#Galileo : fonctionnement du GPS européen

Galileo Satellite System Overview

The transcript provides an overview of the Galileo satellite system, detailing its constellation of 24 satellites orbiting Earth to enable precise positioning and navigation.

Galileo Satellite Constellation

• Galileo consists of 24 satellites positioned approximately 23,000 kilometers above Earth in three different orbits, with 8 satellites per orbit and up to 6 additional reserve satellites.

Satellite Signal Emission

• Satellites emit signals continuously, crucial for determining location. Even with high user numbers, the system remains efficient. Users like Lucas equipped with a Galileo receiver can receive and decode these signals for positioning.

Distance Calculation and Positioning

• Receivers calculate signal travel time from satellites to determine distance using the speed of light. This enables users like Lucas to trilaterate their position accurately by measuring distances from at least three satellites.

Importance of Fourth Satellite Visibility

• A fourth satellite is necessary for clock synchronization among all satellites and receivers due to timing-based operations. Synchronization ensures precise positioning accuracy within nanoseconds, critical for accurate location determination.

Ground Segment Operations

• Galileo comprises not only satellites but also two control centers and 16 ground stations globally. These elements collectively form the ground segment responsible for monitoring system functionality, calculating satellite positions relative to Earth, and ensuring accurate user positioning every 100 minutes.