limited to day observations and relatively clear sky conditions. Active remote 

 sensing systems do not have these limitations. A laser fluorosensor system 

 which is operated from a low-altitude aircraft can have day /night operation and 

 can be used when there is high-altitude cloud cover. Because of the rapid 

 surveillance capability of an active system, it can be used for "ground truth" 

 measurements for high-altitude passive instruments and for localized investi- 

 gations which may require greater spatial resolution than is usually available 

 with passive techniques. Also, a four-wavelength laser fluorosensor system can 

 provide information about the distribution of algae contained in the four algal 

 color groups, whereas current passive techniques do not differentiate between 

 different types of algae. 



This paper discusses the importance of algae and algal measurements, the 

 spectral characteristics of algae, and the development of single- and multiple- 

 wavelength laser fluorosensor systems. Emphasis is given to a detailed deriva- 

 tion of the equation for the fluorescence power received by a laser fluoro- 

 sensor system and to the error analysis for determination of chlorophyll a in 

 vivo concentration by single- and multiple-wavelength laser fluorosensor 

 systems. 



A 

 A r 



A z 

 a 



a ij 

 B 



b jj 

 b 



D 

 F(Xf) 



Hz 



k,ki 

 m 

 N 



SYMBOLS 



matrix of elements a±j 



area of receiving telescope, m^ 



area illuminated by laser at depth z, m^ 



water absorption coefficient, m~' 



constants 



diagonal matrix of elements bjj 



elements of diagonal matrix such that a-M = a^jbjj 



water scattering coefficient, m~^ 



telescope diameter, m 



laser-induced fluorescence emitted from chlorophyll a in vivo at 

 685 nm, W/nm 



laser irradiance per unit laser wavelength bandwidth, W/m^-nm 



(Yg, + Yf) and (Yf + Yi), respectively 



index of refraction for water 



matrix of elements n-; 



