Weather Satellites

Polar orbiting satellite's path around the earthThe world's first meteorological satellite, was launched from Cape Canaveral on April 1, 1960. Named TIROS for Television Infrared Observation Satellite, it demonstrated the advantage of mapping the earth's cloud cover from satellite altitudes. TIROS showed clouds banded and clustered in unexpected ways. Sightings from the surface had not prepared meteorologists for the interpretation of the cloud patterns that the view from an orbiting satellite would show.

TIROS was a polar orbiting satellite. Polar orbiting satellites (POES) continued to be used today and offer the advantage of daily global coverage, by making nearly polar orbits roughly 14.1 times daily. Since the number of orbits per day is not an integer, the orbital tracks do not repeat on a daily basis. Currently in orbit we have morning and afternoon satellites, which provide global coverage four times daily.

Geostationary orbiting satellite's path around the earthThe geostationary (GOES) satellites were placed in orbit beginning in 1966. Unlike POES satellite, GOES satellites orbit at an altitude of 22,236 miles (35,786 km). At this distance the satellite completes one orbit of the earth in 24 hours. The net result is the satellite appears stationary, relative to the earth. This allows them to hover continuously over one position on the surface. Because they stay above a fixed spot on the surface, they provide a constant vigil for the atmospheric "triggers" for severe weather conditions such as tornadoes, flash floods, hail storms, and hurricanes.

There are advantages and disadvantages to each kind of orbit.

  Advantages Disadvantages
Polar Orbits
  • Closer to the earth with an orbit of about 520 miles (833 km) above the surface.
  • Much more detailed images.
  • Excellent views of the polar regions.
  • Cannot see the whole earth's surface at any one time.
  • The path of each orbit changes due to the earth's rotation so no two images are from the same location.
  • Limited to about six or seven images a day since most of the time the satellite is below the earth's horizon and out of range of listening equipment.
  • Always located in the same spot of the sky relative to the earth.
  • Can view the entire earth at all times.
  • Can record images as fast as once every minute.
  • View is always from same perspective so motion of clouds over the earth's surface can be computed.
  • Also receives transmissions from free-floating balloons, buoys and remote automatic data collection stations around the world.
  • Located about 22,000 miles (35,000 km) in space, providing less detail views of the earth.
  • Views of the polar regions are limited due to the earth's curvature.

Next: GOES Images