GOES 3 was a NASA-developed, NOAA-operated, geosynchronous, and operational spacecraft.
The spin-stabilized spacecraft carried (1) a visible infrared spin-scan radiometer (VISSR) to
provide high-quality day/night cloudcover data and to take radiance-derived temperatures of the
earth/atmosphere system, (2) a meteorological data collection and transmission system to relay
processed data from central weather facilities to APT-equipped regional stations and to collect
and retransmit data from remotely located earth-based platforms, and (3) a space environment
monitor (SEM) system to measure proton, electron, and X-ray fluxes and magnetic fields. The
cylindrically shaped spacecraft measured 190.5 cm in diameter and 230 cm in length, exclusive of a
magnetometer that extended an additional 83 cm beyond the cylinder shell. The primary structural
members were a honeycombed equipment shelf and thrust tube. The VISSR telescope was mounted on the
equipment shelf and viewed the earth through a special aperture in the side of the spacecraft.
A support structure extended radially out from the thrust tube and was affixed to the solar panels,
which formed the outer walls of the spacecraft and provided the primary source of electrical power.
Located in the annulus-shaped space between the thrust tube and the solar panels were stationkeeping
and dynamics control equipment, batteries, and most of the SEM equipment. Proper spacecraft
attitude and spin rate (approximately 100 rpm) were maintained by two separate sets of jet thrusters
mounted around the spacecraft equator and activated by ground command. The spacecraft used both
UHF-band and S-band frequencies in its telemetry and command subsystem. A low-power VHF transponder
provided telemetry and command during launch and then served as a backup for the primary subsystem
once the spacecraft attained orbit.