Air defense artillery
Air defense artillery (ADA) is a combat arms branch of the United States Army, with the responsibility of protecting ground forces from aircraft and missile attack. The term anti-aircraft artillery is a more general term for specifically firearms-based air defense weapons.
Recently, the U.S. ADA mission has broadened to include counter-rocket, artillery and mortar, and working jointly with Army aviation in deconflicting the airspace over a brigade combat team. While the usual emphasis is on operations in the field, if the U.S. deploys a national ballistic missile defense system, ADA would operate it were it deployed.
The Army has recognized that there have been no aircraft attacks on U.S. forces in the last several decades, although Iraq used SS-1 SCUD (and derivative) ballistic missiles in the Gulf War and Iraq War, and there is a decreased need for traditional ADA in the field.  There is a need for ballistic missile defense, and new capabilities may allow defense against unguided rockets, artillery and mortars. Cruise missiles are also a possible threat in the field; anti-shipping missiles were used by Iraq in 1991, and comparable land-based systems exist.
It is not being suggested that air attack is impossible, but that offensive counter-air (OCA) operations by the U.S. Air Force, U.S. Navy, and coalition partners have suppressed the enemy air threat before it reached ground forces. The possibilities cannot be ignored:
Counterair operations usually begin early in the conduct of joint operations to produce
the desired degree of air superiority at the times and places chosen by the JFC. However, air
superiority may not totally eliminate the air and missile threat.
In reaction to U.S. proposals to place ballistic missile defense equipment in Eastern Europe, one of Russia's response has been to resume worldwide patrols by their long-range bomber, the Tu-160/NATO: BLACKJACK. Russia has denied that the aircraft will be landing in Cuba and possibly other places in the Western Hemisphere.
Even where there have been symbolic close approaches by foreign military aircraft, it would be likely that a long-range bomber, such as the Tu-160 would be firing standoff missiles, not dropping bombs; detection and missile defense would be paramount. Nonstate actors, however, may present unconventional threats with light or ultralight aircraft, dropping bombs or making suicide attacks.
With new technology, however, ADA may have a renewed role against the very real threats of mortars and unguided rockets used by guerrillas. It is also not implausible that the U.S. might send forces to support a friendly Host Nation (HN), which is threatened by a neighbor with more conventional artillery or attack aircraft capability. Active defense against such threats is termed counter-rocket, artillery and mortar (C-RAM).
After seeing the results of German air-ground cooperation in the Polish campaign, it was clear to the U.S. Army, which included combat aircraft, that better air defense would be necessary. There was disagreement between anti-aircraft artillery and fighter aircraft advocates, who had not yet realized the two classes of weapons could complement one another, as parts of an integrated air defense system.
From assets of the obsolete Coast Artillery, the Air Defense Artillery force was organized. This generated protest from aviators who believed that only aircraft could defeat other aircraft. This was an early example of air visionaries believing they had the ultimate answer, not realizing the value of complementary systems. President Roosevelt sided with public opinion and the aviators, although he saw the air force as having a broader role than air defense.
Observations from the Battle of Britain, however, demonstrated that ADA and fighters were complementary. Especially as radar developed, allowing unified command and control, deployed forces had a combined air defense system. The Germans, by the time the Allies had started strategic bombing, also recognized the value of integrated air defense systems; the Kammhuber Line was a radar-based command and control system, using somewhat different ideas than the British, which employed both artillery and fighters.
Air defense systems
ADA operates a layered defense system, currently based on the MIM-104 Patriot and FIM-92 Stinger missiles, the Patriot-specific radar, and one general-purpose air surveillance radar, but both additional missions and systems are in active consideration or limited deployment.
The AN/MPQ-64 Sentinel air search radar is being linked to an increasing number of Army and joint information systems. ADA roles are being redefined as part of overall restructuring, and taking on roles such as deconfliction for the Brigade Combat Teams' airspace.
Top tier ballistic missile defense
A new system, Terminal High Altitude Area Defense (THAAD) is being added to give greater range and coverage than PAC-3 alone. Both systems are compatible with the longer-range Navy's RIM-161 Standard SM-3 anti-ballistic missile controlled by the AN/SPY-2 upgrade to the AEGIS battle management system on its Ticonderoga-class cruisers and Burke-class destroyers. There are considerable technical similarities, adjusted for the operating environment, between the Navy AN/SPY-2 and the Army AN/TPY-2 radars.
The THAAD missile, which does not yet seem to have a standard missile designation, uses hit-to-kill kinetic energy, with no explosive. It can engage targets up to altitudes up to 150 km (93 miles) away at a range of > 200 km (125 miles) A THAAD battery consists of about nine launch trucks with ten missiles each, two mobile tactical operations centers, and the AN/TPY-2 Ground-Based Radar (GBR).
Based at Fort Bliss, the first operational THAAD battery unit was activated in May 2008. The battery based Fort Bliss, Texas, which will receive 24 missiles, three launchers, one fire control and one radar unit. Full system deployment is planned in 2009.
High and medium altitude
MIM-104 Patriot surface-to-air missiles and associated radar for defense against high-altitude aircraft and theater ballistic missiles. In the current PAC-3 (Patriot advanced capability) version, the range has been decreased from the original aircraft-only version, but, as opposed to the questionable performance in 1991 against Iraqi SS-1 SCUD ballistic missiles, it was much more effective against them in 2003.
Low altitude air defense
For low altitude threats, FIM-92 Stinger missiles ar deployed both as a man-portable air defense system, operated by personnel organic to combat units, and Stinger-carrying vehicles operated by air defense personnel.
While it is not part of the official Army inventory, ADA has deployed some Norwegian SLAMRAAM truck-launched derivatives of the AIM-120 AMRAAM Advanced Medium Range Air Defense missile, as part of U.S. homeland security operations in the Washington D.C. area. SLAMRAAM is expected to replace the vehicle-mounted Stinger systems.
Low-altitude Counter-Rocket, Artillery and Mortar (C-RAM)
Counter-rocket, artillery and mortar (C-RAM) is now an ADA mission. One article, without explicitly naming systems, speaks of knocking down the 100th enemy round News reports suggest that bases in Afghanistan and Iraq are using the Phalanx close-in weapons system (CIWS) as the C-RAM kill mechanism.
There is even a C-RAM official website. Cite error: Invalid
<ref> tag; invalid names, e.g. too many A prominent message seems to be that funds are fully restored for the Forward Area Air Defense (FAAD) system.
Not ADA responsibilities at present, but sensors that could easily become part of the ADA mission, are counterartillery radar: the AN/TPQ-46 Lightweight Countermortar Radar (LCMR), and the medium-range AN/TPQ-36 and long-range AN/TPQ-37 Firefinder radars.
The next logical step, however, is active against against these much smaller targets. There is substantial joint development work with Israel, which has a continuing problem with rocket attack,  although Israel seems to prefer domestic C-RAM systems.
ADA is adapting to the new field threat, as well as specialized homeland defense capabilities, ballistic missile defense, and new roles in deconfliction. 
In keeping with the restructuring of the United States Army, which is moving to a brigade-based rather than division-based force, ADA is doing away with division-level air defense battalions, and creating composite battalions of Patriot and Avenger battalions. By 2009, ADA is expected to consist of:
- 8 Patriot battalions
- 5 composite battalions
- 1 SLAMRAAM battery for the National Capital Area
Obviously, ADA soldiers are proficient with air defense radar, both those associated with specific missiles, and the AN/MPQ-64 Sentinel air warning radar. Sentinel has a good deal of commonality with the AN/TPQ-36. This radar, operated both by the Army and U.S. Marine Corps, is being upgraded from 40 km to 75 km range, and is capable of detecting cruise missiles, helicopters, and unmanned aerial vehicles (UAV) as well as fixed-wing threats.
Warning and deconfliction missions
ADA soldiers are being reassigned to the brigade combat team, unit of employment, and aviation brigade headquarters to restore the air situational awareness that had been provided by divisional ADA battalions. The
A team of ADA and Army aviation personnel now run Air Defense Airspace Management (ADAM) cells in headquarters units in Iraq and Afghanistan, not principally to detect threats but help deconflict the extremely busy airspace full of airplanes, helicopters, UAVs, and sometimes missiles and artillery. It goes beyond the classic ADA function of air and missile defense, and merges it with the Army Aviation Command and Control (A2C2) mission. The cell's soldiers have to be cross-trained in Aviation and ADA functions so they can activate or deactivate restricted operations zones, submitting an air control measure request, deconflicting UAVs, or monitoring air tracks. The ADAM cell systems include:
- Command, control and intelligence
- Tactical Airspace Integration System (TAIS): combines A2C2 and ATC needs, digitizing and interworking between the two control systems
- Air Defense Systems Integrator (ADSI): Combines air track and ballistic missile warning from multiple networks, including intelligence feeds. ADSI is aware of the air tasking order and is aware of the significance of each track, so the ADAM cell can reach the crew of a track violating BCT space. In addition, it provides the BCT staff with situational awareness of its own UAVs and assigned air support.
- Air and Missile Defense Workstation (AMDWS)
- Forward Area Air Defense (FAAD) System.
- Commmunications:UHF, VHF, HF, and satellite
- Artillery tracking
ADAM cells complement Air Force and civilian Air Traffic Control (ATC) centers, which control the airspace outside the BCT-controlled airspace. They jointly clear airspace for preplanned fire missions, notify ATC of BCT airspace violations, and manage emergency requests for clearing airspace for counterfire or demolitions. ATC still maintains the voice contact with pilots.
Deconfliction reflects one of the classic laws of combat: when Mr. Artillery Shell's flight path intersects the path of our helicopter, he is no longer our friend.
Other warning systems
They also operate RAID Eagle Eye surveillance systems, which cover weapons storage sites with EO/IR sensors, radar, flash and acoustic detectors motion detectors. These can be mounted on fixed towers, mobile masts, tethered lighter-than-air aerostats, and HMMWV-mounted masts. The RAID platforms also can serve as communications relays for SINCGARS, EPLRS and a system-specific radio link. These complement Electro-optical artillery detection MASINT systems in testing in Afghanistan could join these roles.
When North Korea was making a controversial intercontinental ballistic missile test, U.S. and Japanese warships, the U.S. ships armed with the AEGIS SM-3 missile, were in the Sea of Japan. Subsequently, the U.S. sold Patriot PAC-3 to Japan for terminal point defense.
Joint development of systems including the point defense Mobile Tactical High Energy Laser (MTHEL), renamed Skyguard  (not to be confused with the Oerlikon-Rheinmetall Skyguard, which is a gun system), as well as the Arrow ABM, have been in progress with Israel. A recent development is linking US BMD detection to Israel's networks. . At least part of this development is putting the Raytheon AN/TPY-2 into Israel, and increasing Israeli access to the downlink from U.S. Defense Support Program staring infrared launch detection satellites including the Defense Support Program.
Arrow intercepts at a higher altitude than PAC-3, and the systems are complementary. If the U.S. should acquire Arrow, it logically would be under the same command as PAC-3, which would form the second tier of land-based theater BMD.
Again in keeping with the realities that air defense, almost by definition, is multi-service, a July 2008 exercise teamed a composite Patriot/Avenger/Sentinel battery to operate jointly with Air Force fighters and a Navy Ticonderoga class cruiser equipped with the AEGIS battle management system.
SLAMRAAM is seen as the "shooter" part of the Joint Land-attack cruise missile Elevated Netted Sensor (JLENS) under development, for fielding in 2011. With JLENS, SLAMRAAM will replace Avenger, which has little capability against cruise missiles.
- Feickert, Andrew (6 January 2005), U.S. Army’s Modular Redesign: Issues for Congress, Order Code RL32476 p. CRS-21
- Joint Publication 3-01: Countering Air and Missile Threats, 05 February 2007 p. I-2
- Solovyov, Dmitry (21 July 2008), "Russian military scoffs at Cuba refuelling report", Reuters
- Parsch, Andreas, "Lockheed Martin THAAD", Designation Systems
- "THAAD Theatre High Altitude Area Defense Missile System, USA", Army Technology
- Rider, Timothy L. (9 May 2008), Countering capability intercepts 100th rocket, mortar in Iraq
- "Israel seeks U.S. Phalanx system for defense against rocket barrage", World Tribune, 30 July 2008
- Lennox, Robert P., "Air and Missile Defense goes Global", Army Magazine
- Fitch, Steven (October-December 2006), "Employing the Air Defense Airspace Management Cell", Air Defense Artillery: 17-18
- "Skyguard Laser Based Counter-MANPADS/C-RAM System, Northrop Grumman", Defense Update, July 14, 2006
- "U.S. to help Israel with missile detection", Reuters, 29 July 2008
- Sieff, Martin (13 February 2007), "Israeli Arrow Hits Missile At Night", United Press International