[mturmon]

The Sentinel data is excellent, and spans several satellite platforms and a huge number of modalities. In some significant cases (surface deformation, imaging spectroscopy, for example) Sentinel surpasses (current!) NASA data. (I use both in various projects.)

In general there are a lot of trades, including ground sampling distance, temporal revisits, and spectral coverage. So it’s good to have options.

Both NASA and ESA do exceptionally well at offering free data for science purposes. All the NASA science data, Earth and otherwise, is free.

People think of this data as a camera that’s pointed at a target, but that’s not how it works now. There are calibration and inversions that have be done to transform the observed electromagnetic data into physically-relevant quantities.

I’m not a commercial user, but it is possible that there are charges for some commercial purposes, or for niche applications that require high volumes or low latency. (Although many missions offer near real time feeds for free as well as slower calibrated feeds.) The data egress costs are a concern for NASA Earth science…I don’t remember the specific numbers but they have been increasing rapidly.

[the_only_law]

Do they have an archive of different datasets they offer. I'd be curious but to see if their are any that pique my interest particularly.

[mturmon]

Start at: https://search.earthdata.nasa.gov/search

Problem is, there are a lot of missions at this point: https://svs.gsfc.nasa.gov/30065

It’s easy to get confused. If you are a potential science user, be sure to get in touch with another savvy user in your domain, or with someone from the instrument team, before you write it up.