We are presenting results of the atmospheric propagation observations which our research group has been conducting since 2012. Over this time, we have gathered statistical data of atmospheric propagation over a number of sites which possibly can be used for radio astronomical observations in the millimetre and sub-millimetre bandwidths. The Zenith opacity was studied by the atmospheric dip method in the 3 mm and 2 mm atmospheric windows. The dataset is recommended to use for estimation of atmospheric propagation for the purpose of radio astronomy and telecommunications. The “tau-meter” (named MIAP-2) allows us to estimate an integral absorption by using the atmospheric dip method. The hardware includes a radiometric system comprising two self-contained radiometers operating in two different bands of 84-99 GHz (λ ~ 3 mm) and 132-148 GHz (λ ~ 2 mm), a rotary support, a control, and a firmware system. The radiometers work in modulation mode within 36 Hz modulation frequency. Floating mirror allows radiometer to scan the sky in the interval of 0 – 88.5 elevation angles (6 total). The output record contains the voltages of synchronous detector for each angle in 2 wavebands. The voltage is proportional to brightness temperature of the sky in corresponding waveband. (It has negative value for technical reasons.) The dataset contains raw data observed by radiometer: Local date and time, a several detector voltages on different elevation angles for 2 wavebands, as well as service information header. The first 6 columns contain optical depth calculated by old method and it’s no more used in data processing since the new algorithm has been invented in 2018.

The work has been supported by: Grant of Ministry of Education by order of the Government of the Russian Federation (contract number 11.G34.31.0029). IEEE Antennas and Propagation Society Eugene F. Knott Memorial Doctoral Research Grants for 2016-17 Russian Fond of Basic Research (RFBR) under the grant number 16-32-0038716 mol_a. Institute of Applied Physics RAS Goverment program 0035-2014-0021. Scholarship issued by RF President [СП-5103.2018.3]. Russian Sciense Foundation under project No 19-19-00499. Presidium RAS Program No. 5: Photonic technologies in probing inhomogeneous media and biological objects. Institute of Applied Physics RAS state program (Project 0035-2019-0005). Institute of Applied Physics RAS state program (Project 0030-2021-0005).