Radar
All-weather, through clouds and at night.
Radar doesn't depend on light or cloud: it sees canopy structure and soil moisture where optical is silent for weeks. In the south, where a cloud front hides the field at the most important moment of the season, it's often the only way not to lose observation.
The method's limit: Radar senses structure and moisture, but not a plant's “colour”, so you can't read biochemistry from it. We use it as an all-weather backbone and to fill optical gaps.
