Polar-orbiters were the first type of
weather satellite, with TIROS1 launching on April 1, 1960. They make approximately
14 orbits daily, covering a further west section of earth with each orbit
as the earth rotates beneath them. Their low altitude of around 500 miles
allows high resolution images while the near-polar orbit allows global
coverage without the distortion over northern latitudes that geo-stationary
satellites suffer from. However the pictures are delayed real-time and
there are only a couple of passes per satellite per day over any given
spot. |
The first operational geosynchronous weather satellite, the
SMS1, was launched on May 17, 1974. Geo-stationary satellites circle the
earth in a geosynchronous orbit, which means they orbit at the same speed
as the earth's rotation. This allows them to "hover" over one
spot on the surface. Their higher altitude of 22,300 miles allows a continuous
full-disc view of the earth, but at a lower resolution than polar-orbiting
satellites. Since the satellite is centered over the equator, there is also
significant distortion over northern latitudes. |
