The Ocean Color Imager is an electro-optic remote sensing instrument with a 702 km swath width and 800 m resolution on board the ROCSAT-1 satellite that was launched in January 1999. It is the first push-broom type spectral-radiometer for measuring radiance from ocean surfaces and atmospheric scattering in six visible and near infrared bands for application research in ocean optics. Described in this paper are OCI's major characteristics, parameters and pre-launch and post-launch performance test results including SNR, MTF, image sharpness, band to band spectral registration and anti-blooming performance.