AST_07XT_003

ASTER L2 Surface Reflectance VNIR and Crosstalk Corrected SWIR V003

Version 003 eng
  • Abstract
    The ASTER L2 Surface Reflectance is a multi-file product that contains atmospherically corrected data for both the Visible Near-Infrared (VNIR) and Shortwave Infrared (SWIR) sensors. Each product delivery includes two data files in Hierarchical Data Format (HDF), one for VNIR, one for SWIR. Users are advised that ASTER SWIR data acquired from late April 2008 to the present exhibit anomalous saturation of values and anomalous striping. This effect is also present for some prior acquisiton periods. Please refer to the ASTER SWIR User Advisory Document (https://lpdaac.usgs.gov/sites/default/files/public/aster/docs/ASTER_SWIR_User_Advisory_July%2018_08.pdf) for more details. VNIR & SWIR Descriptions The ASTER L2 Surface Reflectance (VNIR) is a higher-level product that contains atmospherically corrected visible and near-infrared data. It is generated using the three VNIR bands (between 0.52 and 0.86 µm) from an ASTER Level-1B image. The ASTER L2 Surface Reflectance (SWIR Crosstalk-Corrected) is a higher-level product that contains atmospherically corrected shortwave infra-red data. It is generated using the six SWIR bands (between 1.60 and 2.43 µm) from an ASTER Level-1B image. Atmospheric correction involves deriving a relationship between the surface radiance/reflectance and the top of the atmosphere radiance from information on the scattering and absorbing characteristics of the atmosphere. Once this relationship is established, it is used to convert ASTER VNIR's original radiance values to atmospherically corrected surface radiance and reflectance values. The atmospheric correction algorithm for VNIR is based on a Look-Up Table (LUT) approach that uses results from a Gauss-Seidel iteration of the Radiative Transfer Code (RTC). This methodology is derived from the reflectance-based, vicarious calibration approach of the Remote Sensing Group at the University of Arizona. The algorithm is based on the relationship between the angular distribution of radiance, scattering and absorption in the atmosphere, and the surface properties. The RTC used to generate the LUT for the atmospheric correction is based on the following parameters: solar zenith angle, satellite view angle, relative azimuth angle between the satellite and sun, molecular scattering optical depth, aerosol scattering optical depth, aerosol scatter albedo, aerosol size distribution parameter, and surface reflectance. The size distributions for aerosol are based on either a Junge size distribution or on the set of aerosol types used in the atmospheric correction of Multi-angle Imaging Spectroradiometer (MISR) data. The initial versions of the algorithm rely on external climatological sources for information on atmospheric absorption and scattering parameters. Eventually, this information is likely to come from other Terra sensors like MISR and the Moderate-Resolution Imaging Spectroradiometer (MODIS). A digital elevation model provides the slope and elevation information for accurate modeling of surface reflectance. SWIR Crosstalk Correction The ASTER SWIR sensor is affected by a crosstalk signal scattering problem, a phenomenon discovered after the launch of ASTER aboard the Terra platform in December 1999. The SWIR detector contains 2048 Pt-Si (platinum-silicide) arrays for each of its six spectral bands. There are six pairs of staggered linear CCD arrays for each band that are spaced 1.33 µm apart in the band order 7, 8, 9, 4, 5, and 6. In front of each CCD array pair, there are interference filters that spectrally separate the radiation reflected from the Earth.The source of the crosstalk problem is the ASTER Band 4 detector, whose incident light is reflected by the detectors aluminum-coated parts (especially from the area between the detector plane and band-pass filter), and is then projected on to the other detectors. The problem is further worsened by the band-to-band parallax effect and the distance between the CCD array pairs. Bands 9 and 5 are most affected because of their closeness to the Band 4 detectors. The spectral range of Band 4 is between 1.6 and 1.7 microns (0.092 µm bandwidth), which is not only the widest bandwidth of the SWIR bands (average of 0.052 µm bandwidth for Bands 5 through 9), but is also the strongest in its reflectivity component. Therefore, Band-4s incident radiation is about 4 to 5 times stronger than that of the other bands. All the light hitting the detectors is not absorbed. Some of the light that strikes between the detectors is reflected, and some of the reflected light is re-reflected by the interference filters. Evidence of crosstalk along with the photon spread and ghosting effects is visible in images with strong contrast, especially coastlines and islands.Crosstalk Correction AlgorithmThe Japanese Science team developed the original crosstalk correction algorithm that is used to correct an ASTER Level-1B data set. The original model is based on the fundamental understanding that incident radiation to Band 4 that is reflected or leaked to the other bands will follow a certain pattern of line-shifts in the along-track direction. The kernel function used in the convolution (in the original algorithm) is not considered symmetrical in the cross-track direction. Improved kernel functions are used in the updated algorithm. The radiometric sensitivity coefficients are statistically derived to ensure that a calibration consistency is maintained in both pre- and post-crosstalk correction. Using the Japanese crosstalk correction algorithm, the ASTER Project at JPL has implemented a crosstalk-correction process that is applied to ASTER Level-1B data before deriving the reflectance product.Additional information on the SWIR crosstalk phenomenon is available in the following papers:Iwasaki, A., Fujisada, H., Akao, H. Shindou, O., and Akagi, S., 2002, Enhancement of Spectral Separation Performance for ASTER/SWIR, SPIE Proceedings, v. 4486, p. 42-50.Tonooka, H., and Iwasaki, A., 2003, Improvement of ASTER/SWIR Crosstalk Correction, SPIE Proceedings, v. 5234, p. 168-179.Iwasaki, A., and Tonooka, H., 2005, Validation of a crosstalk correction algorithm for ASTER/SWIR, IEEE Transactions on Geoscience and Remote Sensing, v. 43, Dec. 2005, p. 2747- 2751. V003 data set release date: 2006-10-13 VNIR Data Set Characteristics: Area: ~60km x 60km Image Dimensions: 4200 rows x 4980 columns File Size: ~180 Megabytes Spatial Resolution: 15m Units: None Projection: Universal Transverse Mercator (UTM) Data Format: HDF-EOS or GeoTIFF Data Fields: 3SWIR Data Set Characteristics: Area: ~60km x 60km Image Dimensions: 2100 rows x 2490 columns Spatial Resolution: 30mFile Size: ~75 Megabytes Units: None Projection: Universal Transverse Mercator (UTM) Data Format: HDF-EOS or GeoTIFF Data Fields: 5
  • Version Description
    Not provided
  • DOI

    10.5067/ASTER/AST_07XT.003

    http://dx.doi.org

Data Identification Fields:

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    Processing Level

    2

    ASTER On-Demand L2 Surface Reflectance VNIR and SWIR Crosstalk-Corrected

    Quality
    Users are advised that ASTER SWIR data acquired from late April 2008 to the present exhibit anomalous saturation of values and anomalous striping. This effect is also present for some prior acquisition periods. Please refer to the ASTER SWIR User Advisory Document (https://lpdaac.usgs.gov/sites/default/files/public/aster/docs/ASTER_SWIR_User_Advisory_July%2018_08.pdf) for more details.
    Collection Progress

    In Work

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    See https://lpdaac.usgs.gov/dataset_discovery/aster/aster_policies for redistribution and citation policies.
    Access Constraints

    See https://lpdaac.usgs.gov/dataset_discovery/aster/aster_policies for data access information.

    Publication References
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Related URLs
  • Collection URL

    The Land Processes Distributed Active Archive Center (LP DAAC) is one of several discipline-specific data centers within the NASA Earth Observing System Data and Information System (EOSDIS). The LP DAAC Web page provides information about available data products, services, documentation, order interfaces, and tools.


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    Science Keywords
    • EARTH SCIENCE
    • LAND SURFACE
    • SURFACE RADIATIVE PROPERTIES
    • ALBEDO
    • EARTH SCIENCE
    • LAND SURFACE
    • SURFACE RADIATIVE PROPERTIES
    • REFLECTANCE
Other Descriptive Keywords
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Ancillary Keywords
  • LP DAAC
  • EOSDIS
  • USGS/EROS
  • ESIP
  • USGS
  • LPDAAC
ISO Topic Categories
  • climatologyMeteorologyAtmosphere
  • geoscientificInformation
Additional Attributes
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    INT
    ID of the Data Acquisition Request
    Resolution Range Begin Range End Unit of Measure Accuracy

  • GenerationDateandTime
    DATETIME_STRING
    Date and Time granule produced
    Resolution Range Begin Range End Unit of Measure Accuracy

  • LowerLeftQuadCloudCoverage
    INT
    The percentage of cloud coverage for the lower left quadrant
    Resolution Range Begin Range End Unit of Measure Accuracy

  • LowerRightQuadCloudCoverage
    INT
    The percentage of cloud coverage for the lower right quadrant
    Resolution Range Begin Range End Unit of Measure Accuracy

  • SceneCloudCoverage
    INT
    Percentage of cloud coverage for the whole scene
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Solar_Azimuth_Angle
    FLOAT
    Angle of the sun clockwise from true North
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Solar_Elevation_Angle
    FLOAT
    Angle of the sun above the horizon
    Resolution Range Begin Range End Unit of Measure Accuracy

  • UpperLeftQuadCloudCoverage
    INT
    The percentage of cloud coverage for the upper left quadrant
    Resolution Range Begin Range End Unit of Measure Accuracy

  • UpperRightQuadCloudCoverage
    INT
    The percentage of cloud coverage for the upper right quadrant
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band4_Available
    STRING
    Identifies the status of Band 4 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band5_Available
    STRING
    Identifies the status of Band 5 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band6_Available
    STRING
    Identifies the status of Band 6 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band7_Available
    STRING
    Identifies the status of Band 7 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band8_Available
    STRING
    Identifies the status of Band 8 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • Band9_Available
    STRING
    Identifies the status of Band 9 - [Yes, band is acquired] or [No, band was not acquired]
    Resolution Range Begin Range End Unit of Measure Accuracy

  • RadiometricDBVersion
    STRING
    The version number of the Radiometric Database used in Level 1 processing.
    Resolution Range Begin Range End Unit of Measure Accuracy

  • GeometricDBVersion
    STRING
    The version number of the Geometric Database used in Level 1 processing.
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERGains
    STRING
    Identifies the Gain setting for the Bands: HGH, NOR, LO1, LO2, LOW, OFF
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERGRANULEID
    STRING
    Unique identifier for the data granule held at the ASTER GDS
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERProcessingCenter
    STRING
    Name of the center where these ASTER data were processed
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERVNIRPointingAngle
    FLOAT
    Specifies the pointing angle of the ASTER Visible Near Infrared (VNIR) sensor
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERSWIRPointingAngle
    FLOAT
    Specifies the pointing angle of the ASTER Shortwave Infrared (SWIR) sensor
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERMapOrientationAngle
    FLOAT
    Denotes the angle between the path oriented image and the map oriented image for this ASTER scene.
    Resolution Range Begin Range End Unit of Measure Accuracy
    -180.0 180.0

  • ASTERReceivingCenter
    STRING
    Name of the center where these ASTER data were received
    Resolution Range Begin Range End Unit of Measure Accuracy

  • ASTERSceneOrientationAngle
    FLOAT
    Denotes the azimuth angle made by the meridian at the ASTER scene center and the along-track direction, rotating from North toward East.
    Resolution Range Begin Range End Unit of Measure Accuracy
    0.0 180.0

  • source_granule_ur
    STRING
    Granule-ur of the source granule
    Resolution Range Begin Range End Unit of Measure Accuracy

  • metadata.uuid
    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

    gov.nasa.gsfc.gcmd

  • metadata.extraction_date
    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

    gov.nasa.gsfc.gcmd

  • metadata.keyword_version
    FLOAT
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

    gov.nasa.gsfc.gcmd

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    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

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  • Discipline
    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

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    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

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  • IDN_Node.UUID
    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

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  • Original.Dataset_Citation.DOI
    STRING
    Not provided
    Resolution Range Begin Range End Unit of Measure Accuracy

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  • Original.Metadata_Version
    STRING
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    Resolution Range Begin Range End Unit of Measure Accuracy

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    STRING
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    Resolution Range Begin Range End Unit of Measure Accuracy

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  • Original.xsi:schemaLocation
    STRING
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    Resolution Range Begin Range End Unit of Measure Accuracy

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Acquisition Information Fields:

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Platforms
  • Earth Observation Satellites
    TERRA
    Instruments
    • ASTER
Projects
Project Short Name Campaigns Project Dates
EOSDIS No campaigns listed. No dates provided.
ESIP No campaigns listed. No dates provided.

Temporal Information Fields:

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Spatial Information Fields:

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Location Keywords
    • GEOGRAPHIC REGION
    • GLOBAL

Data Centers

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  • LP DAAC
    ARCHIVER
    Land Processes Distributed Active Archive Center

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  • Data Center Contact
    LP DAAC USER SERVICES

    LP DAAC

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    U.S. Geological Survey (USGS)
    Earth Resources Observation and Science (EROS) Center
    Sioux Falls, South Dakota 57198-0001

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Collection Citations Fields:

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Metadata Dates
Creation
Last Revision