ESSA 5

Description

ESSA 5 was a sun-synchronous operational meteorological satellite designed to take and record daytime earth cloudcover pictures on a global basis for subsequent playback to a ground acquisition facility. The spacecraft was also capable of providing worldwide measurements of reflected solar and long-range radiation leaving the earth. The spacecraft has essentially the same configuration as that of a TIROS spacecraft, i.e., 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). Electric power was provided by approximately 10,000 1- by 2-cm solar cells that were mounted on the cover assembly and by 21 nickel-cadmium batteries. Two redundant Advanced Vidicon Camera System (AVCS) cameras were mounted on opposite sides of the spacecraft, with their optical axes perpendicular to the spin axis. Two sets of flat plate radiometers were also suspended on opposite sides of the satellite, beneath the edge of the baseplate. A pair of crossed-dipole command receiver antennas projected out and down from the baseplate. A monopole telemetry and tracking antenna extended out from the top of the cover assembly. The satellite spin rate was controlled by means of a Magnetic Attitude Spin Coil (MASC), with the spin axis maintained normal to the orbital plane (cartwheel orbit mode) to within plus or minus 1 deg. The MASC was a current-carrying coil mounted in the cover assembly. The magnetic field induced by the current interacted with the earth's magnetic field to provide the torque necessary to maintain a desired spin rate of 9.225 rpm. The spacecraft performed normally after launch until September 22, 1967, when the radiometer experiment failed. The AVCS functioned until October 8, 1969, when the satellite was placed in a standby mode. ESSA 5 was deactivated on February 20, 1970.