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 April 30, 2018, Inmarsat will 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 Marlink's continual growth of the service is driven by long term knowledge, experience, solid partnerships and continuous development of infrastructure. This places Marlink in an ideal position to manage this mandatory process in the most positive way possible for our customers.

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How will I be 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 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 Marlinks Dynamic Coverage Maps web page. 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 to switch your Inmarsat C devices to an adjacent Ocean Region before each migration (click link below and scroll to "Marlink recommendations").
  • 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 program again your terminal(s) for automatic reports. Our Service Desk can do this for you, or provide support and clear instructions to enable you to do it yourself using our DataTrack platform.

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.

Affected services
  • Enhanced Group Calling (EGC) SafetyNet
  • Polling & Data Reporting

Safe services

  • Enhanced Group Calling (EGC) 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.
More information and support

For more information, please go to Marlink's website:

In case of any questions or for further support, please contact Frederik Aidi Hallstrøm: