CICEET Progress Report for the period 9/01/01 through 3/01/02

Project Title: An Autonomous Profiler for Estuarine Research and Monitoring
Principal Investigator(s): Rocky Geyer, Daniel Frye, and Kenneth Doherty

Accomplishments
The objective of this development project is to design, build and deploy a general purpose estuarine winch that can perform hourly profiles of the water column with a standard sensor suite for several months. The sensor module is equipped with an RF link so that data can be delivered to shore on a periodic basis.

During the August 01 to January 02 time period, the underwater winch was tested at the Woods Hole dock using a non-instrumented buoy in place of the buoyant sensor module. These tests were successful and verified the operation of the winch motor, controller and software. Tests were performed to simulate various environmental conditions to determine the response of the winch system in modest waves and currents. These tests, while not extensive, did give us confidence that our approach to mitigating the effects of waves and currents on the winch operation would work successfully under a range of conditions. The bench and dock tests verified our initial estimates for the number of profiles that can be performed by the winch with the present battery pack. Our goal is hourly profiles in up to 20m of water for periods of up to two months.

The sensor module was designed during this period with a Seabird CTD (with pump) as the primary sensor. The buoy has a plastic frame and rigid PVC foam flotation to provide about 10 Kg of net buoyancy. The CTD is positioned horizontally on one side of the float and the controller and RF link are housed in a similar plastic tube on the other side of the float. The sensor module design is shown in the drawing below (Figure 1). We are in the process of building the buoy and hope to have it ready for an initial field trial in Winyah Bay, South Carolina in early March. The March trials will be conducted with the sensor module controller, but without the RF link. Our initial plan was to use an Orbcomm RF link, but because Orbcomm is in financial difficulty and may not be operating in the future, we have decided to use an Iridium link instead. We are waiting for delivery of the Iridium equipment at the moment and hope to have it integrated in time for a scheduled May trial in the Hudson River estuary.

The underwater winch system consists of three basic mechanical units: a battery/electronics housing, turning block and an electric motor driven winch. These mechanical units are packaged in a welded frame constructed of 1.6-cm diameter stainless steel rod. The frame measures 90cm long, 50cm wide and 41cm high. The complete package weighs 95.0 kg in air and 45.0 kg in water.

The battery/electronics housing is machined from 30.5cm o.d. by 2.5cm wall 6061-T6 aluminum tubing and the end caps are machined from 2.5cm aluminum plate. The housing and endcaps are hard coat anodized with zinc anodes attached to both endcaps to mitigate seawater corrosion. The housing contains the battery pack (210 alkaline D-cells), a controller (Onset TattleTale 8), power supplies and necessary electronics. This battery is more than adequate to do hourly profiles in 20m of water for 60 days. The front-end cap has two electrical penetrators, one to power the winch electric motor/brake and one for programming the system before deployment. The housing is attached to the frame by rubber covered stainless steel u-bolts.

We chose not to use active level winding to mitigate the potential effects of biofouling. Instead, we are relying on a small cable fleet angle to maintain even level winding. To accomplish this we placed a turning block 50cm from the winch drum, which reduced the fleet angle to 2.5 degrees. This block is machined from wear resistant plastic and uses Torlon balls for the bearing. The turning block is mounted to the frame and is allowed to rotate to align with the direction of current.

The plastic winch housing contains a 150-Watt electric motor, a 100:1 ratio gearhead and an electric brake. Since the brake cannot work reliably in oil, we are running these components in air. A stainless steel shaft sealed by an o-ring connects the gearhead to a plastic drum that holds 30m of 7/64 diameter Spectra line. This unit is securely bolted to the frame.

Tasks and activities for next reporting period
We have four tasks to complete in the final reporting period. First, we need to verify the performance of the winch, winch controller and sensor module operation in Winyah Bay. This is a one-week test scheduled for early March. Second, we need to integrate the RF link into the sensor module and test it on the bench and at the dock. Third, we plan to demonstrate the complete winch and sensor system during a May Hudson River deployment. Finally, we will document the results of the development and the field trials. An abstract has been submitted to the International Association for Great Lakes Research (see: http://www.iaglr.org/conference/conference.html) and a paper will be presented on the winch development at the June 2002 conference in Winnipeg. We are a few months behind our initial development plan, but if we are successful in the March and May field tests, we should be back on schedule.

Expenditures
We have expended about 71% of the project funds to date. This amount is consistent with the progress made to date.