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About ASC
ASC Projects:
RadioAstron
Millimetron
Suffa (Uzbekistan)

ASC Divisions:
Moscow Branch
PRAO (Pushchino)
 
RT-70 RADIO TELESCOPE
OF INTERNATIONAL RADIO ASTRONOMICAL OBSERVATORY «SUFFA»
Main scientific objectives and radio telescope parameters.

Below is a list of scientific programs and research areas and the corresponding equipment of the radio telescope. List contains in enlarged form all known areas. Currently, priority is given to the search for new sources through deep surveys using matrix receivers at millimeter and sub-millimeter wavelength ranges, molecular and radio spectroscopy, imaging of compact sources using radio interferometry.
The reflective surface of radio telescope is formed by panels of trapezoidal shape with maximum size of 2.5 by 2 meters; the total number of panels is 1188 of 14 sizes. Panels have a special design that allows using pre-alignment of the reflective surface with on average 50 points with RMS better than 50 microns. To provide the operation of the radio telescope at short millimeter wavelength ranges, the shape of the reflecting surface (parabola) must be maintained during the observation under the action of gravity, wind and thermal deformation with an accuracy of ?/D = 20, i.e., 50-70 microns. To this end, each panel is installed on special electrical jacks in its corners, which are mounted on the frame truss of the telescope. Number of electrical jacks is 1440. During the observation, the control system tracks the position of each panel and, if necessary, adjusts them by their relative position to create the optimal shape of the radio telescope reflecting surface (adaptive method). It is supposed that in the wavelength range of 6 cm - 8 mm the shape of the reflecting surface will be maintained through the use of homologous principle of antenna construction frame truss, and at shorter wavelengths by adaptive method.
The secondary mirror with a diameter of 3 (5) meters has the shape of an ellipsoid of rotation with the five degrees of freedom of movement in space. Depending on the diameter it will be point (3 meters) or of individual panels on the frame. Mirror position control is carried out by computation and control complex.
Periscopic (diagonal) mirror has flat elliptical shape. The size of the major axis is 600 mm. Mirror has four degrees of freedom. Subsequently, it can be made adaptive.
COSMOLOGY AND ASTROPHYSICS
Universe and intergalactic medium. Cosmic background, red shift, chemical composition. Deep surveys.
Short millimeter wavelength range. Continuum, spectroscopy, multi-beam system. Super heterodynes, bolometers, multi-channel spectrometer.
GALAXIES AND ITS STRUCTURE
Star evolution, interstellar medium, dust. Quasars, galactic nuclei, neutron stars, black holes, dark matter. Pulsar, exoplanets.
Whole wavelength range.
Continuum, spectroscopy, multi-beam system. Radio interferometry. Bolometers, super heterodynes, wideband and narrowband spectroscopy analyzers, polarimeters. Wideband recording system. Correlator.
SOLAR SYSTEM
Chemical composition of the giant planets atmospheres, comets and gases from volcanoes on the satellites of the planets.
Millimeter wavelength range
Narrowband spectroscopy.
FUNDAMENTAL ASTROMETRY
Development of high-precision inertial system of celestial coordinates.
Interferometry at centimeter and millimeter wavelength ranges.
COORDINATE AND TIME SUPPORT. GEODYNAMICS.
Earth pole position. Accurate determination of distances.
Interferometry including movable radiotelescopes.
APPLIED TASKS
High precision determination of spacecraft’s coordinates.
Multi-beam system.
MAIN DESIGN PARAMETERS OF RT-70 RADIO TELESCOPE ANTENNA
Primary mirror diameter, m 70
Surface geometrical shape Paraboloid of rotation
Focal length, m. 21
Opening angle, deg. 160
Optical scheme Gregory two mirror system
with periscopic mirror
Wavelength range, λ S - millimeter (λ= 0.87 - 10 mm)
М- centimeter (λ = l - 6cm)
Secondary mirror diameter, m 3 (5)
Geometric shape of the mirror surface Ellipsoid of rotation
Inter focal distance of ellipsoid, m 242
Size of diagonal periscopic mirror, mm 600 mm
Equivalent focus of Gregory system, m 571 (345)
Compensation method of main mirror weight deformations – in the wavelength range M,
- in the wavelength range S
Homologous, active form adjustment («adaptive mirror»)
The standard deviation of the primary mirror deformed paraboloid from approximated shape, mm 0.062
Operating panel profile errors (RMS), m 50
Antenna installation type Full-circle
Base type Tower
Telescope mounting Azimuth, with mutually perpendicular not intersecting axes,
Provided mounting and pointing accuracy at wavelength ranges: M, S, angular sec. <2– by detector «angle-code», 22 rank, <1 - by additional system using guide.
Elevation, m 2324
RT-70 RADIO TELESCOPE MAIN PARAMETERS.
Primary mirror diameter – 70 meters.
The geometric area of the aperture mirror 3848 m^2
Surface accuracy (RMS) 0.07 mm.
Operating wavelength ranges
(In priority: II, III, IV)
I II III IV V VI VII
Average wavelength, (mm) 0.87 1.2 1.9 3.3 7.5 13 61
Frequency range, (GHz) 275-373 211-275 125-211 67-116 26.5-50 18-26.6 4-8
Beam,1.02(λ/D) (")at level of 0.5 2.6 3.5 5.6 9.7 22 38 180
Antenna effective area (m^2) 1350 1350 2000 2000 2700 2700 2700
Antenna aperture efficiency 0.3 0.4 0.5 0.6 0.7 0.7 0.7
Sensitivity (RMS) in µJy (integration time 1 minute /8 hours) 480/20 220/10 140/7 100/5 170/8 560/30 800/40
System noise temperature (Кo) (with 3 mm of precipitated water) 380 230 190 160 110 80 60
Receiver noise temperature (Кo) 100 100 100 100 50 30 10
Maximum receiver bandwidth (GHz) 30 30 30 30 10 2 0.1
The telescope control system consists of electric drive, made using the traditional for radio astronomy antennas scheme, and precision-pointing contour, providing operation at the millimeter wavelength range. Electric drive provides pointing on the source and its tracking with required accuracy and speed. It uses a computation and control complex and digital 22-bit (0."3) feedback sensors, installed on the elevation and azimuth axes, and provides pointing on the source within the RMS of 1 arc seconds including errors in the drive mechanisms, and others. At 1 mm wavelength, calculated radiation pattern of the radio telescope is 3 arc seconds. There is special high-precision pointing system of the electrical axis of the antenna on the observed source, which has a range of angles of ± 10 "from the current direction determined by feedback sensors of electric drive, and provides pointing accuracy not worse than 0.3 arc seconds.

Table 2 shows the operating frequency ranges of the radio telescope. Radiometers will be placed at the primary and secondary focus. In the primary focus the change of radiometers will be done using a fixed service tower, in the secondary – 7 radiometers with the fixed mounting and beam switching is done by periscopic mirror. The set of radiometers and its radio physical characteristics are determined by scientific tasks of observations cycle. Preference is set for short-wave part of the millimeter range, the search of weak sources and deep surveys in the continuous spectrum, polarimetry of cosmological background, molecular radiospectroscopy, rapidly changing processes. Within this range are mainly used bolometers (including bolometers grid) which are cooled down to 4 - 0.3 K and super heterodyne receivers also cooled down to 20 - 40 K.

Gregory telescope optical system has a field of view in the secondary focus of 15'–40', depending on the diameter of the secondary mirror 5–3 m. With the radiation pattern of the 3'', 1000 or more element cooled matrix of bolometers or mixer receivers can be placed in the focus.
COMPARISON WITH OTHER OBSERVATORIES
Sensitivity in the millimeter range of RT-70 will be second after the ALMA observatory, located in Chile at an altitude of 5 km above the sea level, and at wavelengths of 7 mm or more – American VLA and GBT telescopes. However, ALMA is an interferometer, and for a number of tasks a single telescope has important advantages: a large field of view and the ability to use the bolometric receivers. Because of this RT-70 can be a unique tool, which will held the deepest surveys of the sky at millimeter wavelengths and other studies of weak but extended objects.
RESEARCH AREAS
Operating wavelength ranges of RT-70 will allow to study the extremely wide range of astronomical objects: from the bodies of the Solar System to the distant galaxies and the CMB. The key areas can be identified as the following:
  • Studies of the star formation and star evolution and their interaction with the interstellar medium through observations of our galaxy: the interstellar medium of gas and dust clouds, star formation regions, water masers, outflows from stars, pulsars, etc. In general, we refer to the spectral measurement of high-resolution polarimetry. Masers for VLBI observations are possible.
  • Determination of the physical parameters of jets of active galactic nuclei near their central black holes by VLBI observations, including the extra-large space-ground bases.
  • Studying the properties of galaxies with redshifts z>1 and clusters of galaxies, study of their evolution, dark matter distribution and refinement of cosmological models. Photometric deep reviews of galaxies, their redshifts determination from the medium-resolution spectra, observations of the Zeldovich-Sunyaev effects on clusters of galaxies. In addition, the RT-70 can solve many other problems, such as the study of planetary atmospheres, observations of gamma-ray bursts afterglows and supernovae, mapping emission of dust and gas in nearby galaxies, the problem of astrometry and clarification of the coordinate system, etc.
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