I. Introduction
Dual-Frequency precipitation radar is recognized as providing better information on drop size distribution (DSD) parameters as well as estimates of rainfall rate from the combination of two-frequency channel radar returns. This radar will be the primary instrument on the Global Precipitation Measurement (GPM) core satellite. The GPM program is an expanded mission of the Tropical Rainfall Measuring Mission (TRMM), which has been successfully measuring precipitation from space for more than five years. The radar in the GPM mission will operate two frequency channels, in Ka—(35.55 GHz) and Ku—(13.6 GHz) bands. If the measured data from both frequency channels are combined to estimate the DSD parameters, then the dual-frequency techniques are applicable.