GNSSsatelliter

GNSSsatelliter are satellites that form the backbone of Global Navigation Satellite Systems (GNSS). They broadcast time-stamped radio signals used to determine position, velocity, and precise time on or near the Earth's surface. GNSS comprises several constellations, most notably the United States GPS, Russia’s GLONASS, the European Galileo, China’s BeiDou, India’s NavIC, and Japan’s regional QZSS augmentation system. Some satellites support regional coverage, while others provide global reach.

Most GNSSsatelliter operate in medium Earth orbit at altitudes around 20,000 kilometers, arranged in multiple orbital planes with specific inclinations. Each satellite carries highly stable atomic clocks and a navigation payload that modulates signals with ephemeris and time data. The satellites transmit on multiple radio frequency bands to support robust positioning and signal integrity.

GNSS receivers on Earth compute a user’s position by measuring the time it takes signals from at least four satellites to reach the receiver, solving for three spatial coordinates and clock bias. Combining data from multiple constellations increases accuracy, availability, and resilience to interference and obstructions.

Satellites have design lifetimes commonly in the 10–15 year range, after which they are replaced or refurbished. Ground control networks monitor and manage the constellation, update navigation messages, and synchronize time across the system. GNSSsatelliter thus enable global positioning, navigation, and timing used in transportation, mapping, surveying, finance, telecommunications, and emergency services.