The military is an organization comprised of interesting apparent paradoxes, oxymoronic semi-stereotypes, and some contradictory anecdotal paradigms established over millennia of applied military art. One of the more realistic apparent military paradoxes is organization in chaos—being able to continue a mission in the face of dedicated opposition. Both Von Clausewitz and Mike Tyson pointed out the difficulty of maintaining a mission objective once the opposition is able to engage.
The ability to manage unforeseen disorder isn’t just a result of leadership acumen (although that’s a necessary ingredient), but a result of proper intelligence and battlefield awareness. More now than ever, the ability to see your enemy first and act upon that information is often the only difference between victory and destruction. The force that can detect and guide a response to the enemy first will almost always win the engagement (Figure 1).
Today, creating and maintaining theater awareness is the realm of advanced sensors linked to Command, Control, Communications, and Intelligence systems (C3I) that establish a network of detection and response to both advance the mission and protect the forces engaged.
Inside the Box
There’s more to military sensor systems than just the information they collect. Since the devices involved are deployed in an incredibly harsh environment, everything involved must be able to survive shock, vibration, moisture, and other things (like clumsy and/or stressed operators) over an extremely wide temperature range. That means sensors have to be packaged well, with ICs, power supplies, and connectors that also meet military requirements.
Another issue to consider are the layers of sensors in every system. There are internal sensors for circuit performance and protection, like current-sense resistors and transient voltage suppressors. There are external sensors that create functionality for the product itself, be it an optical, thermal, or RF sensor. Then there are interface sensors, like device touchscreens, MEMS accelerometers, and gyroscopes. Each system within any given solution must be compliant with military requirements, or it will fail, even if every other subsystem is compliant.
Even at the macro level, internal sensing is as important as the mission-oriented systems. Just as every internal system has to have precision sensing for individual performance, the complete system (vehicle, ship, aircraft) must also carry an array of sensors having nothing to do with detecting enemies; each surrounded by their own web of interlocking requirements (Figure 2). For example, inside a warship, fluid level sensors must not only meet the MIL-L-23886 spec for each device itself, but also meet MIL-S-901C for high-impact shipboard systems along with MIL-STD-167 for mechanical vibration.
Compliant products, like the LS-800 Series Multi-Point Level Switch from Gem Sensors and Controls, must not only measure well and accurately, but have a rugged construction to support larger, more buoyant floats, and be physically stronger for better reliability in contaminated or turbulent media. Of course, it must also be ably configured for a wide range of applications in water, oils, chemicals, and corrosive liquids.
Situational Awareness
Accepting user and environmental information accurately is also a critical aspect of any military system. Many weapon systems not only need to know the enemy’s location, but also where they are in relation to their position. Advanced MEMS-based internal position-detecting subsystems revolutionized how electronic systems establish their coordinates in space. For some military applications, legacy solutions can still deliver the needed performance and reliability.
A solution like the Sherborne Sensors’ A200 range of servo accelerometers must be able to measure vector acceleration with high accuracy (Figure 3). In this case, the solution uses a closed-loop force balance mechanism, with a pendulous mass to develop a torque proportional to the product of its mass unbalance and applied acceleration. Mass movement is detected by a position sensor whose output signal is connected to a servo amplifier. By adjusting the amplifier’s parameters and related electronic networks, the operating characteristics of a servo accelerometer can be optimized to suit a particular application.
Tactical Awareness
Once the housekeeping is done, attention can be turned to the actual combat-oriented functionality. The latest sensing solutions must provide an unheard of functionality level, even as recently as a decade ago. Optical combat sensors are overlooked, as they’re often overshadowed by their longer-ranged RF-based brethren. The newest systems are demonstrating that the optical spectrum is still very useful to military sensing systems.
Deployment complaints about the platform aside, Lockheed Martin’s Electro-Optical Targeting System (EOTS) for the F-35 Lightning II is a high-performance, lightweight, multi-function sensing solution for precision air-to-air and air-to-surface targeting (Figure 4). Integrated into the aircraft fuselage with a rugged sapphire viewport, the device talks to the aircraft via a fiber-optic interface.
Presented as the first sensor to combine forward-looking and infrared search along with track functionality, EOTS enables situational awareness and precision delivery of laser and GPS-guided weapons. Advanced EOTS, the next iteration, will incorporate enhancements and upgrades like short-wave infrared, high-definition television, and an infrared marker.
Theater awareness isn’t just limited to players on the battlefield; there’ve been eyes in the skies for decades that only get better as their sensors improve. One example is hyperspectral image technology from Northrop Grumman, which can provide detailed pictures from orbit with the ability to discern a vehicle hidden by camouflage, or unit of soldiers moving through a patch of woods. Everything creates their own unique spectral fingerprint, and the sensor determines these fingerprints by measuring reflected light (Figure 5).
The system operates across up to 220 wavelengths for precise measurement. For example, where a standard sensor with fewer than 10 bands is capable only of differentiating between gross classes of vegetation, a hyperspectral imager can discriminate a maple from an oak, or wheat from alfalfa. With hyperspectral imaging, a camouflaged missile is easily spotted (even under vegetation).
Putting it Together
Today’s military sensors must operate well on their own, and function as part of a combined-arms approach with an interlaced network of sensing, to detect threats of any nature from any direction. One such way to address this is with a battlefield awareness solution like 3D Advanced Warning System (3DAWS) from BAE Systems, which can provide universal threat detection to an aircrew with a layered countermeasure defense.
The modular and expandable system can integrate with fixed- and rotary-wing aircraft and countermeasure systems, with the flexibility to work with existing radar or laser warning systems. The core of the 3DAWS suite is the passively-cued, semi-active radio frequency 3D Tracker element, which serves as an adjunct to current and future passive threat detection systems.