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How many Iridium satellites are there? 

Iridium has a constellation consisting of 66 low-earth orbiting (LEO) satellites (plus 9 in-orbit spares), cross-linked to operate as a fully meshed network. Several overlapping satellites ensure coverage over the entire globe. 

How do I make a call with my Iridium satellite phone? 

Extend the antenna into its full position and point it straight up at the sky. Press the power button on the phone. You should see the Iridium splash screen, followed by 'Searching' and finally 'Registered'. Once the phone is registered you are ready to dial. 

How do I call a landline or mobile number using an Iridium satellite phone? 

Press the 0 key until the + appears or dial “00”. Dial the country code, area code and phone number. 

•Example: + (country code) (area code/city code) (phone number) 

•Example: + 1 416 253 6008 

How do I call another Iridium satellite phone? 

From your, Iridium satphone, or dial “00” or press and hold the 0 key until the + appears followed by the 8816 Iridium phone number. 

•Example: + 8816 666 9253 

Do Iridium satellite phones support text messaging? 

Yes, it is easy to send a text message and incoming text messages are free. Visit our send a free SMS web page. 

How do I receive calls on my Iridium satellite phone? 

The Iridium phone antenna needs to be fully extended with an unobstructed view of the sky in order to receive a call.  

How do I send an e-mail to an Iridium satellite phone? 

Send your e-mail to iridium telephone (where 8816xxxxxxxxx is the Iridium mobile number) 

How do I check my balance? 

You can check the balance of your Iridium prepaid SIM card by simply dialling 2888, free of charge. 

If I have a pre-paid Iridium satellite contract, how can I top-up my balance? 

Easy! Just visit AST’s top-up portal and top-up as and when you need to. 

How can I test my Iridium satellite phone? 

Iridium post-paid and pre-paid customers can place a free call to 00-1-480-752-5105 to test their phone. An automated message will play stating that the call was successful. If an error message is played or if the call does not connect at all, please contact AST Global Customer Support. 


Truly global satellite radio is a critical communication tool for a variety of scenarios. While standard mobile phones require very little preparation and training, satellite-enabled devices may be unfamiliar to users at first. It is important to ensure your team is familiar with the recommendations of how to best use two-way satellite radio communications. 

Be Prepared Before Talking 

Before using your Iridium Push-to-Talk (PTT) enabled device, charge the battery and turn the phone on. 

Make sure the device is within the geographic area covered by your Iridium PTT talk-group. 

Two-way radios are a “one-at-a-time” system; when you press the Push-to-Talk button, no one else in your group can speak or be heard. In order to make the most of your talk session and avoid blocking other speakers, it is important to think about your message in advance. 

Identify Yourself and the Recipient of Your Message 

There may be a group of intended users all sharing the same PTT talk-group, so it is important to identify yourself and your target audience immediately when you initiate a transmission. Talker’s name will appear on the screen if provided in the Command Centre. 

Be Patient 

The other user(s) in your talk-group may not be able to respond immediately. Give them time to reply. 

Use Short, Clear and Concise Messages 

As two-way radios only allow one person to speak at a time, it is best to keep your transmissions clear and to the point. This gives other users an opportunity to acknowledge your message and/or request further clarification before continuing on with your next point. 

Know-How Much Time You Have To Talk 

You have a total of 40 seconds to say your message before your session expires. If your message is longer than the allowed talk time, simply press the push-to-talk button again and share the rest of your message. 

Pause Before Speaking 

When you first press the PTT button, there can be a short delay before your message transmits which could result in your first few words being truncated. Wait a second before speaking to be sure your listeners receive your whole message. 

Learn the Lingo 

Two-way radio communications are most effective when everyone understands and uses similar language and etiquette, especially when there are more than two people in the talk-group. 

• “Over” – I’ve finished speaking 

• “Say again” – Repeat your last message 

• “Stand-by” – I acknowledge your transmission, but can’t respond right now 

• “Go ahead” – I can respond, go ahead with your message 

• “Roger” – message received and understood 

• “Out” – Conversation is finished, the channel is clear for other users 

Quick Tips 

• Deploy Antenna for maximum signal strength and improved standby use. 

• Keep your device antenna extended and vertically oriented whenever you want/need to be accessible. 

• If the signal strength is weak, attempt repositioning your device. 

• Press the PTT button and wait for the beep before talking. 

• Hold the handset approximately 4 in. (10 cm.) from your mouth when talking. 

• Identify yourself and recipient of the message. 

• Be Patient! The recipient may be busy. 

• Turn the volume to an appropriate level for your environment. 

• Speak slowly and clearly. 

• Test your Iridium PTT-enabled device on a monthly basis. 

• Ask AST Global Customer Support for the latest Iridium PTT firmware. 


What is the difference between Iridium GMDSS and Inmarsat GMDSS? 

Iridium GMDSS offers coverage, capability, and cost advantages over the existing option, providing mariners with enhanced safety at sea never before possible. Iridium GMDSS is the first and only GMDSS solution to offer truly global coverage, including above and below the 65th parallel, enhancing safety at sea and offering reliable coverage where Inmarsat does not.

All Iridium Connected® GMDSS terminals 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.

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 reviews and testing protocols, multiple 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 requirements.

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 us 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.

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

Iridium GMDSS allows ships to quickly send definitive location and identifi cation 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.

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.

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 onboard coordinators cannot speak English or Seaspeak, this is recommended.

What type of information is sent over Iridium SafetyCastSM? 

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.


Please visit our Iridium Certus page to find out more about the network, coverage areas and products available.

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