CNR Institutional Research Information System

Atmospheric radiometry

A Bosisio;
1994
1994
Inglese
6
6
90
93
4
atmospheric propagation
Radiometric observations are of relevance in radio propagation studies essentially because of the high sensitivity that the radiometer performs in measuring the weak incoherent noise generated by the atmosphere. In particular the absorbing effects of the atmospheric "minor" components, oxygen, water vapour and clouds liquid droplets, can be measured, which occur more frequently and last much longer with respect to the rain, although the resulting path attenuation being some one decade lower. In the lower K bands (11/14 GHz), however, where the effects of clear air gases are almost negligible, the use of radiometer is confined to the rain-induced attenuation. Radiometric measurements are usually calibrated by comparison with those concurrently acquired with satellite beacons. The reverse the case in the higher bands, above 20 GHz, where heavy rain fades cannot be directly measured by the radiometer due to saturation effects in the receiver, but the absorption caused by the atmospheric minor components are detected obtaining a reference "clear sky" level used for calibrating the received beacon. Moreover, at such frequencies the possibility is given to retrieve from radiometric measurements the atmospheric total water contents, from which the total non-rainy attenuation can be calculated at other frequencies, as well. From the system-oriented point of view, the importance of these atmospheric effects has been enhanced by the diffusion of new services, typically those like business VSATs, where the radical reduction of the availability, with outage times increased by two decades up to more than 1%, has been chosen as a basic countermeasure to reduce costs. In other words those systems are allowed to be down in the presence of the strong fades due to rain, but should be designed to face the attenuation caused by the non-rainy atmosphere, where the effects of clouds is included as well.
1
info:eu-repo/semantics/article
262
F. Barbaliscia; P.G. Masullo; A. Bosisio; C. Capsoni
01 Contributo su Rivista::01.01 Articolo in rivista
none
01.01 Articolo in rivista
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/20.500.14243/203458
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