During the past several years Sandia National Laboratories has carried out proof-of-concept experiments to demonstrate tunable, efficient, high-energy ultraviolet nanosecond light sources for satellite-based ozone DIAL. We designed our UV sources to generate pulse energies > 200 mJ at 10 Hz in the range of 308-320 nm with optical-to-optical efficiency approaching 25%. We use sum-frequency generation to mix the 532 nm second harmonic of Nd:YAG with near-IR light derived from a self-injection-seeded image-rotating nonplanar-ring optical parametric oscillator. Laboratory configurations using extra- and intra-cavity sum-frequency generation were designed and tested, yielding 1064 nm to 320 nm conversion efficiencies of 21% and 23% respectively, with pulse energies of 190 mJ and 70 mJ. These energies and efficiencies require pump depletion in the parametric oscillator of at least 80% and SFG efficiency approaching 60%. While the results reported here fall slightly short of our original goals, we believe UV pulse energies exceeding 250mJ are possible with additional refinements to our technology. Although the sources tested to date are laboratory prototypes with extensive diagnostics, the core components are compact and mechanically robust and can easily be packaged for satellite deployment.

A conductively cooled pump head with a triangular-prism laser rod is proposed and discussed. A pump absorption efficiency of ~80% and better pump intensity distribution were expected from the results of simulations. An output energy of 95 mJ and an optical-to-optical conversion efficiency of 10% were obtained at a pulse repetition frequency of 5 Hz in normal-mode operation. Using a fused-silica acousto-optic Q-switch, the laser produced an output energy of 21 mJ in a single Q-switched pulse. No parasitic oscillation occurred even when the laser rod with polished lateral surfaces was used in Q-switched operations.

Pulsed lasers are useful for remote sensing of wind and greenhouse gases to better understand the atmosphere and its impact on weather patterns and the environment. It is not always practical to develop and optimize new laser systems empirically due to the time and expense associated with such endeavors. A practical option is to use a laser model to predict various performance parameters and compare these with the needs required for a particular remote sensing application. This approach can be very useful in determining the efficacy of potential laser systems, saving both time and money before proceeding with the actual construction of a laser device. As a pedagogical example, the modeling of diode pumped Tm:Ho:YLF and Tm:Ho:LuLF lasers are examined. Tm:Ho lasers operating around 2.0 μm have been used for wind measurements such as clear air turbulence and wake vortices. The model predictions for the laser systems examined here are compared to the actual laser performance, validating the usefulness of the modeling approach. While Tm:Ho fluoride lasers are used as a pedagogical example, the model is applicable to any lanthanide series pulsed laser system. This provides a useful tool for investigating potential laser systems that meet the requirements desired for a variety of remote sensing applications.

Remote sensing requires efficient lasers that are tunable over a short wavelength range around a particular atmospheric absorption feature of interest. High efficiency usually implies lanthanide series lasers. Although lanthanide series lasers have sufficient tuning capability, they must operate at preselected atmospheric absorption features. Often, there is no commonly available laser that operates at the requisite wavelength. This type of problem can be addressed using compositional tuning to create a laser at a preselected wavelength where none existed before. Quantum mechanics is an invaluable tool to predict the effects of compositional tuning. Quantum mechanical predictions are confirmed with spectroscopic measurements. Laser performance data for a laser that operates at 0.9441 μm, a preselected water vapor absorption feature, are featured.

Remote sensing using mid-infrared wavelength has many applications in pollution surveillance and atmosphere studies. However, high gain, low noise detectors or single photon counters are not available in the mid-infrared wavelength range. One approach to obtain single-photon detection in mid-infrared wavelength is to convert the mid-infrared radiations into visible/near-infrared wavelengths where high efficiency and low dark current detectors are easily available. In this paper, the up-conversion of mid-infrared radiations based on the quasi-phase matching condition of periodically poled lithium niobate (PPLN) is investigated. The bandwidth and efficiency are the two essential parameters for the up-conversion process. The optimal pump wavelength λ_laser^o and PPLN period Λ can be determined from conservations of energy and momentum. Once the λ_laser^o and Λ are defined, the spectral bandwidth corresponding to the full width at half maximum of frequency up-conversion can be calculated. The spectral bandwidth of mid-infrared radiations can exceed 130 nm for a 25 mm PPLN crystal when the pump laser operates in the optimum wavelength. It is wide enough to cover both the on and off wavelengths of the species of interest in a Differential Absorption Lidar. The maximum up-conversion bandwidth usually corresponds to the longest PPLN period allowed by the quasi-phase matching condition. The conversion efficiency increases with the pump laser intensity. Both the external cavity pumping approach with cavity locking technique and the intra-cavity pumping approach can greatly increase the up-conversion efficiency.

A multiple-scattering lidar technique is used to retrieve simultaneously the extinction coefficient and the effective particle diameter of clouds and precipitation. In addition, the linear depolarization ratio is measured to determine the liquid or solid phase of the particles. The reported measurements were made with a ground-based multiple-field-of-view (MFOV) lidar pointed at zenith. The lidar was fired in 10-s bursts, every minute for periods ranging from 30 min to 3 hours. The vertical resolution was selectable from 1.5 to 6 m but typically set at 3 m. The retrieved profiles are collected in the form of time-height maps of 1 min x 3 m resolution of the extinction coefficient, effective particle diameter, and depolarization ratio. Here, we analyze only the cloud layer and identify, from the statistics of the retrieved extinction coefficient and effective droplet diameter, important physical behaviors of water clouds. The results not only demonstrate the validity of the lidar retrievals but show that systematic lidar probings can yield significant information on cloud physics.

The CALIPSO (Cloud Aerosol LIDAR Infrared Pathfinder Satellite Observations) satellite is due to launch from Vandenberg AFB aboard a Delta rocket in April of 2005. CALIPSO is an international mission consisting of NASA, Ball Aerospace and the French space agency CNES. Onboard CALIPSO are three instruments, a two wavelength/two polarization lidar, an Infrared radiometer and a wide field camera. This paper will focus on the software design, development and functionality of the lidar systems including the transmitter and receiver as well as the planned operations paradigm. The operations paradigm simply stated is this: command the payload once a week with all commands being time-tagged, and receive and process health and status from the payload four (4) times per day. Science data totaling over 5 gigabytes a day is down-linked once every 24 hours. A modular approach was used in the design of the flight software where the executable code is separated into 8 loadable modules and the configuration of the individual instruments is accomplished via several loadable tables. This design scheme allows for manageable updates to the executable image and allows the science team to change and experiment with instrument configuration on an as needed basis without over stressing the command uplink system. Redundant copies of all nominal executable image files are kept onboard as is a maintenance image. The Onboard Fault Detection Isolation and Recovery (FDIR) system insures the safety of the payload and all instruments.

Systematic lidar measurements of aerosol backscatter and extinction in the troposphere were performed since May 2000 with the aerosol lidar system operational at IMAA-CNR in Tito Scalo (Potenza) (Southern Italy, 40°36’N, 15°44’E, 820 m above sea level) in the framework of EARLINET. EARLINET is the first European network of 22 advanced lidar stations operating to provide a quantitative climatological database of the horizontal, vertical and temporal distribution of aerosols over Europe. Aerosol backscatter measurements were performed at both 355 nm and 532 nm, while aerosol extinction coefficient was retrieved from simultaneous N₂ Raman backscatter signals at 386.6 nm. The lidar measurements at IMAA have been performed according to a regular schedule of two night time measurements per week (around sunset) and one daytime measurement per week (around 13:00 UT). Further measurements were devoted to observe special events such as Saharan dust, forest fires and volcanic eruptions. A statistical analysis on climatological aerosol extinction-to-backscatter ratio (lidar ratio) data, covering more than three years of systematic lidar observations, has been carried out. These lidar ratio data, in conjunction with an analysis on the air masses backtrajectories, provide information on microphysical properties of the aerosol on a wide range of meteorological conditions. Results obtained starting from both climatological data and special events (Saharan dust and volcanic eruptions) are presented and discussed.

A method of retrieving cloud microphysical properties using combined observations from both cloud lidar and radar is introduced. This retrieval makes use of a variation on the traditional optimal estimation retrieval method, whereby a series of corrections are applied to the state vector during the search for an iterative solution. The retrieval method is applied to lidar and radar observations from the CRYSTAL-FACE experiment, and vertical profiles of ice crystal characteristic diameter, number concentration, and ice water content are retrieved for a cirrus cloud layer observed during the experiment.

A CCD based bistatic lidar (CLidar) system has been developed and constructed to measure scattering in the atmospheric boundary layer. The system used is based on a CCD camera, wide-angle optics and laser. Measuring near the ground with the standard monostatic lidar method is difficult due to the huge change in signal strength with altitude and the incomplete overlap between the laser and the telescope. High spatial (altitude) resolution is also desired near the ground for comparison with in-situ aerosol instruments. Imaging a vertical laser beam from the side with a CCD camera and wide-angle field of view optics overcomes both of these problems. While the molecular signal changes many orders of magnitude in the standard method, it only changes about one order with the CLidar method. In addition, the CLidar resolution near the ground is less than a meter. For perpendicular polarization, the molecular signal is nearly constant all the way to the ground. Other advantages of the CLidar method include low cost and simplicity. The signal is integrated on the CCD rather than with specialized electronics. With the bistatic CLidar method the scattering angle changes with altitude. The variation of scattering intensity with the scattering angle will be influenced by the aerosol size distribution and thus could help provide information on aerosol parameters of interest in the boundary layer.

The Wide-Angle Imaging Lidar (WAIL), a new instrument that measures cloud optical and geometrical properties by means of off-beam lidar returns, was deployed as part of a multi-instrument campaign to probe a cloud field at ARM (Atmospheric Radiation Measurement) Southern Great Plain (SGP) site on March 25, 2002. WAIL is designed to determine physical and geometrical characteristics using the off-beam component of the lidar return that can be adequately modeled within the diffusion approximation. Using WAIL data, we estimate the extinction coefficient and geometrical thickness of a dense cloud layer; from there, we infer optical thickness. Results from the new methodology agree well with counterparts obtained from other instruments located permanently at the SGP ARM site and from the WAIL-like airborne instrument that flew over the site during our observation period.

The NASA Langley Research Center and the NASA Goddard Space Flight Center, have collaborated to design, build and fly a combination backscatter and Differential Absorption Lidar (DIAL) instrument for the measurement of aerosols, temperature and ozone from the NASA DC-8. The AROTAL (Airborne Raman Ozone Temperature and Aerosol Lidar) instrument was flown on two separate Arctic missions to look at ozone loss processes during the late winter-early spring, and to validate measurements made by the SAGE III satellite instrument. Results from this instrument have demonstrated that the SAGE III instrument is in agreement with the lidar retrievals to better than ten per cent.

We have constructed the lidar facility for survey of atmospheric structure over troposphere, stratosphere, mesosphere and low thermosphere over Kototabang (100.3E, 0.2S), Indonesia in the equatorial region. The lidar system consists of the Mie and Raman lidars for tropospheric aerosol, water vapor and cirrus cloud measurements, the Rayleigh lidar for stratospheric and mesospheric temperature measurements and the Resonance lidar for metallic species such as Na, Fe, Ca ion measurements and temperature measurements in the mesopause region. The laser system included in this lidar facility consists of three pulsed Nd:YAG lasers, a pulsed Ti:Sapphire laser seeded by a ring Ti:Sapphire laser and a dye laser. And, the receiving system consists of a Schmidt-Cassegrain telescope with 20cm diameter, a Schmidt-Cassegrain telescope with 35cm diameter and five Newtonian telescopes with 45cm diameter. The most parts of this lidar system are remotely controlled via the Internet from Tokyo Metropolitan University (TMU) in Japan.

Space-borne Doppler lidar is expected to make wind profile observations on a global scale with an accuracy of 1 to 2 m/s. It may solve the problem of the shortage of the accuracy and distribution in the current wind data. We have studied an eye-safe coherent Doppler lidar (CDL) model that could be deployed on the exposed facilities of Japanese Experiment Module (JEM) and that would meet the science requirements. We have good prospects of 500mJ output at 10Hz in a conduction cooling sub-scale laser, which could be a small model of space-borne laser for JEM/CDL. We are making studies on improving the system’s efficiency, reducing its weight, and establishing the fundamental technologies involved. Research on another possibility, e.g. a free flyer, for a demonstration mission besides of JEM/CDL is also valuable to be considered. Development of algorithm for application of coherent lidar system is also in progress through air-borne experiments and ground-based observations.

CTI has demonstrated Q-switched pulse amplification in Tm,Ho:YLF at >400 mJ output pulse energy for 60 mJ of input energy using a single stage 2-pass (on-axis) amplifier. The pulse duration was 800 ns. A double-pass gain of 10 was demonstrated for 35 mJ input pulse energy. The optical-to-optical efficiency for the 2-pass amplifier was 8%. This is the first demonstration of multiple hundred millijoule output and >10 times double-pass amplification in an all conduction-cooled two micron laser pump module: both the laser rod, operating at 200 K, and the pump laser diodes, operating at 300 K, are conduction-cooled to embedded cold-plates that remove heat from the pump module. As such, this design is directly compatible with the use of heatpipe and space radiator technology for thermal management in a space environment.

Space Lidar applications benefits from efficient conductive cooled laser transmitters. Effective thermal management is a key challenge for high-energy laser development. In this paper, the design and performance of a totally conductive cooled 2µm laser is presented. Three heat pipes capable of removing 150 watts of heat both from the pump diode lasers and the rod were used in the design. A 2.5 m long ring resonator with two 5-m radii of curvature mirrors set a 2.36mm diameter TEMoo mode radius in the cavity. Despite the thermal gradient that was created in the Ho:Tm: LuLF crystal due to the cooling method and geometry, almost diffraction limited beam and up to 107 mJ of Q-switched output with a pulse length of 135ns was obtained. Such a laser transmitter can be used as a wind Lidar. It is especially suitable as a CO₂ DIAL since two Q-switched pulses can be acquired for a single pump pulse due to the long lifetime of the Ho: ⁵I₇ and ⁵I₈ transition and the operating wavelength is near rich CO₂ absorption lines.

State of the art 2-micron lasers and other lidar components under development by NASA are being demonstrated and validated in a mobile test bed Doppler wind lidar. A lidar intercomparison facility has been developed to ensure parallel alignment of up to 4 Doppler lidar systems while measuring wind. Investigations of the new components; their operation in a complete system; systematic and random errors; the hybrid (joint coherent and direct detection) approach to global wind measurement; and atmospheric wind behavior are planned. Future uses of the VALIDAR (VALIDation LIDAR) mobile lidar may include comparison with the data from an airborne Doppler wind lidar in preparation for validation by the airborne system of an earth orbiting Doppler wind lidar sensor.

Spaceborne coherent Doppler wind lidars and CO₂ Differential Absorption Lidars (DIALs) at eye-safe 2-μm spectral range have been proposed for several years for accurate global wind and carbon-oxide concentration profiling measurement. These lidar systems require Joule level laser pulse energy from laser transmitter and high efficiency. In this paper, we report a diode-pumped Ho:Tm:LuLF Master-Oscillator-Power-Amplifier (MOPA) developed to demonstrate Joule level output pulse energy. The MOPA consists of one master oscillator and two power amplifiers. The master oscillator was Q-switched and can be operated at single pulse mode or double pulse mode respectively. The single pulse operation is used for a coherent Doppler wind lidar and the double pulse operation for a CO₂ Differential Absorption Lidar (DIAL). The output pulse energy of the master oscillator is 115 mJ for the single pulse operation and 186 mJ for the double pulse operation. To extract more energy from the pumping pulses and increase the efficiency of the MOPA, the first amplifier was set at a double pass configuration. The second amplifier was set at a single pass configuration to avoid the damage problem of the Ho:Tm:LuLF laser rod. Total output pulse energy of 0.63 J with an optical efficiency of 4.1% for single pulse operation and 1.05 J with an optical efficiency of 6.9% for double pulse operation were demonstrated.

We have developed a laser based on an oscillator/amplifier design that uses diode-pumped, conductively cooled Nd:YAG slabs as the gain media. The oscillator is a telescopic ring resonator design that can be easily configured for a range of operational scenarios. An unstable version of the oscillator achieved 125 mJ/pulse with >10% electrical to optical efficiency and an M² of 2.5. Operated in a stable TEM₀₀ mode, the ring laser demonstrated >30 mJ/pulse at 100 Hz with an M² of 1.3. We used the 30 mJ TEM₀₀ output to extract the amplifiers and achieved 300 mJ/pulse of single frequency output at 50 Hz with an M² of 1.5. We also investigated operation of an injection-seeded version of the ring resonator operated in the marginally stable regime without the use of graded reflectivity mirrors. With this approach we demonstrated single-frequency, 50 mJ/pulse operation at 50Hz with an M² of 1.4 and a square, supergaussian profile. Initial third harmonic generation measurements have achieved over 40% conversion to 355 nm.

Over the past few years, the GroundWinds program has produced two operational, ground based, multi-order fringe imaging direct detection Doppler wind LIDARs. The two existing instruments are located in Bartlett, NH and Mauna Loa, HI and operate at a wavelength of 532 nm and 355 nm, respectively. Both systems employ Fabry-Perot etalons as the wavelength resolving element and are capable of detecting Doppler shifts in both Aerosol and Molecular backscatter from 0.25 km to 18 km. Patented technologies demonstrated and developed through this program, such as Photon-Recycling (U.S. patent #6,163,380) and the Circle To Line Optic (U.S. Patent #4,893,003), will be incorporated into the next generation interferometer design and flown on a high altitude (30km) balloon. The opportunity to view the entire troposphere from a downward looking high altitude platform will serve as an empirical reference point for scaling to space. This paper will discuss the BalloonWinds mission concept and top-level specifications of the instrument subsystems. Additionally, this paper will report on the testing and progress of the instrument build and present performance projections based on the as built system.

Three lidar systems are currently in development at University of Hohenheim. A water vapor lidar based on the differential absorption lidar (DIAL) technology working near 815 or 935 nm, a temperature and aerosol lidar employing the rotational Raman technique at 355 nm, and an aerosol lidar working with eye-safe laser radiation near 1.5 μm. The transmitters of these three systems are based on an injection-seeded, diode laser pumped Nd:YAG laser with an average power of 100 W at 1064 nm and a repetition rate of 250 Hz. This laser emits a nearly Gaussian-shaped beam which permits frequency-doubling and tripling with high efficiencies. The frequency-doubled 532-nm radiation is employed for pumping a Ti:Sapphire ring-resonator which will be used for DIAL water vapor measurements. In a second branch, a Cr4+:YAG crystal is pumped with the 1064-nm radiation to reach 1400 to 1500 nm for eye-safe monitoring of aerosol particles and clouds. The 532 and 1064 nm radiation are also used for backscatter lidar observations. Frequency tripling gives 355-nm radiation for measurements of temperature with the rotational Raman technique and particle extinction and particle backscattering coefficients in the UV. High transmitter power and effective use of the received signals will allow scanning operation of these three lidar systems. The lidar transmitters and detectors are designed as modules which can be combined for simultaneous measurements with one scanning telescope unit in a ground-based mobile container. Alternatively, they can be connected to different Nd:YAG pump lasers and to telescope units on separate platforms.

Active remote sensing measurements of the total water vapor column content are presented using a frequency tuned DBR laser (940 nm band) and a hard target return over a 0.4 Km open path.

Human activities have been influencing the global atmosphere since the beginning of the industrial era, causing shifts from its natural state. The measurements have shown that tropospheric ozone is increasing gradually due to anthropogenic activities. Surface ozone is a secondary pollutant, its concentration in lower troposphere depends upon its precursors (CO, CH4, non methane hydrocarbons, NOx) as well as weather and transport phenomenon. The surface ozone exceeding the ambient air quality standard is health hazard to human being, animal and vegetation. The regular information of its concentrations on ground levels is needed for setting ambient air quality objectives and understanding photo chemical air pollution in urban areas. A Differential Absorption Lidar (DIAL) using a tunable CO₂ laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor water vapour, surface ozone, ammonia, ethylene etc. Some times ethylene and surface ozone was found to be more than 40 ppb and 140 ppb respectively which is a health hazard. Seasonal variation in ozone concentrations shows maximum in the months of summer and autumn and minimum in monsoon and winter months. In present communication salient features of experimental set up and results obtained will be presented in detail.

Progress in laser sources for surface and atmospheric remote sensing is placed in the context of 3D mapping and imaging laser radar systems and ambitions for future high resolution mapping systems.

Semiconductor lasers emitting at 1.55 microns are the cornerstone of the high bandwidth optical communications industry. Semiconductor lasers operating at this and other wavelengths are also used in the engineering, biology, chemistry and medical fields. The light emission in most semiconductor lasers is due to the optical transition between the valence and conduction bands of the semiconductor active material. This means that the intrinsic properties of the semiconductor active material i.e., the bandgap energy dictates the emission wavelength. This limits the efficient operation of these lasers at wavelengths above 3 microns. In the mid 1990s this limitation was overcome with the emergence of new laser architectures, such as the intersubband and interband Quantum Cascade (QC) lasers. The emission wavelength in these QC lasers is set by engineering the bandgap to extend the accessible spectral range well beyond 3 microns. Optical radiation from intersubband QC lasers is emitted by electrons undergoing an optical transition between the quantized energy levels in the conduction band rather than by direct transition from the conduction to the valence bands as in conventional semiconductor lasers. Quantum engineering of the electronic energy levels has enabled demonstration of intersubband QC lasers covering a very wide spectral range from 3.5 to 150 microns (except for a window for the Reststrahlen gap). Despite rapid and tremendous progress in the research and development of these QC laser sources, the technology is far from being sufficiently mature to be deployed for use in space instruments. We will discuss our efforts at the Jet Propulsion Laboratory to advance QC laser technology sufficiently to enable their use in new instruments for future NASA Earth and Solar System Exploration missions.

Single-mode (SM) fiber lasers and amplifiers are constrained to low output powers by fundamental physical limitations of the fiber, specifically, by low energy storage and by the onset of nonlinear processes in the fiber. The simplest way to overcome both limiting factors is to increase the core size, but maintaining SM operation imposes an upper limit. Further power scaling is possible with multimode (MM) fiber, but the poor beam quality generally associated MM fiber is unacceptable for many applications. We have developed a technique (bend-loss-induced mode filtering) that allows the core size to be increased significantly beyond the SM limit while maintaining diffraction-limited beam quality and high efficiency. In this method, coiling of the fiber is used as a form of distributed spatial filtering to suppress all but the fundamental mode of a highly MM fiber amplifier. Unlike conventional spatial filtering, in which high-order modes are discarded, the mode-filtering technique does not result is substantial loss of efficiency because high-order modes are suppressed along the entire length of the amplifier and are thus prevented from building up significant intensity. We will review this method and recent experimental results for both cw and pulsed fiber sources, including nonlinear frequency conversion of mode-filtered fiber lasers. Optical damage issues will also be discussed.

Continuous wave (CW) fiber laser systems with output powers in excess of 500 W with good beam quality have now been demonstrated, as have high energy, short pulse, fiber laser systems with output energies in excess of 1 mJ. Fiber laser systems are attractive for many applications because they offer the promise of high efficiency, compact, robust systems. We have investigated fiber lasers for a number of applications requiring high average power and/or pulse energy with good beam quality at a variety of wavelengths. This has led to the development of a number of custom and unique fiber lasers. These include a short pulse, large bandwidth Yb fiber laser for use as a front end for petawatt class laser systems and a narrow bandwidth 0.938 μm output Nd fiber laser in the > 10 W power range.

A direct-detection Doppler lidar for planetary boundary layer wind field measurement utilizing multi-beam Fizeau interferometer (MFI) is proposed. Fringe imaging and edge techniques are popular methods of incoherent wind speed measurement. In boundary layer, where aerosol backscattering is strong, it is good to measure wind velocity with fringe imaging technique. Fabry-Perot interferometers (FPI) are standard instruments in former incoherent lidar. Their performance is restricted from detector channels. However, linear fringes of MFI can be measured directly by linear detector, for example, charge coupled device (CCD). The MFI consists of two flat plates which assembled much like a FPI, but wedged by a small angle. Through three PZTs fixed on one plate, the plates spacing can be tuned and the wedge angle can be adjusted. The physical properties of the MFI are discussed in this paper. The factors affecting the measurement of Doppler frequency shift and the correction methods are analyzed and presented. A set of practical system parameters is proposed. The numerical simulation of system performance is implemented. Under different parameters of MFI, error of horizontal wind speed is compared in boundary layer. It shows that the error can be less than 1m/s using the optimized parameters of MFI.

The Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Quid Pro Quo (QPQ) measurements in collaboration with existing sites and other activities (e.g. field programs) are an important part of the CALIPSO validation program. These sites and field programs will provide data relevant to CALIPSO validation at times when the ground-track of the CALIPSO satellite is within a specified coincident distance. A free exchange of data between CALIPSO and these sites will occur and appropriate protocols of exchange will be followed. The primary CALIPSO validation period begins approximately 45 days after launch and ends about 18 months after launch. Launch is currently planned for the spring of 2005. Coordination of the validation measurements will be made through the CALIPSO website (http://www-calipso.larc.nasa.gov), the CALIPSO QPQ validation website (http://calipsovalidation.hamptonu.edu), email, and mail. This paper describes the details of this coordination.

Pulsed coherent Doppler lidar systems have matured rapidly, especially at solid-state wavelengths. Turnkey systems are commercially available and are being deployed for various aviation applications. Doppler lidar data is used in the airport terminal area to map hazardous wind shear and turbulence levels and to detect and track wake vortices. Future applications could include slant path visibility monitoring. Several permanent installations and rapidly deployable instrument configurations have been achieved. The benefit of the infrared Doppler lidar relative to its microwave counterparts is the ability to sense clear air hazards, especially those in and around local terrain features. The fact that the lidar beam is quite narrow eliminates artifacts associated with sidelobe-induced ground clutter. This paper summarizes our autonomous pulsed lidar developments and reviews sample results.

This paper reports on the results of measurements of the aerosols and the clouds optical properties in the troposphere over Tsukuba, Japan (104.12°E, 36.05°N, 27 above sea level). We carried out the experiments using a high-spectral resolution lidar based on iodine absorption filter with a working wavelength 532 nm and have the opportunity of polarization characteristics of the lidar signal. The results from simultaneously observations of particle backscatter and extinction profiles, lidar ratio (extinction to backscatter ratio) and depolarization ratio during on the four annual seasons are presented. We analyzed the seasonal variations of the particle backscatter, extinction and lidar ratio to investigate climatology of aerosol optical properties, and especially lidar ratio, over this region. The experimental results are compared with results obtained over another places and techniques.

We derived the upper troposphere and lower stratosphere temperatures with the Indo-Japanese Lidar system incorporating Raman capability in addition to existing elastic mode of observation on experimental basis for five months during Jan - May 2003. The derived temperatures are corrected for aerosol transmission, which is calculated from the Nitrogen Raman shifted signals. With a model reference temperature at 35 km, the atmospheric temperature profiles were obtained over an altitude range of 8-28 km. A good comparison between the lidar and radiosonde temperatures were obtained over an altitude range of 8-16 km for a 2-hour integrated measurement with 300-m resolution. However, this technique fails in the strong aerosol regions such as the presence of optically thick cirrus layers in the upper troposphere.

An elastic backscattering lidar system that is capable of operating in daytime, which is considered to be first of its kind in India, has been developed at Gadanki (13.5° N, 79.2° E), a tropical rural site, to provide the vertical profile of the aerosol backscatter ratio at 532nm up to an altitude of 5-6 km (AGL). We made observations of the lower tropospheric aerosols during Dec 2002 - March 2003 with the system. The following observations are bought out from the preliminary analysis of the data. (a) A thick aerosol layer will always be present in the lowermost troposphere which top 1.5 - 2 km above the ground level. We consider that the layer correspond to the local mixing layer. (b) A thin layer of aerosol exists in the free troposphere in the altitude of 3 to 5 km. It is considered that these layers were on the way of long-range transport (c) A clear dust layer appeared at height of 2-3 km during the months Feb and March 2003. The lidar data has also used to retrieve the Convective Boundary Layer (CBL) height over the tropical site Gadanki.

Image filtering by Richardson-Lucy algorithm show an iterative solution for monodimensional signal deconvolution. In this paper the performance of this algorithm will verify when LIDAR signals are pre-filtered by an adaptive low-pass filter. Most interesting results, for real-time deconvolution and filtering of lidar signal, will also showed.

Efficient CW laser oscillation was performed using floating zone-grown Tm:GdVO₄ crystals. The measured absorption spectra of the grown crystals exhibited high absorption coefficient of 13.2 cm^-1 at 799 nm for π polarization, and the absorption coefficient remained more than 4.5 cm^-1 at 808 nm for both π- and σ-polarizations. Using a 808 nm single-stripe laser diode as a pump source, a slope efficiency of 38% and a threshold of 420 mW were achieved with respect to absorbed pump power at room temperature. The highest output power of 235 mW was achieved. The laser could be tuned over 20 nm with rotation of an intracavity etalon. It was demonstrated that Tm:GdVO₄ is an excellent material for use in a 2 μm laser for a compact LD-pumped system.

The history and the number of Korean lidar groups is not so abundant, but the interest on laser remote sensing techniques is rapidly increased by researchers and governmental officers because of recent meteorological and environmental phenomena and social situation. Three kinds of commercial lidars developed by Korean company are working in routine measurements for stratospheric ozone concentration, Asian dusts called Hwangsa, and 3-D distribution of aerosols. The requirement and principles on designing commercial lidars are discussed, and several applied techniques and features of lidar systems to fulfill those conditions are showed.

In an attempt to better understanding climate and better comprehend the effects of clouds and aerosols on the Earth’s Radiation Budget, NASA has been developing several satellite missions. Among them, the Cloud-Aerosol-Lidar and Infrared Pathfinder Spaceborne Observation (CALIPSO) mission will observe clouds and aerosols with a combination of lidar and passive instruments. CALIPSO will fly in formation with EOS Aqua, EOS Aura, Cloudsat and Parasol. This novel satellite formation will provide a unique comprehensive data set of cloud and aerosol optical and physical properties, and radiative fluxes. In this paper, the characterization of global aerosol properties with sparsely sampled observations is investigated using a dataset of aerosol optical depth (AOD) from the MATCH climate model. MATCH is an offline Chemistry and Transport Model (ChTM) primarily developed by NCAR that includes a number of aerosol sources as well as a variety of transformation and removal mechanisms. The CALIPSO satellite is "flown" through this dataset and the aerosol optical depths at the CALIPSO footprint locations are sampled to produce an AOD subset. Averages computed from the subset are compared with averages from the full model output to investigate the magnitude of uncertainties due to sparse sampling of the aerosol field. Initially, uncertainties in satellite sparsely sampled measurements of global aerosol distribution are quantified in terms of zonal averages. The goal of this effort is to determine the correct satellite average scaling to accurately represent global aerosol coverage. Ultimately, sampling errors will also be assessed at regional scales.