Experimental Observations of Two Mountain Glaciers on the Eastern Slope of Mt. Tsurugi by Pi-SAR2 Airborne SAR

We performed airborne synthetic aperture radar (SAR) observations at two glaciers (San’nomado and Komado glaciers) on the eastern slope of Mt. Tsurugi, Japan, in August and October 2013, and August 2014. The Pi-SAR2 system used in this study consists of two X-band SAR antennas. Taking advantage of single-pass interferometry, we have generated digital elevation models (DEM) at each epoch. Differencing the DEMs at August and October 2013, the elevations at the glaciers were reduced by ~20 m or more with errors on the order of ~20 m or more. As we could visually identify the reduction in the snow-covered areas in the SAR images of August and October 2013, those changes are attributable to seasonal melting of the snow but are apparently overestimated. Full polarimetric observations were also performed, indicating significant changes over the glaciers from August to October that were largely due to the reduction in snow cover. We could further identify localized spots that indicated strong intensity in the cross-polarized HV channel (transmission of vertically polarized wave and reception in horizontally polarized channel) over the glaciers. Bright HV signals are unexpected, because HV signals are often interpreted as volume scattering and appear to originate from the inside of the glaciers that are unlikely in the X-band SAR system; no penetration deeper than 1 m is expected in the X-band over the snow/ice areas. We interpret the apparent HV signals as due to double bouncing from both sides of the valley, which were apparently imaged over the glaciers.