KC06 - Radar Scans and Tracking

Question 1

List different Radar functions

Answer 1

• Search / Surveillance
  *Early Warning (EW) and Air Search (AS)
  *Ground Control Intercept (GCI)
  *Target Acquisition (TA)
• Tracking
  *Target Track (TT)
  *Airborne Interceptor (AI)
• Guidance
  *Missile Guidance (MG)
  *Beacon Indicator (BI)
  *Target Illumination (TI)

Question 2

Describe basic search patterns - Search Pattern

Answer 2

It’s the pattern that is traced out by antenna boresight (reticle).
Search Patterns:

• Circular
• Sector
• Spiral
• Helical
• Raster.

Question 3

Define Time-on-Target

Answer 3

Defined as the duration for which the main beam illuminates a target with every sweep, and is dependent on the following:

• The duration of the Time-on-Target should be long enough to allow the radar to detect and process return signals
• Depends on Scan rate and Beamwidth.

Question 4

Describe tracking methods : Lobe Switching

Answer 4

• Early method of target tracking
• Tracks a single target only
• Switches a pencil beam between 2 angles
• Compares the signal from both beams to determine target elevation
• If target is not centred, the system adjusts as required to keep target within boresight.

Question 5

Describe basic search patterns - Circular Scan

Answer 5

The most basic scan type of a radar, 360 degrees of rotation.

Question 5

Describe basic search patterns - Helical Scan

Answer 5

The scan starts at the centre and spins 360 degrees

After completion of each revolution, the scan increases in elevation

Think of weather RADAR

Question 6

Describe basic search patterns - Spiral Scan

Answer 6

The scan starts at the nose (centre) of the aircraft and scan in a circular motion drifting outwards with every scan.

Spiral scans can also be carried out by surface radars

Question 7

Describe basic search patterns - Raster Scan

Answer 7

• Scan pattern starts at one point
• Scans across in azimuth and then up in elevation
  -Then scans back in the opposite direction in azimuth.

Question 8

Describe tracking methods :Conical Scanning (CONSCAN)

Answer 8

• CONSCAN is an Amplitude Modulation based target tracking method
• Many radar pulses are transmitted to and received from the target (as per image)
• Once a pulse is received with target presence, a higher amplitude signal will be indicated to the processor
• The system will adjust to keep target within the boresight as required.

Question 9

Describe tracking methods :Lobe on Receive (LORO) / ConScan on Receive Only (CORSO)

Answer 9

• LORO
  *Transmits a pencil beam in the target’s direction and then opens the receive lobes

*The target cannot determine which receive lobe is open therefore cannot predict when to provide jamming signals to induce bearing or steering errors

*Makes this system more difficult to jam when compared to lobe switching

• CORSO
  *Performs the same process as LORO

Question 10

Describe tracking methods : Monopulse

Answer 10

*Multiple offset beams operated continuously (no switching or scanning)

*Target azimuth is based on amplitude return from a single pulse simultaneously in all beams

*System will adjust to keep aircraft centre on boresight from the amplitude variations.

*Non Scanning

*Position established from a single pulse not compared to previous return strengths

*Can’t slip a jamming pulse in amongst the proper target echoes

*Can be jammed - with advanced techniques

Question 11

Describe tracking methods : Track While Scan

Answer 11

• Not a continuous tracking method
• The beam does not remain ‘Locked On’ the aircraft
• TWS radars can track several targets at once.

Question 12

Describe tracking methods : Search While Track

Answer 12

• Same principle as TWS, however uses active array antenna which can ‘spotlight’ targets as required to keep the track file updated
• Flexibility of active array allows multiple targets to be tracked with small impact to radar search capability.