From the early days of aerial warfare, air forces around the world have sought ways to increase the accuracy and lethality of air-delivered ordnance, but it was not until advances in microchip technology that air forces were able to use precision guidance kits which could be attached to dumb bombs.
Today there are two primary types of guided bombs; Laser Guided Bombs (LGB), and GPS (Global Positioning System) guided bombs; each employ their own unique type of precision guidance kit technology. LGBs are the most common and widespread type of guided bombs. Essentially dumb bombs attached with a semi-active stabilized laser seeker unit on the nose, coupled to a Computer Control Group (CCG) containing guidance and control electronics, a battery, and a pneumatic control augmentation system. Each bomb has front control canards and a rear airflow group for stability. These weapons use their electronics to track targets that are designated by laser (typically in the infrared spectrum) and adjust their glide path to precisely strike the target. Since the weapon is tracking a light signature and not the object itself, the target must be illuminated from a separate source, either by a laser targeting pod on the attacking aircraft, by ground forces, or by a support aircraft ‘lasing’ the target.
Leading the LGB pack is Lockheed Martin and Raytheon’s Paveway series, comprising the Paveway-II, Paveway-III, and the Paveway-IV; the newest variant. Joe Serra, precision guided systems director at Lockheed Martin’s missiles and fire control division, explained the workshare split for Paveway precision guidance kits: “The US government had a lot of interest in bringing in competition for LGBs … So, in 2001 we were qualified for Paveway-II laser guided bomb kits by the US Air Force and the US Navy … One of the big drivers that competition has brought is affordability. I think the Paveway system is recognised as being a very affordable way of delivering conventional ordnance.”
Lockheed Martin is a qualified provider of all three Paveway-II variants to equip the Mk.80 freefall dumb bomb family; namely the GBU-10 Mk.84, GBU-12 Mk.82 and GBU-16 Mk.83. In its most common configuration, the Paveway-II is fixed to the Mk.82 500 pound/lb (227.2 kilogram/kg) dumb bomb resulting in the GBU-12, providing a cheap lightweight PGM suitable for use against vehicles and other small targets. The Paveway-III family has a considerably longer glide range and greater accuracy than the Paveway-II series, but it is substantially more expensive and therefore tends to be limited in use against high-value targets. Paveway-III kits have been used on the larger Mk.84 and BLU-109 2000lb (909kg) weapons, resulting in the GBU-24 and GBU-27 combinations. Paveway-III guidance kits were also used on the GBU-28/B penetration bomb, which used the BLU-109B hardened penetrator bomb during the US-led Operation DESERT STORM in 1991 to evict Iraqi forces from Kuwait. Raytheon is the sole provider of Paveway-III variants.
Adding Capability
In mid-2016, Lockheed Martin tested the new Paveway-II Dual Mode Plus LGB which incorporates new optics and a GPS/INS (Inertial Navigation System) navigation ensemble. Effective against fixed and moving targets, the Paveway-II Dual Mode Plus LGB improves mission effectiveness by providing precision strike capabilities in all-weather conditions (given that laser guidance can be degraded by precipitation or smoke particles) at extended standoff ranges. This Paveway-II LGB configuration easily integrates with aircraft employing legacy Paveway-II LGBs. On 19 September 2016, Lockheed Martin received an $87.6 million contract from the USAF for follow-on production of Paveway II Dual Mode Plus LGB kits.
The Paveway-IV, meanwhile, is a dual mode GPS/INS and laser guided bomb manufactured by Raytheon’s UK subsidiary. The weapon is a guidance kit based on the existing Enhanced Paveway-II Enhanced Computer Control Group (ECCG) with increased penetration performance. The new ECCG contains a Height of Burst (HOB) sensor enabling air burst options, and a Selective Availability Anti Spoofing Module (SAASM) compliant GPS receiver. It can be launched by Inertial Measurement Unit only, given sufficiently good transfer alignment, or by using GPS guidance. Terminal laser guidance is available in either navigation mode. The Paveway-IV has entered service with the Royal Air Force and the Royal Saudi Air Force.
GPS
Lessons learned during Operation DESERT STORM and during US-led interventions in the Balkans in the 1990S showed the value of precision munitions, yet also highlighted the difficulties in employing them: specifically when visibility of a target was degraded due to weather or smoke. The solution was to develop GPS-guided munitions. Such weapons are dependent both on the precision of the measurement system used for location determination, and the precision in setting the coordinates of the target; the latter critically depends on intelligence information.
Satellite-guided weapons like Boeing’s Joint Direct Attack Munition (JDAM) family were designed to negate the issues faced by laser guided munitions. JDAM-equipped dumb bombs are guided by an integrated INS coupled to a GPS receiver. The JDAM family can be employed in all weather conditions, without any need for additional air or ground support. Standard configuration JDAMs have a published range of up to 15 nautical miles/nm (27.7 kilometres/km). Satellite guided munitions work very well, however operational experience proved that guidance to a set of GPS coordinates does not allow flexibility for mid-course correction to prosecute moving, manoeuvring or maritime targets. In 2007 the US Navy and USAF identified an urgent need during ongoing operations in Afghanistan and Iraq for a Direct Attack Moving Target Capability (DAMTC) to enable the precision engagement of high speed moving targets. Supported by Boeing, the services rapidly fielded an add-on laser kit for the JDAM family, thereby creating the dual mode Laser-JDAM (LJDAM) to address this gap. The laser seeker is a cooperative development between Boeing and Elbit Systems. The Precision Laser Guidance Set (PLGS) consists of a DSU-38B laser seeker and a wire harness fixed under the bomb body which connects the DSU-38B with the tail kit. The LJDAM is now in widespread use with the US Navy and Marine Corps. According to Captain Jaime Engdahl, US Navy precision strike weapons programme manager: “The preferred weapon for (the US Navy) is currently the Laser JDAM because of the flexibility to employ either a precision GPS guided weapon through the weather against fixed targets or laser-guided (weapons) against high speed moving targets.”
Boeing has also developed a new wing kit which when connected to the JDAM guidance kit increases the bomb’s range from approximately 12.9nm (24km) to more than 38nm (72km); this variant is dubbed the JDAM-ER (Extended Range): “The JDAM-ER kit takes advantage of the conventional JDAM aircraft interface and Boeing GBU-39 Small Diameter Bomb glide technology,” said Greg Coffey, director for Boeing JDAM programmes: “With the JDAM-ER customers have increased standoff range needed to neutralise current and future threats.” The Royal Australian Air Force is currently only operator of the JDAM-ER.
Current US Navy capabilities in development include a dual mode capability (see above) for 2000lb hard target penetrator weapons. Further enhancements to US direct attack weapons are not currently funded but in the future may include a precision navigation capability in a GPS-denied environment, additional weapon sensors, extended range variants of current direct attack weapons, or the addition of network capabilities to enable flexible targeting of weapons in flight: “At this time the tactical value, or need, for additional capabilities in the current threat environment has not been cited in recent engagements and no requirement exists to further improve our direct attack weapon inventory,” Capt. Engdhal continues, although he added: “The Navy is closely following the development and fielding of extended range variants of JDAM by our international allies although we currently do not have a requirement for JDAM-ER.”
SPICE
Israel’s Rafael Advanced Defence Systems started working on precision-guided, air-to-ground munitions in the early 1960’s, which produced the POPEYE, a precision human-in-the-loop guided missile. Rafael’s first precision guidance kit for dumb bombs was developed in the 1990’s and are marketed as the SPICE (Smart, Precise Impact, Cost-Effective) family. The SPICE family comprises stand-off, autonomous, air-to-ground weapons capable of hitting and destroying targets with pinpoint accuracy and at high attack volumes. SPICE kits use state-of-the-art navigation, guidance and homing techniques to achieve the accurate and effective destruction of high-value enemy targets with a CEP (Circular Error Probable) of three metres (9.8ft). SPICE’s Automatic Target Acquisition capability employs unique scene-matching technology that is able to discern scenery changes, countermeasures, navigation errors and target location errors. The technology works by comparing a real-time image received from the dual Charge-Coupled Device (CCD) and infrared seeker to a reference image stored in the weapon’s computer. SPICE has day, night and adverse weather capabilities, based on its advanced seeker and scene-matching algorithms. SPICE weapons are combat-proven and in service with the Israeli Air Force and several international customers.
The first kit to be developed was the SPICE-2000, which was designed for the 2000lb. general purpose or penetration warheads such as the Mk. 84, RAP-2000 and BLU-109. The SPICE-2000 has a stand-off range of 32.3nm (60km). The next kit to be developed was the SPICE-1000, which as the name denotes, is mated to 1000lb (454kg). general purpose or penetration warheads such as the Mk.83 and RAP-1000. The SPICE-1000 has a stand-off range of 53.9nm (100km). The Israeli Air Force will reach full operational capability with the SPICE-1000 by the end of 2016.
During a mission plan, whether in the air or on the ground, target data consisting of target coordinates, impact angle and azimuth, imagery and topographical data are used to create a mission for each target which the pilot allocates to each weapon before release. Mission parameters are defined according to target type and operational requirements, such as a steep dive angle for deep penetration. The SPICE munition is released outside a threatened area, and performs midcourse navigation autonomously using its INS/GPS to home in on the exact target location with the predefined impact angle and azimuth. While approaching the target, SPICE’s unique scene-matching algorithm compares the optronics image received in real time via the weapon seeker with mission reference intelligence data stored in the weapon’s computer memory. In the homing phase, the system locates the target using scene-matching technology, and uses the tracker to hit it. As a result of this capability, SPICE overcomes target location error and GPS jamming, and dramatically reduces collateral damage. A spokesperson for Rafael told Armada: “Trends which I see include how precision for fixed targets is now evolving into a requirement for moving targets. I believe there will be new homing techniques that allow precision attack for GPS environments, and I see increased stand-off range in order to overcome the risk to the aircrew due to the increased capabilities of air defence systems.”
Worldwide Evolutions
Nations such as India, the People’s Republic of China, South Africa and Turkey are manufacturing their own precision guidance kits for dumb bombs. For example, in October 2010, India developed its first Sudarshan LGB with the help of the Aeronautical Development Establishment, a lab of India’s Defence Research and Development Organisation (DRDO). The project aimed to develop an advanced laser guidance kit to improve the accuracy of 1000lb dumb bombs. The guidance kit consists of a computer control group, canards attached to the front of the warhead for steering, and a wing assembly attached to the rear end to provide lift. The kit can guide a bomb within ten metres (32.8ft) CEP, and if dropped from normal altitude, it has a range of around 4.8nm (nine kilometres). A programme to extend the precision guidance kit capability to further increase its range and accuracy is ongoing.
Similarly, Turkey’s TÜBİTAK Defence Industries Research and Development Institute has developed the HGK guidance kit which converts 2000lb Mk.84 bombs into a precision guided munition. The kit consists of a GPS/INS guidance kit with extendable wings. It enables long range precision strike in all weather conditions with a CEP of six metres (19.6ft). Moreover, South Africa’s Denel Dynamics has partnered in a joint venture with Tawazun Holdings of the United Arab Emirates to develop and manufacture various precision weapons. A version of Denel’s Umbani kit, known as the Al-Tariq is now being manufactured. The Al Tariq provides the user with all-weather, day or night operational capabilities, utilising GPS/INS guidance or infrared, with a complete Automatic Target Recognition (ATR) capability, or a semi-active laser seeker. The system can also be fitted with a radio frequency proximity fuse for area targeting using a pre-fragmented warhead. Depending on configuration, it has autonomous target acquisition with a stand-off range of over 53.9nm (100 km). A wing kit, or motors, can be added to increase stand-off range and low-level (straight and level) launch capability. The weapons’ reported accuracy is as low as three metres CEP. Finally, Safran’s AASM adds precision guidance and propulsion kits to standard bombs, entering operational service in 2008, and in use with the French Air Force in ongoing operations against the Islamic State of Iraq and Syria insurgent organisation. The AASM has a stand-off range exceeding 32.3nm (60km) and allows operators to conduct all-weather, day/night precision ground strikes against fixed and moving targets.
Conclusions
According to the US Navy, the majority of navy weapons being employed in combat are 500lb (227kg); 1000lb and 2000 lb JDAM variants, namely the GBU-38/32/31, against fixed targets. Capt. Engdahl shared the following with Armada: “The dual mode Laser-JDAM has been operationally fielded since 2010 and has provided welcome operational flexibility to engage either moving, or fixed, targets with a single weapon variant. The US Navy, US Air Force, and our international partners will continue to procure modular JDAM tail kits and LJDAM sensor kits for the foreseeable future.”
Precision-guided dumb bombs, both GPS- and Laser-guided, combined with highly effective intelligence, surveillance, and reconnaissance, and improved targeting capabilities have been the key enablers for dramatically increasing warfighting effectiveness and minimising civilian casualties over the past two decades. Munitions like the JDAM family and LGBs are key enablers to provide precision strike capabilities. The future will see continual development of these systems employing multiple modes, new sensors, an increased focus on range, and the ability to operate in GPS-denied environments.
