RESEARCH ARTICLE Rain attenuation statistics at Ka‐band estimated from weather radar observations in Belgium Maryna Lukach 1,2 | Laurent Quibus 3 | Danielle Vanhoenacker‐Janvier 3 | Laurent Delobbe 1 1 Royal Meteorological Institute of Belgium (RMI), Brussels, Belgium 2 National Centre for Atmospheric Science (NCAS), Leeds, UK 3 Université catholique de Louvain, ICTEAM, Louvain‐la‐Neuve, Belgium Correspondence Maryna Lukach, NCAS, Faibairn House, 71‐75 Clarendon Rd, Leeds LS2 9PH, UK. Email: maryna.lukach@ncas.ac.uk Funding information Fonds De La Recherche Scientifique ‐ FNRS, Grant/Award Number: PDR T.1049.15 (NEWPORT) Summary This paper presents rain attenuation statistics for satellite‐ground transmission links at Ka‐band based on 10‐year reflectivity observations from a C‐band weather radar. The ground receiving station and the radar are both located in Belgium. Only precipitation under the freezing level is considered, and the attenuation produced by hail is removed by applying a reflectivity threshold. The radar‐derived attenuations are analyzed to investigate the influence of elevation and azimuthal angles on the attenuation statistics. It is shown that the azimuthal dependence is extremely low. In contrast, the exceedance probability for a given attenuation threshold strongly increases with decreasing elevation angles, as foreseen by ITU‐R recommendations. The radar‐derived attenuations are used to estimate rain attenuation complementary cumulative distribution functions computed according to ITU‐R recommendations for a low Earth orbit satellite. The sensitivity to the hail reflectivity threshold is very limited. In contrast, our results show that reliable attenuation statistics cannot be obtained without taking carefully into account the height of the freezing level. Monthly averages of the freezing levels allow producing satisfactory results, but it is recommended to incorporate freezing level heights with high temporal and spatial resolutions. KEYWORDS Belgium, earth‐space links, Ka‐band, non‐geostationary orbit, rain attenuation, satellite systems, statistics, weather radar 1 | INTRODUCTION Future Earth‐satellite communication links will operate at increasingly high frequencies in order to increase the data rate transmission and to reduce the size of the transmitting system. Frequencies between 25.5 GHz and 27 GHz (Ka‐band) will soon be widely used for earth observation and space science missions. At this frequency range, attenuation by rain is significant, and therefore, it is essential to produce reliable attenuation statistics based on a careful knowledge of the prevailing weather conditions. In most regions of the world, precipitation is characterized by a high variability at very fine spatial and temporal scales. It means that the propagation path is generally heterogeneously filled with precipitation and that a reliable estimation of the attenuation along this path requires three‐dimensional (3D) observations of the precipitation field at high spatial and temporal resolutions. Furthermore, in case of low Earth orbit (LEO) satellites, the propagation path crosses the full 3D hemisphere surrounding the ground station (GS) and necessitates the evaluation of the degradation due to rain in this volume. When available, ground‐based weather radars are the most suitable systems for providing such information. 1 Weather radars scan the atmosphere in all azimuthal directions and several eleva- tion angles, providing a 3D picture of precipitation. The repetition cycle is typically between 5 and 15 minutes. First attempts to deliver cumulative rain fade statistics based on S‐band radar observations date back from the early 70s. 2,3 Further results gave progressively confidence in the use of radar records in compiling attenuation statistics. 4,5 Later on, the advantages of S‐ and C‐band radar Received: 29 November 2017 Revised: 7 May 2018 Accepted: 25 May 2018 DOI: 10.1002/sat.1256 Int J Satell Commun Network. 2018;1–14. © 2018 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/sat 1