Characterization of surface radar cross sections at W-band at moderate incidence angles

This paper presents the results of a recent flight campaign conducted over the Great Lakes region and reports the first observations of the W-band normalized backscattered cross section ( σ0 ) for V and H polarization and the linear depolarization ratios (LDRs) from different types of surfaces at moderate incidence angles (<70°). For sea surfaces, while the observed σ0 behaves as previously reported at small incidence angles, it features a marked decrease with increasing incidence angles between 20° and 50°. There is a strong dependence of normalized backscattered cross sections both on the wind speed and on the wind direction, with larger values found in the presence of higher wind speeds and when the radar antenna is looking upwind. This is in line with theoretical models (though models tend to overpredict the range of variability at a given incidence angle) and with observations at lower frequencies. The LDRs are steadily increasing from values certainly lower than −30 dB, at vertical incidence, to the values of about −10 dB, at the incidence angles of about 60°–70°, with a good matching between observations and theoretical predictions. On the other hand, land surface backscattering properties are not characterized by a strong angular dependence: σ0 and LDR values typically range between −20 and 0 dB and between −15 and −5 dB, respectively. This paper is relevant for spaceborne concepts of W-band radars, which envisage moderate incidence angles to achieve a broad swath needed for global coverage

Transport Layer Coding for Satellite-Based Audio and Multimedia Services to Vehicular Terminals in Ku-band

Satellite radio for vehicles is normally hampered by the problem of the shadowing of the line-of-sight between satellite and receiver. One possible way to overcome this challenge is to provide a new type of radio service, hereafter referred to as personalized satellite radio, in alternative to the streaming approach used for traditional radio: individual audio and multimedia files are broadcasted instead of transmitting a number of distinct continuous streams. The received files are stored in a large cache located in the receiver of each mobile terminal and are sequentially played to generate a service similar to traditional radio/entertainment programmes. The resulting file-based radio approach makes use of higher-layer coding on transport level, to ensure a sufficient file transfer reliability even when some packets are lost due to the shadowing of the line-of-sight path, and of smart techniques to build up an audible programme with no interruptions and full audio quality based upon the available files. The paper presents this novel radio concept and the results of extensive trials which were conducted with a system test-bed developed in the framework of an ESA funded project

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission is one of six high-priority candidate missions (HPCMs) under consideration by the European Commission to enlarge the Copernicus Space Component. Together, the high-priority candidate missions fill gaps in the measurement capability of the existing Copernicus Space Component to address emerging and urgent user requirements in relation to monitoring anthropogenic CO2 emissions, polar environments, and land surfaces. The ambition is to enlarge the Copernicus Space Component with the high-priority candidate missions in the mid-2020s to provide enhanced continuity of services in synergy with the next generation of the existing Copernicus Sentinel missions. CRISTAL will carry a dual-frequency synthetic-aperture radar altimeter as its primary payload for measuring surface height and a passive microwave radiometer to support atmospheric corrections and surface-type classification. The altimeter will have interferometric capabilities at Kuband for improved ground resolution and a second (noninterferometric) Ka-band frequency to provide information on snow layer properties. This paper outlines the user consultations that have supported expansion of the Copernicus Space Component to include the high-priority candidate missions, describes the primary and secondary objectives of the CRISTAL mission, identifies the key contributions the CRISTAL mission will make, and presents a concept-as far as it is already defined-for the mission payload

The Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) high-priority candidate mission

International audienceThe Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission is one of six high-priority candidate missions (HPCMs) under consideration by the Euro-pean Commission to enlarge the Copernicus Space Component. Together, the high-priority candidate missions fill gaps in the measurement capability of the existing Coper-nicus Space Component to address emerging and urgent user requirements in relation to monitoring anthropogenic CO 2 emissions, polar environments, and land surfaces. The ambition is to enlarge the Copernicus Space Component with the high-priority candidate missions in the mid-2020s to provide enhanced continuity of services in synergy with the next generation of the existing Copernicus Sentinel missions. CRISTAL will carry a dual-frequency synthetic-aperture radar altimeter as its primary payload for measuring surface height and a passive microwave radiometer to support atmospheric corrections and surface-type classification. The altimeter will have interferometric capabilities at Ku-band for improved ground resolution and a second (non-interferometric) Ka-band frequency to provide information on snow layer properties. This paper outlines the user consultations that have supported expansion of the Coperni-cus Space Component to include the high-priority candidate missions, describes the primary and secondary objectives of the CRISTAL mission, identifies the key contributions the CRISTAL mission will make, and presents a concept-as far as it is already defined-for the mission payload