OVERVIEW: The AN/SSQ-77B Vertical Line Array Directional Frequency Analysis and Recording (VLAD)  is an "A-size" passive, vertical-line array DIFAR directional sonobuoy.   
 

DETAILS:  The AN/SSQ-77B VLAD is a passive sonobuoy designed to increase signal detection in a high-ambient noise environment.  It uses a vertical line array of omnidirectional hydrophones to form an selectable angled beam to exploit either bottom-bounce or convergence zones and reduce high ambient/shipping noise, while attenuating reception of unwanted noise.  This capablity gives the AN/SSQ-77B the ability to search, detect, and classify a target at extended ranges with minimum expenditure of sonobuoys. 

Like the DICASS it also provides a magnetic bearing to the signal of interest.  It has a frequency capability in the 10 Hz-2,400 Hz range.  It is capable of deploying at depths of 500 or 1,000 feet preset lifetimes of either 1, 4 or 8 hours. 

NOTES:  Fully operational within 4 minutes of entering the water.  Service tests models approved for use in 1978.  Production began in 1980.
 

SOURCES:   Friedman, Norman, and Norman Friedman. The Naval Institute Guide to World Naval Weapon Systems, 1997-1998 Annapolis, Md: Naval Institute Press, 1998, pg. 657-58 ; GlobalSecurity.org - Reliable Security Information. "AN/SSQ-77B Vertical Line Array Directional Frequency Analysis andRecording (VLAD) Sonobuoy." Accessed November 24, 2014. http://www.globalsecurity.org/military/systems/ship/systems/an-ssq-77.htm ; Jane's Underwater Warfare Systems, "AN/SSQ-77B (VLAD)"


