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Contributions to the GSAT 14 Ka-band propagation campaign, designed and carried out by ISRO, has been conducted by ONERA in Shillong (25.6750°N, 91.9136°E), and CNES in Hassan, India since 2015. Two beacon Earth stations operating at 20.2 GHz, and 30.5 GHz, a profiling radiometer, and a rain gauge are available at the experiment site. Two beacon receivers at 20.2 GHz and 30.5 GHz measure the received signal strength with a 10-Hz sampling rate. In the present paper, rain rate and copolar attenuation data have been analysed. Details of the instruments and methodology of the data analysis have been described. A case study in terms of time series variation of rain rate, and copolar attenuation has been shown. The complementary cumulative distribution function (CCDF) of rain rate and copolar attenuation for the total study period has been calculated and compared with ITU-R model. A high year to year variability has been observed. The experimental CCDF shows good matches with Rec. ITU-R P.618-13 above 0.1 % of time exceedance over Shillong. The comparison of 30.5 GHz copolar attenuation data with ITU-R frequency scaling model shows a good match. Difference has been observed between experimental data and ITU-R model over Hassan.

International audience; In this paper, we present a methodology to compare frequency scaling techniques of rain attenuation. This methodology consists in obtaining rain attenuation from beacon measurements, selecting a subset of events, and applying metrics on the obtained time series. Are also discussed methodologies to separate the contributions of clouds and rain to attenuation, as well as a method to identify events affected by noise. The relevance of the approaches is evaluated on a database of satellite beacon attenuation: Italsat beacon measurements from Spino d'Adda (7 years).

International audience; Ce papier présente l'utilisation d'un simulateur atmosphérique reposant sur un modèle de prévision météorologique à haute résolution pour reproduire des statistiques d'atténuations due à la pluie pluriannuelles en bande Ka en Guyane française. Les résultats obtenus à l'aide de ce modèle sont comparés d'une part aux données expérimentales disponibles dans cette région et d'autre part aux modèles de prévision de l'UIT.

International audience; In 2019, new methods to synthesize time series of single-site and multi-site tropospheric impairments on Earth-space paths have been adopted by ITU-R Study Group 3 in Recommendation ITU-R P.1853-2. However, these methods are only applicable in the case of a Geostationary Earth Orbit (GEO). As the deployment of multimedia services from Low-Earth Orbit (LEO) or Medium Earth Orbit (MEO) satellites constellations is gathering momentum worldwide, the access to simple attenuation and tropospheric scintillation time series synthesizers for Non-Geostationary Earth Orbit (NGEO) applications appears to become critical. This paper presents an adaptation of the recommendation ITU-R P.1853-2 to a NGEO link in single site configuration using elevation-dependent parameters to parameterize the statistical distribution of attenuation for time series generation.

International audience; Since 2009, ONERA has been running a Ka-band propagation experiment in Toulouse (south of France). A rain gauge, a microwave profiling radiometer and a beacon receiver able to record the 19.7 GHz signal from Hot Bird 6 satellite and the 20.2 GHz signal from Astra-3B satellite have been deployed. This paper gathers nine years of results from the still ongoing experiment. The annual, monthly and seasonal complementary cumulative distribution functions of rain attenuation are presented. A comparison is made with the annual rain attenuation prediction method of Recommendation ITU-R P.618-13 and its dispersion given by Recommendation ITU-R P.678-3. Fade slope and fade duration statistics are studied for different attenuation thresholds.

International audience; Since April 2019, EUMETSAT and ONERA are conducting a Ka-band site diversity propagation experiment using the 27.5 GHz beacon of the EUTLSAT KA-SAT satellite. The beacon signal is received from the Lario (Italy) and Leuk (Switzerland) Space Centers which are the premises of the Mission Data Acquisition Facility (MDAF) of the Meteosat Third Generation (MTG) System. The main goal of this propagation experiment is to confirm that the two locations benefit from the strong spatial decorrelation of the rain processes (or rain cells) but also to briefly investigate the performances of the Recommendation ITU-R P.618-13 which proposes rain attenuation and site diversity prediction methods.

International audience; A propagation experiment funded by ESA with support from CNES has been deployed in Svalbard (Northern Norway, 80° latitude North) in order to study propagation impairments at Ka-band caused by the troposphere at high latitudes and low elevation angles in representative conditions for GEO satcoms systems in the Artic region. In this context, a NASA Glenn Research Centre beacon receiver, operated by KSAT in Norway, measures the signal from the THOR7 satellite at a 2.65° elevation angle since March 2016. ONERA processes and analyses the data since the beginning of the experiment. At this stage 2 years of propagation data from the satellite have been gathered. An Atmospheric Numerical Simulator relying on the high resolution meteorological model (WRF-ARW) is used to generate 3D states of the atmosphere during a concurrent period to the experiment at high spatial & temporal resolutions. Propagation calculations based upon those outputs are then conducted to derive simulated attenuation time series between the beacon receiver and THOR7. Results show a fairly good statistical agreement between the measured and simulated attenuation time series whereas the simulated statistics seem to underestimate the overall attenuation for all percentages of time.

International audience; 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 3 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.

Background/introduction Description of activity and work performed Conclusion and recommendations Personal/organisational information References, Background/introduction: Lung cancer is the leading cause of cancer-related death among men and women globally. In the last decade, over 224.000 new cases of lung cancer per year have been observed in the United States. Global cancer incidence indicates that the highest...

International audience; Maritime environment, and in particular the sea clutter, has a significant impact on the detection efficiency. Therefore the physical properties of the radar sea clutter must be well mastered. In this paper, we focus on sea clutter data acquired during an experiment called MARLENE, which was held in the Mediterranean Sea region of Toulon, France, in 2014. The aim of this experiment was to characterize the sea environment influence on radar propagation and backscattering for Refractivity From Clutter (RFC) and radar Doppler detection. Three coastal radars, MARSIG (WTD 71), MEMPHIS (FHR) and MEDYCIS (ONERA) were used to acquire sea clutter measurements simultaneously. During the radar measurements, the in-situ oceanic and meteorological conditions were characterized on board of the RV PLANET meteorological ship deployed by WTD 71 and by WAVEWATCH III and SWAN wave models. The paper gives an overview of the MARLENE experiment, presents the radar data and the first results on sea clutter reflectivity and Doppler.

International audience; 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.

International audience; The main objective of this study was to figure out a relationship between space weather environment phenomena (solar activity and geomagnetism) and ionospheric events that impact L-band satellite navigation systems (scintillations, electron content gradients) in the Nordic European area.

Les bandes de fréquences utilisées conventionnellement pour les systèmes fixes de télécommunication par satellites (bandes C et Ku i.e. 4-15 GHz) sont congestionnées. Néanmoins, le marché des télécommunications civil et de défense accuse une demande de plus en plus importante en services multimédia haut-débit. Par conséquent, l'augmentation de la fréquence porteuse vers les bandes Ka et Q/V (20-40/50 GHz) est activement étudiée. Pour des fréquences supérieures à 5 GHz, la propagation des signaux radioélectriques souffre de l'atténuation troposphérique. Parmi les différents contributeurs à l'affaiblissement troposphérique total (atténuation, scintillation, dépolarisation, température de bruit du ciel), les précipitations jouent un rôle prépondérant. Pour compenser la détérioration des conditions de propagation, des techniques de compensation des affaiblissements (FMT: Fade Mitigation Technique) permettant d'adapter en temps réel les caractéristiques du système en fonction de l'état du canal de propagation doivent être employées. Une alternative à l'utilisation de séries temporelles expérimentales peu nombreuses est la génération de séries temporelles synthétiques d'atténuation due à la pluie et d'atténuation totale représentatives d'une liaison donnée. Le manuscrit est organisé autour de cinq articles. La première contribution est dédiée à la modélisation temporelle de l'affaiblissement troposphérique total. Le deuxième article porte sur des améliorations significatives du modèle de génération de séries temporelles d'atténuation due à la pluie recommandé par l'UITR. Les trois contributions suivantes constituent une analyse critique et une modélisation de la variabilité des statistiques du 1er ordre utilisées lors des tests des modèles de canal. La variance de l'estimateur statistique des distributions cumulatives complémentaires de l'atténuation due à la pluie et de l'intensité de précipitation est alors mise en évidence. Un modèle à application mondiale paramétré au moyen de données expérimentales est proposé. Celui-ci permet, d'une part, d'estimer les intervalles de confiance associés aux mesures de propagation et d'autre part, de quantifier le risque en termes de disponibilité annuelle associée à la prédiction d'une marge de propagation donnée. Cette approche est étendue aux variabilités des statistiques jointes. Elle permet alors une évaluation statistique de l'impact des techniques de diversité de site sur les performances systèmes, tant à microéchelle (quelques kms) qu'à macro-échelle (quelques centaines de kms). Nowadays, C and Ku bands used for fixed SATCOM systems are totally congested. However, the demand of the end users for high data rate multimedia services is increasing. Consequently, the use of higher frequency bands (Ka: 20 GHz and Q/V 40/50 GHz) is under investigation. For frequencies higher than 5 GHz, radiowave propagation is strongly affected by tropospheric attenuation. Among the different contributors, rain is the most significant. To compensate the deterioration of the propagation channel, Fade Mitigation Techniques (FMT) are used. The lack of experimental data needed to optimize the real-time control loops of FMT leads to the use of rain attenuation and total attenuation time series synthesizers. The manuscript is a compilation of five articles. The first contribution is dedicated to the temporal modelling of total impairments. The second article aims at providing significant improvements on the rain attenuation time series synthesizer recommended by ITU-R. The last three contributions are a critical analysis and a modelling of the variability observed on the 1st order statistics used to validate propagation channel models. The variance of the statistical estimator of the complementary cumulative distribution functions of rainfall rate and rain attenuation is highlighted. A worldwide model parameterized in compliance with propagation measurements is proposed. It allows the confidence intervals to be estimated and the risk on a required availability associated with a given propagation margin prediction to be quantified. This approach is extended to the variability of joint statistics. It allows the impact of site diversity techniques on system performances at small scale (few kms) and large scale (few hundred of kms) to be evaluated.

Tropospheric phenomena such as clouds and mainly rain cause higher attenuation at 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 (satellite Anik F2); Aveiro, Portugal; Madrid, Spain; and Toulouse, France (satellite HotBird 6 in the last three cases) and have been running since 2004 in Aveiro, 2006 in Ottawa and Madrid, and 2008 in Toulouse. After a brief introduction of the experiments, rain rate and excess attenuation results are discussed, first for a common two-year measurement period and later for the whole database available. Seasonal attenuation statistics for Madrid, Ottawa and Aveiro are compared. Finally, fade duration and fade slope statistics derived at three locations are presented and discussed.

For a few years now, many emerging countries have become important players in the telecommunications market. Due to the underdevelopment and even the lack of terrestrial infrastructure, satellite telecommunications are particularly attractive to these countries. However, one of the major particularities of these countries is that they are mainly located in tropical and equatorial regions. This aspect is put forward here because the Earth-Space propagation has, until now, been mainly studied for temperate regions such as Europe and North America. These studies showed that at the frequency bands currently used for satellite telecommunications systems, the most significant attenuation of the signal was caused by rain. Nevertheless, the characteristics of precipitating events in tropical and equatorial regions are very different from those observed in temperate regions. Therefore, a more in-depth study of the different propagation models in tropical and equatorial regions is now necessary. Additionally, there is, today, a clear lack of experimental data in these regions to validate and optimize existing attenuation models.It is within this problematic that this PhD proposes the use of a new type of hybrid model using a high resolution numerical weather prediction model coupled with an electromagnetic attenuation module. The advantage of such a hybrid model is that it can simulate tropospheric propagation for any type of satellite link. This WRF-EMM model is tested here for the first time in an equatorial region in Kourou, using experimental data collected during the ONERA / CNES propagation campaign in French Guyana. After observing a high monthly variability of the performance of the model, an optimization of the WRF weather model is presented in order to obtain a more adequate configuration for Kourou.; Depuis maintenant quelques années, de nombreux pays émergents deviennent des acteurs importants sur le marché des télécommunications. De par le sous-développement, voire même, l’absence d’infrastructures terrestres, les télécommunications par satellite sont particulièrement attrayantes pour ces pays. Cependant, une des grandes particularités de ces pays est qu’ils se trouvent majoritairement en régions tropicales et équatoriales. Cet aspect est ici mis en avant car la propagation Terre-Espace a été, jusque-là, principalement étudiée pour des régions tempérées telles que l’Europe et l’Amérique du Nord. Ces études ont montré qu’aux bandes de fréquences actuellement utilisées pour les systèmes de télécommunications par satellites, l’atténuation du signal la plus importante était causée par la pluie. Néanmoins, les caractéristiques des évènements précipitants en régions tropicales et équatoriales sont très différentes de celles observées en régions tempérées. De ce fait, une étude plus approfondie des différents modèles de propagation en régions tropicales et équatoriales est aujourd’hui nécessaire. De surcroit, il existe aujourd’hui un manque flagrant de données expérimentales dans ces régions pour permettre de valider et optimiser les modèles d’atténuation existants.C’est dans cette problématique que s’inscrit cette thèse en proposant l’utilisation d’un nouveau type de modèle hybride utilisant un simulateur numérique de l’atmosphère à haute résolution couplé à un module d’atténuation troposphérique. L’intérêt d’un tel modèle hybride est de pouvoir modéliser la propagation troposphérique pour tout type de liaison satellite. Ce modèle WRF-EMM est ici tester pour la première fois en région équatoriale à Kourou, à l’aide des données expérimentales recueillies durant la campagne de propagation ONERA/CNES en Guyane Française. Après l’observation d’une performance du modèle très variable d’un point de vue mensuel, une optimisation du modèle météo est présentée afin d’obtenir une configuration plus adéquate pour Kourou.