Antarctic ice tomography with airborne MIMO synthetic aperture radar

• Main Author: Arenas Pingarrón, Álvaro
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UCL (University College London) 2020
• Subjects: Antarctic; The Antarctic; Filchner Ice Shelf; Antarc*; Antarctica; British Antarctic Survey; Ice Shelf; Ice Shelves
• Online Access: https://discovery.ucl.ac.uk/id/eprint/10116231/6/AlvaroArenasPingarron_Thesis_postVivaCorrections.pdf; https://discovery.ucl.ac.uk/id/eprint/10116231/

The aim of the thesis is the software processing of data acquired by PASIN2 (Polarimetric Airborne Scientific Instrument, mark 2). It is a 150-MHz coherent pulsed synthetic aperture radar (SAR) for 3D imagery beneath the ice thickness of the Antarctic, designed and operated by the British Antarctic Survey (BAS) to map the overflown regions of the continent in a single pass. In conventional single SAR imaging (2D), along-track and range coordinates are obtained. For 3D mapping, the remaining across-track angle dimension is estimated after processing several SAR images, exploiting the multiple-input multiple-output (MIMO) capabilities, with 8 underwing elements (4 below each wing) switching between transmit- and receive-modes, and 4 receive-only below the fuselage. The array is non-uniformly distributed along the wing orientation, perpendicular to the aircraft trajectory. Using Matlab® software, the off-line processing of PASIN2 data consists firstly in amplitude, phase and delay calibration of the different channels; secondly, single SAR imaging resulting from Backprojection algorithm, assuming homogeneous ice medium, and electromagnetic propagation based on refraction and diffraction according to the surveyed area; and finally, the direction of arrival estimation, by combining the available images and applying a high-resolution non-linear technique called MUSIC. To deal with the spatial distribution of PASIN2 array, a pre-processing has been implemented to improve MUSIC outputs. The results lead to 3D map estimations of the bedrock, ice-water interface or subglacial channels, correcting the topography regarding models in which a vertical direction of arrival was wrongly assumed. These observations will be used by environmental scientist to design, optimise or validate climate models. The thesis is framed within a major project of the Natural Environment Research Council (NERC) called ‘Ice shelves in a warming world: Filchner Ice Shelf System, Antarctica’ (NERC reference NE/L013770/1), in which UCL and BAS ...