Tank registration systems for laser radiation
The device LIRD-4 company FOTONA. Source: "Proceedings of the Russian Academy of Rocket and Artillery Sciences"
A similar technique was developed in the offices of Marconi and Goodrich Corporation under the names, respectively, Type 453 and AN / VVR-3. This scheme did not get acclimated due to the inevitable hit of the protruding parts of the tank into the receiving equipment sector, which led either to the appearance of “blind” zones, or to beam re-reflection and signal distortion. Therefore, the sensors simply placed around the perimeter of armored vehicles, thereby providing a circular review. Such a scheme was embodied in the English series HELIO with a set of sensor heads LWD-2, Israelis with LWS-2 in the ARPAM system, Soviet engineers with TSHU-1-11 and TSHU-1-1 in the famous Shtore and the Swedes from Saab Electronic def. with LWS300 sensors in active protection LEDS-100.
A set of equipment LWS-300 complex LEDS-100. Source: "Proceedings of the Russian Academy of Rocket and Artillery Sciences"
The common features of the designated technology is the receiving sector of each of the heads in the range of 450 to 900 azimuth and 30... 600 around the corner of the place. This configuration of the review is explained by the tactical methods of using anti-tank controlled weapons. A strike can be expected either from ground targets, or from a flying technology, which is cautious about covering air defense tanks. Therefore, attack aircraft and helicopters usually illuminate tanks from low altitudes in the 0 sector ... 200 on the corner of the place with the subsequent launch of the rocket. The designers took into account possible vibrations of the body of an armored vehicle and the angle of view of the sensors in the elevation angle was slightly larger than the angle of air attack. Why not put the sensor with a large viewing angle? The fact is that lasers of contactless fuses of artillery shells and mines are working on top of the tank, which, by and large, make it difficult to put obstacles late. The problem is also the sun, the radiation of which is capable of illuminating the receiving device with all the ensuing consequences. Modern range finders and target designators, for the most part, use 1,06 and 1,54 μm lasers — it is for these parameters that the sensitivity of the receiving heads of recording systems has been sharpened.
The next step in the development of the equipment was the expansion of its functionality to the ability to determine not only the fact of irradiation, but also the direction to the laser source. The systems of the first generation could only approximately indicate the enemy illumination - all due to the limited number of sensors with a wide sector of azimuth review. For a more accurate positioning of the enemy would have to weigh the tank a few dozen photodetectors. Therefore, matrix sensors, such as the photodiode FD-246 of the TShU-1-11 photodetector of the “Blind-1” system, came to the scene. The photosensitive field of this photodetector is divided into 12 sectors in the form of strips, onto which laser radiation transmitted through a cylindrical lens is projected. If simplified, the sector of the photodetector, which recorded the most intense illumination with a laser, will determine the direction to the radiation source. A little later, a germanium laser sensor FD-246AM appeared, designed to detect a laser with a spectral range of 1,6 μm. This technique allows to achieve a sufficiently high resolution in 2 ... 30 within the sector viewed by the receiving head to 900. There is another way to determine the direction of the laser source. To do this, joint processing of signals from several sensors is performed, the entrance pupils of which are located at an angle. The angular coordinate is found from the ratio of the signals of these receivers of laser radiation.
The requirements for the resolution of the equipment for recording laser radiation depend on the purpose of the complexes. If it is necessary to accurately guide the power laser emitter to create interference (the Chinese JD-3 on the 99 Object and the American Stingray complex), then the resolution requires about one or two angular minutes. Less strictly to resolution (up to 3 ... 40) are suitable in systems when it is necessary to deploy the tool to the direction of laser illumination - this is implemented in the Curtain, Varta, LEDS-100 KOEP. And quite a low resolution is permissible for the installation of smoke screens in front of the sector of the proposed launch of the rocket - to 200 (Polish Bobravka and English Cerberus). At the moment, the registration of laser radiation has become an obligatory requirement for all the CEEP used on tanks, but the guided weapons turned to a qualitatively different principle of guidance, which raised new questions for the engineers.
The rocket tele-orientation system for laser beams has become a very common “bonus” of anti-tank guided weapons. Developed it in the USSR in 60-ies and implemented on a number of anti-tank complexes: Bastion, Sheksna, Svir, Reflex and Cornet, as well as in the camp of a potential opponent - MAPATS from Rafael, Trigat concern MBDA, LNGWE from Denel Dynamics, as well as Stugna, ALTA from Ukrainian Artem. The laser beam in this case gives a command signal to the tail of the rocket, more precisely, to the onboard photoreceiver. And it does it extremely cunningly - the laser coded beam is a continuous sequence of pulses with frequencies in the kilohertz range. Feel what is at stake? Each laser pulse that hits the FEP receiving window is below their response threshold level. That is, all the systems turned out to be blind in front of the command-beam guidance system for ammunition. They added fuel to the fire with the emitter pankratic system, in accordance with which the width of the laser beam corresponds to the picture plane of the rocket photodetector, and as the ammunition moves away, the angle of divergence of the beam generally decreases! That is, in modern ATGMs, the laser can generally not get on the tank - it will focus exclusively on the tail of the flying missile. This, of course, was a challenge - currently intensive work is underway to create a receiving head with increased sensitivity, capable of determining the complex command-beam signal of a laser.
Model prototype of radiation detection equipment for command-beam guidance systems. Source: "Proceedings of the Russian Academy of Rocket and Artillery Sciences"
Receiving head of AN / VVR3 equipment. Source: "Proceedings of the Russian Academy of Rocket and Artillery Sciences"
This should be the BRILLIANT laser interference station (Beamrider Laser Localization Imaging and Neutralization Tracker), developed in Canada by the DRDS Valcartier Institute, as well as the workings of Marconi and BAE Systema Avionics. But there are already serial samples - the universal indicators 300Mg and AN / VVR3 are equipped with a separate channel for defining command-beam systems. True, this is only the assurances of developers.
A set of radiation detection equipment SSC-1 Obra. Source: "Proceedings of the Russian Academy of Rocket and Artillery Sciences"
The real danger lies in the Abrams SEP and SEP2 tanks modernization program, in accordance with which armored vehicles are equipped with a GPS thermal sight, in which the range finder has a carbon dioxide laser with an “infrared” wavelength 10,6 μm. That is, at the moment, absolutely the majority of tanks in the world will not be able to recognize the irradiation by the range finder of this tank, since they are “sharpened” by the laser wavelength in 1,06 and 1,54 μm. And in the US, more than 2 of thousands of their Abrams have been upgraded in this way. Soon, the designators will switch to a carbon dioxide laser! Suddenly, the Poles distinguished themselves by putting the SSC-91 Obra receiving head from PCO on their PT-1, which can distinguish laser radiation in the 0,6 ... 11 μm band. All the rest now again have to return to the armor infrared photodetectors (as Marconi and Goodrich Corporation previously did) based on ternary compounds of cadmium, mercury and tellurium, capable of recognizing infrared lasers. For this, their electrical cooling systems will be constructed, and in the future, perhaps all the infrared channels of the CEEP will be transferred to uncooled microbolometers. And all this while maintaining a circular view, as well as traditional channels for lasers with a wavelength of 1,06 and 1,54 microns. In any case, engineers from the defense industry will not be idle.
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