(1) Field of the Invention
The present invention relates generally to acoustic countermeasures and, more particularly, to acoustic countermeasures which project a spatial extent. 
(2) Description of the Prior Art
Various types of acoustic countermeasures are well known for use in decoying or jamming acoustic sensors utilized by incoming torpedoes.  One of the weaknesses of acoustic countermeasures that try to decoy or jam a modern threat torpedo is that they have no spatial extent.  Instead, they appear as a point source to the incoming torpedo.  Once the torpedo comes sufficiently close to the countermeasure, the torpedo can use its beam forming capability of its front array to determine that the acoustic energy coming from the countermeasure has no spatial extent, that is, it is emanating from a single point in space.  Thus, it cannot be a target and must be an acoustic countermeasure.  The torpedo then can take the appropriate anti-countermeasure maneuver or tactic and continue to pursue its target. 
The following U.S. patents describe various prior art systems that may be related to the above and/or other telemetry systems:
U.S. Pat.  No.  5,144,587, issued Sep. 1, 1992, to Mason, discloses an expendable moving echo radiator suitable for providing a decoy to attract a homing torpedo and divert the torpedo away from its intended target.  The present invention provides an expandable and collapsible curtain for deployment from a capsule launched from a submarine or other sea vessel.  In its expanded configuration, the curtain is characterized by a physical profile sufficient to reflect acoustic waves and to generate echoes substantially similar to echo signals generated by an actual, full size submarine or other target.  The present invention is further provided with propulsion means, as well as means for enhancing its capability to capture a torpedo's sensors.  It can also be provided with explosives to destroy lured torpedoes.  The expendable device can be used to simulate a submarine for anti-submarine warfare (ASW) training, thereby affording the advantage that a package of easily transportable size becomes a full size submarine-like target.  In using the echo radiator as a target, the expendable device can be preprogrammed or remotely controlled for self-navigation purposes. 
U.S. Pat.  No.  5,253,216, issued Oct. 12, 1993, to Haisfield, discloses a countermeasure for acoustic homing torpedoes where a plurality of sound transducers are transversely arrayed across the attack path of the torpedo.  The transducers are energized in a time sequence to simulate a relative transducer movement in a direction across the path of the torpedo.  The torpedo is thereby misdirected by the high level acoustic signal produced in the transducers slowly changing the location of the signal.  The signal is interrupted to provide a silent period, such absence of a signal being interpreted by the torpedo as a miss causing the torpedo to initiate a turn and commence a search which will “exhaust” the torpedo.  This sequence is repeated while the torpedo is within a close range of the target. 
U.S. Pat.  No.  5,600,087, issued Feb. 4, 1997, to Chace, Jr. et al, discloses an expendable underwater vehicle for use in training naval forces in anti-submarine warfare in ocean waters that is between about three to five feet in length and about five inches in diameter, and it is field programmable.  The expendable underwater vehicle can be programmed in the field at the location where the vehicle actually will be used as a training device.  A system for field programming the vehicle comprises a run geometry generator and a portable interface module.  The run geometry generator downloads the operational parameters to the portable interface module, and the portable interface module then downloads the operational parameters into the vehicle.  These operational parameters are stored in the vehicle and then used by the vehicle during an in-water run. 
U.S. Pat.  No.  6,542,109, issued Apr. 1, 2003, to Lloyd et al, discloses an autonomous off-board defensive aids system for use with a host craft, for example, with combat aircraft or submarines.  More particularly, the host craft deploys a plurality of controllable off-board units to counter an offensive threat or to engage in autonomous offensive actions.  The controllable off-board units implement active stealth facilities: each off-board unit having a receiver unit for detecting impinging detection pulses, for example radar or sonar pulses, and a transmitter unit for generating an artificial detection pulse profile, for example “spoofing” or masking the presence of the host craft.  The controllable off-board units are of two types: tethered and free moving.  The off-board units can have conventional propulsion apparatus, for instance, propellers, rockets or jets.  Off-board units each have control apparatus which allows the off-board units (104, 106) to co-operate.  General commands are conveyed to the control apparatus by control cabling provided in the tether cable. 
The above cited prior art does not disclose a system which gives the appearance to an incoming torpedo or other sonar detectors to be a large object when if fact it is not.  The advantages and benefits to solutions to the above described and/or related problems have been long sought without success.  Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.