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Summary: Since 2009, ONERA has been running Ka band propagation experiments in Toulouse (France, latitude 43.57°N, longitude 1.47°E). A rain gauge was also deployed on site to collect rainfall rate measurements concurrently to beacon data. Since April 2011, the beacon receiver has been recording the 20.2 GHz (vertical polarisation) Astra 3B beacon signal along a slant path of 35.1° of elevation angle. All years of the experiment had excellent data availability, hence giving 12 years of data at Ka band. First, the propagation experiment and the data processing methodology are described. Second, a statistical analysis of rain attenuation and rainfall rate is conducted. Comparisons are then performed with the prediction methods of Recommendations ITU‐R P.837‐7 (rainfall rate), P.618‐13 (rain attenuation) and P.678‐3 (variability of propagation phenomena). [ABSTRACT FROM AUTHOR]

This paper highlights the interest of using an Atmospheric Numerical Simulator (ANS) relying on a high resolution weather forecast model coupled with an ElectroMagnetic Module to compute Ka‐band rain attenuation statistics in an equatorial region. An optimization of the parametrization of the Weather Research and Forecasting meteorological model (WRF) is carried out using measurements collected from a propagation experiment carried out by Centre National d'Études Spatiales and Office National d'Études et de Recherches Aérospatiales near Kourou in French Guiana. Both simulated and experimental annual Complementary Cumulative Distribution Functions of rain attenuation are presented and compared. An additional comparison to the rain attenuation prediction method of Rec. ITU‐R P.618‐13 is presented to evaluate the potentialities of the WRF‐EMM ANS to produce synthetic propagation statistics in equatorial regions. Key Points: Simulation of rain attenuation statistics in an equatorial region based on a meteorological modelAn optimization of the meteorological model is presented to obtain a better reproduction of the propagation channelThe long term statistics of rain attenuation compare better than the method of reference to the experimental data [ABSTRACT FROM AUTHOR]

From January 2017 to December 2021, Office National d’Etudes et de Recherches Aérospatiales (ONERA) and Centre National d’Etudes Spatiales (CNES) operated a beacon receiver able to record the 20.1995 GHz beacon signal of the Amazonas-3 satellite at the Guiana Space Centre in Kourou, French Guiana. A rain gauge was also deployed on site to collect rainfall rate measurements concurrently to beacon data. All years of the experiment, except 2019, had excellent data availability, hence giving four full years of data (2017, 2018, 2020, and 2021). First, the climatic characteristics of French Guiana are shown. Second, the propagation experiment and the data processing methodology are described. Third, the results of the statistical analysis are highlighted and commented. Comparisons are performed with the prediction methods of Recommendation ITU-R P.837-7 (rainfall rate), Recommendation ITU-R P.618-13 (rain attenuation), Recommendation ITU-R P.678-3 (variability of propagation phenomena), and Recommendation ITU-R P.1623-1 (fade dynamics). [ABSTRACT FROM AUTHOR]

Current spatial resolutions achieved by mesoscale weather forecast models allow them to be used to generate the state of the lowest layers of the atmosphere over areas as small as a few square kilometers which corresponds to the typical size of the tropospheric area crossed by Earth-space links. Furthermore, they allow the evolution of the troposphere to be predicted with a time stamp of five minutes instead of every hour with large-scale weather forecast models which makes them attractive for radio propagation predictions for satellite communication applications. This paper aims at studying the capability of the Weather Research and Forecast (WRF) model coupled with an electromagnetic physical model to reproduce rain attenuation statistics for Earth-space paths at Ka-band. To this purpose, one year of propagation measurements collected at 20 GHz in different places at midlatitudes in Toulouse and Salon de Provence (France), Spino d'Adda (Italy), Aveiro (Portugal), and Madrid (Spain), at high latitudes in Svalbard (Norway) and at low latitudes in Kourou are used to make comparisons between simulations and measurements. Comparisons between the simulated and the experimental annual statistics considered in this paper provide encouraging results, with a similar accuracy as Recommendation ITU-R P.618–13 for midlatitude European locations and with better accuracy for a high latitude area in Svalbard and for an equatorial location in French Guiana. [ABSTRACT FROM AUTHOR]

Summary From January 2008 to March 2011, ONERA operated in Toulouse, France, a beacon receiver able to collect the 19.7‐GHz beacon signal of the HotBird 6 satellite. In March 2011, the radio frequency chain was modified to be able to receive the 20.2‐GHz ASTRA 3B beacon to benefit from a higher Equivalent Isotropically Radiated Power of the satellite. Since June 2015, a second beacon receiver has been installed and is able to record the 39.4‐GHz beacon signal of the Alphasat satellite. The objective of this paper is to present the results of the first 2 years of measurements (June 2015 to May 2017) of the Q‐band Alphasat propagation experiment in Toulouse, as well as concurrent measurements collected at Ka‐band with ASTRA 3B. First of all, the propagation experiments are briefly described. Second, the results of the statistical analysis are highlighted. Finally, a deep analysis of the performances of the 2 frequency scaling prediction methods recommended in ITU‐R P.618‐13 is performed. [ABSTRACT FROM AUTHOR]

ONERA, the French Aerospace Lab, and CNES, the French Space Agency, are currently running a Ka-band propagation experiment at the Guiana Space Centre (CSG) in Kourou (French Guiana). A rain gauge and a beacon receiver able to record the 20.2 GHz beacon signal of the Amazonas 3 satellite have been deployed. The equipment is operational since January 1, 2017, and the duration of the experiment has been set to three years. This letter addresses some results of the first year of measurements (from January 2017 to December 2017). The annual and monthly complementary cumulative distribution functions of rainfall rate and rain attenuation are presented as well as a comparison with the rain attenuation prediction method recommended in ITU-R P.618-13. [ABSTRACT FROM AUTHOR]

Since April 2011, ONERA has been operating in Toulouse, France, a beacon receiver able to receive the 20.199 GHz beacon signal of ASTRA 3B. From June 2013 to December 2013, ONERA and CNES successively deployed in the South of France four more beacon receivers in order to characterize the space-time behaviour of the propagation channel at Ka-band. This Site Diversity configuration is of great interest for the development of future high data rate satellite services as it efficiently mitigates severe tropospheric propagation impairments, in particular rain attenuation which is the major issue. The ONERA-CNES Ka-band site diversity experiment consists of three beacon receivers deployed in the area of Toulouse with site separation between 16 and 26 km, and two additional beacon receivers at 140 km and 300 km from Toulouse. This paper aims at providing a complete description of the experimental set-up and the statistical results of the campaign from July 2013 to December 2014. The Complementary Cumulative Distribution Functions (CCDF) of rain attenuation on each site and the Joint Distributions for several pairs of radio links are illustrated. Some comparisons of the measured Diversity Gain with two state-of-the-art prediction models are also presented. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Three global rainfall rate prediction methods are evaluated in their ability to estimate local precipitation statistics, which are the key to predict the impact of rain on the propagation of electromagnetic waves through the atmosphere. Specifically, the International Telecommunication Union-Radiocommunication Sector (ITU-R) P.837-6, model for rainfall statistics estimation (MORSE), and the ITU-R P.837-7 prediction methods are tested against long-term rainfall data collected in 19 sites in Ireland. The results indicate that the ITU-R P.837-7 prediction method delivers the best performance, and that both the ITU-R P.837-6 prediction method and MORSE exhibit a positive bias, likely due to the overestimation of the yearly rain amount in the maps used as input to such models. The results of the testing activity provide information on the accuracy of rainfall rate prediction methods at regional level, an important factor to consider given the direct link between the magnitude of rain-induced attenuation, and the operational frequency of wireless communication links. [ABSTRACT FROM AUTHOR]

The Ka-band propagation experiments conducted by ONERA in Toulouse (43.57°E, 1.47°N) in the southwest of France started in 2009 and is still on-going. The equipment comprises a beacon Earth station, a profiling radiometer, and a rain gauge. The ground station measures the received beacon signal using a 10-Hz sampling rate. The profiling radiometer measures the sky brightness temperatures at five Ka-band and seven V-band channels, surface temperature, surface humidity, and surface pressure. From July 2009 to March 2011, the beacon receiver recorded the 19.7-GHz (horizontal polarization) HotBird 6 beacon signal along a slant path of 38.6° of elevation angle. Since April 2011, the beacon receiver has been recording the 20.2-GHz (vertical polarization) Astra 3B beacon signal along a slant path of 35.1° of elevation angle. This paper aims at providing a complete description of the ONERA Data Processing Tool (in particular the methodology followed to retrieve total attenuation) used to compute 4 years (from July 2009 to June 2013) of copolar attenuation statistics. The experimental setup and the characteristics of the Earth-space links are briefly described. The complementary cumulative distribution function (CCDF) of total attenuation for the whole period is presented and compared with ITU-R recommendations. The measured CCDF of the rainfall rate is computed and compared with ITU-R Rec. P.837 and will also be used as input for the rain attenuation model given in ITU-R Rec. P.618. The measured CCDFs of total attenuation duration and total attenuation slope are also presented. [ABSTRACT FROM PUBLISHER]

SUMMARY This set of two companion papers aims at providing a statistical framework to quantify the inter-annual variability observed on the statistics of rain attenuation or rainfall rate derived from Earth-space propagation measurements. This part I is more specifically devoted to the theoretical study of the variance of estimation of empirical complementary cumulative distribution functions (ECCDFs) derived from Earth-space rain attenuation or rainfall rate time series. To focus the analysis on the statistical variability but without loss of generality, synthetic rain attenuation time series are considered. A large variability on the ECCDFs, which depends on the duration of the synthetic data, is first put into evidence. The variance of estimation is then derived from the properties of the statistical estimator. The formulation is validated numerically, by comparison with the ECCDF variances derived from the synthetic data. The variance of the fluctuations around the CCDF is then shown to be dependent on the average of the correlation function of the time series, on the probability level and on the measurement duration. This variance of estimation is needed as a prerequisite in conjunction with the knowledge of the climatic variability to characterize the yearly fluctuations of propagation statistics computed from experimental time series. The extensions from simulations to experiments as well as the application to system planning are detailed in part II. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY This set of two companion papers aims at providing a model for the inter-annual variability of earth-space propagation statistics and for the inherent risk and CIs. In part I, it was proposed to model the yearly variance σ² of empirical complementary CDFs so that [ABSTRACT FROM AUTHOR]

Propagation effects such as rain or clouds attenuation cause deeper fades in the Ka-band than at lower frequencies. In this collaborative paper, the main results of four long-term Ka-band propagation campaigns are presented. The experiments are carried out in Ottawa, Canada; Aveiro, Portugal; Madrid, Spain; and Toulouse, France. Attenuation statistics are derived from satellite beacon data collected over 6 years at Aveiro, 5 years at Ottawa and Madrid and 2 years at Toulouse. Multi-year measurements allow the production of more stable statistics reflecting the long-term behavior of propagation phenomena and to investigate its year-to-year variability. The beacon signal data was monitored and collected on a continuous basis over the whole measurement period. After a brief introduction of the experiments, rain rate and excess attenuation results are discussed, first for a common measurement period and later for the whole database available. Seasonal attenuation statistics for Ottawa and Aveiro are compared. Finally, fade duration and fade slope statistics derived at three locations are presented and discussed. [ABSTRACT FROM AUTHOR]

In Recommendation ITU-R P.1853-1, a stochastic approach is proposed to generate long-term rain attenuation time series A(t), including rain and no rain periods anywhere in the world. Nevertheless, its dynamic properties have been validated so far from experimental rain attenuation time series collected at mid-latitudes only. In the present paper, an effort is conducted to derive analytically the first- and second-order statistical properties of the ITU rain attenuation time-series synthesizer. It is then shown that the ITU synthesizer does not reproduce the first-order statistics (particularly the rain attenuation cumulative distribution function CDF), however, given as input parameters. It also prevents any rain attenuation correlation function other than exponential to be reproduced, which could be penalizing if a worldwide synthesizer that accounts for the local climatology has to be defined. Therefore, a new rain attenuation time-series synthesizer is proposed. It assumes a mixed Dirac-lognormal modeling of the absolute rain attenuation CDF and relies on a stochastic generation in the Fourier plane. It is then shown analytically that the new synthesizer reproduces much better the first-order statistics given as input parameters and enables any rain attenuation correlation function to be reproduced. The ability of each synthesizer to reproduce absolute rain attenuation CDFs given by Recommendation ITU-R P.618 is finally compared on a worldwide basis. It is then concluded that the new rain attenuation time-series synthesizer reproduces the rain attenuation CDF much better, preserves the rain attenuation dynamics of the current ITU synthesizer for simulations at mid-latitudes, and, if it proves to be necessary for worldwide applications, is able to reproduce any rain attenuation correlation function. [ABSTRACT FROM PUBLISHER]

Background: Cardiac magnetic resonance (CMR) is increasingly used to assess heart diseases. Relevant non-cardiac diseases may also be incidentally found on CMR images. The aim of this study was to determine the prevalence and nature of incidental extra-cardiac findings (IEF) and their clinical impact in non-selected patients referred for CMR., Material/methods: MR images of 762 consecutive patients (515 men, age: 56±18 years) referred for CMR were prospectively interpreted by 2 radiologists blinded for any previous imaging study. IEFs were classified as major when requiring treatment, follow-up, or further investigation. Clinical follow-up was performed by checking hospital information records and by calling referring physicians. The 2 endpoints were: 1) non-cardiac death and new treatment related to major IEFs, and 2) hospitalization related to major IEFs during follow-up., Results: Major IEFs were proven in 129 patients (18.6% of the study population), 14% of those being unknown before CMR. During 15±6 month follow-up, treatment of confirmed major IEFs was initiated in 1.4%, and no non-cardiac deaths occurred. Hospitalization occurred in 8 patients (1.0% of the study population) with confirmed major IEFs and none occurred in the remaining 110 patients with unconfirmed/unexplored major IEFs (p<0.001)., Conclusions: Screening for major IEFs in a population referred for routine CMR changed management in 1.4% of patients. Major IEFs unknown before CMR but without further exploration, however, carried a favorable prognosis over a follow-up period of 15 months.