T/G Layout 1

258

ackground

Geostationary or geosynchronous satellites orbit the Earth at a

speed and altitude (approximately 22,240 miles) that allow

them to continuously hover over one area of the Earth’s

surface and provide constant coverage of that area. The

U.S. Geostationary Operational Environmental Satellites

(GOES) view almost a third of Earth’s surface and provide

continuous western hemisphere coverage.

GOES provides low-resolution direct readout service called

Weather Facsimile (WEFAX). WEFAX transmissions include

visual reproductions of weather forecast maps, temperature

summaries, cloud analyses, etc. via radio waves. WEFAX visi-

ble images have a resolution of eight kilometers, meaning each

pixel represents an area eight kilometers on a side. Infrared images have a resolution

of 4 kilometers. WEFAX is formatted in a 240 lines-per-minute transmission rate.

OES

• Provides continuous day and night weather observations


• Monitors weather events such as hurricanes and other severe storms


• Relays environmental data from surface collection points to a processing center


• Performs facsimile transmission of processed weather data to users (WEFAX)


• Provides low-cost satellite image services; the low resolution version is called
  weather facsimile (WEFAX)


• Monitors the Earth’s magnetic field, the energetic particle flux in the vicinity of the
  satellite, and x-ray emissions from the sun

GOES l-m Primary Sensor Systems:

Imageris a five-channel (one visible, four infrared) imaging radiometer that senses

radiant energy and reflected solar energy from the Earth’s surface and the atmosphere.

The imager also provides a star-sensing capability, used for image navigation and regis-

tration purposes.

Sounderis a 19-channel discrete-filter radiometer that senses specific radiant energy

for vertical atmospheric temperature and moisture profiles, surface and cloud-top tem-

perature, and ozone distribution.

Communications Subsystemincludes weather facsimile (WEFAX) transmission and

the search and rescue (SAR) transponder.

Space Environment Monitor (SEM) consists of a magnetometer, x-ray sensor, high-

energy proton and alpha detector, and an energetic particles sensor, all used for in-situ

surveying of the near-Earth space environment. The real-time data is provided to the

Space Environment Services Center—which receives, monitors, and interprets solar-ter-

restrial data and forecasts special events such as solar flares or geomagnetic storms.

U.S. GE O S TAT I O N A RY

EN V I R O N M E N TA L SAT E L L I T E S

B

G

(^)
figure 93.