Sergio Ribezzo

Differential lidar fluorosensor system used for phytoplankton bloom and seawater quality monitoring in Antarctica

A mobile fluorosensor system has been built to participate in oceanographic campaigns. During the first mission, carried out within the XIII Italian Antarctic Expedition (Research Vessel Italica, November 1997 to January 1998), seawater quality parameters (phytoplankton concentration, yellow matter, turbidity and biomass productivity) were remotely and locally monitored both in the Ross Sea and along the route back to New Zealand. Data were georeferenced by means of a GPS recorder to be subsequently plotted on thematic maps. The core of the system is a compact lidar fluorosensor capable of single or dual laser excitation of the target. In the single excitation mode, the detection of chromophores peculiar to various water impurities is possible, while dual laser excitation is necessary to monitor the phytoplankton photosynthetic activity on the chlorophyll emission channel. A lamp spectrofluorometer, a pulsed amplitude fluorometer (PAM) and a solar radiance detector completed the set of instruments onboard.

Shipborne laser remote sensing of the Venice lagoon

Abstract A complex active remote sensing system has been used on board a small ship to extensively monitor the water quality of the Venice lagoon and nearby open sea. The system was composed of an UV lidar fluorosensor directly pointing to the sea surface and a laser fluorometer monitoring the water inside a cell continuously filled by a pump from a water depth of 1m. During the cruise, both apparata were collecting data in parallel. Laser-Induced Fluorescence (LIF) signals at selected wavelengths were acquired to monitor distributions of the different species. DOM and chlorophyll features were detected by the lidar fluorosensor upon excitation at lambda 355nm, while organic pollutants and oils were scanned in the fluorometer cell by laser emitting at lambda 266nm. In both cases, the accompanying water Raman signal was collected and used for normalizing spectral intensities. Absolute concentrations of different species were obtained off-line, when possible, by calibrating LIF intensities against analytica...

Laser remote monitoring of plant photosynthetic activity

Laboratory measurements of laser induced chlorophyll fluorescence kinetics (Kautsky effect) on dark-adapted vegetation targets (maize, pine-tree) have been performed with a lidar fluorosensor by superimposing probe pulses upon an actinic light. The collected induction curves (fast rise and slow decline) have been used to reveal the occurrence of stresses and the damage produced by a pine-tree parasite. A new two-pulse LIF (laser induced fluorescence) methodology has been investigated both theoretically and experimentally, in view of remotely monitoring the plant photosynthetic activity. This technique may yield information upon the in-vivo photosynthetic processes of plants, revealing a possible stress status (nutrients depletion, presence of herbicides, photoinhibition, etc.). The lidar apparatus used contains two laser sources in order to differentially measure the chlorophyll fluorescence by means of a laser pump-and-probe technique. In fact LIF signals in the red chlorophyll band 690 nm may provide in-vivo information upon photosynthesis process in high order plants and algae. Laser pump-and-probe experimental tests, with excitation 355 nm or 532 nm, already detect the presence of herbicides, and the effects of plant exposure to thermal stresses and to low levels of gaseous pollutants. Laser measured fluorescence yields (Y) have been found to be consistent with those obtained by an in-situ fluorimeter (PAM). With proper choices of experimental parameters (pump and probe laser intensities), Y approaches the theoretical value expected for a healthy dark-adapted plant.

Line tunable tea CO2 laser using SFUR configuration

Abstract We present the first TEA CO 2 line tunable laser to be obtained using the SFUR (Self Filtering Unstable Resonator) technique. Tunability over 64 lines with high energy extraction efficiency ( E =3.8 J on the 10P20 line), single transverse and longitudinal mode operation and diffraction limited divergence are reported. The laser has been developed for the ENEA lidar facility at Frascati.

Laser diagnostics developed for conservation and restoration of cultural inheritance

Different laser induced diagnostics, originally developed for different purposes including material characterization and environmental monitoring, have been applied in the field of Cultural Inheritance preservation with the aim to facilitate successive conservation and restoration actions. In this paper results relevant to three different techniques are reviewed. The use of topologic laser and 3D sensor in checking small artifacts and large surfaces is discussed, the application of Speckle interferometry to defect analysis of ceramic artwork is represented, a demonstration of the capabilities of a time resolved LIF system in the characterization of surface composition of ancient ceramics and frescoes is finally given.

Fluorescence determination of pollutants and natural components in seawater from the onboard mobile lidar apparatus

A shipborne fluorosensor laboratory has been built and used for extensive marine campaigns to monitor the quality of different seawaters including Mediterranean, Northern sea and Antarctic Ross sea. The core of the system is a compact lidar fluorosensor capable of single or dual laser excitation of the target. In the single excitation mode the detection of different chromophores characteristic of water impurities is possible, while the dual laser excitation is necessary to monitor the phytoplankton photosynthetic activity on the chlorophyll emission channel. A lamp spectrofluorometer, a pulsed amplitude fluorometer (PAM) and a solar radiance detector complete the set of instruments on board. Georeferenced data have been collected and released on thematic maps of the different seawater quality parameters (phytoplankton concentration, yellow matter, turbidity, biomass productivity, organic pollutants) remotely and in situ monitored during several marine campaigns.

Remote sea-water quality monitoring by means of a lidar fluorosensor

The lidar fluorosensor, built at ENEA Frascati to remotely monitor the sea-water quality by collecting the water Raman backscattering and induced fluorescence from dispersed oils, suspended matter and chlorophyll, has been employed in a marine campaign in the lower Adriatic sea. Extensive calibration measurements have been undertaken by analyzing with the lidar, both in the laboratory and during the campaigns, sea water samples taken at several places along the Italian coasts. Absolute values of organic matter chlorophyll concentrations have been obtained by calibrating the lidar data with standard physical-chemical methods. This system has been recently upgraded for detecting the phytoplankton photosynthetic activity, by means of the pump-and-probe technique, which has been assessed to monitor the process in microalgae during laboratory experiments.

Spectral and time-resolved measurements of pollutants on water surface by an XeCl laser fluorosensor

An excimer-laser-based Lidar fluorosensor, designed for operation from a mobile station, has been assembled at the ENEA Centre in Frascati, and laboratory measurements on different samples have been performed both with spectral and time resolution. A low divergence, high- power XeCl laser has been used for excitation of typical chemical and biological materials polluting water surfaces. Results were obtained on thin films of oils most frequently found in the Mediterranean sea. A rough correlation has been found connecting the average oil density with both the overall visible fluorescence yield as well as the time decay constants.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Mobile lidar fluorosensor equipment for continuous seawaters monitoring and in situ photosynthetic measurements: the ENEA realisation

Abstract ENEA has recently developed a mobile integrated system composed by a compact lidar fluorosensor capable to operate in single or dual laser excitation mode, by a fluorometer, a PAM, a PAR and a GPS. The mobile lidar fluorosensor equipment has been used on ship borne platforms for extensive marine campaigns in monitoring the quality of seawaters across the Mediterranean, Northern and Antarctic (Ross) Sea. The calibrated lidar data are reported upon a digital cartographic base allowing to gather near-synoptic maps.

New double wavelength CO2 laser source for DIAL measurements

A compact carbon-dioxide laser source has been developed at the ENEA remote sensing laboratory, with the aim of emitting two alternate wavelengths in rapid succession along the same line for use in lidar/DIAL applications. The solutions adopted in the new design successfully overcome many of the problems previously encountered running a lidar test site. The overlapped emission of two different wavelengths beams from a single cavity is a major improvement on the traditional systems which relied on two separate laser sources operating on different lines. Additional upgrading of the receiver apparatus and of the acquisition electronics have led to further improvements in the performance of the complete lidar system. The new design system represents a significant step towards the development of a compact fully mobile lidar.