AERONAUTICAL SURVEILLANCE PANEL

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WP ASP06-02
Agenda Item 5.1
20 March 2009







AERONAUTICAL SURVEILLANCE PANEL (ASP)

Working Group Meeting

Louisville, 20 to 24 April 2009


AERONAUTICAL SURVEILLANCE MANUAL

(Prepared by the TSG Chairman and Gary Furr)


SUMMARY


This working paper describes the editorial changes that were made to
the Aeronautical Surveillance Manual (ASM) subsequent to the
WGW/1 meeting.








1.0 Background

1.1 The Aeronautical Surveillance Manual (ASM) was presented in detail at the
WGW/1 meeting. After the review, the meeting recommended that the ASM
should be published as an ICAO Document and that subsequently, ICAO Doc
9864 and Doc 9688 should be retired.

1.2 The main focus of the Technical Subgroup meeting in February was intended to
be a final editorial review of the ASM before submission to ICAO.

2.0 Input from the Panel Secretary

2.1 Subsequent to the WGW/1 meeting, the Panel Secretary advised the TSG that the
ASM would not be acceptable to ICAO with the Required Surveillance
Performance (RSP) material in its current form. He advised that the concept of
RSP would be acceptable but that it should be presented as general technical
surveillance requirements for surveillance systems.

2.2 The rationale was that ICAO Manuals typically provide details on topics that are
covered in SARPs. Since RSP is not a SARPs requirement, the guidance in the
ASM should not be specific to RSP.

3.0 Action by the TSG

3.1 At the TSG meeting in February 2009, the material on RSP in the main body of
the ASM, and especially in Appendix A, was editorially revised to provide a
general presentation of surveillance requirements.

3.2 A final editorial review was performed after the TSG meeting. The ASM was
then submitted to the Panel Secretary for his review and input to ICAO
Publications.

4.0 ASM as Submitted to ICAO

4.1 The ASM contained in the attachment to this working paper is the version that
was submitted to ICAO.









Doc 9XXX






Aeronautical Surveillance Manual







First Edition



Revision 4.0





INTERNATIONAL CIVIL AVIATION ORGANIZATION






AMENDMENTS
The issue of amendments is announced regularly in the ICAO Journal and in the monthly
Supplement to the Catalogue of ICAO Publications and Audio-visual Training Aids, which
holders of this publication should consult. The space below is provided to keep a record of such
amendments.

RECORD OF AMENDMENTS AND CORRIGENDA

AMENDMENTS

CORRIGENDA
No.
Date
Applicable
Date
entered
Entered
by

No.
Date
Applicable
Date
entered
Entered
by


















































































































































FOREWORD


Air traffic is growing at a significant rate. There is also increasing demand for more operating
flexibility to improve aircraft efficiency, and to reduce the impact of air travel on the
environment. Improved tools are required to safely manage increasing levels and complexity of
air traffic. Aeronautical surveillance is one such important tool in the air traffic management
process.

This manual has been produced as a reference document on aeronautical surveillance for air
traffic control purposes. The main body of this document is intended to be an introduction to the
topic, and should leave the reader with a good understanding of how aeronautical surveillance is
applied in the air traffic management process. Appendices to this document contain detailed
information on primary radar, secondary surveillance radar, multilateration systems and Required
Surveillance Performance. References to these appendices are provided in appropriate places in
the text of the main body. In addition, ICAO and other organizations produce manuals or
standards that provide detailed information on the other issues discussed in this document. These
documents are referenced in the text and also summarized in the List of References.

This document consists for the most part of material developed by the Aeronautical Surveillance
Panel (ASP).

Comments on this manual from States and other parties outside ICAO concerned with
surveillance system development and provision of services would be appreciated. Comments
should be addressed to:

The Secretary General
International Civil Aviation Organization
999 University Street
Montreal, Quebec
Canada H3C 5H7





















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Table of Contents
1

INTRODUCTION..........................................................................................................1

1.1

OVERVIEW...................................................................................................................1

1.2

THE NEED FOR AERONAUTICAL SURVEILLANCE.............................................1

2

SURVEILLANCE SYSTEM DEFINITION..................................................................2

2.1

SURVEILLANCE SYSTEM PURPOSE AND SCOPE................................................2

2.2

DIFFERENT SURVEILLANCE PRINCIPLES.............................................................3

2.2.1

INDEPENDENT NON
-
COOPERATIVE SURVEILLANCE
...................................................3

2.2.2

INDEPENDENT COOPERATIVE SURVEILLANCE
............................................................3

2.2.3

DEPENDENT COOPERATIVE SURVEILLANCE
...............................................................4

2.2.4

SPECIFIC CONCEPT OF SURVEILLANCE
.......................................................................4

3

OPERATIONAL SERVICE DESCRIPTION................................................................4

3.1

AERONAUTICAL SURVEILLANCE APPLICATIONS.............................................4

3.1.1

AREA CONTROL
..........................................................................................................5

3.1.2

APPROACH CONTROL
..................................................................................................6

3.1.3

AERODROME CONTROL
..............................................................................................7

3.1.4

FLIGHT INFORMATION SERVICE
..................................................................................9

3.1.5

ALERTING SERVICE
....................................................................................................9

3.1.6

TRAFFIC ADVISORY SERVICE
(TAS).........................................................................10

3.1.7

Other applications....................................................................................................10

3.2

AIRCRAFT IDENTITY...............................................................................................10

3.2.1

NEED FOR IDENTIFICATION
......................................................................................10

3.2.2

MODE A IDENTITY CODE
...........................................................................................10

3.2.3

AIRCRAFT IDENTIFICATION
......................................................................................11

3.3

REQUIREMENTS FOR AERONAUTICAL SERVICES BASED ON
SURVEILLANCE........................................................................................................11

4

TECHINCAL PERFORMANCE REQUIREMENTS FOR SURVEILLANCE
SYSTEMS.....................................................................................................................................11

4.1

PURPOSE.....................................................................................................................11

4.2

DEFINITION OF PARAMETERS CONTRIBUTING TO QUALITY OF SERVICES.
......................................................................................................................................12

4.3

TECHNICAL SURVEILLANCE SYSTEM PERFORMANCE AND
SURVEILLANCE TECHNOLOGIES.........................................................................13

4.4

TECHNICAL SURVEILLANCE SYSTEM PERFORMANCE DESCRIPTIONS PER
APPLICATION............................................................................................................13

i

4.5

IMPORTANCE OF VERIFYING SURVEILLANCE PERFORMANCE...................13

5

AIR-GROUND SURVEILLANCE SYSTEM DESIGN AND COMPONENTS........13

5.1

COMPONENTS OF AN AERONAUTICAL SURVEILLANCE SYSTEM...............13

5.2

NON COOPERATIVE SENSOR.................................................................................14

5.2.1

PRIMARY SURVEILLANCE RADAR
(
PSR
)...................................................................14

5.3

INDEPENDENT COOPERATIVE SENSOR SYSTEMS...........................................16

5.3.1

SECONDARY SURVEILLANCE RADAR
(
SSR
)
OVERVIEW
............................................16

5.3.2

SSR MODE A
/
C
..........................................................................................................17

5.3.3

SSR MODE S
..............................................................................................................18

5.3.4

SSR ALTERNATIVE ANTENNA CONFIGURATIONS
......................................................20

5.3.5

MULTILATERATION
(
MLAT
)
SYSTEMS
......................................................................21

5.4

DEPENDENT COOPERATIVE SYSTEMS................................................................23

5.4.1

AUTOMATIC DEPENDENT SURVEILLANCE
-
CONTRACT
(
ADS
-
C
)................................23

5.4.2

AUTOMATIC DEPENDENT SURVEILLANCE
-
BROADCAST
(
ADS
-
B
)..............................25

5.4.3

ADS
-
B CHARACTERISTICS
.........................................................................................27

5.5

SURVEILLANCE DATA PROCESSING SYSTEMS................................................28

5.5.1

AIRCRAFT TRACKING TECHNIQUES
..........................................................................28

5.5.2

MOSAIC TRACKING SYSTEMS
...................................................................................28

5.5.3

TRACK FUSION SYSTEMS
..........................................................................................29

5.5.4

POSITION REPORT FUSION SYSTEMS
.........................................................................29

5.6

SURVEILLANCE DATA DISTRIBUTION................................................................29

5.6.1

ASTERIX INTERFACE SPECIFICATIONS
......................................................................29

5.6.2

ASTERIX
ADDRESSING SCHEME
.............................................................................29

6

AIRBORNE SURVEILLANCE SYSTEM DESIGNS AND COMPONENTS...........30

6.1

I
NTRODUCTION
..............................................................................................................30

6.2

ADS-B IN.....................................................................................................................30

6.3

TRAFFIC INFORMATION SERVICE - BROADCAST (TIS-B)...............................30

6.4

ADS-B REBROADCAST............................................................................................31

6.5

AIRBORNE COLLISION AVOIDANCE SYSTEM (ACAS).....................................31

6.5.1

ACAS
OVERVIEW
....................................................................................................31

6.5.2

ACAS
OPERATION
...................................................................................................32

6.5.3

ACAS
HYBRID SURVEILLANCE
................................................................................32

6.5.4

Future ACAS...........................................................................................................32

6.6

DISPLAYS FOR AIRBORNE SURVEILLANCE
.....................................................................32

7

SURVEILLANCE SYSTEM DEPLOYMENT CONSIDERATIONS........................35

ii

7.1

BEST PRACTICES CHECKLIST...............................................................................35

7.2

T
RANSITION TO DEPENDENT SURVEILLANCE SYSTEMS
................................................37

7.3

O
THER ISSUES
................................................................................................................37

7.4

AIRCRAFT INSTALLATION ISSUES.......................................................................38



Appendices

Appendix A Technical Surveillance System Performance Requirements

Appendix B Primary Surveillance Radar

Appendix C SSR Performance Capabilities

Appendix D SSR System Techniques

Appendix E Monopulse SSR

Appendix F Mode S and Mode A/C Compatibility

Appendix G Mode S Cyclic Polynomial Error Detection and Correction

Appendix H Mode S Protocol Considerations

Appendix I Mode S Specific Services

Appendix J Mode S Implementation

Appendix K 1090 MHz Extended Squitters

Appendix L Multilateration Systems

Appendix M 1030/1090 MHz Interference Considerations

Appendix N ASTERIX Interface Specification

Appendix O Airborne Surveillance Equipment Installation and Test Considerations



iii

List of Figures

Figure 1: Surveillance System Boundaries......................................................................................3

Figure 2: Area Control Surveillance Architecture...........................................................................6

Figure 3: Primary Surveillance Radar...........................................................................................16

Figure 4: Secondary Surveillance Radar.......................................................................................19

Figure 5: Multilateration (MLAT) Systems..................................................................................23

Figure 6: Automatic Dependent Surveillance–Contract (ADS-C)................................................25

Figure 7: Automatic Dependent Surveillance-Broadcast (ADS-B)...............................................28

Figure 8: Traffic Information Surveillance-Broadcast (TIS-B).....................................................31




iv


GLOSSARY

Acquisition squitter. The spontaneous periodic transmission by a Mode S transponder
(nominally once per second) of a specified format, including the aircraft address, to permit
passive acquisition.

Aircraft. The term “aircraft” should be understood as “aircraft or vehicle (A/V).”

Aircraft address. A unique combination of 24 bits that is available for assignment to an aircraft
for the purpose of air-ground communications, navigation and surveillance.
Note.— The aircraft address is sometimes referred to as the Mode S address, the aircraft
Mode S address, or the 24-bit address.

Aircraft identification. The information contained in item 7 of the ICAO fight plan and also
used as the radio call sign. When no flight plan is available, the aircraft registration is used.
Note.— The aircraft identification is also referred to as flight identification.

All-call. An intermode or Mode S interrogation that elicits replies from more than one
transponder.

All-call (Mode A/C-only). An intermode interrogation that elicits replies from Mode A/C
transponders only. Mode S transponders do not accept this interrogation.

All-call (Mode S-only). A Mode S interrogation that elicits all-call replies from Mode S
transponders that are currently not in the lockout state for that interrogator code.

All-call (stochastic). A Mode S-only all-call that elicits all-call replies from only a random
subset of the Mode S transponders that are currently not in the lockout state.

Altitude. The vertical distance of a level, point or an object measured above mean sea level.

Antenna (electronically scanned, E-Scan). An SSR antenna consisting of a number of planar
arrays or a circular array of radiating elements. A beam former unit allows it to electronically
steer the beam to the desired azimuth angle by applying phase shifting. The antenna elements
may either be active or passive, depending on the order in which the beam former and
transmitter(s) are set up.

Antenna (hog-trough). An SSR antenna comprising a horizontal linear array of radiating
elements installed in an extended corner reflector assembly (resembling in shape a hog-
trough). The linear array is usually of sufficient length to give an azimuth beamwidth of
between 2° and 3° and the hog-trough reflector achieves typically between ±40° and 45°
vertical beamwidth. For special purposes shorter arrays can be used. These have increased
azimuth beamwidth.

Antenna (large vertical aperture, LVA). An SSR antenna comprising two-dimensional array
radiating elements. A typical LVA consists of a number of columns (each consisting of a
vertical linear array designed to produce beam shaping in the vertical plane) arranged in a
horizontal linear array to produce between 2° and 3° azimuth beamwidth. LVA antennas are
widely used for monopulse SSR systems.
v


Antenna (linear array). An antenna consisting of an array of radiating elements in a straight
line. The desired radiation characteristic of the antenna is obtained by the varied distribution
of radio frequency energy in amplitude or phase so as to produce the shaped “beam” or wave
front.

Antenna (monopulse). See Antenna (sum and difference).

Antenna (sum and difference). A hog-trough or LVA antenna which is electrically split into
two halves. The two half-antenna outputs are added in phase at one output port (sum, Σ) and
added in antiphase at a second output port (difference, Δ) to produce output signals which are
sensitive to the azimuth angle of arrival of received signals, enabling an off-boresight angle
for the signal source to be obtained. This kind of antenna is required for monopulse and
Mode S operation.

Antenna (reflector). An antenna producing the beam by a method analogous to optics. In most
cases the “reflector” surface of the antenna is illuminated by a radio frequency source (e.g., a
radio-frequency “horn” assembly). The dimensions of the reflector antenna both in the
horizontal and vertical plane, together with the characteristics of the illuminating source,
determine the shape and magnitude of the radar beam produced.

Antenna (omnidirectional). An antenna with the same gain in all directions.

Antenna diversity. An installation that consists of top and bottom mounted antennas that is used
in SSR, ACAS and ADS-B systems to improve the transmission and reception capabilities.


Beamwidth. An angle subtended (either in azimuth or elevation) at the half-power points (3 dB
below maximum) of the main beam of an antenna.

Boresight. A main lobe electrical (radio) axis of an antenna.


Capability report. An indication provided by the capability (CA) field of an all-call reply and a
squitter transmission of the communications capability of the Mode S transponder (see also
“data link capability report”), and some information on the aircraft status.

Chip. A 0.25 µs carrier interval following possible data phase reversals in the P6 pulse of Mode
S interrogations (see “data phase reversal”).

Closeout. A command from the Mode S ground station that terminates a communication
transaction.

Cluster. A set of Mode S interrogators with overlapping coverage that use the same interrogator
code. The interrogators communicate with each other to provide acquisition or reacquisition
to neighboring interrogators. The cluster operation requires fewer interrogator codes, and
Mode S aircraft within the cluster airspace normally remain in a state of lockout, which
reduces Mode S all-call transmissions.

Comm-A. A 112-bit interrogation containing the 56-bit MA message field. This field is used by
the uplink SLM and broadcast protocols.
vi


Comm-B. A 112-bit reply containing the 56-bit MB message field. This field is used by the
downlink SLM, ground-initiated and broadcast protocols.

Comm-B Data Selector (BDS). The 8-bit BDS code in a surveillance or Comm-A interrogation
determines the register whose contents are to be transferred in the MB field of the elicited
Comm-B reply. The BDS code is expressed in two groups of 4 bits each, BDS1 (most
significant 4 bits) and BDS2 (least significant 4 bits).

BDS1 code. The BDS1 code is defined in the RR field of a surveillance or Comm-A
interrogation.

BDS2 code. The BDS2 code is defined in the RRS subfield of the SD field of a surveillance
or Comm-A interrogation when DI=7. If no BDS2 code is specified (i.e., DI≠7), it
signifies that BDS2 = 0.

Comm-C. A 112-bit interrogation containing the 80-bit MC message field. This field is used by
the extended length message (ELM) uplink protocol for uplink data transfer and by the
downlink ELM protocol for the transfer of segment readout commands.

Comm-D. A 112-bit reply containing the 80-bit MD message field. This field is used by the
extended length message (ELM) downlink protocol for downlink data transfer and by the
uplink ELM protocol for the transfer of technical acknowledgements.

Control antenna. An SSR antenna having a polar diagram which is designed to “cover” the side
lobes of the main interrogating antenna. It is used to radiate a control pulse which, if it
exceeds in amplitude the associated interrogation signal at the input to the transponder, will
cause the transponder to inhibit responses to the interrogation pulses. Modern SSR antennas
have the control elements built into the main array. The control antenna is also known as the
SLS (side-lobe suppression) antenna. In earlier side-lobe suppression systems, an
omnidirectional antenna was often used for transmitting the P
2
pulse and sometimes also for
transmission of the P
1
pulse (I
2
SLS). Modern antennas for ground SSR use include a “notch”
coinciding with the peak of the main beam.

Control pattern. A polar diagram of the control antenna. Modern integrated SSR antennas have
a “modified cardioid” beamshape.

Control pulse. A pulse (P
2
for Modes A and C, P
5
for Mode S) transmitted by the ground
equipment (SSR interrogator) in order to ensure side-lobe suppression.

Correlation criteria. A number of pulse repetition intervals over which range correlation of
replies must be achieved in a sliding or moving window extractor before the presence (or
tentative presence, subject to further tests) of a plot can be declared.


Data link capability report. Information in a Comm-B reply identifying the complete Comm-A,
Comm-B, ELM and ACAS capabilities of the aircraft installation.

Data phase reversal. A 180
º
phase shift in a Mode S interrogation that is used to encode a
binary ONE. The absence of the phase reversal encodes a binary ZERO.
vii


Dead time. A period of time during which an SSR transponder is inhibited from receiving
signals after a valid interrogation is received and a reply transmitted. The term is also used to
describe the time after the normal range for returns and before the next transmission from an
interrogator or from a primary radar system.

Defruiter. Equipment used to eliminate unsynchronized replies (FRUIT) in an SSR ground
system.

Defruiting. A process by which aircraft replies accepted by the interrogator-receiver are tested
by means of storage and a comparator for synchronism with the interrogation-repetition
frequency. Only replies which are in synchronism (correlate on a repeated basis in range)
will be output from the defruiter. Other replies are rejected as “FRUIT.”

Difference pattern. A receive (1090 MHz) characteristic of a monopulse SSR antenna, obtained
by connecting in antiphase the signals (replies) received by two partial antennas. The
difference pattern has a minimum in the main radiation direction of the antenna and an
amplitude and phase characteristic which varies as a function of angle of arrival of the
received signal. Used in conjunction with the sum output of the antenna, it enables the off-
boresight angle to be found.

Differential phase shift keying (DPSK). Modulation which uses phase reversals preceding
chips to denote binary ONEs and the absence of a phase reversal to denote binary ZEROs.

Downlink. Associated with signals transmitted on the 1090 MHz reply frequency channel.


ERP. Effective radiated power (ERP) is the transmitted power enhanced by the gain of the
antenna less the losses in cables, rotary joints, etc.

Extended length message (ELM) protocol. A series of Comm-C interrogations (uplink ELM)
transmitted without the requirement for intervening replies, or a series of Comm-D replies
(downlink ELM) transmitted without intervening interrogations.

Extended squitter. Spontaneous periodic transmission of a 1090 MHz 112-bit Mode S signal
format containing 56-bits of additional information (e.g., used for ADS-B, TIS-B and
ADS-R).


False plot. A radar plot report which does not correspond to the actual position of a real aircraft
(target), within certain limits.

Field. A defined number of contiguous bits in an interrogation, reply or squitter.

Flight identification. See aircraft identification.

Flight status (FS) field. A field of a Mode S reply indicating if the aircraft is airborne or on-
ground, is transmitting the Mode A/C SPI code or has recently changed its Mode A identity
code.

viii

Framing pulses. Pulses which “frame” the information pulses (code) of SSR Mode A and C
replies (described as F
1
and F
2
respectively). Also known as “bracket pulses.”

FRUIT. A term applied to unwanted SSR replies received by an interrogator which have been
triggered by other SSR interrogators. Fruit is the acronym of False Replies Unsynchronized
In Time, or False Replies Unsynchronized to Interrogator Transmission.


GALILEO. Europe’s own global navigation satellite system, providing a highly accurate,
guaranteed global positioning service under civilian control. It will be inter-operable with
GPS and GLONASS, the two other global satellite navigation systems.

Garbling. A term applied to the overlapping in range and/or azimuth of two or more SSR replies
so that the pulse positions of one reply fall close to or overlap the pulse positions of another
reply, thereby making the decoding of reply data prone to error.

Gain (of antenna). A measure for the antenna of the increased (effective) transmitted power
density radiated in a particular direction as compared to the power density that would have
been radiated from an isotropic antenna (expressed in dB).

Ground-initiated Comm-B protocol (GICB). A procedure initiated by a Mode S ground
station for eliciting a Comm-B message containing aircraft derived data from a Mode S
aircraft installation.


Improved interrogation side-lobe suppression (I
2
SLS). A technique whereby interrogation
pulse P
1
is transmitted via both the main beam and the control beam of the SSR antenna, so
that a transponder in a side-lobe direction more reliably receives a P
1
-P
2
pulse pair.

Intermode interrogations. Interrogations that consist of 3 pulses (P
1
, P
3
and P
4
) and are capable
of eliciting replies a) from both Mode A/C and Mode S transponders or b) from Mode A/C
transponders but not from Mode S transponders (see “All-call”).

Interrogator repetition frequency (IRF). An average number of interrogations per second
transmitted by the radar. Sometimes referred to as “Pulse repetition frequency” (PRF).

Interrogator side-lobe suppression (ISLS). A method of preventing transponder replies to
interrogations transmitted through the ground antenna side lobes.

Interrogator. A surveillance system transmitting on 1030 MHz. The surveillance system may
be fixed or mobile.

Interrogator (mobile). An airborne, ship-borne or ground transportable interrogator. The term
“mobile interrogator” is used for military installations.

Interrogator code (IC). A code used to identify an interrogator in Mode S protocols. It may be
either an interrogator identifier (II) or surveillance identifier (SI) code.

Interrogator identifier (II). One of the codes (1 to 15) used to identify a Mode S ground
station using the multisite protocols.
ix


Surveillance Identifier (SI). One of the codes (1 to 63) used to identify a Mode S ground
station using only surveillance or limited communications protocols. These codes were
added to provide additional codes for surveillance purposes.


Lobing (antenna pattern). A process whereby, due to interference of two waves, one direct and
one reflected, differences in phases cause larger or smaller amplitudes than expected for free
space, causing differences in signal amplitudes.

Lockout state. A state in which a Mode S transponder has been instructed not to accept certain
all-call interrogations. Lockout is deliberately induced by command from the Mode S ground
station.


Mode. SSR interrogation mode as specified in Annex 10, Volume IV, Chapter 2.

Mode A/C transponder. Airborne equipment that generates specified responses to Mode A,
Mode C and intermode interrogations but does not reply to Mode S interrogations.

Mode S. An enhanced mode of SSR that permits selective interrogation and reply capability.

Mode S ground station. Ground equipment that interrogates Mode A/C and Mode S
transponders using intermode and Mode S interrogations. A monopulse capable antenna and
a rotary joint providing at least two channels for sum and difference processing are a pre-
requisite for Mode S operation.

Mode S interrogations. Interrogations consisting of three pulses (P
1
, P
2
and P
6
) that convey
information to and/or elicit replies from Mode S transponders. Mode A/C transponders do
not respond to Mode S interrogations because they are suppressed by the (P
1
-P
2
) pulse pair.

Mode S Surveillance interrogation. A 56-bit Mode S interrogation containing surveillance and
communications control information.

Mode S Surveillance reply. A 56-bit Mode S reply containing surveillance and communications
control information, plus the aircraft’s 4096 identity code or altitude code.

Mode S transponder. Airborne equipment that generates specified responses to Mode A, Mode
C, intermode and Mode S interrogations.

Monopulse. A technique wherein the amplitudes and/or phases of the signals received in
overlapping antenna lobes are compared to estimate the angle of arrival of the signal. The
technique determines the angle of arrival of a single pulse, or reply, within an antenna
beamwidth. The angle of arrival is determined by means of a processor using the replies
received through the sum and difference patterns of the antenna. The monopulse technique is
generally termed “monopulse direction finding.”

Monopulse plot extractor. A plot extractor using monopulse direction-finding techniques. See
also plot extractor.

x

Multisite Comm-B protocol. A procedure to control air-initiated Comm-B message delivery to
Mode S ground stations that have overlapping coverage and that are operating independently
(see “multisite protocol”).

Multisite directed Comm-B protocol. A procedure to ensure that a multisite Comm-B message
closeout is effected only by the particular Mode S ground station selected by the Mode S
airborne installation.

Multisite protocol. Procedures to control message interchange between a Mode S transponder
and Mode S ground stations with overlapping coverage and that are operating independently.
Multisite protocols allow only a single Mode S ground station to close out a message
interchange, thereby assuring that independent operation of Mode S ground stations does not
cause messages to be lost.


Non-selective protocol. Procedures to control message interchange between a Mode S
transponder and Mode S ground stations operating alone or in overlapping coverage with
operations coordinated via ground communications.


Parrot. A fixed transponder referred to as the Position Adjustable Range Reference Orientation
Transponder and used as a field monitor. (See “Remote field monitor”.)

Plot extractor. Signal processing equipment which converts PSR and/or SSR video into an
output data message suitable for transmission through a data transmission medium or
possibly to further data processing equipment.

Pulse repetition frequency (PRF). An average number of pulses/interrogations per second
transmitted by the radar (see “Stagger”). Also known as pulse recurrence frequency.

Pulse train. A sequence of framing and information pulses in the coded SSR reply.


Receiver side-lobe suppression (RSLS). A method, using two (or more) receivers to suppress
aircraft replies which have been received via side lobes of the main beam of the antenna.

Remote field monitor. A system which monitors the uplink and/or downlink performance of an
SSR or Mode S system from a site located at the specified distance from the radar (far field).
The monitor (see “Parrot”) is interrogated by the radar and its replies can be evaluated on the
radar site. In addition, the replies may contain data about certain interrogation parameters as
seen by the monitor.

Reply. A pulse train received at an SSR ground station as a result of successful SSR
interrogation.

Reply preamble. A sequence of four pulses, each with a duration of 0.5 microsecond, indicating
the beginning of a Mode S reply.

Resolution. Ability of a system to distinguish between two or more targets in close proximity to
each other both in range and bearing (azimuth).

xi

Ring-around. Continuous reception of replies to interrogations by the side lobes of the ground
antenna. This normally occurs only at short ranges, usually due to the non-existence of a
side-lobe suppression mechanism or the improper functioning of this mechanism, at either the
interrogator or the transponder side.

Round trip reliability. A probability of receipt of a correct reply, resulting from either an SSR
interrogation or a PSR transmission.


Secondary surveillance radar (SSR) system. A radar system which transmits coded
interrogations to aircraft transponders in various modes and receives coded replies.

Secondary surveillance radar (SSR) transponder. A unit which transmits a response signal on
receiving an SSR interrogation. The term is a derivative of the words transmitter and
responder.

Side lobes (antenna). Lobes of the radiation pattern of an antenna, which are not part of the
main or principal beam. Radar systems can have sufficient sensitivity via side lobes for
successful detection of aircraft (particularly for SSR, but also for PSR). Special precautions
are necessary to protect against these false plots.

Side-lobe suppression (SLS). A mechanism in an SSR transponder activated by the
transmission (radiation) of a control pulse (P
2
or P
5
) of amplitude greater than the antenna
side-lobe signals-in-space, which will enable the transponder to prevent itself from replying
to the side-lobe interrogation signals.

Stagger. Deliberate, controlled variation of the pulse repetition frequency of the SSR to prevent
aircraft plots due to second-time-around replies.

Standard length message (SLM) protocol. A procedure to exchange digital data using Comm-
A interrogations and/or Comm-B replies.

Sum pattern. Normal radiation pattern for the main directional beam of an antenna. Contrasts
with the “difference-pattern,” where parts of the radiating elements of the antenna are
switched in anti-phase to produce signals proportional to the amount by which the source is
off the boresight of the sum pattern.

Suppression. A deliberate inhibition of a transponder’s ability to accept or reply to
interrogations.

Surveillance processing. A general term covering any processing applied to the target reports
after the extraction functions and prior to the data transmission functions. Such processes
include filtering, clutter reduction, data rate control and dynamic angle control.

Sync phase reversal. A first phase reversal in the Mode S P
6
interrogation pulse. It is used to
synchronize the circuitry in the transponder that decodes the P
6
pulse by detecting data phase
reversals, i.e., as a timing reference for subsequent transponder operations related to the
interrogation.


xii

Track. A succession of positions for one aircraft sometimes correlated and smoothed by a
special tracking algorithm.

Transponder transaction cycle. The sequence of transponder operations required by the
reception of an interrogation. The process begins with the recognition of an interrogation and
ends either with the non-acceptance of the interrogation, or the transmission of a reply, or the
completion of processing associated with that interrogation.


Uplink. Associated with signals transmitted on the 1030 MHz interrogation frequency channel.


Validation (code). Process of correlation of the code information used in SSR Mode A/C
systems. Generally two identical codes in two successive replies suffice to validate the code.
In Mode S, code validation occurs inherently when the reply is decoded (and, if appropriate,
error corrected).
Note.— Modern radar systems may provide “smoothed” code information when the so-
called validation serves to indicate non-extrapolated code information.

xiii


LIST OF ACRONYMS

ACAS Airborne collision avoidance system
ADLP Airborne data link processor
ADS-B Automatic dependent surveillance-broadcast
ADS-C `Automatic dependent surveillance contract
ADS-R ADS-B rebroadcast
AICB Air-initiated Comm-B
AIS Aircraft identification subfield
A-SMGCS Advanced - surface movement guidance and control systems
ANSP Air navigation service provider
AP Address parity
ARINC Aeronautical Radio Inc
ARTAS European ATM Surveillance Tracker and Server
ASA Airborne surveillance applications
ASP Aeronautical surveillance panel
ASTERIX All Purpose Structured Eurocontrol Surveillance Information Exchange
ATC Air traffic control
ATM Air traffic management
ATN Aeronautical telecommunication network
ATS Air traffic services
BDS Comm-B data selector
BDS1 Most significant four bits of BDS
BDS2 Least significant four bits of BDS
CA Capability
CC Cross-link capability
CDTI Cockpit display of traffic information
CL Code label
CNS Communication, navigation, and surveillance
CPDLC Controller pilot data link communications
CRC Cyclic redundancy check
CW Continuous wave
DCE Data circuit-terminating equipment
DELM Downlink extended length message
DF Downlink format
DI Designator identifier
DME Distance measuring equipment
DR Downlink request
DS Data selector
DTE Data terminal equipment
EHS Enhanced Surveillance
ELM Extended length message
ELS Elementary Surveillance
ERP Effective radiated power
ES Extended squitter
FDPS Flight data processing system
FIS Flight information service
FOD Foreign object debris
FRUIT False replies from unsynchronized interrogator transmissions in time
xiv

FS Flight status
GDLP Ground data link processor
GDOP Geometric dilution of precision
GICB Ground-initiated Comm-B
GNSS Global Navigation Satellite System
HF High frequency
HRP Horizontal radiation pattern
I
2
SLS Improved interrogator side-lobe suppression
IC Interrogator code
IDS Identifier designator subfield
IFR Instrument flight rules
II Interrogator identifier
IIS Interrogator identifier subfield
ISLS Interrogator side-lobe suppression
ISO International Organization for Standardization
JTIDS Joint Tactical Information Distribution System
LOS Lockout subfield
LVA Large vertical aperture
MA Message Comm-A
MB Message Comm-B
MBS Multisite Comm-B subfield
MC Message Comm-C
MD Message Comm-D
MLAT Multilateration systems
MSO Message start opportunity
MSP Mode S specific protocol
MTL Minimum triggering level
OBA Off-boresight angle
PRM Parallel runway monitoring
PC Protocol
PD Probability of detection
PI Parity/interrogator identifier
PRF Pulse repetition frequency
PSR Primary surveillance radar
RA Resolution advisory
RDPS Radar data processing system
RF Radio frequency
RL Reply length
RNP Required navigation performance
RR Reply request
RRS Reply request subfield
RSLS Receiver side-lobe suppression
RSS Reservation status subfield
RVSM Reduced vertical separation minimum
SD Special designator
SI Surveillance identifier
SLM Standard length message
SLS Side-lobe suppression
SMR Surface movement radar
SNR Signal to noise ratio
SPI Special position identification
xv

SR Service request
SRS Segment request subfield
SSE Mode s specific services entity
SSR Secondary surveillance radar
STC Sensitivity time control
SVC Switched virtual circuit
TACAN Tactical air navigation
TAS Transmission acknowledgement subfield
TCP Transmission control protocol
TDOA Time difference of arrival
TDMA Time difference multiple access
TIS Traffic information service
TIS-B Traffic information service - broadcast
TOA Time of arrival
UAT Universal access transceiver
UDP User datagram protocol
UF Uplink format
UM Utility message
UTC Coordinated universal time
VDLM4 VHF data link mode 4
VHF Very high frequency
VRP Vertical radiation pattern
WAM Wide area multilateration
WGS World geodetic system

xvi

LIST OF REFERENCES

ICAO


ICAO Annex 10 - Vol. III Aeronautical Telecommunications (Part I Digital Data Communication
Systems; Part II Voice Communication Systems)

ICAO Annex 10 - Vol. IV - Aeronautical Telecommunications - (Surveillance Radar and
Collision Avoidance Systems)

ICAO Doc 4444, Procedures for Air Navigation Services – Air Traffic Management (PANS-
ATM)

ICAO Doc 8071, Volume III, Manual on Testing of Radio Navigation Aids

ICAO Doc 8168, Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS)

ICAO Doc 9476, Movement Guidance and Control Systems (SMGCS)

ICAO Doc 9816, Manual on VHF Digital Link (VDL) Mode 4

ICAO Doc 9830, Advanced Surface Movement Guidance and Control Systems (A-SMGCS)
Manual

ICAO Doc 9861, Manual on the Universal Access Transceiver (UAT): Detailed Technical
Specifications, Edition 1

ICAO Doc 9871, Technical Provisions for Mode S Services and Extended Squitter, Edition 1.

ICAO Doc 9863, Airborne Collision Avoidance System (ACAS) Manual.

Eurocae


Eurocae ED-73C, Minimum Operational Performance Standards for Secondary Surveillance
Radar Mode S Transponders

RTCA


RTCA/DO-181D, Minimum Operational Performance Standards for Air Traffic Control Radar
Beacon System/Mode Select (ATCRBS/Mode S) Airborne Equipment

RTCA/DO-260, Minimum Operational Performance Standards for 1090 MHz Automatic
Dependent Surveillance – Broadcast (ADS-B)

RTCA/DO-260A, Minimum Operational Performance Standards for 1090 MHz Extended
Squitter Automatic Dependent Surveillance – Broadcast (ADS-B) and Traffic Information
Services – Broadcast (TIS-B)


xvii
1
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AERONAUTICAL SURVEILLANCE MANUAL


1 INTRODUCTION
1.1
OVERVIEW
Air traffic is growing at a significant rate. There is also increasing demand for more operating
flexibility to improve aircraft efficiency, and to reduce the impact of air travel on the
environment. Improved tools are required to safely manage increasing levels and complexity of
air traffic. Aeronautical surveillance is one such important tool in the air traffic management
process.

This manual has been produced as a reference document on aeronautical surveillance for air
traffic control purposes. The main body of this document is intended to be an introduction to the
topic, and should leave the reader with a good understanding of how aeronautical surveillance is
applied in the air traffic management process. It contains:
• A definition of what is a surveillance system,
• An introduction of operational services supported by surveillance,
• A definition and guidance on how to derive performance for a surveillance system
(Required Surveillance Performance),
• A description of the different components of an air-ground surveillance system,
• A description of the different components of an air-air surveillance system, and
• Considerations on surveillance system deployment.
Appendices contain detailed information on the main topics covered in this document. References
to these appendices are provided in the appropriate places in the text of the main body. In
addition, ICAO and other organizations produce standards and guidance that provide detailed
information on the other issues discussed in this document. These documents are referenced in
the text and also summarized in the List of References.

1.2
THE NEED FOR AERONAUTICAL SURVEILLANCE
Surveillance plays an important role in air traffic management (ATM). The ability to accurately
determine and track the position of aircraft has a direct influence on the minimum distances by
which aircraft must be separated (i.e., separation standards), and therefore on how efficiently a
given airspace may be utilized.

In areas without electronic surveillance, where ATM is reliant on pilots reporting their position
verbally, aircraft have to be separated by relatively large distances to account for the uncertainty
in the reported position because of the delivery delay and the low rate at which the information is
updated.

Conversely in terminal areas where accurate surveillance systems are used and aircraft positions
are updated frequently, the airspace can be used more efficiently by safely accommodating a
higher density of aircraft.

© 2009, ICAO
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Aeronautical surveillance serves to close the gap between expectations of aircraft movements
based on clearances or instructions issued to pilots, and the true trajectories of these aircraft. In
this way the surveillance function provides an indication of any unexpected aircraft movements,
which provides an important safety function.

Accurate surveillance can be used as the basis for automated alerting systems. The ability to
accurately track aircraft enables air traffic control (ATC) to be alerted when an aircraft is detected
to deviate from its assigned altitude or route, or when the future positions of two or more aircraft
are predicted to fall below minimum acceptable separation standards. Alerts may also be
provided when the aircraft strays below the minimum safe altitude or enters a restricted area.

The existing fixed route structure provides increased certainty of aircraft movements, making it
easier for controllers to manage air traffic. With improved navigation performance on board
aircraft, airspace users are demanding greater flexibility to determine the most efficient routes to
satisfy their operating conditions. There is a push for restrictions associated with flying along
fixed routes to be lifted. In such an environment, accurate surveillance is required to assist
controllers in the detection and resolution of any potential conflicts associated with the flexible
use of airspace, which will result in a more dynamic environment.

2 SURVEILLANCE SYSTEM DEFINITION
2.1
SURVEILLANCE SYSTEM PURPOSE AND SCOPE
An aeronautical surveillance system provides position and other related information to air traffic
service (ATS) providers or airborne users on an aircraft or vehicle involved in the ATM process.

In most cases, an aeronautical surveillance system provides its user with knowledge of “who” is
“where” and “when.” Other information provided may include velocity, other identifying
characteristics, or intent. The required data and its technical performance parameters are specific
to the application that it is being used for, such as air-ground or air-air applications. As a
minimum, the aeronautical surveillance system provides position information on aircraft or
vehicles at a known time.

In terms of performance specification, an aeronautical surveillance system could be considered to
be a ‘black box’ providing the surveillance information.

The aeronautical surveillance system is comprised of several elements, which will be operated
based on the requirements of a specific application. Neither the applications nor the end-users are
part of the aeronautical surveillance system. The aeronautical surveillance system provides
interfaces for applications. It usually contains some kind of data processing and a surveillance
sensor at the receiving interface, while there is a source of data at the other end. This could be a
transponder, a broadcast system, or neither (e.g., for primary radar). Between these, there is a
link to exchange the appropriate information.

Figure 1 illustrates a generic functional surveillance system. The boundary of the surveillance
system is at the application interface, i.e., the point where the surveillance system makes the
surveillance information available for use and where performance is checked.

© 2009, ICAO
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Surveillance
System
Surveillance Data Compilation
Surveillance Data Transmission

Local Surveillance
s
ub-
sy
stem
Radio Frequency (RF) data link(s)
Surveillance Users
Remote Surveillance sub-system
Surveillance Sensor(s) / Receiver(s)
Surveillance Data Processing
Performance
measurement
point
Data Sources

Figure 1: Surveillance System Boundaries

More detailed surveillance system implementation examples with air-ground and air-air
capabilities are given in Appendix A.

2.2
DIFFERENT SURVEILLANCE PRINCIPLES
2.2.1
INDEPENDENT NON
-
COOPERATIVE SURVEILLANCE

In this case, the position is derived from measurement not using the cooperation of the remote
vehicle. An example is a system using primary surveillance radar (PSR). This system does not
provide aircraft identity nor any other aircraft data.

2.2.2
INDEPENDENT COOPERATIVE SURVEILLANCE

The position is derived from measurement performed by a local surveillance sub-system (see
Figure 1) using aircraft transmissions. Aircraft derived information can be provided (e.g.,
barometric altitude, aircraft identity, etc.) within these transmissions.
© 2009, ICAO
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2.2.3
DEPENDENT COOPERATIVE SURVEILLANCE

The position is derived on board the vehicle and is provided to the local surveillance sub-system
with other types of information (e.g., aircraft identity, barometric altitude, etc.).

2.2.4
SPECIFIC CONCEPT OF SURVEILLANCE

2.2.4.1
MODE S ELEMENTARY SURVEILLANCE
(
ELS
)
The fundamental concept of Mode S ELS incorporates the capability to downlink aircraft
identification (commonly referred to as flight ID) from aircraft by using the Mode S protocol.

The selective addressing of aircraft used by Mode S overcomes garbling, FRUIT and over-
interrogation (which together constitute RF congestion) while the automatic acquisition of aircraft
identification enhances radar identification and has the capability to relieve the shortage of Mode
A codes.

To support such operation, aircraft must be equipped with a Mode S transponder and incorporate
an aircraft identification feature to permit the flight crew to set the aircraft identification for
transmission by the transponder.

The aircraft identification transmission must correspond with the aircraft identification specified
in item 7 of the ICAO flight plan; or when no flight plan has been filed, the aircraft identification
transmission must correspond to the aircraft registration.

In parts of Europe, there have been mandates issued requiring that all aircraft that fly into
designated airspace will be equipped to support Mode S ELS.

2.2.4.2
MODE S ENHANCED SURVEILLANCE
(
EHS
)
Mode S EHS consists of Mode S ELS supplemented by the extraction of additional specified
downlink aircraft parameters (DAPs) for use in ground air traffic management (ATM) systems.

The provision of actual aircraft derived data, such as magnetic heading, air speed, selected
altitude and vertical rate, enables controllers to reduce the radio telephony (RT) workload and
better assess the separation situations, thus enhancing safety and capacity. It also helps to reduce
the increasing number of cases where aircraft overshoot their assigned altitudes (referred to as
level busts) and improve the performance of other safety net tools.

Mode S EHS is used in designated high density airspace in Europe where most instrument flight
rule (IFR) flights are mandated to provide the airborne parameters.

3 OPERATIONAL SERVICE DESCRIPTION
3.1
AERONAUTICAL SURVEILLANCE APPLICATIONS
Aeronautical surveillance systems are designed to facilitate the safe and efficient flow of air
traffic. Surveillance systems should be selected on the basis of the desired characteristics and
combined to complement each other in the support of a service.
© 2009, ICAO
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A discussion of the type of surveillance required to support each of these applications is presented
below. Details of these surveillance systems are presented in Chapter 5.

In support of applications, the surveillance system should process surveillance data in a manner
that the operational personnel can:

a) be provided with information on the intended movement of each aircraft (or vehicle), or
variations thereof, and with current information on the actual progress of each aircraft (or
vehicle);
b) determine from the information received, the relative positions of known aircraft (or vehicles)
to each other;

Note that the following discussion presents general ideas, rather than prescribing firm
surveillance requirements for any service. Care must be exercised to match the surveillance
system to the environment and operational needs. Aircraft equipage also needs to be considered.

3.1.1
AREA CONTROL

Control areas may encompass large volumes of airspace including oceanic areas. Aircraft are
well established on their flight paths and are typically in cruise mode. Aircraft generally fly at
high speeds in this phase. Changes in altitude and en route are not frequent but may be required
because of conflicting traffic, weather, or for aircraft operating efficiency. Communications
between controllers and flight crew is not as frequent as in other flight phases.

ATC provides longitudinal and vertical separation between aircraft flying along similar routes,
and between aircraft on crossing flight paths. Procedural air traffic control relies on pilots
periodically reporting their position. It is employed in many of these areas if no electronic
surveillance is available.

A surveillance system for area control typically needs to provide surveillance at long distances
from the control center and in remote areas where ground infrastructure may be limited or non-
existent. The surveillance system should support controller safety net alerts such as cleared level
monitoring, route adherence monitoring, and restricted area monitoring. The provision of
medium term conflict detection tools is desirable. Position updates do not need to be as frequent
as in more dynamic environments.

Surveillance systems suitable for area control include ADS-C, particularly in oceanic and remote
areas, SSR, WAM and ADS-B. In some installations long range primary radars are co-located
with the SSR.

The architecture of area control surveillance is illustrated in Figure 2.
© 2009, ICAO
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SSR
Ground
Station
Aircraft
Reports
ABC 123
FL 280
XYZ 456
FL 300
Global
Navigation
Satellite
System
Communications
Satellite
ADS-C
Messages
SSR Interrogation
Transponder Reply
ADS-B
Ground
Station
ADS-C
Message
Processor
ADS-B
Messages
Surveillance
Data
Processor
ATC Display System
Multilateration
SSR
Ground
Station
Aircraft
Reports
ABC 123
FL 280
XYZ 456
FL 300
Global
Navigation
Satellite
System
Communications
Satellite
ADS-C
Messages
SSR Interrogation
Transponder Reply
ADS-B
Ground
Station
ADS-B
Ground
Station
ADS-C
Message
Processor
ADS-B
Messages
Surveillance
Data
Processor
ATC Display System
Multilateration
Multilateration

Figure 2: Area Control Surveillance Architecture

3.1.2
APPROACH CONTROL

Approach control is performed in airspace where arriving aircraft are vectored for an approach to
an aerodrome, while departing aircraft are climbing and maneuvering toward their outbound
route. Changes in altitude and heading are frequent. Arriving traffic may be placed in holding
patterns when demand for services exceeds the aerodrome capacity.

In this environment, the role of ATM is to manage the flow of traffic to and from the aerodrome,
to separate arriving traffic from departing traffic, and to separate traffic from obstructions.

Aircraft are typically separated by shorter distances than in the case of area control in an attempt
to use the airspace more efficiently to accommodate more aircraft. Aircraft speeds are also
generally lower than in the En-Route phase of flight.

A surveillance system supporting an approach control service needs to operate reliably in medium
to high traffic densities. It needs to update target positions frequently to maintain accurate
surveillance of maneuvering aircraft. Support of short term conflict detection tools is desirable.
These tools alert the controller to potential conflicts, allowing action to be taken in a timely
manner.

© 2009, ICAO
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Surveillance systems suitable for approach control include primary radar, SSR, multilateration
(WAM), and ADS-B. Electronically scanned antennas are sometimes used for surveillance of
aircraft on approach to closely spaced parallel runways.

3.1.3
AERODROME CONTROL

This airspace includes aircraft on the aerodrome surface, aircraft that have just departed, and
aircraft on final approach to the aerodrome. Traffic densities are often medium to high in an
attempt to maximize the use of existing aerodrome facilities and to satisfy demand during peak
periods. Aircraft are brought closer to each other than anywhere else in controlled airspace.
Voice communication exchanges between flight crews and ATC are frequent.

The role of ATC is to coordinate airway clearances; to manage the runways, catering for landings
and take-offs; to direct the taxi of arriving traffic to the terminals and departing traffic to the
runway holding points; and to manage the movement of airport vehicles on the maneuvering area.

While the visual sighting of aircraft from the control tower is the primary means of determining
position, during busy periods and in low visibility conditions, a surveillance system greatly
improves the safety and efficiency of aerodrome operations.

A surveillance system supporting an aerodrome control service needs to have high accuracy to
determine the location of targets on relatively narrow runways and taxiways, and have a high
update rate to present a current picture in a rapidly changing environment.

The surveillance system should have the ability to detect both aircraft and vehicles, and
distinguish between closely spaced targets. A means of detecting non-cooperative targets may be
required. Aircraft and vehicles need to be clearly labeled on controller displays to avoid
confusion. The surveillance system should support runway incursion monitoring and other
alerting tools.

Surveillance systems suitable for aerodrome control include primary radar, multilateration, and
ADS-B.

Other surveillance systems such as millimeter wave sensors, video systems, induction loops and
microwave barriers can be used for limited-zone coverage, or in cluster to provide wider
coverage.

3.1.3.1 ADVANCED - SURFACE MOVEMENT GUIDANCE AND CONTROL
SYSTEMS (A-SMGCS)
Advanced Surface Movement Guidance and Control Systems (A-SMGCS) is the adopted term for
the concept of an integrated aerodrome surface movement management system. Such a
conceptual system is required to improve ground movement safety and efficiency in line with the
projected aviation growth in the near future.

The most fundamental function for any A-SMGCS is the surveillance of the aerodrome surface,
together with the initial and final stages of flight. The objective is that both identity and position
of all traffic should be provided, with an adequate update rate to give a continuous flow of traffic
information and to derive speed and direction, if required. To achieve this objective a system
providing cooperative surveillance is likely to be required.
© 2009, ICAO
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For co-operative surveillance, targets need to be equipped with a means of communicating
position and usually identity information to the A-SMGCS. It is also essential that some means
of surveillance is available to enable the system to detect non-co-operative targets including
obstacles and Foreign Object Debris (FOD)

The Surveillance element for an A-SMGCS will therefore comprise several sensor systems. The
information from these systems will be combined by a data fusion process to provide a
comprehensive surveillance package.

Having provided a suitable surveillance system, the A-SMGCS must use the derived information
to monitor the situation on the aerodrome surface and provide alerts when particular situations are
detected. In its simplest form, an air traffic controller will carry out the monitoring and alerting
function using surveillance information presented on a situation display.

For more complex A-SMGCS, automated situation monitoring and alerting will be provided by
the system detecting runway incursions, taxiway alert situations and other hazardous scenarios,
and generating alerts to the controller and possibly directly to the involved pilots and/or vehicle
drivers. Where the system includes automated route planning, the Monitoring/Alerting function
will have to compare the actual route of an aircraft or vehicle with its planned route and give an
alert in the case of non conformance.

In more elementary systems, guidance of movements on the aerodrome surface will be manually
performed by controllers using the Surveillance and Monitoring/ Alerting elements of A-SMGCS
and by giving instructions or manually operating stop bars and taxiway lights. In more complex
systems, fully or partially automated guidance will be provided, with the A-SMGCS having the
ability to automatically control taxiway lights, stop bars and other guidance aids.

An A-SMGCS differs from an SMGCS in that it may provide a full individual service over a
much wider range of weather conditions, traffic density and aerodrome layouts.

More information can be found in ICAO Doc 9476 The SMGCS Manual and Doc 9830, the A-
SMGCS Manual

3.1.3.2 DETECTION OF FOREIGN OBJECT DEBRIS (FOD)
Foreign Object Debris is a day-to-day concern for airport operators. Parts fall off aircraft; tools
fall off service vehicles; litter blows onto runways; and scavengers can be attracted to bird
carcasses. All these things can put an aircraft at risk, and low level damage to engine turbines
after ingesting FOD and tire damage is common.

Airport operators perform regular runway inspections, typically from a vehicle moving at
approximately 50 mph. It is recognized that at this speed, small items will not be seen, but
inspecting the runway more slowly, or more frequently, is simply not practical.

The detection of obstructions is part of the A-SMGCS concept and will bring significant safety
benefits, particularly to runway operations. Systems suitable for FOD detection include
millimeter wave radars, possibly supplemented by cameras for identification.

© 2009, ICAO
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3.1.3.3
P
ARALLEL RUNWAY MONITOR
(PRM)
During instrument meteorological conditions (IMC), airports with parallel runways spaced less
than 4300 feet apart cannot conduct independent simultaneous operations based only on approach
control quality surveillance. This results in decreased capacity during inclement weather.

The major limitation of aerodrome surveillance is update rate, although accuracy may also be an
issue. Update rates of once per 4 or 5 seconds are typical for aerodrome use. Radars with
monopulse capability provide an accuracy of one milliradian but older radars provide less
accuracy.

In order to detect the onset of an acceleration that may lead to a conflict with aircraft on an
approach to an adjacent runway, surveillance in support of PRM requires an accuracy of one
milliradian; and an update rate of 1 to 2 seconds depending on the runway spacing. An update
rate of at least once per 2.4 seconds is required for parallel runways spaced down to 3400 feet
apart. A one second update rate is required for spacing down to 3000 feet.

Current implementations of surveillance systems for PRM are based on electronically scanned (E-
scan) antennas. Multilateration systems are being implemented as an alternative for PRM
systems.

3.1.3.4
P
RECISION
A
PPROACH

A surveillance system can be used to guide aircraft in final approach to runway under degraded
weather conditions. The surveillance system must provide very high performance and
information on aircraft altitude in order to guide the aircraft along a glide path to the runway.
This is general supported by the use of specific radar known as Precision Approach Radar (PAR).
This application remains in use at some military air bases. There are current investigations
regarding the possible use of multilateration to support this application.

3.1.4
FLIGHT INFORMATION SERVICE

Flight information service is a service provided for the purpose of giving advice and information
useful for the safe and efficient conduct of flights. This includes, e.g., the advice on nearby or
crossing traffic.

Surveillance data can support the Flight information service. Service support includes the support
of a traffic data display.

3.1.5
ALERTING SERVICE

Alerting service is a service that provides an indication of unsafe events, as well as notification to
appropriate organizations regarding aircraft in need of search and rescue aid, and assist such
organizations as required.

As a precaution, surveillance systems should support the display of safety-related alerts and
warnings, including conflict alert, conflict prediction, minimum safe altitude warning and
unintentionally duplicated aircraft identity codes.

Surveillance data should be presented to operational personnel in a manner that an alerting
service and, if necessary, search and rescue can be supported. Service support includes display of
© 2009, ICAO
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data and data recording. Replay of recorded data should be possible on maps or other means to
extract absolute position information.

In addition to the general alerting service support, surveillance systems as part of an A-SMGCS
should be able to track and support guidance to emergency vehicles.

3.1.6
TRAFFIC ADVISORY SERVICE
(TAS)


Aircraft fly under one of two sets of rules for separation: visual flight rules (VFR) or instrument
flight rules (IFR). Air traffic controllers have different responsibilities to aircraft operating under
the different sets of rules. While IFR flights are under positive control, VFR pilots can request
flight following, which provides traffic advisory services on a time permitting basis. A traffic
advisory service does not deliver clearances but only advisory information on potentially
conflicting aircraft, and it uses the word “advise” or “suggest” when a course of action is
proposed to an aircraft.

There are no special surveillance requirements for TAS. It can operate with the same quality of
surveillance data that is supporting operations.

3.1.7 Other applications
Surveillance systems are also used in support of other applications such as:

a. ground safety nets (Short Term Conflict Alert (STCA) and Minimum Safe Altitude
Warning (MSAW));
b. airborne safety nets (ACAS);
c. height monitoring (in support of RVSM); or
d. noise monitoring.

3.2
AIRCRAFT IDENTITY
3.2.1
NEED FOR IDENTIFICATION

The labeling of aircraft on displays serves the important function of allowing an aircraft to be
easily identified. Most surveillance systems include provision for determining aircraft
identification. The desired outcome is to have all aircraft labeled with their aircraft identification
usually communicated in the radio call-sign. The call-sign is used to address the flight crew, by
the flight crew to identify themselves in very high frequency (VHF) or high frequency (HF) radio
voice communications, and in controller pilot data link communications (CPDLC).

3.2.2
MODE A IDENTITY CODE

Traditionally an SSR Mode A identity code is assigned to a flight prior to departure or on initial
entry into the defined airspace. The code is entered into the transponder by the pilot. The
surveillance sensor (e.g., SSR or multilateration system) tracks the aircraft on the basis of this
code. The Mode A code is also recorded in the corresponding flight plan for the aircraft. The air
traffic management system obtains the Mode A code and aircraft track from the surveillance
system, and searches for the flight plan with a matching code. Once the flight plan is found, the
processing system reads the aircraft identification in the flight plan and uses this information to
label the aircraft track on the controller’s screen. The correlation of the surveillance track with
© 2009, ICAO
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the flight plan also allows the controller to access flight data associated with the aircraft depicted
on their display system. The Mode A code is released once the aircraft reaches its destination or
leaves the airspace managed by the ATM system. Agreements are sometimes established
between neighboring countries for coordination in the assignment of Mode A codes.

There is a total of 4096 Mode A codes, although there are fewer than this number available for
use, since some are assigned for special purposes. For example, flights for which no flight plans
are logged are normally all assigned fixed codes such as 1200, 2000 or 7000 depending on
regional agreement. The available number of codes imposes constraints in some parts of the
world where it has been reported that flights have been delayed on occasions while waiting for a
code to be released.

3.2.3
AIRCRAFT IDENTIFICATION

With the advent of Mode S radar and ADS-B there are means to simplify the system and move
away from Mode A codes. Mode S radar, MLAT systems and ADS-B allow the aircraft
identification to be obtained directly from the aircraft. ATM systems are beginning to use the
aircraft identification as a means of matching the surveillance track to the corresponding flight
plan. This overcomes the constraints of Mode A codes. It also means that flights for which no
flight plan is logged may also be labeled with their aircraft identification on the controllers
display, allowing easier identification. Aircraft without a flight plan normally report their
registration number as their aircraft identification.

3.3
REQUIREMENTS FOR AERONAUTICAL SERVICES BASED ON
SURVEILLANCE
In addition to the technical considerations contained in this manual (see Chapter 4), operational
requirements need to be fulfilled in order for air traffic controllers to provide services based on
the information from the surveillance system. Aircraft need to be appropriately equipped, air
traffic controllers and flight crews need to be adequately trained, and suitable standards and
procedures need to be employed. Provisions and procedures for the safe management of air
traffic are detailed in Procedures for Air Navigation Services – Air Traffic Management (PANS-
ATM, ICAO Doc 4444). Complementary procedures for pilots and flight crew are the subject of
Procedures for Air Navigation Services – Aircraft Operations (PANS-OPS, ICAO Doc 8168).

4 TECHINCAL PERFORMANCE REQUIREMENTS FOR
SURVEILLANCE SYSTEMS
4.1
PURPOSE
The most fundamental function of an aeronautical surveillance system is to provide identification
and an accurate estimate of the relative position and altitude of aircraft at a given time. The
estimated position needs to be updated at a rate commensurate with the intended application.

Depending on the application that a surveillance system is intended to support and depending on
the environment in which the application is supported, there will be other requirements such as
the need for aircraft velocity or short term intention.

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The performance of a surveillance system is not defined by a single requirement, but by a set of
requirements. This set of requirements will depend on the surveillance application supported.
The requirements relate to the information provided by the surveillance system, specifically for
the target under surveillance. They cover the data to be provided, which could include actual
surveillance performance reports, and the quality of that data. They do not relate to the
presentation of the information on the display.

The technical performance requirements for surveillance systems are not sufficient to authorize a
given operational separation. There are other factors that should be analyzed during the safety
assessment e.g., human factors, procedures, airspace structure, traffic density, etc.

4.2
DEFINITION OF PARAMETERS CONTRIBUTING TO QUALITY OF
SERVICES
• Data fields: the surveillance information (e.g., position, identity, intent of an aircraft) that the
surveillance system is required to deliver;
• Accuracy is applicable to a data item that is elaborated by the system (e.g., measured and/or
calculated). It is the degree of conformity of the elaborated value of a data item with its
actual value at the time when the data item is used;
• Data Integrity is applicable to a data item that is transferred by the system (provided
externally by another system and forwarded without modification to another system, e.g.,
Mode A code, Mode C code). It is the degree of undetected (at system level) non-conformity
of the input value of the data item with its output value. In that case the system is only a
communication medium so it should not modify the value of the data item;
• Availability: is the probability that the required surveillance information will be provided to
the end-users;
• Continuity: is the probability of the surveillance service to perform its intended function
without unscheduled interruptions during intended operation;
• Reliability: is a function of the frequency with which failures occur within the system. The
probability that the system will perform its function within defined performance limits for a
specified period under given operating conditions.
• Update rate: is the time difference between two information reports related to the same
aircraft/vehicle and to the same type of information;
• Integrity (system): is the probability for a specified period of an undetected failure of a
functional element that results in erroneous surveillance information to the end-user.
• Integrity (data): is defined relative to the probability that an error larger than a certain
threshold in the information is undetected (i.e., not alerted) for longer than a time to alert
threshold.
• Coverage: is the volume of airspace that will be covered by the surveillance system and
within which the surveillance system performance parameters meet the requirements.

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4.3
TECHNICAL SURVEILLANCE SYSTEM PERFORMANCE AND
SURVEILLANCE TECHNOLOGIES
Surveillance system performance descriptions are defined as much as possible independently
from the technologies used to provide surveillance. Such approach allows more efficient
surveillance system design depending on environment and available surveillance techniques.

4.4
TECHNICAL SURVEILLANCE SYSTEM PERFORMANCE DESCRIPTIONS
PER APPLICATION
For traceability, the surveillance system performance descriptions are defined per supported
application. When a surveillance system is used to support different applications, the most
stringent requirements must be used.

Examples of surveillance system performance descriptions for most common applications are
described in Appendix A of this document.

4.5
IMPORTANCE OF VERIFYING SURVEILLANCE PERFORMANCE
It should be verified that a surveillance system meets the requirements prior to being put into
operational service. The environment of a surveillance system can change over time e.g.,
surveillance coverage may be impacted by new obstructions; aircraft traffic density may increase;
aircraft routing may change. Also components of a surveillance system may degrade over time.
It is therefore important to put measures in place to ensure continued compliance to performance
requirements. Options include:

• Periodically verifying the performance of the system e.g., to repeat all or part of the
initial verification testing (the initial verification testing can be used as a baseline to
compare against);
• Ensuring that the surveillance system has sufficient built-in tests and external monitoring
to demonstrate continuously that the performance requirements are being met.

It is recommended that periodic testing be put in place in case any changes to the environment not
foreseen and detected by inbuilt testing and monitoring come about.

5 AIR-GROUND SURVEILLANCE SYSTEM DESIGN AND
COMPONENTS
5.1
COMPONENTS OF AN AERONAUTICAL SURVEILLANCE SYSTEM
The aeronautical surveillance system may be broadly divided into four parts:
1. A “Remote Surveillance Sub-System” installed within the target under surveillance (see
remote surveillance sub-system in Figure 1). This surveillance sub-system has two main
functions: to collect the data from different onboard sensors/interfaces and to transmit
them to external users (e.g., local surveillance sub-system located on the ground or in
other targets).
2. A sensor system that provides surveillance information about targets under surveillance.
3. A communication system which connects the sensor systems to a surveillance data
processing system and allows transfer of the surveillance data. Ground communication
may also support control and monitoring of the sensor.
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4. A surveillance data processing system:
a. Combines the data received from the different sensors in one data stream.
b. Optionally integrates the surveillance data with other information e.g., flight
information.
c. Provides/distributes the data to the users in a specified manner removing the possible
different specificities of the different types of sensor.
The sensor is a significant part of the aeronautical surveillance system. It provides surveillance
information which is then presented to air traffic controllers. An overview of sensors currently
used in the implementation of aeronautical surveillance applications is presented below.

5.2
NON COOPERATIVE SENSOR
5.2.1
PRIMARY SURVEILLANCE RADAR
(
PSR
)
5.2.1.1
PSR OVERVIEW

Primary surveillance radar (PSR) works by detecting reflections to transmitted pulses of radio
frequency energy. The PSR ground station typically consists of a transmitter, receiver, and
rotating antenna. The system transmits the pulses, and then detects and processes the resulting
reflections. The slant range of the target is determined by measuring the time from transmission
of the signal to reception of the reflected pulses. The bearing of the target in azimuth is
determined by noting the position of the rotating antenna when the reflected pulses are received.
Reflections are obtained from targets of interest and fixed objects (e.g., buildings), which tends to
create clutter. Special processing techniques are used to remove the clutter.

Primary surveillance radar has not been standardized by ICAO.

The components of primary surveillance radar are illustrated in Figure 3.

5.2.1.2
PSR APPLICATIONS

In the 1960s and 1970s, the PSR was widely used for aeronautical surveillance in En-Route
airspace. From the late 1970s many air navigation service providers (ANSPs) decided to
discontinue the use of PSR in this application because of the high cost, and the inability to
provide identification that became more important with increasing traffic densities. Also,
mandatory requirements for aircraft to carry transponders (see §
5.3
) in airspace with high traffic
meant that surveillance could be provided using secondary surveillance radar (SSR). In many
countries the use of PSR is retained for defense or weather monitoring purposes rather than for
the provision of civil ATC services. The use of PSR for En-Route ATS is expected to continue to
decrease.

PSR also remains a useful tool in busy terminal areas, where it provides surveillance of aircraft
not equipped with a transponder (intruder detection). The future use of traditional primary
surveillance radar is expected to decrease, with the coincident increase in requirements for
transponder carriage and the introduction of other surveillance technologies.

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PSR is also used in airport surface surveillance applications to detect objects that stray onto the
active areas of the airport, and those aircraft with transponders that are configured to ignore
secondary surveillance radar interrogations when on the ground. This latter feature is
incorporated to prevent garbling of secondary surveillance radar signals that occur when a large
number of aircraft are within close proximity of each other.

Today PSR is typically not the main means to provide surveillance service because of lack of
identification. However, as this can be mitigated to some extent, e.g., by voice communication
and specific procedures, some PSR-only surveillance systems are still in operation.

5.2.1.3
PSR CHARACTERISTICS

The capabilities of primary surveillance radar are:

a. The ability to determine the target’s position without requiring any equipment (e.g., a
transponder) to be fitted in the aircraft (i.e., it is able to detect non-cooperative targets),
although the aircraft must be constructed of a material that reflects the transmitted
signals.
b. The ability to detect objects and phenomena other than the tracked aircraft:
• It may be used in aerodrome surface surveillance applications to detect objects that
interfere with protected areas.
• Primary surveillance radars are sometimes configured with a weather channel that