Inmarsat's HQ in London. Credit: Inmarsat

TAMPA, Fla. — Inmarsat has restored maritime and aviation safety capabilities on its I-4 F1 satellite over Asia Pacific but is still trying to recover services for L-band phones that have been down for nearly a week.

All services on the spacecraft have been restored following the outage except for its Global Satellite Phone Service (GSPS), an Inmarsat spokesperson said April 21, although work continues on “optimizing performance and addressing some specific residual issues.”

The operator declined to detail these residual issues but said safety services that include its maritime distress signal business Inmarsat C “are operating normally” on the 18-year-old spacecraft, serving East Asia and the Pacific region.

I-4 F1 suffered a partial loss of power April 16 that “invoked automatic procedures on the satellite that led to the suspension of services,” according to the company.

Maritime safety services were immediately transferred to a contingency satellite elsewhere in the operator’s fleet during the outage, in compliance with rules overseen by the International Mobile Satellite Organization.

These maritime services were transferred back after I-4 F1 was recovered April 18, the same day Inmarsat restored connectivity for aviation customers.

While engineers are still investigating the root cause of the power issue, Inmarsat has ruled out space debris or anything malicious, such as a cyber attack.

The satellite was built by EADS Astrium, now Airbus Defense and Space, and was launched in 2005 with an initial 13-year design life.

The Airbus-built I-6 F1 satellite that launched in December 2021 is slated to replace many of I-4 F1’s L-band services “in the coming months,” Inmarsat said.

Inmarsat has not said how many partners or customers have been affected by its I-4 F1 issues. 

Jason Rainbow writes about satellite telecom, space finance and commercial markets for SpaceNews. He has spent more than a decade covering the global space industry as a business journalist. Previously, he was Group Editor-in-Chief for Finance Information...