Overview of the NASA OCTS GAC Processing Activities

A NASDA and NASA collaboration

OCTS global data set available

The Sensor Intercomparison and Merger for Biological and Interdisciplinary Oceanic Studies (SIMBIOS) Program was developed to provide a consistent, long-term ocean color data set which encompasses the measurements from several satellite instruments and missions. The program was designed to assist the international ocean color community in developing consistent and well-calibrated satellite data sets thatform the bridge between previous, current, and future ocean color missions for the purpose of quantifying the response of the ocean's biology to global change. A very productive collaborative effort between the National Space Development Agency (NASDA) of Japan and the NASA SIMBIOS and the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) Projects has reprocessed the entire Ocean Color and Temperature Scanner (OCTS) global area coverage (GAC) data set and made those products available to the scientific community. As part of the collaboration, NASDA provided the complete OCTS GAC Level-1a data set (November 1996 through June 1997) to NASA along with their unique expertise and analysis of the data products. NASA provided the processing expertise, methodologies and resources, and the archive and distribution support.

The focus of the OCTS GAC reprocessing work was to minimize the potential processing-related differences (atmospheric correction and bio-optical algorithms) between the SeaWiFS and OCTS missions, by reprocessing the entire OCTS GAC mission archive using the same software and algorithms employed for standard SeaWiFS processing. Preliminary descriptions of the data processing stream, the OCTS-specific modifications to the algorithms, and the statistical comparisons between OCTS and SeaWiFS can be found at:


The Goddard Space Flight Center Data and Information Services Center (DISC)/Distributed Active Archive Center (DAAC) will serve as the U.S. long-term archive and distribution site for the scientific community's access to the data set.

The DISC/DAAC will provide the same search and order capabilities for the OCTS data set that are currently available for the SeaWiFS data set. These include temporal/spatial search, concurrent acquisition of ancillary meteorological and ozone data for Level 1A data, and parameter subsetting of Level 3 binned and Standard Mapped Image data. The DISC/DAAC will have the data available in the OCTS WWW Data Browser in December 2001.

NASDA plans to provide archive and distribution support for both the NASA and NASDA processed OCTS data set on their Earth Observation Research Center website at:


In addition, a web-based browse and download utility for the Level-1, Level-2 and Level-3 products can be found at:


The scientific OCTS GAC presentation is scheduled at the American Geophysical Union (AGU) fall meeting in San Francisco (13 December, 2001).

Both agencies look on this activity as a very successful role-model for what interagency scientific collaborations can accomplish and expect that this collaboration, established between Japanese and US scientists, will continue on future missions.