2.7 Satellite Motion and Kepler's Third Law

Satellites

  • any objects that orbits another
  • nautral (moon oribiting a planet, a planet orbiting a start)
  • artificial (used for communication, weather forecasting, navigation, survelliance, expoliration, research)

Newton’s experiment

  • at a certain velocity, a cannon will go all the way around the Earth and return to its orginial position
    • ignore air resistance and get cannon out of the way

 

  • satellites are constantly falling

Satellite Motion

  • mass doesn’t affect speed
  • air resistance prevents satellites from orbiting Earth within its atmosphere
  • yet away from the atmosphere, any object at the right altitude and with the right velocity will orbit the Earth as long as the speed stays constant
  • gravity acts a centripetal force

 

Satellite Types

  • Orbits can be classified according to their altitude
  • Low Earth orbit (LEO): 160-1000 km: used for ISS, satellite imaging, communicaitons
  • Geosynchronous orbit (GSO): 37,786 km: orbital period of exactly one day (24 hours) - time period - orbits same speed the Earth rotates
    • Geosynchronous equatorial orbit (GEO) aka geostaniary orbit: a GSO above the equator, resulting in a satellite that satys above a certain point on the Earth’s surface
  • Medium Earth orbit (MEO)