To send a SMS to an Inmarsat satellite phone you can use their online web form or you can send an email in the following format: 87077642xxxx@message.inmarsat.com (the first part of the email address is the satellite phone number).
To send a SMS to an Iridium satellite phone, you can use their online web form here, or you can send an email in the following format: 8816XXXXXXXX@msg.iridium.com (the first part of the email address is the satellite phone number).
To send a SMS to a Thuraya phone number, you can use their online web form here, or you can send an email in the following format: 88216xxxxxxxx@sms.thuraya.com (the first part of the email address is the satellite phone number).
To send a SMS to a Globalstar phone number, you can use your cellphone, since Globalstar uses US-based phone numbers for its satellite phone users. Note that Globalstar SMS messages to Globastar satellite phones are limited to 17 characters instead of 160, so keep it (very!) short!*
*Globalstar Sat-Fi supports full SMS messages.
If you're going to send an SMS message directly from your cellphone to a satellite phone, you will typically pay between $0.25 to $0.50 per message (Verizon looks to be an exception). We did some investigative reporting to figure out exactly what you would pay with some of the most popular carriers:
T-Mobile: $0.50 per SMS
AT&T: Unable to verify specifically for satellite phones, but looks to be either $0.25 or $0.50 for a SMS message.
Verizon: According to the Verizon rep I spoke with, all SMS messages, even to satellite phones, are free with any Verizon plan.
Sprint: Customer support or sales wouldn't release plan information without proof of a valid Sprint phone number, so we were unable to verify costs for sending an SMS to a satellite phone using a Sprint cellphone.
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