The AN/TPY-2 Surveillance Transportable Radar, also called the Forward Based X-Band Transportable (FBX-T) is a long-range, high-altitude surveillance radar designed to add a tier to existing missile and air defense systems. It is the primary radar for the Terminal High Altitude Area Defense missile system, but also cues the AN/MPQ-53 radar of the MIM-104 Patriot system. Patriot PAC-3 is a lower-altitude missile and aircraft defense system than THAAD.
The U.S. Army developed it and remains responsible for its use by air defense artillery in theater and tactical applications. As a component of national ballistic missile defense, the U.S. Missile Defense Agency is responsible for AN/TPY-2 applications.
It has been deployed in Japan to collect strategic-level information on North Korean missile developments, as well as warning Japan of incoming warheads. Japan has bought both PAC-3 for point defense, and is upgrading the AEGIS systems on its Kongo-class destroyers so they can use the longer-range RIM-161 Standard SM-3 theater ballistic missile defense.
An AN/TPY-2 is based in Alaska as part of national ballistic missile defense deveopment. The U.S. has agreed to provide it to Israel, to complement their two-tier Arrow-2 missile and Patriot PAC-3 missile defense. 
The AN/TPY-2 is a phased-array radar, which operates in the 8.55-10 GHz X band. Raytheon builds it as part of an X-band family, along with the National Missile Defense (NMD) X-Band Radar (XBR) and AN/FPS-129 HAVE STARE.
It complements the fixed AN/FPS-129 HAVE STARE X-Band "large dish" radar, located at Vandenberg Air Force Base.  Smaller mobile X-band dishes, not yet designated, may also be paired with the AN/TPY-2/
- "AN/TPY-2 Transportable Radar Surveillance (Forward Based X-Band Transportable [FBX-T])", Globalsecurity.com
- Williams, Dan (29 July 2008), "U.S. to help Israel with missile detection", Reuters
- Raytheon Awarded $304 Million for Ballistic Missile Defense System Upgrades, PRNewswire, 11 July2007
- "AN/FPS-129 HAVE STARE X-Band Dish radar", Globalsecurity.com