Top panel: Change in the components used to calculate the GOES-16 MgII_EXIS index (Eq. (8)) as a function of time, which is a proxy for solar exposure. The blue wing signal declines more rapidly than the red wing and h and k line signals. Bottom panel: Comparing index values calculated from observations taken quarterly from an offset position from β = 0.9° (black) track the impact of signal decline on the absolute index value. Because spectra taken at β = 0.9° also show very weak sensitivity loss, the β = 0°/β = 0.9° ratio differences must be increased by ~10% (red) in order to calculate the total impact of instrument degradation.