TIROS 8

Description

TIROS 8 (Television and InfraRed Observation Satellite) was designed to develop improved capabilities for obtained and using TV cloudcover pictures from satellites. The spin-stabilized spacecraft was in the form of an 18-sided right prism, 107 cm across opposite corners and 56 cm high, with a reinforced baseplate carrying most of the subsystems and a cover assembly (hat). Electrical power was supplied to the spacecraft by approximately 9000 1- by 2-cm silicon solar cells mounted on the cover assemby and by 21 nickel-cadmium batteries. A single monopole antenna for reception of ground commands extended from the top of the cover assembly. A pair of crossed-dipole telemetry antennas (235 Mhz) projected down and diagonally out from the baseplate. Mounted around the edge of the baseplate were five diametrically opposed paris of small solid-fuel thrusters that maintained the satellite spin rate between 8 and 12 rpm. Proper attitude was maintained to within a 1- to 2-deg accuracy by use of a magnetic control device consisting of 250 coil of wire wound around the outer surface of the spacecraft. The interaction by the induced magnetic field in the spacecraft and the earth's magnetic field provided the torque necessary for attitude control. TIROS 8 was the first satellite to be equipped with Automatic Picture Transmission (APT) capabilities. The APT experiment provided real-time earth-cloud pictures taken by the satellite to any properly equipped ground receiving station. In addition to an APT camera system, the satellite carried one wide-angle (104 deg) TV camera. Pictures taken by the TV camera were transmitted directly or were stored in a tape recorder on board for subsequent playback, depending on whether the spacecraft was within or beyond communication range of either of two ground receiving stations. The spacecraft performed normally after launch. Over 50 ground stations participated in the APT experiment, which was terminated by the end of April 1964 to degradation of the APT camera. The wide-angle TV camera transmitted useful data until February 12, 1966. The satellite was deactivated on July 1, 1967, after being left on for an additional time period for engineering purposes.