Correlation matrix of estimated parameters from the combined 2W and SST mode, highlighting a significantly reduced off-diagonal correlation among tidal Love numbers k₂₂, k₃₁, k₃₃, k₄₂, k₄₄) and low-degree gravity field coefficients (C_2,0 to C_40,0, C_2,1, C_2,2, S_2,1, and S_2,2). This demonstrates the combined mode’s ability to reduce parameter interdependencies and improve the robustness and interpretability of the gravity field estimation.