Design Criteria for Precipitation Measurement Systems based on Satellite Downlink Monitoring

Opportunistic rain rate retrieval from rain-induced attenuation on GEO-sat downlinks (>10GHz) is a very promising technique, because of its sensitivity to rain intensity and the availability of low-cost receivers. Comparison experiments recently carried out using raingauges and weather radar have demonstrated both feasibility and effectiveness of this approach and its potential to improve worldwide precipitation monitoring including scarcely or ungauged regions. However, to implement systems based on this approach, different design options need to be considered. This contribution discusses the following design criteria. 1. Operating frequency. The most popular frequency interval for direct-to-home (DTH) satellite broadcasting is the Ku-band (10.7–12.75GHz). Satellite operators are also moving to Ka-band (17.3–21.2GHz), which offers greater bandwidth, but is also much more susceptible to rain attenuation. 2. Type of signal to be monitored. A GEO broadcast satellite radiates both DVB-S/S2 signals which can be received inside the satellite footprint area using cheap DTH equipment and beacons for tracking purposes which require special receivers. 3. Rain-sensitive link parameter to be measured. Either received signal power or signal-to-noise ratio vary in the presence of rain and are to be extracted from the received signal. 4. Receiving hardware. Depending on the monitored signal and measured parameter, it can be either a cheap off-the-shelf DTH device or a dedicated implementation. 5. Rain retrieval algorithm applied to measurements. 6. Auxiliary information necessary for rain retrieval algorithm, e.g. radio link geometry and meteorological data.