Pulse Heavy and Light test moorings as deployed, October 2008

Pulse Light and Pulse Heavy are two test designs deployed to help us learn about what would be the best platform for our instruments. The main difference between Pulse Light and Pulse Heavy is that Pulse Heavy has an extra 450 m of wire and a water filled damper at bottom of the top section of the mooring. To make up for this Pulse Light has a taller bottom section. The water damper on Pulse Heavy adds inertial mass to the lower part of the top section, and because of the rubber elements higher up this mass helps to better isolate the instrument package from accelerations due to wave action on the surface float. The other benefit of having the the extra weight in the bottom of the top section is that it keeps the mooring more upright. As you can see in the figures below the schematics Pulse Light runs the risk of being completely stretched out due to current. If a wave slams the surface float when the mooring is stretched out completely the rubber elements could fail.

Pulse light's advantages are; less drag (as it has a smaller subsurface profile), and less stress on the rubber element due to not having that inertial mass.

By looking at the engineering data returned from these 2 moorings we hope to derive a final design that we can instrument with a number of Biogeochemical sensors for deployment in October  2009.

Click here to read report about this deployment.