The ocean's midwater realm is the next frontier for underwater robots. The mesopelagic or "twilight" zone encompasses depths from 200 to 1000 meters where sunlight is dim. This vast region plays a key role in regulating ocean chemistry and biology, which in turn strongly effects global climate. The mesopelagic zone holds much of our planet's fish populations as well as poorly understood processes that couple the ocean surface to the seafloor including vertical fluxes of plankton, organic and inorganic particles, bubbles, and droplets. Mesopelagic features are often mobile, patchy, and ephemeral, so surveys and sampling can be very difficult. Recent studies have found that mesopelagic biomass including fish are dramatically underestimated, yet investigations of patterns and processes in this region are strongly constrained by available technology.<br/><br/>This program will produce a unique new robot that will enable unprecedented scientific access to midwater environments, complementing existing survey and sampling tools. The robot will use cameras, lights, and oceanographic sensors to autonomously track slow-moving individual targets such as migrating mid-water animals, descending particles, and rising bubbles and droplets without disturbing those targets. It will also have the ability to detect and follow fine-scale oceanographic features such as thin layers that hold critical nutrients. Finally, the robot will take samples utilizing on-board intelligence to determine precisely when and where to sample. Under this program, the robot will be built and tested under a collaboration between the Woods Hole Oceanographic Institution, the Monterey Bay Aquarium Research Institute, Stanford University, and the University of Texas Rio Grande Valley.