The first combat use of aircraft was seen during World War I when simple iron bombs were dropped over the sides on to enemy positions. The military value of aircraft was quickly recognised following these simple beginnings, the modern multi-role airforce being the development of this. However the simple iron bomb has changed relatively little while the method of delivery has slowly evolved. During World War II attacks on enemy infrastructure and civilian areas utilised massed fleets of large aircraft dropping thousands of bombs. This was the only near-sure way of destroying the target, targetting methods remained relatively primitive. However this was an expensive (in all ways; economic, material and manpower) way of winning battles.

In the 1960's the U.S. initiated research into the use of lasers for targetting weaponry. This research eventually led to the development of the PAVE KNIFE designation system combined with the Paveway laser guidance kit (an adaptor kit which was fitted to standard dumb iron bombs). The basic idea is quite simple, a target is illuminated with laser light. The guidance unit attached to the bomb uses the reflected cone of energy to then stear the bomb (via a set of attached fins) to the target. The PAVE KNIFE system, developed by Aeronautronic-Ford was first deployed during the Vietnam conflict, introducing the world to precision guided bombs for the first time. Development of both the designation and guidance systems has continued apace since that time yielding a range of precision attack systems.

Paveway III (GBU-24) © WAPJ

The most common form of Laser Guided Bomb system currently deployed amongst Western airforces is the Paveway II guidance unit combined with one of several designation systems. The Paveway II system, introduced in 1976 is a major development of the original Paveway I with improvements including; folding wings and improved canards, upgraded sensor optics, reduced weight, reduced start-up times and improved field of view. Additionally it introduced the ability to detect laser light emissions coded using a Pulse Frequency Repetition technique. This introduces both superior security (it becomes harder to spoof the seeker) and an ability to simultaneously attack several targets in close proximity to each other. Following on from Paveway II is Paveway III, first declared capable in 1983 but only becoming common in the 1990's. The major improvements introduced in this generation enable the bomb to be delivered from significantly lower altitudes and at greater range to targets. Hence Paveway III is also refered to as an LLLGB, Low Level Laser Guided Bomb. A further upgrade to the Paveway series, termed Enhanced Paveway (or GBU-24E/B in the U.S.) incorporates a GPS/INS package into the guidance system. This will increase the stand-off launch capability and compensate for problems with poor or even complete loss of laser designation, eg. poor or changeable weather, smoke, etc.

Both the Paveway II and III consist of essentially three components; a CCG (Computer Control Group), canards and an airfoil package. The CCG, containing the electronics, batteries and sensor is fitted to the nose of the bomb. To this is mounted the full-scale moveable canards which provide the primary control surfaces. The term full-scale means the canards can be varied only from a zero deflection to a maximum deflection and not in-between. The airfoil package, comprising four retractable wings is fitted to the rear of the bomb and providing the primary lift surfaces. The package is designed to fit most standard general or penetrator bombs. In RAF use Paveway II is generally fitted to 1000lb general purpose bombs while Paveway III, introduced only recently to the inventory is fitted to 2000lb devices. In late-2000 the RAF committed to purchasing Enhanced Paveway as part of its committment to seek more autonomous weapons.

Attack profiles for delivery of laser guided ordnance will vary depending on several factors; the target, air to surface defences, whether laser designation is required or being supplied by a third party, etc. However once the launch aircraft has released the bomb the flight profile comprises of basically three phases. The first of these is ballistic whereby the bomb follows a normal ballistic trajectory away from the launch platform, the wings will deploy during this phase. The second or transition phase is where initial acquisition of the designating laser takes place. Once a lock has been achieved the guidance system will use the canards to try and keep the bomb within the cone of reflected laser energy. The final terminal phase occurs when the reflected laser centres on the seeker causing the bomb to dive to the target.

To utilise any of the Paveway series, or indeed any laser guided bomb a designation system is required. Just as Paveway as been progressively developed so have the designators. Simple early systems where quickly superceded with increasingly sophisticated units, often incorporating other sensors and aids for the parent aircraft. In some cases the designators are integrated within the aircraft itself, others are supplied as externally carried pods. Some of the most common units still in use are; Pave Spike, LANTIRN, Litening and TIALD. Of these Litening and TIALD are often considered to be the most advanced of their type currently available.

Litening designation pod © WAPJ

LITENING, a product of Israel's Rafael Industries is a highly capable designation and navigation system. The unit comprises a pod containing 5 major sensors; a high resolution CCD, FLIR, laser illuminator, Laser detector and a strap-down system. The FLIR provides day and night imaging of targets with three operational modes; wide, medium and narrow fields of view. The medium and narrow modes are designed for target identification and typically used when lasing a target with the laser designator. The wide field mode can be used by the pilot as a night vision aid and navigation. For situations where the FLIR imagery is compromised the CCD can be utilised. Unique to LITENING is the laser detector which can be used for detecting targets being designated by other allied forces. The strap-down system aids in stabilising the optics and ensures they are properly aligned with the parent aircraft. The German Luftwaffe are one customer of LITENING who currently deploy it on their Phantom F-4ICE aircraft. It is also likely to find use on the Phantom's replacement, the Typhoon.

The TIALD or Thermal Imaging And Laser Designation system was developed by GEC-Marconi during the late-80's and early-90's. In fact it was rushed into service early during the Gulf Conflict fitted to RAF Bucaneers which acted as designators for Tornado GR.1's. The first versions of TIALD were constructed, like LITENING, as pods carried externally by the parent aircraft. The units, designed to operate 24 hours a day comprise a high resolution FLIR, laser designator and strap-down system. Most older designation systems required the pilot or navigator to keep the target in-track manually. However TIALD allows automatic tracking of the specified target allowing the pilot and navigator to typically concentrate on other matters. TIALD has been progressively upgraded since the prototypes first saw action including being made suitable for single seat aircraft. At present RAF Tornado GR.1, Jaguar and Harrier GR.7 bombers carry the Series-400 pod. The Tornado GR.4's are equipped with an internal version of the series-400 unit, however problems discovered during recent missions has resulted in urgent upgrades being required. There is a possible future upgrade to a Series-500 specification, this may find use on the Eurofighter Typhoon till ATS (Advanced or Aerial Targetting System) an Anglo-French project developing a new designator completes in the next few years.

Although laser designation has enabled great advances in precision bombing it does have some serious limitations. Unless the target is unobscured with little to no smoke, fog or mist in the area it is highly possible that the laser light will be scattered causing the bomb to lose lock or fail to acquire entirely. This of course can lead to a missed target and potentially very serious collateral damage. The Enchanced Paveway goes a long way to circumvent this problem using GPS/INS guidance to augment the laser. However it adds to an already high cost (not only in terms of the bomb seeker kit but also the designator) and still requires that some form of laser designation take place. An alternative to laser based guidance is to use a stand-off weapon such as Storm Shadow or TAURUS. However these are an expensive solution and can only be carried in low quantities by small fighter bomber aircraft.

Boeing JDAM © Boeing Inc.

In the 1990's following the Gulf Conflict the U.S. recognised these problems and initiated several projects to examine solutions. One of these was JDAM, Joint Direct Attack Munition which like Paveway consists of an add-on kit for existing iron bombs. The kit comprises a tail unit containing the GPS (Global Positioning System) and 3-axis INS (Inertial Navigation System) guidance system. To this are attached four fins which provide for both flight control and lift, stabilisation (and additional lift) is provided by strakes attached to the sides of the bomb. By utilising GPS/INS the weapon becomes fully autonomous once released while being unaffected by weather or target conditions. The cost of the system can also be held down by using standard commercial off the shelf (COTS) components.

There are a range of available delivery options for JDAM depending on the situation and capabilities of the launch aircraft. However they fall into basically two categories; pre-planned and inflight (re-)targetting. In the former case all the target details including the desired bomb release envelope are uploaded to the aircraft before take-off. While in flight the JDAM unit receives updates from the aircrafts own INS/GPS systems allowing it to track its own position and compensate for alterations to the desired release window. When the pilot is within the pre-determined release envelope (or as near as possible to it) the bomb is released. The on-board GPS/INS system then guides the weapon to the preset target coordinates. If for any reason GPS information is unavailable the system will instead rely purely on INS, which although not as accurate as GPS should keep the bomb within an acceptable impact distance. The second method of delivery allows the pilot to redesignate targets while in-flight. Whether or not this can be achieved depends upon the launch aircraft having the capability to accurately acquire a target and determine its coordinates.

The currently deployed models have a range of around 15nm (this of course depends on launch conditions since the bomb remains in free fall) allowing bomb release at far safer distances than can be achieved with laser designation. Once released the launch aircraft is free to navigate reducing its exposure to enemy defences, another bonus over laser designation.

During some 245 live trials at White Sands Missile Range in New Mexico JDAM has achieved a flight reliability rating of some 95% and CEPs (Circular Error Probable) of some 9.6 metres (in GPS guided mode, INS only mode would result in lower CEPs of around 30 metres). These trials have also proved the weapons all-weather ability which in itself is a significant improvement over laser guided ordnance. The first production JDAM kit was delivered to the U.S. Air Force in June 1998. Over the life of the contract some 87,500 JDAM kits will be produced for the U.S. Department of Defence alone. So far it has been cleared for carriage on a range of U.S. bombers including the B-1, B-2, B-52 and the F-16 Falcon and USN/USMC F-18 Hornet. In time this will be extended to include the F-15E, F-22 and perhaps the F-117.

A number of improvements are either in development or planning to improve the accuracy and range of JDAM. These should see the range being improved to around 35nm (again subject to launch conditions) and an ability to fit the kit to smaller 500lb bombs. Other potential improvements may see the fitting of a rocket booster and/or new warhead to improve the bombs penetrator capabilities. As well as these more basic upgrades there are other projects underway to produce a low cost terminal seeker to further improve accuracy. One of these projects, DAMASK (Direct Attack Munition Affordable SeeKer) uses commerical off the shelf components to integrate a cheap imaging seeker into JDAM. The aim here is to improve the CEP to a mere 3 metres. As with the basic JDAM, DAMASK could be operated in two modes; pre-planned and in-flight targetting. The pre-planned data would utilise reconnaisance data of the target to provide an accurate image for the seeker to lock on to. For in-flight targetting the launch aircraft could utilise a high resolution FLIR or SAR (Synthetic Apeture Radar) imagery for use by the DAMASK seeker.

The first JDAM to be dropped in anger was made by a USN F-18 during one of the many on-going confrontations between Iraq and the U.S./UK. More recently the B-2 stealth bomber dropped JDAM's over Bosnia in its first operational sorties. Unfortunately one of these attacks included an incident involving the accidental bombing of the Chinese Embassy in Belgrade.

As well as USAF and the USN the Royal Air Force are believed to extremely interested in the weapon. This follows experiences in Kosovo where poor weather resulted in many missions being scrapped due to an inability to drop purely laser guided ordnance.