Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Trade Journal
Publication Acceptance Date: 9/1/2009
Publication Date: 10/1/2009
Citation: O'Neill, P., Jackson, T.J., Entekhabi, D., Njoku, E. 2009. Survey of L Band tower and airborne sensor systems relevant to upcoming soil moisture missions. IEEE Geoscience and Remote Sensing Newsletter. 151:13-16. Interpretive Summary:
Technical Abstract: Basic research on the physics of microwave remote sensing of soil moisture has been conducted for almost thirty years using ground-based (tower- or truck-mounted) microwave instruments at L band frequencies. Early small point-scale studies were aimed at improved understanding and verification of microwave theory, determination of the most sensitive instrument characteristics for soil moisture measurement, and development of accurate microwave soil moisture retrieval algorithms. Work has continued on both the form of these algorithms and generation of baseline quantifications for algorithm parameterizations. Collectively, these studies have demonstrated the usefulness of microwave remote sensing for soil moisture estimation and have led directly to the soil moisture retrieval algorithms proposed for upcoming satellites. Sensors on airborne platforms have similarly played a vital role in the development of microwave soil moisture remote sensing. Various airborne L-band radars and radiometers have flown during field campaigns to acquire large-area microwave imagery for geophysical model development and soil moisture retrieval algorithm refinement, and for basic hydrologic and scaling research. In order to guide near future efforts related to the NASA Soil Moisture Active Passive satellite (launch 2013), a survey of existing and planned L-band instruments has been conducted covering the microwave remote sensing community in both the United States and abroad. The ground-based and airborne L-Band sensors identified in this survey are valuable resources which will help to enable the success of upcoming space missions through both pre-launch and post-launch activities, including: (1) refinements of current algorithm parameterizations to improve the accuracy of microwave soil moisture retrievals, (2) acquisition of long-term measurements to assess seasonal to year-round changes, (3) examination of “more difficult” scenes such as the continuum of trees from small orchards to mature forests to extend the range of accurate soil moisture retrievals to denser land covers, (4) improved understanding of spatial scaling and scene heterogeneity issues, and (5) calibration / validation of satellite measurements during the missions.