Abstract
This work describes the first global scale assessment of a Global Navigation Satellite Systems Reflectometry (GNSS-R) experiment performed on-board the Soil Moisture Active Passive (SMAP) mission for soil moisture and biomass determination. Scattered GPS L2 signals (1227.6 MHz) were collected by the SMAP’s dual-polarization (Horizontal H and Vertical V) radar receiver and then processed on-ground using a known replica of the GPS L2C code. The scattering properties over land are evaluated using the Signal-to-Noise Ratio (SNR), the Polarimetric Ratio (PR), and the width of the waveforms’ trailing and leading edges. These parameters show sensitivity to the effects of the Earth’s topography and Above Ground Biomass (ABG) even over Amazonian and Boreal forests. These effects are shown to be an important factor in precise soil moisture and biomass determination. Additionally, it is found that PR shows sensitivity to soil moisture content over different land cover types. In particular, the following values of the PR are found over: (a) tropical forests ~−1.2 dB; (b) boreal forests ~0.8 dB; (c) Greenland ~2.8 dB; and (d) the Sahara Desert ~3.2 dB.
Highlights
The concept of multistatic scatterometry was proposed by Hall and Cordey in 1988 [1]
Recent airborne [21] and stratospheric balloon [28] flight experiments have been performed using new instruments and circular polarization antennas (RHCP and LHCP) for geophysical parameter retrieval over land surfaces, and wetlands. These experiments have shown the capability of Global Navigation Satellite Systems Reflectometry (GNSS-R) techniques for wetlands monitoring even from high altitude platforms (~27 km) [28] because of the high spatial resolution provided by the coherent component of the scattered field
This study presents results from a serendipitous GNSS-R experiment performed on-board the Soil Moisture Active Passive (SMAP) mission [29] over continental areas
Summary
The concept of multistatic scatterometry was proposed by Hall and Cordey in 1988 [1]. Global Navigation Satellite System (CyGNSS) GPS L1 C/A code-based constellation was recently launched on 15 December 2016 [17], providing an unprecedented sampling of the Earth’s surface. Recent airborne [21] and stratospheric balloon [28] flight experiments have been performed using new instruments and circular polarization antennas (RHCP and LHCP) for geophysical parameter retrieval over land surfaces, and wetlands These experiments have shown the capability of GNSS-R techniques for wetlands monitoring even from high altitude platforms (~27 km) [28] because of the high spatial resolution provided by the coherent component of the scattered field. This study presents results from a serendipitous GNSS-R experiment performed on-board the SMAP mission [29] over continental areas This unique data set, which provides very high-gain GPS.
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