From about 1392 kilometers (865 miles) above Earth, two wide-angle television cameras mounted on either side of the spacecraft took in 10.4-million square kilometers (4-million square miles) per photo.
The Improved TIROS Operational Satellite (ITOS) opened the world of radiometric measurement to meteorologists—information about surface temperatures on the ground, at sea level, or at the cloud tops obtained by scanning devices sensitive to energy that is invisible to the naked eye. ITOS spacecraft could return accurate day or night surface and cloud-cover images. Seven of these satellites were launched between 1970 and 1973.
_TIROS_ was presented to the National Air and Space Museum by the National Aeronautics and Space Administration; _TOS_ is from the National Oceanic and Atmospheric Administration; _ITOS_ is from the Astro-Electronics Division of RCA, Inc.
[Illustration: 37. Artist’s concept of ITOS weather satellite illustrating how the weather eye takes night-time (infrared) cloud-cover pictures.]
[Illustration: 38. Ground inflation test on _Echo 1_, the world’s first passive communications satellite.]
Communications satellites can be grouped into two broad categories. Passive vehicles reflect signals from one ground station to another. Active satellites accept ground signals and either amplify and rebroadcast them immediately or record messages for later transmission.
The Echo satellite balloons typified the passive category of communications spacecraft. These satellites “bounced” radio signals from one ground station to another. Uninflated Echo payloads were carried into orbit packed in special storage containers. When released in space, the balloon was inflated by chemicals packed inside which subliminated to produce inflating gas. The mylar plastic skin of the satellite was sandwiched between two layers of aluminum foil. _Echo 2_—on display—included a system for releasing gas over a long period of time to maintain the satellite’s spherical shape. Launched January 25, 1964, _Echo 2_ was the first satellite used for communication experiments between the United States and the Soviet Union.
Project West Ford, launched May 9, 1963, was a unique experiment in passive satellite communications. It was not a solid vehicle, but a series of 400-million tiny individual copper filaments called dipoles. The dipoles formed a reflective layer some 64,300 kilometers (40,000 miles) long, 32 kilometers (20 miles) thick, and 32 kilometers (20 miles) wide. The distance between the individual dipoles averaged 536 meters (one-third mile). The West Ford experiment proved disappointing, and advances in the design of active communications satellites made further experiments of this nature unnecessary.