Hydrological optics has a rich history, playing a significant role in physical, chemical, and biological oceanography. The success over the last 30 years has provided oceanographers with a non-invasive means to study regional and global scale physical, chemical, and biological processes (Figure 1). The ability to map the color of the world’s oceans has been used to estimate global ocean productivity (Longhurst et al., 1995; Platt and Sathyendranath, 1988; Sathyendranath et al., 1989; Behrenfeld and Falkowski, 1997), aid in understanding radiant heating processes (Ohlman et al., 2000), assist in delineating oceanic biotic provinces (Longhurst, 1998), and document regional shelf break frontal processes (Ryan et al., 1999a, 1999b). The scientific utility of mapping ocean color led to wide community support that has resulted in three generations of satellites launched by the United States, complemented by an international constellation of ocean color satellites from Europe, Japan, China, and India.

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