ATM Communications Navigation
and Surveillance
SYST 460 560
Fall 2003
G.L. Donohue
Evolution of CNS/ATM
1922 ATC begins
1935, an airline consortium opened
the first Airway Traffic Control
Station
1930 Control Tower
Page 11-15 Katon, Fried
1940s Impact of
radar
Airway Centers
ADS-B GPS
1960s & 70s
Radio Frequencies
Name
Abbreviation
Frequency
Wave length
VLF
3 to 30 kHz
100 to 10km
Low
LF
30 to 300 kHz
10 to 1km
Medium
MF
300 to 3000 kHz
1km to 100 m
High
HF
3 to 30 MHz
100 to 10m
Very high
VHF
30 to 300 MHz
10 to 1cm
Ultrahigh
UHF
300 to 3000 MHz
1m to 10cm
Super high
SHF
3 to 30 GHz
10 to 1cm
Extremely high
EHF
30 to 300 GHz
10 to 1mm
Frequency
Very low
Line-of-Sight Waves
VHF and UHF have about 70 nmi. Range at 6,000 ft. altitude
Line-of-sight range
Weather
• Instrument meteorological conditions (IMC) are weather
conditions in which visibility is restricted, typically less
than 3 miles
• Acft operating in IMC are supposed to fly under IFR
Visibility Categories (by ICAO)
(1)
• Category I
– Decision height not lower than 200 ft; visibility not
less than 2600 ft, or Runway Visual Range (RVR) not
less than 1800 ft with appropriate runway lighting.
– The pilot must have visual reference to the runway at
the 200ft DH above the runway or abort the landing.
– Acft require ILS and marker-beacon receiver beyond
other requirements for flights under IFR.
– Category I approaches are performed routinely by
pilots with instrument ratings
Visibility Categories (by ICAO)
(2)
• Category II
– DH not lower than 100 ft & RVR not less than 1200 ft
(350m)
– The pilot must see the runway above the DH or abort
the landing
– Additional equipment that acft must carry include
dual ILS receivers, either a radar altimeter or an
inner-marker receiver to measure the DH, an
autopilot coupler or dual flight directors, two pilots,
rain-removal equipment (wipers or chemicals), and
missed-approach attitude guidance. An auto-throttle
system also may be required
Visibility Categories (by ICAO)
(3)
• Category III subdivided into
– IIIA. DH lower than 100 ft and RVR not less than 700
ft (200m)-sometimes called see to land: it requires a
fail-passive autopilot or a head-up display
– IIIB. DH low than 50 ft & RVR not less than 150 ft
(50m)-sometimes called see to taxi; it requires a failoperational autopilot & an automatic rollout to
taxing speed
– IIIC. Zero visibility. No DH or RVR limits. It has not
been approved anywhere in the world
Decision Height
• Acfts are certified for decision heights, as are crews
• When a crew lands an acft at an airport, the highest of
the three DHs applies.
• An abort at the DH is based on visibility
• Alert height is the altitude below which landing may
continue in case of equipment failure
– Typical Alert height is 100 ft
Integrated Avionics Subsystems
(1)
1.
Navigation
2.
Communication
– intercom among the crew members & one or more external
two-way voice & data links
3.
Flight control
– Stability augmentation & autopilot
– The former points the airframe & controls its oscillations
– The latter provides such functions as attitude-hold, headinghold, altitude hold
4.
Engine control
– The electronic control of engine thrust(throttle management)
Integrated Avionics Subsystems
(2)
5.
Flight management
–
Stores the coordinates of en-route waypoints and
calculates the steering signals to fly toward them
6. Subsystem monitoring & control
–
Displays faults in all subsystems and recommends
actions to be taken
7. Collision-avoidance
–
Predicts impending collision with other acft or the
ground & recommends an avoidance maneuver
Integrated Avionics Subsystems
(3)
Weather detection
– Observes weather ahead of the acft so that the
route of flight can be alerted to avoid
thunderstorms & areas of high wind shears
– Sensors are usually radar and laser
9.
Emergency locator transmitter(ELT)
– Is triggered automatically on high-g impact or
manually
– Emit distinctive tones on 121.5, 243, and 406 MHz
8.
The Vehicle
Avionics Placement on multi-purpose transport
Architecture (1)
• Displays;
– Present information from avionics to the pilot
– Information consists of vertical and horizontal navigation data,
flight-control data (e.g. speed and angle of attack), and
communication data (radio frequencies)
Architecture (2)
• Flight controls;
– The means of inputting information from the pilot to the
avionics
– Traditionally consists of rudder pedals and a control-column or
stick
– Switches are mounted on the control column, stick, throttle,
and hand-controllers
Architecture (3)
•
Computation;
– The method of processing sensor data
– Two extreme organizations exist:
1. Centralized; Data from all sensors are collected
in a bank of central computer in which software
from several subsystems are intermingled
2. Decentralized; Each traditional subsystem
retains its integrity
Architecture (4)
•
•
Data buses
– Copper or fiber-optics paths among sensors,
computers, actuators, displays, and controls
Safety partitioning
– Commercial acft sometimes divide the avionics to;
1. Highly redundant safety-critical flight-control
system
2. Dually redundant ,mission-critical flightmanagement system
3. Non-redundant maintenance system
– Military acrft sometimes partition their avionics for
reason other than safety
Architecture (5)
• Environment
– Avionics equipment are subject to;
• acft-generated electricity-power transient, whose
effects are reduced by filtering and batteries,
• externally generated disturbances from radio
transmitters, lightening, and high-intensity
radiated fields
– The effect of external disturbances are reduced by
• shielding metal wires and by using fiberoptic data
buses
• add a Faraday shielding to meal skin of the acft
Architecture (6)
• Standards
– Navaid signals in space are standardized by ICAO
– Interfaces among airborne subsystems, within the
acft, are standardized by Aeronautical Radio INC.
(ARINC), Annapolis Maryland, a nonprofit
organization owned by member airlines
– Other Standards are set by:
• Radio Technical Commissions for Aeronautics,
Washington DC
• European Organization for Civil Aviation
Equipment (EUROCAE)
• etc.
Human Navigator
• Large acft often had (before 1970) a third crew member,
flight engineer:
– To operate engines and acft subsystems e.g. air
conditioning and hydraulics)
– Use celestial fixes for positioning
• Production of cockpits with inertial, doppler, and radio
equipments facilitated the automatically stations
selection, position/waypoint steering calculations and
eliminated the number of cockpit crew to two or one.
Communications is the Glue for ATMCNS
Context for Communication Architecture
Operational
Concepts
Services
Flt Plan Service
Functional
Capabilities
FP Processing
Message Types
FUNCTIONAL
Traffic Mgmt Synchronization
Process user
preferences
Message Types
ARCHITECTURE
Communications Architecture
Enabling
Communication
Links
•
•
•
•
•
•
•
•
•
•
VHF-AM
ACARS
VDL-2
VDL-3
VDL-4
VDL-B
SATCOM
MODE-S
UAT
HFDL
ATC Advisory
Tech
Concepts
•
•
•
•
•
•
•
•
•
FIS
TIS
CPDLC
CPC
DSSDL
AOCDL
ADS-B
AUTOMET
APAXS
Air-Ground Comm Functional Architecture
AIRBORNE WEATHER OBSERVATION
VOICE
OPERATIONS, MAINTENANCE
MESSAGING
AIRCRAFT
NEGOTIATION
ADS-B
AIRCRAFT
POSITION/
INTENT
AUTOMET
FIS TIS APAXS
•WEATHER
•NAS
STATUS
CPC
ADS-B
CPDLC
DSSDL
NATIONAL
WEATHER
SERVICE
AIR
TRAFFIC
CONTROL
•TV, RADIO
•INTERNET
AOC
COMM
Commercial
Service Provider
NWIS
OTHER
AUTHORIZED
USERS
•INTERNATIONAL
•MILITARY
•FBO’S
AIRLINES
OPERATIONS
CENTER
Benefits Driven Concept
Aircraft
Technical
Concepts
Range of User Equipage
Automated
Negotiation
Dynamic Data
Static Data
Air Traffic Control
• CPC
• CPDLC
• AOCDL
2-way
Strategic CDM
• CPC
• CPDLC
• DSSDL
•
•
•
•
TIS
ADS-B
FIS
AUTOMET
• FIS
Broadcast
Tactical Control
AOCDL
Aeronautical Operational Control
Humanbased
DSSbased
Info
Base
Functional Analysis
•
9 Technical Concepts
•
Defined Message categories and message types for
each Technical Concept
•
Concept Description
•
Concept Diagram
Architecture Alternatives Summary
Operational Concept
Aircraft continuously receive
Flight Information to enable
common situational awareness
Aircraft continuously receive
Traffic Information to enable
common situational awareness
Technical VHF-AM
Concept
VDL-2/
ATN
VDL-3/
ATN
SATCOMBroadcast
3
TIS
3
3
3
3
SATCOM2way
3
CPDLC
3
DSSDL
3
Acceptable Alternative
UAT
3
Controller - Pilot messaging
supports efficient Clearances,
Flight Plan Modifications, and
Advisories (including Hazardous
Weather Alerts)
3
Mode-S
3
CPC
Aircraft report airborne weather
to improve weather
nowcasting/forecasting
Passengers enjoy in-flight
television, radio, telephone, and
internet service
VDL-B
FIS
Controller - Pilot Communication
Aircraft exchange performance /
preference data with ATC to
optimize decision support
Aircraft continously broadcast
their position and intent to
enable optimum maneuvering
Pilot - AOC data exchange
supports efficient air carrier/air
transport operations and
maintenance
VDL-4/
ATN
3
ADS-B
3
3
AOCDL
3
3
3
AUTOMET
3
3
3
3
APAXS
NAS Architecture
AATT CSA Recommendation
3
Operational Concept - Tech Concept
Operational Concept
Aircraft continuously receive Flight Information to
enable common situational awareness
Aircraft continuously receive Traffic Information to
enable common situational awareness
Controller - Pilot messaging supports efficient
Clearances, Flight Plan Modifications, and
Advisories (including Hazardous Weather Alerts)
Technical Concept
Flight Information Services (FIS)
Controller - Pilot voice communication
Controller Pilot Communications (CPC)
Aircraft exchange performance / preference data
with ATC to optimize decision support
Decision Support System Data Link
(DSSDL)
Aircraft continuously broadcast their position and
intent to enable optimum maneuvering
Automated Dependent Surveillance-Broadcast
(ADS-B)
Pilot - AOC messaging supports efficient air
carrier/air transport operations and maintenance
Airline Operational Control Data Link (AOCDL)
Aircraft report airborne weather to improve weather
nowcasting/forecasting
Passengers enjoy in-flight television, radio, internet,
and entertainment service
Automated Meteorological Transmission
(AUTOMET)
Aeronautical Passenger Services
(APAXS)
Traffic Information Services (TIS)
Controller-Pilot Data Link Communications
(CPDLC)
Message Categories
TECHNICAL CONCEPT
Msg
Category #
MESSAGE
CATEGORY
MESSAGE CONTENT
Flight Information Services (FIS)
1
Flight Information
Dynamic NAS status data and weather data
Traffic Information Services (TIS)
2
Traffic Information
Controller-Pilot Data Link
Communications (CPDLC)
Controller-Pilot Communications
(CPC)
Decision Support System Data
Link (DSSDL)
Airline Operational Control Data
Link (AOCDL)
Automated Dependent
Surveillance-Broadcast (ADS-B)
Automated Meteorological
Transmission (AUTOMET)
Aeronautical Passenger Services
(APAXS)
3
Controller – Pilot
Messaging
Controller – Pilot
Voice
Aircraft – ATC
Messaging
Aircraft-AOC
Messaging
ADS Reporting
Real time aircraft position data (including
trajectory information) provided by ATC.
Clearances, Flight Plan Modifications, and
Advisories
Clearances, Flight Plan Modifications, and
Advisories
Aircraft performance / preference
4
5
6
7
8
9
Aircraft Weather
Reporting
Passenger Services
Air carrier / air transport operations and
maintenance
Aircraft continuously broadcast their position
and intent
Aircraft report airborne weather (wind
velocity/magnitude, temperature, humidity)
In-flight television, radio, and entertainment
services including internet services
Concept Description - Flight Information
Service
 Aircraft continually receive dynamic
Flight Information to enable common
situational awareness
• Weather Information
• NAS Status
• NAS Traffic Flow Status
Note: We assume that static data will be loaded on
aircraft via portable storage media prior to flight.
FIS Message Set
Msg
ID
(M#)
M15
Message Category
Definition/Comment
Convection
33
M17
Departure ATIS
Includes data regarding cloud tops, freezing level, lightning activity, projected decay, water content,
etc.
AutomaticTerminal Information Service (Airport Domain)
M18
Destination Field Conditions
33
M20
En Route Strategic General Imagery
Combination of text, icons, and graphics potentially describing NOTAM information, RCR readings,
ramp snow conditions, de-icing necessity, arrival rates, etc.
Backup for synthesized weather products or for direct imagery requirement. Examples include
satellite photos, lightning strike data, hand drawn surface analysis.
M21
FIS Planning - ATIS
AutomaticTerminal Information Service (Terminal Domain)
M22
FIS Planning Services
Includes real-time weather advisories and warnings
M26
General Hazard
A general hazard product would likely include weather hazards in addition to other known hazards
(traffic, terrain..)
33
M27
Icing (Terminal Tactical)
May not be practical, difficult to implement. Would depend on automatic reports from in flight aircraft to
a central ground location for constant plotting, updating and reporting.
33
M28
Icing/ Flight Conditions (En Route Far
IMC and icing are included in this product aimed at GA.
Term, Near Term Strategic, Tactical)
Low Level Wind Shear (Terminal Tactical) This product may identify dangerous shearing winds caused by microbursts, frontal passage, etc.
Generated from ground-based sensors, fused with NEXRAD or TDWR data to create a near-ground
level view.
Radar Mosaic
Real-time broadcasts of NEXRAD or TDWR-type RADAR pictures in the terminal area.
M29
M35
Source
(1)
80
33
80
80
33
33
33
M37
Surface Conditions (En Route Far Term
Strategic)
This product will project surface conditions to enhance situational awareness and support contingency
planning
33
M39
Turbulence (En Route Far Term and Near Strategic Turbulence information will become one of the most important future products. A true tactical
Term Strategic, En route Tactical)
product may not be feasible but future product may combine current sensed condition with next
available nowcast.
33
M40
Winds/Temperature (En Route Far Term
and Near Term Strategic)
33
This product contains information on Enroute winds and temperatures
Note: (1) Source 33 is the Data Communications Requirements, Technology and Solutions for Aviation Weather
Information Systems (Phase I Report), Lockheed Martin Aeronautical Systems 1999
Source 80 is RTCA DO 237, Aeronautical Spectrum Planning, 1997
Flight Information Service - FIS
Ground Systems
Air / Ground Comm
Aircraft
NAS / SUA
STATUS
A
C
ATIS
OASIS
CSP
Comm
Network
FIS
PROC
VDL
Comm
Network
Comm
I/F
VDL
RCVR
• NOTAM
NWIS INTEGRATED
NETWORK
WARP
SATCOM
NEXRAD
NWS
Wx
Vendor(s)
N
E
T
W
O
R
K
AAIS
MFDS
SAT
COM
RCVR
UAT
XCVR
UAT Comm
Network
Comm
Network
ADAS
Wx
Sensor(s)
Portable
Storage
Media
UAT
GroundBased
Pilot PC
Traffic Information Services TIS
Ground Systems
ADS-B
GND
RCVR
Primary
Secondary
Air / Ground Comm
ADS-B
XCVR
VDL-B
Comm
Network
VDL-B
VDL-B
XCVR
Comm
Network
SATCOM
RCVR
SATCOM
Automation
L
A
N
Comm
I/F
ATC
Facility
Aircraft
A
C
N
E
T
W
O
R
K
ADS-B
Processor
AAIS
MFDS
•CDTI
CSP
UAT
XCVR
UAT Comm
Network
UAT
Controller / Pilot Data Link Communications
CPDLC
Ground Systems
Air / Ground Comm
Aircraft
ARTCC
Automation
L
A
N
Comm
I/F
AAIS
A
C
VDL Comm
Network
TRACON
VDL-3
XCVR
Automation
L
A
N
Comm
I/F
Automation
L
A
N
Comm
I/F
TOWER
FSS
Automation
L
A
N
Comm
I/F
N
E
T
W
O
R
K
MFDS
CPC Controller/Pilot Voice Communication
Ground Systems
ATC
Voice
Comm
Head
Voice
Switch
Air / Ground Comm
FTI
Comm
Network
Aircraft
VHF
Voice
Radio
Pilot
Voice
Existing
A/G Radio
VDL
Radio
NEXCOM
RADIO
Voice
Data
Decision Support System Data Link DSSDL
Ground Systems
Air / Ground Comm
Aircraft
ARTCC
Automation
L
A
N
Comm
I/F
FTI Comm
Network
TRACON
Automation
L
A
N
VDL-3
XCVR
Comm
I/F
TOWER
Automation
L
A
N
Comm
I/F
A
C
N
E
T
W
O
R
K
AAIS
FMS
Aeronautical Operational Control Data Link
AOCDL
AOC
Automation
L
A
N
Comm
I/F
AAIS
CSP
VDL-2 Comm
Network
A
C
VDL-2
XCVR
N
E
T
W
O
R
K
MFDS
FMS
Ground Systems
Air / Ground Comm
Aircraft
AOCDL Message Set
Msg ID
(M#)
M8
M9
M10
M11
M12
M19
M23
M25
M30
M33
Message Type
Airline Maintenance Support: Electronic Database
Updating
Airline Maintenance Support: In-Flight Emergency
Support
Airline Maintenance Support: Non-Routine
Maintenance/ Information Reporting
Airline Maintenance Support: On-Board Trouble
Shooting (non-routine)
Airline Maintenance Support: Maintenance/ Information
Reporting
Diagnostic Data
Flight Data Recorder
Gate Assignment
Out/ Off/ On/ In
Position Reports
Automatic Dependent Surveillance
- Broadcast ADS-B
Ground Systems
Air / Ground Comm
Aircraft
AAIS
GPS
GPS
RCVR
Primary
Secondary
Comm
Network
N
E
T
W
O
R
K
ADS-B
GND
RCVR
ADS-B
XCVR
Automation
L
A
N
Comm
I/F
ATC
Facility
A
C
MFDS
FMS
ADS-B
Automated Meteorological Transmission AUTOMET
NASA
AOC
NWS
UAT
Comm
Network
CSP
Comm
Network
PROC
Comm
I/F
VDL
Comm
Network
FSL
SATCOM
Ground Systems
Air / Ground Comm
UAT
XCVR
VDL
XCVR
A
C
N
E
T
W
O
R
K
SAT
COM
XCVR
Aircraft
Wx
Sensor(s)
FMS
Data Link Summary
Data Link
HFDL
ACARS
Single
Channel
Data Rate
kbps
1.8
2.4
Capacity for
Aeronautical
Communications
Channels
Available
to Aircraft
Channels
2
10
Channels
1
1
# Aircraft
Sharing
Channel
(Expected
Maximum)
Aircraft
50
25
Comments
Intended for Oceanic
ACARS should be in decline as
users transition to VDL Mode 2
System can expand indefinitely as
user demand grows
Assumes NEXCOM will deploy to
all phases of flight
Intended for surveillance
Intended for FIS
Intended for surveillance
Intended for surveillance/FIS
Assumes satellites past service life
Planned future satellite
VDL Mode 2
31.5
4+
1
150
VDL Mode 3
31.5*
~300
1
60
VDL Mode 4
VDL – B
Mode-S
UAT
SATCOM
Future
SATCOM
Future Ka
Satellite
19.2
31.5
1000**
1000
384
1-2
2
1
1
15
1
1
1
1
1
500
Broadcast
500
500
~200
2,000
~50
~50
~200
Estimated capability - assumes
capacity split for satellite beams
Fourth
Generation
Satellite
>100,000
>100
>100
Unknown
Based on frequency license filings
*
**
Channel split between voice and data.
The Mode-S data link is limited to a secondary, non-interference basis with the surveillance function and has a capacity of 300 bps per
aircraft in track per sensor (RTCA/DO-237).
Top Down Architecture FTI
Network
NEXCOM
Site
VDL-3
Primary 2-way
CPC / CPDLC / DSSDL
CSP
Interface
CSP
Network
VDL-2
Secondary 2-way
AOC / AUTOMET
FTI
Network
CSP
Network
SATCOM
FIS / TIS / APAXS
FTI
Network
ADS-B
Site
UAT
VDL-4
Mode-S
Data Transmit
ADS-B
Ground
Link
Aircraft
2007 Architecture - UAT Data
Ground
Link
Aircraft
FTI
Network
NEXCOM
Site
VHF-AM
CPC - Voice
CSP
Interface
CSP
Network
VDL-2
Secondary 2-way
CPDLC / DSSDL
AOC / AUTOMET
FTI
Network
CSP
Network
VDL-B
FIS - Regional
FTI
Network
ADS-B
Site
CSP Network
FIS / TIS
UAT
Data Transmit
ADS-B
SATCOM
APAXS
Navigation / Surveillance Functions
Augmentation Network
VOR Site
FTI
Network
Radar
Site
WAAS / LAAS
VOR
Mode-A/C/S
Navigation Rcvr
WAAS / LAAS / VOR
Surveillance Xpndr
Separation / TCAS
Communication Architecture Schedule - FIS
00
Avionics
Systems
Ground-Comm
Air-Ground Comm
Certification
02
03
SATCOM Ant / Rcvr
Research
Standards
01
04
05
06
07
08 09 10 11 12 13 14 15
Integrated Demo
FIS-B SATCOM
FIS-B
UAT
FIS-B
SATCOM
FIS-B SATCOM
FIS-B
FIS Data Compression
Research
Link Simulation
Standards
VDL-B
Systems
(data links)
UAT
SATCOM
V- SATCOM
Research
Standards
NAS Wide Info System
NWIS Data
AOC / CDM Network
Systems
WARP Wx Network
FTI
NWIS
System Operational time span
Communication Architecture Schedule - TIS
00
Avionics
Research
01
02
03
SATCOM Ant / Rcvr
04
05
Air-Ground Comm
08 09 10 11 12 13 14 15
Integrated Demo
UAT
Systems
SATCOM
TIS-B SATCOM
Certification
Ground-Comm
07
TIS-B SATCOM
Standards
Research
06
VDL-B
TIS Data Compression
Link Simulation
TIS-B SATCOM
Standards
UAT
VDL-B
Systems
(data links)
SATCOM
Research
Standards
V- SATCOM
NAS Wide Info System
NWIS Data
AOC / CDM Network
Systems
FTI
NWIS
System Operational time span
Communication Architecture Schedule - CPDLC
00
01
Avionics
Research
Standards
02
Voice Synthesis
Air-Ground Comm
05
(data links)
Research
Standards
07
08 09 10 11 12 13 14 15
Demo
CPDLC
VDL-3 MMR
CPDLC VDL-3
CPDLC VDL-2
Prioritization of HzWx on VDL-2
Additional
MSG for
Hz Wx
Standards
Systems
06
VDL-2 MMR
Certification
Ground-Comm
04
Voice
Synthesis
CPDLC
Systems
Research
03
VDL-2
VDL-3
NAS Wide Info System
NWIS Data
DLAP
Systems
DLAP -R
FTI
NWIS
System Operational time span
Communication Architecture Schedule - AOCDL
00
Avionics
Research
Standards
02
03
04
05
07
Systems
DSSDL
AUTOMET
VDL-2 MMR
VDL-2 MMR
CPDLC
AOCDL
AOCDL VDL-2
Research
CPDLC VDL-2
DSSDL VDL-2
DSSDL
Integrated Demo
DSSDL
Integrated Demo
Standards
Systems
(data links)
VDL-2
VDL-2 Mod 1
Research
Standards
Systems
08 09 10 11 12 13 14 15
Integrated Demo
DSSDL
AUTOMET
CPDLC
06
VDL-2 MMR
Certification
Ground-Comm Air-Ground Comm
01
DLAP - M1
DLAP
FTI
NWIS
System Operational time span
DSSDL
Communication Architecture Schedule - ADS-B
00
Avionics
Research
01
02
03
ADS-B
Mode-S / UAT / VDL-4
Systems
ADS-B Mode-S / UAT
Air-Ground Comm
Certification
Ground-Comm
05
SF-21, CAPSTONE
Standards
Research
04
ADS-B Link Evaluation
Standards
Technology
Link Decision
Systems
(data links)
Research
Standards
Systems
Mode-S
UAT
VDL-4
NAS Wide Info System
NWIS Data
FTI
NWIS
System Operational time span
06
07
08 09 10 11 12 13 14 15
Communication Architecture Schedule - Cross-cutting
Ground-Comm
Air-Ground Comm
Cross-cutting
00
01
02
03
04
05
06
07
08 09 10 11 12 13 14 15
NAS Wide Info System
Research
Multifunction Display
Information Security
NWIS Data
Standards
Symbology
Mode-S
UAT
VHF-AM
Systems
(data links)
VDL-B
C, Ku, S SATCOM
VDL-2
VDL-3
SATCOM
Systems
AOC / CDM Network
V- SATCOM
FTI
WARP Wx Network
System Operational time span
NWIS
Cross Cutting Technology Gaps
Architecture
Requirement
2007/2015
2015
2007
Cross Cutting Technology
Issues
System or
Component
Segment
Ground
New System
Required
Com. Interface to Distributed NAS
New System x
Wide Database (standard data
set, access protocol, user
verification)
Information Security
Improved Datalink
Required
Authentication
New System x
Data Validation
Improved System x
Protection from Interference
Improved System x
Air
Space
NAS-Wide Information System
x
x
x
x
x
Navigation
Navigation: Geometry of The Earth
• For navigational purposes, the earth’s surface can be
represented by an ellipsoid of rotation around the
Earth’s spin axis
• The size & shape of the best-fitting ellipsoid is chosen to
match the sea-level equal-potential surface.
Geometry of The Earth
Fig 2.2
Median section
of the earth,
showing the
reference
ellipsoid &
gravity field
Coordinate Frames
•
The position, velocity and attitude of the aircraft must
be expressed in a coordinate frame: WGS-84
Navigation
coordinate frame
Navigation Phases
Picture courtesy of MITRE Corporation
Aircraft System Hierarchy
Heading
attitude
•Inertial
air data
•Doppler
Star line
of sight
Deadreckoning
computations
Celestial
equations
To cockpit display
pointing sensor
Attitude
•Position
Way
points
•Velocity
•Attitude
Most probable
position
computation
Position
computations
•Satellite
(GPS)
•Radar
Range, bearing
to displays, FMS
Steering signals
to autopilot
•Positioning
sensors
•Radio(VOR,
DME, Loran,
Omega)
Time to go
Course
To map display
Positioning
computations
Position
data
Velocity
Block diagram of an
aircraft navigation system
To weapon computers
Terminal Area Navigation
1.
Departure: begins from maneuvering out the runway,
ends when acft leaves the terminal-control area
2.
Approach: acft enters the terminal area, ends when it
intercepts the landing aid at an approach fix
•
Standard Instrument Departure (SIDs) & Standard
Terminal Approach Route (STARs)
•
Vertical navigation Barometric sensors
•
Heading vectors  Assigned by traffic controller
En Route Navigation
• Leads from the origin to the destination and alternate
destinations
• Airways are defined by navaids over the land and by
lat/long over water fixes
• The width of airways and their lateral separation
depends on the quality of the navigation system
• From 1990s use of GPS has allowed precise navigation
• In the US en-route navigation error must be less than 2.8
nm over land & 12 nm over ocean
Approach Navigation
• Begins at acquisition of the landing aid until the airport
is in sight or the acrft is on the runway, depending on the
capabilities of the landing aid
• Decision height (DH): altitude above the runway at
which the approach must be aborted if the runway is not
in sight
– The better the landing aids, the lower the the DH
– DHs are published for each runway at each airport
– An acrft executing a non precision approach must
abort if the runway is not visible at the minimum
descent altitude (typically=700 ft above the runway)
Landing Navigation
• Begins at the DH ends when the acrf exits the runway
• Navigation may be visual or navigational set’s may be
coupled to a autopilot
• A radio altimeter measures the height of the main
landing gear above the runway for guiding the flare
• The rollout is guided by the landing aid (e.g. the ILS
localizer)
Missed Approach
• Is initiated at the pilot’s option or at the traffic
controller’s request, typically because of poor visibility.
And alignment with the runway
• The flight path and altitude profile are published
• Consists of a climb to a predetermined holding fix at
which the acrf awaits further instructions
• Terminal area navaids are used
VHF Omnidirectional
Range(VOR)
•
Receiver characteristics
– The airborne equipment comprises a horizontally polarized receiving antenna &
a receiver. This receiver detects the 30 Hz amplitude modulation produced by
the rotating pattern & compares it with the 30 Hz frequency-modulated
reference.
– Fig 4.16
Doppler VOR
• Doppler VOR applies the principles of wide antenna aperture to the
reduction of site error
• The solution used in US by FAA involves a 44-ft diameter circle of
52 Alford loops, together with a single Alfrod loop in the center
• Reference phaseThe central Alford loop radiates an omnidirectional continuous wave that is amplitude modulated at 30 Hz
• The circle of 52 Alford loops is fed by a capacitive commutator so as
to simulate the rotation of a single antenna at a radius of 22ft
• Rotation is at 30rps, & a carrier frequency 9960 Hz higher than that
in the central antenna is fed to the commutator
• With 44-ft diameter & a rotation speed of 30 rps, the peripheral
speed is on the order of 1400 meters per second, or 480 wavelengths
per second at VOR radio frequencies
Distance-Measuring Equipment
(DME) (1)
• DME is a internationally
standard pulse-ranging
system for acft,
operating in the 960 to
1215 MHz band. In the
US in 1996, there were
over 4600 sets in use by
scheduled airlines and
about 90,000 sets by GA
DME Operation
Distance-Measuring Equipment
(DME) (2)
• The acft interrogator transmits pulses on one of 126
frequencies, spaced 1 MHz apart, in the 1025 to 1150
MHz band. Paired pulses are used in order to reduce
interference from other pulse systems. The ground
beacon(transponder) receives these pulses & after a 50
sec fixed delay, retransmits them back to the acft. The
airborne automatically compares the elapsed time
between transmission and reception, subtracts out the
fixed 50 sec delay, & displays the result on a meter
calibrated in nautical miles.
Hyperbolic Systems
• Named after the hyperbolic lines of position (LOP) that
they produce rather than the circles
–
–
–
–
Loran-C
Omega
Decca
Chayka
Measure the time-difference
between the signal from two or
more transmitting station
Measure the phase-difference
between the signal transmitted
from pairs of stations
Long-Range Navigation(Loran)
•
•
A hyperbolic radio-navigation system beginning before
outbreak of WW II
1. Uses ground waves at low frequencies, thereby
securing an operating range of over 1000 mi,
independent of line of sight
2. Uses pulse technique to avoid sky-wave
contamination
3. A hyperbolic systemit is not subject to the site
errors of point-source systems
4. Uses a form of cycle (phase) measurements to
improve precision
All modern systems are of the Loran-C variety
Long-Range Navigation (Loran-C)
• Is a low-frequency radio-navigation aid operating in the radio
spectrum of 90 to 110 kHz
• Consists of at least three transmitting stations in groups forming
chains
• Using a Loran-C receiver, a user gets location information by
measuring the very small difference in arrival times of the pulses for
each Master -Secondary pair
• Each Master-Secondary pair measurement is a time difference. One
time difference is a set of points that are, mathematically, a
hyperbola. Therefore, position is the intersection of two hyperbolas.
Knowing the exact location of the transmitters and the pulse
spacing, it is possible to convert Loran time difference information
into latitude and longitude
Loran-C (2)
Signal shape
Position determination
Loran-C (2)
NAVSTAR Global Positioning
System
• GPS was conceived as a U.S. Department of Defense (DoD) multiservice program in 1973, bearing some resemblance to & consisting
of the best elements of two predecessor development programs:
– The U.S. Navy’s TIMATION program
– The U.S. Air Force’s program
• GPS is a passive, survivable, continuous, space-based system that
provides any suitably equipped user with highly accurate threedimensional position, velocity, and time information anywhere on or
near the earth
Principles of GPS & System
Operation
• GPS is basically a ranging system, although precise Doppler
measurements are also available
• To provide accurate ranging measurements, which are time-ofarrival measurements, very accurate timing is required in the
satellite. (t<3 nsec)
– GPS satellite contain redundant atomic frequency standards
• To provide continues 3D navigation solutions to dynamic users, a
sufficient number of satellite are required to provide geometrically
spaced simultaneous measurements.
• To provide those geometrically spaced simultaneous measurements
on a worldwide continues basis, relatively high-altitude satellite
orbits are required
GPS Satellite System Configuration
• Consists of three segments
– Space segment
– Control segment
– User segment
GPS System Configuration
General System Characteristics
• The GPS satellites are in approximately 12 hour
orbits(11 hours, 57 minutes, and 57.27 seconds) at an
altitude of approximately 11,000 nmi
• The total number of satellite in the constellation has
changed over the years ~24
• Each satellite transmits signals at two frequencies at LBand to permit ionosphere refraction corrections by
properly equipped users
General System Characteristics
• The GPS satellites are in approximately 12 hour
orbits(11 hours, 57 minutes, and 57.27 seconds) at an
altitude of approximately 11,000 nmi
• The total number of satellite in the constellation has
changed over the years ~24
• Each satellite transmits signals at two frequencies at LBand to permit ionosphere refraction corrections by
properly equipped users
The GPS segments
Segments
Input
Function
Product
Space
•Satellite
commands
•Provide atomic time scale
•PRN RF signals
•Generate PRN RF signals
•Navigation message
•Navigation
messages
•Store & forward navigation message
•Telemetry
•PRN RF signals
•Estimate time & ephemeris
•Navigation message
•Telemetry
•Predict time & ephemeris
•Satellite commands
•Universal
coordinated
•Manage space assets
Control
•Time(UTC)
User
•PRN RF signals
•Navigation
messages
•Solve navigation equations
•Position, velocity, & time
GPS Space Segment
• The space segment is comprised of the satellite constellation made
up of multiple satellites. The satellite provides the basic navigation
frame of reference and transmit the radio signals from which the
user can collect measurements required for his navigation solution
• Knowledge of the satellites’ position and time history (ephemeris
and time) is also required for the user’s solutions.
• The satellite also transmit that information via data modulation of
the signals
•CDMA @ 1.2 to 1.5 GHz
•LB and “P” “C”
•Very accurate atomic clocks ~< nanosecond
GPS Control Segment
• Consists of three major elements
– Monitor stations that track the satellites’ transmitted
signals & collect measurements similar to those that
the user collect for their navigation
– A master control station that uses these
measurements to determine & predict the satellites’
ephemeris & time history and subsequently to upload
parameters that the satellite modulate on the
transmitted signals
– Ground station antennas that perform the upload
control of the satellite
User Segment
• Is comprised of the receiving equipment and processors
that perform the navigation solution
• These equipments come in a variety of forms and
functions, depending upon the navigation application
Basics of Satellite Radio
Navigation (1)
•
Different types of user equipments solve a basic set of equations for their solutions,
using the ranging and/or range rate (or change in range) measurements as input to a
least-squares, or a Kalman filter algorithm.
•
Fig 5.2
Ranging satellite
radio-navigation
solution
Basics of Satellite Radio
Navigation (2)
•
The measurements are not range & range rate (or change in range), but quantities
described as pseudorange & pseudorange rate (or change in pseudorange). This is
because they consisit of errors, dominated by timing errors, that are part of the
solution. For example, if only ranging type measurements are made, the actual
measurement is of the form
PRi  Ri  ct si  ctu   PRi
PRi is the measured peseudorange from satellite i
Ri is the geometric range to that satellite, t siis the clock error in satellite i, tuis the
user’s clock error, c is the speed of light and  PRi is the sum of various correctable
or uncorrectable measurements error
Basics of Satellite Radio
Navigation (3)
• Neglecting for the moment the clock and other measurement errors,
the range to satellite i is given as
Ri 
 X si  X u 2  Ysi  Yu 2  Z si  Zu 2
X si , Ysi andZ siare the earth-centered, earth fixed (ECEF) position
components of the satellite at the time of transmission and
X u , Yu andZ uare the ECEF user position components at that time
Atmospheric Effects on Satellite
Communication
• Ionosphere:
– Shell of electrons and electrically charged atoms & molecules
that surrounds the earth
– Stretching from 50km to more than 1000km
– Result of ultraviolet radiation from sun
– Free electrons affect the propagation of radio waves
– At frequency below about 30 MHz acts like a mirror bending the
radio wave to the earth thereby allowing long distance
communication
– At higher frequencies (satellite radio navigation) radio waves
pass through the ionosphere
System Accuracy
• GPS provides two positioning services, the Precise Positioning
Service (PPS) & the Standard Positioning Service (SPS)
• The PPS can be denied to unauthorized users, but SPS is available
free of charge to any user worldwide
• Users that are crypto capable are authorized to use crypto keys to
always have access to the PPS. These users are normally military
users, including NATO and other friendly countries. These keys
allow the authorized user to acquire & track the encrypted precise
(P) code on both frequencies & to correct for international
degradation of the signal
– WAAS < 3 m horizontal
< 7.5 m vertical
– GPS 15m
Automatic Landing Systems (1)
•
1.
Air carrier acft that are authorized for precisionapproach below category II must have automatic
landing (auto-land) system.
Guidance & control requirements by FAA
– For category II: the coupled autopilot or crew hold
the acft within the vertical error of +or- 12 ft at the
100ft height on a 3deg glide path
– For category III: the demonstrated touchdown
dispersions should be limited to 1500ft
longtudinally & -or+ 27ft laterally
Automatic Landing Systems (2)
Flare Guidance

During the final approach the glide-slope gain in
the auto-land system is reduced in a programmed
fashion. Supplementary sensors must supply the
vertical guidance below 100ft
3.
Lateral Guidance

Tracking of the localizer is aided by heading (or
integral-of-roll), roll, or roll-rate signals supplied to
the autopilot and by rate & acceleration data from
on-board inertial system
2.
Instrument Landing System(ILS)
(1)
• Is a collection of radio transmitting stations used to guide acft to a
specific runway.
• In 1996 nearly 100 airports worldwide had at least one runway
certified to Category III with ILS
• More than one ILS in high density airports
• About 1500 ILSs are in use at airports throughout the US
Instrument Landing System(ILS)
(2)
• ILS typically includes:
– The localizer antenna is centered on the runway beyond the stop end to
provide lateral guidance
– The glide slope antenna, located beside the runway near the threshold
to provide vertical guidance
– Marker beacons located at discrete positions along the approach path;
to alert pilots of their progress along the glide-path
– Radiation monitors that, in case of ILS failure alarm the control tower,
may shut-down a Category I or II ILS, or switch a Category III ILS to
backup transmitters
ILS Guidance Signals (1)
• The localizer, glide slope, and marker beacons radiate continues
wave, horizontally polarized, radio frequency, energy
• The frequency bands of operation are
– Localizer, 40 channels from 108-112 MHz
– Glide slop, 40 channels from 329-335 MHz
– Marker beacons, all on a signal frequency of 75 MHz
ILS Guidance Signals (2)
•
•
•
The localizer establishes a radiation pattern in space that provides a
deviation signal in the acft when it is displaced laterally from the vertical
plane containing the runway centerline
The deviation signal drives the left-right needle of the pilot’s cross-pointer
display & may be wired to the autopilot/flight-control system for coupled
approaches
The deviation signal is proportional to azimuth angle usually out to 5 deg or
more either side of the center line
ILS Guidance Signals (3)
Sum & difference
radiation patterns
for the course
(CRS) &
clearance (CLR)
signals of a
directional
localizer array
The Localizer (1)
•
The typical localizer is an array usually located 600 to 1000 ft beyond the stop end
antenna of the runway
•
The array axis is perpendicular to the runway center line
Log-periodic
dipole antenna
used in many
localizer arrays
The Localizer (2)
Category IIIB localizer
The Glide Slope (1)
•
•
There are five different of glide-slope arrays in common use; three are
image systems & two are not
Image arrays depend on reflections from level ground in the direction of
approaching acft to form the radiation pattern
– The three image systems are null-referenced system, with two antennas
supported on a vertical mast 14 & 28 ft above the ground plane
– The sideband-reference system, with two antennas 7 and 22ft above the ground
plane
– The capture-effect system, with 3 antennas 14, 28, and 42 ft above the ground
plane
The Glide Slope(2)
Category IIIB
capture-effect
glideslope & Tasker
transmissometer
The Glide Slope (3)
Glide-slope pattern
near the runway. DDM
counters are
symmetrical around
the vertical, but signal
strength drops rapidly
off course
The Glide Slope (4)
•
The cable radiators of the end-fire array are installed on stands 40 in. high & are site
alongside the runway near desired touchdown point
•
Fig 13.10
•
Fig 13.11
Standard end-fire glide-slope
system layout
Front slotted-cable radiator
of an end-fire glide slope
ILS Marker Beacons (1)
• Marker beacons provide pilot alerts along the approach path
• Each beacon radiates a fan-shaped vertical beam that is
approximately +or- 40deg wide along the glide path by +-85deg wide
perpendicular to the path
– The outer marker(OM) is placed under the approach course near the
point of glide-path intercept & it is modulated with two 400 Hz Morsecode dashed per second
ILS Accuracy Allocation
Standard lighting Pattern
•
Airports at which Category II landings are permitted must be equipped with the
standard lighting pattern
Category III
runway
configuration
The Mechanics of Landing (1)
1.
•
•
The approach
Day & night landings are permitted under visual flight rules (VFR) when
the ceiling exceeds 1000 ft & the horizontal visibility exceeds 3 mi, as
juged by the airport control tower
In deteriorated weather, operations must be conducted ubder Instrument
Flight Rules (IFR)
–
An IFR approach is procedure is either non-precision (lateral guidance only)
or precision (both lateral & vertical guidance signals)
•
Category I, II, and III operations are precision-approach procedures
The Mechanics of Landing (2)
• An afct landing under IFR must transition from cruising flight to
the final approach along the extended runway center line by using
the standard approach procedures published for each airport
• Approach altitudes are measured barometrically, and the transition
flight path is defined by initial & final approach fixes (IAF & FAF)
using VOR, VOR/DME
• Radar vectors may be given to the crew by approach control
The Mechanics of Landing (3)
•
From approximately 1500 ft above runway, a precision approach is guided
by radio beams generated by ILS. Large acft maintain a speed of 100 to
150 knots during descent along the glide path beginning at the FAF (outer
marker)
•
The glide-path angle is set by obstacle-clearance and noise-abatement
considerations with 3 deg as the international civil standard
•
The sink rate is 6 to 16 ft/sec, depending on the acft’s speed & on headwinds
The Mechanics of Landing (4)
•
The ICAO standard: glide path will cross the runway threshold at a height
between 50 & 60 ft. Thus, the projected glide path intercepts the runway
surface about 1000 ft from the threshold.
Wheel path
for instrument
landing of a
jet acft
Wide Area Augmentation
System(WAAS)
•
•
•
Developed by the FAA in parallel with European Geostationary
Navigation Overlay Service (EGNOS) & Japan MTSAT SatelliteBased Augmentation System
A safety-critical system consisting of a signal-in-space & a ground
network to support en-route through precision approach air
navigation
The WAAS augments GPS with three services all phases of flight
down to category I precision approach
1. A ground integrity broadcast that will meet the Required
Navigation Performance (RNP)
2. Wide area differential GPS (WADGPS) corrections that will
provide accuracy for GPS users so as to meet RNP accuracy
requirements
3. A ranging function that will provide additional availability &
reliability that will help satisfy the RNP availability
requirements
WAAS Concept (1)
WAAS Concept (2)
Inmarsat-3 four ocean-region deployment
showing 5deg elevation contours
WAAS Concept (3)
• Uses geostationary satellite to broadcast the integrity &
correction data to users for all of the GPS satellites
visible to the WAAS network
• A slightly modified GPS avionics receiver can receive
these broadcasts
• Since the codes will be synchronized to the WAAS
network time, which is the reference time of the
WADGPS corrections, the signals can also be used for
ranging
WAAS Concept (4)
• A sufficient number of GEOs provides enough
augmentation to satisfy RNP availability & reliability
requirements
• In the WAAS concept, a network of monitoring stations
(wide area reference stations, WRSs) continuously track
the GPS (&GEO) satellite & rely the tracking
information to a central processing facility
• # Geo  2 minimum & 4 desired
WAAS Concept (5)
• The central processing facility (wide area master station,
WMS)m in turn, determines the health & WADGPS
corrections for each signal in space & relays this
information, via the broadcast messages, to the ground
earth station (GESs) for uplink to the GEOs
• The WMS also determines & relays the GEO ephemeris
& clock state messages to the GEOs
Surveillance
GPS+WAAS+DL = ADS-B
Automatic Dependent Surveillance Broadcast (ADS-B)
• A technology designed to address both airspace and
ground-based movement needs.
• Collaborative decision making is possible through ADSB surveillance information available to both ATC and
aircrews.
• ADS-B combined with predictable, repeatable flight
paths allow for increased airspace efficiencies in high
density terminal areas or when weather conditions
preclude visual operations.
• Additionally, ADS-B allow for enhanced ground
movement management (aircraft and vehicles) and
improved airside safety
ADS-B
A/A
A/G
AAC
AAIS
AATT
ACARS
ADAS
ADS
ADS-B
AFSS
AIM
AIRMET
AM
AMS
AMS(R)S
AMSRS
AMSS
AOC
ARINC
ARTCC
ASIST
ASOS
ASR-9
ASR-WSP
ATC
ATC DSS
ATCSCC
ATCT
ATIS
ATM
ATN
ATS
ATSP
AvSP
AWIN
AWIN
AWOS
BER
BER
CD
CDM
CDMA
CDTI
Air to Air
Air to Ground
Airlines administrative communications
Advanced Aircraft Information System
Advanced Air Transportation Technologies
aircraft communications addressing and reporting system
AWOS data acquisition system
Automatic Dependent Surveillance
Automatic Dependent Surveillance - Broadcast
automated flight service station
Aeronautical Information Manual
Airman's Information Manual
amplitude modulation
acquisition management system
Aeronautical Mobile Satellite (Route) Service
Aeronautical Mobile Satellite (Route) Service
Aeronautical Mobile Satellite System
airline operations center
Aeronautical Radio Inc.
Air route traffic control center
Aeronautics Safety Investment Strategy Team
automated surface observing system
airport surveillance radar- nine
airport surveillance radar- weather system processor
Air Traffic Control
Air Traffic Control Decision Support Systems
Air traffic Control System Command Center
Air Traffic Control Tower
Automatic Terminal Information Service
air traffic management
Aeronautical Telecommunication Network
air traffic services
air traffic service provider
Aviation Safety Program
Aviation Weather Information Services
Aviation Weather Information
automated weather observing system
bit error rate
Bit Error Rate
compact disk
Collaborative Decision Making
Code Division Multple Access
Cockpit Display of Traffic Information
CNS
CONOPS
CONUS
COTS
CP
CPDLC
CPU
CSA
CSMA
CTAS
CWA
D8PSK
DA
DAG-TM
DoD
DOT
DOTS
DSR
EMC
EMI
FAA
FANS
FANS 1/A
FAR
FAR
FBO
FBWTG
FCC
FDM
FDP
FEC
FEDSIM
FFP1
FIS
FL
FMS
FOQA
FP
FSS
FSS
G/G
G/T
GA
Communications, Navigation and Surveillance
concept of operations
Continental United States
Commericial Off-The-Shelf
conflict probe
Controller-Pilot Data Link Communications System
central processing unit
communications system architecture
Carrier Sense Multiple Access
Center-TRACON Automation system
Center Weather Advisory
Differential Eight-Level Phase Shift Keying
descent advisor
Distributed Air/Ground Traffic Management
Department of Defense
Department of Transportation
dynamic ocean tracking system
Display System Replacement
Electromagnetic Capability
Electromagnetic Interference
Federal Aviation Administration
Future Air Navigation System
future air navigation system
Federal Air Regulations
Federal Aviation Regulation
Fixed Base Operator
FAA bulk weather telecommunications gateway
Federal Communications Commission
flight data management
flight data processor
Frame error check
Federal Systems Integration and Management Center
Free Flight Phase 1
Flight Information Service
flight level
Flight Management System
Flight Operational Quality Assurance
flight plan
flight service station
Fixed Satellite Service
Ground-to-Ground
Gain to System Noise Temperature Ratio
General Aviation
GEO
GPS
HARS
HF
HF
ICAO
IF
IFE
IFR
IFR
IMC
IOC
IP
ITWS
IWF
KBPS
LAN
LEO
LLWAS
MBO
MDCRS
MEO
METAR
MFD
MOC
MOPS
MSS
MTBF
N/A
NAS
NAS RD
NASA
NATCA
NAWIS
NESDIS
NEXCOM
NEXRAD
NLDN
NOTAM
NWS
NWS/OSO
OASIS
OAT
ODAPS
PFAST
Geostationary Earth Orbit
Global Positioning System
high altitude route system
high frequency
High Frequency
International Civil Aviation Organization
interface
In-Flight Entertainment
Instrument flight rules
Instrument Flight Rules
instrument meteorological conditions
initial operating capability
Internet Protocol
Integrated terminal weather system
Integrated Weather Forecast
Kilobites Per Second
Local Area Network
Low Earth Orbit
Low-level wind shear alert system
Military Base Operations
Meteorological Data Collection and Reporting System
Medium Earth Orbit
meteorological aviation report
Multifunctional Display
Mission Operational Control
minimum operational performance standards
Mobile Satellite Service
Mean Time Between Failure
Not Applicable
National Airspace System
NAS Requirements Document
National Aeronautics and Space Administration
National Air Traffic Controllers Association
National Aeronautics and Space Administration
national environmental satellite, data, and information service
Next Generation A/G Communications System
next generation radar
national lightning detection network
Notice to Airman
National Weather Service
National Weather Service/Office of Systems Operations
operational and supportability implementation system
Office of Advanced Technology
oceanic display and planning system
passive final approach spacing tool
PIREP
PIREPS
PSK
QAM
QoS
RA
RCP
RD
RF
RTCA
RTO
RVR
SAIC
SAR
SARP
SATCOM
SIGMET
SOW
SPECI
SSR
STC
SUA
TAF
TBD
TDWR
TFM
TIS
TM
TMS
TRACON
TRM
TWDL
TWEB
TWIP
VDL
VFR
VHF
VOR
WAAS
WAN
WARP
WJHTC
WMSCR
Wx
WxAP
Pilots Report
pilot reports
Phase Shift Keying
Quadrature Modulation
Quality of Service
resolution advisory
Required Communications Performance
requirements document
Radio Frequency
RTCA, Incorporated
Research Task Order
runway visual range
Science Applications International Corporation
Search and Rescue
Standards and Recommended Practices
Satellite Communications
Significant Meteorological Information
Statement of Work
Special Weather Report
Secondary Surveillance Radar
supplemental type certificate
Special Use Air Space
Terminal Aerodrome Forecast
to be determined
terminal Doppler weather radar
traffic flow management
Traffic Information Services
traffic management
traffic management system
Terminal Radar Approach Control Facility
Technical Reference Model
Two-Way Data Link
Transcribed Weather Broadcast
terminal weather information for pilots
very high frequency digital link
visual flight rules
very high frequency
VHF-Omni Directional Range
Wide Area Augmentation System
Wide Area Network
weather and radar processor
William J. Hughes Technical Center
weather message switching center replacement
Weather
weather accident prevention