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We have developed a global vicarious calibration scheme for spaceborne ocean-color sensors, simulating top-of-atmosphere radiance globally using a radiative transfer model, SeaWiFS Level 3 eight-day mean products, and an in-water optical model. This is a relative calibration against two channels used to detect aerosol properties; however, it enables us to determine the spatial and temporal characteristics of the vicarious calibration coefficients (Kvc) without in situ observations. We applied this scheme to the NASDA Global Imager (GLI), which operated from January 25, 2003 to October 24, 2003. Kvc exhibited the following properties: (1) channel characteristics of 1.0-1.1 (GLI was lower than the simulation) in channels 1-9 (380-565 nm), nearly 1.0 in channels 10-19 (625-865 nm), and 0.91-0.98 in channels 24-29 (1050-2210 nm); (2) scan-angle dependency and its temporal changes in channels 1-3; and (3) scan-mirror side differences and temporal changes. Applying Kvc to GLI ocean-color processing produced outputs consistent with the ground observation data. This scheme is also useful for generating consistent products from different ocean-color sensors in orbit.