Full text: Mesures physiques et signatures en télédétection

A.K. Chekalyuk (1) and G. Guyot (2) 
(1) Moscow State University, 119899 Moscow (Russia) 
(2) INRA, Bioclimatologie, 84143 Montfavet Cedex (France) 
The section was devoted to presentation of recent advances in laser active remote sensing applied to 
environmental monitoring. Four papers from France, Russia, Sweden and USA were presented in plenary session 
on 20 January and 14 papers (France, Germany, Italy, Japan, Russia, USA) in poster sessions during the 
From the last colloquium (Courchevel) a strong evolution can be noted. Three years ago, the research 
teams were just starting to consider the blue fluorescence besides the red chlorophyll fluorescence. In Vai d’Isere, 
the blue fluorescence was extensively used and analysed, giving complementary information on the physiological 
status of the plants. The second evolution is relative to the development of operational field equipment for the 
remote determination of plant fluorescence and a prototype was presented by a company in the exhibition 
coupled with the symposium. 
Due to its capability for remote monitoring in vivo plant fluorescence, the lidar technique has a great potential in 
the measurement of parameters related to the physiological status of vegetation A number of presented papers 
were devoted to recent progress in this promising direction. 
1.1. Advances in instrumentation 
Three new promising techniques were presented. The two first provide complementary information to the method, 
suggested by Lichtenthaler et al., based on the measurement of the ratio of spectral components. The third 
concerns fluorescence imaging systems. 
Pump and probe lidar technique : developed by Chekalyuk and Gorbunov (Russia) it is based on the 
simultaneous use of two lasers : the "pump" gives actinic saturating light pulses changing, for a short time, the 
functional state of the photosynthetic apparatus, and the low intensity pulses of the "probe" enables the direct 
determination of the ongoing photosynthesis efficiency. This technique has been successfully tested on 
phytoplankton and higher plants. 
Time resolved fluorescence : the interest of the measurement of the fluorescence life time instead of the 
fluorescence intensity, was discussed in the preceding colloquium (Courchevel). But in Val d'Isère the results of 
the first measurements performed in field or near-field condition were presented. A prototype of lidar and 
interpretation algorithms have been developed in a collaborative efforts of LURE, INRA Bioclimatologie and 
CEC JRC (Ispra). In addition the analysis of the time resolved reflected signal, seems to be a promising way for 
analysing the threedimentions! structure of a plant canopy, as reported by Camenen et al (INRA, France). 
Fluorescence imaging : a new approach in methodology and instrumentation has been implemented by 
S van berg et al. (Sweden), Lichtenthaler (Germany) and Miehe (France). The basic idea is the use of fluorescence 
imaging system for 2D monitoring of plant leaves. The Swedish equipment is able to acquire remotely 
fluorescence images in four spectral bands (blue and red). 
Towards passive measurements : The measurement of blue and red fluorescence intensity in the Fraunhofer 
lines of the solar spectrum was also proposed and discussed. This approach based on hyper-spectral resolution 
measurements could be the starting point of a new way for identifying and monitoring plant canopies. 

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