The question of whether the diffuser plate for calibration can be mounted 

 on the ATN spacecraft is now under study. In summary, the OCSWG found that 

 a quite acceptable CZCS program could be carried out from the ATN, that 

 there are no insurmountable technical problems in moving the orbit closer 

 to noon, and that there are no serious problems in mounting the CZCS on the 

 ATN. 



5.2 MEASUREMENT CHANNELS 



The Nimbus-7 CZCS program demonstrated the feasibility of determining 

 ocean chlorophyll levels (and diffuse attenuation coefficients), from 

 multi-channel visible space-borne observations (see Appendix B for dis- 

 cussions of the algorithms). The OCSWG requirement is to resolve the 

 chlorophyll concentration to within 50 percent over a range of concentra- 

 tion from .05 to 10.0 yg chU in the open ocean and outer continental 

 shelf areas. Radiance observations to 10 bit accuracy are required at a 

 minimum of six of the following eight wavelengths, dependent on water-mass 

 type: 



Wavelength (nm) Bandwidth (nm) 



443 20 



490 20 



520 20 



560 20 



590 20 



670 20 



765 40 (Notched for 02 A band 759-770nm) 



867 45 



The 490 and 590 nm channels are useful under special circumstances to 

 extend the observations into more turbid coastal waters. 



5.3 SPATIAL RESOLUTION 



The chlorophyll distribution in the ocean is patchy on all scales down to 

 the sub-kilometer level (Table 2-1). Thus, to adequately map phyto- 

 plankton variation in high-concentration shelf areas, which is the major 

 goal of the first MAREX studies, a satellite must be able to resolve about 

 a kilometer of the ocean. This small spot size also permits measurements 



5-5 



