-Here is part two of the episode about independent systems which will deal with constellations. Two main projects were launched, which were both started in the early 1990s and were completed in the late 1990s when the systems were operational. The first project was Globalstar and was launched in the United States. It was commercialized in 2000. It offers a constellation of 44 satellites. The distribution of the satellites is illustrated here with a figure of by Lloyd Wood, an expert in constellations. Globalstar offers hybrid terminals, which can provide GSM services, 2G, and connect to terrestrial networks or switch to the satellite network. According to your location, you can select what type of network to use. and be interconnected to terrestrial networks. The main issue with Globalstar is that it requires major terrestrial infrastructures. Why? To understand, let us have a look at how we can communicate through Globalstar. Let us consider for example one user in Europe who wants to communicate with a user in California. The question is, how can the system allow them to communicate with each other? First, if the system has a global coverage, both our users find themselves under a satellite spot. The problem is that given the coverage of the Earth and of LEO systems, we are not under the same satellite in Europe and in California. How can the user in Europe communicate with the user in California? To do so, the message is sent to a terrestrial station near the caller. The message will reach the terrestrial station through the satellite. Said station will use a terrestrial network to send the message to another station, which will then send it to the callee. As you can see, the user is not independent from terrestrial systems. If, for instance, you find yourself in the middle of the Pacific Ocean, you are not likely to find a station allowing you to communicate. It is the same in the middle of the desert. There will be a lot of issues, which I explain here as Globalstar's limits. In a nutshell, even though you have complete coverage because satellites are covering the whole planet, your service may not cover all users. Globalstar requires a terrestrial station under the same spot to be able to communicate. You will need the material means to set up a terrestrial station and the political right to do so. You need to sign agreements with foreign operators, which is not always possible when you belong to the US government. This was a commercial failure since the aim was to offer such services to the general public. However, terminals are more expensive and they cannot really be used for niche applications since it does not offer global coverage. Then, you also have Iridium. Iridium was also launched in the 1990s. It had much more satellites. Its name comes from the iridium atom whose atomic number is 77. It was supposed to have 77 satellites before settling for 66 in the end. It is a constellation of 66 satellites created by Motorola, which invested five billion dollars in this system. Unfortunately, it was planned to open it to the general public in 1999. But that year, for Globalstar as well, was the start of the GSM. The GSM became globally used. The GSM was highly competitive and much less costly than satellite systems. Satellite systems, which aimed at being cheaper and at competing with terrestrial systems, have collapsed in the face of the GSM and its very low cost. They cost ten to fifteen times more than the GSM. An Iridium terminal costs 1 000 to 1 500 dollars. One minute of communication costs 6, 7 or 9 dollars, which is very expensive compared to the GSM. The competition killed Iridium but it remains a technical prowess. I will explain how it works, as I did with Globalstar. We ask the same question, how can a user in Europe and another in the United States, communicate with each other? It will work a little differently. Both are under a smaller satellite spot. This time, the data will be sent to the satellite, which will relay it to another satellite, then another, then another, until it reaches the satellite under which the callee stands, when it will send the message. Very few terrestrial infrastructures are needed. I did not include them but we just need some system control. There is no need for a terrestrial station under a specific spot to be able to communicate. This is essential as it gives the system global coverage. Iridium and Globalstar's mistake was to try and open the service to the public. However, it soon became a niche service since you can communicate from anywhere on the planet and both poles are covered, which is great for expeditions or the military. 50% of Iridium's turnover comes from the military. And for example after 9/11, we realized that terrestrial infrastructures could stop working or become saturated, and it provides an alternative. Sales increased after that. The US government bought Iridium, then sold its operating rights to a company called Iridium for one billion dollars. So four billion dollars just vanished into thin air, which is a shame. It is profitable again, and slightly more so than Globalstar. Iridium is in the process of changing its satellite systems. Thales Alenia Space is leading this change. I included an illustration of Iridium NEXT, by TAS, at the top of the slide. Those were independent systems. Let us move on to the interconnection with terrestrial systems.
