TIROS 5

Description

TIROS 5 (Television and InfraRed Observation Satellite) was designed to further demonstrate the capability of a spacecraft to observe, record, and transmit TV cloudcover pictures for use in operational weather analysis and forecasting. The spin-stabilized satellite 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 assembly 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. The satellite spin rate was maintained between 8 and 12 rpm by the use of five diametrically opposed pairs of small solid-fuel thrusters mounted around the edge of the baseplate. Proper attitude was maintained to within a 1- to 2-deg accuracy by use of a magnetic control device consisting of 250 cores of wire wound around the outer surface of the spacecraft. The interaction between the induced magnetic field in the spacecraft and the earth's magnetic field provided the necessary torque for attitude control. The satellite was equipped with two 1.27-cm vidicon TV cameras, one medium angle and one wide angle, for taking earth cloudcover pictures. The pictures were transmitted directly to either of two ground receiving stations or were stored in a tape recorder on board for subsequent playback depending on whether the satellite was within or beyond the communication range of the station. The greater orbital inclination of TIROS 5 (58 deg vs 48 deg for previous TIROS spacecraft) extended the effective TV coverage from 65 deg n to 65 deg s lat. With the exception of the failure of the medium-angle camera 17 days after launch, the satellite performed normally until May 14, 1963, when it was deactivated after the shutter electronics failed on the wide-angle camera.