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Ramonville-Saint-Agne, France

Amberg V.,French National Center for Space Studies | Dechoz C.,French National Center for Space Studies | Bernard L.,MAGELLIUM | Greslou D.,French National Center for Space Studies | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering

This paper deals with the problem of retrieving attitude perturbances in the framework of the PLEIADES-HR optical satellites. Thus, two complementary methods are compared. The first one uses the high agility capacity of satellites to acquire stars in an inertial steering mode. The second method exploits the fact that multispectral CCD arrays are shifted in the telescope focal plane in the velocity direction: for a same ground point, the resulting images are not affected by the same attitude perturbances. The resulting misregistrations can be exploited to deduce information about the attitude platform. Both methods have been applied to PLEIADES-HR satellites, during commissioning period. © 2013 SPIE. Source

Meyer N.,University Paul Sabatier | Lauwers-Cances V.,University Paul Sabatier | Lauwers-Cances V.,Toulouse University Hospital Center | Lourari S.,University Paul Sabatier | And 8 more authors.
British Journal of Dermatology

Background Early diagnosis and rapid surgical excision are essential for improving the prognosis of patients with melanoma. Reflectance confocal microscopy has been validated as a feasible procedure for in vivo diagnosis of melanoma but cannot be used to measure tumour thickness. However, ultrasonography and optical coherence tomography may allow melanoma thickness to be measured in vivo. Objectives To validate the accuracy and reliability of high-frequency ultrasonography (HFUS) and optical coherence tomography for assessing melanoma thickness in vivo. Methods We conducted a prospective study on 131 patients with at least one equivocal melanocytic lesion. Each lesion underwent optical coherence tomography and HFUS assessment, followed by excision and pathological examination. Histopathology was considered to be the gold standard for assessing melanoma thickness. Repeatability, inter- and intrarater reproducibility and reliability were evaluated for each imaging procedure. Results Ultrasonography showed a good level of agreement with histology [intraclass correlation coefficient (ICC) 0·807; 95% confidence interval (CI) 0·703-0·877] and excellent inter-rater reproducibility (G = 0·97), resulting in reliable in vivo assessment of melanoma thickness. The 930-nm optical coherence tomography showed a poor level of agreement with histopathology (ICC 0·0; 95% CI -0·2-0·2) and the inter-rater reproducibility was null (G = 0·00). Conclusions HFUS is a reliable and reproducible noninvasive method for assessing melanoma thickness. Routine use of HFUS may allow single-step excision of equivocal melanocytic lesions, with surgical margins determined by in vivo assessment of tumour thickness. What's already known about this topic? Early diagnosis and complete surgical excision with defined margins, depending on tumour thickness, is the recommended strategy for improving melanoma prognosis. Most primary melanomas require a two-step surgical procedure, with excision of the tumour followed by re-excision determined by histopathological assessment of tumour thickness. What does this study add? High-frequency ultrasonography is a reliable tool that provides reproducible results for in vivo evaluation of melanoma tumour thickness. This method could enable single-step surgical excision of melanoma. © 2014 British Association of Dermatologists. Source

Ristorcelli T.,MAGELLIUM | Ristorcelli T.,ONERA | Ristorcelli T.,Higher Institute of Aeronautics and Space | Hamoir D.,ONERA | Briottet X.,ONERA
IEEE Geoscience and Remote Sensing Letters

A possible step in dimensioning future space-based full-waveform lidar sensors is to predict space signals from commercial airborne laser scanner data. This method has proved able to simulate passive satellite sensors with precise accounting of the scene heterogeneity effects. In this letter, we use the DELiS code (n-Dimensional Estimation of Lidar Signals) to numerically evaluate a simple, efficient aggregation method for combining airborne lidar measurements (submeter footprints) into space lidar signals (decametric footprints). Two main sources of error are studied: the heterogeneity of the scene combined with an insufficient coverage by the airborne scanner, and the multiple scattering of the laser pulse in vegetation. It is found that for three different types of vegetation (corn, orchard, rainforest), and in three usual scanning configurations, the satellite signal can be derived with good precision. However, multiple scattering in the vegetation is shown to induce errors of up to 30% of the total backscattered signal depending on the wavelength. © 2013 IEEE. Source

Huck A.,MAGELLIUM | Guillaume M.,Fresnel Institute | Guillaume M.,Ecole Centrale Marseille
IEEE Transactions on Geoscience and Remote Sensing

This paper addresses the problem of anomaly detection in hyperspectral images. We propose and exploit a data model to establish the link between two main approaches in the area of anomaly detection, which are the hypothesis testing (HT) and projection pursuit. We show that combining these two approaches enables one to overcome some limitations of each method when taken separately. Indeed, the resulting detection algorithm, namely, anomalous component pursuit (ACP) has an asymptotically constant false-alarm rate, like HT-based detectors, and enables anomaly spectral discrimination, including the estimation of the number of classes. We assess the ACP algorithm on real-world data, in terms of detection and discrimination, and discuss some theoretical limitations. © 2010 IEEE. Source

Amberg V.,French National Center for Space Studies | Bernard L.,MAGELLIUM | Latry C.,French National Center for Space Studies
Proceedings of SPIE - The International Society for Optical Engineering

PLEIADES-HR is an earth observing system developed by the French National Space Agency, CNES. It consists of two satellites launched on December 2011 (PHR-1A) and December 2012 (PHR-1B). Each satellite is designed to provide optical 70 cm resolution panchromatic and 2.80m colored images to civilian and defense users. During commissioning period of these satellites, thanks to their extreme agility, new calibration methods have been tested based on the observation of celestial bodies, and stars in particular. It has then been made possible to perform MTF and defocus measurement (in order to refocus), geometrical bias computation, focal plane assessment, absolute calibration, ghost images localization, micro-vibrations measurement, etc. This article deals with the problem of satellite refocusing. By using images of stars, the problem can be considered as a phase diversity inverse problem. Significant evolution has been brought to the previous method developed during the commissioning period in order to improve accuracy and reduce operating constraints of the method. © 2015 SPIE. Source

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