The early October deployment from the Aurora Australis of two test designs for Pulse went well despite the usual rough weather in the Southern Ocean. The aim of these deployments is to test and learn about the mooring dynamics, stresses and efficacy of our current designs. The Pulse project requires long deployments in the deep ocean in one of the roughest environments in the global ocean, and presents a number of design challenges.
The photo on the right shows some important elements of the Pulse mooring.
The big yellow foam donut is the surface float which supplies plenty of buoyancy to ensure that the top of the our mooring stays on the surface, even during rough weather. This modular float system, designed by Danny McLaughlan, will be used for many of the IMOS moorings. In the centre of the yellow donut is a stainless steel can that holds batteries and electronics including a telemetry/logging system developed by Matt Sherlock and Dave Hughes. The Iridium satellite antennas are protected from the slamming of the waves by transmitting right through the plastic lid of the can. 12 days after deployment, we are successfully receiving GPS locations and, for the first time, getting a subset of mooring tension and surface motion data. This should lead to a great leap forward in our understanding of Pulse mooring dynamics even if the mooring fails.
The black steel object with the red ball attached is a mock up of the cage that will hold the water sampler and biogeochemical sensors when the fully instrumented Pulse mooring is deployed. This mock up is a stand in for the real payload of the Pulse mooring.
On the lower right of the photo you can see two strands of rubber. These are the rubber elements that isolate the water sampler sensor/sensor package from some of the jarring due to wave action on the surface float. (Go to Facilities/SOTS/Implementation page for a schematic of the mooring.) The design challenge for Pulse is not only to create a surface mooring that can endure the Southern Ocean but one that dampens the accelerations the surface float experiences enough so that the water sampler and biogeochemical sensors can function and survive long deployments.