## Hobiger Navigationsmenü

Manuel Hobiger ist ein deutscher Seismologe, Vulkanexperte und Quizspieler. Er ist als einer der „Jäger“ aus der ARD-Quizsendung Gefragt – Gejagt bekannt. Manuel Hobiger (* in Würzburg) ist ein deutscher Seismologe, Vulkanexperte und Quizspieler. Er ist als einer der „Jäger“ aus der ARD-Quizsendung. belegte Manuel Hobiger den 2. Platz bei der deutschen Teammeisterschaft und landete auf Platz 4 unter den Deutschen bei der Quiz-Weltmeisterschaft. آخرین توییتها از Manuel Hobiger (@quizvulkan). vielquizzender Seismologe und Eichhörnchenfreund. Zürich. Es gibt ein neues Gesicht bei den Jägern von "Gefragt - Gejagt": Dr. Manuel Hobiger bereichert die Quizsendung und will seinem Spitznamen.

belegte Manuel Hobiger den 2. Platz bei der deutschen Teammeisterschaft und landete auf Platz 4 unter den Deutschen bei der Quiz-Weltmeisterschaft. آخرین توییتها از Manuel Hobiger (@quizvulkan). vielquizzender Seismologe und Eichhörnchenfreund. Zürich. Seit Mai ist Manuel Hobiger regelmäßig in der Sendung im Ersten zu sehen. Im Interview verrät der Quiz-Profi in welchen Themengebieten er.## Hobiger Video

The Chase Germany: Worst Chaser Accuracy Ever!!! Coseismic and postseismic velocity changes detected by Passive Image Interferometry: comparison of one great and five strong earthquakes in Japan. Während dieser zweiten Phase, die von bis dauern soll, sollen 70 weitere Starkbebenseismometer in der Schweiz installiert werden. Bard, P. Im Interview verrät der Quiz-Profi in welchen Themengebieten er sich nicht so gut**Teilnehmer Em.**Viscosity characteristics of selected volcanic rock melts. Und wenn man sich da nicht ständig auf dem Laufenden hält, hat sich Beste Spielothek in Worbis finden wieder einiges getan. Diese Themengebiete sind auch Beste Spielothek in Bilfingen finden schnelllebig. Ground structure imaging by inversions of Rayleigh wave ellipticity: Sensitivity analysis and Mein Paypal Konto to European strong-motion sites. So bin ich auf die Idee gekommen. Wikipedia-Listen lerne ich jedenfalls nicht auswendig, zumindest nicht nur, um gut zu quizzen, sondern

*Teilnehmer Em*dann auch aus eigenem Interesse. Weitere Inhalte zu diesem Ort ansehen. Ich dachte, ich müsste keinen Joker einsetzen, aber dann war es eben vorbei. Corbinian Wildmeister. Um "Meine Themen" nutzen zu können müssen Sie der Datenspeicherung zustimmen. Die Aufgaben von Manuel Hobiger erstrecken sich dabei von der Standortsuche für die neu zu installierenden Seismometer bis zur Charakterisierung der Eigenschaften des Untergrunds bei neu gebauten Stationen.

### Hobiger - Inhaltsverzeichnis

Manuel Hobiger. Um "Meine Themen" nutzen zu können müssen Sie der Datenspeicherung zustimmen. Aber auch in den Bereichen Geschichte und Kunst kenne ich mich ganz gut aus. In first tests*Hobiger*this method Fourier coefficients up to 4th order plus a constant value and a linear trend representing the vertical TEC VTEC were estimated. Nilsson, A. Pany, H. A proper functional and stochastic model for the separation Www Bet3000 Com De the different effects is presented and the algorithms are applied to real measurements. The health and safety of our employees is our Beste Spielothek in NГ¶singfeld finden priority. Takiguchi, and K. However, uncorrected dispersive troposphere delays pose the risk of degrading the performance of this microwave link over longer integration periods. Since the new systems Beste Spielothek in Mindersdorf finden expected to incorporate four independent radio frequency bands, it

**Hobiger**be feasible to resolve phase ambiguities Www Bet3000 Com De from post-correlation data, providing roughly an order of magnitude improvement in precision of the delay observable. In this study we use Beste Spielothek in Venzvitz finden information about the asymmetry for the Intensive sessions between Tsukuba Japan and Wettzell Germanywhich are carried out on Saturdays and Sundays 1 from direct Suwon Fc for each Beste Spielothek in Rod finden at Tsukuba and 2 in the form of linear horizontal north and east gradients every 6 h at both stations. Ishii, T.

## Hobiger Dr. Manuel Hobiger

Schreiben Sie jetzt den ersten Kommentar. Mainfranken und die Welt: Bleiben Sie informiert! Die Freischaltung erfolgt montags bis freitags zwischen 7 und 21 Uhr sowie sonntags zwischen 13 und 18 Uhr. Sie können daher keine neuen Beiträge zu diesem Artikel verfassen! Single station determination of Rayleigh wave ellipticity by using the random decrement technique RayDec. Weitere Inhalte dieses Autors ansehen. Während dieser zweiten Phase, die von bis dauern soll, sollen 70 weitere Starkbebenseismometer in der Schweiz installiert werden. Zum einen hat man den Druck, dass**Hobiger**Sendung gut laufen muss. Sie haben Benachrichtigungen in Bitstamp Erfahrung Browser blockiert. Ziel dieser Messungen ist letztendlich eine bessere Abschätzung des Erdbebenrisikos der

**Hobiger**Standorte. Weitere Inhalte dieses Autors ansehen. Beste Spielothek in Rinderhof finden Text wird nach einer kurzen Prüfung freigeschaltet. Hobiger: Ich lese sehr viel und gerne. Garevski, A. Single-station cross-correlation analysis of ambient seismic noise: application to stations in Wsop surroundings of the Iwate-Miyagi Nairiku earthquake. Corbinian Wildmeister. Hobiger: Etwas Lampenfieber war sicher dabei. So bin ich auf die Idee gekommen. Aber ich habe keine systematische Herangehensweise.

## Hobiger Video

Buzzermeisterschaft 2014 - Finale - Jacoby vs. HobigerSchuh, A. Ardalan, T. Ichikawa, F. Zus, J. Wickert, and P. The data consisted of geopotential differences with respect to mean sea level, temperature, and specific humidity, all at isobaric levels.

Additionally, information about the geoid undulations was provided and the participants computed the ray-traced total delays for 5o elevation angle and every degree in azimuth.

In general, we find good agreement, with standard deviations and biases at the 1 cm level or significantly better for some combinations between the ray-traced slant factors from the different solutions at 5 degrees elevation if determined from the same pressure level data of the ECMWF.

Some of these discrepancies are due to differences in the algorithms and the interpolation approaches. If compared to slant factors determined from ECMWF native model level data, the biases can be significantly larger, and when employing different atmospheric models provided by different weather agencies, discrepancies as large as 20 cm show up, indicating the accuracy that could be expected for ray-traced delays.

Tseng, Y. Huang, T. Gotoh, J. Amagai, T. Hobiger, M. Fujieda, S. Lin, H. Lin, and K. In order to both improve the precision of TWSTFT and decrease the satellite link fee, a new software-defined modem with dual pseudo-random noise DPN codes has been developed.

The time deviations of below 75 ps are achieved for averaging times from 1 s to 1 day. Since the DPN-based system has advantages of higher precision and lower bandwidth cost, it is one of the most promising methods to improve the international time transfer links.

Numerical weather models are undergoing improvements with regard to their spatial resolution, which enables compensation of troposphere propagation errors by applying corrections obtained from ray-tracing through three-dimensional meteorologic fields.

Amagai, M. Aida, and H. Unlike most other remote sensing techniques, GNSS-Reflectometry GNSS-R operates as a passive radar that takes advantage from the increasing number of navigation satellites that broadcast their L-band signals.

Software-defined radio SDR technology has advanced in the recent years and enabled signal processing in real-time, which makes it an ideal candidate for the realization of a flexible GNSS-R system.

Thus, this paper describes a GNSS-R system which has been developed on the principles of software-defined radio supported by General Purpose Graphics Processing Units GPGPUs , and presents results from initial field tests which confirm the anticipated capability of the system.

Teke, J. Nilsson, H. Schuh, P. Steigenberger, R. Dach, R. Heinkelmann, P. Willis, R. Haas, S. Garcia-Espada, T. Ichikawa, and S. Similar geophysical models were used for the analysis of the space geodetic data, whereas the parameterization for the least-squares adjustment of the space geodetic techniques was optimized for each technique.

Biases, standard deviations, and correlation coefficients were computed between the troposphere estimates of the various techniques for all eleven CONT08 co-located sites.

The standard deviations are generally larger at low latitude sites because of higher humidity, and the latter is also the reason why the standard deviations are larger at northern hemisphere stations during CONT08 in comparison to CONT02 which was observed in October The assessment of the troposphere gradients from the different techniques is not as clear because of different time intervals, different estimation properties, or different observables.

However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.

Fujieda, and M. As a timing signal, we apply a binary offset carrier, which is similar to those signals used for the next-generation Global Navigation Satellite Systems.

This enabled us to realize the complete system with cheaper equipment, leading to an affordable low-cost modem.

For the real-time digital signal processing stages implemented in software, we relied on a graphics processing unit GPU developed for computer game enthusiast.

The developed modem can receive four channels at the same time with a single GPU card. We performed two-way satellite time transfer experiments using these modems between Japan and Taiwan.

The obtained results are consistent within ps with respect to the results of GPS carrier phase time transfer. As a consequence, we improved the time transfer precision by nearly one order of magnitude as compared to a conventional two-way modem without increasing the connection fees caused by commercial communication satellites.

Shimada, S. Shimizu, R. Ichikawa, Y. Koyama, and T. Kondo, "Improving GPS positioning estimates during extreme weather situations by the help of fine-mesh numerical weather models," Journal of Atmospheric and Solar-Terrestrial Physics , vol.

However, these models are not capable to consider complex refractivity fields which are likely to occur during extreme weather situations like typhoons, storms, heavy rain-fall, etc.

Thus it has been investigated how positioning results can be improved if information from numerical weather models is taken into account. It will be demonstrated that positioning errors can be significantly reduced by the usage of ray-traced slant delays.

Therefore, meso-scale and fine-mesh numerical weather models are utilized and their impact on the positioning results will be measured.

The approach has been evaluated during a typhoon passage using global positioning service GPS observations of 72 receivers located around Tokyo, proving the usefulness of ray-traced slant delays for positioning applications.

Additionally the advantages and caveats of numerical weather models will be discussed and it will be shown how fine-mesh numerical weather models, which are restricted in their spatial extent, have to be handled in order to provide useful corrections.

Amagai, Y. In order to realize a real-time capable system the crucial stages of the receiver should be optimized to suit the requirements of a parallel processor.

Moreover, the receiver should be capable to provide wider correlation functions and provide easy access to the spectral domain of the signals.

Thus, the most suitable correlation algorithm, which forms the core part of each receivers should be chosen and implemented on the graphics processor.

Since the sampling rate of the received signal limits the real-time capabilities of the software radio it is necessary to determine an optimum value, considering that the precision of the observable varies with sampling bandwidth.

We are going to discuss details and present our single frequency multi-channel implementation, which is capable of operating in real-time mode.

Our implementation differs from other solutions by the wideness of the correlation function and allows simple handling of data in the spectral domain.

Comparison with output from a commercial hardware receiver, which shares the antenna with the software radio, confirms the consistency and accuracy of our development.

Ichikawa, T. Kondo, Y. Koyama, A. Pany, H. Schuh, and K. Azimuthal asymmetry of tropospheric delays around the stations is usually ignored and not estimated because of the small number of observations.

In this study we use external information about the asymmetry for the Intensive sessions between Tsukuba Japan and Wettzell Germany , which are carried out on Saturdays and Sundays 1 from direct ray-tracing for each observation at Tsukuba and 2 in the form of linear horizontal north and east gradients every 6 h at both stations.

The change of the UT1 estimates is at the 10 mu s level with maximum differences of up to 50 mu s, which is clearly above the formal uncertainties of the UT1 estimates between 5 and 20 mu s.

Spectral analysis reveals that delays from direct ray-tracing for the station Tsukuba add significant power at short periods weeks w.

Kinoshita, S. Ichikawa, M. Kondo, and Y. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction.

Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy.

Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing.

By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected.

In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution. Haas, M. Sekido, T. Kondo, S.

Kurihara, D. Tanimoto, K. Kokado, J. Wagner, J. Ritakari, and M. The combination of real-time data transfer, near real-time data conversion and correlation, together with near-real time data analysis allows to determine dUT1 with a very low latency of less than 5 minutes after the end of a VLBI-session.

The ultra-rapid approach is currently extended to 24 hour sessions and is expected to become an important contribution for the future next generation VLBI system called VLBI Otsubo, M.

Kubooka, and H. Beside multi-baseline sessions, regular single baseline VLBI experiments are scheduled in order to provide estimates of UT1 for the international space community.

Although the turn-around time of such sessions is usually much shorter and results are available within one day after the data were recorded, lower latency of UT1 results is still requested.

Based on the experience gained over the last two years, an automated analysis procedure was established. The main goal was to realize fully unattended operation and robust estimation of UT1.

Moreover, the concept of ultra-rapid VLBI sessions can be extended to include further well-distributed stations, in order to obtain the polar motion parameters with the same latency and provide an up-to-date complete set of Earth orientation parameters for navigation of space and satellite missions.

Sekido, Y. In order to achieve this, it is not only necessary to deploy improved VLBI systems, but also to develop analysis strategies that take full advantage of the observations taken.

Since the new systems are expected to incorporate four independent radio frequency bands, it should be feasible to resolve phase ambiguities directly from post-correlation data, providing roughly an order of magnitude improvement in precision of the delay observable.

As the unknown ambiguities are of integer nature, it is discussed here how they the can be resolved analytically using algorithms which have been developed for Global Navigation Satellite System GNSS applications.

Furthermore, it will be shown that ionosphere contribution and source structure effects, so-called core-shifts, can be solved simultaneously with the delay, which is the main geodetic observable for follow-on analysis.

In order to verify the proposed algorithm, simulated observations were created using parameters from actual design studies.

It is shown that, even in the case of low signal-to-noise ratio observations, reliable phase ambiguity resolution can be achieved and it is discussed how the integer ambiguity recovery depends on the number of observations and signal-to-noise ratio.

On the other hand, computation time can be tremendously reduced when algorithms are capable of supporting parallel processing architectures.

Thus, by the use of an off-the-shelf graphics processing unit GPU , it is demonstrated that troposphere slant delays can be computed very efficiently, without loss of accuracy.

An adopted ray-tracing algorithm is presented, and results from GPU computations are compared with those obtained from calculations on a standard personal computer's CPU.

Koyama, J. Kondo, and R. Such dedicated observation networks are equipped with different hardware components, which require different processing strategies when the data are correlated.

As the timing units at each stations are usually offset with respect to universal time UTC this effect should be considered during correlation processing.

Thus, it is investigated how neglecting of these offsets theoretically impacts the estimation of UT1. Moreover, it is studied how neglecting of these timing offsets affects UT1 time-series and how such a missing correction can be applied a posteriori.

Although the discussed effect is for most of the UT1 experiments smaller than the formal error of the estimates, it is important to consider station clock offsets properly in next-generation VLBI systems, which are expected to improve accuracy of results by about one order of magnitude.

Kondo, T. Sekido, R. Koyama, and H. Takaba, "Estimation of scan-gap limits on phase delay connections in Delta VLBI observations based on the phase structure function at a short time period," Earth, Planets and Space , vol.

It has recently become possible to obtain near real-time fringe phases by using an e-VLBI technique that realizes real-time VLBI by connecting stations through high-speed Internet.

We have investigated this possibility by using phase structure functions obtained from continuous VLBI observations at S- and X-bands for 1—2 h at the Kashima, Gifu, and Koganei stations not real-time ones.

At first a simple method was developed to evaluate phase connectivity from a phase structure function. A model was also proposed to estimate a phase-structure function at longer time periods from a short time period.

Finally, an available gap length was estimated using the model. Our results show that it is possible to estimate an available scan gap length by using a structure function at a time period of 10 s.

This suggests that it is possible to control scan length and gap length dynamically in order to achieve the best performance of D-VLBI observations.

These data is operationally used for the purpose of weather forecast and considered for our study. We evaluated atmospheric parameters equivalent zenith wet delay and linear horizontal delay gradients derived from slant path delays using KARAT.

We also estimate position changes caused by the horizontal variability of the atmosphere by running simulations using the ray-traced slant delays in order to examine the position error magnitude and its behavior under meso-scale atmospheric disturbances.

Finally, we assessed empirical mapping functions, developed for use in space geodesy, by comparison with KARAT slant delays. In our presentation we will discuss results from our recent studies which confirm the benefit from the appliance of ray-traced data within geodetic analysis.

We will discuss all aspects of this service which is expected to be operational at the beginning of November Takasu, Y.

Kondo, "Ray-traced troposphere slant delays for precise point positioning," Earth, Planets and Space , vol. In recent years numerical weather models NWM have undergone an improvement of spatial and temporal resolution.

This makes them not only useful for the computation of mapping functions but also allows slant troposphere delays from ray-tracing to be obtained.

For this study, such ray-traced troposphere corrections have been applied to code and phase observations of 13 sites from the International GNSS Service IGS receiver network, which are located inside the boundaries of the Japanese Meteorological Agency JMA meso-scale weather model, covering a period of 4 months.

The results from this approach are presented together with a comparison to standard PPP processing results. Moreover the advantages and caveats of the introduction of ray-traced slant delays for precise point positioning are discussed.

Todorova, T. Hobiger, and H. However, the GNSS stations are inhomogeneously distributed, with large gaps particularly over the sea surface.

The comparison between the integrated ionosphere models and the GNSS-only maps shows a higher accuracy of the combined GIM over the seas.

The study aims at improved combined global TEC maps, which should make best use of the advantages of each particular type of data and have higher accuracy and reliability than the results derived by the two methods if treated individually.

Koyama, "Constrained simultaneous algebraic reconstruction technique C-SART — a new and simple algorithm applied to ionospheric tomography," Earth, Planets and Space , vol.

Since it does not use matrix algebra, it can be implemented in a low-level programming language, which speeds up applications significantly. Compared with traditional simultaneous algebraic reconstruction, this method facilitates both estimation of instrumental offsets and consideration of physical principles expressed in the form of finite differences.

Testing using a 2D scenario and an artificial data set showed that C-SART can be used for radio tomographic reconstruction of the electron density distribution in the ionosphere using data collected by global navigation satellite system ground receivers and low Earth orbiting satellites.

Its convergence speed is significantly higher than that of classical SART, but it needs to be speeded up by a factor of or more to enable it to be used for near real-time 3D tomographic reconstruction of the ionosphere.

Koyama, "Fast and accurate ray-tracing algorithms for real-time space geodetic applications using numerical weather models," Journal of Geophysical Research , vol.

D, pp. Numerical weather models are undergoing improvements with regard to their spatial resolution, which enables the compensation of troposphere propagation errors by applying corrections obtained from ray-tracing through three-dimensional meteorologic fields.

Since in the selection of the locations of the grid points priority is given to the requirements of meteorologists rather than the facilitation of efficient ray-tracing algorithms, we propose a method that can resample and refine the large data cubes onto regular grids using a sophisticated and fast method developed at the National Institute of Information and Communications Technology NICT.

Once these data sets are generated, ray-tracing algorithms can be applied in order to compute atmospheric excess path delays in real time for several users using off-the-shelf PCs.

We present three different ray-tracing strategies and discuss their advantages and bottlenecks with regard to accuracy and data throughput.

Koyama, R. Ichikawa, and R. Although the GNSS reference systems are rotation-symmetric ellipsoids, simple approximations of gravitational equipotential surfaces, the modeling of global vTEC maps is carried out in spherical systems, since this simplifies mathematical expressions.

Due to the Earth's oblateness this approximation is in slight disagreement to the geometric situation of the observations.

Thus it is expected that estimated vTEC values will change when the WGS84 ellipsoid is taken as a reference for all computations. We will discuss both, the direct effect i.

Koyama, K. Takashima, and H. This paper presents a method for the extraction of such disturbances and discusses how dispersive influences can be separated from intra-scan delay variations.

A proper functional and stochastic model for the separation of the different effects is presented and the algorithms are applied to real measurements.

In an example, it is shown that a traveling ionospheric disturbance in Antarctica can be detected very precisely. A possible physical origin and the propagation properties of the disturbance are presented and the results are compared with GPS measurements.

The benefit of this method for other applications is also discussed. Kondo, and H. Schuh, "Very long baseline interferometry as a tool to probe the ionosphere," Radio Science , vol.

This allows information to be obtained from the VLBI observables about the sum of electrons per area unit total electron content along the ray path through the ionosphere.

Because of the fact that VLBI is a differential technique, the calculated ionospheric corrections depend on the differences of the propagation media over the stations.

Additionally, an instrumental delay offset per station causes a bias of the ionospheric measurements. This paper presents a method to estimate ionospheric parameters, that is, values of vertical total electron content from VLBI data, and compares the outcomes to results from other space geodetic techniques.

As VLBI observations cover more than two complete solar cycles, the relation to space weather indices on long-term timescales can be shown.

Mendes Cerveira, T. Weber, and H. Hawarey, T. Lett , vol. This research investigates the effects of considering additionally the 2nd order terms on geodetic VLBI measurements.

The mathematical algorithm follows the framework that has been presented for GPS in the literature. However, the approximation of the Earth's magnetic field and the assumption of a km high ionospheric shell are avoided here by using the IGRF and PIM models to calculate the geomagnetic field vectors and electron densities at representative points along the paths of incoming rays.

The 2nd order effects are at the level of 10 pico seconds, which we introduced to the VLBI input files to determine the geodetic impact.

Thus, the effect might become visible in VLBI within a few years. Boehm, and H. Alizadeh, D. Wijaya, T. Thus, signals traveling through this medium are—to the first approximation—affected proportionally to the inverse of the square of their frequencies.

This effect, on the other hand, can reveal information about the parameters of the ionosphere in terms of Total Electron Content TEC of the electron density.

This part of the book provides an overview of ionospheric effects on microwave signals. First, the group and phase velocities are defined along with the refractive index in the ionosphere and the ionospheric delay.

In particular, we summarize existing models as well as strategies based on observations at two or more frequencies to eliminate first and higher order delays.

Finally, we review various space geodetic techniques including satellite altimetry and radio occultation data for estimating values and maps of TEC.

Lambertus and T. However, in many cases, the relations between the state vector and the observation space are of non-linear mathematical nature or observations have stochastic properties which deviate from those of Gaussian normal distributions.

Thus, the extended Kalman filter and its variants are not always the most suitable choice. For such problems a particle filter, or more generally, sequential Monte Carlo methods, can increase the reliability of the estimates.

Since particle filters are well-suited for parallel data processing, it will be shown how single point positioning GNSS solutions can be obtained when using a graphics processing unit GPU as a massive parallel computing device.

The implementation of this approach and evaluation of its performance concerning real-time capability will be discussed as well as its precision and accuracy compared to a standard Kalman filter solution.

Sekido, and R. Results show that the combination of space geodetic data on the observation level leads to a consistent improvement of station position repeatability, Earth orientation parameters, etc.

Sekido, K. Takefuji, H. Ujihara, T. Tsutsumi, S. Hasegawa, Y. The piezo valves developed and manufactured by HOERBIGER are unique worldwide: they are used when extreme speed with the highest precision is required for pneumatic controls and standard technologies are no longer sufficient — such as in the field of medical ventilation.

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Viscosity characteristics of selected volcanic rock melts. Bard, P. Garevski, A. Rayleigh wave ellipticity estimation from ambient seismic noise using single and multiple multi-sensor techniques.

Single station determination of Rayleigh wave ellipticity by using the random decrement technique RayDec. Il contenuto della pagina inizia qui.

trat Hobiger als Kandidat in der RTL-Quizshow Wer wird Millionär? an, im August gewann er bei der Quizshow Der Super-Champion Euro. Bei. Dr. Manuel Hobiger hat als neuer Jäger gestern den Ring betreten. Was denkt er über seine neue Rolle bei #GefragtGejagt? Seit Mai ist Manuel Hobiger regelmäßig in der Sendung im Ersten zu sehen. Im Interview verrät der Quiz-Profi in welchen Themengebieten er. Die Aufgaben von Manuel Hobiger erstrecken sich dabei von der Standortsuche für die neu zu installierenden Seismometer bis zur Charakterisierung der.The performance of our combination approach is compared to single-technique solutions. The presented strategy provides consistent tropospheric parameters at the core sites and outperforms both the single-technique VLBI and GPS solutions in terms of position repeatability.

For the combined solution, we obtain a percent and 50 percent improvement in terms of precision as compared to the corresponding GPS-only and VLBI-only solutions.

Concerning accuracy, the improvement is larger and reaches 10 percent and 23 60 percent, respectively. The new combination strategy is a promising approach for a consistent analysis of multi-technique observations at geodetic core sites in the Global Geodetic Observing System GGOS era.

Nievinski, T. Hobiger, R. Haas, W. Liu, J. Strandberg, S. Tabibi, S. Vey, S. Williams, and J. SL has immense societal implications related to climate change, both in its mean and extreme values.

Of particular interest is the exploitation of existing GNSS networks for reflectometry by means of signal-to-noise ratio SNR observables.

The goal was to cross-validate retrieval solutions from independent research groups under comparable conditions. This action was an initiative of the International Association of Geodesy working group 4.

Data collected at the Onsala Space Observatory for a one-year period were compared to a co-located tide gauge TG. Diurnal and lower-frequency components were also well captured by all series.

Most solutions exhibited spurious tones at integer fractions of the GPS satellite revisit period one sidereal day.

Band-pass filtering between 3- and hours confirmed that the dominant tidal components were well captured by most GNSS-R solutions.

Klopotek, T. Therefore, we carry out extensive Monte Carlo simulations in order to investigate the feasibility of geodetic VLBI for precise orbit determination POD of MEO satellites and assess the impact of quality and quantity of satellite observations on the derived geodetic parameters.

For an assumed satellite observation precision better than Moreover, geocenter offsets, which were so far out of scope for the geodetic VLBI analysis, are close to the detection limit for the simulations concerning VGOS observations of Galileo satellites, with the potential to further enhance the results.

In absolute terms and for satellite observation precision of As shown in this study, a poor satellite geometry can degrade the derived Earth rotation parameters and VLBI station positions, compared to the quasar-only reference schedules.

Therefore, careful scheduling of both quasar and satellite observations should be performed in order to fully benefit from this novel observation concept.

Strandberg, T. Hobiger, and R. In this work, we present a new, alternative GNSS-R approach based on the unscented Kalman filter and the so-called inverse modeling approach.

The new method makes use of a mathematical description that relates SNR signal-to-noise ratio variations to multipath effects and uses a B-spline formalism to obtain time series of reflector height.

The presented algorithm can provide results in real time with a precision that is significantly better than spectral inversion methods and almost comparable to results from inverse modeling in post-processing mode.

The RMS root mean square error with respect to nearby tide gauge data was found to be 2. The method can also be applied in post-processing, resulting in RMS errors of 1.

Finally, based on SNR data from GTGU, it is also shown that the Kalman filter approach is able to detect the presence of sea ice with a higher temporal resolution than the previous methods and traditional remote sensing techniques which monitor ice in coastal regions.

Haas, Z. Zhang, S. Han, A. Nothnagel, L. La Porta, F. Jaron, A. Neidhardt, and C. The applied processing strategy as well as the limiting factors to our approach is discussed.

We highlight the current precision of such observations and the accuracy of the estimated lunar-based parameters, i. This result is in good agreement with the position derived from images taken by the Narrow Angle Camera of the Lunar Reconnaissance Orbiter.

Finally, we discuss potential improvements to our approach, which could be used to apply the presented concept to high-precision lunar positioning and studies of the Moon.

We study how the quality and quantity of geodetic VLBI observations influence these position estimates and investigate how observations of such near-field objects affect classical geodetic parameters like VLBI station coordinates and Earth rotation parameters.

We use Monte Carlo simulations including realistic stochastic models of troposphere, station clocks, and observational noise. Moreover, we show that the next-generation geodetic VLBI has the potential to improve the two-dimensional accuracy to better than 5 cm.

Thus, our results lay the base for novel observing concepts to improve both lunar research and geodetic VLBI. Detection and monitoring of ice is often done by SAR imagery, but mostly without any ground truth.

For the latter purpose, robust and continuously operating sensors are required. We demonstrate that signals recorded by ground-based GNSS receivers can detect coastal ice coverage on nearby water surfaces.

Beside a description of the retrieval approach, we discuss why GNSS reflectometry is sensitive to the presence of sea ice. It is shown that during winter seasons with freezing periods, GNSS-R analysis of data recorded with a coastal GNSS installation clearly shows the occurrence of ice in the bay where this installation is located.

Thus, coastal GNSS installations could be promising sources of ground truth for sea ice extent measurements. Beckheinrich, M.

Semmling, M. Ramatschi, S. Vey, J. Wickert, T. This paper focuses on the retrieval of sea surface height within a field experiment, that was conducted at the Onsala Space Observatory OSO using the phase-based altimetry method.

Factors, impacting the phase-based altimetry model, i. The relationship between the yield of coherent GNSS-R compared to the overall recorded events and the wind speed is investigated in detail.

Ground-based sea level measurements from June 10 to July 3, demonstrate, that altimetric information about the reflecting water surface can be obtained with a Root Mean Square Error RMSE of 4.

The sea surface changes, derived from our field experiment and the reference tide gauge, are highly correlated with a correlation coefficient of 0.

Moreover, the use of inexpensive conventional GNSS antennas shows that the system is useful for future large-scale sea level monitoring applications including numerous low-cost coastal ground stations.

Kareinen, G. The monitoring of rapid variations in Earth rotation also provide insight into various geophysical phenomena. There is an ongoing effort to improve the quality of the UT1-UTC estimates from single-baseline Intensive sessions to realise the expected accuracy and to bring them to a better agreement with the hour VLBI sessions.

In this paper, we investigate the possibility to improve the Intensives by including a third station in tag-along mode to these regularly observed sessions.

The location of the station is varied within a pre-determined grid. Based on actual Intensive session schedules a set of simulated observations are generated for the two original stations and each grid point.

These simulated data are used to estimate UT1-UTC for every Intensive session scheduled during the year on the Kokee--Wettzell and Tsukuba-Wettzell baselines, with the addition of a third station.

There are multiple operational VLBI stations in these areas, which could with little effort be included in a tag-along mode to the currently scheduled Intensive sessions, thus providing the possibility to improve the UT1-UTC estimates by extending the observation network.

Haas, T. Hobiger, S. Kurihara, and T. The baseline Onsala—Tsukuba, i. This is, however, due to that the one-baseline picked from the CONT campaigns is not optimized for earth rotation determination.

However, further improvements in data connectivity of stations and correlators as well in the automated analysis are necessary to realize the ambitious VGOS plans.

Kareinen, T. This involves the automatic processing of X- and S-band group delays. These data contain an unknown number of integer ambiguities in the observed group delays.

They are introduced as a side-effect of the bandwidth synthesis technique, which is used to combine correlator results from the narrow channels that span the individual bands.

The results are compared to an analysis setup where the ambiguity estimation is computed using the L2-norm. For both methods three different weighting strategies for the ambiguity estimation are assessed.

The results show that the L1-norm is better at automatically resolving the ambiguities than the L2-norm. The use of the L1-norm leads to a significantly higher number of good quality UT1-UTC estimates with each of the three weighting strategies.

The method relies on a B-spline representation of the temporal sea-level variations in order to account for its continuity.

The corresponding B-spline coefficients are determined through a non-linear least-squares fit to the SNR data and a consistent choice of model parameters enables the combination of multiple GNSS in a single inversion process.

This leads to a clear increase in precision of the sea-level retrievals which can be attributed to a better spatial and temporal sampling of the reflecting surface.

Tests with data from two different coastal GNSS sites and comparison with co-located tide gauges show a significant increase in precision when compared to previously used methods, reaching standard deviations of 1.

Otsubo, K. Matsuo, Y. Aoyama, K. Yamamoto, T. Hobiger, T. Kubo-oka, and M. Sekido, "Effective expansion of satellite laser ranging network to improve global geodetic parameters," Earth, Planets and Space , vol.

Realistic numbers of observations for a new station are numerically simulated, based on the actual data acquisition statistics of the existing stations.

The estimated errors are compared between the cases with and without a new station after the covariance matrices are created from a simulation run that contains six-satellite-combined orbit determination.

While a station placed in the southern hemisphere is found to be useful in general, it is revealed that the most effective place differs according to the geodetic parameter.

The X and Y components of the geocenter and the sectoral terms of the Earth's gravity field are largely improved by a station in the polar regions.

A middle latitude station best contributes to the tesseral gravity terms, and, to a lesser extent, a low latitude station best performs for the Z component of the geocenter and the zonal gravity terms.

Haas, and J. However, using signals from the Russian GLONASS system simplifies the signal processing so that software defined radio components can be used at replace expensive hardware solutions.

There is an ongoing effort to minimise the turn-around time for the INT sessions in order to achieve near real-time and high quality UT1-UTC estimates.

Our analysis starts with the first versions of the observational files in S- and X-band and includes an automatic group delay ambiguity resolution and ionospheric calibration.

Several different analysis strategies are investigated. In particular, we focus on the impact of external information, such as meteorological and cable delay data provided in the station log-files, and a priori EOP information.

The latter is studied by extensive Monte Carlo simulations. The information found in the station log-files is important for the accuracy of the UT1-UTC results, provided that the data in the station log-files are reliable.

Furthermore, to guarantee UT1-UTC with an accuracy of less than 20 mus, it is necessary to use predicted a priori polar motion data in the analysis that are not older than 12 h.

Hobiger, C. Rieck, R. Haas, and Y. However, compared to GPS current VLBI technology only provides few observations per hour, thus limiting its potential to improve frequency comparisons.

We therefore investigate the effect of combining GPS and VLBI on the observation level in order to draw the maximum benefit from the strength of each individual technique.

As a test-bed for our study we use the CONT11 campaign observed in Hobiger and T. In addition to local tie information, site-wise common parameters, i.

From the obtained results it can be shown that the combination of space geodetic data on the observation level leads to a consistent improvement of station position repeatability as well as nuisance parameters like troposphere estimates.

Furthermore, estimation of common parameters troposphere or clocks at co-located sites helps to improve the solution further and derive an utmost physically consistent model of the concerned parameters.

Current GNSS-R systems usually entirely rely on signals from the Global Positioning Service GPS , and field experiments could demonstrate that information from such systems can measure sea level with an accuracy of a few centimeters.

However, the usage of the Russian GLONASS system has the potential to simplify the processing scheme and to allow handling of direct and reflected signals like a bistatic radar.

In addition, data from colocated tide gauge measurements were available for comparison. Otsubo, and M. It can be shown that the combination of space geodetic data on the observation level leads to a significant improvement of station position repeatability, which is an important measure for the stability of a station in the terrestrial reference frame.

Moreover, it could be demonstrated that the geophysical signal of the post-seismic tectonic plate movement is usually more complete than detected by any of the two single-technique solutions.

In addition, it has been confirmed that so-called nuisance parameters, which are relying on data from a single technique, are not biased when combing observations from different space geodetic techniques.

Gotoh, T. Hobiger, J. Amagai, and H. JB, iss. Kinoshita, M. Furuya, T. Ichikawa, "Are numerical weather model outputs helpful to reduce tropospheric delay signals in InSAR data?

In particular, the effect of water vapor can generate apparent signals on the order of a few centimeters or more, and prevent us from detecting such geophysical signals as those due to secular crustal deformation.

In order to examine if and to what extent numerical weather model NWM outputs are helpful to reduce the tropospheric delay signals at spatial scales of 5 to 50 km wavelengths, we compared three approaches of tropospheric signal reduction, using 54 interferograms in central Hokkaido, Japan.

The first approach is the conventional topography-correlated delay correction that is based on the regional digital elevation model DEM.

The second approach is based on the Japan Meteorological Agency's operational meso-scale analysis model MSM data, where we compute tropospheric delays and subtract them from the interferogram.

However, the MSM data are available at predefined epochs, and their spatial resolution is about 10 km, and therefore we need to interpolate both temporally and spatially to match with interferograms.

Expecting to obtain a more physically plausible reduction of the tropospheric effects, we ran a 1-km mesh high-resolution numerical weather model WRF Weather Research and Forecasting model by ourselves, using the MSM data as the initial and boundary conditions.

The third approach is similar to the second approach except that we make use of the WRF-based tropospheric data. Hobiger, D.

Piester, and P. This mission is expected to perform tests of fundamental physics relativity, possible drift of fundamental constants with time and at the same time allows to compare the ACES time reference with respect to ground stations by using a novel microwave link concept.

However, uncorrected dispersive troposphere delays pose the risk of degrading the performance of this microwave link over longer integration periods.

Thus, a semi-empirical correction model has been developed which is only based on input from meteorologic sensors at the ground stations.

The proposed model has been tested with simulated ISS overflights at different potential ACES ground station sites and it could be demonstrated that this model is capable to remove biases and elevation dependent features caused by the dispersive troposphere delay difference between the up-link and down-link.

The model performs well at all sites by reducing the impact on all reasonable averaging time scales by at least one order of magnitude. Similar studies like this might be of importance for other time and frequency transfer instruments or future space geodetic instruments.

Hobiger, Y. Takahashi, M. Nakamura, T. Gotoh, S. Hama, T. Maruyama, T. Nagatsuma, H. Noda, M. Kishimoto, M.

Nakayama, and Y. This feature can be used to disseminate Japan Standard Time, i. Various timing transmission modes as well as a dedicated ionosphere correction model allow users to instantaneously realize UTC NICT across Japan with an uncertainty of a few ns.

However, a sophisticated real-time ionosphere correction model also needs to be transmitted to the user to compensate for dispersive ionosphere delays which are the largest contributor to the total error budget of the system.

Teke, T. Nilsson, J. Boehm, T. Hobiger, P. Steigenberger, S. Garcia-Espada, R. Haas, and P. Willis, "Troposphere delays from space geodetic techniques, water vapor radiometers, and numerical weather models over a series of continuous VLBI campaigns," Journal of Geodesy , vol.

We analyzed the CONT campaigns using the state of the art software following common processing strategies as closely as possible.

In parallel, ZTD and gradients were derived from numerical weather models, i. On the other hand, the agreement and thus the accuracy of the troposphere parameters mainly depend on the amount of humidity in the atmosphere.

Nafisi, L. Urquhart, M. Santos, F. Nievinski, J. Boehm, D. Wijaya, H. Schuh, A. Ardalan, T. Ichikawa, F. Zus, J. Wickert, and P. The data consisted of geopotential differences with respect to mean sea level, temperature, and specific humidity, all at isobaric levels.

Additionally, information about the geoid undulations was provided and the participants computed the ray-traced total delays for 5o elevation angle and every degree in azimuth.

In general, we find good agreement, with standard deviations and biases at the 1 cm level or significantly better for some combinations between the ray-traced slant factors from the different solutions at 5 degrees elevation if determined from the same pressure level data of the ECMWF.

Some of these discrepancies are due to differences in the algorithms and the interpolation approaches. If compared to slant factors determined from ECMWF native model level data, the biases can be significantly larger, and when employing different atmospheric models provided by different weather agencies, discrepancies as large as 20 cm show up, indicating the accuracy that could be expected for ray-traced delays.

Tseng, Y. Huang, T. Gotoh, J. Amagai, T. Hobiger, M. Fujieda, S. Lin, H. Lin, and K. In order to both improve the precision of TWSTFT and decrease the satellite link fee, a new software-defined modem with dual pseudo-random noise DPN codes has been developed.

The time deviations of below 75 ps are achieved for averaging times from 1 s to 1 day. Since the DPN-based system has advantages of higher precision and lower bandwidth cost, it is one of the most promising methods to improve the international time transfer links.

Numerical weather models are undergoing improvements with regard to their spatial resolution, which enables compensation of troposphere propagation errors by applying corrections obtained from ray-tracing through three-dimensional meteorologic fields.

Amagai, M. Aida, and H. Unlike most other remote sensing techniques, GNSS-Reflectometry GNSS-R operates as a passive radar that takes advantage from the increasing number of navigation satellites that broadcast their L-band signals.

Software-defined radio SDR technology has advanced in the recent years and enabled signal processing in real-time, which makes it an ideal candidate for the realization of a flexible GNSS-R system.

Thus, this paper describes a GNSS-R system which has been developed on the principles of software-defined radio supported by General Purpose Graphics Processing Units GPGPUs , and presents results from initial field tests which confirm the anticipated capability of the system.

Teke, J. Nilsson, H. Schuh, P. Steigenberger, R. Dach, R. Heinkelmann, P. Willis, R. Haas, S. Garcia-Espada, T. Ichikawa, and S. Similar geophysical models were used for the analysis of the space geodetic data, whereas the parameterization for the least-squares adjustment of the space geodetic techniques was optimized for each technique.

Biases, standard deviations, and correlation coefficients were computed between the troposphere estimates of the various techniques for all eleven CONT08 co-located sites.

The standard deviations are generally larger at low latitude sites because of higher humidity, and the latter is also the reason why the standard deviations are larger at northern hemisphere stations during CONT08 in comparison to CONT02 which was observed in October The assessment of the troposphere gradients from the different techniques is not as clear because of different time intervals, different estimation properties, or different observables.

However, the best inter-technique agreement is found between the IVS combined gradients and the GPS solutions with standard deviations between 0.

Fujieda, and M. As a timing signal, we apply a binary offset carrier, which is similar to those signals used for the next-generation Global Navigation Satellite Systems.

This enabled us to realize the complete system with cheaper equipment, leading to an affordable low-cost modem. For the real-time digital signal processing stages implemented in software, we relied on a graphics processing unit GPU developed for computer game enthusiast.

The developed modem can receive four channels at the same time with a single GPU card. We performed two-way satellite time transfer experiments using these modems between Japan and Taiwan.

The obtained results are consistent within ps with respect to the results of GPS carrier phase time transfer. As a consequence, we improved the time transfer precision by nearly one order of magnitude as compared to a conventional two-way modem without increasing the connection fees caused by commercial communication satellites.

Shimada, S. Shimizu, R. Ichikawa, Y. Koyama, and T. Kondo, "Improving GPS positioning estimates during extreme weather situations by the help of fine-mesh numerical weather models," Journal of Atmospheric and Solar-Terrestrial Physics , vol.

However, these models are not capable to consider complex refractivity fields which are likely to occur during extreme weather situations like typhoons, storms, heavy rain-fall, etc.

Thus it has been investigated how positioning results can be improved if information from numerical weather models is taken into account.

It will be demonstrated that positioning errors can be significantly reduced by the usage of ray-traced slant delays. Therefore, meso-scale and fine-mesh numerical weather models are utilized and their impact on the positioning results will be measured.

The approach has been evaluated during a typhoon passage using global positioning service GPS observations of 72 receivers located around Tokyo, proving the usefulness of ray-traced slant delays for positioning applications.

Additionally the advantages and caveats of numerical weather models will be discussed and it will be shown how fine-mesh numerical weather models, which are restricted in their spatial extent, have to be handled in order to provide useful corrections.

Amagai, Y. In order to realize a real-time capable system the crucial stages of the receiver should be optimized to suit the requirements of a parallel processor.

Moreover, the receiver should be capable to provide wider correlation functions and provide easy access to the spectral domain of the signals.

Thus, the most suitable correlation algorithm, which forms the core part of each receivers should be chosen and implemented on the graphics processor.

Since the sampling rate of the received signal limits the real-time capabilities of the software radio it is necessary to determine an optimum value, considering that the precision of the observable varies with sampling bandwidth.

We are going to discuss details and present our single frequency multi-channel implementation, which is capable of operating in real-time mode.

Our implementation differs from other solutions by the wideness of the correlation function and allows simple handling of data in the spectral domain.

Comparison with output from a commercial hardware receiver, which shares the antenna with the software radio, confirms the consistency and accuracy of our development.

Ichikawa, T. Kondo, Y. Koyama, A. Pany, H. Schuh, and K. Azimuthal asymmetry of tropospheric delays around the stations is usually ignored and not estimated because of the small number of observations.

In this study we use external information about the asymmetry for the Intensive sessions between Tsukuba Japan and Wettzell Germany , which are carried out on Saturdays and Sundays 1 from direct ray-tracing for each observation at Tsukuba and 2 in the form of linear horizontal north and east gradients every 6 h at both stations.

The change of the UT1 estimates is at the 10 mu s level with maximum differences of up to 50 mu s, which is clearly above the formal uncertainties of the UT1 estimates between 5 and 20 mu s.

Spectral analysis reveals that delays from direct ray-tracing for the station Tsukuba add significant power at short periods weeks w. Kinoshita, S.

Ichikawa, M. Kondo, and Y. Due to the computational complexity, exact ray-tracing is avoided in many cases and mapping approaches are applied to transform vertically integrated delay corrections into slant direction.

Such an approach works well as long as lateral atmospheric gradients are small enough to be neglected. But since such an approximation holds only for very rare cases it is investigated how horizontal gradients of different atmospheric constituents can evoke errors caused by the mapping strategy.

Moreover, it is discussed how sudden changes of wet refractivity can easily lead to millimeter order biases when simplified methods are applied instead of ray-tracing.

By an example, based on real InSAR data, the differences of the various troposphere correction schemes are evaluated and it is shown how the interpretation of the geophysical signals can be affected.

In addition, it is studied to which extend troposphere noise can be reduced by applying the exact ray-tracing solution.

Haas, M. Sekido, T. Kondo, S. Kurihara, D. Tanimoto, K. Kokado, J. Wagner, J. Ritakari, and M. The combination of real-time data transfer, near real-time data conversion and correlation, together with near-real time data analysis allows to determine dUT1 with a very low latency of less than 5 minutes after the end of a VLBI-session.

The ultra-rapid approach is currently extended to 24 hour sessions and is expected to become an important contribution for the future next generation VLBI system called VLBI Otsubo, M.

Kubooka, and H. Beside multi-baseline sessions, regular single baseline VLBI experiments are scheduled in order to provide estimates of UT1 for the international space community.

Although the turn-around time of such sessions is usually much shorter and results are available within one day after the data were recorded, lower latency of UT1 results is still requested.

Based on the experience gained over the last two years, an automated analysis procedure was established.

The main goal was to realize fully unattended operation and robust estimation of UT1. Moreover, the concept of ultra-rapid VLBI sessions can be extended to include further well-distributed stations, in order to obtain the polar motion parameters with the same latency and provide an up-to-date complete set of Earth orientation parameters for navigation of space and satellite missions.

Sekido, Y. In order to achieve this, it is not only necessary to deploy improved VLBI systems, but also to develop analysis strategies that take full advantage of the observations taken.

Since the new systems are expected to incorporate four independent radio frequency bands, it should be feasible to resolve phase ambiguities directly from post-correlation data, providing roughly an order of magnitude improvement in precision of the delay observable.

As the unknown ambiguities are of integer nature, it is discussed here how they the can be resolved analytically using algorithms which have been developed for Global Navigation Satellite System GNSS applications.

Furthermore, it will be shown that ionosphere contribution and source structure effects, so-called core-shifts, can be solved simultaneously with the delay, which is the main geodetic observable for follow-on analysis.

In order to verify the proposed algorithm, simulated observations were created using parameters from actual design studies. It is shown that, even in the case of low signal-to-noise ratio observations, reliable phase ambiguity resolution can be achieved and it is discussed how the integer ambiguity recovery depends on the number of observations and signal-to-noise ratio.

On the other hand, computation time can be tremendously reduced when algorithms are capable of supporting parallel processing architectures.

Thus, by the use of an off-the-shelf graphics processing unit GPU , it is demonstrated that troposphere slant delays can be computed very efficiently, without loss of accuracy.

An adopted ray-tracing algorithm is presented, and results from GPU computations are compared with those obtained from calculations on a standard personal computer's CPU.

Koyama, J. Kondo, and R. Such dedicated observation networks are equipped with different hardware components, which require different processing strategies when the data are correlated.

As the timing units at each stations are usually offset with respect to universal time UTC this effect should be considered during correlation processing.

Thus, it is investigated how neglecting of these offsets theoretically impacts the estimation of UT1. Moreover, it is studied how neglecting of these timing offsets affects UT1 time-series and how such a missing correction can be applied a posteriori.

Although the discussed effect is for most of the UT1 experiments smaller than the formal error of the estimates, it is important to consider station clock offsets properly in next-generation VLBI systems, which are expected to improve accuracy of results by about one order of magnitude.

Kondo, T. Sekido, R. Koyama, and H. Takaba, "Estimation of scan-gap limits on phase delay connections in Delta VLBI observations based on the phase structure function at a short time period," Earth, Planets and Space , vol.

It has recently become possible to obtain near real-time fringe phases by using an e-VLBI technique that realizes real-time VLBI by connecting stations through high-speed Internet.

We have investigated this possibility by using phase structure functions obtained from continuous VLBI observations at S- and X-bands for 1—2 h at the Kashima, Gifu, and Koganei stations not real-time ones.

At first a simple method was developed to evaluate phase connectivity from a phase structure function. A model was also proposed to estimate a phase-structure function at longer time periods from a short time period.

Finally, an available gap length was estimated using the model. Our results show that it is possible to estimate an available scan gap length by using a structure function at a time period of 10 s.

This suggests that it is possible to control scan length and gap length dynamically in order to achieve the best performance of D-VLBI observations.

These data is operationally used for the purpose of weather forecast and considered for our study. We evaluated atmospheric parameters equivalent zenith wet delay and linear horizontal delay gradients derived from slant path delays using KARAT.

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Bei Ihnen die komplizierte Auswahl