## 2 Datasets  
### Passive Microwave Data-GPM Mission  
The GPM Mission, is an international space network of satellites designed to provide precipitation observations every three hours anywhere around the world. As shown in Table 1, the GPM constellation consists of several operational, research, and development satellites that include (or will include) the operational US NOAA and European MetOp polar orbiting series, the US Defence Meteorological Program satellites, the US Joint Polar Satellite System, together with the Japanese GCOM-W1 (Global Change Observation Mission-Water) mission, and the French-Indian Megha-Tropiques mission. The GPM core satellite, the \"observatory\", carries a dual frequency precipitation radar (DPR) using Ku band at 13 GHz and Ka band at 35 GHz and a canonical-scanning microwave imager (GMI) operating from 10 to 183 GHz with 13 channels. It builds upon the Tropical Rainfall Measuring Mission (TRMM) heritage [7] but provides retrieval accuracy and higher sensitivity to slight rainfall (smaller than 2.5 mm/h according to the definition of the Glossary of Meteorology [20], such a reference will be considered also for other rainfall categories mentioned in the paper) and snowfall detection relative to TRMM. DPR and GMI, during their life-time, will generate an observational database on the microphysical properties of precipitating particles. The GPM concept is based on the deployment of a \"Core\" observatory carrying active and passive microwave sensors in a non-Sun-synchronous orbit to serve as a physics observatory to gain insights into precipitation systems and as a calibration reference to unify and refine precipitation estimates from a constellation of diverse satellites. Through the inter-calibration of radiometric data obtained from this constellation of different sensors, an accurate unified precipitation retrieval algorithm, using a common hydrometeor database and working in the different environmental conditions, has been developed [21]. These data set will be used to provide rainy pixels and to train the NN performing the rainfall retrieval.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**SATELLITE** & **SENSOR** & **LIFE SPAN** \\ \hline
**Global Precipitation Measurement Core** & **GPM Microwave Imager/Dual Frequency** & **2014– beyond 2021** \\  & **Precipitation Radar** & **2012–2018** \\ \hline
**Global Change Observation Mission-Water 1** & **Advance Microwave Scanning Radiometer 2** & **2012–2018** \\  & Sondeur Atmospherique du Profil d’Humidite & 2011–2017 \\  & Intertropical par Radiometrie & 2011–2015 \\ \hline
**Defence Meteorological Satellite Program-Flight 17** & **Special Sensor Microwave Imager/Sounder** & **2011–2015** \\
**Defence Meteorological Satellite Program-Flight 18** & **Special Sensor Microwave Imager/Sounder** & **2011–2016** \\
**Defence Meteorological Satellite Program-Flight 19** & **Special Sensor Microwave Imager/Sounder** & **2014– beyond 2021** \\ \hline Defence Meteorological Satellite Program-Flight 20 & **Special Sensor Microwave Imager/Sounder** & 2020–N/A \\
**Meteorological Operational Satellites-A** & **Microwave Humidity Sounder** & **2011–2014** \\ \hline \hline \end{tabular}
\end{table}
Table 1: Launch schedules and life spans of Global Precipitation Measurement constellation satellites. Satellites used in this study are in bold.