Laser Detecting Systems
Enhancing Survivability and Lethality on the Battlefield
Whether engaged in an asymmetric fight with an insurgent or a conventional battle with a “near-peer” adversary, today's battlefield presents combatants with significant challenges. Rapidly advancing technology and increased lethality of weapon systems have forced the military to develop and deliver more effective technologies to protect our air and vehicle crews. One such critical technology – laser detecting systems – is designed to detect and alert crews to laser-aided threats.
The number and types of laser-aided threats that are present on today's battlefield have increased exponentially over the past decade. These systems use a laser to increase a weapon's probability of a hit and kill of its adversary. These types of lasers typically fall within three categories: Laser Range Finders (LRF), Laser Target Designators (LTD) and Beamrider Missiles (LBR). Examples of each of these types of laser-aided weapons systems are depicted in Figure 1. Each of these examples poses significant risks to unknowing air and vehicle crews on today's battlefield.
Laser Range Finders and Laser Designators
Laser range finders are the most prevalent laser-aided systems found today. They are relatively cheap to produce and export. They are typically used as a single pulse designed to send and receive the reflection of laser energy in order to calculate distance to a target. These systems can range from an embedded laser in a sophisticated fire control system to a low-power model as part of ranging binoculars. These systems have become so cheap and easy to produce that some have even made their way into commercial applications such as handheld devices that allow a golfer to determine which club to use to reach the green.
Like range finders, laser designators have also become increasingly prevalent as part of the world's armed forces standard inventory. Laser designators are primarily used to mark a target for a projectile and then use the laser to help the projectile hone in on its intended target. Designators have multiple pulses and can be encoded to achieve better accuracy with their corresponding weapons. Typically, the system is not employed until the projectile is closer to terminal impact. This minimizes the time for a targeted crew to identify it is being “painted” until the projectile strikes its intended target.
Typically, laser range finders and designators fall within two wavelengths: 1.06 µm (non-eye-safe) and 1.54 µm (eye-safe). Over 90 percent of these use solid state ionic rods for their material (Nd: YAG, Nd: glass, Er: YAG) and have peak powers in excess of 1MW.
The most lethal of all laser-aided threats, the beamrider missile is a family of weapons designed to use a laser to steer a projectile onto an enemy platform. The major difference between this type of system and those that employ either a range finder or designator is that the laser energy is concentrated not on the intended platform, but rather on the tail end of the inbound missile. This low signal strength makes this type of system much harder to detect initially. Over time, as the missile gets closer to its intended target, signal strength increases. Early detection is essential to maximizing warning and reaction time for the targeted crew.
These systems typically come in both continuous wave (CW) and pulse wave (PW) configurations. Depending on the application, the missile itself may be able to fly at subsonic or supersonic speeds, significantly impacting the need for early warning times.
An example of this type of system is the Russian-built AT-14 Kornet Anti-Tank Guided Missile (ATGM). First introduced in 1998, the Kornet is a 152mm caliber munition with the capability to penetrate over 1000mm of rolled homogeneous armor (RHA). It has a maximum effective range of 5.5 km and has been sold to over 25 countries, making it one of the most lethal and proliferated ATGMs in the world. Figure 2 depicts the Kornet ATGM launcher and missile.
The Kornet most recently has been employed by the Islamic State of Iraq and Syria (ISIS) against the Iraqi army. A recent video posted to YouTube shows just how powerful the weapon system can be to an unsuspecting tank crew (Figure 3).
Laser Warning Systems
UTC Aerospace Systems has been designing and manufacturing laser warning systems for over 40 years. They have delivered over 4,000 airborne and 2,000 ground systems to both U.S. and non-U.S. government customers, and their systems are deployed on a number of rotorcraft and ground combat vehicle platforms.
An effective laser warning system must exhibit the following key performance criteria in order to meet customer demands:
High Probability of Detection (PoD) – This is simply reporting all laser events that occurred. Typically this means a PoD in the high 90 percent range.
Low False Alarms – This is defined as reporting something that did not happen. If a system exhibits a high degree of false alarms, the user will not trust the system and will shut it off.
Detect all weapons with enough warning time – This will allow the crew to take evasive action, return fire or employ countermeasures.
Perform all of the above in all different conditions – As an electro-optical device, the system must have a high dynamic range to perform in bright daylight and dark night conditions, and under all types of engagement scenarios.
Balancing all of these system level requirements together to maximize system performance is critical in providing crews with the maximum survivability possible.
An example of a currently deployed laser warning system is the UTC Aerospace Systems AN/AVR-2B(V) Laser Detecting Set. First introduced in 1997, the 2B is the U.S. Army laser detecting system for the Blackhawk and other rotor-craft and is an integral part of the aircraft survivability suite. The 2B has demonstrated consistently excellent performance in the detection and declaration of laser-aided threats. The system typically consists of four sensor units (depicted in Figure 4) that are oriented around the platform (fore and aft) providing 360° coverage and a controller referred to as a signal comparator module (SCM) located inside the aircraft.
An additional configuration for larger platforms consists of two additional sensor units mounted mid-airframe in order to provide necessary coverage. The system is powered through the platform and integrated as part of the vehicle bus. This interface provides vehicle data that enhances system performance, such as reported angle of arrival (AoA) of threat lasers.
UTC Aerospace Systems is introducing a new laser warning system designed to be a common system across the U.S. Army ground combat fleet. The AN/VVR-4 Laser Detecting Set incorporates the lineage of its predecessors with increased functionality (Figure 5).
The system incorporates an additional angle of arrival (AoA) detector which gives the targeted crew enhanced situational awareness.
The AN/VVR-4 can be integrated either as a stand-alone threat warning receiver delivering audio and visual warning through the vehicle's intercom system (AN/VIC-3) and onboard situational awareness displays, or fully integrated within the vehicle's fire control system. The latter option enhances the crew's lethality and survivability in that the system can pass along critical threat information to the fire control system, allowing slew-to-cue of onboard weapon systems to the origin of the laser with high accuracy.
The laser warning system can also serve as a critical sensor within an overall active protection system (APS) construct. The early identification of a laser range finder or beamrider missile can alert the tracking mechanisms of a “hard kill” system of a potential inbound threat, thus reducing overall system response time. The laser warning system can also provide critical laser information of an active designator that can also be used as part of a “soft-kill” countermeasure system designed to spoof an incoming projectile or trigger onboard smoke.
In addition, UTAS is working as part of the U.S. Army Modular Active Protection System (MAPS) community of interest to establish a standard architecture by which this type of sensor can be incorporated into an overall active protection system framework. This open systems architecture will more readily allow systems like the VVR-4 to make software changes as the threat and conditions on the battlefield evolve.
As threats evolve on today's and tomorrow's battlefield, laser warning systems continue to be a critical enabler to survivability of our air and ground crews. Integrated with current and future survivability systems, a laser warning system provides valuable warning time and threat information, thus increasing the crew's survivability and lethality toward hostile threats.
This article was written by Brian Gephart, Senior Program Manager, ISR & Space Systems, UTC Aerospace Systems (Charlotte, NC). For more information, Click Here .