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General Notes

Work on the A-135 program began in late 1968; with a two tier system similar to the US SPARTAN/SPRINT system adopted by late 1969.

On 10 June 1971, USSR Council of Ministers Resolution No. 376-119 was issued, authorizing the creation of the A-135 missile defense system, to consist of two systems:

"Амур" (Amur) Long Range Interception Firing Complex

"Амур-П" (Amur-P) – Prototype Long Range Interception Firing Complex

Plans called for three Amur complexes near Moscow at distances from 600 to 800 km, backed up by three S-225 [С-225] universal air defense system complexes.

In December 1971, the preliminary design of the A-135/Amur system was completed and OKB Fakel was selected as the main contractor for development of the long range two-stage exoatmospheric interceptor A-925/51T6.

Following the signing of the ABM Treaty in June 1972, the Amur/A-135 system was redesigned to accommodate all assets within an area of 100 km in the Moscow region. The S-225 complexes were removed from the system, but the short-range high speed interceptor missile PRS-1/5Ya26 [ПРС-1/5Я26] developed for the S-225 was selected as the short-range atmospheric tier for A-135, continuing development under a new GRAU Index [53T6].

The redesigned A-135 system was presented to the Ministry of Defense in 1973 and approved by the end of 1973.

The system was redesigned yet again following the signing of the 1974 ABM Treaty Protocol which reduced each side's ABM deployment areas from two [National Capital + ICBM field] to just one site per country.

This redesign lasted 1975-1976; while testing of missile prototypes began in 1973 and continued into the 1980s:

• August 1979: First 53T6 Silo Launch (exploded 5 seconds after launch due to defect in silo gas deflector)

• July 1981: First 53T6 launch with closed command loop guidance.

• April 1982: First interception of ballistic target (8K65 IRBM), passing within 50m of target at a range of 40 km.

• 18 June 1982: Two Amur-P (5Ж60П / 50Zh60P) [51T6] GORGON are launched, one intercepting a SS-20 Mod 1 SABER (15Ж45 БГРК «Пионер») IRBM launched from the Kapustin Yar test range, while the other intercepted a SS-N-8 SAWFLY (Р-29) launched by a DELTA I (Pr 667B Murena) SSBN.

• Factory Tests of “First Stage” of A-135 complex with Elbrus-1 computer and radar analog signal processing were carried out from November 1982 to March 1984, with 8 launches of 51T6 and 5 launches of 53T6 at the Sary Shagan test range.

• Installation of “Second Stage” equipment (Elbrus-2 computer and radar digital signal processing) was carried out at Sary Shagan from March 1984 to November 1987. When enough equipment was installed, testing of the “Second Stage” complex began and lasted from March 1987 to October 1987. During these tests, 2 x 51T6 launches and 3 x 53T6 launches were conducted. Following the conclusion of these tests against 2 ballistic targets and 36 passing ballistic targets, it was considered that the A-135 system could meet it's specified performance, which included destroying Pershing II MaRVs.

• A third round of tests at Shary Shagan began and lasted from January to July 1988, seeing 2 x 51T6 and 3 x 53T6 expended against 5 ballistic targets and 16 passing ballistic targets.

Deliveries of service 51T6/53T6 missiles began to units in 1990, with the system accepted into trial operation in December 1990, with trial combat duty beginning on 11 February 1991.

At the time of trial duty, the total compute in the DON-2N's KVP-135 command post was about 1000 MIPS divided amongst four x 10-CPU Elbrus-2 MVK computers, each running at 250 MIPS each. (One source claims only 125 MIPS, but this may be for the early 1987 prototypes at Shary Shagan, not the later models in Moscow).

When the Don-2NP (Дон-2НП) (HORSE LEG) prototype at Sary Shagan [46.00306, 73.64926] began operation in the mid to late 1970s, it was with the earlier Elbrus-1 computers, which provided only 15 MIPS per computer. The Soviet computing industry took from 1979 to 1986 to deliver an operational Elbrus-1; and the Elbrus-2 itself, which saw first prototypes in 1984 and limited production in 1987 – required a redesign in 1992 to make it reliable.

Experimental work began at the Amur-P test complex during 1989-1990 to reduce the lower boundary and increase the outer boundary of the target engagement zone for the 53T6 missile; along with the Samolet-M («Самолет-М») program, intended to equip the 53T6 with a non-nuclear warhead.

Formal combat alert began on 1 December 1995, with it being officially accepted into service in 1996.

In 2003, the 51T6 missiles were decommissioned, leaving only the 53T6s.

In the early 2000s, the Elbrus-2 computer network in the KVP-135 [КВП-135] Command Post was replaced with a local network using Elbrus-90 micro servers.

Currently the 1st Moscow Order of Lenin Special Purpose Air and Missile Defense Army (1-я Московская ордена Ленина армия противовоздушной и противоракетной обороны особого назначения) operates the A-135 complex through the 9th Anti-Ballistic Missile Defense Division (9-ой Дивизией ПРО).

Known specifications of the Moscow A-135 complex are:

[LINK TO ARCHIVED RUSSIAN LANGUAGE COMMENTARY ON A-135]

5Н20 [5N20] DON-2N [Дон-2Н] (PILL BOX) Radar:

Construction of the radar itself began in 1978; with the radar bunker complete by 1980, allowing installation of internal equipment which was largely complete by around 1983-84.

The development of the Don-2N radar required:

• Development and use of the Dnepr CAD computing complex with two (later four) ES 1050 and ES 1045 class computers for radar hardware.

• Development of CAD → CNC pipelines, to the point that some production lines were “automated” completely on computers, with no physical paperwork between them.

• Special permission from the USSR State Planning Committee to use gold plated conductors to meet the specifications of extremely low losses and high dynamic stability over electrical lengths required for the “special computer” systems. At 50 meters of cable per computer cabinet, and with over 500 cabinets required for the special computer system; the amount of gold needed was on the order of tens of kilograms.

• Development of “special computer” hardware with massive computing power to handle the demands of fully digital radar signals processing – all prior efforts (including the 1970s US Safeguard) used analog signal processing.

• Development of an active phased array with distributed power across the array; through the “Servant” (Сервант) module, which used three series-connected microwave amplification stages to produce megawatt-level pulsed output power with vacuum tubes.

The radar complex operates on the dual redundancy principle where three identical devices are installed:

Operating Device
Hot Standby Device
Cold Standby Device

Due to the massive power of the radar, biological fences surround it to protect personnel in the open from the radar and there are underground tunnels over 1 km in length connecting the radar complex with the outer perimeter; to enable personnel to move in and out while the radar is in operation.

[IMAGE OF BIOFENCE]

[IMAGE OF FACILITY ALERT LEVELS 1 | 2 | 3]

Deeper Technical Details

Each side of the pyramid contains a 18m circular [250m2] active phased array antenna; which is driven by 72 modules arranged in a 8 x 9 configuration. The modules themselves are about 8 meters long and weigh 3000 kg.

[IMAGE OF MAIN CIRCULAR RADAR]

[IMAGE OF RADAR MODULES – 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ]

Next to each 18m antenna, separated by a “gate” is a smaller 10.4m x 10.4m [108.16m2] square phased array antenna.

[IMAGE OF SECONDARY SQUARE RADAR]

[IMAGE SHOWING SEPARATION “GATES” IN BETWEEN RADARS]

Analysis of imagery of this antenna reveals several things:

First, If we assume that this smaller antenna has the same antenna gain and efficiency as the larger 4000 MHz antenna (it has to be able to control missiles out to maximum range) the frequency of it has to be around 6140 MHz. This eliminates Russian-language theories of it being the DON-2N transmitter antenna (similar to the older S-225 FLAT TWIN radar), and confirms that it is the missile telemetry radar.

(NOTE: Confirmation that DON-2N has an 18m diameter radar is obtained via scaling off THIS image)

Second, looking at the old SAFEGUARD MSR (IMAGE) reveals that you don't need a very large antenna for simple missile telemetry – the MSR missile telemetry transmitter was only 1.2~m diameter [1.31m2 area] versus the MSR array's 3.96m diameter [12.3m2 area], a ratio of 9.38x. If that secondary radar was truly for missile telemetry only and had the same aperture ratio (9.38) as on the Safeguard MSR, it would be about 26~ m2 in area. Instead, it's a massive 108 m2.

This means that it's more than just a missile telemetry transmitter; but a functionally separate radar that's lumped in with the larger 18m Phased Array as part of the 5N20 Radar Complex.

Third, the fact that the Don-2N radar could see 5 cm metal spheres at a range of 1500 to 2000 km during the 1994-1995 ODERACS (Orbital Debris Radar Calibration Sphere) shuttle experiments [STS-60 & STS-63] confirms that the secondary arrays are operating at 6135 MHz (4.89 cm), and can see those 5 cm spheres. This has massive implications for decoy discrimination.

Elsewhere, very little is actually known about the radar other than vague public figures of it consuming 250 MW; but we can estimate using the early AN/SPY-1 radars, which pushed 4.2 MW through 12m2 apertures, for 0.35 MW/m2 as a baseline:

Primary: 87.5 MW
Secondary: 37.8 MW
Total Per Face: 125.3 MW

This is backed up by statements from radar designers:

«Сервант» состоял из трех последовательно включенных СВЧ-каскадов усиления с выходной импульсной мощностью мегаваттного уровня.

“The "Servant" consisted of three series-connected microwave amplification stages with a megawatt-level pulsed output power.”

87.5 MW divided by 72 modules = 1.21 MW per module, which aligns with the above; and shows my estimates are within order of magnitude credibility.

Given that the entire complex is cited as requiring 250 MW; this means that there is enough generating capacity on site to drive two faces simultaneously at full power, which makes sense as two faces would provide coverage of a significant portion of likely incoming ballistic missile trajectories; and the complex can timeshare the faces to provide 360 degree track updates; with preference given to the faces facing the greatest incoming attack threat at that moment.

[IMAGE OF FACE ORIENTATIONS – 1 | 2]

Most of the time, the 5N20 Radar Complex is in standby mode; undoubtedly due to the massive power draw of the full complex, and also to preserve the operating life time of the vacuum-tube based T/R modules; with the BMD C3I complex relying on other early warning radars around Russia to provide it with situational awareness.

When combat mode is initiated, sirens sound on the exterior grounds, warning personnel that they have presumably 15 to 20 seconds to reach shelter before the radar lights off. Internally, the complex switches to autonomous power from nearby on-site generators, and the cooling systems are activated. If the cooling system fails, water is drawn from on-site wells into the emergency cooling system and then dumped externally onto the complex grounds.

[Engagement Sequence (#1) as seen from the A-135 System's Commander's Office]
[Closeup of Engagement Sequence #2]
[Closeup of Engagement Sequence #3]
[Closeup of Engagement Sequence #4 – Showing a massive exchange and more of the radar envelope]
[Closeup of Engagement Sequence #5 – Showing an alternate side of the control center]
[Closeup of Engagement Sequence #6 – Showing Readout of Parameters]
[Closeup of Engagement Sequence #7 – Showing Readout of Parameters]

Condensed DON-2N Specifications:

Four Faces installed at 60 deg, 150 deg, 240 deg and 330 deg; giving 360 deg coverage when combined.

Each face has a primary and secondary antenna:

PRIMARY: 18m diameter circular phased array [250m2 aperture] operating at 4000 MHz Frequency (7.5 cm); 87.5 MW Peak

SECONDARY: 10.4m x 10.4m square phased array [108m2 aperture] operating at 6135 Mhz Frequency (4.89 cm); 37.8 MW Peak

The primary radar is an early active electronically steeered phased array -- it contains 72 T/R modules each capable of providing 1+ MW power, and can form 30 beams at once; along with having fully digital radar signals processing.

Only enough power/cooling is installed at the site for two faces to be operated simultaneously; presumably the site "time shares" faces at full power.

Estimated Ranges against the Standard Radar Target (0.005m2) are 2,500 km for the SECONDARY radar; it's likely the PRIMARY can see just as far.

PRS-1 / 53T6 [ПРС-1 (53Т6)] Endo-Atmospheric Interceptor Missile (ABM-3A GAZELLE)

Length: 12~ m
Diameter: 1.7 to 1.8m
Weight: 10,000 kg
Thrust: 1000 tonnes-force over 4 seconds
Burnout Speed: 5.5 km/sec, reached in 4 seconds
Reaches a 30 km altitude in 6 seconds
Acceleration: 210G longitudinal, 90G transverse

NOTE: There are rumors that the Soviets experimented/thought about developing a 53T6 Silo Launcher system utilizing a drum-type revolver system for combat reloading of ABM silos to stay within the limitations of the ABM treaty.

PRS-1M (53T6M) [ПРС-1М (53Т6М)] Modernized GAZELLE

Acceleration: 300G longitudinal.

NOTES: Tested circa 2018. Has kill zone that is nearly 50 percent larger in altitude and range than the 53T6. It can reliably intercept enemy ICBM warheads at altitudes well above 50 kilometers. Approximately 1.33 times faster (vBO) than 53T6. Smaller warhead.

(LINK) (LINK)

51T6 Exo-Atmospheric Interceptor Missile (ABM-4 GORGON)

First Stage: 41A6 Solid Motor, 5 second burn time
Second Stage: NTO/UDMH Liquid Motor

NOTES: Modernized A-350R [А-350Р]. Preliminary design was completed in 1973-74 with finalization in 1976. Can be retargeted mid-flight.