Comparison Campaign of VLBI Data Analysis Software - First Results

During the development of the Vienna VLBI Software VieVS at the Institute of Geodesy and Geophysics at Vienna University of Technology, a special comparison setup was developed with the goal of easily finding links between deviations of results achieved with different software packages and certain parameters of the observation. The object of comparison is the computed time delay, a value calculated for each observation including all relevant models and corrections that need to be applied in geodetic VLBI analysis. Besides investigating the effects of the various models on the total delay, results of comparisons between VieVS and Occam 6.1 are shown. Using the same methods, a Comparison Campaign of VLBI data analysis software called DeDeCC is about to be launched within the IVS soon

On the Analysis of VLBI Observations to GNSS Satellites

Space geodetic techniques such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS) are used for the determination of celestial and terrestrial reference frames and Earth orientation parameters. It is of utmost importance to combine the observations from the different techniques to fully exploit the strengths and unique characteristics of the techniques, however, inaccurate local ties are problematic for a rigorous combination. To improve the link between the techniques, tests are under way to observe GNSS signals with VLBI radio telescopes directly, and to observe GNSS signals in GNSS antennas with subsequent processing in the VLBI system (“GNSS-VLBI Hybrid System”) including VLBI correlation. In both cases, the GNSS data type is the difference between the ranges from two stations to a satellite. However, it is still difficult to acquire those observations and thus we apply post-processed range measurements from a precise point positioning (PPP) solution with the C5++ software to build those single differences which are then used in the Vienna VLBI Software (VieVS). We use the CONT11 data set with identical clocks at seven sites to validate the models in VieVS and to assess the impact of the combined solution on the geodetic products

Short Report of IVS Working Group 5 (WG5) on Space Science Applications - An IVS Perspective

No abstract availabl

Relatório de estágio em farmácia comunitária

Relatório de estágio realizado no âmbito do Mestrado Integrado em Ciências Farmacêuticas, apresentado à Faculdade de Farmácia da Universidade de Coimbr

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK.

BACKGROUND: A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. METHODS: This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5 × 1010 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1 - relative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. FINDINGS: Between April 23 and Nov 4, 2020, 23 848 participants were enrolled and 11 636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0-75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4-97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; pinteraction=0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8-80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74 341 person-months of safety follow-up (median 3·4 months, IQR 1·3-4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. INTERPRETATION: ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials. FUNDING: UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, Bill & Melinda Gates Foundation, Lemann Foundation, Rede D'Or, Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK

Background A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. Methods This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5 × 1010 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1 - relative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. Findings Between April 23 and Nov 4, 2020, 23 848 participants were enrolled and 11 636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0–75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4–97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; pinteraction=0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8–80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74 341 person-months of safety follow-up (median 3·4 months, IQR 1·3–4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. Interpretation ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials

VLBI-Beobachtungen zu Satelliten zur Verknüpfung von Referenzrahmen

Abweichender Titel laut Übersetzung der Verfasserin/des VerfassersZsfassung in dt. SpracheDie Radiointerferometrie auf langen Basen (VLBI, Very Long Baseline Interferometry) ist ein Standardverfahren in der Geodäsie zur Bestimmung des himmelsfesten Referenzrahmens (CRF, Celestial Reference Frame), des erdfesten Koordinatenrahmens (TRF, Terrestrial Reference Frame) und der Erdorientierungsparameter (EOP, Earth Orientation Parameter) zur Verknüpfung dieser beiden. Außerdem kommt die VLBI in der Raumschiffnavigation zum Einsatz, wo in den letzten Jahren gewaltige Entwicklungen zu beobachten waren. Heutige Realisierungen des TRF kombinieren die Messungen von unterschiedlichen geodätischen Weltraumverfahren und sind auf eine gute Verknüpfung dieser Systeme angewiesen. Für eine weitere Verbesserung, sowie das Ziel einer konsistenten Bestimmung des gesamten Systems aus CRF-EOP-TRF verfolgend, werden alternative Methoden zur Verknüpfung der unterschiedlichen modernen geodätischen Weltraumverfahren gesucht. Eine vielversprechende Methode hierfür sind VLBI-Beobachtungen zu Satelliten. Damit soll die Verknüpfung entweder mittels eines eigens dafür konzipierten Satelliten oder durch direktes Anmessen von Satelliten globaler Satellitennavigationssysteme (GNSS, Global Navigation Satellite Systems) erfolgen. Herzstück der vorgelegten Arbeit ist eine umfassende Simulationsstudie zu geeigneten Beobachtungsstrategien, die eine Ableitung präziser Stationskoordinaten im System des beobachteten Satelliten erlauben. Für Satelliten zwischen 1000 und 20000 Kilometern Flughöhe gelingt dies mit einer Genauigkeit von wenigen Millimetern. Dafür wird der Ansatz von Wochenlösungen gewählt, d.h. ein Satellit wird von einem regionalen oder globalen Netzwerk für sieben Tage durchgehend beobachtet. Sollen Satelliten des GNSS beobachtet werden, ist die gewählte Beobachtungsstrategie nicht zielführend und es wird die Kombination mit einer klassischen VLBI Kampagne zu Radioquellen bzw. die Beobachtung einer Satellitenkonstellation untersucht.Very Long Baseline Interferometry (VLBI) is a well-probed space geodetic technique used to determine the Celestial Reference Frame (CRF), the Terrestrial Reference Frame (TRF) and the Earth Orientation Parameters (EOP) in between. Alternatively, VLBI is generally used in spacecraft tracking. Today's most precise and reliable realizations of the TRF rely on the measurements of several space geodetic techniques and the corresponding inter-technique ties. For future improvement, alternative methods for connecting the various space geodetic techniques, establishing precise frame ties, are urgently needed. A promising solution is the use of VLBI satellite observations, either in combination with a so-called space tie realized by a dedicated satellite or by directly observing satellites of the Global Navigation Satellite Systems (GNSS) with VLBI. This thesis contains a detailed simulation study of VLBI observations to satellites, identifying adequate observing strategies for the precise determination of antenna positions on Earth in the satellite's system. For satellites at heights between 1000 and 20000 km, adequate observation strategies are found that allow the determination of the station coordinates at the level of a few millimeters. Hereby, the approach of weekly solutions in chosen, meaning that one satellite is observed by either a regional or a global antenna network during seven consecutive days. In the case of VLBI observations to a satellite of the GNSS, alternative observing strategies are needed. In this thesis the combination with a classical VLBI session observing extragalactic radio sources or the observation of a satellite constellation are also introduced.14

VLBI satellite tracking for the realization of frame ties

Adresse des Verl.: 1040 Wien, Gußhausstraße 27-29German Research Foundation14

On the Analysis of VLBI Observations to GNSS Satellites

Space geodetic techniques such as Very Long Baseline Interferometry (VLBI) and Global Navigation Satellite Systems (GNSS) are used for the determination of celestial and terrestrial reference frames and Earth orientation parameters. It is of utmost importance to combine the observations from the different techniques to fully exploit the strengths and unique characteristics of the techniques, however, inaccurate local ties are problematic for a rigorous combination. To improve the link between the techniques, tests are under way to observe GNSS signals with VLBI radio telescopes directly, and to observe GNSS signals in GNSS antennas with subsequent processing in the VLBI system (“GNSS-VLBI Hybrid System”) including VLBI correlation.In both cases, the GNSS data type is the difference between the ranges from two stations to a satellite. However, it is still difficult to acquire those observations and thus we apply post-processed range measurements from a precise point positioning (PPP) solution with the C5++ software to build those single differences which are then used in the Vienna VLBI Software (VieVS). We use the CONT11 data set with identical clocks at seven sites to validate the models in VieVS and to assess the impact of the combined solution on the geodetic products