Vesuvius National Park Monitoring by COSMO-SkyMED PingPong Data Analysis

COSMO-SkyMed (CSK) is the largest Italian investment in Space Systems for Earth Observation commissioned and funded by Italian Space Agency (ASI) and Italian Ministry of Defense (MoD). The system consist of a constellation of four Low Earth Orbit mid-sized satellites, each equipped with a multi-mode high-resolution Synthetic Aperture Radar (SAR) operating at X-band. Such a SAR constellation ensures a dense spatial coverage and a revisit time lower than 12 hours. Hence, the CSK constellation is of particular relevance for time-changing scenarios, such as vegetated and cultivated areas. Vegetation is a key element in the Earth ecosystem since it is involved in the regulation of various biogeochemical cycles, e.g., water, carbon, nitrogen, it influences the energy balance at the Earth's surface and within the atmospheric boundary layer and plays a major role in climate change. Vegetation converts solar energy into biomass and forms the base of all food chains, affects soil characteristics over time including soil volume, chemistry and texture, provides wildlife habitat and it is critically important for the production of food. Hence, the observation of vegetation is a key issue for the earth observation. In the recent years CSK data have been exploited in order to observe forested and vegetated areas. In [1] forest stand height is estimated by exploiting CSK Spotlight Detected Ground Multi-look (DGM) mode data, together with X-band TerraSAR-X data. In [2] the coherence between two CSK Stripmap HImage interferometric mode data acquired on two different days is assessed in order to discriminate forest types of various densities. In [3] a crop classification is carried out by exploiting multitemporal CSK dual-polarimetric PinPong mode data. Results show that multitemporal information improves the classification accuracy both for the single (HH/HV) and the double polarization (HH+HV). In particular, the co-polarized channel provides worst results for discriminating crops with respect to the use of the double polarization, while the cross-polarized channel becomes comparable to the use of double polarization when the number of HV polarized images increases significatively. In this study, X-band CSK dual-polarimetric (HH+VV) PingPong mode SAR data are first exploited to observe vegetation. The CSK PingPong mode implements a Stripmap acquisition by alternating a pair of transmitting /receiving polarizations across bursts, i.e. VV, HH, HV and VH, by means of an antenna steering [4]. In this case, the phase link between two polarimetric acquisitions is not preserved. The CSK instrument operating in dual-polarimetric PingPong mode acts like an along-track interferometer (ATI), with the fore and the aft antennas given by the combination of antenna steering and polarization switching, that acquires two complex SAR images of the observed scene in different polarizations, e.g. HH and VV, at slightly different times. Let's say ?p the time lag between the two complex acquisitions, the correlation between the co-polarized channels must be interpreted in terms of the relationship between ?p and the coherence time of the observed scene. First experiments undertaken using X-band CSK PingPong mode (HH+VV) data collected on June 12, 2011 over the Campania region, Italy, show promising results.