TIROS 4

Description

TIROS 4 (Television and InfraRed Observation Satellite) was a spin-stabilized meteorological spacecraft designed to test experimental television techniques and infrared equipment. The satellite was in the form of an 18-sided right prism, 107 cm in diameter and 56 cm high. The top and sides of the spacecraft were covered with approximately 9000 1- by 2-cm silicon solar cells. It was equipped with two independent television camera subsystems for taking cloudcover pictures and three radiometers (two-channel low-resolution, omnidirectional, and five-channel scanning) for measuring radiation from the earth and its atmosphere. The satellite spin rate was maintained between 8 and 12 rpm by the use of five diametrically opposed pairs of small solid-fuel thrusters. The satellite spin axis could be oriented to within 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 flight control system also optimized the performance of the solar cells and TV cameras and protected the five-channel infrared radiometer from prolonged exposure to direct sunlight. With the exception of the degraded response of the five-channel scanning radiometer, the spacecraft performed normally until May 3, 1962, when one camera failed. On June 10, 1962, the other camera's tape recorder failed. The scanning radiometer provided usable data until June 30, 1062. A complete description and performance summary for TIROS 4, is presented in the 'Journal of the British Interplanetary Society,' Vol. 19, 386-409, 1963-4.