The Ground/Air Task-Oriented Radar (G/ATOR), in development by the Marine Corps, is a three-dimensional short- to medium-range tactical radar designed to detect, identify, and track low-level cruise missiles, manned aircraft, and unmanned aerial vehicles as well as rockets and mortar and artillery fire. Thanks to advances in digital radar technology, G/ATOR will be a highly mobile, multirole radar system that will perform the functions of five different legacy ground-based radars it is slated to replace, providing increased range, accuracy, tactical mobility, and reliability.

The radar will perform air surveillance, cue air defense weapons, perform counter-fire target acquisition (of enemy artillery and mortar firing locations), and provide data to air traffic controllers.

Consolidating these functions into a single multi-role radar will dramatically reduce Marine Corps logistics, operating, and training costs.

The incremental program will allow the Marine Corps to “neck down” over time to only two primary radars – the expeditionary short- to medium-range G/ATOR and the large, transportable TPS-59(V)3 long-range air surveillance radar.

The G/ATOR program is currently in the Engineering and Manufacturing Development phase. Northrop Grumman Electronic Systems in Baltimore, Md., is the prime contractor.

The entire G/ATOR system is transported by only two up-armored vehicles – a six-wheel, 7-ton Medium Tactical Vehicle Replacement (MTVR) all-terrain truck built by Oshkosh, and a single HMMWV. In a G/ATOR’s operational configuration, its large radar antenna array is mounted on a trailer towed by the MTVR, and is folded down flat during movement. The trailer has electro-mechanically controlled legs for automated leveling during setup. The MTVR truck carries a pallet with a generator and the HMMWV carries the radar system’s Communications-Electronic Group (CEG) on a pallet. Both pallets can be self-extracted from the vehicles.

G/ATOR will be fielded over time in increments. Increment I, scheduled for an initial operational capability (IOC) and a full-rate production decision in 2016, is the air surveillance and short-range air defense radar, which will replace the TPS-63, MPQ-62, and UPS-3 radars. Increment I will provide all the basic hardware for future increments, which will add new capabilities through mission-specific software packages.

Increment II, slated for an IOC in 2017, will add the enemy artillery and mortar target-locating capability, replacing the existing TPQ-46 radar. Increment IV, scheduled for an IOC in 2018, will add military air traffic control functionality, replacing the Marine Corps’ TPS-73 radar and the Airport Surveillance Radar portion of the TPN-31A Air Traffic Navigation, Integration, and Coordination System.

Lee Bond, the G/ATOR program manager within the Program Executive Office for Land Systems, said that Increment III, which previously encompassed tactical enhancements to the other increments, has essentially been deferred until the other three increments are well in hand.

The incremental program will allow the Marine Corps to “neck down” over time to only two primary radars – the expeditionary short- to medium-range G/ATOR and the large, transportable TPS-59(V)3 long-range air surveillance radar.

G/ATOR Increment I also will serve as a gap-filler radar, covering areas out of view of the TPS-59(V)3 due to line-of-sight limitations.

With the exception of the MTVR vehicle, the major G/ATOR system components – the trailer with antenna array, the HMMWV with the CEG pallet, and the generator pallet – will be transportable in external sling loads by Marine Corps heavy-lift helicopters and MV-22 Osprey tilt-rotor aircraft.

The key to achieving G/ATOR’s multi-role capabilities within a highly mobile expeditionary system is active electronically scanned array (AESA) radar technology. Unlike mechanically scanned radars with curved-dish antennas, an active phased-array radar can steer its agile beams electronically. G/ATOR’s antenna array is made up of over 2,600 highly reliable small solid-state transmit-receive modules, each a small radar in itself that can alternate between transmitting and receiving. AESA radars can operate in multiple modes simultaneously and can track significantly more targets than older systems.

G/ATOR has a planar, or flat-face, phased-array antenna that is 10 feet tall and 7 feet wide. The antenna rotates on the trailer to provide 360-degree coverage against airborne threats, mechanically scanning in azimuth and electronically scanning in elevation. For some missions, the antenna will be stationary and will scan a sector of the airspace it is facing electronically in two dimensions – azimuth and elevation.

Bond said the need to keep weight down to allow the radar system to be airlifted with rotary-wing aircraft “drove us to an air-cooled array instead of a more common but much heavier closed-loop liquid cooling system.” The array has to be kept at a constant temperature across all of its transmit-receive modules for peak performance, he said, and the air cooling has proven to be very effective. “Despite the fact that G/ATOR has a larger array and sees literally twice as far as the legacy systems it will replace,” Bond said, “it’s much lighter, primarily due to the AESA active elements on the array and the air cooling system.”

In March 2009, Northrop Grumman successfully completed the G/ATOR program’s Critical Design Review, the final hurdle before the company began building the first Increment I engineering development model (EDM) prototype system. Northrop Grumman now has two EDMs undergoing contractor integration and testing, with Government Developmental Test scheduled to begin next year.

Milestone C approval for low-rate initial production of the G/ATOR Increment I radar system is scheduled in 2013. The Marine Corps’ Approved Acquisition Objective (AAO) is a total of 67 G/ATOR systems – 17 Increment I radars, 38 Increment IIs, and 12 Increment IVs.

In February 2009, then-Under Secretary of Defense for Acquisition, Technology, and Logistics John Young designated G/ATOR, also referred to as the Multi-Role Radar System, as a Department of Defense Special Interest Program that could potentially meet the ground-based radar requirements of the other services.

This article first appeared in Marine Corps Outlook: 2011-2012 Edition.