1. Design of a Low-cost Acoustic Modem for Moored Oceanographic Applications Bridget Benson, Grace Chang, Derek Manov, Brian Graham, Ryan Kastner University of California Santa Barbara WUWNet Presentation September 25 th 2006

2. Outline Motivation Requirements Design Experimental Results Meeting the Requirements for the SB CHARM Future Work

3. Motivation To understand the ocean we must be able to observe large regions for long periods of time Such data could help predict earthquakes, tsunamis, or spread of a toxic algal bloom Platforms to measure large sets of data for long periods have been and are being established

4. Cabled Observatories NEPTUNE LEO Martha’s Vineyard Coastal Observatory

5. Moorings MBARI Ocean Observing System (MOOS) EOM cable in this mooring system parted in a storm on December 15, 2002.

6. Mooring Modem Requirements Sensor to Modem Interfacing Packaging Power Low Cost Data Transmission Range Data Transmission Rate Oceanic Motion Resistance Acoustic Interference

7. Mooring Modem Design Transmitter: Receiver:

8. Mooring Modem Specifications Power Supply: 12 V Sampling Frequency: 8 kHz Data Rate: 80 bps Carrier Frequency: 50 kHz Frequency Separation: 320 Hz Transducer Beam Width: 20 o

9. Experimental Set-Up

10. Experimental Results Distance (ft) DirectionBit Errors Data Errors BERDER 4Vertical210.0020.033 9Vertical10 0.0100.333 10Horizontal000.000 17Horizontal440.0040.133 1920 Degrees 1040.0100.133 25Horizontal1760.0180.200

11. Experimental Results

12. SB CHARM

13. Meeting the Requirements for the SB CHARM RequirementSB CHARMMooring Modem Sensor-to-Modem Interfacing RS-232 Data ProtocolX PackagingWater proof and biofoul resistant X PowerMooring batteries must last 6 months X Low-CostMinimum 9 modems9 x $100.00 = $900.00 Data Transmission Range 6 meters (~20 ft)25 ft Data Transmission Rate 200 bps80 bps Oceanic Motion Resistance Speeds of 1 m/s contribute to frequency deviation of 1 – 40 Hz Bandpass Filters designed to withstand 40Hz deviation Acoustic InterferenceADCP operates at 300 kHz F mark =1040 Hz F space =1360 Hz F c = 50 kHz

14. Future Work Determine actual power consumption and battery life of mooring modems Reduce size of the Mooring Modem design and waterproof the electronics Implement error correcting codes to reduce the BER Determine how to network the Mooring Modems Interface the Mooring Modem with oceanographic sensors using RS-232 protocol Test the Mooring Modem on the SB CHARM at depths 0, 4, 10, and 22m

15. Acknowledgements W.M Keck Foundation Hua Lee and Ronald Iltis