STUDY OF ROBUST TOA DISCRIMINATORS FOR SPACE-BASED RADAR ALTIMETER

Abstract

This paper provides a study of robust TOA discriminators used in ground-based retracking of a space-based altimeter da-ta. Requirements to an on-board TOA tracking loop are limited to reliable locking of received echo-signal within the tracking window, while fine measuring of altimetry parameters (orbit height, SWH, etc.) is a task of the Earth-based retracking. In the robust algorithms TOA-measuring is performed without using any echo physical model. It can improve space-based altimeter operation near the coastline where terrain areas falling into the illuminated spot distort the received signal significantly versus the one from the “pure” water surface. Analytic calculation of noise errors is fulfilled for the OCOG. Besides, the threshold discriminators and simulation results are presented, as well as comparison of the robust discriminators against the optimal (within the classical model framework) one. Despite the robust types yield to the optimal one in the accuracy of TOA estimate, the loss is not catastrophic and often can be treated as an acceptable pay-ment for low sensibility to the deviation of scattering characteristics of a sounded surface from classical models.

Keywords

• satellite altimeter
• echo-signal
• toa-discriminator
• robustness
• offset centre of gravity
• threshold discriminator
• standard deviation