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Data Set ID:
NSIDC-0206

SMEX02 Airborne Synthetic Aperture Radar (AIRSAR) Data, Iowa, Version 1

This data set contains radar backscatter measurments taken over the Soil Moisture Experiments 2002 (SMEX02) Walnut Creek Watershed area in Iowa, USA.

Geographic Coverage

Parameter(s):
  • Radar > Radar Backscatter
  • Radar > Radar Imagery
Spatial Coverage:
  • N: 42.389, S: 41.308, E: -93.017, W: -93.913

Spatial Resolution:
  • 7.5 x 7.5
Temporal Coverage:
  • 1 July 2002 to 9 July 2002
Temporal Resolution: Not specified
Data Format(s):
  • Binary
  • ASCII Text
Platform(s) AIRCRAFT
Sensor(s): AIRSAR
Version: V1
Data Contributor(s): Thomas Jackson, Rajat Bindlish, Rogier Van der Velde
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. 2004. SMEX02 Airborne Synthetic Aperture Radar (AIRSAR) Data, Iowa, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/EPHBHKBQEJ09. [Date Accessed].

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Notice: 
The documentation for this data set was provided solely by the Principal Investigator(s) and was not further developed, thoroughly reviewed, or edited by NSIDC. Thus, support for this data set may be limited.

Detailed Data Description

In AIRSAR’s POLSAR mode, the data consist of three bands (C-, L- and P-band) each with four polarizations (HH, VV, HV and VH), for a total of 12 channels. Basic characteristics of the AIRSAR are listed in table 1. Additional information can be found at http://airsar.jpl.nasa.gov/data/data_format.pdf.

Table 1. AIRSAR Antenna parameters
Bane C (5.31 Ghz), L (1.26 Ghz), P (0.45Ghz)
Incidence angles 0o – 75o (theoretical, in practice between 20o and 60o )
Altitude ≈ 8 km
Bandwidth 20 MHz
Range Resolution 7.5 m

Format

The data are provided in ASCII and binary (compressed Stokes matrix) formats.

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File and Directory Structure

There is one folder for each POLSAR scene ID, using the JPL label for the name of the folder and in the format of cm####.

Some POLSAR scene directories contain a “filtered_p” sub-directory. A P-band filter was applied to these data files to reduce the impact of interference in the Pband imagery. However, there may be a small amount of p-band interference still present in the data and the P-band filter is not effective in all cases. Because the P-band filter may adversely impact the calibration of the data, both the filtered and unfiltered files are provided.

The following remarks should be noted before downloading and using the data:

- for July 5th , one scene of flight line 2 (JPL label cm6503) is not available at the ftp-site.

- On July 8th, an additional scene seems to be acquired for flight line 1(JPL_label cm6484), named N-S flight line ‘1b ’. The datasets labeled cm6478 and cm6483 contain exactly the same scene. However a different processing is applied to the two datasets, see the log files for details.

- for July 9th, S-N flight line ‘1’ is not available.

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File Naming Convention

The “CM” indicates that the data are in a compressed Stokes matrix format. CM is followed by a four-digit output product number (JPL label); this number is unique for each scene. See tables 2-6.

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File Size

The files range in size from 1 KB – 164,750 KB

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Spatial Coverage

Southernmost Latitude: 41.308° N

Northernmost Latitude: 42.389° N

Westernmost Longitude: 93.937° W

Easternmost Longitude: 93.017° W

Spatial Resolution

7.5 m

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Temporal Coverage

Measurements were taken on July 1, 5, 7, 8, and 9, 2002. Flights occurred twice each day over each of the three flight lines.

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Parameter or Variable

Parameter Description

In AIRSAR’s POLSAR mode, the radar instrument collects backscattering coefficients at quad polarization [HH, VV, HV and VH in the C-, L- and P-band frequency ranges.

The POLSAR operating mode of the AIRSAR instrument collects twelve channels of data, four in each of the three frequencies of AIRSAR: P-, L-, and C-band. The four data channels are:

HH horizontally polarized transmit wave, horizontally polarized receive wave

HV horizontally polarized transmit wave, vertically polarized receive wave

VH vertically polarized receive wave, horizontally polarized receive wave

VV vertically polarized receive wave, vertically polarized receive wave

The compressed Stokes matrix data are oriented so that each pixel sample is decreasing azimuth (along track) and each pixel line is of increasing range (crosstrack).

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Software and Tools

Any application that can read ASCII or binary (compressed Stokes matrix) files

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Data Acquisition and Processing

During the Soil Moisture Experiments in 2002 (SMEX02) the AIRSAR instrument onboard NASA’s DC-8 flew on 5 days: July 1, 5, 7, 8, and 9. Each day, three flight lines were flown over the SMEX02 study area capturing two scenes per flight line. Two flight lines were east-west in orientation and were concentrated around the Walnut Creek (WC) watershed. The other line was north-south orientated, and covered both the WC watershed and the regional study area. The flight lines are shown in figure 1.

Figure 1. DC-8 flight lines

The JPL labels used for the file names do not correspond to a specific location, a specific date or specific flight line. For convenience, the geolocation of the various flight lines are specified in tables 2-6. Note that the ‘top right’ and ‘lower left’ coordinate are approximated and can only be used as an indication for the data coverage of a specific scene.

Table 2. AIRSAR flight lines and the corresponding JPL labels for the 1st of July
Top right* Lower left*
JPL_label Latitude Longitude Latitude Longitude Heading Line Number
cm6476 42.4424 -93.7415 41.7025 -93.5354 S-N 1
cm6591 42.6237 -93.5677 42.0761 -93.3609 N-S 1
cm6568 42.0252 -93.9101 41.8730 -93.1756 E-W 2
cm6468 42.0042 -93.9963 41.8504 -93.2635 E-W 2
cm6461 42.0664 -93.0143 41.9126 -92.9682 W-E 3
cm6539 42.0453 -94.0006 41.8907 -93.2677 W-E 3

*coordinates are approximations and should not be used to process the data

Table 3. AIRSAR flight lines and the corresponding JPL labels for the 5th of July
Top right* Lower left*
JPL_label Latitude Longitude Latitude Longitude Heading Line Number
cm6582 42.3579 -93.7512 41.8103 -93.5458 S-N 1
cm6596 42.6441 -93.5587 42.0966 -93.3518 N-S 1
cm6506 42.0189 -93.9808 41.8665 -93.1736 E-W 2
cm6503 41.9973 -93.9461 41.8447 -93.2119 E-W 2
cm6456 42.0730 -93.985 41.9192 -92.9385 W-E 3
cm6557 42.0519 -93.9837 41.8973 -93.2507 W-E 3

*coordinates are approximations and should not be used to process the data

Table 4. AIRSAR flight lines and the corresponding JPL labels for the 7th of July
Top right* Lower left*
JPL_label Latitude Longitude Latitude Longitude Heading Line Number
cm6586 42.3648 -93.7563 41.8172 -93.5508 S-N 1
cm6592 42.6355 -93.5552 42.0880 -93.3483 N-S 1
cm6565 42.0156 -93.1678 41.8634 -93.9021 E-W 2
cm6574 41.9936 -93.1646 41.8416 -93.8987 E-W 2
cm6538 42.0281 -94.0133 41.9207 -92.9679 W-E 3
cm6460 42.0980 -93.2467 41.8972 -93.9792 W-E 3

*coordinates are approximations and should not be used to process the data

Table 5. AIRSAR flight lines and the corresponding JPL labels for the 8th of July
Top right* Lower left*
JPL_label Latitude Longitude Latitude Longitude Heading Line Number
cm6478 42.2920 -93.7507 41.7230 -93.5447 S-N 1
cm6483 42.2920 -93.7507 41.7230 -93.5447 S-N 1
cm6590 42.6254 -93.5591 42.0779 -93.3522 N-S 1
cm6484 42.7765 -93.7517 42.2075 -93.5456 S-N 1^b
cm6511 42.0189 -93.9150 41.8669 -93.1806 E-W 2
cm6477 41.9983 -94.2315 41.8445 -93.1837 E-W 2
cm6455 42.0715 -93.9924 41.9179 -92.9465 W-E 3
cm6573 42.0515 -94.0024 41.8968 -93.2695 W-E 3

*coordinates are approximations and should not be used to process the data

Table 6. AIRSAR flight lines and the corresponding JPL labels for the 9th of July
Top right* Lower left*
JPL_label Latitude Longitude Latitude Longitude Heading Line Number
cm6593 42.6400 -93.5583 42.0925 -93.3514 N-S 1
cm6553 42.0183 -93.9235 42.0925 -93.1890 E-W 2
cm6518 41.9968 -93.9067 41.8445 -93.1728 E-W 2
cm6457 42.0719 -94.0112 41.9181 -92.9658 W-E 3
cm6513 42.0519 -94.0090 41.8973 -93.2769 W-E 3

*coordinates are approximations and should not be used to process the data

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References and Related Publications

Contacts and Acknowledgments

Dr. Thomas J. Jackson, USDA ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD.

Dr. Rajat Bindlish, USDA ARS Hydrology and Remote Sensing Laboratory, Beltsville, MD.

Dr. Rogier Van der Velde, USDA ARS Soil Tilth Laboratory, Beltsville, MD. 

Document Information

DOCUMENT CREATION DATE

26 March 2013

No technical references available for this data set.
No FAQs or How Tos available for this data set.

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