Artificial Earth satellites – these are man-made objects placed by rockets into Earth’s orbit to perform tasks such as telecommunications, navigation (GPS), weather observation, scientific research, or military intelligence. They remain in space thanks to orbital motion, being in a state of continuous fall, which balances the Earth’s gravity. Artificial satellites operate mainly in low Earth orbit (LEO), geostationary orbit (GEO), or sun-synchronous orbit, serving for communication, meteorology, navigation, and scientific research.
The first artificial satellite of the Earth was the Soviet Sputnik 1, launched on October 4, 1957. Since then, over 8,000 satellites have been sent into Earth’s orbit and into outer space, and seven consecutive ones orbit planets other than ours. However, of the nearly 5,000 satellites currently in orbit, only about 2,000 are fully functional, which is less than 40%. A satellite’s orbital period around the Earth does not depend on its altitude above the Earth’s surface. To move around the Earth, a satellite must have a speed of at least 10 km/s.
The largest artificial satellite of the Earth is the ISS = International Space Station. The most distant satellite from Earth is the Voyager 1 probe – moving at a speed of 38,026.79 miles per hour (17.0 km/s) relative to the Sun.
Main applications and types of artificial satellites:
Telecommunications: Transmission of TV signals, internet (e.g., Starlink), and telephony.
- Navigation: Positioning systems (GPS, Galileo, GLONASS).
- Meteorological: Weather and climate monitoring (e.g., Meteosat, NOAA).
- Observational (Remote Sensing): Earth imaging, environmental research,
- Scientific and research: Space telescopes, study of the atmosphere and ionosphere.
- Military satellites: Providing independent Earth observation (reconnaissance), tracking enemy troop movements, intercepting communication signals, and early warning against missile attacks. They operate regardless of weather and time of day, using advanced sensors, including synthetic aperture radar (SAR), which allows for precise imaging in all conditions.
Key information:
Orbits: Satellites are placed at various altitudes – from low Earth orbit (LEO, e.g., International Space Station ISS), through medium Earth orbit (MEO), up to geostationary orbit (GEO).
Number: Thousands of satellites are currently orbiting the Earth, only some of which are actively functioning, while the rest are space debris.
Observation: Some objects, like Starlink satellites, are visible from Earth as „trains” moving across the sky.
Space race: The launch of Sputnik 1 began the space age and the rivalry between the USSR and the USA.
Here is a list of the most famous artificial satellites:
Sputnik 1 (1957): Soviet probe, the first artificial Earth satellite, which started the space age.
- Sputnik 2 (1957, USSR): Carried the first living creature – the dog Laika – into orbit.
- Vanguard 1 (1958, USA): The first satellite to use solar batteries, which allowed for long-term operation.
- Explorer 1 (1958): The first American satellite, through which radiation belts (Van Allen belts) were discovered.
- TIROS-1 (1960, USA): The first meteorological satellite, which revolutionized weather forecasting.
- Telstar 1 (1962, USA): The first active telecommunications satellite, enabled the transmission of television signals across the Atlantic.
- Syncom 3 (1964, USA): The first satellite placed in geostationary orbit.
- International Space Station (ISS): The largest inhabited artificial satellite, serving as a scientific laboratory.
- Starlink (SpaceX): A megaconstellation of thousands of small satellites in low orbit, providing internet, often visible from Earth as a „train.”
- Hubble Space Telescope: A breakthrough telescope observing the cosmos in visible and UV light.
- GPS Satellites (Navstar): A system of navigation satellites enabling precise determination of location on Earth.
- Sentinel (ESA): Satellites of the Copernicus program monitoring the environment and climate.
