4 Criteria and requirements for earth stations
4.1 Functional requirements
4.1.1 Earth stations serving the GMDSS should:
- be in continuous operation;
- be connected to an associated RCC;
- keep continuous watch on all appropriate satellite communication channels; and
- be capable of transmission and reception of at least the maritime distress and safety communications services included in paragraph 3.1.
4.2.1 The earth station should be capable of automatically recognizing the priority of ship-to-shore and shore-to-ship communications, and should process maritime mobile communications while preserving the four levels of priority specified in paragraph 3.3.1.
4.2.2 Priority access should be given for distress alerts and calls in real time. In any case, distress alerts and calls should be given priority treatment by providing immediate access to satellite channels, and distress alerts and calls for store and forward systems should be placed ahead of all routine traffic. Any satellite system designed for use in the GMDSS should be able to recognize the four levels of priority and give appropriate access for communications in the ship-to-shore direction and in the shore-to-ship direction for distress, urgency and safety traffic originated by RCCs or other Search and Rescue Authorities.
4.2.3 Limitations in existing public switched networks concerning facilities for indication and use of priority access codes might necessitate special arrangements such as use of leased lines between, for example, MSI providers and the earth station, until such facilities become available in the public switched network.
Satellite systems participating in the GMDSS should make arrangements to ensure that it will always be possible for an MRCC to obtain an immediate connection to a maritime mobile terminal and that the MRCC could use the systems for SAR alerting and communication without any delay. This may be achieved by a process of pre-emption or by other suitable means approved by IMSO.
4.4 Routeing of maritime distress alerts
4.4.1 The satellite system should have reliable communication links to one or more associated MRCCs. These links may be implemented directly between the MRCC and an earth station, or some other suitable point in the system’s network. The arrangements between the system and the MRCC are subject to approval by the national administration.
4.4.2 The system’s network should be capable of automatically recognizing maritime distress and safety communications and of routeing, as far as possible automatically, maritime distress alerts/calls directly to the associated MRCC, via a highly reliable communication link. In cases where capability exists, the system may route alerts directly to the responsible RCC as defined in the IAMSAR Manual.
4.4.3 The earth station or other relevant part of the system’s network should be provided with an aural and visual alarm to alert a designated responsible person in the event that automatic connection to the MRCC cannot be achieved within 60 seconds. In this case, all necessary action should be taken to immediately inform the MRCC of the details of the distress alert or call. Personnel should always be available to react to such an alarm so as to ensure that the distress alert or call can be forwarded to an MRCC within 5 minutes of the alarm being triggered. All messages with distress or urgency priority should sound an alarm at the earth station or other relevant part of the system’s network, which should require manual cancellation.
4.4.4 The MRCC should be provided with reliable communication links to the system’s network for efficient handling of shore-to-ship distress alert relays and distress traffic, preferably via dedicated communication links.
The system should be capable of automatically identifying ship earth stations. If other identification than the Maritime Mobile Service Identity (MMSI) is used in the system, the means should be provided 24 h per day to easily identify the ship and to provide the MRCC with all the appropriate additional information necessary for effecting the rescue, including the MMSI number where available.
4.6 Voice communication systems
4.6.1 The communication links for mobile-satellite voice communication systems should be connectable to the public switched network in accordance with relevant ITU-T Recommendations.
4.6.2 Satellite systems using the public switched network for routeing maritime distress calls and distress traffic to and from MRCCs should, upon receipt of ship-to-shore or shore-to-ship distress alerts/calls or distress traffic, immediately attempt to establish the connection necessary for transfer of the distress alert or distress message.
4.7 Data communication systems
4.7.1 The communication links for mobile-satellite data communication systems should be connectable to the public data communication network in accordance with relevant ITU-T Recommendations. The system should provide the capability to transfer the identity of the calling subscriber to the called subscriber. Maritime distress alerts/calls and distress messages should include the ship identity and the earth station identity, or other means of identifying the point of access to the satellite network.
4.7.2 Satellite systems using the public switched network for routeing distress alerts/calls and distress traffic to and from MRCCs should, on receipt of ship-to-shore or shore-to-ship distress alerts/calls or distress traffic, immediately attempt to establish the connection necessary for transfer of the distress alert or distress message.
4.8 Store and forward systems
Satellite systems using store and forward communication systems should:
- make an initial attempt to deliver a ship-to-shore or shore-to-ship message within 60 seconds for any maritime distress alert or distress traffic, and within 10 minutes for all other maritime messages, from the time the receiving station receives the message (the message should include the ship identity and the earth station or system identity); and
- generate notification of non-delivery immediately once the message is considered non-deliverable, for maritime distress alerts and distress messages not later than 4 minutes after reception of the alert or message.
4.9 Facilities for broadcasting Maritime Safety Information
4.9.1 Satellite systems forming part of the GMDSS should technically be capable of offering facilities for broadcasting Maritime Safety Information (MSI) from MRCCs and authorized providers of MSI, such as Hydrographic Offices and Meteorological Offices, to ships at sea.
4.9.2 Such facilities for broadcast of MSI should provide for automatic, continuous and reliable reception on board ships and should, as a minimum, fulfil the requirements specified in sections 4.9.3 to 4.9.8 below.
4.9.3 The facilities should provide for recognition and processing of the four levels of priority specified in paragraph 3.3.1.
4.9.4 It should be possible to address the broadcast of MSI to all properly equipped ships within a specified area for at least the following types of areas:
- the entire region covered by the satellite or system over which the transmission is made;
- the NAVAREAs/METAREAs as established by the International Maritime Organization (IMO), the International Hydrographic Organization (IHO) and the World Meteorological Organization (WMO) respectively; and
- a temporary area chosen and specified by the originator of the MSI message, including circular or rectangular user-specified areas appropriate for broadcast of distress alert relays and search and rescue co-ordinating communications.
4.9.5 The facilities should provide for transmission of at least the types of Maritime Safety Information required by SOLAS, as follows:
- search and rescue co-ordination information, including distress alert relays;
- navigational warnings; and
- meteorological warnings and forecasts.
4.9.6 The facilities for broadcast of navigational and meteorological warnings should include possibilities for:
- scheduling the broadcast at fixed times or transmitting messages as unscheduled broadcast transmissions; and
- automatic repetition of the broadcast with time intervals and number of broadcast transmissions as specified by the MSI provider, or until cancelled by the MSI provider.
4.9.7 The facilities should provide for marking MSI messages with a unique identity, enabling the shipborne equipment that receives these broadcasts to automatically ignore messages already received.
4.9.8 The broadcasting service should in addition provide facilities for broadcasts similar to NAVTEX to coastal areas not covered by the International NAVTEX Service, in accordance with the identification system (i.e., the identification characters B1, B2, B3, B4) used in the International NAVTEX Service.