A unique object is located several tens of kilometers northeast of Moscow. It has the shape of a truncated tetrahedral pyramid with a base width of about 130 meters and a height of about 35 meters. On each facet of this structure there are characteristic round and square panels that can tell a knowledgeable person what is hidden under them. Behind the four round panels are four active phased antenna arrays with a diameter of 18 meters, behind the square ones - anti-missile control antennas about 10x10 meters in size. The object itself is a multifunctional radar station "Don-2N" and is designed to control outer space over Russia and neighboring countries, as well as to detect and ensure the destruction of detected ballistic missiles.
In fact, the Don-2N radar station is the central element of the Moscow anti-missile defense system. The capabilities of the station make it possible not only to detect potentially dangerous objects at altitudes up to 40 thousand kilometers, but also to provide guidance for anti-missiles. The station is equipped with four phased antenna arrays at once, thanks to which it can observe the entire surrounding space and provide data on detected targets.
The history of the Don-2N radar began back in 1963, when the Moscow Radio Engineering Institute of the USSR Academy of Sciences (now OAO RTI named after Academician AL Mints) was tasked with creating a new target detection system for a promising anti-missile defense complex. Initially, it was planned to create a radar station operating in the decimeter range. However, a few months after the start of work, the staff of the institute came to the conclusion that the characteristics of such a system were insufficient. The decimeter station could not provide sufficient accuracy in detecting targets, which in a real situation could have fatal consequences. Therefore, at the beginning of the next 1964, RTI began developing a new centimeter attachment. With the help of this equipment, it was planned to give the new station acceptable characteristics, as well as to provide comparative simplicity and ease of operation, since the attachment was supposed to work as part of a system built with extensive use of existing technologies and developments.
However, even in this case, the new proposal was considered unpromising. It was required to make a completely new radar station with a good foundation for the future. In this regard, the remainder of 1964 and the entire next year, the employees of the Radio Engineering Institute spent on the creation of five different versions of a promising station. But for the third time, the project did not produce any practically applicable results. All five options had their own problems and were not recommended for further work. An analysis of the work done and the technical proposals put forward led to the emergence of another version of the appearance of a promising radar. A little later, it was this version that became the basis for the future Don-2N station.
In the first months of 1966, RTI employees began work on the Don project, during which it was planned to create two radars operating in different bands at once. The decimeter system was supposed to be made in ground and ship versions, which would allow not only to monitor outer space from its own territory, but to monitor the positional areas of enemy missiles with the help of ships with radars located off its coast. The centimeter station, in turn, was made exclusively in the ground version. It was proposed to include in its tasks not only the detection of enemy missiles, but also the guidance of interceptor missiles. According to the first versions of the project, the centimeter radar was supposed to "scan" a sector with a width of 90 °. Thus, to ensure all-round visibility, it was required to simultaneously build four identical stations at once.
By the time the preliminary design of the Don centimeter station was completed, all work on the second UHF system had been stopped. The level of development of radio electronics made it possible to combine all the necessary developments in one ground station and ensure that the requirements were met. Since 1968, RTI employees have developed equipment designed to operate only in the centimeter range. As for other frequencies, meter waves were chosen for early warning stations for missile attacks.
In 1969, the Radio Engineering Institute was instructed to begin the development of a preliminary project "Don-N", in which it was necessary to use the existing developments in previous programs in the field of radar stations. At the same time, the requirements of the customer, represented by the Ministry of Defense, were quite large. The fact is that the specified characteristics of the range and altitude of the tracked targets turned out to be too large for the electronics available at that time. In the late sixties, even the newest electronic equipment could not reliably track and track complex ballistic targets at ranges of about two thousand kilometers.
To accomplish the assigned tasks, a number of serious studies and tests had to be carried out. At the same time, there was a proposal to partially simplify the missile defense system, dividing it into two echelons and equipping it with two types of missiles. In this case, the construction of one radar with an integrated system for guiding two types of missiles looked convenient and optimal from an economic point of view. It took some more time to determine the final appearance of the future radar, and only in the middle of 1972 the full-fledged implementation of the Don-N project began.
To fulfill the required characteristics, it was proposed to equip the promising radar station with a new computer complex, the development of which started simultaneously with the start of the full-fledged design of the Don-N. Soon, the multifunctional radar acquired most of the features that have survived to this day. In particular, RTI engineers decided on an approximate building structure: a truncated pyramid with fixed phased antenna arrays on each of the four edges and separate square antennas for missile control. The correct calculation of the position of the antennas made it possible to provide a complete view of the entire upper hemisphere: the "field of vision" of the station was limited only by the relief of the surrounding area and the features of the propagation of the radio signal.
In the future, the project was improved and certain adjustments were made to it. First of all, the innovations concerned signal processing equipment. For example, the Elbrus-2 supercomputer was created for operation as part of the radar station. However, even with the most advanced electronic equipment, the computer complex of the station was reduced only to the size of more than a thousand cabinets. To cool this amount of electronics, the project had to provide a special system with water pipes and heat exchangers. The total length of all pipes has exceeded several hundred kilometers. The connection of all elements of the radar equipment required about 20 thousand.kilometers of cables.
In 1978 the project, which by this time had changed its name to "Don-2N", reached the stage of construction of a workstation. It is worth noting that at about the same time a similar complex was built at the Sary-Shagan test site, but it differed from the one near Moscow in size, equipment used and, as a result, capabilities. In about ten years of construction and installation of equipment, builders installed more than 30 thousand tons of metal structures, poured over 50 thousand tons of concrete and laid a colossal amount of cables, pipes, etc. Since 1980, the installation of radio-electronic equipment has been going on at the facility, which lasted until 1987.
Only a quarter of a century after the start of its creation, a new multifunctional radar station "Don-2N" took up combat duty. In 1989, the complex began tracking objects in outer space. According to open data, the radar is capable of detecting a target at an altitude of 40 thousand kilometers. The detection range of a target such as the warhead of an intercontinental missile is about 3700 km. Radar transmitters are capable of delivering pulsed signal power up to 250 MW. Phased antenna arrays and a computer complex provide the determination of the angular coordinates of the target with an accuracy of about 25-35 arc seconds. The accuracy of determining the range is about 10 meters. According to various sources, the Don-2N station can track up to hundreds of objects and aim up to several dozen interceptor missiles at them. One shift of station operators consists of one hundred people.
During the first years of operation of the Don-2N radar, its characteristics, as well as the very fact of its existence, were not disclosed. However, already in 1992, Russia and the United States agreed to jointly conduct a program, the purpose of which was to determine the possibility of detecting and tracking small objects in Earth's orbit. The program was named ODERACS (Orbital DEbris RAdar Calibration Spheres).
The first experiment within the program (ODERACS-1) was planned for the winter of 1992, but did not take place for technical reasons. Only two years later, the American shuttle Discovery, during the ODERACS-1R experiment, threw six metal balls into space. The balls remained in orbit for several months, and at that time they were monitored by American radars and the Russian Don-2N radar station. It is noteworthy that the balls measuring 15 and 10 centimeters (two balls of each size) were able to notice and track all the stations participating in the experiment. Only Russian servicemen managed to detect two five-centimeter balls. In the next experiment, ODERACS-2, the shuttle Discovery threw out three balls and three dipole reflectors. The results of the experiment, with the exception of some nuances, turned out to be similar. The Don-2N radar could find the smallest balls at distances of up to two thousand kilometers.
Unfortunately, the overwhelming majority of information about the capabilities and service of the Don-2N multifunctional radar remains classified. Therefore, the available information about the complex is often scarce and fragmentary. Nevertheless, some conclusions can be drawn from the available data. Information about the possibility of simultaneous tracking of hundreds of targets suggests that one radar is capable of detecting a limited nuclear strike against the covered area. After detection, the station independently guides missiles at targets, and, according to various sources, it can issue commands to 25-30 missiles at once. Due to the lack of accurate data on the state of the missile component, it is difficult to talk about the potential capabilities of the entire missile defense system of Moscow. Thus, at present, the potential of the Don-2N radar station may not be fully utilized due to the lack of a sufficient number of missiles. However, this is only an assumption, since the exact data on the state of Moscow's entire missile defense remains secret.