EW2 - Electronic Support Receivers

Question 1

Describe the function of Electronic Support Receiver Groups: Radar Warning Receiver

Answer 1

• Sensitive to RF energy falling on antennae.
• Pre programmed to known or expected threats.
• Indicates type, location and threat level.
• RF, PW and PRI compared with library of known emitters.
• DF derived from signal amplitude comparison.
• Audio alarm triggered.
• Allow aircrew to employ tactical & EW countermeasures rapidly.

Question 2

Describe the function of Electronic Support Receiver Groups: Missile Approach Warning System

Answer 2

Must have low false alarm rate (FAR).
* MAWS types are:
– IR.
– Pulse Doppler.
– UV.

Detects UV radiation produced when missile is in its boost phase.
* Cannot detect a missile after motor burnout / coast phase –hence ‘missile approach’.
* Systems may include active radar to detect approaching projectile to overcome limitation.

Question 3

Describe the function of Electronic Support Receiver Groups: Laser Warning Receivers

Answer 3

• Detect coherent nature of laser light.
• Discriminate between types of laser systems:
  – Laser Target Designators (LTD),
  – Laser Range Finders (LRF) &,
  – Laser Beam Riders (LBR).
• Can provide AOA.

Question 4

Describe the stages of missile flight.

Answer 4

Launch
– Compressed air launches missile from its container.
– Prevents operator from being burnt by hot exhaust gas.
– Approx. 0.5s duration.

Boost
– Missile ignites engines, burns fuel - hot flame and exhaust.
– Source of IR, UV energy and smoke.
– Phase length depends on the missile.

Coast
– Once all fuel in missile expended, missile continues using own inertia.
– Speed is fast, friction heating of nose and control surfaces.
– Continues to emit IR energy.
– No flame = no UV or smoke.

Question 5

Describe IR MAWS

Answer 5

• Detects high-intensity spike of mid-range IR & a flare of optical radiation at missile boost.
• Missile skin surrounding engine & leading edges of missile continue to emit IR radiation after burnout.
• Disadvantages:
  – Hard to distinguish small head of missile from background sources
  (rocks, cars & other heat sources).

Question 6

what are the ES Receiver Groups

Answer 6

• ESM System (SIGINT)
• Radar Warning Receivers (RWR)
• Missile Approach Warning Systems (MAWS)
• Laser Warning Receivers (LWR)

Question 7

Describe UV MAWS

Answer 7

• Detects UV emitted by missile launch & boost phases (from
  rocket flames).
• Tuned to detect in Solar Blind Region;
  – Solar UV (0.23 – 0.28µm) absorbed in upper atmosphere.
  – Therefore, not triggered by sun.
• Disadvantages:
  – Still hard to distinguish from background UV clutter (illumination flares,
  diesel fires, arc welders etc).

Question 8

Pulse Doppler (PD) MAWS

Answer 8

• Uses an active radar on the protected aircraft.
• Detects high Doppler shift returns;
  – High velocity object – e.g., a missile.
• Disadvantages:
  – Continuous radiation used to provide homing signal to missile, or be
  detected by any RWR/ESM.