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Posted: April 13, 2018

U.S. Coast Guard: Inmarsat network migration impact on maritime distress and safety services

The following article was posted on the U.S. Coast Guard's Maritime Commons Blog and is available online.

This post was updated April 10, 2018 to reflect that Inmarsat will begin the migration 1400 UTC May 9, 2018 instead of April 16, 2018, as originally announced. For the latest information, visit the Inmarsat website provided in our blog post.

Inmarsat has announced that it will migrate Inmarsat-C, Mini C, and Fleet 77 used for Global Maritime Distress & Safety System (GMDSS), Long Range Identification and Tracking (LRIT) and Ship Security Alerting Systems (SSAS) from their I-3 to their I-4 Network. This migration will begin 1000 UTC on May 9, 2018 and take approximately nine months to complete.

Inmarsat notified the IMO Sub-Committee on Navigation, Communications and Search and Rescue, at its fifth session Feb. 19-23, 2018, that they have developed a plan to migrate mobile satellite communication services. This plan includes the Inmarsat-C, SafetyNET, and Fleet 77 services, from the primary Inmarsat-3 satellites over to the Inmarsat-4 satellites within 2018.

The Inmarsat I-3 satellites are predicted to reach end-of-life between 2019 and 2020. These services must be migrated onto the I-4 satellites in order to ensure their continuity.

The details on the migration of the Inmarsat-C services for GMDSS can be found at It describes the impact of the migration and provides an overview on how to prepare for it. Inmarsat will periodically update this webpage as migration continues.