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Overview
A satellite is an object that orbits a larger body. Natural satellites include moons orbiting planets. Artificial satellites include human-made spacecraft placed in orbit for communication, navigation, weather monitoring, science, defense, Earth observation, and exploration.
Natural and Artificial Satellites
Natural satellites form through astronomical processes or are captured by gravity. Artificial satellites are designed, launched, and operated by humans. Both follow the same basic gravitational principles.
How Satellites Orbit
A satellite remains in orbit because it has sideways velocity while gravity pulls it inward. It continuously falls around the central body rather than falling directly into it.
Altitude and Period
Orbital altitude affects orbital period. Satellites farther from Earth generally take longer to complete one orbit. Low Earth orbit satellites circle Earth quickly, while higher satellites can have much longer periods.
Low Earth Orbit
Low Earth orbit is relatively close to Earth and is used for many imaging, science, crewed spacecraft, and communications missions. Satellites in this region move quickly and may experience small atmospheric drag.
Geostationary Orbit
A geostationary satellite orbits above Earth's equator with a period matching Earth's rotation. To observers on the ground, it appears to remain over the same location. This is useful for communications and weather monitoring.
Satellite Functions
Satellites support global positioning, communications, television broadcasting, weather forecasting, climate observation, military surveillance, disaster monitoring, astronomy, and scientific measurement.
Orbital Decay
Satellites in low orbits can slowly lose energy due to atmospheric drag. As energy decreases, the orbit can shrink until the satellite reenters the atmosphere unless corrected.
Space Debris
Artificial satellites share orbital regions with debris from old spacecraft, rocket stages, and collisions. Space debris creates risk because objects in orbit move at very high speeds.
Common Mistakes
A common mistake is thinking satellites are outside Earth's gravity. Satellites remain under gravity; gravity is what keeps them in orbit. Another mistake is assuming all satellites have the same altitude, speed, or purpose.
Why This Matters in Physics
Satellites connect orbital motion to practical technology. They show how gravitation, circular motion, energy, navigation, communication, and engineering combine in real systems.