Space technology that can help us preserve the environment

This question sounds somewhat controversial because people usually associate space missions with harm to our atmosphere (don't forget about fuel emissions, ozone layer depletion, etc.).  However, many space agencies, including NASA, are concerned with the state of the environment. You've mentioned Sentinel-6, but NASA has several other space technologies aimed at preserving the environment. One of NASA's developments is a small satellite with a carbon-detecting device used to measure carbon emissions and evaluate the quality of air. EnMap program, developed by OHB, is used for monitoring the Earth's ecosystems. Sensor technology captures even more that we can notice and transfers this data to scientists. Joint Polar Satellite System (JPSS) has 7 sensors that monitor oceans, climate, atmosphere, near-earth space, radiation, etc.
Research on this topic never stops, and world-famous space agencies continue working on similar projects, so
 I'm sure that we'll probably see new environmental satellites soon.

I assume not many people know about such missions like Santinel 6 and the necessity of that missions to environmental preservation and another stuff that makes work scientists easier. The Sentinel-6 satellite will be capable of delivering more precise, and finer spatial resolution images, as well as the ability to recover a higher quantity of data in both ice-covered and coastal regions.
Yeah, I`ve heard about NASA`s project aimed at environmental preservation and projects by other space companies which manufacture satellites and microsatellites base onenvironmental observation

A lot of what NASA invents for their missions end up being adopted in everyday life. As a former researcher, I've found that research, regardless of its conclusiveness, never goes in vain.

Any astronomy buff can tell you that silver backed insulation, memory foam, and even the treadmill were inspired from NASA inventions, and are still used today. From that principle alone, there will always be unintended purposes from such inventions. Concerning the Sentinel-6 satellite, I have no idea how it could "control sea levels" - that's something you'd have to elaborate on.