Satellite-based Communications

Navigation system performance requirements are defined for single aircraft and for the total system that includes the Signal-In–Space, the airborne equipment, and the ability of the aircraft to fly the desired trajectory. All the navigation aids must fulfill four basic performance requirements in order to be certified i.e. continuity, availability, integrity and accuracy.

1. Continuity: It is the ability of the entire system to carry out its function without interruption during planned operating period.
2. Availability: It is the ability of the system to transmit signals of the required quality most of the time. This is a critical requirement in landing guidance and for this reason stand by equipment is added to ground-based aids.
3. Integrity: It is the ability of the navigational aid (s) to warn the pilot that it has failed or giving incorrect message.
4. Accuracy: It is the ability of the navigational aid(s) is to guide the path of an aircraft within pre- defined tolerances.

Galileo is Europa’s contribution to the next generation Global Navigation Satellite System (GNSS) intended to provide the European Nations with greater independence by delivering a civil controlled satellite based navigation system. Implementation of Galileo is expected to stimulate growth in the use of GNSS technology in intermodal transport systems thereby improving mobility safety and quality of life whilst also stimulating economic growth in the areas of receiver manufactures and application development. When considering the possibility of a failure of GPS to maintain a service, the implications for commercial customer in the fields such as telecom, location based services and financial community are clearly not acceptable. For these reasons and in consideration of the potential impacts on European business, the European Commission (EC) and the European Space Agency (ESA) has embarked on the definition phase of Galileo.

The current base line for Galileo calls for a constellation of around 30 middle Earth orbiting (MEO) satellites. The option of including some GEOS in the constellation is not rule out and indeed. Some interesting options could become available if GEOS are used to complement the system. The option of delivering a search and rescue service is also being analyzed for both technical and economic viability.

Frederic Gaspoz