Testing Sequoia’s LISST-Holo on an Autonomous Underwater Vehicle
[Sequoia, Updated Sept 2, 2014, text and pictures supplied by Dr. John Ryan, MBARI]
The Monterey Bay Aquarium Research Institute (MBARI) tested Sequoia’s LISST-HOLO sensor in April 2011, during a coastal oceanography study in Monterey Bay, California. The experiment was part of a project that is advancing ocean observing systems, of which autonomous underwater vehicles (AUVs) are an essential component. MBARI’s AUV advancements — contributing to observing system capabilities — include longer endurance, enhanced onboard decision making, intelligent sample acquisition and return, autonomous coordination of multiple AUVs, and augmented sensing for interdisciplinary research. The April experiment provided an opportunity to test how LISST-HOLO may augment sensing capabilities for interdisciplinary research with AUVs.
The study region is strongly influenced by wind--driven coastal upwelling, which supplies cold, nutrient--rich waters to the bay and promotes the growth of microscopic algae (Figure 1).
Figure 1. Experiment description. The map (left) shows a filament of upwelled water extending across the mouth of Monterey Bay. The boxes in the track of AUV Dorado indicate frontal locations identified by AUV Tethys (frontal position changed with time). Vertical sections of water column properties (right) are shown for the upper 40 m along the Dorado survey track.
The April experiment utilized two AUVs in efforts to map and sample the different water types and the boundary (front) between them. AUV Tethys, a long--endurance AUV, autonomously monitored frontal locations and provided this information to AUV Dorado, which was equipped with a water sample acquisition system and a larger sensor payload, including LISST-HOLO. The AUVs described environmental and biological changes influencing the detection of microscopic life by a moored autonomous molecular analytical device, the Environmental Sample Processor (ESP, see map in Figure 1).
LISST-HOLO was deployed on AUV Dorado. Plankton diversity imaged by LISST-HOLO during the survey shown in Figure 1 is illustrated in Figure 2. A key research goal of the experiment synthesis is to understand the different plankton populations that develop in different water types as well as the frontal zones between them. For this purpose, information from LISST-HOLO images is being integrated with data from other AUV sensors (Figure 1), as well as results of molecular analysis of water samples acquired by the AUV.
Figure 2. A LISST-HOLO diversity montage from the Dorado AUV survey shown in Figure 1.