The Inherent Optical Properties (IOP) suite provides per-pixel inherent optical properties - quantities that describe how seawater and its constituents absorb and scatter light, independent of illumination or viewing geometry. IOPs are retrieved from spectral Remote Sensing Reflectance (Rrs) using Generalized Inherent Optical Properties (GIOP) model and are delivered at the sensor’s native Level-2 swath resolution, and Level-3 mapped daily/8-day/monthly composites (typically 4–9 km). These products support water-type classification, water-clarity assessment, biogeochemical studies, and forward/adjoint radiative-transfer applications, and they enable more robust cross-sensor comparisons than purely apparent (AOP) products.

Geophysical variables in this suite include:
• a_λ — Total absorption coefficient at wavelength λ (sum of pure water + phytoplankton + CDOM/detritus, m⁻¹)
• bb_λ — Total backscattering coefficient at wavelength λ (m⁻¹)
• aph_443 — Phytoplankton absorption coefficient at 443 nm (m⁻¹)
• aph_unc_443 — Uncertainty in absorption due to phytoplankton at 443 nm (m⁻¹)
• adg_443 — Combined CDOM + non-algal detritus absorption coefficient at 443nm; accompanied by adg_s (spectral slope, units nm⁻¹).
• adg_unc_443 — Uncertainty in absorption due to gelbstoff and detrital material at 443 nm (m⁻¹).
• bbp_443 — Particulate backscattering coefficient at 443nm (m⁻¹); include bbp_s (power-law slope, unitless) describing spectral shape.
• bbp_unc_443 — Uncertainty in particulate backscattering at 443 nm (m⁻¹).
• rrsdiff — Fractional mean Rrs difference.
• l2_flags — Level-2 processing flags (bitmask; see per-variable attributes for flag_masks and flag_meanings)

The processing of Sentinel-3 products is funded by NASA's Satellite Needs Working Group (SNWG) which provides data products developed to meet the needs of stakeholders from US government agencies.