Cyrano IV doubles the range of Cyrano II, adding monopulse radar, MTI, and terrain following. Focus on the Mirage F1, the Cyrano IVM-R variant, and reliability.
Summary
The Mirage F1 takes on a new dimension with Thomson-CSF’s Cyrano IV. Compared to the Cyrano II, the air-to-air range increases to 100 km (≈ 54 NM), a twofold increase, with a monopulse radar offering an angular accuracy of 2°. The introduction of MTI and clutter rejection greater than 40 dB enables look-down/shoot-down against low-flying targets against the ground. The Cyrano IVM/IVM-R versions add terrain following (1.5 m resolution) and the integration of a laser rangefinder (± 5 m), paving the way for all-weather and very low altitude profiles. On the support side, the adoption of GaAs T/R modules and a modular architecture increases MTBF by approximately 50%, which translates into fewer failures per flight hour and longer maintenance cycles. The package consolidates the use of short- and medium-range missiles, improves low-altitude mission survivability, and standardizes air-to-ground support based on coordinates, with measurable gains in pilot workload and detection efficiency.
The Cyrano IV’s leap in capability on the Mirage F1
The Cyrano IV is designed to exploit the aerodynamic profile of the Mirage F1, whose swept wing and side air intake allow for more stable antennas in terms of incidence. The air-to-air range of 100 km requires a cleaner RF chain and more robust signal processing than that of the Cyrano II. The technological leap is reflected in the cockpit by a more readable display of tracking symbols and better-organized modes. During interception, an angular accuracy of 2° reduces aiming error and improves tracking quality, thereby improving first-intention BVR firing when the rules of engagement allow it. On a fighter template, this means that the lateral uncertainty box at 50 km is around 1.7 km, compared to twice that on previous generations, with concrete effects on firing preparation time and firing solution stability.
The leap in performance is not just a question of maximum range. Detection consistency, particularly at high angles and with small altitude differences with the target, relies on precise management of the secondary lobes and surveillance lobes. The ability to maintain a reliable track during sustained turns, which are common during interception, highlights the mechanical rigidity of the antenna platform and the frequency stability of the transmitter. Combined with the short- and medium-range missiles used on the Mirage F1 (e.g., R.550 and Super 530), this tracking quality reduces the need for additional maneuvers and makes the attack “cleaner” under tight time constraints. In short, the Cyrano IV transforms a versatile airframe into a credible all-weather interceptor, with repeatable performance and a more manageable cognitive load for the pilot.
The air-to-air chain: monopulse, MTI, and look-down/shoot-down
The heart of the progress lies in the combination of monopulse radar and MTI. Monopulse compares the signals received on several channels in a single pulse, which immediately provides the aforementioned 2° accuracy and increased immunity to amplitude fluctuations. This architecture reduces angular jitter, stabilizes tracks, and improves Doppler filter recalibration. MTI uses radial velocity to discriminate a target moving against an apparently stationary ground background. In practice, the chain offers clutter rejection > 40 dB, which makes it possible to isolate low-altitude targets with modest intrinsic echoes. The term look-down/shoot-down refers precisely to this capability: detecting and engaging a target lower than the carrier, despite terrain clutter.
Operationally, these Doppler-based processes enable medium-altitude hunting profiles against very low-altitude penetrations. The logic of use consists of “locking on” to the target in monopulse tracking mode and then stabilizing the track by managing Doppler notches and terrain masks. At 100 km, initial detection gives the pilot time to optimize energy and heading, while monopulse tracking quickly locks the angle for a stable firing solution. Robustness to target maneuvers is due to the fact that the angle measurement is not averaged over several pulses, but decided instantly. In a dense environment, this reduces track breaks and lock losses at critical moments. The human-machine interface is simplified: fewer “break locks” and more continuity in the use of weapons, including short-range seeker-guided firing under tight alignment constraints.
The air-to-ground transformation: Cyrano IVM-R, terrain following and laser
The Cyrano IVM/IVM-R upgrades add a complete air-to-ground block. Terrain following uses a controlled aperture beam and a correlation mode that reproduces an altitude profile in front of the aircraft. The 1.5 m resolution mentioned above reflects the precision of radar mapping on the longitudinal axis, which is sufficient to pilot trajectories at very low altitudes while respecting a predefined safety floor. At these speeds, a 1.5 m step provides adequate control margins to filter out small irregularities and follow the average slope without inducing piloting-control oscillations.
The addition of a laser rangefinder (accuracy ± 5 m) revolutionizes conventional air-to-ground support. Using known coordinates or a designated point, laser measurement replaces less accurate estimates based on angle and noisy radar range over uncooperative terrain. The radar-laser combination improves the delivery of falling or energy-guided weapons by reducing last-minute pointing errors. In poor weather, the crew retains a consistent navigation and attack solution, switching between laser telemetry and radar estimation depending on the atmospheric transparency window.
These additions are only relevant if the ergonomics follow suit. The Cyrano IVM-R reorganizes modes: display priorities, alert logic, reduced air-to-air/air-to-ground transitions. The benefit can be seen in mixed profiles, typical of air forces with small fleets: a Mirage F1 can intercept on exit from the zone and then switch to a support mission with minimal reconfiguration, while maintaining solid radar situational awareness over complex terrain, even in low visibility conditions.
Availability and maintenance: GaAs and modularity
Reliability determines deployment. By migrating to GaAs-based RF subassemblies and modular T/R modules, the chain achieves an MTBF approximately 50% higher than previous iterations. The gain is not cosmetic: on a fleet operating at a sustained pace, this reduces unexpected withdrawals, stabilizes planning, and reduces workshop hours per flight hour. Modularity allows a faulty module to be quickly replaced without removing the entire antenna. The effect is twofold: increased availability and contained life cycle costs.
On the test bench, the frequency stability and thermal performance of GaAs improve channel alignment, thereby enhancing monopulse quality and clutter rejection. In hot environments, maintaining these characteristics reduces the need for recalibration. A redesigned cooling architecture improves heat dissipation, preventing gain drift at the end of the flight. On the flight line, updated technical documentation combines simplified testing and drawer-based fault isolation. The result is tangible: more sorties per day and fewer aircraft grounded due to a single failure.
The improvement in MTBF has an impact on training: crews fly on a more available and predictable system. For planners, the probability of a “down radar” during critical windows is reduced, which secures high-value air-to-air missions and low-altitude radar-guided penetrations. For the workshop, cannibalization is reduced, the supply chain is simplified by module families, and spare parts are sized more accurately.
Operational effects and legacy on doctrine
The combination of 100 km range, 2° monopulse radar, MTI, and look-down/shoot-down changes the way interceptions are conducted. Units can maintain optimal altitude while saving fuel, while retaining the ability to detect very low penetrations. The decision window is widening, and the number of energy recoveries is decreasing. In air-to-ground operations, the arrival of the Cyrano IVM-R and laser rangefinder refines support based on coordinates and secures trajectories at very low altitudes through terrain following. In poor weather conditions, all-weather capability becomes a daily reality rather than a theoretical concept.
In terms of capacity, increased MTBF and GaAs modularity help to maintain mixed fleets at a reasonable cost. The forces that align the Mirage F1 with other platforms can build a common doctrine: Doppler air-to-air modes, look-down procedures, and rapid switch to air-to-ground. This legacy informs the following radars: strict separation of modes, clear display hierarchy, deeper Doppler processing, terrain tracking coupled with accurate telemetry. The result is a common core of practices that endure: medium-altitude interception, low-altitude target engagement, TBA penetration with extended weather windows.
The trajectory of the Cyrano IV illustrates a lasting lesson: effectiveness comes from a coherent whole rather than a single record-breaking feature. Useful range, monopulse accuracy, Doppler filtering, terrain tracking, laser telemetry, MTBF reliability, and modular GaAs support all combine to increase operational effectiveness at a controlled cost. Contemporary programs retain this overall logic, adding multi-sensor fusion and denser data links, but the foundation laid by the Mirage F1 remains relevant for understanding what makes a fighter radar truly versatile.
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