Over the past 30 years, environmental service agencies have stated a need for continuous, dependable, timely, and high-quality observations of the Earth and its environment. The new generation Geostationary Operational Environmental Satellites (GOES I through M) provide half-hourly observations to fill the need. The instruments on board the satellites measure Earth-emitted and reflected radia¢ion from which atmospheric temperature, winds, moisture, and cloud cover data can be derived.

The GOES I-M series of satellites is owned and operated by the National Oceanic and Atmospheric Administration (NOAA). The National Aeronautics and Space Administration (NASA) manages the design, development, and launch of the spacecraft. Once the satellite is launched and checked out, NOAA assumes responsibility for the command and control, data receipt, and product generation and distribution.

Each satellite in the series carries two major instruments: an Imager and a Sounder. These instruments acquire highresolution visible and infrared data, as well as temperature and moisture profiles of the atmosphere. They continuously transmit these data to ground terminals where the data are processed for rebroadcast to primary weather services both in the United States and around the world, including the global research community.

The GOES I-M mission is scheduled to run from the mid-1990s into the first decade of the 21st century. Each element of the mission has been designed to meet all in-orbit performance requirements for at least five years.

The GOES I-M system performs the following basic functions:

GOES provides the instantaneous relay functions for the SARSAT system. A dedicated search and rescue transponder on board GOES is designed to detect emergency distress signals originating from Earth-based sources. These unique identification signals are normally combined with signals received by a low-Earth orbiting satellite system and relayed to a search and rescue ground terminal. The combined data are used to perform effective search and rescue operations.

The GOES I-M system serves a region covering the central and eastern Pacific Ocean; North, Central, and South America; and the central and western Atlantic Ocean. Pacific coverage includes Hawaii and the Gulf of Alaska. This is accomplished by two satellites, GOES West located at 135¡ west longitude and GOES East at 75¡ west longitude. A common ground station, the CDA station located at Wallops, Virgirlia, supports the interface to both satellites. The NOAA Satellite Operations Control Center (SOCC), in Suitland, Maryland, provides spacecraft scheduling, health and safety monitoring, and engineering analyses.

Delivery of products involves ground processing of the raw instrument data for radiometric calibration and Earth location information, and retransmission to the satellite for relay to the data user community. The processed data are received at the control center and disseminated to the National Weather Service's (NWS) National Meteorological Center, Camp Springs, Maryland, and NWS forecast offices, including the National Hurricane Center, Miami, Florida, and the National Severe Storms Forecast Center, Kansas City, Missouri. Processed data are also received by Department of Defense installations, universities, and numerous private commercial users.