The GOCE (Global Ocean Circulation Explorer) satellite mission, scheduled for launch in 2005, is designed to map out the Earth's gravity field to high accuracy on a global scale over a nominal lifetime of 2 years. Changes in the gravity field are caused by the redistribution of mass within the Earth and on or above its surface. Since GOCE will fly at a low orbit (250 km), it will be under influence of mass redistribution. Therefore, in this paper, based on Global Soil Wetness Project data, we both estimate the impact of some land hydroligical phenomena (evapotranspiration, runoff, snow cover, and soil moisture) in terms of orbit perturbation and gravity gradient at GOCE altitude on a global scale. Compared with the expected GOCE error characteristics, that study shows that only annual signals up to degree and order 20 should be recovered by GOCE mission. |