Sentinel 3
Video 1. Sentinel-3 mission introduction (source: ESA)
Sentinel-3's primary objective is to measure sea surface topography, land and sea surface temperature, and ocean and land surface color with high accuracy and reliability to support ocean forecasting systems, environmental monitoring, and climate monitoring. Sentinel-3 observational data also support applications based on vegetation monitoring, fire detection, inland water (water level of rivers and lakes), cryosphere (thickness of land and sea ice), and atmospheric studies.
The mission carries four main instruments: the ocean and land color instrument OLCI (Ocean and Land Color Instrument), the sea and land temperature instrument SLSTR (Sea and Land Surface Temperature Instrument), the artificial radar altimeter SRAL (SAR Radar Altimeter), the microwave radiation radiometer MWR (Microwave Radiometer).
While Sentinel-2 records 13 spectral channels with a spatial resolution of 10, 20 or 60 meters every 5 days or more frequently, the Sentinel-3 OLCI instrument records 21 spectral channels (Table 1) with a spatial resolution of 300 meters approximately every 2 days.
Table 1. Sentinel-3 technical parameters as an overview table (sources: NASA Earthdata, SentinelHub).
| Channel | Resolution (m/px) | Wavelength (nm) | Bandwidth (nm) | Usage and Application |
|---|---|---|---|---|
| 1 (B01) | 300 | 400 | 15 | Aerosol correction, improved determination of water constituents |
| 2 (B02) | 300 | 412 | 10 | Yellow substances and sediment pigments (turbidity/turbidity). |
| 3 (B03) | 300 | 442,5 | 10 | Chlorophyll absorption (maximum), biogeochemistry, vegetation. |
| 4 (B04) | 300 | 490 | 10 | Chlorophyll and other pigments |
| 5 (B05) | 300 | 510 | 10 | Chlorophyll and other sediment pigments |
| 6 (B06) | 300 | 560 | 10 | Chlorophyll absorption (minimum) |
| 7 (B07) | 300 | 620 | 10 | Sediments deposition |
| 8 (B08) | 300 | 665 | 10 | Chlorophyll absorption 2nd maximum, sediments, yellow matter/vegetation. |
| 9 (B09) | 300 | 673,75 | 7,5 | Determination of fluorescence and more accurate consideration of image distortions (so-called smile effect) with 665 and 680 nm spectral channels. |
| 10 (B10) | 300 | 681,25 | 7,5 | Chlorophyll fluorescence peak, red edge region (at the border of visible red and infrared) |
| 11 (B11) | 300 | 708,75 | 10 | Chlorophyll basal level, red edge transition zone |
| B12 (SWIR) | 300 | 753,75 | 7,5 | Oxygen absorption/clouds, vegetation. |
| 13 (B13) | 300 | 761,25 | 2,5 | Oxygen absorption, aerosol correction |
| 14 (B14) | 300 | 764,375 | 3,75 | Atmospheric correction |
| 15 (B15) | 300 | 767,5 | 2,5 | O2A (cloud top pressure) fluorescence over land. |
| 16 (B16) | 300 | 778,75 | 15 | Atmospheric/aerosol correction |
| 17 (B17) | 300 | 865 | 20 | Atmospheric/aerosol correction, clouds, pixel accurate alignment. |
| 18 (B18) | 300 | 885 | 10 | Water vapor absorption reference, vegetation monitoring |
| 19 (B19) | 300 | 900 | 10 | Water vapor absorption/vegetation tracking (max reflectance). |
| 20 (B20) | 300 | 940 | 20 | Water vapor absorption, atmospheric/aerosol correction |
| 21 (B21) | 300 | 1020 | 40 | Atmospheric/aerosol correction |
Sentinel-3 data is actively used for scientific research in Estonia. For example, Tartu Observatory uses this data to study the water quality of inland lakes. When sensors placed in the water detect higher concentrations of chlorophyll-a at specific points, OLCI (Ocean and Land Colour Instrument) data can help identify cyanobacteria blooms across the entire water body. This clearly highlights one of the advantages of space-based data over on-site measurements. Changes in phytoplankton composition and decreased water transparency are linked to eutrophication and climate change, making the monitoring of these parameters essential for understanding the ecosystems of water bodies. The resolution of Sentinel-3 images is lower compared to the Sentinel-2 mission because it focuses on a wider geographic area and requires less detailed data to provide an overview (Figure 1).
Figure 1. Copernicus Sentinel-3 SLSTR RBT data, suitable for environmental monitoring and climate studies
Sentinel-3A and Sentinel-3B work together to systematically measure Earth's oceans, land, ice, and atmosphere to monitor and understand large-scale global dynamics, and to provide essential near-real-time information for ocean and weather forecasting. Two follow-up satellites, Sentinel-3C and Sentinel-3D, are scheduled for launch in 2025 and 2028, respectively, to ensure the continuity of the Sentinel-3 mission.