To provide the functionality for locating an underwater acoustic pinger, we have developed a passive acoustic system that uses four Reson TC4013 hydrophone elements and an Analog Devices SHARC-21369 digital signal processor to determine the relative direction to such a pinger. It is capable of discriminating between multiple pingers of different frequencies operating simultaneously and listening to only the one at the selected frequency, and can operate in the 20-35 kHz range.
All of the hydrophone circuitry is enclosed in an external pressure vessel. This enclosure has 2 custom pass-through glands, a custom JTAG connector and a single SEACON MCBH-6 connector for serial communications. The custom pass-through glands include a single hydrophone element potting gland and a triple hydrophone element potting gland. These glands ensure signal integrity from elements to the hydrophones board and over JTAG. An acrylic hull was chosen to allow for easy visual debugging without needing to open the enclosure.
The hydrophones feed the computer heading and elevation information accurate to within +/- 1 degree, which is used in the mission to navigate to the pinger. When the elevation drops from 90 degrees to near zero, the vision mission is activated and the vehicle visually identifies the recovery object and drops down on it.
Tachyon completing the hydrophones section of the mission
