Solar geometry

Per-pixel solar zenith angle for the terminator blends.

Per-pixel solar zenith angle for the day/terminator/night blends.

Feeds the confidence-factor blending weights (Eqs. 20-21) and the baseline-image blend (Eq. 25). Implemented with pyorbital’s astronomy routines on the area’s lon/lat arrays.

shachen.solar.solar_zenith(area: AreaDefinition, when: datetime) → DataArray

Solar zenith angle in degrees on area’s grid, dims (y, x).

when is the (naive UTC) observation time; the scene start time is accurate enough for the 30-deg-wide terminator blend. Off-disk pixels (non-finite lon/lat) are NaN.