Iridium GMDSS 
Frequently Asked Questions

Iridium GMDSS FAQ

Real choice is on the horizon.

Iridium GMDSS will enhance your safety at sea, offering reliable coverage where no other options exist. Scroll below for answers to your questions in anticipation of service launch.

To learn more about Iridium GMDSS or to find a Service Provider,
please visit www.Iridium.com/GMDSS.

Frequently Asked Questions

General Questions

Other Questions

What is the difference between Iridium GMDSS and Inmarsat GMDSS?

Iridium GMDSS will offer coverage, capability, and cost advantages over the existing option, providing mariners with enhanced safety at sea never before possible. Iridium GMDSS will be the first and only GMDSS solution to offer truly global coverage, including polar regions, enhancing safety at sea and offering reliable coverage where Inmarsat does not.

All Iridium Connected® GMDSS terminals will come standard with functionality for all satellite GMDSS services, and will initiate both Distress Alert and Safety Voice quickly with the press of just one button. The initial Iridium Connected GMDSS terminal from Lars Thrane is expected to supply all three satellite GMDSS services at about 25 percent of the cost of the current equipment required to do the same, allowing more vessels to access these life-saving services.

Why is Iridium working to offer GMDSS services?

Over the past 15 years, Iridium and its Value-Added Manufacturers have built an impressive track record of providing global safety and security to mariners everywhere. Today, Iridium equipment is already used on more than 50,000 vessels around the world. The Iridium network is resilient, robust, and a trusted provider for the maritime market. The addition of Iridium GMDSS services will allow mariners to feel safer anywhere at sea.

No other company has been able to provide this service. How do I know that Iridium is reliable?

More than 1.4 million people, organizations, and things rely on Iridium to provide critical communications all over the world. Iridium’s crosslinked mesh architecture creates a web of coverage encompassing 100% of the planet from Low Earth Orbit, providing low-latency, weather resilient services unlike any other satellite provider.

As Iridium developed its GMDSS service, it underwent a multi-year process that included strict testing protocols, multiple reviews with panels of experts, and examinations to obtain Recognition from the International Maritime Organization (IMO) and a Letter of Compliance from IMO’s GMDSS regulator, the International Mobile Satellite Organization (IMSO). Furthermore, IMSO conducts quarterly examinations of Iridium’s operations to ensure that they continue to be in compliance with the IMO's requirements.

What other maritime safety services does Iridium offer?

Iridium and its partners are committed to providing global safety and security to mariners everywhere. Today, Iridium Connected equipment is already used on 50,000 vessels around the world for non-GMDSS safety and security purposes including Ship Security Alert System (SSAS), Long-Range Identification Tracking (LRIT), Search & Rescue (SAR), Fisheries VMS & Catch Reporting, Emissions Monitoring (MRV), E-Navigation, Anti-Piracy & Citadel Solutions, and Ice Navigation. To learn more about Iridium maritime safety solutions, please visit https://www.iridium.com/solutions/maritime/safety/.

Iridium GMDSS Services

Rescue Coordination Centers

Iridium Connected® Equipment

Iridium SafetyCastSM (MSI)

Iridium GMDSS Services

Iridium GMDSS will provide truly global safety services to mariners, even in the polar regions.
The Iridium Connected LT-3100S GMDSS Terminal during Alpha and Beta Trials

Where do Iridium GMDSS services work?

Iridium will provide unprecedented coverage by enabling GMDSS satellite services around the entire globe, including over the Arctic and Antarctic waters in Sea Area A4, even in adverse weather.

How much does Iridium GMDSS cost?

Iridium GMDSS distress services are available at no charge to subscribers. There are a number of commercial plans available to cover standard calling and data communications through Iridium Connected equipment, including GMDSS terminals. Please contact an Iridium GMDSS service provider to learn more.

Do standard Iridium voice and data services work during a distress call?

As required by the IMO, commercial services are "pre-empted" by Priority GMDSS traffic, meaning your distress call will take priority over other voice and data services. This is done by design to ensure the safety of your crew and vessel.

Do Iridium GMDSS services work with or as a companion to the existing Inmarsat GMDSS service?

Iridium Connected GMDSS terminals can work alongside existing GMDSS equipment to add services and improve coverage.

What happens if an Iridium Connected vessel is in a zone with no Iridium METAREA/NAVAREA?

Iridium will launch with a majority of METAREAs and NAVAREAs broadcasting information to vessels with Iridium Connected equipment. If a METAREA or NAVAREA coordinator does not send their information to the Iridium GMDSS system, then the vessel will not receive the weather and navigation broadcasts for that region, though GMDSS Distress Alert and Safety Voice will still be available. Iridium continues to work with the remaining METAREAs and NAVAREAs to bring this critical safety information to vessels traveling anywhere in the world.  Vessel owners should always consult with their flag administration and Port State Authorities to ensure they are operating in a compliant manner.

Is there a list of certified Iridium GMDSS service providers?

Approved Iridium GMDSS Service Providers can be found at www.iridium.com/gmdss

What is the added benefit of Iridium GMDSS for non-SOLAS vessels?

The Iridium network is a trusted provider of safety and security services to more than 50,000 vessels around the world (80 percent of which are non-SOLAS). Many smaller, non-SOLAS vessels rely on GMDSS and other safety services to allow their crews to feel truly safe anywhere at sea.

Iridium GMDSS allows ships to quickly send definitive location and identification information to a Rescue Coordination Centers (RCC) and speak to an RCC operator to share key distress information, within 30 seconds of pressing the red distress button. Additionally, Iridium GMDSS includes Iridium SafetyCastSM, which delivers important navigational and meteorological information to vessels with Iridium onboard, enabling proactive safety measures. Iridium’s global GMDSS services could have a significant effect on the success of a Search and Rescue operation. 

Will Iridium GMDSS be available on Iridium Certus® at the time of service launch? If not, will I need to change equipment when it is?

Iridium GMDSS services will initially be available exclusively through Lars Thrane’s LT-3100S terminal, which operates on Iridium’s narrowband services.

Iridium Certus maritime equipment manufacturers are currently working with Iridium to meet regulatory requirements to offer GMDSS through these terminals as well. More details will be shared as the process continues.

Iridium GMDSS Equipment: LT-3100S

Who manufactures Iridium GMDSS terminals?

Lars Thrane is manufacturing the first Iridium Connected® GMDSS terminal, LT-3100S. Iridium Certus maritime equipment manufacturers Cobham, Thales, and Intellian are currently working with Iridium to develop auxiliary equipment for their existing broadband terminals to offer GMDSS through the Iridium Certus platform. More details will be shared as the process continues.

How does the LT-3100S compare to the Inmarsat-C?

Iridium GMDSS will enhance safety at sea, offering reliable coverage where Inmarsat does not, including Arctic and Antarctic waters in Sea Area A4. Unlike the competitive solution, the LT-3100S comes standard with functionality for all satellite GMDSS services: Distress Alert, Safety Voice, and Maritime Safety Information (MSI). Plus, Iridium Connected GMDSS terminals will initiate both Distress Alert and Safety Voice quickly with the press of a button.

The LT-3100S will be available for about 25 percent of the cost of the current equipment required to do the same, allowing more vessels to access these life-saving services anywhere in the world. Please contact an Iridium GMDSS service provider to learn more.

What countries have type-approved the LT-3100S?

Iridium Equipment used to comply with SOLAS must be Type Approved by their Flag State. For vessels that are not using Iridium GMDSS Equipment to comply with SOLAS requirements (such as non-SOLAS vessels), Type Approval is not an issue. 

In September 2020, the European Union’s Marine Equipment Directive (MED) type-approved the LT-3100S. This approval is recognized by all members of the European Union, as well as many other countries. The United States, Canada, and Marshall Islands have independently type-approved the LT-3100S. Lars Thrane continues to receive additional approvals in anticipation of the commercial service launch of Iridium GMDSS.

How can a vessel owner be sure Iridium GMDSS equipment satisfies regulatory requirements?

Iridium has obtained Recognition from the International Maritime Organization (IMO) and a Letter of Compliance from IMO’s GMDSS regulator, the International Mobile Satellite Organization (IMSO), to be a provider of GMDSS. As always, vessel owners are ultimately responsible for working with their flag administration and Port State Authorities on all compliance questions.

Can you cancel a false alarm?

Yes, the process for cancelling a Distress Alarm on the LT-3100S is quite simple and easy. When the Red Button is pressed to activate a Distress Alert, an option to cancel the Distress Alert appears on the screen. The operator can simply select this option and confirm the cancellation. Once a Distress Alert has been cancelled, the Rescue Coordination Center (RCC) will be notified. Please note that the RCC may still follow-up with the vessel.

Does the LT-3100S have a battery backup in case of vessel or power failure?

The LT-3100S should be connected to an approved GMDSS power supply along with the other GMDSS communications equipment to ensure ongoing connectivity in the event of power loss. 

When will alternative Iridium Connected GMDSS terminals be available to market?

Iridium Certus maritime equipment manufacturers Cobham, Thales, and Intellian are currently working with Iridium to develop auxiliary equipment for their existing broadband terminals to offer GMDSS through the Iridium Certus platform. More details will be shared as the process continues.

The Iridium Connected LT-3100S GMDSS Terminal during Alpha and Beta Trials
The Iridium Connected LT-3100S GMDSS below-deck unit during GMDSS testing.

Rescue Coordination Centres (RCCs)

Iridium presents its GMDSS service at an International Maritime Organization hearing.

Will I receive a notice that my distress signal is being addressed?

Within 10 seconds of being activated, the LT-3100S terminal will display a “delivered” notification, indicating that Iridium’s centralized GMDSS system has received the Distress Alert. Once the Rescue Coordination Center (RCC) has acknowledged their receipt of the Distress Alert, the terminal will display an “acknowledged” notification.

After the first "Distress" notification, the terminal will automatically initiate a Distress Call from the terminal to the RCC, allowing those onboard to share additional details about the distress situation, including the nature of the emergency and other information, such as how many people are on-board.

Are Iridium GMDSS services only available in English?

The default for GMDSS services is the international maritime language “Seaspeak”, which is based on English. However, Iridium GMDSS users can select a specific Rescue Coordination Center from their own region or country for all emergency communications, regardless of vessel location. If the on-board coordinators cannot speak English or Seaspeak, this is recommended.

Maritime Safety Information (MSI) / Iridium SafetyCastSM

What type of information is sent over Iridium SafetyCast?

Maritime Safety Information (MSI) is transmitted through an Enhanced Group Call (EGC) service called Iridium SafetyCast. The main type of information broadcast through this service is navigational and meteorological information and warnings. Depending on location, additional information, such as anti-piracy and ice reports, may be available. RCCs can also broadcast safety-related information through Iridium SafetyCast.

In what languages is MSI broadcast?

All international EGC broadcasts are sent in English; however, some Coastal Warning information may be sent in a national language.

Will Iridium GMDSS offer a maritime broadcasting service like Inmarsat’s Fleetnet?

In addition to supporting all three satellite GMDSS services in one terminal, Iridium Connected GMDSS equipment enables other safety and non-safety capabilities including shore-to-ship distress calling, maritime assistance, and standard calling and messaging (SMS).

If you have additional questions, please contact gmdss@iridium.com.