Sonobuoys

A sonobuoy is a device used to detect and identify moving underwater objects. Typically, a sonobuoy is used to detect submarines by either listening for the sounds produced by propellers and machinery (passive detection) or by bouncing a sonar "ping" off the surface of the submarine (active detection).

Specialized sonobuoys can also detect electric fields and magnetic anomalies, as well as measuring environmental parameters like water temperature versus depth, air temperature, barometric pressure, and wave height. Sonobuoys are generally dropped from aircraft that are equipped with a means to launch them, and electronic equipment to receive and process data sent by the sonobuoy.

Sonobuoys are classified by size (A, B, C, etc.) and type (active, passive or measurement). Most U.S.-manufactured sonobuoys are A-size (approx. 4 7/8 in. X 36 in.). Some countries have moved to half-size, or A/2, as a preferred configuration.

During the Cold War, passive detection in deep water was the strategy of choice to covertly track nuclear submarines around the world. Since former Soviet Union and NATO relations have changed, detection needs have fluctuated. An increase in the number of diesel electric submarines under the flag of third world nations has led to an increase in the interest in active sonobuoys and shallow water detection techniques. Sparton is a source of critical and top-flight R&D in modern Anti-Submarine Warfare (ASW) technology.

Passive Sonobuoys from Sparton

Buoys with different characteristics other than those listed can be designed and built to customer requirements, following a careful analysis of needs. Sparton has designed and manufactured many sonobuoy variations over the years, and continues to make high-performance, high-reliability buoys.

Localization, or the precise determination of a submarine's location, course, and speed, is done with passive sonobuoys whenever possible. In the 1980's, when airborne US Navy searched for submarines, passive sonobuoys typically performed the majority of initial detections. Passive tactics are used because they deny a submarine the knowledge that a tracking aircraft is present. The 'A' size (36 inches long) sonobuoys discussed below can be air-launched since they all employ a parachute to retard their descent and provide descent stability. They can also be hand-launched over the side of a ship. All employ a seawater battery, which is energized upon saltwater contact. Once energized, a mechanism for inflating a float with CO2 gas is activated, suspending the sonobuoy. The sensors are then released to specified depths. Passive buoys use hydrophones to convert underwater sound into electrical signals, which are amplified and frequency modulated for VHF transmission. Some buoys have precision-calibrated hydrophones. Most sonobuoys automatically scuttle within 8 hours of deployment. Sonobuoys are typically shipped in a Sonobuoy Launch Container (SLC) that serves as the shipping, storage, and aircraft launch container.

DIFAR Passive Buoys

The following passive buoys are the buoys of choice. Known as DIFAR buoys (Directional Frequency Analysis and Ranging), the main sensor is a hydrophone that has directional detection capabilities. The latest generation of DIFAR sonobuoys offers various sensor types, electronic selection and post-launch control.

AN/SSQ-53D DIFAR

The AN/SSQ-53D is the most widely used sensor for all phases of ASW search, localization, and tracking. Basic capabilities include three depth operation (90, 400 and 1000 feet), five life selections (0.5, 1, 2, 4 and 8 hours), DIFAR sensor, and the capability to set one VHF transmitter channel out of 99 available channels. The life, depth, and channels may be set via Electronic Function Selection (EFS) prior to launch.

AN/SSQ-53F DIFAR

The AN/SSQ-53F DIFAR is the latest directional passive sonobuoy being produced for the U.S. Navy. Basic capabilities include four depth operation (90, 200, 400 and 1000 feet), five life selections (0.5, 1, 2, 4 and 8 hours), DIFAR, Constant Shallow Omni Sensor (COS) or Calibrated Omni, sensor selection capability, DIFAR AGC (Automatic Gain Control) On/Off and the capability to set one VHF transmitter channel out of 96 available channels. Depth, life, sensor, AGC, and channel selection may be set via Electronic Function Selection (EFS) prior to launch, and all but depth selection after deployment via Command Function Select (CFS). This buoy automatically scuttles after 8 hours.

AN/SSQ-77C VLAD

This passive buoy is again an improvement in the evolution of passive detection. It has the directional capabilities of the Q53 DIFAR and, additionally, a vertical line array (VLAD) of omnidirectional hydrophones for improved tracking capability in a noisy, high-traffic environment. There are five different operating life selections (0.5, 1, 2, 4 or 8 hours) and three depths (200, 500, 1000 ft). Depth, life, and channel selection may be set via Electronic Function Selection (EFS) prior to launch, and all but depth selection after deployment via digital Command Function Select (CFS).

Active Sonobuoys

Buoys with different characteristics other than those listed can be designed and built to customer requirements, following a careful analysis of needs. Sparton has designed and manufactured many sonobuoy variations over the years, and continues to make high-performance, high-reliability buoys.

Target detection becomes difficult against a very quiet submarine, a submarine in attack mode, or in extreme environmental conditions. In these situations, it is critical to localize the target quickly and accurately. This is when active sonobuoys are used. The released acoustic energy ("ping") from an active sonobuoy and the resultant return signal enable an accurate fix on the submarine in both range and bearing. When two or more fixes are obtained, the velocity and the course of the submarine can be established.

The following 'A' size sonobuoys can be air-launched from fixed or rotary-wing aircraft, since they all employ a parachute to retard their descent and provide descent stability. The buoys are also easily deployable from the deck of a surface vessel. Descent of the sonobuoy is stabilized and slowed by a parachute. They also all employ a seawater battery (silver chloride), which is energized upon entry into salt water. As with the passive buoys, once energized, a mechanism for inflating a float with CO2 gas is activated, suspending the sonobuoy. The sensors are then released to specified depths. These buoys use a transducer to introduce acoustic energy into the water ("ping") and use the transducer to receive the return echoes, which are then amplified and frequency modulated for VHF transmission. Generally, these buoys are designed for deeper depths than the passive buoys. All of the buoys scuttle after a preset length of operation.

AN/SSQ-62D

The AN/SSQ-62D is the sonobuoy component of the Directional Command-Activated Sonobuoy System (DICASS). Under direct command from an Anti Submarine Warfare (ASW) aircraft, it can determine the range, bearing and velocity of a target using sonar techniques. The AN/SSQ-62D is composed of two main sections: a surface unit and a subsurface unit. The surface unit receives commands from the controlling aircraft via a UHF receiver, and sends target information to the aircraft, via a VHF transmitter. The subsurface unit transmits sonar pulses in the ocean upon command from the aircraft and receives sonar target echoes for transmission to the aircraft. The sonobuoy will accept command signals only after a decoder identifies the correct address code. The command capability includes mid-depth or deep depth selection, sonar ping, and scuttle. Upon deployment, a VHF transmitter emits a continuous FM carrier signal. This signal indicates that the sonobuoy is operating in a passive mode and is ready to receive commands.

AN/SSQ-62E

This sophisticated device is the sonobuoy component of the Directional Command-Activated Sonobuoy System (DICASS). It is a commandable system that can be manipulated at deployment for send-to depth and establish a sonar ("ping") pattern after a correct address code has been established. This occurs only after the buoy has established contact with the aircraft. Prior to aircraft contact, the buoy is in a passive mode. When commanded from an ASW aircraft, the AN/SSQ-62E can be used to determine range, bearing, and velocity of a target. It is capable of operating on any of 96 RF channels and 4 sonar channels, within one unit. The sonobuoy is composed of two main sections: a surface unit, and a subsurface unit. The surface unit receives commands from the controlling aircraft, via a UHF receiver, and sends target information to the aircraft via a VHF transmitter. The subsurface unit transmits sonar pulses in the ocean upon command from the aircraft and processes sonar target echoes for transmission to the aircraft. It is commandable using either the analog Command Signal Generator (CSG) or the digital Command Function Select (CFS). The CSG command capability includes depth selection within two depth families, scuttle, and sonar ping. The CFS command capability includes selection of all depths, RF power (on/off), RF channel, and sonic channel. Upon deployment, a VHF transmitter emits a continuous FM carrier signal. This signal indicates that the sonobuoy is operating in a passive mode and is ready to receive commands.

Other underwater Signaling and Receiving Devices

AN/SSQ-36B

Prior to deployment of any detection sonobuoys, it is advisable to have a vertical temperature profile of the ocean. The AN/SSQ-36B Bathythermograph provides a low-cost method to obtain vertical temperature profiles of the ocean for research purposes. This approach provides near synoptic area surveys while eliminating costly vessel time. The AN/SSQ-36B is widely used for airborne Anti-Submarine Warfare (ASW) applications to evaluate local effects of seawater temperature on sonar propagation and acoustic range prediction. This buoy has an operating life of approximately 12 minutes at which the temperature probe is at a depth of 800 meters (2625 ft). The sensors are calibrated for an accuracy of ± 1 degree F at a descent rate of 5 feet per second. VHF transmissions from this buoy are processed to read temperature versus descent in real time. It can be air launched or over-the-side launched, is 'A' size (can be 'G' size), and is 99 channel selectable. The transmitter output is ¼ Watt. The Sparton AN/SSQ-36B is extremely reliable in high sea states.

MK-84 MOD 1 SUS

The Sparton Signal Underwater Sound (SUS) device is used primarily for one-way acoustic communication with submarines. The device can be set to generate one of five distinct, coded sequences. Four of these sequences consist of a continuous tone that alternates in frequency in accordance with the timing sequence defined in the Code Table (see specifications). The fifth sequence is a continuous tone at a single frequency. Third harmonics of the fundamental frequencies are also generated at levels slightly less than those of the fundamentals. A five-position switch on the side of the unit accomplishes settings. The MK-84 is designed to provide a source level of 160 dB per micro-Pascal within two (2) seconds of water entry and throughout its one-minute life. Sparton is the only manufacturer of the MK-84.

To get more technical details on Sparton sonobuoys, or to discuss new product possibilities, please call us at +1 (386) 740-5472 or fax us at +1 (386) 740-5372.

If you are a foreign customer, and desire to order a Sparton sonobuoy, please reference the following directions for completing a DSP-83 Form in order that Sparton may export product to you.

Form DSP-83 | DSP-83 Instructions