The PIs request funding to build on and maintain Scripps' world-class shallow-water subbottom imaging and multibeam mapping capability. Toward this goal, we are collaborating with Florida Atlantic University, and Edgetech to build the next generation synthetic-aperture-sonar (SAS) CHIRP, and integrate this subbottom imaging system with a narrow-beam RESON SeaBat 7125 shallow-water, pole-mounted swath bathymetry and backscatter system. These imaging systems will form the backbone of Scripps' shallow-water instrument pool, which will be made available to the U.S. research and education community.
The next generation CHIRP system will significantly improve penetration, spatial resolution and dynamic range of subbottom imagery. The combination of synthetic aperture processing, receiving array geometry and projector advances is expected to improve subsurface penetration by at least a factor of 4 over conventional CHIRP sonars. The SAS-CHIRP system will also suppress surface multiples using beam forming and the wing elevation angle, providing even greater "true" depth penetration in the shallowest of environments. Increased penetration will be achieved without increasing sound output level, which has obvious environmental benefits. The multibeam system will be deployed on a pole mount for use on multiple vessels, giving greater flexibility for use with small ships, operating in shallow waters. This system provides high-resolution coverage of the seafloor with 256 focused 0.5 x 1° beams (400 kHz) and yields 130° swath coverage (4X water depth) in water depths ranging from 1 - 200 m.
Broader Impacts:
The proposed system should offer a big leap in seafloor and subsurface mapping capability applicable to a range of tasks including geohazards and tsunamic issues. Driscoll has a good track record of involving students in his work and this should result in the training of the next generation of high-resolution subfloor mappers. Driscoll also has an excellent record of offering undergraduate training and will no doubt use the tools proposed here for these efforts too. Being able to resolve fine-scale, three-dimensional structures in complex sediment stratigraphies is a capability that will benefit a wide range of science. The integration of a portable swath mapping system to the existing SUBSCAN capability at SCRIPPS would be an important regional capability for fundamental mapping, and time-series imaging of high-priority areas. If the SAS CHIRP succeeds in increasing the penetration and resolution of subbottom data as well, the capability will be even more heavily sought after and advance research programs in a number of fields including, benthic habitat studies, coastal change, vulnerability of coastal zone to catastrophic hazards (earthquake and tsunami), sediment transport mechanics, sedimentary process studies linked to the NSF Margins program (Source-to-Sink comes to mind), and varied interests of the State(s) in environmental studies of nearshore areas.
