The Patriot missile system plays a key role for nations around the world in efforts to safeguard their airspace from evolving threats, from high-flying ballistic missiles to low-flying drones.

The MIM-104 Patriot System, called the Patriot, is a surface to air missile system used by the US Army and forces of other nations including Saudi Arabia, the United Arab Emirates (UAE), Israel, Kuwait, Qatar, Bahrain, Taiwan, Greece, the Netherlands, Germany, Spain, Japan and South Korea, according to the Missile Defense Advocacy Alliance.

In November 2017, Romania, Poland and Sweden struck deals with the United States to buy Patriot systems. Most recently, Switzerland became the 18th global Patriot partner in April, when the country was awarded a contract to use the system as the backbone of its air defense.

The Patriot missile defense system can detect, track and engage unmanned aerial vehicles, cruise missiles and short-range or tactical ballistic missiles. It is considered one of the most advanced air defense systems in the US arsenal.

It consists of six major components: a missile, launcher, radar set, control station, power generator unit and high-frequency antenna mast, and uses an advanced aerial interceptor missile and high-performance radar systems.

The system can independently search for and engage targets using what is commonly called the "detect to kill" system.

The missiles are designed to explode near incoming missiles to disrupt their flight, with the system using a two-shot method that aims to guarantee destruction of the target.

Decades of service

The system was initially developed in the United States in the 1960s and has undergone extensive upgrades over the years. It was designed to intercept and destroy enemy aircraft, tactical ballistic missiles and cruise missiles.

In the decades since its first design, the Patriot system has developed into an adaptable, multi-functional defense system capable of thwarting a variety of aerial threats.

Since it was first fielded, five nations have used the Patriot in more than 250 combat engagements against manned and unmanned aircraft, cruise missiles, and tactical ballistic missiles, according to manufacturer RTX (formerly known as Raytheon).

Since January 2015, Patriot has intercepted more than 150 ballistic missiles in combat operations around the world. RTX engineers track each use of the Patriot to uncover new ways to improve or enhance the system, so it will continue to respond to the constantly changing and developing threats.

The Patriot partnership, a consortium of the 18 nations that use the system, invests together in enhancements and upgrades to the system.

New capability for the PAC-3 system

The latest version is the Patriot Advanced Capability-3 Missile Segment Enhancement (PAC-3 MSE), which completed its testing in November 2017. This upgrade significantly increased Patriot capabilities with upgraded missiles and use of the Link 16 communications system.

It can engage and destroy more advanced ballistic missiles than can previous iterations. The agile system also can be moved and set up quickly.

PAC-3 uses a sophisticated phased-array radar that provides 360-degree coverage and the ability to track multiple targets simultaneously.

The modified Patriot launcher can carry various combinations of three types of missiles. It can fire 16 PAC-3 Cost Reduction Initiative (CRI) missiles and target eight inbound ballistic missiles, and uses semi-active or active radar at altitudes of up to 36,000 meters and distances out to 160km.

The more advanced PAC-3 MSE features larger, dual pulse solid rocket motors; larger fins; and upgraded actuators and thermal batteries to achieve greater speeds and maneuverability for defeating more-advanced ballistic and cruise missiles. It can defend a larger area than its predecessor can.

The Patriot radar is notable for combining surveillance, tracking and engagement -- a departure from the design of some other air defense systems. It is equipped with electronic "counter-countermeasures" and is highly resistant to radar jamming, electronic counter-measures and the use of radar warning receivers.

As the world faces ever-increasing security threats from drones and missiles, the Patriot consortium is investing in continued upgrades to the system.

In 2018, RTX announced a five-year, $2.3 billion plan to further upgrade the Patriot system. The plan includes developing new cutting-edge methods to search for and defeat the wide range of evolving threats. The company is also working to enhance Patriot's ability to counter electronic countermeasures and conduct combat identification.

The Patriot system is a worldwide leader for its reliability and versatility -- and it continues to improve with each upgrade.