National Weather Service United States Department of Commerce

Weather Satellites

There are two basic types of weather satellite based upon their orbits.

Polar Orbiting Satellites

The 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.

First television picture from space. TIROS-1 Satellite, April 1, 1960.

TIROS was a polar orbiting satellite meaning the satellite orbited in a latitudinal motion which takes it over the north and south poles. Today, polar orbiting satellite round the Earth 14.1 times daily.

Since the number of orbits per day is not a whole number, the orbital tracks do not repeat on a daily basis. Currently in orbit there are morning and afternoon satellites passes, which provide global coverage four times daily.

The advantages to polar orbiting satellites are...

  • Closer to the earth with an orbit of about 520 miles (833 km) above the surface.
  • The closer orbit provided much more detailed images.
  • Excellent views of the polar regions.

The disadvantages are that the satellite...

  • 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.

Go to the Alaska Aviation Weather Unit page for images from the polar orbiting satellites and the tropical regions from the NOAA Satellite and Information Service (NESDIS).

Geostationary Satellites

The first geostationary satellite was launched in 1966. Unlike polar orbiting satellite, geostationary satellites orbit at a much higher altitude of 22,236 miles (35,786 km). Positioned over the equator, 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.

NASA image from ATS-I, December 11, 1966, the first geostationary satellite. North America is in the upper right (Baja California most noticeable) and South America at the far bottom right.

Early geostationary satellites were "spin stabilized" meaning they maintained stability by rotating and therefore viewing the earth only about 10% of the time. Current satellites are stabilized now in a way that they always view the earth.

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.

Geostationary satellite are the bread and butter satellites for the meteorologist. Their advantages are...
  • They always located in the same spot of the sky relative to the earth.
  • They view the entire earth at all times.
  • They can record images as fast as once every minute.
  • Since their view is always from same perspective, motion of clouds over the earth's surface can be computed.
  • They also receive transmissions from free-floating balloons, buoys and remote automatic data collection stations around the world.
The disadvantages of geostationary satellites are...
  • Their location, at 22,300 miles (35,000 km) above the Earth, provides lower detailed views.
  • Views of the polar regions are limited due to the earth's curvature.

Moving Geo"stationary" Satellites

Despite the fact that GOES satellites are stationary relative to their position over the earth, that position can and does get moved. As newer satellites are placed in orbit older versions are moved into storage positions where they can be called upon again if needed.

As such these satellites have rocket engines to do the moving but not likely in a way as you may normally think.

The distance from the earth at which GOES satellites orbit matches the earth rotation (about 22,300 miles/35,000 kilometers). If this distance was less than the satellite would orbit faster than the earth's rotation. An orbit at a greater distance would be slower than the earth's rotation.

If the satellite was orbiting faster then, relative to the earth, the point over which it appears would move east. A slower orbiting satellite would appear to the earth as moving west.

Therein lies the method for moving these "stationary" satellites. The rocket engines do not move them faster or slower to change positions but closer or farther away from the earth. When they are in the desired new position, the rockets are fired again to return them to the distance where they become "stationary" again.

GOES-R Series

In November 2016 the newest geostationary satellite, GOES-R, was launched. After a year undergoing through testing, it was designated GOES-16 and placed in operation located over 70ºW longitude. Also known as GOES-East this satellite marks a vast improvement over the previous aging GOES satellites.

The next GOES-R series satellite was launched March 1, 2018. After testing it was designated GOES-17 (GOES West) and currently operates over 137ºW.

Both GOES-16 and GOES-17 will cover the Weather Hemisphere from the West coast of Africa to as far west as New Zealand. Two additional GOES-R series satellites will eventually be launched to help provide dedicated service through the year 2036.

GOES-R series satellite.