Measurements and Evaluations of the Atmospheric Transparency at Short Millimeter Wavelengths at Candidate Sites for Millimeter- and Sub-Millimeter-Wave Telescopes

Abstract

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.

Cryogenic Systems for Astronomical Research in the Special Astrophysical Observatory of the Russian Academy of Sciences

“…SAO RAS does not have an exceptional astroclimate [18,19], and the altitude above sea level is not very significant: BTA is at an altitude of 2100 m, and RATAN-600 is at an altitude of 970 m. The astroclimate is quite satisfactory for observations in the entire radio range of RATAN-600 observations down to millimeter waves. The location of BTA has a satisfactory astroclimate in the optical and near-infrared ranges.…”

“…At the same time, the astroclimate studies [18,19] make it possible to work reliably in the two lower sub-THz transparency windows (3 mm and 2 mm) without any problem. There are reliable and rather long periods in winter when there is good atmospheric quality of around 0.1 Np absorption at the zenith in the 1.3 mm transparency window.…”

Design and Simulation of Tunneling Diodes with 2D Insulators for Rectenna Switches

“…As telecommunication is entering into the 5G and soon 6G era, both a fast response and a large bandwidth are needed, pushing the limit of frequency toward the high end of the RF range (>100 GHz) [5]. For example, millimeter waves and terahertz signals will be used in 6G technology [6,7]. The 100 GHz signal demands 10 ps in response time, approaching the limit in transit time for an electron to diffuse across a silicon PN junction diode.…”

Design and Simulation of Tunneling Diodes With 2D Insulators for Rectenna Switches

“…As telecommunication is entering into the 5G and soon 6G era, both a fast response and a large bandwidth are needed, pushing the limit of frequency toward the high end of the RF range (>100 GHz) [5]. For example, millimeter waves and terahertz signals will be used in 6G technology [6,7]. The 100 GHz signal demands 10 ps in response time, approaching the limit in transit time for an electron to diffuse across a silicon PN junction diode.…”