Processing of the CZCS data, as well as all of the rest of the Nimbus data, 

 proved to be far more of a problem than anticipated before launch. In 

 order to handle the large volume of data that would be collected by an 

 imaging sensor such as the CZCS with an operating time up to two hours per 

 day, and a return signal rate of 800,000 bits per second, a special pro- 

 cessing line was established at NASA/Goddard Space Flight Center (GSFC) 

 using the latest in automatic data processing techniques. Unfortunately, 

 these techniques were not at a state that they could handle such a large 

 volume routinely, and only as a result of intense effort by the GSFC data 

 processing staff was a routine flow of data finally accomplished approxi- 

 mately two years after launch. This delay in data availability forced a 

 corresponding delay in analysis of the data comparison with measurements 

 made shortly after the launch of the spacecraft. When data was finally 

 available for such analysis, however, comparisons with ship measurements 

 showed the correlation of derived and surface-measured pigment concentra- 

 tions and diffuse attentuation coefficients were quite good in open 

 oceans, with accuracy degrading in areas of high sediment suspension due to 

 the limited number of spectral bands available. 



Although the validation of the CZCS-derived pigment concentration, C , is 

 still underway, the results up to this point in time are very encouraging. 

 (A complete description of the CZCS algorithms is presented in Appendix B.) 

 The initial comparisons between CZCS imagery and surface pigments measured 

 continuously along ship tracks carried out by Gordon et al. (1980) and 

 Smith and Wilson (1981) suggested that C could be retrieved from the 

 imagery to within about a factor of two. Subsequently, Smith and Baker 

 (1982) and Gordon et al. (1982) have shown that accuracies of the order of 

 +30 percent in C are possible for Morel's Case 1 waters (Morel and 

 Prieur, 1977; see also, Appendix B). An example of the Gordon et al. 

 (1982) comparison between CZCS-derived (heavy line) and ship-measured 

 (light line) pigments is presented in Figure 2-2. The ship track is from 

 Georges Bank (left edge) to Delaware Bay (right edge) and the ship data 

 were taken within +12 hours of the satellite overpass on Orbit 3240. 

 Atmospheric correction was effected by applying the techniques described 

 in Appendix B to a Warm Core Gulf Stream Ring centered about 150 km from 



2-6 



