Source: USGS
A quote to note from this interview with Barbara Ryan:
“The data policy for Landsat was a paradigm shift for the world. There is no doubt about it.”

Above the Earth, Below the Surface: Landsat’s Role in Monitoring Water Quality
Safeguarding freshwater resources is crucial, and while scientists use a variety of ground-based techniques to gauge water quality, the Landsat program has provided water quality data from orbit for decades.