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Iridium GMDSS · Distress Alert · Safety Voice · SafetyCast
Satellite distress alerting, direct Safety Voice with rescue authorities and reception of maritime safety information, with coverage that reaches the Arctic, Antarctica and the North Pole. Satcenter supplies, installs and commissions Iridium GMDSS systems for shipowners, vessel managers and shipyards, from Rotterdam and Istanbul.
Global Maritime Distress and Safety System
Iridium GMDSS is a maritime satellite distress and safety service that runs over the Iridium network. It is part of the Global Maritime Distress and Safety System (GMDSS): the international framework that lets ships send distress alerts, communicate with rescue authorities and receive safety information.
The IMO recognises both Iridium and Inmarsat as providers of satellite communication systems for GMDSS. An approved Iridium GMDSS installation can meet the satellite communication requirements that apply within the vessel's wider radio safety arrangement.
The GMDSS terminal is one part of that arrangement. VHF/DSC, MF/HF where required, EPIRBs, search and rescue locating devices and MSI receivers are assessed for the vessel as well.
Satcenter helps you choose a system that suits your vessel, flag and trading area: from a dedicated safety terminal to an Iridium Certus GMDSS system that also carries operational voice and data.
Three safety services in one system
A dedicated distress control sends the vessel's identity, position and distress details to a Rescue Coordination Centre (RCC), so rescue authorities can identify the vessel and start coordinating assistance.
The bridge team speaks directly with the rescue authorities to explain the situation. GMDSS distress and safety traffic is handled with priority over routine commercial traffic.
Iridium SafetyCast delivers navigational warnings, meteorological warnings and forecasts, and search and rescue information from participating authorised providers.
Why Iridium for GMDSS
The low Earth orbit network covers the planet pole to pole, including the geographic North Pole. Relevant for expedition vessels, research ships, fishing fleets and ships trading at high latitudes. Reception still depends on correct installation and a clear antenna view of the sky.
Safety Voice lets the bridge describe the incident and discuss rescue coordination with an RCC. Inmarsat C supports messaging and alerting, but no voice calls.
Certus GMDSS systems such as the LT-4200S or C700 GMDSS also carry routine calls and IP data, next to Starlink, OneWeb or VSAT. Distress and safety functions always keep priority.
Different antenna sizes, bridge interfaces and data classes let the system be chosen around the vessel. In some approved configurations, suitable existing cabling can be reused after inspection.
Iridium vs Inmarsat C
Both are established options for maritime satellite safety communication. The right choice depends on the vessel's routes, existing equipment, required functions and approved radio arrangement.
| Requirement | Iridium GMDSS | Inmarsat C / approved Mini-C GMDSS |
|---|---|---|
| Satellite network | Low Earth orbit (LEO) | Geostationary (GEO) |
| Coverage | Pole to pole, including polar waters | Extensive ocean coverage, excluding the extreme polar regions |
| Satellite distress alerting | Yes, with an approved system | Yes, with an approved system |
| Voice communication | Safety Voice and routine voice, depending on configuration | No voice through Inmarsat C |
| Safety information | Iridium SafetyCast; check operational broadcasts for the route | Inmarsat SafetyNET |
| Routine communications | Voice and messaging; Certus models add IP data | Low-rate messaging and reporting |
| LRIT and SSAS | Available on selected approved configurations | Available on suitably equipped and approved configurations |
| Replacement decision | Subject to vessel, flag, MSI and survey assessment | Can remain appropriate for an existing compliant installation |
Consider Iridium GMDSS when the vessel needs polar satellite coverage, direct safety voice, a replacement for ageing equipment, or a Certus installation that combines safety services with essential IP connectivity.
A working, supported Inmarsat C installation may continue to meet the vessel's needs. Keeping it avoids unnecessary replacement work and can support the required MSI reception arrangement. Installing Iridium alongside Inmarsat C can add complementary capabilities, but the overall arrangement is assessed as a whole: two terminals do not automatically fulfil every redundancy requirement. For Inmarsat services, see Inmarsat maritime connectivity.
An approved Iridium installation can replace Inmarsat C in an accepted vessel configuration, but it is not an automatic equipment swap. Before replacement, the review covers:
For Dutch-flagged vessels, published guidance sets specific MSI conditions and asks owners planning a replacement to contact the vessel's Recognised Organisation. Satcenter plans the technical scope and coordinates the required checks with the parties involved.
The product families below are a starting point for selection. Final supply is confirmed against availability, current certificates, firmware, accessories and acceptance for your vessel.
| System | Service class | Voice | Maximum IP data | Best suited to |
|---|---|---|---|---|
| Lars Thrane LT-3100S | Iridium GMDSS | Safety Voice and routine voice | Modem data, SMS | Dedicated safety installation |
| Lars Thrane LT-4100S | Certus 100 | 2 channels | 88 / 22 kbps | GMDSS with light IP data |
| Lars Thrane LT-4200S | Certus 200 | 3 channels | 176 / 176 kbps | GMDSS with more operational data |
| Intellian C100M GMDSS | Certus 100 | Yes | Certus 100 class | Compact safety retrofit |
| Intellian C200M GMDSS | Certus 200 | Yes | Certus 200 class | Safety, voice and essential IP data |
| Intellian C700 GMDSS | Certus 700 | Yes | Certus 700 class | Safety plus higher-capacity L-band |
The LT-3100S combines Distress Alert, Safety Voice and MSI reception with routine voice, SMS and modem data. It also supports SSAS and LRIT in the appropriate configuration. A practical choice for vessels that want a dedicated Iridium safety installation without Certus IP bandwidth.
The LT-4100S adds Certus 100 connectivity with two voice channels and maximum IP data rates of 88 kbps download and 22 kbps upload. It suits vessels that need essential messaging, light data applications and fixed satellite telephony alongside the safety functions.
The LT-4200S supports three voice channels and IP data rates of up to 176 kbps in both directions. It is an option for operational email, selected remote applications and controlled backup connectivity.
Intellian announced the commercial launch of the C100M GMDSS in July 2026 with MED Wheelmark and UK MER Red Ensign approvals. The system pairs a compact antenna with a bridge-mounted Safety Control Unit. Support for both standard coaxial and NMEA 2000 cabling can allow suitable existing antenna cabling to be reused after inspection.
The C200M GMDSS combines the maritime antenna, the below-deck unit and a dedicated Safety Display Terminal, bringing GMDSS functionality together with Certus 200 connectivity for routine operational applications.
The Intellian C700 GMDSS combines Iridium safety services with Certus 700 operational connectivity: an option for vessels that want GMDSS and an L-band companion to a higher-capacity broadband system. Existing C700 installations may have an upgrade path with a Safety Display Terminal and handset. Compatibility, software, accessories and flag acceptance are confirmed for each installation.
Thales describes WaveLINK as a GMDSS solution that combines a dedicated panel computer with VesseLINK on Iridium Certus GMDSS. Its published functions include distress alerting, Safety Voice, MSI, LRIT and SSAS. We check the current approved configuration, equipment compatibility and delivery status for your project.
Furuno unveiled the SOLION-100 in September 2026, with retrofit availability expected in late 2026 and newbuild availability in 2027. For projects considering this terminal, Satcenter reviews the published specification and confirms availability and approval status before quotation.
Send us your existing terminal model, vessel flag and trading area. We will recommend a suitable Iridium GMDSS system and outline the installation scope.
Certus, phones and GMDSS
No. An Iridium 9555 or Extreme 9575 handheld satellite phone does not replace an approved GMDSS terminal.
Likewise, a standard Intellian C700, C200M, SAILOR 4300 or Thales VesseLINK installation should not be assumed to be GMDSS compliant. Compliance depends on the complete approved equipment configuration, including the safety interfaces, software, power arrangements and installation.
For routine satellite voice and data, and for Iridium as the third link in a failover setup, see our page on Iridium Certus maritime connectivity and satellite phones.
Installation & commissioning
We plan the equipment and the installation together, so the system fits the vessel's bridge, antenna arrangement and operational schedule. Our project scope can include:
Formal statutory acceptance and certification remain with the relevant authorised parties. Tests follow the prescribed test procedures.
Planning a port call or dry dock? Share the port, attendance window and existing equipment list, and we will prepare the installation scope.
Rotterdam · Istanbul · worldwide
Installations and retrofits in Rotterdam, Amsterdam and Antwerp, during port calls or at the shipyard.
Attendance from Istanbul for vessels in Turkish ports and shipyards, including dry-dock projects.
Engineers mobilised to other European and international ports, with equipment shipped ahead to the vessel.
After handover
Satcenter supports your installation after handover with troubleshooting, configuration help and planned service attendance. Depending on the agreed scope, support can include:
For Certus GMDSS systems that also carry operational data, we manage traffic policies, application access and backup connectivity settings, with safety traffic always taking priority. Round-the-clock help is available through our 24/7 maritime support.
Pricing
The installed price depends on the terminal, required accessories, cabling, power arrangements, airtime service and commissioning scope. A useful quotation identifies:
Send us your vessel information and we will prepare an itemised proposal covering equipment, installation and ongoing service.
FAQ
Answers to the questions shipowners, superintendents and masters ask us most about Iridium GMDSS.
Yes. The IMO recognises Iridium as a satellite communication system provider for GMDSS. The selected equipment and the complete installation must also meet the requirements that apply to your vessel.
GMDSS requirements generally apply to SOLAS passenger ships and to cargo ships of 300 GT and above on international voyages, subject to applicable provisions and exemptions. Iridium itself is not mandatory: the required radio arrangement depends on the vessel and its operation. National rules can also apply to other vessels.
The Iridium satellite network covers the North Pole and the other polar regions. Installation suitability, environmental limits and the required MSI reception arrangement are assessed as well.
No. Network coverage and operational NAVAREA/METAREA broadcasts are separate matters. The broadcast status and flag requirements are checked for the planned routes.
Under the modernised SOLAS definition, Sea Area A3 depends on the recognised satellite service supported by the ship earth station on board. Iridium's global footprint can extend the vessel's A3 coverage into polar waters. This does not remove the need to assess the full radio equipment arrangement.
In an accepted vessel configuration, yes. Before replacement we review flag acceptance, trading area, MSI reception, radio redundancy, power arrangements and any LRIT or SSAS functions that run on the existing terminal.
Selected approved Certus GMDSS systems support routine IP data as well as safety services. Available bandwidth and permitted use depend on the terminal, configuration and service plan, and safety traffic always takes priority.
No. A standard Starlink installation is not an approved GMDSS ship earth station. It supports everyday connectivity, while dedicated approved equipment provides the required safety communication functions. See our Starlink maritime installation page.
Yes. Satcenter provides equipment supply, installation, commissioning and ongoing technical support, with attendance and service scope agreed around your vessel.
Connectivity
Get in touch
Planning a new installation, replacing Inmarsat C or upgrading an existing Certus terminal? Include the vessel name and IMO number, flag and vessel type, trading area, existing GMDSS and satellite equipment, installation port and preferred date, and any LRIT, SSAS or backup data requirements. You can also reach us at info@satcenter.tv or +31 85 560 71 20 (call or WhatsApp).
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