Inmarsat I-3 to I-4 migration notice: Inmarsat C and Fleet 77 services

The satellites that form the Inmarsat-3 (I-3) L-band constellation have been in operation for many years. Three of the four satellites in the constellation are now approaching the end of their operational life and Inmarsat has planned the transition of services from the I-3 fleet onto our Inmarsat-4 (I-4) constellation.

The services that will be migrated include: Inmarsat C, Mini C, Fleet 77, Swift 64 and Classic Aero.

A number of these legacy services have been operated successfully over our I-4 satellites previously and therefore minimal service impact is anticipated. Inmarsat has also been working closely with terminal manufacturers to ensure that their devices can operate over the I-4 satellites with the minimum of intervention required by the user.

The migration will start on the 4th of April 2018 and will take approximately nine months to complete. The approach is to migrate these services satellite by satellite, commencing with the Atlantic Ocean Region West.


I-3 to I-4 migration Timing
Atlantic Ocean Region West (AORW) I-3 to I-4 Americas (AMER) Starting April 4th, 2018
Pacific Ocean Region (POR) I-3 to I-4 Asia/Pacific (APAC) End Q2 2018
Atlantic Ocean Region East (AORE) I-3 moved from 15.5W to 54W (I-3 F5 satellite) End Q3 2018
Indian Ocean Region (IOR) I-3 to I-4 Alphasat EMEA End Q4 2018


Due to the move from the I-3 to the I-4 satellites, the coverage areas will change, and users will need to ensure that their devices are pointed to the relevant satellite. This process will generally be managed by the terminal automatically without the need for user intervention. However, in some instances, users will need to manually repoint their devices to the appropriate satellite.

Inmarsat C users should ensure that their local applications (e.g. data reporting) will operate correctly if they are using a different Inmarsat satellite.

Classic Aero and Swift 64 users are advised to contact their equipment manufacturers to confirm whether a configuration update will be required to support the migration.

Each migration step will cause a short outage while services are moved onto the I-4 satellites. Under supervision of the International Mobile Satellite Organisation (IMSO), the Global Maritime Distress Safety System (GMDSS) and Maritime Safety Services will be closely monitored during the migration, as will the Classic Aero Safety Service. These safety services will be restored first with the highest priority.

Several new benefits will result from this migration:

-More secure flow of data

-Simplified and optimized network process

-Improved accuracy and speed of position tracking

We will be communicating with you throughout the planning and execution phases of the migration, providing additional details as and when necessary.

Ocean regions footprints before migration:








Ocean regions footprints after migration:







If you have any questions or concerns, please contact us: