1. Jessner, A. (2011). Report on Windfarms and RadioAstronomy. Available at http://www.craf.eu/CRAF-11-01.pdf .
2. Jessner, A. (2010). Wind Power and RadioAstronomy. Available at http://www.craf.eu/windturb/Wind%20Power%20and%20Radio%20Astronomy.ppt .
3. Mattsson, S. (2010). Windturbines vs Radiosystems. Available at http://www.craf.eu/windturb/Vindkraft_Chalmers-Onsala_100427.ppt .
4. Bendz, E. (2010). Electromagnetic Interference from Wind Turbines on Onsala Space Observatory. Available at http
V. Bezrukov, A. Berzinsh, G. Gaigals, A. Lesinsh and J. Trokshs
Bezrukovs, V. I. (2010). Preparing VIRAC Radiotelescope RT-32 for receiving and processing the signals related to Artificial Earth Satellites. 40 th Young European Radio Astronomers Conference (YERAC) , Spain, July 5-8.
Bezrukov, D., & Ryabov, B. (2009). Prospects of solar microwave observations at the Ventspils radio-astronomy centre. Latv. J. Phys. Tec. Sci. , (5), 13-18.
Sika, Z., Bezrukov, D., Bezrukov, V., & Bondarenko, V. (1997). Reconstruction of the movement
Prospects of Solar Microwave Observations at the Ventspils Radio-Astronomy Center
The paper concerns the prospects, technical issues and unique possibilities of solar microwave observations using the RT-32 radio telescope of the Ventspils International Radio-Astronomy Center. The solar physics tasks are discussed that are to be solved based on the observations of the large-scale coronal structures and radio flux fluctuations of as well as the magnetic structure of solar active regions.
Sabine Upnere, Normunds Jekabsons, Roberts Joffe, Valerijs Bezrukovs and Vladislavs Bezrukovs
Analysis of Wind Influence to Radio Astronomy Observations at Irbene Radio-telescope Complex
The results of modelling wind-related deformations in an RT-16 radio telescope (located at Irbene, Latvia) mirror system are presented. The Finite Volume method is used for the development of a Computational Fluid Dynamic model of turbulent airflow around the telescope. An open sourced Computational Fluid Dynamic toolkit OpenFOAM is used for the solution of Partial Different Equations. Notable model difficulties arise due to the open nature of the air flow leading to unknown far field turbulence parameters. Our future plans are to create a unified, coupled, liquid-solid interaction model for RT-32/RT-16 antennas.
In the present paper, recent measurement results of refurbished Irbene RT-16 radio telescope receiving system performance are presented. The aim of the research is to evaluate characteristics of RT-16, which will allow carrying out necessary amplitude calibration in both single dish and VLBI observations, to improve the performance of existing system as well as to monitor, control and compare performance if possible changes in the receiving system will occur in future. The evaluated receiving system is 16 m Cassegrain antenna equipped with a cryogenic receiver with frequency range from 4.5 to 8.8 GHz, which is divided into four sub-bands. Multiple calibration sessions have been carried out by observing stable astronomical sources with known flux density by using in-house made total power registration backend. First, pointing offset calibration has been carried out and pointing model coefficients calculated and applied. Then, amplitude calibration, namely antenna sensitivity, calibration diode equivalent flux density and gain curve measurements have been carried out by observing calibration sources at different antenna elevations at each of the receiver sub-bands. Beam patterns have also been evaluated at different frequency bands. As a whole, acquired data will serve as a reference point for comparison in future performance evaluation of RT-16.
One of the main research directions of Ventspils International Radio Astronomy Centre (VIRAC) is radio astronomy and astrophysics. The instrumental base for the centre comprised two fully steerable parabolic antennas, RT-16 and RT-32 (i.e. with the mirror diameter of 16 m and 32 m). After long reconstruction, radio telescope RT-32 is currently equipped with the receiving and data acquisition systems that allow observing in a wide frequency range from 327 MHz to 9 GHz. New Antenna Control Unit (ACU) allows stable, fast and precise pointing of antenna. Time and frequency distribution service provide 5, 10 and 100 MHz reference frequency, 1PPS signals and precise time stamps by NTP protocol and in the IRIG-B format by coaxial cable.
For the radio astronomical observations, main requirement of spatially Very Long Base Line Interferometric (VLBI) observations for the observatory is precise synchronization of the received and sampled data and linking to the exact time stamps. During October 2015, radio telescope RT-32 performance was tested in several successful VLBI experiments. The obtained results confirm the efficiency of the chosen methods of synchronization and the ability to reproduce them on similar antennas.
The microwave regions with low brightness temperature are found to overlap the regions of the depressed coronal emission and open field lines at the periphery of two solar active regions (ARs). The imaging microwave observations of the Sun with the Nobeyama Radio heliograph at 1.76 cm, the MRO-14 radio telescope of Metsähovi Radio Observatory at 0.8 cm, and the RT-32 of Ventspils International Radio Astronomy Centre in the range 3.2-4.7 cm are used. To reduce the noise in the intensity distribution of the RT-32 maps of the Sun, one wavelet plane of “à trous” wavelet space decomposition is subtracted from each map. To locate the open-field regions, the full-Sun coronal magnetic fields with the potential field source surface (PFSS) model for RSS = 1.8 Rʘ are simulated. We conclude that the revealed LTRs present narrow coronal hole-like regions near two ARs and imply an extra investigation on the plasma outflow.
Application of Recovering Procedures to RT-32 Radio Maps of the Sun
The generalized maximum entropy method (GMEM) is proven to recover both positive and negative local microwave sources on the 2.7 cm maps of the Sun taken with the radiotelescope RT-32 of the Ventspils International Radio Astronomy Center (VIRAC). The maps of the Sun need to be recovered due to high intensity of the side lobes of the RT-32 diagram pattern - up to 30% at 2.7 cm. The presence of negative local sources associated with Hα filaments is inferred from the 2.7 cm maps of the Sun (RT-32) compared with the 1.76 cm maps of the Sun (Nobeyama Radio Heliograph).
The basic application of RT-32 and RT-16 parabolic antennas is radio astronomy observations, both the radio-telescopes have been upgraded with state-of-the art cryogenic receivers, and now a large-scale modernization of the infrastructure is underway. Since the radio-astronomical observations are not full-time activities, a research work has been done to clear up whether these antennas, besides the mentioned activities, can be used as a satellite ground station. The main goal of this added functionality is to make possible the use of the extremely high reception systems’ figure-of-merit thus raising the satellite downlink data rates without increasing the on-board power consumption, which would be particularly important for developers of small satellites. In this paper, the progress in the research project is reported, which includes successful S-band satellite signal reception experiments and possible options as to integration of the related equipment into the system so that both functionalities could successfully coexist. Performance of the existing and the upgraded antenna positioning systems is estimated to determine if the latter are usable even for servicing low-Earth orbiting satellites. In addition, possible options are considered as to upgrading the system with automatic beam tracking capability, which would increase the antenna pointing accuracy even further.
R. Joffe, N. Jēkabsons, A. Bērziņš, M. Klapers and S. Upnere
The main objective of the work was to analyze the operation of the large radio telescope RT-32 at the Ventspils International Radio Astronomy Centre (VIRAC). The analysis has been performed in order to evaluate dimensional changes in the RT- 32 structural base due to reorientation of the antenna mirror. Three different orientations of the dish were considered, and the dimensional changes in the load carrying substructure were measured. The measurements were made to estimate possible effect of the geometrical changes of the antenna due to gravitational loads on the overall performance of the radio telescope with respect to the obtained astronomical results, their accuracy and validity. Comprehensive mapping and classification of the corrosive damage of steel elements in the antenna have been done. A preliminary numerical analysis by the finite element method was carried out to demonstrate the overall effect of the damaged steel beams on the geometrical distortion of the antenna surface.