Vol. 4, No. 2, 171-178, 2005

Abstract
The feasibility of retrieving changes in the depth of snow cover by means of the LISA (LInear SAR) Ground-Based Synthetic Aperture Radar system has been investigated. The LISA instrument consists of a computer-controlled sledge moving along a linear axis 5 m long, a set of transmit and receive antennas, a network analyzer, and a C-Band amplifier. All the equipment is installed inside a temperature controlled container. The centre frequency used in the measurement campaign is 5.83 GHz (C-band), with a 60 MHz bandwidth. The resolution of a single SAR image is in the order of 6 m in azimuth and 2.5 m in range, while in the interferometric mode, the range resolution in the coherence images is below 2 mm in the line-of-sight direction. Typical image products of LISA are similar to those of space or aerial radar missions. The only particularity of LISA is that the image covers a much smaller area (a few square km). However, it has the advantage of providing images at a much larger acquisition rate (about some tens in a single day). Over several weeks this amounts to a very large time-series of radar images that gives the opportunity to assess the feasibility of using a GB-SAR (Ground Based Synthetic Aperture Radar) system to monitor structural changes of the snow cover. The availability of a sensor network and meteo stations on the slope gives the possibility of validating the retrieval scheme.

The retrieval techniques that are going to be assessed will be those previously developed for space-borne and air-borne SAR imagery. The two principal indicators of the structural changes in the snow cover are the interferometric phase and the coherence. Using the data acquired by the ground sensors, an inversion scheme to monitor the snow cover depth has been calibrated with available ground-truth data for various temporal windows spanning a few days. The results prove the linear relationship between the interferometric phase and the snow depth when the acquisition conditions permit a high coherence, confirming the potential use of a GB-SAR system to monitor the snow cover.

ISSN 1729-3782