Thursday, August 11, 2005

Digital Domain

eDefense Online Senior Editor Brendan Rivers recently wrote a story about how the US Air Force awarded Raytheon a contract to develop a networked passive geolocation capability for the AN/ALR-69A(V) radar-warning receiver (RWR) that would be used for pinpointing the locations of enemy radio-frequency (RF) emitters (see USAF to Locate Enemy Using RWRs). Geolocation is the ability to derive the x,y,z coordinates of a radio or radar source by getting multiple bearings on it from a given receiver over time or by multiple receivers networked together.

The contract, awarded by the USAF's Warner Robins Air Logistics Center (Robins AFB, GA) under the Advanced Tactical Targeting Technology (AT3) program, calls for the development of the necessary software algorithms and a Frequency and Time Module (FTM) that would provide this new capability to the all-digital, wideband ARL-69A(V) RWR -- itself an upgrade of the ALR-69(V), which is currently installed on USAF F-16, A-10, C-130, and MH-53 aircraft. RWRs with these enhancements fitted onboard multiple aircraft could then share their time and frequency measurements, along with GPS data, via datalink, to come up with a much more precise location of an enemy emitter. Because it is a completely digital, wideband system, the ALR-69A(V) can perform the necessary signal processing at sufficient speeds for such accurate and rapid geolocation.

The geolocation data acquired and shared among other aircraft could then be used to target air-defense sites and other emitter sources with GPS-aided precision-guided munitions that could be employed from other fighter aircraft in the area. The USAF is looking at equipping not just F-16s but a variety of aircraft with the AT3 capability, in particular F-15s and A-10s. What's particularly interesting is that this capability would distribute the suppression/destruction of enemy air defenses (S/DEAD) mission generally among front-line aircraft, rather than leaving it in entirely in the hands of specialist squadrons and aircraft types, such as the F-16C/J. According to one source, the US Navy has also expressed interest in providing AT3 for its F/A-18E/F Super Hornets. Although the Super Hornet is equipped with the ALR-67(V)3 RWR, that system is also being upgraded to an all-digital version, which would enable it to perform AT3's geolocation measurements.

This development dovetails nicely with electronic attack options reportedly under consideration by the US Air Force for its future F/A-22 Raptor and F-35 Joint Strike Fighter (JSF) aircraft. Neither aircraft is due to receive an internal RF jammer because their low-radar cross-section designs and advanced BAE Systems AN/ALR-94 RWRs (common to both) are intended to enable the aircraft to detect and avoid enemy air-defense sites passively. So how will electronic attack be possible? Both the Raptor and the JSF are to receive active electronically scanning phased-array (AESA) radar systems -- the Northrop Grumman AN/APG-77 in the former and the Northrop Grumman AN/APG-81 for the latter. With the right software, these all digital radar emitters can be used as spot jammers, directing pencil beams against "pop-up" threats. A similar role of an AESA radar is already under consideration for the PS-05/A Mk5 NORA radar in development for Sweden's Gripen by Ericsson and Raytheon (see Gripen Settles In). In addition to its usual functions, the NORA -- "Not Only Radar" -- system will also perform passive electronic reconnaissance and active jamming of enemy radars within its operational frequency range (I-J bands).

The advent of all-digital mission avionics is advancing the day where multiple discrete systems will no longer be required for distinct functions. Emitters and receivers will be tuned to whatever function is required by application software. Moreover, as datalinks increase in bandwidth and networks increase in scope, many of the duties that are currently handled by specialists will be addressable by an expanding array of multi-mission platforms and crews.


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