On a recent warm afternoon at the Potomac River Test Range, recreational speedboats and jet skis plied the cool waters as a handful of Navy engineers gathered shoreside under a reconnaissance and surveillance tower, to begin powering up a mobile engineering lab that is mounted 40-feet in the air. One member of the Navy group pointed out a good target of opportunity in the distance, and as that speedboat slowed to round a curve in the river, the shore party engaged their radar system and began to evaluate the resulting data.
The day’s test bears some outward resemblance to opening moments of a clash between hostile surface warfare vessels, with the 40-foot tower acting as a proxy for the radar mast on a ship. If it had been a real hostile encounter, those personnel could quickly help bring salvoes of naval artillery fire raining down on their target. However this being the peaceful Potomac River, the test and evaluation exercise ended at the data collection stage. The team also displayed a constant awareness of the need to be a safe and non-disruptive presence on the river. “We are good from a safety perspective,” lead engineer Said Darham proactively noted earlier that afternoon, citing a robust list of checks and crosschecks that have been completed prior to the test event.
Since the summer of 2020, Darham and his team of engineers at Naval Surface Warfare Center Dahlgren Division have been using the radar prototype as a test asset and risk reduction system in support of the Navy’s Future X-Band Radar (FXR) program. If all goes according to plan, FXR will one day replace the legacy SPQ-9B radar system, which has almost two decades of field experience spotting far-off targets from aircraft carriers, amphibious assault ships, amphibious transport dock ships, guided missile cruisers, destroyers and Coast Guard cutters.
The project sponsor for FXR called on the expertise at Dahlgren to support foreign comparative testing and determine how the latest technology in use by allied and partner nations stacks up against domestically manufactured X-band radars. The team at Dahlgren noted that equipment currently under assessment compares favorably on several metrics. “Size, weight, power, cost and cooling are paramount,” Darham explained, adding that “the radar prototype we are testing can go a long way towards meeting those objectives.”
The equipment now undergoing testing on the Potomac did not actually start as a radar. According to Darham, the engineers started with a commercial-off-the-shelf antenna designed specifically for military aircraft. After modifications at Dahlgren, the aircraft system now points out over the water and can respond to the unique features of a naval environment. This is the equipment housed inside the tower-top mobile engineering lab. Testing is conducted at the Potomac River Test Range because it combines some of the benefits of a controlled laboratory environment, with real world activity like speedboats and shore vegetation that act like “sea clutter” and “land clutter” for radar testing purposes.
“The clutter profile that an aircraft antenna sees is very different from the one that a ship antenna sees,” Darham explained. “We want to continue to collect data with the aircraft AESA, generate clutter maps and implement clever algorithms to distinguish between what is a target of interest and what is not.” Darham also referred to comparisons of various performance metrics, such as electromagnetic interference survivability, out-of-band blocking capability and the interconnected statistics for size, weight, power, cost and cooling, which are known collectively as “SWaPC2.”
“The sponsor and industry partners are helping establish future baseline concepts for FXR that meet the Navy’s need for next generation radars,” Darham explained. “Having an X-band radar prototype in a naval-like environment serves as a test and evaluation playground to support current and future active sensor thrusts.”