Sonobuoys are absolutely critical tools in a Navy's efforts to keep enemy submarines at bay. We see them chucked out of maritime patrol aircraft and helicopters over and over again, but we really haven't seen how they can transform once in the water. A video that came to our attention via @RealAirPower1 on Twitter, shows exactly that, with one advanced sonobuoy going through a total metamorphosis of shape and structure once at depth.
There are a number of types of sonobuoys that do different things, but they all fall primarily into two classes, active and passive. Active send actual acoustic pings through the water looking for the return off of a submarine's hull, while passive buoys allow for listening for the sounds made by submarines. Active buoys are usually more complex and far more expensive than their passive counterparts. Remember, these are disposable pieces of hardware. You can read all about the difference and how active buoys are becoming more essential than ever in this past feature of ours.
Some passive sonobuoys are also quite complex as they can rely on detecting and processing active sonar returns from pings that originate from a different source. This is called a bistatic sonar concept.
Such a system is exactly what we are seeing in the video. It appears to be AN/SSQ-101 Air-Deployable Active Recieve (ADAR) sonobuoy, which is a remarkably complex passive sonobuoy. It fits in an A-sized sonobuoy canister like most sonobuoys, but the look of this container is very deceiving.
Once it hits the water, the sonobuoy packed inside breaks into sections that drop down further into the water and it ultimately deploys a massive pentagram-shaped hydrophone array consisting of a whopping 40 hydrophones. It takes around 240 seconds, or four minutes, for the entire array to deploy and become fully operational. Once it is, and other active sonar systems are in use, it can provide very accurate location info of a target.
Here is a bit more about the system from FAS.org:
The AN/SSQ-101 Air Deployable Active Receiver (ADAR) sonobuoy is an A-size, expendable, non-repairable sonobuoy. It is an acoustic data receiver capable of in-buoy beamforming and transmission of received real-time acoustic signals back to any monitoring unit(s). The primary mission is to receive active search signals (i.e., long-range echo detection of quiet, slow moving targets). The ADAR does not drive technological breakthroughs, but does use existing hardware and processing technology.
The ADAR sonobuoy is an expendable unit capable of receiving UHF downlink commands and sending real-time beamformed acoustic data via a VHF digital uplink to the monitoring unit. The ADAR will be a free-floating acoustic data receiver that will operate in conjunction with an acoustic source. The buoy will also scuttle automatically upon detection of a low voltage state or completion of its six-hour life.The ADAR is expended by all compatible ASW aircraft or OTS by shipboard personnel and operated in conjunction with an independent transmitting acoustic source. The EFS selector is used to select depth (one of three) and the default acoustic beamform band (one of two).
Once in the water the acoustic frequency band can be changed, the RF channel can be changed, and the RF can be turned on or off via downlink command function select. Once activated, the sonobuoy receives, beamforms, and transmits real-time acoustic data in the selected frequency band to the monitoring unit. The separately deployed acoustic source will be commanded to "ping," ensonifying the water and any target present, generating an acoustic "return" that is received and transmitted by the ADAR receiver. Aboard the monitoring unit, the data is processed and displayed (visual and aural), providing the operator a means of determining range, bearing, amplitude and possibly Doppler (coherent acoustic sources only) on submarine targets.
The AN/SSQ-101, it's not only a sonobuoy, it's a transformer.
Contact the author: Tyler@thedrive.com