.c.Mahantango, Pennsylvania

T. Engman and J. Wang
Goddard Space Flight Center (GSFC)

	Mahantango will be one of several SIR-C/X-SAR hydrology test sites.  The hydrology studies at Mahantango will be conducted in a 400 km2.  A series of aircraft flights with a P-,  L-,  and C-band polarimeter (a synthetic aperture radar system with multiple polarizations), an L-band microwave radiometer, as well as visible and infrared sensors have been made over the test site during July 1990.  Extensive ground truth measurements on soil moisture, vegetation cover, surface roughness, hydrological, and climatological information have been acquired to support the studies.  Similar data will be  collected during the SIR-C/X-SAR mission.
	The objectives of the two studies being carried out at the Mahantango site are:
1)	To determine and compare soil moisture patterns within one or more humid watersheds using SAR data, ground-based measurements, and hydrologic modeling;
2)	To use radar-derived soil moisture patterns to characterize the hydrologic regime within a catchment;
3)	To identify runoff-producing characteristics of humid zone watersheds by seasonal and daily differences in the distribution of soil moisture;
4)	To establish the feasibility of using space radar data as the basis for scaling up from small-scale, process-oriented hydrologic models to the larger scale water balance models necessary to define and quantify the land phase of GCMs;
5)	To analyze the backscattered signals from SIR-C/X-SAR as a function of surface soil moisture, vegetation type, and roughness;
6)	To compare theoretical models of microwave backscatter and emission with SIR-C/X-SAR observations, the L-band and C-band airborne polarimeter system, and the L-band push-broom microwave radiometer (PBMR).  The PBMR could also estimate the bare-field soil moisture over a large area which could be a secondary source of ground truth data for SIR-C/X-SAR.
7)	To conduct water balance studies of two regions of limited area, one vegetated and one bare.