GLOBAL POSITIONING SYSTEM Syllabus GS Paper 3 - Sci and Tech)

Context: Recently, few everyday technologies have had the revolutionary impact that the Global Positioning System (GPS) has, transforming everything from civilian use to military operations, precision scientific studies, urban planning, and disaster risk estimation, significantly altering our sense of place and expectations of location.

Global Positioning System (GPS)

• About: The U.S. Department of Defence initiated the GPS program in 1973.
• First Satellite: It was launched as part of the program in 1978.
• Composition: The modern GPS satellite constellation comprises 24 satellites.

oThese satellites move around the Earth in six orbits.

• Satellite Orbits and Configuration: The satellites in the GPS constellation are positioned in six orbits.

oEach orbit, located 20,200 km above the Earth, is occupied by four satellites.

• 3 Main Components of GPS Program: The GPS program is structured into three main components: the space segment, the control segment, and the user segment.
• Space Segment: The space segment encompasses the 24 satellites forming the GPS constellation.

How does GPS work?

• GPS Satellite Broadcasting: Each GPS satellite continuously broadcasts a radio signal that contains information about its location in orbit, operational status, and the emission time of the signal.
• Code-Division Multiple Access: The signals are encoded using code-division multiple access, allowing multiple signals to be transmitted in the same channel, and enabling a receiver to disentangle them.
• Encoding Types: Coarse/Acquisition Mode, which civilians can use to access basic GPS data.
• Precise Mode: Encrypted and reserved for military use.

Other countries and their navigation system:

• Global: Russia's Global Navigation Satellite System (GLONASS), China's BeiDouNavigation Satellite System, and the European Union's Galileo.
• Regional: Japan's Quasi-Zenith Satellite System (QZSS) and India’s Indian Regional Navigation Satellite System (IRNSS) or NavIC