Level-2 SYN

SENTINEL-3 Synergy Level-2 SYN Product

The Level-2 SYN product (SY_2_SYN) is produced by the Synergy Level-1/2 SDR software and contains surface reflectance and aerosol parameters over land.

Table 1: SYNERGY Level 2 product physical composition
Product Package Type Description
SY_2_SYN__ Land surface reflectance and aerosol geophysical parameters
Product Level Distribution Timeliness Product Category Application Domain Spatial Resolution
2 NTC User LND 300 m
Product Dissemination Unit Number of Package components Number of Measurement Data Files Number of Annotation Data Files Number of Representation Information Files
Stripe 38 29 9 0


All measurement datasets are provided on the OLCI image grid, similar to the one included in the OLCI L1b product, consisting of N_COL_OLC x N_LINE_OLC pixels with:

  • N_COL_OLC = 4865 columns acquired
  • N_LINE_OLC = 60,000 lines acquired for one orbit

Some sub-sampled annotations and atmospheric datasets are provided on the OLCI tie-points grid.
The measurement data files included in this product provide:

  • Level-2 Surface Directional Reflectance (SDR) with their associated error estimates for the sun-reflective SLSTR channels (S1 to S6 for both nadir and oblique views except S4 dedicated to cloud detection) and for all OLCI channels, except for the oxygen absorption bands Oa13, Oa14, Oa15, and the water vapour bands Oa19 Oa20
  • Level-2 aerosol optical thickness at 550 m (referenced as T550) with error estimates
  • Level-2 Angstrom coefficient (referenced as A550).

Several associated variables are also provided in annotation data files.

  • Aerosol Model Index Number (AMIN). For practical and technical reason, the SYN L2 processing is only taken into account the Continental model. This parameter is then always set to 1.
  • Status flag computed by SYN Level-2 processing providing information about cloud, snow or land presence.
  • Flags corresponding to OLCI quality and classifications flags and to SLSTR exception summary and confidence flags.
  • DEM-corrected latitude, longitude and altitude.
  • OLCI time stamps.
  • Solar and viewing azimuth/zenith angles for each OLCI sub-sampled tie-point.
  • Some geophysical atmospheric data (derived from ECMWF files) such as the mean sea level pressure, the total column ozone and water vapour.
Table 2: Description of Level-2 SYN product
Variables Description Units Input Bands
SDR Atmospherically corrected Surface Directional Reflectance (also called Lambert Equivalent Reflectance (LER) or Bidirectional Reflectance Factor (BRF)).
Each dataset includes a single SYN channel

SLSTR S1 – S5, S6 channels
All OLCI channels except Oa13, Oa14, Oa15, Oa19 and Oa20


T550 Aerosol Optical Thickness (AOT)
at a wavelength of 550 nm
dimensionless SLSTR S1 – S3, S5 and S6 channels
All OLCI channels except Oa13, Oa14, Oa15, Oa19 and Oa20
A550 Estimated Aerosol Angstrom Exponent at a reference waveband of 550 nm. dimensionless SLSTR S1 – S3, S5 and S6 channels
All OLCI channels except Oa13, Oa14, Oa15, Oa19 and Oa20


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