Thousands of miles from shore the most reliable communications link typically comes over satellite. That came to an abrupt end over the Pacific this week as one of Inmarsat‘s satellites went offline. The I-4F1 satellite covering the region is no longer passing traffic leaving planes, ships, agricultural machinery, and many other systems in the dark.
The outage started at approximately 22:50 21:14 UTC on 16 April 2023. More than 24 hours later the satellite is still offline, with the company reporting via a partner provider that it hopes to restore service by 12:00 UTC on the 18th of April.
That timing would be for the beginning of service reactivation. The satellite delivers connectivity to multiple services; Classic Aero is expected to be the first to come back online.
For airlines flying across the affected region this outage means limited communications between pilots and their dispatchers or air traffic controllers. Instead of communicating via the L-band link they will have to revert to HF radios and manual position reports.
Longer-term, the outage here could open the potential for Iridium to become a viable partner in the aero safety services market. Back in 2020 the company finally gained certification for its GMDSS maritime solution, over objections from Inmarsat about the limited reliability of the Iridium constellation’s performance.
NOTAMs were issued by ATC in the US, Japan, Australia, New Zealand, and Papa New Guinea (and maybe others) regarding the outage.
And as for what caused the outage, Inmarsat is not saying much of anything right now. After a half year of testing over the Atlantic, the I-6 F1 satellite repositioned to the Pacific theatre last month and linked up with ground stations in Australia. Inmarsat had planned to start bringing services into production this quarter. That’s an awfully big coincidence for now. But definitely one worth thinking more about. And, of course, there is a certain irony that the new satellite was supposed to augment and eventually replace coverage provided by I-4 F1. But it is not available to deliver that service yet when the old satellite perhaps needs it most.
In many ways the airplanes are lucky. They have backup methods of communication available. Some of the tractors, for example, simply cannot operate in the fields as they do not have the precise navigation needed without the satellite link.
Update: At ~1840 UTC on 18 April Inmarsat issued the following statement:
Inmarsat experienced an outage on its I-4 F1 satellite, which provides L-band services for East Asia and the Pacific region, at 21.14 UTC on Sunday 16 April. This resulted in the temporary loss of services from the satellite and the company immediately instigated its recovery procedures.
Safety services are being prioritised and Inmarsat can confirm that immediately following the incident, it instigated the process to transfer maritime safety services, in line with the IMSO approved operational process to a contingency satellite. That process was completed successfully.
Inmarsat Classic Aero recovery has now started and is expected to be operational in a matter of hours. This will be followed by the transfer of Inmarsat-C services from the contingency satellite back to I-4 F1 and then a focus on the restoration of other services.
All other satellites in the L-band fleet are unaffected by the incident. This includes Inmarsat’s two new L-band satellites – I-6 F1 and F2 – which will be joined in 2027 by a further three new micro L-band satellites, the Inmarsat-8s, specifically designed to enhance safety service back-up for L-band customers.
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