Rüdiger Haas - Academia.edu (original) (raw)

Papers by Rüdiger Haas

A multi-sensor approach to estimation of tropospheric delays Y. Bar-Sever (l), S. Byun (l), R. Ha... more A multi-sensor approach to estimation of tropospheric delays Y. Bar-Sever (l), S. Byun (l), R. Haas (2), S. Keihm (l), Tim Munson (l), A1 Tanner (l), Larry Young (1)

EGU General Assembly Conference Abstracts, Apr 1, 2019

Inverse modeling of ground-based GNSS reflections has the potential to improve existing GNSS-R ap... more Inverse modeling of ground-based GNSS reflections has the potential to improve existing GNSS-R applications and lead to novel concepts for retrieving geophysical parameters around existing or deliberately built GNSS sites. As we will show in this paper, consistent, accurate and precise determination of sea-surface heights can be realized. Moreover, we demonstrate that it is possible to detect sea-ice freeze states at coastal GNSS sites. In addition, it will be shown how the inverse modeling approach can be used for self-calibration of troposphere delays, which would otherwise bias the target parameters and need to be corrected for by external measurements or data-sets.

We present a new method to retrieve sea level from GNSS SNR data that relies upon inverse modelli... more We present a new method to retrieve sea level from GNSS SNR data that relies upon inverse modelling of the detrended SNR. This method can simultaneously use data from both GPS and GLONASS, and both L1 and L2 frequencies, to improve the solution with respect to prior studies. Results from the GNSS-R installation at Onsala Space Observatory are presented and the retrieved sea level heights are compared with a co-located pressure mareograph. The method is found to give an RMS error of 1.8 cm. The results are also compared against previous implementations of GNSS tide gauges and found to have lower RMS than both the earlier SNR algorithm and also the dual receiver, phase delay method.

EGU General Assembly Conference Abstracts, Apr 1, 2018

We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their... more We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their inauguration. The di↵erent components of the VGOS systems are briefly described, and the development towards routine operations.

Zur Erfassung von Erdrotationsparametern, zur Bestimmung von Veränderungen an der Erdkruste, aber... more Zur Erfassung von Erdrotationsparametern, zur Bestimmung von Veränderungen an der Erdkruste, aber auch zur Ableitung eines himmels-und erdfesten Referenzrahmens sind präzise Beobachtungen von sogenannten geodätischen Raumtechniken wie bspw. Very Long Baseline Interferometry (VLBI) notwendig. Hierfür registrieren VLBI-Radioteleskope die ausgesandten Radiowellen von punktförmigen Radioquellen (Quasare). Die Empfangseigenschaften eines VLBI-Radioteleskops hängen maßgeblich von den geometrischen Eigenschaften des Hauptreflektors ab. Hierzu zählen zum einen die Fertigungsqualität, die sich als Abweichung von der Idealform quantifizieren lässt, und zum anderen die geometrische Stabilität. Unter der geometrischen Stabilität soll hier die Langzeitstabilität, aber auch die Stabilität gegenüber variierenden äußeren Einflüssen verstanden werden. Temperaturveränderungen, Insolationen, Schnee-und Windlasten aber auch das Eigengewicht deformieren den Hauptreflektor-teilweise elevationsabhängig-und beeinflussen somit die Empfangseigenschaften.

The main reflector of VLBI radio telescopes is affected by several disturbing forces. Temperature... more The main reflector of VLBI radio telescopes is affected by several disturbing forces. Temperature, wind, insolation or snow load deform the surface of the reflector and impair the receiving properties. Depending on the elevation orientation of the main reflector, the dead load of the dish w.r.t. the gravitation field of the Earth influence the surface negatively. In recent years, surface deformations and variations of the focal length have been analyzed by several groups. The common mathematical model to describe the main reflector is an ordinary rotational paraboloid. Due to the reflector design improvements, the surface of the main reflector of many of the upcoming VGOS radio telescopes cannot be parameterized by an ordinary rotational paraboloid. We present a unified mathematical model that overcomes this limitation and which is valid for the ordinary surface design as well as the new ring-focus reflector design of VGOS radio telescopes. The model is used for an independent confirmation of the specifications of the new Onsala twin telescopes at the Onsala Space Observatory.

We participated in 39 IVS sessions, including CONT14. Eleven out of the initially planned session... more We participated in 39 IVS sessions, including CONT14. Eleven out of the initially planned sessions could not be observed due to the installation of a new radome for the 20-m radio telescope. As in the previous six years, we used several of the sessions that involved both Onsala and Tsukuba to perform ultrarapid UT1-UTC sessions together with our colleagues in Tsukuba. This included the complete CONT14 campaign where near real-time UT1-UTC on the baseline Onsala-Tsukuba could be determined. The procurement of the telescopes for the Onsala Twin Telescopes was started in the summer of 2014. The contract to buy two VGOS radio telescopes was signed at the end of the year.

We present long term trends in the amount of atmospheric water vapor at the Swedish West Coast de... more We present long term trends in the amount of atmospheric water vapor at the Swedish West Coast derived from four different techniques. Three of the techniques, geodetic Very Long Baseline Interferometry (VLBI), GPS and ground-based microwave radiometry, are co-located at the the Onsala Space Observatory, while the fourth technique, radiosondes, is operated at Gothenburg-Landvetter Airport in about 37 km distance to Onsala. The time series cover up to 30 years of data. The four techniques detect individual positive trends in the integrated water vapor (IWV) on the order of 0.3 to 0.6 kg/m 2 per decade. The IWV data derived from the techniques have correlation coefficients on the order of 0.95 and better and rootmean-square differences of less than x.x. However, there is no perfect agreement between the IWV trends derived by the four techniques, which partly might be explained by different temporal sampling and data gaps.

We have measured the key deforming parameters of the Onsala 20 m telescope with laser based track... more We have measured the key deforming parameters of the Onsala 20 m telescope with laser based tracker, scanner and electronic distance meters. The parameters show both thermal and elevation dependence at an order of some millimeters, and are therefore potential significant contributors to a scale error in VLBI analysis.

This report briefly summarizes the activities of the IVS Analysis Center at the Onsala Space Obse... more This report briefly summarizes the activities of the IVS Analysis Center at the Onsala Space Observatory during 2014 and gives examples of results of ongoing work. 1 General Information We concentrate on research topics that are relevant for space geodesy and geosciences. These research topics are related to data observed with geodetic VLBI and complementing techniques.

Astronomy and Astrophysics, Sep 1, 2016

Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agen... more Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims. The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods. We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results. We achieved, on average, mHz precision (30 µm/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to ∼50 m.

This page was generated automatically upon download from the ETH Zurich Research Collection. For ... more This page was generated automatically upon download from the ETH Zurich Research Collection. For more information, please consult the Terms of use.

The Global Geodetic Observing System (GGOS) requires a globally distributed network utilizing nex... more The Global Geodetic Observing System (GGOS) requires a globally distributed network utilizing next generation Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) technology to meet the objectives of GGOS. It is expected that about 30 core sites will be established globally to ensure adequate network density and geometry. The proposal presented here highlights opportunities for VLBI network densification. We consider both southern Africa and Antarctica sites for the establishment of new VLBI sites. We have made u-v coverage plots and geodetic VLBI simulations for several sites, and evaluate these in terms of their scientific value. Both the southern Africa and Antarctica sites should be equipped with VGOS compatible antennas. In particular we propose the establishment of a new core fundamental station in Antarctica, operated and funded by an international consortium. This core GGOS site could be located at either the Norwegian (Troll) or South African Antarctic...

We report the results of position ties for short baselines at eight geodetic sites based on phase... more We report the results of position ties for short baselines at eight geodetic sites based on phase delays that are extracted from global geodetic very-long-baseline interferometry (VLBI) observations rather than dedicated short-baseline experiments. An analysis of phase delay observables from two antennas at the Geodetic Observatory Wettzell, Germany, extracted from 107 global 24-hour VLBI sessions since 2019 yields weighted root-mean-square scatters about the mean baseline vector of 0.3, 0.3, and 0.8 mm in the east, north, and up directions, respectively. Position ties are also obtained for other short baselines between legacy antennas and nearby, newly built antennas. They are critical for maintaining a consistent continuation of the realization of the terrestrial reference frame, especially when including the new VGOS network. The phase delays of the baseline WETTZ13N-WETTZELL enable an investigation of sources of error at the sub-millimeter level. We found that a systematic variation of larger than 1 mm can be introduced to the up estimates of this baseline vector when atmospheric delays were estimated. Although the sub-millimeter repeatability has been achieved for the baseline vector WETTZ13N-WETTZELL, we conclude that long term monitoring should be conducted for more short baselines to assess the instrumental effects, in particular the systematic differences between phase delays and group delays, and to find common solutions for reducing them. This will be an important step towards the goal of global geodesy at the 1 mm level.

Journal of Geodynamics, 2013

The deformation of the anelastic Earth as a response to external forces from the Moon and Sun is ... more The deformation of the anelastic Earth as a response to external forces from the Moon and Sun is characterized with proportionality parameters, the socalled Love and Shida numbers. The increasing precision and quality of the VLBI (Very Long Baseline Interferometry) measurements allow determining those parameters. In particular, the long history of the VLBI data enables the estimation of Love and Shida numbers at the low frequencies with the longest period of a tidal wave at 18.6 years. In this study we analyze 27 years of VLBI measurements (1984.0-2011.0) following the recent IERS Conventions 2010. In several global solutions, we estimate the complex Love and Shida numbers of the solid Earth tides for the main long-period tidal waves. Furthermore, we determine the Love and Shida numbers of the rotational deformation due to polar motion, the so-called pole tide.

A multi-sensor approach to estimation of tropospheric delays Y. Bar-Sever (l), S. Byun (l), R. Ha... more A multi-sensor approach to estimation of tropospheric delays Y. Bar-Sever (l), S. Byun (l), R. Haas (2), S. Keihm (l), Tim Munson (l), A1 Tanner (l), Larry Young (1)

EGU General Assembly Conference Abstracts, Apr 1, 2019

Inverse modeling of ground-based GNSS reflections has the potential to improve existing GNSS-R ap... more Inverse modeling of ground-based GNSS reflections has the potential to improve existing GNSS-R applications and lead to novel concepts for retrieving geophysical parameters around existing or deliberately built GNSS sites. As we will show in this paper, consistent, accurate and precise determination of sea-surface heights can be realized. Moreover, we demonstrate that it is possible to detect sea-ice freeze states at coastal GNSS sites. In addition, it will be shown how the inverse modeling approach can be used for self-calibration of troposphere delays, which would otherwise bias the target parameters and need to be corrected for by external measurements or data-sets.

We present a new method to retrieve sea level from GNSS SNR data that relies upon inverse modelli... more We present a new method to retrieve sea level from GNSS SNR data that relies upon inverse modelling of the detrended SNR. This method can simultaneously use data from both GPS and GLONASS, and both L1 and L2 frequencies, to improve the solution with respect to prior studies. Results from the GNSS-R installation at Onsala Space Observatory are presented and the retrieved sea level heights are compared with a co-located pressure mareograph. The method is found to give an RMS error of 1.8 cm. The results are also compared against previous implementations of GNSS tide gauges and found to have lower RMS than both the earlier SNR algorithm and also the dual receiver, phase delay method.

EGU General Assembly Conference Abstracts, Apr 1, 2018

We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their... more We give a brief overview on the status of the Onsala twin telescopes (OTT), two years after their inauguration. The di↵erent components of the VGOS systems are briefly described, and the development towards routine operations.

Zur Erfassung von Erdrotationsparametern, zur Bestimmung von Veränderungen an der Erdkruste, aber... more Zur Erfassung von Erdrotationsparametern, zur Bestimmung von Veränderungen an der Erdkruste, aber auch zur Ableitung eines himmels-und erdfesten Referenzrahmens sind präzise Beobachtungen von sogenannten geodätischen Raumtechniken wie bspw. Very Long Baseline Interferometry (VLBI) notwendig. Hierfür registrieren VLBI-Radioteleskope die ausgesandten Radiowellen von punktförmigen Radioquellen (Quasare). Die Empfangseigenschaften eines VLBI-Radioteleskops hängen maßgeblich von den geometrischen Eigenschaften des Hauptreflektors ab. Hierzu zählen zum einen die Fertigungsqualität, die sich als Abweichung von der Idealform quantifizieren lässt, und zum anderen die geometrische Stabilität. Unter der geometrischen Stabilität soll hier die Langzeitstabilität, aber auch die Stabilität gegenüber variierenden äußeren Einflüssen verstanden werden. Temperaturveränderungen, Insolationen, Schnee-und Windlasten aber auch das Eigengewicht deformieren den Hauptreflektor-teilweise elevationsabhängig-und beeinflussen somit die Empfangseigenschaften.

The main reflector of VLBI radio telescopes is affected by several disturbing forces. Temperature... more The main reflector of VLBI radio telescopes is affected by several disturbing forces. Temperature, wind, insolation or snow load deform the surface of the reflector and impair the receiving properties. Depending on the elevation orientation of the main reflector, the dead load of the dish w.r.t. the gravitation field of the Earth influence the surface negatively. In recent years, surface deformations and variations of the focal length have been analyzed by several groups. The common mathematical model to describe the main reflector is an ordinary rotational paraboloid. Due to the reflector design improvements, the surface of the main reflector of many of the upcoming VGOS radio telescopes cannot be parameterized by an ordinary rotational paraboloid. We present a unified mathematical model that overcomes this limitation and which is valid for the ordinary surface design as well as the new ring-focus reflector design of VGOS radio telescopes. The model is used for an independent confirmation of the specifications of the new Onsala twin telescopes at the Onsala Space Observatory.

We participated in 39 IVS sessions, including CONT14. Eleven out of the initially planned session... more We participated in 39 IVS sessions, including CONT14. Eleven out of the initially planned sessions could not be observed due to the installation of a new radome for the 20-m radio telescope. As in the previous six years, we used several of the sessions that involved both Onsala and Tsukuba to perform ultrarapid UT1-UTC sessions together with our colleagues in Tsukuba. This included the complete CONT14 campaign where near real-time UT1-UTC on the baseline Onsala-Tsukuba could be determined. The procurement of the telescopes for the Onsala Twin Telescopes was started in the summer of 2014. The contract to buy two VGOS radio telescopes was signed at the end of the year.

We present long term trends in the amount of atmospheric water vapor at the Swedish West Coast de... more We present long term trends in the amount of atmospheric water vapor at the Swedish West Coast derived from four different techniques. Three of the techniques, geodetic Very Long Baseline Interferometry (VLBI), GPS and ground-based microwave radiometry, are co-located at the the Onsala Space Observatory, while the fourth technique, radiosondes, is operated at Gothenburg-Landvetter Airport in about 37 km distance to Onsala. The time series cover up to 30 years of data. The four techniques detect individual positive trends in the integrated water vapor (IWV) on the order of 0.3 to 0.6 kg/m 2 per decade. The IWV data derived from the techniques have correlation coefficients on the order of 0.95 and better and rootmean-square differences of less than x.x. However, there is no perfect agreement between the IWV trends derived by the four techniques, which partly might be explained by different temporal sampling and data gaps.

We have measured the key deforming parameters of the Onsala 20 m telescope with laser based track... more We have measured the key deforming parameters of the Onsala 20 m telescope with laser based tracker, scanner and electronic distance meters. The parameters show both thermal and elevation dependence at an order of some millimeters, and are therefore potential significant contributors to a scale error in VLBI analysis.

This report briefly summarizes the activities of the IVS Analysis Center at the Onsala Space Obse... more This report briefly summarizes the activities of the IVS Analysis Center at the Onsala Space Observatory during 2014 and gives examples of results of ongoing work. 1 General Information We concentrate on research topics that are relevant for space geodesy and geosciences. These research topics are related to data observed with geodetic VLBI and complementing techniques.

Astronomy and Astrophysics, Sep 1, 2016

Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agen... more Context. The closest ever fly-by of the Martian moon Phobos, performed by the European Space Agency's Mars Express spacecraft, gives a unique opportunity to sharpen and test the Planetary Radio Interferometry and Doppler Experiments (PRIDE) technique in the interest of studying planet-satellite systems. Aims. The aim of this work is to demonstrate a technique of providing high precision positional and Doppler measurements of planetary spacecraft using the Mars Express spacecraft. The technique will be used in the framework of Planetary Radio Interferometry and Doppler Experiments in various planetary missions, in particular in fly-by mode. Methods. We advanced a novel approach to spacecraft data processing using the techniques of Doppler and phase-referenced very long baseline interferometry spacecraft tracking. Results. We achieved, on average, mHz precision (30 µm/s at a 10 s integration time) for radial three-way Doppler estimates and sub-nanoradian precision for lateral position measurements, which in a linear measure (at a distance of 1.4 AU) corresponds to ∼50 m.

This page was generated automatically upon download from the ETH Zurich Research Collection. For ... more This page was generated automatically upon download from the ETH Zurich Research Collection. For more information, please consult the Terms of use.

The Global Geodetic Observing System (GGOS) requires a globally distributed network utilizing nex... more The Global Geodetic Observing System (GGOS) requires a globally distributed network utilizing next generation Satellite Laser Ranging (SLR) and Very Long Baseline Interferometry (VLBI) technology to meet the objectives of GGOS. It is expected that about 30 core sites will be established globally to ensure adequate network density and geometry. The proposal presented here highlights opportunities for VLBI network densification. We consider both southern Africa and Antarctica sites for the establishment of new VLBI sites. We have made u-v coverage plots and geodetic VLBI simulations for several sites, and evaluate these in terms of their scientific value. Both the southern Africa and Antarctica sites should be equipped with VGOS compatible antennas. In particular we propose the establishment of a new core fundamental station in Antarctica, operated and funded by an international consortium. This core GGOS site could be located at either the Norwegian (Troll) or South African Antarctic...

We report the results of position ties for short baselines at eight geodetic sites based on phase... more We report the results of position ties for short baselines at eight geodetic sites based on phase delays that are extracted from global geodetic very-long-baseline interferometry (VLBI) observations rather than dedicated short-baseline experiments. An analysis of phase delay observables from two antennas at the Geodetic Observatory Wettzell, Germany, extracted from 107 global 24-hour VLBI sessions since 2019 yields weighted root-mean-square scatters about the mean baseline vector of 0.3, 0.3, and 0.8 mm in the east, north, and up directions, respectively. Position ties are also obtained for other short baselines between legacy antennas and nearby, newly built antennas. They are critical for maintaining a consistent continuation of the realization of the terrestrial reference frame, especially when including the new VGOS network. The phase delays of the baseline WETTZ13N-WETTZELL enable an investigation of sources of error at the sub-millimeter level. We found that a systematic variation of larger than 1 mm can be introduced to the up estimates of this baseline vector when atmospheric delays were estimated. Although the sub-millimeter repeatability has been achieved for the baseline vector WETTZ13N-WETTZELL, we conclude that long term monitoring should be conducted for more short baselines to assess the instrumental effects, in particular the systematic differences between phase delays and group delays, and to find common solutions for reducing them. This will be an important step towards the goal of global geodesy at the 1 mm level.

Journal of Geodynamics, 2013

The deformation of the anelastic Earth as a response to external forces from the Moon and Sun is ... more The deformation of the anelastic Earth as a response to external forces from the Moon and Sun is characterized with proportionality parameters, the socalled Love and Shida numbers. The increasing precision and quality of the VLBI (Very Long Baseline Interferometry) measurements allow determining those parameters. In particular, the long history of the VLBI data enables the estimation of Love and Shida numbers at the low frequencies with the longest period of a tidal wave at 18.6 years. In this study we analyze 27 years of VLBI measurements (1984.0-2011.0) following the recent IERS Conventions 2010. In several global solutions, we estimate the complex Love and Shida numbers of the solid Earth tides for the main long-period tidal waves. Furthermore, we determine the Love and Shida numbers of the rotational deformation due to polar motion, the so-called pole tide.