Radio Science

Comparing model and measured rainfall rates obtained from a combination of remotely sensed and in situ observations


  • P. J. Hardaker,

  • A. R. Holt,

  • J. W. F. Goddard


The Olympus program was designed to develop new telecommunications technology in space and develop new market applications. This study analyzes attenuation data from two of the Olympus satellite beacons, those operating at 19.77 and 12.502 GHz. It is shown that the difference in the two attenuations provides estimates of rainfall rate that are in close agreement with rain gauge and distrometer measurements at the ground receiver site and along the propagation path. Modeling demonstrates that the attenuation difference using 19.77 and 12.502 GHz is a useful estimator of rainfall because it is largely independent of drop shape and size distribution, making it linearly related to rainfall rate. Attenuation along the propagation path due to the melting layer or ice introduces inaccuracies into estimates of rainfall. However, this difficulty would be eliminated if the method were to be used on terrestrial line-of-site links. Thus attenuation difference provides a means of improving the quality of rainfall estimates when used together with gauges and radar observations.