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APPLICATION OF
SECONDARY
SURVEILLANCE
RADAR(SSR) IN
MILITARY
IDENTIFICATIONFRIEND OR
FOE(IFF)
TECHNOLOGY
PREPARED BYADRIJA CHOWDHURY
1

INTRODUCTION
 Surveillance systems provide breakthrough performance
in the Detection, Interrogation, Identification, Tracking &
Data Extraction of targets in severe environments
 Aim on Civil and Military air traffic control, battle
management, efficient decision making in air defense
system & keeping friendly forces out of harms way
 Modern Methods of surveillance IFF systems
 TCAS
 FLIR etc
2

SURVEILLANCE IN DEFENSE
SYSTEMS
SURVEILLANCE ~
 A radar system used for locating the position of both
civilian as well military aircrafts & ships, or ground
vehicles & most commonly in air traffic management
 Used by ATC to indicate the position of aircraft while
flying or on airport surface
 Makes use of radio waves
 Also gives information like-speed, range, bearing,
altitude & direction of aircrafts
 Most Important function- Identifies the friendly aircrafts
& ships and distinguishes them from the hostile ones
3

OBJECTIVES
OF SURVEILLANCE
 For civil as well as air traffic control &
management – safely directing traffic
 For extracting various information regarding the
targets
 For defense mechanism
• Identifying the friendly forces out of many &
keeping them out of harms way
• Thus reducing the risk of enemy attack

4

Secondary Surveillance
Radar (SSR)
 Also known as ‘INTERROGATOR’
 A radar system used in ATC that
relies on a piece of equipment that
is placed within the aircraft & is
known as a 'transponder‘
 For IFF system it is basically
synchronized with the PSR on
ground station
 Gives additional information unlike
PSR
5

IFF-A MODERN METHOD OF
SURVEILLANCE
 IFF is IDENTIFICATION-FRIEND OR FOE
 A system that distinguishes FRIENDS from FOES
 Based on the application of Secondary Surveillance
Radar
 Inception-1935, U.S. Initially was developed to identify
U.S aircrafts
 Mainly works on these major modes of operation






MODE 1
MODE 2
MODE 3/A
MODE 4
MODE C
MODE S newly developed

6

HISTORY AND DEVELOPMENT OF
IFF
• The technology IFF was
developed during
WORLD WAR-II by
British and American
military
• Sir ROBERT WATSON
WATT invented the first IFF
transponder and SSR in
1935
• This technology was later
used by Civil Aviation in
1950s.
7

FEATURES OF IFF
 Detection And Tracking
 Identification
 Interrogation
 Data Extraction
 Air Traffic Control And Management
 Efficient decision making during battles and wars

8

WORKING PRINCIPLE OF IFF
SYSTEM
 Ground based transmitter known as interrogator that
is the Secondary Surveillance radar synchronized
with primary radar, transmits a radio
signal(interrogating signal) to the aircraft’s
transponder at 1030 Megahertz by selecting a
unique transponder code
 Transponder receives the signal and decodes it
 After decoding, the transponder replies back to the
interrogator for that particular transponder code
 Now the interrogator will decode the reply and report
back to ATC and thus we will get the display

10

WORKING PRINCIPLE (Contd.)

11

RADAR DISPLAY
What appear on
radar display?
• Aircraft Identity.
• Altitude
• Speed
• Direction
• Example
• MH092 FL280
• 585
• Meaning: Flight
Malaysian 092
cruising at
28’000ft with
speed of
585knots

TRANSPONDER CODES (XPNDR CODES)
• Transponder codes are four digit numbers transmitted by
the transponder in an aircraft in response to an
interrogation signal assisted by air traffic controllers in
traffic separation. A discrete transponder code (often
called a squawk code) is assigned by air traffic controllers
to uniquely identify an aircraft.
• Squawk codes are four-digit octal numbers; the dials on a
transponder read from zero to seven, inclusive. Thus the
lowest possible squawk is 0000 and the highest is 7777.
Four octal digits can represent up to 4096 different codes,
which is why such transponders are often called "4096
code transponders” (ROUTINE & EMERGENGY CODES)
13

MODES OF OPERATION OF IFF
SYSTEMS
 Mode 1 is a non-secure method used to track aircrafts; codes
manually set by pilot but assigned by ATC(military only)
 Mode 2 is for identification; identifies the tail no.(military only)
 Mode 3/A is the standard system also used by civilian
aircrafts to relay their position to ground controllers throughout
the world for ATC. Used in conjunction with MODE C(military
& civilian)
 Mode 4 is secure encrypted IFF(the only true method of
determining friend or foe); only military
 Mode "C" is the altitude encoder(military & civilian)
 Newly developed Mode S does selective interrogation; each aircraft
can be addressed using its unique 24 bit address(military & civilian)
but not implemented yet
 Mode 5-advanced mode of Mode S under processing
14

CHARACTERISTICS OF IFF MODES

15

PROBLEMS WITH
IFF
 FRUIT
 GARBLE
 FAILURE OF TRANSPONDER
 WRONG ENCRYPTION KEYS
 BATTLE DAMAGE

16

CONCLUSION
o IFF technology serves as one of the best methods
of surveillance
o Multipurpose fulfilment
o MODE S & MODE 5-GOOD FUTURE ASPECTS
 Less power required as Transmitter is typically more
efficient
 If the SSR interrogates selectively Mode S can reduce
power even more as it can replace both Mode 3/A &
Mode C as together both modes would consume a lot
of power

17

END OF THE PRESENTATION
BUT NOT THE END OF THE
              DEVELOPMENT
                         OF
               IFF AND SSR
18

ACRONYMS
•
•
•
•
•
•
•
•

IFF~IDENTIFICATION-FRIEND OR FOE
TCAS~TRAFFIC COLLISION AVOIDANCE SYSTEM
FLIR~FORWARD LOOKING INFRARED RADAR
ATC~AIR TRAFFIC CONTROL
FAA~FEDERAL AVIATION AUTHORITY
SSR~SECONDARY SURVEILLANCE RADAR
PSR~PRIMARY SURVEILLANCE RADAR
FRUIT~FALSE REPLIES UNSYNCHRONISED WITH
INTERROGATOR TRANSMISSION or FALSE
REPLIES UNSYNCHRONISED IN TIME
21

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