## 4 Conclusions  
The current progress in the development of new subTHz instruments, such as antennas, gyrotrons, and receivers, allows some very ambitious applications to be implemented. In particular, tasks such as mapping the lunar surface or locating space debris can be conducted at a much higher resolution when the instruments are located in places with satisfactory microwave astroclimate, as shown in the present work.  
Estimations of possible locations for subTHz instruments in Eurasia made by analysis of space and meteo data have revealed some promising sites, including those that will enhance the EHT coverage. However, all these locations are not as good as the record-breaking radio astronomy sites of the southern hemisphere, and additional studies are required for better estimation of subTHz instrument prospects in northeastern Eurasia. The expeditionary measurements presented here confirmed good prospects for some locations in Dagestan. Based on the performed measurements of atmosphere propagation, corrections to the current plan of the Suffa project have been outlined. It has been proved that it would be much more practical to install a relatively small (15-21 m) high-quality (RMS \(<\) 50 \(\upmu\)m) mirror, which would ensure efficient operation in the 1.3 and 0.8 mm transparency windows on the slope of the neighboring Aktashtau mountain (3200 m) to add it to the main 70 m antenna of the Suffa observatory built on the plateau at 2400 m. RT-70 should be operated only with cm and mm waves not shorter than 3 mm.  
Simulations of the radar and telecommunication systems' performance under atmospheric conditions allow us to adjust existing plans of the new antennas and predict more conclusively the plausibility of such instruments as space debris surveillance radars or deep-space communication hubs, at the same time taking into account the advent of extremely powerful gyrotrons and low-noise superconducting receivers presented in this article.  
Conceptualization, M.G.; Data curation, S.S.; Formal analysis, K.M.; Investigation, G.B., A.G., D.D., I.L., A.M. and A.K.; Project administration, G.D.; Supervision, Y.B. and G.S.; Writing--original draft, V.V. All authors have read and agreed to the published version of the manuscript.  
Figure 9: (**a**) Dagestan, Miskindja, Mount Shalbuzdag, 4142 m. (**b**) Measurements at \(\lambda\) 3 mm \(\tau\) = 0.07–0.1 NP at 3600 m and at 2900, respectively, at \(\lambda\) 2 mm \(\tau\) = 0.07–0.12 NP at 3600 m and at 2900, respectively, 7 November 2021. In terms of the water vapor level, it corresponds to a very impressive PWV 2–4 mm.  
**Funding:** This work was supported by the Russian Science Foundation (RSF), Project # 19-79-30071.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The authors are very grateful to [PERSON] and [PERSON] for useful discussions. The authors are grateful to the management and staff of the Dagestan and Vladikavkaz scientific centers of RAS, SAO RAS, IAP RAS, Kh. I. Ibragimov Complex Research Institute RAS, Alexeev NNSTU and Lebedev PI RAS for kindly providing the research equipment and assistance in conducting expeditions.  
**Conflicts of Interest:** The authors declare no conflict of interest.