There are a number of internet papers available that describe multi-static sonar and the benefits. For example, you may wish to read the following papers:  https://www.researchgate.net/publication/221916141_Advances_in_Multistatic_Sonar or https://apps.dtic.mil/dtic/tr/fulltext/u2/1060262.pdf

Yes, the encapsulation material needs to be taken into account to optimise performance. Encapsulation materials are typically chosen to be waterproof and offer an appropriate level of physical protection for a given application. From an acoustic performance viewpoint, the chosen material would typically be acoustically transparent, i.e. have an appropriately matched acoustic impedance.

It is also important to consider the impact of encapsulation material upon the whole system, for example the impact on flow noise if the encapsulation layer is the final layer (e.g. where no sonar dome is used).

As noted in the webinar, quasi-real data will be important to deliver the 10,000's images that are often needed to train new Machine Learning solutions. The use of Augmented Learning could be considered a use of quasi-real data (e.g. rotations, stretches or flips of images). Another form of quasi-real data is the inject of targets of interest into environmental data - there are two challenges in this:

1. Having a realistic boundary around the injected new data so that it does not look like a pasted-in discontinuity

2. The realism of synthetic data that is mixed with real data otherwise you develop and prove signal processing which is well matched to your simulator but does not work in the real world environment

As discussed in the webinar there could be a limit in that increasing sensitivity may result in you only measuring more noise and hence the true dynamic range of your system becomes more limited.

There are already some data packet formats defined for open systems that have been around for a number of years. However, there is no a universal data packet format recognised by all systems. Even if it was possible to define and agree a universal standard the downside of that approach is that it could actually stifle innovation because technology develops so fast. The important criteria is that open systems use an open data format that is published to relevant manufacturers.

There are two parts to this question:

1. An 'open' communication mechanism which can be used by anyone - for example, use of the OMG's Data Distribution System (DDS)

2. The ability to understand the format and content of data being passed over the communications link

Both aspects are important to avoid any supplier lock-in. OMG has developed the OARIS data format which is a step forward to having an open high level track interface for systems, but as yet no lower level 'raw' common data formats are defined possibly due to each system having its own system-specific data characteristics.

The domain is facing an interesting skills diversity challenge. Whilst Navies move to increasing adoption of uncrewed/autonomous systems, there is an increasing need to have staff who are skilled in systems-of-systems development, integration and testing - these appear to be new and developing skills in the market place. Understanding acoustics combined with autonomy behaviours arises the debate about whether the sensor or platform is driving the priorities in the solution - does the sensor or "taxi" take priority? However Navies are not stopping use of major assets, so there remains the need to have staff who are end-to-end "sonarists" - it can take 10+ years to develop someone who can act as a subject matter expert Design Authority for major sonar systems. Whilst suppliers are increasing use of COTS components there is a skill in selecting and understanding limitations of COTS hardware - and this is not just performance as some suppliers ban some hardware components from being used in military systems.

Directionality is a key component of any Sonar system whether achieved from the array itself or in combination with beam forming. Vector sensors are certainly a useful means to achieve directionality at source. Various forms of vector sensors have been around for many years and are already in use in operational systems at sea. There are a number of suppliers producing innovative vector sensors which have potential application in both current and future systems. Vector sensors may have application in uncrewed systems, for example, where space, weight and power are at a premium i.e. they have the potential to offer an efficient means of delivering the required directionality and associated performance. Directional sensors need to be considered as part of an holistic system design to ensure optimum overall trade-offs. For example vector sensors triple the amount of data processing and digitisation hardware needed - and in power-limited environments (such as uncrewed systems) does the performance benefit of a vector sensor provide more capability than the reduced range from the increased power demands.

The use of a specific type of piezo-electric material in a sensor should be considered as a complete system. The decision to use, what can be more expensive, single crystal material needs to understand what characteristics are being sought from the material, e.g. power draw or wider bandwidth. The same will apply to new ceramic formulations whether this be textured or porous ceramic. At a system/product level customers need to understand whether the cost verses performance of new materials is something that value-for-money assessments and budgets allow. Customers demanding higher performance solutions that can only be delivered through advanced materials (such as single crystal) will create the market pull necessary to allow the commercialisation of such technologies.   

The panel agreed that additional sensors types are of benefit and that multi-sensor processing across traditional sensor system boundaries are challenges for the future.