Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy.

The objective of this study, named AWARDS (Advanced microWAve Radiometers in Deep space Stations), is the preliminary design of a transmission Media Calibration System (MCS) to be located at an ESA Deep Space Antenna (DSA) site. The crucial aspect is the capability to accurately retrieve the tropospheric path delay along the line-of-sight of the deep space probe in order to allow precise tropospheric calibration of deep space observables (range and range-rate) with particular reference to the BepiColombo spacecraft and its primary DSA at Cebreros (ES). The study focuses on two main aspects which lead to the preliminary design of the Mercury Orbiter Radioscience Experiment (MORE) MCS: the characterization of current microwave radiometers (MWRs) available at ESA/ESTEC and the atmospheric fluctuation effects on the MCS error budget, in terms of the Allan standard deviation (ASD). In the course of the study, further critical aspects have been identified (effects of Sun contamination, effects of ground noise emission), and mitigation strategies have been proposed. The final outcome is a preliminary design of the MWR (and the entire MCS) to be deployed at the ESA/ESTRACK (ESA Tracking station network) sites and being compliant with MORE requirements.

In this work we propose a model for the Probability Density Function (PDF) of the elevation angle and the PDF of the attenuation conditioned to the elevation angle at W-band and in all-weather conditions. The proposed models are suitable to retrieve the PDF of the total attenuation at variable elevation for application to non-geostationary satellite communication links at W-band. The models, based on the Generalized Extreme Value (GEV) distribution, were developed and tested exploiting W-band Sun-tracking microwave radiometer measurements available from two independent measurements campaigns in Milano (Italy) and Rome (New York, USA), the only two datasets available in the world to date. The obtained results are satisfactory with a good agreement between models and measurements and highlighting a potential relationship between the GEV parameters and the local climatology.

In response to the current need for a reliable interference and frequency coordination analysis, especially within the ground segment of satellite systems, atmospheric refraction and terrain diffraction phenomena play a key role from a radiowave propagation point of view. While it is convenient to use an ITU-R model for the case of the atmospheric refraction, several different types of models for terrain diffraction are identified in the literature. On the other hand, only a limited amount of experimental data is globally available to address their performance. This is why we carried out own short-term terrain diffraction measurements at the frequencies from L- to Q-band. During the trials, truck-mounted access platforms reaching up to 46 m above ground level were used and terrain profiles with path lengths from 7 km up to 50 km for various combinations of transmitter and receiver heights were addressed. Based on the obtained experimental dataset, the performance of the delta-Bullington and Deygout models, currently recommended by the ITU-R for the purposes of interference analysis, and the terrain diffraction models based on the UTD and parabolic equation approach has been addressed in terms of the testing variable defined in this paper.

The candidate frequency bands for the extension of the DVB-S2/RCS broadband satellite systems to fully support mobility are the Ku (12/14 GHz) and Ka (20/30 GHz). At these frequencies, rainfall is a significant propagation impairment which has to be taken into account together with other propagation effects due to mobility, such as multipath, shadowing and blockage. Experimental measurement campaigns conducted so far for Ku/Ka-band land mobile satellite (LMS) channels have mainly focused on the characterization of the mobility effects and have not considered any possible relation between the mobility and rainfall effects. However, recent limited work has indicated that these two fading sources are not independent. The present analysis represents a first approximation addressing this open problem. Emphasis is put on the line-of-sight (LOS) state of a Ku/Ka-band LMS channel, which can be modeled by the Ricean distribution and a high K-factor. A novel analytical model relating the Ricean K-factor with the rain fading effects is presented based on which, an analytical prediction model for the distribution of the Ricean K-factor is derived. The proposed analysis is flexible, can be applied on a global scale and incorporate the impact of several important operational, climatic and geometrical parameters of a mobile satellite system on its channel multipath behavior. Useful numerical results are provided, the need for further experimental verification data is pointed out and specific future planned work is also mentioned.