This data set provides brightness temperature data acquired during the Soil Moisture Experiment 2003 (SMEX03) by the Special Sensor Microwave/Imager (SSM/I) conducted in the SMEX03 Oklahoma, the Alabama/Georgia, and Brazil study areas.
Get Data
DOWNLOADING DATA VIA HTTPS
To learn more about Earthdata Login and to register for an account, please see How to Register with Earthdata Login. Once you have logged in, data can be downloaded via a Web browser, command line, or client. For help with downloading data, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.
SMEX03 SSM/I Brightness Temperature Data, Alabama, Version 1
Geographic Coverage
Parameter(s): |
|
---|---|
Spatial Coverage: |
|
Spatial Resolution: | Not Specified |
Temporal Coverage: |
|
Temporal Resolution: | Not specified |
Data Format(s): |
|
Platform(s) | DMSP, DMSP 5D-2/F13, DMSP 5D-2/F14, DMSP 5D-2/F15 |
Sensor(s): | SSM/I |
Version: | V1 |
Data Contributor(s): | Thomas Jackson |
Metadata XML: | View Metadata Record |
Data Citation
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.
Jackson, T. 2008. SMEX03 SSM/I Brightness Temperature Data, Alabama, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/YLI4RKVMWFB3. [Date Accessed].Detailed Data Description
Data are provided in ASCII text files (.txt).
The following tables describe the column headings for the low (*.lo.txt) and high (*.hi.txt) frequency data files.
Column
|
Parameter
|
---|---|
1
|
Latitude in degrees North |
2
|
Longitude in degrees West |
3
|
Tb 19 v-pol |
4
|
Tb 19 h-pol |
5
|
Tb 22 v-pol |
6
|
Tb 37 v-pol |
7
|
Tb 37 h-pol |
Column
|
Parameter
|
---|---|
1
|
Latitude in degrees North |
2
|
Longitude in degrees West |
3
|
Tb 85 v-pol |
4
|
Tb 85 h-pol |
The top directory level contains tarred and gzipped files containing the data for each SMEX03 study region and the readme file as shown in Figure 1.

Data files are named according to the following convention. Table 3 describes the naming convention variables.
File Naming ConventionTDmmddyyyysstttt.rr.txt
Example File NameTD04292003132345.hi.txt
Variable | Description |
---|---|
mm |
month |
dd |
day |
yyyy |
year |
ss |
satellite number |
tttt |
start time of swath (hour and minute of local standard time) |
rr |
frequency set (lo or hi) |
Tarred and gzipped files are named according to the following convention, where reg
indicates the SMEX03 special region. Table 4 lists the regions
File Naming Conventionreg_SSMI.tar.gz
Example File NameALGA_SSMI.tar.gz
Region Code | Region Name |
---|---|
ALGA | Alabama and Georgia |
BZ | Brazil |
OK | Oklahoma |
41 MB to 188 MB
Total volume is approximately 275 MB for all data. Volume by region is approximately:
Alabama / Georgia: 42 MB
Oklahoma: 188 MB
Brazil: 45 MB
Alabama / Georgia:
Southernmost Latitude: 28.0° N
Northernmost Latitude: 38.0° N
Westernmost Longitude: 90.0° W
Easternmost Longitude: 80.0° W
Oklahoma:
Southernmost Latitude: 30.0° N
Northernmost Latitude: 40.0° N
Westernmost Longitude: 103.0° W
Easternmost Longitude: 93.0° W
Brazil:
Southernmost Latitude: 20.0° S
Northernmost Latitude: 0.0° S
Westernmost Longitude: 60.0° W
Easternmost Longitude: 40.0° W
Alabama / Georgia: 29 April 2003 to 29 September 2003
Oklahoma: 29 April 2003 to 23 September 2003
Brazil: 29 September 2003 to 28 February 2004
Temporal Resolution
For a given satellite, coverage is possible twice a day, approximately 12 hours apart, on the ascending and descending passes.
Brightness Temperature (Tb) in units of kelvin (K)
Parameter Description
The brightness temperatures are given by channel: 19.3, 22.2, 37.0, and 85.5 GHz.
Sample Data Record
Low Frequencies: The following is a sample from the file TD04292003132343.lo.txt. The first three lines are shown. See Format for column headings.
28.04 -85.46 212.17 157.06 246.36 224.99 174.41 28.08 -85.20 212.98 158.99 248.69 227.32 178.99 28.12 -84.95 211.80 156.60 247.29 228.85 183.20
High Frequency: The following is a sample from the file TD04292003132343.hi.txt The first three lines are shown. See Format for column headings.
28.01 -84.92 270.57 258.45 28.02 -84.79 267.10 252.69 28.03 -84.66 267.13 250.93
Software and Tools
Data Acquisition and Processing
Data are first acquired as antenna temperatures in Temperature Data Record (TDR) format. Latitude and longitude coordinates for each pixel are included with these records. When a study area is specified in the data search procedure, all orbits that cross that area are extracted. On a given day, it is possible to have coverage by each of the three satellites twice a day. It is also possible to have no coverage.
Processing Steps
Additional processing consists of eliminating scans without coverage in the SMEX03 study regions, converting the antenna temperatures to brightness temperatures, and reformatting the data into ASCII files. The processed data files include a latitude and longitude assigned to each data point.
SSM/I is a seven-channel, four-frequency, linearly polarized passive microwave radiometric system. It is a conical scanning total power microwave radiometer system operating at a look angle of 53 degrees. The nominal swath width is 1400 km. Data are collected at 128 points across track on every scan at 85 GHz. Only 64 points of observation are made across track on every other scan at the other frequencies.
SSM/I is flown aboard Defense Meteorological Satellite Program (DMSP) satellites F8, F10, F11, F12, F13, F14, and F15. Table 5 lists the characteristics of the relevant platforms that were in operation during SMEX03.
Satellite
|
Launch Date
|
Supported Through
|
Ascending Equatorial Crossing Time (local time)
|
---|---|---|---|
F13
|
March 1995
|
present
|
18:15
|
F14
|
May 1997
|
present
|
20:21
|
F15
|
December 1999
|
present
|
21:31
|
The SSM/Is orbit the earth about 14.1 times per day with an orbital period of about 102 minutes. The minimum data unit, an orbit, consists of two passes. These are pole-to-pole swaths, one ascending (south to north) and one descending (north to south). The first pass of a Coordinated Universal Time (UTC) day is defined as the first complete pass of the day.
For more information, see the Special Sensor Microwave Imagery (SSM/I) Web page.
References and Related Publications
Contacts and Acknowledgments
Thomas J. Jackson
USDA ARS Hydrology and Remote Sensing Lab
Bldg. 007, Rm. 104, BARC-West
Beltsville, MD 20705
USA
Document Information
DOCUMENT CREATION DATE
1 April 2008
DOCUMENT REVISION DATE
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org