Development and deployment of a precision underwater positioning
system for in situ laser Raman spectroscopy in the deep ocean

Sheri N. White,a William Kirkwood,b Alana Sherman,b
Mark Brown,b Richard Henthorn,b Karen Salamy,b Peter Walz,b
Edward T. Peltzerb and Peter G. Brewerb

a: Department of Applied Ocean Physics & Engineering, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
b: Research & Development, Monterey Bay Aquarium Research Institute, 7700 Sandholdt Road, Moss Landing, CA 95039, USA

Deep-Sea Research I (2005) 52: 2376-2389. doi:10.1016/j.dsr.2005.09.002.

Received: 2005 April 5.
Revised: 2005 August 31.
Accepted: 2005 September 9.


ABSTRACT

The field of ocean geochemistry has recently been expanded to include in situ laser Raman spectroscopic measurements in the deep ocean. While this technique has proved to be successful for transparent targets, such as fluids and gases, difficulty exists in using deep submergence vehicle manipulators to position and control the very small laser spot with respect to opaque samples of interest, such as many rocks, minerals, bacterial mats, and seafloor gas hydrates. We have developed, tested, and successfully deployed by remotely operated vehicle (ROV) a precision underwater positioner (PUP) which provides the stability and precision movement required to perform spectroscopic measurements using the Deep Ocean Raman In situ Spectrometer (DORISS) instrument on opaque targets in the deep ocean for geochemical research. The positioner is also adaptable to other sensors, such as electrodes, which require precise control and positioning on the seafloor. PUP is capable of translating the DORISS optical head with a precision of 0.1 mm in three dimensions over a range of at least 15 cm, at depths up to 4000 m, and under the normal range of oceanic conditions (T, P, current velocity). The positioner is controlled, and spectra are obtained, in real time via Ethernet by scientists aboard the surface vessel. This capability has allowed us to acquire high quality Raman spectra of targets such as rocks, shells, and gas hydrates on the seafloor, including the ability to scan the laser spot across a rock surface in sub-millimeter increments to identify the constituent mineral grains. These developments have greatly enhanced the ability to obtain in situ Raman spectra on the seafloor from an enormous range of specimens.

© 2005 Elsevier Ltd. All rights reserved.


Acknowledgements

We thank the officers and crews of the R/V Point Lobos and R/V Western Flyer, and the ROV teams of Ventana and Tiburon, for their skill and support at sea; collaborator John Freeman of Washington University, St. Louis; Jill Pasteris of Washington University, St. Louis for use of the granite sample; the technical support of John Ferreira, Jim Scholfield, Randy Pricket, Duane Thompson, Tom Marion, and Jose Rosal; and the comments of the editor and three anonymous reviewers. Funding was provided by a grant to MBARI from the David and Lucile Packard Foundation.


This page was last updated on 20070510.