Development of the Ground-based Sub-THz Radio Telescopes

The project for development of the first Russian radio telescope for subterahertz ground-based astronomy on the basis of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS) is presented. Today, the observatory operates two main telescopes: the optical 6-m BTA telescope and the 600-m ring radio antenna RATAN-600. Development of the new parabolic antenna telescope for short mm wavelengths has begun. The project is carried in broad cooperation of academic institutes, universities and industrial enterprises of Russia. The first step involves creating a prototype instrument based on the 6 m BTA optical telescope equipped with a sub- THz radio receiver system. In the next stage we plan to start developing a new generation instrument with an antenna diameter of 15 m, designed to work in the atmosphere transparency window from 0.8 mm to 3 mm that coincides with the working range of the Event Horizon Telescope (EHT). The accuracy of the antenna surface should be better than 40 microns (RMS), which will enable both astrophysical research and use in new telecommunication systems or as a space debris radar. The paper presents the formulation of initial data for the technical specification of the antenna and the study of the microwave climate at different sites selected as possible regions for the new observatory. We also give a set of technical solutions for the main critical elements of the future observatory based at domestic production possibilities. Among them there are the elements of wide-aperture antennas, the telescope pointing and guiding systems, superconducting detectors and superheterodyne receivers, cryogenic systems providing sub-Kelvin temperature levels, hydrogen masers as time/frequency standards for the very long-base interferometry (VLBI).