August 17, 1998
SUBJECT: SA-19 Firing engagement sequence.
- (U) Overview. The SA-19 missile is a two-stage command-guided missile. The missile system is composed of the fire control unit, launcher, missile tracker, and the canistered missile, and is supported by the direct-view optics (DVO) and the HOT SHOT target tracking and acquisition radars onboard the 2S6M. Typical reaction time is 8-12 seconds.
- (U) Fire-control system. The integrated fire-control system of the 2S6M incorporates the following components:
- Target acquisition radar (TAR) (1RL144), operating in the E-band, with a max. range of 20 km.
- Target tracking radar (TTR) (1RL144M), operating in the J-band, with a max. range of 18 km.
- IFF system (1RL138), operating in C-and D-band.
- Direct-view Optics (DVO).
- Fire-control computer.
(U) The TAR antenna is mounted at the rear of the turret and is folded down when not in use. This radar provides primary search capability in addition to measurement of range and bearing. This radar can detect targets out to maximum range of approximately 20 km. It is a coherent system that has sufficient accuracy to permit its use as a range back up for fire-control purposes. The TAR emits a fan beam covering 4.50 in azimuth and 150 in elevation. The beam is pointed at a constant elevation of 7.50 to permit detection of low-altitude targets. The antenna rotates at approximately 1 r/s, which gives a rapid update of the airspace around the 2S6M. The choice of a frequency in the E-band for the TAR is an advantage since there is low attenuation in inclement weather (rain, snow, and fog) at this frequency and therefore the acquisition radar is not degraded in such conditions.
(U) The TTR antenna is mounted at the front section of the turret and has two fundamental functions that depend on whether the guns or missiles are selected. The tracking radar constantly relays target range, elevation and bearing to the fire-control computer, and on the basis if these data the computer generated the laying commands for the weapon system. A stabilized optical sight is used as a back up tracking channel, allowing target data to be relayed to the fire-control computer. This sight is also used to calculate the deviation of a missile's flight path from the line-of-sight, these data being automatically relayed to the fire control computer and used to generate correction signals. During a gun engagement, the TTR functions as an automatic target tracker, feeding target position data to the fire-control computer. During missile engagement, the tracking radar locks onto the target and then lays the optical sight on the target. Subsequently the gunner assumes the target-tracking function with the electro-optic sight, and the radar is used for relaying guidance commands to the SA-19 missile. The tracking radar emits pulse-position-modulated codes for missile guidance. The TTR is a two-channel monopulse design featuring an MTI processor and a digital range-tracking system. The tracking radar is generally cued with coarse range and angle data from the TAR. Alternatively, the targeting information can be passed by means of the command and control network.
3. (U) Fire engagement sequence. During a missile action the radar first locks on the target, as in the case of gun employment, and then lays the slaved optical sight on the target. Subsequently the gunner assumes target tracking functions through his optical sight, and the radar is used for relaying the trajectory correction commands to the missile in flight. Immediately prior to the launch, the turret is turned slightly off-axis, so that the smoke caused by the launch will not obstruct the sight on the target. The 2S6M must be stationary during the launch sequence, in order to avoid damage to the missile while it leaves the launch tube. Immediately after launch, the weapon system is lowered again into the lock position (-60) in order to keep the line of sight free and because the turret is not moved during the target tracking. The missile is accelerated to around 900m/s (Mach 3) by a rocket booster. After the booster is jettisoned, a pulsed light source in the missile's tail is activated, allowing automatic tracking of the missile in flight by the optical sight. During the entire flight time of the missile, the gunner must constantly maintain the crosshair of the optical sight on the target; the deviation of the missile's flight path form the line-of-sight is automatically computed and used to generate course correction signals. These are then transmitted to the missile in flight through the tracking radar, which during a missile engagement sequence doubles as fire-control radar. Missile employment is only possible in daylight and fair visibility conditions, because the target needs to be tracking with the optical sight for the entire duration of the engagement sequence.
- (U) Operating Modes. The radar and fire-control system of the 2S6M can be employed in five different operating modes:
- Mode 1: Automated radar tracking. This is the main operating mode.
- Mode 2: Manual electro-optical angle track with range data from either radar.
- Mode 3: Inertial tracking.
- Mode 4: Radar on manual electro-optic angle track with range estimation.
- Mode 5: Ground target engagement.
- In the main operating mode, after the tracking radar has locked-on to a target, tracking is automatic and most data are relayed directly to the computer. The optical sight can either be slaved to the line-of-sight to the target (in preparation for the missile launch) or used independently for further target acquisition. The weapons are laid automatically and the crew's tasks are limited to selecting the weapons and pressing the fire key; when the missiles are used, as previously indicated the gunner must keep his sight on the target for the entire duration of the engagement sequence. The remaining three operation modes are intended for degraded conditions, bypassing a failed subsystem or replacing it with an alternate working mode. However, these modes produce lower accuracy and/or slower operation and the vehicle must be stationary. The fifth mode is applied during the engagement of ground targets. The radar system is shut off, and a reticle is inserted into the optical sight; the lead angle is automatically computed according to bearing and distance, and the laying speed is then proportional to the movements of the gunner's control stick.
Author: Penny L. Mellies
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