Hana Krásná | Tu Wien (original) (raw)

Papers by Hana Krásná

Research paper thumbnail of Verifying the impact of additional breaks in station coordinates on VLBI scale drift

Research paper thumbnail of Evaluating the feasibility of short-integration scans based on the 2022 VGOS-R&D program

arXiv (Cornell University), Nov 29, 2023

In this work, we report on activities focusing on improving the observation strategy of the Very ... more In this work, we report on activities focusing on improving the observation strategy of the Very Long Baseline Interferometry (VLBI) Global Observing System (VGOS). During six dedicated 24-hour Research and Development (R&D) sessions conducted in 2022, the effectiveness of a signal-to-noise ratio (SNR)based scheduling approach with observation times as short as 5-20 seconds was explored. The sessions utilized a full 8 Gbps observing mode and incorporated elements such as dedicated calibration scans, a VGOS frequency source-flux catalog, improved sky-coverage parameterization, and more. The number of scans scheduled per station increased by 2.34 times compared to operational VGOS-OPS sessions, resulting in a 2.58 times increase in the number of observations per station. Remarkably, the percentage of successful observations per baseline matched the fixed 30-second observation approach employed in VGOS-OPS, demonstrating the effectiveness of the SNR-based scheduling approach.

Research paper thumbnail of VLBI celestial and terrestrial reference frames VIE2022b

Astronomy & Astrophysics

Context. We present the computation of global reference frames from very long baseline interferom... more Context. We present the computation of global reference frames from very long baseline interferometry (VLBI) observations at the Vienna International VLBI Service for Geodesy and Astrometry (IVS) Analysis Center (VIE) in detail. We focus on the celestial and terrestrial frames from our two latest solutions VIE2020 and VIE2022b. Aims. The current international celestial and terrestrial reference frames, ICRF3 and ITRF2020, include VLBI observations until March 2018 (at the standard geodetic and astrometric radio frequencies 2.3 and 8.4 GHz) and December 2020, respectively. We provide terrestrial and celestial reference frames including VLBI sessions until June 2022 organized by the IVS. Methods. Vienna terrestrial and celestial reference frames are computed in a common least squares adjustment of geodetic and astro-metric VLBI observations with the Vienna VLBI and Satellite Software (VieVS). Results. We provide high-precision celestial and terrestrial reference frames computed from 2...

Research paper thumbnail of Terrestrial Datum Definition Methods in VLBI Global Solutions

International Association of Geodesy symposia, 2024

Research paper thumbnail of Current status and future perspectives of VLBI global solutions

The realization of a terrestrial and celestial reference frame is a fundamental requirement for a... more The realization of a terrestrial and celestial reference frame is a fundamental requirement for all ground- and space-based observations, making the interpretation of key global processes on Earth possible and therefore contributing to a better understanding of the Earth system. In this matter, the space-geodetic technique called Very Long Baseline Interferometry (VLBI) provides the perfect link between stations on the Earth's surface and extragalactic sources with a quasi-fixed position. In the process of an intra-technique combination, it is possible to estimate parameters that are common to all VLBI sessions in a common least squares adjustment, resulting in, e.g., catalogs of station and source positions (and station velocities) at a certain reference epoch. We present the current status of our new state-of-the-art and stand-alone Python software for the combination of VLBI sessions developed at the VLBI Analysis Center in Vienna. The combination process is based on homogeni...

Research paper thumbnail of Intricacies of the estimation of the ICRF3

EGU General Assembly Conference Abstracts, Apr 1, 2016

Research paper thumbnail of Determining the Galactocentric Acceleration Vector from VLBI and its Impact on the Reference Frames

23rd European VLBI Group for Geodesy and Astrometry Working Meeting, Nov 1, 2017

Research paper thumbnail of A two-level approach to VLBI terrestrial and celestial reference frames using both least-squares adjustment and Kalman filter algorithms

Research paper thumbnail of The K-band Celestial Reference Frame: First Imaging Results

Research paper thumbnail of Estimating a Celestial Reference Frame in the Presence of Source Structure

Research paper thumbnail of The K-Band (24 GHz) Celestial Reference Frame Determined from Very Long Baseline Interferometry Sessions Conducted Over the Past 20 Years

International Association of Geodesy Symposia

The third realization of the International Celestial Reference Frame (ICRF3) was adopted in Augus... more The third realization of the International Celestial Reference Frame (ICRF3) was adopted in August 2018 and includes positions of extragalactic objects at three frequencies: 8.4 GHz, 24 GHz, and 32 GHz. In this paper, we present celestial reference frames estimated from Very Long Baseline Interferometry measurements at K-band (24 GHz) including data until June 2022. The data set starts in May 2002 and currently consists of more than 120 24h observing sessions performed over the past 20 years. Since the publication of ICRF3, the additional observations of the sources during the last four years allow maintenance of the celestial reference frame and more than 200 additional radio sources ensure an expansion of the frame. A study of the presented solutions is carried out helping us to understand systematic differences between the astrometric catalogs and moving us towards a better next ICRF solution. We compare K-band solutions (VIE-K-2022b and USNO-K-2022July05) computed by two analyst...

Research paper thumbnail of On more than two decades of Celestial Reference Frame VLBI observations in the deep south: IVS-CRDS (1995–2021)

Publications of the Astronomical Society of Australia

The International VLBI Service for Geodesy and Astrometry (IVS) regularly provides high-quality d... more The International VLBI Service for Geodesy and Astrometry (IVS) regularly provides high-quality data to produce Earth Orientation Parameters (EOP), and for the maintenance and realisation of the International Terrestrial and Celestial Reference Frames, ITRF and ICRF. The first iteration of the celestial reference frame (CRF) at radio wavelengths, the ICRF1, was adopted by the International Astronomical Union (IAU) in 1997 to replace the FK5 optical frame. Soon after, the IVS began official operations and in 2009 there was a significant increase in data sufficient to warrant a second iteration of the CRF, ICRF2. The most recent ICRF3, was adopted by the IAU in 2018. However, due to the geographic distribution of observing stations being concentrated in the Northern hemisphere, CRFs are generally weaker in the South due to there being fewer Southern Hemisphere observations. To increase the Southern Hemisphere observations, and the density, precision of the sources, a series of deep So...

Research paper thumbnail of Hartebeesthoek Radio Astronomy Observatory (HartRAO) antenna axis offset determined by geodetic VLBI analysis and ground survey

South African Journal of Geomatics

In the Very Long Baseline Interferometry (VLBI) space geodetic technique, various station-specifi... more In the Very Long Baseline Interferometry (VLBI) space geodetic technique, various station-specific error sources corrupt the observable VLBI delay. An antenna axis offset (AO) model is applied in the VLBI data analysis for antennas with non-intersecting rotational axes, such as the 26-m and 15-m antennas for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The a priori AO values recommended by the International VLBI Service for Geodesy and Astrometry (IVS) for use in geodetic VLBI data analysis are taken, where possible, from values measured in ground surveys. The a priori AO values used for the HartRAO antennas in geodetic VLBI analysis have been identified as possible sources of error. The a priori AO value of 6695.3 mm for the 26-m antenna originates from a 2003 co-locational ground survey, conducted before a major bearing repair in 2008, which could have changed the AO. The a priori AO value of 1495.0 mm for the 15-m antenna was determined in 2007 in only a preliminary ...

Research paper thumbnail of The Australian mixed-mode observing program

Journal of Geodesy

Global geodetic VLBI is upgrading to its next-generation observing system, VGOS. This upgrade has... more Global geodetic VLBI is upgrading to its next-generation observing system, VGOS. This upgrade has turned out to be a process over multiple years, until VGOS reaches its full capabilities with the envisaged continuous observations. Until then, for the Australian stations, the upgrade means ceasing their legacy S/X observations, leaving a large gap in the global network as well as in the station time series. The Australian mixed-mode observing program is a series of sessions where the VGOS stations in Hobart and Katherine observe legacy S/X VLBI together with other stations in the region. This paper describes the technical details of these observations and their processing strategies and discusses their suitability for geodetic results by comparison with those of standard legacy S/X sessions. The presented mixed-mode sessions allow a continuation of the station time series, a benefit for the stations themselves as well as for future realisations of the terrestrial and celestial refere...

Research paper thumbnail of VLBI celestial reference frames and assessment with Gaia

Mit der Entdeckung von Quasaren (extragalaktische Radioquellen) in den 1960ern wurde das Feld der... more Mit der Entdeckung von Quasaren (extragalaktische Radioquellen) in den 1960ern wurde das Feld der Astrometrie revolutioniert. Durch die große Entfernung dieser Quellen ist die Eigenbewegung vernachlässigbar, wodurch sie zum idealen Referenzpunkt werden. Beobachtet werden diese Quellen mit der Very Long Baseline Interferometry (VLBI), welche ein Netzwerk aus Radioteleskopen benutzt um hochgenaue Positionen zu bestimmen. Nur einige Jahrzehnte nach der Entdeckung von extragalaktischen Radioquellen wurde der bis dato genaueste Sternenkatalog im optischen Frequenzbereich durch einen Katalog von Quasaren im Radiofrequenzbereich als empfohlener Standard abgelöst. Für drei Jahrzehnte war die Genauigkeit der VLBI außer Reichweite für Verfahren im optischen Bereich des elektromagnetischen Spektrums. Das hat sich mit der Satellitenmission Gaia der European Space Agency (ESA), welche 2013 gestartet wurde, geändert. Gaia wurde entwickelt um die Milchstraße zu vermessen, allerdings misst Gaia unt...

Research paper thumbnail of Simulations of VLBI observations with the Onsala Twin Telescope

Der International VLBI Service for Geodesy and Astrometry (IVS) entwickelte das VLBI2010 Konzept ... more Der International VLBI Service for Geodesy and Astrometry (IVS) entwickelte das VLBI2010 Konzept um die Genauigkeit der geodätischen Very Long Baseline Interferometry (VLBI) auf 1 mm für Stationspositionen und 0.1 mm/Jahr für Stationsgeschwindigkeiten zu verbessern. Dafür sollen Breitbandbeobachtungen mit schnellen Teleskopen verwendet werden, sowie Zwillingsteleskope um die Atmosphäre besser bestimmen zu können. Diese gilt als limitierender Faktor der geodätischen VLBI. Einige Projekte zur Realisierung des VLBI Konzeptes wurden bereits gestartet, wie unter anderem das Onsala Twin Telescope Projekt, dessen Zielsetzung ist, ein Zwillingsteleskop in Onsala ab 2016 zu betreiben. In dieser Arbeit wurde ein globales VLBI Netzwerk geplant, simuliert und analysiert. Als Grundlage wurde das CONT11 Netzwerk gewählt, eine 15 Tage lange Kampagne, die momentan die besten geodätischen Ergebnisse liefert. Die Ergebnisse des existierenden 20 m Teleskops in Onsala und des geplanten Zwillingstelesko...

Research paper thumbnail of Untersuchung von geophysikalischen Auflasteffekten mit der VLBI

Die Aufgabe dieser Arbeit ist die Untersuchung von geophysikalischen Auflasteffekten mittels Very... more Die Aufgabe dieser Arbeit ist die Untersuchung von geophysikalischen Auflasteffekten mittels Very Long Baseline Interferometry (VLBI). Als geophysikalische Auflasteffekte werden die ozeanischen, atmosphärischen und hydrologischen Massenumverteilungen bezeichnet. Diese haben einen Einfluss auf die Variation der Koordinaten der VLBI Station. Hauptsächlich werden geophysikalische Auflasteffekte in den Höhenkoordinaten der Stationen sichtbar. Die Einflüsse an den Stationen können recht unterschiedlich sein, je nach dem in welchem Breitengrad (atmosphärische Auflasteffekte) und in welcher Entfernung zum Meer (ozeanische Auflasteffekte) und zu Gebieten mit großer variabler Wasserspeicherung von Bodenwasser, Grundwasser, Schnee und Eis, sowie von Flüssen, Seen und Feuchtgebieten (hydrologische Auflasteffekte) die VLBI Stationen stehen. Für diese Untersuchung werden VLBI Beobachtungen aus den Jahren 2000 bis 2012 von 118 Stationen herangezogen und mit VieVS und Matlab untersucht. Aus diesen...

Research paper thumbnail of Impact of Seasonal Surface Displacement on Earth Rotation and Global Reference Frames

International VLBI Service for Geodesy and Astrometry 2014 General Meeting Proceedings: "VGOS: The New VLBI Network, Dec 1, 2014

Research paper thumbnail of Baseline dependent weights in VieVS

Research paper thumbnail of The K-band (24 GHz) Celestial Reference Frame Can it be more accurate than SX (8 GHz)?

30th IAU General Assembly, Aug 1, 2018

Research paper thumbnail of Verifying the impact of additional breaks in station coordinates on VLBI scale drift

Research paper thumbnail of Evaluating the feasibility of short-integration scans based on the 2022 VGOS-R&D program

arXiv (Cornell University), Nov 29, 2023

In this work, we report on activities focusing on improving the observation strategy of the Very ... more In this work, we report on activities focusing on improving the observation strategy of the Very Long Baseline Interferometry (VLBI) Global Observing System (VGOS). During six dedicated 24-hour Research and Development (R&D) sessions conducted in 2022, the effectiveness of a signal-to-noise ratio (SNR)based scheduling approach with observation times as short as 5-20 seconds was explored. The sessions utilized a full 8 Gbps observing mode and incorporated elements such as dedicated calibration scans, a VGOS frequency source-flux catalog, improved sky-coverage parameterization, and more. The number of scans scheduled per station increased by 2.34 times compared to operational VGOS-OPS sessions, resulting in a 2.58 times increase in the number of observations per station. Remarkably, the percentage of successful observations per baseline matched the fixed 30-second observation approach employed in VGOS-OPS, demonstrating the effectiveness of the SNR-based scheduling approach.

Research paper thumbnail of VLBI celestial and terrestrial reference frames VIE2022b

Astronomy & Astrophysics

Context. We present the computation of global reference frames from very long baseline interferom... more Context. We present the computation of global reference frames from very long baseline interferometry (VLBI) observations at the Vienna International VLBI Service for Geodesy and Astrometry (IVS) Analysis Center (VIE) in detail. We focus on the celestial and terrestrial frames from our two latest solutions VIE2020 and VIE2022b. Aims. The current international celestial and terrestrial reference frames, ICRF3 and ITRF2020, include VLBI observations until March 2018 (at the standard geodetic and astrometric radio frequencies 2.3 and 8.4 GHz) and December 2020, respectively. We provide terrestrial and celestial reference frames including VLBI sessions until June 2022 organized by the IVS. Methods. Vienna terrestrial and celestial reference frames are computed in a common least squares adjustment of geodetic and astro-metric VLBI observations with the Vienna VLBI and Satellite Software (VieVS). Results. We provide high-precision celestial and terrestrial reference frames computed from 2...

Research paper thumbnail of Terrestrial Datum Definition Methods in VLBI Global Solutions

International Association of Geodesy symposia, 2024

Research paper thumbnail of Current status and future perspectives of VLBI global solutions

The realization of a terrestrial and celestial reference frame is a fundamental requirement for a... more The realization of a terrestrial and celestial reference frame is a fundamental requirement for all ground- and space-based observations, making the interpretation of key global processes on Earth possible and therefore contributing to a better understanding of the Earth system. In this matter, the space-geodetic technique called Very Long Baseline Interferometry (VLBI) provides the perfect link between stations on the Earth's surface and extragalactic sources with a quasi-fixed position. In the process of an intra-technique combination, it is possible to estimate parameters that are common to all VLBI sessions in a common least squares adjustment, resulting in, e.g., catalogs of station and source positions (and station velocities) at a certain reference epoch. We present the current status of our new state-of-the-art and stand-alone Python software for the combination of VLBI sessions developed at the VLBI Analysis Center in Vienna. The combination process is based on homogeni...

Research paper thumbnail of Intricacies of the estimation of the ICRF3

EGU General Assembly Conference Abstracts, Apr 1, 2016

Research paper thumbnail of Determining the Galactocentric Acceleration Vector from VLBI and its Impact on the Reference Frames

23rd European VLBI Group for Geodesy and Astrometry Working Meeting, Nov 1, 2017

Research paper thumbnail of A two-level approach to VLBI terrestrial and celestial reference frames using both least-squares adjustment and Kalman filter algorithms

Research paper thumbnail of The K-band Celestial Reference Frame: First Imaging Results

Research paper thumbnail of Estimating a Celestial Reference Frame in the Presence of Source Structure

Research paper thumbnail of The K-Band (24 GHz) Celestial Reference Frame Determined from Very Long Baseline Interferometry Sessions Conducted Over the Past 20 Years

International Association of Geodesy Symposia

The third realization of the International Celestial Reference Frame (ICRF3) was adopted in Augus... more The third realization of the International Celestial Reference Frame (ICRF3) was adopted in August 2018 and includes positions of extragalactic objects at three frequencies: 8.4 GHz, 24 GHz, and 32 GHz. In this paper, we present celestial reference frames estimated from Very Long Baseline Interferometry measurements at K-band (24 GHz) including data until June 2022. The data set starts in May 2002 and currently consists of more than 120 24h observing sessions performed over the past 20 years. Since the publication of ICRF3, the additional observations of the sources during the last four years allow maintenance of the celestial reference frame and more than 200 additional radio sources ensure an expansion of the frame. A study of the presented solutions is carried out helping us to understand systematic differences between the astrometric catalogs and moving us towards a better next ICRF solution. We compare K-band solutions (VIE-K-2022b and USNO-K-2022July05) computed by two analyst...

Research paper thumbnail of On more than two decades of Celestial Reference Frame VLBI observations in the deep south: IVS-CRDS (1995–2021)

Publications of the Astronomical Society of Australia

The International VLBI Service for Geodesy and Astrometry (IVS) regularly provides high-quality d... more The International VLBI Service for Geodesy and Astrometry (IVS) regularly provides high-quality data to produce Earth Orientation Parameters (EOP), and for the maintenance and realisation of the International Terrestrial and Celestial Reference Frames, ITRF and ICRF. The first iteration of the celestial reference frame (CRF) at radio wavelengths, the ICRF1, was adopted by the International Astronomical Union (IAU) in 1997 to replace the FK5 optical frame. Soon after, the IVS began official operations and in 2009 there was a significant increase in data sufficient to warrant a second iteration of the CRF, ICRF2. The most recent ICRF3, was adopted by the IAU in 2018. However, due to the geographic distribution of observing stations being concentrated in the Northern hemisphere, CRFs are generally weaker in the South due to there being fewer Southern Hemisphere observations. To increase the Southern Hemisphere observations, and the density, precision of the sources, a series of deep So...

Research paper thumbnail of Hartebeesthoek Radio Astronomy Observatory (HartRAO) antenna axis offset determined by geodetic VLBI analysis and ground survey

South African Journal of Geomatics

In the Very Long Baseline Interferometry (VLBI) space geodetic technique, various station-specifi... more In the Very Long Baseline Interferometry (VLBI) space geodetic technique, various station-specific error sources corrupt the observable VLBI delay. An antenna axis offset (AO) model is applied in the VLBI data analysis for antennas with non-intersecting rotational axes, such as the 26-m and 15-m antennas for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The a priori AO values recommended by the International VLBI Service for Geodesy and Astrometry (IVS) for use in geodetic VLBI data analysis are taken, where possible, from values measured in ground surveys. The a priori AO values used for the HartRAO antennas in geodetic VLBI analysis have been identified as possible sources of error. The a priori AO value of 6695.3 mm for the 26-m antenna originates from a 2003 co-locational ground survey, conducted before a major bearing repair in 2008, which could have changed the AO. The a priori AO value of 1495.0 mm for the 15-m antenna was determined in 2007 in only a preliminary ...

Research paper thumbnail of The Australian mixed-mode observing program

Journal of Geodesy

Global geodetic VLBI is upgrading to its next-generation observing system, VGOS. This upgrade has... more Global geodetic VLBI is upgrading to its next-generation observing system, VGOS. This upgrade has turned out to be a process over multiple years, until VGOS reaches its full capabilities with the envisaged continuous observations. Until then, for the Australian stations, the upgrade means ceasing their legacy S/X observations, leaving a large gap in the global network as well as in the station time series. The Australian mixed-mode observing program is a series of sessions where the VGOS stations in Hobart and Katherine observe legacy S/X VLBI together with other stations in the region. This paper describes the technical details of these observations and their processing strategies and discusses their suitability for geodetic results by comparison with those of standard legacy S/X sessions. The presented mixed-mode sessions allow a continuation of the station time series, a benefit for the stations themselves as well as for future realisations of the terrestrial and celestial refere...

Research paper thumbnail of VLBI celestial reference frames and assessment with Gaia

Mit der Entdeckung von Quasaren (extragalaktische Radioquellen) in den 1960ern wurde das Feld der... more Mit der Entdeckung von Quasaren (extragalaktische Radioquellen) in den 1960ern wurde das Feld der Astrometrie revolutioniert. Durch die große Entfernung dieser Quellen ist die Eigenbewegung vernachlässigbar, wodurch sie zum idealen Referenzpunkt werden. Beobachtet werden diese Quellen mit der Very Long Baseline Interferometry (VLBI), welche ein Netzwerk aus Radioteleskopen benutzt um hochgenaue Positionen zu bestimmen. Nur einige Jahrzehnte nach der Entdeckung von extragalaktischen Radioquellen wurde der bis dato genaueste Sternenkatalog im optischen Frequenzbereich durch einen Katalog von Quasaren im Radiofrequenzbereich als empfohlener Standard abgelöst. Für drei Jahrzehnte war die Genauigkeit der VLBI außer Reichweite für Verfahren im optischen Bereich des elektromagnetischen Spektrums. Das hat sich mit der Satellitenmission Gaia der European Space Agency (ESA), welche 2013 gestartet wurde, geändert. Gaia wurde entwickelt um die Milchstraße zu vermessen, allerdings misst Gaia unt...

Research paper thumbnail of Simulations of VLBI observations with the Onsala Twin Telescope

Der International VLBI Service for Geodesy and Astrometry (IVS) entwickelte das VLBI2010 Konzept ... more Der International VLBI Service for Geodesy and Astrometry (IVS) entwickelte das VLBI2010 Konzept um die Genauigkeit der geodätischen Very Long Baseline Interferometry (VLBI) auf 1 mm für Stationspositionen und 0.1 mm/Jahr für Stationsgeschwindigkeiten zu verbessern. Dafür sollen Breitbandbeobachtungen mit schnellen Teleskopen verwendet werden, sowie Zwillingsteleskope um die Atmosphäre besser bestimmen zu können. Diese gilt als limitierender Faktor der geodätischen VLBI. Einige Projekte zur Realisierung des VLBI Konzeptes wurden bereits gestartet, wie unter anderem das Onsala Twin Telescope Projekt, dessen Zielsetzung ist, ein Zwillingsteleskop in Onsala ab 2016 zu betreiben. In dieser Arbeit wurde ein globales VLBI Netzwerk geplant, simuliert und analysiert. Als Grundlage wurde das CONT11 Netzwerk gewählt, eine 15 Tage lange Kampagne, die momentan die besten geodätischen Ergebnisse liefert. Die Ergebnisse des existierenden 20 m Teleskops in Onsala und des geplanten Zwillingstelesko...

Research paper thumbnail of Untersuchung von geophysikalischen Auflasteffekten mit der VLBI

Die Aufgabe dieser Arbeit ist die Untersuchung von geophysikalischen Auflasteffekten mittels Very... more Die Aufgabe dieser Arbeit ist die Untersuchung von geophysikalischen Auflasteffekten mittels Very Long Baseline Interferometry (VLBI). Als geophysikalische Auflasteffekte werden die ozeanischen, atmosphärischen und hydrologischen Massenumverteilungen bezeichnet. Diese haben einen Einfluss auf die Variation der Koordinaten der VLBI Station. Hauptsächlich werden geophysikalische Auflasteffekte in den Höhenkoordinaten der Stationen sichtbar. Die Einflüsse an den Stationen können recht unterschiedlich sein, je nach dem in welchem Breitengrad (atmosphärische Auflasteffekte) und in welcher Entfernung zum Meer (ozeanische Auflasteffekte) und zu Gebieten mit großer variabler Wasserspeicherung von Bodenwasser, Grundwasser, Schnee und Eis, sowie von Flüssen, Seen und Feuchtgebieten (hydrologische Auflasteffekte) die VLBI Stationen stehen. Für diese Untersuchung werden VLBI Beobachtungen aus den Jahren 2000 bis 2012 von 118 Stationen herangezogen und mit VieVS und Matlab untersucht. Aus diesen...

Research paper thumbnail of Impact of Seasonal Surface Displacement on Earth Rotation and Global Reference Frames

International VLBI Service for Geodesy and Astrometry 2014 General Meeting Proceedings: "VGOS: The New VLBI Network, Dec 1, 2014

Research paper thumbnail of Baseline dependent weights in VieVS

Research paper thumbnail of The K-band (24 GHz) Celestial Reference Frame Can it be more accurate than SX (8 GHz)?

30th IAU General Assembly, Aug 1, 2018