Sentinel-3

The Copernicus ocean-and-land monitoring satellite, run jointly by ESA and EUMETSAT. Where Sentinel-2 is a fine-detail land camera, Sentinel-3 trades resolution for breadth — wide-swath, near-daily measurements of ocean colour, sea-surface temperature, and water height. Not a NASA mission, but the data are free and open, and the atlas leans on it for ocean and inland-water questions where MODIS/PACE coverage needs a complement.

What it sees

• OLCI — 21 visible/near-IR bands at ~300 m, the ocean-colour and land-colour imager (chlorophyll, suspended sediment, vegetation).
• SLSTR — dual-view thermal-infrared radiometer at ~500 m–1 km, optimized for accurate sea-surface temperature and active-fire detection.
• SRAL — radar altimeter measuring sea-surface height, significant wave height, and inland water levels.

Why it matters

• Operational, climate-quality ocean colour and SST — designed for long-term continuity, not a one-off science demo.
• The OLCI 300 m resolution resolves inland lakes and coastal waters that coarser sensors smear out — key for cyanobacteria / harmful-algal-bloom monitoring (the CyAN use case).
• SLSTR’s dual-view design gives some of the most accurate spaceborne SST available.

Where to get the data

• Copernicus Data Space Ecosystem: dataspace.copernicus.eu — full archive, processing APIs.
• EUMETSAT Data Store: data.eumetsat.int — the operational marine/atmosphere distribution point.
• Copernicus Marine Service (CMEMS): value-added ocean products built on Sentinel-3.

What it enables

• Ocean chlorophyll and primary-productivity monitoring (ocean)
• Inland-water quality and cyanobacteria tracking, e.g. CyAN-style products (water)
• Sea-surface temperature for weather, climate, and fisheries (ocean)
• Land vegetation index (OTCI) and active-fire detection (land)
• Sea-level and inland water-level altimetry (water)

Gotchas

• Two product families. “Marine” (operational, EUMETSAT timeliness tiers) vs “Land/non-time-critical” (ESA) — make sure you grab the right stream.
• Coarse pixels. ~300 m OLCI and ~1 km SLSTR are great for synoptic views but cannot resolve small features the way Sentinel-2 can.
• Cloud-limited. Optical/thermal bands are blocked by cloud; SST and ocean colour need clear sky.
• L2 corrections matter. Atmospheric correction over turbid/coastal water is hard — validate before trusting near-shore chlorophyll.

Related missions

• PACE (NASA): hyperspectral ocean colour — finer spectral detail, complements Sentinel-3’s broad coverage.
• MODIS (NASA): the long-baseline ocean-colour + SST record Sentinel-3 extends and densifies.
• Sentinel-2 (ESA): higher-resolution land/inland-water companion in the Copernicus family.

Related datasets