Aliasing and Polar Gap Effects on Geopotential Coefficient Estimation: Space-wise Simulation Study of GOCE and GRACE

Abstract

The effects of aliasing and polar data gap have been investigated analytically and numerically for the upcoming dedicated gravity satellite missions. It is verified that they could cause more significant systematic error in the solution via least-squares estimation than the effect from the instrument's noise. Both effects produce similar error trends in the geoid height estimation, while they corrupt coefficients corresponding to different spectral domains. This paper develops possible methods to reduce the errors caused by them. A new scheme is proposed to decrease the aliasing error and a combination solution is suggested to reduce the corruption due to the polar data gap. Numerical results are computed through GOCE and GRACE simulation studies. It is shown that the geoid error due to the aliasing is reduced near the poles from 11 cm to less than 1 cm by estimating 20% more coefficients beyond the Nyquist limit and the geoid error due to the polar data gap in the GOCE mission is reduced to less than 1cm by including GRACE measurements in the polar areas.