## 2 Methods and Hardware for Application of subTHz Instruments
### Prospects for Gyrotrons on the Sufffa Antenna for Radar and Telecommunication Applications
The results for the directions close to the zenith direction for the 2500 m elevation (like Suffix) with the atmosphere yield only 500 km for a 3-mm radar. Only low orbits of space debris and satellites are available. If the antenna is installed at sea level, \(r\) becomes about 100 km and makes detection of the object of interest totally impossible. The scenarios for radars at 1.3 mm and 0.8 mm are much worse, and \(r\) is less than the thickness of the atmosphere. A more complex approach can be implemented if we take into account not only the absorption of the atmosphere, but also its scattering and turbulence. It is a main problem of the HUSIR project, and the influence of turbulences should be investigated at specific places of radar antennas. The turbulence patterns are dramatically different in different locations and are the subject of our further research. For the zenith direction, the solutions are obviously the best, and when the ray is inclined towards the horizon, the range of (\(r\)) worsens following the cosine function. At an angle of 60 degrees, the thickness of the atmosphere along the beam doubles, as well as the absorption. When the power is attenuated by 1 dB/km (a familiar figure for long subTHz waves at 3 mm), it is not too critical. For shorter subTHz waves (1.3 and 0.8), the figures are between 10 and 100 dB/km. A double passage of a wave through the atmosphere will cause a drop in the received signal power by 100 dB and decrease the range by a factor of 300. These losses are too significant to provide effective communications, astronomical observations, and, in particular, radar operation. Nevertheless, simulations of the atmospheric conditions typical for high mountains (3-5 km) and the best parameters of the contemporary components of radar systems have been performed and are rather promising. It yields only \(\sim\)7 km of the beam diameter on the Moon's surface for a 3 mm beam and a spatial resolution of \(\sim\)5-7 cm for space debris at the \(\sim\)800 km range. Communication estimates look more optimistic as the signal has to travel through the atmosphere only once. The equation for assessing the communication performance includes only a square root, unlike the radar's fourth root in Equation (3). The operating range increases essentially; actually, one can speak about any distance. Everyone knows of the Voyagers [31] as a brilliant example of deep-space communication. Their data transfer can reach extremely far distances, but with very low data transfer rates, practically bit-to-bit transfer. However, Voyagers traveling since 1977 are now at a distance of 20 billion km (\(\sim\)2 \(\times\) 10\({}^{-3}\) light-years), use a frequency of only 8 GHz, and the 3.5 m antenna is still in contact with the Earth. Let us estimate what messages to extraterrestrial civilizations can be sent using the available gyrotron devices. For example, one can transmit to the Moon at least 500 TV channels simultaneously in a 10 kW CW 3 mm signal and the 4 GHz gain bandwidth. An aggregate of 1000 synchronized gyrotrons with a total power of 2 GW at 160 GHz and a 100 \(\times\) 100 m\({}^{2}\) phase array yields the \(\sim\)10\({}^{8}\) gain compared to that of the Voyagers channel. At this power level, a signal can reach places in the Universe located 4.6 \(\times\) 10\({}^{10}\) light-years from Earth, where there are 500 billion galaxies and \(\sim\)10\({}^{20}\) stars. Indeed, the SETI (Search for Extraterrestrial Intelligence) [24] program is a rather exotic example demonstrating the possibilities of gyrotrons. However, because of high-speed communication with current Martian and future deep-space missions, we have an excellent reason to use subTHz gyrotrons and low-noise cryogenic receivers to increase rates.