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INDIGO Missile System

Sistel (Sistemi Elettronici) was established in 1967 by five Italian companies with interests in missiles, rocket propulsion and electronics. It is owned 35 per cent by Montecatini Edison, 20 per cent each by Fiat, Contraves Italiana and Finmeccanica, and 5 per cent by Snia. In 1969 Sistel took over most of Contraves' missile work and the complete staff of the company's Missile Division.

By 1974 Sistel was continuing a gradual evolution of its Indigo low-level surface-to-air missile but had no production contract. The Italian Army's qualification tests of the towed-launcher version — for fixed-point defence — were finished at the end of 1973, and trials of the selfpropelled variant for troop protection will continue throughout 1974, with the latest series of firings taking place this month in Sardinia. About 100 qualification launches have been made altogether.

On the basis of experience in the Middle East October war Sistel was confident that there was a market for the towed Indigo launcher coupled with Oerlikon 35mm or Bofors 40mm guns for close-range work. Both missiles and guns can be directed by Contraves' Superfledermaus fire-control system.

Indigo is a low-level and very-low-level anti-aircraft missile which became operational in 1972 with the Italian Services. It is fired from towed or self-propelled launchers and is designed for use with a wide range of existing fire-control systems such as Contraves' Superfledermaus (in the towed version), or Thomson-CSF Mirador Eldorado acquisition and tracking radars coupled with Officine Galileo's fire-control unit (when the self-propelled launcher is used). The six-round missile launcher can be deployed on a gradient of up to 7° and can be trained and elevated extremely rapidly. Indigo may be fired singly or in salvo (two missiles), the method of operation being selected by the engagement computer, but with a manual override being possible. A Sea Indigo naval version of Indigo for shipboard point defence was under study. It would use Contraves' Sea Hunter fire-control system.

In the conflict between missile and aircraft, which calls to mind the old conflict between guns and armor, what assumes particular importance is counteraction at those low flight altitudes which offer attacking aircraft greater possibilities of evading search radar, besides allowing them to take advantage of the orographic characteristics of the combat zone in the best possible way.

It is the opinion of experts that the most advantageous altitudes are 50 to 300 in. In an attack using conventional explosives for mobile targets, a timely recognition of the target itself is necessary. That necessitates flying at an altitude of not less than 100 m and a speed of not more than Mach 0.8 (850 km/hr). The launch will then take place from a distance of 2— 3 km. For fixed targets, the distance does not change, but the speed can be as great as Mach 1.2 (1,270 km/hr). Therefore , it is necessary for the defensive weapons systems to have very short reaction times and to be equipped with missiles having high performance capabilities. In the case of an attack using air—to—surface missiles or remote—controlled bombs with nuclear charge, the launch could be made from a distance of about 15 km. Consequently, the defensive systems must have a broad acquisition range and weapons with a considerable range.

The development of the INDIGO was promoted by the Italian Ministry of Defense in order to resolve, in accorflance with the specifications established by NATO, the problem of close defense against low—altitude attacks. Studies on that subject were begun in 1962 by the Contraves Co. and continued until, in 1969, the entire program was undertaken by the Sistel Co. (formed with the participation of Contraves itself and other Italian companies), which studied three versions of the missile launcher : one towed on land, one shipborne, and a self—propelled land version. By 1976, after an extensive and favorable series of tests made at the Sardinia proving grounds, the first version of the weapon (the towed land model) was fully operational.

The INDIGO had the following characteristics : length, 3,076 m; diameter , 195 mm ; launch weight, 120 k g. It has an advanced aerodynamic configuration. The cruciform control wings have an 813—mm span. They are installed very near the center of gravity, which thus permits a rapid response to signals emitted by the guidance system. In line with those wings are the stabilizing tail fins. The propulsion is ensured by a solid—propellant booster which produces a 3,750—kg thrust and burns for 2.5 seč~nds . At the end of combustion the missile reaches a speed of Mach 2.5 (2,650 km/hr) and its weight is reduced to 80 kg. The range is as much as 10 km and the operational height is between tree level and 5,000 m.

In case of possible evasive maneuvers by the target, the flying time can be a maximum of 30 seconds. If the missile fails to intercept the target after that interval, it self—destructs. The missile can withstand a longitudinal force of 40 g and a lateral force of 30 g.

The warhead weighs a total of 22 kg and is of the fragmentation type, symmetrical around the axis. It has an impact fuze and an infrared proximity fuze. The circuits of the guidance system are run by batteries which are activated at launch time . The antennas of the radio receivers and an infrared rransmitter are mounted on the four stabilizing tailfins. The antennas have great directivity and electronic disturbances which may be emitted by the target are therefore very much attenuated.

The guidance system may be operated in two ways:

  1. “All—weather” using radio control on a radar director beam combined with an infrared device, which after the launch keeps the missile on the radar beam;
  2. “Fair weather” (very useful if weather conditions permit its use and when the enemy uses strong ECM). The infrared device , as in the first mode of operation, keeps the missile within the sighting field, and then, using a narrower beam , computes the movement of the missile with respect to the line of sight of the optical instrument which functions jointly with the infrared device. The missile has flares which facilitate the operation.

The launcher, which was designed to be easily transported by aircraft, helicopters, and motor vehicles, is made up of a complex of six tubes, which also serve as ramps. It can be deployed on any terrain which does not have a slope of more than 70, and it is capable of making rapid movements in elevation and azimuth, with enough of a range to cover the entire space above . However, in the shipborne version , called SEA INDIGO the launcher is quadruple and always easily reloadable .

Why did these Napoleonic plans did not come true? The fact is that this air defense system was based on the old ideology. Two launchers (12 missiles) provided for the use of only one radar guidance, and that missile channel is also equal to one. Thus, the entire anti-aircraft complex, shown in the figure below, could fire only one missile at a single target at a time. In this regard, the Indigo-MEI air defense system was inferior not only to the Soviet Osa complexes (two-channel on the rocket), but also to the Rolands experienced around the same years and even to the Rapier’s older ones, at least.

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Page last modified: 28-04-2019 18:50:11 ZULU