From: Brent Roman [brent@mbari.org] Sent: Wednesday, September 18, 2002 5:56 PM To: Paul Chandler; Bill Kirkwood; Duane Edgington; Tom O'Reilly; Jim Bellingham Cc: Hans Thomas; Mark Sibenac; Mark Chaffey; Ed Mellinger; Lance McBride; Gene Massion; Scott Jensen Subject: Notes from Benthos visit Hi, I just returned from a two day seminar at Benthos on acoustic modems. Obviously, the focus was on their commercial offerings. Here are some highlights. Let me know if you want more details on anything in particular: NOAA is, by far, the largest installed base of Benthos modems. They have been deployed in their tsunami warning system for over 2 years. NOAA has found it useful to add baffling for transducers near the surface to better reject multipath interference. There are 6 buoys deployed currently with plans to deploy 10 more in the near future. NOAA uses the previous generation of Benthos modems. They run them at a very conservative 300 baud and report 98% reliable packet troughput during the entire course of a 1 year deployment. SPAWAR wants to use the Benthos modems on their REMIS AUVs because they cannot get the WHOI modems from WHOI or Hydroid. They are, understandably, very concerned about interoperability at data rates higher that the very basic 80bits/second modulation scheme currently supported by both Benthos and WHOI. There does at least appear to be a WHOI proposal to standardize three modem operating bands designated A, B, and C. Unfortunately, these do not correspond to the low, medium and high bands currently supported by the Benthos transducers. Benthos intends to migrate to the A, B, and C bands. However, this indicates of how far we have to go to achieve real-world interoperability. Joe Rice of NPS will be spending the next 2 weeks off Halifax testing a SEAWEB deployment. The Canadian Navy has indicated a desire to adapt the same modem technology as the US does. Both Benthos and NPS have independent programs to develop small, directional transducers. The Benthos approach relies on multiple transducers mounted an integrated package including carefully designed baffles between them to direct the acoustic energy. The NPS directional transducer exploits higher order physical modes of two stacked, cylindrical transducers to create a small phased array. The really cool aspects of this are that the "beam" may be steered electronically and the that the modem electronics may be mounted in the center of the cylinders to achieve a _very_ compact package. A company called "Acoustikos" in Cataumet, MA is marketing a complete "Underwater Camera Imaging System" incorporating the latest Benthos modem for real-time image acquisition. see: http://www.falmouth.com Paul Chandler has a CD containing all the Benthos presentation slides which he has agreed to post on some shared drive. I'll be getting the NPS presentations from Joe Rice when he returns from Halifax. -- Brent Roman MBARI Software Engineer Tel: (831) 775-1808 7700 Sandholdt Road, Moss Landing, CA 95039 mailto:brent@mbari.org http://www.mbari.org/~brent