NRL looks to make surveillance radar more motion-sensitive

The Navy, like all of the military services, collects plenty of ISR (intelligence, reconnaissance and surveillance) data, but it is seeking to refine that data by accounting more precisely for moving targets.

The Naval Research Laboratory notes that watercraft can have a variety of motions, both forward and side-to-side, which can create blurring problems for some radar algorithms. So the lab is working with General Atomics Aeronautical Systems to integrate maritime mode inverse synthetic aperture radar (maritime-ISAR) into the company’s Lynx Multi-Mode Radar that is used with the MQ-9 Reaper and Predator XP unmanned aerial systems, according to an NRL release.*

“Because ships and small watercraft at sea are usually in motion — having both forward velocity and other linear and angular motions, for example, pitch and roll and heave and sway — this creates a problem for typical ISAR platforms,” Thomas Pizzillo, head of the NRL Radar Analysis Branch, said in the release. “The addition of a maritime-ISAR mode to the General Atomics Lynx radar, as a software only upgrade, is the most cost effective alternative to introduce this capability to the MQ-9 fleet.” The MQ-9 is flown most often by the Air Force, although the Navy and other government agencies also use versions of the aircraft.

As NRL points out, synthetic aperture radar systems operate from a moving platform such as a UAS, but assume that what it’s looking at is stationary, such as a building or other object on the ground. When its target moves, it can create a smear in its otherwise high-quality image. Adding ISAR algorithms will account for the motion.

“Often with unknown velocities, both linear and angular, it is a much more difficult problem because the motions are not known as in typical ISAR,” Pizzillo said. “NRL has successfully adapted the necessary changes to ISAR image formation in which the rotational motion of the target is not known beforehand. This provides the end-user with an imaging software tool that can produce high-quality imagery in conditions with significantly complex target motion.”

* An earlier version of this story mistakenly referred to NRL as ONR in two places.