About Inmarsat: The Gold Standard in Maritime Safety
Inmarsat has been the backbone of global maritime and aviation safety for decades. Operating a sophisticated fleet of geostationary satellites, Inmarsat provides near-global coverage (excluding extreme polar regions). Sending a Free SMS to Inmarsat is the primary way for families to reach seafarers and for companies to coordinate logistics in areas without cellular reception.
Technical Specifications
| Constellation Type | Geostationary (GEO) |
| Latest Generation | Inmarsat-6 (I-6) F1 & F2 |
| Orbital Altitude | 35,786 km (22,236 miles) |
| Coverage Area | Global (Excluding Poles) |
| Number Prefix | +870 (Universal) |
Inmarsat I-6 Satellite Constellation
The current Inmarsat-6 satellites are the most advanced commercial communications satellites ever launched. Positioned at 35,786 km in geostationary orbit, they provide both L-band (for SMS and voice) and Ka-band services. This dual-band capability ensures that your satellite text message has the highest priority and stability, even during solar storms or heavy weather at sea.
Instructions for Sending SMS to +870
Follow these guidelines for guaranteed message delivery to Inmarsat terminals:
- Unified Prefix: Use the universal Inmarsat prefix +870 followed by the 9-digit terminal number. Note: Older prefixes like +871 or +873 are no longer in use.
- Message Length: Standard 160 characters. Avoid long messages as they may be split and arrive out of order on older IsatPhone Pro models.
- Signature: Since Inmarsat phones may not show your mobile number as the sender, always include your name at the end of the text.
- Sky Access: The recipient must be outdoors with a clear view of the sky towards the satellite's position (South if in the Northern Hemisphere, North if in the Southern).
Why +870?
The +870 country code is the Single Network Access (SNAC) code for all Inmarsat services. It simplifies global routing, meaning you don't need to know which specific ocean region (Atlantic, Indian, or Pacific) the satellite phone is currently located in.