There are 150,000 Inmarsat terminals out on the market today. The four Inmarsat satellites are in a geosynchronous (GEO) orbit with the globe, giving them a fixed position over the equator at a high altitude of 36,000 km. It is a high orbit, geostationary system.

To set up an Inmarsat terminal you will need to do some antenna work. Reviewing a map, you will determine which of the four satellites is closest to your location. The handset has a menu where the info is keyed in. The antenna is then moved to point toward the closest satellite. Another antenna adjustment is next – the angel (or azimuths). As the satellites are located in a fixed position over Earth, you will point the flat antenna straight up if you are right below the satellite, or in a sharp angle if you are positioned further away.
It's all pretty straightforward, and there is a signal that will beep when the antenna is set in proper position.

Inmarsat covers the entire globe except North of 80 deg North and South of 80 deg South. You can't use Inmarsat in the interior of Antarctica. Inmarsat is however used frequently by polar stations and ships around Antarctica's coast.

The antenna will not work indoors, but will often transmit through a single glass window.

Inmarsat is orbiting at almost 50 times the height of the low orbit systems (LEO) like Iridium and Globalstar. This has some practical applications:

1. The Inmarsat information (signals) need to travel nearly 100 times the distance (up and down) compared to LEO systems. This makes for a high degree of "latency" or delay, which is quite annoying when talking to sponsors or family back home. Sending data (one-way) provides no problems.

2. The distance implies a stronger signal – which requires more power. The standard mini-M batteries drain in no time.

3. The unit becomes large and bulky compared to the small handheld units from Iridium and Globalstar.

4.  Inmarsat claims their system is more cost efficient – which unfortunately won't show on your bill. Both airtime and terminal costs today are way above the handheld systems.

Those are the cons. So what about the pros?

Inmarsat is a reliable system. When hooked up it will most probably work for the length of the expedition. If you plan to send high speed data there is really no other choice.

The M4/GAN is almost as small as the original mini-M, but fast! With ISDN capability (64 kb/s) the M4 makes it possible to send high quality video. 

At $10.000 it's expensive, and 4 kg/10 lbs (+ computer + solar panels) is not what you want in your back-pack at 8000 meter. But the cost is actually a bargain compared to what it used to be to send video over satellite.

A new high-speed alternative –  Regional BGAN –  was launched by Inmarsat at the end of 2002. Check separate link to your left.


The Mini-M (oh faithful companion), has been the unit for mountaineers and sailors in earlier years. Today however, the Mini-M has more or less lost  to competition from Iridium, Globalstar and Thuraya.

The handhelds are considerably smaller, cheaper and much faster (Thuraya and Globalstar) when it comes to data speed.  You should think twice before buying a Mini-M today. The GANs are instead the way to go, for video and other high speed computer transmissions from stationary (BC) camps, cruising vessels or other situations where weight is not an issue.
 

The leading producers of Inmarsat terminals are two Scandinavian companies: Thrane & Thrane from Denmark and Nera from Norway. If you don't have an extremely good pitch,  don't bother to call them for sponsorship. They get expedition proposals every day.  Note that Nera uses the name Worldcommunicator for the M4 and Worldphone for Mini-M.

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