Implementation of a rain measurement mode into RA-2 radar altimeter

Rain radar systems are complex if properly designed in terms of hardware (antenna, transmitter, receiver, etc.) and software (processing algorithms) so that the requirements can be met. It should be easier to utilize an already existing radar system rather than to design a dedicated system. The altimeter radar is perhaps the best choice for testing the feasibility of rain measurement from space, because nadir viewing allows for good vertical resolution of the storm structure and the band in which most altimeters operate (Ku band) is well suited for rain observation. The most stringent requirement to be met for rain observation is that one related to the minimum measurable rainfall rate. In fact, this requirement can be translated into a requirement of the amplitude of the range sidelobe levels, due to the pulse compression technique which can mask the rain echo