GALILEO

 Galileo is a joint initiative of the European Commission ( EC ) and the European Space Agency ( ESA ) 

When fully operational the system will have 30 satellites in three planes , placed equally around the equator with semi - major axes of 30000 km and an inclination of 56 ْ 

The satellites are to be for search and rescue as well as navigation 

The reason for this European initiative is that satellite navigation users in Europe can only get positions from US GPS or Russian GLONASS satellites 

The military operators of both systems will give no guarantee that they will maintain an uninterrupted service 

The first experimental Galileo satellite has been launched and the remaining satellites should be in orbit by 2008 

With GPS GLONASS and Galileo it will be possible to get high accuracy positions in the urban canyons of high rise cities because there could be as many as 90 satellites available 

But the strongest argument the one most likely to get the system off the ground is the business case for Galileo namely the European aerospace , manufacturing and service provider business opportunities 

The system cost is currently estimated to  be 3200 million euros with a total expected return to Europe over 20 year of 90 000 million euros 

The European strategy appears to be that EGNOS will compensate for the shortcomings of GPS and GLONASS for civil access to the necessary accuracy and integrity but Europe’s civil satellite infrastructure is not under Europe’s control 

There will be two Galileo Control Centres ( GCC ) in Europe controlling the satellites and carrying out the navigation mission management 

Twenty Galileo Sensor Stations ( GSS ) in a global network will send data to the GCCs through communications network where integrity information  and time signal synchronization of all satellite and ground station clock will be computed 

Data exchange between the GCCs and satellites will be through 15 uplink stations 

The services to be delivered have been identified as Open Access for most non - specialist users a Safety - of Life capability with appropriate accuracy and integrity , Commercial services and a more secure Public Regulated Navigation service 

Galileo will be interoperable with GPS , GLONASS and EGNOS and this has influenced the design of the satellite signals and reference standards 

The Open , Commercial and Safety of Life services will have two open navigation signals with separate frequencies for ionospheric correction 

Data is to be added to one ranging code and the other ranging code is to be used for more precise and robust navigation measurements 

In principle no ranging code is to be encrypted so that the signals may support Open and Safety of Life services 

Service providers may encrypt one of data less ranging codes for commercial applications , such as for a Universal Mobile Telecommunications System - GSM 

However whether this will be compatible with a Safety of Life service is questionable 

There will be a third navigation signal that will enable three carrier phase ambiguity resolution which might be an encrypted ranging code for commercial service exploitation 

There will be integrity data for safety of life applications and there may be encrypted data for commercial service exploitation 

Commercial data might include GPS signal corrections or location maps 

The Public Regulated Navigation service will also have two navigation signals with encrypted codes and data 

The signals will be on separate frequencies for ionospheric correction and no separate frequencies from Open services so that there may be local jamming of Open signals without affecting the Public Regulated Navigation Services 

The applications for the Public Regulated Navigation Services are seen as those for national security police , emergency services , critical energy , transport and telecommunications applications and economic and industrial activities of European strategic interest such as baking services 

It is likely there will be a restricted distribution of receivers manged by national governments 

A local component driven by user and market needs , public regulation , and finance may have differential corrections for single frequency users leading to an accuracy of better that one metre 

Three carrier phase ambiguity resolution will improve that to better than 0.1 metre 

The Local component may report integrity with a time to alarm of one second 

Such a system would enhance mobile phone networks , e.g E911 in urban canyons and have indoor applications 

Pseudolites , local ground based transmitters that broadcast a Galileo type signal , could be included for increasing the availability of the Galileo service in a defined local area 

The search and rescue transponder on each Galileo satellite will be coordinated by the Cospas - Sarsat International Satellite System for search and rescue operations 

It will have to be compatible with the Global Maritime Distress and Safety System ( GMDSS ) and be able to respond to signals from Emergency Position Indicating Radio Beacons ( EPIRB ) 

An added facility may be for an acknowledgement signal to be received by the vessel or aircraft in distress through the broadcast Galileo signals 

The table below shows the planned signals and frequencies 

The satellite launch programme has similar time scales to that of EGNOS