久世 宏明

The retrieval of the aerosol optical thickness (AOT) from remotely-sensed data relies on the adopted aerosol model. However, the method of this technique has been rather limited because of the high variability of the surface albedo, in addition to the spatial variability in the aerosol properties over the land surfaces. To overcome unsolved problems, we proposed a method for the visibility-derived AOT estimation from SKYNET-based measurement and daytime satellite images with a custom aerosol model over the Chiba area (35.62 degrees N, 140.10 degrees E), which is located in the greater Tokyo metropolitan area in Japan. Different from conventionally-used aerosol models for the boundary layer, we created a custom aerosol model by using sky-radiometer observation data of aerosol volume size distribution and refractive indices, coupled with spectral response functions (SPFs) of satellite visible bands to alleviate the wide range of path-scattered radiance. We utilized the radiative transfer code 6S to implement the radiative transfer calculation based on the created custom aerosol model. The concurrent data from ground-based measurement are used in the radiative analysis, namely the temporal variation of AOT from SKYNET. The radiative estimation conducted under clear-sky conditions with minimum aerosol loading is used for the determination of the surface albedo, so that the 6S simulation yields a well-defined relation between total radiance and surface albedo. We made look-up tables (LUTs) pixel-by-pixel over the Chiba area for the custom aerosol model to retrieve the satellite AOT distribution based on the surface albedo. Therefore, such a reference of surface albedo generated from clear-sky conditions, in turn, can be employed to retrieve the spatial distribution of AOT on both clear and relatively turbid days. The value for the AOTs retrieved using the custom aerosol model is found to be stable than conventionally-used typical aerosol models, indicating that our method yields substantially better performance.

We describe a portable Raman lidar system that can remotely detect oil leakages in water. The system has been developed based on a frequency-doubled, Q-switched Nd:YAG laser, operated at 532 nm with a receiver telescope equipped with some filters and photomultipliers. Stand-off detection of oil is achieved in a 6-m-long water tank, which allowed us to considerably increase the survey capability of subsea infrastructures, including both the range observation and target identification.

We demonstrate the remote detection method of oils in water by laser Raman spectroscopy. A frequency-doubled, Q-switched Nd:YAG laser at 532 nm was used as a light source, and oils in water were identified in the optical cells placed 2 and 4 m away in a water tank by using the Raman signals at 2910 cm−1 from oils. The results show that the configuration of underwater remote Raman spectroscopy can be a useful alternative method for detecting oil leaks from subsea pipelines, potentially providing more capability of target selectivity as compared with fluorescence detection

Nighttime clouds are detected using a camera without a NIR-cut filter by exploring the pixel value distribution in each red, green, and blue (RGB) color space from clear and 100% cloudy sky images. The removal of the NIR-cut filter enhances the pixel values of each color space due to the additional NIR signals. Cloud pixels can be separated from clear sky pixels by only using each color space and applying the appropriate threshold. Exploring different cloud detection methods is vital in our ongoing research activity collecting clear and cloudy sky images in other countries using this camera.

Aerosol optical properties are measured near the surface level using sampling instruments and a near-horizontal lidar. The values of the aerosol extinction coefficient inside the instruments are derived from nephelometer and aethalometer data, while the ambient values are measured from the lidar. The information on aerosol size distribution from optical particle counters is used to simulate extinction coefficients using the Mie scattering theory, with corrections on the humidity growth of hygroscopic particles. By applying this method to the continuous data obtained from November to December 2018 at Chiba, Japan, we elucidate the temporal variations of near-surface aerosol properties, including the complex refractive index, single scattering albedo, and Angstrom exponent. The results indicate how aerosol particles change their properties between the dry, instrumental conditions and relatively humid setting of the ambient atmosphere.

Aerosol optical properties are measured near the surface level using sampling instruments and a near-horizontal lidar. The values of the aerosol extinction coefficient inside the instruments are derived from nephelometer and aethalometer data, while the ambient values are measured from the lidar. The information on aerosol size distribution from optical particle counters is used to simulate extinction coefficients using the Mie scattering theory, with corrections on the humidity growth of hygroscopic particles. By applying this method to the continuous data obtained from November to December 2018 at Chiba, Japan, we elucidate the temporal variations of near-surface aerosol properties, including the complex refractive index, single scattering albedo, and Angstrom exponent. The results indicate how aerosol particles change their properties between the dry, instrumental conditions and relatively humid setting of the ambient atmosphere.

Aerosol optical properties are measured near the surface level using sampling instruments and a near-horizontal lidar. The values of the aerosol extinction coefficient inside the instruments are derived from nephelometer and aethalometer data, while the ambient values are measured from the lidar. The information on aerosol size distribution from optical particle counters is used to simulate extinction coefficients using the Mie scattering theory, with corrections on the humidity growth of hygroscopic particles. By applying this method to the continuous data obtained from November to December 2018 at Chiba, Japan, we elucidate the temporal variations of near-surface aerosol properties, including the complex refractive index, single scattering albedo, and Angstrom exponent. The results indicate how aerosol particles change their properties between the dry, instrumental conditions and relatively humid setting of the ambient atmosphere. (C) 2020 Optical Society of America

© 2020 Optical Society of America A feasibility study of coherent differential absorption lidar is conducted using a 1.53-µm wavelength for simultaneously retrieving the water vapor density and wind speed profiles. We selected the ON and OFF wavelengths to be 1531.383 and 1531.555 nm, respectively, for minimizing the effect of the temperature change in the atmosphere. The systematic measurement error can be reduced to below 5% by stabilizing the ON wavelength from −64 to 102 MHz around the center of the water vapor absorption line. Analysis of the speckle and photon statistics errors reveal that the relative error of the water vapor density is less than 10% at the altitude from 0.1 to 1.7 km with the 100 m range resolution with 10 min data accumulation time. The simultaneous measurement of wind speed and direction can also be achieved by employing a conical scan mechanism.

© 2020 Optical Society of America. In Ref. [1], the title of the paper was corrected. The article was corrected online on 2 March 2020.

© 2019 Elsevier B.V. Laser induced breakdown spectroscopy (LIBS) based on femtosecond laser pulses has widely been used for analyzing chemical elements in samples. In this research, we achieved the double-pulse operation with a two-polarizer configuration, and the signal enhancement factor of 4–15 was observed as compared with the single pulse LIBS scheme. It is found that with the change in interpulse delay time between 0 and 150 ps, the laser-fluence dependence of the LIBS signal enhancement can be classified into three types that are characterized by the different behavior of linear and quadratic intensity increase, followed by the intensity saturation. Such different responses are presumably ascribable to the mechanisms of electron-ion relaxation and plasma reheating. Also, different behavior is seen for the signal enhancement with different laser intensity and beam diameter while the laser fluence is kept constant. This indicates that generally, the use of a larger beam diameter is recommended for increasing the signal enhancement factor.

Laser beam propagation in highly random media can potentially be applied to various optical studies, though the light penetration is often limited to the surface or skin regions of the targets. In free space, it is known that the use of a non-diffractive beam (Bessel beam) is useful for achieving a long-distance propagation by reducing the influence of diffraction. In our previous work [Z. Peng, and T. Shiina, Opt. Commun. 391, 94-99 (2017)], the generation and propagation of such a non-diffractive beam were studied in a scattering medium of colloidal suspension (diluted milk) up to the concentration of 1.2% using cell lengths between 10 and 30 cm. The transformation from an annular beam to a non-diffractive beam was observed using a detector with a narrow view angle of 5.5 mrad. In the present study, experimental results are reported for much higher concentrations using shorter cell lengths of 3 and 5 cm. It is found that a non-diffractive beam is generated as a central peak superposed on widely distributed intensity due to multiple scattering. The polarization property is preserved during the transformation from annular ring to central peak. M the propagation distance of 3 cm, the intensity of non-diffractive beam is maximized with a high media concentration of 22.0% which yields the scattering coefficient of 5 cm(-)(1). Furthermore, it is found that the media concentration range that leads to the generation of the non-diffractive beam becomes wider for such shorter propagation distances.

Monitoring of near-surface aerosol is important for both public health issues and radiation budget studies. In this study, we report a continuous observation method of aerosol particles by means of a vertical Mie-scattering lidar in combination with other optical and sampling instruments operated at the ground level. In the Fernald method used for processing the lidar signal, the most appropriate value of lidar ratio at 532 nm is estimated from the Mie-scattering calculation. The input parameters, namely, the mode radius, variance, and both real and imaginary parts of refractive index, are so determined as to reproduce the data from ground-based sampling instruments. Instead of the far-end boundary condition, the extinction coefficient at the surface level is used for constraining the retrieved aerosol extinction profile. The correction of the truncation and relative humidity (RH) effects on the scattering data from the sampling is made with the help of the optical data from a visibility-meter. We discuss the observed features in both low and high RH cases. Such a capability will be useful for uninterrupted lidar observations of near-surface aerosols irrespective of the presence of clouds that often hinders signal observations at higher altitudes where the aerosol-free atmosphere is assumed for the conventional Fernald analysis.

The combined use of remote sensing and in-situ monitoring instruments could help improve the assessment of near-surface aerosol properties. In this paper, we analyze the diurnal behavior of aerosol extinction coefficients, alpha(Ext)(lambda), at lambda=349 and 550 nm using a lidar and a present weather detector, respectively. We utilize the aerosol optical thickness (AOT), single scattering albedo (SSA), and Angstrom exponent (AE) from SKYNET sky radiometer, and AE from aethalometer, and the number distribution from optical particle counter to evaluate the effect of relative humidity (RH) on aerosol extinction coefficients. It is found that although alpha(Ex)(lambda) often exhibits a positive correlation with the ambient RH, this relation is obscured when both the number distribution and particle size change simultaneously. Moreover, alpha(Ext) at 349 nm is more sensitive to this change than at 550 nm.

Studying near-surface aerosol properties is of importance for a better assessment of the aerosol effect on radiative forcing. We employ the data from a near-horizontal lidar to investigate the diurnal behavior of aerosol extinction and single scattering albedo (SSA) at 349 nm. The response of these parameters to ambient relative humidity (RH) is examined for the data from a one-month campaign conducted in Chiba, Japan, during November 2017, a transition period from fall to winter. The Klett method and adaptive slope method are used in deriving the aerosol extinction coefficient from the lidar data, while the SSA values are retrieved using an aethalometer. Also, a visibility-meter is used to examine the aerosol loading inside the atmospheric boundary layer. It is found that the aerosol growth during the deliquescence phase is more readily observed than the contraction in the efflorescence phase. The decrease of SSA before the deliquescence RH is found for approximately 46% of the deliquescence cases, presumably representing the particle shrinkage of soot particles.

© 2020 40th Asian Conference on Remote Sensing, ACRS 2019: "Progress of Remote Sensing Technology for Smart Future". All rights reserved. Atmospheric aerosol has a pivotal role in both air-pollution and radiation budget studies. In this paper, we retrieve the spatial distribution of aerosol optical thickness (AOT) over Chiba Area from daytime images of Himawari-8 geostationary satellite. The concurrent data from ground-based measurements are used in the analysis, namely the temporal variation of AOT from a sunphotometer and sky-radiometer located at the Center for Environmental Remote Sensing (CEReS), Chiba University. Also, the information on vertical profiles of aerosols and clouds is obtained from the data of NIES (National Institute for Environmental Studies) lidar operated also on the campus of Chiba University. We employ the MODTRAN (MODerate resolution atmospheric TRANsmission) radiative transfer code for simulating the radiance components that reach the AHI sensor onboard the satellite. The retrieval of AOT is based on look-up tables (LUTs) that are calculated for plausible values of both AOT and the surface reflectance for each of the AHI bands. The choice of aerosol model is optimized with the help of sunphotometer and sky-radiometer data coupled with the surface-based weather and aerosol sampling data. Additional information that is available from the present approach is the influence of thin clouds such as cirrus, since the discrimination of aerosol and cirrus effects is usually a difficult task in most of the atmospheric correction studies. We discuss the seasonal changes of AOT and surface reflectance from the present analysis based on LUTs. It is demonstrated that for each season, the satellite data observed on a clear day with minimum aerosol loading can be used to establish a good reference for the analysis of various satellite data such as MODIS or Landsat to evaluate the AOT distribution over the Chiba area.

© 2020 40th Asian Conference on Remote Sensing, ACRS 2019: "Progress of Remote Sensing Technology for Smart Future". All rights reserved. Clouds control the radiation balance and water circulation in the atmosphere, and hence, the characterization of clouds and their behavior is one of the important tasks for both satellite and ground-based remote sensing. In the present study, we retrieve cloud physical (e.g., cloud types, cloud coverage and phase) and optical (e.g., opacity) information by employing Himawari-8 meteorological satellite data over the Japan area. The cloud coverage information is obtained from bands 1, 6, 8, 9, 13, 14, 15 and 16 of the Himawari-8 AHI (Advanced Himawari Imager) sensor. The cloud altitudes are retrieved from CALIPSO (Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation) data, while the concurrent data of aerosol are obtained from the ground-based instruments, namely, a sunphotometer, an integrated nephelometer, and an aethalometer. The sunphotometer measures aerosol optical thickness at wavelengths of 450, 550, and 770 nm. CALIPSO data provide the vertical distribution of aerosols and clouds as well as that of cloud phase when it passes over Chiba. We apply the split window algorithm (SWA) to classify clouds into nine different types. We compare the resulting cloud types with results based on the HCAI (High Resolution Cloud Analysis Information) algorithm developed by the Japan Meteorological Agency. The comparison indicates that good agreements are found for cirrus, whereas some differences are seen for cumulonimbus and middle cloud underneath dense cirrus regions. As a whole, the implementation of these methods on datasets derived from long-term observation can offer climatological trends of cloud occurrence over different areas in Japan.

© 2019 Published under licence by IOP Publishing Ltd. Aerosols play an important role in the Earth's radiation budget through the reflection of incoming solar radiation and formation of cloud droplets working as cloud condensation nuclei. The understanding on aerosol optical properties in troposphere, especially their behavior near the ground level, is still insufficient for precise evaluation of their impact. Although a sunphotometer can provide the aerosol optical thickness, its application is limited to daytime under near cloud free conditions. A visibility meter, on the other hand, can give the value of visibility, but the operation wavelength is limited to a single wavelength, e.g. 875 nm. To attain the multi-wavelength observation of aerosol extinction coefficient near the surface level, here we propose the use of a four-color light emitting diode (LED) source emitting at 455, 530, 590, and 625 nm as a light source for the long-path measurement of aerosol extinction. A near-horizontal light path with a round-trip distance of around 630 m has been established inside the campus of Chiba University. A collimated light beam is produced with a 130 mm diameter telescope, and the reflected beam from a retro-reflector is detected using a 200 mm diameter telescope connected to a photodiode. A sinusoidal wave modulation is applied to the LED source, and the resulting modulated signal amplitude is detected and recorded using a digital oscilloscope (Iwatsu, DS-5614A). The results of the recent observation are discussed in conjunction with the concurrent records of a visibility meter (Vaisala, PWD52) and a nephelometer (TSI3563) that can measure the aerosol scattering coefficient.

© Taiwan Association for Aerosol Research. In this study, we used ground instruments, namely, a visibility meter, an integrating nephelometer, an aethalometer, a lidar, and a weather monitor, to measure the scattering enhancement factor, f(RH), which quantifies the effect of ambient relative humidity (RH) on aerosol light-scattering, and to generate a model of its annual variation in the city of Chiba, Japan. First, the f(RH) values were calculated with chemical analysis data. Second, visibility-meter and aethalometer data were used to model the monthly trends of f(RH) at 550 nm. The f(RH) values were higher during summer than during the other three seasons, which can be attributed to the general pattern of the regional climatology as well as the loading of different particle types into the lower troposphere. Third, the f(RH) values at 532 nm were obtained from lidar and aethalometer measurements. Low and constant f(RH) values were observed during November, whereas higher and increasing f(RH) values were observed during May. Also, dust events during March 2015 showed decreasing f(RH) with increasing RH.

© 2019 IEEE. Precise evaluation of cloud types is indispensable for the detailed analysis of the Earth's radiation budget. The split window algorithm (SWA) is an algorithm that has been widely employed for cloud type classification from meteorological satellite imagery. In this study, we apply the SWA to analyze the clouds that appear in the Japan area using the imagery of Himawari-8 meteorological satellite. The brightness temperature (BT) information from band 13 (BT13, 10 μm) and band 15 (BT15, 12 μm) are employed with the BT difference (BTD) between these two bands (BTD13-15). For daytime analysis, the albedo of band 1 (0.47 μm) is also used to discriminate the cloudy and cloud-free areas. The validation of the resulting cloud type (SWA13-15), which includes ten classes including cloud-free condition, is carried out using the space-borne lidar data concurrent with the satellite observations. In addition, two different classifiers, namely, the sequential minimal optimization (SMO) and Naïve Bayes (NB) classifiers are tested with the results of SWA. When about 10% of 2 million data points are used for training the classifiers, the test results reveal that the correctly classified points are 97.0% and 89.5% for the first dataset (observed in July 2015) and 97.4%, and 92.1% for the second dataset (July 2016) for SMO and NB, respectively.

© 2019 IEEE. Images of nighttime clouds from a ground-based camera are compared with lidar-derived nighttime cloud base heights for the purpose of quantifying the relationship of cloud heights with average pixel values and investigating the effectiveness of a low-cost camera (without IR filter) to detect nighttime clouds. Images from low-level clouds show higher average pixel values than high-level clouds. The decreasing pixel values with increasing cloud base height is quantified by a simple fitting analysis. This result indicates that average pixel values of nighttime clouds can be used to estimate cloud base height.

© 2019 Published under licence by IOP Publishing Ltd. Ultrasonic wave is suitable to be used as information carrier in short-range remote sensing practices. When developing a short-range ultrasonic remote sensing device, the object distance measurement routine shall produce an accurate result. In a few-meter or several-meter object detection or imaging, millimeter accuracy is required, therefore, a calibration becomes crucial. This article addresses the process and the result of our research on calibrating the distance between the device and the backscattering object. Our approach consists of investigating potential delay contributors, recognizing the practical delay contributors by analysing the program routine, formulating the calibration equation and applying the calibration equation in the computation.

Forest fire is the main problem in Indonesia and 75% occurred in peatland area, mainly in open area. Fast-growing commercial oil palm and paper pulp tree plantations, especially in Sumatera and Kalimantan has led to widespread deforestation and drainage in peatland area. Therefore, detection of dry-flammable peatland area is important to support land and forest fires prevention. The purpose of this research is to develop simple model for detection of dry-flammable peatland area by using Synthetic Aperture Radar (SAR) ALOS-2 L-Band data. Synthetic Aperture Radar ALOS-2 operating in L-Band frequency have advantages for peatland monitoring compare to other radar satellite data due to its longest wavelength and higher resolution which made a possibility to penetrate peatland surface. In this research, statistic approach was used to calculate relationship and develop model between backscattering coefficient (BC) and groundwater table (GWT). The study area is located in Sungai Apit, Siak Regency, Riau Province, Indonesia. The GWT were measured from 18 points sampling. Backscattering coefficient then calculated based on ALOS-2 L-Band calibration from JAXA for level 1.1.(Single Look Complex) data. Based on this research, the result of the relationship between GWT and backscattering coefficient is -0.5 both for HH and VV polarization. The equation model were developed by using linear regression based on the relationship between GWT and backscattering coefficient of HH and VV polarization. By using the information of backscattering coefficient of HH and VV polarization, we can calculate GWT of the peatland area. GWT more than 40 cm is classify as dry-flammable peatland area. We have termed the model Simple Dry-Flammable Peatland Detection SAR Model.

© 2018 Optical Society of America. We have developed a method to monitor the slant column density of nitrogen dioxide in the lower troposphere using a compact hyperspectral camera with a high spectral resolution of 1 nm at the full width half-maximum. Measurements of skylight spectra were conducted in wavelength regions of 460–490 nm and 550–610 nm to retrieve the slant column densities of nitrogen dioxide, in addition to water vapor and oxygen dimer. The results of ground-based measurements are shown for the cases of urban air pollution and aircraft emission near an airport runway.

© The Authors, published by EDP Sciences, 2018. A compact LED lidar was constructed and fieldtested with the aim to observe the Mars' dust devils. To be able to fit it on the Mars rover, a specialized Cassegrain telescope was designed to be within a 10 cm-cube, with a field of view of 3mrad. The transmitter has 385 nm LED light source with 3 cm opening, 70mrad divergence, 0.75W (7.5nJ/10ns) pulse power, and 500 kHz repetition frequency. The configuration of the optical system is biaxial to easily configure the overlap between their optical axes.

© 2013 IEEE. Complex topography and geological formation are the primary causes of frequent land deformation occurrence at Kelok Sembilan area, West Sumatra, Indonesia. This paper presents a research work on land mapping and land deformation monitoring carried out using persistent scatterer interferometry (PSI) synthetic aperture radar (SAR) technique at Kelok Sembilan bridge region. In this paper, 13 ascending Advanced Land Observation Satellite Phased Array L-band Synthetic Aperture Radar (ALOS PALSAR) scenes, taken from July 2007 to November 2010, were processed using PSI-SAR technique. Then, the land deformation analysis was performed in two of the critical landslide areas near the Kelok Sembilan bridge. For validation purpose, the results were compared with in situ ground measurement data obtained using both differential global positioning system technique, and 3-D photogrammetry technique based unmanned aerial vehicle. The land deformation analysis showed that both of the investigation areas are suffering a severe land movement of approximately -100 mm every year. In addition to that, the validation results showed erroneousness of less than 0.3%.

The influence of aerosols to the atmosphere has been discussed in the context of the Earth radiation budget and global climate change. Therefore, precise monitoring of aerosol parameters is important for better understanding of their real characteristics and impacts on the environment. In this study, we report on a novel method of concurrent measurements of aerosol near the surface level by means of slant-path (SP) and plan position indicator (PPI) lidars. The SP lidar utilizes a diode-laser-pumped Nd:YAG laser operating at 532 nm, while the PPI is based on a Nd:YLF laser at 349 nm. The PPI system including the laser transmitter and telescope section is rotated over 360° for covering all the horizontal directions with the maximum observation range up to around 3 km. At the same time, the SP lidar is employed for monitoring the near surface region that cannot be covered by vertical observation lidars. Furthermore, the backscattered signals recorded by both PPI and SP lidars are analyzed using the Fernald method to retrieve aerosol extinction coefficient by employing lidar ratios for 349 and 532 nm. These values of lidar ratio are estimated by adjusting and fitting parameters in the Mie scattering calculation (mode radius, variance, and both real and imaginary parts of refractive index) to real data from ground-based sampling instruments, namely, the scattering coefficient, absorption coefficient, and size distribution observed with an integrating nephelometer, an aethalometer, and an optical particle counter, respectively. Real-time values of the extinction coefficient inside the atmospheric boundary-layer are derived as the summation of scattering and absorption coefficients. The results are then compared with those from a vertical lidar, operated by the National Institute of Environmental Studies (NIES) on the campus of Chiba University. We discuss the observed features of aerosol characteristics that vary both temporally and spatially.

The influence of aerosols to the atmosphere has been discussed in the context of the Earth radiation budget and global climate change. Therefore, precise monitoring of aerosol parameters is important for better understanding of their real characteristics and impacts on the environment. In this study, we report on a novel method of concurrent measurements of aerosol near the surface level by means of slant-path (SP) and plan position indicator (PPI) lidars. The SP lidar utilizes a diode-laser-pumped Nd:YAG laser operating at 532 nm, while the PPI is based on a Nd:YLF laser at 349 nm. The PPI system including the laser transmitter and telescope section is rotated over 360 degrees for covering all the horizontal directions with the maximum observation range up to around 3 km. At the same time, the SP lidar is employed for monitoring the near surface region that cannot be covered by vertical observation lidars. Furthermore, the backscattered signals recorded by both PPI and SP lidars are analyzed using the Fernald method to retrieve aerosol extinction coefficient by employing lidar ratios for 349 and 532 nm. These values of lidar ratio are estimated by adjusting and fitting parameters in the Mie scattering calculation (mode radius, variance, and both real and imaginary parts of refractive index) to real data from ground-based sampling instruments, namely, the scattering coefficient, absorption coefficient, and size distribution observed with an integrating nephelometer, an aethalometer, and an optical particle counter, respectively. Real-time values of the extinction coefficient inside the atmospheric boundary-layer are derived as the summation of scattering and absorption coefficients. The results are then compared with those from a vertical lidar, operated by the National Institute of Environmental Studies (NIES) on the campus of Chiba University. We discuss the observed features of aerosol characteristics that vary both temporally and spatially.

© 2018 SPIE. We focused on the propagation property of an annular beam in strong scattering random media such as nimbostratus or dense fog. An annular beam as a lidar transmitted beam can propagate a longer distance even through atmospheric fluctuation. The reason is that an annular beam can self-transform to a non-diffracting beam, which is called non-diffractive effect. In this work, the center peak intensity as result of non-diffractive effect was generated after the propagation of an annular beam in random media with different concentrations and propagation distances. The linear relationship between the propagation distance and the transport mean free path calculated from the media concentration that caused the maximum center peak intensity was obtained. The generation condition of the non-diffractive beam was discussed under arbitrary parameters of beam diameter, propagation distance and media concentration.

Dust and water vapor are important constituents in the Martian atmosphere, exerting significant influence on the heat balance of the atmosphere and surface. We have developed a method to retrieve optical and physical properties of Martian dust from spectral intensities of direct and scattered solar radiation to be measured using a multi-wavelength environmental camera onboard a Mars lander. Martian dust is assumed to be composed of silicate-like substrate and hematite-like inclusion, having spheroidal shape with a monomodal gamma size distribution. Error analysis based on simulated data reveals that appropriate combinations of three bands centered at 450, 550, and 675 nm wavelengths and 4 scattering angles of 3 degrees, 10 degrees, 50 degrees, and 120 degrees lead to good retrieval of four dust parameters, namely, aerosol optical depth, effective radius and variance of size distribution, and volume mixing ratio of hematite. Retrieval error increases when some of the observational parameters such as color ratio or aureole are omitted from the retrieval. Also, the capability of retrieving total column water vapor is examined through observations of direct and scattered solar radiation intensities at 925, 935, and 972 nm. The simulation and error analysis presented here will be useful for designing an environmental camera that can elucidate the dust and water vapor properties in a future Mars lander mission.

The aim of the paper is to analyse hyperspectral images using tensor principal component analysis of multiway data sets. The mathematical and computational backgrounds of pattern recognition are the geometries in Hilbert space for functional analysis and applied linear algebra for numerical analysis, respectively. Because of high-resolution sampling in the colour channels, images observed by a hyperspectral camera system are expressed by three-mode tensors. The Tucker-3 decomposition of a three-mode tensor is used in behaviourmetric science and psychology for the extraction of relations among three entries as an extension of the usual principal component analysis for statistical analysis. Hyperspectral images express spectral information of two-dimensional images on the imaging plane. Therefore, for statistical analysis, we adopt the Tucker-3 decomposition. The Tucker-3 decomposition of hyperspectral images extracts statistically dominant information from hyperspectral images. Tensor principal component analysis allows us to extract dominant light-channel information from hyperspectral images.

SKYNET and Aerosol Robotic Network (AERONET) retrieved aerosol single scattering albedo (SSA) values of four sites, Chiba (Japan), Pune (India), Valencia (Spain), and Seoul (Korea), were compared to understand the factors behind often noted large SSA differences between them. SKYNET and AERONET algorithms are found to produce nearly same SSAs for similarity in input data, suggesting that SSA differences between them are primarily due to quality of input data due to different calibration and/or observation protocols as well as difference in quality assurance criteria. The most plausible reason for high SSAs in SKYNET is found to be underestimated calibration constant for sky radiance (). The disk scan method (scan area: 1 degrees x1 degrees area of solar disk) of SKYNET is noted to produce stable wavelength-dependent values in comparison to those determined from the integrating sphere used by AERONET to calibrate sky radiance. Aerosol optical thickness (AOT) difference between them can be the next important factor for their SSA difference, if AOTs between them are not consistent. Inconsistent values of surface albedo while analyzing data of SKYNET and AERONET can also bring SSA difference between them, but the effect of surface albedo is secondary. The aerosol nonsphericity effect is found to be less important for SSA difference between these two networks.

A compact Raman lidar has been developed for studying phase changes of water in the atmosphere under the influence of ionization radiation. The Raman lidar is operated at the wavelength of 349 nm and backscattered Raman signals of liquid and vapor phase water are detected at 396 and 400 nm, respectively. Alpha particles emitted from Am-241 of 9 MBq ionize air molecules in a scattering chamber, and the resulting ions lead to the formation of liquid water droplets. From the analysis of Raman signal intensities, it has been found that the increase in the liquid water Raman channel is approximately 3 times as much as the decrease in the vapor phase water Raman channel, which is consistent with the theoretical prediction based on the Raman cross-sections. In addition, the radius of the water droplet is estimated to be 0.2 mu m.

Average concentration of carbon dioxide (CO2) has been measured over a path length of 5.1 km in the lower troposphere by the method of differential optical absorption spectroscopy (DOAS) using a near-infrared light source based on amplified spontaneous emission. The analysis of CO2 absorption intensity around 1575 nm observed during 10 days over the Chiba city area has revealed that the CO2 concentration varied in the range of around 360-450 ppmv, with presumable influence of air mass advection from nearby industrial facilities. In addition, a good correlation has been found in relative humidity values between the DOAS and meteorological station data. As a whole, the present result indicates the usefulness of such a DOAS approach for measuring the concentration of CO2 averaged over an optical path of a few kilometers in the lower troposphere. (C) 2015 Optical Society of America

Concentration measurement of oxygen gas is required for better monitoring and control of various types of combustion systems. As compared with conventional zirconia oxygen sensors, tunable diode laser absorption spectroscopy can provide faster response, with smaller interference of inflammable gases. In this paper we report the concentration measurement of oxygen molecules using the absorption band (A-band) of 760 nm wavelength. A periodically poled LiNbO₃ crystal (PPLN) is employed for the frequency doubling of 1520 nm light from a distributed feedback laser, resulting in the 760 nm output power of 1.8 mW. The wavelength modulation spectroscopy with dual beam configuration enables the cancellation of the common mode noise from diode laser as well as excess etalon noise that arises from optical paths including the PPLN module. With the cell length of 200 mm, the absorption measurement using the R11Q12 line at 760.445 nm has led to a minimum detectable absorbance of 3.7×10^-4 m^-1. A dynamic response faster than 1 s was seen when the oxygen concentration was changed between 0% and 24% while the laser wavelength was fixed at the absorption peak.

Fluorescence originating from chlorophyll provides information on the photosynthetic activities of vegetation. We have developed a ground-based remote sensing observation system that enables the stand-off measurements of fluorescence spectrum as well as two-dimensional distribution of fluorescence imagery. The initial laboratory test was conducted by means of the laser induced fluorescence (LIF) method and solar radiation reflected from a cold mirror. Also we describe the field observation based on the direct solar radiation induced fluorescence (SRIF) scheme that has been applied to various vegetation canopies with stand-off distances of 20-30 m.

We propose a stand-off system that enables detection and classification of CBRNe (Chemical, Biological, Radioactive, Nuclear aerosol and explosive solids). The system is an integrated lidar using a high-power (terawatt) femtosecond laser. The detection and classification of various hazardous targets with stand-off distances from several hundred meters to a few kilometers are achieved by means of laser-induced breakdown spectroscopy (LIBS) and two-photon fluorescence (TPF) techniques. In this work, we report on the technical considerations on the system design of the present hybrid lidar system consisting of a nanosecond laser and a femtosecond laser. Also, we describe the current progress in our laboratory experiments that have demonstrated the stand-off detection and classification of various simulants. For the R and N detection scheme, cesium chloride aerosols have successfully been detected by LIBS using a high-power femtosecond laser. For the B detection scheme, TPF signals of organic aerosols such as riboflavin have clearly been recorded. In addition, a compact femtosecond laser has been employed for the LIBS classification of organic plastics employed as e-simulants.

Fusion of images with different spatial resolutions has the capability of improving visualization and spatial resolution and enhancing structural/textural information of the involved images, while preserving the spectral information in multi-spectral (MS) images. In this paper, various fusion methods have been examined in the data fusion of GeoEye-1 and QuickBird imagery, followed by subsequent image control. The effectiveness of five techniques, the Gram-Schmidt (GS), high-pass filtering (HPF), modified intensity-hue-saturation (M-IHS), fast Fourier transform (FFT)-enhanced IHS (FFT-E) and wavelet principal component analysis (W-PCA), has been evaluated through visual inspection, histogram analysis and correlation analysis. Also, image quality information is assessed by means of global spectral information (relative dimensionless global error, relative average spectral error), spectral distortion (peak signal-to-noise ratio), spectral (bias, root means square error) and spatial information (mean, standard deviation) of the fused images. In addition, the extraction of object boundary is tested and evaluated using Canny edge detection. The results show that most of the image fusion techniques preserve spectral information of original image, but occasionally with some spectral distortion. It has been found that the GS method, followed by HPF, yields the best information quality in the fused image, suitable for improving visual interpretation and data quality from the viewpoint of remote sensing applications.