Peter M. Zemlyanukha

In recent years, Russia has been actively searching for and studying the astroclimate of potential sites for a large millimeter/submillimeter (MM/subMM) telescope, including as part of the Eurasian Submillimeter Telescopes (ESMT) project. To this end, suitable sites were identified and new astropoints were established in northern Eurasia between 2021 and 2023: Khulugaysha Peak (Eastern Sayan Mountains), Kurapdag Mountain in the Agulsky District of Dagestan, and the Tashanta APT in the Altai Republic. The astronomical site of the Large Alt-Azimuthal Telescope (BTA, Pastukhova Mountain) was selected as reference location for comparing atmospheric characteristics. The new astropoints are characterized by low values of precipitable water vapor and total cloud cover. Meteorological measurements indicate a high frequency of weak surface wind gusts in the villages of Tashanta and Khulugaysh, as well as regular gusts exceeding 30 m/s near Mount Kurapdag. As alternatives to Mount Kurapdag, we consider Mount Jufudag in the Agulsky District and the high-mountain Shunudag Plateau in the Kulinsky District of Dagestan. This paper compares the astroclimatic conditions of Mount Jufudag and the Shunudag Plateau with those of Mount Kurapdag, Mount Pastukhova and other astropoints. Maps of precipitated water vapor, total cloud cover, and wind gust speed for the North Caucasus were obtained using Era-5 reanalysis data, and their median estimates are provided, taking into account the terrain. The mesoscale WRF model was used to achieve greater map detail. The paper presents the first results of measurements of optical thickness and precipitated water vapor in the area of Mount Jufudag and the Shunudag plateau, obtained using a two-channel radiometric atmospheric transparency meter IPAR-2 in March-April 2025. The first results of measurements of meteorological parameters and astronomy seeing in the area of Mount Jufudag using an ultrasonic weather station and Polar-2 optical monitor are presented.

The paper examines radiometric methods for determining the optical thickness of the atmosphere and precipitated water vapor. The paper presents the first results of measurements of the radio brightness temperature of the atmosphere Tb, atmospheric transmission and precipitated water vapor (PWV) at the locations of RATAN-600, BTA and ZTSh using a two-channel atmospheric radiometer IPAR-2. Good convergence of the results of direct radiometric measurements of precipitated water vapor with PWV estimates obtained from moisture profiles and specific moisture content of the surface layer atmosphere is shown. Further plans for measuring atmospheric transmittance and PWV around Mt.Jufudag in the Agulsky district of Dagestan are presented.

Present survey is a continuation of our research of high mass star forming regions in the lines of deuterated molecules, the first results of which were published in [1]. This paper presents the results of observations of 50 objects in the line of ortho modification of singly deuterated ammonia NH 2 D 111s-101aat frequency 85.9 GHz, carried out with the 20-m radio telescope of the Onsala Space Observatory (Sweden). This line is detected in 29 sources. The analysis of obtained data, as well as the fact that gas density in the investigated sources, according to independent estimates, is significantly lower than the critical density for this NH 2 D transition, indicate non-LTE excitation of NH 2 D. Based on non-LTE modeling estimates of the relative content of the NH 2 D molecule and the degree of deuterium enrichment were obtained, and the dependencies of these parameters on temperature and velocity dispersion were analyzed with and without taking into account detection limits assuming the same gas density in all sources. An anticorrelation between the NH 2 D relative abundances and the kinetic temperature is revealed in the temperature range 15–50 K. At the same time, significant decrease in the ratio of the NH 2 D/NH 3 abundances with increasing temperature, predicted by the available chemical models, is not observed under the adopted assumptions. An anti-correlation was also revealed between the relative content of the main isotopologue of ammonia NH 3 and the velocity dispersion, while no statistically significant correlation with the kinetic temperature of sources in the same temperature range was found.

This article presents the results of evaluating the possibility of conducting radio astronomy studies in the windows of atmospheric transparency ~100, ~230, and ~350 GHz using the optical Big Telescope Alt-Azimuthal (BTA) of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). A list of some promising astronomical tasks is proposed. The astroclimat conditions at the BTA site and possible optical, cryogenic, and mechanical interfaces for mounting a superconducting radio receiver at the focus of the optical telescope are considered. As a receiving system, arrays of detectors cooled to ~0.3 K based on the superconductor–insulator–normal metal–insulator–superconductor (SINIS) structure are proposed. The implementation of the project will make it possible to use the BTA site of the SAO RAS not only to solve some astronomical problems (it is possible to consider the implementation of a single observatory, the VLBI (very-long-baseline interferometry) mode in the Suffa, EHT (Event Horizon Telescope), and Millimetron projects), but it will also be used to test various cryogenic detectors in a real observatory.

The article presents the results of evaluating the possibility of conducting radio astronomy studies in the windows of atmospheric transparency ~100, ~230 and ~350 GHz using the optical Big Telescope Alt-Azimuthal (BTA) of the SAO RAS. A list of some promising astronomical tasks is proposed. The astroclimat conditions at the BTA site and possible optical, cryogenic and mechanical interfaces for mounting a superconducting radio receiver at the focus of the optical telescope are considered. As a receiving system, arrays of detectors cooled to ~0.3 K based on the Superconductor – Insulator – Normal metal – Insulator – Superconductor (SINIS) structure are proposed. The implementation of the project will make it possible to use the BTA site of the SAO RAS not only to solve some astronomical problems (it is possible to consider the implementation of a single observatory, the VLBI mode in the Suffa, EHT and Millimetron projects), but will also be used to test various cryogenic detectors in a real observatory.

Radio astronomical observations at millimeter and submillimeter wavelengths are a very important tool for astrophysical research. However, there is a huge area in northeastern Eurasia, including the whole Russian territory, which lacks sufficiently large radio telescopes effectively operating at these wavelengths. In this review, we describe our long-term efforts to find suitable sites for such radio telescopes in this area, that is, sites with good atmospheric transparency at millimeter and submillimeter waves. We describe methods and instruments used for measurements and evaluations of the atmospheric opacity. They include special radiometric systems, which are used for estimations of the atmospheric opacity in the transparency windows from the sky brightness measurements. Evaluation of the precipitable water vapor from such measurements by the artificial neural network is discussed. Other approaches use water vapor radiometers, global atmospheric models and signals of the Global Navigation Satellite Systems. To date, long-term radiometric monitoring has been performed at several candidate sites, and atmospheric conditions for many sites have been evaluated using global atmospheric models. Several sites with the best atmospheric transparency at millimeter and submillimeter wavelengths have been selected. They can be effectively used for astronomical observations, at least in the major atmospheric transparency windows at 1.3 mm and 0.85 mm. In general, the results show that northeastern Eurasia is a promising area for submillimeter astronomy. These results can also be used for space communications and radar systems.