Close

Service Interruption

The NSIDC Web site and data services are currently having intermittent problems and may be unavailable. We are working to restore these services as soon as possible and apologize for any inconvenience this may cause. Please contact NSIDC User Services for assistance.



SMEX02 Airborne GPS Bistatic Radar Data, Iowa

View Catalog Page

Entry ID

NSIDC-0275

Summary

This data set contains measurements of Global Positioning System (GPS) signals reflected from the Earth’s surface and collected on an airborne platform. The measurements were taken over the Soil Moisture Experiments 2002 (SMEX02) Walnut Creek Watershed area in Iowa, USA. The reflections collected were from flat agricultural land with mostly corn and soybean crops in mid-development. Data were collected on 19, 25, 27 June 2002 and 1, 2, 5-8 July 2002.

The data are categorized by campaigns and dates, and are processed into levels. Level “0” files are text files directly from the receiver. Levels above “0” are output in Hierarchical Data Format (HDF) format, ordered in UTC time and gzipped. The HDF files contain metadata in the form of attributes that describe the data seta and variables. The variables also contain attributes to self-describe the individual data pieces.

A modified GPS Delay Mapping Receiver (DMR) tracks and measures the direct, line-of-sight, right hand circularly polarized (RHCP) signal of a GPS satellite. It also simultaneously measures the delayed, Earth- reflected, near-specular, left hand circularly polarized (LHCP) GPS signal. The DMR was mounted on the NCAR C-130 along with the Jet Propulsion Laboratory (JPL) Passive and Active L- and S-band (PALS) microwave instrument. GPS signal reflections were collected using the standard hemispherical RHCP antenna mounted on the roof of the aircraft, and a reversed polarization LHCP hemispherical antenna mounted on the belly. The receiver position is computed from either an external navigation source or the receiver's own GPS navigation solution, whichever is more accurate. The GPS surface reflections are georeferenced to a composite Earth consisting of the WGS-84 ellipsoid, the EGM96 geoid, and the GTOPO30 elevation model.

The primary objective was to collect land reflections for sensitivity of the reflected GPS power to temporal and spatial soil moisture and foliage attenuation. The measurements are a form of bistatic radar and can be used to estimate the surface scattering coefficient (roughness and/or dielectric properties) and path delays between the direct and reflected GPS signals. Scattering coefficients can be used to estimate changes in surface soil moisture.

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.

Geographic Coverage

 

Spatial Coordinates:
N: 42.005°     S: 41.915°     E: -93.4°     W: -93.8°    

Data Set Citation

Dataset Creator: Masters, D.
Dataset Title: SMEX02 Airborne GPS Bistatic Radar Data, Iowa
Dataset Release Date: 2005-08-11
Dataset Release Place: Boulder, Colorado USA
Dataset Publisher: CCAR: University of Colorado, Colorado Center for Astrodynamics Research
Online Resource: http://nsidc.org/data/nsidc-0275.html

Temporal Coverage

Start Date: 2002-06-19
Stop Date: 2002-07-08

Location Keywords

  • CONTINENT NORTH AMERICA UNITED STATES OF AMERICA

Science Keywords

  • Spectral/Engineering Radar Radar Imagery

Ancillary Keywords

  • bistatic radar
  • GPS
  • Soil Moisture
  • Surface Roughness

Platform

  • GPS Global Positioning System Satellites

Instrument

  • GPS RECEIVERS

Project

  • SMEX02 Soil Moisture Experiments in 2002
  • ISMEX Iowa Soil Moisture Experiment

Use Constraints

These data are considered exploratory. The techniques to estimate geophysical parameters from these data are being continuously refined. Usage of these data is granted without restriction, but acknowledgment of the source and PI is appreciated.

Data Set Progress

in work

Data Center

NASA DAAC at the National Snow and Ice Data Center
Data Center URL: http://nsidc.org/daac/index.html

Data Center Personnel

Name: NSIDC User Services
Phone: 1 303 492-6199
Fax: 1 303 492-2468
Email: nsidc@nsidc.org
Contact Address:

  • National Snow and Ice Data Center
  • CIRES, 449 UCB
  • University of Colorado

City: Boulder
Province or State: CO
Postal Code: 80309-0449
Country: USA

National Snow and Ice Data Center
Data Center URL: http://nsidc.org

Data Center Personnel

Name: NSIDC User Services
Phone: 1 303 492-6199
Fax: 1 303 492-2468
Email: nsidc@nsidc.org
Contact Address:

  • National Snow and Ice Data Center
  • CIRES, 449 UCB
  • University of Colorado

City: Boulder
Province or State: CO
Postal Code: 80309-0449
Country: USA

Distribution

Distribution Media: FTP
Distribution Format: HDF

Personnel

Dallas Masters
Role: INVESTIGATOR
Phone: 1 303 492.4075
Fax: 1 303 492.2825
Contact Address:

  • University of Colorado
  • University of Colorado
  • University of Colorado
  • CB 431/ CCAR

City: Boulder
Province or State: CO
Postal Code: 80309-0431
Country: USA

Dallas Masters
Role: INVESTIGATOR
Phone: 1 303 492.4075
Fax: 1 303 492.2825
Contact Address:

  • University of Colorado
  • University of Colorado
  • University of Colorado
  • CB 431/ CCAR

City: Boulder
Province or State: CO
Postal Code: 80309-0431
Country: USA

Stephen Katzberg
Role: INVESTIGATOR
Contact Address:

  • NASA Langley Research Center
  • M.S. 328
  • NASA-Langley Research Center

City: Hampton
Province or State: VA
Postal Code: 23681-0001

Related URL

VIEW PROJECT HOME PAGE
NSIDC AMSR-E Validation Data

VIEW PROJECT HOME PAGE
Soil Moisture Experiment (SMEX)

VIEW PROJECT HOME PAGE
Soil Moisture Experiment (SMEX)

Metadata Name and Version

Metadata Name: CEOS IDN DIF
Metadata Version: 9.7

Creation and Review Dates

DIF Creation Date: 2005-08-11
Last DIF Revision Date: 2013-10-10

Metadata Views

DIF Text-Only

Directory Interchange Format (DIF) in plain text

DIF XML

Directory Interchange Format (DIF) in Extensible Markup Language (XML)

FGDC HTML

U.S. Federal Geographic Data Committee (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM)

ISO HTML

International Organization for Standardization (ISO) 19115:2003 Geographic Information Metadata

Back to Top