Canada's history both in aviation and in satellite communications development spans several decades. The introduction of aeronautical mobile satellite communications will serve our requirements for airspace management in areas not served by line-of-sight radio and radar facilities. The ensuing improvements in air safety and operating efficiency are eagerly awaited by the aviation community

Sim, Dave

English

NASA Technical Reports Server

Aeronautical Mobile Satellite Service:
Air Traffic Control Applications
Dave Sim
Transport Canada AANFBL
Ottawa, Ontario
KIA 0N8 CANADA
Phone: 613-998-4870
ABSTRACT
Canada's history both in
aviation and in satellite
communications development spans
several decades. The introduction
of aeronautical mobile satellite
communications will serve our
requirements for airspace
management in areas not served by
line-of-sight radio and radar
facilities. The ensuing
improvements in air safety and
operating efficiency are eagerly
awaited by the aviation community.
AVIATION IN CANADA
Canadians reflect with pride
upon our aviation heritage. We
recall our triumphs in developing
aircraft to meet our varied needs,
including the de Havilland Beaver,
Otters, Dash-7 and Dash-8, the
AVRO Jetliner and the Arrow, and
the Canadair Challenger corporate
jet. Canadian aviators have
traversed the vastness of our
nation, bringing travellers, mail
and cargo to the most isolated
points of human settlement.
There are over twenty eight
thousand civil aircraft registered
in Canada today. Twenty-five
percent of these are registered
for commercial operation, and of
these some five hundred and fifty
are classed as heavy commercial,
over 13,500 kilograms. Although
ninety percent of our population
occupies the ten percent of our
land along the Canada - United
States border, and is well served
by major airlines, the aviation
community acknowledges the
immense, sparsely populated
northern region, with many
isolated settlements. For many
Canadians, the only regular
contact with the world outside
their community is the 'sched
flight' which brings them mail,
groceries, and medical attention.
For most of us, though,
domestic and international air
carriers provide the travel
services we need, to fly to
another city for a business
meeting, or to warmer climates for
a relaxing holiday. Transport
Canada's Aviation Industry Review I
reports that over sixty-five
million passengers passed through
Canadian airports in 1988,
evidence of the popularity of air
travel.
For airline, commercial and
private pilots alike, there are
two fundamental requirements for
safe and efficient flying - the
ability to navigate from place to
place, and the ability to
communicate with ground support
facilities.
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International Mobile Satellite Conference, Ottawa, 1990
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WHY AIR TRAFFIC CONTROL?
Airspace is a resource which
must be managed to maintain the
highest level of safety to the
public. It is necessary to
control the movement of air
traffic where conflicts may occur,
and where airspace and airport
facilities must be shared.
Transport Canada is the federal
government department responsible
for regulating and managing air
traffic in Canada's domestic
airspace. Transport Canada
provides communications,
navigation aids, and surveillance
systems for air traffic control.
As well, the International Civil
Aviation Organization has
delegated to Canada and Britain,
the responsibility to provide air
traffic services for aircraft
traversing the northern portion of
the North Atlantic Ocean.
COMMUNICATIONS, NAVIGATION
AND SURVEILLANCE
Pilots must be able to
communicate - to express and
acknowledge instructions, to
indicate intentions and
threatening situations, and to
report their locations. They must
be able to navigate - to know
where they are and to establish
routes between locations. They
must come under surveillance, so
that air traffic control agencies
are aware of their positions and
can safely manage the traffic
within their domains.
In southern Canada, aircraft
utilize double-sideband, amplitude
modulated, very high frequency
(VHF) radios for communications,
where ground facilities are within
the line-of-sight range of about
three hundred kilometres. Ground-
based radio aids to navigation and
surveillance radar coverage
coincide with VHF radio coverage.
These three elements of
communication, navigation and
surveillance systems allow for the
efficient aircraft operations in
more densely populated areas.
During flights over isolated
areas such as the Canadian North
or the oceanic regions,
communication over several
thousand kilometres is possible
with single-sideband, high
frequency (HF) radios. Since HF
radio propagation is subject to
fading, the quality of these links
may vary from excellent to barely
intelligible. Yet, HF radio
remains our standard for long
distance aeronautical
communications. Ground based
navigation aids are not available,
and radar surveillance is replaced
by voice radio position reports
from aircrews. It is in such
areas that satellite services will
offer major improvements in air
traffic control.
CANADA IN SPACE
In 1959, as Canadians watched
SPUTNIK cross our night sky, we
committed ourselves to join the
race for space. A milestone was
set in 1962 with the launch of the
first Canadian satellite, Alouette
i. From this early work in space
technology, Canada has maintained
a leading role in the development
and implementation of space-based
communications. The family of
Anik satellites has established C
and Ku-band networks for fixed
land services. The launching of
MSAT in 1993 will introduce
domestic L-band mobile satellite
services.
INITIAL AERONAUTICAL EXPERIMENTS
Clearly, our capabilities in
International Mobile Satellite Conference, Ottawa, 1990
571
satellite communications should
combine with our requirements for
long range aeronautical
communications to form an air
traffic control communications
network. Indeed, there is a
global requirement for such a
system, for air traffic is world
wide. Let us summarize the
efforts have been undertaken to
date.
Initial satellite
communications flight trials were
undertaken early in the 1960s.
The International Civil Aviation
Organization (ICAO) established a
panel of experts knows as ASTRA -
the Application of Space
Techniques Related to Aviation.
From the work of this panel came
the Aerosat program, undertaken by
a consortium of Canada, the United
States, and the forerunner of the
European Space Agency. The
Aerosat program was comprised of
a space segment and a coordinated
ground segment. The launch of the
satellite was scheduled for 1979,
but the program was terminated in
1976. The international fuel
crisis of the early 1970s caused
a withdrawal of funding for the
project. It was agreed, however,
that the investigations into the
potential uses of satellites by
civil aviation should continue, so
an ICAO committee known as ARC -
the Aviation Review Committee, was
formed.
From the Aviation Review
Committee studies between 1978 and
1982 came the recommendation for
the use of a shared space segment
for air-ground data link
communications. Shared access
avoids the high costs associated
with a dedicated satellite, making
satellite services more affordable
for the aviation community. In
1983, ICAO accepted a second ARC
recommendation, and formed the
Special Committee on the Future
Air Navigation Systems, knows as
the FANS Committee. The FANS
Committee has identified, studied
and advised on the development of
new aeronautical communications,
navigation and surveillance
systems for use over the next
twenty five years, z As suggested
by the FANS Committee, ICAO has
approved the Aeronautical Mobile
Satellite Services Panel which is
developing Standards and
Recommended Practices (SARPS) for
aeronautical satellite
communications.
SYSTEM ARCHITECTURE
A system architecture has been
defined which will provide both
data link communications for air
traffic services and aeronautical
operations control, and the
capacity to accommodate high data
rates, digital voice and passenger
correspondence. The RF links from
aircraft to satellite at 1646.5 -
1656.5 MHz and from satellite to
aircraft at 1545.0 - 1555.0 MHz
will provide for several
categories of communications which
will be assigned different
priorities. These aeronautical
frequencies are extensions to
existing L-band mobile services
which are available through
INMARSAT satellites from Teleglobe
Canada. INMARSAT has defined the
system in their Aeronautical
System Definition Manual. 3 The
airline industry is applying the
system definition in ARINC
Characteristic 741. 4 Regional
systems, such as MSAT, will
service areas not covered by
INMARSAT's global beams.
SATCOM APPLICATIONS
Civil aviation authorities,
airlines and satellite service
providers are presently
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International Mobile Satellite Conference, Ottawa, f990
undertaking trials to establish
operational requirements and
procedures for satellite
communications. Many applications
are being investigated, including
direct controller to pilot data
communications, automatic aircraft
position reporting, and air
traffic services general message
handling.
When aircraft journey beyond
the range of VHF radio coverage,
HF radio is used to communicate
between air traffic controllers
and aircrews. The controller no
longer speaks directly to the
crews, as messages are relayed
through HF radio operators. The
variable quality of HF reception
and the extra link in the
communications chain causes delays
in aircraft position reporting and
in requesting and granting
clearances for manoeuvres. The
uncertainties which result lead to
the allocation of large volumes of
airspace for each aircraft to
insure that no conflict can exist.
This generous use of airspace
limits the ability to fly fuel
efficient direct routes. Over the
North Atlantic, several hundred
daily flights must compete for
slots in the airway track system
which dictates a sixty mile
lateral separation between
aircraft.
Some of the information which
is periodically reported by
aircrews is the location of their
craft in space. Since radar
coverage in unavailable, this
position reporting is the
controller's means of managing
traffic within his airspace.
Because of delays, this data may
not be up-to-date. The planned
implementation of Automatic
Dependent Surveillance will
provide automatic, regular
position reporting by satellite
data link from an aircraft's
flight computers to the
controller. As aircraft
navigation accuracy improves with
the expansion of the Global
Positioning Satellite system
(GPS), the controller will have at
hand information as accurate as
surveillance radar position data.
CANADIAN ACTIVITIES
Transport Canada has
established a program to
investigate the application of
aeronautical satellite services
for direct communications, for
position reporting and for other
data i ink messages. The
development of ICAO Standards and
Recommended Practices is being
supported. Canadian manufacturers
are under contract to develop
satcom avionics with advanced
modulation schemes. Clearance
information is delivered by VHF
data link to eastbound trans-
Atlantic aircraft from the Gander,
Newfoundland, Oceanic Control
Centre.
In an experiment with Air
Canada, several Boeing 767
aircraft are tracked across North
American airspace using automatic
position reporting through
existing VHF data link facilities.
With the introduction of Boeing
747-400 aircraft with satcom
avionics in 1991, it is planned to
extend this experiment to include
North Atlantic flights which will
access INMARSAT and Teleglobe
Canada facilities. As part of
this preliminary Automatic
Dependent Surveillance work, a
message processor and graphical
situation display are being
developed for trials at the Gander
Oceanic Control Centre. This
system, to be completed by the
Fall of 1990, will process and
display position reports
transmitted from aircraft
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navigation computers and will
enable direct message
communications between air traffic
controllers and aircraft flight
deck displays. Position reports
will automatically be compared to
flight plans to check for
conformity to assigned routes.
An agreement is in place
between Transport Canada and the
United States Department of
Transportation - Federal Aviation
Administration, to share
information on the development of
aeronautical mobile satellite
services, and to cooperate in pre-
operation Automatic Dependent
Surveillance trials over both the
Pacific and Atlantic oceans.
Development work now ongoing in
several ICAO member states will
lead to operational Automatic
Dependent Surveillance and direct
controller to pilot communications
by the second half of this decade.
Canadian agencies will interface
with Teleglobe and the European
consortium SITA for international
satellite traffic over INMARSAT
spacecraft, and with MSAT service
providers for domestic
communications.
introduction of operational
satellite services for air traffic
control will be one of the most
important advances of the past
forty years of aviation.
REFERENCES
i. Transport Canada. 1988.
Aviation Industry Review 1988.
2. Internatlonal Civil Aviation
Organization. 1988. Future Air
Navigation Systems - FANS/4
Report.
3. INMARSAT. 1990. Aeronautical
System Definition Manual, Module
1: System Definition.
4. Aeronautical Radio Inc. 1990.
ARINC Characteristic 741:
Aviation Satellite Communication
System.
WHAT DO WE GAIN?
The benefits of satellite
communications to the aviation
community will be substantial.
Aviation safety, always the prime
concern, will improve as air
traffic controllers and pilots
exchange reliable and timely
information necessary for airspace
management. The efficiency of
airline operations will improve as
delays and ambiguity are reduced,
and routing and scheduling are
optimized.
Aeronautical communications is
about to enter the space age. The
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International Mobile Satellite Conference, Ottawa, t990


Aeronautical mobile satellite service: Air traffic control applications

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