scholarly journals Visibility study of Galileo satellites from a VLBI network

2021 ◽  
Author(s):  
Helene Wolf ◽  
Johannes Böhm ◽  
Matthias Schartner ◽  
Urs Hugentobler
Keyword(s):  
Reference Frames ◽  
Direct Determination ◽  
Satellite Constellation ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Satellite Scheduling ◽  
Observation Geometry ◽  
The Impact

<p>Over the last years, ideas have been proposed to install a Very Long Baseline Interferometry (VLBI) transmitter on one or more satellites of the Galileo constellation. Satellites transmitting signals that can be observed by VLBI telescopes provide the opportunity of extending the current VLBI research with observations to geodetic satellites. These observations offer a variety of new possibilities such as high precision tying of space geodetic techniques but also the direct determination of the absolute orientation of the satellite constellation with respect to the International Celestial Reference Frame (ICRF) and have implications on the determination of long-term reference frames. </p><p>This contribution provides a visibility study of the Galileo satellites from a VLBI network. The newly developed satellite scheduling module in VieSched++ is used to determine the time periods during which a satellite is observable from a VLBI network. The possible satellite observations are evaluated through the number of stations from which a satellite is observable. Moreover, the impact on determining the orientation of the satellite constellation, caused by the observation geometry, is investigated with using the UT1-UTC Dilution of Precision (UDOP) factor.</p>

Earth Orientation Parameter Estimation by Integrating VLBI and GNSS on the Observation Level

2021 ◽  
Author(s):  
Jungang Wang ◽  
Kyriakos Balidakis ◽  
Maorong Ge ◽  
Robert Heinkelmann ◽  
Harald Schuh
Keyword(s):  
Polar Motion ◽  
Reference Frames ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Earth Orientation ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Global Navigation Satellite ◽  
The Impact ◽  
Globally Distributed

<p>The terrestrial and celestial reference frames are linked by the Earth Orientation Parameters (EOP), which describe the irregularities of the Earth's rotation and are determined by the space geodetic techniques, namely, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The satellite geodetic techniques (SLR, GNSS, and DORIS) cannot determine the UT1-UTC or celestial pole offsets (CPO), rendering VLBI the only technique capable of determining full EOP set. On the other hand, the GNSS technique provides precise polar motion estimates due to the continuous observations from a globally distributed network. Integrating VLBI and GNSS provides the full set of EOP and guarantees a superior accuracy than any single-technique solution.</p><p>In this study we focus on the integrated estimation of the full EOP set from GNSS and VLBI. Using five VLBI continuous observing campaigns (CONT05–CONT17), the GNSS and VLBI observations are processed concurrently in a common least-squares estimator. The impact of applying global ties (EOP), local ties, and tropospheric ties, and combinations thereof is investigated. The polar motion estimates in integrated solution are dominated by the huge GNSS observations, and the accuracy in terms of weighted root mean squares (WRMS) is ~40 μas compared to the IERS 14 C04 product, which is much better than that of the VLBI-only solution. The UT1-UTC and CPO in the integrated solution also show slight improvement compared to the VLBI-only solution. Moreover, the CPO agreement between the two networks in CONT17, i.e., the VLBA and IVS networks, shows an improvement of 20% to 40% in the integrated solution with different types of ties applied.</p>

scholarly journals Satellite Scheduling with VieSched++ : current status and future plans

2020 ◽  
Author(s):  
Helene Wolf ◽  
Matthias Schartner ◽  
Johannes Böhm ◽  
Andreas Hellerschmied
Keyword(s):  
Reference Frames ◽  
Very Long Baseline Interferometry ◽  
Satellite Observations ◽  
Current Status ◽  
Long Baseline ◽  
Automatic Mode ◽  
Space Geodetic Techniques ◽  
Satellite Scheduling ◽  
Space Ties ◽  
Future Plans

<p>Observing extragalactic radio sources is an integral part of Very Long Baseline Interferometry (VLBI) but observing satellites also provides a variety of new possibilities. Interesting scientific applications can be found in providing space ties instead of using local ties for connecting reference frames of different space-geodetic techniques. To generate schedules including observations to satellites a dedicated module has been implemented in the new scheduling software VieSched++.</p><p><br>This newly developed module determines possible satellite observations considering several observation conditions, such as the visibility from the selected station network and antenna slew rates. A schedule including observations to quasars and satellites can be generated in a semi-automatic mode. The scheduling of the satellite scans is done manually by the user who can select and adjust the possible satellite observations before adding them to the schedule. The remaining part of the schedule is filled automatically by the software VieSched++ using the general optimization algorithm with observations to quasars. In this poster an overview of the current status of the satellite scheduling module in VieSched++ is given, as well as an outlook to highlight future plans. </p>

scholarly journals Treated wastewater irrigation effects on soil hydraulic conductivity and aggregate stability of loamy soils in Israel

2015 ◽  
Vol 63 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Karsten Schacht ◽  
Bernd Marschner
Keyword(s):  
Hydraulic Conductivity ◽  
Chemical Properties ◽  
Aggregate Stability ◽  
Treated Wastewater ◽  
Soil Aggregate Stability ◽  
Irrigation Effects ◽  
Physical And Chemical ◽  
The Impact

Abstract The use of treated wastewater (TWW) for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW) resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC) and soil aggregate stability (SAS). To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm) were collected for analyzing SAS and determination of selected soil chemical and physical characteristics. The mean HC values decreased at all TWW sites by 42.9% up to 50.8% compared to FW sites. The SAS was 11.3% to 32.4% lower at all TWW sites. Soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) were generally higher at TWW sites. These results indicate the use of TWW for irrigation is a viable, but potentially deleterious option, as it influences soil physical and chemical properties.

scholarly journals Diagenetic formation of uranium-silica polymers in lake sediments over 3,300 years

2021 ◽  
Vol 118 (4) ◽  
pp. e2021844118
Author(s):  
Pierre Lefebvre ◽  
Alkiviadis Gourgiotis ◽  
Arnaud Mangeret ◽  
Pierre Sabatier ◽  
Pierre Le Pape ◽  
...  
Keyword(s):  
Contaminated Sediments ◽  
Mining Areas ◽  
Subsurface Environments ◽  
Geochemical Reactivity ◽  
High Silica ◽  
Long Term Behavior ◽  
The Impact ◽  
X Ray Absorption

The long-term fate of uranium-contaminated sediments, especially downstream former mining areas, is a widespread environmental challenge. Essential for their management is the proper understanding of uranium (U) immobilization mechanisms in reducing environments. In particular, the long-term behavior of noncrystalline U(IV) species and their possible evolution to more stable phases in subsurface conditions is poorly documented, which limits our ability to predict U long-term geochemical reactivity. Here, we report direct evidence for the evolution of U speciation over 3,300 y in naturally highly U-enriched sediments (350–760 µg ⋅ g−1 U) from Lake Nègre (Mercantour Massif, Mediterranean Alps, France) by combining U isotopic data (δ238U and (234U/238U)) with U L3-edge X-ray absorption fine structure spectroscopy. Constant isotopic ratios over the entire sediment core indicate stable U sources and accumulation modes, allowing for determination of the impact of aging on U speciation. We demonstrate that, after sediment deposition, mononuclear U(IV) species associated with organic matter transformed into authigenic polymeric U(IV)–silica species that might have partially converted to a nanocrystalline coffinite (UIVSiO4·nH2O)-like phase. This diagenetic transformation occurred in less than 700 y and is consistent with the high silica availability of sediments in which diatoms are abundant. It also yields consistency with laboratory studies that proposed the formation of colloidal polynuclear U(IV)–silica species, as precursors for coffinite formation. However, the incomplete transformation observed here only slightly reduces the potential lability of U, which could have important implications to evaluate the long-term management of U-contaminated sediments and, by extension, of U-bearing wastes in silica-rich subsurface environments.

scholarly journals Nonperturbative Uncertainties on the Transverse Momentum Distribution of Electroweak Bosons and on the Determination of the W Boson Mass at the LHC

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Giuseppe Bozzi ◽  
Andrea Signori
Keyword(s):  
Transverse Momentum ◽  
W Boson ◽  
Direct Determination ◽  
Boson Mass ◽  
Proton Proton ◽  
Theoretical Predictions ◽  
Quark Transverse Momentum ◽  
The Impact ◽  
Proton Proton Collisions

In this contribution we present an overview of recent results concerning the impact of a possible flavour dependence of the intrinsic quark transverse momentum on electroweak observables. In particular, we focus on the qT spectrum of electroweak gauge bosons produced in proton-proton collisions at the LHC and on the direct determination of the W boson mass. We show that these effects are comparable in size to other nonperturbative effects commonly included in phenomenological analyses and should thus be included in precise theoretical predictions for present and future hadron colliders.

National Mapping’s Astro-Geodetic Complex

1973 ◽  
Vol 2 (4) ◽  
pp. 203-206
Author(s):  
J. McK. Luck ◽  
M. J. Miller ◽  
P. J. Morgan
Keyword(s):  
Air Force ◽  
Continental Drift ◽  
Direct Determination ◽  
Lunar Laser Ranging ◽  
Plate Movement ◽  
Cambridge Research ◽  
Lunar Laser ◽  
Lunar Ephemeris

The Division of National Mapping has received, on long term loan from NASA and in co-operation with the Smithsonian Astrophysical Observatory, a Lunar Laser Ranging instrument consisting of a gigawatt pulsed ruby laser, a 150 cm aspheric Ritchey-Chretien telescope, and associated electronic equipment. The instrument was formerly operated by the Air Force Cambridge Research Laboratories at Mount Lemmon in Arizona. Its principal use by National Mapping will be direct determination of the distance between the telescope and any of the three retro-reflector arrays placed on the Moon at Hadley’s Rille, Fra Mauro and Mare Tranquillitatis by Apollo astronauts. Full scale operation in conjunction with similar instruments well separated in latitude and longitude, in particular at Mount McDonald in Texas and Mount Haleakala in Hawaii, will permit determination of Earth rotation and polar motion, lunar ephemeris and libration, and tectonic plate movement or continental drift, which justifies its use in a geodetic environment.

Experimental Analysis of the Impact on the Durability of Concrete Additions

2016 ◽  
Vol 249 ◽  
pp. 73-78 ◽  
Author(s):  
Vladimír Suchánek ◽  
Kateřina Hájková
Keyword(s):  
Free Fall ◽  
Concrete Surface ◽  
Hardened Concrete ◽  
Concrete Mixer ◽  
Long Term Monitoring ◽  
The Impact ◽  
Term Monitoring ◽  
Furnace Slag

This report deals with long term monitoring of durability properties of concrete using different weight doses of various kinds of additions. Particularly limestone, silica fume as a 50% suspension and blast furnace slag were used. Even though the basic recipe is based on the designed concrete, all the fresh concrete was made with a free-fall concrete mixer in the laboratory. This report deals with long-term monitoring of cement concrete surface resistance to water and defrosting chemicals (achieved 475 cycles). The article also describes results of following tests: determination of concrete frost resistance, depth of water penetration under pressure and depth of chloride penetration. Standard tests of fresh and hardened concrete specimens complement the experiment.

scholarly journals X. A method of measuring the pressure produced in the detonation of high, explosives or by the impact of bullets

1914 ◽  
Vol 213 (497-508) ◽  
pp. 437-456 ◽  
Keyword(s):  
Practical Interest ◽  
Direct Determination ◽  
High Explosives ◽  
Time Curve ◽  
Considerable Difficulty ◽  
Cylindrical Steel ◽  
Set Up ◽  
The Right ◽  
The Impact

The determination of the actual pressures produced by a blow such as that of a rifle bullet or by the detonation of high explosives is a problem of much scientific and practical interest but of considerable difficulty. It is easy to measure the transfer of momentum associated with the blow, which is equal to the average pressure developed, multiplied by the time during which it acts, but the separation of these two factors has not hitherto been effected. The direct determination of a force acting for a few hundred-thousandths of a second presents difficulties which may perhaps be called insuperable, but the measurement of the other factor, the duration of the blow, is more feasible. In the case of impacts such as those of spheres or rods moving at moderate velocities the time of contact can be determined electrically with considerable accuracy.* The present paper contains an account of a method of analysing experimentally more violent blows and of measuring their duration and the pressures developed. If a rifle bullet be fired against the end of a cylindrical steel rod there is a definite pressure applied on the end of the rod at each instant of time during the period of impact and the pressure can be plotted as a function of the time. The pressure-time curve is a perfectly definite thing, though the ordinates are expressed in tons and the abscissae in millionths of a second; the pressure starts when the nose of the bullet first strikes the end of the rod and it continues until the bullet has been completely set up or stopped by the impact. Subject to qualifications, which will be considered later, the result of applying this varying pressure to the end is to send along the rod a wave of pressure which, so long as the elasticity is perfect, travels without change of type. If the pressure in different sections of the rod be plotted at any instant (fig. l) then at a later time the same curve shifted to the right by a distance proportional to the time will represent the then distribution of pressure. The velocity with which the wave travels in steel is approximately 17,000 feet per second. As the wave travels over any section of the rod, that section successively experiences pressures represented by the successive ordinates of the curve as they pass over it. Thus the curve also represents the relation between the pressure at any point of the rod and the time, the scale being such that one inch represents the time taken by the wave to travel that distance which is very nearly 1/200,000 of a second. In particular the curve giving the distribution of pressure in the rod along its length is, assuming perfect elasticity, the same as the curve connecting the pressure applied at the end and the time, the scale of time being that just given.

scholarly journals Impact of quality on improvement of business performance and customer satisfaction

2021 ◽  
Vol 11 (1) ◽  
pp. 20-28
Author(s):  
Milena Cvjetković ◽  
Marko Vasiljević ◽  
Milovan Cvjetković ◽  
Milica Josimović
Keyword(s):  
Customer Satisfaction ◽  
Growth And Development ◽  
Business Performance ◽  
Consumer Confidence ◽  
Efficient Manner ◽  
Mutual Relations ◽  
High Level ◽  
The Impact

In an immense market struggle, the only effective way to build a long-term competitive advantage is to provide a high level of quality. Offering quality to the market, the organization creates loyal consumers on the basis of which it achieves its profitability, growth and development. The research presented in this paper is aimed at determination of the impact of quality on improving business performance and customer satisfaction. Correlation analysis confirmed this influence on the basis of obtained statistically significant mutual relations between the analyzed variables. Quality was shown to have an impact on improving the business performance of the organization, primarily on profitability through the improvement of leadership and relationship management. The impact of quality on customer satisfaction was also confirmed, where the engagement of people and the management of mutual relations had the greatest impact on consumer confidence. The research confirmed that the training of employees in terms of quality had a statistically significant impact on improving customer satisfaction, if it is conducted in an efficient manner.

GNSS and VLBI integrated processing at the observation level

2020 ◽  
Author(s):  
Jungang Wang ◽  
Kyriakos Balidakis ◽  
Maorong Ge ◽  
Robert Heinkelmann ◽  
Harald Schuh
Keyword(s):  
Reference Frames ◽  
Global Navigation Satellite Systems ◽  
Current Status ◽  
Normal Equation ◽  
Observation Level ◽  
Satellite Systems ◽  
Navigation Data ◽  
Long Baseline ◽  
Integrated Processing ◽  
The Impact

<p>The terrestrial and celestial reference frames, which serve as the basis for geodesy and astronomy, are mainly determined and maintained by space geodetic techniques such as Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite). These techniques are also used together to determine the Earth Orientation Parameters (EOP), which are very important for precise positioning, navigation and timing. Currently, the combination of all these techniques is done on the parameter level (ITRF) or on the normal equation level (DTRF), which are well-known and convenient methods but may suffer from some inconsistency.</p><p>Unlike the combination on the parameter or normal equation levels, the integrated processing at the observation level exploits the lengths and unique features of different techniques, and is valuable in determining homogeneous reference frames and EOP, and to connect the terrestrial, celestial, and dynamic frames. We are applying the integrated GNSS, VLBI and SLR data processing in the current Positioning And Navigation Data Analyst (PANDA) software, which aims on processing multi-geodetic techniques on the observation level. We present the strategy and current status of the integrated GNSS and VLBI processing and demonstrate the benefit of integrating GNSS for VLBI using 14 years of VLBI intensive sessions (2001-2014) and five CONT campaigns (2005-2017). We discuss the impact of applying tropospheric tie and local tie in the integrated processing.</p>

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