Counter - battery radar A counter - battery radar detects artillery projectiles fired by one or more guns , howitzer s , mortar s and rocket launchers and from their trajectories locates the position on the ground of the weapon that fired it . Alternatively , or in addition , it may determine where the projectile will land . The normal purpose of a counter - battery radar is to locate hostile batteries up to about 50 km away depending on the radar ' s capabilities . If the radar is fast and has fast communications , then it may be possible to provide some warning to troops targeted by the incoming projectiles . However , many projectiles have a time of flight under a minute , which makes it difficult to give warnings without a highly automated communication system , unless the target is in the vicinity of the radar . Counter - battery radars can also be used to observe the fire of friendly artillery and calculate corrections to adjust its fire onto a particular place . Radar is the most recently developed means of locating hostile artillery . The emergence of indirect fire in World War I saw the development of sound ranging , flash spotting and air reconnaissance , both visual and photographic . Radars , like sound ranging and flash spotting , require hostile guns , etc . , to fire before they can be located . History . The first radars were developed for anti - aircraft purposes just before World War II . These were soon followed by fire control radars for ships and coastal artillery batteries . The latter could observe the splashes of water from missing shots , enabling corrections to be plotted . Generally the shells could not be seen directly , as there were too small and rounded to make a strong return , and traveled too quickly for the mechanical antennas of the era to follow . Radar operators in light anti - aircraft batteries close to the front line found they were able to track mortar bombs . This was likely helped by the fins of the bomb producing a partial corner cube that strongly reflected the signal . These accidental intercepts led to their dedicated use in this role , with special secondary instruments if necessary , and development of radars designed for mortar locating . Dedicated mortar - locating radars were common starting in the 1960s and were used until around 2000 . Locating mortars was relatively easy because their trajectory was sufficiently close to parabolic that the simple mathematics of parabolas could be used with analogue computers . Better radars were also able to detect howitzers when firing in high angle ( elevation greater than 45 degrees ) , although such use was quite rare . Low angle trajectories normally used by guns , howitzers and rockets were more difficult . By the early 1970s radar systems capable of locating guns appeared possible , and many European members of NATO embarked on the joint Project Zenda . This was short - lived for unclear reasons , but the US embarked on Firefinder program and Hughes developed the necessary algorithms , although it took two or three years of difficult work . The next step forward was European when in 1986 France , Germany and UK agreed the ' List of Military Requirements ' for a new counter - battery radar . The distinguishing feature was that instead of just locating individual guns , etc . , the radar was able to locate many simultaneously and group them into batteries with a centre point , dimensions and attitude of the long axis of the battery . This radar eventually reached service as EuroART ' s COBRA system . Simultaneous with the development of COBRA , Norway and Sweden developed a smaller , more mobile counter - battery radar known as ARTHUR . It was taken into service in 1999 and is today used by 7 NATO countries and The Republic Of South Korea . New versions of ARTHUR is developed resulting in a radar with twice the performances of the original . Operations in Iraq and Afghanistan led to a new need for a small counter - mortar radar for use in forward operating bases , providing 360 degree coverage and requiring a minimal crew . In another back to the future step it has also proved possible to add counter - battery software to battlefield airspace surveillance radars . Description . The basic technique is to track a projectile for sufficient time to record a segment of the trajectory . This is usually done automatically , but some early and not so early radars required the operator to manually track the projectile . Once a trajectory segment is captured it can then be processed to determine its point of origin on the ground . Before digital terrain databases this involved manual iteration with a paper map to check the altitude at the coordinates , change the location altitude and recompute the coordinates until a satisfactory location was found . The additional problem was finding the projectile in flight in the first place . The conical shaped beam of a traditional radar had to be pointing in the right direction , and to have sufficient power and accuracy the beam couldn ' t have too large an angle , typically about 25 degrees , which made finding projectile quite difficult . One technique was to deploy listening posts that told the radar operator roughly where to point the beam , in some cases the radar didn ' t switch on until this point to make it less vulnerable to electronic counter - measures ( ECM ) . However , conventional radar beams were not notably effective . Since a parabola is defined by just two points then tracking a segment of the trajectory was not notably efficient . The Royal Radar Establishment in the UK developed a different approach for their Green Archer system . Instead of a conical beam , the radar signal was produced in the form of a fan , about 40 degrees wide and 1 degree high . A Foster scanner modified the signal to cause it to focus on a horizontal location that rapidly scanned back and forth . This allowed it to comprehensively scan a small " slice " of the sky . The operator would watch for mortar bombs to pass through the slice , locating its range with pulse timing , its horizontal location by the location of the Foster scanner at that instant , and it ' s vertical location from the known angle of the thin beam . The operator would then flick the antenna to a second angle facing higher into the air , and wait for the signal to appear there . This produced the necessary two points that could be processed by an analogue computer . A similar system was the US AN / MPQ - 4A , although this was a somewhat later design and somewhat more automated as a result . However , once phased array radars compact enough for field use and with reasonable digital computing power appeared they offered a better solution . A phased array radar has many transmitter / receiver modules which use differential tuning to rapidly scan up to a 90 degree arc without moving the antenna . They can detect and track anything in their field of view , providing they have sufficient computing power . They can filter out the targets of no interest ( e . g . aircraft ) and depending on their capability track a useful proportion of the rest . Counter - battery radars used to be mostly X band because this offers the greatest accuracy for the small radar targets . However , in the radars produced today C and S is the common . Ku bands have also been used . Projectile detection ranges are governed by the radar cross section ( RCS ) of the projectiles . Typical RCS are : The best modern radars can detect howitzer shells at around 30 km and rockets / mortars at 50 + km . Of course the trajectory has to be high enough to be seen by the radar at these ranges , and since the best locating results for guns and rockets are achieved with a reasonable length of trajectory segment close to the gun , long range detection does not guarantee good locating results . The accuracy of location is typically given by a circular error probable ( CEP ) ( the circle around the target in which 50 % of locations will fall ) expressed as a percentage of range . Modern radars typically give CEPs around 0 . 3 - 0 . 4 % of range . However , with these figures long range accuracy may be insufficient to satisfy the Rules of Engagement for counter - battery fire in counter insurgency operations . Radars typically have a crew of 4 – 8 soldiers , although only one is needed to actually operate the radar . Older types were mostly trailer mounted with a separate generator , so took 15 – 30 minutes to bring into action and need a larger crew . However , self - propelled ones have been used since the 1960s . To produce accurate locations radars have to know their own precise coordinates and be precisely oriented . Until about 1980 this relied on conventional artillery survey , although gyroscopic orientation from the mid - 1960s helped . Modern radars have an integral Inertial Navigation System , often aided by GPS . Radars can detect projectiles at considerable distances , and larger projectiles give stronger reflected signals ( RCS ) . Detection ranges depend on capturing at least several seconds of a trajectory and can be limited by the radar horizon and the height of the trajectory . For non - parabolic trajectories it is also important to capture a trajectory as close as possible to its source in order to obtain the necessary accuracy . Action on locating hostile artillery depends on policy and circumstances . In some armies , radars may have authority to send target details to counter - battery fire units and order them to fire , in others they may merely report data to an HQ that then takes action . Modern radars usually record the target as well as the firing position of hostile artillery . However , this is usually for intelligence purposes because there is seldom time to alert the target with sufficient warning time in a battlefield environment , even with data communications . However , there are exceptions . The new Lightweight Counter Mortar Radar ( LCMR – AN / TPQ 48 ) is crewed by two soldiers and designed to be deployed inside forward positions , in these circumstances it can immediately alert adjacent troops as well as pass target data to mortars close by for counter - fire . Threats . Radars are vulnerable and high value targets ; they are easy to detect and locate if the enemy has the necessary ELINT / ESM capability . The consequences of this detection are likely to be attack by artillery fire or aircraft ( including anti - radiation missiles ) or ECM . The usual measures against detection are using a radar horizon to screen from ground based detection , minimising transmission time and using alerting arrangements to tell the radar when hostile artillery is active . Deploying radars singly and moving frequently reduces exposure to attack . However , in low threat environments , such as the Balkans in the 1990s , they may transit continuously and deploy in clusters to provide all - around surveillance . In other circumstances , particularly counter - insurgency , where ground attack with direct fire or short range indirect fire is the main threat radars deploy in defended localities but do not need to move , unless they need to cover a different area .