Shuichi Rokugawa

A temperature and emissivity separation algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASAs Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE/spl Delta/T) of /spl les/0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTERs TES algorithm hybridizes three established algorithms, first estimating the normalized emissivities and then calculating emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES should be able to recover temperatures within about /spl plusmn/1.5 K and emissivities within about /spl plusmn/0.015. Validation using airborne simulator images taken over playas and ponds in central Nevada demonstrates that, with proper atmospheric compensation, it is possible to meet the theoretical expectations. The main sources of uncertainty in the output temperature and emissivity images are the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTERs precision, calibration, and atmospheric compensation.

Temperature and emissivity separation from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images

The ASTER scanner on NASAs EOS-AM1 satellite (launch: 1998) will collect five channels of TIR data with an NE(Delta) T of less than or equal to 0.3 degrees Kelvin to estimate surface kinetic temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature/emissivity separation (TES) is difficult because there are five measurements but six unknowns. Various approaches have been used to constrain the extra degree of freedom. ASTERs TES algorithm hybridizes three established algorithms, first estimating the temperature by the normalized emissivity method, and then using it to calculate emissivity band ratios. An empirical relationship predicts the minimum emissivity from the spectral contrast (min-max difference: MMD) of the ratioed values, permitting recovery of the emissivity spectrum. TES uses an iterative approach to remove reflected sky irradiance. Based on numerical simulation, TES can recover temperatures within about plus or minus 1.5 degrees Kelvin, and emissivities within about plus or minus 0.015. Limitations arise from the empirical relationship between emissivity values and spectral contrast, compensation for reflected sky irradiance, and ASTERs precision, calibration and atmospheric correction. Improvements of TES before launch will focus on refining the MMD relationship.

Detection and Volume Estimation of Large-Scale Landslides Based on Elevation-Change Analysis Using DEMs Extracted From High-Resolution Satellite Stereo Imagery

A new technique for quickly assessing extensive areas of large-scale landslides that uses digital elevation models (DEMs) extracted from high-resolution satellite images is presented in this paper. The proposed technique observes the elevation changes by using multitemporal DEMs. Five-meter-resolution DEMs from SPOT-5 images are applied to two large-scale landslide disasters: the landslides triggered by the 2004 Mid Niigata prefecture earthquake (magnitude 6.8; a moderate-topography area in Central Japan), and the landslides caused by the 2004 typhoon Mindulle (a steep-topography area in Central Taiwan). Both events yielded elevation changes in excess of 10 m. We assess the DEMs produced by the proposed method and their landslide application. We find three main results. 1) The elevation difference error increases with the slope angle. The root-mean-square error was 4-5 m on slopes lower than 30deg in both areas, whereas it was 5-6 m for slopes that exceeded 30deg in moderate topographies and 5-9 m in steep topographies. 2) The proposed technique well delineated the large-scale landslides. The total rate of successful area detection was over 70% for slopes under 40 deg but under 40% for slopes that exceeded 40 deg. 3) The landslide volume could be roughly estimated in units of 100times103 m3. The developed technique well supports damage assessments of large-scale landslides because the location, depth, and volume can be quantitatively determined by remote sensing

Estimating Broadband Emissivity of Arid Regions and Its Seasonal Variations Using Thermal Infrared Remote Sensing

Surface emissivity in the thermal infrared region is an important parameter for determining the surface radiation budget in climate, weather, and hydrological models. This paper focuses on estimating the spatial and temporal variations of the surface emissivities using thermal infrared remotely sensed data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard NASAs Terra satellite. We developed a regression approach to use the ASTER and MODIS data for estimating the broadband emissivity (BBE; 8-13.5 mum). The regressions were calibrated using a library of spectral emissivity data for terrestrial materials. We applied these regressions to ASTER and MODIS data to obtain emissivity maps for several arid regions of the Earth. In the 8-9-mum band for sparsely or nonvegetated desert areas, emissivity values between 0.66 and 0.96 have been observed, which are due to the low emissivity of quartz-rich sands at these wavelengths. As a result, the range of BBE is between 0.86 and 0.96. The seasonal variation over a two-year period and the dependence on land cover/soil type were also investigated.

Estimation of ultrasonic scattering attenuation in partially frozen brines using magnetic resonance images

Seismic attenuation is not due entirely to intrinsic properties; a component due to scattering effects is included. Although different techniques have been used to experimentally investigate the attenuation of seismic waves, not so many laboratory measurements of attenuation have taken into account the effect of scattering attenuation. Herein, partially frozen brine as a solid-liquid coexistence system is used to investigate attenuation phenomena. We obtained a series of 2D apparent diffusion coefficient (ADC) maps of the ice-brine coexisting system using a diffusion-weighted magnetic resonance imaging (DW-MRI) technique at −5°C , and found a strongly heterogeneous spatial distribution of unfrozen brine. From these maps, we constructed a synthetic seismic data set propagating through 2D media, and generated synthetic data with a second-order finite-difference scheme for the 2D acoustic wave equation. We estimated ultrasonic scattering attenuation in such systems by the centroid frequency shift method and ...

Laboratory experiments on compressional ultrasonic wave attenuation in partially frozen brines

Often, the loss mechanisms responsible for seismic attenuation are unclear and controversial. We used partially frozen brine as a solid-liquid coexistence system to investigate attenuation phenomena. Ultrasonic wave-transmission measurements on an ice-brine coexisting system were conducted to examine the influence of unfrozen brine in the pore microstructure on ultrasonic waves. We observed the variations of a 150–1000 kHz wave transmitted through a liquid system to a solid-liquid coexistence system, changing its temperature from 20°C to – 15°C . We quantitatively estimated attenuation in a frequency range of 350–600 kHz by considering different distances between the source and receiver transducers. We also estimated the total amount of frozen brine at each temperature by using the pulsed nuclear magnetic resonance (NMR) technique and related those results to attenuation results. The waveform analyses indicate that ultrasonic attenuation in an ice-brine coexisting system reaches its peak at −3°C , at whic...

A comparison of thermal infrared emissivity spectra measured in situ, in the laboratory, and derived from thermal infrared multispectral scanner (TIMS) data in Cuprite, Nevada, U.S.A.

In order to obtain ground truth data for multispectral thermal infrared sensors such as TIMS and ASTER, in situ spectral emissivity measurements were made during field surveys. These spectral emissivity measurements and laboratory spectral reflectance measurements of field samples were compared to emissivity spectra extracted from TIMS data at the surveyed points. The results indicate that emissivity spectra derived from the TIMS data agree well in shape with the spectra measured in situ or in the laboratory.

Seismic reflector imaging by prestack time migration in the Kakkonda geothermal field, Japan

We show that a prestack migration method improves the S/N ratio of seismic reflection profiling in the Kakkonda geothermal field where seismic reflection data are of poor quality. We use non-iterative prestack time migration (PSTM), which does not require multiple iterations to determine the velocity structure for prestack time migration. The optimum constant migration velocity can be determined at each image point from a migration velocity analysis based on primary diffraction patterns. Our results delineate a strong reflector beneath a zone of high seismicity. According to the correspondence between the fracture distribution, the distribution of microearthquakes, and geothermal structure, this reflector is interpreted to be a zone of low-angle fractures saturated with hydrothermal fluids, and to be strongly controlled by the geothermal structure.

Current status of Hyperspectral Imager Suite (HISUI)

Hyperspectral Imager Suite (HISUI) is a future spaceborne hyperspectral and multispectral Earth imaging system being developed by Japanese Ministry of Economy, Trade, and Industry (METI). HISUI project is currently being promoted by three organizations each of which has a contract with METI together with several scientists from universities and national research institutes. The current status of HISUI project will be introduced in the presentation.

Early evaluation of ASTER emissivity products and its application to environmental and geologic studies

Land Surface Emissivity product is one of standard products generated from Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) on NASAs Terra satellite launched in December 1999. This product is important for detailed lithologic mapping and precise land surface temperature determination. The accuracy of ASTER-derived emissivity is a function of various factors such as radiometric calibration of the instrument, assumptions used in a temperature-emissivity separation algorithm, and spatial temperature/material mixture in a pixel. In this study, the effects of spatial material mixture on ASTER-derived emissivity are investigated as one of the validation activities of this product. First, the mixture effects on ASTER-derived emissivity are evaluated through numerical simulations under various land surface material and temperature conditions. Also, at several sites including Cuprite, Nevada, ASTER-derived emissivity and airborne sensor-derived emissivity are compared. Applications of ASTER emissivity products to environmental and geologic studies will be also presented.