Merkava with ears? It's ALWACS!

In the past months a number of photographs has been posted online, which shows some of the older, upgraded Merkava main battle tanks (MBTs) featuring so called "ears". In different forums people have speculated about the purpose of the oddly shaped turret add-ons, suggesting that these might be part of a 360° close proximity surveillance system or radars for detecting the launch of rocket propelled grenades or anti-tank missiles.

Operational Merkava tanks with "ears"

In fact the upgraded Merkava II and Merkava III tanks are fitted with the advanced laser warning and countermeasure system (ALWACS), which is made by the local manufacturer Elbit Systems. The ALWACS is a softkill active protection system (APS) capable of defeating anti-tank guided missiles (ATGMs) and other sorts of laser-guided ammunition, by distracting them or by hiding the tank using a multi-spectral smoke screen. ALWACS has also been proposed for adoption on the troubled Arjun Mk. 2 tank upgrade for the Indian Army; however it was not adopted into the upgrade package in favor of other components such as heavy explosive reactive armor (ERA).

The ALWACS softkill system has been proposed for adoption on the Arjun tank

Incoming threats are indirecly detected by the Elbit-made E-LAWS laser warning sensors. In case of the Merkava III tanks, these are usually mounted atop a mast on the turret; however there are also some cases where the E-LAWS modules are bolted to the turret sides. These laser warning sensors are also used on other vehicles inlcuding the TAM 2C upgrade for the Argentine Army and the British Ajax recon vehicle. If a laser source triggers the warning system, the direction of the source is calculated and the countermeasures are being engaged. The ALWACS softkill system includes two different types of defensive measures: the VIRCMs (vehicle infrared counter-measures) and multi-spectral smoke grenades.

Each VIRCM module consists of four smaller infrared (IR) jammers, which are set at different angles and cover more than 90° of azimuth; the coverage in elevation is probably limited to about 45°, maybe even less. The IR jammers can confuse missiles that are utilizing IR signales for semi-automatic guidance along the line of sight (SACLOS). The upgraded Merkava tanks feature two VIRCMs (one on the left and on of the right side of the turret rear bustle), covering a large portion of the sides and rear.  However the Merkava tanks fitted with the ALWACS softkill APS don't feature any additional smoke grenade launchers; it is not known if the smoke grenades used by the Merkava tanks are capable of blocking the most common IR and laser wavelengths.

The ports of the VIRCMs are open; also note the mast with E-LAWS on the center of the turret roof

The advanced laser warning and countermeasure system is essentially a more modern equivalent to the Soviet-made Shtora electro-optical countermeasure system and other simple softkill systems like the Ukranian Varta, which utilize laser warners to activate IR jammers and/or to launch smoke grenades. Similiar systems also include the LEDS-50 laser warning and the LEDS-100 softkill system from SAAB Electronics, the US AN/VLQ 6 missile countermeasure device (MCD), which is an infrared jammer not connected to a laser warning system, and Rheinmetall's ROSY_L. ROSY_L consists of multiple smoke grenade launchers in a 40 mm calibre, which are controlled by a manual control unit or by a computer control unit. The computer can be connected to sensor systems such as laser warners and accoustic sensors belonging to the company's SAS product suite in order to create a softkill system known as ROSY_L ISS (integrated sensor suite).

MUSS features optical sensors aswell as rotatable launchers and jammers.

The ALWACS is however not as advanced as the multifunctional self-protection system (MUSS) from German manufacturer Hensoldt, which has been fielded on the Puma infantry fighting vehicle (IFV) and is being tested by QinetiQ for a possible adoption on the British Challenger 2 main battle tank and other armored vehicles as part of the Medusa program. 

Aside of laser warners, the MUSS softkill system features optical UV sensors for threat detection and tracking, it therefore can detect and engage missiles that are not fired from a launcher with laser-rangefinder. Furthermore the IR jammer and multi-spectral smoke grenade launchers from MUSS are rotatable, allowing the system to protect a vehicle along the full 360° azimuth - systems like Shtora, Varta, the MCD and ALWACS are usually not capable to do so.