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ESSA 3 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-wave radiation leaving the earth. The spacecraft had essentially the same configuration as that of a TIROS satellite, 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). Electrical power was provided by approximately 12,000 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. ESSA 3 performed normally until January 20, 1967, when the radiometer experiment failed. The first AVCS camera failed on September 29, 1967, the remaining camera failed on October 9, 1968, and the satellite was deactivated on December 2, 1968.

Alternate Names

  • 02435
  • ESSA3
  • TOS-A

Facts in Brief

Launch Date: 1966-10-02
Launch Vehicle: Delta
Launch Site: Vandenberg AFB, United States
Mass: 145 kg

Funding Agency

  • Environmental Science Service Administration (United States)


  • Earth Science

Additional Information

Questions and comments about this spacecraft can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Mr. William H. JonesProject ManagerNASA Goddard Space Flight
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