NMFS Biological Opinion on U.S. Navy training ... - Govsupport.us

FINAL PROGRAMMATIC BIOLOGICAL OPINION ON U.S. NAVY ACTIVITIES IN THE HAWAII RANGE COMPLEX 2008-2013
Most sonobuoys are passive, but some can generate active acoustic signals, as well as listen passively. Dipping sonar
is an active or passive sonar device lowered on cable by helicopters to detect or maintain contact with underwater
targets. During an Undersea Warfare Exercise, the active modes of these sonar system are only used briefly to
localize contacts and are not used in primary search capacity. Because active mode dipping sonar use is very brief
(2-5 pulses of 3.5-700 msec), it is extremely unlikely its use would have any effect on marine mammals.
Torpedoes. Torpedoes are the primary anti-submarine warfare weapon used by surface ships, aircraft, and submarines.
The guidance systems of these weapons can be autonomous or electronically controlled from the launching
platform through an attached wire. The autonomous guidance systems are acoustically based. They operate either
passively, exploiting the emitted sound energy by the target, or actively ensonifying the target and using the received
echoes for guidance. All torpedoes used for anti-submarine warfare during a Undersea Warfare Exercise are
typically located in the range area managed by PMRF and would be non-explosive and recovered after use.
Acoustic Device Countermeasures. These countermeasures act as decoys by making sounds that simulate submarines
to prevent torpedo attacks.
Training Targets. Anti-submarine warfare training targets are used to simulate target submarines. They are equipped
with one or a combination of the following devices: (1) acoustic projectors emanating sounds to simulate submarine
acoustic signatures; (2) echo repeaters to simulate the characteristics of the echo of a particular sonar signal reflected
from a specific type of submarine; and (3) magnetic sources to trigger magnetic detectors.
Range Sources. Range pingers are active acoustic devices that allow each of the in-water platforms on the range (for
example, ships, submarines, target simulators, and exercise torpedoes) to be tracked by hydrophones in the range
transducer nodes. In addition to passively tracking the pinger signal from each range participant, the range
transducer nodes also are capable of transmitting acoustic signals for a limited set of functions. These functions
include submarine warning signals, acoustic commands to submarine target simulators (acoustic command link), and
occasional voice or data communications (received by participating ships and submarines on range).
Other Training Activities During Undersea Warfare Exercises
In addition to the anti-submarine warfare exercises, Undersea Warfare Exercises typically include the following
activities:
Anti-submarine warfare exercises which are designed to provide crews of anti-submarine ships, aircraft (including
airships), submarines, and helicopters experience in locating and pursuing underwater targets and dropping inert
torpedo weapons. The exercise involves locating and pursuing underwater targets and dropping inert torpedoes and
inert air-dropped mines from anti-submarine aircraft and helicopters. Weapon recovery boats and helicopters are
used to locate and recover the targets, torpedoes, and mines.
As with RIMPAC exercises, sonobuoys used during USWEX exercises are generally limited to areas greater than 183
meters (100 fathoms, or 600 feet) in depth. Before dropping sonobuoys, crews visually determine that an area is
clear. Although the altitude varies at which buoys are dropped, the potential for drift during descent generally favors
release at lower altitudes, where visual searches for marine mammals or sea turtles are more effective. When the
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