Best Practices Guide for AUV Polar Operations

AUV Mission Planning

The planning phase is the activity which precedes the deployment of the AUV. In this phase, the manner in which the AUV will be operated is determined. Aspects that may be included include the integration of new mission or payload sensors, the acquisition of spare parts for the vehicle or the payload, logistic and mobilization planning or how the shipment is going to get to the ice and into the water, mission simulation, issues related to insurance for personnel and the vehicle, and finally environmental issues.

All of these aspects need to be considered to some degree when planning any underwater vehicle mission. The principle differences with polar operations are that the areas of operation are generally very remote and that some form of ice cover is generally present. The remote nature of the operations makes communications with outside agencies sporadic. Re-supply is generally very costly and time consuming, and there may be periods where weather precludes any such operation.

This environment provides its own challenges to the AUV operator. Generally speaking, it is not a suitable environment for testing new equipment or concepts. Consequently, planning often involves the testing of such equipment and integrations in open water prior to a deployment. There may be instances in which the operator feels that it is too risky to carry a particular piece of equipment in the AUV during a polar operation.

The condition of the ice surface will be fundamentally important where Ice-Based missions are concerned. The thickness must be studied from a safety perspective, as well as from the perspective of having to make a hole through which the AUV can operate. Other holes for remote communications and positioning may also be required, and as these are likely to be smaller, they will require some plan to ensure that they do not freeze over.

Ice cover also alters the environment in which the vehicle operates. Because of the ice cover and the absence of sea state and shipping, acoustic conditions are likely to be much better than in open water. The downside of this is that the ice cover is going to create more severe acoustic multi-paths in shallow water. These factors need to be considered in planning missions and if possible, acoustic data from prior missions in the area should be referenced. For Sea-Based operations, the mission will encounter the same conditions under-ice, however at the interface, conditions may be significantly worse.

Environmental and weather data may not be as accurate or as frequent as it is in other parts of the world. Local knowledge may be an important source of information.

The conduct of operations in areas of ice cover also dictates that some plans exist in the event that the vehicle is lost or becomes disabled. Such a plan may require the availability of specialized rescue equipment.

In the event that the operator wishes to obtain insurance to cover loss of the AUV, the underwriter will look for evidence of a rescue plan. In addition, a fault-tolerant design and a well thought out fault management strategy may reduce the premium.

Best Practice for Planning AUV Missions Under-Ice

In many cases, environmental regulations are developed specifically for polar regions, and these should be fully understood prior to the commencement of operations. These regulations may include provisions for dealing with polar wildlife.

The remote aspects of most polar operations dictate that all of the equipment and spare parts needed to support the operation be acquired and taken to the site. New equipment integrations and new procedures should be thoroughly tested in open water. Consider limiting the use of particularly risky equipment or procedures.

Planning should consider in detail the ice conditions and their probable impact on

  1. the safety of an ice-based camp, if applicable,
  2. the ability and time required to make ice holes, and
  3. likely acoustic conditions and their impact on the range of acoustic telemetry as well as sonar sensor coverage.

Future weather conditions may not be accurately predicted, and the best practice is to seek out local knowledge as a secondary source for planning polar operations.

Careful attention should be given to the design or design modification of the vehicle such that it is tolerant to sub-system failure and capable of managing fault. A fully thought out rescue plan is necessary.

© 2007