A Northrop Grumman RQ-4A Global Hawk unmanned air vehicle equipped with a maritime-mode radar is set to be delivered to the US Navy, with abbreviated flight testing to follow.

The USN launched the Global Hawk maritime demonstration originally as a precursor to the now-delayed Broad Area Maritime Surveillance (BAMS) programme, buying two vehicles and a maritime-mode software upgrade.

The demonstration is continuing despite an indefinite delay to BAMS and a move by US Congress to sharply curtail the experiment's scope. Lawmakers deleted funding for a hardware upgrade to provide a 360°-scan inverse synthetic-aperture radar (ISAR) capability, says Steven Sheridan, director of reconnaissance and surveillance systems for payload supplier Raytheon.

Instead, the two Global Hawks will have software that allows the existing SAR sensor to pick up maritime targets using the ISAR technique, in which Doppler shift from the motion of the target, such as a ship rolling on waves, generates the image. In SAR mode, aircraft motion is used to create the high-resolution image.

The navy is to keep both Global Hawks in service after the demonstration, but it is unclear in what role, or how they will shape the planned competition for BAMS.

Source: Flight International