Sentinel-2

ESA’s optical workhorse for the Copernicus program — a two-satellite constellation that images all of Earth’s land (and coastal/inland water) in true colour at 10 m, every five days. Not a NASA mission and not in NASA’s DAACs, but the data are free and open, and the atlas uses them anywhere you need finer detail than Landsat or daily MODIS/VIIRS can give.

What it sees

• MSI (MultiSpectral Instrument) — 13 spectral bands spanning visible, near-infrared, and shortwave-infrared.
• Three native resolutions: 10 m (blue, green, red, NIR), 20 m (red-edge, SWIR — vegetation + moisture), 60 m (atmospheric correction bands).
• Wide 290 km swath — the secret to the fast 5-day global revisit.

Why it matters

• 10 m, free, every 5 days — the highest-resolution global optical record anyone can download without paying.
• The red-edge bands (missing on Landsat) make it exceptional for crop type, plant health, and stress detection.
• Pairs naturally with Landsat (the Harmonized Landsat Sentinel-2, HLS, product fuses both into one 30 m every-2-3-day series).

Where to get the data

• Copernicus Data Space Ecosystem: dataspace.copernicus.eu — the official ESA source, full archive + processing APIs.
• AWS Open Data: s3://sentinel-2-l2a-cogs — cloud-optimized GeoTIFFs, no egress fees.
• Element84 Earth Search: STAC API at earth-search.aws.element84.com — best for programmatic search.
• Microsoft Planetary Computer: STAC + hosted compute.

What it enables

• Land-cover and land-use mapping at field scale
• Crop monitoring, yield estimation, irrigation tracking (agriculture)
• Deforestation and forest-disturbance detection (biosphere)
• Inland and coastal water-quality / algal-bloom monitoring (water)
• Disaster mapping (floods, fire scars) at higher detail than daily sensors

Gotchas

• Optical means cloud-limited. Unlike Sentinel-1 radar, clouds block the view; cloudy regions get sparse usable scenes.
• L1C vs L2A. L1C is top-of-atmosphere; almost everyone wants L2A (surface reflectance, atmospherically corrected). Older archive segments may need processing to L2A yourself.
• Tiling system. Data come in 100×100 km MGRS tiles; an area of interest can straddle several tiles.
• Band resolutions differ. You must resample to combine 10 m, 20 m, and 60 m bands.

Related missions

• Landsat 9 (NASA+USGS): coarser (30 m) but with thermal bands and a 50-year archive; harmonized with Sentinel-2 via HLS.
• Sentinel-3 (ESA): coarser, wider-swath ocean/land colour companion in the Copernicus family.
• MODIS / VIIRS (NASA): daily global coverage, but much coarser pixels.

Related datasets