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Verrières-le-Buisson, France

Kerr Y.H.,CNRS Center for the Study of the Biosphere from Space | Waldteufel P.,IPSL LATMOS | Wigneron J.-P.,French National Institute for Agricultural Research | Delwart S.,European Space Agency | And 11 more authors.
Proceedings of the IEEE | Year: 2010

It is now well understood that data on soil moisture and sea surface salinity (SSS) are required to improve meteorological and climate predictions. These two quantities are not yet available globally or with adequate temporal or spatial sampling. It is recognized that a spaceborne L-band radiometer with a suitable antenna is the most promising way of fulfilling this gap. With these scientific objectives and technical solution at the heart of a proposed mission concept the European Space Agency (ESA) selected the Soil Moisture and Ocean Salinity (SMOS) mission as its second Earth Explorer Opportunity Mission. The development of the SMOS mission was led by ESA in collaboration with the Centre National d'Etudes Spatiales (CNES) in France and the Centro para el Desarrollo Tecnologico Industrial (CDTI) in Spain. SMOS carries a single payload, an L-Band 2-D interferometric radiometer operating in the 14001427-MHz protected band. The instrument receives the radiation emitted from Earth's surface, which can then be related to the moisture content in the first few centimeters of soil over land, and to salinity in the surface waters of the oceans. SMOS will achieve an unprecedented maximum spatial resolution of 50 km at L-band over land (43 km on average over the field of view), providing multiangular dual polarized (or fully polarized) brightness temperatures over the globe. SMOS has a revisit time of less than 3 days so as to retrieve soil moisture and ocean salinity data, meeting the mission's science objectives. The caveat in relation to its sampling requirements is that SMOS will have a somewhat reduced sensitivity when compared to conventional radiometers. The SMOS satellite was launched successfully on November 2, 2009. © 2006 IEEE.

Kerr Y.H.,CNRS Center for the Study of the Biosphere from Space | Waldteufel P.,IPSL LATMOS | Richaume P.,CNRS Center for the Study of the Biosphere from Space | Wigneron J.P.,French National Institute for Agricultural Research | And 9 more authors.
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

The Soil Moisture and Ocean Salinity (SMOS) mission is European Space Agency (ESA's) second Earth Explorer Opportunity mission, launched in November 2009. It is a joint program between ESA Centre National d'Etudes Spatiales (CNES) and Centro para el Desarrollo Tecnologico Industrial. SMOS carries a single payload, an L-Band 2-D interferometric radiometer in the 1400-1427 MHz protected band. This wavelength penetrates well through the atmosphere, and hence the instrument probes the earth surface emissivity. Surface emissivity can then be related to the moisture content in the first few centimeters of soil, and, after some surface roughness and temperature corrections, to the sea surface salinity over ocean. The goal of the level 2 algorithm is thus to deliver global soil moisture (SM) maps with a desired accuracy of 0.04 m3/m3. To reach this goal, a retrieval algorithm was developed and implemented in the ground segment which processes level 1 to level 2 data. Level 1 consists mainly of angular brightness temperatures (TB), while level 2 consists of geophysical products in swath mode, i.e., as acquired by the sensor during a half orbit from pole to pole. In this context, a group of institutes prepared the SMOS algorithm theoretical basis documents to be used to produce the operational algorithm. The principle of the SM retrieval algorithm is based on an iterative approach which aims at minimizing a cost function. The main component of the cost function is given by the sum of the squared weighted differences between measured and modeled TB data, for a variety of incidence angles. The algorithm finds the best set of the parameters, e.g., SM and vegetation characteristics, which drive the direct TB model and minimizes the cost function. The end user Level 2 SM product contains SM, vegetation opacity, and estimated dielectric constant of any surface, TB computed at 42.5 °, flags and quality indices, and other parameters of interest. This paper gives an overview of the algorithm, discusses the caveats, and provides a glimpse of the Cal Val exercises. © 2012 IEEE.

Josset D.,SSAI | Hu Y.,NASA | Pelon J.,IPSL LATMOS | Zhai P.,SSAI | Lucker P.,SSAI
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2011

We have determined the CLOUDSAT/sea spray relationship and used it to analyze cirrus clouds optical depth. Differences arise between the different sensors and need to be further investigated. The direct optical depth measurements will greatly improve our. © 2011 IEEE.

Welsh B.Y.,University of California at Berkeley | Wheatley J.,University of California at Berkeley | Siegmund O.H.W.,University of California at Berkeley | Lallement R.,IPSL LATMOS
Astrophysical Journal Letters | Year: 2010

We present high resolution (R = 114,000) ultraviolet measurements of the interstellar absorption line profiles of the C IV (1550 Å) high ionization doublet recorded toward the nearby B2Ve star HD 158427 (d ∼ 74 pc). These data, which were recorded with the recently re-furbished Space Telescope Imaging Spectrograph instrument on the Hubble Space Telescope, represent the most convincing detection yet of highly ionized C IV absorption that can be associated with interstellar gas located within the boundary of the Local Cavity (LC). Two highly ionized gas clouds at V 1 = -24.3kms-1 and V 2 = -41.3kms-1 are revealed in both C IV absorption lines, with the V 1 component almost certainly being due to absorption by the Local Interstellar Cloud (d < 5 pc). Although the observed column densities for both cloud components can be explained by the predictions of current theoretical models of the local interstellar medium, the narrow Doppler width of the V 2 line profile (b = 6.8kms-1) indicates an unusually low gas temperature of ≤34,000 K for this highly ionized component. It is conjectured that the V 2 cloud may be due to an outflow of highly ionized and hot gas from the nearby Loop I superbubble. These new data also indicate that absorption due to highly ionized gas in the LC can be best described as being "patchy" in nature. © 2010. The American Astronomical Society. All rights reserved.

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