Two year operation of the Precipitation Radar (PR) onboard TRMM satellite

The Tropical Rainfall Measuring Mission (TRMM) satellite was successfully launched in November 1997. Since then, Precipitation Radar (PR) onboard TRMM has been producing unique and useful global data sets of the rainfall. After two year operation of its nominal 3 years´ mission life, the PR is showing very stable performance. For example, power monitor shows that SSPA has been working stable and temperature monitor shows short term cycle (depending on satellite orbital period) and long term cycle (depending on beta angle) within designed temperature range. Internal calibration has been performed everyday and its results show that receiver system is working stable and is not needed to change calibration table after setting internal attenuator as 9 dB in February 1998. Overall performance of the PR is examined by external calibration experiments with active radar calibrator (ARC) which has been performed every other month. The results of the external calibration experiment confirmed the stability of the PR