Inmarsat C I-4 Migration

Important action required for Inmarsat C users

As you may be aware, the Inmarsat-3 (I-3) constellation of satellites are reaching the end of their lifespan, which has made it necessary for Inmarsat to roll out the end of life process for several of their legacy services, and to migrate those that will continue onto Inmarsat-4 (I-4). One such service to be migrated is Inmarsat C. From the end of Q1 2018, Inmarsat has started to migrate traffic from its Inmarsat C service from I-3 to I-4.

This migration applies to all users of Inmarsat C, but you are in safe hands with Marlink. Marlink is today responsible for almost half of the global traffic on Inmarsat C, which forms the basis of vital maritime safety and vessel tracking and positioning systems. This significant market share and our continual growth of the service is driven by long term knowledge, experience, solid partnerships and continuous development of infrastructure. This places us in an ideal position to manage this mandatory process in the most positive way possible for our customers.

The migration AORW > AMER, originally scheduled for 16 April 2018, took place by Inmarsat on May 9 at 14h00 UTC after it had been postponed. The first migration was a success with a short outage of just 13 minutes, with no real impact on the customers and the business. We can also confirm that the new configuration and infrastructure are stable, and providing complete satisfaction.

Phase two of the migration from Pacific Ocean Region (POR) I-3 satellite to the Asia/Pacific (APAC) I-4 satellite successfully took place on 29 August 2018 at 06:00 UTC. The migration was executed smoothly with no major disruptions reported. An outage of only 20 minutes was experienced, which was significantly less than anticipated considering the enormity of the traffic to be shifted between these different generations of satellites.


On 30 October 2018 at 11:00 UTC, Inmarsat will migrate traffic from its Inmarsat C service from Atlantic Ocean Region East (AOR-E)* I-3 F2 satellite to I-3 F5 satellite.

*Note that AOR-E is part of the overall I-3 to I-4 migration programme but it is not moving to the I-4 constellation.

 Important information concerning changes in Inmarsat C coverage over the Greenland Sea after the migration of Inmarsat AOR-E satellite from 15.5W to 54W

Due to the planned migration of the Atlantic Ocean Region East (AOR-E) from 15.5W (I-3 F2 satellite) to 54W (I-3 F5 satellite), there will be a change in Inmarsat C coverage over the Greenland Sea between Greenland and Norway. This situation is unavoidable due to the approaching end-of-life of the Inmarsat I-3 satellites.

The area affected by the AORE migration is between Svalbard and Greenland in the Greenland Sea. It is difficult to define the exact region, as the precise service availability for Inmarsat C in this area depends on the terminal type, the location of the terminal, the operation of the vessel (roll and pitch), the time of day and the local environmental conditions.

Where is the affected area?

The area in question is shown in cross-hatched green in the map below. This area includes part of NAVAREA 1 (coordinated by UK) and part of NAVAREA 19 (coordinated by Norway). Note that this is a simplified map that shows only the 54W, 15.5W and 64E Inmarsat I-3 satellites. The 98W and 143.5E satellites do not cover the affected area, therefore, they are not shown on this map.

Note: the map is showing the worst-case scenario with the 5° elevation limit. We could expect Inmarsat C to work at lower elevation.

The Inmarsat C coverage in the affected area should now be improved since the Indian Ocean Region Satellite (IOR) was migrated from 64E to 25E on the 12th December 2018. The period between the migrations of AORE and IOR was kept as short as possible to reduce the impact on users.

How does this change affect SOLAS (Safety of Life at Sea) and Non-SOLAS vessels?

It is important to stress that it is a Global Maritime Distress and Safety System (GMDSS) requirement that all SOLAS vessels must have multiple communication systems (i.e. MF/HF DSC equipment, EPIRB, VHF, etc.), therefore, SOLAS vessels will always have the ability to send and receive Distress, Urgency and Safety communications, even when they are outside the satellite coverage area.

All vessels (including non-SOLAS) operating in the affected area will receive an automatic alarm from their Inmarsat C terminals when they move outside the satellite coverage area.

What are the consequences on Inmarsat C business in that area?

Vessels sailing in the impacted region, between Step 3 and Step 4 of the migration, might be prevented from transmitting or receiving messages via Inmarsat C, impacting private correspondence and SSAS transmissions.

Additionally, vessels reporting their positions to the shore-side for commercial purposes (Inmarsat C tracking) or for regulation (LRIT or VMS) might stop reporting while transiting or sailing in the affected zone. Finally, Enhanced Group Call (EGC) messages might not be received either.

Affected Services and Advice

Marlink reminds users that Polling & Data Reporting are the services which are potentially the most affected.

Every step in the migration plan results in an approximate shift of 40 degrees westward of the coverage of a logical ocean region. This new satellite position will mean a change in coverage area for a small number of users, who will need to take the appropriate measures to ensure their system works without major disruption.

Before the migration, if your Inmarsat C terminal is located between 62.5°East and 24°East and is logged into AOR-E Ocean Region, you are strongly recommended to log your terminal into Indian Ocean Region (IOR) to ensure continuity of service. Furthermore, make sure that your local applications (Data Reporting or SCADA or others) will operate correctly if the migration requires those applications to use a different ocean region.

During the migration (30 October 2018 from 11:00 UTC) you may experience a short interruption of service. Shore to ship messages will continue to be accepted by the LES and will be queued for delivery after the migration. Ship to shore messages will be queued on the terminal and delivered once the terminal re-establishes communications with the satellite.

After the migration, ensure your terminal is logged into the relevant ocean region. It might happen that Inmarsat C terminals do not start the log-in process automatically. In that case, you should manually log into an ocean region or reboot (Log-out and relog-in) the terminal manually.


A number of new benefits will result from this migration:

  • More secure flow of data

In parallel with the migration, Marlink together with Inmarsat has invested in a redundant (back-up) Network Coordination Station (NCS) to direct and manage frequencies. This will ensure data flows more securely, with significantly less room for error or latency.

  • Simplified and optimised network process

Whereas today, Inmarsat C messages are transmitted via Marlink’s Aussaguel and Eik Land Earth Stations, we take this opportunity to renew and simplify our global organisation. Following the migration, transmissions will be managed centrally and directly by Inmarsat. This simplifies and shortens the communication chain, making the flow of data more secure.

  • Improved accuracy and speed of position tracking

As part of Marlink’s ongoing commitment to Inmarsat C, we have followed the advice of Inmarsat to optionally transmit messages over IP following the migration. This modernisation will ensure more secure, faster transmission for customers and subsequently, improved tracking and positioning (e.g. LRIT).


Every step in the migration plan results in an approximate shift of 40 degrees westward of the coverage of a logical ocean region. This new satellite position will mean a change in coverage area for a small number of users, who will need to follow a simple process to reconfigure their affected terminal(s) to their new satellite coverage area.

There are between 1 and 3 simple steps for customers to follow to ensure a smooth transition:

  • Check if your terminals are affected by the migration by referring to our Dynamic Coverage Maps (below). These maps highlight the shift in coverage areas and will help you to easily determine whether your terminals will require an update
  • If your terminals are unaffected – you do not need to take any further action
  • If your terminals are affected and to avoid issues with your Inmarsat C devices just after each phase of the migration, we recommend you switch your Inmarsat C devices to an adjacent Ocean Region before each migration (see “Marlink recommendation”)
  • Be prepared to reprogram your affected terminals which cannot be switched in advance, onto the relevant new satellite region. If it is not yet the case, you might have to reload your DNID in the new region and reprogram your terminal(s) for automatic reports. For those who do not have access to Marlink’s DataTrack platform, our Service Desk can provide support and clear instructions to facilitate the transition

A few points to note

Following the migration process, poll commands will likely be sent by hundreds, if not thousands of users, flooding the system with messages which will be put in a queue. Expect significant delays during this period.

In a small number of cases, customers could face issues if utilising very old hardware e.g. those over 12 years old. (Trimble hardware in particular may need extra attention, since this hardware manufacturer is no longer operational.) In these cases, we recommend considering a replacement ahead of time to mitigate service disruption.


  • To avoid issues with your Inmarsat C devices right after each phase of the migration, we recommend switching your Inmarsat C devices to an adjacent Ocean Region before each migration. Switching devices in advance will make the migration smoother and will avoid possible outages in tracking operations
    • Before phase #1 switch devices located between 24°E and 20°W to AORE
    • Before phase #2 switch devices located between 104°W and 138,5°W to AMER/AORW
    • Before phase #3 switch devices located between 62,5°E and 24°E to IOR
    • Before phase #4 switch devices located between 142°E and 70°E to APAC/POR
  • We recommend controlling the Ocean Regions where your DNID(s) has been downloaded in the past. If a DNID is available in the 4 Ocean Regions the migration has no effect on position/data reporting
  • After a migration, do not try to send poll commands immediately because it will just increase the pending queue at NCS level. Take your time!
  • If you are using automatisms or robots to send poll commands deactivate it or enlarge the time-out to avoid loops and larger pending queues at NCS Level


  • Polling & Data Reporting

Safe services

  • Enhanced Group Calling (SafetyNet & FleetNet)
  • Ship-to-Shore and Shore-to-Ship messaging

Special notes

  • We might face small delays just after each migration due to important number of requests sent to the NCS
  • Inmarsat C is a Store&Forward service. As such, messages are treated by the LES anyway. We do not expect any loss of messages
  • We might face losses of Poll commands due to NCS overloading


  • Step1: AOR-W I-3 to AMER I-4 = Achieved
  • Step2: POR I-3 to APAC I-4 = Achieved
  • Step3: AOR-E I-3 moved from 15.5W to 54W = Achieved
  • Step4: IOR I-3 to Alphasat EMEA I-4 = Achieved


This migration will ultimately result in a new satellite environment and new benefits for customers, with very little (if any) action required. Please help us to support you in this process and ensure you are as well prepared as possible by following the simple steps outlined.

To facilitate this very important process, we need a point of contact from your company to ensure a smooth transition process.

Please send an email to:, with your appointed person’s name, telephone number and email address.

In case of any questions, or for further support, please contact Marlink’s Service Desk or your Key Account Manager.



Coverage map for Inmarsat I-4 migration

Inmarsat C Migration – Our Commitment to You!

We would like to assure our customers and partners that a vast and long-term planning process has taken place with regards to the planned I-4 Migration process by Inmarsat. A number of considerations, potential issues and technical aspects have been reported in advance to Inmarsat by our Engineers and Inmarsat C experts Whilst we work in very close coordination, ultimately the migration process is under the control of Inmarsat. Therefore, despite Marlink’s efforts and specialist support to ensure a smooth migration, a 100% predictable outcome cannot be guaranteed. However, as always, Marlink’s dedicated support team will be available throughout the migration phases to support and help partners and end users and will continue to put professionalism and exceptional customer support at the forefront for our customers and partners!

Select your current Inmarsat C coverage region from the options shown, then switch on the button below it to see how it will be affected following the I4 Migration (tbc)

Phase 1: Atlantic Ocean Region West (AOR-W) to Americas (AMER) 09 May 2018 at 14:00UTC

Phase 2: Pacific Ocean Region (POR) to Asia Pacific (APAC)- 29 August 2018 at 06:00 UTC

Phase 3: Atlantic Ocean Region East (AOR-E)- 30 October 2018 at 11:00 UTC

Phase 4: Indian Ocean Region (IOR) to Europe/Middle East Ocean Regions (EMEA)