Wideband Interferometry in Synthetic Aperture Sonar

Abstract

is a principal scientist at FFI, while Andreas Austeng is a professor at UiO. I am employed at FFI, where I started in 1998 after receiving my degree of Cand. Scient. in Physics from the University of Bergen. The work on the thesis was conducted as a part of my job over the years 2011 -2021, and was funded by FFI's projects on synthetic aperture sonar (SAS). These SAS projects have been run and financed through a collaboration between FFI, Kongsberg Maritime and the Royal Norwegian Navy. This thesis includes a collection of five papers, placed and presented in a larger common perspective. I first place the title topic of "Advanced SAS" in a greater context. Then I present each of the individual papers, and give an updated review on their topics. I follow up with a discussion on my contributions in a greater perspective, before I summarize my findings and conclude.

Repeat-Pass Synthetic Aperture Sonar Micronavigation Using Redundant Phase Center Arrays

“…Again, the results are shown at a slant range of 85 m with similar results being observed at the other ranges. Furthermore, the other interpass ping pair combinations, denoted by · (12) p−1,p and · (21) p−1,p , yielded similar values. Obviously, the intrapass values · (11) p−1,p and · (22) p−1,p are identical to those computed previously.…”

“…The coherence values are shown in Fig. 5(a) for the directly corresponding interpass ping pairs denoted in Section II-B by · (12) p,p . The number of overlapping phase centers in the direct interpass pairs varied between N/2 = 18 (near a ping offset transition) and N = 36.…”

“…We denote these estimates using the superscripts · (12) and · (21) for estimates from the first pass to the second pass and vice versa, respectively. Assuming, as before, that only adjacent ping pairs have RPCs, three additional RPC arrays can be formed between the passes, yielding the estimates Δx (12) p,p ,Δθ (12) p,p…”

“…where the correlation function Γ is defined by (8) and the superscript · (12) denotes the interpass correlation.…”

“…These include coherent change detection [11] and repeat-pass interferometric bathymetry estimation. Although interferometric SAS [12] and repeat-pass interferometric synthetic aperture radar [13] are widely used, repeat-pass interferometric SAS is still in its infancy. Coherent repeat-pass processing adds further challenges to the navigation problem since navigation errors can accumulate substantially between passes and temporal and angular changes can act to reduce signal coherence.…”