Onboard surface detection algorithm for TRMM precipitation radar

An algorithm that detects the surface echo peak position in a radar echo ra nge profile has been developed for the TRMM Precipitation Radar (PR). The p urpose of the surface echo peak detection is to determine the range window in which "over-sample" data are collected. The surface echo position in the range profile is variable due to the systematic change of satellite geodet ic altitude and surface topography. The dynamic control of the over-sample range window using the surface detection algorithm contributes significantl y to the reduction of PR data rate that should be sent to the ground statio n. The algorithm employs an alpha-beta tracking filter and has three functi ons; surface tracking, lock-off detection and tracking loop initialization. After the launch of the TRMM satellite, a series of initial check-out of t he PR was conducted. The performance of the algorithm was evaluated through the initial check-out and two-years operation of the PR. The results indic ate that the algorithm is working as expected and basically meets the speci fication; however, it is found that some functions such as the tracking loo p initialization algorithm need to be improved.