Uses of Computers in space exploration
Before the computer, proto-quantitative geography was developed with the aid of various calculating machines, but it was only after Herman Hollerith (1860–1929) combined punched cards with the then-recent electromagnetic inventions that it became possible to count and classify in a much shorter time and with greater detail and precision than by any previous methods. But through the 1950s the machines required to perform these operations remained expensive, large, and clumsy. A turning point occurred in 1982 with the introduction of ARC/INFO, a geographical information software package that combines traditional automated systems with advanced spatial data-based handling capability. This is accomplished by combining a series of layers each with a different theme: relief, roads, political boundaries, settlements, and so on—the desideratum of the regional geographer. Specifically, ARC/INFO uses both vector (line) and raster (tabular) storage; transformations can be undertaken and questions asked concerning numbers, distance, addresses, and so forth. The utility of such a system to those who are concerned with geographical distributions is enormous, as is time saved by these procedures. Maps can be made using the system and simulated, three-dimensional representations produced. It can also be animated to show, for example, population change through time. The machines on which these procedures can be accomplished have been incredibly reduced in size, price, and availability.
Equally as remarkable as the widespread utility of the computer to geography have been the space programs of various countries and consortia. As in the case of the computer, space technology did not arrive fully developed without a period of gestation, partly alluded to above in the references to aerial photography. A breakthrough similar to that of the computer was made when German rocket scientists joined the incipient United States space program, and that of the Soviet Union, following World War II. Prior to this, around 1910, the Germans had used rockets fitted with cameras to image small areas of the Earth. The range of these missiles was increased in World War II when, as Vergeltungswaffe 2 (V-2) rockets, they were used for military purposes. From 1960, the Television and Infra-Red Observation Satellite (TIROS), a series of unmanned satellites, was launched in the United States, and demonstrated the ability to gather weather data from above Earth's cloud layers, the first important use of the new technology. Meanwhile the Soviets launched the Synchronously Programmed User Terminal and Network Interface (Sputnik) in 1957, imaged the previously unseen side of the Moon in 1959, and put a human in space in 1961. The next year marked the first manned space flight by the United States, which soon began a series of missions imaging the Earth from space—Gemini (1965–1966), and Apollo (1968–1969), with hand-held cameras loaded with color and, later, color infrared (CIR) film, which had been perfected during World War II. As mentioned above, it was the Apollo 11 mission in 1969 that landed humans on the Moon. Subsequently, nonphotographic systems were also used so that the term "Remote Sensing of the Environment" was coined to replace air photo interpretation, which was included in the definition.
The next development was continuous, extensive surveillance of the planet Earth, first accomplished by the Earth Resources Technology Satellite (ERTS) in 1972. Another similar satellite was launched in 1975, and the program was renamed Land Remote Sensing Satellite (Landsat). Since that time, the surface of the Earth (except the polar regions that the system does not cover) has been scanned by Landsat every nine days. By international agreement Landsat imagery, which is telemetered to the Earth in at least four multispectral bands, is available to users in any part of the world. The French Satellite Pour l'Observation de la Terre (SPOT) and various Russian satellite programs produce very high quality images but, unlike Landsat, do not have continuous satellite coverage of the Earth. However, other countries and consortia (such as the European Space Center) make contributions to existing programs, as in the case of Britain and Australia. At the time of writing China has successfully launched an extraterrestrial satellite, recalling the early interest of the Chinese in gunpowder and rockets, and the United States has an operating imaging system on Mars.