21.1. Types of Satellites

In April of 1960, the meteorological world was turned upside down with the launch of the first successful meteorological satellite. For the first time, meteorologists could get an idea of what the “big picture” looked like in an instant. These first satellites were nothing more than television cameras launched into orbit. Since then satellite technology has increased to the point that a continuous stream of information is sent back to earth 24 hours a day, 7 days a week. With the advancements in technology, we now have different kinds of satellites observing weather conditions, each focusing on different regions of earth.

While there are numerous types of observations that are collected by satellites, the most widely known and used to observe mid-latitude cyclones are visible, infrared, and water vapor imagery. These three types of imagery are discussed next.

Geostationary Earth Orbiting (GEO)

One kind of satellite in use is known as a geostationary earth orbiting (GEO) satellite. These satellites are launched to an altitude of 19,312 nautical miles (22,224 miles) where their forward speed matches that of earth’s rotation. What does this mean? These satellites appear to be stationary in the sky, if observed from earth. These satellites always observe the same portion of the atmosphere each and every day.

There are two operational GEO satellites positioned over the Continental U.S. they are referred to as the Geostationary Operational Environment Satellite (GOES) 16 and 18. GOES-16 is centered over the western Atlantic Ocean (75W) and observes the central and eastern portions of the United States and has been operational since 2017. GOES-18 is centered of the eastern Pacific Ocean and observes the western portion of the United States since late 2022. These are the primary satellites currently used in forecasting synoptic scale weather patterns.

Low Earth Orbiting (LEO)

Another kind of satellite in use today is known as a low earth orbiting (LEO) satellite. These satellites are only launched to an altitude of around 500 nautical miles (575 miles). At an altitude of this height, these satellites are not in a geostationary orbit. Instead, these satellites appear to be synchronized with the sun, meaning that if viewed from the surface of the sun, these satellites would be stationary. These satellites complete a revolution about the earth in about 1.5 hours. Thus, it takes about 1.5 hours between images from a LEO satellite in the polar regions. Because these satellites make frequent passes over the Polar Regions, the term Polar Orbiter Environmental Satellite (POES) is given to these satellites launched by the United States. It should be noted that the resolution of POES satellites infrared imagery is about 4 times that of the imagery from GOES.