Counter-rocket, artillery and mortar

Template:TOC-right Counter-mortar, artillery and rocket (C-RAM) is the U.S. Army term for a new defensive technique. It is a new mission for the Air Defense Artillery branch. While the U.S. has operational C-RAM in Iraq, Israel is actively developing C-RAM to protect urban areas, which it sees as a having different constraints than the U.S. military system. Denmark and Germany are also building C-RAM.

Previous "counter-artillery" systems, such as the AN/TPQ-36, tracked a shell back to its point of origin, but relied on counterbattery methods to prevent the next attack: counterbattery gives the coordinates to one's own artillery, which fires on the enemy point of origin attempting to destroy the weapons there. Counterartillery sensors only detect, and counterbattery is preemptive deadly force. C-RAM, instead, is active defense: it intercepts and destroys the rocket, artillery shell, or mortar shell in midair. the C-RAM system proper does not attack the point of origin.

From a doctrinal standpoint, the Army speaks of "seven pillars" of C-RAM, but not all of the "pillars" are truly active defenses: shape, sense, warn, intercept, respond, command and control, and protect.

Active defense	Preemptive	Passive defense
Command and control direct active defense, passive defense and response	Respond "application of lethal fires before or after RAM attacks"	shape "actions taken to deny the enemy's use of tactically advantageous terrain or to channel enemy forces into areas where they can be observed."
sense		protect:actions taken to harden sites or disperse assets to mitigate the effects of RAM attacks.
warn (cue C-RAM interceptor)		warn threatened troops to take cover; friendly aircraft to stay out of engagement volume
intercept

Counterbattery methods are inappropriate for situations where the threat is from guerillas firing unguided rockets or mortars from urban areas. Rockets, in such situations, may be launched from single-use launchers fired by a timer, so there is no equipment to destroy. More importantly, even if there were a mortar, counterbattery into an urban area would be apt to cause unacceptable civilian casualties. If the counterbattery weapon used antipersonnel or "dual-purpose" cluster submunitions, the percentage of submunitions that do not detonate, but still are dangerous, effectively creates an antipersonnel minefield. There is a international initiative to ban antipersonnel mines, so such methods become even more unattractive.

While there are anti-ballistic missiles and surface-to-air missiles, they are designed to engage much larger targets than artillery, light rockets, and mortars; a typical mortar shell is 81mm in diameter and approximately 240mm long. Such shells have successfully been shot down at Balad Air Base in Iraq. One article, without explicitly naming systems, speaks of knocking down the 100th enemy round

Command and control

For the U.S., the Forward Area Air Defense (FAAD) is considered the core of the initial C-RAM systems. FAAD interfaces with multiple sensors and information feeds in the Air Defense Artillery cell at Brigade Combat Team level.

Sense

Several U.S. systems provide C-RAM sensing, starting with the AN/TPQ-46 Light-Weight Counter-Mortar Radar, which gives short-range but 360 degree coverage. AN/TPQ-36 and AN/TPQ-37 radars have, respectively, medium and long range, but are directional.

While not all the details have been released, it is likely that electro-optical sensors give warning; there is an electro-optical as well as radar fire control sensor on the current Land-Based Phalanx Weapon System (LPWS) intercepting autocannon. Another potential sensor is the Unattended Transient Acoustic MASINT Sensor (UTAMS)

Warn

There is more than one kind of warning that must be sent out. Obviously, soldiers in the potential impact area need to be directed to take cover. Friendly aircraft also need to know about both the incoming threat projectiles and the fact that C-RAM is about to engage it, so they do not fly into the trajectory of either.

In the initial U.S. implementation, the Wireless Audio Visual Emergency System (WAVES) receives warning from sensors and alerts soldiers threatened by the weapons.

Friendly aircraft are tracked with the AN/MPQ-64 Sentinel radar, which has a good deal of commonality with the AN/TPQ-36. The Sentinel feeds into FAAD.

Intercept

Operational systems intercept C-RAM autocannon, although lasers have been demonstrated against the threat. Israel has a small missile in development.

In use in Iraq and Afghanistan is the LPWS, a modification of the Phalanx close-in weapons system, a 20mm autocannon originally deployed to protect ships against sea-skimming anti-shipping missiles (ASM). Phalanx was effective against older, subsonic missiles, but is being replaced against the increased threat of high-performance missiles such as the Russian Moskit.

LPWS has two radar and a forward-looking infrared sensor. The first radar, which searches for the target after being cued, is a Ku-band with Moving Target Indicator. The fire control radar is also Ku-band, using pulse Doppler techniques. Phalanx always used two radars: it followed the target with one, and tracked its own stream of shells with the other; its fire control computer moved the gunfire to intercept the target. The FLIR sensor is new; it also has a recorder that allows review of engagements.

Land warfare RAM, however, while smaller than ASM, are, in some respects, easier to track. They are on a ballistic trajectory that can be predicted, against the clean background of the sky. In contrast, a sea-skimming missile will fly just above the water, taking advantage of the radar clutter of waves, and also often maneuvers just before impact, guiding all the way into the target.