viernes, 19 de marzo de 2010

Airborne Radar That Tracks Missiles

Two giants in the airborne radar field have joined to develop a new radar that can detect and track, not only ground targets and aircraft, but also cruise missiles. It's a unique system designed by a unique partnership.
James W. Ramsey
Existing airborne radars can detect and track moving ground vehicles and aircraft. Now the U.S. Air Force is developing the first airborne surveillance radar capable of detecting and tracking low-flying cruise missiles. And despite budget uncertainties, the development program is on schedule.
Two leading U.S. radar providers, Northrop Grumman and Raytheon, are teamed in a unique partnership to develop the new sensor in the Multi-Platform Radar Technology Insertion Program (MP-RTIP). Northrop Grumman is the prime contractor, but it splits development and initial production work on the new radar system 50-50 with Raytheon. This arrangement to develop the radar for the new E-10A wide-area surveillance (WAS) aircraft and the Northrop Grumman Global Hawk unmanned air vehicle (UAV) seems to be working. "The program is progressing well," declares Col. Joseph Smyth, commander of the E-10/MP-RTIP systems group at the USAF's Electronic Systems Center.
The radar program successfully completed its final design review in June 2004, and a laboratory-based prototype system was tested at Raytheon's El Segundo, Calif., facility last September.
Following the award of a six-year, $888-million contract for the program's system development and demonstration (SDD) phase, the companies have been procuring components and preparing to build the first flyable system, scheduled to be tested on a Global Hawk surrogate aircraft in October 2006. At the same time a larger version of the modular scalable radar will be produced for test flight on a Boeing 767-400ER test bed, the anticipated aircraft platform of choice for the E-10A program.
Comparison to JSTARS
Both contractors and the service claim that the new radar will enhance the USAF's ability to track and identify stationary and moving vehicles, as well as hard-to-detect cruise missiles. It also will perform battlefield command and control functions.
Unlike currently fielded airborne systems, such as the E-8C Joint Surveillance Attack Radar System (JSTARS), the MP-RTIP radar will be able to collect ground moving target indicator (GMTI) imagery and synthetic aperture radar (SAR) still images nearly simultaneously. The radar also will be able to detect, track and identify more targets faster and with higher resolution than ever before, according to Dave Mazur, MP-RTIP program manager at Northrop Grumman's Integrated Systems sector in El Segundo.
"The key difference in this radar over the JSTARS radar is the fact that it includes missile defense. That capability doesn't exist today in an airborne platform," says Mazur. "And this radar, in comparison, offers increased range, accuracy and resolution, and faster revisit time."
The Air Force concurs. "The MP-RTIP being designed for the E-10A will provide five to 10 times the air-to-ground surveillance capability of JSTARS," Col. Smyth adds. What assures this capability is the new radar's larger aperture, the increased available power to the system, and its active electronically scanned array (AESA) antenna, which automatically scans in both azimuth and elevation," Mazur explains. "That means we can almost instantly revisit several areas at one time. Each pulse can be doing a different technique."
"Not only can you run [software] modes in sequence, you can interleave them," adds Tom Bradley, Raytheon's MP-RTIP program manager. He explains that, with one asset tasked to carry out significantly different missions, the platform will be able to collect and integrate "all types of intelligence on ground moving targets, imagery and low-flying threats," and provide the user with a comprehensive threat picture.
Both contractors bring considerable AESA antenna experience to the table. Northrop Grumman has developed radar systems for the new F-22 and F-35 fighters, while Raytheon is providing similar radars for the F-15 and F/A-18E/Fs. (The first operational unit equipped with Raytheon's AESA radars is an F-15 squadron based in Alaska). Raytheon also is upgrading the active array radar for Northrop Grumman's B-2 bomber program.
While not planned to replace the E-3A Airborne Warning and Control System (AWACS) radar, MP-RTIP can track conventional aircraft as well as cruise missiles. "The frequency we operate at--X-band--is different from [that used by] AWACS," says Mazur. (The Air Force's AWACS uses S-band radar.) "This allows us to have a very narrow beam, which allows [the radar] to be very accurate. We need that to track cruise missiles. This is a feature we can exploit to augment the AWACS capability."
An AESA includes thousands of transmit and receive modules that are assembled onto "subarrays" inserted into the antenna. The antenna then sends the radio frequency (RF) signals to a receiver, and the radar support electronics processes them.
While the antenna remains stationary, the beam is steered electronically. And the radar's electronic scanning capability moves the beam much more rapidly than previous systems, promoting improved radar searching and multiple tracking capabilities. By removing gimbals and other moving parts associated with manually scanned antennas, AESA offers increased reliability, Raytheon and Northrop claim.
Radar Size
The MP-RTIP radar being developed for the E-10A is a side-looking radar, whose antenna aperture units and associated avionics are mounted in a pod underneath the fuselage, forward of the wing root. While the antenna doesn't move in azimuth or elevation, it does rotate on gimbals 180 degrees to look out the other side of the aircraft.
The radar antenna for the Global Hawk measures 1.5 feet (0.46 m) tall by 5 feet (1.5 m) long. On the E-10A the antenna is considerably larger: 4 feet (1.2 m) tall by 20 feet (6.1 m) long. (The JSTARS pod measures 2 by 24 feet [0.6 by 7.3 m]).
The MP-RTIP requires a widebody aircraft such as the B767, primarily because of the radar's height. "You need something with a big enough landing gear, to account for a hard landing with all tires blown, and you are riding on the rims, and your shocks are fully compressed," Mazur explains. "You must have adequate clearance, so you don't go in there and scrape off the radar."
Most of the electronic equipment supporting the radar--including receivers/exciters, power conditioning units and processors--are mounted inside the E-10A's cargo bay. A separate (helicopter) jet engine, mounted in the cargo bay in a fireproof enclosure, powers the radar.
In terms of radar hardware, Global Hawk bears a "two box" system, with the antenna mounted below the aircraft and the signal processor inside an avionics bay. The radar mode software resides in the signal processor, which is responsible for controlling the radar, running it and processing the data.
Scalable Radar
The USAF's original intent was to make MP-RTIP a radar upgrade for JSTARS--the service's airborne ground surveillance, targeting and battle management system--which has been used effectively in the Iraq war. But MP-RTIP evolved into an advanced system that a widebody platform could best accommodate. (JSTARS uses the narrowbody Boeing 707.)
MP-RTIP was designed to be a scalable radar, using the same basic architecture and common software, but with a smaller aperture to accommodate later model Global Hawks. (A scenario is envisioned using both the Global Hawk and E-10A together for battlefield surveillance and air-to-air detection.)
Teaming Arrangement
Northrop Grumman Integrated Systems is the prime contractor for MP-RTIP, although its program management, modeling and simulation, and Global Hawk flight test activities account for only about 10 percent of the program. The other 90 percent involves the radar's design, development and testing. These activities are split evenly between Raytheon's Space and Airborne Systems unit in El Segundo and Northrop Grumman's Electronics Systems sector in Baltimore and Norwalk, Conn. All work on MP-RTIP falls under Mazur's realm of responsibility.
"Northrop Grumman and Raytheon are fierce competitors in the radar world, so bringing these two teams together to work on this program smoothly has been a challenge. But we've been very successful at it," boasts Mazur. (In fact, the Air Force granted the two contractors 100 percent of incentive award fees for successful teamwork in the contract's first phase.)
As for hardware, Raytheon is providing the MP-RTIP's "front-end" RF aperture unit (RFAU) antenna assemblies on the E-10A, while Northrop Grumman Electronic Systems provides the radar back-end. "We build the aperture assemblies into an antenna and provide receivers/exciters, cabinets and a radar signal processor," says Russ Conklin, MP-RTIP program manager for Northrop Grumman Electronic Systems. Northrop Grumman is responsible for the E-10A's radar integration and testing at its systems integration laboratory in a former Norden facility in Connecticut.
On Global Hawk the contractors' roles are reversed. Northrop Grumman builds the antenna elements and Raytheon, the back-end. Raytheon is responsible for integration and testing at its systems integration lab in El Segundo. There the software modes are added prior to flight test--and for testing on the Global Hawk.
"We at Raytheon build the currently used Global Hawk radar sensor, which has SAR and MTI [moving target indicator] modes, and we have a lot of experience putting it out in the field," says Raytheon's Bradley. "Northrop Grumman is doing Joint STARS and brings that system experience forward."
"Global Hawk is reconnaissance, and Joint STARS is really surveillance," he adds. "Now you're creating a platform that can do both. And by adding some air-to-air mode support, it also is going to be doing cruise missile defense."
The basic MP-RTIP software on the E-10A and Global Hawk are common. Both Raytheon and Northrop Grumman, together, are writing the radar operating services (ROS), built-in test (BIT) and calibration. One team member or the other is writing independently each of the three major radar modes: GMTI, SAR and airborne moving target indicator (AMTI).
Fitting MP-RTIP on Global Hawk is a plus for the E-10A program, Mazur says, because a number of the MP-RTIP modes are common between the two platforms. "We can do a lot of the integration and testing and validation before we get to the E-10A platform, so it helps us save test time on the E-10A portion. It is more expensive to run a B767 than to fly a Global Hawk."
Raytheon also brings its transmit/receive (TR) module manufacturing capability to the program. "We have a dedicated factory down in Texas [attained when Raytheon acquired Texas Instruments in Dallas]," Bradley points out.
Both Raytheon and Northrop Grumman Electronic Systems work closely with Mercury Computer Systems, a commercial off-the-shelf (COTS) vendor in Chelmsford, Mass., that provides processors for radar signal processing and the receiver/exciter hardware.
Morales Romero Karelis
CI 18089995

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