Operations in challenging environments

The application of AUV technology for exploration and investigation is moving into new environments. This valuable technology has improved our ability to accomplish nearbottom surveys in the open ocean. Now the needs of new users are necessitating adaptation of AUV technologies to a variety of interesting and challenging underwater environments. Under-ice missions promise to open the important polar regions to the observational power of autonomous platforms (Kunz, et al., 2008) (McEwen, Thomas, Weber, & Psota, 2005). Obviously navigation under-ice is very important to the safety of such mission; the AUV must be able to return a safe region for recovery. Possibly not so obvious are the challenges presented by the acoustics of under-ice environments. The upward refracting acoustic environment can create shadow zones, restricting the means of communication and positioning. Furthermore the ice cover can shift at significant speeds relative to the seafloor, creating dynamic environment for navigation (von der Heydt, Duckworth, & Baggeroer, 1985) (Deffenbaugh, Schmidt, & Bellingham, 1993).

Another environment that presents new challenges for AUV operations is coastal zones. The littoral zone has been recognized by military users as a key new frontier for operations. Similarly, environmental assessment of shallow marine environments (e.g., coral reefs) is pushing AUV missions towards the coast. From a navigation perspective, these shallow water environments can be more dynamic than the deep ocean with increased multipath and high background noise from breaking waves and other disturbances. A last example of new environments for AUV operations is the exploration of freshwater caves, cenotes, using novel AUVs. Research expeditions have used three dimensional SLAM-based to map these underwater caves. Interestingly, these expeditions are supported by resources for space exploration because of the analogy between cenote exploration and the environment operators anticipate for autonomous exploration of other planets (Kumagni, 2007).

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