Green Chlorophyll Index (GCI) can be used to estimate the leaf chlorophyll concentration in various species of plants. The chlorophyll content reflects the physiological state of vegetation: it decreases in stressed plants. The index is especially helpful in monitoring the impact of seasonality, environmental stresses, and the result of applied pesticides on plant health, among other things.

Sentinel = (B08/B03)-1
Landsat 8-9 = (nir08/green)-1
Firefly = (B118/B022)-1