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Hospital-acquired infections (HAIs) are a cause of continuously increasing morbidity and mortality. Most of these infections are caused by a limited set of bacterial species, which share the capability to efficiently spread from patient to patient and to easily acquire antibiotic resistance determinants. This renders correct and rapid species identification and antibiotic susceptibility testing (AST) important and underscores the relevance of bacterial epidemiological typing. The latter is needed for the sensitive detection and exact tracing of nosocomial spread of these potentially multidrug-resistant microorganisms (MDRO). Many microbial typing technologies have been developed and put to some level of executive practice, but it seems that the continued evolution in methodology has currently reached an apex: there is likely to be scientific and practical consensus on the ultimate typing potential of bacterial whole-genome sequencing (WGS). The possibility to perform pan-genomic nucleotide-to-nucleotide comparisons between strains belonging to a single species and to detect even minute changes in nucleotide order will identify closely related organisms, while upon accumulation of such mutations, independent descend can be assumed. Calibration of difference levels [i.e. number of single nucleotide polymorphisms (SNPs)] into categories of inter-strain relatedness needs to be performed in order to generate robust, portable typing schemes. Here, we will briefly discuss the state of affairs regarding bacterial epidemiology based upon WGS, its relatedness with the nomenclature of former typing approaches and the continuing need for a global typing language. [ABSTRACT FROM AUTHOR]

The SARAL/AltiKa mission is a complement of the Jason altimeter series. A two-channels (23.8 GHz and 37 GHz) microwave radiometer (MWR) is combined to the altimeter in order to correct the altimeter range for the excess path delay (referred as WTC for wet tropospheric correction. First, the in-flight calibration of AltiKa MWR is assessed from a systematic comparison to other radiometers using a complete set of metrics (comparison to simulations and over geophysical targets). Then the “mixed” empirical approach successfully used for Envisat shows nonoptimal performances for the WTC retrieval. In order to find the potential sources of issues, this method is compared to a purely empirical relationship established between measured brightness temperatures (TB) and altimeter backscattering coefficient () on one hand and modeled WTC on the other hand. Various retrieval configurations for both AltiKa MWR and advanced microwave radiometer (AMR) on Jason-2, are for the first time systematically compared with respect to their performances against the variance of sea surface height differences at crossovers. Finally, the issues on the “mixed” approach are attributed to the differences between simulated and measuredat Ka-band. Now, a configuration of the empirical approach proved to have performances closed to what is initially expected with the “mixed” approach. [ABSTRACT FROM PUBLISHER]

Following the successful launch of the SARAL space mission in February 2013, the reliability of the innovative AltiKa altimeter has been demonstrated for deep ocean applications, where Ka-band performances are excellent. With the objective to ensure the complementarity but also the continuity with the altimeter Level-2 products provided in the open ocean, the Prototype for Expertise on AltiKa for Coastal, Hydrology and Ice (PEACHI) project has been set up as an initiative of the French space agency, CNES, to provide a data set of research-grade Level-2 parameters that might be interesting for SARAL secondary objectives on the study of coastal dynamics, inland waters, polar oceans, or continental and sea ices. Thus, the PEACHI prototype has been developed to process and accurately tune dedicated algorithms for the assessment of Ka-band parameters, from the instrument processing to geophysical corrections. As a result, the PEACHI prototype routinely provides end users with new or improved altimeter corrections for scientific applications dedicated to mesoscale monitoring but also synergistic science. [ABSTRACT FROM PUBLISHER]

On 25 February 2013, the SARAL satellite was launched from the Indian Sriharikota launch site. The key feature of the altimetric payload has been the selection of Ka-band. Using Ka-band avoids the need for a second frequency to correct for the ionosphere delay and eases the sharing of the antenna by the altimeter and the radiometer. The use of the Ka-band also allows the improvement of the range measurement accuracy in a ratio close to 2 due to the use of a wider bandwidth and to a better pulse to pulse echo decorrelation. Eventually, Ka-band antenna aperture is reduced, which limits the pollution within useful ground footprint. A summary of the results obtained during the in-flight assessment phase is given. All the tracking modes have also been gone through. Eventually, a new high data rate mode, called “HD mode” is implemented on AltiKa and has been used. The performance assessment is excellent: the range measurement accuracy is close to 1 cm for 1s averaging and the Significant Wave Height (SWH) noise is less than 5 cm (for a 2m SWH at 1?). The tracking success is close to 100% over oceans and 96% over all surfaces. [ABSTRACT FROM PUBLISHER]

On 25 February 2013, the Satellite for Argos and AltiKa (SARAL) was launched from the Indian Sriharikota launch site. The AltiKa payload consisted of an altimeter and a radiometer. This paper describes the AltiKa radiometer. This instrument has been studied for several years by CNES, TAS-F, ASTRIUM-F and a set of science laboratories, and AltiKa is the first compact instrument embedding simultaneously the altimeter and radiometer functions. AltiKa radiometer is a dual frequency instrument working in K (23.8 GHz) and Ka band (37 GHz), it is based on the total power principle, with direct detection receivers. On-ground acceptance tests exhibited a very high level of performance: less than 0.2 dB has been estimated for both sensitivity and absolute accuracy in both frequencies. This paper focuses on the in-flight performances that have been observed since the launch. All the instrument observable characterizations are nominal, and in-flight sensitivity has been estimated lower than 0.2 K. [ABSTRACT FROM PUBLISHER]

Sea level is one of the 50 Essential Climate Variables (ECVs) listed by the Global Climate Observing System (GCOS) in climate change monitoring. In the past two decades, sea level has been routinely measured from space using satellite altimetry techniques. In order to address a number of important scientific questions such as "Is sea level rise accelerating?", "Can we close the sea level budget?", "What are the causes of the regional and interannual variability?", "Can we already detect the anthropogenic forcing signature and separate it from the internal/natural climate variability?", and "What are the coastal impacts of sea level rise?", the accuracy of altimetry-based sea level records at global and regional scales needs to be significantly improved. For example, the global mean and regional sea level trend uncertainty should become better than 0.3 and 0.5 mm year-1, respectively (currently 0.6 and 1-2 mm year-1). Similarly, interannual global mean sea level variations (currently uncertain to 2-3 mm) need to be monitored with better accuracy. In this paper, we present various data improvements achieved within the European Space Agency (ESA) Climate Change Initiative (ESA CCI) project on "Sea Level" during its first phase (2010-2013), using multi-mission satellite altimetry data over the 1993-2010 time span. In a first step, using a new processing system with dedicated algorithms and adapted data processing strategies, an improved set of sea level products has been produced. The main improvements include: reduction of orbit errors and wet/dry atmospheric correction errors, reduction of instrumental drifts and bias, intercalibration biases, intercalibration between missions and combination of the different sea level data sets, and an improvement of the reference mean sea surface. We also present preliminary independent validations of the SL_cci products, based on tide gauges comparison and a sea level budget closure approach, as well as comparisons with ocean reanalyses and climate model outputs. [ABSTRACT FROM AUTHOR]

In this article, the author discusses the performance of solid and liquid culture media for the detection of Mycobacterium tuberculosis in clinical materials with the help of meta-analysis of various works of other researchers. Topics related to detection discussed include smear staining and microscopy, colorimetric nitrate reductase assay (NRA), and blood agar in resource-limited settings reduced the mean time to detection of mycobacteria.

The observation of ocean scales smaller than 100 km with low-resolution mode (LRM) altimetry products is degraded by the existence of a 'hump artifact' visible on sea surface height (SSH) spectra. Through an analysis of simulations and actual data from multiple missions, this paper shows that the hump originates in a response to inhomogeneities in backscatter strength. Current retrackers cannot fit their Brown model properly because they were designed for a scene with homogeneous backscatter properties. The error is also smoothed along track because of the size and shape of the LRM disc-shaped footprint. Therefore, the hump is modulated by the altimeter design and altitude and by the retracker used. Because of the random nature of the phenomenon, a large majority of long topography segments (e.g., hundreds to thousands of kilometers) is affected. However, within these segments, a substantial fraction of the corruption is contained in small subsets of data (e.g., less than 10%). This paper shows that oceanography users interested in small-scale SSH signals can mitigate the hump corruption by using better editing and postprocessing algorithms on the 20-Hz rate of current products. Last, the thin stripe-shaped footprint of Cryosat-2's synthetic aperture radar mode (SARM) is not affected by the hump artifact, thus improving the observation of topography features ranging from 30 to 100 km. The differences between SARM and pseudo-LRM sigma0 can also be used to detect major hump events on pseudo-LRM data, which might be an asset to design/validate a new generation of algorithms aimed at reducing the hump artifact on the existing LRM record. [ABSTRACT FROM AUTHOR]

As long-term stability of altimeter backscatter coefficient (σ0) can impact the accuracy of the Global Mean Sea Level (GMSL) trend through the Sea State Bias (SSB) correction, it is important to accurately monitor its evolution in order to detect potential instabilities. This study aims to characterize long-term uncertainties from several altimeter missions. The originality of our approach is to perform comparisons between wind speed estimations deduced from σ0measurements and from ERA-interim reanalysis. Thanks to the good temporal correlation between the Global Wind Speed (GWS) evolution issued from altimeters and the atmospheric reanalysis, the detection of small drifts is possible in the altimeter time series. In particular, drifts have been detected on Jason-1 GWS between mid-2004 and 2005 and on Envisat prior to 2004. They are associated to σ0jumps of approximately 0.03 dB. Larger anomalies have been detected on TOPEX σ0data with variations reaching 0.2 dB. These low altimeter wind speed variations originate from small σ0changes are within the instrumental stability requirements. However, via the SSB calculation, their impact on the GMSL evolution is estimated close to 0.1 mm/yr over the altimetry 20-year period. In addition, they strongly affect inter-annual GMSL variations with associated errors reaching 2 mm. [ABSTRACT FROM AUTHOR]

This article deals with the recent improvements of the Global and Regional Mean Sea Level trend using Envisat data. It focuses on the methodology based on comparison with Jason-1, Jason-2, and in situ data and shows that Envisat is now getting more reliable for MSL studies, as a comparison reference for future missions. Notably, Jason-1/Envisat comparisons enabled to detect a weakness in the orbit standard solution, now improved for all altimetric missions including Jason-2. [ABSTRACT FROM AUTHOR]

This study presents a new method of precise altimeter absolute calibration using a dedicated microwave transponder, which acts as an altimeter signal repeater that can be deployed at any sub-track position both in coastal regions and inland. The Austrian Academy of Sciences operates an altimeter transponder at the Gavdos calibration/validation facility located beneath a Jason cross-over point. We discuss the capabilities and strengths of the transponder technique in general and in the particular case of a dedicated calibration campaign carried out in 2011. For the accomplishment of this campaign, including 26 ascending and descending Jason-2 passes, the onboard Poseidon-3 altimeter had to be switched to the DIODE/DEM mode for every overflight. Four different methods have been developed to analyze the transponder generated waveforms, provided by S-IGDR and S-GDR products, respectively. The resulting biases of the altimetric ranges have proven to be stable (3 mm rms) and agree to a large extent among the proposed algorithms. However, the absolute bias value of 25.8 ± 0.3 cm derived from the transponder calibration technique shows a significant deviation of several centimeters compared with the ones resulting from conventional techniques. Possible causes of this behavior are under further investigation. [ABSTRACT FROM AUTHOR]

This article focuses on the determination and the validation of the new Mean Sea Surface from the CNES/CLS. This new model merges multiple satellite altimeters over 16 years of observations. Particular attention was paid on the analysis of the oceanic variability. Then a novel method was applied to remove this variability and to take into account different kinds of errors that affect the data. Several types of validations were performed to estimate the quality of the shortest topographic structures and to quantify the accuracy of the mean oceanic content at a larger scale. [ABSTRACT FROM AUTHOR]

Altimeter missions have provided accurate measurements of sea surface height since 1992 not only with TOPEX/Poseidon but also with Jason-1, Envisat, and recently Jason-2. The overall quality assessment of altimeter data can be performed by analyzing their internal consistency and the cross-comparison between all missions. In this study, in situ measurements are used as an external, independent reference to enable further quality assessment of the altimeter sea level. The most up-to-date altimeter data are assessed and compared with those from tide gauges and Argo profiling floats. The first focus is on detection of global and regional drifts in altimeter sea surface height compared with in situ measurements. A second point is that the method can assess the impact of new altimeter standards (e.g., orbit solution, instrumental correction, retracking algorithm) thanks to in situ observations. Finally, the study shows how multiple and reliable altimeter products are used to detect potential anomalies in tide gauges. The results demonstrate the close link between these three steps of the method: while the detection of altimeter drifts using in situ measurements is corrected by computing new altimeter standards whose impact can then be estimated, the improved altimeter sea level time series are used as input for controlling the quality of in situ observations. [ABSTRACT FROM AUTHOR]

Sea level monitoring in the Arctic Ocean can provide useful information in the context of a rapid change of several parts of the Arctic climate system. Satellite altimetry systems are affected by various problems at high latitudes. As a consequence, no precise and reliable mean sea level record is available yet from altimetry products. After identifying some of the issues that affect satellite altimetry in the Arctic Ocean region, we describe the tailored processing that has been applied to along-track mono-mission altimetry data. We generate a new dataset of weekly gridded sea level anomaly fields over the Arctic region for the period spanning from 1993 to 2009 based on multisatellite altimetry missions. We demonstrate the improvements achieved by this new dataset, among which a better data coverage. The grids are used to describe some features of mean sea level variability in the Arctic Ocean both at basin-wide and local scales. The regional trend estimated for the Arctic Ocean mean sea level over all latitudes from 66°N to 82°N is 3.6 mm/yr with an uncertainty of 1.3 mm/yr (90% confidence) and without any glacial isostatic adjustment (GIA) correction applied. The record displays large inter-annual variability, but no strong correlation with climate indices was found. Spatial patterns in sea level trends and variability over the Arctic region are also investigated. [ABSTRACT FROM AUTHOR]

The ageing of Jason-1, the risk of losing control of the satellite, and the collision risk with TOPEX/Poseidon (still in orbit and no longer maneuverable) initiated a reflection on a so-called “extension of life phase” (EoL) phase that would involve moving Jason-1 to a new orbit to mitigate collision risks while optimizing its science return. This paper describes three practical consequences of any such EoL phase: 1) the ability to build an unprecedented low inclination and high precision geodetic dataset, 2) the loss of coordination with Jason-2 and the associated mesoscale (and sea state) sampling degradation, and 3) the increased topography height error budget stemming from the use of a gridded mean sea surface in place of the classical repeat track analysis that operational systems have been using and improving for almost two decades. More than 17,000 potential orbits were analyzed to identify desirable altitude ranges that could host a Jason-1 EoL phase. The objective was to minimize the sampling degradation of ocean observations (primary objective of Jason-1) while securing a good geodetic EoL dataset (secondary objective of Jason-1). After a first automated screening and scoring process, the final orbit candidates are analyzed through an end-to-end Observing System Simulation Experiment (OSSE) protocol, assessing the multimission observational capability of the EoL phase in a DUACS/AVISO-like system. All EoL orbits are shown to be largely inferior to the interleaved orbit as far as oceanography is concerned. Yet some EoL options are shown to be more desirable than others because their sampling patterns blend well with Jason-2. Good geodetic orbit options could provide a unique bathymetry-oriented dataset and help improve gridded mean sea surfaces (MSS), while repetitive options with a short cycle could cancel some additional EoL errors if a conservative repeat track strategy is preferred. [ABSTRACT FROM AUTHOR]

The ageing of Jason-1, the risk of losing control of the satellite, and the collision risk with TOPEX/Poseidon (still in orbit and no longer maneuverable) initiated a reflection on a so-called "extension of life phase" (EoL) phase that would involve moving Jason-1 to a new orbit to mitigate collision risks while optimizing its science return. This paper describes three practical consequences of any such EoL phase: 1) the ability to build an unprecedented low inclination and high precision geodetic dataset, 2) the loss of coordination with Jason-2 and the associated mesoscale (and sea state) sampling degradation, and 3) the increased topography height error budget stemming from the use of a gridded mean sea surface in place of the classical repeat track analysis that operational systems have been using and improving for almost two decades. More than 17,000 potential orbits were analyzed to identify desirable altitude ranges that could host a Jason-1 EoL phase. The objective was to minimize the sampling degradation of ocean observations (primary objective of Jason-1) while securing a good geodetic EoL dataset (secondary objective of Jason-1 ). After a first automated screening and scoring process, the final orbit candidates are analyzed through an end-to-end Observing System Simulation Experiment (OSSE) protocol, assessing the multimission observational capability of the EoL phase in a DUACS/AVISO-like system. All EoL orbits are shown to be largely inferior to the interleaved orbit as far as oceanography is concerned. Yet some EoL options are shown to be more desirable than others because their sampling patterns blend well with Jason-2. Good geodetic orbit options could provide a unique bathymetry-oriented dataset and help improve gridded mean sea surfaces (MSS), while repetitive options with a short cycle could cancel some additional EoL errors if a conservative repeat track strategy is preferred. [ABSTRACT FROM AUTHOR]

This study presents a new method of precise altimeter absolute calibration using a dedicated microwave transponder which acts as an altimeter signal repeater that can be deployed at any sub-track position both in coastal regions and inland. The Austrian Academy of Sciences operates an altimeter transponder at the Gavdos calibration/validation facility located beneath a Jason cross-over point. We discuss the capabilities and strengths of the transponder technique in general and in the particular case of a dedicated calibration campaign carried out in 2011. For the accomplishment of this campaign, including 26 ascending and descending Jason-2 passes, the onboard Poseidon-3 altimeter had to be switched to the DIODE/DEM mode for every overflight. Four different methods have been developed to analyze the transponder generated waveforms, provided by S-IGDR and S-GDR products, respectively. The resulting biases of the altimetric ranges have proven to be stable (3 mm rms) and agree to a large extent among the proposed algorithms. However, the absolute bias value of 25.8 ± 0.3 cm derived from the transponder calibration technique shows a significant deviation of several centimeters compared with the ones resulting from conventional techniques. Possible causes of this behavior are under further investigation. [ABSTRACT FROM AUTHOR]

As long-term stability of altimeter backscatter coefficient (σ0) can impact the accuracy of the Global Mean Sea Level (GMSL) trend through the Sea State Bias (SSB) correction, it is important to accurately monitor its evolution in order to detect potential instabilities. This study aims to characterize long-term uncertainties from several altimeter missions. The originality of our approach is to perform comparisons between wind speed estimations deduced from σ0 measurements and from ERA-interim reanalysis. Thanks to the good temporal correlation between the Global Wind Speed (GWS) evolution issued from altimeters and the atmospheric reanalysis, the detection of small drifts is possible in the altimeter time series. In particular, drifts have been detected on Jason-1 GWS between mid-2004 and 2005 and on Envisat prior to 2004. They are associated to σ0 jumps of approximately 0.03 dB. Larger anomalies have been detected on TOPEX σ0 data with variations reaching 0.2 dB. These low altimeter wind speed variations originate from small σ0 changes are within the instrumental stability requirements. However via the SSB calculation, their impact on the GMSL evolution is estimated close to 0.1 mm/yr over the altimetry 20-year period. In addition, they strongly affect inter-annual GMSL variations with associated errors reaching 2 mm. [ABSTRACT FROM AUTHOR]

This article deals with the recent improvements of the Global and Regional Mean Sea Level trend using Envisat data. It focuses on the methodology based on comparison with Jason-1, Jason-2, and in situ data and shows that Envisat is now getting more reliable for MSL studies, as a comparison reference for future missions. Notably, Jason-1/Envisat comparisons enabled to detect a weakness in the orbit standard solution, now improved for all altimetric missions including Jason-2. [ABSTRACT FROM AUTHOR]

Sea level monitoring in the Arctic Ocean can provide useful information in the context of a rapid change of several parts of the Arctic climate system. Satellite altimetry systems are affected by various problems at high latitudes. As a consequence, no precise and reliable mean sea level record is available yet from altimetry products. After identifying some of the issues that affect satellite altimetry in the Arctic Ocean region, we describe the tailored processing that has been applied to along-track mono-mission altimetry data. We generate a new dataset of weekly gridded sea level anomaly fields over the Arctic region for the period spanning from 1993 to 2009 based on multisatellite altimetry missions. We demonstrate the improvements achieved by this new dataset, among which a better data coverage. The grids are used to describe some features of mean sea level variability in the Arctic Ocean both at basin-wide and local scales. The regional trend estimated for the Arctic Ocean mean sea level over all latitudes from 66°N to 82°N is 3.6 mm/yr with an uncertainty of 1.3 mm/yr (90% confidence) and without any glacial isostatic adjustment (GIA) correction applied. The record displays large inter-annual variability, but no strong correlation with climate indices was found. Spatial patterns in sea level trends and variability over the Arctic region are also investigated. [ABSTRACT FROM AUTHOR]

Altimeter missions have provided accurate measurements of sea surface height since 1992 not only with TOPEX/Poseidon but also with Jason-i, Envisat, and recently Jason- 2. The overall quality assessment of altimeter data can be performed by analyzing their internal consistency and the cross-comparison between all missions. In this study, in situ measurements are used as an external, independent reference to enable further quality assessment of the altimeter sea level. The most up-to-date altimeter data are assessed and compared with those from tide gauges and Argo profiling floats. The first focus is on detection of global and regional drifts in altimeter sea surface height compared with in situ measurements. A second point is that the method can assess the impact of new altimeter standards (e.g., orbit solution, instrumental correction, retracking algorithm) thanks to in situ observations. Finally, the study shows how multiple and reliable altimeter products are used to detect potential anomalies in tide gauges. The results demonstrate the close link between these three steps of the method: while the detection of altimeter drifts using in situ measurements is corrected by computing new altimeter standards whose impact can then be estimated, the improved altimeter sea level time series are used as input for controlling the quality of in situ observations. [ABSTRACT FROM AUTHOR]

This article focuses on the determination and the validation of the new Mean Sea Surface from the CNES/CLS. This new model merges multiple satellite altimeters over 16 years of observations. Particular attention was paid on the analysis of the oceanic variability. Then a novel method was applied to remove this variability and to take into account different kinds of errors that affect the data. Several types of validations were performed to estimate the quality of the shortest topographic structures and to quantify the accuracy of the mean oceanic content at a larger scale. [ABSTRACT FROM AUTHOR]

We investigate sea level variability in the Arctic Ocean from observations. Variability estimates are derived both at the basin scale and on smaller local spatial scales. The periods of the signals studied vary from high frequency (intra-annual) to long term trends. We also investigate the mechanisms responsible for the observed variability. Different data types are used, the main one being a recent reprocessing of satellite altimetry data in the Arctic Ocean. Satellite altimetry data is compared to tide gauges measurements, steric sea level derived from temperature and salinity fields and GRACE ocean mass estimates. We establish a consistent regional sea level budget over the GRACE availability era (2003- 2009) showing that the sea level drop observed by altimetry over this period is driven by ocean mass loss rather than steric effects. The comparison of altimetry and tide gauges time series show that the two techniques are in good agreement regarding sea level trends. Coastal areas of high variability in the altimetry record are also consistent with tide gauges records. An EOF analysis of September mean altimetry fields allows identifying two regions of wind driven variability in the Arctic Ocean: the Beaufort Gyre region and the coastal European and Russian Arctic. Such patterns are related to atmospheric regimes through the Arctic Oscillation and Dipole Anomaly. [ABSTRACT FROM AUTHOR]

Calibration of the wind speed is an issue not only for the provision of an accurate metocean parameter but also for the stability of the whole altimetry system across several flying missions. Wind speed is one of the parameters used to derive the sea state bias correction and therefore affects the sea surface height measurement. The analysis performed in this paper benefits from an in-house reprocessing exercise of 1 year of Jason-2 data with both the 3- and 4-parameter Maximum Likelihood Estimator (MLE-3, and MLE-4) retracking algorithms. It took into account the new altimeter characterization file that will be used in the upcoming official reprocessing activity to generate version C of the Jason-2 Geophysical Data Record products. Updated comparison of MLE-3 and MLE-4 data confirms that the MLE-3 algorithm gives less high-frequency variations in σ0. A calibration of the Jason-2 wind speed estimates has been performed based on a bias-adjustment of the radar backscatter data (+0.32 dB for MLE-3 data and +0.28 dB for MLE-4 ones) between Jason-2 and Jason-1. This allows us to re-assess the sea state bias differences between these two instruments from recomputed solutions and to show that there is no SSB difference between the two altimeters at cm-level. [ABSTRACT FROM PUBLISHER]

For more than 13 years, the multisatellite DUACS system has been providing the altimetry community with Near Real Time and Delayed Time products ranging from reduced GDR (also known as CorrSSH) to along-track Sea Level Anomalies (SLA) and multimission Maps of Sea Level Anomalies (MSLA). A post-Jason-2 description of the DUACS system is given, with input data, processing and products, and a focus on the DT-2010 reprocessing involving a total of almost 60 years worth of altimetry data from GEOSAT to Jason-2. Less than one month after launch, Jason-2 proved to be a strong asset for multisatellite applications as it was able to replace Jason-1 as the reference mission in DUACS. Furthermore, the new Jason-2/Jason-1 tandem configuration provides an unprecedented duo for mesoscale and circulation observation. More generally, the quality of Jason-2 has a large impact in DUACS on a number of fronts: in the continuity of the reference mission for climate applications exploiting DUACS products, in the new multi-reference orbit error reduction scheme, or for new metrics derived from a Degrees of Freedom of Signal analysis applied to the multimission mapping. This paper gives an overview of the many impacts of the integration of Jason-2 into DUACS. [ABSTRACT FROM PUBLISHER]

OSTM/Jason-2 (Ocean Surface Topography mission, named Jason-2 in this paper) satellite was successfully launched on June 20, 2008, and was put on its nominal orbit on July 4, 2008. Up to January 26, 2009, Jason-2 was flying in formation with Jason-1 only 55 seconds apart before Jason-1 was moved to its new interleaved orbit. The objectives of this paper are to assess Jason-2 data quality and to estimate the altimetry system performance from the beginning of the mission, using Geophysical Data Records (GDRs) products. Our study will focus on Jason-1/Jason-2 cross-calibration using the opportunity that the missions were on the same ground track separated by 55 seconds during the formation flight phase. This allows us to precisely assess parameter discrepancies and Sea Surface Height (SSH) consistency between both missions in order to detect geographically correlated biases, jumps or drifts. From the results presented in this paper, it is demonstrated that the Jason-2 mission fulfils the requirements of high precision altimetry, which is crucial for future oceanographic studies and applications. In particular, it allows continuation of the observation of the Mean Sea Level (MSL) variations at the same (or better) accuracy as Jason-1 and TOPEX/Poseidon, which was one of the challenges of the Jason-2 mission. Potential improvements and open issues are also identified, with the objective of still making progress in terms of altimetry data quality. [ABSTRACT FROM AUTHOR]

For all altimeter missions, precise estimates of geophysical parameters are obtained thanks to an algorithm called “retracking” that fits an analytical model to the measured waveforms. The Brown model provides a good representation of the return echo over deep ocean surfaces and is commonly used. Many different chains can be considered (and have already been tested) for this processing. An unweighted Least Square Estimate derived from a Maximum Likelihood Estimator (MLE) (Dumont 1985; Rodriguez 1988) is implemented in most altimeter ground processing approaches (TOPEX, Jason-1, Jason-2, and Envisat). The aim of this paper is to evaluate the performance of two retracking algorithms based on the same least square principle: The MLE3 algorithm estimates three parameters (range, significant wave height, and power) whereas the MLE4 estimates four parameters (the three previous ones and the slope of the waveform trailing edge). MLE3 was used on Jason-1 before star tracker problems occurred. The MLE4 algorithm has been used for Jason-1 Version B products and onward and for Jason-2 products from the start of the mission. Both algorithms are compared in the paper. Advantages and drawbacks of both algorithms are pointed out showing notable benefits provided by MLE4 especially for waveforms that do not conform to the Brown model. [ABSTRACT FROM AUTHOR]

We present a Jason-2 sea state bias (SSB) model from the first year of GDR products along with updates of Jason-1, TOPEX-A, and TOPEX-B solutions. Our re-evaluation of the Jason-1 SSB focused on data from the new version (C) of the GDR while for TOPEX, the updated solutions benefited from the availability of both a set of new precise orbits that are consistent with Jason-2 and an updated set of state-of-the-art geophysical corrections. Therefore, derived from homogeneous sea surface height (SSH) data to minimize geographically correlated SSH differences between missions, these empirical SSB models contribute to the consistency between Jason-2 and Jason-1 SSH data and between TOPEX and Jason-1 data during their respective tandem phase and thus to the stability of the whole altimetry system over the past 17-year period. [ABSTRACT FROM AUTHOR]

Background: The safety and immunogenicity of Viatim, a combined hepatitis A (HA) and typhoid fever (Vi) vaccine, were compared with the monovalent component vaccines up to and 1 month after a booster dose at 3 years.Methods: Healthy, adult volunteers were randomized to receive Viatim (group A, n = 179) or separate HA and Vi vaccines (group B, n = 181); subgroups were boosted after 3 years with Viatim (groups C and D, n = 56 and 46, respectively). Local and systemic reactions were recorded for 28 days postvaccination. Seroconversion and seroprotection rates and geometric mean antibody concentrations were measured at 14 and 28 days, 1, 2, and 3 years postvaccination, and 28 days after the booster dose.Results: Local and systemic safety profiles were equivalent between the two groups. Immediate local reactions were infrequent (1 in group A and 2 in group B). Local reactions, consisting mostly of mild or moderate pain, were least frequent with monovalent HA. Antibody concentrations to both antigens were similar in groups A and B, in which HA seroprotection rates (> or = 20 mIU/mL) were respectively, 98.7% and 100% at day 28, and 99.1% and 99.0% after 3 years, achieving 100% after the booster. Vi seroprotection rates (> or = 1 microg/mL) of 85.2% and 84.9% after 28 days fell to 32.1% and 35.6% after 3 years, increasing to 67.3% and 69.8% after the booster dose.Conclusions: The combined HA/Vi vaccine, Viatim, had equivalent tolerability and safety and was as rapidly immunogenic as its component monovalent vaccines when given concurrently. A booster dose after 3 years significantly increased antibody levels with some evidence of relative hyporesponsiveness of the typhoid response. [ABSTRACT FROM AUTHOR]