Sample image of L2 Surface Radiance VNIR.
Sample image for L2 Surface Radiance 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 for more details.
The ASTER On-Demand L2 Surface Radiance 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 hdf 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. VNIR is always the bigger of the two.
VNIR & SWIR Descriptions
The ASTER On-Demand L2 Surface Radiance (VNIR) is a higher-level product that contains atmospherically corrected visible and near-infrared data. It is generated using the 3 VNIR bands (between 0.52 and 0.86 µm) from an ASTER Level-1B image.
The ASTER On-Demand L2 Surface Radiance (SWIR Crosstalk-Uncorrected) is a higher-level product that contains atmospherically corrected shortwave infra-red data. It is generated using the 6 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.
VNIR
Area | ~60 km x 60 km |
Image Dimensions | 4200 rows x 4980 columns |
File Size | 180 MB |
Spatial Resolution | 15 m |
Projection | Universal Transverse Mercator (UTM) |
Data Format | HDF-EOS or GeoTIFF |
Vgroup Data Fields | 3 |
SWIR
Area | ~60 km x 60 km |
Image Dimensions | 2100 rows x 2490 columns |
File Size | ~75 MB |
Spatial Resolution | 30 m |
Projection | Universal Transverse Mercator (UTM) |
Data Format | HDF-EOS or GeoTIFF |
Vgroup Data Fields | 6 |
VNIR (15 Meters)
Vgroup Data Fields/ Spectral Range (µm) |
Units | Data Type | Valid Range | Band Scale Factor |
Band 1 (0.52–0.60) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.676000 |
Band 2 (0.63–0.69) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.708000 |
Band 3N (0.78–0.86) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.862000 |
SWIR (30 Meters)
Vgroup Data Fields/ Spectral Range (µm) |
Units | Data Type | Valid Range | Band Scale Factor |
Band 4 (1.600–1.700) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.217400 |
Band 5 (2.145–2.185) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.069600 |
Band 6 (2.185–2.225) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.062500 |
Band 7 (2.235–2.285) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.059700 |
Band 8 (2.295–2.365) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.041780 |
Band 9 (2.360–2.430) | w/m2/sr/µm | 16-bit signed integer | 0–32767 | 0.031800 |
There are 3 groups of ancillary data inputs used in the atmospheric correction of ASTER radiance and reflectance:
Please find the current ASTER-related Pricing, Payment, and Redistribution policies on the ASTER Policies Section of this Web Site.
LP DAAC Acknowledgement and Citations Policy
In the event that data distributed from the Land Processes DAAC are incorporated into your research, please supply the following acknowledgment within your published work: "These data are distributed by the Land Processes Distributed Active Archive Center (LP DAAC), located at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center (lpdaac.usgs.gov)." If possible, please e-mail or send us reprints/citations of papers or oral presentations based on data obtained from the LP DAAC (see below for mailing address and e-mail address). This will help us to stay informed of how the data are being utilized.
LP DAAC User Services
U.S. Geological Survey (USGS)
Earth Resources Observation and Science (EROS) Center
47914 252nd Street
Sioux Falls, SD 57198-0001
The full archive record for this data product is available through the WIST and GloVis search and order interfaces.
Please find a link to (and information about) these data access tools on the Get Data Section of this Web Site.
U.S. Geological Survey (USGS)
Center for Earth Resources Observation and Science (EROS)
47914 252nd Street
Sioux Falls, SD 57198-0001
Phone Number: | 605-594-6116 |
Toll Free: | 866-573-3222 |
866-LPE-DAAC | |
Fax: | 605-594-6963 |
Email: | lpdaac@eos.nasa.gov |
Web: | http://lpdaac.usgs.gov |