Soil Moisture

Soil Properties

Soil Temperature

Vegetation and Land Cover

Aircraft Remote Sensing

Satellite Remote Sensing

It is well established that an L band sensor is optimal for soil moisture sensing (Jackson, 1993). There are new technologies being developed that make spaceborne systems feasible. However, even if missions currently under consideration were selected for satellite implementation it would be several years before launch. There are current and near future satellite observing systems that, while not ideal for soil moisture measurement, can provide information for some conditions. These systems include the Special Sensor Microwave/Imager (SSM/I), the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), and the Advanced Microwave Scanning Radiometer (AMSR).

Of these instruments, AMSR holds the greatest promise for soil moisture. Soil moisture retrieval algorithms for AMSR have been proposed but have not been rigorously evaluated. There are few data sets available for this purpose. Considering the fact that these instruments will be launched on Aqua and ADEOS-II in the next year, this is a critical issue that needs to be addressed for both algorithm development and validation. The Southern Great Plains 1999 (SGP99) Experiment was developed to address this significant gap in our knowledge base. The goals of this effort are to understand how to effectively interpret and utilize satellite microwave data that are available now or will be in the near future and to explore new approaches that may enhance the ability to measure soil moisture from space.

SGP99 involved a series of aircraft flights with a variety of C, S and L band microwave instruments. This experiment was the first to use several of these instruments. This has been the focus of several previous investigations and provides an excellent test bed for evaluating new sensor systems and algorithms. Land cover conditions in the region, especially at this time of the year are favorable for C band soil moisture retrieval. Data collection focused on the period of July 8th through the 21st.