Monia Negusini - Profile on Academia.edu (original) (raw)

Papers by Monia Negusini

Journal of Geodesy, 2011

Time-series of zenith wet and total troposphere delays as well as north and east gradients are co... more Time-series of zenith wet and total troposphere delays as well as north and east gradients are compared, and zenith total delays (Z T D) are combined on the level of parameter estimates. Input data sets are provided by ten Analysis Centers (ACs) of the International VLBI Service for Geodesy and Astrometry (IVS) for the CONT08 campaign (12-26 August 2008). The inconsistent usage of meteorological data and models, such as mapping functions, causes R. Heinkelmann (B) Deutsches Geodätisches Forschungsinstitut (DGFI),

The measurement of the reference point of the VLBI antenna at Ny-Ålesund using GPS

The precise link between different space geodesy techniques (e.g.: GPS, SLR, DORIS or VLBI) is a ... more The precise link between different space geodesy techniques (e.g.: GPS, SLR, DORIS or VLBI) is a fundamental task at any location where more than one technique is available. In the case of a VLBI antenna this task is, in general, quite difficult due to the dimension of the antenna and the fact that the reference point is, in many cases,

Italy INAF Data Center Report

... The IRA started to store geodetic VLBI databases in 1989, but the databases archived in Bolog... more ... The IRA started to store geodetic VLBI databases in 1989, but the databases archived in Bologna mostly contain data including European antennas from 1987 onward. ... The Internet address of this computer is sarip.ira.inaf.it. ...

Ground-Based Water Vapor Retrieval in Antarctica: An Assessment

IEEE Transactions on Geoscience and Remote Sensing, 2016

GPS-derived Precipitable Water Vapour in Antarctica and validation with radiosoundings

ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximate... more ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximately one third or less than that present at mid latitudes. On the Antarctic Plateau, it drops down to less than a few mm. As a consequence, the use of GPS data in sensing the atmosphere can be reliably applied only on coastal areas, were the PWV is large enough to exceed the sensitivity of the method. Radio-soundings (RS) are periodically performed at several coastal Antarctic stations, where permanent GPS equipments are also installed. The sites to be analyzed were selected according to the radiosonde equipment: the Vaisala sensors' readings were corrected specifically with ad hoc models. The co-location of GPS and radio-soundings allows us to validate the PWV content with totally independent techniques. In this investigation we present the results of the analysis of continuous long time series of GPS data acquired at Mawson (MAW1), Casey (CAS1), Davis (DAV1), McMurdo (MCM4) and Mario Zucchelli (TNB1) stations over twelve years (1999-2010). Particularly, at each site, the PWV is determined with GPS data and the same parameter derived from the analysis of the radio-sounding is used for validation. The GPS analysis is optimized for Antarctic data, using specific atmospheric models (e.g. the Vienna Mapping Function) and particular care in the data screening and elimination. The ZHD values are extracted from a grid model provided by the TU Wien (http://ggosatm.hg.tuwien.ac.at/DELAY/GRID) and bilienarly interpolated at the site location. At MZS, surface met parameters are available and used to compute the ZHD which is compared with the corresponding grid-derived ZHD series. We find discrepancies and a seasonal signal that straightforwardly impact the PW time series.

The geodetic activity at Medicina radio-astronomical observatory (Italy) has being continued in 2... more The geodetic activity at Medicina radio-astronomical observatory (Italy) has being continued in 2002 with the third survey of the local network. Previous surveys had been carried out in 2000 and 2001. Our main purpose was to monitor the stability of the VLBI reference point after two major interventions on the VLBI antenna: in August 2002 there has been a substitution of the track while in 2001 the concrete under the track has been completely replaced. It has also been the second year in which we have surveyed colocated VLBI and GPS antennas thus estimating a new value for the eccentricity vector connecting the Reference Point of each technique. The importance of co-locations and local ties in different aspects of space geodesy and especially in ITRF computation is well known. We concentrate here on the surveying aspects and on the local ground control network presenting the results of the most recent campaign performed in September 2002 in Medicina (Italy). 2002 local survey data analysis (terrestrial and GPS data) and eccentricity estimate are presented and compared to 2001 results. Eccentricities are estimated using a new and comprehensive methodology that has been presented at the EGS 2003 and is extensively described in a paper by Sarti et al. recently submitted to Journal of Geodesy.

The Medicina and Noto VLBI antennas are Az-El telescopes that experience gravitational deformatio... more The Medicina and Noto VLBI antennas are Az-El telescopes that experience gravitational deformations as they move in elevation. The ideal parabolic shape of the primary mirrors is therefore perturbed and the dishes are deformed according to the elevation pointing position of the antenna. Receivers at different frequencies, in particular the S/X geodetic receivers, are placed on the quadrupode, at the primary focus position; they also experience a displacement due to gravitational forces as the elevation changes. A third effect induced by gravity is the sag which might be possibly experienced by the dish as the elevation changes.

During the measurement sessions gravity might induce significant deformations in large VLBI teles... more During the measurement sessions gravity might induce significant deformations in large VLBI telescopes. If neglected or mismodelled, these deformations might bias the phase of the incoming signal thus corrupting the estimate of some crucial geodetic parameters (e.g. the height component of VLBI Reference Point). This paper describes a multi-technique approach implemented for measuring and quantifying the gravity-dependent deformations experienced by the 32-m diameter VLBI antenna of Medicina (Northern Italy). Such an approach integrates three different methods: Terrestrial Triangulations and Trilaterations (TTT), Laser Scanning (LS) and a Finite Element Model (FEM) of the antenna. The combination of the observations performed with these methods allows to accurately define an elevation-dependent model of the signal path variation which appears to be, for the Medicina telescope, non negligible. In the range [0, 90] deg the signal path increases monotonically by almost 2 cm. The effect of such a variation has not been introduced in actual VLBI analysis yet; nevertheless this is the task we are going to pursue in the very next future.

GPS-derived Precipitable Water Vapour in Antarctica and validation with radiosoundings

ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximate... more ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximately one third or less than that present at mid latitudes. On the Antarctic Plateau, it drops down to less than a few mm. As a consequence, the use of GPS data in sensing the atmosphere can be reliably applied only on coastal areas, were the PWV is large enough to exceed the sensitivity of the method. Radio-soundings (RS) are periodically performed at several coastal Antarctic stations, where permanent GPS equipments are also installed. The sites to be analyzed were selected according to the radiosonde equipment: the Vaisala sensors' readings were corrected specifically with ad hoc models. The co-location of GPS and radio-soundings allows us to validate the PWV content with totally independent techniques. In this investigation we present the results of the analysis of continuous long time series of GPS data acquired at Mawson (MAW1), Casey (CAS1), Davis (DAV1), McMurdo (MCM4) and Mario Zucchelli (TNB1) stations over twelve years (1999-2010). Particularly, at each site, the PWV is determined with GPS data and the same parameter derived from the analysis of the radio-sounding is used for validation. The GPS analysis is optimized for Antarctic data, using specific atmospheric models (e.g. the Vienna Mapping Function) and particular care in the data screening and elimination. The ZHD values are extracted from a grid model provided by the TU Wien (http://ggosatm.hg.tuwien.ac.at/DELAY/GRID) and bilienarly interpolated at the site location. At MZS, surface met parameters are available and used to compute the ZHD which is compared with the corresponding grid-derived ZHD series. We find discrepancies and a seasonal signal that straightforwardly impact the PW time series.

Terra Nova Bay GPS permanent station

GPS and Radiosonde Derived Precipitable Water Vapour Content and its Relationship with 5 Years of Long-Wave Radiation Measurements at “Mario Zucchelli” Station, Terra Nova Bay, Antarctica

The GPS data set acquired over a six-year period spanning 2000-2005 by the permanent GPS station ... more The GPS data set acquired over a six-year period spanning 2000-2005 by the permanent GPS station TNB1 installed at Mario Zucchelli station is here analyzed, with the aim of retrieving the Precipitable Water (PW) content. Precise calculations and measurements of the mean ...

Annals of Geophysics, 2010

geodetic networks where the coordinates attain a 1-mm level of precision. Technique-dependent bia... more geodetic networks where the coordinates attain a 1-mm level of precision. Technique-dependent bias can degrade the VLBI positioning accuracy if it is present and unaccounted for. Among the potential bias, gravitational flexure of VLBI telescopes can vary the path traveled by the incoming radio signal and induce a bias in the height component of the station position. We process here more than 100 European VLBI sessions spanning 1990-2009 with VLBI time delay/Solve software, as the only VLBI analysis package that can be used to correct signal-path variation (SPV) due to gravitational flexure of VLBI telescopes. Currently, SPV models are neglected in VLBI data analysis. To determine the kinematics of the European area over the last 20 years and to assess the effects of telescope gravitational deformation on geodetic VLBI estimates, we perform two VLBI solutions with and without SPV models for telescopes in Medicina (northern Italy) and Noto (southern Italy). The two solutions differ by 8.8 mm and 7.2 mm in their height components, with this bias being one order of magnitude larger than the formal errors of the estimated heights. SPV models impact uniquely on the height component of stations where SPVs are modeled. Velocities are not affected by the use of the Medicina and Noto SPV models, and we show that the crustal kinematics derived from VLBI does not suffer from a lack of information with regard to the flexure of other telescopes.

During the measurement sessions gravity might induce significant deformations in large VLBI teles... more During the measurement sessions gravity might induce significant deformations in large VLBI telescopes. If neglected or mismodelled, these deformations might bias the phase of the incoming signal thus corrupting the estimate of some crucial geodetic parameters (e.g. the height component of VLBI Reference Point). This paper describes a multi-technique approach implemented for measuring and quantifying the gravity-dependent deformations experienced by the 32-m diameter VLBI antenna of Medicina (Northern Italy). Such an approach integrates three different methods: Terrestrial Triangulations and Trilaterations (TTT), Laser Scanning (LS) and a Finite Element Model (FEM) of the antenna. The combination of the observations performed with these methods allows to accurately define an elevation-dependent model of the signal path variation which appears to be, for the Medicina telescope, non negligible. In the range [0, 90] deg the signal path increases monotonically by almost 2 cm. The effect of such a variation has not been introduced in actual VLBI analysis yet; nevertheless this is the task we are going to pursue in the very next future.

Tropospheric Parameters Estimated by Geodetic VLBI Data IVS

Geodetic techniques applied to the study of the Etna volcano area (Italy)

International Journal of Earth Sciences, 2011

Volcanic behaviour of Mt. Etna is due to the complex interaction between both the local and the r... more Volcanic behaviour of Mt. Etna is due to the complex interaction between both the local and the regional stress field involving the eastern Sicily. Eruptions could trigger (be triggered?) during crust extension and/or compression, which are strictly linked with the dynamics of the lower mantle. In this study, very long baseline interferometry (VLBI) space geodesy technique has been used in

VLBI telescopes' gravitational deformations investigated with terrestrial surveying methods

Colocation of VLBI reference point and GPS permanent station using rapid static and kinematic GPS

During a one day measurement campaign carried out in 2001 and 2002, we used rapid static and kine... more During a one day measurement campaign carried out in 2001 and 2002, we used rapid static and kinematic GPS techniques in order to determine the reference point of the VLBI antenna situated at the radioastronomical observatory of Medicina. Triangulation and trilateration using high precision total stations have demonstrated millimetre accuracy but can be very time consuming. This latter approach also

VLBI height corrections due to gravitational deformation of antenna structures

From an analysis of regional European VLBI data we evaluate the impact of a VLBI signal path corr... more From an analysis of regional European VLBI data we evaluate the impact of a VLBI signal path correction model developed to account for gravitational deformations of the antenna structures. The model was derived from a combination of terrestrial surveying methods applied to telescopes at Medicina and Noto in Italy. We find that the model corrections shift the derived height components

Height biases and scale variations in VLBI networks due to antenna gravitational deformations

The impact of signal path variations (SPVs) caused by antenna gravity deformations on geodetic VL... more The impact of signal path variations (SPVs) caused by antenna gravity deformations on geodetic VLBI results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models, estimates of the antenna reference point (ARP) positions are shifted

In April 2002 the IVS (International VLBI Service for Geodesy and Astrometry) set up the IVS Pilo... more In April 2002 the IVS (International VLBI Service for Geodesy and Astrometry) set up the IVS Pilot Project - Tropospheric Parameters and the Institute of Geodesy and Geophysics (IGG), Vienna, was asked to coordinate the project. After a call for participation six IVS Analysis Centers have joined the project and submitted their estimates of tropospheric parameters (wet and total zenith

Journal of Geodesy, 2011

Time-series of zenith wet and total troposphere delays as well as north and east gradients are co... more Time-series of zenith wet and total troposphere delays as well as north and east gradients are compared, and zenith total delays (Z T D) are combined on the level of parameter estimates. Input data sets are provided by ten Analysis Centers (ACs) of the International VLBI Service for Geodesy and Astrometry (IVS) for the CONT08 campaign (12-26 August 2008). The inconsistent usage of meteorological data and models, such as mapping functions, causes R. Heinkelmann (B) Deutsches Geodätisches Forschungsinstitut (DGFI),

The measurement of the reference point of the VLBI antenna at Ny-Ålesund using GPS

The precise link between different space geodesy techniques (e.g.: GPS, SLR, DORIS or VLBI) is a ... more The precise link between different space geodesy techniques (e.g.: GPS, SLR, DORIS or VLBI) is a fundamental task at any location where more than one technique is available. In the case of a VLBI antenna this task is, in general, quite difficult due to the dimension of the antenna and the fact that the reference point is, in many cases,

Italy INAF Data Center Report

... The IRA started to store geodetic VLBI databases in 1989, but the databases archived in Bolog... more ... The IRA started to store geodetic VLBI databases in 1989, but the databases archived in Bologna mostly contain data including European antennas from 1987 onward. ... The Internet address of this computer is sarip.ira.inaf.it. ...

Ground-Based Water Vapor Retrieval in Antarctica: An Assessment

IEEE Transactions on Geoscience and Remote Sensing, 2016

GPS-derived Precipitable Water Vapour in Antarctica and validation with radiosoundings

ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximate... more ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximately one third or less than that present at mid latitudes. On the Antarctic Plateau, it drops down to less than a few mm. As a consequence, the use of GPS data in sensing the atmosphere can be reliably applied only on coastal areas, were the PWV is large enough to exceed the sensitivity of the method. Radio-soundings (RS) are periodically performed at several coastal Antarctic stations, where permanent GPS equipments are also installed. The sites to be analyzed were selected according to the radiosonde equipment: the Vaisala sensors' readings were corrected specifically with ad hoc models. The co-location of GPS and radio-soundings allows us to validate the PWV content with totally independent techniques. In this investigation we present the results of the analysis of continuous long time series of GPS data acquired at Mawson (MAW1), Casey (CAS1), Davis (DAV1), McMurdo (MCM4) and Mario Zucchelli (TNB1) stations over twelve years (1999-2010). Particularly, at each site, the PWV is determined with GPS data and the same parameter derived from the analysis of the radio-sounding is used for validation. The GPS analysis is optimized for Antarctic data, using specific atmospheric models (e.g. the Vienna Mapping Function) and particular care in the data screening and elimination. The ZHD values are extracted from a grid model provided by the TU Wien (http://ggosatm.hg.tuwien.ac.at/DELAY/GRID) and bilienarly interpolated at the site location. At MZS, surface met parameters are available and used to compute the ZHD which is compared with the corresponding grid-derived ZHD series. We find discrepancies and a seasonal signal that straightforwardly impact the PW time series.

The geodetic activity at Medicina radio-astronomical observatory (Italy) has being continued in 2... more The geodetic activity at Medicina radio-astronomical observatory (Italy) has being continued in 2002 with the third survey of the local network. Previous surveys had been carried out in 2000 and 2001. Our main purpose was to monitor the stability of the VLBI reference point after two major interventions on the VLBI antenna: in August 2002 there has been a substitution of the track while in 2001 the concrete under the track has been completely replaced. It has also been the second year in which we have surveyed colocated VLBI and GPS antennas thus estimating a new value for the eccentricity vector connecting the Reference Point of each technique. The importance of co-locations and local ties in different aspects of space geodesy and especially in ITRF computation is well known. We concentrate here on the surveying aspects and on the local ground control network presenting the results of the most recent campaign performed in September 2002 in Medicina (Italy). 2002 local survey data analysis (terrestrial and GPS data) and eccentricity estimate are presented and compared to 2001 results. Eccentricities are estimated using a new and comprehensive methodology that has been presented at the EGS 2003 and is extensively described in a paper by Sarti et al. recently submitted to Journal of Geodesy.

The Medicina and Noto VLBI antennas are Az-El telescopes that experience gravitational deformatio... more The Medicina and Noto VLBI antennas are Az-El telescopes that experience gravitational deformations as they move in elevation. The ideal parabolic shape of the primary mirrors is therefore perturbed and the dishes are deformed according to the elevation pointing position of the antenna. Receivers at different frequencies, in particular the S/X geodetic receivers, are placed on the quadrupode, at the primary focus position; they also experience a displacement due to gravitational forces as the elevation changes. A third effect induced by gravity is the sag which might be possibly experienced by the dish as the elevation changes.

During the measurement sessions gravity might induce significant deformations in large VLBI teles... more During the measurement sessions gravity might induce significant deformations in large VLBI telescopes. If neglected or mismodelled, these deformations might bias the phase of the incoming signal thus corrupting the estimate of some crucial geodetic parameters (e.g. the height component of VLBI Reference Point). This paper describes a multi-technique approach implemented for measuring and quantifying the gravity-dependent deformations experienced by the 32-m diameter VLBI antenna of Medicina (Northern Italy). Such an approach integrates three different methods: Terrestrial Triangulations and Trilaterations (TTT), Laser Scanning (LS) and a Finite Element Model (FEM) of the antenna. The combination of the observations performed with these methods allows to accurately define an elevation-dependent model of the signal path variation which appears to be, for the Medicina telescope, non negligible. In the range [0, 90] deg the signal path increases monotonically by almost 2 cm. The effect of such a variation has not been introduced in actual VLBI analysis yet; nevertheless this is the task we are going to pursue in the very next future.

GPS-derived Precipitable Water Vapour in Antarctica and validation with radiosoundings

ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximate... more ABSTRACT In Polar regions, the atmospheric precipitable water vapour (PWV) content is approximately one third or less than that present at mid latitudes. On the Antarctic Plateau, it drops down to less than a few mm. As a consequence, the use of GPS data in sensing the atmosphere can be reliably applied only on coastal areas, were the PWV is large enough to exceed the sensitivity of the method. Radio-soundings (RS) are periodically performed at several coastal Antarctic stations, where permanent GPS equipments are also installed. The sites to be analyzed were selected according to the radiosonde equipment: the Vaisala sensors' readings were corrected specifically with ad hoc models. The co-location of GPS and radio-soundings allows us to validate the PWV content with totally independent techniques. In this investigation we present the results of the analysis of continuous long time series of GPS data acquired at Mawson (MAW1), Casey (CAS1), Davis (DAV1), McMurdo (MCM4) and Mario Zucchelli (TNB1) stations over twelve years (1999-2010). Particularly, at each site, the PWV is determined with GPS data and the same parameter derived from the analysis of the radio-sounding is used for validation. The GPS analysis is optimized for Antarctic data, using specific atmospheric models (e.g. the Vienna Mapping Function) and particular care in the data screening and elimination. The ZHD values are extracted from a grid model provided by the TU Wien (http://ggosatm.hg.tuwien.ac.at/DELAY/GRID) and bilienarly interpolated at the site location. At MZS, surface met parameters are available and used to compute the ZHD which is compared with the corresponding grid-derived ZHD series. We find discrepancies and a seasonal signal that straightforwardly impact the PW time series.

Terra Nova Bay GPS permanent station

GPS and Radiosonde Derived Precipitable Water Vapour Content and its Relationship with 5 Years of Long-Wave Radiation Measurements at “Mario Zucchelli” Station, Terra Nova Bay, Antarctica

The GPS data set acquired over a six-year period spanning 2000-2005 by the permanent GPS station ... more The GPS data set acquired over a six-year period spanning 2000-2005 by the permanent GPS station TNB1 installed at Mario Zucchelli station is here analyzed, with the aim of retrieving the Precipitable Water (PW) content. Precise calculations and measurements of the mean ...

Annals of Geophysics, 2010

geodetic networks where the coordinates attain a 1-mm level of precision. Technique-dependent bia... more geodetic networks where the coordinates attain a 1-mm level of precision. Technique-dependent bias can degrade the VLBI positioning accuracy if it is present and unaccounted for. Among the potential bias, gravitational flexure of VLBI telescopes can vary the path traveled by the incoming radio signal and induce a bias in the height component of the station position. We process here more than 100 European VLBI sessions spanning 1990-2009 with VLBI time delay/Solve software, as the only VLBI analysis package that can be used to correct signal-path variation (SPV) due to gravitational flexure of VLBI telescopes. Currently, SPV models are neglected in VLBI data analysis. To determine the kinematics of the European area over the last 20 years and to assess the effects of telescope gravitational deformation on geodetic VLBI estimates, we perform two VLBI solutions with and without SPV models for telescopes in Medicina (northern Italy) and Noto (southern Italy). The two solutions differ by 8.8 mm and 7.2 mm in their height components, with this bias being one order of magnitude larger than the formal errors of the estimated heights. SPV models impact uniquely on the height component of stations where SPVs are modeled. Velocities are not affected by the use of the Medicina and Noto SPV models, and we show that the crustal kinematics derived from VLBI does not suffer from a lack of information with regard to the flexure of other telescopes.

During the measurement sessions gravity might induce significant deformations in large VLBI teles... more During the measurement sessions gravity might induce significant deformations in large VLBI telescopes. If neglected or mismodelled, these deformations might bias the phase of the incoming signal thus corrupting the estimate of some crucial geodetic parameters (e.g. the height component of VLBI Reference Point). This paper describes a multi-technique approach implemented for measuring and quantifying the gravity-dependent deformations experienced by the 32-m diameter VLBI antenna of Medicina (Northern Italy). Such an approach integrates three different methods: Terrestrial Triangulations and Trilaterations (TTT), Laser Scanning (LS) and a Finite Element Model (FEM) of the antenna. The combination of the observations performed with these methods allows to accurately define an elevation-dependent model of the signal path variation which appears to be, for the Medicina telescope, non negligible. In the range [0, 90] deg the signal path increases monotonically by almost 2 cm. The effect of such a variation has not been introduced in actual VLBI analysis yet; nevertheless this is the task we are going to pursue in the very next future.

Tropospheric Parameters Estimated by Geodetic VLBI Data IVS

Geodetic techniques applied to the study of the Etna volcano area (Italy)

International Journal of Earth Sciences, 2011

Volcanic behaviour of Mt. Etna is due to the complex interaction between both the local and the r... more Volcanic behaviour of Mt. Etna is due to the complex interaction between both the local and the regional stress field involving the eastern Sicily. Eruptions could trigger (be triggered?) during crust extension and/or compression, which are strictly linked with the dynamics of the lower mantle. In this study, very long baseline interferometry (VLBI) space geodesy technique has been used in

VLBI telescopes' gravitational deformations investigated with terrestrial surveying methods

Colocation of VLBI reference point and GPS permanent station using rapid static and kinematic GPS

During a one day measurement campaign carried out in 2001 and 2002, we used rapid static and kine... more During a one day measurement campaign carried out in 2001 and 2002, we used rapid static and kinematic GPS techniques in order to determine the reference point of the VLBI antenna situated at the radioastronomical observatory of Medicina. Triangulation and trilateration using high precision total stations have demonstrated millimetre accuracy but can be very time consuming. This latter approach also

VLBI height corrections due to gravitational deformation of antenna structures

From an analysis of regional European VLBI data we evaluate the impact of a VLBI signal path corr... more From an analysis of regional European VLBI data we evaluate the impact of a VLBI signal path correction model developed to account for gravitational deformations of the antenna structures. The model was derived from a combination of terrestrial surveying methods applied to telescopes at Medicina and Noto in Italy. We find that the model corrections shift the derived height components

Height biases and scale variations in VLBI networks due to antenna gravitational deformations

The impact of signal path variations (SPVs) caused by antenna gravity deformations on geodetic VL... more The impact of signal path variations (SPVs) caused by antenna gravity deformations on geodetic VLBI results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models, estimates of the antenna reference point (ARP) positions are shifted

In April 2002 the IVS (International VLBI Service for Geodesy and Astrometry) set up the IVS Pilo... more In April 2002 the IVS (International VLBI Service for Geodesy and Astrometry) set up the IVS Pilot Project - Tropospheric Parameters and the Institute of Geodesy and Geophysics (IGG), Vienna, was asked to coordinate the project. After a call for participation six IVS Analysis Centers have joined the project and submitted their estimates of tropospheric parameters (wet and total zenith