This PDF file contains the front matter associated with SPIE Proceedings Volume 8379, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Three-dimensional (3D) topographic imaging using Short wavelength infrared (SWIR) Laser Detection and Range (LADAR) systems have been successfully demonstrated on various platforms. LADAR imaging provides coverage down to inch-level fidelity and allows for effective wide-area terrain mapping. Recently Spectrolab has demonstrated a compact 32×32 LADAR camera with single photon-level sensitivity with small size, weight, and power (SWAP) budget. This camera has many special features such as non-uniform bias correction, variable range gate width from 2 microseconds to 6 microseconds, windowing for smaller arrays, and shorted pixel protection. Boeing integrated this camera with a 1.06 μm pulse laser on various platforms and had demonstrated 3D imaging. In this presentation, the operation details of this camera and 3D imaging demonstration using this camera on various platforms will be presented.

Future robots and autonomous vehicles require compact low-cost Laser Detection and Ranging (LADAR) systems for autonomous navigation. Army Research Laboratory (ARL) had recently demonstrated a brass-board short-range eye-safe MEMS scanning LADAR system for robotic applications. Boeing Spectrolab is doing a tech-transfer (CRADA) of this system and has built a compact MEMS scanning LADAR system with additional improvements in receiver sensitivity, laser system, and data processing system. Improved system sensitivity, low-cost, miniaturization, and low power consumption are the main goals for the commercialization of this LADAR system. The receiver sensitivity has been improved by 2x using large-area InGaAs PIN detectors with low-noise amplifiers. The FPGA code has been updated to extend the range to 50 meters and detect up to 3 targets per pixel. Range accuracy has been improved through the implementation of an optical T-Zero input line. A compact commercially available erbium fiber laser operating at 1550 nm wavelength is used as a transmitter, thus reducing the size of the LADAR system considerably from the ARL brassboard system. The computer interface has been consolidated to allow image data and configuration data (configuration settings and system status) to pass through a single Ethernet port. In this presentation we will discuss the system architecture and future improvements to receiver sensitivity using avalanche photodiodes.

3D laser sensor is a real-time remote sensor which offers 3D images of scenes. In this paper, we demonstrate a new concept of the pulsed 3D laser sensor with 2D scanning of a transmitting beam and a scan-less receiver. The system achieves the fast and long-range 3D imaging with a relatively simple system configuration. We newly developed a highaspect APD array, a receiver IC, and a range and intensity detector. By combining these devices, we realized a 160 × 120 pixels range imaging with an on-line frame rate of 8 Hz at a distance of about 50 m.

Future planetary and lunar landers can benefit from a hazard detection (HD) system that employs a lidar to create a highresolution 3D terrain map in the vicinity of the landing site and an onboard computer to process the lidar data and identify the safest landing site within the surveyed area. A divert maneuver would then be executed to land in this safe site. An HD system enables landing in regions with a relatively high hazard abundance that would otherwise be considered unacceptably risky, but are of high interest to the scientific community. A key component of a HD system is a lidar with the ability to generate a 3D terrain image with the required range precision in the prescribed time and fits within the project resource constraints. In this paper, we present the results obtained during performance testing of a prototype "GoldenEye" 3D flash lidar developed by ASC, Inc. The testing was performed at JPL with the lidar and the targets separated by 200 m. The analysis of the lidar performance obtained for different target types and albedos, pulse energies, and fields of view is presented and compared to key HD lidar requirements identified for the Mars 2018 lander.

The goal of this work is to determine methods for detecting trails using statistics of LiDAR point cloud data, while avoiding reliance on a Digital Elevation Model (DEM). Creation of a DEM is a subjective process that requires assumptions be made about the density of the data points, the curvature of the ground, and other factors which can lead to very dierent results in the nal DEM product, with no single correct" result. Exploitation of point cloud data also lends itself well to automation. A LiDAR point cloud based trail detection scheme has been designed in which statistical measures of local neighborhoods of LiDAR points are calculated, image processing techniques employed to mask non-trail areas, and a constrained region growing scheme used to determine a nal trails map. Results of the LiDAR point cloud based trail detection scheme are presented and compared to a DEM-based trail detection scheme. Large trails are detected fairly reliably with some missing gaps, while smaller trails are detected less reliably. Overall results of the LiDAR point cloud based methods are comparable to the DEM-based results, with fewer false alarms.

Recent advances in LIDAR technologies have increased the resolution of airborne instruments to the sub-meter level, which opens up the possibility of creating detailed maps over a large area. The ability to map complex 3D structure is especially challenging in urban environments, where both natural and manmade obstructions make comprehensive mapping difficult. LIDAR remains unsurpassed in its capability to capture fine geometric details in this type of environment, making it the ideal choice for many purposes. One important application of urban remote sensing is the creation of line-of-sight maps, or viewsheds, which determine the visibility of areas from a given point within a scene. Using a voxelized approach to LIDAR processing allows us to retain detail in overlapping structures, and we show how this provides a better framework for handling line-of-sight calculations than existing approaches. Including additional information about the instrument position during the data collection allows us to identify any scene areas which are poorly sampled, and to determine any detrimental effect on line-of-sight maps. An experiment conducted during the summer of 2011 collected both visible imagery and LIDAR at multiple returns per square meter of the downtown region of Rochester, NY. We demonstrate our voxelized technique on this large real-world dataset, and derive where errors in line-of-sight mapping are likely to occur.

Road-side bombs are a real and continuing threat to soldiers in theater. CAE USA recently developed a prototype Volume based Intelligence Surveillance Reconnaissance (VISR) sensor platform for IED detection. This vehicle-mounted, prototype sensor system uses a high data rate LiDAR (1.33 million range measurements per second) to generate a 3D mapping of roadways. The mapped data is used as a reference to generate real-time change detection on future trips on the same roadways. The prototype VISR system is briefly described. The focus of this paper is the methodology used to process the 3D LiDAR data, in real-time, to detect small changes on and near the roadway ahead of a vehicle traveling at moderate speeds with sufficient warning to stop the vehicle at a safe distance from the threat. The system relies on accurate navigation equipment to geo-reference the reference run and the change-detection run. Since it was recognized early in the project that detection of small changes could not be achieved with accurate navigation solutions alone, a scene alignment algorithm was developed to register the reference run with the change detection run prior to applying the change detection algorithm. Good success was achieved in simultaneous real time processing of scene alignment plus change detection.

As for the characteristic of the data acquired by laser radar and the three dimentional point cloud in disorder, and by combining the abundant in three dimentional information of point cloud with the specific textural information of distance images, we raised a new algorithm on the reconstruction of laser radar based on simplified point cloud and distance images. In this article, we take advantage of the feature that Delaunay triangulation have to raise a simplified algorithm to achieve the model network. In this algorithm, at first we build up the Delaunay triangulation, then comfirm the vector by calculating the distance that every vertex in the network from the adjacency vertex, and then calculate the intersection angle that the vector with triangle around; at the same time set the angular threshold in order to generate the new Delaunay triangulation. Experimental results show that this algorithm can accomplish the simplication of triangulation without affecting the accuracy of the modeling, along with the detailed, textural and shading information, we can achieve 3D reconstruction of the target images effectively.

LADAR technology is used in remote sensing to monitor many parameters like particles and gases suspended in the atmosphere, measure velocity, 3-D mapping, etc. Its application for 3-D mapping is of great interest in the geospatial community. A LADAR system is capable of scanning the surface of an object by forming thousands or millions of points in the 3-D space. New advances in LADAR technology have been pushing towards 4-D data (x, y, z, and time). These systems are capable of operating in the same way as a video camera up to 30 frames per second. Sampling a scene in the 4-D domain is very attractive for military and civilian applications. This work presents an algorithm capable of using the 4-D measurements recorded by a LADAR system to generate a 3-D video. The algorithm provides a feature extraction tool that is used to identify and rank safe landing zones within the 3-D video point cloud dataset. We use parameters such as terrain irregularities, terrain slope or gradients, and distances from vertical obstructions to identify and rank safe landing zones. Other additional mission specific requirements can be included to further filter and rank safe landing zones.

Real-time awareness and rapid target detection are critical for the success of military missions. New technologies capable of detecting targets concealed in forest areas are needed in order to track and identify possible threats. Currently, LAser Detection And Ranging (LADAR) systems are capable of detecting obscured targets; however, tracking capabilities are severely limited. Now, a new LADAR-derived technology is under development to generate 4-D datasets (3-D video in a point cloud format). As such, there is a new need for algorithms that are able to process data in real time. We propose an algorithm capable of removing vegetation and other objects that may obfuscate concealed targets in a real 3-D environment. The algorithm is based on wavelets and can be used as a pre-processing step in a target recognition algorithm. Applications of the algorithm in a real-time 3-D system could help make pilots aware of high risk hidden targets such as tanks and weapons, among others. We will be using a 4-D simulated point cloud data to demonstrate the capabilities of our algorithm.

Tracking of extended targets in high definition, 360-degree 3D-LIDAR (Light Detection and Ranging) measurements is a challenging task and a current research topic. It is a key component in robotic applications, and is relevant to path planning and collision avoidance. This paper proposes a new method without a geometric model to simultaneously track and accumulate 3D-LIDAR measurements of an object. The method itself is based on a particle filter and uses an object-related local 3D grid for each object. No geometric object hypothesis is needed. Accumulation allows coping with occlusions. The prediction step of the particle filter is governed by a motion model consisting of a deterministic and a probabilistic part. Since this paper is focused on tracking ground vehicles, a bicycle model is used for the deterministic part. The probabilistic part depends on the current state of each particle. A function for calculating the current probability density function for state transition is developed. It is derived in detail and based on a database consisting of vehicle dynamics measurements over several hundreds of kilometers. The adaptive probability density function narrows down the gating area for measurement data association. The second part of the proposed method addresses weighting the particles with a cost function. Different 3D-griddependent cost functions are presented and evaluated. Evaluations with real 3D-LIDAR measurements show the performance of the proposed method. The results are also compared to ground truth data.

The new generation of laser-based imaging sensors enables collection of range images at video rate at the expense of somewhat low spatial and range resolution. Combining several successive range images, instead of having to analyze each image separately, is a way to improve the performance of feature extraction and target classification. In the robotics community, occupancy grids are commonly used as a framework for combining sensor readings into a representation that indicates passable (free) and non-passable (occupied) parts of the environment. In this paper we demonstrate how 3D occupancy grids can be used for outlier removal, registration quality assessment and measuring the degree of unexplored space around a target, which may improve target detection and classification. Examples using data from a maritime scene, acquired with a 3D FLASH sensor, are shown.

Bare earth extraction is an important component to LADAR data analysis in terms of terrain classification. The challenge in providing accurate digital models is augmented when there is diverse topography within the data set or complex combinations of vegetation and built structures. A successful approach provides a flexible methodology (adaptable for topography and/or environment) that is capable of integrating multiple ladar point cloud data attributes. A newly developed approach (TE-SiP) uses a 2nd and 3rd order spatial derivative for each point in the DEM to determine sets of contiguous regions of similar elevation. Specifically, the derivative of the central point represents the curvature of the terrain at that position. Contiguous sets of high (positive or negative) values define sharp edges such as building edges or cliffs. This method is independent of the slope, such that very steep, but continuous topography still have relatively low curvature values and are preserved in the terrain classification. Next, a recursive segmentation method identifies unique features of homogeneity on the surface separated by areas of high curvature. An iterative selection process is used to eliminate regions containing buildings or vegetation from the terrain surface. This technique was tested on a variety of existing LADAR surveys, each with varying levels of topographic complexity. The results shown here include developed and forested regions in the Dominican Republic.

A methodology for laser radar / ladar imaging through atmospheric turbulence is studied for target feature extraction, acquisition, tracking, identification, etc. The procedure follows sequentially by (1) laser-mode propagation through the outward atmospheric path, which is modeled by using multiple turbulence phase-screens; (2) the propagated laser mode illuminates a target which is modeled using multiple facets; and (3) simultaneously, or near simultaneously, the return path turbulence effects are modeled by a reverse order Cn 2(h), Lo, and lo set of phase-screens assuming a plane-wave. This return path amplitude & phase screen is then used to create a pupil plus atmospheric effects impulse-response which is used to (4) accurately construct the image of a diffuse target on the detector focal plane array using conventional Fourier optics. Agreement of both the outward and the return path phase-screen matrices with their respective analytical turbulence parameters, which are independently computed, is shown. The Fourier optics construction process of the target's image is reviewed, and typical diffuse target images of facet model objects are presented illustrating scintillation and speckle effects. The images may then be used in algorithm development for a specific system performance determination.

Ground based remote sensing technologies such as scanning lidar systems (light detection and ranging) are increasingly being used to characterize ambient aerosols due to key advantages (i.e., wide area of regard (10 km²), fast response time, high spatial resolution (<10 m) and high sensitivity). Scanning lidar allows for 3D imaging of atmospheric motion and aerosol variability. Space Dynamics Laboratory at Utah State University, in conjunction with the USDA-ARS, has developed and successfully deployed a three-wavelength lidar system called Aglite to characterize particles in diverse settings. Aglite generates near real-time imagery of particle size distribution and size-segregated mass concentration in addition to the ability to calculate whole facility emission rates. Based on over nine years of field and laboratory experience, we present concentration and emission rate results from various measurements in military and civilian deployments.

We report on ground and airborne atmospheric methane measurements with a differential absorption lidar using an optical parametric amplifier (OPA). Methane is a strong greenhouse gas on Earth and its accurate global mapping is urgently needed to understand climate change. We are developing a nanosecond-pulsed OPA for remote measurements of methane from an Earth-orbiting satellite. We have successfully demonstrated the detection of methane on the ground and from an airplane at ~11-km altitude.

Formaldehyde is a trace species that plays a key role in atmospheric chemistry. It is an important indicator of nonmethane volatile organic compound emissions. Also, it is a key reactive intermediate formed during the photochemical oxidation in the troposphere. Because the lifetime of formaldehyde in the atmosphere is fairly short (several hours), its presence signals hydrocarbon emission areas. The importance of measuring formaldehyde concentrations has been recognized by the National Academy's Decadal Survey and two of NASA's forthcoming missions the GEO-CAPE and GACM target its measurement. There are several techniques some of which are highly sensitive (detection limit ~ 50 parts-per-trillion) for in-situ measurement of formaldehyde and many reported atmospheric measurements. However there appear to be no reported standoff lidar techniques for range resolved measurements of atmospheric formaldehyde profiles. In this paper, we describe a formaldehyde lidar profiler based on differential laser induced fluorescence technique. The UV absorption band in the 352 - 357nm is well suited for laser excitation with frequency tripled Neodymium lasers and measuring the strong fluorescence in the 390 - 500nm region. Preliminary nighttime measurements of formaldehyde were demonstrated with a lidar using a commercial Nd:YAG laser (354.7 nm) with a rather large linewidth (~.02 nm). The measured sensitivity was ~1 ppb at 1 km with 100 meters range resolution even with this non-optimized system. In this paper we describe our approach for increasing the sensitivity by many orders and for daytime operation by improving the laser parameters (power and linewidth) and optimizing the receiver.

At the University of Hawaii, we have developed compact time-resolved (TR) Raman, and fluorescence spectrometers suitable for planetary exploration under NASA's Mars Instrument Development Program. The compact Raman and fluorescence spectrometers consist of custom miniature spectrographs based on volume holographic gratings, and custom miniature intensified CCD cameras. These spectrographs have been interfaced with a regular 50 mm camera lens as well as with a three and a half inch diameter telescope for remotely interrogating minerals, water, water-ice and dry ice. Using a small frequency-doubled Nd:YAG pulsed laser (35 mJ/pulse, 20 Hz) and 50 mm camera lens, TRRaman and LINF spectra of minerals, and bio-minerals can be measured within 30 s under super-critical CO₂, and with 3.5-inch telescope these samples can be interrogated to 50 m radial distance during day time and nighttime. The fluorescence spectrograph is capable of measuring TR- laser-induced fluorescence excited with 355 nm laser in the spectral range 400-800 nm spectral range. The TR-fluorescence spectra allow measurement of LINF from rare-earths and transition-metal ions in time domain, and also assist in differentiating between abiogenic minerals from organic and biogenic materials based on the fluorescence lifetime. Biological materials are also identified from their characteristic short-lived (<10 ns) laser-induced fluorescence lifetime. These instruments will play important role in planetary exploration especially in NASA's future Mars Sample Return Mission, and lander and rover missions.

The Active Sensing of CO2 Emissions over Nights Days and Seasons (ASCENDS) mission recommended by the NRC Decadal Survey has a desired accuracy of 0.3% in carbon dioxide mixing ratio (XCO2) retrievals requiring careful selection and optimization of the instrument parameters. NASA Langley Research Center (LaRC) is investigating 1.57 micron carbon dioxide as well as the 1.26-1.27 micron oxygen bands for our proposed ASCENDS mission requirements investigation. Simulation studies are underway for these bands to select optimum instrument parameters. The simulations are based on a multi-wavelength lidar modeling framework being developed at NASA LaRC to predict the performance of CO₂ and O₂ sensing from space and airborne platforms. The modeling framework consists of a lidar simulation module and a line-by-line calculation component with interchangeable lineshape routines to test the performance of alternative lineshape models in the simulations. As an option the line-by-line radiative transfer model (LBLRTM) program may also be used for line-by-line calculations. The modeling framework is being used to perform error analysis, establish optimum measurement wavelengths as well as to identify the best lineshape models to be used in CO₂ and O₂ retrievals. Several additional programs for HITRAN database management and related simulations are planned to be included in the framework. The description of the modeling framework with selected results of the simulation studies for CO₂ and O₂ sensing is presented in this paper.

An initialization method using airborne Doppler wind lidar data was developed and evaluated for a mass-consistent diagnostic wind model over complex terrain. The wind profiles were retrieved from the airborne lidar using a conical scanning scheme and a signal processing algorithm specifically designed for the airborne lidar system. An objective data analysis method in complex terrain was then applied to those wind profiles to produce a threedimensional wind field for model initialization. The model results using the lidar data initialization were compared with independent surface weather observational data and profiles from a microwave radar wind profiler. For the complex terrain in the Salinas valley, the model evaluation with a limited number of observations indicated that the diagnostic wind model with airborne Doppler lidar data produced a reasonably good wind field in moderate to strong wind conditions. However, caution must be stressed for weak wind conditions in which the flow is thermally driven as the mass-consistent diagnostic wind model is not equipped to handle such cases.

A pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia flew on the NASA's DC-8 aircraft during the NASA Genesis and Rapid Intensification Processes (GRIP) during the summer of 2010. The participation was part of the project Doppler Aerosol Wind Lidar (DAWN) Air. Selected results of airborne wind profiling are presented and compared with the dropsonde data for verification purposes. Panoramic presentations of different wind parameters over a nominal observation time span are also presented for selected GRIP data sets. The real-time data acquisition and analysis software that was employed during the GRIP campaign is introduced with its unique features.

Two different noise whitening methods in airborne wind profiling with a pulsed 2-micron coherent Doppler lidar system at NASA Langley Research Center in Virginia are presented. In order to provide accurate wind parameter estimates from the airborne lidar data acquired during the NASA Genesis and Rapid Intensification Processes (GRIP) campaign in 2010, the adverse effects of background instrument noise must be compensated properly in the early stage of data processing. The results of the two methods are presented using selected GRIP data and compared with the dropsonde data for verification purposes.

In this study of atmospheric effects on Geiger Mode laser ranging and detection (LADAR), the parameter space is explored primarily using the Air Force Institute of Technology Center for Directed Energy's (AFIT/CDE) Laser Environmental Effects Definition and Reference (LEEDR) code. The expected performance of LADAR systems is assessed at operationally representative wavelengths of 1.064, 1.56 and 2.039 μm at a number of locations worldwide. Signal attenuation and background noise are characterized using LEEDR. These results are compared to standard atmosphere and Fast Atmospheric Signature Code (FASCODE) assessments. Scenarios evaluated are based on air-toground engagements including both down looking oblique and vertical geometries in which anticipated clear air aerosols are expected to occur. Engagement geometry variations are considered to determine optimum employment techniques to exploit or defeat the environmental conditions. Results, presented primarily in the form of worldwide plots of notional signal to noise ratios, show a significant climate dependence, but large variances between climatological and standard atmosphere assessments. An overall average absolute mean difference ratio of 1.03 is found when climatological signal-to-noise ratios at 40 locations are compared to their equivalent standard atmosphere assessment. Atmospheric transmission is shown to not always correlate with signal-to-noise ratios between different atmosphere profiles. Allowing aerosols to swell with relative humidity proves to be significant especially for up looking geometries reducing the signal-to-noise ratio several orders of magnitude. Turbulence blurring effects that impact tracking and imaging show that the LADAR system has little capability at a 50km range yet the turbulence has little impact at a 3km range.

Many of the recent small, low power ladar systems provide detection sensitivities on the photon(s) level for altimetry applications. These "photon-counting" instruments, many times, are the operational solution to high altitude or space based platforms where low signal strength and size limitations must be accommodated. Despite the many existing algorithms for lidar data product generation, there remains a void in techniques available for handling the increased noise level in the photon-counting measurements as the larger analog systems do not exhibit such low SNR. Solar background noise poses a significant challenge to accurately extract surface features from the data. Thus, filtering is required prior to implementation of other post-processing efforts. This paper presents several methodologies for noise filtering photoncounting data. Techniques include modified Canny Edge Detection, PDF-based signal extraction, and localized statistical analysis. The Canny Edge detection identifies features in a rasterized data product using a Gaussian filter and gradient calculation to extract signal photons. PDF-based analysis matches local probability density functions with the aggregate, thereby extracting probable signal points. The localized statistical method assigns thresholding values based on a weighted local mean of angular variances. These approaches have demonstrated the ability to remove noise and subsequently provide accurate surface (ground/canopy) determination. The results presented here are based on analysis of multiple data sets acquired with the high altitude NASA MABEL system and photon-counting data supplied by Sigma Space Inc. configured to simulate the NASA upcoming ICESat-2 mission instrument expected data product.

Time-of-Flight range measurements rely on the unambiguous assignment of each received echo signal to its causative emitted pulse signal. The maximum unambiguous measurement range depends on the signal group velocity in the propagation medium and the source signals' pulse repetition interval. When this range is exceeded an echo signal and its preceding pulse signal are not associated any longer and the result is ambiguous. We introduce a novel, two-stage approach which significantly increases the maximum unambiguous measurement range by applying a specifically coded pulse-position-modulation scheme to the train of emitted pulses in the first step. In the second step the analysis of resulting measurement ranges allows the unambiguous decision for the correct ranges. In this regard we also present a unique feature of a group of digital codes which helps to enhance detection robustness. Results are given on the basis of time-of-flight measurements from scanning LIDAR, where this technique has been implemented for the first time.

The fusion of imaging ladar information and digital imagery results in 2.5-D surfaces covered with texture information. Called "texel images," these datasets, when taken from dierent viewpoints, can be combined to create 3-D images of buildings, vehicles, or other objects. These 3-D images can then be further processed for automatic target recognition, or viewed in a 3-D viewer for tactical planning purposes. This paper presents a procedure for calibration, error correction, and fusing of ladar and digital camera information from a single hand-held sensor to create accurate texel images. A brief description of a prototype sensor is given, along with calibration technique used with the sensor, which is applicable to other imaging ladar/digital image sensor systems. The method combines systematic error correction of the ladar data, correction for lens distortion of the digital camera image, and fusion of the ladar to the camera data in a single process. The result is a texel image acquired directly from the sensor. Examples of the resulting images, with improvements from the proposed algorithm, are presented.

Scanning LIDARs are widely used as 3D sensors for navigation due to their ability to provide 3D information of terrains and obstacles with a high degree of precision. The optics of conventional scanning LIDARs are generally monostatic, i.e. launch beam and return beam share the same optical path in scanning optics. As a consequence, LIDARs with monostatic optics suffer poor performance at short range (<5m) due to scattering from internal optics and insufficient dynamic range of a LIDAR receiver to cover both short range and long range (1km) . This drawback is undesirable for rover navigation since it is critical for low profile rovers to see well at short range. It is also an issue for LIDARs used in applications involving aerosol penetration since the scattering from nearby aerosol particles can disable LIDARs at short range. In many cases, multiple 3D sensors have to be used for navigation. To overcome these limitations, Neptec has previously developed a scanning LIDAR (called TriDAR) with specially designed triangulation optics that is capable of high speed scanning. In this paper, the reported WABS (Wide Angle Bistatic Scanning) LIDAR has demonstrated a few major advances over the TriDAR design. While it retains the benefit of bistatic optics as seen from TriDAR, in which launch beam path and return beam path are separated in space, it significantly improves performance in term of field-of-view, receiving optical aperture and sensor size. The WABS LIDAR design was prototyped under a contract with the Canadian Space Agency. The LIDAR prototype was used as the 3D sensor for the navigation system on a lunar rover prototype. It demonstrated good performance of FOV (45°×60°) and minimum range spec (1.5m); both are critical for rover navigation and hazard avoidance. The paper discusses design concept and objective of the WABS LIDAR; it also presents some test results.

This paper will report experiments and analysis of slant path imaging using 1.5 μm and 0.8 μm gated imaging. The investigation is a follow up on the measurement reported last year at the laser radar conference at SPIE Orlando. The sensor, a SWIR camera was collecting both passive and active images along a 2 km long path over an airfield. The sensor was elevated by a lift in steps from 1.6-13.5 meters. Targets were resolution charts and also human targets. The human target was holding various items and also performing certain tasks some of high of relevance in defence and security. One of the main purposes with this investigation was to compare the recognition of these human targets and their activities with the resolution information obtained from conventional resolution charts. The data collection of human targets was also made from out roof top laboratory at about 13 m height above ground. The turbulence was measured along the path with anemometers and scintillometers. The camera was collecting both passive and active images in the SWIR region. We also included the Obzerv camera working at 0.8 μm in some tests. The paper will present images for both passive and active modes obtained at different elevations and discuss the results from both technical and system perspectives.

We have developed a LIDAR system with a sensor head which, although it includes a scanning mechanism, is less than 20 cc in size. The system is not only small, but is also highly sensitive. Our LIDAR system is based on time-of-flight measurements, and incorporates an optical fiber. The main feature of our system is the utilization of optical amplifiers for both the transmitter and the receiver, and the optical amplifiers enable us to exceed the detection limit set by thermal noise. In conventional LIDAR systems the detection limit is determined by the thermal noise, because the avalanche photo-diodes (APD) and trans-impedance amplifiers (TIA) that they use detect the received signals directly. In the case of our LIDAR system, the received signal is amplified by an optical fiber amplifier before reaching the photo diode and the TIA. Therefore, our LIDAR system boosts the signal level before the weak incoming signal is depleted by thermal noise. There are conditions under which the noise figure for the combination of an optical fiber amplifier and a photo diode is superior to the noise figure for an avalanche photo diode. We optimized the gains of the optical fiber amplifier and the TIA in our LIDAR system such that it would be capable of detecting a single photon. As a result, the detection limit of our system is determined by shot noise. We have previously demonstrated optical pre-amplified LIDAR with a perfect co-axial optical system[1]. For this we used a variable optical attenuator to remove internal reflection from the transmission and receiving lenses. However, the optical attenuator had an insertion loss of 6dB which reduced the sensitivity of the LIDAR. We re-designed the optical system such that it was semi-co-axial and removed the variable optical attenuator. As a result, we succeeded in scanning up to a range of 80 m. This small and highly sensitive measurement technology shows great potential for use in LIDAR.

The compact High Speed Scanning Lidar (HSSL) was designed to meet the requirements for a rover GN&C sensor. The eye-safe HSSL's fast scanning speed, low volume and low power, make it the ideal choice for a variety of real-time and non-real-time applications including: 3D Mapping; Vehicle guidance and Navigation; Obstacle Detection; Orbiter Rendezvous; Spacecraft Landing / Hazard Avoidance. The HSSL comprises two main hardware units: Sensor Head and Control Unit. In a rover application, the Sensor Head mounts on the top of the rover while the Control Unit can be mounted on the rover deck or within its avionics bay. An Operator Computer is used to command the lidar and immediately display the acquired scan data. The innovative lidar design concept was a result of an extensive trade study conducted during the initial phase of an exploration rover program. The lidar utilizes an innovative scanner coupled with a compact fiber laser and high-speed timing electronics. Compared to existing compact lidar systems, distinguishing features of the HSSL include its high accuracy, high resolution, high refresh rate and large field of view. Other benefits of this design include the capability to quickly configure scan settings to fit various operational modes.

At last year, we have been developing 3D scanning LIDAR designated as KIDAR-B25, which features the 3D scanning structure based on an optically and mechanically coupled instrument. In contrast with previous scanning LIDARs, vertical scanning is realized using two stepping motors synchronized with movement and moves in a spiral. From the results of outdoor experiments conducted last year to evaluate and measure the LIDAR performance and stability, we identified some limitations and problems that should be resolved. In the first instance, the samples per second are inefficient for use in detection, object clustering, and classification. In addition, the accuracy and precision of distance at every point is seriously affected by the reflectance and distance of the target. Therefore, we have focused on improving the 3D LIDAR range finding performance, speed of measurement, and stability regardless of environmental variation. Toward the realization of these goals, in this paper, we deal with two improvements compared with previous 3D LIDAR.

Light detection and ranging (LIDAR) has been used in remote sensing systems, obstacle avoidance systems on planetary landers, rendezvous docking systems, and formation flight control systems. A wide dynamic range is necessary for LIDAR systems on planetary landers and in rendezvous docking systems. For example, a dynamic range of 60 dB was required for the receiving system used in the Hayabusa mission to measure distances between 50 m and 50 km. In addition, the obstacle detection and avoidance system of a planetary lander requires a ranging resolution of better than 10 cm. For planetary landers, the Institute of Space and Astronautical Science/Japan Aerospace Exploration Agency is developing a readout integrated circuit (ROIC) for LIDAR reception. This report introduces the design of the customized IC and reports the results of preliminary experiments evaluating the prototype, LIDARX04.

Advanced LIDAR applications such as next gen: Micro Pulse; Time of Flight (e.g., Satellite Laser Ranging); Coherent and Incoherent Doppler (e.g., Wind LIDAR); High Spectral Resolution; Differential Absorption (DIAL); photon counting LIDAR (e.g., 3D LIDAR); are placing more demanding requirements on conventional lasers (e.g., increased rep rates, etc.) and have inspired the development of new types of laser sources. Today, solid state lasers are used for wind sensing, 2D laser Radar, 3D scanning and flash LIDAR. In this paper, we report on the development of compact, highly efficient, high power all-solidstate diode pulsed pumped ns lasers, as well as, high average power/high pulse energy sub nanosecond (<1ns) and picosecond (<100ps) lasers for these next gen LIDAR applications.

Due to a large number of available Airborne Lidar Bathymetry (ALB) survey datasets and scheduled future surveys, there is a growing need from coastal mapping communities to estimate the accuracy of ALB as a function of the survey system and environmental conditions. Knowledge of ALB accuracy can also be used to evaluate the quality of products derived from ALB surveying. This paper presents theoretical and experimental results focused on the relationship between sea surface conditions and the accuracy of ALB measurements. The simulated environmental conditions were defined according to the typical conditions under which successful ALB surveys can be conducted. The theoretical part of the research included simulations, where the ray-path geometry of the laser beam was monitored below the water surface. Wave-tank experiments were conducted to support the simulations. A cross section of the laser beam was monitored underwater using a green laser with and without wind-driven waves. The results of the study show that capillary waves and small gravity waves distort the laser footprint. Because sea-state condition is related to wind at a first-order approximation, it is possible to suggest wind speed thresholds for different ALB survey projects that vary in accuracy requirements. If wind or wave information were collected during an ALB survey, then it is possible to evaluate the change in accuracy of ALB survey due to different sea surface conditions.

There is a demand from the authorities to have good maps of the coastal environment for their exploitation and preservation of the coastal areas. The goal for environmental mapping and monitoring is to differentiate between vegetation and non-vegetated bottoms and, if possible, to differentiate between species. Airborne lidar bathymetry is an interesting method for mapping shallow underwater habitats. In general, the maximum depth range for airborne laser exceeds the possible depth range for passive sensors. Today, operational lidar systems are able to capture the bottom (or vegetation) topography as well as estimations of the bottom reflectivity using e.g. reflected bottom pulse power. In this paper we study the possibilities and advantages for environmental mapping, if laser sensing would be further developed from single wavelength depth sounding systems to include multiple emission wavelengths and fluorescence receiver channels. Our results show that an airborne fluorescence lidar has several interesting features which might be useful in mapping underwater habitats. An example is the laser induced fluorescence giving rise to the emission spectrum which could be used for classification together with the elastic lidar signal. In the first part of our study, vegetation and substrate samples were collected and their spectral reflectance and fluorescence were subsequently measured in laboratory. A laser wavelength of 532 nm was used for excitation of the samples. The choice of 532 nm as excitation wavelength is motivated by the fact that this wavelength is commonly used in bathymetric laser scanners and that the excitation wavelengths are limited to the visual region as e.g. ultraviolet radiation is highly attenuated in water. The second part of our work consisted of theoretical performance calculations for a potential real system, and comparison of separability between species and substrate signatures using selected wavelength regions for fluorescence sensing.

This work reports on the design, construction and commissioning of a ultraviolet scanning Raman lidar system, which is deployed at the Otlica observatory in Slovenia. The system uses a fast parabolic mirror as a receiver and a frequency-tripled Q-Switched Nd:YAG pulsed laser as a transmitter, both are mounted on a common frame with steerable elevation angle. Custom optics using a low f-number aspheric lens were designed to focus the light into a UV-enhanced optical ber, used to transfer the lidar return signal from the telescope to the polychromator. Vibrational Raman spectra of N₂ and H₂O were separated using narrow-band interference lters combined with dichroic beam splitters. System functionality and performance was assessed in a series of preliminary experiments and by the comparison of the retrieved results to radiosonde data.

In the previous study, we have demonstrated the first development result of the 3D imaging LADAR (LAser Detection And Ranging) which can obtain the 3D data using linear array receiver. The system consists of in-house-made key components. The linear array receiver consists of the previously reported APD (Avalanche Photo Diode) array, the ROIC (Read Out Integrated Circuit) array assembled in one package, and the transmitting optics using pupil divide method which realizes a uniform illumination on a target. In this paper, we report the advanced 3D imaging LADAR with improved ROIC. The ROIC has the function to set the optimum threshold for pulse peak detection in each element and switch the measurement range width on a case by case basis. Moreover, the response of MUX in ROIC is improved. Installing this ROIC, we realized 256× 256 pixels range imaging with an on-line frame rate of more than 30 Hz. Then, we tried online object detection with the obtained 3D image using a simple detection algorithm. We demonstrated system has the potential to detect the object even in the scene with some clutters.

A laser radar (LADAR) system with a Geiger mode avalanche photodiode (GAPD) is used extensively due to its high detection sensitivity. However, this system requires a certain amount of time to receive subsequent signals after detecting the previous one. This dead time, usually 10 ns to 10 μs, is determined by the material composition of the detector and the design of the quenching circuits. Therefore, when we measure objects in close proximity to other objects along the optical axis using the LADAR system with GAPD, it is difficult to separate them clearly owing to the dead time problem. One example for that is a case of hidden objects behind partially transparent blinds. In this paper, we suggested a modified LADAR system with GAPD to remove the dead time problem by adopting an additional linear mode avalanche photodiode (LAPD) as a complementary detector. Because the LAPD does not have dead time while still maintaining relatively low detection sensitivity, the proposed system can measure an object placed within the dead time with high detection sensitivity. Light is emitted from the pulsed laser of a light source and is delivered into a fast photodiode to generate a start signal. Most of laser pulses are directed onto the target and scattered from the surfaces of targets. The scattered light in the field-of-view of the system is divided by a polarizing beam splitter, after which it becomes incident to two different types of APDs, the GAPD and the LAPD. The GAPD receives the signals from the target with high sensitivity, and the signals scattered in the dead time zone are then detected by the LAPD. The obtained signals are analyzed at the same time. In this way, the signals scattered from objects placed within the dead time can be distinguished clearly.

In this paper, a new method to improve the SNR by temporal filtering method in LADAR system using two Geiger-mode avalanche photodiodes (GmAPDs) is proposed. The new method is implemented by using two GmAPDs with beam splitter and employing AND process to their ends. Then, timing circuitry receives the electrical signals only if each GmAPDs generates the electrical signals simultaneously. Though this method decreases the energy of a laser-return pulse scattered from the target, it is highly effective in reducing the false-alarm probability because of the randomly distributed noise on the time domain. Then it needs not any image processing steps. The experiments are performed to prove the advantage of the new method proposed with varying the time bin size. The experimental results represent that the improvement of SNR.