There are several different services, all having different satellites, and they are not interchangeable. The three major satellites are Iridium, Inmarsat, and Globalstar. All of these networks come with satellite constellations orbiting above the earth. Iridium is the only satellite network that offers 100% global coverage, even at the North Pole. Their satellite constellation consists of 66 satellites that orbit in a pattern that covers the entire planet.
Since Iridium’s satellites are constantly moving around the sky at 17,000 miles per hour, even if you cannot get a signal at one zone, it will only be a matter of time until a satellite moves in a better position to offer you a connection. With Iridium satellite phones, you will always have a connection at any location on the earth.
Globalstar has a similar network as Iridium, except it offers 24 satellites and does not offer coverage near the poles. However, it works the same way and offers you a signal within a particular space, even if you must wait. Inmarsat service, however, works very differently between the two. They own 13 satellites, each serving different purposes. However, only three of the satellites account for standard communication.
Despite having only three satellites to aid communication, their satellites are much further away from the earth. This means that each satellite provides a larger bandwidth of coverage. These satellites are also in geosynchronous orbit, which means they are in perfect sync with the earth’s orbit. Due to their geosynchronous capabilities, you do not have to worry about losing the signal. However, since the satellites are stationary, you may have to move until you find a signal using an Inmarsat satellite phone.