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

07 February 2018

Dear Inmarsat Customer

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 we are contacting you to outline our plans for the transition of services from the I-3 fleet onto our Inmarsat-4 (I-4) constellation (as shown in the table below).

Our primary objective is to ensure that the transition process is simple and seamless for our partners and end-users.

The services we will be migrating 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. We have 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 at the end of Q1 2018 and will take approximately nine months to complete. Our approach is to migrate these services satellite by satellite, commencing with the Atlantic Ocean Region West.

I - 3 to I - 4 migration


  • Atlantic Ocean Region West (AORW) I-3 to I-4 Americas (AMER)    -  End Q1 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.

Final dates for the transfer of services to each I-4 satellite will be confirmed approximately four weeks prior to the start of the migration.

Inmarsat has been working closely with Land Earth Station Operators (LESOs) and Distribution Partners (DPs) since 2015 to plan the migration process and reduce to a minimum any potential impact on end-users’ terminals and applications. Inmarsat and its LESOs and DPs are contacting customers to ensure they are aware of the migration and of the steps that they may need to take.