Patterns in GRACE-FO LRI Post-Fit Range Rate Residuals

The LRI on GRACE Follow-On (GRACE-FO) provided range and range rate measurements for more than 4 years. At our institute we produce monthly gravity field coefficients from these observation data. We apply different techniques to analyse the post-fit range rate residuals and the post-fit range acceleration residuals to identify unknown characteristics and systematic effects within the LRI measurement system. We identified several effect: the range rate effect, the panel effect, the CNR effect and the polar effect. All these effects have not been detected in the KBR residuals. Beside the current status of GRACE/GRACE-FO processing standards at our institute, the focus lies on the characterisation of the range rate effect as well as the panel effect. The range rate effect occurs when the range rate observation is around 0 m/s and shows a very specific butterfly pattern. The panel effect is induced by the interaction of the spacecraft body panels and the sun. There is also an interaction of the LRI steering mirrors observable when the LRI laser beam is aligned with the sun.