Reliability of two REMUS-100 AUVs based on fault log analysis and elicited expert judgment

Reliability is especially important for autonomous underwater vehicles (AUVs) that have made the transition to operational use. However, in contrast to the unmanned air vehicle community, there has been little sharing in the open literature of detailed fault histories of commercial AUVs from which an assessment of their reliability can be made. In this paper, we declare the fault history of two REMUS-100 AUVs manufactured by Hydroid Inc. and operated by the Center for Coastal Marine Sciences at California Polytechnic State University. The data set contains the faults and incidents recorded from 186 missions between 5 November 2003 and 14 January 2009. Interaction between the faults or incidents with the AUV and the operating environment complicate matters when it comes to estimating probability of loss. Through a formal process of eliciting expert judgment the paper provides optimistic and pessimistic estimates of loss of the REMUS vehicles in open water, coastal, under sea ice and under ice shelf operations. Vehicle-specific risk mitigation methods are explored, and recommendations made for reviewing the fault history data using behavioural aggregation through interaction among a group of experts rather than simple mathematical aggregation as in this paper.