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ITOS 1 (TIROS-M) was the prototype spacecraft for the second generation of operational sun-synchronous meteorological spacecraft. The primary objective of ITOS 1 was to provide improved operational infrared and visual observations of earth cloud cover for use in weather analysis and forecasting. Secondary objectives included providing both solar proton and global heat balance data on a regular daily basis. To accomplish these tasks, the spacecraft carried four cameras, two television cameras for Automatic Picture Transmission (APT) and two Advanced Vidicon Camera System (AVCS) cameras. It also carried a low-resolution Flat Plate Radiometer (FPR), a Solar Proton Monitor (SPM), and two scanning radiometers that not only measured emitted infrared radiation, but also served as a backup system for the APT and AVCS cameras. The nearly cubical spacecraft measured 1 by 1 by 1.2 m. The TV cameras and infrared sensors were mounted on the satellite baseplate with their optical axes directed verticially earthward. The satellite was equipped with three curved solar panels that were folded during launch and deployed after orbit was achieved. Each panel measured over 4.2 m in length when unfolded and was covered with 3420 solar cells, each measuring 2 by 2 cm. The ITOS 1 dynamics and attitude control system maintained desired spacecraft orientation through gyroscopic principles incorporated into the satellite design. Earth orientation of the satellite body was maintained by taking advantage of the precession induced from a momentum flywheel so that the satellite body precession rate of one revolution per orbit provided the desired 'earth looking' attitude. Minor adjustments in attitude and orientation were made by means of magnetic coils and by varying the speed of the momentum flywheel. Launched into a near-polar orbit, the spacecraft and experiments performed normally until the incremental tape recorder failed on November 16, 1970, resulting in partial loss of SPM and FPR data. Overheating developed in the satellite attitude control system during March 1971. Attempts to correct the problem were unsuccessful, and the spacecraft was deactivated on June 18, 1971.

Alternate Names

  • 04320
  • ITOS1

Facts in Brief

Launch Date: 1970-01-23
Launch Vehicle: Delta
Launch Site: Vandenberg AFB, United States
Mass: 309 kg

Funding Agency

  • Environmental Science Service Administration (United States)


  • Space Physics
  • Earth Science

Additional Information

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



NameRoleOriginal AffiliationE-mail
Mr. Charles M. HunterGeneral ContactNASA Goddard Space Flight Center
Mr. William H. JonesProject ManagerNASA Goddard Space Flight
Mr. Isidore L. GoldbergProject ScientistNASA Goddard Space Flight Center
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