Ocean tide aliasing in spaceborne gravimetry: a data-driven determination of the tidal alias spectrum
19/09/2016 | 14:45 | Session 1: New missions and concept performance
Author(s): Wei Liu, Nico Sneeuw, Siavash Iran Pour, Weiping Jiang, Mohammad Tourian and Tilo Reubelt
Wei Liu, Nico Sneeuw, Siavash Iran Pour, Weiping Jiang, Mohammad Tourian and Tilo Reubelt
Ocean tides cause notable alias errors for single-pair spaceborne gravimetry missions like GRACE. Undersampling from satellite orbit induces the aliasing of high-frequency tidal signals into the long wavelengths of the gravity signal. Moreover, ocean tide models used for de-aliasing in the gravity field retrieval carry errors, which will directly alias into the recovered gravity field. In case of repeat orbits, the spectrum of tidal alias errors can be estimated and the tide errors can be corrected from the recovered gravity field in a post-processing mode.
The recovered gravity field solutions containing tidal aliasing errors can be considered as a discrete time series. We here investigate the tidal de-aliasing by post-processing such discrete time series. The de-aliasing results not only depend on the period but also on the length of time series. Based on the spectral characteristics of the time series, a data-driven method for computing alias periods is introduced in the case of repeat orbit missions. When we use these alias periods, the post-processing procedure outperforms the usage of conventional alias periods from orbit sampling in terms of modelling the ocean tidal aliasing errors.