Miniaturized Active Electronically-Scanned Array (AESA) radar gives the U.S. Army a wide-area, near-all-weather surveillance sensor for the Grey Eagle Unmanned Aircraft System (UAS) and the tethered aerostat Persistent Threat Detection System (PTDS).
The Northrop Grumman STARLite was to deploy to Afghanistan aboard the PTDS in the first quarter of this year and will go to war on the Hellfire-armed Grey Eagle UAS in early 2012. Both platforms will downlink high-resolution Synthetic Aperture Radar (SAR) imagery and Ground Moving Target Indication (GMTI) data to United States joint-service and allied military forces.
“This is an interoperable radar,” explained Phil Owen, lead engineer for UAS payloads at the Army Aviation and Missile Command (AMCOM) at Redstone Arsenal, Ala. “It is using exclusively Open NATO standards. Any other exploiter out in the field can utilize this data without special software. That makes a huge difference in exploitation.”
The Ku-band radar works in strip mode to image a large area along a programmed path or in spot mode to take a close look at specific targets. Actual performance numbers for the new sensor are undisclosed, but the Army credits STARLite with greater than 40 kilometer range and better than 0.3 meter resolution.
In addition, a GMTI mode is required to track vehicles moving from about 10 to 70 km/h on a digital map. A Dismounted Moving Target Indicator (DMTI) introduced on the PTDS uncovers enemies on foot, and DMTI software will become part of the baseline radar on the Grey Eagle as well.
Every production Grey Eagle will carry the Northrop Grumman AN/ZPY-1 radar and Raytheon AN/AAS-53 Common Sensor Payload. ( Avionics, August 2008, page 24.) The radar covers a wide area and cues the electro-optical sensor to identify or laser-designate targets with two clicks at the operator’s station. “It’s a very Open Architecture-type of system, very warfighter-friendly,” said Joe Parsley, UAS and rotary wing systems senior manager at Northrop Grumman Electronic Systems (NGES). “Without STARLite, you could be searching all day, if you had good weather.”
Company Effort
The 63-pound STARLite came from a company-funded effort at NGES. The Baltimore radar house had previously developed the 165-pound AN/ZPQ-1 Tactical Endurance Synthetic Aperture Radar (TESAR). The single-channel TESAR with electronically scanned receiver array was the first UAS sensor with SAR and GMTI functionality and deployed to Bosnia in 1995 on the Air Force RQ-1A Predator. STARLite has two channels to provide greater GMTI accuracy, and it benefits from later commercial-off-the-shelf electronics.
“Certainly, it’s much lighter weight and lower power, which allows it to be used on a wide array of platforms,” noted system engineering lead Mike Mazzoni, with the Army Program Manager, Robotics and Unmanned Sensors (PM RUS) at Aberdeen Proving Ground, Md.
PM RUS, under the Program Executive Officer, Intelligence, Electronic Warfare and Sensors (PEO IEW&S), is the Army sponsor for STARLite and the General Atomics Lynx II Block 30 multi-mode radar now in Quick Reaction Capability (QRC) units in Afghanistan and Iraq. The QRC radar weighs about 80 pounds and was developed under a 2004 System Development and Demonstration contract to equip the Extended Range Multi-Purpose (ERMP) UAS, later Sky Warrior and now Grey Eagle.
Northrop Grumman targeted the Army market and began STARLite development around 2005. The company won a best-value competition in April 2008 and delivered the first two production sets in February 2010. The new radar had no commonality with TESAR, but leveraging AESA production processes and facilities enabled Northrop Grumman to evolve a low-risk solution through several test versions.
“The production system is a lot smaller,” said Parsley. “We took the obsolescence issues and addressed those. Technology enabled us to downsize.”
The current STARLite fills just 1.1 cubic feet with four line replaceable units (LRUs) — radar electronics, antenna assembly, INS/GPS and power supply — and draws only 600 watts. Built-In Test routines isolate faults down to the LRU and make STARLite compatible with a two-level field-and-depot maintenance scheme.
Responsive AESA radars with arrays of individual transmitter/receiver modules provide innovative search-and-track functions and enhanced reliability by eliminating mechanical sweep. However, like TESAR, STARLite uses a single array of modules electronically scanned only in elevation. Azimuth still depends on a mechanical gimbal for a 360-degree field of regard. “If we did not have the gimbal, we’d had to have multiple faces on the array for more weight, complexity and cost,” noted Parsley.
The STARLite contract awarded in 2008 bought more than 70 radars. Northrop Grumman at this writing had delivered more than 30 systems, including seven to General Atomics Aeronautical Systems, Inc. (GA-ASI) for integration on the MQ-1C. The GA-ASI radar already on the Grey Eagle has an inertial measurement unit and GPS receiver and can take inputs from the aircraft navigation system via Mil-Std-1553 databus, Ethernet or RS422 bus. The Grey Eagle architecture also has an on-board Ethernet connected to the data link and treats the radar as a node on the network.
STARLite has a Northrop Grumman LN-251 digital INS/GPS navigator to integrate with air vehicle systems. It requires no Tactical Common Data Link changes and needs no more bandwidth allocation than the current radar. PM RUS and Northrop Grumman also made a special effort to make the new radar readily compatible with the Army One System Ground Control Station and other exploitation equipment. “I consider us kind of ground-station agnostic,” said Parsley. “It doesn’t matter; as long as there’s a Windows-based system, we can roll right into that system.”
The Army and contractor worked to optimize the STARLite operator interface. “We actually had the users involved with development of the ground control application,” said STARLite Lead Engineer Joe Deroba, with the Communications-Electronics Research, Development and Engineering Center (CERDEC) at Aberdeen Proving Ground. “They were able to comment on the design and ease-of-use.”
Feedback from users, for example, ultimately enabled operators to input targets in military grid coordinates as well as latitude and longitude. “Simple things like that are important to operators,” said Deroba. “An engineer who’s used to lat-long might not realize it.”
The Army plans to field 13 Grey Eagle-equipped companies, each with 12 aircraft, mobile and portable ground control stations, and ground data terminals. The service already has 37 mobile, relocatable PTDS aerostats with multi-mission payloads integrated with the Army command information architecture by Lockheed Martin Mission Systems & Sensors (MS2) in Owego, N.Y. Not all PTDS aerostats will have STARLite.
The two platforms emphasize different radar modes. At altitudes greater than 25,000 feet and speeds to 150 knots, Grey Eagle SAR uses aircraft motion to image large areas. The PTDS is fixed by a 5,000-foot fiberoptic tether and uses GMTI and DMTI to combat insurgents placing improvised explosive devices.
“We’re all about GMTI right now,” noted Phil Owen at AMCOM.
The baseline radar integrated into the PTDS and Grey Eagle is meanwhile undergoing product improvements. “We are in the process of qualifying the extended range antenna,” said Northrop Grumman’s Parsley. “It would almost double the range in some cases.”
Northrop Grumman is independently testing a littoral maritime capability for STARLite on the company’s Twin Otter, based in the Baltimore area. Though the Army canceled its XM-157 Fire Scout unmanned helicopter program, the Navy has deployed the ship-launched MQ-8B Fire Scout to Central Command and may need a lightweight radar.
There is no requirement to integrate the STARLite radar on the RQ-7B Shadow brigade-level UAS, but Northrop Grumman expects to fly an AN/ZPY-1(V)2 radar in June with a weight of just 45 to 50 pounds. The lighter STARLite trades a standalone power supply for a card in the electronics LRU and switches to a lighter IMU. It nevertheless promises range equal to the baseline system today.
“There is not a specific program that has identified it,” said Parsley. “We’re getting a lot of interest from the smaller UAVs and other platforms of interest because of its smaller size and weight.”
CERDEC at Aberdeen Proving Ground now has a STARLite Systems Integration Laboratory to augment the current radar modes and introduce new ones. Phil Owen at AMCOM acknowledged, “We’re looking at options to get a little bit of ground penetration with it. Another thing we’re looking at is to expand the GMTI capabilities to cover a larger area.”