Relax acquisition_type to be a free string.

[emmanuelmathot]

Soome Sentinel-2 products may distinguish different calibration types. OGC® Earth Observation Metadata profile of Observations & Measurements used to have a subtype but this is probably not a good logic. We would prefer to relax acquisition_type to be a free text and thus allow data provider to specify custom acquisition types.

[m-mohr]

Could we get some examples from different satellites across different providers? I'm always a bit hesitant with free text fields as it often is due being too lazy to align.

[emmanuelmathot]

That's actually exactly the point. Even if the broad type often covers just nominal acquisition or calibration, each mission has their own calibration definition (e.g. cal1', cal2`). In ogc 157r4, they created productsubtype for that purpose. IMO, this is even a worst solution