Performance and Evaluation of Satellites Tiros I and Tiros II

The design and ins trumentat ion of the first two Tiros satellites and their associated ground-based data-acquisit ion stat ions, the performance of the systems after launch, and the subsequent performance evaluation are briefly described. Representative TV photographs of Earth and i t s cloud cover taken by Tiros are reproduced. The Tiros I system proved the feasibility of TV observation of meteorological phenomena from a satell ite as a practical aid to weather research and forecasting. The evaluation program produced data providing the basis for ins trumentat ion design improvements in Tiros II and revealed an unexpected torque due to the Earth's magnet ic field,, which caused a slow angular drift of the spin-axis vector. From the latter discovery, a magnet i c at t i tude control arrangement used to neutralize the torque or to control i t as a m e a n s of l imited steering of the satellite was conceived for Tiros II. The performance of Tiros II corroborated t h e conclusions drawn from Tiros I and confirmed the operational feasibility of the new devices aboard. Further, both civilian and military weather agencies are making operational use of the Tiros II data.