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SMEX03 ASTER Level-1B Data: Oklahoma

Summary

As part of the Soil Moisture Experiments 2003 (SMEX03), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images for 02 July 2003 and 18 July 2003 were acquired. For each day, five ASTER Level-1B scenes were mosaicked for the Oklahoma North and Oklahoma South, USA regional study areas. The data include three Visible and Near-infrared (VNIR) bands with a spatial resolution of 15 m, six Shortwave Infrared (SWIR) bands with a spatial resolution of 30 m, and five Thermal Infrared (TIR) bands with a spatial resolution of 90 m. The 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

The following example shows how to cite the use of this data set in a publication. For more information, see our Use and Copyright Web page.

Jackson, T. 2008. SMEX03 ASTER Level-1B Data: Oklahoma. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview Table

Category Description
Data format Binary data files (little-endian)
Spatial coverage and resolution Oklahoma North:
Southernmost Latitude: 36.12° N
Northernmost Latitude: 36.85° N
Westernmost Longitude: 98.00° W
Easternmost Longitude: 97.48° W

Oklahoma South:
Southernmost Latitude: 34.45° N
Northernmost Latitude: 35.40° N
Westernmost Longitude: 98.26° W
Easternmost Longitude: 97.74° W

VNIR: 15 m
SWIR: 30 m
TIR: 90 m
Temporal coverage and resolution 02 July 2003
18 July 2003

Measurements were made once daily for each region.
Tools for accessing data ArcView, ENVI, or other similar software package
File naming convention aster_mmddyyyy_sss_bxx(x).bil
File size 1.1 to 58.5 MB: binary files
1 KB: header files
Parameter Radiance
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)

Thomas Jackson
USDA ARS Hydrology Lab
Bldg. 007, Rm. 104, BARC-West
Beltsville, MD 20705 USA

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 ASTER Level-1B data are scaled radiance Data Numbers stored as 16 bit unsigned integers in little-endian byte order, and consist of one binary file per band. Each binary file is accompanied by a tab-delimited ASCII header file. Missing data are set to zero. Depending on the band, the binary files have a different number of columns and rows:


To convert from Data Number (DN) to radiance at the sensor, the unit conversion coefficients are used. Refer to Equation 1. For more information, refer to the ASTER User Handbook (PDF, 3.6 MB).

The DN can be converted to radiance by using the following equation:

Radiance = (DNvalue - 1) * unit conversion coefficient (Equation 1)

The conversion coefficients are listed in Table 1.

Table 1: Unit Conversion Coefficients
Subsystem Band
No.

Unit Conversion
Coefficient
(W/(m*sr*µm)/DN)

VNIR 1 0.676
2 0.708
3N 0.862
SWIR 4 0.2174
5 0.0696
6 0.0625
7 0.0597
8 0.0417
9 0.0318
TIR 10 0.006822
11 0.006780
12 0.006590
13 0.005693
14 0.005225

File and Directory Structure

Data are available on the FTP site in the following directory: /pub/DATASETS/AVDM/data/soil_moisture/SMEX03/Oklahoma/satellite/ASTER/. Within the /ASTER/directory, there are two sub-directories as described in Table 2.

Table 2: Directory Description
Directory Description
OKN Contains all Oklahoma North files for each sample date, two files per spectral band: one binary file and one header file
OKS Contains all Oklahoma South files for each sample date, two files per spectral band: one binary file and one header file

File Naming Convention

Files are named according to the following convention:

aster_mmddyyyy_sss_bxx(x).bil
aster_mmddyyyy_sss_bxx(x)
.hdr

where:

Table 3: Description of File Name Variables
Variable Description
mm 2-digit month
dd 2-digit day
yyyy 4-digit year
sss Site (oks = Oklahoma South, okn = Oklahoma North)
bxx(x) Band number (for example, b03N refers to Band 3, Nadir-looking)
.bil Indicates that this is a Band-Interleaved-by-Line binary data file.
.hdr Indicates that this is a header file.

Example: aster_07022003_okn_b10.bil (contains 02 July 2003 band 10 data for the Oklahoma North regional study area)


File Size

The binary data files range in size from 1.1 to 58.5 MB. The header files are 1 KB each.

Spatial Coverage

Data coverage includes the Oklahoma North and Oklahoma South regional study areas:

Oklahoma North:
Southernmost Latitude: 36.12° N
Northernmost Latitude: 36.85° N
Westernmost Longitude: 98.00° W
Easternmost Longitude: 97.48° W

Oklahoma South:
Southernmost Latitude: 34.45° N
Northernmost Latitude: 35.40° N
Westernmost Longitude: 98.26° W
Easternmost Longitude: 97.74° W

A detailed geographic description of the data set is shown in Table 4. The coordinates are in the Universal Transverse Mercator (UTM) Zone 14 projection and World Geodetic System (WGS) 84 datum.

Table 4: Geolocation of the Images
Site Subsystem Image Coordinates (Northing and Easting)
Upper left Upper right Lower left Lower right
OKS VNIR 555600E
3920100N
618000E
3920100N
555600E
3812100N
618000E
3812100N
SWIR 555600E
3920100N
618000E
3920100N
555600E
3812100N
618000E
3812100N
TIR 555570E
3920130N
617940E
3920130N
555570E
3812130N
617940E
3812130N
OKN VNIR 585795E
4081005N
640995E
4081005N
585795E
3997005N
640995E
3997005N
SWIR 585780E
4081020N
640980E
4081020N
585780E
3997020N
640980E
3997020N
TIR 585720E
4081050N
640980E
4081050N
585780E
3997080N
640980E
3997080N

Spatial Resolution

VNIR, SWIR, and TIR have different resolutions: 15, 30, and 90 meters, respectively. Each ASTER scene covers an area of approximately 60 x 60 km.

Projection

Universal Transverse Mercator (UTM): Zone 14, World Geodetic System 1984 (WGS 84)

Temporal Coverage

Data were collected once daily for each region on 02 July 2003 and 18 July 2003. These data should be used with the recognition that they represent a single point in time. Satellite overpass times for each date and location are listed below:

Parameter or Variable

The parameter of this data set is radiance as expressed in units of W/(m2*sr*μm).

Parameter Description

Radiance is the measure of the amount of electromagnetic radiation reflected or emitted by an object or surface.

Sample Data Record

Figure 1 shows a sample image from this data set.

SMEX03 ASTER Oklahoma North sample image
Figure 1. Oklahoma North 02 July 2003 Sample Image

3. Data Access and Tools

Data Access

Data are available via FTP.

Volume

The total data volume is approximately 900 MB.

Software and Tools

Tools appropriate for viewing these data are ArcView, ENVI, or other similar software packages.

Related Data Collections

4. Data Acquisition and Processing

Sensor or Instrument Description

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral imager launched on board NASA's Terra spacecraft in December 1999. ASTER covers a wide spectral region with 14 bands from the visible to the thermal infrared with high spatial, spectral, and radiometric resolution. An additional backward-looking near-infrared band provides stereo coverage.

ASTER consists of three subsystems, or sensors. The high-resolution VNIR radiometer observes solar radiation reflected from the Earth's surface in three visible and near-infrared bands (1-3). The VNIR radiometer has a pointing capability of plus or minus 24 degrees 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 the Earth's surface (bands 4-9). SWIR can also change the boresight in the cross-track direction by plus or minus 8.55 degrees from nadir using a pointing mechanism. TIR is an advanced radiometer with five spectral bands (10-14) to detect emitted, thermal infrared radiation. See the ASTER User Handbook (PDF, 3.6 MB) for more information. Refer to Table 5 for spectral ranges.

Table 5: Subsystem Spectral Ranges
Subsystem Band
No.

Spectral Range
(µm)

VNIR 1 0.52-0.60
2 0.63-0.69
3N 0.78-0.86
SWIR 4 1.60-1.70
5 2.145-2.185
6 2.185-2.225
7 2.235-2.285
8 2.295-2.365
9 2.360-2.430
TIR 10 8.125-8.475
11 8.475-8.825
12 8.925-9.275
13 10.25-10.95
14 10.95-11.65

Data Acquisition Methods

For each day, five ASTER scenes were mosaicked to form one image. The smaller regional study areas of Oklahoma North and Oklahoma South were then extracted. Data are Level-1B with geometric and radiometric corrections applied.

5. References and Related Publications

Abrams, Michael and Simon Gaskin. ASTER User Handbook: Advanced Spaceborne Thermal Emission and Reflection Radiometer. Version 2. Jet Propulsion Laboratory. http://asterweb.jpl.nasa.gov/content/03_data/04_Documents/aster_user_guide_v2.pdf, 3.6 MB.

Please see the USDA SMEX 03 Web site for in-depth information on the science mission and goal of the SMEX project.

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document:

AMSER-E Advanced Scanning Microwave Radiometer - Earth Observing System
ASTER Advanced Spaceborne Thermal Emission and Reflection Radiometer
DN Data Number
ENVI Environment for Visualizing Images
FTP File Transfer Protocol
JPL Jet Propulsion Laboratory
NSIDC National Snow and Ice Data Center
OKN Oklahoma North
OKS Oklahoma South
SMEX03 Soil Moisture Experiment 2003
SWIR Shortwave Infrared
URL Uniform Resource Locator
USDA United States Department of Agriculture
UTM Universal Transverse Mercator
TIR Thermal Infrared
VNIR Visible and Near-Infrared
WGS 84 World Geodetic System 1984

Document Creation Date

December 2007

Document URL

http://nsidc.org/data/docs/daac/nsidc0325_smex03_aster_level1b_ok.gd.html