Remote multi-colour fluorescence imaging and spectral recordings of vegetation

A system for remote monitoring of vegetation fluorescence involving both spectral recordings and imaging features has been constructed. The system instrumentation for the different measuring modes is explained and data from some measurement campaigns are shown. The excitation source of the authors´ remote sensing system is a frequency tripled Nd:YAG laser including a deuterium containing Raman-shifting cell with an output wavelength of 397 nm. The receiving optics includes a Newtonian telescope, and the received fluorescence is directed to either an OMA system or to a secondary split-mirror telescope equipped with an image-intensified CCD detector. With different optical filters in front of each telescope segment, up to four fluorescence images at different wavelength bands are recorded simultaneously. The multi-colour fluorescence images are computer processed to form images of a ratio at two wavelengths. Two types of secondary telescopes were tested: a 4-channel Cassegrainian telescope for direct 2D imaging and a 2-channel telescope for push-broom scanning of images. Comparisons of the two imaging systems and their respective applications are discussed. In particular, the push-broom system could be quite effective for airborne vegetation monitoring