FIGURE.1 Technology advances and capabilities possible by combining them.

tencies, and it must remain so in the face of a submarine threat that will increase significantly-perhaps even dramatically-in the 21st century. This increase, which is being fueled by the proliferation of advanced submarine quieting, sensors, and processing techniques and technologies, could result in the submarine becoming the dominant threat to the accomplishment of naval missions. The psychology of both submarine and mine warfare enhances the effectiveness of the threat, since the adversary has only to possess these weapons to cause arriving forces to operate as if the threat were present and active. The presence of submarines in an adversary's inventory means that effective ASW is needed early on to provide intelligence, prepare the battle space, clear the area for operations, monitor choke points, and protect surface units. The primary weakness in ASW is the detection of quiet submarines. There are also shortfalls in the areas of effective weapons, fire control, and self-defense, but each of these problems generally follows from detection limitations.

Robust technological opportunities exist by which U.S. ASW capabilities can be enhanced to deal with future submarine threats. These advances and the capabilities possible from combinations of them are shown in Figure.1. However, resources and proper focusing of research are required to exploit these opportunities. In particular, significant gains in passive sonar appear possible based on larger multidimensional arrays of lightweight, smaller, cheaper sensors and telemetry; multichannel processing exploiting the advancing massively parallel computing technology; and robust characterization or incorporation of the ocean environment. These gains can be applied directly to active acoustics as well.

For tactical passive sonars, it is estimated that current programmed improvements will achieve a 10- to 15-decibel improvement in the near-term, with an additional 10 to 20 dB being possible over the time frame of this study if the technological advances shown in Figure .1 are exploited. These gains would more than offset the anticipated quieting of future submarines. Passive surveillance sensors should gain 15 to 20 dB from these same technologies, which will