When artificial satellites became reality some 40 years ago, meteorologists were among the first to make use of their new potential.
The main requirement of the weather forecaster was for a snapshot of the atmosphere at a particular place and time, but as spacecraft became more sophisticated it became obvious their images could be useful to many other disciplines as well. One of the latest examples is the use of satellite data to control malaria.
The name of the disease, malaria, meaning "bad air", is because it was supposed in ancient times to be caused by noxious gases exuded by a marsh.
Nowadays, however, we know that malaria is spread by the mosquito. There are some 2,500 known mosquito species, having a worldwide distribution extending from the equatorial rain forests to the Arctic, but not all are dangerous in the context of malaria. The villain is the genus called Anopheles, which thrives in the high temperatures of the lower latitudes.
The mosquito, however, is but a messenger. The disease itself is spread by the parasite Plasmodium, which resides in the saliva of an infected insect. When Anopheles bites a person, it injects saliva into the wound as an anticoagulant to ease the flow of the blood it sucks for food.
The parasite, thus released into the bloodstream, travels very quickly to the liver where Plasmodium, as it were, regroups to plan its main attack. After an incubation period of a month or so, microscopic organisms are released to attack systematically the red blood cells that carry oxygen around the body - very often to the extent that death ensues.
Weather and climate affect the spread of malaria in several different ways. Stagnant water, for example, is essential for Anopheles to lay its eggs and breed successfully; if these breeding grounds dry out, the eggs do not survive.
Provided, however, that there is sufficient rainfall to provide the breeding sites, then the higher the average temperature the greater the reproductive success of the mosquito, and the more widely the malarial infection can be spread.
Now Anopheles often breeds in inaccessible areas where its presence cannot be detected easily from the ground. But the environmental factors that facilitate its procreation - the altitude and general nature of the terrain, the local rainfall over a period and the prevailing temperature - can all be monitored accurately and continuously by satellite.
Remote sensing therefore, allows the authorities in affected countries to map the areas where the species is likely to be thriving at any given time, introduce appropriate control measures such as spraying, and thereby reduce malaria.