LUH-GRACE2018: A new time series of monthly gravity field solutions from GRACE

Abstract

In this contribution, we present a new time series of monthly gravity field solutions mainly obtained from GRACE K band range rate (KBRR) measurements. Our monthly solutions are computed using the in-house developed GRACE-SIGMA software. The processing is based on variational equations and consists of two main steps. In the first step, 3-hourly orbital arcs of the two satellites and the state transition and sensitivity matrices are dynamically integrated using a tailored Gauss-Jackson integrator. In this step, initial state vectors and 3D accelerometer bias parameters are adjusted using GRACE L1B reduced dynamic positions as main observations. In the second step, normal equations are accumulated and the normalized spherical harmonic coefficients up to degree and order 80 are estimated along with empirical and previously mentioned parameters from step 1. Here we use KBRR measurements as main observations and introduce reduced dynamic positions to solve for the low frequency coefficients. In terms of degree standard deviations, our gravity field solutions agree well with solutions of CSR, GFZ and JPL. In this contribution, processing details and derived mass variations are presented. The new time series, entitled as LUH-GRACE2018, can be downloaded from IfE or ICGEM websites.