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Purpose: High resolution investigation of spectral lines of space sources requires low intrinsic noise of the radio telescope receiving system. It is provided with both input cryogenic amplifiers and low phase noise of local oscillators. To make spectral studies, it is neces ary to be able to tune the frequencies of local oscillators with a small frequency step. The paper presents the results of developing the frequency synthesizers, which simultaneously provide both a very high frequency resolution and low level of phase noise. The results of measurements of natural noise of the RT-32 radio telescope radio receiving systems are given also. Design/methodology/approach: The RT-32 receiving systems are constructed as heterodyne receivers with two stages of frequency conversion. Tuning of receiving systems with a frequency step of 10 or 20 MHz is provided by local oscillators of the first frequency conversion stage, and precise tuning is provided due to the ultra-high resolution 0.0001 MHz) of DDS-based (direct digital synthesizer) local oscillators of the second frequency conversion stage. Findings: It is shown that the application of direct digital synthesizers is possible only with the low values of frequency multiplication factors, as well as under the conditions of careful filtering of all reference signals. The parameters of the local oscillators were measured with the N9951A spectrum analyzer (Keysight Technologies) with the high resolution and wide dynamic range. To measure the radio telescope receiving system noise characteristics, a special matched loads with the possibility of cooling down to the liquid nitrogen temperature were made. The noise temperature measurements were made in different cross sections of the RT-32 receiving system. Comparison of such measurements in different configurations makes it possible to provide a preliminary estimation of the RT-32 self noise in the C- and K-bands. Conclusions: The results of measurements of self noise of radio receiving systems and phase noise of local oscillators of the RT-32 radio telescope show that within the C-band the radio telescope is capable to perform high-sensitive studies in both a wide frequency band and a narrow frequency band with the high spectral resolution. Within the K-band, the natural noise is comparable (≈60÷80 K) with the external noise that also allows studying the radiation of maser radio sources.

Purpose: Technical capabilities of the MARK-4B antenna system necessary for its further using as a 32-meter radiotelescope (RT-32) and making simultaneous spectral radioastronomical observations in the C and K frequency ranges, are investigated. Design/methodology/approach:The studies use the results of our own measurements made with the МАRK-4В antenna system, expert reviews, open information sources, technical documentation of the MARK-4B antenna system, radio astronomy and computer simulation methods and comparative analysis of this antenna main parameters with the corresponding parameters of the world’s best active radio telescopes. Combining different approaches allows us to determine the requirements for the receiving system, parameters of the spectrometer, calibration techniques and optimize the МАRK-4В antenna system modernization procedure. Findings: The radio telescope main parameters required for spectral observations in the C and K frequency ranges are determined. The antenna pointing system capabilities are specified. For the MARK-4B antenna system working frequency range, the main spectral lines of various molecules available for research have been considered. The transitions radiating the most intensive spectral lines are listed. The radio astronomical problems that can be solved using the MARK-4B in the mode of spectral observations are formulated. The required parameters of the spectrum analyzer and the receiver’s self-noise temperature are determined. Calibration techniques of the recorded signal are described, which are necessary for carrying out spectral observations. Conclusions: The here presented studies show that for making spectral observations based on the beam-waveguide MARK-4B antenna system, it is technically possible to create the RT-32 radio telescope with quality technical characteristics corresponding to the world-best analogs. Modernization of the beamwaveguide MARK-4B antenna system will allow at the first stage to create in Ukraine the dual-band radio-telescope permitting to make simultaneous spectral and/or continued observations in the C and K ranges. Henceforth, the amount of simultaneously working ranges can be increased.

Purpose: Creating a radio telescope based on the MARK-4B antenna system being developed for telecommunication applications, determining the possibilities of using the broadband multirange operation of a beam wave-guided antenna system and to evaluate the antenna characteristics using the radioastronomical measurements. Design/methodology/approach: Acomprehensive analysis of all the MARK-4B systems allows to select the blocks and nodes to be replaced or upgraded. The analysis of the reflector and subreflector design, beam wave-guide, corrugated horn, and feeder system allows determining the possible frequency ranges of the radio telescope being created. Installing a broadband receiver with the stipulated calibration capabilities using cooled and uncooled load attenuators allows to determine the antenna system temperature. Guiding the antenna to the calibration sources and recording scans due to the Earth rotation eliminates the systematic errors or errors of the pointing system. In this way the width of the radiation pattern and the effective area of the radio telescope are determined. Findings: An analysis of the antenna design was made and the priority stages of the reconstruction of the MARK-4B antenna system were determined. The narrow-band transmitter and the C-band receiver were dismantled and a wide-band receiver (range 4.6 - 5.1 GHz) with a detector and the possibility of changing the signal integration time were installed. The observed results have allowed to initially estimate the system temperature mea-surements which allow us to hope that the RT-32 radio telescope (Zolotchiv, Lviv region, Ukraine) together with the cooled receiver will have low self noise. A new antenna pointing system has been calculated and installed which using in the C-band has allowed astronomical tests of the radiation pattern width (≈7.2') and the level of its side lobes (–12.5 dB), effective area (≈680 m2) and surface utilization factor (≈0.84). Conclusions: The completed measurements and calculations show that the MARK-4B antenna system allows to createhighly efficient radio astronomy instrument. The developed for now receiving and pointing systems for the RT-32 radio telescope testify to the high potential of Ukrainian science. Further cooperation between scientific research and high technologies will lead to the creation of an effective Ukrainian radio telescope of the centimeter wavelength range.