Current terrestrial and hydrographic laser remote sensing research and applications are briefly reviewed. New progress in airborne oceanic lidar instrumentation and applications is then highlighted. Topics include the unique role of airborne active-passive (laser- solar) correlation spectroscopy methods in oceanic radiative transfer studies. Based on a perceived need for high resolution, improved specificity, and wider range of applicability than fluorescence methods, laser-induced resonance Raman and atomic emission spectra of oceanic constituents are suggested.

Recently a number of airborne nadir scanning laser radars have been developed for both military and civilian applications. These have range resolutions on the order of 10 cm but relatively moderate area coverage rates, in the range 1000 - 10,000 m²/s (3.6 - 36 km²/h) when operating in a high resolution mode with 0.25 m spot distance. Technology development in laser sources, scanning techniques and signal processing will probably improve the area coverage substantially and lead to compact systems suitable for new applications, including the use in UAV:s. Present nadir capability could be combined with a forward looking capability for guidance and obstacle avoidance in autonomous or semi-autonomous systems. The paper will investigate the potential performance of such combined systems using state-of-the-art lasers and receiver technology. Among the applications for both military and civilian users we note the collection of 3-D data for terrain modeling and object recognition. For these functions signal processing using multiple echo and intensity information is of great value as well as adding passive senor information. Full wave form processing will further improve the information for example to characterize trees. The use of high resolution 3-D data in synthetic environments is obvious and will be discussed. Experimental data collected with a commercial laser system, TopEye, developed by Saab Dynamics, will be shown and some image examples will be discussed in relation to different applications.

The results of experiment on airborne laser sounding of coastal sea waters about Northern Scotland are described. The aircraft- laboratory of Institute of Atmospheric optics with Makrel-2 lidar was used. As a rule, the flights were carried out at height 300 M above water with average speed of 320 km/h. The pulse repetition rate of laser shots changed from 5 up to 25 Hz. The total length of flight lines above water surface has made about 8000 km. The processing of signals was made by a method of logarithmic derivative with statistical processing. The large attention was given to neutralization of influence of afterpulses, arising in photomultipliers, and especially strongly interfering to sounding of water.

Control of underwater noise radiated by naval vessels relies on two factors. First, ship design for quiet operation, and second, provision of additional control features to monitor and manage the acoustic signature according to operational requirements. While the first is the most crucial factor, the second gains in significance when quiet to ultra-quiet operation is required. Self-monitoring of farfield acoustic signature is inherently problematic because of the difficulty in providing real-time information on radiated sound at large distances from the vessel. A variety of less direct, but currently more effective methods may be employed. However, the one proposed here is based on direct optical sensing of underwater sound through laser Doppler velocimetry in the acoustic nearfield of a vessel. The merits and shortcomings of the technique are discussed, including some of the problems contributing to the presently poor signal-to-noise ratio. While it appears that the technique may be feasible at low frequencies of 10 to less than 1000 Hz, some serious noise limitation such as those due to Brownian diffusive motion need to be overcome first.

Last years the interest in using the airborne laser scanning systems has much more increased. One of the applications is the 3-D modeling of the scene. The promising accuracy of the airborne laser scanner measurements is usually 5 - 10 cm in X,Y, and 10 - 30 cm in the Z direction. This does not, however, fully describe the performances of the systems if a 3-D model of a target is needed. How precise and accurate will the 3-D model be, for example? How good does it fit in the real object? In order to answer these questions, a comparison of the three-dimensional models generated from the laser data acquired in different ways must be done. The cheapest and more flexible way to do it is a simulation. This paper examines scanning techniques mainly used in laser remote sensing for topographic and mapping purposes today. A simulation program has been developed for this aim. The scan patterns generated based on those like such commercially available laser scanning system as TopoSys, ALTM-1020, TopEye, and 3-D profilometer create. The program allows to change a number of flight parameters, i.e. the flight speed, the flight altitude, roll, pitch and yaw angles. Basically, the concern was the image geometry. No radiometric analyses were performed. Some example pictures presented. The results showed that the 3-D model generated from the data collected in a way TopoSys does is much accurate and informative compared to ALTM-1020 or TopEye from the point of view of the geometry.

The Institute of Navigation/University Stuttgart has developed an airborne Scanning Laser Altitude and Reflectance Sensor. This paper describes an approach to automatically detect and extract artificial surface objects using the data of imaging laser altimeters. Laser altimeters register surface topography directly in three spatial dimensions by measuring the distance to individual surface points. Beyond mere ranging advanced imaging laser altimeters like the Scanning Laser Altitude and Reflectance Sensor (ScaLARS) are also able to actively measure surface reflectance. By fusing both the 3-D geometry and surface reflectance, object detection and identification can be done automatically. In a first step, surface objects are detected by applying a morphology-based filter to the elevation data. In order to detect also large buildings which tend to make morphological filtering fail an additional approach based on a progressive local histogram analysis of elevation is used. The detected surface objects are then separated into artificial objects (buildings) and natural objects (vegetation) in the second step, using surface reflectance data, and/or elevation 'texture' and surface orientation. To demonstrate the effectiveness of these identification criteria, they are applied to a test data set collected with the ScaLARS laser altimeter.

The stem volume, basal area And mean height of Norway spruce and Scots pine stands and individual trees were derived using canopy height metrics by means of a laser scanner TopoSys-1. Due to the high pulse rate of the laser scanner, individual tree statistics could be obtained. Methods to generate DTM and tree crown map from laser data were reported. Stand-wise and tree-wise field inventory data was regressed against laser-derived features. The coefficients of determination were in the range between 0.84 and 0.88 for the stem volume, basal area and mean height. The obtained accuracy was equivalent to conventional stand-wise forest inventory implying that the described approach can be used operationally. Further, it was shown that the tree height estimation accuracy of single and dominant trees was 1.5 m using the laser scanner. The accuracy of conventional clinometer measurements is typically better than 0.5 m but the time spent for height measurements is enormous. With the laser, the height of all dominant trees could be assessed within a fraction of time.

This paper describes a velocimetry system using scintillation of a laser-beam with spatial filters based on sensor arrays for a laser- based gas flux monitor. In the eddy correlation method, gas flux is obtained by mutual relation between the gas density and the flow velocity. The velocimetry system is developed to support the flow velocity monitor portion of the laser-based gas flux monitor with a long span for measurement. In order to sense not only the flow velocity but also the flow direction, two photo diode arrays are arranged with difference of a quarter period of the weighting function between them; the two output signals from the sensor arrays have phase difference of either (pi) /2 or -(pi) /2 depending on the sense of flow direction. In order to obtain the flow velocity and the flow direction instantly, an electronic apparatus built by the authors extracts frequency and phase from crude outputs of the pair of sensors. A feasibility of the velocimetry was confirmed indoors by measurement of the flow- velocity vector of the convection. Measured flow-velocity vector of the upward flow agreed comparatively with results of an ultrasonic anemometer.

Experimental investigations of the fluorescence intensity of plants in red and ultraviolet spectral ranges induced by the laser radiation have been carried out during one year. Dependence of the quantum yield of chlorophyll a fluorescence on plant species has been established and investigated. The largest range of seasonal variations of the fluorescence intensity was observed for the deciduous trees. Seasonal variations of the florescence intensity have the tendency to insignificant variations for the coniferous trees. Application of the fluorescence method to the remote specific categorization of the plant tissue and determination of the chlorophyll content is shown to be promising.

Chlorophyll fluorescence has been widely applied as a non-invasive technique for the in vivo analysis of plant stress. In this work, the two-dimensional image analysis of the fluorescence signal was used to evaluate the physiological status of heavy metal stressed leaves, based on their photosynthetic capacity. Chlorophyll fluorescence (greater than 650 nm) emission of control and heavy metal treated plants registered at different times during the blue light illumination of the leaves show abnormal patterns of non- homogeneous spatial distribution of the fluorescence emission from metal-treated plants. This is correlated to an altered photosynthetic functionality in different parts of the leaves. Quantitative evaluation of the photosynthetic activity can be made on data extracted after simple arithmetical pixel-point processing of fluorescence images taken at different time during the illumination process. The altered fluorescence emission was observed in absence of other visual symptoms that could testify problems at the level of the photosynthetic apparatus. This indicates that chlorophyll fluorescence imaging is a suitable tool for the early, pre-visual detection of plant stress also in the case of heavy metal stress.

In this paper, a compact, new UV-A laser induced fluorescence imaging system implemented in an all-road car for near-field remote sensing of vegetation will be described. It has been developed as a part of a European Community Program INTERREG II* and is consisting of three main parts: excitation, detection and control units. The excitation light pulses (10 ns) are produced by a frequency tripled Nd:YAG laser emitting at 355 nm with a variable repetition rate up to approximately equals 22 kHz and a pulse energy typically of 40 (mu) J. The laser spot size is adjusted by means of a variable beam expander. Fluorescence images are recorded via entrance lenses and 10 nm bandpass filters with a gated intensified digital CCD camera operating at 50 frames per second. The 'head of the system' (laser and camera) can be directed in site and azimuth, and can be high until a 6 meters height. All the functions like the system positioning, localization and distance detection, spot size adjustment, focus, sharpness, selection of the filter, laser and camera synchronization, gain of the intensifier, real time visualization of images, acquisition time are controlled by a newly developed software which also allows image storage, analysis and treatment. Examples of remote sensing fluorescence images recorded at a distance between 10 and 30 m are presented.

The chlorophyll fluorescence parameters Fv/Fo and Fd/Fs (equals Rfd690), related to the quantum conversion capacity at dark-adapted and light-adapted state of the photosynthetic apparatus respectively, have been evaluated as possible indicators of drought and heat tolerance in winter wheat. The measurements were carried out on primary leaves of 8-day old seedlings. Rfd values decreased in 8 days by 20% (p less than or equal to 0.01) only under severe water limitation and for the drought susceptible genotype. The photosynthetic apparatus was more sensitive to high temperature with both ratios, Fv/Fo and Rfd690, showing mean decrease (p less than or equal to 0.001) of 27% and 43%, respectively, in 5 days at 35 degrees Celsius. The susceptible cultivars decreased of up to 42% and 65% and the drought and heat tolerant genotypes only 7% and 12% for Fv/Fo and Rfd690, respectively. The Fv/Fo ratio correlated well (p less than or equal to 0.05 and p less than or equal to 0.01) with seedling responses to oxidative and osmotic stresses. The Rfd690-values correlated better with all physiological parameters considered and with the deviations from linear regression of drought susceptibility index DSI (r equals -0.84, p less than or equal to 0.01) on yield potential showing the highest potential to predict drought and heat tolerance. In addition the blue, green, red and far-red fluorescence have been determined using a laser-induced-fluorescence imaging system in entire seedlings of wheat and triticale grown under optimal laboratory conditions. The ratios F690/F740 and F440/F520 correlated well (p less than or equal to 0.05) with the total chlorophyll content (detected by the SPAD-chlorophyll-meter) and the specific leaf dry weight (SLDW) showing the potential of the both fluorescence ratios to discriminate genetic differences between cultivars for these leaf structural sources of water use efficiency (WUE) improvement.

In atmospheric sensing, one application that has demonstrated several impressive successes over the last two decades is LIght Detection And Ranging (LIDAR). With elastic signal returns, this technique remotely provides information such as the particle density and, for a multiple field of view LIDAR, the distribution in size of the aerosols as a function of the range along the probing laser beam. For this type of application, the return signal has the same spectrum than the laser source. Some specific techniques, such as Raman or resonant LIDARs, collect the return signal at wavelengths other than the source. However, these signals are usually narrow spectrally and are collected with a single bandpass spectral filter. Recently, the Canadian Defence Research and Development Branch has initiated the evaluation of a novel LIDAR concept which opens the possibility of collecting simultaneously the detailed spectral information contained in spectrally wide return signals. One drawback with this approach is the loss of simultaneous information at multiple ranges, i.e., the spectral information is available only for a specific range. Nevertheless, there are applications where the partial loss of range information is compensated by the gain resulting from the spectral information. This paper describes the concept and reviews the general model predicting the capability of this technique for the standoff detection of bioaerosols. It shows a numerical simulation of the anticipated spectral profiles collected with the proposed active range-gated fluorescent LIDAR for a particular bioaerosol as a function of ranges, and for both day and night operational scenarios.

Continuous monitoring of atmospheric water vapor mixing ratio profiles, especially within the planetary boundary layer is required for weather assessment, global circulation models and atmospheric studies. Although conventional lidar techniques based on Raman scattering or differential absorption are capable of such measurements, they are usually large, expensive systems with high power lasers which pose eye safety problems. This paper describes a compact, cost effective, eye-safe, Raman lidar operating in the solar blind wavelength region that can be used for autonomous daytime and nighttime monitoring of water vapor in the lower atmosphere. The performance of the compact Raman lidar was simulated and also experimentally verified with a bread-board lidar. Daytime measurements of up to 2.5 km and nighttime measurements to over 3 km with 10% accuracy can be obtained with less than 10 minutes of averaging.

The Mini-Raman Lidar System (MRLS) is a 'proof-of-principle' chemical sensor that combines the spectral fingerprinting of solar- blind UV Raman spectroscopy with the principles of lidar to open a new venue of short-range (meters to tens of meters), non-contact detection and identification of unknown substances on surfaces. The device has potential application to 'first responders' at the site of a chemical spill. The MRLS is portable and has been used both in the lab and in the field. Theoretical estimates and actual laboratory data suggest the possibility of detecting contaminants with a surface coverage of less than 1g/m² at a distance of three meters for one second of signal integration. Increasing the optical throughput efficiency, integrating pattern recognition software, and incorporating a laser with a wavelength near 250 nm are the primary goals for the development of a prototype system.

One of the major threats presented by a chemical agent attack is that of a munition exploding overhead and 'raining' aerosols which can contaminate surfaces when they impact. Since contact with these surfaces can be fatal, it is imperative to know when such an attack has taken place and the likely threat density and location. We present the results of an experiment designed to show the utility of a CO₂ lidar in detecting such an attack. Testing occurred at Dugway Proving Grounds, Utah and involved the simulation of an explosive airburst chemical attack. Explosions occurred at a height of 30 m and liquid droplets from two chemicals, PEG-200 (polyethylene glycol 200) and TEP (triethylphosphate), were expelled and fell to the ground. The munition was the U.S. Army M9 Simulator, Projectile, Airburst, Liquid (SPAL) system that is designed for chemical warfare training exercises. The instrument that was used to detect the presence of the aerosols was the Laser Standoff Chemical Detector (LSCD) which is a light detection and ranging (LIDAR) system that utilizes a rapidly tunable, pulsed CO₂ laser. The LIDAR scanned a horizontal path approximately 5 - 8 m above the ground in order to measure the concentration of liquid deposition. The LIDAR data were later correlated with card data to determine how well the system could predict the location and quantity of liquid deposition on the ground.

The Air Force Research Laboratory (AFRL) Laser Remote Optical Sensing (LROS) program has developed the Laser Airborne Remote Sensing (LARS) system for chemical detection using the differential absorption lidar (DIAL) technique. Airborne tests during the last year resulted in chemical detection at a slant range of 30 km. As the next step in the development process, concepts for a compact, semi-autonomous DIAL system are being considered. This paper describes the conceptual design and external interfaces of the acquisition, processing, and control system computers required to operate a semi-autonomous DIAL system. The conceptual design of the VME-based real-time computer system uses three CPUs: (1) a data acquisition and control CPU which synchronizes experiment timing and pulsed CO₂ laser operation while controlling lidar subsystem components such as pointing and tracking, wavelength sequencing, and optical alignment; (2) a data reduction CPU which serves as the semi-autonomous controller and performs real-time data reduction; and (3) a data analysis CPU which performs chemometric analysis including chemical identification and concentration. The triple-CPU and multi-layered software decouple time-critical and non-critical tasks allowing great flexibility in flight-time display and processing.

The Air Force Research Laboratory (AFRL) Active Remote Sensing Branch has developed the Laser Airborne Remote Sensing (LARS) system for chemical detection using the differential absorption lidar (DIAL) technique. The system is based on a high-power CO₂ laser which can use either the standard ¹²C¹⁶O₂ or the ¹³C¹⁶O₂ carbon dioxide isotopes as the lasing medium, and has output energies of up to 5 J on the stronger laser transitions. The lidar system is mounted on a flight-qualified optical breadboard designed for installation into the AFRL Argus C- 135E optical testbed aircraft. The Phase I ground tests were conducted at Kirtland AFB in 1997, prior to the LARS flight tests performed in September 1997 at Kirtland AFB and the Idaho National Engineering and Environmental Laboratory (INEEL). The Phase II ground tests were conducted in 1998 to determine the optimum performance of the LARS system, after the incorporation of modification and improvements suggested by the flight test results. This paper will present some of the chemical detection and radiometric results obtained during the Phase II ground tests.

By combining the capability of a differential absorption lidar (DIAL) and the excellent characteristics of a micro pulse lidar (MPL) we have designed and tested a micro pulse DIAL system, which could be operated from the ground or airborne platform, to monitor the atmospheric water vapor mixing ratio. To maintain the compact and rugged optical frame work of an MPL it employs a diode pumped tunable Cr:LiSAF laser operating at 825 - 840 nm range, a fiber optic beam delivery system, and an APD photon counting detector. The system parameters were optimized through extensive DIAL simulations, and the design concept was tested by building a breadboard lidar system. Based on the results of the simulations and the performance of the breadboard lidar the Micro Pulse DIAL system design has been refined to (1) minimize scattered laser light -- the major source of signal induced bias, (2) permit near field measurements from less than 400 m, (3) produce a compact, rugged, eye-safe instrument with a day and night operating capability. The lidar system is expected to provide 150 m vertical resolution, high accuracy (approximately 5%), and 3 km range looking up from the ground.

A wavelength agile coherent LIDAR system is under development at the Air Force Research Laboratory (AFRL). Coherent lidar has the potential of longer-range sensitivity than conventional direct detection systems. AFRL is conducting risk reduction experiments to address issues involved with coherent LIDAR. Issues include speckle noise inherent to heterodyne detection, robust signal analysis algorithm development, and integration of a wavelength agile laser as the local oscillator to the receiver. The transmitter laser, developed for the LARS program, is a high energy TE CO₂ laser hardened for airborne operations. Performance of the wavelength agile local oscillator laser is presented, and preliminary data from risk reduction experiments.

The DLR ground-based cw Doppler lidar has been developed for wind and turbulence measurements in the Atmospheric Boundary Layer. Moreover, it is used for experimental investigations of aircraft wake vortices. By the present paper measurements of wake vortices generated by military-type fixed-wing as well as rotor-wing aircraft will be presented. The experimental data has been analyzed regarding the structure and circulation of wake vortices, partly also regarding their temporal development. The influence of flight parameters has been measured during several consecutive fly-bys. Small variations in the velocity profiles could be observed which were overlayed by the signatures of the variable wind and turbulence field, a problem which can only be solved by statistical treatment. The influence of the aircraft design could be demonstrated by comparison of the vortex signatures generated by two B707-type aircraft with pronounced differences in aircraft design.

In this paper, we describe the automatic damage assessment process we developed to assess the extent of battle damage based on laser rdar (Ladar) images taken before and after a strike. The process is composed of three modules, the image registration module, the damage isolation module, and the damage assessment module. In the image registration module, distortion in the raw range data was first compensated to obtain the actual heights of the objects. Then, Ladar images taken before and after the strike were aligned according to their pixel intensities. In the damage isolation module, changes between the two sets of images were compared to isolate the locations of the actual damage. Factors such as sensor noise, sensor perspective difference, debris, and movement of vehicles, which all contribute to changes in the images, were automatically discounted in this module. The approximate location of the damage, if it existed, was passed to the damage assessment module to determine the extent of the damage using the region growing technique. This process enables fast and accurate evaluation of a strike with as little human supervision as possible.

Laser radar systems are required for various military applications including obstacle detection, target recognition, and terrain mapping. Each application requires different system parameters such as pulse energy, repetition rate, and field of view. This paper presents a review of a multifunction laser radar system under construction for the Cooperative Eyesafe Laser Radar Program (CELRAP) of the U.S. Army CECOM Night Vision and Electronic Sensors Directorate.

The SPAce Readiness Coherent Lidar Experiment (SPARCLE) is the first demonstration of a coherent Doppler wind lidar in space. Coherent lidars can accurately measure the wind velocity by extracting the Doppler frequency shift in the back-scattered signal from the atmosphere through optical heterodyne (coherent) detection. Coherent detection is therefore highly sensitive to aberrations in the signal phase front, and to relative alignment between the signal and the local oscillator beams. The telescope and scanning optics consist of an off-axis Mersenne telescope followed by a rotating wedge of silicon and a window of fused silica. The wedge is in very close proximity to the experiment window, and is essentially in contact with the scanner motor/encoder system. The can environment temperature is nominally 20 degrees Celsius, the window ranges from -20 degrees Celsius to 0 degrees Celsius, and the scanner motor/encoder system alone could generate temperatures as high as 35 degrees Celsius. This thermal environment, coupled with the relatively large sensitivity of silicon's refractie index to temperature, has required careful thermal design and compensation techniques. This paper discusses the optical issues of these thermal effects and a variety of methods used to ameliorate them.

One of the major applications of space-based Doppler wind lidar is to improve atmospheric analyses and numerical weather prediction (NWP). Since the mid 1980s, Observing System Simulation Experiments (OSSEs) have been conducted in order to evaluate the potential impact of lidar winds on NWP. These experiments have shown tremendous potential for satellite lidar observations to improve atmospheric analyses and forecasts. In addition, the OSSEs are providing an evaluation of trade-offs in lidar design, and are currently being used to define the specific requirements for lidar winds in terms of horizontal and vertical coverage and accuracy.

This paper presents the development of a laser range scanner (LARS) as a three-dimensional sensor for space applications. The scanner is a versatile system capable of doing surface imaging, target ranging and tracking. It is capable of short range (0.5 m to 20 m) and long range (20 m to 10 km) sensing using triangulation and time-of-flight (TOF) methods respectively. At short range (1 m), the resolution is sub-millimeter and drops gradually with distance (2 cm at 10 m). For long range, the TOF provides a constant resolution of plus or minus 3 cm, independent of range. The LARS could complement the existing Canadian Space Vision System (CSVS) for robotic manipulation. As an active vision system, the LARS is immune to sunlight and adverse lighting; this is a major advantage over the CSVS, as outlined in this paper. The LARS could also replace existing radar systems used for rendezvous and docking. There are clear advantages of an optical system over a microwave radar in terms of size, mass, power and precision. Equipped with two high-speed galvanometers, the laser can be steered to address any point in a 30 degree X 30 degree field of view. The scanning can be continuous (raster scan, Lissajous) or direct (random). This gives the scanner the ability to register high-resolution 3D images of range and intensity (up to 4000 X 4000 pixels) and to perform point target tracking as well as object recognition and geometrical tracking. The imaging capability of the scanner using an eye-safe laser is demonstrated. An efficient fiber laser delivers 60 mW of CW or 3 (mu) J pulses at 20 kHz for TOF operation. Implementation of search and track of multiple targets is also demonstrated. For a single target, refresh rates up to 137 Hz is possible. Considerations for space qualification of the scanner are discussed. Typical space operations, such as docking, object attitude tracking, and inspections are described.

The Video Guidance Sensor (VGS), part of NASA's Automated Rendezvous and Capture program, was flown on Shuttle mission STS-95 in October of 1998 to test on-orbit the functional characteristics of the VGS. This was the second flight of the VGS (the first flight was in 1997 on STS-87), and this time long-range tracking data was gathered during the experiment. The flight experiment sensor was designed to operate from 1.5 meter range out to 110 meter range, with a field-of-view of 16 by 21 degrees. The VGS tracked its target at a 5 Hz rate and returned 6-degree-of-freedom information on the target's position and attitude relative to the sensor. The VGS was mounted in the Shuttle cargo bay, and its target was mounted on the Spartan spacecraft being carried on this mission. The orbital testing of the VGS included operations with the target on the Shuttle's Remote Manipulator System (RMS) at the start of the 10-day mission, long-range data during the Shuttle rendezvous with the Spartan two days later, and some more RMS operations later in the mission. The data returned from the orbital testing included VGS diagnostics, acquisition, and tracking data, RMS positions, hand-held laser range data, tapes of the data from the VGS video camera, and orbital positioning data from the Spartan and the Shuttle to allow correlation of the VGS data with orbital best- estimate-of-truth data. The Video Guidance Sensor performed well in all phases of the testing, and the VGS is being incorporated into the ground testing of a complete automated rendezvous and docking system. Work on the development of the next generation VGS is continuing.

The recent development of optical phased arrays (OPAs) enables practical, electronically programmable, control of laser beams for laser radar and other advanced optical sensors. OPAs are the direct analog of microwave phased array antennas; they are electronically programmable optical elements that control the phase distribution on an optical aperture in order to control beam direction and shape. Operating principles and construction of OPAs are briefly described and current and potential performance capabilities are summarized. An OPA supports spatial-domain beam control such as agile or continuous scanning patterns, adaptive electronic focus control, and far-field beam shape control, as well as the generation of multiple beams from a single input beam (pattern generation, or fanout). OPAs also support time-domain beam control, including precision time delay or positioning of short pulses, pulse compression and expansion, and the generation of dense pulse bursts from a single pulse. All of these functions are software controllable, which enables mission-flexible and mission-adaptive optical systems, including so-called 'smart' optical systems with autonomous alignment and calibration capabilities. These and other electronically programmable capabilities are discussed. As a concrete example of an advanced sensor enabled by the OPA, the potential for an adaptable-format, high-resolution, multi-beam laser radar with no moving parts is discussed.

These are several laser based techniques available for measuring the distance to diffusely scattering surfaces. The most used method is the triangulation probe where the image of a laser spot is viewed at an angle to the incident beam direction. In the paper will be shown how the non scanning white light interferometer can be used for measurement of distance or distance differences to surfaces which are extremely yeregh in an optical sense. The light is divided by a beamsplitter and reflected from two surfaces, one reference and one object surface. After recombination it is spatially filtered. At distance difference causes a delay between the reflections. The delay can be measured with the nonscanning white-light interferometer by finding the positions of the correlation peaks. Since there are no moving parts the interferometer can be used to measure rapidly moving objects.

A high repetition rate diode pumped Erbium glass laser was demonstrated at 50 Hz with Q-switched outputs up to 15 mj by various Q-switch methods.

The author for the first time develops the elementary theory of laser on vibronic crystal with electron excitation allowing to describe theoretically the main generation characteristics of laser electron -- oscillatory and recombination transitions in a dielectric ion crystal of a vibronic type, pumped both by electron, and combined (optical and electron) technique. On the basis of the mentioned above elementary theory the estimations of main generation characteristics for laser transitions in a crystal Al₂O₃:Ti³⁺, excited by a pulsed electron beam are carried out. In particular, there are determined optimum (for generation energy in a pulse) parameters of pulsed electron excitation for laser transition ²E - ²T_2g of an ion Ti³⁺: electron energy in a beam 200 - 300 keV, current density 1 kA/cm². Thus the wavelength tunable band of laser radiation reaches from 0.6 microns up to 1.1 microns, and under certain conditions -- from 0.55 microns up to 1.3 microns. The basic opportunity of simultaneous laser generation on the recombination transition bands from 0.29 microns up to 0.45 microns is discussed. The examples of laser complexes with new architecture are given which by numerical modeling allow to predict an opportunity of laser generation energy in a pulse up of to 1 J and average output power up to 100 W and more inside a wavelength tunable range approximately from 0.55 microns up to 1.3 microns, that can be of interest for a wide range of laser radar technologies.

The numerical use of the fast Hankel transform E-field propagator is described in this paper. For azimuthally symmetric E-field applications, this propagator is a useful tool for solving many common problems such as super-Gaussian and unstable resonator laser mode propagation within optical trains and then out to a target. Overlap integrals for coherent ladar may be easily computed. In addition, laser resonators with gain medium may be analyzed for mode structure and output power incorporating g_o(r), I_sat(r), and extinction(r) with radially varying reflectivity and phase optics.

A compact and light weight imaging laser radar system is being developed for an advanced exo-atmospheric missile interceptor platform for the Discriminating Interceptor Technology Program (DITP). The laser radar will be used in combination with a two- color passive IR sensor to provide high angular resolution information for long range tracking and discrimination of multiple targets. A direct-detection approach at 532 nm has been chosen to provide the best overall capability in a system which can be fielded in the near term. The laser radar is designed to operate at 25 W for a limited run time and output short 1.3 ns pulses at 100 Hz. A high speed 10 X 10 pixel receiver capable of efficient single photon detection is also being developed.

This paper presents a 3D-Imaging Laser Scanner (3D-ILS) for close range survey for up to 10 meters. The 3D-ISL is eyesafe and works with a visible semiconductor laser diode transmitting at 670 nm. The large ranging dynamic is achieved by measuring the phase difference between the transmitted and received intensity modulated signal. Due to the high modulation frequency of 314 MHz measurement accuracies about 0.1 mm are possible with high measurement rates. Besides the slant range, the system detects laser light backscattered from the object surface under survey. This means that three dimensional images are obtained, if the scanner moves the laserbeam line by line across the object's surface. After explaining the functioning of the 3D-ILS and calculating the theoretical slant ranging performance, typical application examples will be presented which verify the theoretical results and demonstrate the wide application field for the laser scanner which is e.g. CAD, CAM, rapid prototyping, close range-, industrial- and architectural-survey. An application highlight is the survey of a reconstructed skeleton of a dinosaur.

We present a detection process capable of directly imaging the transverse amplitude, phase, and Doppler shift of coherent electromagnetic fields. Based on coherent detection principles governing conventional heterodyned RADAR/LADAR systems, Fourier Transform Heterodyne incorporates transverse spatial encoding of the reference local oscillator for image capture. Appropriate selection of spatial encoding functions allows image retrieval by way of classic Fourier manipulations. Of practical interest: (1) imaging may be accomplished with a single element detector/sensor requiring no additional scanning or moving components, (2) as detection is governed by heterodyne principles, near quantum limited performance is achievable, (3) a wide variety of appropriate spatial encoding functions exist that may be adaptively configured in real-time for applications requiring optimal detection, and (4) the concept is general with the applicable electromagnetic spectrum encompassing the RF through optical.

Scannerless laser radar (LADAR) is the next revolutionary step in laser radar technology. It has the potential to dramatically increase the image frame rate over raster-scanned systems while eliminating mechanical moving parts. The system presented here uses a negative lens to diverge the light from a pulsed laser to floodlight illuminate a target. Return light is collected by a commercial camera lens, an image intensifier tube applies a modulated gain, and a relay lens focuses the resulting image onto a commercial CCD camera. To produce range data, a minimum of three snapshots is required while modulating the gain of the image intensifier tube's microchannel plate (MCP) at a MHz rate. Since November 1997 the scannerless LADAR designed by Sandia National Laboratories has undergone extensive testing. It has been taken on numerous field tests and has imaged calibrated panels up to a distance of 1 km on an outdoor range. Images have been taken at ranges over a kilometer and can be taken at much longer ranges with modified range gate settings. Sample imagery and potential applications are presented here. The accuracy of range imagery produced by this scannerless LADAR has been evaluated and the range resolution was found to be approximately 15 cm. Its sensitivity was also quantified and found to be many factors better than raster- scanned direct detection LADAR systems. Additionally, the effect of the number of snapshots and the phase spacing between them on the quality of the range data has been evaluated. Overall, the impressive results produced by scannerless LADAR are ideal for autonomous munitions guidance and various other applications.

We describe the research and development of a scannerless three- dimensional (3-D) imaging laser radar (ladar) performed at the Army Research Laboratory for reconnaissance applications. Range information is obtained by a frequency modulation/continuous wave (FM/cw) radar technique implemented by amplitude modulation of a near-IR diode laser with an rf subcarrier that is linearly frequency modulated. The diode's output is projected to floodlight the downrange image area. The returned signal is focused onto the cathode of an image intensifier tube (IIT) where it is mixed with a delayed replica of the laser modulation applied to the cathode bias to modulate the tube gain. The output image of the IIT is modulated at an intermediate frequency (IF) that is sampled in time by a conventional charge-coupled device (CCD) camera. Image frames over one period of the frequency modulation are collected and stored. A discrete Fourier transform is calculated over the IF waveform to establish the ranges to all scatterers in a pixel. This processing scheme yields a scannerless ladar possessing high range resolution with no range ambiguities. We constructed a breadboard version of this ladar and used it to collect 256 X 256 pixel images of targets at 1-km ranges with 0.375-m range resolution. We present imagery collected during field experiments and discuss the direction of future research to enhance the ladar's performance.

Gated viewing using short pulse lasers and fast cameras offers many new possibilities in imaging compared with passive EO imaging. Among these we note ranging capability, large target-to-background contrast also in low visibility, good penetration capability trough obscurants and vegetation as well as through shadows in buildings, cars, etc. We also note that short wavelength laser systems have better angular resolution than long-wave infrared systems of the same aperture size. This gives an interesting potential of combined IR and laser systems for target detection and classification. Beside military applications civilian applications of gated viewing for search and rescue as well as vehicle enhanced vision and other applications are in progress. This presentation investigates the performance for gated viewing systems during different atmospheric conditions, including obscurants and gives examples of experimental data. The paper also deals with signal processing of gated viewing images for target detection. This is performed in two steps. First, image frames containing information of interest are found. In a second step those frames are investigated further to evaluate if man-made objects are present. In this step a sequence of images (video frames) are set up as a 3-D volume to incorporate spatial information. The object will then be detected using a set of quadrature filters operating on the volume.

We present the modeling and the performances of a Polarization Active Imager at (lambda) equals 806 nm. The device is operating in a monostatic configuration, using a semiconductor laser to illuminate the target and a telescope to create the image on a CCD matrix. Dual images (intensity and polarization degree) of different scenes are obtained by a new method (only 2 images acquisition) and analyzed, showing the experimental validation of this concept. The application of this active imager to the detection of target buried in the background (same reflectivity but different polarization degree) is proposed.

We present the concept of a wide-field-of-view and atmospheric- distortion-insensitive coherent detection. We propose to mix a local oscillator plane wave and a focused backscattered signal on the detector. In first approximation, the field-of-view is only limited by the size of the detector. An original experimental set- up at (lambda) equals 633 nm is presented to validate this technique. We control the phase of the backscattered signal using a liquid-crystal spatial light modulator (SLM). This permits us to steer or to distort the wave front of the backscattered signal in order to measure and compare the field-of-view and the atmospheric perturbations sensitivity of the two set-ups. We will present the performances (wide field-of-view, distortion sensitivity, . . .) of our architecture.

Direct detection imaging Laser Radar (LADAR) produces 3-dimensional range imagery that can be processed to provide target acquisition and precision aimpoint definition in real time. This paper describes the current status of the Parallel Multichannel Imaging LADAR Receiver (PMR), developed under an SBIR Phase II program by the Air Force Research Laboratory, Munitions Directorate (AFRL/MN). The heart of the PMR is the Multichannel Optical Receiver Photonic Hybrid (MORPH), a high performance 16-channel LADAR receiver card which includes fiber-coupled detectors, pulse discrimination, and range counting circuitry on a 3 X 5 inch circuit card. The MORPH provides high downrange resolution (3 inches), multiple-hit (8 per channel) range and reflectance data for each detector. Silicon (Si) and indium gallium arsenide (InGaAs) pin diode or avalanche photodiode (APD) detectors are supported. The modular PMR uses an array of MORPH circuit cards to form a compact multichannel imaging LADAR receiver with any multiple of 16 channels. A 32-channel system measures 3 X 5 X 1.4 inches and weighs 1 lb. A prototype PMR system is currently undergoing field-testing. This paper focuses on field test results and applications of the PMR technology.

Direct-detection laser radars can measure the range and the intensity returns from a target, with or without clutter, for each part of the target resolved in angle by the optical system. Because the ladar's angular resolution is in micro-radians, there are generally at least a few angular pixels 'on target.' In addition, for narrow pulse (approximately 1 ns) ladar systems, there may be ten or so sequential intensity measurements in range per pixel as the laser pulse propagates down the target's surface. The output image is, therefore, potentially a three dimensional 'cube' of intensity measurements and quantized in the range axis by the range-bin size or 'voxel' size. This is known as 'range resolved angle-angle-intensity' ladar. In a previous paper we transformed this 3D-matrix image into the spatial-frequency domain using 3D- Fourier transforms and followed conventional 2D template correlation techniques to perform target recognition and identification. During this previous study, it was noted that the 2D range-bins could be placed in sequence and 2D filtering used on these synthetic images. Results of 3D and 2D-sequence target correlators using the 'joint transform correlator,' 'the inverse filter,' the 'phase-only matched-filter,' the 'binary phase-only filter,' and the classical 'matched filter' are presented here. Far-field test data using conical shaped targets are used to study the 3D and 2D correlators, and the effects of laser speckle are discussed. Recent developments in negative-binomial driven shot- noise effects in range-resolved direct-detection ladar are reviewed as well. These 3D or 2D-sequence template correlators may supplement or refine less computationally intensive algorithms such as total signal; range-extent; x-z, y-z, and x-y plane image centroid estimation; and image moments.

This paper describes a 1.55 micrometer coherent fiber laser radar designed and developed at ONERA in France. This eye-safe Doppler system uses a 0.5 W codoped Erbium/Ytterbium fiber laser and a compact fiber optical architecture. The system has been tested at distances up to 1 km. Experimental results are presented and performances compared to the theoretical model taking into account atmospheric propagation.

The talk will review the measurement capabilities of the FLD system and highlight key features of some major subsystems developed under the program which currently reflect the state-of-the-art.

Some peculiarities in ranging with the space-based lidar BALKAN of the Earth surface are considered for two modes of the space station MIR orientation, which were used during measurement experiments in 1995 - 1996, and some results, that were presented earlier, are refined. Ranging of the ocean surface, which considered as reference at the first measurement stage, allows one to estimate a contribution of various sources to the measurement accuracy. The probable causes of the systematic difference between the values of slant range measured with the lidar and ballistic calculated data on range are discussed.

The development of a portable, eye-safe, ground-based ozone lidar instrument specialized for ozone differential absorption lidar (DIAL) measurements in the troposphere is presented. This compact prototype instrument is intended to operate at remote field sites and to serve as the basic unit for future monitoring projects requiring multi-instrument networks. In order for the lidar technology to be widely deployed in networks, it must be fairly easy to use and maintain as well as being cost-competitive with a ground station launching ozone sondes several times a week. The chosen laser transmitter for the system is an all-solid state tunable frequency-doubled OPO which produces 25 mJ uv pulses. Progress with alternative solid-state uv laser sources based upon an IR-pumped OPO and based upon stimulated Raman scattering in barium nitrate will be discussed. The receiver incorporates highly efficient dielectric coatings, a parabolic primary and a narrow- bandpass grating-based filter. Dual analog and photon-counting detector channels are incorporated to extend the measurement range. All data acquisition and control hardware is incorporated in an industrial PC-based system. A flexible, user-friendly graphical user interface is written in LabVIEW for data acquisition and online processing and display.

A ground-based lidar system for differential absorption lidar measurements of methane and trace gases in the 1.45 - 4 micrometer wavelength region is described. An optical parametric oscillator pumped by an injection-seeded frequency-doubled Nd:YAG laser is employed as a radiation source. The expected minimum detectable range of the system is about 1000 meters for range resolved measurements of methane. The system performance is being tested through measurements of sources of atmospheric methane and aerosols.

We have designed a series of original techniques able to obtain non-destructively the 2D distribution of the several important parameters. Laser scanning of dynamically loaded solar cell has been shown to give a distribution of the dark current density since this value determines the local heat power and the reflectivity of the cell surface. An additional positive voltage bias at local laser irradiation and typical working conditions applies to the solar cell due to the concentration of current lines within the illuminated spot and due to the voltage drop depending of the local emitter resistivity. Quantitative comparison of the resistance sensitive photocurrent distribution and such distribution in the resistance independent conditions gives an information about local resistivity. The analysis of LBIC signal obtained from the whole battery at the different bias voltage and illumination conditions has shown to investigate the contribution of each cell to the total efficiency and the energy losses, switching to the output contacts of the battery only. This approach makes it possible to monitor the cell characteristics in encapsulated modules directly in loading conditions and without their destruction.

The scheme of multiwaves laser irradiator (MWLI) for remote sounding design is suggested. Experimental example of 3-waves laser irradiator, consisting of XeCl*-excimer laser complex and added by an SRS-converters, is describing. The possibility of simultaneous generation at three lines (273 nm, 308 nm and 353 nm) is demonstrated. The possibilities of discrete (Raman) conversion in wide spectral range and fine tuning within up to 1 nm is demonstrated, too.

Pulsed Doppler lidar sensors can provide accurate range-resolved wind velocity measurements with sufficient spatial resolution to detect turbulent wind features. Application of this technology to commercial airliners would enable much-needed advanced warning of moderate to severe turbulence ahead. CTI, with NASA/Dryden, has developed the Airborne Coherent Lidar for Advanced Inflight Measurements (ACLAIM) which was recently flight tested aboard a research aircraft. This paper presents results from these initial engineering flights, with validated demonstration of Doppler lidar wind turbulence detection using the observed spatial and temporal variations in the longitudinal component of the wind field.

This paper discusses the design and current development status of the coherent lidar transceiver being developed by Coherent Technologies Inc for the NASA program, SPARCLE (SPAce Readiness Coherent Lidar Experiment). SPARCLE is intended as a precursor mission to a fully operational satellite system, measuring global wind profiles from the Space Shuttle, with a planned launch date in March 2001.

Schwartz Electro-Optics, Inc. (SEO) is developing a second- generation LIDAR-based long range aerosol detection and assessment system called the Counter-Proliferation Long Range-Biological Standoff Detection System (CP LR-BSDS) for the U.S. Army Soldier and Biological Chemical Command (SBCCOM). CP LR-BSDS will be a palletized, self-contained system for use on the Army's UH-60A (Blackhawk) helicopter for long range detection and shape classification of long-line source aerosol clouds. This paper presents the key subsystem design considerations and operational characteristics of the CP LR-BSDS.

The Video Guidance Sensor is a key component of NASA's Automated Rendezvous & Capture Program. The Video Guidance Sensor operates from the space shuttle cargo bay and uses laser illumination of a passive target mounted on a SPARTAN satellite. The on-board camera and signal processor determine the relative position and attitude between the target and sensor. The Video Guidance Sensor flew on space shuttle mission STS-95 in November of 1998 and was a marked success. Theoretical models of the optical performance predicted the experimental results from the mission well.

A 1.5 micron wavelength KTP OPO Lidar system has been developed and used to study the sensitivity and the system signal-to-noise ratio for hard target and atmospheric aerosol lidar returns. Optimization of the receiver system was studied that included the use of different sizes, types of detectors, and the effect of laser beam quality factor, M², on the telescope overlap function. Detectors that were studied included several different sizes of InGaAs APDs, direct photodetectors, a transferred-electron intensified photodiode (TE-IPD), and a PMT. The influence of the diffraction or beam quality factor (M²) of the OPO laser was studied and found to have a significant influence on the overlap of the transmit and receiver field of view. This overlap function is also influenced by the size of the lidar detector since a large M² value can overfill the detector/telescope field of view so that small (high speed) detectors may be subject to a large reduction in the lidar signal. The size of the photodiodes and APDs used in the initial OPO lidar experiments were of the order of 0.1 mm to 2 mm, while the TE-IPD and the PMT are larger in acceptance area. Some initial experimental measurements with the photodetectors and APD, and projected theoretical comparisons with the TE-IPD and PMT detectors have been made.

This paper reports progress on the development of a fast modulating retroreflector for a free space optical data link. A previous publication reported sustaining video over a 17 meter link using a multiple quantum well shutter with a diameter of 0.5 cm at a rate on the order of 0.5 Mbps, limited by the demonstration electronics. This work describes improvements in the device performance, which is on the order of 4 Mbps to 6 Mbps with a Bit Error Rates of 10^-6 over a robust optical link. This device lends itself to an array configuration for long range applications and will clearly support T1 rates of 1.54 Mbps, and higher.

The laser data acquired by the airborne laser scanner, called TopoSys-1, in the forest area has been evaluated in this study. The test site was the boreal forest of 0.5 km by 2.0 km in size in southern Finland. The laser scanning system provided 127 measurements per scan line across the flight direction at the pulse repetition rate of 83 kHz. Both the First pulse and Last pulse modes were employed. The position of the carrying platform was determined using the integrated DGPS/INS system. The original laser data set used in the analyses was geocoded but unfiltered. The files only consisted of X, Y, Z coordinates of each sample. First, the whole laser data were classified in four classes, namely: ground, vegetation, buildings, and erroneous points using the TerraScan software on top Microstation SE. After that the ground points were further processed when the still present vegetation removed. Finally, the Digital Elevation Models (DEMs) were generated. The terrain variation was from 91.3 m to 128.4 m. The DEM made from the laser data was compared with the reference DEM available at that moment. The systematic error was 1.03 meters. The standard deviation between the two DEMs was 2.77 meters. Using ground control points, the systematic error can be overcome. However, a more accurate reference DEM is needed for the future comparison. In addition, a map of the true tree heights in the area was generated at the cell size of 1 m by 1 m. The clear-cut areas can be more easily seen than using the aerial photographs.

This paper presents experimental results on burst illumination laser (BIL) imagery for long range a identification. Our interest is to study the feasibility of an identification sensor operating in both night and day conditions. An experiment is performed on a 1 km distance with a pulsed Nd:Yag laser and a time gated camera.

Cloud ceiling determination using laser radar (lidar) is a well known application of this remote sensing technique. It is no problem to measure large distances up to some kilometers, since the particles of interest (water droplets) reflect the laser radiation pretty well, even when using very tiny light sources (eye safety criterion). This detection of white scatterers (clouds) points of course to the question whether it will be possible to measure dark particles for example smoke as well. The possible measurement range of the remote sensing smoke detectors cover medium scale observations, like corridor sensors, as well as large scale systems, like replacing fire alarm sensors in a tunnel by one single lidar system. It will be reported on the double impact using the laser radar technique: the range resolved measurement of black smoke as well as using the transmission path of the laser light as a control device.

Most of the dust monitors are based on optical principle: the scattered light intensity is registered. The classical approach is using the multiple photon optical signal intensity and processing. Single photon detection -- photon counting is exploited in Satellite Laser Ranging and was implemented in space born application for Mars Surveyor Program 98, as well. The main advantage of single photon detection is an extreme sensitivity, the entire digital approach, no analog signal is treated. All the light intensity information is acquired on the basis of statistical data treatment. The dust detector consists of the LED diode based transmitter, single photon solid state diode detector and the digital data processing unit. The light beam from the LED diode passing the dust column is detected in a photo detector. The detector employs the avalanche Silicon photodiode 40 micrometers diameter active area and is operated in a passive gating and active quenching mode above its breakdown voltage. The detector provides uniform digital pulses, one for each photon detected. The light intensity measurement is converted into the photon flux counting -- frequency or event counting. The microcomputer controlled data processing electronics counts the detector output pulses, accounts for detector dark count rate, calibration constants, and computes the corresponding dust concentration averaged over desired period. The second LED located close to the detector is used as a reference light source to eliminate the temperature, aging and sensor contamination influence. The laboratory measurements show the long term and temperature stability of the scale within 1%. The setup was tested at the cement plant smoke stack and compared to the commercial optical dust concentration monitor operating on analog multiphoton principle. Due to an extreme optical sensitivity of the photon counting detector, the energy balance is favorable to realize lightweight equipment by a factor of ten in comparison to analogue-based device. The photon counting principle along with the self-calibration setup does not require re-calibration. The optical apertures involved are of the order of millimeters what reduces the problems of contamination of the device by the dust monitored. As no collimating optics is used, the no optical alignment is required.

The development of a reliable and mass production active sensor for anticollision systems could save thousands of lives on roads (6000 victims per year, Italy only). The first choice is between mm-wave radar and laser radar: despite of the better performances in good visibility conditions and a more mature and cheaper technology, ladars don't encounter the favorable opinion of car makers due to their non-operativeness in fog conditions. In the present work, the development of new ladars using 1.55 micrometer sources is investigated, in order to improve performances in good (human) visibility conditions as well as in fog conditions. Two prototypes using two different techniques (random modulation and pulsed one) have been made.

We investigate a laser range finder for obstacle detection in automotive field. This device is based on the use of an eye-safe pulsed microchip laser, emitting near 1.55 micrometer. The technology of solid-state microchip lasers is a good way to obtain a compact, reliable and low cost laser source. Passively Q-switched microchip lasers are of great interest for time of flight range finding: short pulse duration and high peak power have been obtained. A short pulse duration gives good precision and high peak power gives a long range of detection. The distance measurement is obtained with an ASIC chronometer which implements the time-of- flight technique. We also developed reception circuit for start and stop signals and data input/output. The ASIC chronometer is based on two complementary techniques: a clock counter for coarse measurement and multiple slopes generator for fine measurement.

The operation of laser radar in an automotive collision avoidance system under poor visibility conditions is analyzed. The equations were formulated to calculate (1) the signals returned to a laser radar system by a reflecting target positioned at a given range and (2) signals caused by the scattering of laser radiation by atmospheric particles only. The dependence of calculated signals on the density and the scattering properties of the atmospheric medium on one hand and on the geometry of the system on the other hand was studied. The multiple scattering processes were included in these calculations, and the polarization properties of the calculated signals were analyzed. An experimental verification of the theoretical results in a clear atmosphere and in a dense atmospheric environment has been performed. Good agreement was achieved only when multiple scattering was included in the theory. It is shown that multiple scattering is the main contributor to the signals received from the medium. Utilization of the results of this work can reduce significantly the very high false alarm rate typical for dense atmospheric conditions where successful anti- collision system performance is most crucial.

Using a recent theory of scintillation, including the development of a probability density function (PDF) for the irradiance, a theoretical analysis is carried out on the system performance of a coherent array receiver in terms of the scintillation index, the implied carrier-to-noise (CNR), and signal fade statistics. We also describe a field experiment in which measured data from a wave reflected from a rough (Lambertian) target located 1000 m from the transceiver was used to calculate the scintillation index, CNR, and probability of fade. The results of this study support the theoretical models.

For control of space debris of both artificial and natural (asteroid) origin, the ground-based optical array was proposed. Image processing algorithms in the ground aperture synthesis array are proposed and studied. Considering 'island' nature array OTF showed that our modified method version of triple correlations is optimal for phase locking of spatial spectrum from the object between 'islands' and the iterational algorithm for the equation evolvent of the locked phases is proposed for the phase restoration. The experimental research of perspective technologies for image forming and processing in a ground-based aperture synthesis array was carried out by the methods of physical and machine simulation. The results of model experiment confirmed the efficiency of proposed perspective technologies for reaching of high angular resolution.

A 3D imaging laser sensor is presented providing rapid acquisition of 3D data of naturally reflecting objects. The sensor is of a rugged and compact design, is eye-safe, and can be used even in adverse environmental conditions for a wide range of applications. The sensor makes use of high-speed laser ranging based on the time- of-flight method with pulsed laser diodes and of mechanically scanning the laser beam and the optical axis of the rangefinder's receiver. The maximum achievable range to non-cooperative targets is up to 350 m. The field-of-view of the sensor is settable by software commands and can be up to 80 degrees X 340 degrees with an angular resolution of the scanning mechanism of up to 0.018 degrees. Data are provided at a standard parallel interface allowing easy integration with any standard PC based system for data visualization and data processing. The primary data include for each independent range measurement the coordinates in the sensor's local polar coordinate system, and the intensity of the received laser pulse to provide information on target's reflectivity. These data are provided with an average data rate up to 8000 measurements per second. A PC based acquisition program allows on-line color-encoded visualization, data storage, and data export as ASCII data, VRML data, and other widely used formats. Data acquired with the sensor are presented and accuracy and ranging capability are discussed.