One of the most immediately useful types of satellites, meteorological or weather satellites have made possible much more accurate forecasts in recent years. They carry cameras to take pictures of cloud cover in visible and infrared light so that they can produce images at night as well as during the day. They carry a variety of other sensors to measure the temperature of the land and sea surface and at different levels in the atmosphere, and also water vapour and ozone concentration. Many carry instruments to collect meteorological data from unmanned weather platforms in remote locations. The great advantage of using satellites is that they can look at the state of the weather over the whole world, not just where there happen to be weather stations and meteorologists. In particular they can spy on the mid-oceans, where much of the world's weather originates. The US pioneered weather study from space with the launch of Tiros 1 in 1960. A further nine Tiros (television and infrared observation satellite) satellites were launched over the next five years. Improvements followed with ESSA (Environmental Science Service Administration) satellites (1966-1969) and ITOS (improved Tiros operational satellite) satellites from 1970, the later ones being given NOAA designations, NOAA being the National Oceanographic and Atmospheric Administration. The latest of this family is the Tiros N satellite, first flown in 1978. The operational satellites have NOAA designations: NOAA 9, 10 and 11 are currently in service. Like their predecessor, they carry a Sarsat (search and rescue satellite) instrument package for emergency use by planes and ships in distress. NOAA satellites operate in a relatively low polar orbit, as do the Soviet Meteor weather satellites. They scan the whole of the Earth's surface as it revolves beneath them. Since 1975 weather satellites have also been operating in geostationary orbits so that they remain 'fixed' over a certain point on Earth. The US GOES-1 was the first operational satellite of this type, GOES standing for 'geostationary operational environmental satellite'. GOES satellites are currently positioned east and west of the Americas. Europe uses geostationary satellites called Meteosat, located on the Greenwich meridian (0 degrees longitude). Like the GOES satellites, it takes pictures of the whole hemisphere it views once every half-hour.
