Development of oil spill detection techniques for satellite optical sensors and their application to monitor oil spill discharge in Mediterranean sea

Satellite remote sensing has proved to be an effective support in timely detection and monitoring of marine oil pollution, mainly due to illegal ship discharges. In this context, we have developed a new methodology and technique for optical oil spill detection, which make use of MODIS L2 and MERIS L1B satellite top of atmosphere (TOA) reflectance imagery, for the first time in a highly automated way. The main idea was combining wide swaths and short revisit times of optical sensors with SAR observations, generally used in oil spill monitoring. This arises from the necessity to overcome the SAR reduced coverage and long revisit time of the monitoring area. This can be done now, given the MODIS and MERIS higher spatial resolution with respect to older sensors (250-300 m vs. 1 km), which consents the identification of smaller spills deriving from illicit discharge at sea. The procedure to obtain identifiable spills in optical reflectance images involves removal of oceanic and atmospheric natural variability, in order to enhance oil-water contrast; image clustering, which purpose is to segment the oil spill eventually presents in the image; finally, the application of a set of criteria for the elimination of those features which look like spills (look-alikes). The final result is a classification of oil spill candidate regions by means of a score based on the above criteria.

Enhancement of Trajectory Determination of Orbiter Spacecraft by Using Pairs of Planetary Optical Images

The subject of the present thesis is about the enhancement of orbiter spacecraft navigation capabilities obtained by the standard radiometric link, taking advantage of an imaging payload and making use of a novel definition of optical measurements. An ESA Mission to Mercury called BepiColombo, was selected as a reference case for this study, and in particular its Mercury Planetary Orbiter (MPO), because of the presence of SIMBIO-SYS, an instrument suite part of the MPO payload, capable of acquiring high resolution images of the surface of Mercury. The use of optical measurements for navigation, can provide complementary informations with respect to Doppler, for enhanced performances or a relaxation of the radio tracking requisites in term of ground station schedule. Classical optical techniques based on centroids, limbs or landmarks, were the base to a novel idea for optical navigation, inspired by concepts of stereoscopic vision. In brief, the relation between two overlapped images acquired by a nadir pointed orbiter spacecraft at different times, was defined, and this information was then formulated into an optical measurement, to be processed by a navigation filter. The formulation of this novel optical observable is presented, moreover the analysis of the possible impact on the mission budget and images scheduling is addressed. Simulations are conducted using an orbit determination software already in use for spacecraft navigation in which the proposed optical measurements were implemented and the final results are given.

Advanced imaging study in cerebrovascular pathology for the personalization of therapy: from the capillary microcirculation to the vessel wall

Objectives: To investigate the use of intravascular optical coherence tomography (IVOCT) for carotid artery stenting (CAS) procedures in patients with atherosclerotic stenosis. Examine possible markers that might identify the onset of new cerebral ischemic lesions on MRI. Specifically, attention was drawn to the morphological features of the used dual layer stent, which could be underestimated during traditional CAS procedures. Secondary goals are to compare the safety and efficacy of different CAS techniques and the accuracy of the vessel analysis software’s on pre-operative CTA examination used to quantify ICA stenosis with the gold standard IVOCT. Material and Methods: Ten patients underwent CAS procedure with flow-arrest technique and IVOCT evaluations prior to and following stent deployment, while five matched patients underwent CAS procedure with distal embolic protection device (EPD) technique. All patients underwent 24-hours 3T MRI examination to check for ischemic lesions; all patients were treated with the same dual-layer stent. Results: Patients with new ischemic lesions demonstrated peculiar stent configuration in the distal end, and a strong Spearman’s rank order correlation was found among the volume of new DWI lesions and the stent configuration in its distal end (Rs: 0.81; p <0.001). No statistically significant differences were observed in the total burden of new ischemic lesions for each technique. The vessel analysis software's on CTA comparison demonstrated a higher diagnostic accuracy in the degree of ICA stenosis compared to the gold standard of IVOCT of the specialized software (ROC curve = 0.63; p = 0.06) compared to the general software (ROC curve = 0.57, p = 0.31). Conclusions: Study’s results support the use of IVOCT to allow recognition of potential features that can predict the onset of new cerebral ischemic lesions. Additionally, IVOCT made it possible to evaluate specialized software's increased accuracy in the pre-operative evaluation of ICA atherosclerotic stenosis.