Space navigation systems and the role of clocks. The adopted solutions in the existing GPS system and in the planned Galileo system

Summary form only for tutorial. This tutorial will present the general principles and nomenclature for orbits, space navigation, different types of navigation, and their requirements for electronic measurements. It will explore the role of the atomic clocks and time scales in global navigation. The tutorial will also give the important characteristics of the existing Global Positioning System and of the future GALILEO System, which will become operative in 2008 or 2009. Finally,the tutorial will cover some particular solutions for some very specific requirements, primarily for the use of systems in air and sea navigation in restricted areas. The tutorial will present its information in this sequence: Principle of navigation, orbits, and systems of localization Time scales and clocks in navigation systems Description of the GPS navigation system and the Galileo project Timing systems in GPS and Galileo