Radar Doppler Multifunction

The first prototype of the RDM flew in January 1980 and production deliveries began in early 1983.[1] Thomson funded development of the RDM from the Cyrano IV at a cost of FFr350m (~US$50m); the RDI air intercept derivative was funded by the French government.[1] The RDM was intended for export Mirage 2000's and the first 50 for the French Air Force; the remaining 150 French Mirage 2000C's would have the RDI.[1] In the end only 37 aircraft were fitted with the RDM, the first production RDI was delivered in December 1986.[2] The two radars are interchangeable in the aircraft but have little in common electronically; the biggest difference is that the RDI increases the look-down/shoot-down range in pulse doppler mode from 20 nautical miles (37 km) to 50 nmi (93 km),[1] and supports the improved Super 530D missile. Allegedly the French Air Force would have preferred to wait until the RDI was ready and have an all-RDI fleet, but the government insisted that they take aircraft with RDM so that it could be marketed abroad as the front-line radar of France.[3]

RDM operates in the X-band with a coherent travelling-wave-tube transmitter and an inverted-Cassegrain antenna 655 mm (25.8 in) in diameter.[1] The RDM operates in air defence/air superiority, strike and air-to-sea modes. In the air-to-air role, the system can look up or down, range while searching, track-while-scan, provide continuous tracking, generate aiming signals for air combat and compute attack and firing envelopes. For the strike role it provides real-beam ground-mapping, navigation updating, contour-mapping, terrain-avoidance, blind let-down, air-to-ground ranging and Ground Moving Target Indication (GMTI).

In the maritime role it provides long-range search, track-while-scan and continuous tracking and can designate targets for active missiles. For air-to-air combat, the RDM provides a 120° cone of coverage, the antenna scanning at either 50 or 100°/s, with ±60, ±30 or ±15° scan. For air-to-air gun attacks, the 3.5° beam can be locked to the target at up to 19 km (10 nmi) range, with automatic tracking within the head-up display field of view, or in a 'super-search' area, or in a vertical search mode. Options include a Continuous Wave Illuminator (CWI) and Doppler Beam Sharpening (DBS). Comprehensive Electronic Counter-Countermeasures (ECCM) are incorporated.

The manufacturers claim that RDM will detect 90% of 5m² RCS fighter-sized targets out to 50 nmi (93 km) in clear air using a four-bar search pattern over 120° in azimuth, and 60 nmi (111 km) with a single-bar pattern over 30° in azimuth, dropping to 20 nmi (37 km) in pulse-Doppler look-down mode.[1] RDI uses a higher pulse-repetition frequency for its dedicated interception role, increasing clear-air range to around 66 nmi (122 km) and 50 nmi (93 km) is possible in look-down mode.[1]

• AI.24 Foxhunter - contemporary British radar on the Tornado F3
• AN/APG-63 radar family - contemporary US radar on the F-15 Eagle
• RBE2 - Radar à Balayage Electronique 2, radar on the Rafale