Reprocessing of the OCTS Global Dataset, a Collaborative Effort Between NASDA and the NASA SIMBIOS Project

As a payload on the ADEOS spacecraft, the Ocean Color and Temperature Scanner (OCTS) was launched and operated by the National Space Development Agency (NASDA) of Japan in August of 1996. The OCTS instrument began routine imaging in November of 1996, making it the first operational mission dedicated to the acquisition and monitoring of oceanic chlorophyll concentration on a global scale. Although the ADEOS spacecraft suffered a catastrophic failure less than eleven months after launch, the data collected during the OCTS mission lifetime is of great value to the Earth science community, as it can provide important information on the baseline state of the worlds oceans prior to the El Nino event of 1997-1998. The second global ocean color mission to be launched was the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), which has been collecting global data continuously since September of 1997. The unfortunate gap between the end of OCTS operations and the start of SeaWiFS operations makes direct sensor to sensor comparisons impossible, thus leaving considerable uncertainty in any effort to extend the SeaWiFS global ocean color timeseries back to the pre-1997 El Nino period, or to study the propagation of Kelvin and Rossby waves associated with the transition into El Nino. This uncertainty can result from relative differences in instrument calibrations, as well as differences in the atmospheric correction and bio-optical algorithms employed. The focus of the present work is to minimize the potential differences in the atmospheric correction and bio-optical algorithms between the two sensors, by reprocessing the entire OCTS GAC mission archive using the same software and algorithms employed for standard SeaWiFS processing. The data processing stream will be presented, and OCTS-specific modifications to the algorithms will be discussed. Statistical comparisons between OCTS and SeaWiFS will be shown, and remaining processing issues will be highlighted. Finally, the OCTS product list and data distribution procedures will be provided.