Showing papers on "VNIR published in 2001"

The performance of the satellite-borne Hyperion hyperspectral VNIR-SWIR imaging system for mineral mapping at Mount Fitton, South Australia

Abstract: Satellite-based hyperspectral imaging became a reality in November 2000 with the successful launch and operation of the Hyperion system on board the EO-1 platform. Hyperion is a pushbroom imager with 220 spectral bands in the 400-2500 nm wavelength range, a 30 meter pixel size and a 7.5 km swath. Pre-launch characterization of Hyperion measured low signal to noise (SNR<40:1) for the geologically significant shortwave infrared (SWIR) wavelength region (2000-2500 nm). The impact of this low SNR on Hyperion's capacity to resolve spectral detail was evaluated for the Mount Fitton test site in South Australia, which comprises a diverse range of minerals with narrow, diagnostic absorption bands in the SWIR. Following radiative transfer correction of the Hyperion radiance at sensor data to surface radiance (apparent reflectance), diagnostic spectral signatures were clearly apparent, including: green vegetation; talc; dolomite; chlorite; white mica and possibly tremolite. Even though the derived surface composition maps generated from these image endmembers were noisy (both random and column), they were nonetheless spatially coherent and correlated well with the known geology. In addition, the Hyperion data were used to measure and map spectral shifts of <10 nm in the SWIR related to white mica chemical variations.

EO-1 Advanced Land Imager overview and spatial performance

Abstract: The Advanced Land Imager (ALI) is the primary instrument flown on the first Earth Observing mission (EO-1), which was developed under NASA's New Millennium Program (NMP). The ALI contains a number of innovative features. These include the basic instrument architecture which employs a push-broom data collection mode, a wide field of view optical design, compact multi-spectral detector arrays, non-cryogenic HgCdTe for the short wave infrared bands, silicon carbide optics, and a multi-level solar calibration technique. The sensor includes detector arrays that operate in ten bands, one panchromatic, six VNIR and three SWIR, spanning the range from 0.433 to 2.35 /spl mu/m. This paper describes the instrument design, provides an overview of the ground testing and calibration of the instrument and a summary of the sensor performance in space. In particular, the spatial imaging performance of ALI is discussed. Sample images are shown that demonstrate the improved capability of the sensor in terms of Pan band resolution and signal-to-noise ratio in all bands. On-orbit images have been analyzed and the results are compared with pre-launch calibrations. The instrument performance appears to meet all expectations.

ASTER geometric performance

Abstract: The ASTER system is flying on the Terra spacecraft since December 18, 1999. After the instrument check, multispectral images ranging from visible to thermal infrared have been provided using three subsystems, i.e., VNIR, SWIR and TIR. To deliver data products with high quality from the viewpoint of the geolocation and band-to-band registration performance, the fundamental program called the Level-1 processing has been developed. On December 1, 2000, the official data products (Version 1.0) were released, where the band-to-band registration accuracy in the subsystem was better than 0.3 pixels and that between subsystems was better than 0.5 pixels. On May 1, 2001, the validated data products have been released by improving the geometric performance, where the band-to-band registration in the subsystem is better than 0.1 pixels and that between subsystems is better than 0.2 pixels. In this paper, the characteristics of the images and the effect of geometric parameters on the image quality of the ASTER system, which consists of four telescopes and a cross-track pointing function, are analyzed by image matching method based on a cross-correlation function.

Comparison of surface reflectance measurements from three ASD FieldSpec FR spectroradiometers and one ASD FieldSpec VNIR spectroradiometer

Abstract: The Remote Sensing Group (RSG) of the Optical Sciences Center at the University of Arizona uses reflectance-based vicarious calibration techniques that rely on groundbased test sites to calibrate a variety of sensors. This method requires accurate surface reflectance of the test site to be measured at the same time as sensor overflight. Atmospheric measurements are also made to characterize scattering by aerosols and molecules. The results of these ground-based measurements are put into a radiative transfer code to predict the at sensor radiance. The result is compared to the output from the sensor to give the radiometric calibration. To measure the surface reflectance properties of various ground-based test sites, the RSG makes use of Analytical Spectral Devices (ASD) FieldSpec spectroradiometers that cover the 350-2500nm range. The accuracy and repeatability of these instruments are critical to the success of this method because errors in the vicarious calibrations are proportional to errors in the retrieved reflectance. Three different full range (FR) Analytical Spectral Devices and one visible and near infrared (VNIR) Analytical Spectral Device are compared in tests that include those done under well-controlled environmental conditions.

Aggregation of Hyperion hyperspectral spectral bands into Landsat-&ETM+ spectral bands

Abstract: The Landsat 7 ETM+ spectral bands centered at 479 nm, 561 nm, 661 nm and 834 mn (Bands 1, 2, 3, and 4) fall nicely across the Hyperion VNIR hyperspectral response region. They have bandwidths of 67 nm, 78 nm, 60 nm and 120 nm, respectively. The Hyperion spectral bandwidth of 10.2 nm results in 10 to 15 Hyperion spectral samples across each Landsat band in the VNIR. When the Hyperion spectral responses in the 10.2 nm bands are properly weighted to aggregate to a given Landsat band, the radiometric response of the Landsat band can be reproduced by Hyperion. This is done for Bands 2, 3 and 4 on the scene 7 of Lake Frome, Australia collected simultaneously by Hyperion and Landsat on January 21, 2001. The initial comparison of the radiances from Hyperion synthesized into the ETM+ bands with the Landsat-7 ETM+ radiances showed differences of 15-23%, with ETM+ being higher. Prior to launch a laboratory standard comparison showed differences of 10-13% in the same direction.

The impact of viewing geometry on material discriminability in hyperspectral images

Abstract: An increase in the off-nadir viewing angle for an airborne visible/near-infrared through short-wave infrared (VNIR/SWIR) imaging spectrometer leads to a decrease in upward atmospheric transmittance and an increase in line-of-sight scattered path radiance. These effects combine to reduce the spectral contrast between different materials in the sensed signal. The authors analyze the impact of viewing angle on material discriminability for 237 materials over a wide range of conditions. Material discriminability is quantified using a statistical algorithm that employs a subspace model to represent the set of spectra for a material as conditions vary. The authors show that reliable material discrimination is possible over a range of conditions even for large off-nadir viewing angles. They illustrate the performance of material identification over different viewing angles using simulated forest and desert hyperspectral digital imagery collection experiment (HYDICE) images.

Spectral indices for lithologic mapping with ASTER thermal infrared data applying to a part of Beishan Mountains, Gansu, China

Abstract: The ASTER sensor aboard the Terra platform has a capability of spectral measurement not only in visible and near infrared (VNIR) and shortwave infrared (SWIR) regions but also in thermal infrared (TIR) region with a spatial resolution adequate for geological applications. This paper proposes several spectral indices for rock type mapping using ASTER TIR data and applies them to a part of the Beishan Mountains in China. The result indicates that the indices are very useful in lithologic mapping.

The impact of viewing geometry on vision through the atmosphere

Abstract: An increase in the off-nadir viewing angle for an airborne visible/near-infrared through short-wave infrared (VNIR/SWIR) imaging spectrometer leads to a decrease in upward atmospheric transmittance and an increase in line-of-sight scattered path radiance. These effects combine to reduce the spectral contrast between different materials in the sensed signal. We analyze the impact of viewing angle on material discriminability for 237 materials over a wide range of conditions. Material discriminability is quantified using a statistical algorithm that employs a subspace model to represent the set of spectra for a material as conditions vary. We show that reliable material discrimination is possible over a range of conditions even for large off-nadir viewing angles. We illustrate the performance of material identification over different viewing angles using simulated forest hyperspectral images.

Analysis of Hot Springs in Yellowstone National Park Using ASTER and AVIRIS Remote Sensing

Abstract: Data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Airborne Visible/IR Image Spectrometer (AVIRIS) were used to characterize hot spring deposits in the Lower, Midway, and Upper Geyser Basins of Yellowstone National Park from the visible/near infrared (VNIR) to thermal infrared (TIR) wavelengths. Field observations of these basins provided the critical ground truth for comparison to the remote sensing results. Fourteen study sites were selected based on diversity in size, deposit type, and thermal activity. Field work included detailed site surveys such as land cover analysis, photography, Global Positioning System (GPS) data collection, radiometric analysis, and VNIR spectroscopy. Samples of hot spring deposits, geyser deposits, and soil were also collected. Analysis of ASTER provided broad scale characteristics of the hot springs and their deposits, including the identification of thermal anomalies. AVIRIS high spectral resolution short-wave infrared (SWIR) spectroscopy provided the ability to detect hydrothermally altered minerals as well as a calibration for the multispectral SWIR ASTER data. From the image analysis, differences in these basins were identified including the extent of thermal alteration, the location and abundance of alteration minerals, and a comparison of active, near-extinct, and extinct geysers. The activity level of each region was determined using a combination of the VNIR-SWIR-TIR spectral differences as well as the presence of elevated temperatures, detected by the TIR subsystem of ASTER. The results of this study can be applied to the exploration of extinct mineralized hydrothermal deposits on both Earth and Mars.

Detectability of buried mines in 3- to 5-μm and 8-to 12-μm regions for various soils using hyperspectral signatures

Abstract: This is a follow-up work to analyze completely the detectability of the buried mines for the spectral regions extending from Visible/Near IR (VNIR) to Longwave IR (LWIR). Similar to previous work focusing on the VNIR region (1) this paper presents the quantitative detectability of the buried mines in the 3-5)mum and 8-12)mum regions. Specifically, this paper presents a statistical analysis for the buried mines in specified spectral regions for various soils and burial durations. As shown in the previous work (1) the performance based on the single hypothesis test using the distance measure was better than the intensity thresholding method. This paper focuses on only the distance measure method for statistical analysis of the data, and subsequently, classification to quantify the detectability of the buried mines in the 3 to 5 and 8 to 12 micron regions.

Analysis of data from a thermal infrared hyperspectral instrument

Abstract: While reflection band hyperspectral instruments have been in use for over a decade, only recently has data from airborne thermal IR hyperspectral instruments become available. One such instrument is the Airborne Hyperspectral Imager (AHI). AHI is a pushbroom sensor developed by the University of Hawaii that spans the 8 to 11.5 micrometer spectral band with 32 spectral bands and 256 simultaneous spatial channels. While many analysis techniques used for reflection band hyperspectral processing can be applied to the thermal band, new procedures had to be developed. In particular, sensor noise and sensor non-linearity induced spectral artifacts are a greater problem than for the VNIR and SWIR. The process begins with calibration, with different calibration files being used to optimize the reduction of sensor artifacts such as shading and striping. Once the data has been calibrated to radiance units, the absorption and path radiance effects of the atmosphere can be removed, if atmospheric truth is available. Following this step, the apparent emissivity is calculated for every pixel in each band. The data is now in a form that is analogous to the apparent reflectance images developed for reflection band data. At this point spectral analysis techniques can be applied to classify the image. The procedure used here was to use an automated endmember determination algorithm, N- FINDR, to determine spectral endmembers and unmix the data cube into fractional abundances. Since some endmembers are likely to result from residual sensor and cultural artifacts, the automated endmember determination and unmixing procedure is performed interactively to optimize results. Both the fractional abundance planes and the endmember spectra themselves are then reviewed for artifacts. Selected abundance planes that correspond to real minerals can then be combined into a classification map. In this paper, AHI data collected for two applications: the detection of buried land mine application and a geological remote sensing application will be presented using similar processing steps.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Visible imaging spectrometer and infrared radiometer (VISIR) for coastal zones and land applications

Abstract: 12 The VISIR instrument has been designed as a lightweight facility to be embarked on future low Earth orbit operational satellites whose mission requirements include monitoring of open oceans, coastal zones and land surface areas. The instrument consists of an imaging spectrometer working in the visible range, dual-band thermal infrared radiometer and a single-band imager in the short-wave infrared. The instrument provides two operational modes, namely the global mode (ground pixel 1200 m, swath 1200 km) and the regional mode (ground pixel 300 m, swath 100 km) with steering capability. The high radiometric performances achieved in both operational modes show the capability to detect very small radiometric changes such as those induced by typical variations of the water quality parameters (chlorophyll, suspended sediments, yellow substance) and surface temperature anomalies. VISIR can achieve many of the MERIS and ATSR/AVHRR performance characteristics within a considerable smaller envelope that can lead to a more affordable instrument. The performances are achieved thanks to a newly designed high-performance (f/2.0 optical spectrometer based on a double-Schmidt configuration, the use of hybrid CMOS detectors for the VNIR and uncooled microbolometers for the TIR, and a hybrid whiskbroom scanning technique. This solution is an excellent compromise as regards the cost/benefit ratio, achieving many of the performances required for a coastal zone earth watching mission, with considerable simplifications with respect to equivalent existing instruments that can lead to much more affordable budgets in terms of mass, power and cost. The spectrometer has the potential to match other type of applications in different spectral bands and/or with different spatial and spectral resolution.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Remote sensing in multi-angle and airborne imaging system

Abstract: From the concept of multi angle remote sensing, the method of designing an airborne multi angle TIR/VNIR imaging system (AMTIS) was introduced The design was validated by flight experiments Some useful high quality multi angle and multi spectra image data were obtained

Examples of atmospheric characterization using hyperspectral data in the VNIR, SWIR and MWIR

Abstract: A conventional approach to HSI processing and exploitation has been to first perform atmospheric compensation so that surface features can be properly characterized. In this paper, the application of visible and IR spectral information to atmospheric characterization is discussed and illustrated with hyperspectral data in the VNIR, SWIR and MWIR data. AVIRIS and ARES data are utilized. The Airborne Visible-InfraRed Imaging Spectrometer (AVIRIS) sensor contains 224 bands, each with a spectral bandwidth of approximately 10 nm, allowing it to cover the entire range between 4 and 2.5 mm. For a NASA ER-2 flight altitude of 20 km, each pixel is 20 m in size, yielding a ground swath width of approximately 10 km. The Airborne Remote Earth Sensing (ARES) sensor was flown on a NASA WB-57 aircraft operated from approximately 15 km altitude. Spectral radiance data from 2.0 to 6.0 micrometers in 75 contiguous bands were collected. Pixel resolution is approximately 17 by 4.5 m2 with a swath width of 800 m. Examples of data applications include atmospheric water vapor retrieval, aerosol characterization, delineation of natural and manmade clouds/plumes, and cloud depiction. It is illustrated that though each application may only require a few spectral bands, the ultimate strength of HSI exploitation lies in the simultaneous and adaptive retrievals of atmospheric and surface features. Inter-relationships among different bands are also demonstrated and these are the physical basis for the optimal exploitation of spectral information.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Discussion on the requirements of VNIR hyperspectral data for agricultural applications according to PHI data and CSAM model

Abstract: According to the application of PHI data to agricultural information extraction both in Changzhou, China and Nagano. Japan. we found that the results closely depend on the hyperspectral remote sensing data quality. As the spectral features of vegetation are particular with high shape similarity but with high intensity variation, the quality requirements are special. The general factors of pixel size, band combination and noise limit for different information objects are discussed in this paper. According to the two models of CSAM and IARS, with rice as example, it shows that a pixel size of 1.2 meter is suitable in the areas such as Changzhou and Nagano. The top-priority range of VNIR should be the red edge of 670-780 nm and fine-division is necessary with a suggestion of about 40 bands with 3 nm resolution. While in belts of 400-670 and 780-900 nm. wider and less bands are acceptable. According to the application of IARS and the linear property of rice spectra. it was suggested that S/N in order of /spl times/10 is enough for plant recognition. but for species classification for a certain plant, it should be square with all order up to /spl times/10/sup 2/-/spl times/ 10/sup 3/.

VISIR- visible imaging spectrometer and infra-red radiometer for coastal zones and land applications

Abstract: The VISIR instrument has been designed as a lightweight facility to be embarked on future low Earth orbit operational satellites whose mission requirements include monitoring of open oceans, coastal zones and land surfaceareas. The instrument consists of an imaging spectrometer working in the visible range, a dual-band thermal infrared radiometer and a single-band imager in the short-wave infrared. The instrument provides two operational modes, namely the "global mode" (ground pixel 1200 m, swath 1200 km) and the "regional mode" (ground pixel 300 m, swath 100 km) with steering capability. The high radiometric performances achieved in both operational modes show the capability to detect very small radiometric changes such as those induced by typical variations of the water quality parameters (chlorophyll, suspended sediments, yellow substance) and surface temperature anomalies. VISIR can achieve many of the MERIS and ATSR/AVHRR performance characteristics within a considerable smaller envelope that can lead to a more affordable instrument. The performances are achieved thanks to a newly designed high-performance (f/2.0) optical spectrometer based on a double-Schmidt configuration, the use of hybrid CMOS detectors for the VNIR and uncooled microbolometers for the TIR, and a hybrid whiskbroom scanning technique. This solution is an excellent compromise as regards the cost/benefit ratio, achieving many of the performances required for a coastal zone earth watching mission, with considerable simplifications with respect to equivalent existing instruments that can lead to much more affordable budgets in terms of mass, power and cost. The spectrometer has the potential to match other type of applications in different spectral bands and/or with different spatial and spectral resolution.

ASTER observations of the spectral emissivity for arid lands

Abstract: On May 9, 2000 the Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) on the Terra satellite obtained data over the Jornada Experimental Range test site along the Rio Grande river and the White Sand National Monument in New Mexico. ASTER has 14 channels from the visible and near-infrared (VNIR) through the thermal infrared (TIR) with 15 m resolution in the VNIR and 90 m in the TIR. The overpass time is approximately 11 a.m. With 5 channels between 8 and 12 /spl mu/m these multispectral TIR data from ASTER provide the opportunity to separate the temperature and emissivity effects observed in the thermal emission from the land surface. Ground measurements during these overflights included surface temperature, vegetation type and condition and limited surface emissivity measurements. There was also an aircraft flight with the MODIS/ASTER simulator on June 14, 2000, unfortunately not coincident with a satellite overpass. Preliminary results indicate good agreement between ASTER brightness temperatures and ground measures. Analysis of earlier aircraft data has shown that the multispectral TIR data are very effective for estimating both the surface temperature and emissivity. These results will be compared with those obtained from the ASTER data for this site. With multispectral, thermal infrared observations provided by ASTER it is possible for the first time to estimate the spectral emissivity. variation for these surfaces on a global basis at high spatial resolution.

Registration and BRDF extraction of airborne multi-angular images in different resolutions

Abstract: An auto-registration algorithm is designed for multi-angular remote sensing, which refines the image warping function in a step-by-step way. It first uses a wavelet transform to degrade the original images to a series of low resolution ones, then constructs warping function with B-splines, and refines the B-splines according to control points found by a correlation based method. The algorithm is tested with images acquired in North-China by an airborne multi-angular TIR/VNIR imaging system. Results show the advantage of B-splines in comparison with polynomial or thin-plate splines. After registration is done, we give an example for BRDF extraction.

Modeling and structural parameters inversion of crop for multiangular remote sensing observations

Abstract: Recently, more and more multiangular sensors have been launched into the space. These multiangular remote sensing observations can provide more directional information of land surface objectives than only nadir observation. To well model the directional observations in visible and near infrared (VNIR) band, bi-directional reflectance distribution function (BRDF) is much useful according to its characteristic. In this paper, we developed a geometric-optical and gap probability model to model the BRDF observations of crop while crop in the beginning of its life. This model validated by the field data of summer corn taking in 2000 in Luancheng, Hebei Province. The results show: this model can simulate the BRDF well, and it is simple to use for the horizontal homogeneous crop considering the change of leaf area index (LAI), leaf angle distribution (LAD) etc. The ultimate aim of the quantitative remote sensing is inversion. Although multiangular remote sensing observations can provide more directional information, the inversion is still difficult due to noise, ill-posed problems, etc. In this paper, we use the multi-stage, sample-direction dependent, target-decisions (MSDT) inversion strategy and above model to inverse, study how to use the prior knowledge, improve sign-noise ratio in inversion and how to divide the datasets and parameters during inversion process. The model and the methods we studied in this paper maybe an initial trial and need further study.