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LEO constellation delivers modern global GMDSS
US company combines low Earth orbit satellites and integrated terminals to provide global, redundant and always-available GMDSS safety communications
Satellite technology has become more resilient, delivering global coverage of the Global Maritime Distress and Safety System (GMDSS) through a low Earth orbit (LEO) constellation and multi-functional shipboard terminals.
Iridium Communications’ LEO constellation provides a layer of redundancy for GMDSS maritime safety communications with satellites continuously moving across the globe.
“There is always at least one overhead, ensuring true pole-to-pole coverage and eliminating any regional blind spots,” said Iridium Communications vice president and general manager for maritime, Wouter Deknopper.
“With Iridium’s cross-linked LEO architecture, if a satellite were to go out, communication is relayed using satellites in the same orbit until it can be downlinked to the Earth,” he explains. “Handoffs between satellites serving a subscriber occur approximately once every seven minutes, ensuring mariners will stay connected no matter what.”
US-based Iridium’s Certus GMDSS is an alternative to legacy GMDSS terminals that communicate with geostationary (GEO) satellites, which orbit above the equator and depend on ground station visibility.
“While this architecture has supported maritime safety for years, since GMDSS was deployed in 1992, it is inherently limited,” said Mr Deknopper. “Coverage gaps persist at high latitudes, and service outages can disrupt entire regions.”
He provided an example: in April 2023, a GEO satellite supporting GMDSS services experienced a multi-day outage over Asia, leaving vessels in the region without access to distress alerting via satellite. “A stark reminder of the risks of relying on single-orbit, non-redundant systems,” said Mr Deknopper.
Iridium Certus GMDSS terminals integrate multiple safety functions, including distress alerting; safety voice; maritime safety information; ship security alert system; and long-range identification and tracking.
“A single terminal gives fleets the ability to cut data costs and streamline their installed bridge unit equipment,” said Mr Deknopper.
“It also supports non-safety voice communications and IP data, giving crews reliable access to both emergency and operational tools all in one system.”
Also in this terminal is L-band Certus broadband communications with Iridium’s LEO constellation, which can be primary connectivity or a companion service for Ku-band and Ka-band very small aperture terminal (VSAT) services.
“Whether SOLAS or non-SOLAS, having an Iridium Certus GMDSS terminal on board provides the fastest weather-resilient broadband service available for conducting ships’ business when other systems are blocked or unavailable,” said Mr Deknopper.
“The system also provides service depending on needs, letting vessel operators choose the bandwidth, size and cost that works best for their needs.
“Whether it is a compact terminal for a small vessel or a higher-throughput option for a commercial fleet, all configurations maintain full GMDSS compliance and global availability.”
Maritime equipment providers, including Cobham Satcom, Intellian, Lars Thrane and Thales, now offer or are developing Iridium Certus GMDSS terminals for vessels of all sizes and purposes, which Mr Deknopper said will “help shipowners modernise safely and efficiently,” as Iridium Certus GMDSS is global, redundant and always available, “to keep mariners informed and safe while traversing the world’s oceans.”
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