Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.asc.rssi.ru/RadioAstron/publications/articles/ar_2013,57,153_en.pdf Äàòà èçìåíåíèÿ: Fri Jul 19 10:26:23 2013 Äàòà èíäåêñèðîâàíèÿ: Thu Feb 27 21:59:03 2014 Êîäèðîâêà: IBM-866 Ïîèñêîâûå ñëîâà: optical telescope

ISSN 1063-7729, Astronomy Reports, 2013, Vol. 57, No. 3, pp. 153í194. c Pleiades Publishing, Ltd., 2013. Original Russian Text c N.S. Kardashev, V.V. Khartov, V.V. Abramov, V.Yu. Avdeev, A.V. Alakoz, Yu.A. Aleksandrov, S.Ananthakrishnan, V.V. Andreyanov, A.S. Andrianov, N.M. Antonov, M.I. Artyukhov, M.Yu. Arkhipov, W. Baan, N.G. Babakin, N. Bartel', V.E. Babyshkin, K.G. Belousov, A.A. Belyaev, J.J. Berulis, B.F. Bur ke, A.V. Biryukov, A.E. Bubnov, M.S. Burgin, G. Busca, A.A. Bykadorov, V.S. Bychkova, V.I. Vasil'kov, K.J. Wellington, I.S. Vinogradov, R. Wietfeldt, P.A. Voitsik, A.S. Gvamichava, I.A. Girin, L.I. Gurvits, R.D. Dagkesamanskii, L.D'Addario, G. Giovannini, D.L. Jauncey, P.E. Dewdney, A.A. D'yakov, V.E. Zharov, V.I. Zhuravlev, G.S. Zaslavskii, M.V. Zakhvatkin, A.N. Zinov'ev, Yu. Ilinen, A.V. Ipatov, B.Z. Kanevski, I.A. Knorin, J.L. Casse, K.I. Kellermann, Yu.A. Kovalev, Yu.Yu. Kovalev, A.V. Kovalenko, B.L. Kogan, R.V. Komaev, A.A. Konovalenko, G.D. Kopelyanski, Yu.A. Korneev, V.I. Kostenko, A.N. Kotik, B.B. Kreisman, A.Yu. Kukushkin, V.F. Kulishenko, D.N. Cooper, A.M. Kut'kin, W.H. Cannon, M.G. Larionov, M.M. Lisakov, L.N. Litvinenko, S.F. Likhachev, L.N. Likhacheva, A.P. Lobanov, S.V. Logvinenko, G. Langston, K. McCracken, S.Yu. Medvedev, M.V. Melekhin, A.V. Menderov, D.W. Murphy, T.A. Mizyakina, Yu.V. Mozgovoi, N.Ya. Nikolaev, B.S. Novikov, I.D. Novikov, V.V. Oreshko, Yu.K. Pavlenko, I.N. Pashchenko, Yu.N. Ponomarev, M.V. Popov, A. Pravin-Kumar, R.A. Preston, V.N. Pyshnov, I.A. Rakhimov, V.M. Rozhkov, J.D. Romney, P. Rocha, V.A. Rudakov, A. Rè sè n, S.V. Sazankov, B.A. Sakharov, ai ane S.K. Semenov, V.A. Serebrennikov, R.T. Schilizzi, D.P. Skulachev, V.I. Slysh, A.I. Smirnov, J.G. Smith, V.A. Soglasnov, K.V. Sokolovskii, L.H. Son daar, V.A. Stepan'yants, M.S. Turygin, S.Yu. Turygin, A.G. Tuchin, S. Urpo, S.D. Fedorchuk, A.M. Finkel'shtein, E.B. Fomalont, I. Fejes, A.N. Fomina, Yu.B. Khapin, G.S. Tsar evskii, J.A. Zensus, A.A. Chuprikov, M.V. Shatskaya, N.Ya. Shapirovskaya, A.I. Sheikhet, A.E. Shirshakov, A. Schmid, L.A. Shnyreva, V.V. Shpilevskii, R.D. Ekers, V.E. Yakimov, 2013, published in Astronomicheskii Zhurnal, 2013, Vol. 90, No. 3, pp. 179í222.

"RadioAstron"--A Telescope with a Size of 300 000 km: Main Parameters and First Observational Results
N. S. Kardashev1* , V. V. Khartov2 , V. V. Abramov3 , V. Yu. Avdeev1 , A. V. Alakoz1 , Yu. A. Aleksandrov1 , S. Ananthakrishnan4 , V. V. Andreyanov1 , A. S. Andrianov1 , N. M. Antonov1 , M. I. Artyukhov2, M. Yu. Arkhipov1* , W. Baan5 , N. G. Babakin1 , V. E. Babyshkin2, N. Bartel'26 , K. G. Belousov1 , A. A. Belyaev6 , J. J. Berulis1 , B.F.Burke7 , A. V. Biryukov1, A. E. Bubnov8 , M. S. Burgin1 , G. Busca9 , A. A. Bykadorov10, V. S. Bychkova1, V. I. Vasil'kov1, K. J. Wellington11 , I. S. Vinogradov1 , R. Wietfeldt12 , P. A. Voitsik1 , A. S. Gvamichava1, I.A.Girin1 , L.I.Gurvits13, 14 , R.D.Dagkesamanskii1 , L. D'Addario12 , G. Giovannini15, 16 , D. L. Jauncey11 , P. E. Dewdney17 , A. A. D'yakov18, V. E. Zharov19 , V. I. Zhuravlev1 , G.S.Zaslavskii20, M.V.Zakhvatkin20, A. N. Zinov'ev1 , Yu. Ilinen21 , A. V. Ipatov18 , B.Z.Kanevskii1 , I. A. Knorin1 , J.L.Casse13 , K. I. Kellermann22 , Yu. A. Kovalev1 , Yu. Yu. Kovalev1, 23 , A. V. Kovalenko1 , B. L. Kogan24 , R. V. Komaev2 , A. A. Konovalenko25 , G. D. Kopelyanskii1, Yu. A. Korneev1 , V. I. Kostenko1 , A. N. Kotik1 , B. B. Kreisman1 , A. Yu. Kukushkin8, V. F. Kulishenko25 , D. N. Cooper11 , A. M. Kut'kin1 , W. H. Cannon26 , M. G. Larionov1 , M. M. Lisakov1, L. N. Litvinenko25 , S. F. Likhachev1, L. N. Likhacheva1, A.P.Lobanov23 , S.V.Logvinenko1 , G. Langston27 , K. McCracken11 , S. Yu. Medvedev6 , M.V.Melekhin2 , A.V.Menderov2 , D. W. Murphy12 , T. A. Mizyakina1, Yu. V. Mozgovoi2 , N. Ya. Nikolaev1 , B. S. Novikov8, 1 , I. D. Novikov1 , V. V. Oreshko1 , Yu. K. Pavlenko6 , I. N. Pashchenko1 , Yu. N. Ponomarev1 , M.V.Popov1 , A. Pravin-Kumar4 , R. A. Preston12 , V. N. Pyshnov1 , I. A. Rakhimov18, V. M. Rozhkov28 , èè J. D. Romney29 , P. Rocha9 , V. A. Rudakov1 , A. Raisanen30 , S. V. Sazankov1, 6 2 2 B. A. Sakharov , S. K. Semenov , V. A. Serebrennikov , R. T. Schilizzi31, D. P. Skulachev8, V. I. Slysh1 , A. I. Smirnov1 , J. G. Smith12 , V. A. Soglasnov1 , K. V. Sokolovskii1, 19 , L. H. Sondaar5 , V. A. Stepan'yants20 , M. S. Turygin3 , S. Yu. Turygin3 , A. G. Tuchin20 , S. Urpo30 , S. D. Fedorchuk1, A. M. Finkel'shtein18 , E. B. Fomalont22 , I. Fejes32 , A. N. Fomina33 , Yu. B. Khapin8 , G. S. Tsarevskii1 , J. A. Zensus23 , A. A. Chuprikov1, M. V. Shatskaya1, N. Ya. Shapirovskaya1, A. I. Sheikhet2 , A. E. Shirshakov2, A. Schmidt23 , L. A. Shnyreva1 , V. V. Shpilevskii18, R. D. Ekers11 , and V. E. Yakimov1
Astro Space Center, Lebedev Physical Institute, Moscow, Russia 2 Lavochkin Scientific and Production Association, ul. Leningradskaya 24, Khimki, Moscow region, 141400 Russia 3 Institute of Radio Technology and Electronics, Russian Academy of Sciences, Moscow, Russia Giant Metrewave Radio Telescope, Tata Institute of Fundamental Research, P.B. 6, Narayangoan, Tal-Junnar, Pune, Maharashtra, India 5 Netherlands Institute for Radio Astronomy (ASTRON), P. O. Box 2, 7990 AA Dwingeloo, The Netherlands 6 "Vremya-Ch" Joint Stock Company, ul. Osharskaya 67, Nizhni Novgorod, 603105 Russia 7 Massachusetts Institute of Technology, Cambridge, MA, USA 8 Space Research Institute, Russian Academy of Sciences, Moscow, Russia 9 Observatoire de Neuchatel, Neuchatel, Switzerland 153
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"Salut-27" Private Joint Stock Company, Research and Production Enterprise, Nizhni Novgorod, 603105 Russia 11 Australia Telescope National Facility, CSIRO Division of Radio Physics, Sydney, Australia 12 NASA Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91011, USA 13 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands 14 Faculty of Aerospace Engineering, Delft University of Technology, Kluyerveg 1, 2629 HS Delft, The Netherlands 15 INAF-Istituto di Radioastronomia di Bologna, Via Gobetti 101, I-40129 Bologna, Italy 16 Dipartimento di Astronomia, Universita di Bologna, via Zamboni 33, 40126 Bologna, Italy 17 SKA Program Development Office, University of Manchester, Manchester M13 9PL, United Kingdom 18 Institute of Applied Astronomy, Russian Academy of Sciences, Saint Petersburg, Russia 19 Sternberg Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia 20 Keldysh Institute of Applied Mathematics, Russian Academy of Sciences, Miusskaya 4, Moscow, 125047 Russia 21 Ilinen Company, Helsinki, Finland 22 National Radio Astronomy Observatory, Edgemont Rd., Charlottesville, VA 22903-2475, USA 23 Max Planck Institute for Radio Astronomy, 69 Auf dem Hugel, 53121 Bonn, Germany è 24 Moscow Energy Institute, Moscow, Russia 25 Radio Astronomy Institute, National Academy of Sciences of Ukraine, ul. Krasnoznamennaya 24, Khar'kov, 61002 Ukraine 26 Department of Physics and Astronomy, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada 27 National Radio Astronomy Observatory, P. O. Box 2, Rt. 28/92, Green Bank, WV 24944-0002, USA 28 Raketno-Kosmicheskie Sistemy, ul. Aviamotornaya 53, Moscow 111250, Russia 29 National Radio Astronomy Observatory, P. O. Box 0, 1003 Lopezville Rd., Socorro, NM 87801-7000, USA 30 Department of Radio Science and Engineering, Aalto University, P. O. Box 13000, FI-00076 Aalto, Finland 31 University of Manchester, Jodrell Bank Centre for Astrophysics, Manchester, M13 9PL, United Kingdom 32 è FOMI Satellite Geodetic Obsevatory, Renc, Hungary 33 Ekologiya i Radiosvyaz, Private Joint Stock Company, ul. Vaneeva 34, kv. 21, 603105, Nizhni Novgorod, Russia
Received July 5, 2012; in final form, July 12, 2012

Abstract--The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna groundí space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and groundíspace interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun. DOI: 10.1134/S1063772913030025

*

E-mail: ykovalev@avunda.asc.rssi.ru

1. INTRODUCTION A method for obtaining very high angular resolution in radio astronomy and a specific scheme for the
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realization of this method are presented in [1í3]. It was noted that radio interferometers on Earth and in space could operate with very long baselines between antennas, with independent registration of the signals at each antenna. Such radio interferometers were first operated in 1967 in Canada [4] and the USA [5]. The first trans-continental interferometers were realized in 1968í1969, between telescopes in the USA and Sweden [6], and also between the Deep Space Network antennas in the USA and Australia [7, 8]. Some of the first observations with trans-continental radio interferometers were carried out jointly by radio astronomers in the USSR and USA in 1969, using the 43-m Green Bank radio telescope (USA) and the 22-m Simeiz telescope (USSR) [9, 10]. Such observations were subsequently carried out between all continents. Modern trans-continental radio interferometers can achieve angular resolutions of fractions of a milliarcsecond (mas). These observations show that most active galactic nuclei (AGNs) possess unresolved components, even on the longest projected ground baselines (approximately 10 000 km); see, e.g., [11, 12] and references therein. The possibility of creating space interferometers was discussed at a scientific session of the Division of General Physics and Astronomy of the USSR Academy of Sciences on December 23, 1970 [13]. The first EarthíSpace interferometer projects emerged at that time. In the 1970s, the Space Research Institute of the USSR Academy of Sciences (IKI) working jointly with industrial partners created the first space radio telescope (SRT), which had a 10-m diameter reflector. This telescope had a trussed, opening construction with a reticulated reflecting surface and receivers tuned to 12 and 72 cm. This radio telescope was delivered to the Salyut-6 manned orbital station by the cargo ship Progress in Summer 1979, where it was tested using astronomical objects with the participation of the cosmonauts V.A. Lyakhov and V.V. Ryumin [14, 15]. One of the outcomes of these experiments was the decision to use a rigid reflecting surface for the RadioAstron project. A decree of the Council of Ministers of the USSR announcing the development of six spacecraft for astrophysical investigations at the Lavochkin Scientific and Production Association was made in 1980. These included the decimeter- and centimeter-wavelength interferometer RadioAstron (the Spektr-R project), as well as the millimeter and submillimeter radio telescope Millimetron (the Spektr-M project) [16]. The technical specifications for the RadioAstron project had already been prepared in 1979. The first international conference on this project took place in Moscow on December 17í18, 1985. Agreements were signed, and an international group concerned
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with the development of onboard radio-astronomy receivers based on sets of individual technical specifications was formed. These technical specifications were developed and issued in 1984í1985 by the Astrophysics Division of IKI, headed by I.S. Shklovskii. The group included specialists from the USSR, the Netherlands, the Federal Republic of Germany, Australia, Finland, and India. In the early 1990s, the flight models of the first receivers at 1.35, 6.2, and 18 cm and onboard blocks of input low-noise amplifiers (LNAs) for the 92-cm receiver were delivered to the Astro Space Center of the Lebedev Physical Institute (ASC; formed in 1990 from the IKI Astrophysics Division and the Radio Astronomy Station of the Lebedev Physical Insitute in Pushchino). The 18-cm receiver and 92-cm amplifier blocks form part of the complex of scientific equipment used with the RadioAstron SRT in flight today. The first successful space interferometer was realized in 1986í1988 using the 5-m diameter antenna of the NASA TDRSS geostationary satellite (USA), which operated at 2 and 13 cm, together with several ground-based radio telescopes [17, 18]. The first SRT specially designed for interferometry was the HALCA satellite of the VSOP project, launched by Japan in 1997 [19, 20]. This 8-m diameter antenna was mounted on a satellite that orbited the Earth in an elliptical orbit with a period of 6.3 h and a maximum distance from the center of the Earth of 28 000 km. This SRT successfully functioned at wavelengths of 6 and 18 cm until 2003. Both of these space interferometers confirmed not only the possibility, but also the scientific necessity of further developing groundíspace radio Very Long Baseline Interferometry (VLBI), in particular of enhancing the angular resolution obtained by increasing the size of the orbit and of expanding the range of wavelengths observed. All of this experience was taken into account when preparing the RadioAstron project. The RadioAstron SRT is a 10-m diameter reflecting antenna equipped with a complex of 1.35, 6.2, 18, and 92 cm receivers. A Navigator module space platform was used to install the RadioAstron antenna and equipment complex into the Spektr-R spacecraft [21í25]. The arrangement of the SRT and equipment complex in the Navigator module is shown in Fig. 1.1 A general block schematic of the antenna and equipment complex of the SRT is shown in Fig. 2. The precision carbon-fiber panels of the main antenna of the SRT were manufactured and tested in Russia, and then at the European Space Research and Technology Center (ESTEC) of the European
1

All figures referred to in the Introduction (Figs. 1, 2, 4, 5, 7í 10) are discussed in more detail in later sections of this paper. Figs. 4aí4l and Figs. 7aí7g are presented as color inserts.


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Space Agency in 1994 (Nordwijk, the Netherlands; Fig. 4a). Tests of the model SRT and the equipment complex of the interferometer (Fig. 4b) were carried out from Autumn 2003 through Summer 2004 at the Pushchino Radio Astronomy Observatory (PRAO) of the ASC. The main parameters of the model SRT were measured during these tests using observations of astronomical radio sources, and test observations in an interferometric regime were carried out using the SRT together with the PRAO 22-m radio telescope. This 22-m radio telescope was subsequently outfitted with additional equipment enabling its use as a ground station for tracking the Spektr-R spacecraft in flight. The last ground tests of the SRT with the Navigator module occured at the Lavochkin Association (Figs. 4c, 4d). At the suggestion of the International Grote Reber Foundation, a memorial plate with a portrait of the pioneer radio astronomer Grote Reber (1911í2002) was installed on the SRT (Fig. 4e). A poster with an image of symbols of the organizations and countries participating in the RadioAstron project was placed on the fairing of the Zenit-3F rocket used to launch the Spektr-R spacecraft (Fig. 4f). Figs. 4gí4i show the transport of the rocket carrier with the Spektr-R spacecraft and the Fregat booster to the launch position. The launch of the Zenit-3F rocket with the Spektr-R spacecraft took place on July 18, 2011 at 5 h 31 min 17.91 s Moscow daylight saving time, from the 45th launch pad of the Baikonur cosmodrome (Figs. 4j, 4k). On that same day at 14 : 25, the booster and spacecraft, which had separated from it, were photographed using a 45.5-cm optical telescope in New Mexico, at the request of the Keldysh Institute of Applied Mathematics (IAM) of the Russian Academy of Sciences (Fig. 5). The SRT was successfully deployed on July 23, 2011 (a general view of the Spektr-R spacecraft in space is shown in Fig. 4l). After this, it was possible to begin the inflight tests planned for the first six months of flight: verifying the functioning of the service systems and the scientific equipment of the spacecraft, measuring and updating the characteristics of the orbit, measuring the main parameters of the SRT, searching for fringes in the groundíspace interferometer signal, and beginning the Early Science Program (ESP) of astrophysical investigations. Let us now present a brief history of key astronomical observations in the first half year of the inflight tests of the SRT. The radio-astronomy receivers were successfully turned on for the first time in midSeptember 2011, and regular tests of the onboard scientific equipment were begun. Radiometric measurements of the parameters of the SRT using radioastronomical methods and observations of various astronomical objects during operation of the SRT in

a single-dish regime began on September 27, 2011 (Figs. 7a, 7b, 8aí8c). The adjustment and testing of the high-data-rate radio channel for transmitting data between the SRT and the ground tracking station in Pushchino in an interferometric regime were conducted in parallel. Measurements at 92, 18, 6.2, and 1.35 cm began with observations of the Cassiopeia A supernova remnant (Figs. 7a, 8a, 8b), then went on to observations of Jupiter, the Moon, the Crab Nebula (Fig. 7b), the Seyfert galaxy 3 84, and the quasars 3 273 and 3 279, as well as cosmic masers (Figs. 9aí9c) and pulsars (Figs. 7f, 7g, 10). Tests of the groundíspace radio interferometer at 18, 6.2, 92, and then 1.35 cm began with observations of the quasar 0212+735 at 18 cm on November 15, 2011 (Fig. 7c). These tests were conducted at various distances of the SRT from the Earth, from the minimum distance to the maximum distance of about 330 000 km, and using observations of various extragalactic and Galactic objects: quasars and galaxies, pulsars, and molecular maser sources radiating in narrow radio lines (Figs. 7cí7f). Further, we describe the construction of the SRT and the configuration of the onboard science complex (Section 2); the launch and inflight tests of the Spektr-R spacecraft and ground control complex (Section 3); the parameters of the orbit and the means used to measure and refine them (Section 4); measurement of the main parameters of the SRT based on astronomical sources (Section 5); and verification of the functioning of the groundíspace interferometer (first fringes) and the first observational results (Section 6). In conclusion, we list directions for further studies. The Appendix presents a possible interpretation of the antenna measurements at 1.35 cm. 2. CONSTRUCTION OF THE SRT AND CONFIGURATION OF THE ONBOARD SCIENCE COMPLEX The automated Spektr-R spacecraft was designed to carry an SRT to be used as an orbiting element in groundíspace VLBI experiments. It includes the Navigator service module (with the Lavochkin Association as the lead organization) [21] and a science complex containing the scientific equipment to be used for the international RadioAstron project (with the ASC as the lead organization) together with the 10-m parabolic antenna itself (jointly developed by the Lavochkin Association and the ASC) [22, 23]. In addition, the spacecraft carried the scientific equipment associated with the Plazma-F project (with IKI as the lead organization), designed for studies of cosmic plasma along the orbit of Spektr-R (this equipment and experiment are described in [26, 27]).
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2.1. Construction of the Antenna
The design of the SRT antenna was based on the need to fit the deployable 10-m reflector in its folded state into the payload compartment of the rocket underneath the fairing, which has a specified internal diameter of 3.8 m, and also to ensure the required precision of the reflecting surface after its deployment. According to the technical specifications, the maximum allowed deviation (tolerance) of the dish surface of the radio telescope from the profile for an ideal paraboloid of rotation under all conditions is ‘2 mm [28]. The reflecting surface is formed of the central part of the dish, with a diameter of 3 m, and 27 radial petal segments, which open synchronously in orbit. A general schematic of the components of the SRT in the Spektr-R spacecraft is presented in Fig. 1. The main structural elements of the dish are the following: --focal module truss (serves to regulate the position of the feedhorns); --reflector truss (fastens the focal module to the focal container); --cylindrical compartment (designed to fix the central dish and the reflector-petal opening mechanism, and also to house the two onboard hydrogen masers); --a transitional truss between the SRT and the Navigator service module (used for the installation of the scientific-equipment container). The petal positions were aligned on the ground before launch, to allow the creation of the precision reflecting surface upon deployment. This was carried out in two stages. In the first, each petal was adjusted individually using adjustment screws at 45 points on a specialized weight-unloading support, taking into account the mass and the position of the axis of rotation of the petal. In the second, the positions of the petals were aligned after assembling the reflector, by varying the lengths of struts fixed to the positions of the petals in the open state. The central dish was fixed on a cylindrical compartment using nine regulating support units. Measurements showed that, after the alignment on the ground, in the presence of backlash and taking into account uncertainties in the manufacture and weight distribution, the maximum deviation of the reflector surface from the theoretical shape of a paraboloid did not exceed ‘1 mm. A thermal regulation system (TRS) for the petals, cylindrical compartment, focal and scientificcontainers, focal unit, and onboard hydrogen masers was designed, to ensure reliable functioning of the instrumentation complex and minimization of thermal structural deformations [29]. A cold plate with the blocks of LNAs for the 1.35, 6.2, and 18-cm receivers
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mounted on it was connected to the antenna-feed assembly (AFA) and installed in the focal unit of the SRT; the TRS radiator of the cold plate was installed in the shaded side of the focal container (Fig. 1). The TRS of the cold plate was designed to provide the required thermal regime for the LNAs and the central part of the AFA: maintaining the temperatures of the LNA sites between 125 and 155 K, and the sites of the antenna feeds (for 1.35, 6.2, and 18 cm) between 150 and 200 K, throughout the normal operation of the SRT. The geometrical area of shadowing of the SRT dish by the TRS cold-plate radiator does not exceed 1 m2 . The maximum thermal energy deposited onto the cold plate from the LNAs is no greater than 0.3 W. Heat flow due to thermal connections with other structural elements of the SRT is from 5 to 15 W (this varies primarily with the position of the SRT relative to the Sun). There is a thermal connection between the LNAs and AFA along waveguides and cables. According to housekeeping data, the temperature regimes for the cylindrical compartment, containers, focal unit, and onboard hydrogen masers of the SRT in flight correspond to the projected requirements.

2.2. Onboard Science Complex
The onboard science complex was constructed starting in 1985, as a collaboration between Soviet and foreign organizations. This was carried out in accordance with the general technical requirements for the design of scientific equipment for the SpektrR spacecraft and the technical specifications for the specific scientific instruments developed by the lead organization for the RadioAstron project--the Astrophysics Division of IKI, which became the Astro Space Center of the Lebedev Physical Institute in 1990. The spacecraft was designed at the Lavochkin Association. The first onboard receivers began to be delivered to the ASC in the early 1990s. Ground radioastronomical tests of the SRT were carried out at the PRAO in 2003í2004 (see Fig. 4b in the color insert), and acceptance tests of the entire onboard complex of scientific and service instruments together with the spacecraft were conducted in 2009í2011. A functional schematic of the onboard science complex is presented in Fig. 2. The science complex consists of the following instruments and blocks, located in the corresponding modules, shown in Figs. 1 and 2. (1) The block of co-axial antenna feeds operating at the radio-astronomy bands 1.35, 6.2, 18, and 92 cm in right- and left-circular polarizations is located in the thermally stabilized, cooled focal unit of


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Focal container Radiator for thermal regulation of the cold plate Focal-module truss Focal unit Antenna-feed assembly Support ring with petal lock system Support rods Central dish surface Reflector petals

Spacer base Petal opening mechanism Narrow-beam antenna High-information radio complex Transitional truss Scientific-equipment container Hydrogen frequency standard Wide-beam antenna Navigator basic module

Fig. 1. Arrangement of the SRT in the Navigator basic module.

the focal module, together with the LNA blocks for the 1.35, 6.2, and 18-cm receivers. (2) The radio-astronomy receivers operating at the four wavelengths indicated above, for both incident polarizations (denoted RAR in Fig. 2; with individual sources of secondary electric power) are located in the refrigerated, hermetic focal container. The 92-cm LNA is located inside the 92-cm receiver. Structurally, the 92-cm receiver is joined to the block containing the pulse phase calibration units for all the receiver wavelengths. The output signals of the receivers at the intermediate frequency (IF) arrive at the IF selecter, which patches the output IF signals to the corresponding input frequency converters of the formatter for further conversion to lower frequencies. The focal container also houses a frequency generator, consisting of two heterodyne ultra-high frequency generator blocks (HUHF Gen-1 and 2) with their sources of secondary electrical power and two analysis and control units (ACU-F) with a powerswitching unit (Fig. 2).

(3) Two onboard hydrogen frequency standards (OHFSs; H maser in Fig. 2) and the (scientific) instrument container are installed in the instrument module. Two onboard rubidium frequency standards (ORFS; Rb standard in Fig. 2), a frequency generator with a double block forming the heterodyne and clock frequency generator (HCF Gen.) and two associated power sources, two analogídigital converters for the signals from the formatter block, and the two analysis and control units of the scientific container (ACU-I) with their power supplies are housed in the thermally stable, hermetic scientificcontainer. The Spektr-R sattelite with the SRT onboard is a unique piece of space science instrumentation. The entire complex of onboard equipment and the telescope are designed for a single task: multi-frequency observations of very weak radio emission at centimeter and decimeter wavelengths located far below the intrinsic noise levels of the receiver systems, and the multi-stage conversion of these signals with the very highest available phase stability into a videoband from 0 to 16 MHz, providing high-speed recording and
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Co-axial antenna feedhorns (AFA SRT) Focal unit
AO1.35 AO-92 AO- AO-18 6

LNA 1.35 cm 2-channel 1.35-cm RAR, K-band Power supply ACU-F
TM control Commands

LNA 6 cm 2-channel 6-cm RAR, C-band

LNA 18 cm 2-channel 18-cm RAR, L-band 2-channel 2-chan92-cm LNA+ nel RAR, P-band PCB

HUHF Gen.

Commands

IF selecter Focal container

ACU-I Power supply HCF Gen. "I"
5 MHz-Rb TM control

Formatter-1 Instrument container

Formatter-2

"Q"

"I"

"Q"

Rb standard (ORFS-SRT)

15 MHz-PLL

5 MHz-÷

H maser (OHFS-SRT)

HDRRC PLL
8.4 GHz

ADT 15-GHz-1

ADT 15-GHz-2

15 MHz-÷

7.2 GHz

HDRRC UD tracking antenna

Fig. 2. General block schematic of the SRT. LNA represents a low-noise amplifier; FM TRS, the focal-module thermalregulation system; RAR, a radio-astronomy receiver; PCB, the pulsed phase-calibration block; IF, an intermediate frequency; TM, telemetry; Rb standard, the rubidium frequency standard; H maser, the onboard hydrogen frequency standard (two copies); HCF Gen., the heterodyne and clock frequency generator; HUHF Gen., the heterodyne ultra-high frequency generator; ACU-F and ACU-I, the analysis and control units for the focal and instrument containers, respectively; HDRRC, the high-data-rate radio complex; PLL, the phase link loop; I and Q, the interferometric data fluxes in these Stokes parameters; ADT 15-GHz-1 and 2, the astronomical data transmitters at 15 GHz; UD tracking antenna, the two-dish, unidirectional, 1.5-m HDRRC antenna.

transmission of the onboard data on the Earth. To successfully carry out this task, all