The Ocean Color Instrument (OCI) is the primary instrument aboard NASA's Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite. OCI is a highly advanced optical spectrometer used to measure properties of light over portions of the electromagnetic spectrum. It enables continuous measurement of light at a finer wavelength resolution than previous NASA satellite sensors and extends key system ocean color data records for climate studies.

The color of the ocean is determined by the interaction of sunlight with substances or particles present in seawater such as chlorophyll, a green pigment found in most phytoplankton species. By monitoring global phytoplankton distribution and abundance with unprecedented detail, OCI data help us better understand the complex systems that drive ocean ecology.