SATELLITE IMAGERY

AAWU HOME

There are two types of GOES and Polar Orbiter imagery available through the AAWU homepage: 

Visible imagery is like a regular camera taking a picture from space. Visible imagery has the best detail when there is enough sunlight to see the clouds. This type of imagery is useless at night when its dark. Outer space is black in a visible satellite image. 

Infrared (IR) imagery takes a picture of wavelengths past the red end of the light spectrum. It captures the temperature of the clouds or ground. The IR pictures show bright white for the coldest land surfaces and highest clouds. Warmer surfaces are shown as darker shades of gray to black. Outer space is white (very cold) in an IR satellite image. Infrared imagery is as useful at night as it is during the day, because the surfaces continue to emit their characteristic infrared radiation even though the sun is down. 

Types of Satellites

GOES

Geostationary Operational Environmental Satellites or GOES satellites orbit the earth at an altitude of 22,000 miles above the equator once every 24 hours, keeping pace with the earth's rotation. Thus, the satellites appear to remain fixed above the same point on earth, which is why they are called "geostationary".    GOES West orbits near the equator over the eastern Pacific Ocean, and can see as far north as Northern Alaska, though images become distorted the farther north you look. 

GOES images are produced every 15 minutes over the entire viewing area. Because of this, GOES pictures can be easily looped to see storm system and cloud movements. Loops are useful even in far northern Alaska to determine if a white or gray area is clouds or snowy ground. Clouds move, ground doesn't. 

Polar Orbiter

Two Polar orbiter satellites constantly circle the earth in an almost north-south orbit, passing close to the poles. They follow the sun and so take continuous visible and IR pictures. 

Polar orbiter satellites take pictures of the earth directly below, so the resolution is much higher than GOES pictures, even in the mid latitudes. Polar orbiter pictures show great details in the polar areas where GOES pictures are very distorted. 

Since these pictures are taken from different places with respect to the Earth's surface, they don't work well when looped. Also, on different passes, some territory is missed, so we end up with stripes of picture. It may be hours between pictures over the same spot. Also, since the satellites follow the sun, there are typically no new pictures of Alaska between 9PM and 5AM Alaska Standard Time.