Using data provided by the gravity recovery and climate experiment (GRACE) twin-satellite mission, scientists from various disciplines have been able, for the first time, to observe directly the redistribution of mass in the world's ocean, the mass balance of the Greenland and Antarctica ice sheets, water stock changes in the Amazon and many other areas, and the co- and post-seismic gravity effects associated with large seismic events such as the December 2004 Sumatra-Andaman Earthquake.
However, a significant problem that users of monthly GRACE gravity field solutions face is the presence of correlated and resolution-dependent noise in the provided spherical harmonic coefficients. The reason for this peculiar characteristic is GRACE's mission geometry in connection with potential limitations in current analysis strategies. The GRACE A and B twin-satellites fly in a single orbital plane, and the inter-satellite ranging observable used in gravity modeling translates into a distinct along-track sensitivity.
The new algorithm for anisotropically de-correlating ("de-striping") GRACE errors accounts for this along-track sensitivity pattern (Kusche et al., 2009). Depending on the application (e.g. whether one is interested in deriving monthly mass changes or rather inter-annual or even secular trends), variable additional smoothing can be applied. Tests have shown that the signal to noise ratio of the obtained maps of surface mass variability (large signal in the Amazon vs. low signal in the Sahara) is much better than with Gaussian filtering applied.