.c.…tztal, Austria


Titles of Investigations:

I.		SIR-C Investigations of Snow Properties in Alpine Terrain

II.		High Alpine SAR Experiment

Principal Investigators:

I.		Dr. Jeff Dozier
		University of California - Santa Barbara

II.		Dr. Helmut Rott
		University of Innsbruck

Site Description:

	With increasing world population, the demand for further exploitation of the resources of marginal land use areas such as the high alpine zones is growing.  The fragile ecosystems of these areas call for detailed studies of the environmental processes to assess the potential impact of human activities.  Earth observations from space provide closer insights to these processes and establish the basis for better management of renewable and non-renewable resources.  Cloud cover presents a key problem to remote sensing of mountain areas with optical instruments.  Radar is both weather-independent and is sensitive to dielectric and roughness properties of the target areas.  Therefore, radar is a valuable tool in mountainous regions.
	Previous studies have shown the potential of SAR for various applications in high mountain areas (Hall and Ormsby, 1983; Rott, 1984; Rott and MŠtzler, 1987).  To date, spaceborne SAR experiments have been limited to L-band HH (horizontal polarization transmitted, horizontally polarized received) data.  Theoretical and experimental investigations have shown that shorter wavelengths should be more useful for specific applications such as snow hydrology, glaciology, and rock discrimination in alpine areas (Rott et al., 1985; Rott and MŠtzler, 1987).  SIR-C/X-SAR is the first chance to investigate the possibilities of multifrequency and multipolarization spaceborne radar in alpine areas.
	Recognizing the need for improved information on high alpine areas all over the world, we believe that it is crucially important to understand the relations between satellite measurements and physical target properties, and to develop standard algorithms for satellite data analysis.  These goals are best achieved in test areas where extensive field measurements are carried out and proper validation of data analysis methods is possible.
	For these reasons, …tztal in the Austrian Alps has been chosen as a model site for application of multiple parameter SAR in high alpine areas.  Geoscientific investigations have been carried out at this site since the end of the nineteenth century, and various institutes have research stations in the area (Hoinkes, 1968; Kuhn, 1981; Moser and Peterson, 1981, Patzelt, 1987).  A spaceborne SAR experiment was carried out in 1981 (Rott, 1984a; Rott and Domik, 1985).	A map of the test site is shown in Figure 1.  The area, which rises from altitudes of about 1500 to 3774 m is partially covered by glaciers.  The optimum time of the year for the experiment would be mid-June to mid-October.  For a part of the planned investigation, data from the winter period are also required.

Objectives:

I.		a)	Estimate snow-covered area and distribution of snow water equivalence over alpine drainage basins.

		b)	Estimate spectral albedo of snow cover.

		c)	Model spatial distribution of snow surface energy exchange, melt rate and snow metamorphism.

II.		a)	Using surveyed test sites in the Alps, monitor glacier properties, map the seasonal snow cover, map geological and erosional features, obtain topographic mapping from radar stereo imagery, map alpine vegetation and sub-alpine forests.

Field Measurements:

I. 		a)	Validate remotely sensed measurements with intensive snow surveys coincident with SIR-C flights, and with scatterometer measurements at one site.  To insure that results are not site-specific, field and satellite investigations will be carried out at other test sites in different climates including at sites in the Sierra Nevada (California) and Tien Shan (Xinjiang, northwest China).  	

		b)	Use optical sensor data to estimate grain size of surface snow layer and its contamination by absorbing impurities such as dust or soot.  Use these parameters to extend albedo throughout the solar spectrum.  AVIRIS data will be requested for US. sites and Landsat Thematic Mapper data will be used for foreign sites.

		c)	Use parameters measured from satellite or aircraft, local micrometeorological data, and digital elevation grids to drive basin-wide energy balance model of snowpack.

II.		a)	The physical properties and the back scattering signatures of the main targets will be measured on the ground and compared with the multi-parameter SAR signatures. 

		b)	Digital elevation data, detailed thematic maps, and field measurements will be used for data analysis and validation. 

		c)	Airborne  imagery and optical satellite imagery will be obtained for comparison and will be used for generating multi-sensor data sets. 

Crew Observations:

1)	Crew Journal: Describe the snow, vegetation extent, and cloud cover at the site.

2)	Cameras: Hercules and Hasselblad will be used to photograph the snow extent and to obtain stereo images of the site.

Coverage Requirements:

The minimum coverage requirements for the …tztal, Austria test site are two (2) stereoscopic angles.

Anticipated Results:

I.		a)	Evaluation of the capability to model processes in the Earth's alpine snow cover.

		b)	SIR-C measurements of the snow cover will be calibrated with physical measurements of snow characteristics, thus providing excellent data for evaluation of models of the electromagnetic properties of snow.

II.		a)	Improve the understanding of the capabilities of spaceborne SAR for detection of physical properties of the seasonal snow cover and glaciers, and for deriving geological and erosional features;

		b)	Assess the feasibility of extracting information on alpine vegetation and sub-alpine forests from multiparameter SAR data;

		c)	Improve digital methods for thematic mapping of glaciers, snow cover, geologic structures and erosional features;

		d)	Improve methods for high-precision contour and line mapping using radar stereo imagery and assess mapping accuracies;

		e)	Assess the possibility for external radar calibration through backscatter measurements on homogeneous glacial areas; and

		f)	Determine the optimum SAR parameters for future advanced earth observation systems regarding operational tasks in alpine terrain.