E n v i ronmental (also known as meteorological or weather) satellites are unmanned space-
ships that carry a variety of sensors to observe Earth. Two types of meteorological satellite
systems are used to ensure comprehensive coverage. The two types of satellites are
named for their orbit paths—geostationary and polar- o r b i t i n g.
Both types of satellites carry remote-sensing equipment to obtain visible and infrare d
images of Earth. The images can be captured and displayed with a direct re a d o u t
g round station (direct readout is the ability to obtain information directly from satellites).
Satellite images can also be obtained via the Intern e t.
It is important to note that satellite imagery should be used in conjunction with other data.
Satellite imagery was not intended to serve as either an isloated or comprehensive re s o u rc e.
The U.S. launched the world’s first environmental satellite, and continues to operate both
g e o s t a t i o n a ry and polar-orbiter systems. Direct readout from U.S. geostationary satellites is
called Weather Facsimile (WEFAX). Direct readout from U.S. polar-orbiting satellites is
called Automatic Picture Transmission (APT). Both WEFAX and APT* are essentially
, re f e rring specifically to U.S. satellite data. Direct readout from other nations’ satel-
lites is correctly re f e rred to as either geostationary or polar-orbiting satellite data.
The following activities specify whether geostationary or polar-orbiter data (images) will
be used, and whether visible or infrared images are needed.
- The terms WEFAX and APT refer to low-resolution satellite imagery. High re s o l u t i o n
( m o re detailed) data is available, but re q u i res more expensive equipment than is usually
found in the pre-college classro o m.
f i g u re 62.
IM A G E RY F R O M
EN V I R O N M E N TA L SAT E L L I T E S
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geostationary polar-orbiter
WEFAX APT