Coastal Zone Color Scanner

The Coastal Zone Color Scanner (or CZCS) was a multi-channel scanning radiometer aboard the Nimbus 7 satellite, predominately designed for water remote sensing. Nimbus 7 was launched 24 October 1978, and CZCS became operational on 2 November 1978. It was only designed to operate for one year (as a proof-of-concept), but in fact remained in service until 22 June 1986. Its operation on board the Nimbus 7 was limited to alternate days as it shared its power with the passive microwave Scanning Multichannel Microwave Radiometer.

CZCS measured reflected solar energy in six channels, at a resolution of 800 meters. These measurements were used to map chlorophyll concentration in water, sediment distribution, salinity, and the temperature of coastal waters and ocean currents. CZCS lay the foundations for subsequent satellite ocean color sensors, and formed a cornerstone for international efforts to understand the ocean's role in the carbon cycle.

The most significant product of the CZCS was its collection of so-called ocean color imagery. The "color" of the ocean in CZCS images comes from substances in the water, particularly phytoplankton (microscopic, free-floating photosynthetic organisms), as well as inorganic particulates.

Because ocean color data is related to the presence of phytoplankton and particulates, it can be used to calculate the concentrations of material in surface waters and the level of biological activity; as phytoplankton concentration increases, ocean color shifts from blue to green (note that most CZCS images are false colored, so that high levels of phytoplankton appear as red or orange). Satellite-based ocean color observations provide a global picture of life in the world's oceans, because phytoplankton is the basis for the vast majority of oceanic food chains. By recording images over a period of years, scientists also gained a better understanding of how the phytoplankton biomass changed over time; for instance, red tide blooms could be observed when they grew. Ocean color measurements are also of interest because phytoplankton removes carbon dioxide from the sea water during photosynthesis, and so forms an important part of the global carbon cycle.

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