Pierguido Sarti

Pierguido Sarti
National Institute of Astrophysics | INAF · Istituto di Radioastronomia - Bologna

Ph.D.

About

59
Publications
5,800
Reads
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502
Citations
Additional affiliations
December 2011 - present
California Institute of Technology
January 2005 - present
INAF-Istituto Nazionale di Astrofisica
January 2000 - January 2005
Italian National Research Council
Education
February 1997
University of Bologna
Field of study
  • Topography and Geodesy
March 1992
University of Bologna
Field of study
  • Physics

Publications

Publications (59)
Article
Full-text available
The atmospheric humidity in the Polar Regions is an important factor for the global budget of water vapour, which is a significant indicator of Earth’s climate state and evolution. The Global Navigation Satellite System (GNSS) can make a valuable contribution in the calculation of the amount of Precipitable Water Vapour (PW). The PW values retrieve...
Article
The atmospheric water vapor is an important indicator of the Earth's climate state and evolution. We therefore aimed at calculating the content and long-term variation of the precipitable water vapor at five coastal Antarctic stations, i.e., Casey, Davis, Mawson, McMurdo, and Mario Zucchelli. To do that, we processed the 12-year time series of GPS...
Article
Full-text available
This paper compares three different methods capable of estimating the deflection of the vertical (DoV): one is based on the joint use of high precision spirit leveling and Global Navigation Satellite Systems (GNSS), a second uses astro-geodetic measurements and the third gravimetric geoid models. The working data sets refer to the geodetic Internat...
Article
Global geodetic observatories (GGO) play an increasingly important role both for scientific and societal applications, in particular for the maintenance and evolution of the reference frame and those applications that rely on the reference frame for their viability. The International Association of Geodesy (IAG), through the Global Geodetic Observi...
Data
Very Long Baseline Interferometry (VLBI) is a primary space-geodetic technique for determining precise coordinates on the Earth, for monitoring the variable Earth rotation and orientation with highest precision, and for deriving many other parameters of the Earth system. The International VLBI Service for Geodesy and Astrometry (IVS, http://ivscc.g...
Article
Full-text available
Since 1998, the Italian Antarctic Programme has been funding space geodetic activities based on the use of episodic and permanent global positioning system (GPS) observations. As well as their exploitation in geodynamics, these data can be used to sense the atmosphere and to retrieve and monitor its water vapor content and variations. The surface p...
Article
The Italian geodetic infrastructure in Antarctica has been constantly developed during the last two decades. The integration of geodetic instruments with other geophysical sensors has been driving the planning and design of the geodetic infrastructure at Mario Zucchelli Station (MZS) and in a wide area around the base. Our purpose is to maximize th...
Article
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...
Article
We process the total-station surveys performed at the ITRF co-location site Medicina (Northern Italy) over the decade (2001-2010) with the purpose of determining the extent of local intrasite motions and relating them to local geophysical processes, the geological setting and the design of the ground pillars. In addition, continuous observations ac...
Chapter
Tie vectors (TVs) measured at co-location sites carry fundamental information for the computation of the International Terrestrial Reference Frame (ITRF). The combination of the different frames stemming from each space geodetic (SG) technique relies on the availability and accuracy of the relative positions between reference points of co-located S...
Article
The 64-m Sardinia Radio Telescope (SRT) is currently under construction in Sardinia (Italy). To ensure future surveying and monitoring operations at an utmost level of accuracy, we aim at selecting the optimal design and the most cost-effective solution for the establishment of the local ground control network (LGCN). We simulate and test 45 data s...
Article
The combination of space geodetic techniques nowadays relies on the provision of accurate tie vectors locally measured on the ground at geodetic co-location sites. Co-location of space geodetic sensors on-board orbiting spacecraft (i.e. space co-locations) is an appealing solution to mitigate the shortcomings of terrestrial local ties, but their im...
Poster
During the Antarctic Italian expedition carried out in 1999 a geodetic network was materialized on rocky outcrops throughout the Northern Victoria Land (NVL), Antarctica. The project, named VLNDEF (Victoria Land Network for DEFormation control), started with the goal to detect neotectonic phenomena present in the region and to supply metrical infor...
Article
Full-text available
Very-long-baseline interferometry (VLBI) is used for establishing global 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 t...
Article
This paper sets the rules for an optimal definition of precise signal path variation (SPV) models, revising and highlighting the deficiencies in the calculations adopted in previous studies and improving the computational approach. Hence, the linear coefficients that define the SPV model are rigorously determined. The equations that are presented d...
Article
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 model...
Article
Improved computation of gravity-dependent signal path variation models for Cassegrainian VLBI telescopes with tapered illumination functions
Article
The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (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 gravitationa...
Article
Ground-based dual-frequency GPS observations can be used to create images of electron density. This is well established for the Arctic ionosphere; here one of the first results is presented for the Antarctic. In this study, the GPS receivers in the Antarctic are supplemented with another GPS receiver onboard CHAMP. The aim of the study is to demons...
Article
ITRF combinations rely on the availability of accurate tie vectors linking reference points of space geodetic techniques. Co-located instruments are assumed to move consistently and no local relative motion is taken into account. Instabilities may degrade the quality of the co-location itself and perturb the result of ITRF combinations. This work a...
Article
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...
Article
Tie vectors (TVs) between co-located space geodetic instruments are essential for combining terrestrial reference frames (TRFs) realised using different techniques. They provide relative positioning between instrumental reference points (RPs) which are part of a global geodetic network such as the international terrestrial reference frame (ITRF). T...
Article
The very long baseline interferometry (VLBI) antenna in Medicina (Italy) is a 32-m AZ-EL mount that was surveyed several times, adopting an indirect method, for the purpose of estimating the eccentricity vector between the co-located VLBI and Global Positioning System instruments. In order to fulfill this task, targets were located in different par...
Article
Laser scanning surveys were performed on the primary mirror of the very long baseline interferometry (VLBI) telescopes situated at Medicina and Noto observatories, with the specific purpose of investigating (1) gravity deformation patterns of the radio telescopes' primary reflector and (2) the magnitude and relative variations of focal length as th...
Article
Full-text available
Medicina (Northern Italy) and Noto (Sicily) 32 m, AZ-EL, VLBI radio tele- scopes are managed by the Institute of Radioas- tronomy and funded by the National Institute of Astrophysics. They have been successfully per- forming geodetic observations since the end of the 80s. Nowadays, geodetic research is no longer an IRA institutional research activi...
Chapter
Local ties are key elements for the computation of combined space geodetic products: the different ITRF realizations determined by merging single technique geodetic reference frames rely on the availability of accurate eccentricities (or intra-site vectors) linking the instrumental reference points (RPs) at co-located observatories. If the RPs cann...
Article
Full-text available
During the measurement sessions gravity might induce significant deformations in large VLBI telescopes. If neglected or mismod-elled, 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-techni...
Article
Precise measurement and maintenance of the Terrestrial Reference Frame (TRF) is essential to long-term monitoring of global change. The TRF is realized through the integration of high precision GNSS, SLR, VLBI and DORIS networks. Each of these techniques has unique strengths and weaknesses. Station positions and velocities from the different techni...
Chapter
Scientific investigations in Antarctica are, for many different reasons, a challenging and fascinating task. Measurements, observations and field operations must be carefully planned well in advance and the capacity of successfully meeting the goals of a scientific project is often related to the capacity of forecasting and anticipating the many di...
Conference Paper
Full-text available
We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radiotelescope capable to operate with high efficiency in the 0.3-116 GHz frequency range. The instrument is the result of a scientific and technical collaboration among three Structures of the Italian National Institu...
Chapter
Full-text available
The Italian “Mario Zucchelli” Station (-74° 41′ 55′′.6997 N, 164° 06′ 10′′. 5887 E), situated at Terra Nova Bay, Northern Victoria Land, is equipped with a permanent Global Positioning System receiver (TNB1), continuously observing since 1998. “Mario Zucchelli” is an Antarctic experimental facility where a large number of scientific observations ar...
Article
We assess the accuracy of some indirect approaches to invariant point (IVP), or system reference point, determination of satellite laser ranging (SLR) and very long baseline interferometry (VLBI) systems using both observed and simulated survey data sets. Indirect IVP determination involves the observation of targets located on these systems during...
Article
Full-text available
Sardinia Radio Telescope (SRT) potentials in geodesy are mostly connected to VLBI techniques and they may have a remarkable impact on both national and international geodetic science. A development plan concerning geodetic technical instrumentation should be provided soon, so as to perform geodetic observations with the SRT in the near future. The...
Article
Full-text available
The Osservatorio Astronomico di Cagliari (OAC) space geodesy group collaborates with the space geodesy group of the Istituto di Radioastronomia (IRA) in Bologna, forming a joint group involved in the SRT project. Planned activities, concerning geodetic and site-related surveys, will be briefly treated.
Article
This position paper focuses on the computation of local ties between co-located space geodetic instruments using terrestrial data, and on SINEX generation. We address also some important aspects related to the Reference Point (RP) definition for the various instrument types, i.e. VLBI, SLR, GPS and DORIS. The main issue is related to the data analy...
Article
This paper describes our experiences in measuring the GPS-VLBI eccentricity at Medicina (Italy). It has been re-measured yearly during three different terrestrial surveys (2001, 2002 and 2003) and corresponding SINEX files with full variance covariance information were produced. The eccentricity vector connecting the GPS and the VLBI reference poin...
Article
A new and comprehensive method is presented that can be used for estimating eccentricity vectors between global positioning system (GPS) antennas, doppler orbitography and radiopositioning integrated by satellites (DORIS) antennas, azimuth-elevation (AZ-EL) very long baseline interferometry (VLBI) telescopes, and satellite laser ranging (SLR) and l...
Article
Full-text available
In the frame of the 1999-2000 Italian expedition in Antarctica a scientific programme for geodynamic purposes in the northern Victoria Land begun. The new project VLNDEF (Victoria Land Network for DEFormation control) deals with the monitoring of crustal deformations within the investigated area. The newly-monumented GPS stations and the following...
Article
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 c...
Article
The Western Svalbard fold-and-thrust belt has a complex tectonic history linked to the openning of the Northern Atlantic Ocean. The last recognised important tectonic event in this area is dated from the Late Tertiary when the Ny Aalesund tertiary basin has been overthrust by carboniferous rocks. Thus the area of Ny Aalesund (Western Svalbard) is s...
Article
We present a comprehensive operational methodology, based on classical geodesy triangulation and trilateration, that allows the determination of reference points of the five space geodesy techniques used in ITRF computation (i.e.: DORIS, GPS, LLR, SLR, VLBI). Most of the times, for a single technique, the reference point is not accessible and measu...
Article
For two years, CNR (ITALY) has been involved in a complete renovation of the way Space Geodesy coloocated instruments are surveyed. Local ties are one of the most problematic part of International Terrestrial Reference Frame (ITRF) computation since the accuracy of Space Geodesy techniques has decreased to a few millimeters level. Therefore everybo...
Article
Full-text available
The paper discusses the long time series analysis of GPS permanent station located at Terra Nova Bay, East Antarctica (Victoria Land). The station (TNB1) was monumented during the 1997–1998 Italian expedition in Antarctica and the data collection started on January 1998. TNB1 is included in the Victoria Land network for deformation control (VLNDEF)...
Article
Surveying the reference point of VLBI radiotelescopes within a local ground control network is, nowadays, a very important task. Reference point can be determined using a molteplicity of approaches. We have choosen and tested a purely theoretical ap- proach, writing two routines for best-fitting 3-D surfaces computation. Surveying the antenna struc...
Article
VLNDEF (Victoria Land Network for DEFormation control) project started in 1999 with the aim to measure a network for the study of regional geodynamics of northern Victoria Land. In 1999-2000 and 2000-01 italian expeditions, a network of 25 stations with an average distance of 70 km covering the area from Terra Nova Bay, italian sta- tion in Antarct...
Article
VLBI technique allows high precision estimates of relevant geodetic parameters. Dur- ing the last years research has been stressed on the improvement of VLBI observations and analysis and results are well within the centimetre level. VLBI applied to geo- dynamics therefore allows regional and global plate motions studies with very high precision. T...
Article
Full-text available
During a 6 days campaign in June 2001, we have performed a local survey at Medicina Observatory using classical geodesy and GPS techniques in order to determine the effects of an undergone track repair. We have determined the position of the reference point P within a local and ITRF2000 (epoch 1997.0) reference frames using trilateration and triang...
Chapter
During 1999 – 2000 Italian expedition in Antarctica started a new Geodetic Program with the aim to extend Northward and Southward the existing GPS geodetic network for the crustal deformation control of northern Victoria Land. The network is named VLNDEF (Victoria Land Network for DEFormationn control). A network of 20 stations, spanning an area of...
Conference Paper
The aim of this work is to contribute to the effort of increasing the accuracy of VLBI geodetic parameters. We are investigating a route to disentangle the coupling between the values of the vertical coordinates and the tropospheric contributions at each site, estimated from the VLBI analysis. We present results from a novel route of analysis which...
Article
The European VLBI Network has been performing a regular series of geodetic observations (EUROPE) whose main aim is to detect and monitor deformations in the European part of the Eurasian plate with high accuracy. The interaction between the African and Eurasian plates drives the tectonic motions detected in the Southern part of Europe that, with th...
Article
Full-text available
Large VLBI telescopes undergo gravitational deformations which affect both geodetic and astronomic observations as well as the real reference point (RP) position (i.e. the reference point which is directly linked to and determined by the physics of the VLBI observations). As a consequence, the accuracy of eccentricity vectors determined with high p...
Article
Full-text available
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...
Article
Full-text available
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 geod...

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