This PDF file contains the front matter associated with SPIE Proceedings Volume 9645, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

A double-pulsed, 2-μm Integrated Path Differential Absorption (IPDA) lidar instrument for atmospheric carbon dioxide (CO₂) measurements is successfully developed at NASA Langley Research Center (LaRC). Based on direct detection technique, the instrument can be operated on ground or onboard a small aircraft. Key features of this compact, rugged and reliable IPDA lidar includes high transmitted laser energy, wavelength tuning, switching and locking, and sensitive detection. As a proof of concept, the IPDA ground and airborne CO₂ measurement and validation will be presented. Ground validation of the IPDA lidar column CO₂ measurements were conducted at NASA LaRC using hard targets and a calibrated in situ sensor. Airborne validation, conducted onboard the NASA B-200 aircraft, included CO₂ plume detection from power stations incinerators, in-flight CO₂ in situ sensor and air sampling at different altitude, conducted by NOAA at the same site. Airborne measurements, spanning for 20 hours, were obtained from different targets such as soil, vegetation, sand, snow and ocean. In addition, cloud slicing was examined over the ocean. These flight validations were conducted at different altitudes, up to 6 km, with different wavelength controlled weighing functions. CO₂ measurement results agree with modeling results from different sensors.

We propose an integrated path differential absorption lidar system based on all-semiconductor laser sources and single photon counting detection for column-averaged measurements of atmospheric CO₂. The Random Modulated Continuous Wave (RM-CW) approach has been selected as the best suited to semiconductor lasers. In a RM-CW lidar, a pseudo random sequence is sent to the atmosphere and the received signal reflected from the target is correlated with the original sequence in order to retrieve the path length. The transmitter design is based on two monolithic Master Oscillator Power Amplifiers (MOPAs), providing the on-line and off-line wavelengths close to the selected absorption line around 1.57 µm. Each MOPA consists of a frequency stabilized distributed feedback master oscillator, a bent modulator section, and a tapered amplifier. This design allows the emitters to deliver high power and high quality laser beams with good spectral properties. An output power above 400 mW with a SMSR higher than 45 dB and modulation capability have been demonstrated. On the side of the receiver, our theoretical and experimental results indicate that the major noise contribution comes from the ambient light and detector noise. For this reason narrow band optical filters are required in the envisioned space-borne applications. In this contribution, we present the latest progresses regarding the design, modeling and characterization of the transmitter, the receiver, the frequency stabilization unit and the complete system.

Global atmospheric carbon dioxide (CO₂) measurements for the NASA Active Sensing of CO₂ Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO₂ sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO₂ measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO₂ measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO₂ number density measurements to column CO₂ mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

Integrated-path differential absorption lidar (IPDIAL) is an attractive technique to monitor greenhouse gases from space. For that purpose, suitable absorption lines have been identified as good candidates around 2.05 μm for CO₂, 2.29 μm for CH₄, and 2.06 μm for H₂O. In this context, we have developed a high energy transmitter around 2 μm based on frequency conversion in a nested cavity doubly resonant optical parametric oscillator (NesCOPO) followed by high energy parametric amplification. This master oscillator power amplifier (MOPA) architecture enables the generation of tunable single-frequency high energy nanosecond pulses (tens of mJ) suitable for atmospheric DIAL applications. Moreover, taking advantage of the wide spectral coverage capability of the NesCOPO, we demonstrate the potential for this single emitter to address the aforementioned spectral lines, without the use of additional seeding devices. The emitter provides energies up to 20 mJ for the signal waves in the vicinity of CO₂ and H₂O lines, and 16 mJ at 2290 nm for the CH₄ line. By implementing a control loop based on a wavemeter frequency measurement, the signal fluctuations can be maintained below 1 MHz rms for 10 s averaging time. Finally, from optical heterodyne analysis of the beat note between our emitter and a stabilized laser diode, the optical parametric source linewidth was estimated to be better than 60 MHz (Full width at half maximum).

The Langley Mobile Ozone Lidar (LMOL) is a compact mobile differential absorption lidar (DIAL) system that was developed at NASA Langley Research Center, Hampton, VA, USA to provide ozone, aerosol and cloud atmospheric measurements in a mobile trailer for ground-based atmospheric air quality campaigns. This lidar is part of the Tropospheric Ozone Lidar Network (TOLNet) currently made up of six other ozone lidars across the U.S and Canada. This lidar has been deployed to Denver, CO July 15-August 15, 2014 for the DISCOVER-AQ air quality campaign. Ozone and aerosol profiles were taken showing the influence of emissions from the Denver region. Results of ozone concentration, aerosol scattering ratio, boundary layer height and clouds will be presented with emphasis on regional air quality.

New Lidar applications related to aircraft safety in the area of an airport include mapping wind velocity and monitoring turbulences within a radius longer than 8km in a short acquisition time (360° map in 1 minute). During landing and takeoff, a minimal distance separation between aircrafts is set by referring to wake turbulence categories. However, it was shown that wake vortices can dissipate quicker because of atmospheric turbulence (characterized by eddy dissipation rate - EDR) or can be transported out of the way on oncoming traffic by cross-winds. Long range scanning Lidars provide radial wind data that can be used to calculate EDR.

To reach long range within a short acquisition time, coherent wind Lidars require high power (~kW), narrow linewidth (few MHz) pulsed laser sources with nearly TF limited pulse duration (~1μs). Eyesafe, all-fiber laser sources based on MOPFA (master oscillator, power fiber amplifier) architecture offer many advantages over bulk sources such as low sensitivity to vibrations, efficiency and versatility. However, narrow linewidth pulsed fiber lasers and amplifiers are usually limited by nonlinear effects such as stimulated Brillouin scattering (SBS) to 300W with commercial fibers. We investigated various solutions to push this limit further. For example, a source based on a new fiber composition yielded a peak power of 1120W for 650ns pulse duration with excellent beam quality. Based on these innovative solutions we built a Lidar with a record range of 16km in 0.1s averaging time.

In this proceeding, we present some recent results obtained with our wind Lidars based on these high power sources with record ranges. EDR measurements using the developed algorithm based on structure function calculation are presented, as well as its validation with simulations and measurements campaign results.

A low-coherence continuous wave Doppler Lidar using a synthetic broadband source has been suggested recently. The main advantages are electronically adjustable spatial resolution, strong discrimination between signal contributions from different locations and the enabling of after-measurement numerical range scanning. In this paper an advanced concept is presented with an efficient suppression of unavoidable perturbations from inside the measurement setup.

We propose a multi-kHz Single-Photon Counting (SPC) space LIDAR, exploiting low energy pulses with high repetition frequency (PRF). The high PRF allows one to overcome the low signal limitations, as many return shots can be collected from nearly the same scattering area. The ALART space instrument exhibits a multi-beam design, providing height retrieval over a wide area and terrain slope measurements. This novel technique, working with low SNRs, allows multiple beam generation with a single laser, limiting mass and power consumption. As the receiver has a certain probability to detect multiple photons from different levels of canopy, a histogram is constructed and used to retrieve the properties of the target tree, by means of a modal decomposition of the reconstructed waveform. A field demonstrator of the ALART space instrument is currently being developed by a European consortium led by cosine | measurement systems and funded by ESA under the TRP program. The demonstrator requirements have been derived to be representative of the target instrument and it will be tested in an equipped tower in woodland areas in the Netherlands. The employed detectors are state-of-the-art CMOS Single-Photon Avalanche Diode (SPAD) matrices with 1024 pixels. Each pixel is independently equipped with an integrated Time-to-Digital Converter (TDC), achieving a timing accuracy that is much lower than the SPAD dead time, resulting in a distance resolution in the centimeter range. The instrument emits nanosecond laser pulses with energy on the order of several μJ, at a PRF of ~ 10 kHz, and projects on ground a three-beams pattern. An extensive field measurement campaign will validate the employed technologies and algorithms for vegetation height retrieval.

The planetary boundary layer (PBL) is an important region of study in the troposphere and one of its more important variable: the PBL height (PBLH) is not easy to detect, mainly in stable conditions due to its complexity. In order to detect the PBLH in stable conditions, in this paper, we apply the low-lev jet (LLJ) method using Doppler lidar measurements, which consists on detecting the LLJ and its maximum velocity height, corresponding to the PBLH. In addition, we analyze this method by comparing and relating it with the variance and bulk Richardson number (BRN) method, ensuring its efficiency.

This work focuses on the evaluation of the abilities of a numerical weather prediction model to simulate water vapor profiles retrieved by multiwavelength Raman lidar measurements. In this work water vapor mixing ratio profiles are retrieved based on lidar measurements at 387 and 407 nm Raman channels. Relative humidity profiles are calculated based on the combination of humidity measurements from lidar and temperature measurements from a microwave radiometer. Simulated water vapor mixing ratio and relative humidity are diagnosed using the Weather Research and Forecasting (WRF) model with 1 × 1 km grid and 1-h temporal resolutions. The accuracy of the WRF model in means of water vapor simulation is assessed by addressing to the experimental datasets based on lidar measurements. All the data used in this work were collected during an international field campaign From Hygrosopic Aerosols to Cloud Droplets (the HygrA-CD campaign) organized from May to June 2014 in Athens, Greece.

Surface elevation is one of the importance information for GIS. Usually surface elevation can acquired from many sources such as satellite imageries, aerial photograph, SAR data or LiDAR by photogrammetry, remote sensing methodology. However the most trust information describe the actual surface elevation is Leveling from terrestrial survey. Leveling is giving the highest accuracy but in the other hand is also long period process spending a lot of budget and resources, moreover the LiDAR technology is new era to measure surface elevation. ICESat/GLAS is spaceborne LiDAR platform, a scientific satellite lunched by NASA in 2003. The study area was located at the middle part of Thailand between 12. ° - 14° North and 98° -100° East Latitude and Longitude. The main idea is to compare and evaluate about elevation between ICESat/GLAS Altimetry and mean sea level of Thailand. Data are collected from various sources, including the ICESat/GLAS altimetry data product from NASA, mean sea level from Royal Thai Survey Department (RTSD). For methodology, is to transform ICESat GLA14 from TOPX/Poseidon-Jason ellipsoid to WGS84 ellipsoid. In addition, ICESat/GLAS altimetry that extracted form centroid of laser footprint and mean sea level were compared and evaluated by 1st Layer National Vertical Reference Network. The result is shown that generally the range of elevation between ICESat/GLAS and mean sea level is wildly from 0. 8 to 25 meters in study area.

Over the past two years a new system capable of measuring the 2-D spatial distribution of atmospheric CO₂ over areas on the order of 1 km² and time scales of a few minutes, has been developed and demonstrated. The Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE) - developed under a cooperative agreement with the National Energy Technology Laboratory (NETL) of the U.S. Department of Energy (DOE) - attempts to improve monitoring capabilities of Ground Carbon Storage (GCS) sites. GreenLITE sensors are based on an intensity modulated continuous wave (IM-CW) approach developed at ITT (now part of Harris Corp.) in 2004. The GreenLITE system recently completed a remote deployment of nearly 4,000 hours at a GCS site in Illinois. It provided continuous, real-time spatial distribution maps of CO₂ via an open web-based interface from February to August 2015. In early 2015 we began work on a new implementation of GreenLITE capable of providing similar measurements over a 25 km² area and are planning to test the system over a 5 km range late summer 2015. If successful the system will be deployed in an urban environment late 2015, demonstrating the utility of real-time 2-D spatial mapping of CO₂ concentrations at this scale. This paper will review the concept for this new measurement capability, including results from the 1 km system. Ultimately, the measurement concept can be adapted to other greenhouse gases such as CH₄ and NO₂.

This paper presents a new method about how to classify different types of aerosols by lidar measurements. Two lidar equations containing the optic parameters (backscatter coefficient, extinction coefficient ) about two different types of aerosols, background aerosol and cloud, were built. The solutions about the two lidar equations, optic parameters inversion, were given to classify the background aerosol and cloud. The lidar signals generated from backscatter of two different types of aerosols, with two different extinction to backscatter coefficient ratio ( S_aer1, S_aer2), were simulated, and the optic parameters inversion from the two simulated lidar signals were almost identical to the simulation parameters for different types of aerosols. Two types of aerosols, the background aerosol and cloud, were simultaneously measured by lidar, and were obviously discriminated by using this new method. The simulations and measurements results verified the new method for aerosols classifications.

The atmosphere over Penang Island is monitored for one year using a ground based Lidar. The Lidar signals are processed to obtain the AOD, extinction coefficients and the PBL heights to provide an overview of the atmospheric conditions in Penang. The data are averaged daily and plotted for the year of 2014. The AOD and extinction coefficients display seasonal trends that increase during the monsoon seasons (Southwest monsoon and Northeast monsoon) and decrease during the inter-monsoon seasons. During the monsoon seasons, a mixture of clear and hazy atmospheric conditions is found due to the presence of rain which removes the particulates or aerosols from the atmosphere. If no rain occurs, aerosols transported over Penang will stay in the atmosphere and be removed after a certain period. The average AOD is 0.4034 for year 2014 with a maximum of 1.0787 on a hazy day and a minimum of 0.0354 on a clear day. The extinction coefficient range is quite wide especially during the monsoonal months owing to the intervention of aerosol layers in the atmosphere of Penang. A clear day will have a smaller range of extinction coefficients. The planetary boundary layer has an average height of 0.878 km. Thicker PBLs are found after monsoon seasons as the aerosols has sunk to the earth surface from higher altitudes. The PBL has an opposing trend to the AOD and extinction coefficients. The atmosphere over Penang Island consists of a mixture of marine particles and fine particles that are mainly transported to Penang by the monsoon winds from the surrounding sea and biomass burnings in the neighboring SEA countries. An overview of the atmospheric conditions in Penang for a whole year is meaningful for further research.

Suspended atmospheric particles i.e. aerosol particles go through many chemical and physical processes and those interactions and transformations may cause particle change in size, structure and composition regulated by mechanisms, which are also present in clouds. These interactions play a great role in the radiation transfer in the atmosphere and are not completely understood as competing effects might occur which are known as indirect aerosol effects. Performing measurements and experiments in remote sensing to improve the knowledge of these processes are also a challenge. In face of that we propose a multi-platform approach based lidar, sun photometry and satellite observations which should be characterized under a scenario perspective in which given the cloud height, geometric and optical geometries in a diurnal/nocturnal basis will make possible to apply different analytical tools in each a set of product that specify the aerosol present in the vicinity of clouds, their optical and physical properties. These scenarios are meant to aid in tagging the expected products and help in creating a robust database to systematically study the aerosol-cloud interaction.In total we will present 6 scenarios: 3 under daylight conditions, 3 under at nighttime. Each scenario and their counterpart should be able to provide the cloud base/top height, aerosol backscattering profile and cloud optical/geometric thickness. In each instance we should count on a 5 wavelength Raman lidar system measurement, a collocated sun photometer and CALIPSO/MODIS observation from AQUA/TERRA platforms. To further improve the aerosol cloud interaction the Raman lidar system should have a water vapor channel or moreover a liquid water channel. In our study we will present a two-day case study to show the methodology feasibility and its potential application.

The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors.

A portable imaging lidar using continuous wave(CW) laser is built for the remote sensing of aerosol in lower boundary layer. The output beam from a simple, stable powered CW laser no modulated is transmitted into the atmosphere, and backscattered light from along the visible beam path is imaged onto a charge-coupled-device (CCD) camera. It can be used to scan atmosphere from different angles. The horizontal measurements are obtained and compared with those obtained by the America Belfort model 6230A visibility meter. The horizontal results show that the average relative error is below 20%. The temporal-spatial variations of aerosol profiles in low boundary layer are presented and discuss.

We report the development of a differential absorption lidar instrument (DIAL) designed and built specifically for the measurement of anthropogenic greenhouse gases in the atmosphere. The DIAL is integrated into a commercial astronomical telescope to provide high-quality receiver optics and enable automated scanning for three-dimensional lidar acquisition. The instrument is portable and can be set up within a few hours in the field. The laser source is a pulsed optical parametric oscillator (OPO) which outputs light at a wavelength tunable near 1.6 μm. This wavelength region, which is also used in telecommunications devices, provides access to absorption lines in both carbon dioxide at 1573 nm and methane at 1646 nm. To achieve the critical temperature stability required for a laserbased field instrument the four-mirror OPO cavity is machined from a single aluminium block. A piezoactuator adjusts the cavity length to achieve resonance and this is maintained over temperature changes through the use of a feedback loop. The laser output is continuously monitored with pyroelectric detectors and a custom-built wavemeter. The OPO is injection seeded by a temperature-stabilized distributed feedback laser diode (DFB-LD) with a wavelength locked to the absorption line centre (on-line) using a gas cell containing pure carbon dioxide. A second DFB-LD is tuned to a nearby wavelength (off-line) to provide the reference required for differential absorption measurements. A similar system has been designed and built to provide the injection seeding wavelengths for methane. The system integrates the DFB-LDs, drivers, locking electronics, gas cell and balanced photodetectors. The results of test measurements of carbon dioxide are presented and the development of the system is discussed, including the adaptation required for the measurement of methane.