845 
(X = 532 nm). The width of this band (at half-height) would correspondingly 
vary from 10 to 18 nm in this case. This allows some optimalization of the 
spectrum detected by changing the wavelength of excitation to avoid bands 
overlapping in particular cases, as well as to provide appropriate spectral 
position of WRS signal. 
The in vivo chlorophyll fluorescence provides contribution at 685 nm 
(Fig.2) with a half-height of about 20 nm. From this point the utilization of 
the second harmonic of Nd:YAG laser at 532 nm may be considered as 
near-optimal (Klyshko and Fadeev, 1978). When excited with a UV source, the 
DOM fluorescence shows an extremely broad band, overlapping the whole visible 
spectrum from UV to the far red area (e.g. see Reuter, 1993; Patsayeva, 1994) 
and possessing a maximum emission at 440 nm. The spectra of oil products 
(dissolved or being in film on water surface) can vary in a wide range, 
depending on the kind of product and its "water history". More detailed 
information on this, as well as concerning the problem of distinguishing 
between oil and contribution to the spectrum one may find in (Patsayeva, 
1994). We should just underline here, that the relative contributions of 
different fluorescent bands to the total spectrum can vary in a very wide 
range, particularly in coastal waters. It can lead to significant difficulties 
in spectral processing and data interpretation, and should be taken into 
account. 
3 - LIDAR-FLUOROSENSOR INSTRUMENTATION 
3.1. Lasers 
The general requirements for a laser to be utilized in lidar-fluorosensor 
system are pulsed operation, nanosecond pulse duration, high reliability, 
convenience of operation in field condition, compact size and light weight, 
low power consumption. In Table 1 one can find some general characteristics of 
suitable lasers available. The right three columns reflect the relative 
efficiency of lasers application to excite fluorescence of particular objects 
(oil, dissolved organic matter (DOM), chlorophyll-a (Chl-a)), taking into 
account the parameters listed and optical characteristics of water and 
objects. 
Table 1. General characteristics of lasers utilized in lidar-fluorosensors 
Laser 
type 
Wa velength 
nm 
Pu lse 
power, 
mJ 
Pulse 
per 
second 
Oil 
DOM 
Chl-a 
Excimer XeCl 
308 
100-200 
50-200 
*** 
* * 
- 
Nitrogen 
337 
0 . 1-1 
10 2 -10 3 
* 
* * 
Nd:YAG 
355 
10-50 
5-10 
* 
* * 
* 
Dye 
3 90-450 
10-30 
5-20 
- 
* 
** 
Nd:YAG 
532 
30-150 
5-20 
- 
* 
*** 
3.2. Detecting systems 
The telescope of 20-30 cm aperture (Newton- or Cassegrain-type) is generally 
used to collect an optical response from the water column caused by pulsed 
laser excitation. Due to high variability in detection conditions (moving