Anti-Terrorism - Detection, Indications, and Warnings

Underwater objects of interest are often marked by placing an acoustic marker or pinger either on or very near to the object. This device is left on site until revisited at some later time by another system able to localize it. Current marker/pinger technology typically transmits energy in a narrow spectral band. The implications of such a transmission are: the signals are easily detectable by undesirable observers; two or more markers transmitting simultaneously will cause confusion in detection and bearing estimation. Furthermore, current marker/pinger technology would be wasteful of energy in broadband signaling, resulting in unnecessarily reduced operational life. Our Phase One efforts concentrated on the development of a robust, broadband signaling scheme based upon our acoustic communications (acomms) technology, and on the development of a new technology for efficient conversion of electrical power to broadband acoustic power. These combined developments will permit the construction of a smart marker with the following capabilities: 1. We propose to operate the marker in a 10 kHz band, with the low end of the band suitable for the ONR-designated band C. However, the center frequency could be higher and the band much wider to suit application. 2. Among other configurations, the markers will be configured to operate in conjunction with both the existing Benthos ATM 885 and the WHOI Micromodem operating in band C. 3. We will provide a minimum1 km range for a battery-powered marker. 4. We plan to provide as many as three operating modes for battery-powered units. Modes will include a fully "awake" mode, a "drowsy" mode, and a hibernation mode. Continuous "awake" operation will result in a battery life of about 22 days. 5. Our preferred mode of operation is to command an individual marker to respond with a coded, "covert" frequency hopping (FH) sequence. Other signaling modes are possible. 6. We are planning a single device that can be used from shallow water to 500 m depth. 7. We will provide both diver-held and vehicle-mounted devices for interrogating the markers and for estimating range and bearing.