## 1 Introduction  
Starting from aerial photos, optical satellite remote sensing has played an important role in the field of archaeological investigations over the last few decades [1; 2; 3]. Shadow, crop and soil marks [4; 5; 6; 7] are well-known indicators of the presence of ancient buried and surface remains widely used for archaeological photo-interpretation. Their visibility from space is due to the fact that the presence of emerging, shallow and buried remains modifies albedo as well as physical and chemical surface parameters compared to the surrounding areas. Over the years, several papers have analyzed and discussed the use of optical satellite sensors to detect archaeological marks. In particular, before the availability of Very High Resolution (VHR) satellite data (_i.e._, with a spatial resolution of around 1 m and less), many authors focused on the use of Landsat, SPOT and ASTER or declassified satellite data [8; 9; 10]. The advent of VHR satellite imagery, such as that provided by Ikonos and QuickBird, has significantly increased interest in space archaeology, as is evident from the greater number of publications in the field spanning from the detection of previously unrecorded sites to greater knowledge and improve management and protection of archaeological areas. Up to now, the use of optical satellite imagery along with aerial photographs in archaeology has been more extensive than radar data. It is nevertheless important to consider that the occurrence of SIR-A/B/C, AIRSAR and SRTM SAR data from the National Aeronautics and Space Administration (NASA)/Jet Propulsion Laboratory (JPL) opened up an era of radar remote sensing in archaeology back in the 1980s at desert sites [11; 12] and tropical regions [13; 14]. Recently, archaeological investigations conducted by SAR data have moved forward to another stage focusing on archaeological detection and monitoring using backscattering change detection [15, 16], polarimetric enhancement [17, 18], penetration [19] and deformation anomaly diagnosis [20, 21, 22] utilizing second-generation spaceborne SAR systems represented by multi-band, polarization and high-resolution systems, e.g., ALOS PALSAR, TerraSAR-X/TanDEM-X, COSMO-SkyMed and Radarsat-2. All the above-mentioned investigations deal with the penetration or polarimetric capabilities of satellite SAR L and C-band systems, but no one has systematically investigated the potentiality of the SAR X-band to detect archaeological shadow, crop and soil marks, though some experiments have been proposed [23] using simulated data and have correlated shadow/dark marks seen in the SAR images to archaeological features [15, 24]. Only in recent years have some investigations been carried out using aerial [25] and space SAR [26] to detect traces of archaeological interest. In particular, the NASA project [25] attempted to devise a systematic method and protocol to survey large areas merging aerial SAR and satellite multispectral data. COSMO-SkyMed data were used to obtain both images and DEMs, but they were considered less useful in detecting archaeological marks or materials associated with archaeological sites. In [26] the use of multitemporal COSMO-SkyMed as a first attempt at identifying known archaeological marks is proposed. In this case, the multi-temporal analysis was adopted to reduce the speckle noise that affects SAR data. Although several achievements have been made in recent years, the exploitation of SAR remote sensing to detect archaeological marks is still in its infancy, especially for X-band data, such as COSMO-SkyMed (for additional details see [27]). Comparing the currently available satellite SAR systems operating in L and C-bands with those operating in X-band it is expected that the latter will provide information on a larger variety of small archaeological features mainly thanks to its greater geometric resolution. This paper is a pioneering effort to assess the potential of satellite SAR X-band data in the detection of archaeological marks.