April 26, 2022: As part of the latest U.S. military aid for Ukraine, the Americans are sending combat-tested artillery spotting radars as well as Sentinel air surveillance radars that detect helicopters, UAVs and cruise missiles up to 75 kilometers distant and alert ground units within range via encrypted military radio. Sentinel is particularly useful for ground troops armed with American Stinger or other manpads (Man Portable Air Defense Missile Systems) . Ukraine has a lot of Cold War era Ilga (SA-18) and over a thousand other systems from NATO nations. Ukrainian troops also have better communications than the Russians and could link nearby manpad teams with Sentinel and alert them when a likely target approaches.

In 2017 the AN/TPQ-53 FireFinder artillery spotting radar systems were updated to fix some problems discovered with early models. The TPG-53 was introduced in 2012 as the replacement for the older AN PQ-36/37 FireFinder artillery spotting radar with the new and improved AN/TPQ-53. While the new system was an improvement, the army began getting more and more reports from users in combat zones of false positives; the radar showing something incoming when there wasn’t anything, as well as difficulty distinguishing between artillery shells, rockets and mortar shells. There were also reports that the new system did not handle multiple incoming shells well, being unable to provide data on where it was all coming from. The U.S. Army halted distribution after 38 of the new systems went into service and delayed production of another hundred until the problems could be fixed. A series of tests were conducted in 2015 to document the problems so the manufacturer could fix them. These fixes have been completed and verified by more tests so now manufacturing can continue.

Despite these problems, the new system was seen as an improvement. Troops in Afghanistan continued to call the new version "FireFinder" or "counterfire radar" even though the new TPQ-53 is a visibly new and different looking system, each consisting of two trucks (one for the radar, the other for the control center and backup generator). For the troops in Afghanistan the TPQ-53 was a success because the most common threat was individual mortar shells being fired at a base. The TPQ-53 was faster and more reliable at dealing with that.

AN/TPQ-53 was sent to Afghanistan for final testing in 2010. In early 2012 the army ordered 51 of the AN/TPQ-53 systems. Easier to use and repair, as well as more reliable than its predecessor (the AN/TPQ-36/37), the TPQ-53 could also scan all around (360 degrees), rather than just 90 degrees (as with the older system), and was faster as well. Americans buy TPQ-53s, for about $9 million each. The older FireFinder is cheaper and still gets the job done. This is why some countries (like Iraq) prefer the cheaper older FireFinder. Many Iraqis have seen the older FireFinder in action. They know it works and so do the Ukrainians.

FireFinder would be particularly effective dealing with Russian artillery and unguided rockets, especially if the Ukrainians have the PGK (Projectile Guidance Kit) 155mm fuze. The PGK fuze turns an unguided 155mm shell into a GPS/INS guided one. These were found to be exceptionally useful in Syria and Iraq and, in mid-2017, the U.S. Army ordered another 5,600 PGK fuzes and has been building a large stockpile. The army still uses unguided artillery shells for situations that don’t require precise accuracy for each shell but the PGK provides options that can be implemented quickly to turn any “dumb” shell into a smart one. It is unknown if any of these PGK fuzes have been sent to Ukraine. If PGKs were available, they would work well with the new Zusana-2 8x8 155mm self-propelled artillery systems being purchased by western neighbor Slovakia. Zusana-2 is highly automated with a modern fire control system so it can, in less than a minute, halt, fire one or two PGK equipped shells with the location data provided by FireFinder to destroy Russian artillery and then move on before being targeted itself. Russia too has counterfire radars and guided shells, but no combination of radar and guided shells quick enough to catch Zuzanna-2s employing such “shoot and scoot” tactics. The Zuzanna-2 armor offers some protection from shell fragments and blast effects on equipment and its three-man crew. Ukraine is about to receive Excalibur GPS guided 155mm shells from several NATO countries. Excalibur is more accurate than a shell with a PGK fuze but a lot more expensive.

The older FireFinder (AN/TPQ-36/37) radar had to overcome a bad reputation it acquired when it first came to Iraq. That was often for failing to detect incoming mortar fire. These were problems that were fixed. FireFinder was developed in the 1970s, based on Vietnam experience with enemy mortar and rocket attacks but didn't get a real combat workout until after September 11, 2001.

Both the old and new FireFinders are radar systems which, when they spot an incoming shell, calculate where it came from and transmit the location to a nearby artillery unit, which then fires on where the mortar is (or was). This process takes 3-4 minutes (or less, for experienced troops). FireFinder worked as advertised but got little use until U.S. troops entered Iraq. After that FireFinder was very effective and heavily used. Too heavily used. There were not a lot of spare parts stockpiled for FireFinder and several hundred million dollars-worth had to be quickly ordered. The manufacturer also introduced some new components that were more reliable and easier to maintain.

There were still problems. Some FireFinders failed to catch incoming fire because the enemy was using tactics that fooled the radar. For example, in Iraq American bases were generally on higher ground than the mortars firing at them. Putting bases on the high ground enables you to watch more of the surrounding terrain. But FireFinder needs a line-of-sight to get a good fix on the firing weapon's position. If the mortar was too far below the radar, FireFinder could not accurately spot where the fire was coming from.

Another problem was that if the mortar was too close, FireFinder was much less likely to quickly determine where the fire was coming from. Enemy mortar teams got as close as they could before firing. This still made the mortar teams vulnerable to counterattack by coalition troops but not the immediate (in a few minutes) artillery fire that FireFinder can make happen under the right conditions.

At first, the army was going to halt further upgrades on FireFinder, which, after all, was developed back in the 1970s, and begin developing the TPQ-53, a new system that can better deal with the kinds of problems encountered in Iraq. But FireFinder had been so useful that new upgrades were pursued anyway, while work continued on the TPQ-53. The upgrades have also been made available to other users of FireFinder (including allies in the Middle East, Egypt, Israel, Jordan, Saudi Arabia, and Turkey). FireFinders are still doing most of the work out there, and TPQ-53 won’t replace a significant number of them until the mid-2020s.

The AN/MPQ-64 Sentinel entered service in 2007 and about 300 of them are currently in use. Sentinel is light and compact enough to be trailer mounted and towed or mounted in the back of a 4x4 truck along with a generator. Sentinel can be ready for action in less than 15 minutes and ready to be moved again in less than ten. Some Sentinel users are East Europe NATO members and Ukraine may already have some Sentinels.

FireFinder and Sentinel were designed to operate together, merging their data into a single display of all aerial and ground-based threats detected and being tracked, American troops are training the Ukrainians on how to use both systems and Ukraine may also be using joint operation software for the two systems. Ukrainians have proved more adept at dealing with systems like this than the Russians and may use FireFinder/Sentinel to establish widespread protection against Russian low-altitude threats. After all, one Sentinel system can monitor a circular area 150 kilometers in diameter.