Passive Remote Sensing of Lake Ice and Snow using Wideband Autocorrelation Radiometer (WiBAR).

Abstract

Snow cover plays a vital role in providing the water supplies for domestic, industrial, and agricultural purposes. Conventionally, differential scatter darkening technique is used to detect the snow thickness. This technique is region specific and depends on the statistics of snow grain sizes. Ice formation process and ice thickness monitoring are important parameters in analyzing the overall pressure exerted to the off-shore structures such as wind farms. The traditional method for measuring the lake ice thickness is by a cumbersome drilling process through the ice. For future in-situ or remote planetary applications, the detection and analysis of ice sheets on or near the surface is one of the primary objectives of many planetary exploration missions. These applications demonstrate the requirement for an accurate remote sensing instrument, which can estimate the ice thickness without disturbing or breaking the ice. In this work, a novel microwave remote sensing technique to accurately estimate the thickness of any layered low-absorbing media including snow pack and fresh water ice using wideband autocorrelation radiometer (WiBAR) is presented. This technique relies on finding the autocorrelation response of the upwelling brightness temperature. The autocorrelation response provides enough information to estimate the microwave travel time delay of the doubly reflected thermal emission between the top and bottom interfaces an consequently the thickness of the snow or ice layer can be obtained. Several post processing techniques are developed to capture the periodicity of the ripples in the power spectral density domain. These techniques are capable of detecting very weak ripples deeply buried under noise. A compressive sensing based algorithm is also developed for detecting the thickness of ice/snow layers using 1/10 of the Nyquist rate samples. We have successfully designed, implemented, and tested a handheld ground base ice/snow thickness sensor in the frequency range of 1-3GHz or 7-10GHz under several scenarios including snow on top of undulated and vegetation covered terrain, ice over the lake water, air gap above a water surface and below a dielectric sheet, and snow cover under the forest canopy in the presence of radio frequency interference (RFI) with accuracy of within 1.5cm.