Prospection and Monitoring of the Archaeological Heritage of Nasca, Peru, with ENVISAT ASAR DEODATO TAPETE 1 * , FRANCESCA CIGNA 2 , NICOLA MASINI 3,5 AND ROSA LASAPONARA 4,5 1 Institute for the Conservation and Valorization of Cultural Heritage, National Research Council, Via Madonna del Piano 10, I-50019, Sesto Fiorentino, Florence, Italy 2 British Geological Survey, Natural Environment Research Council, Nicker Hill, Keyworth, Nottingham, NG12 5GG, United Kingdom 3 Institute for Archaeological and Monumental Heritage, National Research Council, Contrada S. Loja, I-85050, Tito Scalo, Potenza, Italy 4 Institute of Methodologies for Environmental Analysis, National Research Council, Contrada S. Loja, I-85050, Tito Scalo, Potenza, Italy 5 Italian mission of heritage Conservation and Archaeogeophysics (ITACA) in Peru ABSTRACT The processing method based on synthetic aperture radar (SAR) amplitude information presented by Cigna et al. (2013, this issue) was used to extract the backscattering coefficient (s 0 ) from ENVISAT advanced SAR (ASAR) scenes to investigate the archaeological heritage of the Nasca region, southern Peru. Average backscattering and s 0 time series in 2003–2007 were obtained for some of the most famous groups of the Nazca Lines, as well as for the adobe structures of the Ceremonial Centre of Cahuachi, and allowed the recognition of anthropogenic features on arid and bare soil. Despite the expected constraints due to the medium spatial resolution of the ASAR scenes (~30 m), some features related to the Nasca ancient aqueduct systems (puquios) were detected, and water level changes were inferred from amplitude change detection maps and s 0 time series. The SAR-based prospection results were also compared with a vegetation index derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data for 2003, 2004 and 2007. The changes observed over Cahuachi and the neighbouring archaeological mounds are then discussed in light of the recent conservation history of the site and the contemporary archaeological excavations. The research opens interesting perspectives for routine use of SAR data for purposes of archaeological prospection and condition monitoring in (semi-)arid and desert regions. Copyright © 2013 John Wiley & Sons, Ltd. Key words: Archaeological prospection; SAR processing; backscattering coefficient; change detection; Nasca; Peru Introduction The cultural and natural richness of the Nasca region, southern Peru (Figure 1a), is not as yet fully discovered and interpreted. This heritage raises archaeological and (palaeo-) environmental questions, to which sci- entists are currently trying to respond by means of Earth observation (EO) techniques (e.g. Lefort et al., 2004; Lambers and Sauerbier, 2006; Ruescas et al., 2009; Braun, 2010). The latter, in most cases, are used complementarily to conventional and in situ investiga- tions (e.g. Lasaponara et al., 2011; Richter et al., 2011). Among others, we mention here the activities being car- ried out by the Italian mission of heritage Conservation and Archaeogeophysics (ITACA), directly involving the researchers from the Institutes for Archaeological and Monumental Heritage (IBAM), and Methodologies for Environmental Analysis (IMAA) of the National Research Council (CNR) of Italy. A comprehensive review of this mission has been depicted recently by Masini et al. (2012) who discuss the main outcomes achieved from 2007 to date over the region of Nasca. * Correspondence to: D. Tapete, Institute for the Conservation and Valorization of Cultural Heritage, National Research Council, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Florence, Italy. Email: deodato.tapete@gmail.com Copyright © 2013 John Wiley & Sons, Ltd. Received 10 February 2013 Accepted 7 April 2013 Archaeological Prospection Archaeol. Prospect. 20, 133–147 (2013) Published online 21 May 2013 in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/arp.1449