We developed a coherent 2-μm differential absorption and wind lidar to measure CO₂ concentration and line-of-sight wind speed. The wavelength of on-line laser was set at the R30 absorption line center of CO₂ and the atmospheric transmission for the on-line backscattered signal caused by CO₂ is large. Measurable range of CO₂ measurement was limited. A laser frequency offset locking system was installed into the laser system to improved measurable range of CO₂ measurement. Two single-frequency continuous wave lasers are used for the laser frequency offset locking. One laser (center, λ_Center) of the two continuous lasers is directly locked to the R30 absorption line center of CO₂ and the other (on-line, λ_On) is frequency-shifted to λ_Center laser. Although long-range CO₂ measurement depends on the laser frequency offset, the installation of the laser frequency offset realized vertical CO₂ measurement in a range of up to the upper troposphere.

For the application to the global CO₂ monitoring from the space-borne active sensor have been studied. We have developed the Laser Absorption Sensor (LAS) system for ground-based CO₂ monitoring using the wavelength of 1.6 micron. Furthermore, we have also reported about measurement result with short time fluctuation corresponding to the concentration of 4 ppm (rms) in 32 s intervals and 1 km path. In this paper, we discuss how to achieve this performance.

A pulsed, 2-μm coherent Differential Absorption Lidar (DIAL) / Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO₂ profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO₂ Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop.

The accurate measurement of energy in the application of lidar system for CO₂ measurement is critical. Different techniques of energy estimation in the online and offline pulses are investigated for post processing of lidar returns. The cornerstone of the technique is the accurate estimation of the spectrum of lidar signal and background noise. Since the background noise is not the ideal white Gaussian noise, simple average level estimation of noise level is not well fit in the energy estimation of lidar signal and noise. A brief review of the methods is presented in this paper.

The design of the software for a 2-micron coherent high-speed Doppler lidar system for CO₂ measurement at NASA Langley Research Center is discussed in this paper. The specific strategy and design topology to meet the requirements of the system are reviewed. In order to attain the high-speed digitization of the different types of signals to be sampled on multiple channels, a carefully planned design of the control software is imperative. Samples of digitized data from each channel and their roles in data analysis post processing are also presented. Several challenges of extremely-fast, high volume data acquisition are discussed. The software must check the validity of each lidar return as well as other monitoring channel data in real-time. For such high-speed data acquisition systems, the software is a key component that enables the entire scope of CO₂ measurement studies using commercially available system components.

A general overview of the development of a data acquisition and processing system is presented for a pulsed, 2-micron coherent Doppler Lidar system located in NASA Langley Research Center in Hampton, Virginia, USA. It is a comprehensive system that performs high-speed data acquisition, analysis, and data display both in real time and offline. The first flight missions are scheduled for the summer of 2010 as part of the NASA Genesis and Rapid Intensification Processes (GRIP) campaign for the study of hurricanes. The system as well as the control software is reviewed and its requirements and unique features are discussed.

Nowadays air-flow and certain gas measurements in near range are needed as a lidar application. Lidar optics, however, has blind area because it takes a certain distance to overlap the transmitting beam and the receiver's field of view. To detect the near range lidar echo with the narrow field of view, the optical design should be adequate. In this study, several cases of concrete lidar systems for near range measurement will be introduced. The near range compact Raman lidar applications, here the author mainly explain, are hydrogen leakage gas detection up to 50m ahead, monitoring exhaust fume at an intersection, air-flow measurement for a closed space such as a exhibition hall, and so on. The system should be compact as the near range lidar. The optical design should be simple to accomplish the near range measurement. The author has started the theoretical calculation of the lidar echo simulation with the various types of optical designs such as biaxial, coaxial and inline optics, which has common optics for the transmitting and receiving optics. The signal-to-noise ratio will be also estimated in the viewpoint of lowering transmitting beam power for eye-safe. The near range from zero to a few hundred meters is a target distance. The calculated results were compared and evaluated with the optical specification of the actual lidar. Now, the studies are extended, and the several types of near range lidars were developed mainly for the disaster prediction. They are certain gas detection, heavy rain prediction and lightning stroke detection. The "inline" optics adapt to the various kinds of lidar techniques, such as usual Mie lidar, Raman lidar, and polarization lidar. In this report, such a variety of the inline lidars are also introduced.

In inelastic Raman scattering the scattered signal consists of radiation that has undergone a frequency shift which is characteristic for the stationary energy states of an irradiated molecule. Nowadays, Raman and fluorescence spectroscopy is commonly used in chemistry. Information on the radiation that results from transition between the vibrational energy states of the excited molecules, respectively, is specific to the chemical bonds and symmetry of molecules. This radiation therefore provides unique information regarding the irradiated molecule according to which the molecular species can be identified. Raman spectroscopy represents a particularly powerful tool for laser remote sensing because it allows us to both identify and quantify the trace constituent relative to the major constituents of a mixture. In this paper we present a multi-channel spectrometric lidar system which allows us to measure Raman and fluorescence spectrums that give us information on chemical signatures characteristic for chemical components of aerosol particles and pollutions. In the following, we describe the methodology, the system and we show experimental results.

A two-wavelength (532 and 355nm) High-Spectral-Resolution Lidar (HSRL) system for the next-generation aerosol-monitoring lidar network is being developed. Depolarization measurement functions at two wavelengths (532 and 1064nm) have been added to this lidar system. This lidar system provides 2α+3β+2δ data: extinction coefficients (α) at 355 and 532nm; backscatter coefficients (β) at 355, 532, and 1064nm; and depolarization ratios (δ) at 532 and 1064nm. This system combines use of previously developed HSRL techniques with an iodine absorption filter for 532nm and a Fabry-Perot etalon for 355nm. A 532nm HSRL and 1064nm receiver were constructed for this lidar. We also developed a system to automatically tune the laser wavelength of this lidar to an iodine absorption line. We conducted preliminary measurements using the constructed systems. The temporal and vertical variation of aerosols could be determined. The constructed 532nm HSRL could measure molecule Rayleigh backscatter signals, indicating that the developed laser wavelength tuning system worked well. We further are developing an algorithm to retrieve the vertical distributions of the concentration and particle sizes of black carbon, dust, sea salt, and a mixture of sulfate, nitrate, and organic carbon, which are the principal aerosol components in the atmosphere, using the 2α+3β+2δ data.

Most every aspect of our lives depends upon plants, trees and grasses, i.e. vegetation. Not only they make us relaxant, feed us, but also they absorb carbon dioxide, and provide us with oxygen. Therefore, it is very important to watch the spatial distribution of vegetation biomass and changes in biomass over time, representing invaluable information to improve present assessments and future projections of the terrestrial carbon cycle. This paper proposes an ISS-JEM-EF borne lidar for taking actively the range-resolved NDVI value using dual wavelength (660nm/1320nm) pulsed laser transmitters and to measure the canopy height simultaneously using an imaging detection system with a 2D array detector for information of vegetation biomass.

An optimum design of neodymium lasers operating near 1320 nm was experimentally investigated. A conductively cooled Q-switched Nd:YAG laser with two birefringent filter plates produced 18 mJ of energy at 1319 nm. On the other hand, a Nd:YLF laser allowed us to achieve operations at a single emission line without wavelength selectors because of its favorable birefringent properties. An output energy of 42 mJ in a single Q-switched pulse at 1313 nm was obtained with a c-cut Nd:YLF rod.

This paper presents the results of recent studies on tropospheric aerosols, including Asian dust and forest fire smoke using the NIES Lidar Network, CALIPSO/CALIOP and chemical transport models. The NIES Lidar Network is a network of two-wavelength (532nm, 1064nm) polarization (532nm) lidars in East Asia. Currently the lidars are continuously operated at about 20 locations in Japan, Korea, China, Mongolia, and Thailand, in cooperation with various research institutes and universities. The network is a part of the Asian Dust Network (ADNet), SKYNET, and the GAW Aerosol Lidar Observation Network (GALION). The data from most of the lidar stations are transferred to NIES in realtime and automatically processed to derive the attenuated backscattering coefficients at 532nm and 1064nm, the volume depolarization ratio at 532nm, and the estimated dust and spherical aerosol extinction coefficients at 532nm. The data from the network are used in various research activities on Asian dust, regional air pollution, and the effects of aerosols on climate and the environment. The data are also used for real-time monitoring (for early warning assessment) of Asian dust. The results of recent studies on long-range transport of Asian dust, optical characteristics of forest fire plumes, aerosol climatology, etc. will be described.

The time-of-flight of light pulses has long been used as a direct measure of distance, but the state-of-the-art measurement precision using conventional light pulses or microwaves reaches only several hundreds of micromeres. This is due to the bandwidth limit of the photodetectors available today, which is in the picosecond range at best. Here, we improve the time-of-flight precision to the nanometer regime by timing femtosecond pulses through phase-locking control of the pulse repetition rate using the optical cross-correlation technique that exploits a second-harmonic birefringence crystal and a balance photodetector. The enhanced capability is maintained at long range without periodic ambiguity, being well suited to terrestrial lidar applications such as geodetic surveying, range finders and absolute altimeters. This method could also be applied to future space missions of formation-flying satellites for synthetic aperture imaging and remote experiments related to the general relativity theory.

We present a systematic comparison of different analyses of satellite-retrieved extinction profile based on the satellite - measurements with those derived from ground based Lidar. Also compared is the Lidar-derived aerosol optical depth (AOD) with passive sensor derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellite data are used as these comparisons and that is a bit complex because spatial and temporal coincident data for clear sky conditions are needed for its comparisons to other Lidar data. Although limitation of the number of coincident dataset and expected errors are unknown, the satellite based aerosol extinction coefficients agree to those measured by ground-based Lidar within 0.02km-1. The two different satellite-derived AODs differ by 30% in comparison to the average of the coincident.

This document is a review of our investigations of the atmosphere and ocean radiative components are presented. Paper is focused on three major factors must taken into account at the Far Eastern region. The first is atmosphere aerosols, the second - ozone and the third - phytoplankton communities. Here we discuss how aerosols are distributed in the atmosphere (spatiotemporal characteristics), how they interacts with other atmosphere constituents, its impaction on cirrus clouds formation. We also present atmosphere ozone layer dynamics and its wintertime specific features, discuss primary and secondary maxima evolution and causes of secondary maximum formation.