2008
39.
Sekido, Mamoru; Kondo, Tetsuro; Wagner, Jan; Hobiger, Thomas; Kokado, Kensuke; Takiguchi, Hiroshi; Koyama, Yasuhiro; Haas, Rüdiger; Ritakari, Jouko; Kurihara, Shinobu
Development of e-VLBI Technologies for Ultra-rapid UT1 Measurement Proceedings Article
In: NICT IVS Technical Development Center News, pp. 28-30, 2008.
@inproceedings{TDC08d,
title = {Development of e-VLBI Technologies for Ultra-rapid UT1 Measurement},
author = {Mamoru Sekido and Tetsuro Kondo and Jan Wagner and Thomas Hobiger and Kensuke Kokado and Hiroshi Takiguchi and Yasuhiro Koyama and Rüdiger Haas and Jouko Ritakari and Shinobu Kurihara},
url = {http://www2.nict.go.jp/w/w114/stsi/ivstdc/news_29/pdf/tdcnews_29.pdf},
year = {2008},
date = {2008-01-01},
booktitle = {NICT IVS Technical Development Center News},
number = {29},
pages = {28-30},
abstract = {Ultra-rapid UT1 measurements have been realized under the collaboration
between NICT, GSI(Japan), Onsala Observatory(Sweden),and Metsaehovi
Radio Observatory(Finland). This achievement was made by a combination
of software and hardware technologies with components of so called
e-VLBI. This paper describes the components, which contributed the
Ultra-rapid UT1 measurements.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Ultra-rapid UT1 measurements have been realized under the collaboration
between NICT, GSI(Japan), Onsala Observatory(Sweden),and Metsaehovi
Radio Observatory(Finland). This achievement was made by a combination
of software and hardware technologies with components of so called
e-VLBI. This paper describes the components, which contributed the
Ultra-rapid UT1 measurements.
between NICT, GSI(Japan), Onsala Observatory(Sweden),and Metsaehovi
Radio Observatory(Finland). This achievement was made by a combination
of software and hardware technologies with components of so called
e-VLBI. This paper describes the components, which contributed the
Ultra-rapid UT1 measurements.
38.
Hobiger, Thomas; Ichikawa, Ryuichi; Koyama, Yasuhiro; Kondo, Tetsuro
Real-time ray-tracing through numerical weather models for space geodesy Proceedings Article
In: NICT IVS Technical Development Center News, pp. 31-33, 2008.
@inproceedings{TDC08e,
title = {Real-time ray-tracing through numerical weather models for space
geodesy},
author = {Thomas Hobiger and Ryuichi Ichikawa and Yasuhiro Koyama and Tetsuro Kondo},
url = {http://www2.nict.go.jp/w/w114/stsi/ivstdc/news_29/pdf/tdcnews_29.pdf},
year = {2008},
date = {2008-01-01},
booktitle = {NICT IVS Technical Development Center News},
number = {29},
pages = {31-33},
abstract = {Numerical weather models have undergone an improvement of spatial
and temporal resolution in the recent years, which made their use
for space geodetic applications feasible. Ray-tracing through such
models permits the computation of total troposphere delays and ray-bending
angles. At the National Institute of Information and Communications
Technology (NICT) the so-called KAshima RAy-tracing Tools (KARAT)
have been developed which allow to obtain troposphere delay corrections
in real-time. Together with fine-mesh weather models from the Japanese
Meteorological Agency (JMA) huge parts of the East Asian region,
including Japan, Korea, Taiwan and East China, can be covered. Thus
a short overview about the capabilities and functions of KARAT will
be given and computation performance issues will be discussed. The
ray-traced total troposphere slant delays can be used as a correction
of space geodetic data on the observation level. Additionally, an
overview will be given about the upcoming on-line service, which
permits the reduction of troposphere delays from user-submitted data.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Numerical weather models have undergone an improvement of spatial
and temporal resolution in the recent years, which made their use
for space geodetic applications feasible. Ray-tracing through such
models permits the computation of total troposphere delays and ray-bending
angles. At the National Institute of Information and Communications
Technology (NICT) the so-called KAshima RAy-tracing Tools (KARAT)
have been developed which allow to obtain troposphere delay corrections
in real-time. Together with fine-mesh weather models from the Japanese
Meteorological Agency (JMA) huge parts of the East Asian region,
including Japan, Korea, Taiwan and East China, can be covered. Thus
a short overview about the capabilities and functions of KARAT will
be given and computation performance issues will be discussed. The
ray-traced total troposphere slant delays can be used as a correction
of space geodetic data on the observation level. Additionally, an
overview will be given about the upcoming on-line service, which
permits the reduction of troposphere delays from user-submitted data.
and temporal resolution in the recent years, which made their use
for space geodetic applications feasible. Ray-tracing through such
models permits the computation of total troposphere delays and ray-bending
angles. At the National Institute of Information and Communications
Technology (NICT) the so-called KAshima RAy-tracing Tools (KARAT)
have been developed which allow to obtain troposphere delay corrections
in real-time. Together with fine-mesh weather models from the Japanese
Meteorological Agency (JMA) huge parts of the East Asian region,
including Japan, Korea, Taiwan and East China, can be covered. Thus
a short overview about the capabilities and functions of KARAT will
be given and computation performance issues will be discussed. The
ray-traced total troposphere slant delays can be used as a correction
of space geodetic data on the observation level. Additionally, an
overview will be given about the upcoming on-line service, which
permits the reduction of troposphere delays from user-submitted data.
37.
Takiguchi, Hiroshi; Koyama, Yasuhiro; Ichikawa, Ryuichi; Gotoh, Tadahiro; Ishii, Atsutoshi; Hobiger, Thomas; Hosokawa, Mizuhiko
VLBI measurements for time and frequency transfer Proceedings Article
In: Proc. of the European Frequency and Time Forum 2008, 2008.
@inproceedings{EFTF08,
title = {VLBI measurements for time and frequency transfer},
author = {Hiroshi Takiguchi and Yasuhiro Koyama and Ryuichi Ichikawa and Tadahiro Gotoh and Atsutoshi Ishii and Thomas Hobiger and Mizuhiko Hosokawa},
year = {2008},
date = {2008-01-01},
booktitle = {Proc. of the European Frequency and Time Forum 2008},
number = {1},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2007
36.
Hobiger, Thomas; Ichikawa, Ryuichi; Koyama, Yasuhiro; Kondo, Tetsuro
Kashima Ray-Tracing Service (KARATS) -Fast ray-tracing through numerical weather models for real-time positioning applications in East Asia Proceedings Article
In: Proceedings of the 18th European VLBI for Geodesy and Astrometry Working Meeting, Geowissenschaftliche Mittteilungen, pp. 181–185, 2007.
@inproceedings{EVGA07a,
title = {Kashima Ray-Tracing Service (KARATS) -Fast ray-tracing through numerical
weather models for real-time positioning applications in East Asia},
author = {Thomas Hobiger and Ryuichi Ichikawa and Yasuhiro Koyama and Tetsuro Kondo},
url = {http://mars.hg.tuwien.ac.at/~evga/proceedings/All_papers.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {Proceedings of the 18th European VLBI for Geodesy and Astrometry
Working Meeting, Geowissenschaftliche Mittteilungen},
number = {79},
pages = {181–185},
abstract = {Numerical weather models (NWMs) have undergone a significant improvement
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Numerical weather models (NWMs) have undergone a significant improvement
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.
35.
Hobiger, Thomas; Ichikawa, Ryuichi; Koyama, Yasuhiro; Kondo, Tetsuro
Kashima Ray-Tracing Service (KARATS) - Fast ray-tracing through numerical weather models for real-time positioning applications Proceedings Article
In: NICT IVS Technical Development Center News, pp. 16–19, 2007.
@inproceedings{TDCnews07a,
title = {Kashima Ray-Tracing Service (KARATS) - Fast ray-tracing through
numerical weather models for real-time positioning applications},
author = {Thomas Hobiger and Ryuichi Ichikawa and Yasuhiro Koyama and Tetsuro Kondo},
url = {http://www2.nict.go.jp/w/w114/stsi/ivstdc/news_28/pdf/tdcnews_28.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {NICT IVS Technical Development Center News},
number = {28},
pages = {16–19},
abstract = {Numerical weather models (NWMs) have undergone a significant improvement
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Numerical weather models (NWMs) have undergone a significant improvement
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.
of accuracy and spatial resolution. Therefore such models can be
used to correct for the excess delay which is caused when signals
are propagation through the troposphere. The Kashima Ray-Tracing
Service (KARATS) is capable of reading, re-griding and ray-tracing
NWMs which cover East Asia countries including Japan, Korea, Taiwan
and parts of China and Russia. Optimized algorithms and the upcoming
multi-core technology permit real-time computation of troposphere
corrections. First tests have shown that KARATS is capable to remove
nearly all of the tropospheric delay and that precision and accuracy
of estimated station coordinates are improved significantly.
34.
Hobiger, Thomas; Kondo, Tetsuro; Koyama, Yasuhiro; Ichikawa, Ryuichi; Weber, Robert
Effect of the Earth's oblateness on the estimation of global vertical total electron content maps Journal Article
In: Geophys. Res. Lett., vol. 34, pp. L11113, 2007.
@article{GRL07,
title = {Effect of the Earth's oblateness on the estimation of global vertical
total electron content maps},
author = {Thomas Hobiger and Tetsuro Kondo and Yasuhiro Koyama and Ryuichi Ichikawa and Robert Weber},
doi = {doi:10.1029/2007GL029792},
year = {2007},
date = {2007-01-01},
journal = {Geophys. Res. Lett.},
volume = {34},
pages = {L11113},
abstract = {Global Navigation Satellite Systems like the Global Positioning System
and the Russian counterpart GLONASS permit the estimation of ionosphere
parameters in the form of vertical total electron content (vTEC)
values. 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.e due to a shift of the ionospheric pierce point)
and the indirect effect, caused by a change of the mapping function,
on global vTEC values using a single layer model of the ionosphere.
We show that the estimated global TEC maps change slightly by up
to +/-0.4 TECU when refined mathematical models are considered and
we discuss how differential code biases are affected by this change.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Global Navigation Satellite Systems like the Global Positioning System
and the Russian counterpart GLONASS permit the estimation of ionosphere
parameters in the form of vertical total electron content (vTEC)
values. 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.e due to a shift of the ionospheric pierce point)
and the indirect effect, caused by a change of the mapping function,
on global vTEC values using a single layer model of the ionosphere.
We show that the estimated global TEC maps change slightly by up
to +/-0.4 TECU when refined mathematical models are considered and
we discuss how differential code biases are affected by this change.
and the Russian counterpart GLONASS permit the estimation of ionosphere
parameters in the form of vertical total electron content (vTEC)
values. 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.e due to a shift of the ionospheric pierce point)
and the indirect effect, caused by a change of the mapping function,
on global vTEC values using a single layer model of the ionosphere.
We show that the estimated global TEC maps change slightly by up
to +/-0.4 TECU when refined mathematical models are considered and
we discuss how differential code biases are affected by this change.
33.
Hobiger, Thomas; Kondo, Tetsuro; Koyama, Yasuhiro; Takashima, Kazuhiro; Schuh, Harald
Using VLBI fringe-phase information from geodetic experiments for short-period ionospheric studies Journal Article
In: Journal of Geodesy, vol. 81, no. 6, pp. 389–401, 2007, (doi:10.1007/s00190-007-0142-4).
@article{JoG07,
title = {Using VLBI fringe-phase information from geodetic experiments for
short-period ionospheric studies},
author = {Thomas Hobiger and Tetsuro Kondo and Yasuhiro Koyama and Kazuhiro Takashima and Harald Schuh},
url = {http://www.springerlink.com/content/f42018r3r0rj0751},
year = {2007},
date = {2007-01-01},
journal = {Journal of Geodesy},
volume = {81},
number = {6},
pages = {389–401},
abstract = {The usage of Very Long Baseline Interferometry (VLBI) fringe-phase
information in geodetic VLBI is a new field of research, which can
be used for the detection of short-period (i.e., several minutes)
variations (scintillations) of the ionosphere. 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.},
note = {doi:10.1007/s00190-007-0142-4},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The usage of Very Long Baseline Interferometry (VLBI) fringe-phase
information in geodetic VLBI is a new field of research, which can
be used for the detection of short-period (i.e., several minutes)
variations (scintillations) of the ionosphere. 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.
information in geodetic VLBI is a new field of research, which can
be used for the detection of short-period (i.e., several minutes)
variations (scintillations) of the ionosphere. 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.
32.
Hobiger, Thomas; Koyama, Yasuhiro; Kondo, Tetsuro
MK3TOOLS & NetCDF - storing VLBI data in a machine independent array oriented dataformat Proceedings Article
In: Proceedings of the 18th European VLBI for Geodesy and Astrometry Working Meeting, Geowissenschaftliche Mittteilungen, pp. 194–195, 2007.
@inproceedings{EVGA07b,
title = {MK3TOOLS & NetCDF - storing VLBI data in a machine independent array
oriented dataformat},
author = {Thomas Hobiger and Yasuhiro Koyama and Tetsuro Kondo},
url = {http://mars.hg.tuwien.ac.at/~evga/proceedings/All_papers.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {Proceedings of the 18th European VLBI for Geodesy and Astrometry
Working Meeting, Geowissenschaftliche Mittteilungen},
number = {79},
pages = {194–195},
abstract = {In the beginning of 2002 the International VLBI Service (IVS) has
agreed to introduce a Platform-independent VLBI exchange format (PIVEX)
which permits the exchange of observational data and stimulates the
researchacross different analysis groups. Unfortunately PIVEX has
never been implemented and many analysis software packages are still
depending on prior processing (e.g. ambiguity resolution and computation
of ionosphere corrections) done by CALC/SOLVE. Thus MK3TOOLS which
handles MK3 databases without CALC/SOLVE being installed has been
developed. It uses the NetCDF format to store the data and since
interfaces exist for a variety of programming languages (FORTRAN,
C/C++, JAVA, Perl,Python) it can be easily incorporated in existing
and upcoming analysis software packages.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In the beginning of 2002 the International VLBI Service (IVS) has
agreed to introduce a Platform-independent VLBI exchange format (PIVEX)
which permits the exchange of observational data and stimulates the
researchacross different analysis groups. Unfortunately PIVEX has
never been implemented and many analysis software packages are still
depending on prior processing (e.g. ambiguity resolution and computation
of ionosphere corrections) done by CALC/SOLVE. Thus MK3TOOLS which
handles MK3 databases without CALC/SOLVE being installed has been
developed. It uses the NetCDF format to store the data and since
interfaces exist for a variety of programming languages (FORTRAN,
C/C++, JAVA, Perl,Python) it can be easily incorporated in existing
and upcoming analysis software packages.
agreed to introduce a Platform-independent VLBI exchange format (PIVEX)
which permits the exchange of observational data and stimulates the
researchacross different analysis groups. Unfortunately PIVEX has
never been implemented and many analysis software packages are still
depending on prior processing (e.g. ambiguity resolution and computation
of ionosphere corrections) done by CALC/SOLVE. Thus MK3TOOLS which
handles MK3 databases without CALC/SOLVE being installed has been
developed. It uses the NetCDF format to store the data and since
interfaces exist for a variety of programming languages (FORTRAN,
C/C++, JAVA, Perl,Python) it can be easily incorporated in existing
and upcoming analysis software packages.
31.
Ichikawa, Ryuichi; Hobiger, Thomas; Koyama, Yasuhiro; Kondo, Tetsuro
An Evaluation of Geodetic Position Error Simulated using the Fast Ray Tracing Algorithms through the JMA Mesoscale Numerical Weather Data Proceedings Article
In: NICT IVS Technical Development Center News, pp. 20–21, 2007.
@inproceedings{TDCnews07b,
title = {An Evaluation of Geodetic Position Error Simulated using the Fast
Ray Tracing Algorithms through the JMA Mesoscale Numerical Weather
Data},
author = {Ryuichi Ichikawa and Thomas Hobiger and Yasuhiro Koyama and Tetsuro Kondo},
url = {http://www2.nict.go.jp/w/w114/stsi/ivstdc/news_28/pdf/tdcnews_28.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {NICT IVS Technical Development Center News},
number = {28},
pages = {20–21},
abstract = {We simultaneously calculate atmospheric parameters (zenith total delay
and a gradient vector) and position errors estimated from atmospheric
slant path delays obtained by new ray tracing technique [Hobiger
et al., 2007] through the meso-scale numerical weather data with
10 km horizontal resolution. In this numerical calculation we find
that the large horizontal position errors up to 40 mm associated
with severe rain fall event.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
We simultaneously calculate atmospheric parameters (zenith total delay
and a gradient vector) and position errors estimated from atmospheric
slant path delays obtained by new ray tracing technique [Hobiger
et al., 2007] through the meso-scale numerical weather data with
10 km horizontal resolution. In this numerical calculation we find
that the large horizontal position errors up to 40 mm associated
with severe rain fall event.
and a gradient vector) and position errors estimated from atmospheric
slant path delays obtained by new ray tracing technique [Hobiger
et al., 2007] through the meso-scale numerical weather data with
10 km horizontal resolution. In this numerical calculation we find
that the large horizontal position errors up to 40 mm associated
with severe rain fall event.
30.
Ichikawa, Ryuichi; Sekido, Mamoru; Hobiger, Thomas; Kondo, Tetsuro; Koyama, Yasuhiro
Analysis Center at National Institute of Information and Communications Technology Proceedings Article
In: Behrend, D.; Baver, K. (Ed.): International VLBI Service for Geodesy and Astrometry 2006 Annual Report, pp. 216–219, 2007.
@inproceedings{IVSAR06b,
title = {Analysis Center at National Institute of Information and
Communications Technology},
author = {Ryuichi Ichikawa and Mamoru Sekido and Thomas Hobiger and Tetsuro Kondo and Yasuhiro Koyama},
editor = {D. Behrend and K. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2006/pdf/acnict.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2006 Annual
Report},
number = {NASA/TP-2007-214151},
pages = {216–219},
abstract = {This report summarizes the activities of the Analysis Center at National
Institute of Information and Communications Technology (NICT) for
the year 2006.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
This report summarizes the activities of the Analysis Center at National
Institute of Information and Communications Technology (NICT) for
the year 2006.
Institute of Information and Communications Technology (NICT) for
the year 2006.
29.
Schuh, Harald; Johannes, Boehm; Heinkelmann, Robert; Hobiger, Thomas; Cerveira, Paulo Jorge Mendes; Pany, Andrea; Tanir, Emine; Teke, Kamil; Todorova, Sonja; Wresnik, Joerg
Vienna IGG Special Analysis Center Annual Report 2006 Proceedings Article
In: Behrend, D.; Baver, K. (Ed.): International VLBI Service for Geodesy and Astrometry 2006 Annual Report, pp. 208–211, 2007.
@inproceedings{IVSAR06a,
title = {Vienna IGG Special Analysis Center Annual Report 2006},
author = {Harald Schuh and Boehm Johannes and Robert Heinkelmann and Thomas Hobiger and Paulo Jorge Mendes Cerveira and Andrea Pany and Emine Tanir and Kamil Teke and Sonja Todorova and Joerg Wresnik},
editor = {D. Behrend and K. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2006/pdf/acigg.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2006 Annual
Report},
number = {NASA/TP-2007-214151},
pages = {208–211},
abstract = {Among other studies in 2006, the Institute of Geodesy and Geophysics
(IGG) at the Vienna University of Technology has carried out Monte-Carlo
simulations to assist the development of a new geodetic VLBI system
(VLBI2010). These investigations are critical for the definition
of the observing strategy and network configuration, and it has been
shown that the troposphere is the limiting factor for the precision
and accuracy of the new system.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Among other studies in 2006, the Institute of Geodesy and Geophysics
(IGG) at the Vienna University of Technology has carried out Monte-Carlo
simulations to assist the development of a new geodetic VLBI system
(VLBI2010). These investigations are critical for the definition
of the observing strategy and network configuration, and it has been
shown that the troposphere is the limiting factor for the precision
and accuracy of the new system.
(IGG) at the Vienna University of Technology has carried out Monte-Carlo
simulations to assist the development of a new geodetic VLBI system
(VLBI2010). These investigations are critical for the definition
of the observing strategy and network configuration, and it has been
shown that the troposphere is the limiting factor for the precision
and accuracy of the new system.
28.
Takiguchi, Hiroshi; Hobiger, Thomas; Ishii, Atsutoshi; Ichikawa, Ryuichi; Koyama, Yasuhiro
Comparison with GPS time transfer and VLBI time transfer Proceedings Article
In: NICT IVS Technical Development Center News, pp. 20–21, 2007.
@inproceedings{TDCnews07c,
title = {Comparison with GPS time transfer and VLBI time transfer},
author = {Hiroshi Takiguchi and Thomas Hobiger and Atsutoshi Ishii and Ryuichi Ichikawa and Yasuhiro Koyama},
url = {http://www2.nict.go.jp/w/w114/stsi/ivstdc/news_28/pdf/tdcnews_28.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {NICT IVS Technical Development Center News},
number = {28},
pages = {20–21},
abstract = {To compare the results with Global Positioning System (GPS) Time Transfer
and Very Long Baseline Interferometry (VLBI) Time Transfer, we carried
out the geodetic VLBI experiments for four times. The averaged formal
error (1 sigma) of the clock offsets that were estimated every one
hour in the geodetic VLBI analysis procedure (CALC/SOLVE), was 33
picoseconds. Especially,in the case of using K5/VSSP32 system, the
averaged formal error was 29 picoseconds. The results of the VLBI
time transfer were very consistent with the results of the GPS time
transfer. The difference of both results was about +/-500 picoseconds.
In term of frequency stability, the Allan deviation showed that VLBI
time transfer is more stable than GPS time transfer between 2000
seconds to 60000 seconds (uncertainty of under 3x10-14 ).},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
To compare the results with Global Positioning System (GPS) Time Transfer
and Very Long Baseline Interferometry (VLBI) Time Transfer, we carried
out the geodetic VLBI experiments for four times. The averaged formal
error (1 sigma) of the clock offsets that were estimated every one
hour in the geodetic VLBI analysis procedure (CALC/SOLVE), was 33
picoseconds. Especially,in the case of using K5/VSSP32 system, the
averaged formal error was 29 picoseconds. The results of the VLBI
time transfer were very consistent with the results of the GPS time
transfer. The difference of both results was about +/-500 picoseconds.
In term of frequency stability, the Allan deviation showed that VLBI
time transfer is more stable than GPS time transfer between 2000
seconds to 60000 seconds (uncertainty of under 3x10-14 ).
and Very Long Baseline Interferometry (VLBI) Time Transfer, we carried
out the geodetic VLBI experiments for four times. The averaged formal
error (1 sigma) of the clock offsets that were estimated every one
hour in the geodetic VLBI analysis procedure (CALC/SOLVE), was 33
picoseconds. Especially,in the case of using K5/VSSP32 system, the
averaged formal error was 29 picoseconds. The results of the VLBI
time transfer were very consistent with the results of the GPS time
transfer. The difference of both results was about +/-500 picoseconds.
In term of frequency stability, the Allan deviation showed that VLBI
time transfer is more stable than GPS time transfer between 2000
seconds to 60000 seconds (uncertainty of under 3x10-14 ).
27.
Todorova, Sonya; Schuh, Harald; Hobiger, Thomas; Hernandez-Pajares, Manuel
Global models of the ionosphere obtained by integration of GNSS and satellite altimetry data Proceedings Article
In: Vermessung und Geoinformation (VGI), pp. 80–89, 2007.
@inproceedings{VGI07,
title = {Global models of the ionosphere obtained by integration of GNSS
and satellite altimetry data},
author = {Sonya Todorova and Harald Schuh and Thomas Hobiger and Manuel Hernandez-Pajares},
url = {http://www.ovg.at/uploads/media/VGI_2007-2_05_Todorova_Hobiger_Schuh_Hernandez-Pajares.pdf},
year = {2007},
date = {2007-01-01},
booktitle = {Vermessung und Geoinformation (VGI)},
volume = {92},
number = {2},
pages = {80–89},
abstract = {The high free-electron and ion density in the ionosphere disturbs
both the group and phase velocity of the signals of all space geodetic
techniques, operating in the microwave band. In first approximation
this delay is proportional to the so-called Slant Total Electron
Content (STEC) along the ray path and can be corrected only if the
measurements are carried out at two distinct frequencies. On the
other hand, this effect allows information to be gained about the
parameters of the ionosphere in terms of Total Electron Content (TEC)
values. The classical input data for the development of Global Ionosphere
Maps (GIM) of the total electron content is obtained from dual-frequency
Global Navigation Satellite System (GNSS) observations. However,
the GNSS stations are inhomogeneously distributed, with large gaps
particularly over the sea surface, which lowers the precision of
the GIM over these areas. On their part, dual-frequency satellite
altimetry missions such as Jason-1 provide information about the
ionosphere precisely above the sea surface. Due to the limited spread
of the measurements and some open questions related to their systematic
errors, the ionospheric data from satellite altimetry is used only
for cross-validation of the GNSS GIM so far. It can be anticipated
however, that some specifics of the ionosphere parameters derived
by satellite altimetry will partly balance the inhomogeneity of the
GNSS data. In this study we create two-hourly GIM from GNSS data
and additionally introduce satellite altimetry observations, which
help to compensate the insufficient GNSS coverage of the oceans.
Furthermore, this method allows the independent estimation of systematic
instrumental errors, affecting the two types of measurements. Thus,
besides the daily values of the Differential Code Biases (DCB) for
all GNSS satellites and receivers, also a constant daily bias for
the Jason-1 satellite is estimated and investigated.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The high free-electron and ion density in the ionosphere disturbs
both the group and phase velocity of the signals of all space geodetic
techniques, operating in the microwave band. In first approximation
this delay is proportional to the so-called Slant Total Electron
Content (STEC) along the ray path and can be corrected only if the
measurements are carried out at two distinct frequencies. On the
other hand, this effect allows information to be gained about the
parameters of the ionosphere in terms of Total Electron Content (TEC)
values. The classical input data for the development of Global Ionosphere
Maps (GIM) of the total electron content is obtained from dual-frequency
Global Navigation Satellite System (GNSS) observations. However,
the GNSS stations are inhomogeneously distributed, with large gaps
particularly over the sea surface, which lowers the precision of
the GIM over these areas. On their part, dual-frequency satellite
altimetry missions such as Jason-1 provide information about the
ionosphere precisely above the sea surface. Due to the limited spread
of the measurements and some open questions related to their systematic
errors, the ionospheric data from satellite altimetry is used only
for cross-validation of the GNSS GIM so far. It can be anticipated
however, that some specifics of the ionosphere parameters derived
by satellite altimetry will partly balance the inhomogeneity of the
GNSS data. In this study we create two-hourly GIM from GNSS data
and additionally introduce satellite altimetry observations, which
help to compensate the insufficient GNSS coverage of the oceans.
Furthermore, this method allows the independent estimation of systematic
instrumental errors, affecting the two types of measurements. Thus,
besides the daily values of the Differential Code Biases (DCB) for
all GNSS satellites and receivers, also a constant daily bias for
the Jason-1 satellite is estimated and investigated.
both the group and phase velocity of the signals of all space geodetic
techniques, operating in the microwave band. In first approximation
this delay is proportional to the so-called Slant Total Electron
Content (STEC) along the ray path and can be corrected only if the
measurements are carried out at two distinct frequencies. On the
other hand, this effect allows information to be gained about the
parameters of the ionosphere in terms of Total Electron Content (TEC)
values. The classical input data for the development of Global Ionosphere
Maps (GIM) of the total electron content is obtained from dual-frequency
Global Navigation Satellite System (GNSS) observations. However,
the GNSS stations are inhomogeneously distributed, with large gaps
particularly over the sea surface, which lowers the precision of
the GIM over these areas. On their part, dual-frequency satellite
altimetry missions such as Jason-1 provide information about the
ionosphere precisely above the sea surface. Due to the limited spread
of the measurements and some open questions related to their systematic
errors, the ionospheric data from satellite altimetry is used only
for cross-validation of the GNSS GIM so far. It can be anticipated
however, that some specifics of the ionosphere parameters derived
by satellite altimetry will partly balance the inhomogeneity of the
GNSS data. In this study we create two-hourly GIM from GNSS data
and additionally introduce satellite altimetry observations, which
help to compensate the insufficient GNSS coverage of the oceans.
Furthermore, this method allows the independent estimation of systematic
instrumental errors, affecting the two types of measurements. Thus,
besides the daily values of the Differential Code Biases (DCB) for
all GNSS satellites and receivers, also a constant daily bias for
the Jason-1 satellite is estimated and investigated.
2006
26.
Hobiger, Thomas; Kondo, Tetsuro; Schuh, Harald
VLBI as a Tool to Probe the Ionosphere Proceedings Article
In: Behrend, Dirk; Baver, Karen (Ed.): International VLBI Service for Geodesy and Astrometry 2006 General Meeting Proceedings, pp. 344–348, 2006.
@inproceedings{IVSmeet06a,
title = {VLBI as a Tool to Probe the Ionosphere},
author = {Thomas Hobiger and Tetsuro Kondo and Harald Schuh},
editor = {Dirk Behrend and Karen Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2006/pdf/hobiger1.pdf},
year = {2006},
date = {2006-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2006 General
Meeting Proceedings},
number = {NASA/CP-2006-214140},
pages = {344–348},
abstract = {By a method, developed within project VLBIonos at the IGG, Vienna
it is possible to estimate ionospheric parameters in terms of vertical
total electron content from VLBI data without any external information
(Hobiger et al., 2006). This paper deals with the results from this
approach and cross-validates them against GPS, satellite altimetry
data and measurements of solar flux. As geodetic VLBI observations
cover more than two complete solar cycles, longer than all other
space geodetic techniques using radio signals, the relation to space
weather indices on long time-scales can be shown. It can be stated
that the overall agreement between VLBI and GPS is within the formal
error of each technique and that both systems detect the same periods
of ionospheric variations.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
By a method, developed within project VLBIonos at the IGG, Vienna
it is possible to estimate ionospheric parameters in terms of vertical
total electron content from VLBI data without any external information
(Hobiger et al., 2006). This paper deals with the results from this
approach and cross-validates them against GPS, satellite altimetry
data and measurements of solar flux. As geodetic VLBI observations
cover more than two complete solar cycles, longer than all other
space geodetic techniques using radio signals, the relation to space
weather indices on long time-scales can be shown. It can be stated
that the overall agreement between VLBI and GPS is within the formal
error of each technique and that both systems detect the same periods
of ionospheric variations.
it is possible to estimate ionospheric parameters in terms of vertical
total electron content from VLBI data without any external information
(Hobiger et al., 2006). This paper deals with the results from this
approach and cross-validates them against GPS, satellite altimetry
data and measurements of solar flux. As geodetic VLBI observations
cover more than two complete solar cycles, longer than all other
space geodetic techniques using radio signals, the relation to space
weather indices on long time-scales can be shown. It can be stated
that the overall agreement between VLBI and GPS is within the formal
error of each technique and that both systems detect the same periods
of ionospheric variations.
25.
Hobiger, Thomas; Kondo, Tetsuro; Schuh, Harald
Very long baseline interferometry as a tool to probe the ionosphere Journal Article
In: Radio Science, vol. 41, no. 1, pp. RS1006, 2006, (doi:10.1029/2005RS003297).
@article{RadioSci06,
title = {Very long baseline interferometry as a tool to probe the ionosphere},
author = {Thomas Hobiger and Tetsuro Kondo and Harald Schuh},
url = {http://www.agu.org/pubs/crossref/2006.../2005RS003297.shtml},
year = {2006},
date = {2006-01-01},
journal = {Radio Science},
volume = {41},
number = {1},
pages = {RS1006},
abstract = {In geodetic very long baseline interferometry (VLBI), the observations
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. 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.},
note = {doi:10.1029/2005RS003297},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In geodetic very long baseline interferometry (VLBI), the observations
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. 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.
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. 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.
24.
Hobiger, Thomas; Kondo, Tetsuro; Takashima, Kazuhiro; Schuh, Harald
Detection of Short Period Ionosphere Variations from VLBI Fringe Phases Proceedings Article
In: Behrend, Dirk; Baver, Karen (Ed.): International VLBI Service for Geodesy and Astrometry 2006 General Meeting Proceedings, pp. 348–350, 2006.
@inproceedings{IVSmeet06b,
title = {Detection of Short Period Ionosphere Variations from VLBI
Fringe Phases},
author = {Thomas Hobiger and Tetsuro Kondo and Kazuhiro Takashima and Harald Schuh},
editor = {Dirk Behrend and Karen Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2006/pdf/hobiger2.pdf},
year = {2006},
date = {2006-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2006 General
Meeting Proceedings},
number = {NASA/CP-2006-214140},
pages = {348–350},
abstract = {The usage of fringe phase information from VLBI measurements is a
new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations) of the
ionosphere. A method for the extraction of such disturbances has
been developed and it is discussed how dispersive influences can
be separated from intra-scan delay variations. It is shown that a
short period variation can be detected very precisely, if the SNR
is high enough. Physical origins of such disturbances are discussed
and fields of application will be mentioned. This paper is an extended
abstract of the paper Hobiger et al. (2006)},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The usage of fringe phase information from VLBI measurements is a
new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations) of the
ionosphere. A method for the extraction of such disturbances has
been developed and it is discussed how dispersive influences can
be separated from intra-scan delay variations. It is shown that a
short period variation can be detected very precisely, if the SNR
is high enough. Physical origins of such disturbances are discussed
and fields of application will be mentioned. This paper is an extended
abstract of the paper Hobiger et al. (2006)
new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations) of the
ionosphere. A method for the extraction of such disturbances has
been developed and it is discussed how dispersive influences can
be separated from intra-scan delay variations. It is shown that a
short period variation can be detected very precisely, if the SNR
is high enough. Physical origins of such disturbances are discussed
and fields of application will be mentioned. This paper is an extended
abstract of the paper Hobiger et al. (2006)
23.
Krankowski, Andrzej; Hobiger, Thomas; Schuh, Harald; Kosek, W.; Popinski, W.
Wavelet Analysis of TEC Measurements Obtained Using Dual Frequency Space and Satellite Techniques Proceedings Article
In: Proc. of the Journees 2005, pp. 290–293, 2006.
@inproceedings{Jour06,
title = {Wavelet Analysis of TEC Measurements Obtained Using Dual
Frequency Space and Satellite Techniques},
author = {Andrzej Krankowski and Thomas Hobiger and Harald Schuh and W. Kosek and W. Popinski},
url = {http://syrte.obspm.fr/journees2005/s5_04_Krankowski.pdf},
year = {2006},
date = {2006-01-01},
booktitle = {Proc. of the Journees 2005},
pages = {290–293},
abstract = {An extensive database of Total Electron Content (TEC) measurements
has become available from both ground- and space-based observations.
Global Positioning System (GPS) and Very Long Baseline Interferometry
(VLBI) observations collected at the IGS (International GNSS Service)
and the IVS (International VLBI Service for Geodesy and Astrometry)
stations over Europe were used to obtain TEC data during the time
interval 1995 till 2003. In this paper, the wavelet analysis is used
to determine the wavelet time-frequency spectra of TEC data above
one European collocation station - Wettzell. The GPS and VLBI TEC
time series of quiet and disturbed ionospheric conditions, utilized
in this study, cover one solar cycle. A very good agreement between
semidiurnal, diurnal, semiannual, and annual oscillations of TEC
estimated using GPS and VLBI observations was obtained. The diurnal
and annual oscillations are the most energetic and clearly visible
ones especially during increasing and maximum solar activity.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
An extensive database of Total Electron Content (TEC) measurements
has become available from both ground- and space-based observations.
Global Positioning System (GPS) and Very Long Baseline Interferometry
(VLBI) observations collected at the IGS (International GNSS Service)
and the IVS (International VLBI Service for Geodesy and Astrometry)
stations over Europe were used to obtain TEC data during the time
interval 1995 till 2003. In this paper, the wavelet analysis is used
to determine the wavelet time-frequency spectra of TEC data above
one European collocation station - Wettzell. The GPS and VLBI TEC
time series of quiet and disturbed ionospheric conditions, utilized
in this study, cover one solar cycle. A very good agreement between
semidiurnal, diurnal, semiannual, and annual oscillations of TEC
estimated using GPS and VLBI observations was obtained. The diurnal
and annual oscillations are the most energetic and clearly visible
ones especially during increasing and maximum solar activity.
has become available from both ground- and space-based observations.
Global Positioning System (GPS) and Very Long Baseline Interferometry
(VLBI) observations collected at the IGS (International GNSS Service)
and the IVS (International VLBI Service for Geodesy and Astrometry)
stations over Europe were used to obtain TEC data during the time
interval 1995 till 2003. In this paper, the wavelet analysis is used
to determine the wavelet time-frequency spectra of TEC data above
one European collocation station - Wettzell. The GPS and VLBI TEC
time series of quiet and disturbed ionospheric conditions, utilized
in this study, cover one solar cycle. A very good agreement between
semidiurnal, diurnal, semiannual, and annual oscillations of TEC
estimated using GPS and VLBI observations was obtained. The diurnal
and annual oscillations are the most energetic and clearly visible
ones especially during increasing and maximum solar activity.
22.
Cerveira, Paulo Jorge Mendes; Hobiger, Thomas; Weber, Robert; Schuh, Harald
Spatial spectral inversion of SOPAC GPS data Journal Article
In: Proceeding of the IAG Scientific Assembly 2005, vol. 130, pp. 194 – 201, 2006.
@article{IAG06,
title = {Spatial spectral inversion of SOPAC GPS data},
author = {Paulo Jorge Mendes Cerveira and Thomas Hobiger and Robert Weber and Harald Schuh},
year = {2006},
date = {2006-01-01},
journal = {Proceeding of the IAG Scientific Assembly 2005},
volume = {130},
pages = {194 – 201},
publisher = {Springer},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
21.
Schuh, Harald; Johannes, Boehm; Heinkelmann, Robert; Hobiger, Thomas; Todorova, Sonja; Wresnik, Joerg
Vienna IGG Special Analysis Center Annual Report 2005 Proceedings Article
In: Behrend, D.; Baver, K. (Ed.): International VLBI Service for Geodesy and Astrometry 2005 Annual Report, pp. 245–248, 2006.
@inproceedings{IVSAR05,
title = {Vienna IGG Special Analysis Center Annual Report 2005},
author = {Harald Schuh and Boehm Johannes and Robert Heinkelmann and Thomas Hobiger and Sonja Todorova and Joerg Wresnik},
editor = {D. Behrend and K. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2005/pdf/acigg.pdf},
year = {2006},
date = {2006-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2005 Annual
Report},
number = {NASA/TP-2006-214136},
pages = {245–248},
abstract = {In 2005 the Institute of Geodesy and Geophysics (IGG) at the Vienna
University of Technology continued its investigations in atmospheric
research for geodetic VLBI: Among other topics, it was dealing with
the neutral atmosphere in terms of long time series of tropospheric
parameters and with the ionosphere in particular by determining ionospheric
parameters from VLBI observations. Furthermore, it started simulation
studies which are dedicated to the new VLBI2010 observing system.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In 2005 the Institute of Geodesy and Geophysics (IGG) at the Vienna
University of Technology continued its investigations in atmospheric
research for geodetic VLBI: Among other topics, it was dealing with
the neutral atmosphere in terms of long time series of tropospheric
parameters and with the ionosphere in particular by determining ionospheric
parameters from VLBI observations. Furthermore, it started simulation
studies which are dedicated to the new VLBI2010 observing system.
University of Technology continued its investigations in atmospheric
research for geodetic VLBI: Among other topics, it was dealing with
the neutral atmosphere in terms of long time series of tropospheric
parameters and with the ionosphere in particular by determining ionospheric
parameters from VLBI observations. Furthermore, it started simulation
studies which are dedicated to the new VLBI2010 observing system.
20.
Todorova, Sonja; Hobiger, Thomas; Schuh, Harald
Combination of GPS and satellite altimetry data for global ionosphere maps Proceedings Article
In: Proceedings of the International Scientific Conference SGEM 2006, June 12-16, 2006, Albena, Bulgaria, pp. 265–277, 2006.
@inproceedings{SGEM06,
title = {Combination of GPS and satellite altimetry data for global ionosphere
maps},
author = {Sonja Todorova and Thomas Hobiger and Harald Schuh},
year = {2006},
date = {2006-01-01},
booktitle = {Proceedings of the International Scientific Conference SGEM 2006,
June 12-16, 2006, Albena, Bulgaria},
volume = {2},
pages = {265–277},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2005
19.
Hawarey, Mosab; Hobiger, Thomas; Schuh, Harald
Effects of the 2nd order ionospheric terms on VLBI measurements Journal Article
In: Geophys. Res. Lett, vol. 32, no. 11, pp. L11304, 2005, (doi:10.1029/2005GL022729).
@article{GRL05,
title = {Effects of the 2nd order ionospheric terms on VLBI measurements},
author = {Mosab Hawarey and Thomas Hobiger and Harald Schuh},
url = {http://www.agu.org/pubs/crossref/2005.../2005GL022729.shtml},
year = {2005},
date = {2005-01-01},
journal = {Geophys. Res. Lett},
volume = {32},
number = {11},
pages = {L11304},
abstract = {Current VLBI software packages take into account ionospheric terms
of 1st order only. 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 400-km high ionospheric shell
are avoided here by using the IGRF and PIM models to calculate the
geomagnetic field vectors and electron densities at 100 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. Results of the VLBI
software OCCAM reveal a maximum difference between baseline lengths
with and without 2nd order ionospheric terms equivalent to 0.5 mm.
Thus, the effect might become visible in VLBI within a few years.},
note = {doi:10.1029/2005GL022729},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Current VLBI software packages take into account ionospheric terms
of 1st order only. 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 400-km high ionospheric shell
are avoided here by using the IGRF and PIM models to calculate the
geomagnetic field vectors and electron densities at 100 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. Results of the VLBI
software OCCAM reveal a maximum difference between baseline lengths
with and without 2nd order ionospheric terms equivalent to 0.5 mm.
Thus, the effect might become visible in VLBI within a few years.
of 1st order only. 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 400-km high ionospheric shell
are avoided here by using the IGRF and PIM models to calculate the
geomagnetic field vectors and electron densities at 100 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. Results of the VLBI
software OCCAM reveal a maximum difference between baseline lengths
with and without 2nd order ionospheric terms equivalent to 0.5 mm.
Thus, the effect might become visible in VLBI within a few years.
18.
Hobiger, Thomas
VLBI as a tool to probe the ionosphere PhD Thesis
Inst. of Geodesy and Geophysics, Vienna Univ. of Technology, 2005, ISSN: 1811-8380.
@phdthesis{phd05,
title = {VLBI as a tool to probe the ionosphere},
author = {Thomas Hobiger},
url = {http://aleph.ub.tuwien.ac.at/F/CBMVL7ADL37B93U3KFBFLTPN34UGNESM8AKK4CJLPXY45FLE63-00313?func=full-set-set&set_number=023237&set_entry=000008&format=999},
issn = {1811-8380},
year = {2005},
date = {2005-01-01},
volume = {75},
publisher = {Veroeffentlichung des Instituts fuer Geodaesie und Geophysik},
school = {Inst. of Geodesy and Geophysics, Vienna Univ. of Technology},
series = {Geowissenschaftliche Mitteilungen},
abstract = {Precise measurements with dual frequency instruments have a long tradition
in geodesy. Among several techniques Very Long Baseline Interferometry
(VLBI) started its routine observations already in the late 80ies
and has carried them out until today. The dual frequency receiving
systems, operating at X- and S-band, were designed to correct ionospheric
time delays within geodetic analysis. The potential for ionospheric
research of this correction was disregarded until the community around
the Global Position System (GPS) showed that parameters of the ionosphere
can be deduced from dual frequency satellite measurements. With this
thesis a method has been developed, which enables estimation of similar
parameters from dual frequency VLBI measurements without any external
information. Due to 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.
Within this thesis a method is presented, which is capable of estimating
ionospheric parameters, i.e. values of vertical total electron content,
from VLBI data. The obtained results are cross-validated against
GPS, satellite altimetry data and theoretical models of the ionosphere.
As VLBI observations cover more than two complete solar cycles, longer
than all other space geodetic techniques using radio signals, the
relation to space weather indices on long time-scales can be shown.
Generally it can be stated that the overall agreement between VLBI
and GPS is within the formal error of each technique and that both
systems detect the same periods of ionospheric variations. But only
VLBI is able to reveal long period signals like the solar cycle,
since it covers a sufficiently long time-span. Apart from explanations
for small biases among the techniques also deficiencies of theoretical
models are discussed. Instrumental biases, a by-product of ionospheric
parameter estimation, demonstrate how receiving systems evolved with
the time, as instrumental changes are absorbed in this parameter.
The usage of (fringe) phase information from VLBI measurements is
a new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations). A method
for the extraction of such disturbances is discussed and by an example
it is shown that such a short period variation can be detected very
precisely. Therefore VLBI can be used to detect both, long-term trends
and short period variations of the ionosphere and thus it can contribute
to ionospheric research as a new independent technique.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Precise measurements with dual frequency instruments have a long tradition
in geodesy. Among several techniques Very Long Baseline Interferometry
(VLBI) started its routine observations already in the late 80ies
and has carried them out until today. The dual frequency receiving
systems, operating at X- and S-band, were designed to correct ionospheric
time delays within geodetic analysis. The potential for ionospheric
research of this correction was disregarded until the community around
the Global Position System (GPS) showed that parameters of the ionosphere
can be deduced from dual frequency satellite measurements. With this
thesis a method has been developed, which enables estimation of similar
parameters from dual frequency VLBI measurements without any external
information. Due to 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.
Within this thesis a method is presented, which is capable of estimating
ionospheric parameters, i.e. values of vertical total electron content,
from VLBI data. The obtained results are cross-validated against
GPS, satellite altimetry data and theoretical models of the ionosphere.
As VLBI observations cover more than two complete solar cycles, longer
than all other space geodetic techniques using radio signals, the
relation to space weather indices on long time-scales can be shown.
Generally it can be stated that the overall agreement between VLBI
and GPS is within the formal error of each technique and that both
systems detect the same periods of ionospheric variations. But only
VLBI is able to reveal long period signals like the solar cycle,
since it covers a sufficiently long time-span. Apart from explanations
for small biases among the techniques also deficiencies of theoretical
models are discussed. Instrumental biases, a by-product of ionospheric
parameter estimation, demonstrate how receiving systems evolved with
the time, as instrumental changes are absorbed in this parameter.
The usage of (fringe) phase information from VLBI measurements is
a new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations). A method
for the extraction of such disturbances is discussed and by an example
it is shown that such a short period variation can be detected very
precisely. Therefore VLBI can be used to detect both, long-term trends
and short period variations of the ionosphere and thus it can contribute
to ionospheric research as a new independent technique.
in geodesy. Among several techniques Very Long Baseline Interferometry
(VLBI) started its routine observations already in the late 80ies
and has carried them out until today. The dual frequency receiving
systems, operating at X- and S-band, were designed to correct ionospheric
time delays within geodetic analysis. The potential for ionospheric
research of this correction was disregarded until the community around
the Global Position System (GPS) showed that parameters of the ionosphere
can be deduced from dual frequency satellite measurements. With this
thesis a method has been developed, which enables estimation of similar
parameters from dual frequency VLBI measurements without any external
information. Due to 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.
Within this thesis a method is presented, which is capable of estimating
ionospheric parameters, i.e. values of vertical total electron content,
from VLBI data. The obtained results are cross-validated against
GPS, satellite altimetry data and theoretical models of the ionosphere.
As VLBI observations cover more than two complete solar cycles, longer
than all other space geodetic techniques using radio signals, the
relation to space weather indices on long time-scales can be shown.
Generally it can be stated that the overall agreement between VLBI
and GPS is within the formal error of each technique and that both
systems detect the same periods of ionospheric variations. But only
VLBI is able to reveal long period signals like the solar cycle,
since it covers a sufficiently long time-span. Apart from explanations
for small biases among the techniques also deficiencies of theoretical
models are discussed. Instrumental biases, a by-product of ionospheric
parameter estimation, demonstrate how receiving systems evolved with
the time, as instrumental changes are absorbed in this parameter.
The usage of (fringe) phase information from VLBI measurements is
a new and challenging field of research, which can be utilized for
the detection of short period variations (scintillations). A method
for the extraction of such disturbances is discussed and by an example
it is shown that such a short period variation can be detected very
precisely. Therefore VLBI can be used to detect both, long-term trends
and short period variations of the ionosphere and thus it can contribute
to ionospheric research as a new independent technique.
17.
Hobiger, Thomas; Boehm, Johannes; Schuh, Harald
VLBIONOS - Probing the ionosphere by means of very long baseline interferometry Journal Article
In: A Window on the Future of Geodesy, Proceedings of the IAG General Assembly, Sapporo, Japan, June 30 - July 11, 2003, vol. 128, pp. 131 – 136, 2005.
@article{IAG05,
title = {VLBIONOS - Probing the ionosphere by means of very long baseline
interferometry},
author = {Thomas Hobiger and Johannes Boehm and Harald Schuh},
editor = {F. Sanso},
year = {2005},
date = {2005-01-01},
journal = {A Window on the Future of Geodesy, Proceedings of the IAG General
Assembly, Sapporo, Japan, June 30 - July 11, 2003},
volume = {128},
pages = {131 – 136},
publisher = {Springer},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
16.
Hobiger, Thomas; Kondo, Tetsuro
An FX software correlator based on Matlab Proceedings Article
In: Vennebusch, M.; Nothnagel, A. (Ed.): Proceedings of the 17th Working Meeting on European VLBI for Geodesy and Astrometry, pp. 34–38, 2005.
@inproceedings{EURVLBI05b,
title = {An FX software correlator based on Matlab},
author = {Thomas Hobiger and Tetsuro Kondo},
editor = {M. Vennebusch and A. Nothnagel},
url = {http://www.evga.org/Documents/proceedings17wm.pdf},
year = {2005},
date = {2005-01-01},
booktitle = {Proceedings of the 17th Working Meeting on European VLBI for Geodesy
and Astrometry},
pages = {34–38},
abstract = {Normally data obtained by very long baseline interferometry (VLBI)
are correlated by designated processors containing wired logic components.
Additionally, several software correlators, which are able to do
the same tasks, were designed in the last years. These software systems
are more flexible and can be adopted easier for special tasks than
hard-wired correlators. Usually such systems are coded in Assembler,
Fortran or C/C++ in order to gain maximum speed. We have chosen Matlab
6.5, a commercial mathematical software package, to implement an
FX correlator including single band delay search. Functionality is
similar to IP-VLBI(K5/VSSP) software correlator, developed at Kashima
Space Research Center, NICT, and other data formats (Mark5) can be
analyzed using conversion tools. The software correlator presented
here is not able to provide high data throughput but development
and debugging times were much less than with other programming languages.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Normally data obtained by very long baseline interferometry (VLBI)
are correlated by designated processors containing wired logic components.
Additionally, several software correlators, which are able to do
the same tasks, were designed in the last years. These software systems
are more flexible and can be adopted easier for special tasks than
hard-wired correlators. Usually such systems are coded in Assembler,
Fortran or C/C++ in order to gain maximum speed. We have chosen Matlab
6.5, a commercial mathematical software package, to implement an
FX correlator including single band delay search. Functionality is
similar to IP-VLBI(K5/VSSP) software correlator, developed at Kashima
Space Research Center, NICT, and other data formats (Mark5) can be
analyzed using conversion tools. The software correlator presented
here is not able to provide high data throughput but development
and debugging times were much less than with other programming languages.
are correlated by designated processors containing wired logic components.
Additionally, several software correlators, which are able to do
the same tasks, were designed in the last years. These software systems
are more flexible and can be adopted easier for special tasks than
hard-wired correlators. Usually such systems are coded in Assembler,
Fortran or C/C++ in order to gain maximum speed. We have chosen Matlab
6.5, a commercial mathematical software package, to implement an
FX correlator including single band delay search. Functionality is
similar to IP-VLBI(K5/VSSP) software correlator, developed at Kashima
Space Research Center, NICT, and other data formats (Mark5) can be
analyzed using conversion tools. The software correlator presented
here is not able to provide high data throughput but development
and debugging times were much less than with other programming languages.
15.
Hobiger, Thomas; Kondo, Tetsuro; Schuh, Harald
Estimation of absolute TEC values by VLBI Proceedings Article
In: Vennebusch, M.; Nothnagel, A. (Ed.): Proceedings of the 17th Working Meeting on European VLBI for Geodesy and Astrometry, pp. 102–106, 2005.
@inproceedings{EURVLBI05a,
title = {Estimation of absolute TEC values by VLBI},
author = {Thomas Hobiger and Tetsuro Kondo and Harald Schuh},
editor = {M. Vennebusch and A. Nothnagel},
url = {http://www.evga.org/Documents/proceedings17wm.pdf},
year = {2005},
date = {2005-01-01},
booktitle = {Proceedings of the 17th Working Meeting on European VLBI for Geodesy
and Astrometry},
pages = {102–106},
abstract = {Geodetic VLBI observations are carried out at two distinct frequencies
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behavior of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point what allows
to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
Instrumental offsets can be separated from the ionospheric parameters
by a least-squares fit. Additional parameters of a model, which relates
TEC values measured at the intersection point of the ray path with
the infinitely thin ionospheric layer to vertical TEC values above
the station, are estimated. The results agree well with other techniques
like GPS, what will be shown, too.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Geodetic VLBI observations are carried out at two distinct frequencies
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behavior of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point what allows
to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
Instrumental offsets can be separated from the ionospheric parameters
by a least-squares fit. Additional parameters of a model, which relates
TEC values measured at the intersection point of the ray path with
the infinitely thin ionospheric layer to vertical TEC values above
the station, are estimated. The results agree well with other techniques
like GPS, what will be shown, too.
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behavior of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point what allows
to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
Instrumental offsets can be separated from the ionospheric parameters
by a least-squares fit. Additional parameters of a model, which relates
TEC values measured at the intersection point of the ray path with
the infinitely thin ionospheric layer to vertical TEC values above
the station, are estimated. The results agree well with other techniques
like GPS, what will be shown, too.
14.
Ichikawa, Ryuichi; Sekido, Mamuro; Takeuchi, Hiroshi; Koyama, Yasuhiro; Hobiger, Thomas; Kondo, Tetsuro
Analysis Center at National Institute of Information and Communications Technology Proceedings Article
In: Behrend, D.; Baver, K. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 Annual Report, pp. 231–234, 2005.
@inproceedings{IVSAR04b,
title = {Analysis Center at National Institute of Information and
Communications Technology},
author = {Ryuichi Ichikawa and Mamuro Sekido and Hiroshi Takeuchi and Yasuhiro Koyama and Thomas Hobiger and Tetsuro Kondo},
editor = {D. Behrend and K. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2004/pdf/acnict.pdf},
year = {2005},
date = {2005-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 Annual
Report},
number = {NASA/TP-2005-212772},
pages = {231–234},
abstract = {This report summarizes the activities of the Analysis Center at National
Institute of Information and Communications Technology (NICT, former
CRL) for the year 2004. By using the state-of-art e-VLBI systems,
we performed the international EOP session between Westford and Kashima,
differential VLBI measurements for the precise tracking the spacecraft
HAYABUSA and geodetic experiments. In particular, we achieved the
most rapid estimation of UT1-UTC with a latency of four and half
hours. In addition, we performed ionospheric studies, the development
of automatic GPS data processing system, and satellite communication
experiments.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
This report summarizes the activities of the Analysis Center at National
Institute of Information and Communications Technology (NICT, former
CRL) for the year 2004. By using the state-of-art e-VLBI systems,
we performed the international EOP session between Westford and Kashima,
differential VLBI measurements for the precise tracking the spacecraft
HAYABUSA and geodetic experiments. In particular, we achieved the
most rapid estimation of UT1-UTC with a latency of four and half
hours. In addition, we performed ionospheric studies, the development
of automatic GPS data processing system, and satellite communication
experiments.
Institute of Information and Communications Technology (NICT, former
CRL) for the year 2004. By using the state-of-art e-VLBI systems,
we performed the international EOP session between Westford and Kashima,
differential VLBI measurements for the precise tracking the spacecraft
HAYABUSA and geodetic experiments. In particular, we achieved the
most rapid estimation of UT1-UTC with a latency of four and half
hours. In addition, we performed ionospheric studies, the development
of automatic GPS data processing system, and satellite communication
experiments.
13.
Schuh, Harald; Johannes, Boehm; Heinkelmann, Robert; Hobiger, Thomas; Todorova, Sonja
Vienna IGG Special Analysis Center Annual Report 2004 Proceedings Article
In: Behrend, D.; Baver, K. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 Annual Report, pp. 221–224, 2005.
@inproceedings{IVSAR04a,
title = {Vienna IGG Special Analysis Center Annual Report 2004},
author = {Harald Schuh and Boehm Johannes and Robert Heinkelmann and Thomas Hobiger and Sonja Todorova},
editor = {D. Behrend and K. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2004/pdf/acigg.pdf},
year = {2005},
date = {2005-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 Annual
Report},
number = {NASA/TP-2005-212772},
pages = {221–224},
abstract = {In 2004 the Institute of Geodesy and Geophysics (IGG) at the Vienna
University of Technology has continued its investigations in atmospheric
research for geodetic VLBI. Among other items, it started the comparison
and combination of long time series of tropospheric parameters within
the IVS (``VLBI for climate studies''). So far, six analysis centers
(ACs) have agreed to take part (four ACs already submitted). This
will allow a robust combination of the tropospheric parameters and
a reliable determination of trends and seasonal signals in the time
series.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In 2004 the Institute of Geodesy and Geophysics (IGG) at the Vienna
University of Technology has continued its investigations in atmospheric
research for geodetic VLBI. Among other items, it started the comparison
and combination of long time series of tropospheric parameters within
the IVS (``VLBI for climate studies''). So far, six analysis centers
(ACs) have agreed to take part (four ACs already submitted). This
will allow a robust combination of the tropospheric parameters and
a reliable determination of trends and seasonal signals in the time
series.
University of Technology has continued its investigations in atmospheric
research for geodetic VLBI. Among other items, it started the comparison
and combination of long time series of tropospheric parameters within
the IVS (``VLBI for climate studies''). So far, six analysis centers
(ACs) have agreed to take part (four ACs already submitted). This
will allow a robust combination of the tropospheric parameters and
a reliable determination of trends and seasonal signals in the time
series.
12.
Todorova, Sonja; Hobiger, Thomas; Weber, Robert; Schuh, Harald
Using GPS for determination of the ionosphere Proceedings Article
In: Proceedings of the International Scientific Conference SGEM 2005, June 13-17, 2005, Albena, Bulgaria, pp. 605–613, 2005.
@inproceedings{SGEM05,
title = {Using GPS for determination of the ionosphere},
author = {Sonja Todorova and Thomas Hobiger and Robert Weber and Harald Schuh},
year = {2005},
date = {2005-01-01},
booktitle = {Proceedings of the International Scientific Conference SGEM 2005,
June 13-17, 2005, Albena, Bulgaria},
pages = {605–613},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2004
11.
Hobiger, Thomas; Schuh, Harald
Modelling Vertical Total Electron Content from VLBI Observations Proceedings Article
In: Vandenberg, Nancy R.; Baver, Karen D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings, pp. 306–310, 2004.
@inproceedings{IVSmeet04a,
title = {Modelling Vertical Total Electron Content from VLBI Observations},
author = {Thomas Hobiger and Harald Schuh},
editor = {Nancy R. Vandenberg and Karen D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2004/pdf/hobiger2.pdf},
year = {2004},
date = {2004-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 General
Meeting Proceedings},
number = {NASA/CP-2004-212255},
pages = {306–310},
abstract = {The vertical total electron content (VTEC) can be understood as the
sum of electrons in a column ranging in zenith direction from the
ground through the ionosphere with a footprint size of one square
meter. Although VLBI is a differential technique it is possible to
derive absolute TEC values for each station from VLBI observations
as shown in prior papers and presentations. At the Institute of Geodesy
and Geophysics, Vienna, investigations of the functional and stochastical
model have been made. An approach dealing with trigonometric functions
that allows direct conclusions on amplitudes and phases of the sub-daily
periods is presented. Other strategies using piece-wise linear functions
and an extended piece-wise linear approach with adaptive interval
widths are shown, too. The usage of kernel functions, in this case
of Gaussian type, as a very general approach for modelling the ionosphere,
is illustrated. The weights of a delay observable used for the stochastical
model should also consider the zenith distance on each station and
a corresponding weighting function is applied.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The vertical total electron content (VTEC) can be understood as the
sum of electrons in a column ranging in zenith direction from the
ground through the ionosphere with a footprint size of one square
meter. Although VLBI is a differential technique it is possible to
derive absolute TEC values for each station from VLBI observations
as shown in prior papers and presentations. At the Institute of Geodesy
and Geophysics, Vienna, investigations of the functional and stochastical
model have been made. An approach dealing with trigonometric functions
that allows direct conclusions on amplitudes and phases of the sub-daily
periods is presented. Other strategies using piece-wise linear functions
and an extended piece-wise linear approach with adaptive interval
widths are shown, too. The usage of kernel functions, in this case
of Gaussian type, as a very general approach for modelling the ionosphere,
is illustrated. The weights of a delay observable used for the stochastical
model should also consider the zenith distance on each station and
a corresponding weighting function is applied.
sum of electrons in a column ranging in zenith direction from the
ground through the ionosphere with a footprint size of one square
meter. Although VLBI is a differential technique it is possible to
derive absolute TEC values for each station from VLBI observations
as shown in prior papers and presentations. At the Institute of Geodesy
and Geophysics, Vienna, investigations of the functional and stochastical
model have been made. An approach dealing with trigonometric functions
that allows direct conclusions on amplitudes and phases of the sub-daily
periods is presented. Other strategies using piece-wise linear functions
and an extended piece-wise linear approach with adaptive interval
widths are shown, too. The usage of kernel functions, in this case
of Gaussian type, as a very general approach for modelling the ionosphere,
is illustrated. The weights of a delay observable used for the stochastical
model should also consider the zenith distance on each station and
a corresponding weighting function is applied.
10.
Hobiger, Thomas; Schuh, Harald
How VLBI Contributes to Ionospheric Research Proceedings Article
In: Vandenberg, Nancy R.; Baver, Karen D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings, pp. 437–441, 2004.
@inproceedings{IVSmeet04b,
title = {How VLBI Contributes to Ionospheric Research},
author = {Thomas Hobiger and Harald Schuh},
editor = {Nancy R. Vandenberg and Karen D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2004/pdf/hobiger3.pdf},
year = {2004},
date = {2004-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 General
Meeting Proceedings},
number = {NASA/CP-2004-212255},
pages = {437–441},
abstract = {Geodetic VLBI observations are carried out at two distinct frequencies
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behaviour of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point which allows
us to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
If horizontal gradients in the ionosphere above the stations are
neglected we are able to separate the instrumental offsets from the
ionospheric parameters by a least-squares fit. A weakness of this
approach is the assumption that the TEC values are assigned to the
station coordinates but not to the geographical coordinates of the
intersection point of the ray path and the infinitely thin ionospheric
layer. Nevertheless, the results agree well with results of other
techniques like GPS on short and long time scales.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Geodetic VLBI observations are carried out at two distinct frequencies
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behaviour of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point which allows
us to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
If horizontal gradients in the ionosphere above the stations are
neglected we are able to separate the instrumental offsets from the
ionospheric parameters by a least-squares fit. A weakness of this
approach is the assumption that the TEC values are assigned to the
station coordinates but not to the geographical coordinates of the
intersection point of the ray path and the infinitely thin ionospheric
layer. Nevertheless, the results agree well with results of other
techniques like GPS on short and long time scales.
in order to determine ionospheric delay corrections. Each ionospheric
delay corresponds to the total electron content (TEC) along the ray
path through the ionosphere. Because VLBI is a differential technique
the observed ionospheric delays represent the differences of the
behaviour of the propagation media above each two stations. Additionally,
there is a constant instrumental delay offset per baseline that contributes
to the observed ionospheric delay. This instrumental offset is independent
of azimuth and elevation in which the antennas point which allows
us to separate it from the variable ionospheric parameters for each
station which can be represented by different functional approaches.
If horizontal gradients in the ionosphere above the stations are
neglected we are able to separate the instrumental offsets from the
ionospheric parameters by a least-squares fit. A weakness of this
approach is the assumption that the TEC values are assigned to the
station coordinates but not to the geographical coordinates of the
intersection point of the ray path and the infinitely thin ionospheric
layer. Nevertheless, the results agree well with results of other
techniques like GPS on short and long time scales.
9.
Hobiger, Thomas; Todorova, Sonya; Schuh, Harald
Ionospheric Parameters Obtained by Different Space Geodetic Techniques during CONT02 Proceedings Article
In: Vandenberg, Nancy R.; Baver, Karen D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings, pp. 442–446, 2004.
@inproceedings{IVSmeet04c,
title = {Ionospheric Parameters Obtained by Different Space Geodetic
Techniques during CONT02},
author = {Thomas Hobiger and Sonya Todorova and Harald Schuh},
editor = {Nancy R. Vandenberg and Karen D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2004/pdf/hobiger1.pdf},
year = {2004},
date = {2004-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 General
Meeting Proceedings},
number = {NASA/CP-2004-212255},
pages = {442–446},
abstract = {The goal of the CONT02 campaign in October 2002 was the acquisition
of the best possible VLBI data to demonstrate the high accuracy of
which VLBI is capable. The campaign provides the chance to study
the ionosphere continously over a period of more than two weeks by
means of VLBI. Vertical total electron content (VTEC) values above
the contributing stations were determined. By comparison with results
from other techniques, like GPS or satellite altimetry, systematic
differences could be detected of which the reasons are still unclear.
Anyway, the histograms of the differences show that generally the
agreement is very good between the parameters derived by VLBI and
the results from other space geodetic techniques. This is also confirmed
by Fourier and wavelet analyses which reveal variations with the
same periods (diurnal, semi-diurnal and quarter-diurnal) in GPS and
VLBI time series.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The goal of the CONT02 campaign in October 2002 was the acquisition
of the best possible VLBI data to demonstrate the high accuracy of
which VLBI is capable. The campaign provides the chance to study
the ionosphere continously over a period of more than two weeks by
means of VLBI. Vertical total electron content (VTEC) values above
the contributing stations were determined. By comparison with results
from other techniques, like GPS or satellite altimetry, systematic
differences could be detected of which the reasons are still unclear.
Anyway, the histograms of the differences show that generally the
agreement is very good between the parameters derived by VLBI and
the results from other space geodetic techniques. This is also confirmed
by Fourier and wavelet analyses which reveal variations with the
same periods (diurnal, semi-diurnal and quarter-diurnal) in GPS and
VLBI time series.
of the best possible VLBI data to demonstrate the high accuracy of
which VLBI is capable. The campaign provides the chance to study
the ionosphere continously over a period of more than two weeks by
means of VLBI. Vertical total electron content (VTEC) values above
the contributing stations were determined. By comparison with results
from other techniques, like GPS or satellite altimetry, systematic
differences could be detected of which the reasons are still unclear.
Anyway, the histograms of the differences show that generally the
agreement is very good between the parameters derived by VLBI and
the results from other space geodetic techniques. This is also confirmed
by Fourier and wavelet analyses which reveal variations with the
same periods (diurnal, semi-diurnal and quarter-diurnal) in GPS and
VLBI time series.
8.
Schuh, Harald; Johannes, Boehm; Hobiger, Thomas
Vienna IGG Special Analysis Center Annual Report 2003 Proceedings Article
In: Vandenberg, N. R.; Baver, K. D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 Annual Report, pp. 197–200, 2004.
@inproceedings{IVSAR03,
title = {Vienna IGG Special Analysis Center Annual Report 2003},
author = {Harald Schuh and Boehm Johannes and Thomas Hobiger},
editor = {N. R. Vandenberg and K. D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2003/pdf/acigg.pdf},
year = {2004},
date = {2004-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 Annual
Report},
number = {NASA/TP-2004-212254},
pages = {197–200},
abstract = {Since July 2003 the combined tropospheric parameters determined at
IGG (Schuh and Boehm, 2003) are regular IVS products provided by
the IVS Data Centers one month after the availability of each new
session database. Additionally, a forthcoming project within IVS-TROP
has been initialized that is dealing with the combination of long
time series of tropospheric parameters derived from VLBI for climate
studies. The IGG has continued its research on the determination
of ionospheric parameters from VLBI data.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Since July 2003 the combined tropospheric parameters determined at
IGG (Schuh and Boehm, 2003) are regular IVS products provided by
the IVS Data Centers one month after the availability of each new
session database. Additionally, a forthcoming project within IVS-TROP
has been initialized that is dealing with the combination of long
time series of tropospheric parameters derived from VLBI for climate
studies. The IGG has continued its research on the determination
of ionospheric parameters from VLBI data.
IGG (Schuh and Boehm, 2003) are regular IVS products provided by
the IVS Data Centers one month after the availability of each new
session database. Additionally, a forthcoming project within IVS-TROP
has been initialized that is dealing with the combination of long
time series of tropospheric parameters derived from VLBI for climate
studies. The IGG has continued its research on the determination
of ionospheric parameters from VLBI data.
7.
Winkler, Wolfgang; Bogensberger, Boris; Karel, Wilfried; Kistenich, Michael; Pacher, Gerold; Pany, Andrea; Roncat, Andreas; Summer, Gerhard; Boehm, Johannes; Hobiger, Thomas; Weber, Robert; Schuh, Harald
VIEPROJ1 - A Students' VLBI Project Proceedings Article
In: Vandenberg, Nancy R.; Baver, Karen D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings, pp. 105–108, 2004.
@inproceedings{IVSmeet04d,
title = {VIEPROJ1 - A Students' VLBI Project},
author = {Wolfgang Winkler and Boris Bogensberger and Wilfried Karel and Michael Kistenich and Gerold Pacher and Andrea Pany and Andreas Roncat and Gerhard Summer and Johannes Boehm and Thomas Hobiger and Robert Weber and Harald Schuh},
editor = {Nancy R. Vandenberg and Karen D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/general-meeting/2004/pdf/winkler1.pdf},
year = {2004},
date = {2004-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 General
Meeting Proceedings},
number = {NASA/CP-2004-212255},
pages = {105–108},
abstract = {The VLBI project VIEPROJ1 was planned and executed involving university
students doing the main work in every step. It was part of the lecture
(diploma course) ``Auswertung geodaetischer Weltraumverfahren'' (space
geodetic techniques), within the curriculum of Vermessung und Geoinformation
(geodesy and geoinformation) at the Vienna University of Technology.
The lecture was held by Prof. Harald Schuh and Prof. Robert Weber.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The VLBI project VIEPROJ1 was planned and executed involving university
students doing the main work in every step. It was part of the lecture
(diploma course) ``Auswertung geodaetischer Weltraumverfahren'' (space
geodetic techniques), within the curriculum of Vermessung und Geoinformation
(geodesy and geoinformation) at the Vienna University of Technology.
The lecture was held by Prof. Harald Schuh and Prof. Robert Weber.
students doing the main work in every step. It was part of the lecture
(diploma course) ``Auswertung geodaetischer Weltraumverfahren'' (space
geodetic techniques), within the curriculum of Vermessung und Geoinformation
(geodesy and geoinformation) at the Vienna University of Technology.
The lecture was held by Prof. Harald Schuh and Prof. Robert Weber.
2003
6.
Hobiger, Thomas; Boehm, Johannes; Schuh, Harald
VLBIONOS - Probing the ionosphere by means of very long baseline interferometry Proceedings Article
In: Oesterreichische Zeitschrift fuer Vermessung & Geoinformation (VGI), 2003.
@inproceedings{VGI03,
title = {VLBIONOS - Probing the ionosphere by means of very long baseline
interferometry},
author = {Thomas Hobiger and Johannes Boehm and Harald Schuh},
year = {2003},
date = {2003-01-01},
booktitle = {Oesterreichische Zeitschrift fuer Vermessung & Geoinformation (VGI)},
number = {1/2003},
abstract = {In geodetic VLBI the observations are performed at two distinct frequencies
(2.3 and 8.4 GHz) in order to determine ionospheric delay corrections.
This allows to gain information from VLBI observables about the sum
of electrons (total electron content - TEC) along the ray path through
the ionosphere. Due to the fact that VLBI is a differential technique
only the differences in the behavior of the propagation media over
the stations determine the leading signs and the absolute values
of the observed ionospheric delays. However, there is an instrumental
delay offset per baseline that shifts the measurements by a constant
value. This offset is thought to be independent of the azimuth and
elevation in which the antennas point what allows to separate the
ionospheric parameters for each station from the ionospheric offsets
per baseline in a least-squares adjustment process. In first tests
of this method Fourier coefficients up to 4th order plus a constant
value and a linear trend representing the vertical TEC (VTEC) were
estimated. Slant TEC (STEC) values are converted into VTEC values
by a mapping function. The disadvantage of this approach is the assumption
that these values are assigned to the station coordinates coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinite thin ionospheric layer. The precision
of the estimated values is about 2-3 TEC units (TECU). These results
agree within 5-15 TECU with other techniques like GPS which. A second
approach, developed at the TU-Vienna, using piece-wise linear functions
provides better results.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In geodetic VLBI the observations are performed at two distinct frequencies
(2.3 and 8.4 GHz) in order to determine ionospheric delay corrections.
This allows to gain information from VLBI observables about the sum
of electrons (total electron content - TEC) along the ray path through
the ionosphere. Due to the fact that VLBI is a differential technique
only the differences in the behavior of the propagation media over
the stations determine the leading signs and the absolute values
of the observed ionospheric delays. However, there is an instrumental
delay offset per baseline that shifts the measurements by a constant
value. This offset is thought to be independent of the azimuth and
elevation in which the antennas point what allows to separate the
ionospheric parameters for each station from the ionospheric offsets
per baseline in a least-squares adjustment process. In first tests
of this method Fourier coefficients up to 4th order plus a constant
value and a linear trend representing the vertical TEC (VTEC) were
estimated. Slant TEC (STEC) values are converted into VTEC values
by a mapping function. The disadvantage of this approach is the assumption
that these values are assigned to the station coordinates coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinite thin ionospheric layer. The precision
of the estimated values is about 2-3 TEC units (TECU). These results
agree within 5-15 TECU with other techniques like GPS which. A second
approach, developed at the TU-Vienna, using piece-wise linear functions
provides better results.
(2.3 and 8.4 GHz) in order to determine ionospheric delay corrections.
This allows to gain information from VLBI observables about the sum
of electrons (total electron content - TEC) along the ray path through
the ionosphere. Due to the fact that VLBI is a differential technique
only the differences in the behavior of the propagation media over
the stations determine the leading signs and the absolute values
of the observed ionospheric delays. However, there is an instrumental
delay offset per baseline that shifts the measurements by a constant
value. This offset is thought to be independent of the azimuth and
elevation in which the antennas point what allows to separate the
ionospheric parameters for each station from the ionospheric offsets
per baseline in a least-squares adjustment process. In first tests
of this method Fourier coefficients up to 4th order plus a constant
value and a linear trend representing the vertical TEC (VTEC) were
estimated. Slant TEC (STEC) values are converted into VTEC values
by a mapping function. The disadvantage of this approach is the assumption
that these values are assigned to the station coordinates coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinite thin ionospheric layer. The precision
of the estimated values is about 2-3 TEC units (TECU). These results
agree within 5-15 TECU with other techniques like GPS which. A second
approach, developed at the TU-Vienna, using piece-wise linear functions
provides better results.
5.
Hobiger, Thomas; Boehm, Johannes; Todorova, Sonya; Schuh, Harald
The project "VLBIonos" - how VLBI contributes to ionospheric research Proceedings Article
In: Schwegmann, W.; Thorandt, V. (Ed.): Proceedings of the 16th Working Meeting on European VLBI for Geodesy and Astrometry, pp. 291–298, 2003.
@inproceedings{EVLBI03,
title = {The project "VLBIonos" - how VLBI contributes to ionospheric
research},
author = {Thomas Hobiger and Johannes Boehm and Sonya Todorova and Harald Schuh},
editor = {W. Schwegmann and V. Thorandt},
url = {ftp://ftp.leipzig.ifag.de/pub/analysis/papers/291-Hobiger.pdf},
year = {2003},
date = {2003-01-01},
booktitle = {Proceedings of the 16th Working Meeting on European VLBI for Geodesy
and Astrometry},
pages = {291–298},
abstract = {In geodetic Very Long Baseline Interferometry (VLBI) the observations
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. This allows information
to be obtained from the VLBI observables about the sum of electrons
(total electron content - TEC) along the ray path through the ionosphere.
Due to the fact that VLBI is a differential technique, only the differences
in the behavior of the propagation media over the stations determine
the values of the observed ionospheric delays. However, in a first
simple approach, an instrumental delay offset per baseline shifts
the TEC measurements by a constant value. This offset is independent
of the azimuth and elevation of the observed radio source and allows
separation of the ionospheric parameters for each station from the
instrumental delay offsets per baseline in a least-squares adjustment.
In first tests of this method Fourier coefficients up to the 4th
order plus a constant value and a linear trend were estimated to
represent the vertical TEC (VTEC). Slant TEC (STEC) values are converted
into VTEC values by a mapping function. A disadvantage of this approach
is the assumption that these values are assigned to the station coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinitely thin ionospheric layer. The precision
of the estimated values is about +/- 5 to +/- 7 TEC units (TECU).
The results obtained from VLBI agree with a standard deviation of
+/- 10 TECU with other techniques like GPS, and rarely exceed 20
TECU. A second approach, developed at the TU Vienna, using piece-wise
linear functions (VTM – Vienna TEC model) was also tested.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In geodetic Very Long Baseline Interferometry (VLBI) the observations
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. This allows information
to be obtained from the VLBI observables about the sum of electrons
(total electron content - TEC) along the ray path through the ionosphere.
Due to the fact that VLBI is a differential technique, only the differences
in the behavior of the propagation media over the stations determine
the values of the observed ionospheric delays. However, in a first
simple approach, an instrumental delay offset per baseline shifts
the TEC measurements by a constant value. This offset is independent
of the azimuth and elevation of the observed radio source and allows
separation of the ionospheric parameters for each station from the
instrumental delay offsets per baseline in a least-squares adjustment.
In first tests of this method Fourier coefficients up to the 4th
order plus a constant value and a linear trend were estimated to
represent the vertical TEC (VTEC). Slant TEC (STEC) values are converted
into VTEC values by a mapping function. A disadvantage of this approach
is the assumption that these values are assigned to the station coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinitely thin ionospheric layer. The precision
of the estimated values is about +/- 5 to +/- 7 TEC units (TECU).
The results obtained from VLBI agree with a standard deviation of
+/- 10 TECU with other techniques like GPS, and rarely exceed 20
TECU. A second approach, developed at the TU Vienna, using piece-wise
linear functions (VTM – Vienna TEC model) was also tested.
are performed at two distinct frequencies (2.3 and 8.4 GHz) in order
to determine ionospheric delay corrections. This allows information
to be obtained from the VLBI observables about the sum of electrons
(total electron content - TEC) along the ray path through the ionosphere.
Due to the fact that VLBI is a differential technique, only the differences
in the behavior of the propagation media over the stations determine
the values of the observed ionospheric delays. However, in a first
simple approach, an instrumental delay offset per baseline shifts
the TEC measurements by a constant value. This offset is independent
of the azimuth and elevation of the observed radio source and allows
separation of the ionospheric parameters for each station from the
instrumental delay offsets per baseline in a least-squares adjustment.
In first tests of this method Fourier coefficients up to the 4th
order plus a constant value and a linear trend were estimated to
represent the vertical TEC (VTEC). Slant TEC (STEC) values are converted
into VTEC values by a mapping function. A disadvantage of this approach
is the assumption that these values are assigned to the station coordinates
but not to the geographical coordinates of the intersection point
of the ray path and the infinitely thin ionospheric layer. The precision
of the estimated values is about +/- 5 to +/- 7 TEC units (TECU).
The results obtained from VLBI agree with a standard deviation of
+/- 10 TECU with other techniques like GPS, and rarely exceed 20
TECU. A second approach, developed at the TU Vienna, using piece-wise
linear functions (VTM – Vienna TEC model) was also tested.
4.
Schuh, Harald; Boehm, Johannes; Hobiger, Thomas
Vienna IGG Special Analysis Center Annual Report 2002 Proceedings Article
In: Vandenberg, N. R.; Baver, K. D. (Ed.): International VLBI Service for Geodesy and Astrometry 2004 Annual Report, pp. 261–264, 2003.
@inproceedings{IVSAR02,
title = {Vienna IGG Special Analysis Center Annual Report 2002},
author = {Harald Schuh and Johannes Boehm and Thomas Hobiger},
editor = {N. R. Vandenberg and K. D. Baver},
url = {ftp://ivscc.gsfc.nasa.gov/pub/annual-report/2002/pdf/acigg.pdf},
year = {2003},
date = {2003-01-01},
booktitle = {International VLBI Service for Geodesy and Astrometry 2004 Annual
Report},
number = {NASA/TP-2003-211619},
pages = {261–264},
abstract = {In April 2002, the Institute of Geodesy and Geophysics (IGG), Vienna,
was asked by the IVS Directing Board to coordinate the IVS Pilot
Project - Tropospheric Parameters. This project aims at providing
tropospheric parameters (total and wet zenith delays) on a regular
basis as IVS products. As of January 2003, seven IVS Analysis Centers
have joined the project and the combined time series determined so
far are of high quality (Schuh et al., 2003). The IGG also continued
its research on the determination of ionospheric parameters using
VLBI data.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
In April 2002, the Institute of Geodesy and Geophysics (IGG), Vienna,
was asked by the IVS Directing Board to coordinate the IVS Pilot
Project - Tropospheric Parameters. This project aims at providing
tropospheric parameters (total and wet zenith delays) on a regular
basis as IVS products. As of January 2003, seven IVS Analysis Centers
have joined the project and the combined time series determined so
far are of high quality (Schuh et al., 2003). The IGG also continued
its research on the determination of ionospheric parameters using
VLBI data.
was asked by the IVS Directing Board to coordinate the IVS Pilot
Project - Tropospheric Parameters. This project aims at providing
tropospheric parameters (total and wet zenith delays) on a regular
basis as IVS products. As of January 2003, seven IVS Analysis Centers
have joined the project and the combined time series determined so
far are of high quality (Schuh et al., 2003). The IGG also continued
its research on the determination of ionospheric parameters using
VLBI data.
3.
Todorova, Sonja; Hobiger, Thomas; Weber, Robert; Schuh, Harald
Regional ionosphere modelling with GPS and comparison with other techniques Proceedings Article
In: Proceedings of the Symposium "Modern Technologies, Education and Professional Practice in the Globalizing World", November 06-07, Sofia, 2003, 2003.
@inproceedings{SGEM03,
title = {Regional ionosphere modelling with GPS and comparison with other
techniques},
author = {Sonja Todorova and Thomas Hobiger and Robert Weber and Harald Schuh},
year = {2003},
date = {2003-01-01},
booktitle = {Proceedings of the Symposium "Modern Technologies, Education and
Professional Practice in the Globalizing World", November 06-07,
Sofia, 2003},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
0000
2.
Sonnleitner, Clemens; Hobiger, Thomas
Wide-area Multilateration Airspace Surveillance with Unsynchronized Low-Cost ADS-B Receivers Using TDOA Observations Journal Article
In: NAVIGATION: Journal of the Institute of Navigation year = 2025, vol. 72, no. 3, pp. 1-30, 0000.
@article{Sonnleitnernavi.704,
title = {Wide-area Multilateration Airspace Surveillance with Unsynchronized Low-Cost ADS-B Receivers Using TDOA Observations},
author = {Clemens Sonnleitner and Thomas Hobiger},
url = {https://navi.ion.org/content/72/3/navi.704},
doi = {10.33012/navi.704},
journal = {NAVIGATION: Journal of the Institute of Navigation year = 2025},
volume = {72},
number = {3},
pages = {1-30},
abstract = {Abstract This paper proposes and evaluates a novel approach for wide area multilateration (WAM) airspace surveillance based on time difference of arrival (TDOA) navigation. Unlike commercial Automatic Dependent Surveillance-Broadcast (ADS-B)-based WAM solutions, which require high-grade clock synchronization, the framework proposed here achieves airspace surveillance without the need for highly stable clocks or time synchronization between ground stations. In the proposed approach, aircraft 3D positions and velocities and the relative clock offsets of the receivers are estimated consistently using an extended Kalman filter (EKF). The accuracy of the 3D aircraft position estimates was tested using simulated ADS-B messages across a variety of different ground station network configurations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract This paper proposes and evaluates a novel approach for wide area multilateration (WAM) airspace surveillance based on time difference of arrival (TDOA) navigation. Unlike commercial Automatic Dependent Surveillance-Broadcast (ADS-B)-based WAM solutions, which require high-grade clock synchronization, the framework proposed here achieves airspace surveillance without the need for highly stable clocks or time synchronization between ground stations. In the proposed approach, aircraft 3D positions and velocities and the relative clock offsets of the receivers are estimated consistently using an extended Kalman filter (EKF). The accuracy of the 3D aircraft position estimates was tested using simulated ADS-B messages across a variety of different ground station network configurations.
1.
Gutsche, He; Hobiger, Thomas; Winkler, Stefan
Addressing Inaccurate Phase Center Offsets in Precise Orbit Determination for Agile Satellite Missions Journal Article
In: NAVIGATION: Journal of the Institute of Navigation year = 2024, vol. 71, no. 4, pp. 1-22, 0000.
@article{Gutsche24Nav,
title = {Addressing Inaccurate Phase Center Offsets in Precise Orbit Determination for Agile Satellite Missions},
author = {He Gutsche and Thomas Hobiger and Stefan Winkler},
url = {https://navi.ion.org/content/71/4/navi.671},
doi = {10.33012/navi.671},
journal = {NAVIGATION: Journal of the Institute of Navigation year = 2024},
volume = {71},
number = {4},
pages = {1-22},
abstract = {Incorrect offsets between a satellite’s center of mass and its global navigation satellite system antenna phase center pose challenges to the precise orbit determination (POD) of many current Earth observation missions. Based on hardware-in-the-loop simulations, this paper demonstrates the more adverse effects on agile satellites, which perform frequent attitude maneuvers around all spacecraft axes. However, findings obtained from an observability analysis and Monte Carlo simulations indicate that rapid attitude changes enable the direct estimation of otherwise unobservable offsets. Application to the POD of agile satellites leads to a consistent and significant performance improvement in the presence of incorrect phase center offsets. Directly estimated corrections for the phase center offset of Sentinel-6A, which performs slews on several occasions, are consistent with values obtained from other studies via independent methods. These results underscore the possibility of estimating the lever arm for both agile and non-agile satellites in dedicated calibration maneuvers.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Incorrect offsets between a satellite’s center of mass and its global navigation satellite system antenna phase center pose challenges to the precise orbit determination (POD) of many current Earth observation missions. Based on hardware-in-the-loop simulations, this paper demonstrates the more adverse effects on agile satellites, which perform frequent attitude maneuvers around all spacecraft axes. However, findings obtained from an observability analysis and Monte Carlo simulations indicate that rapid attitude changes enable the direct estimation of otherwise unobservable offsets. Application to the POD of agile satellites leads to a consistent and significant performance improvement in the presence of incorrect phase center offsets. Directly estimated corrections for the phase center offset of Sentinel-6A, which performs slews on several occasions, are consistent with values obtained from other studies via independent methods. These results underscore the possibility of estimating the lever arm for both agile and non-agile satellites in dedicated calibration maneuvers.
