Advancing Underwater Communication via the mini-PANDA
28 February 2010
"Suppose you want to recover the system at an earlier time than that of the programmed time, you can send an acoustic command to the buoy and then it operates the release mechanism and the system pops up on the sea surface. It is more flexible that way and one still has a back up time release operation in case the acoustic commands were not successful."
Dr Venugopalan Pallayil, Deputy Head of Acoustics Research Laboratory and Manager (Operations) at the Tropical Marine Science Institute.
Mini-PANDA: Dr Pallayil with the mini-Pop-up Ambient Noise Data Acquisition system
Recording and retrieving underwater data is now easier through the use of mini-PANDA or mini-Pop-up Ambient Noise Data Acquisition system. Developed by the Acoustic Research Laboratory (ARL) of the NUS Tropical Marine Science Institute (TMSI), the mini-PANDA is mainly used to collect underwater sounds, man-made or natural. It is the first electronic product by TMSI to have been licensed for production to ST Engineering (InfoComm).
Elaborating on the mini-PANDA's applications, Deputy Head of ARL and Manager (Operations) at TMSI, Dr Venugopalan Pallayil said that in Naval sonar operations, it is useful to know the type and level of noise that may interfere with the system so that the operator can take appropriate measures to combat their effects. These noise characteristics depend on the sea environment and can vary from place to place. The mini-PANDA can record such noises and the results of analysis of these data provide enough input for experienced sonar operators to re-adjust the parameters of their sonar system for a better detection performance. TMSI has been working on collecting ambient noise data and building a database which could be useful for scientific applications. Recently, a variation of this equipment had been used as communication nodes for creating an underwater network.
The mini-PANDA is unique in that once it is deployed to the seabed, researchers can still "talk" to the system through acoustic commands. Explaining how the mini-PANDA works, Dr Pallayil said: "One can program the system for a specific period and frequency of recording through acoustic remote control. ARL has built a graphic user interface through which the user could do just that." In fact, the mini-PANDA system is capable of recording data continuously for 54 hours unattended!
The mini-PANDA system is built around a modified fiobuoy® system manufactured by an Australian company namely Fiomarine® and used in underwater mooring applications. The initial idea of using these buoys for underwater recording applications was conceived by ARL researchers led by Dr John Potter, who was also the Head of ARL at that time. Originally, the fiobuoy® came with a time release mechanism, which can be programmed for system recovery at a specified time. However, in the mini-PANDA system, the TMSI researchers built in an acoustic release mechanism which uses a technique of activating the release mechanism by sending specific acoustic commands remotely from a surface transmitter.
"Suppose you want to recover the system at an earlier time than that of the programmed time, you can send an acoustic command to the buoy and then it operates the release mechanism and the system pops up on the sea surface. It is more flexible that way and one still has a back up time release operation in case the acoustic commands were not successful," said Dr Pallayil.
The mini-PANDA is eco-friendly in that it does not pollute or leave unnecessary materials on the seabed. This differs from other mooring equipments used underwater. "Normally for many mooring systems when the system is recovered, the weight is abandoned on the sea bottom," noted Dr Pallayil. In the case of mini-PANDA system, the weight also can be recovered through the use of a special way of attachment of the mooring weight to the fiobuoy?. The system has no surface expressions and hence do not cause any hindrance to the surface vessel traffic, unlike many other traditional moored systems.
Though the system is licensed for production commercially, lack of a good underwater calibration facility is still a worrying problem when it comes to standardising the unit performance.
When asked what is next in the development of the mini-PANDA, Dr Pallayil said that work was being done on the A-PANDA (Advanced PANDA) which is an upgraded system of the mini-PANDA. With the A-PANDA, multiple hydrophones (underwater sound receivers) are used as opposed to the mini-PANDA which uses only one hydrophone. "With this new system, we can sow a field of A-PANDA system and use the information from the sound received by the multiple sensors to get a track of a surface ship."
Dr Pallayil also said that ARL plans to look into upgrading the electronics of the current mini-PANDA system as it has already been six years since the system was first developed.