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M-4 Osa-M


NATO: SA-N-4 Gecko


Overview


Osa-M

Osa-M system with ZIF-122 launcher with 9M33M missiles in foreground and associated fire control radar in the background.
Source: Unknown author - © Copyright lies with original owner

Origin
Soviet Union
Type
Naval SAM system
Entered service
1971
Status
In service
Development
1960’s
Developer
Soviet Union
Production
1970 - ?
Producer
Soviet Union
Designations
SA-N-4 Gecko (NATO reporting name)
M-4 (Soviet navy designation)
4K33 (GRAU index for system)
9M33M (GRAU index for missile)
Pop Group (NATO reporting name for radar)
Notable users
Soviet Union
Russia

Description


Introduction

The Osa-M is a naval SAM system of Soviet origin. It was developed to act as a point defense system against aircraft and inbound anti-ship missiles. Over time it was upgraded to for more effectiveness against low flying targets.

Design

The Osa-M is derived from the land based 9K33 Osa self-propelled SAM system. There is a 70% commonality in missile design and guidance systems. Whereas the land based 9K33 is one of the first self-propelled SAM systems where radars, operators and missiles are on the same vehicle, the Osa-M has a more modular layout. The search and fire control radar are located away from the ZIF-122 twin rail launcher. A unique feature of the launcher is that when it the system is not in use the launcher is retracted below deck and covered by a large round door.

Guidance

Targets are identified by the ship’s main air surveillance radar and handed off to the Osa-M system. The guidance section consist of a tracking radar and a fire control radar. NATO reporting name is “Pop Group”. The tracking radar provides targets coordinates while the fire control radar is used to plot the course between the missile in flight and the target. The 9M33M missile used command guidance via radio frequency. A single target is engaged at a time.

Firepower

The ZIF-122 launcher has two missiles ready to launch. 40 additional missiles are stored in the magazine below deck. The maximum range is about 10 km and targets may be engaged out to altitudes of over 3.5 km. The main role of the Osa-M is to intercept inbound subsonic anti-ship missiles. Therefore all upgrades were focussed at the minimum altitude. With the latest modification sea skimming missiles 5 m above sea level can be engaged.

Platforms

The Osa-M was fitted to a variety of Soviet ships. These range from corvettes to cruisers. Minimum ships size for the Osa-M is quoted as 500 t displacement. Over time the Osa-M system was supplemented in the anti-missile role by combined gun and missile systems such as the Kashtan.

Variants


ZIF-122 with 9M33M missiles

Moskva missile cruiser Osa-M air defense system off the coast of Syria on December 18, 2015
Source: Russian MoD - © GNU Attribution Share Alike license

Variants of the Osa-M system

Osa-M
Original naval SAM system based on the 9M33 missile. Introduced in 1971.
Osa-MA
Improved Osa-M system. Capable of engaging targets 25 to 60 m above sea level. Adopted in 1979.
Osa-MA2
Further upgrade of the Osa-M system. Able to engage sea skimming targets as low as 5 m above sea level. Introduced in the mid 1980’s.

Details


Facts 9M33M ZIF-122
General
Origin
Soviet Union
Type
Surface to air missile
Dimensions
Diameter
0.206 m body
Wingspan
0.65 m
Length
3.158 m
Weight
128 kg
Guidance
Guidance mode
Command guidance
Interface
Radio frequency
Warhead
Type
HE-fragmentation
Weight
19 kg
Fuze
Contact and radio proximity fuze
Engagement envelope
Propulsion
Single-stage solid propellant rocket motor
Speed
500 m/s
Range
10 km
Altitude
Over 3.5 km maximum
5 m minimum

Media