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SMEX02 ASTER Level 1B Data, Iowa

Summary

This data set is part of the Soil Moisture Experiment 2002 (SMEX02). Investigators acquired a series of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images from the Terra satellite. Three ASTER scenes were mosaicked and the regional study area extracted to form one image for each of ASTER's 14 spectral channels. These data represent a single snapshot; the satellite overpass time was 17:20 GMT on 1 July 2002. The study area is the Walnut Creek Watershed area in Iowa, USA, covering 41.70 to 42.73°N and 93.16 to 93.84°W.

These ASTER Level 1B data include three Visible and Near-infrared (VNIR) bands with 15 m spatial resolution, six Shortwave Infrared (SWIR) bands with 30 m spatial resolution, and five Thermal Infrared (TIR) bands with 90 m spatial resolution. The data are L1B (radiance) data with geometric and radiometric correction.

The data are in unsigned integer binary files in terms of scaled radiance, one file for each band. Data are available via FTP.

These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.

Citing These Data

Jackson, T. and M. Cosh. 2003. SMEX02 ASTER Level 1B Data, Iowa. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format Unsigned integer binary files with no header information. Data are scaled radiances (digital numbers (DN)).
Spatial coverage and resolution 42°N, 93°W. VNIR resolution of 15 m, SWIR resolution of 30 m, and TIR resolution of 90 m.
Temporal coverage and resolution 1 July 2002.
Tools for accessing data Open these files in an appropriate image processing or image viewing application.
File naming convention Example file name: ASTER_mmddyyyy_bxx(x).bil
mm = month, dd = day, yyyy = year, xx(x) = band number.
File size SWIR files are 13.5 MB, TIR files are 1.5 MB, and VNIR files are 54.1 MB.
Parameter(s) TIR, SWIR, and VNIR radiance imagery.
Procedures for obtaining data Data are available via FTP.

Table of Contents

1. Contacts and Acknowledgments
2. Detailed Data Description
3. Data Access and Tools
4. Data Acquisition and Processing
5. References and Related Publications
6. Document Information

1. Contacts and Acknowledgments

Investigator(s) Name and Title

Thomas J. Jackson, Hydrologist, Michael H. Cosh, General Physical Scientist, and Lynn McKee, Soil Scientist, USDA ARS Hydrology Lab.

Technical Contact

NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449  USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org

2. Detailed Data Description

Format

The data are in unsigned integer binary files in terms of scaled radiance, one file for each band, in PC byte order (little endian). There is no header information included in these files.
VNIR files (bands 1-3) are 3702 columns by 7662 rows.
SWIR files (bands 4-9) are 1852 columns by 3832 rows.
TIR files (bands 10-14) are 618 columns by 1278 rows.

The digit number (DN) was converted to radiance (W/(m2*sr*μm) using the following equation:

Radiance=(DNvalue-1)x unit conversion coefficients.

File Naming Convention

File names use the following conventions:
ASTER_mmddyyyy_bxx(x).bil
where: mm = month, dd = day, yyyy = year, xx(x) = band number. For example, in the file "ASTER_07012002_b7.bil," data were collected on 1 July 2002 by the SWIR band 7.

File Sizes

SWIR files are 13.5 MB, TIR files are 1.5 MB, and VNIR files are 54.1 MB.

Spatial Coverage

Southernmost Latitude: 41.70°N
Northernmost Latitude: 42.73°N
Westernmost Longitude: 93.84°W
Easternmost Longitude: 93.16°W

The following table shows the Universal Transverse Mercator (UTM) geographic locations of the various sensor data. (UTM coordinates are in meters.)

Sensor VNIR SWIR TIR
Easting Northing Easting Northing Easting Northing
Upper Left 431093 E4731101 N 431077 E4731113 N 431076 E4731102 N
Upper Right486608 E4731101 N486607 E4731113 N486606 E4731102 N
Lower Left 431093 E4616186 N431077 E4616183 N431076 E4616173 N
Lower Right486608 E4616186 N486607 E4616183 N486606 E4616173 N

Spatial Resolution

VNIR has 15 m resolution, SWIR has 30 m resolution, and TIR has 90 m resolution.

Projection

Universal Transverse Mercator (UTM) Zone 15

Temporal Coverage and Resolution

Data were collected on 1 July 2002 by the ASTER instrument.

Parameter or Variable

Parameter Description

The parameters are VNIR, SWIR, and TIR radiance imagery. Three ASTER scenes were mosaicked and the regional study area extracted to form one image for each of ASTER's 14 spectral channels.

Sample Data Record

The following sample shows a portion of the data file "ASTER_07012002_b7.bil."

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

Total volume is 251 MB.

Software and Tools

Open these files in an appropriate image processing or image viewing application.

Related Data Collections

See Soil Moisture Experiment (SMEX) for more information.

4. Data Acquisition and Processing

Sensor or Instrument Description

ASTER is an advanced optical sensor of 14 spectral channels ranging from the visible to thermal infrared region.

The high-resolution VNIR radiometer observes solar radiation reflected from Earth's surface in three visible and near-infrared bands (1-3). The spectral region is 0.52-0.86 μm. VNIR has a pointing capability of +/-24° from nadir in the cross-track direction. The radiometer is calibrated in orbit using halogen lamps.

SWIR is a high-resolution, multispectral radiometer that detects reflected solar radiation from Earth's surface in the wavelength region of 1.6 - 2.43 μm (bands 4-9). SWIR can also change the boresight in the cross-track direction by +/-8.55° from nadir using a pointing mechanism.

TIR is an advanced radiometer with five spectral bands (10-14) in the thermal infrared (8-12 μm).

For more information, please see the ASTER User Guide.

The band spectral range and conversion coefficients are listed in the following table.

Sensor Band Number Spectral Range (μm) Unit Conversion Coefficient
(W/(m2*sr*μm)/DN)
VNIR 1 0.52-0.60 0.676
2 0.63-0.69 0.708
3N 0.78-0.86 0.862
SWIR 4 1.60-1.70 0.2174
5 2.145-2.185 0.0696
6 2.185-2.225 0.0625
7 2.235-2.285 0.0597
8 2.295-2.365 0.0417
9 2.360-2.430 0.0318
TIR10 8.125-8.475 0.006822
11 8.475-8.825 0.006780
12 8.925-9.275 0.006590
13 10.25-10.95 0.005693
14 10.95-11.65 0.005225

5. References and Related Publications

ASTER User Guide

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
GMT Greenwich Mean Time
NDWI Normalized Difference Water Index
SMEX Soil Moisture Experiment
SWIR Short-Wave Infrared
TIR Thermal Infrared
UTM Universal Transverse Mercator
VNIR Visible Near Infrared

Document Creation Date

November 2003

Document URL

http://nsidc.org/data/docs/daac/nsidc0197_smex_aster.gd.html