C & C Technologies, Inc. of Lafayette, Louisiana is spearheading a technical research program to advance the state of the art regarding under ice Autonomous Underwater Vehicle (AUV) survey operations. This program, funded by Shell Offshore, Inc., focuses on five areas of research, which include:.
Remote Stations for AUV Navigation and Communication,
AUV Net Recovery,
AUV Recovery by ROV,
AUV Upward Looking Multibeam Sonar, and
AUV Whale Avoidance.
Form factors for the remote stations were developed following the evaluation of the potential hardware components and an examination of AUV mission requirements. Analysis was performed to determine how best to utilize the remote stations to gain the maximum utility of an AUV under the ice. Two methods for facilitating the recovery of an AUV under ice were examined:
recovery by a deployed net and
recovery by an ROV.
Net recovery research involved the construction of a full-scale prototype to deploy through a hole in the ice, extend, and capture the AUV. Research into ROV recovery under ice included developing a methodology to hold the AUV in place so it could be captured by the ROV. This involved the evaluation of several scenarios, which included securing the AUV to the sea floor with a drop anchor and making the AUV negatively buoyant with either a floodable ballast tank or by the release of syntactic foam. Research into the integration of an upward looking multibeam involved the analysis of currently available systems. A comparative analysis of power consumption, size, weight, and software interfacing of the potential candidate systems was performed. C & C collaborated with Kongsberg Maritime about the potential to enhance the HUGIN AUV's embedded obstacle avoidance system for whale avoidance. This paper provides details on each of these five areas of research and details the scope, methodology, findings, and resulting recommendations.
In 2009 Shell Offshore, Inc. entered into discussions with C & C Technologies, Inc. to evaluate the feasibility of applying AUV technology to Arctic mapping operations. The objective is to develop technology to allow operations within Shell lease blocks in the Beaufort and Chukchi Seas offshore Alaska during periods of ice cover. Capabilities would include the supply of positioning updates to the AUV while operating under the ice, communications with the AUV while under ice, retrieving the vehicle from under ice (both disabled and under direct control), mammal avoidance, and integration of upward looking sonar to measure ice thickness and study its morphology. These enabling technologies are not currently integrated into routine commercial AUV operations.
The purpose of remote stations is to reduce the risk of losing the AUV and to improve mission performance. Remote stations can provide AUV communications, positioning updates, command and control, or any combination thereof (Figure 1). The cost, complexity, and size of each remote station will vary depending upon the capabilities required.
The least sophisticated remote station is a "listen only" station. It would passively monitor AUV status acoustically broadcasted either automatically at regular intervals, only when interrogated, or in a combination. This remote station would have an Acoustic Data Link (ADL) to receive the AUV acoustic data, which would then be converted to RS-232 serial data. The serial data would be fed into a data telemetry radio and transmitted to the AUV Base of Operations.