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Envisat Ocean Altimetry Performance Assessment and Cross-calibration

Yannice Faugere, Joël Dorandeu, Fabien Lefevre, Nicolas Picot, Pierre Femenias
2006 Sensors  
Nearly three years of Envisat altimetric observations over ocean are available in Geophysical Data Record (GDR) products. The quality assessment of these data is routinely performed at the CLS Space Oceanography Division in the frame of the CNES Segment Sol Altimétrie et Orbitographie (SSALTO) and ESA French Processing and Archiving Center (F-PAC) activities. This paper presents the main results in terms of Envisat data quality: verification of data availability and validity, monitoring of the
more » ... ost relevant altimeter (ocean1 retracking) and radiometer parameters, assessment of the Envisat altimeter system performances. This includes a cross-calibration analysis of Envisat data with Jason-1, ERS-2 and T/P. Envisat data show good general quality. A good orbit quality and a low level of noise allow Envisat to reach the high level of accuracy of other precise missions such as T/P and Jason-1. Some issues raised in this paper, as the gravity induced orbit errors, will be solved in the next version of GDR products. Some others, as the Envisat Mean Sea Level in the first year, still need further investigation.
doi:10.3390/s6030100 fatcat:exzi7el6j5ehbh54hfqpjwl5vi

Copernicus Sentinel-1 satellites: sensitivity of antenna offset estimation to orbit and observation modelling

Heike Peter, Jaime Fernández, Pierre Féménias
2020 Advances in Geosciences  
Abstract. The SAR (Synthetic Aperture Radar) Copernicus Sentinel-1 satellites require a high orbit accuracy of 5 cm in 3D in comparison to external processing facilities. The official orbit products delivered by the Copernicus POD (Precise Orbit Determination) Service fulfil this requirement. Nevertheless, analyses have shown discrepancies in the orbit results for the two satellites Sentinel-1A and Sentinel-1B. Since the satellites are identical in construction estimated orbit parameters like
more » ... e scale factor for the radiation pressure are expected to be at the same magnitude, which is not the case. Estimation of GPS antenna offsets leads to differences between the two satellites, which might explain the discrepancies in the estimated orbit parameters. Such offset estimations are, however, very sensitive to orbit and observation modelling. It has to be assured that the results are not biased by insufficient models. First of all, stabilisation of the antenna offset estimation is achieved by improving the observation modelling by applying single receiver ambiguity resolution. The Copernicus Sentinel-1 satellites have a very complex shape with the long SAR antenna and the two large solar arrays. Antenna offset estimation based on different satellite models may give results which differ by up to 1.5 cm. The dispersion of the estimates is quite large depending also on eclipse and non-eclipse periods. Consideration of simple assumptions on satellite self-shadowing effects improves the satellite model and also the results of the antenna offset estimation. Finally, more consistent results for the two Sentinel-1 satellites are achieved by applying the antenna offset estimates.
doi:10.5194/adgeo-50-87-2020 fatcat:w5yu7wud65h5nhuap64owtaebi

Calibrating the SAR SSH of Sentinel-3A and CryoSat-2 over the Corsica Facilities

Pascal Bonnefond, Olivier Laurain, Pierre Exertier, François Boy, Thierry Guinle, Nicolas Picot, Sylvie Labroue, Matthias Raynal, Craig Donlon, Pierre Féménias, Tommaso Parrinello, Salvatore Dinardo
2018 Remote Sensing  
doi:10.3390/rs10010092 fatcat:7rogvvgwsfeyhamzxctnb64lrm

Identification of Novel Zoonotic Activity of Bartonella spp., France

Muriel Vayssier-Taussat, Sara Moutailler, Françoise Féménia, Philippe Raymond, Olivier Croce, Bernard La Scola, Pierre Edouard Fournier, Didier Raoult
2016 Emerging Infectious Diseases  
Certain Bartonella species are known to cause afebrile bacteremia in humans and other mammals, including B. quintana, the agent of trench fever, and B. henselae, the agent of cat scratch disease. Reports have indicated that animal-associated Bartonella species may cause paucisymptomatic bacteremia and endocarditis in humans. We identified potentially zoonotic strains from 6 Bartonella species in samples from patients who had chronic, subjective symptoms and who reported tick bites. Three
more » ... were B. henselae and 3 were from other animal-associated Bartonella spp. (B. doshiae, B. schoenbuchensis, and B. tribocorum). Genomic analysis of the isolated strains revealed differences from previously sequenced Bartonella strains. Our investigation identifed 3 novel Bartonella spp. strains with human pathogenic potential and showed that Bartonella spp. may be the cause of undifferentiated chronic illness in humans who have been bitten by ticks.
doi:10.3201/eid.2203.150269 fatcat:42zklmetqbewvmi2a4pvua4sba

Defining a Sea Ice Flag for Envisat Altimetry Mission

Ngan Tran, Fanny Girard-Ardhuin, Robert Ezraty, Hui Feng, Pierre Femenias
2009 IEEE Geoscience and Remote Sensing Letters  
This letter presents the development of a sea ice flag algorithm for the Envisat altimetry mission to detect sea ice corrupted sea surface height data within quality control processing. The algorithm takes advantage of having both passive and active microwave sensors on the same platform with coregistered measurements. Its performances have been evaluated based on collocations between the along-track Envisat data with reference maps built from combination of daily grids of sea ice concentration
more » ... from SSM/I sensors and backscatter cross section from SeaWinds scatterometer on QuikSCAT satellite.
doi:10.1109/lgrs.2008.2005275 fatcat:333ol2wj75dslihl6lznfrux5q

Sentinel-3 Microwave Radiometers: Instrument Description, Calibration and Geophysical Products Performances

Marie-Laure Frery, Mathilde Siméon, Christophe Goldstein, Pierre Féménias, Franck Borde, Alexandre Houpert, Ana Olea Garcia
2020 Remote Sensing  
Copernicus Sentinel-3 Surface Topography Mission embarks a two-channel microwave radiometer combined with the altimeter in order to correct the altimeter range for the excess path delay resulting from the presence of water vapour in the troposphere. The in-flight calibration of a single instrument is the critical point to achieve the expected performances. In the context of a constellation, the inter-calibration is even more important. After a presentation of the instrument design, we present
more » ... e diagnoses used for the calibration of Sentinel-3A, using vicarious calibration over specific areas and double difference methods. The inter-calibration of Sentinel-3B with Sentinel-3A is performed during the tandem phase, using the residual differences of co-located measurements. Finally performances are assessed at crossover points with two parameters, first the wet troposphere correction by comparison with Jason-3; secondly on the Sea Surface Height by difference of variance. Analysis results have shown that Sentinel-3A is well calibrated, consistent with other instruments, and that Sentinel-3B is calibrated within 0.4 K with Sentinel-3A as a reference. Performances and stability fulfill the requirements for both missions.
doi:10.3390/rs12162590 fatcat:u5fq5rurojbavmpktwfgb7a5m4

Identification of Novel Zoonotic Activity of Bartonella spp., France

Muriel Vayssier-Taussat, Sara Moutailler, Françoise Féménia, Philippe Raymond, Olivier Croce, Bernard La Scola, Pierre-Edouard Fournier, Didier Raoult
2016 Emerging Infectious Diseases  
Certain Bartonella species are known to cause afebrile bacteremia in humans and other mammals, including B. quintana, the agent of trench fever, and B. henselae, the agent of cat scratch disease. Reports have indicated that animal-associated Bartonella species may cause paucisymptomatic bacteremia and endocarditis in humans. We identified potentially zoonotic strains from 6 Bartonella species in samples from patients who had chronic, subjective symptoms and who reported tick bites. Three
more » ... were B. henselae and 3 were from other animal-associated Bartonella spp. (B. doshiae, B. schoenbuchensis, and B. tribocorum). Genomic analysis of the isolated strains revealed differences from previously sequenced Bartonella strains. Our investigation identifed 3 novel Bartonella spp. strains with human pathogenic potential and showed that Bartonella spp. may be the cause of undifferentiated chronic illness in humans who have been bitten by ticks.
doi:10.3201/eid2203.150269 pmid:26885624 pmcid:PMC4766919 fatcat:3wod7cfs25ekzdksmzehpc4pqq

Speckle nulling wavefront control for Palomar and Keck

Michael Bottom, Bruno Femenia, Elsa Huby, Dimitri Mawet, Richard Dekany, Jennifer Milburn, Eugene Serabyn, Enrico Marchetti, Laird M. Close, Jean-Pierre Véran
2016 Adaptive Optics Systems V  
Femenia-Castella et al., these proceedings).  ... 
doi:10.1117/12.2233025 fatcat:mqglrkdyrbhyjdwvmdnzvmtfsm

Validation of Envisat Rain Detection and Rain Rate Estimates by Comparing With TRMM Data

Ngan Tran, Jean Tournadre, Pierre Femenias
2008 IEEE Geoscience and Remote Sensing Letters  
Féménias is with the European Space Research Institute for Earth Observation (ESRIN), European Space Agency, 00044 Frascati, Italy.  ... 
doi:10.1109/lgrs.2008.2002043 fatcat:jmd7zqvgafdztmocas5f2zr2nu

CryoSat ocean product quality status and future evolution

Jerome Bouffard, Marc Naeije, Christopher J. Banks, Francisco M. Calafat, Paolo Cipollini, Helen M. Snaith, Erica Webb, Amanda Hall, Rubinder Mannan, Pierre Féménias, Tommaso Parrinello
2018 Advances in Space Research  
J., Webb, E., Scagliola, M., Garcia-Mondéjar, A., Baker, S., Brockley, D., Gaudelli, J., Muir, A., Hall, A., Mannan, R., Roca, M., Fornari, M., Féménias P. and Parrinello T. (2017).  ...  ., Féménias, P., Parrinello T. and Bojkov B. (2016) . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39  ... 
doi:10.1016/j.asr.2017.11.043 fatcat:wwhbk3yvxbds3la4czajwtt4we

Snow Facies Over Ice Sheets Derived From Envisat Active and Passive Observations

Ngan Tran, FrÉdÉrique Remy, Hui Feng, Pierre Femenias
2008 IEEE Transactions on Geoscience and Remote Sensing  
This paper aims to separate different snow regions over the terrestrial ice sheets based on their measured microwave signatures. It takes advantage of coregistered data from passive and active sensors on the Environmental Satellite (Envisat) to directly derive a snow facies indicator in a point-by-point basis. This paper represents the first attempt of this kind in exploiting nadir-viewing and dual-frequency data from both altimeter and radiometer sensors. The approach is based on a clustering
more » ... ethod. Such representation of the data by means of fewer clusters necessarily loses fine details but achieves simplification in geographical representation and eases the description of the condition of the ice sheets in 2004. Our approach broadens the description of the snow pack by taking into account characteristics such as surface roughness, grain size, stratification, and snowmelt effects, whereas the latter has often solely been considered in most previous work. Such partition of the ice sheets might help to better understand relationships between microwave signatures and snow morphology. It could also be useful for estimating elevation uncertainty in altimeter data, which, in turn, is essential to correctly interpret the significance of the rates of elevation change in a changing climate and to convert elevation change to snow mass change.
doi:10.1109/tgrs.2008.2000818 fatcat:lga44abhvngk3eb3rnwprz2cry

CryoSat instrument performance and ice product quality status

Jerome Bouffard, Erica Webb, Michele Scagliola, Albert Garcia-Mondéjar, Steven Baker, David Brockley, Julia Gaudelli, Alan Muir, Amanda Hall, Rubinder Mannan, Mònica Roca, Marco Fornari (+2 others)
2018 Advances in Space Research  
14 Over the past 20 years, satellite radar altimetry has shown its ability to revolutionise our 15 understanding of the ocean and climate. Previously, these advances were largely limited to 16 ice-free regions, neglecting large portions of the Polar Regions. Launched in 2010, the 17 European Space Agency's (ESA) polar-orbiting CryoSat satellite was specifically designed to 18 measure changes in the thickness of polar sea ice and the elevation of the ice sheets and 19 mountain glaciers. To reach
more » ... this goal, the CryoSat products have to meet the highest 20 performance standards, achieved through continual improvements of the associated 21 Instrument Processing Facilities. Since April 2015, the CryoSat ice products are generated 22 with Baseline-C, which represented a major processor upgrade. Several improvements were 23 implemented in this new Baseline, most notably the release of freeboard data within the Level 24 2 products. The Baseline-C upgrade has brought significant improvements to the quality of 25 Level-1B and Level-2 products relative to the previous Baseline-B products, which in turn is 26 expected to have a positive impact on the scientific exploitation of CryoSat measurements 27 over land ice and sea ice. This paper provides an overview of the CryoSat ice data quality 28 assessment and evolutions, covering all quality control and calibration activities performed by 29 2 ESA and its partners. Also discussed are the forthcoming evolutions of the processing chains 30 and improvements anticipated in the next processing Baseline. 31 32
doi:10.1016/j.asr.2017.11.024 fatcat:yv7w6u3wf5gx7ilnympuuoatyy

REAPER: Reprocessing 12 Years of ERS-1 and ERS-2 Altimeters and Microwave Radiometer Data

David J. Brockley, Steven Baker, Pierre Femenias, Bernat Martinez, Franz-Heinrich Massmann, Michiel Otten, Frederic Paul, Bruno Picard, Pierre Prandi, Monica Roca, Sergei Rudenko, Remko Scharroo (+1 others)
2017 IEEE Transactions on Geoscience and Remote Sensing  
Féménias, Bernat Martinez, Franz-Heinrich Massmann, Michiel Otten, Frederic Paul, Bruno Picard, Pierre Prandi, Mònica Roca, Sergei Rudenko, Remko Scharroo, and Pieter Visser changes in data processing  ...  performance (ageing or damage), orbital effects on hardware (thermal flexure), or REAPER: Reprocessing 12 years of ERS-1 and ERS-2 Altimeter and Microwave Radiometer Data David Brockley, Steven Baker, Pierre  ... 
doi:10.1109/tgrs.2017.2709343 fatcat:4pfajjftebhwzbiajqjzhbprq4

S3MPC: Improvement on Inland Water Tracking and Water Level Monitoring from the OLTC Onboard Sentinel-3 Altimeters

Nicolas Taburet, Lionel Zawadzki, Maxime Vayre, Denis Blumstein, Sophie Le Gac, François Boy, Matthias Raynal, Sylvie Labroue, Jean-François Crétaux, Pierre Femenias
2020 Remote Sensing  
The Sentinel-3A and Sentinel-3B satellites were launched, respectively, on 16 February 2016 and 25 April 2018 as part of the European Copernicus program. The Sentinel-3 Surface Topography Mission makes use of the altimeter instruments onboard Sentinel-3A and Sentinel-3B to provide elevation measurements not only of the ocean water level but also of the inland waters and ice caps. For the first time, the altimeters onboard Sentinel-3A and Sentinel-3B are operated in Synthetic Aperture Radar mode
more » ... over all Earth surfaces. They also benefit from elevation priors (the Open-Loop Tracking Command) allowing them to precisely position their receiving window to track the backscattered signal from the inland water targets to be monitored rather than relying on the traditional Closed-Loop tracking mode. This paper makes use of the Sentinel-3A/Sentinel-3B tandem phase to assess the benefits of the Open-Loop tracking mode compared to Closed-Loop. Longer time series are also used to highlight the improvements in terms of the percentage of points over which the altimeter hooks on water surfaces and water surface height estimation brought by the switch of Sentinel-3A from the Closed-Loop to Open-Loop tracking mode as well as the successive Open-Loop Tracking Command updates. In particular, it is shown that from a Level-3 water level product service perspective, the increase in the number of water bodies with valid water surface height estimates is of the order of 25% in Open-Loop with respect to Closed-Loop with similar precision. It is also emphasized that the Open-Loop Tracking Command update onboard Sentinel-3A from v. 4.2 to v. 5.0 yielded a 30% increase in the number of water bodies over which valid water surface height could be estimated. Eventually, the importance of knowing whether a water target was associated with a fine-tuned Open-Loop Tracking Command or an interpolated one is stressed and the recommendation to provide such a flag in the Sentinel-3 Level2 Payload Data Ground Segment products is emitted.
doi:10.3390/rs12183055 doaj:a50821742d1d48b0891a442a5c409345 fatcat:zdbuli6pire5jn5vtwpagwa62u

The QACITS pointing sensor: from theory to on-sky operation on Keck/NIRC2 [article]

Elsa Huby, Olivier Absil, Dimitri Mawet, Pierre Baudoz, Bruno Femenìa Castellà, Michael Bottom, Henry Ngo, Eugene Serabyn
2016 arXiv   pre-print
Small inner working angle coronagraphs are essential to benefit from the full potential of large and future extremely large ground-based telescopes, especially in the context of the detection and characterization of exoplanets. Among existing solutions, the vortex coronagraph stands as one of the most effective and promising solutions. However, for focal-plane coronagraph, a small inner working angle comes necessarily at the cost of a high sensitivity to pointing errors. This is the reason why
more » ... pointing control system is imperative to stabilize the star on the vortex center against pointing drifts due to mechanical flexures, that generally occur during observation due for instance to temperature and/or gravity variations. We have therefore developed a technique called QACITS (Quadrant Analysis of Coronagraphic Images for Tip-tilt Sensing), which is based on the analysis of the coronagraphic image shape to infer the amount of pointing error. It has been shown that the flux gradient in the image is directly related to the amount of tip-tilt affecting the beam. The main advantage of this technique is that it does not require any additional setup and can thus be easily implemented on all current facilities equipped with a vortex phase mask. In this paper, we focus on the implementation of the QACITS sensor at Keck/NIRC2, where an L-band AGPM has been recently commissioned (June and October 2015), successfully validating the QACITS estimator in the case of a centrally obstructed pupil. The algorithm has been designed to be easily handled by any user observing in vortex mode, which is available for science in shared risk mode since 2016B.
arXiv:1607.05497v1 fatcat:il6zz7vx3jddvkedjr23i2en6u
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