There exist different Global Navigation Satellite System (GNSS), GPS (US), GLONASS (Russian), COMPASS (Chinese) and GALILEO (European). GALILEO, is the newest, and it consists in 30 satellites which are made in Bremen, Germany, and tested in ESA ESTEC, Netherlands, orbiting in MEO (Medium Earth Orbit) at 23,222km, becoming in the first civilian navigation system in the world. According to the ESA, this first GALILEO satellite generation will be removed in 2022 in order to be replaced by the second one.
GALILEO will provide a very high accuracy positioning and inter-operability with GPS and GLONASS. Its first four satellites were launched in 2011 and 2012 which constituted the In-Orbit Validation (IOV) phase. Initial Operational Capability (IOC), the next phase, is being carried out by next year providing a first performance of the system. Today, august 21st 2014, the 5th and 6th GALILEO satellites will be launched. The idea is to send each 3 or 4 months a couple of them until complete the constellation, according to the ESA. When 18 satellites (the 4 IOV plus other 14 from the IOC) have been launched, the ESA will start the last phase, Full Operational Capability (FOC) that will make the system working at 100%, sending the 12 satellites left, covering beyond the Norway north cape.
GALILEO satellite broadcast 10 different navigation signals making it possible to offer the open (OS), safety-of-life (SOL), commercial (CS) and public regulated services (PRS). They will be available in IOC phase. The reason to broadcast 10 signals was to improve its flexibility giving to each one a specific characteristic with the aim to adapt it to different user profiles. Moreover, this also allows a GALILEO receiver to estimate better the ionospheric delay error. These signals cohabit with the GPS and GLONASS signals therefore it is necessary to avoid interferences between them. To solve it, GALILEO has used a different modulation called Binary Offset Carrier, BOC(1,1) which works the problem out.
Another feature of GALILEO is the Search and Rescue (SAR) function that will allow the user to contact the emergency centers while using a GALILEO device. This already exists with GPS, however, GALILEO adapts a new feature that any other GNSS has, a feedback after the emergency contact, implementing it in the band of 1545MHz.
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