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Roussel N.,University Paul Sabatier | Ramillien G.,University Paul Sabatier | Frappart F.,University Paul Sabatier | Darrozes J.,University Paul Sabatier | And 4 more authors.
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2015

Ocean altimetric applications of GNSS-R have particularly been developed through the last decades. Interference Pattern Technique (IPT) based on the analysis of the Signal-to-Noise Ratio (SNR) of a classical GNSS antenna presents the main advantage of being applicable everywhere by using a single geodetic antenna and a classical GNSS receiver, transforming them to real wave/tide gauges. Such a technique has been already tested in various configurations of acquisition of surface-reflected GNSS signals with an accuracy of a few centimeters. Nevertheless, the traditional method for estimating the reflecting surface-antenna height is limited by an approximation: the vertical velocity of the reflecting surface must be negligible. This article presents a significant improvement of the IPT technique to solve this problem and broaden the scope of SNR-based tide monitoring. This method was validated in situ, with an antenna placed at 60 meters above the Atlantic Ocean surface which variations reach ±3 meters, and amplitude rate of the semi-diurnal tide up to 0.5 mm/s. Over the three months of SNR records for sea level determination, we found linear correlations of 0.94 by comparing with a traditional tide gauge. Our SNR-based time series was also compared to the TUGO tide theoretical model [1] and amplitudes and phases of the main astronomical periods (6-, 12- and 24-h) were perfectly well detected. © 2015 IEEE. Source


Maurice S.,CNRS Institute for research in astrophysics and planetology | Wiens R.C.,Los Alamos National Laboratory | Saccoccio M.,French National Center for Space Studies | Barraclough B.,Los Alamos National Laboratory | And 70 more authors.
Space Science Reviews | Year: 2012

ChemCam is a remote sensing instrument suite on board the Curiosity rover (NASA) that uses Laser-Induced Breakdown Spectroscopy (LIBS) to provide the elemental composition of soils and rocks at the surface of Mars from a distance of 1.3 to 7 m, and a telescopic imager to return high resolution context and micro-images at distances greater than 1.16 m. We describe five analytical capabilities: rock classification, quantitative composition, depth profiling, context imaging, and passive spectroscopy. They serve as a toolbox to address most of the science questions at Gale crater. ChemCam consists of a Mast-Unit (laser, telescope, camera, and electronics) and a Body-Unit (spectrometers, digital processing unit, and optical demultiplexer), which are connected by an optical fiber and an electrical interface. We then report on the development, integration, and testing of the Mast-Unit, and summarize some key characteristics of ChemCam. This confirmed that nominal or better than nominal performances were achieved for critical parameters, in particular power density (>1 GW/cm 2). The analysis spot diameter varies from 350 μm at 2 m to 550 μm at 7 m distance. For remote imaging, the camera field of view is 20 mrad for 1024×1024 pixels. Field tests demonstrated that the resolution (∼90 μrad) made it possible to identify laser shots on a wide variety of images. This is sufficient for visualizing laser shot pits and textures of rocks and soils. An auto-exposure capability optimizes the dynamical range of the images. Dedicated hardware and software focus the telescope, with precision that is appropriate for the LIBS and imaging depths-of-field. The light emitted by the plasma is collected and sent to the Body-Unit via a 6 m optical fiber. The companion to this paper (Wiens et al. this issue) reports on the development of the Body-Unit, on the analysis of the emitted light, and on the good match between instrument performance and science specifications. © 2012 Springer Science+Business Media B.V. Source

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