In-depth verification of Sentinel-1 and TerraSAR-X geolocation accuracy using the Australian Corner Reflector Array

This article shows how the array of corner reflectors (CRs) in Queensland, Australia, together with highly accurate geodetic synthetic aperture radar (SAR) techniques—also called imaging geodesy—can be used to measure the absolute and relative geometric fidelity of SAR missions. We describe, in detail, the end-to-end methodology and apply it to TerraSAR-X Stripmap (SM) and ScanSAR (SC) data and to Sentinel-1interferometric wide swath (IW) data. Geometric distortions within images that are caused by commonly used SAR processor approximations are explained, and we show how to correct them during postprocessing. Our results, supported by the analysis of 140 images across the different SAR modes and using the 40 reflectors of the array, confirm our methodology and achieve the limits predicted by theory for both Sentinel-1 and TerraSAR-X. After our corrections, the Sentinel-1 residual errors are 6 cm in range and 26 cm in azimuth, including all error sources. The findings are confirmed by the mutual independent processing carried out at University of Zurich (UZH) and German Aerospace Center (DLR). This represents an improve�ment of the geolocation accuracy by approximately a factor of four in range and a factor of two in azimuth compared with the standard Sentinel-1 products. The TerraSAR-X results are even better. The achieved geolocation accuracy now approaches that of the global navigation satellite system (GNSS)-based survey of the CRs positions, which highlights the potential of the end-to-end SAR methodology for imaging geodesy

Convective scale weather analysis and forecasting

How satellite data can be used to improve insight into the mesoscale behavior of the atmosphere is demonstrated with emphasis on the GOES-VAS sounding and image data. This geostationary satellite has the unique ability to observe frequently the atmosphere (sounders) and its cloud cover (visible and infrared) from the synoptic scale down to the cloud scale. These uniformly calibrated data sets can be combined with conventional data to reveal many of the features important in mesoscale weather development and evolution

An introduction to the interim digital SAR processor and the characteristics of the associated Seasat SAR imagery

Basic engineering data regarding the Interim Digital SAR Processor (IDP) and the digitally correlated Seasat synthetic aperature radar (SAR) imagery are presented. The correlation function and IDP hardware/software configuration are described, and a preliminary performance assessment presented. The geometric and radiometric characteristics, with special emphasis on those peculiar to the IDP produced imagery, are described

Pioneer Venus

Venus before Pioneer, the Pioneer Venus mission, Pioneer Venus spacecraft, scientific investigation, mission to Venus scientific results, and results of Soviet studies of Venus are addressed. A chronology of exploration of Venus from Earth before the Pioneer Venus mission and Venus nomenclature and mythology are provided

Bi-Ventricular Myocardial Performance in Heart Failure: A New Approach to Evaluate Interventricular Dyssynchrony

Aims: Patients with heart failure (HF) exhibit ventricular dyssynchrony with negative effects on ventricular systolic and diastolic performance and poor prognosis. There is no consensus about the best approach for estimating the dyssynchrony and for selecting candidates for resynchronization therapy (CRT). We sought to evaluate whether Myocardial Performance Index (MPI), calculated as differences between left and right ventricle (LV, RV), ΔMPI, represents a marker of interventricular dyssynchrony. Methods: The study included 40 patients (22 males, 18 females, mean age 71±13) with NYHA functional class II-III, chronic heart failure (77% ischaemic), in optimal drug therapy for at least three months. All patients underwent a complete two-dimensional and Tissue Doppler Echocardiography (TDE), including an assessment of MPI in both ventricles. Results: Significant correlations were found between ΔMPI and QRS (r = 0.41, p < 0.001), with NYHA (r = 0.66, p < 0.001), with SPWMD (r = 0.32, p < 0.05), with LV ejection fraction (r = -0.32, p < 0.05), with Spv wave at the septal site of LV (r = -0.32, p < 0.05), and with IVMD (r = 0.44, p < 0.001). Ten patients have been re-evaluated six months after CRT implantation, and ΔMPI significantly correlated with the difference between basal LVEF and six months after CRT implantation (r = 0.43, p < 0.04). Conclusion: The ΔMPI could represent an integrative marker of interventricular dyssynchrony and could be considered as a new parameter in the patient selection process to be undergone CRT

Characterization of the dynamics of the atmosphere of Venus with doppler velocimetry

Tese de doutoramento (co-tutela), Astronomia e Astrofísica, Observatoire de Paris, Universidade de Lisboa, 2013Currently the study of the Venus’ atmosphere grows as a theme of major interest among the astrophysics scientific community. The most significant aspect of the general circulation of the atmosphere of Venus is its retrograde super-rotation. A complete characterization of this dynamical phenomenon is crucial for understanding its driving mechanisms. This work participates in the international effort to characterize the atmospheric dynamics of this planet in coordination with orbiter missions, in particular with Venus Express. The objectives of this study are to investigate the nature of the processes governing the super-rotation of the atmosphere of Venus using ground-based observations, thereby complementing measurements by orbiter instruments.This thesis analyzes observations of Venus made with two different instruments and Doppler velocimetry techniques.The first part of the thesis presents ground-based Doppler velocimetry measurements of the zonal winds based on observations carried out with the Ultraviolet and Visual Echelle Spectrograph at ESO’s Very Large Telescope. Using Doppler-shifted Fraunhofer lines from the solar spectrum, this high resolution spectrograph (R 100,000) allows to measure the velocity of Venus’ upper cloud layer with a precision of about 5 ms1. Under the assumption of predominantly zonal flow, this method allows the simultaneous direct measurement of the zonal velocity across a range of latitudes and local times in the day side. The technique, based on long slit spectroscopy combined with the observations’ high spatial resolution, has provided the first ground-based characterization of the latitudinal profile of zonal wind in the atmosphere of Venus, the first zonal wind field map in the visible, as well as new constraints on wind variations with local time. Mean zonal wind amplitudes were measured between 106 21 and 127 14 ms1 at latitudes between 18 N and 34 S, with the zonal wind being approximately uniform in 2:6 -wide latitude bands (0:3” at disk center).The zonal wind profile retrieved is consistent with previous spacecraft measurements based on cloud tracking, but with non-negligible variability in local time (longitude) and in latitude. Near 50 the presence of moderate jets is apparent in both hemispheres, with the southern jet being stronger by 10 ms1. Small scale wind variations with local time are also present at low and mid-latitudes (Machado et al., 2012).The second part of the thesis presents results of Venus’ mesospheric winds at cloud top level, based on ground-based Doppler velocimetry of cloud-top winds and inter comparison of cloud tracking measurements from the Venus Express spacecraft.Doppler wind velocimetry obtained with the 3.60 m Canada-France-Hawaii telescope (CFHT) and the visible spectrograph ESPaDOnS in February 2011 consisted of high-resolution spectra of Fraunhofer lines in the visible range to measure the wind velocity using the Doppler shift of solar radiation scattered by cloud top particles in the observer’s direction (Widemann et al., 2007, 2008; Machado et al., 2013). The complete optical spectrum was collected at a phase angle = (68:7 0:3) , at a resolution of about 80,000. The obtained ground-based measurements on Venus are compared with simultaneous observations using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument from the VEx orbiter. CFHT observations included various points of the dayside hemisphere observed at a phase angle of 67 from CFHT, between +10 N and 60 S, by steps of 10 , and from sub-Earth longitude [ E ] = 0 to -50 corresponding to 7:30a - 10:50a, while VIRTIS-M UV (0.38 m) cloud tracking measurements extended on the dayside south hemisphere between 30 and 50 S and 9:05a - 10:50a at simultaneous spacecraft orbit VV1786. Doppler wind retrievals using either 1- or 2-wind circulation regimes are in good agreement with measurements based on cloud tracking from Venus Express.Were observed zonal wind field variations in the latitudinal and temporal scales within stable mean background velocities of vz = 117.35 18.0 ms1 on Feb. 19, and vz = 117.5 14.5 ms1 on Feb. 21, respectively. It is presented the first unambiguous detection from the ground of a poleward meridional wind flow on the morning dayside hemisphere, of 18.8 11.5 ms1 on Feb. 19, and 19.0 8.3 ms1 on Feb. 21. Wind temporal, local variation at the hour-scale of 18.5 ms1 were detected near morning terminator at low latitude. To provide the best description of the wind field observed, the retrieved results were compared to a series of wind circulation models and their characterization at cloud top level.The data analysis technique allowed an unambiguous characterization of the zonal wind latitudinal profile and its temporal variability, as well as an investigation of large-scale planetary waves signature and their role in the maintenance of the zonal super-rotation, and suggest that detection and investigation of large-scale planetary waves can be carried out with this technique.These studies complement the independent observations of the european space mission Venus Express, in particular as regards the study of atmospheric super-rotation, meridional flow and its variability.Fundação para a Ciência e a Tecnologia (FCT, PhD grant SFRH/BD/66473/2009

NASA/MSFC FY-85 Atmospheric Processes Research Review

The two main areas of focus for the research program are global scale processes and mesoscale processes. Geophysical fluid processes, satellite doppler lidar, satellite data analysis, atmospheric electricity, doppler lidar wind research, and mesoscale modeling are among the topics covered

Asteroseismology and Interferometry

Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like pulsators, have boosted the impact of this field of research within Astrophysics and have led to a significant increase in the size of the research community. In the present paper we start by reviewing the basic observational and theoretical properties of classical and solar-like pulsators and present results from some of the most recent and outstanding studies of these stars. We centre our review on those classes of pulsators for which interferometric studies are expected to provide a significant input. We discuss current limitations to asteroseismic studies, including difficulties in mode identification and in the accurate determination of global parameters of pulsating stars, and, after a brief review of those aspects of interferometry that are most relevant in this context, anticipate how interferometric observations may contribute to overcome these limitations. Moreover, we present results of recent pilot studies of pulsating stars involving both asteroseismic and interferometric constraints and look into the future, summarizing ongoing efforts concerning the development of future instruments and satellite missions which are expected to have an impact in this field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume 14, Issue 3-4, pp. 217-36