INMARSAT’s Role in the Global Maritime Distress and Safety System
(GMDSS INMARSAT)
The introduction of the Global Maritime Distress and Safety System (GMDSS) on 1 February
1992 marked the most important change in maritime safety since the advent of radio in
1899. The proven benefits of satellite communications, with high reliability, simple
operation and multi -modal capabilities, cannot be ignored and are, in fact, being
enthusiastically welcomed on ships of all kinds for their business and social features, as well
as the serious business of distress and safety communications.
Beginning
1
February
1992,
the
use
of
modern
satellite
technology
has
resulted
in a
total
transformation
of
the
maritime
distress
communications
system.
Whereas the old system for maritime distress and safety communications relied primarily
on the capability of a ship in distress to alert only other ships for assistance, the GMDSS
emphasizes the ability to alert shore -based search and rescue authorities, in addition to
shipping in the immediate vicinity, in order to achieve co -coordinated assistance and rescue
operations.
The GMDSS is a better, simpler and more efficient distress and safety communications
system. It relies heavily on well-proven automation and makes extensive use of Inmarsat's
satellites for rapid and reliable communications. The GMDSS applies to all cargo ships of
300 tonnes gross tonnage and upwards and to all passenger ships on international voyages
subject to the SOLAS 1974 Convention, as amended.
GMDSS provision via Inmarsat maritime safety services is shown in diagram A below:
Inmarsat's key role in the GMDSS can be summarized as follows:
• Inmarsat provides the space segment necessary for instant and reliable distress and
safety satellite communications for the maritime community.
• Inmarsat offers three satellite communications systems, designed to provide most of
the gmdss medium - and long-range functions: Inmarsat-A, Inmarsat-B and Inmarsat-
C.
• Inmarsat also provides a valuable distress alerting facility through Inmarsat-E, which is
an L-band Emergency Position Indicating Radio Beacon (epirb).
DISTRESS ALERTING: SHIP-TO-SHORE
Inmarsat-A/B:
Initiated at the press of a dedicated button on the vessel's Ship Earth Station (SES),
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distress alerts are given priority access in the Inmarsat system. The distress alert is then
routed, usually automatically, through an Inmarsat Land Earth Station (LES) to an
associated Rescue Coordination Centre (RCC) ashore.
Inmarsat-C:
Also initiated at the press of a button, a distress alert from the vessel's SES ensures the
highest priority for automatic routing through the Inmarsat system to an RCC.
Inmarsat-E:
“Any delay in receiving a distress alert can mean the difference between rescuing survivors
and recovering bodies”
(Steve Huxley, GMDSS District Staff Officer, Falmouth MRCC)
An Inmarsat L-band satellite EPIRB is an alternative means for sending the distress alert.
EPIRB transmissions can be initiated manually when the EPIRB is out of the cradle,
remotely from a remote control unit (RCU) when the EPIRB is in the cradle, or
automatically when the EPIRB floats free if a ship sinks. The time taken from transmitting
an Inmarsat-E distress alert and its receipt at an RCC is typically less than one minute.
DISTRESS ALERTING: SHORE-TO-SHIP
Initiated by RCCs ashore, ships are alerted through automatic receipt of distress alert
relays transmitted via the International SafetyNET Service of the Enhanced Group Call
(EGC) capabilities of the Inmarsat-C system. Ordinary telex group calls to Inmarsat-A or -
B SESs can also be used to supplement this.
SEARCH AND RESCUE COORDINATION COMMUNICATIONS
Inmarsat terminals on board ships can be utilised for originating and receiving
communications with other ships involved in distress incidents and for communications with
RCCs. When multiple ships are involved, the EGC system is advantageous for operational
updates and planning actions from RCCs.
DISSEMINATION OF MARITIME SAFETY INFORMATION
Navigational and meteorological information is transmitted from ships to shore authorities
through the Inmarsat-A, -B or -C systems. Shore authorities in hydrographic,
meteorological and search and rescue offices initiate maritime Safety Information (MSI).
Messages are entered into the International SafetyNET Service for transmission to ships
through the EGC system, with the appropriate priority.
GENERAL RADIOCOMMUNICATIONS
Virtually all of the telecommunications services found in offices ashore are available to and
from ships equipped with Inmarsat SESs. This results in ships having capabilities for high
quality, reliable and automatic communications via voice, facsimile, telex, data, high-speed
data and E-mail. These capabilities can be used for obtaining advice and assistance from
experts ashore in efforts to solve problems before they develop into emergency situations.
A series of 2-digit service codes has been established to make it faster for ships to make
connections for a number of special purposes, both safety and routine. Of these, there are
six (6), which are specifically for safety services and provide a rapid connection to an RCC,
meteorological office, hydrographic office, ship reporting centre or medical centre.
Satellite communications via Inmarsat bring rapid and reliable communications to the aid of
seafarers - to help them avoid danger and to provide a means for summoning assistance
when all else fails. The ability to communicate with a vessel anywhere in the world, at any
time of day or night will appeal to all owners/operators of ships. The ability to immediately
contact an RCC or technical experts ashore for assistance will, on the other hand, appeal to
all seafarers. For all parties, the availability of a reliable and flexible system for both safety
and commercial communications is the ultimate bonus.
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International Maritime Satellite Organization (INMARSAT)
Before 1984, most ships could not communicate with each other although they could
receive a distress alert. At that time, the range of transmission on MF was only 150 miles
so that ships beyond this distance from the nearest coastal station, it is essentially a ship-
to-ship distress system
The advent of satellite communication led the IMO to commence a study of maritime
satellite communication with assistance from the International Radio Consultative
Committee (CCIR) of ITU in 1972.
In 1976, IMO adopted the Convention on the Establishment of the International Maritime
Satellite Organization (INMARSAT). In 1979, the Convention entered into force and
INMARSAT became operational.
Also in 1979, the International Conference on Maritime Search and Rescue adopted the
International Convention on Maritime Search and Rescue, 1979 (1979 SAR Convention),
with the ultimate objective to establish a global plan for maritime search and rescue based
on a framework of multilateral or bilateral agreements between neighbouring states on the
provision of SAR services in coastal and adjacent ocean waters to achieve co-operation and
mutual support in responding to distress incidents.
With the assistance of ITU, CCIR, other international organizations such as the World
Meteorological Organization (WMO), the International Hydrographic Organization (IHO),
INMARSAT and the COSPAS-SARSAT partners, IMO developed and proved the various
equipment and techniques used in the global maritime distress and safety system
(GMDSS). The ITU also established the appropriate regulatory framework for the
implementation of the GMDSS.
INMARSAT became a limited company in April 1999 and serves a broad range of markets.
Starting with a user base of 900 ships during the early 1980s, it now supports links for
telephone, facsimile and data communications at up to 64 kbits/s to more than 210,000
ships, vehicles, aircrafts and portable terminals.
The Inmarsat-E System
The Inmarsat-E system provides global maritime distress alerting via Inmarsat satellites
operating at L-Band. Distress alerts transmitted from Inmarsat-E Emergency Position
Indicating Radio Beacons (EPIRBs) are relayed through Inmarsat satellites to dedicated
receiving equipment located at four Land Earth Stations (LESs):
• Raisting, Germany
• Niles Canyon, USA
• Perth, Australia; and
• Goonhilly, UK.
The distress alert transmitted by an EPIRB will always be received by two LESs in each
ocean region, giving 100 percent duplication for each ocean region in case of failures or
outages associated with any of the LESs. Table below shows the relationship between the
satellites, the Inmarsat LESs and their associated maritime rescue co-ordination centre
(MRCC).
Atlantic Ocean Region–East (AOR-E)
Atlantic Ocean Region-West (AOR-W)
Goonhilly LES
Falmouth MRCC
Niles Canyon LES
United States Coast Guard
Raisting LES
Bremen MRCC
Goonhilly LES
Falmouth MRCC
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The Inmarsat-E system was first proposed in the 1970’s and the concept was developed
and tested in the 1980’s. Pre-operational service began in the Atlantic Ocean Region East
(AOR-E) in 1993. Full, global operation began in January 1997. The Inmarsat-E system was
runner -up in the safety section of the Seatrade Awards in 1998.
Inmarsat-E EPIRBs are approved by the IMO as complying with the requirements within the
GMDSS to have a satellite EPIRB fitted.
After activation, there is a two-minute wait, during which an audible and visual signal in the
EPIRB warns that a distress alert is about to be sent. This allows for the cancellation of
inadvertent manual activation and thereby reduces the chance of a false alert being sent.
Then, once the GPS position is confirmed within the integral GPS receiver, the distress alert
is transmitted.
Because the Inmarsat-E EPIRB will always be in view of at least one Inmarsat geostationary
satellite, and does not have to wait for an orbiting satellite to come into view, the time
taken from the transmission of a distress alert to reception at the MRCC is within five
minutes and typically less than one minute.
Following reception of the distress alert, it is immediately and automatically forwarded by
an X.25 link to the associated Maritime Rescue Co-ordination Centre (MRCC) so that
appropriate action can be taken.
The Inmarsat-E system supports "Float Free" EPIRBs that incorporate the following
features:
• Global Positioning System (GPS) position, accurate to within 200 metres;
• automatic activation when the EPIRB is released by "Floating free";
• remote activation and information input from optional remote control unit on the
vessel’s bridge;
• high intensity, low duty cycle strobe light.
• optional Search and Rescue Radar Transponder (SART);
• optional 121.5MHz locator beacon.
The size of the EPIRB is between 220mm and 700mm high and
weighs about 1200g, (depending on manufacturer and model).
Examples are shown below
Mk.IV Inmarsat-E EPIRB (also available with integrated SART)
from Fastnet GmbH
(Right)
Global-3 Inmarsat-E EPIRB from navtec GmbH
(Left)
Pacific Ocean Region (POR)
Indian Ocean Region (IOR)
Perth LES
Canberra MRCC
Raisting LES
Bremen MRCC
Niles Canyon LES
United States Coast Guard
Perth LES
Canberra MRCC
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The EPIRB may be activated in any of three ways:
1. From an optional remote control unit on the bridge or the conning position of the
vessel, when the EPIRB is in its cradle;
2. Manually, by using a switch on the side of the equipment if the EPIRB has been
carried into the survival craft; or
3. Automatically, as soon as the EPIRB has been released by immersion in water
(hydrostatic release).
The carriage of a satellite EPIRB is required on SOLAS ships by the GMDSS and this
requirement came into effect on 1 August 1993.
GMDSS regulations apply to all vessels of over 300 gross registered tonnes and all
passenger vessels engaged on international voyages. However, distress incidents occur on
small craft not covered by GMDSS regulations, such as pleasure craft etc., much more
frequently than on larger vessels.
Although such vessels may use the GMDSS approved models, there are also non-GMDSS
versions of the Inmarsat-E EPIRB available. Both types of Inmarsat-E EPIRB will enable
them to transmit distress alerts and obtain the services of rescue authorities much faster
and more reliably than by conventional means.
The picture below shows a typical non-GMDSS Inmarsat-E
EPIRB:
DAS-30A non-GMDSS Inmarsat-E EPIRB from Fastnet
GmbH
Registration
It is imperative that owners of all Inmarsat-E EPIRBs
register them with Inmarsat, giving details of the vessel or
craft on which they are installed, as soon as possible after
installation. MRCCs hold details of all registered Inmarsat-
E EPIRBs and as the position contained in the distress alert
is accurate to within 200 metres, Search and Rescue (SAR)
authorities can be alerted and start to take appropriate
action within minutes.
The registration database held at Inmarsat is replicated at each of the Inmarsat-E
associated MRCCs and is keeps updated. Thus, in the event of an alert, the MRCC staff can
immediately identify the vessel from which the EPIRB alert has been sent, without the
necessity of contacting Inmarsat.
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