In mid-2018 the U.S. Army increased its spending on SLEP (service-life-extension program) work on its older MGM140 ATACMS (Army Tactical Missile Systems) artillery rockets. Nearly 4,000 ATACMS have been built since the missile entered service in the late 1980s. In the late 1990s a longer range, GPS guided version was introduced but by then most of the current ATACMS missiles were built and production slowed to very little by 2007. The SLEP program will refurbish and upgrade the older, shorter range (165 kilometers), unguided ATACMS so they have features of the latest models. The SLEP will produce a like-new guided missile with a ten year shelf life and a 250-300 kilometer range (depending on warhead type).
Older ATACMS will undergo SLEP at the rate of 300-500 a year until all, or most, of the ATACMS stockpile, has been refurbished. By the mid-2020s a replacement for ATACMS called Deepstrike is supposed to enter service. This will be a thinner rocket so that two can be fit into a MLRS container that currently holds one ATACMS. Deepstrike will be capable of longer (up to 500 kilometers) range and even more capable guidance system features. At that point, there will still be several thousand SLEPed ATACMS that are built to accept new warheads with new features (like ground penetration to destroy underground facilities) and more capable guidance systems.
The ATACMS is a 610mm ballistic missile that fits in the same size container that normally holds six 227mm MLRS rockets. The latest upgrades have been to the guidance system. In 2017 ATACMS was given the ability to hit moving targets, specifically ships at sea. ATACMS has sufficient range for that and the U.S. pioneered the development of terminal guidance systems for ballistic missiles in the 1970s (the Pershing mobile missile). Since then the U.S. has developed similar guidance systems so that high-speed missiles can hit moving targets. So it was not a difficult feat to develop a terminal guidance system for ATACMS that searches for a certain size ship and heads for it while moving at more than a thousand meters a second (faster than a very speedy bullet). The ATACMS guidance system has also received a proximity detonation capability to that it can be programmed to explode in the air above a target. All the current ATACMS needs is the GPS coordinates of the moving target (which can be on land or sea). Since max flight time (at max range) is only a few minutes it is easy to predict where the moving target will be based on aerial, satellite or sonar detection. It takes less than a minute to update the guidance system and launch. If nothing else this will give potential naval foes something more to worry about and be a popular export item as well.
Most current ATACMS are armed with a 227 kg (500 pound) high explosive warhead. The U.S. used over 700 ATACMS, most of them in Iraq and Afghanistan combat operations and their performance was excellent, especially the guided ones. Nearly 4,000 ATACMS have been built since the mid-1980s and about 70 percent are still available for another upgrade. In addition to those used in combat about three percent were fired for training or testing. ATACMS currently use GPS guidance to hit targets up to 300 kilometers away.
When the U.S. Army first introduced ATACMS in the late 1980s it designed fancy warheads that distributed lots of smaller bomblets because the first ATACMS were unguided. While these worked, there was always a problem with some of the bomblets not self-destructing and later going off when civilians, or American troops, came along. Not a popular weapon. Then, when a version with GPS guidance and a single 227 kg (500 pound) high explosive (or "unitary") warhead was introduced, it proved very popular. ATACMS currently cost about $1.3 million dollars each. A 500 pound JDAM costs about $40,000, although you can at least double that to cover the expense of operating the jet fighter or bomber that delivered it. This makes ATACMS sort of like the popular 500 pound JDAM smart bomb used by the air force but not requiring an aircraft to deliver it. ATACMS can be used in any weather conditions at any time and on short notice. It also travels a lot faster than any aircraft. Despite the growing use of inexpensive UAVS to deliver smaller JDAMS or even smaller 49 kg Hellfire missiles or 120 kg (280 pound) SDB (small diameter bombs) the ATACMS is always available to get something on the target right away.
Another advantage of ATACMS is the ability to quickly move it and its launcher by air to anywhere in the world. This is because of HIMARS. Only costing about $3 million each, these smaller, truck mounted MLRS (HIMARS) rocket launcher systems carries only one, six rocket (or one ATACMS) container (instead of two in the original MLRS vehicle). But the 12 ton truck can fit into a C-130 transport (unlike the 22 ton tracked MLRS) and is much cheaper to operate. The first HIMARS entered service in 2005, about a year after GPS guided rockets did. HIMARS proved more effective and popular than expected. HIMARS can carry one ATACMS and sometimes does.