Satellites and the ISS

In short: Satellites orbit the Earth and serve navigation, communication, weather observation and research. The International Space Station ISS is an inhabited laboratory at about 400 kilometres altitude.

In more detail: A satellite is constantly falling around the Earth: its high speed keeps it from crashing (schwerkraft-und-freier-fall).

In detail

• Orbits: Low (LEO), medium (e.g. GPS) and geostationary (about 36,000 km).
• Geostationary: Appears to stand still above a point; television and weather.
• Navigation: GPS, Galileo, GLONASS (navigation-gps-funktionsweise).
• Earth observation: Climate data, maps, disaster warning.
• ISS: Orbits the Earth about 16 times a day; the crew experiences weightlessness.
• Weightlessness: Not missing gravity but free fall.
• Visible: The ISS can be seen as a bright, fast-moving light in the sky.
• Space debris: Fragments endanger satellites (mars-und-raumfahrt).