Bradley Fighting Vehicle Getting New Eyes
The Bradley fighting vehicle, which transports U.S. Army infantry and cavalry troops, operates alongside the Abrams main battle tank and provides the firepower to support dismounted soldiers or attack enemy armor and fortifications.
The Army has been working for several years to improve the Bradley in a series of upgrade programs. The most modern versions of the Bradley are the M2A3 infantry and M3A3 cavalry fighting vehicles.
Among the capability enhancements found in both the M2A3 and M3A3 vehicles is the "improved Bradley acquisition subsystem," or IBAS.
The 2nd Infantry Battalion, 8th Infantry Regiment of the 4th Mechanized Infantry Division, at Fort Hood, Texas, became the first unit equipped with the modernized M2A3 Bradley in May.
IBAS uses second-generation forward-looking infrared (Gen II FLIR) technology to help the Bradley crew acquire and identify targets in night or day. Under the Army's horizontal technology integration (HTI) initiative, IBAS shares its Gen II FLIR with other platforms.
The Army plans to modernize about 1,100 Bradleys with IBAS, a commander's independent viewer (CIV), and Force XXI digital command and control improvements, including a MIL-STD-1553 databus. DRS Technologies, based in Parsippany, N.J., received a low-rate, initial-production contract in January 2000, for the IBAS subsystems. A decision to transition IBAS to full production in 2001, is expected later this year.
The Gen II FLIR sensor of the new Bradley sight is packaged in a B-kit, a working sensor, which is also common to the commander's independent thermal viewer on the M1A2 Abrams tank and the long-range advanced scout surveillance system (LRAS3) on the M1025 scout vehicle. The same B-kit is a candidate to upgrade the Marine Corps' Abrams tanks and other ground vehicles worldwide.
Seeing Through a Storm
With its second-generation thermal imager, IBAS addresses the shortcomings of the first-generation common module FLIRs used on the M2A2 Bradley in Operation Desert Storm. The original Bradley TOW 2 subsystem (T2SS) has both a thermal imaging FLIR and direct view optics to aim the TOW 2 (tube launched, optically tracked, wire guided) missile and the 25mm cannon.
While the first-generation thermal imager sees in the dark, it has an effective range which is less than the maximum stand-off range of the missile. The range of the first-generation sight is cut even more in dense fog, dust or other battlefield obscurants.
The shorter-range targeting sensor puts the Bradley at greater risk by forcing the vehicle closer to the enemy for target acquisition, identification and recognition. Even under ideal conditions, the lack of detail in first-generation FLIR imagery makes it difficult to distinguish friends from enemies. Command and control is difficult to optimize without the ability to pass digital information and imagery between units.
The Army sought the M2A3 Bradley upgrade after assessing the threats expected for the 21st century battlefield. IBAS integrates Gen II FLIR with daylight television, direct view optics and an improved TOW missile control subsystem. It provides the modernized Bradley with a more sensitive targeting sensor effective under all battlefield conditions, and one able to see farther than the maximum range of the TOW missile.
The greater range and sharper picture provided by IBAS improve the survivability and lethality of the vehicle, boost the probability of hit for the missile and gun, and reduce the chances of fratricide. Compared with the first-generation sighting system, the Army calculated that IBAS with Gen II FLIR increases target detection range by 78 percent at night and 56 percent in daylight.
Once the target is detected, IBAS improves identification capability by 232 percent at night and 70 percent in daylight. Clear Gen II FLIR imagery improves recognition of identified targets by 468 percent at night and 154 percent by day.
The M2A3 makes IBAS imagery available to the vehicle gunner and commander, and the infantry squad leader on their individual displays. The squad leader's display enhances the situational awareness of the foot soldiers before they dismount.
IBAS also generates digital imagery that can be shared with joint service units and allied forces through the databus, modem and radios of the Bradley. The 4th Infantry Division is scheduled to become the Army's first digitized division late this year, and procedures for transmitting imagery via the single channel ground and airborne radio system (SINCGARS) and other radios are under development.
On the digital battlefield, forward-positioned M2A3 and M3A3 vehicles will send real-time Gen II FLIR quality and/or TV imagery with Global Positioning System location data to supporting ground or air units.
Common-module FLIR technology developed in the early 1970s, and incorporated in the original Bradley sight uses up to 60 individual infrared detectors to sense thermal contrast. First-generation FLIR also connects each detector to processing electronics via individual wires passing through the vacuum dewar assembly, which is a container used to keep the thermal imager cooled. Image quality is limited both by the number of detectors and the noise generated by processing electronics outside the dewar.
By comparison, second-generation FLIR demonstrated in the early 1990s provides more detectors and less noise. The Gen II FLIR in IBAS contains a 480-by-4 element infrared focal plane array detector inside the dewar. While the additional detectors enhance the sensitivity and resolution of the thermal imager, cooled amplifiers boost the signal-to-noise ratio. Gen II FLIR consequently captures more detail in distant objects, even those with less thermal contrast. It provides imagery with television-like clarity that contains more information for aided target tracking.
IBAS has a 2X and 4X electronic zoom. At the lower magnification, the Gen II FLIR with its additional detectors provides a 7.5 by 13.3-degree wide field of view, about twice that of first-generation thermal imagers.
The U.S. Army fielded its first Gen II FLIR based on the SADA II (standard advanced dewar assembly) technology in TOW ITAS, the improved target acquisition system used on missile-armed high-mobility multipurpose wheeled vehicles. While IBAS uses a slightly different GEN II FLIR, more than 20 percent of IBAS hardware and 35 percent of IBAS software are common to the earlier ITAS. The improved Bradley acquisition subsystem integrates more advanced capabilities into the M2A3 and M3A3 vehicles and shares its B-kit with other platforms.
The TOW missile requires the Bradley gunner to keep the tracking gate of the sight on the target until impact. IBAS reduces the targeting timelines and the vulnerability of the launching vehicle with an aided dual-target tracker that enables the gunner to track simultaneously two targets in the same field of view. The Bradley gunner uses the aided tracking function to engage the primary threat while tracking the next target, and can fire a second missile as soon as the first TOW round impacts.
The aided target tracker also guides the missile for the first 3.5 seconds of flight, eliminating erratic gunner movements at launch and decreasing the time needed for the gunner to re-acquire the target after the "white-out" that accompanies launch. In addition, IBAS has expansion slots to provide a technological bridge to next-generation fire-and-forget missiles.
Together, the commander's independent viewer and IBAS give the modernized Bradley complementary sensors to engage more targets all around the vehicle. The databus of the new Bradley enables the vehicle commander to cue the gunner's IBAS image to targets found by the CIV, and permits the commander to see IBAS imagery and take control of the weapons system.
Like the early sighting system, IBAS has direct view optics to give the gunner clear color targeting imagery in daylight. Unlike the earlier sight, IBAS integrates a charge-coupled device television camera with daylight (day TV) and near-infrared bands to provide sharp monochrome imagery under low thermal contrast conditions unfavorable for FLIRs.
While the TOW missile can be fired only from a stationary vehicle, the 25mm cannon can be fired on the move. Unlike the early Bradley sight, IBAS has a two-axis stabilized mirror head that helps fire accurately on the move. Like the T2SS, IBAS uses the Bradley eye-safe laser range finder to gauge target distance accurate to within plus or minus 5 meters. Bradley gunners with accurate range data can put fire on target without a telltale tracer round to first determine distance.
Compared with the primitive built-in test capabilities of the TOW 2 sight subsystem, IBAS isolates faults down to the circuit card or shop replaceable unit to speed troubleshooting and repairs. It eliminates the regular 180-day verification test required with the T2SS. The new sighting system also incorporates automatic boresighting capability to eliminate lengthy boresighting routines and special equipment. A modular design facilitates repairs and upgrades.
Gen II FLIRs for the modernized Bradley, Abrams and LRAS3 scout will be supported by a common supply depot and the same specialists and test equipment. With common B-Kits, about 17 major components are interchangeable between the sensor systems of the three vehicles.
Joe Hall is IBAS product manager at DRS Optronics, a unit of DRS Technologies Inc., in Palm Bay, Fla.