km. However, even at that altitude, the influence of the atmospheric back- 

 scatter was quite obvious as it began to dominate the color signal reflec- 

 ted from the ocean surface. This raised the question of whether the rather 

 poorly reflected ocean could be sensed through the entire atmosphere from a 

 spacecraft, and if the contributions of the Rayleigh backscatter and aero- 

 sol backscatter could be effectively removed from the signal seen by a 

 spacecraft. Additional NASA-supported studies in 1971 and 1972 with Lear 

 Jet and U-2 aircraft and a rapid scan spectrometer at altitudes of 14.9 and 

 19.8 km, demonstrated that this concept could be used to develop spacecraft 

 equipment for the purpose of estimating ocean water column chlorophyll 

 from earth satellites. This became possible through the realization that 

 problems associated with the scattering properties of the atmosphere, as 

 well as direct reflectance of the sun from the sea surface (glint), could 

 be either avoided or corrected (Hovis and Leung, 1977). 



The first satellite-borne ocean color sensor, the Coastal Zone Color 

 Scanner (CZCS), was launched aboard Nimbus-7 in October 1978 (refer to 

 Table 1-3). It has four visible and two infrared (one of which is thermal) 

 bands, with a sensitivity about 60 times that of the Landsat-1 multi- 

 spectral scanner. Unlike many satellite sensors of ocean properties 

 (Table 1-3), the CZCS responds to more than the features of the mere 

 surface of the sea and is sensitive to algal pigment concentrations in the 

 upper 20 to 30 percent of the euphotic zone. A predicatable relationship 

 was established between the CZCS estimates of pigments and plankton 

 chlorophyll measurements made aboard a ship in the Gulf of Mexico (Gordon 

 et. al., 1980). Other shelf studies within the Southern California Bight 

 (Smith and Baker, 1982) and coastal waters mouth of New England (Gordon et. 

 al., 1982) have also compared ship track chlorophyll data and CZCS data. 

 In all three coastal regions there was great spatial variability of in vivo 

 chlorophyll, with a striking agreement between the two methods (+30 to 40 

 percent). The widespread evolution and dissipation of high and low 

 chlorophyll features over a period of 13 days in the Southern California 

 Bight (Frontispiece) was dramatically captured in these CZCS images (Smith 



1-6 



