The 5N62 Square Pair is the engagement radar for the S-200 / SA-5 Gammon SAM system series. It is a coherent FMCW design with a capability to autonomously search small volumes, track targets and provide illumination for the 5V21 and 5V28 missile seekers.

The  K-1/K-1V/M Transmitter/Receiver Cabin houses the radiofrequency hardware and mounted the 5N62 antenna head. The K-2 Fire Control Centre van houses the operator consoles and supporting electronics. The K-3 Launch Control Centre van is used to control and sequence the individual 5P72 launchers with the 5V72 missile rounds. The K-9  Battery Command Post van is used to integrate track data provided by the acquisition radars, such as the P-14 Tall King or P-35/37 Bar Lock, and supporting heightfinders such as the PRV-17 Side Net / Odd Pair, and an IFF interrogator such as the 1L22 Parol.

The 5E23 computer was another innovation, it was introduced to calculate key parameters for use by the autopilot.

The missile is equipped with a telemetry downlink used to communicate missile systems status to the launching battery, the transmitter doubling up as a tracking beacon for the Square Pair. Some sources also credit this channel with an uplink capability, specifically intended to initiate the warhead in nuclear armed variants, and to arm the radio proximity fuse and initiate the self destruct.

The 5I43 (later 5I47) 65 SHP turbine onboard power supply provides power for the vacuum tube based (in early variants) electronics, control actuator hydraulics, and to drive the powerplant turbopumps (NB the term APU cannot be applied, even if its design resembles a modern APU, since the 5I43/5I47 is sole power supply in the vehicle).

This complex high density design is modelled on the arrangement in the Scud ballistic missile, where main propellants are tapped to drive a gas generator, which drives a turbine coupled to the propellant pumps for the main engine. Unlike a ballistic missile, where control power is irrelevant once the main engine has ceased its burn, a SAM requires power to its systems until impact. As a result the 5I43 uses its own isolated fuel system, but burning the same fuel type as the cruise engine.

The turbine in the 5I43 is spun up prelaunch by a one shot gas cartridge, upon which the hypergolic fuel is introduced into the gas generator and used to drive the turbine. In turn the turbine transfers torque to the main fuel pumps, a hydraulic pump, and a pair of electrical generators, with additional electrical transformers embedded in the unit. At launch the start and stable operation of the 5I43 is a precondition for main engine ignition, and subsequent solid booster initiation. If the turbine power supply fails to start, the missile launch is immediately aborted. The turbine power supply is the cause of the characteristic perpendicular smoke plume sometimes observed in footage of S-200 missile launches.

The PRD-81/5S25/5S28 solid propellant boosters were initially tested using RST-43 and RSNDI-59 propellant, production units then using RAM-10K filler. After the 3-5 sec burn duration these strap-on solids are jettisoned. Separation is facilitated by shaping to exploit aerodynamic forces.

The sustainer powerplant is an Isayev 5D12 single chamber design, replaced in later models by the improved 5D67. The design is not restartable in flight, but can be throttled from 3,200 kp to 10,000 kp, to optimise thrust across the flight profile, using pre-programmed settings issued by the mission computer. This capability is used to permit optimised profiles, trading range against climb rate and altitude.

The powerplant is fuelled with the widely used, and toxic/corrosive, AK-27P oxidiser melange in a 1680 kg tank, and TG-02 fuel in a 586 kg  tank. All propellants tanks are pressurised by a compressed air tank.

The missile is prior to launch fed with electrical power and cooling air from the launcher. Once Built In Test (BIT) has completed, the seeker is tuned, and steered to acquire the target. Once target lock is achieved, the turbine power supply is started, and once stable the weapon transitions to internal power, and the sustainer engine is started. Only then are the solid boosters initiated and the missile can depart the launch rail. Initial 0.45 - 0.85 seconds of flight are unguided, upon which the autopilot is engaged and the controls go active.

Russian sources do not describe the altitude profiles of the missile trajectory, but do state that during the first 30 seconds of flight the autopilot employs a constant lead angle control law, after which it transitions to a conventional P-nav algorithm.

Operator training guide manuals translated from Russian and distributed to Warsaw Pact allies state that two primary flight regimes are employed, one for “close” and the other for “distant” targets, the transition being at slant ranges of 70 ~ 80 km (38 - 43 NMI).

If a target is designated to be “close”, and with either t_flight< 60 [sec] and H ≤ 20,000 [m] (shallow trajectory) or t_flight< 70 [sec] and H > 20,000 [m] (steep trajectory), then a conventional P-nav control law is employed for the whole duration of the flight.

If a target is designated to be “distant”, and with either t_flight≥ 60 [sec] and H ≤ 20,000 [m] (shallow trajectory) or t_flight≥ 70 [sec] and H > 20,000 [m] (steep trajectory), then the missile flies with two discrete control laws applied, one for midcourse flight, the other for terminal homing. The midcourse flight regime control law is a constant lead angle (ε=35º; β=0º or 15º) rule, with the missile switching over to the P-nav control law for terminal homing.

This strategy was adopted to maximise range against distant targets, as the P-nav algorithm can be wasteful of kinetic and potential energy.

The cumbersome 5Yu24 rail loader was used to transfer the missile from the 5T53 transporter to the 5P72 launcher. It also is carried by 5T82 semitrailer (above and below)(via www.s-200.de).

Early model S-200A Angara K-3 Launch Control Centre van. Note the multiple cable harness connectors at the lower front of the van, and above ground rectangular cable ducting (Almaz brochure via Free SAM Simulator).

	K-2 Fire Control Centre Stations K-2 series Fire Control Centre van crew stations (© 2010, Free SAM Simulator, posted with permission). The K-2 series Fire Control Centre van would qualify in part, under Western nomenclature, as a fire control van, and in part, as a radar control and management van for the 5N62 Square Pair. The 5N62 Square Pair is used to acquire the target, perform fine tracking, and provide FMCW illumination for the semi-active homing missile seekers. The K-2 van houses all of the radar consoles, but also houses the Plamya fire control computer which performs pre-launch and post launch missile trajectory calculations. Missile telemetry and command link functions are all controlled from the K-2 van. K-2 series Fire Control Centre van crew (Russian Internet via www.s200-wega.de). K-2 Fire Control station console (© 2010, Free SAM Simulator, posted with permission). K-2 target acquisition station console. The operator uses video from the Tall King, Odd Pair and IADS track data to acquire the target using the FMCW 5N62 Square Pair  (© 2010, Free SAM Simulator, posted with permission). K-2 target tracking and illumination station console. The operator maintains a fine track of the target using the 5N62 Square Pair FMCW waveform, in a number of possible modes. CW illumination was fixed frequency and without range tracking (© 2010, Free SAM Simulator, posted with permission). Above, below: K-2 van Plamya KV fire control computer (© 2010, Free SAM Simulator, posted with permission).

Semi-mobile configuration of the improved K-1M van with 5N62 Square Pair FMCW tracker/illuminator on display at Kecel in Hungary. Note the Square Pair at maximum elevation angle in the background  (Image © Miroslav Gyűrösi).