10 Aug 06. Northrop Grumman Corporation has successfully designed, built and flight demonstrated one of the world’s first synthetic aperture laser radar systems.
Under Defense Advanced Research Projects Agency (DARPA) funding, the Synthetic Aperture Ladar for Tactical Imaging (SALTI) program transfers synthetic aperture radar (SAR) technologies, proven in numerous radio frequency radars, into the laser radar domain, providing unprecedented resolution at significantly improved standoff ranges.
“This is an historic milestone: an airborne laser radar has successfully
demonstrated the SAR technique,” said Chris Patrick, Northrop Grumman’s SALTI program manager. “Until now, all optical systems and laser radars were limited in resolution by the size of their aperture. Now, much higher resolutions are possible. The diffraction limit has been surpassed.”
The tests, held March 31 – April 3 at Edwards Air Force Base, proved that SAR works at optical wavelengths, enabling high-resolution, nearly photographic quality imagery at distances much further than current electro-optical systems can provide.
The tests included a series of flights on board a Northrop Grumman BAC 1-11 test aircraft, which were supported by the Air Force Research Laboratory and the 412th Test Wing.
“Synthetic aperture laser radar technology is aimed at satisfying the critical need for reliable long-range Battlefield Awareness,” said Dr. Jennifer Ricklin, DARPA’s program manager for the SALTI program. “SALTI combines the long-range day/night access afforded by conventional SAR with the interpretability of high-resolution optical imaging, along with the exploitability of three-dimensional imagery.”
Synthetic aperture ladar can enhance mission effectiveness across the spectrum of air assets, from fighters and bombers to surveillance aircraft and unmanned aerial vehicles. To help explore these potential applications, Northrop Grumman has been asked by DARPA to continue testing this new capability at additional ranges and under various environmental conditions.
08 Aug 06. A radar antenna the length of a football field that would weigh less than the 22 players in action on it is in development by Raytheon Company under terms of an $8m contract associated with the Integrated Sensor is Structure or ISIS program from the Defense Advanced Research Projects Agency (DARPA).
The active electronically scanned array (AESA) antenna would be bonded to the hull of an unmanned airship 150 to 300 meters (164 to 328 yards) in length that could hover for long periods above the jet stream at altitudes of 65,000 to 70,000 feet. The antenna would transmit on UHF and X-band. Raytheon Space and Airborne Systems (SAS) is a leader in AESA technology, which uses no moving parts to scan at nearly the speed of light.
“DARPA wants to be able to look for airborne and ground-based targets and to communicate directly with the battlefield from a single antenna,” said Michael Wechsberg, director of radio frequency systems programs for the Advanced Concepts and Technology group of SAS.
The low-power density radar would derive its extraordinary sensitivity from an extremely large aperture that would occupy much of the surface of the blimp-like airship.
“The mission is to develop an inordinately sensitive and lightweight sensor that can be integrated into the structure of an airship, which could remain essentially motionless over an area for a long time,” Wechsberg said. “That would let us see targets moving very slowly from a platform that would be difficult to find, let alone to knock down.”
Developing the lightweight radar antenna technology is only part of the assignment. SAS is also charged with devising a means to bond the radar to the hull or other structure of the airship to save weight.
“Using the hull as the support structure for the antenna eliminates thousands of pounds that would ordinarily