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|Year of Publication||2011|
The GALILEO System is an independent, global, European-controlled, satellite-based navigation system that aims at providing a number of guaranteed services to users equipped with Galileo-compatible receivers. The definition of the GALILEO Services is based on a comprehensive review of user needs and market analysis. The Galileo mission and services was elaborated during the initial definition phase in consultation with user communities and the Member States and evolve to the services currently provided and described in further paragraphs from this article.
There are some services provided autonomously by Galileo and other services resulting from the combined use of Galileo and other systems. This leads to the classification of the Galileo services into four categories:
- GALILEO satellite-only services: These services are provided worldwide and independently from other systems by combining the signals broadcast by the Galileo satellites. There is a wide range of possible applications with different operational requirements that have been grouped around the following reference services:
- Galileo Open Service (OS).
- Galileo High Accuracy Service (HAS), previously known as Galileo Commercial Service (CS).
- Galileo Public Regulated Service (PRS).
- Galileo Support to Search and Rescue Service (SAR).
- GALILEO locally assisted services: The Galileo satellite-only services can be enhanced on a local basis through a combination of local elements. The result is the provision of local services.
- EGNOS services: EGNOS , the European regional satellite-based augmentation system (SBAS), will provide,in future evolutions, augmentation information to both GPS and Galileo constellations, to improve the performance of those global navigation systems. EGNOS v3 will provide new capabilities to support the augmentation of a second GPS signal (L5) and of the Galileo signals E1-E5. .
- Galileo combined services: All the above-mentioned services can be combined with services provided by other navigation or communication systems. This possibility will improve the GNSS services availability at user level and open the door to a wide range of applications. The result will be the provision of combined services.
More information related to EGNOS and Galileo locally assisted services could be found in their related articles in Navipedia.
GALILEO satellite-only services
The following Galileo satellite-only services will be provided worldwide and independently from other systems by combining Galileo signals-in-space  when it achieves its Full Operational Capability:
- Galileo Open Service (OS) results from a combination of open signals, free of user charge, and provides position and timing performance. This service will include authentication capabilities in the future through Galileo OS-NMA;
- Galileo High Accuracy Service (HAS) A service complementing the OS by providing an additional navigation signal and added-value services in a different frequency band. The HAS signal can be encrypted in order to control the access to the Galileo HAS services.
- Galileo Public Regulated Service (PRS) provides position and timing to specific users requiring a high continuity of service, with controlled access. The Public Regulated Service is restricted to government-authorized users, for sensitive applications which require a high level of service continuity. This service is intended for security and strategic infrastructure (e.g. energy, telecommunications and finance);
- Galileo Support to Search and Rescue Service (SAR) represents the contribution of Europe to the international COSPAS-SARSAT co-operative effort on humanitarian Search and Rescue activities. Galileo is to play an important part of the Medium Earth Orbit Search and Rescue system (MEOSAR). Galileo satellites are able to pick up signals from emergency beacons carried on ships, planes or persons and ultimately send these back to national rescue centers. From this, a rescue center can know the precise location of an accident. At least one Galileo satellite will be in view of any point on Earth so near real-time distress alert is possible. In some cases, feedback could be sent back to a beacon, something which is only made possible by Galileo.
The Galileo program was structured according to three main phases: In-Orbit Validation (IOV), Initial Operational Capability (IOC) and Full Operational Capability (FOC). Galileo Initial Services  are the first step towards the Full Operational Capability. The initial services offered by Galileo are Open Service (OS), the Public Regulated Service (PRS) and the Search and Rescue (SAR) service. The Return Link Capability of the Search and Rescue service was declared in January 2020.  The performance of Galileo will gradually improve as additional services are added to the constellation.
For more information about performances of each service, see the article Galileo Performances.