The National Aeronautics and Space Administration's two Synchronous Meteorological
Satellites were developed to explore the
use of meteorological
satellites in synchronous orbit. (Satellites in such orbits remain above a selected point on the Earth's surface.) Each satellite was a 243-kg (535-lb) aluminum cylinder with a diameter of 190.5 cm (74.8 in) and a height of 345 cm (135.85 in). A spin-scan radiometer provided images in both the visible (0.9 km/0.5 mi resolution) and infrared (9 km /5 mi resolution) region for both day and night coverage.A three-stage Delta launch vehicle with nine strap-on motors launched SMS 1 from Cape Kennedy on May 17, 1974, carrying the satellite to a point 36,357 km (22,591 mi) over the equator at 45¡ west longitude. The satellite was later relocated over 75¡ west longitude. With the orbiting of SMS 2 on Feb. 6, 1975, to a position on the equator at 135¡ west longitude, the two satellites could provide continuous 24-hr
observations in visible and infrared light. Together they provided around-the-clock observations, transmitting cloud-cover images of the Western Hemisphere once every 30 min.