XM1156 Precision Guidance Kit
The XM1156 Precision Guidance Kit is a U.S. Army program to develop a precision guidance system for existing 155 mm artillery shells. The prime contractor is Alliant Techsystems and the industry team includes Interstate Electronics Corporation.
In operation the PGK screws into the nose of the projectile much like conventional fuzes. In addition to the fuzing function it provides a GPS guidance package and control surfaces to correct the flight of the shell. This is analogous to the addition of a Joint Direct Attack Munition (JDAM) tail-kit to a dumb iron bomb, creating a precision guided munition. The system began production in 2009, was first expected to be in service by 2010, but later was fielded in spring 2013.
A conventional unguided M549A1 155 mm artillery projectile has a circular error probability (CEP) of 267 m (876 ft) at its maximum range, meaning that rounds can be expected to land within 267 meters of their intended target. This has made unguided artillery dangerous to use in close combat for fear of friendly fire and collateral damage. The M982 Excalibur was fielded as a guided shell that effectively hit within 6 m (20 ft) of a target, but the Army developed the XM1156 as a cheaper alternative. The PGK fuse can be screwed onto existing M549A1 and M795 projectiles, be fired from M109A6 Paladin and M777A2 Howitzer artillery systems, and hits within 50 m (160 ft) of the target at any range.
Small aerodynamic fins pop out of the system to steer the shell on target. Its GPS receiver compares the PGK's flight pattern to the coordinates of where it should hit, and the fins adjust its path to match where the round will actually impact. A fail safe exists where if the shell does not impact within 150 m (490 ft) of the intended target, it will land but not explode; the PGK "decides" five seconds after launch whether it expects to impact close enough to detonate. This safety feature is expected to give soldiers more confidence when calling in artillery support close to their position.
- June 2006: Raytheon downselected from XM1156 competition.
- July 2006: BAE Systems and Alliant Techsystems selected to take part in a competitive Technical Development (TD) program.
- May 2007: System Demonstration and Development (SDD) contract awarded to Alliant Techsystems.
- October 2012: Soldiers from Fort Bliss became the first troops to fire the XM1156 guidance kit. 24 PGK-equipped projectiles were fired.
In March 2013, the 15th Field Artillery Regiment in Afghanistan began training on equipment related to the XM1156, and began fielding PGK rounds shortly after, with initial fielding completed by the end of June 2013. The U.S. Army received 2,400 PGK-equipped shells and the U.S. Marine Corps received 700 shells.
- Guidance: GPS
- Unit cost: < $3,000 
- XM1156 Precision Guidance Kit (PGK) - Global Security
- "ATK Precision Guidance Kit (PGK) - ATK".
- "ATK To Make Precision Artillery Shell - defensenews.com".
- Fort Bliss Soldiers First To Fire Army's New Near-Precision Artillery Rounds - Army.mil, December 11, 2012
- XM1156 Precision Guidance Kit Heads to Afghanistan - Defensemedianetwork.com, 26 April 2013
- Army Ships Precision Guidance Kits to Artillery Units in Afghanistan - Defensetech.org, 10 May 2013
- "ATK Awarded Precision Guidance Kit Contract After Multi-Day Competitive Shoot-Off - ATK".
- FMS: Australia Requests Precision Guidance Kits for 155mm Munitions - Deagel.com, 12 August 2013
- "Precision Guidance Kit (PGK) Improving the Accuracy of Artillery Fire - Defense Update".
- Army munitions officials eye pending developments - Aviation Week
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