TIROS-1 instruments.

TIROS-1 orbited some 700 km above the Earth at an inclination of 48° to the equator, in an approximate polar orbit. It spun at 12 revolutions per minute, producing images of 500 lines at 500 pixels/line.

TIROS-1 functioned for only three months but returned nearly 23,000 images in that time, and was soon followed by other satellites in the same series. For the first time meteorologists could actually see the distribution of weather systems over the surface of the Earth and no longer had to rely on inferences from widely scattered conventional observations.

At the time of launch the suitability of a satellite to monitor weather was as yet unproven. TIROS-1's objectives were to test observation technologies, with the long-term aim of developing a global meteorological information system.

The satellite was fitted with two television cameras (one with a wide angle lens, the other a telephoto) which captured some of the first images of earth from a low polar orbit (see image right). Both cameras were attached to magnetic tape recorders which stored photographs while the satellite was out of range of the ground station network.

TIROS-1 came to a premature end when the satellite suffered an electrical fault on June 15 1960. However, the TIROS programme went on to launch another nine satellites and decisively proved the usefulness of weather observation from space.

The USA also pioneered the first geostationary weather satellite when it launched the experimental ATS-I on 7 December 1966. This combined communication / meteorological satellite was also the first of a series. It operated initially over Ecuador, but was allowed to slowly drift westward, reaching 151°W by 1978. The satellite included two meteorological experiments on board, providing half-hourly full earth disc images at a resolution of 3.2 km, and also relaying weather facsimile (WEFAX) data. Over its twelve-year life span, ATS-I provided useful data for the first six years, up to 1972.

Within a decade the USA had established - and demonstrated the value of - the two classes of meteorological satellites forming the basis of the systems which have been in operation ever since. TIROS-1 was a forerunner of today's polar-orbiting satellites such as the USA NOAA series and EUMETSAT's Metop.

Further reading:

EUMETSAT: The early years
TIROS-1 (NASA)
1946: The first photo from space

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