Data Set ID: 
SNEX17_UWScat

SnowEx17 Ground-Based UWScat Ku- and X-Band Frequency Modulated Continuous Wave Radar, Version 1

This data set consists of ground-based scatterometer data acquired during the SnowEx 2017 campaign at Grand Mesa, Colorado, USA, a snow-covered, forested study site about 40 miles east of the city of Grand Junction, CO. The data comprise operational parameters used during data acquisition, Mueller matrices for each acquisition, and the nearfield-corrected normalized radar cross section (NRCS) in VV, VH, HV, and HH polarizations. Range profile data are also provided for each scan which report the raw power returned as a function of range from the antenna.

This is the most recent version of these data.

Version Summary: 

Initial release

STANDARD Level of Service

Data: Data integrity and usability verified

Documentation: Key metadata and user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools

See All Level of Service Details

Parameter(s):
  • RADAR > RADAR CROSS-SECTION
Data Format(s):
  • ASCII Text
Spatial Coverage:
N: 39.05385, 
S: 39.017636, 
E: -108.032553, 
W: -108.09457
Platform(s):GROUND-BASED OBSERVATIONS
Spatial Resolution:
  • 30 cm x 30 cm
Sensor(s):SCATTEROMETERS
Temporal Coverage:
  • 21 February 2017 to 25 February 2017
Version(s):V1
Temporal ResolutionNot applicableMetadata XML:View Metadata Record
Data Contributor(s):Richard Kelly, Aaron Thompson

Geographic Coverage

Other Access Options

Other Access Options

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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.

Kelly, R. and A. Thompson. 2018. SnowEx17 Ground-Based UWScat Ku- and X-Band Frequency Modulated Continuous Wave Radar, 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/ZW3UUYUZRYJO. [Date Accessed].
Created: 
11 July 2018
Last modified: 
2 October 2018

Data Description

Parameters

This data file contains relative power observations (in decibels, dB) from the University of Waterloo Scatterometer (UWScat).

File Information

Format

Data are formatted as plain text (.txt) and MUE (.mue) files.  Both text and MUE files can be opened with any software that reads plain text (e.g. Microsoft Word, Microsoft Notepad, TextEdit).

Extensible Markup Language (.xml) files with associated metadata are also provided.

File Contents

One MUE file is provided for each scan. From top to bottom, each MUE file contains the following information:

  • the number of azimuth sweeps
  • list of elevation angles used in the scan
  • estimate of the peak range for each elevation angle 
  • near field-corrected Mueller matrices for each elevation angle
  • near field-corrected Normalized Radar Cross Sections (NRCS) for the following polarizations:

    • HH = horizontal transmit, horizontal receive
    • VV = vertical transmit, vertical receive
    • HV = horizontal transmit, vertical receive
    • VH = vertical transmit, horizontal receive
One UWScat scan produces thirteen text files. Each text file contains the range profiles from a specific elevation angle and the following six columns of data: 
  1. count
  2. range from the antenna (m)
  3. relative power - VV (dB)
  4. relative power - HH (dB)
  5. relative power - VH (dB)
  6. relative power - HV (dB)

Sample File

Figure 1 shows a sample range profile (text file). For a sample MUE file, see the SnowEx17 UWScat MUE README file on the technical references tab. This is the same README file referenced in each MUE file header.

Figure 1. Sample data from file SnowEx17_UWScat_20170221-232231-Ku-N_25_Range_Profile.txt.

Directory Structure

Data files are organized into folders based on the date of the scan start time (Figure 2). Within each folder, one MUE, one XML, and 13 text files are available for each UWScat scan (Figure 3).

Figure 2. Directory structure for SnowEx17 Ground-Based UWScat Ku- and X-Band Frequency Modulated Continuous Wave Radar.
Figure 3. Files available for each UWScat scan.

Naming Convention

Text files utilize the following naming convention:

SnowEx17_UWScat_[yyyymmdd]-[hhmmss]-[??]-[b]_[##]_Range_Profile.txt

where:

Table 1. Text File Naming Convention
Variable Description
SnowEx17_UWScat
Short name for SnowEx17 Ground-Based UWScat Ku- and X-Band Frequency Modulated Continuous Wave Radar
yyyymmdd
Year, month, day of acquisition
hhmmss
Hour, minute, second of start time, in Coordinated Universal Time (UTC)
??
Frequency of scan (Ku or X)
b Beam mode (N = narrow, F = flood)
## Elevation angle of scan in degrees (typically between 25° and 62°)

Examples:

SnowEx17_UWScat_20170225-001850-X-N_37_Range_Profile.txt
SnowEx17_UWScat_20170225-001850-X-N_40_Range_Profile.txt

SnowEx17_UWScat_20170225-001850-X-N_43_Range_Profile.txt

MUE files utilize the following naming convention:

SnowEx17_UWScat_[yyyymmdd]-[hhmmss]-[??]-[b].mue

where:

Table 2. MUE File Naming Convention
Variable Description
SnowEx17_UWScat Short name for SnowEx17 Ground-Based University of Waterloo Scatterometer (UWScat) Ku- and X-Band Frequency Modulated Continuous Wave Radar
yyyymmdd Year, month, day of acquisition
hhmmss Hour, minute, second of start time in UTC
??
Frequency of scan (Ku or X) 
b Beam mode (N = narrow, F = flood)

Examples:

SnowEx17_UWScat_20170225-001850-X-N.mue
SnowEx17_UWScat_20170225-172726-Ku-N.mue

SnowEx17_UWScat_20170225-174035-Ku-F.mue

Since file names include the scan start time in UTC, there are instances when sequential scans at the same site were recorded on different dates. For example, the scans from 21 February 2017 have file names which reflect the following start times:

  • Ku-band scan: 2017/02/21 23:22:31 UTC
  • X-band scan: 2017/02/22 00:07:22 UTC

File Size

Text files are approximately 19 KB.

MUE files range between approximately 3.4 KB and 13 KB. 

The complete set of MUE files is approximately 84 KB; the complete set of text files is approximately 4 MB.

The total data set is approximately 4.1 MB.

Spatial Information

Coverage

Northernmost Latitude: 39.05385° N
Southernmost Latitude: 39.01764° N
Easternmost Longitude: 108.03255° W
Westernmost Longitude: 108.09457° W

Resolution

30 cm

Temporal Information

Coverage

Data were collected between 21 February and 25 February 2017.

Data Acquisition and Processing

Summary

The scatterometer data includes operation parameters used during data acquisition; Mueller matrices for each acquisition; the near field-corrected NRCS in VV, VH, HV, and HH polarizations; and range profiles for each scan. The Mueller matrices can be used to generate polarization responses (e.g. polarization histograms), while the NRCS can be used for modeling and for comparisons with other studies. 

Acquisition

Figure 4. Illustration of the University of Waterloo Scatterometer (UWScat) field set-up. The azimuth angle (ϴ) is drawn in blue, and the elevation angle (Φ) is drawn in red.

Data were collected using the University of Waterloo Scatterometer (UWScat), shown in Figure 4. This ground-based instrument was mounted to a tripod on the snow surface, with the antenna positioned approximately two meters above the snow surface (when the elevation angle = 90°). The location of the scatterometer was marked by handheld GPS units. 

The UWScat operated at the Ku-band (12 - 18 GHz) and X-band (8 - 12 GHz) frequencies over azimuth and elevation sweeps programed by the user(s). Ku- and X-band frequencies were scanned one at a time from the same position. Each scan took approximately 10 minutes to complete. Between scans, the radio frequency (RF) head was switched between Ku- and X-band frequencies; this explains why there is a time offset between scans at each site. 

All scans were performed in narrow-beam mode, except for the 25 February 2017 Ku-band scan, which recorded in both narrow- and flood-beam mode. In narrow-beam mode, a single antenna was used to send and receive signals; in flood-beam mode, separate antennas were used to send and receive signals, improving sensitivity at long distances.

More details about data acquisition and scan locations can be found under Technical References.

Processing

After acquisition, data were corrected using a calibration file (created at the time of data acquisition) and in-scene calibration targets. Additional post-processing included manually selecting the peak return for each range profile from within a user-specified range interval, using a Hanning window to reduce side lobes, subtracting system leakage by means of boxcar averaging and in-scene sky observations, and near-field reflectivity corrections (Sekelsky 2002).

    Instrumentation

    Description

    University of Waterloo Scatterometer (UWScat) specifications are shown in Table 3.

    Table 3. UWScat Parameters
    Parameter Value
    Ku-narrow Far-Field Distance 5.44 m
    Ku-flood Far-Field Distance 3.03 m
    X-narrow Far-Field Distance 17.10 m
    Maximum Range 34.00 m

    Version History

    Version 1.

    Related Data Sets

    Other SnowEx Data Sets

    Related Websites

    NASA SnowEx Campaign

    Contacts and Acknowledgments

    Dr. Richard Kelly, PI
    University of Waterloo
    Waterloo, Ontario N2L 3G1

    Canada

    Mr. Aaron Thompson, Technical Contact
    University of Waterloo
    Waterloo, Ontario N2L 3G1

    Canada

    References

    King, J. M. L., R. Kelly, A. Kasurak, C. Duguay, G. Gunn, and J. B. Mead. 2013. UW-Scat: A Ground-Based Dual-Frequency Scatterometer for Observation of Snow Properties. IEEE Geoscience and Remote Sensing Letters 10(3): 528-532. DOI: 10.1109/LGRS.2012.2212177

    Sekelsky, S. M. 2002. Near-Field Reflectivity and Antenna Boresight Gain Corrections for Millimeter-Wave Atmospheric Radars. J. of Atmospheric and Oceanic Technology 19: 468-477. DOI: 10.1175/1520-0426(2002)019<0468:NFRAAB>2.0.CO;2

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