The Tropical Rainfall Measuring Mission (TRMM) is a joint venture by CRL, NASDA and NASA and has been conducting observations on schedule. On November 28, 2000, we cerebrate the third anniversary of the mission launch. This mission using the Precipitation Radar (PR) will be the first spaceborne rain radar and observes water cycle three-dimensional process. TRMM regularly obtains good scientific results such as three-dimensional quantitative rain observations over ocean and land, quantitative understanding of rain distribution in tropical areas with annual changes such as El Nino, and global soil wetness estimated by a satellite sensor for the first time. It also contributes to improving the accuracy of weather forecasts by four-dimensional data assimilation. This symposium will be held to recognize these results and future prospects for rain observation.