Since the launch of the first geostationary satellite in 1964, Earth-space communications systems have been evolving quickly, even at a faster pace in the last two decades: in recent years, SatCom systems have been extended to include large non-geosynchronous constellations for the provision of broadband worldwide coverage at frequencies in the 20-50 GHz range. The same scenario characterizes space exploration and Earth observation systems, which are enabled by deep space sondes and LEO satellites embarking high resolution sensors and operating in the same frequency band. Almost concurrently with the evolution of Earth-space communication systems, also the world of terrestrial mobile communications has been facing a gradual but constant enhancement, moving from the first analogue generation (1G) to the recent 4^th generation (4G), which is the current standard in several Countries across the world. Nowadays, the 5^th generation (5G) is quickly progressing towards maturity, while the 6^th one (6G) is already a research topic worldwide. While up to the 4G, mobile terrestrial systems have been employing frequencies limited approximately to 5 GHz, the need to support the always increasing demand of data rate and traffic has pushed to use, in 5G networks, the millimeter-wave portion of the spectrum for radio access, specifically carrier frequencies of at least 26 GHz.

As a result, due to the fast increase in wireless systems for both Earth-space and terrestrial communications, the radio frequency spectrum is becoming more and more a precious resource, which has pushed to share several frequency bands among different radio services, and among the different operators of similar radio services. To ensure the satisfactory coexistence of the terrestrial and Earth-space systems involved, it is important to be able to predict with reasonable accuracy the interference potential among them. Several mechanisms typically concur to generating interference, including scattering induced by hydrometeors, on which the PRISM project focuses. This effect can occur whenever tropospheric particles (e.g. rain drops, hail, snow particles, …) fill the volume defined by the intersection of the antenna beams of two links operating at the same frequency: each particle will scatter a part of the impinging electromagnetic power in almost all directions, including the path to the interfered receiver.

In this context the main objective of the PRISM project is to develop a comprehensive model to predict interference due to precipitation scatter, which, in turn, aims at supporting frequency management practices and radio regulatory activities. The model aims at being applicable to diversified scenarios with different characteristics, including: interference between an Earth station for space services (e.g. satellite communications, space exploration and Earth observation) and a terrestrial station that is part of mobile networks (e.g. a base station and terrestrial link); interference induced on a satellite by any terrestrial station part of mobile networks; interference between a satellite and another satellite. The model development will involve the deep investigation of the scattering features of all atmospheric particles and, more in general, of the atmospheric effects impairing the propagation of electromagnetic waves. The model’s accuracy will be tested against radiowave propagation data collected in the framework of a past European Cooperation in Science and Technology Action.

PRISM is funded by the European Space Agency and the project outcomes will be submitted to the Study Group 3 of the International Telecommunication Union – Radiocommunication Sector (ITU-R), focused on radiowave propagation, with the aim of improving the model currently adopted by such standardization body.