t enn i , 31 [I , 21, in ‘Radiofysica’ [3] and later on in 14. 51.

32 m antenna in Ventspils, the latter is nowadays used by the Institute of Radio Astronomy in Riga. All 32 m antennas have a good surface quality, but they are currently not too much used. Another type of 32- meter antenna has been designed for the Quasar pro- ject and the 32m radio-telescope near Svetloe (near St. Petersburg) is an example of such type of antenna. Other antennas o f the latter [I I ] type are realised in Zelensjuk and Badari (near Irkutsk) and potentially near Starya Pustin (near Nizhny Novgorod). Near Moscow the 64 m receiving antenna was realised in the early eighties (Bear Lakes) and a similar type of antenna has been constructed in the late nineties in Kalaizin (near Tver). The subject here concerns the impressive 70 m antenna (started in 1973, finished in the 1978) near Evpatoria. A similar type of antenna was realised later on near Ussurijsk in the far east of Russia and a start was made with the realisation of the large radio telescope antenna in Uzbekistan (Suffa plateau), The latter realisation was delayed by the political events and its current realisation is subject of collaborative efforts between Russia and Uzbekistan.

L , 1 ~~~~~ ~~~

There were many design bureaux and institutes in- volved in this large project to realise the antenna, with to mention one ofthem: ‘Special Construction Bureau for Machine building’ from St. Petersburg (Tel: +7- 8 12-245-3619). The latter organisation has currently the metal parts for the ‘Suffa’antenna, waiting for realisation in Uzbekistan (some information might be found in the Astro Space Centre web pages, www.asc.rssi.ru). The design bureau for these anten- nas was involved in the early sixties in the realisation of more than 600 antennas with a diameter between 2.6 and 32 meter as well as the antennas on-board the 9 tracking vessels amongst which the ‘Kosmonaut Vladimir Komarov’, ‘Kosmonaut Yuri Gagarin’ and ‘Academik Serge Korolev’. Other involvements in- cluded a large thermal vacuum facility with a volume of 1OOOOm 3 and launch facility aspects for the ‘Byran’ and ‘Energya’rocket (the latter was trans- ported horizontally and erected before launch).

The RT-70 antenna facility is unique in the sense, that it was the first shaped dual reflector antenna with such a large diameter, which had a homologue sup-

0-7803-7881-4/03/$17.00 02003 IEEE.

.\. h. Konovalenko, L. N. Lytvynenko, C. G. hl. van ‘t Klooster

porting construction and which, thanks to the shaping of the reflector surfaces, realised an aperture effi- ciency of near to 80 %. Just to indicate the sizing as- pect: the Westerbork radiotelescope consists of 14 antennas (25 m diameter) and has a collecting area of some 3500 to 4000 m2, slightly smaller than the Effelsberg 100 meter radio telescope, but slightly lar- ger than the collecting area of RT-70 (at a wavelength assumed to be 5 cm wavelength).

Such a type of reflector shaping exercises for high efficiency dual reflector antennas was ongoing in the early sixties already 161, slightly earlier than else- where 171. Furthermore, in order to realise the capabil- ity to switch fast between different frequency bands, a dedicated feed system arrangement has been devel- oped, in which 6 feeds were placed on a circle near the secondary focus. A small dual reflector assembly with two shaped nearly elliptical reflectors has been constructed with a possibility to rotate and so to select as a sort periscope one of the 6 feeds to the total large dual reflector assembly. The latter small dual-reflector assembly permits to use one of the 6 feeds at the time and - by rotation within a short time - permits to change frequency band. It is only 4 to 5 X in size at the lowest frequency band. Such sizing is known for its diffraction losses, but special efforts were imple- mented (sort of spoilers) to reduce the effects of dif- fraction losses. The effect of small size reflectors and shaping was discussed later on in [8].

For the higher fiequency bands these losses are less pronounced, as the relative sizes become larger in terms of wavelength. Today a comparable rotating dual reflector system is also considered for implemen- tation in the 64 m radio telescope to be realised in Sardinia [9, IO].

As is indicated in [I-51, the effects ofgravitational compensation have been thoroughly studied and ap- proximate formulas were derived with radio astro- nomical methods to correct pointing as a function of elevation and azimuth, this leading to good diagrams for the different angular directions and a pointing knowledge for the best diagram was optimised. The Gregorian subreflector can be translated and can be axially displaced.

A decision for the Gregorian configuration was supported by investigations, from which a better noise temperature was apparent (less spill-over, better roll- off at the edge of the main reflector) and from which more complete correction possibilities for phase dis- tortions were derived for gravity compensation. The RT-70 was constructed with upgrading to shorter wavelength in mind, as a very good demonstration of antenna design capabilities.

The ongoing developments today include the in- stallation of receive capability at X = 21, 18, 13, 3.5 and also I .35cm with sufficiently low noise tempera- ture, while a wider bandwidth is achieved than in ear- lier measurements.

There are two new receivers installed in the RT-70 antenna, operating at 327 MHz and 4.8 GHz respec-

tively. The ‘Saturn‘-association in Kiev develops an 18 cm receiver, which will be installed this year (2002). The latter “Saturn“-association has very good experience in the realization of cryogenically cooled receivers at all wavelengths as considered for the “Radio-Astron”-project, as well as for other applica- tions like in Ratan 600.

There is the interest to equip the RT-70 antenna with S- and X-band receivers, permitting the antenna to handle telemetry data in receive. With such a set of receivers, the total set of capabilities is more flexible, permitting the data downlinking for scientific mis- sions as well as telecom missions. The latter reception capability would also be functional for the require- ments for astrometry, as well as eventual support pos- sibilities for other scientific missions like for example Mars-Express (exploring discussions between ESA and the Ukrainian Space Agency took place early April in 2001,). Today the ‘Saturn’-association is de- veloping these receivers and may install them in the RT-70 during the years 2002-2003.

There is the possibility to use the feed for X = 18 cm for both Right-hand and Lefi-hand circular polarization, with an overall effective area of 2300 m2. The 327 MHz hand ( A = 92 cm) is supported with a feed array with four helix antennas positioned around the secondary focus. The effective area at 327 MHz is 1400 mz and the associated antenna pattern has a Half Power Beam Width of HPBW = 50 arcminutes.

There is the plan to install also a 22 GHz ( A = 1.35 cm) receiver. With the capabilities then available, the Radio-Astron mission can be supported with a large ground-based radio telescope. The question about an eventual 32 GHz receiver is open, because the current surface accuracy should be re-assessed.

In the early beginning there have been carried out experiments even at a wavelength X = 8 mm, with a resulting effective area o f 900 mz [3J. As the RT-70 is rather well designed, some improvement might be anticipated from such an investigation, but this is somewhat at the limit. Also the pointing capability is then an aspect, which should be investigated, in com- bination with the capability to adapt the position of the movable sub-reflector.

2. RECENT ACHIEVEMENTS In the last year the concept of a radio astronomy up- grade and use of RT-70 antenna as one of the largest centimeter-decimeter wavelength antennas, was pro- posed by the Institute of Radio Astronomy (IRA). The RT-70 antenna belongs to the National Control and Space Facilities Test Center (Evpatoria) under the Ukrainian Space Agency (Fig. I ) .

This upgrading activity is supported by the Na- tional Ukrainian Space Agency (NSAU) with a nurn- ber of Ukrainian and Russian organizations.

The principal purpose is the realisation of a set of high sensitive modern radio astronomy equipment, to put it into operation and to cany out scientific investi- gations with RT-70 for the most perspective fields of

58 Intcrnadonal Conference on Antenna Theory and Techniques, 9-12 September, 2003, Sevastopol, Ukraine

Fig. 1. The 70 meter Radio Telescope (RT-70)

RT-70,327 MHr, 8.1998,A6600 m2,0A-S0,T,-lo0 K

Time (s)

Fig. 2. Patterns, Virgo A as source, upper left: cen- tral scan, other scans at + and -30 angular minutes wrt peak

ground-space radio astronomy. The following topical areas are considered for this purpose: s International very long base interferometer (VLBI)

experiments including activities in the frame of ground-space interferometer projects (VSOP, VSOP-2, Radioastron) associated with the ulti- mate capability of angular resolution realization.

0 Single-dish high sensitive broad band investiga- tions of galactic and extragalactic objects in con- tinuum and spectral lines for the study of physical and evolution processes in the Universe.

RT-70,325 MHz, Cas A, DAC, 4 x 1024 C27m o.wm .20,w,6 ............................... ~!~~ .......................... ~1~ ........

E O,W,2 . ~ . .. ~

.E 0 . m ...~ ..~ ! ...... ~ ~~

Radio Telescope RT-70 m ETatoria and Space Invesdgations

International Conference on , h e n n a Theory and Techniques, 9-12 September, 2003, Sevastopol, Ukraine 59

Fig. 3. Results at Evpatoria of reception of carbon recombination lines in four frequency bands. Cassiopeia as source. 4.8GHz, 11.1998 Acr-2I00m2, OA-3.5', TS-2S-3O K , ~ 1 ~ - 1 0 0 4 0 0 MHz

Radar investigations of natural and artificial solar system objects including the using of VLBI meth- ods for planets, asteroids, meteors, space debri, satellites. Ground-space investigations of the interplanetary medium by signals transmission from deep space satellites and natural space radio sources. VLBI radio astrometry for coordinate-time tasks, geodynamics, precise space navigation.

During the years 1998-1999 a number of technical and scientific works was carried out.

The following new equipment was developed and installed into the RT-70 antenna for the 325 MHz frequency range: an antenna feed; a radio receiver including low noise preamplifier, high selective filters for interference rejection, frequency transformers and amplifiers, heterodynes, continuum radiometer, digital correlometers, the Mark I1 recording system. Antenna measurements show as system parameters: system temperature about 100 K; effective area 600 m2. The beam-width is SO angular minutes.

Fig. 2 illustrates the registration of the antenna pat- tern with Virgo A as reference radio source. The up- per-left pattern is the central scan, the other two scans correspond to the scans with a shift of _+ 30 angular

A. -i. Konovalenko, L. N. Lytvynenko, C. G. M. van ‘t Klooster

Fig. 4. Test result, Cygnus A as a source, different receiving stations involved

Fig. 5. Response for an interferometer baseline. Re- ception at Evpatoria and Svetloe near St. Petersburg

minutes away from the main direction. The antenna pattern is symmetrical for both cross-sections and some pointing information is deduced from the pat- terns at t and -30 angular minutes.

Fig. 3 shows observations of carbon recombination lines observations with digital correlation-meters in four eequency bands towards Cassiopeia A. All four recom- bination lines were detected very reliably. During August and November 1998 a number of VLBl experiments have been carried out with the international low fre- quency VLBl net as a precursor for the future “Radio Astron” project. The magnetic tapes are processed in JPL laboratory in USA. New equipment for 4.8GHz is a two-channel receiver with a micro-cryogenic closed cy- cle system cooled to a temperature of 6-8 K. The re- ceiver can be used both for radio astronomy observations and for the radar-working regime. The intermediate fre- quency range is I O M O O MHz.

The S2 registration system was installed temporally by the Institute of Applied Astronomy (St Petersburg, Russia [ I I]). The test have shown that the system total noise temperature is 25-35 U, the effective area is of an order of 2000 rn2 and the beam-width is about 3 angular minutes. With the given 2000 m2 effective area, the reader should be in a position to estimate other parameters associated like GIT at 4.8 GHz as something like 53.5 dB/K.

Fig. 4 shows the result of a test experiment with Cygnus A as reference radio source. During the June 1999 a number of 4.8 GHz VLBI experiments were carried out. Fringes were detected with high reliabil- ity, for example, on the baseline Evpatoria (Ukraine) - Svetloe. For the information to the reader: Svetloe is near St. Petersburg, see [ I I ] for a description of that 32 m antenna (QUAZAR) by V. Gratchev.

Fig. 6. Radar response spectra for the reflected spectra from Venus

Fig. 5 shows the interferometer response for this baseline (- 2000 km) during the observations of qua- sar 0745+241. The horizontal axes, correspond to the delay (0-8 mks) and power spectra (04 .15 Hz). We can observe a strong localization of the signal for both parameters (time and frequency) with very high sig- nal-to-noise ratio. It confirms the high reliability and quality of the experiment.

Furthermore, Fig. 6 shows mutual spectra of re- flected signal from the Venus during radar experiments in VLBI mode for frequency band of 200 Hz. The sig- nal-to-noise ratio is very high. Fringes were detected successfully. The processing was made by the Institute of Applied Astronomy, St. Petersburg, Russia.

Furthermore, the first test ground-space VLBl ex- periment was carried out on RT-70 antenna within the frame of the VSOP (Halca) project. The quasar 1351- 145 was observed together with space radio telescope and with some ground-based antennas in southern part of the Earth. Now the S2 magnetic tapes are prepared for processing in Canada. With these achievements the first step in the creation of a modem ground-space radio astronomy center on the base of RT-70 antenna has ended. There are very good perspectives for future developments in this domain ofresearch.

During the recent years the next steps in the develop- ment and upgrade of RT-70 antenna (Evpatoria) were carried out. It was connected with the installations of new equipment and methods as well as with the single- dish investigations, VLBl experiments, preparation of the participation in the ground-space interferometer pro- jects and radar investigations of natural and artificial solar system objects with using of VLBl methods for planets, asteroids, meteors, space debris, satellites.

GO International Conference on Antenna Theory and Techniques, 9-12 September, 2003, Sewstoppol, Ukraine

Radio Telescope RT-70 in Evpatona and Space Investigations

Beam Width at 6 cm wavelength

5010.32 5010.72 .. 5009.92

Fig. 7. Echo signal spectrum, to be further detailed in the workshop

3.5 arcmin.

3. SPACE DEBRI A N D RADAR INVESTIGATIONS

New results are presented in this report involving the Evpatoria antenna, in the context of space debris research.

The RT-70 antenna. Evpatoria belongs to the world-largest antenna systems and is a "Europe- unique" receiving antenna capable of being fed with a high-power transmitter. The associated critical system parameters are given in Table I .

Way back in the eighties the RT-70 antenna was re- peatedly used in radar research o f planets and asteroids. In recent years this transmit-receive system has been upgraded and equipped with new radio-astronomical facilities. This has enabled expansion o f various radio- astronomical research and resuming radar experiments, including those employing the VLBI-methods. In 1999 the international 6-cm experiments for Venus and Mars were a success. There was radiation and reception in Evpatoria (Ukraine), reception in Svetloe (Russia) and

Table 1.

Main dish diameter: I 7 0 m I I

2200 mz Effective area at 6 cm wave- length:

I Transmitter output: I 100-200 k W I

I 0.5-1 GW I PG-factor (product of antenna inout and gain):

I I

- I I

Sysein noise temperature with

Polarization Circular

Shanghai (China). The interference lobes informative o f the planet surface were recorded with high signal-to- noise ratio on all baselines.

When one considers the RT-70 power budget. the system, when used together wi th an available receiv- ing antenna o f 32-m in diameter, can be easily shown to be capable o f detecting space debri-partifiles with a size o f some mm on orbits to 400 km and accordingly some cm at geo-stationary orbits.

In 2001 an initial series of space-debri radar ex- periments was carried out, after a system upgrade and high-power transmitter repair. The transmitter tubes have been repaired in Kiev. The experiments con- sisted in radiating a continuous signal with a power level of roughly 100kW at the frequency around 5 GHz (in some cases there was used a frequency modulation) towards the cataloged space vehicle fragments o f about I -m scattering cross-section, mainly in geo-stationary orbits. In testing also other targets l ike reference satellites in a high-elliptic orbit (apogee to 19,000 km) were considered as well. Dif- ferent antennas in Russia and other countries (Svetloe, Kalyazin, Bear Lakes - Russia, MERLIN - Great Britain, Medicina - Italy, Torun - Poland, Shanghai - China, and others) were receiving the signals. In total more than IOobjects were explored. In silent intervals between the radiation sessions the above antennas were receiving the radio emission from quasi-stellar sources with coordinates very close to the debris objects. This allowed to monitor the antenna pointing accuracy, serviceability o f receiving equip- ment and to utilize a new VLBI-radar method to es- sentially improve the positioning accuracy with the differential radio-astrometry method.

Practically all signals echoed from the studied ob- jects were reliably detected with all antennas. As an example, Fig. 7 illustrates spectra o f the echo signals recorded by the MERLIN and Bear Lakes antennas.

International Conference on ;\ntenru Theory and Techniques, 9-12 September, 2003, Sewstopol, Ukmine 61

A. ,i. Konovalenko, L. N. Lytry-nenko, C. G. hl. van ‘t Klooster

62 Internanonal Conference on .inrenix Theory and Techniques, 9-12 September, 2003, Sewstopol, Ukrame

4. OTHER LARGE APERTURE ANTENNAS Not far away from the RT-70 system there are some other large cm-wavelength antenna configurations in the Ukraine. These antennas are the RT-22 (Simeiz), the RT-32 (Evpatoria) and the RT-32 (Simferopol) antenna (Fig. 8). They all can well effectively receive the echoes of space debris echoes in the research ses- sions. Further improvement of the RT-70 transmit- receive system, in particular the increase of the trans- mitter output power and frequency deviation, is of current concern.

There has been accumulated a lot of data on meteor trails in the upper atmosphere, these data were ac- quired in the meter wavelengths. There are strong arguments to hold a remarkable part of the latter data as caused by space-debri partifiles. The radar search- ing of parent bodies in meteor streams at centimeter wavelength is of interest.

Further development of VLBI-radar of space bodies is of interest as it ensures an unprecedented positioning accuracy and thus fixes the actual traces ofthese bodies.

The Ukraine’s radar system satisfies up-to-date re- quirements for supporting investigations into space .~ debris problems.

The RT-70 space-object radar pilot experiments did already give evidence for promising prospects for expansion into this direction.

Many Ukrainian organizations (the Institute of Ra- dio Astronomy of the National Academy of Sciences of Ukraine being the leading institution) participated in preparation and equipment of the RT-70 system, as well as in the research activity. Within the frame of a Ukraine-Russia cooperative agreement, several Rus- sian organizations actively contribute to these efforts too - ASC FIAN, IRE RAS, (Moscow), IAA RAS (St.-Petersburg), NlRFl (NizhnyNovgorod), et al. It indicates the continuation and strong interest to main- tain this unique instrument.

5. CONCLUSIONS The radio telescope RT-70 has been described in outline and somewhat in history. It is a very elegant antenna design with at its time of construction very advanced solutions implemented for various technical problems.

Nowadays there is a continuous effort ongoing to maintain the operational capabilities of this unique instrument. A number of activities have been outlined. Recent results have been indicated and the interest to use such antenna for different applications related to space projects has become clearer.

REFERENCES 1. 1. N. Knjasev, 0 . S. Viktorov, B. P. Riskov,

L. M. Fedosejev, D. B. Roshdestvenski. “Antenna Facility with a 70 Meter Diameter Reflector (RT- 70),” Antenni, (Russian) Issue 3 1, Publicing House Radio and Communication, Moscow 1984.

2. A. N. Kozlov, V. V. Tarasov, V. A. Grishmanov- sky, B. G. Sergejev, “Summary and Experimental Investigations of the Radio Technical Characteris-

Fig. 8. The 32 meter antenna as built near Evpatoria and near Simferopol

tics of the Antenna RT-70”, Antenni, (Russian) Is- sue 31, Publicing House Radio and Communica- tion, Moscow 1984.

3. A.M. Aslanian, A. G. Gulian, A. N. Kozlov, V. B. Tarasov, P. M. Marturosian, V. A. Grishma- novskij, B. G. Sergeev, “Measurements of the Main Parameters of the Antenna RT-70,” (Rus- sian), Radiofysika, Issue XXVII, No 5 , 1984.

4. V. A. Grishmanovsky, A. N. Kozlov, V. B. Tara- SOY, “The Main Principles of a 70-m Radio Telescope Reflecting System Design” (English...), IEEE Transactions on Microwave Theory and Techniques, Vol. 40 No. 6 June 1992.

5 . R. V. Bakitko, M. B. Vasiljev, A. C. Vinitski, V. A. Grishmanovsky, A. L. Zaitsev, V. V. Kersha- novits, E. L. Molotov, V. P. Oreshkin, G. M. PeUov, 0. N. Rchiga, V. I . Rogalski, A. S. Selivanov “Radio Systems for Interplanetary Satellitesw” (Russian), ISBN 5-256-01054-9, Publishing House Radio and Communication, Moscow 1993.

6. V. Y. Kinber, “On Two Reflector Antennas”, Ra- dio Eng. Electron. Physics, Vol. 6, June 1962.

7. V. Galindo, “Design of Dual Reflectgor Antennas with Arbitrary Phase and Amplitude Distribution”, Proc. IEEE Antenna and Propagation Symposium, Boulder Colorado, July 1963.

8. P. S. Kildal, “Comments on ‘Synthesis of Offset Dual Shaped Subreflector Antennas for Control of Cassegrain Aperture Distributions”, IEEE Trans- actions on Antennas and Propagation, Vol. AP-32, No IO, Oct 1984

9. R. Ambrosini, “Sardinia Radio Telescope (SRT), A Feasibility Study for a 64 m Active Surface Radio Tele- scope” W o h h o p on Large Antennas in Radio Astron- omy, Feb. 1996 ESTEC, Noordwijk, m e Netherlands ht tp: / /~.estec .~.nVconferencff i96002/p~g.h~1.

IO. G. Cortes-Medellin, NAIC, USA, “The 64m Sar- dinia Radio Telescope Optics Design”, IEEE APS Conf. emece, San Antonio, Texas, USA, 2002

1 I . A. Finkelstein, E. Korkin, B. Poperechenko, S. Smolentzev, V. Gratchev, A. Ipatov, V. Kuzmin, E. Molotov,“VLBI Activity in IAA, St. Petersburg: New 32-m Radio Telescope for VLBI”. Workshop on Large Antennas in Radio Astronomy, Feb. 1996 ESTEC, Noordwijk, the Netherlands. http://www.estec.esa.nl/conferencesi96002/prog.htm I