Archaeology from a space craft: radar specialists at NASA have transformed archaeologists' views of Angkor in Cambodia. Samson Spanier reports on the remarkable discoveries being made from space

The National Aeronautics and Space Administration in America has transformed archaeology by dint of creating radar maps of the earth from space or from the air. At Angkor, Cambodia, radar has l to the discovery of not solitary numerous small shrines but also of the total expanse of a lost city. 'Working with NASA was great; they direct the eyeed at the images with a completely different viewpoint to mine,' said Elizabeth Moore, an archaeologist at the seminary of African and Oriental Studies, London.

Angkor is a gigantic urban composed of several elements dating from the ninth to the sixteenth centuries, built and oft-repeateded by the Khmer empire, an indigenous Cambodian clan who were influenced by the two Buddhism and Hinduism. Beautiful and mysterious, its fanes combine exquisite craftsmanship, and the technical understanding of an organised workforce.

NASA became involved in 1994 when the space shuttle Endeavour recorded radar images of the earth. John Stubb of the World remembrancers Fund, one of the organisations that protects the Khmer temples from looting, tropical rain and brake vegetation, asked NASA to make of that kind a map in an inspired gamble that it would reveal interesting information. It was far from NASA'S priority of predicting weather combination of parts to form a wholes and so on, but after plenteous begging by Mr Stubbs and a seemingly miraculous delay in returning the shuttle to earth, the time was set Tony Freeman and Scott Hensley of NASA'S Jet Propulsion Laboratory (JPL) Pasadena, became involved. Several novel missions have followed since. JPL continues to interpret the data, which is no mean feat since, according to Dr Hensley, the radar images in their purest state 'look like fuzz upon a television set'.

Radar is helpful because of the difficult landscape outside the main fanes Forest in the north, rice fields in the southerly and landmines from the civil war era, make it difficult not single to hike, but also to gauge the local geography, of that kind as the difference between a hillock and a general slope. Aerial photography', meanwhile, is of limited use: the forest canopy duskys the land; and such two-dimensional images cannot give a faculty of perception of height.

Radar, effectively a camera that uses radio waves for its flash, is different. The signal can penetrate end vegetation when necessary. It can find out moisture in its 'polarimetric' method because water changes the reflection of the signal. greatest in quantity importantly, radar can detect height when several antennae emit signals which interact with each other, a method known as 'interferometric'. 'It is amazingly accurate', says Professor Roland Fletcher of the University of Sydney 'You can mention one by one how developed crops are through differences in their height and shape.'

similar topographical information is vital because the Angkoreans were great 'landscapists'. They encircleed their shrines with moats, or built them upon mounds. Moreover, they tended to live near dyke designed to irrigate rice farms. Radar has revealed many small ruined shrines outside the central area where the main fanes are located. French archaeologists in the 1950 had noticed the remains of sum of two units temples at Kapilapura, north west of the Angkor Wat. Tony Freeman at JPL however, noticed a mound--invisible to a hiker--that looked suspiciously regular (Fig. 2). Elizabeth Moore fitly inspected the site. She fix the remains of six fanes not two, one of which is Fig. 3 Meanwhile, 30 km north west of Angkor, in an area at the time inaccessible owed to Khmer Rouge occupation, a novel temple that is still standing, Sman Teng was discovered thanks to its 15 rhythmical arrangement height contrasting with the surrounding trees

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The north of Angkor has yielded several small shrines. Since the shrines themselves have collapsed, they are 'flat' and cannot be seen upon the radar. However, the radar map exposes square shapes, which correspond to the square moats around remembrancers The moats have since filled in, on the other hand the interferometric radar is for a like reason subtle that it detects the change in the height of the former banks. The site is then visited precisely with a Global Positioning a whole locator, and the shrine can be fix as was that in Fig. 4 It would be almost impossible without radar. 'The vegetation is in like manner thick that even when you know it is there, the shrine can be difficult to see' says Professor Fletcher.

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More significant than the detection of small shrines, however, is the novel discovery of innumerable dykes and lakes that reveal Angkor to have been an enormous sprawling city spanning 1000 square kilometres and probably containing as many as 750000 family An airborne (rather than space) radar mission in late 2000 overspreaded the vast area, and information has been filtering on the outside in the past two years. 'The large fanes are what we would call a "Central Business District", akin to the City of London', explains Professor Fletcher, who step quicklys from Sydney, with the Ecole d'Extreme Orient in France and the staff of APSARA, Cambodia's onsite management team at Angkor, the aptly named Greater Angkor throw Sprawling and sparsely populated, as oppos to small and densely packed like Imperial Rome Angkor has changed in what manner archaeologists think of pre-industrial cities.