APPENDIX A. SENSORS 



One difficulty in interpreting remotely sensed ocean color measurements 

 arises from the fact that the thermocline and the chlorophyll maximum often 

 occur at depths in excess of three to four optical attenuation lengths, 

 depending upon season, weather and location. Thus, to provide physical and 

 biological interpretation of the information contained in the CZCS images, 

 it is important to understand the dynamic three-dimensional ocean 

 processes that create them, including, for example, the effects of local 

 upwelling on phytoplankton productivity, the effects of internal waves on 

 the variability of the chlorophyll maximum, and the complex interaction of 

 wind events on nutrient, phytoplankton, and zooplankton relationships. 



Such measurements can best be made by sensing from iji situ instruments 

 which have the capability of eventually examining the vertical, physical, 

 and biological structure of the euphotic zone of the ocean. Improved 

 accuracy and interpretation of Ocean Color Imager (OCI) data will 

 therefore result if additional satellite, airborne, in situ , and in vitro 

 measurements are taken coincident ly with satellite ocean color measure- 

 ments. A summary of various satellite ocean sensor performance charac- 

 teristics is presented in Table A-l (After Stewart, 1981). 



A.l OCEAN COLOR IMAGER 



Since the development of a new sensor always involves some risk, the modi- 

 fication of an existing design is often preferable with respect both to 

 cost and probability of success. The Nimbus-7 CZCS has proved to be an 

 excellent system with a useful life of over 3 years and is therefore the 

 leading candidate for a system designed to measure global oceanic chloro- 

 phyll concentration. 



The modifications to the CZCS design necessary to generate the required 

 sensor system are as follows: 



a. Remove the thermal (10.5 - 12.5 m) channel and its associated 

 passive cryogenic cooler. 



A-l 



