The contract requires the company to upgrade the customer's long-range, high-altitude, all-weather Patriot system to the most advanced configuration available.
The Configuration 3+ upgrades include the Post Deployment Build 8 software and hardware suite.
Raytheon Integrated Air and Missile Defense vice-president Ralph Acaba said: "Patriot saves lives. Our customer faces a very real, evolving threat; by upgrading Patriot, they will continue to protect their civilians, military and critical infrastructure."
The upgrades will allow Patriot to use the PAC-3 MSE interceptor missile and improve the air defence system's ability to destroy tactical ballistic missiles.
The customer is one of 13 nations using the Patriot integrated air and missile defence system, Raytheon said in a statement.
Designed to counter threats from tactical ballistic missiles, cruise missiles, drones and advanced aircraft, Patriot has so far completed more than 1,400 flight tests and 3,000 ground trials.
Raytheon has also been contracted by the Netherlands to modernise its Patriot systems.
Patriot was recently upgraded with GaN-based AESA radar technology to increase its detection range and power, as well as enable 360° coverage.
The improvements allow the system to fire multiple missile types to destroy a range of threats.