AST_09 v003

ASTER L2 Surface Radiance VNIR and SWIR


PI: U.S./Japan ASTER Science Team

Description

The ASTER Surface Radiance VNIR and SWIR (AST_09) is a multi-file product that contains atmospherically corrected data for both the Visible and Near Infrared (VNIR) and Shortwave Infrared (SWIR) sensors. Each product delivery includes two Hierarchical Data Format - Earth Observing System (HDF-EOS) files: one for the VNIR, and the other for the SWIR. They are distinguished from one another by a one-second difference in the production time that appears as part of the file name. The more obvious distinguishing feature is the file size; the VNIR file is always the larger of the two. Both the VNIR and SWIR data are atmospherically corrected and are generated using the bands of the corresponding ASTER Level 1B image.

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Characteristics

Improvements/Changes from Previous Versions

The Science Scalable Scripts-based Science Processor for Missions (S4PM) Version 3.4 algorithm has additional input data options that provide better input data coverage (simultaneously acquired MODIS data versus 6-hourly modeled NCEP input data) and consequently more accurate Level 2 output data. The updated algorithm includes the following improvements:

  • A new option has been added to use MODIS Version 6.1 (MOD07_L2) Temperature, Water Vapor, and Pressure inputs. The default order option will remain as National Centers for Environmental Prediction (NCEP)/Global Data Assimilation System (GDAS).
  • The default for the Ozone input data was switched from NCEP/Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS) to the new Total Ozone Analysis using Solar Backscatter UltraViolet Version 2 (SBUV/2) and TOVS (TOAST)/Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS) option.
  • The Level 2 algorithm has been updated to provide a fall back option for the Temperature/Water Vapor/Pressure and Ozone input selections. Both selections will automatically revert to the next lower input if the selected input is not available.
    • The Temperature/Water Vapor/Pressure input will fall back from MOD07 to NCEP/GDAS then to Climatology.
    • The Ozone input will fall back from TOAST/EPTOMS to OZ_DLY/TOVS then to Climatology.
  • Users can check the OPERATIONALQUALITYFLAGEXPLANATION field in the metadata file of the output product file to see if a fall back has occurred and identify which input source was used to generate the Level 2 product files.
  • Level 2 SWIR outputs are only available for scenes acquired prior to April 2008. Scenes processed after this time contain fill values.

Collection and Granule

Collection

Characteristic Description
CollectionTerra ASTER
DOI10.5067/ASTER/AST_09.003
File Size~119 MB
Temporal ResolutionOther
Temporal Extent2000-03-06 to Present
Spatial ExtentGlobal
Coordinate SystemUniversal Transverse Mercator (UTM)
DatumWorld Geodetic System (WGS84)
File FormatHDF-EOS or GeoTIFF
Geographic Dimensions~60 km x 60 km

Granule

Characteristic Description
Number of Science Dataset (SDS) Layers9
Columns/Rows4200 (VNIR) and 2100 (SWIR) x 4980 (VNIR) and 2490 (SWIR)
Pixel Size15 m (VNIR) and 30 m (SWIR)

Layers

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
VNIR_Band1 15 meter resolution VNIR Band 1 (0.52 to 0.60 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.676000
VNIR_Band2 15 meter resolution VNIR Band 2 (0.63 to 0.69 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.708000
VNIR_Band3N 15 meter resolution VNIR Band 3 (0.78 to 0.86 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.862000
SWIR_Band4 30 meter resolution SWIR Band 4 (1.600 to 1.700 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.217400
SWIR_Band5 30 meter resolution SWIR Band 5 (2.145 to 2.185 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.069600
SWIR_Band6 30 meter resolution SWIR Band 6 (2.185 to 2.225 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.062500
SWIR_Band7 30 meter resolution SWIR Band 7 (2.235 to 2.285 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.059700
SWIR_Band8 30 meter resolution SWIR Band 8 (2.295 to 2.365 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.041780
SWIR_Band9 30 meter resolution SWIR Band 9 (2.360 to 2.430 µm) W/m²/sr/μm 16-bit signed integer N/A N/A 0 to 32767 0.031800

There are three groups of ancillary data inputs used in the atmospheric correction of ASTER Level 2 products:

  1. Ozone data input: The default for the Ozone input data is the new Total Ozone Analysis using Solar Backscatter UltraViolet Version 2 (SBUV/2) and TOVS (TOAST)/Earth Probe-Total Ozone Mapping Spectrometer (EPTOMS) option. The fall back option is the National Centers for Environmental Prediction (NCEP)/Television Infrared Observation Satellite (TIROS) Operational Vertical Sounder (TOVS). The NCEP/TOVS data are acquired from a NOAA satellite, and provides the ancillary column ozone data twice daily. The second fall back option is the Naval Research Laboratory's (NRL) Ozone Climatology dataset.
  2. Aerosol data input: The NRL Aerosol Climatology ancillary data are the only available input.
  3. Temperature, Atmospheric pressure, and Moisture Profile data inputs: Simultaneously acquired MODIS Version 6.1 (MOD07_L2) Temperature, Water Vapor, and Pressure inputs were added as a new option on October 23, 2019. The default order option will remain as the NCEP-Global Data Assimilation System (GDAS) which is available every 6 hours. The second alternative is the NRL Climatology data which are based on modeling, simulation, and prediction. They are static, monthly, averaged datasets, therefore, used only as a last resort.

Known Issues

Users are advised that ASTER SWIR data acquired from 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 for more details.

Documentation

Using the Data

E-Learning

View from NASA Terra's Zoom Lens: All About the ASTER Sensor

Tools

Citation

DOI: 10.5067/ASTER/AST_09.003

About the Image

Terra ASTER surface radiance band combination 3n-2-1 data from the AST_09 product over Canada on August 2, 2018.

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