The Cetabuoys and Hydrophones
From 2003-2012 we transmitted live humpback whale songs to our website via moored buoys and a radio repeater system; we have since migrated our broadcasting to Wave Glider® based cell data systems. Our buoys are called Cetabuoys named after Cetacea, the order of marine mammals which includes whales, dolphins and porpoise. The equipment of the CetaBuoy project can be broken down into six major components:
1. The CetaBuoys and Hydrophones
2. Buoy Electronics
3. The Radio Repeater System
4. The Shore Controller and other interface tools
5. The Software for Web Interface
6. Rigging and Location
The CetaBuoys (or "buoys" for short) are 10 feet tall and 4 inches wide, with an outer shell of thick ABS plastic.
The outer layer of the buoy has a foil, or "wing" which provides a dramatic reduction in drag from the water. The wing is foam-filled for additional buoyancy, and has a solar panel on the area above water (the upper 3-4 feet), for battery support and additional power.
The solar panel on the buoy allows it to remain in the water for the entire season without needing to be pulled for battery recharging.
The radio, batteries, and electronics package are housed within the inner casing, with ballast at the bottom for stability. This inner casing is designed to be slid into the CetaBuoy intact, and can easily be removed for repairs, diagnostics, or enhancements to the electronics.
The CetaBuoy is designed to float upright with approximately 2 feet out of the water and 8 feet underwater. The "wing" or wedge on the outer casing is foam-filled for buoyancy, and is designed to reduce drag in strong ocean currents, while minimizing kelp entanglement.
The heart of our entire system is our Control Board - known currently as the JEM5. (Jupiter Electronics Module - 5th generation)
The GPS (global positioning system) receiving antenna and UHF (ultra-high frequency) transceiving antenna are located at the top of the "sled" (the inner casing of the buoy) and connect to the JEM5.
The JEM5 transmits the GPS and UHF communications to the Shore Controller, and receives commands from the Shore Controller as well as Handheld Controllers. This is how the whales' sound, as well as, other data are transmitted.
Communications with JEM5 can be also used to:
1. Set transmit durations
2. Choose when to transmit
3. Receive and sends telemetry information to & from shore
4. Control solar charging of batteries
There are also six batteries (12 volts of power) recharged by the onboard solar panel These can also be charged through the hydrophone connector so that the batteries can be kept at full capacity while in storage.
The Radio Repeater System
The Radio Repeater System is at the Kahua Ranch on the western slope of the Kohala mountains, and provide bi-directional repeating of the radio signal.
When the buoy transmits, the radio on the mountain hears it and simultaneously retransmits it on another frequency. The faint signal coming from the buoy is amplified by the repeater to the Shore Control.
Conversely, when the Shore Control System transmits commands to the buoys they are picked up by the Repeater and simultaneously retransmitted to the buoys. The Repeater transmits on different channels for the different buoys.
The Repeater System allows us to cover a very wide area (40-50 miles) for listening to the whales. Before installing the system we had about 1-2 miles of coverage.
When the whale sings (or makes feeding or other calls) the sound is picked up by our hydrophone and transmitted by our CetaBuoy.
The signal is then picked up by the radio tower at Kahua Ranch and relayed to our server. The server, using satellite communications or direct internet links, broadcasts the sounds onto the internet.
The historic Kahua Ranch has graciously allowed us to install a radio system on their grounds, 3800 feet above sea level.
The Shore Control System
The Shore Control System, housed in our laboratory facilities, consists of a computer connected directly to the internet, and also connected to a control box which is connected to the Radio Repeater.
The computer runs software that, when commanded through the web, tells a control box what commands to send to the radio or through the radio to the buoys. This allows remote control of the system from anywhere in the world that we have internet access.
There is also a small computer network, radio transceiver connected to an antenna mounted on the roof of our lab which sends transmissions to and from the Repeater. If the Repeater fails, this transceiver can work as a backup, but only to a maximum 2 mile radius.
We also use a small (handheld) hardware control system which translates commands from the computer so that they control the radio receiver.
Software for Web Interface
We have a small web-server in our lab which provides a buoy administration page. This is our web-interface. Using it we can send different commands (or queries) to all buoys at once, or to a specific buoy, such as:
1) Start transmitting now
2) Your transmit time should be x minutes long
3) What is your GPS latitude/longitude?
4) What is the water temperature?
5) Hydrophone gain can be controlled also, to adjust to the distance the whales are from the buoys.
We automated some of the features (a sort of "autopilot"). Some examples of autopilot functions:
1) Can keep track of battery voltage as reported by each buoy
2) If voltage gets too low, the buoy will be put into standby mode so that it can charge its battery
3) When voltage is high enough, buoy can be reactivated
Rigging and Location
We use a 6000 lb weight anchorline to connect to an anchor about 250 feet down. The hydrophone itself is connected to a separate line at a depth of approximately 65 feet, with a "standoff" to keep it separated from the anchorline and prevent extraneous noise from the rigging. The anchor is made of 300 lbs. of steel plates, deployed ~ 1nm from shore in ~300' of water. The entire system is retrieved at the end of the season.