Costal Zone Color Scanner (CZCS) was the first of its kind sensor flown in 1978 for ocean studies. It gave quantitative estimate of phytoplankton. After that, many missions were launched by various agencies like IRS-P3-MOS, Sea-WiFS, OCTS, MODIS, MERIS etc. The data from these sensors was utilized to study, develop retrieval algorithms, validate the models and define the new sensor parameters for better extraction and estimation of chlorophyll and other ocean biological and physical parameters on a routine basis. ISRO's Ocean Color Monitor (OCM-1) was launched in 1999 onboard Oceansat-1 (IRS-P4), polar orbiting satellite. This paper highlights some of the important features, specifications and performance of OCM sensor. It also briefly gives some of the enhancements planned for OCM-II. OCM provides multi-spectral imagery with narrow spectral width having large field of view of ±43° and ground resolution of 360m. The sensor is designed to cater to land and ocean applications globally and accordingly it has high radiometric sensitivity with large dynamic range. The radiometric performance is realized using low noise circuit designs and practices. The optics and detectors are mounted on a highly stable structure, which facilitates achieving band-to-band registration, minimizes veiling glare and temperature excursions and avoids sun glints. To provide continuity in services, OCM-II is being developed for Oceansat-II, slated launch second half of 2007. OCM is the only sensor which meets both ocean and land applications simultaneously.