| Monday, February 21 | ||
| Session 1. Highlights and Challenges of VLBI, Chair: Arthur Niell | ||
| 09:00 | Welcome | |
| 09:15 | IVS Chair's Address Wolfgang Schlüter Bundesamt für Kartographie und Geodäsie (BKG) | |
| 09:30 | IVS Coordinating Center Report
Nancy Vandenberg NVI, Inc./Goddard Space Flight Center | |
| 09:45 | From Quasars to Benchmarks: VLBI Links Heaven to Earth (invited) James Campbell Geodetic Institute, University of Bonn | |
| Abstract: Very Long Baseline Interferometry is able to provide a direct geometrical tie to the extragalactic radio sources which represent the best possible realization of an inertial system. By this token, VLBI can measure Earth rotation and orientation as well as precise station positions and their velocities without involving the gravity field of the Earth. In the broader context of Earth observation and the monitoring of geodynamic processes these and many more unique features have allowed the VLBI technique to achieve pioneering feats such as the determination of present-day plate tectonic motions, post glacial rebound, sub-daily Earth rotation variations and parameters of general relativity. In this contribution, some of the highlights of the history of VLBI will be passed in review and directions of future developments will be pointed out. | ||
| 10:15 | The Role of VLBI Among the Geodetic Space Techniques within
CSTG (invited) Hermann Drewes DGFI | |
| Abstract: The main objectives of the Commission on International Coordination of Space Techniques for Geodesy and Geodynamics (CSTG) for the next future are the optimum integration of all geodetic observation techniques in a unique global network, the International Space Geodetic Network (ISGN), and the combined processing of all heterogeneous space geodetic measurements in a common data analysis procedure. The combination of different techniques will provide more reliability and a higher accuracy of the results. Each of the techniques plays an important role in this procedure and provides some unique tools for the geodetic parameter estimation. VLBI is not only unique in connecting the celestial and the terrestrial reference frames, but it gives also other indispensable information about geodetic parameters, which the satellite techniques cannot solve for independently. Only the inclusion of VLBI observations will guarantee the continuity and stability of geodetic reference systems. | ||
| 10:45 | BREAK/Poster Session 1 | |
| 11:15 | Astronomical VLBI: Comparison and Contrast with Geodetic/Astrometric
VLBI (invited) Craig Walker NRAO | |
| Abstract: The same equipment that is used for studies of the Earth using geodetic VLBI can also used to study the astronomical objects that are the sources of the detected radio emission. Much of the world's VLBI infrastructure, including the VLBA, JIVE, and many of the antennas, are devoted mainly to astronomy. Targets for astronomical VLBI are generally energetic, non-thermal sources such as active galactic nuclei (quasars etc), active stars, astrophysical masers, pulsars, and supernovae. A variety of illustrative astronomical results will be presented. Astronomical VLBI observations require a wider variety of observing styles and frequency bands than geodetic VLBI. Individual astronomical observations are proposed, scheduled, and reduced by the astronomers who will publish the results. This contrasts with the geodesy style where large data bases of highly processed data are accumulated by operational groups and used by many geophysicists. Some of the culture conflicts, plus the ways geodesy and astronomy benefit each other will be covered. | ||
| 11:45 | The ICRF and Relationships Between Frames (invited) Chopo Ma NASA Goddard Space Flight Center | |
| Abstract: The ICRF, a catalog of VLBI source positions, is now the basis for astrometry and geodesy. Its construction and extension/maintenance will be discussed as well as the interaction of the ICRF, ITRF, and EOP/nutation. | ||
| 12:00 | ITRF Status and Plans for ITRF2000 (invited) Zuheir Altamimi Institut Geographique National, France | |
| Abstract: The status of the International Terrestrial Reference Frame (ITRF) and the procedure of its implementation are presented. We will focus on VLBI contributions to ITRF and their relationships to the other IERS techniques in terms of TRF definition as well as quality assessment. Future plans for ITRF2000 will be outlined. | ||
| 12:15 | LUNCH | |
| 14:00 | Geophysical Applications of Earth Rotation Measurements (invited) Tom Herring MIT | |
| Abstract: Measurements of the variations in Earth rotation have improved dramatically over the last few decades. These measurements are usually viewed in three separate ways: (a) The motions of the Earth's rotation axis with respect the crust (polar motion); (b) the variations in the rate of rotation (length-of-day, LOD); and (c) motions of the Earth's roation axis in space (nutations). VLBI is only technique available that can make reliable measurements of all of these components over long periods of time. The requirements for such stability are for (a) a stable terrestrial reference frame and for (b) and (c) a stable inertial reference frame with the latter being unique to VLBI. We discuss the relationship between and the accuracy of different space geodetic for making measurements of Earth rotation variations and the geophysical applications of each of the measurement types. | ||
| 14:30 | It's About Time! (invited) Tom Clark NASA/GSFC | |
| Abstract: Everything we do in VLBI is connected to time. In this contribution, we review 28 orders of magnitude of the spectrum of time ranging from a few hundred femtoseconds (i.e. one degree of phase at X-band ~ pi x 10**-13 sec) upwards to tens of millions of years ( i.e. ten million years ~ pi x 10**14 seconds). In this discussion, we will pay special attention to the relation between the underlying oscillator (the frequency standard that defines a clock’s rate) and the time kept by the clock (which counts the oscillations of the frequency standard). We will consider two different types of time – time kept by counting an atomic frequency standard (Hydrogen Maser or Cesium), and time reckoned by the rotation of the Earth underneath the stars and sun. | ||
| Session 2. Field Stations and Data Acquisition, Chair: Shigeru Matsuzaka | ||
| 15:00 | IVS Network Coordinator Report Ed Himwich NVI, Inc./GSFC | |
| Abstract: There several initiatives underway to assist the stations in doing as good a job as possible acquiring data. These include: (1) development of nominal performance specifications to help stations evaluate their own performance internally, (2) web based text and graphics describing station performance in experiments, and (3) periodic station visits to help improve communications, provide additional operational training, and give feedback to technology developers. These and other aspects of network coordination will be discussed. | ||
| 15:15 | BREAK/Poster Session 1 | |
| 15:45 | VLBI Electronics for Analysts: From the Feed to the Recorder (invited) Brian Corey MIT Haystack Observatory | |
| Abstract: This talk will describe how some of the critical electronic components in a VLBI system work, with an emphasis on analog electronics such as mixers, amplifiers, and phase calibrators. The ideal behavior of such devices will be described, as well as what the likely effects on VLBI observables are when a component fails or is used improperly (e.g., when an amplifier is overdriven). The basic principles of operation will be treated, without delving into the underlying semiconductor physics. | ||
| 16:15 | VLBI Data Acquisition and Recorder Systems: A Summary and
Comparison (invited) Bill Petrachenko Geodetic Survey Division, NRCan | |
| Abstract: The major specifications and a brief functional description of each VLBI data acquisition and recorder system currently in use for geodetic applications (K4, MKIII/IV, S2, VLBA) will be provided. The similarities and differences between systems will be discussed and summarized. | ||
| 16:45 | An Introduction to the Field System (invited) Ed Himwich NVI, Inc./GSFC | |
| Abstract: The Field System (FS) is a suite of programs that provides the coordinating control of VLBI data acquisition at many stations. The intention of this talk is to give those who aren't familiar with station operations some background on how operations are conducted. The basic features of the FS and operations will be described. Areas for future development will be discussed and may be of interest to those who operate stations as well. | ||
| 17:30 | Planning the Chiefs Meeting for February, 2001 (splinter meeting) Ed Himwich NVI, Inc./GSFC | |
| Purpose: The Chiefs Meeting is one of the primary training forums for geodetic VLBI operations. This splinter meeting is intended to help develop a consensus about the format, and possibly the date, of the next Chiefs Meeting. A significant issue to be discussed is whether we should continue the historical style of large infrequent meetings, move to smaller more focused and more frequent meetings, or some combinations of these. Another important topic will be collaborating with other groups, such as the EVN, on the organization of these meetings. | ||
|
Tuesday, February 22 | ||
| Session 3. Technology and Data Acquisition, Chair: Wayne Cannon | ||
| 09:00 | IVS Technology Coordinator Report Alan Whitney MIT Haystack Observatory | |
| Abstract: Much progress has been made over the last year in defining a 'VLBI Standard Interface' specification. This specification, a joint effort between the geodetic and astronomy VLBI communities, is being developed in an effort to specify standard interfaces to/from a VLBI 'data transmission system' (usually tape-based) so that data collected on inhomogeneous systems can be processed at a correlator. The first step of defining a hardware interface is almost complete, and efforts at software standardization are planned. This presentation will explain the philosophy of the VSI as well as some of the details of the interface specification. Though it will take some years before all VLBI systems adhere to VSI, this step should lead to an eventual major improvement in worldwide VLBI compatibility. | ||
| 09:20 | Geodetic VLBI Observations Using the Giga-Bit VLBI System Yasuhiro Koyama(1), Tetsuro Kondo(1), Junichi Nakajima(1), Mamoru Seki do(1), Ryuichi Ichikawa(1), Eiji Kawai(1), Hiroshi Okubo(1), Hiro Osaki(1), Hiro shi Takaba(2), Minoru Yoshida(2), and Ken-ichi Wakamatsu(2) (1) Kashima Space Research Center, Communications Research Laboratory (2) Gifu University | |
| Abstract: A mobile VLBI system with a 3-m antenna has been transported to the campus of Gifu University. Its first geodetic VLBI experiment with the 34-m antenna station at Kashima is scheduled in January by using the Giga-Bit VLBI system. The details of the experiment and its preliminary results will be reported. | ||
| 09:35 | Concept for an Affordable High-Data-Rate VLBI Recording and
Playback System Alan Whitney MIT Haystack Observatory | |
| Abstract: Recent and continuing developments of magnetic-tape data-storage systems for the computer industry provide a basis on which to create a high-performance, affordable high-data-rate (HDR) recording and playback system. Such a system would be suitable for VLBI and other applications which demand sustained data rates of a gigabit/sec (Gbps) or higher. These systems should be based on mostly-off-the-shelf hardware which will be readily available from the computer industry, with a minimum of custom design, and which can easily grow to higher data rates as the recording industry advances. Furthermore, they must be capable of unattended operation for at least 24 hours. Based on currently-announced tape products and projected industry roadmaps, the cost *per Gbps* for such systems will drop from a Year 2000 cost of ~$100K/Gbps to ~$14K/Gbps by ~2007 . This suggests that HDR systems in the range of ~8 Gbps may be available for ~$110K before the end of the next decade. | ||
| 09:50 | BREAK/Poster Session 2 | |
| Session 4. Local Surveys, Chair: Hayo Hase | ||
| 10:30 | The Importance of Local Surveys for Tying Techniques Together
(invited) John Bosworth (1) and Jim Long (2) (1) NASA Goddard Space Flight Center, (2) AlliedSignal Technical Services Co. | |
| Abstract: The synergistic benefits of combining observations from multiple space geodesy techniques located at a site is a main reason behind the proposal for the establishment of the International Space Geodetic and Gravimetric Network (ISGN). However, the full benefits of inter-comparison are only realized when the spatial relationships between the different space geodetic systems are accurately determined. These spatial relationships are best determined and documented by developing a local reference network of stable ground monuments and conducting periodic surveys to tie together the reference points (for example: the intersection of rotation axes of a VLBI antenna) of the space geodetic systems and the ground monument network. The data obtained from local surveys is vital to helping understand any systematic errors within an individual technique and to helping identify any local movement or deformation of the space geodetic systems over time. | ||
| 11:00 | Local Surveys of VLBI Telescopes: Conceptual and Practical
Issues (invited) Axel Nothnagel (1) and Ludwig Combrinck (2) Geodetic Institute, University of Bonn, (2) HartRAO | |
| Abstract: Using geodetic VLBI techniques we are able to determine station coordinates and displacement rates at millimeter accuracy levels. These results are very sensitive to local telescope displacements caused by natural phenomena or man-made modifications. In order to separate the local effects from those which are of interest such as crustal movements, land uplift and subsidence, we need to measure the position of the telescopes in the local vicinity. Local networks within walking distance of the telescope should be complemented by extended networks which provide links to geologically stable areas. In this presentation we describe the measurement procedures for local survey networks (footprints) using conventional theodolite and GPS based techniques. | ||
| 11:30 | A New GPS-VLBI Tie at the Onsala Telescope Sten Bergstrand, Rudiger Haas, Jan M. Johansson Onsala Space Observatory, Onsala, SWEDEN | |
| Abstract: Onsala is a collocated reference site reference site for IVS as well as IGS. In order to establish a new type of tie between the two observational methods, we have installed two GPS antennas on the 20m VLBI telescope. One of the antennas is permanently mounted on the apex of the subreflector support structure, the other one is intermittently attached close to the vertex of the parabola with a rigid support. Since mid 1999, repeated measurements have been performed pointing the VLBI telescope at the zenith position. First results from the analysis of these observations will be presented. | ||
| 11:45 | VLBI Determinations of Local Telescope Displacements Haas (1), R., A. Nothnagel (2), D. Behrend (3) (1) OSO, Onsala/Sweden, (2) GIUB, Bonn/Germany, (3) IEEC, Barcelona/Spain | |
| Abstract: Three VLBI telescopes participating in observations of the European geodetic VLBI network were subject to significant local displacements in the last years. In 1996 track and wheel was repaired at Medicina/Italy and Effelsberg/Germany while at Madrid/Spain similar work was carried out in 1997. At all three sites local survey measurements were performed that indicate site displacements due to the repair work. In our paper we determine the local site displacements directly from the observations in the European geodetic VLBI network and compare them to the values derived by local survey. | ||
| 12:00 | LUNCH | |
| Session 5. Observing Programs, Chair: Paolo Tomasi | ||
| 13:30 | The CORE Program Chopo Ma (1), Cynthia Thomas (2), Nancy Vandenberg (2) (1) NASA Goddard Space Flight Center, (2) NVI, Inc./GSFC | |
| Abstract: Various aspects of the Continuous Observations of the Rotation of the Earth (CORE) program will be discussed, including the science goals, validation strategy, observing status, and evolutionary plan. | ||
| 13:45 | The European VLBI Project James Campbell and Axel Nothnagel Geodetic Institute, University of Bonn | |
| Abstract: The project aims at determining present-day vertical motions of the Earth's crust by measuring the vertical position differences between the fixed VLBI-stations in Europe with very high accuracy at regular intervals of time using the geodetic VLBI and GPS techniques. The VLBI observations have been continuing through 1998 and 1999 at a rate of six experiments per year with slightly different station configurations. The vertical site motions derived in the analysis of the 7-year time series start to show significant trends relative to Wettzell (held fixed): at the station of Medicina we found subsidence of -4.8 mm/y, probably related to groundwater and gas withdrawal in the Po-plains. At Onsala and Ny Alesund a small uplifts of about +1 to +2 mm/y were detected. These may be associated with the postglacial uplift in Scandinavia. The uplift of +2.3 mm/y at Madrid may be due to local effects which are also seen in the GPS- data from the nearby IGS stations. | ||
| 14:00 | Current Activities in the EVN Huib van Langevelde Joint Institute for VLBI in Europe | |
| Abstract: A report will be given on the status of astronomical VLBI in Europe. The EVN has switched over to observing in MkIV and VLBA mode mostly and is currently in the process of upgrading VLBA type terminals to MkIV. The new observing modes have proven to be reliable, more problems originate from the use of mixed thin and thick tapes. Becasue of the VSOP (Space VLBI) project, the EVN is still operated in 4 sessions a year. New developments have been the advent of UHF and 5cm receivers and work on frequency flexibility. More and more observing programs use phase referencing techniques. The situation with correlators for the EVN is tight. Using the MkIV/VLBA modes has been made possible through the VLBA correlator. The EVN MkIV correlator at JIVE is operational, albeit for a limited number of observing modes and with limited throughput. | ||
| 14:15 | Overview of Observations on the VLBA Craig Walker NRAO | |
| Abstract: The VLBA is a dedicated instrument for VLBI consisting of 10 antennas and a correlation center. The VLBA is primarily an astronomical imaging instrument, but does do occasional geodetic and astrometric observations. In this talk, I will give an overview of observing activity on the VLBA to place the geodetic observations in context. | ||
| 14:30 | Differential VLBI Observations Among a Lunar Orbiter, the Moon,
and QSOs Nobuyuki Kawano(1), Hideo Hanada(1), Takahiro Iwata(2) and Yasuhiro Koy ama(3) (1)National Astronomical Observatory of Japan, (2)National Space Development Agency of Japan, (3)CRL | |
| Abstract: A Japanese lunar explorer, SELENE will be launched in 2003. It will send two radio transmitters for differential VLBI observations. One is on board the orbiter and the other is placed on the Moon for selenodesy. It is expected that many VLBI stations take part in the observations. | ||
| 14:45 | A Southern Hemisphere Observing Program to Strengthen the ICRF:
Benefits for Astrometry, Geodesy, and Astronomy A.L. Fey, K.J. Johnston (USNO); D.L. Jauncey, J.E. Reynolds, A.K. Tziou mis (ATNF);|P. McCulloch, M.E. Costa, S.J. Ellingsen (UTas); G.D. Nicolson (HART RAO) | |
| Abstract: We will discuss our program of Southern Hemsiphere astromety and imaging observations in support of the International Celestial Reference Frame. Benefits of these observations to the geodesy/astrometry community will also be discussed as well as the benefits of the imaging observations to astronomy. | ||
| 15:00 | A Proposed Astrometric Observing Program for Densifying the ICRF in the Northern Hemisphere P. Charlot (1), B. Viateau (1)(4), A. Baudry (1), C. Ma (2), A. Fey (3) , T. M. Eubanks (3), C. Jacobs (4), O. Sovers (4) (1) Observatoire de Bordeaux, (2) NASA/GSFC, (3) USNO, (4) JPL | |
| Abstract: The International Celestial Reference Frame (ICRF) could be of significant importance to the astronomy community for observing weak objects (radio stars, pulsars, "radio-quiet" active galactic nuclei) angularly close to ICRF sources with the phase-referencing technique. However, the current distribution of the ICRF sources is found to be largely non-uniform, which precludes the wide use of the ICRF as a catalog of calibrators for phase-referencing observations. We show that adding 150 new sources at appropriate sky location would reduce the distance to the nearest ICRF source for any randomly-chosen sky location in the northern hemisphere from 13 deg. to less than 6 deg., close to the requirement of the phase-referencing technique. Accordingly, a set of 150 such sources has been selected from the JVAS catalog of flat spectrum radio sources and filtered out using the VLBA calibrator survey. An astrometric VLBI program has been submitted to the European VLBI Network (EVN) to observe these sources jointly with additional geodetic stations. The use of the EVN is essential to this project since most of the new sources will be weaker and thus difficult to observe with standard geodetic networks. | ||
| 15:15 | The S2 Geodetic VLBI Program in Canada: Operations, Experiments,
and Results Klatt(1), Berube(1), Bujold(1), Cannon(2), Feil(2), Novikov(2), Petrachenko(1), Popelar(1), Searle(2,1) (1)Geodetic Survey Division, NRCan (2)SGL, CRESTech | |
| Abstract: We will report on experiments performed using the frequency-switched S2 VLBI system by the Canadian VLBI Technical Development Center. Operational issues (including Analysis) specific to the S2 system will be addressed. Completed experiments will be described and results will be presented. The authors hope to raise a discussion on future plans for S2-based Geodesy within the IVS. | ||
| 15:30 | New Uses for the VLBI Network Tom Clark NASA/GSFC | |
Abstract:
Every VLBI group in the world seems to face a common problem:
We do not have enough money to operate and make improvements !!
In this contribution I will discuss several possibilities for “new business” that can help to
support the network without hurting the primary VLBI programs. Some of these are
already being done:
| ||
| 15:45 | BREAK/Poster Session 2 | |
| Session 6. Correlators, Chair: Tetsuro Kondo | ||
| 16:15 | How Do VLBI Correlators Work? (invited) Alan Whitney MIT Haystack Observatory | |
| Abstract: The VLBI correlator provides the 'glue' that brings all the data from separate antennas together to make them look like one! In principle, the job is a straightforward correlation of the data from the individual sites to form an interferometer beam. In practice, however, these antennas are on a rotating earth with imperfect clocks, a messy atmosphere, with data recorded at hundreds of megabit/sec on magnetic tapes with glass reels shipped thousands of miles from every corner of the earth. This talk will attempt to explain the job that the correlator has to do, how it processes the recorded data to create high-precision group-delay measurements that are the cornerstone of the geodetic and geodynamic observing programs. | ||
| 16:45 | Early Experiences with the Mark IV Correlator Kerry Kingham and Jim Martin U. S. Naval Observatory | |
| Abstract: The new Mark IV Correlator is taking over production correlation from the Mark IIIA Correlator that has been the workhorse of Geodetic VLBI for the last 14 years. Early experiences with the new correlator at USNO will be described as will the capabilities expected to be available during the initial developmental year. | ||
| 17:00 | The Bonn Mark IV Correlator Project
W. Alef (1), J.A. Zensus (1), A. Müskens (2), W. Schlüter (3) (1) Max-Planck-Institut for Radioastronomie, Bonn, (2) Geodetic Institute, University of Bonn, (3) Bundesamt für Kartographie und Geodäsie | |
| Abstract: We describe the present status of the VLBI correlator status in Bonn: The old MK III correlator has been made Y2K compliant, but is expected to be taken out of operation this year. We will report our first experience with the new MK IV correlator, jointly operated by the MPIfR and the BKG, as well as our short-term and long-term plans, both with respect to astronomical and geodetic requirements. | ||
| 17:30 | Maintenance Support Issues (splinter meeting)
Arthur Niell MIT Haystack Observatory | |
| 19:00 | Busses depart for IVS Dinner | |
| 19:30 | IVS Dinner | |
|
Wednesday, February 23 | ||
| Session 7. Analysis Part 1, Chair: Jim Ray | ||
| 09:00 | IVS Analysis Coordinator report Axel Nothnagel | |
| Abstract: The International VLBI Service for Geodesy and Astrometry (IVS) was officially inaugurated on March 1, 1999. Since then a number of activities have been initiated in order to establish the routine service functions of IVS as set forth in its Terms of Reference. One of the main thrusts of IVS is the coordination of the worldwide geodetic and astrometric VLBI analysis resources. Starting from routine analyses of observing sessions at individual analysis centers, comparisons of the Earth orientation results are presently being carried out by the IVS Analysis Coordinator. The results of these comparisons are displayed graphically and numerically on a special web page. Comparisons of TRF and CRF are currently being investigated aiming at rigorous combinations. | ||
| 09:15 | Geodetic Analysis Overview (invited) Harald Schuh DGFI | |
| Abstract: For the VLBI data analysis the best presently available knowledge is used to mathematically recreate, as closely as possible, the situation at the time of observation. The goal is to determine precise values of the parameters we are interested in, e.g. baseline components, radio source positions or Earth orientation parameters. In the talk a general overview about data analysis of geodetic/astrometric VLBI experiments will be given. The procedure of data analysis will be explained and the geophysical, environmental and instrumental effects which have to be taken into account will be presented. | ||
| 09:45 | Instrumental Errors of Geodetic VLBI Leonid Petrov Geodetic Institute of the University of Bonn | |
| Abstract: A model of VLBI observables includes effects of geometry, environment of signal propagation and delays in the data acquisition system itself. Imperfection of the model of instrumental effects can be a considerable source of errors in the estimates of the targeted parameters. The method of investigation and classification of instrumental contributions to delay is proposed. Two effects: spurious signals in phase calibration and instrumental polarization are considered in details. The methods of their detection, evaluation and calibration are shown. Influence of these effects on the final results is discussed. | ||
| 10:00 | Mark IV Data Analysis - Software Changes and Early Experiences Brent Archinal U. S. Naval Observatory | |
| Abstract: Data from the Mark IV correlator hardware/software system should first become available in late November, 1999. For various reasons, this data is formatted differently than that of the earlier Mark III and IIIA systems, for example because additional types of data and diagnostic information are available. Changes have been made and will continue to be made to the "Calc/Solve" analysis system in order to process the data in this new format. These changes and early experience in processing such data will be discussed, and some questions will be raised about whether further changes, i.e. in algorithms, weighting, and databases may be appropriate or even necessary. | ||
| 10:15 | VLBI Data Analysis with a Full Variance-Covariance Matrix Harald Schuh and Volker Tesmer DGFI, Munich, Germany | |
| Abstract: The complete model of least-squares adjustment contains the full variance-covariance matrix of the observables. Its diagonal elements can be computed from the a-priori errors of the observables. The off-diagonal elements can be derived from the a-priori errors and from the correlation coefficients between each pair of observables. However, in present standard VLBI solutions, only the variances of the observed time delays are introduced, whereas the covariances are set to zero, i.e. no a-priori correlations between the observables of a VLBI-session are taken into account. Correlations are due to imperfections of the models used in VLBI data analysis, e.g. for correcting the observables due to tropospheric refraction. Correlation coefficients are in particular high for temporally close observations. They also depend on the geometry of the network. Other reasons for correlations are observation of the same radio source due to systematic influences of the source position and of the source structure. For the IRIS-S sessions since 1994 the correlation coefficients were determined empirically, the a-priori correlation matrices were designed and were entered into the VLBI data analysis. The OCCAM 3.4 VLBI software had been modified for that purpose by introducing the full variance-covariance matrix. The results were compared with those of an uncorrelated approach. The formal errors of the results usually increased and hence became more realistic. The repeatability of the baseline lengths and of the height components improved significantly. | ||
| 10:30 | BREAK | |
| 11:00 | Optimal Estimation of Earth Orientation Parameters Using VLBI Leonid Petrov Geodetic Institute of the University of Bonn | |
| Abstract: The problem of the best strategy for estimation of the Earth orientation parameters using VLBI is considered. The present strategy for evaluation of 6 parameters for each session: UT1, UT1 rate, pole coordinates, nutation offsets contains internal contradictions and it has known deficiencies. The problem of optimization of the estimation process is considered. Different alternative parameterizations are presented. Series of the Earth orientation parameters obtained by different methods are shown and their differences are discussed. | ||
| 11:15 | Improvement of VLBI EOP Accuracy and Precision Dan MacMillan (1) and Chopo Ma (2) (1) NVI, Inc./GSFC and (2) NASA Goddard Space Flight Center | |
| Abstract: In the CORE program, EOP measurements will be made with several different networks, each operating on a different day. It is essential that systematic differences between EOP derived by the different networks be minimized. Observed biases between the simultaneous CORE-A and NEOS-A sessions are about 70-80 uas. The observed differences are consistent with an increase in the formal precision of the measurements by factors ranging from 1.2 to 1.7. We discuss the possible sources of unmodeled error that account for these factors, the sensitivities of network differences to modeling errors, and possible strategies for reducing network differences. | ||
| 11:30 | First Results of the 1999 Tsukuba-Wettzell UT1 Intensive
Test Series Nothnagel A. (1), Hase H. (1), Kilger R. (1), Ogi S. (2), Takashima K .(2), Thorandt V. (1), Ullrich D. (1) Forschungsgruppe Satellitengeodaesie, Germany (1), Geographical Survey Institut e, Japan (2) | |
| Abstract: Between May 25, 1999 and June 18, 1999, 13 observing sessions of about 2 hours duration each were observed on the baseline Tsukuba - Wettzell for the determination of UT1-UTC. The signals were recorded with the K4 recording system which was temporarily installed at Wettzell during that time. The schedule consisted of 20 scans, similar to that of the IRIS-Intensive series. The quick-look analysis produced formal errors between 5 and 20 microseconds depending on the number of successful observations. | ||
| 11:45 | Ocean Loading Tides for, in and from VLBI Hans-Georg Scherneck, Ruediger Haas, Alessandro Laudati Onsala Space Observatory, Chalmers University of Technology | |
| Abstract: The general problem of predicting surface displacements due to ocean tide loading will be reviewed. This includes the procedures in the IERS conventions and the suggestions for their next issue. In order to increase modeling accuracy we focus on the tides in the Gulf of Maine. This area is difficult to represent in global tide models. The VLBI station of Westford is located close enough to open up a model inversion opportunity. We have revived an ocean tide model to compute fully time-dependent solutions; in one run we included forcing by air pressure using ECMWF pressure fields and the corresponding geostrophic wind. We will show observed ocean loading parameters and discuss the remaining discrepancies with respect to the model results. | ||
| 12:00 | Improved atmospheric mapping functions for VLBI and GPS Arthur Niell MIT Haystack Observatory | |
| Abstract: New mapping functions based on in situ meteorological parameters have been developed for calculating the radio path length through the atmosphere at elevations down to 3 degrees. The hydrostatic component is based on the geopotential height of the 200 mb isobaric pressure level. It provides a factor of two improvement in accuracy and precision over previous hydrostatic mapping functions at mid-latitudes. The wet component is calculated from the profile of wet refractivity but will provide an improvement of only about twenty-five percent. However, since the effect of known errors in the hydrostatic mapping function dominates that from the wet component, except near the equator, implementation of these mapping functions should reduce the contribution of the atmosphere to errors in estimates by VLBI and GPS of both the vertical component of site position and the radio propagation delay due to water vapor in the atmosphere. | ||
| 12:15 | LUNCH | |
| Session 8. Analysis Part 2, Chair: Harald Schuh | ||
| 14:00 | Atmospheric Parameters Derived from Simultaneous Observations
with Space Geodetic and Remote Sensing Techniques at OSO Haas, R., L. P. Gradinarsky, G. Elgered, J. M. Johansson Onsala Space Observatory (OSO), Chalmers University of Technology (CUT), SE-43992 ONSALA (Sweden) | |
| Abstract: Onsala Space Observatory (OSO) participates as network station in the International VLBI Service for Geodesy and Astrometry (IVS), is also permanent GPS site in in the International GPS Service (IGS) and performs continuously observations using a microwave radiometer. These three independent techniques are affected by the propagation delay of radio waves in the atmosphere. We present results for atmospheric parameters derived with the three collocated techniques. We study in particular the effect of different analysis strategies with respect to a priori constraints for the variability of the turbulent atmosphere on the derived results. Temporal structure functions for atmospheric parameters derived from the three techniques will be presented. | ||
| 14:15 | Calibration of Atmospherically Induced Delay Fluctuations G.M. Resch, C.S. Jacobs, S.J. Keihm, G.E. Lanyi, C.J. Naudet, A.L. Rile y, H.W. Rosenberger, A.B. Tanner Jet Propulsion Laboratory, California Institute of Technology | |
| Abstract: We have completed a new generation of water vapor radiometers (i.e. the A- series WVR) in order to support radio science experiments with the Cassini spacecraft. These new instruments sense 3 frequencies in the vicinity of the 22.2 GHz emission line of water vapor within a 1 degree beamwidth, co-point with the radio telescope down to 10 degree elevation, and features almost an order of magnitude improvement in temperature stability compared with earlier WVR designs. For many radio science experiments, the error budget is likely to be dominated by path delay fluctuations due to atmospheric water vapor along the line-of-sight to the spacecraft. In order to demonstrate the performance of these new WVR's we have attempted to calibrate the delay fluctuations as seen by a radio inteferometer operating over a 20 km baseline with a WVR near each antenna. The characteristics of these new WVR's will be described and performance will be presented indicating an accuracy of 200 - 500 micron in tracking path delay fluctuations over timescales of 10 sec to 30 minutes. | ||
| 14:30 | Stability of the ICRF: A Time Series Approach Martine Feissel and Anne-Marie Gontier Observatoire de Paris | |
| Abstract: The qualification and maintenance of the International Celestial Reference Frame (ICRF) are currently based on global statistics on the complete data set of observations. As the founding hypothesis in the selection of extragalactic objects for accessing a quasi-inertial reference system is that their directions are fixed in space, the time variability of some of the sources is only used as a rejection criterion. The rest of the sources are considered as having apparent motions with white noise spectrum. Time series analysis of the source coordinates bring new insight in the selection and qualification of ICRF sources as well as in the estimation of the observation needs. | ||
| 14:45 | Improving the ICRF Using the Radio Reference Frame Image Database D.A. Boboltz, A.L. Fey, R.A. Gaume, K.J. Johnston U. S. Naval Observatory | |
| Abstract: We discuss U.S. Naval Observatory's ongoing program to monitor ICRF sources for variability and source structure using the VLBA and geodetic stations. The RRFID currently contains over 2200 snapshot images of over 425 compact extragalactic radio sources. Applications of the RRFID to astrometric/geodetic observations, especially intrinsic source structure corrections, will be presented. | ||
| 15:00 | Combination of VLBI, GPS, and SLR Data at the Observation Level - A Status Report P. H. Andersen Forsvarets forskningsinstitutt, Kjeller, Norway, and Institute of Theoretical Astrophysics, University of Oslo, Norway | |
| Abstract: A significant number of VLBI and SLR stations are equipped with GPS receivers. A few true fundamental stations with all three techniques even exist. Each technique has its strength and weakness with respect to the determination of geodetic parameters and together they complement each other in a way that should be fully taken advantage of in the data analysis. The simultaneous analysis of different data types at the observation level, due consideration of the physical interrelations, and presentation of results in a common reference system, are the main ideas behind the development of the GEOSAT software. A new and improved version of the software has been implemented with an automatic generation of 1) observation residuals and observation partial derivatives for VLBI, GPS and SLR, consistent at the 0.1 ppb level, and 2) a simultaneous arc-by-arc UD-filtering at the observations level. A very advanced multi-level (presently four parameter levels including stochastic parameter representations at each level) SRIF arc combination software for long-term solutions has been developed and validated. The main elements of the processing scheme will be presented. The first results with a simultaneous analysis of different space geodetic data types (VLBI, GPS, and SLR) at the observation level were presented at the IERS-98 symposium in Potsdam and at GPS99 in Tsukuba. The analysis has recently been extended with significantly more observations. Results (Earth orientation parameters, geocenter, radio source coordinates, station coordinates,...) from the new analysis will be presented. It is demonstrated that UT1 and the nutation parameters can be determined also for days where VLBI data is unavailable. | ||
| 15:15 | BREAK | |
| 15:45 | UTC and UT1: New Timing Products from the IGS (invited) Jim Ray U. S. Naval Observatory | |
| Abstract: The IGS and its Analysis Centers are engaged in developing new products related to time, some of which are relevant to the IVS community. Global comparisons and dissemination of atomic time are being developed in a pilot project with the BIPM; project information is available at http://maia.usno.navy.mil/gpst.html. In addition, high- quality estimates of universal time are now being made based on the observed motions of the GPS orbit planes. While these cannot replace the need for VLBI determinations of UT1, they are nonetheless very valuable for densifying the VLBI-based time series and for providing extremely rapid turnaround results necessary for real-time applications. | ||
| 16:15 | Cooperation and Common Interests of the IGS and the IVS (invited) Tim Springer University of Berne | |
| 16:45 | Closing Remarks and IVS Future Plans
Wolfgang Schlüter | |
| 17:00 | ADJOURN | |
|
Poster Session 1. IVS Component Reports, Chair: Richard Kilger | ||
| Network Stations | ||
|
Matera CGS VLBI Station Status
P. Colucci, D. Del Rosso, E. Lunalbi, F. Vespe ASI/Telespazio | ||
| Abstract: This poster summarises the status of the VLBI station at the Matera CGS centre. Also an overview of the technical characteristics of the system, last upgrades performed and some staff addresses will be given. | ||
|
The Geodetic Observatory O'Higgins: A Contribution to IVS in the Southern Hemisphere Andreas Reinhold(2), Hayo Hase(1),Wolfgang Schlüter(1), Reiner Wojdziak(2) (1)Bundesamt für Kartographie und Geodäsie, Fundamentalstation Wettzell, (2) Aussenstelle Leipzig | ||
| Abstract: The O'Higgins ERS/VLBI station was built in the years 1989 to 1991 and the first VLBI data acquisition took place in January 1992. In the presently IVS-network O'Higgins is one of the southest stations and it was the first station for VLBI measurements in Antarctica. During 14 campaigns more than 45 VLBI experiments were carried out successful. Additional geodetic systems were installed at the station since 1995. A permanent working Turbo Rogue GPS-Receiver, a Tide Gauge Measuring System and since 1996 a PRARE Ground Unit are working at the surroundings of the VLBI-radiotelescope. The poster will give an overview about results of all geodetic tasks in O'Higgins - Antarctica and a view to the planned future work at the station to establish the MkIV system for effectiv VLBI experiments in the Southern Hemisphere. | ||
|
The IVS Activities at Onsala Space Observatory Haas, R. G. Elgered, H.-G. Scherneck, J.M. Johansson, S. Bergstrand, L. P. Gradinarsky, B. Stoew, J, Boerjesson, H. Bouma Onsala Space Observatory (OSO), Chalmers University of Technology (CUT), ONSALA (Sweden) | ||
| Abstract: Onsala Space Observatory is active in the IVS as a network station, a technical development center, and a special analysis center. We present the activities during 1999 relevant to these three IVS components. | ||
|
Noto VLBI Station: Technological Research Activity Gino Tuccari Istituto di Radioastronomia CNR | ||
| Abstract: A description is presented regarding the principal research activities in the technological field. Recent developments and results are showed with particular emphasis to the geodetic aspects. | ||
|
VLBI Activities at GSI Shigeru Matsuzaka and Misao Ishihara Geographical Survey Institute | ||
| Abstract: Introduce recent activities of GSI's VLBI, its system overview etc. | ||
|
TIGO: Its Contribution to ITRF/IERS Hayo Hase, Armin Boeer, Stefan Riepl, Wolfgang Schlüter Bundesamt für Kartographie und Geodäsie (BKG) | ||
| Abstract: TIGO is a transportable Fundamental Station for geodesy. TIGO consists of VLBI and SLR modules as well as of GPS-array, atomic clock ensemble, super-conducting gravity meter, seismometer, meteorological sensor including a water-vapour radiometer and a server for the LAN. The power generators allow the operation at remote sites. TIGO's primary purpose is to contribute to the global reference systems for geodesy (ITRF). Its transportability will allow to place TIGO at a very beneficial site for a more homogeneity in the network of Fundamental Stations within the ITRF. | ||
|
20-m Radiotelescope at Fundamentalstation Wettzell Richard Kilger, et al. Forschungsgruppe Satellitengeodaesie, German y | ||
|
The New 40-meter Radiotelescope of OAN at Yebes Francisco Colomer OAN | ||
| Abstract: We present the characteristics of the 40 meter radiotelescope that OAN/IGN is constructing at Yebes (Spain). The new instrument will provide modern capabilities to geodetic and astronomical VLBI studies after its completion, expected by 2003. More information will be available at http://www.oan.es/cay/40m. | ||
|
Gilmore Creek Geophysical Observatory 2000 status Rich Strand NASA/GCGO | ||
| Abstract: Poster will discuss current status and display pictures of the data collection instruments operating at GCGO. | ||
|
Kokee Park Geophysical Observatory 2000 Clyde Cox AlliedSignal Technical Services Corp. | ||
| Abstract: Photos and Status of Kokee Park. | ||
| Operation Centers | ||
|
CORE Operations Center: 2000 and Beyond
Cynthia Thomas and Nancy Vandenberg NVI, Inc./Goddard Space Flight Center | ||
| Abstract: The poster will display the new CORE sessions that will start in calendar year 2000 and future years. A map of the CORE Mark IV stations and the evolution of CORE will also be displayed. | ||
| Data Centers | ||
|
The Paris Observatory Data Center (OPAR)
Najat Essaifi Paris Observatory | ||
| Abstract: Presentation of the Paris data center: organisation, files and structure. | ||
|
Status and Development of the IVS Data Center at BKG Leipzig
Volkmar Thorandt, Dieter Ullrich, Rainer Wojdziak Bundesamt für Kartographie und Geodäsie (BKG) | ||
| Abstract: The poster presents the status of the BKG Data Center as one of the three primary IVS Data Centers. It gives an overview of data stock, software, structure and organisation. | ||
|
The IVS Data Center at the CDDIS: An Overview Carey Noll and Maurice Dube NASA/GSFC | ||
| Abstract: The data centers supporting the IVS are repositories for VLBI observing schedules, station log files, and data products and are the primary means of distributing this information to the user community. This paper will detail information about IVS data flow and data center activities in general as well as information about the activities at CDDIS data center. A discussion on archiving methodology and use of the data centers will also be presented. An on-line demonstration (PC and Internet connection required) of the IVS data center at the CDDIS will be conducted | ||
| Analysis Centers | ||
|
The Paris Observatory Analysis Centre OPAR
Anne-Marie Gontier, Martine Feissel, Najat Essaifi, Didier Jean-Alexis Paris Observatory | ||
| Abstract: The poster will present the OPAR Analysis Center, its organisation and the general scientific aims. The current status of the operational calculations for the Earth's orientation will be given. | ||
|
IAA Analysis Center Activity in 1999 Zinovy Malkin IAA RAS | ||
|
Contribution of the BKG analysis group to the IVS analysis activities
Volkmar Thorandt, Dieter Ullrich, Gerald Engelhardt Bundesamt für Kartographie und Geodäsie (BKG) | ||
| Abstract: This poster gives an overview of the activities of the VLBI group at BKG Leipzig (technical equipment, history, recent analysis activities as part of the GIUB-BKG Analysis Center). The group produces "Session EOP" and TRF solutions as IVS analysis products. A comparison of VLBI- and GPS-based velocities for the German VLBI station O'Higgins (Antarctica) is given, furthermore spherical distance changes to some Southern Hemisphere stations. | ||
|
GSFC VLBI Analysis Center Activities Chopo Ma (1), David Gordon (2), Dan MacMillan (3), and Karen Baver (2) (1) NASA/GSFC, (2) Raytheon ITSS and NASA/GSFC, (3) NVI Inc. and NASA/GSFC | ||
| Abstract: An overview of the past, current, and future activities of the Goddard Space Flight Center VLBI Analysis Center, including recent software development activities; CORE program activities; the ICRF and other general research activities; and results of recent software comparisons and validation tests. | ||
| Technology Development Centers | ||
|
Recent Activities at Communications Research Laboratory
Tetsuro Kondo and CRL VLBI Group Communications Research Laboratory | ||
| Abstract: Recent VLBI related activities at Communications Research Laboratory (CRL) will be introduced. Giga-bit VLBI system is just about ready for a geodetic application. We will conduct a geodetic VLBI experiment using a giga-bit system between a 3-m antenna at Gifu and Kashima 34 m antenna in January, 2000. We are also planning to start the development of new real-time VLBI technique using IP (Internet Protocol) soon. Details will be presented in the meeting. | ||
|
The Canadian Transportable VLBI Antenna Mario Berube Geodetic Survey Division, NRCan | ||
| Abstract: A poster describing the 3.6m-diameter Canadian Transportable VLBI Antenna will be presented. This antenna is an integral part of the activities in the Canadian VLBI Technical Development Center and has been involved in a number of S2 frequency-switched VLBI system tests. | ||
|
The S2 VLBI System: DAS, RT/PT and Correlator Petrachenko(1), Bujold(1), Cannon(2,4), Carlson(3), Dewdney(3), Feil(2), Newby(2), Novikov(2), Popelar(1), Wietfeldt(5) (1)Geodetic Survey Division, NRCan (2)SGL, CRESTech, (3)DRAO, NRC, (4)York University, (5)JPL | ||
| Abstract: The S2 VLBI System synthesizes the wide IF bandwidths required by geodetic vlbi by rapidly switching the LO frequency in a small number of BBC's. Data is recorded on an array of VHS transports. Functional descriptions and specifications will be provided for the S2 Data Acquisition System (DAS), the S2 Record and Playback Terminals (RT and PT) and the S2 Correlator. | ||
|
Poster Session 2. IVS Analysis Reports, Chair: Ruediger Haas | ||
|
Determination of EOP with OCCAM and ERA Packages
Elena Skurikhina and Maria Sokolskaya Institute of Applied Astronomy, Russian Academy of Sciences | ||
| Abstract:
The EOP series obtained with OCCAM, v. 3.5, and ERA, v. 7 packages from
NEOS-A and CORE-A VLBI measurements for the period 1997-1999 have been
analyzed. 155 NEOS-A and 62 CORE-A VLBI sessions have been processed. Both
ERA and OCCAM packages process the data with models compliance with the IERS
Conventions (1996). The stations coordinates are taken from the ITRF97.
Coordinates of radio sources are taken from either RSC(IAA)99R02 or NGS files
for sources absent in RSC(IAA)99R02. In ERA package the five Earth
orientation parameters, their diurnal linear trends and coefficients of
Legendre polynomials, that approximate the stations clock and troposphere
zenith path delays, are estimated in the least square solutions. In OCCAM
package the Kalman filtering is used for estimation of stochastic parameters
such as tropospheric zenith path delay and station clocks by random work model.
To analyze the packages the series of EOP was obtained with ERA and OCCAM for NEOS-A and CORE-A programs and compared. The comparison of EOP obtained with OCCAM shows better agreement with IERS(EOP)C04 series, than those obtained with ERA. Corrected rms of estimated values obtained with ERA are less than those obtained with OCCAM for approximately 0.1 uas for Xp, Yp, dPsi, dEps and around the same for UTC. The differences NEOS-C04 and CORE-C04 of estimated values obtained with ERA and OCCAM have been analyzed for correlations. The coefficients of correlation exceed 0.45 for Yp, 0.55 for Xp and are about 0.70 for UTC. The differences between EOP estimated from NEOS-A and CORE-A observations are also calculated with OCCAM and ERA for this period. They do not have linear trend in any EOP but seem to have hidden periodicities. These differences calculated with OCCAM and ERA are similar and of significant correlation. | ||
|
A Catalogue of Radio Source Coordinates Obtained from NEOS and CORE VLBI Programs Maria Sokolskaya, Zinovy Malkin Institute of Applied Astronomy, Russian Academy of Sciences | ||
| Abstract: A new catalogue of radio sources coordinates is constructed as a combination of catalogues derived from NEOS and CORE VLBI programs for the period 1997-1999 using ERA package. The main goal of this study is to investigate systematic differences between source coordinates derived from geodetic VLBI observations made on various set of stations. At the first stage nine catalogues were obtained from observations of NEOS-A, CORE-A and CORE-B observations for 1997, 1998 and 1999. At the next stage three catalogues were derived from global (for whole period 1997-1999) processing of observations of NEOS-A, CORE-A and CORE-B. Finally, after analysis of differences between catalogues and time variations of source coordinates combined catalogue have been constructed. | ||
|
Status of IADA: An Intelligent Assostant for Data Analysis in VLBI W. Schwegmann, H. Schuh DGFI, Munich, Germany | ||
| Abstract: The poster will give an overview about the status of the development of a Knowledge-Based System (KBS) for the automation of the VLBI data analysis. In a KBS the knowledge about a problem domain is isolated and stored. It is processed by a domain-independent problem solving component. The concept of an Intelligent Assistant for Data Analysis in VLBI (IADA) will be described; it will be shown how the knowledge about the data analysis can be modeled and how these knowledge can be applied to the data analysis. To automate the data analysis using the existing software, i.e. the MarkIII Data Analysis System, and the KBS an Interface has to be developed to transfer data and information between the two components. An example will be given for this exchange of information during the VLBI data analysis. | ||
|
GINS: A New Multi-Technique Software for VLBI Analysis U. Meyer (1), P. Charlot (2), R. Biancale (1) (1) CNES/GRGS Toulouse, ( 2) Observatoire de Bordeaux | ||
| Abstract: The GINS software, developed initially for analysis of satellite geodetic technique data (SLR, DORIS, GPS), has recently been extended with a VLBI module for analysis of both Earth-based and space VLBI observations. We present the status of its development and discuss future plans. These include analysis of space VLBI data from the VSOP/HALCA satellite as well as multi-technique (VLBI/SLR/DORIS/GPS) combinations of geodetic data at the observation level. | ||
|
An Experimental Campaign for Evaluation of Wet Delay Variations Using WVRs in the Kanto District, Central Japan Ichikawa, et al. Kashima Space Research Center, Communications Research | ||
| Abstract: Radio signal delay associated with the neutral atmosphere is one of the major error sources for space-based geodetic techniques such as the Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI). Recently, several anisotropic mapping functions have been developed for the purpose of better modeling these propagation delays, thereby improving the repeatability of horizontal site coordinates. The anisotropic mapping function is considered a powerful tool for removing or calibrating the effects of horizontal variability of atmosphere from GPS and VLBI analyses. Atmospheric gradients are assumed to have a simple linear form in the anisotropic mapping function. However, it suggested that this assumption is not always appropriate in the context of intense mesoscale phenomena such as the passing of cold front, heavy rainfall events, and severe storms. Thus, in June 1998 we initiated a field experiment for detecting and characterizing water vapor variations using water vapor radiometers(WVRs) in the Kanto district of central Japan. A preliminary analysis of our findings indicates that the atmospheric gradients solutions are significantly different in spite of relatively short distance between Tsukuba and Kashima (about 54 km). This result suggests that the meso-scale weather pattern caused such large differences. | ||
|
Optical Linked VLBI Observations
Juichi Nakajima, et al. CRL, Japan | ||
| Abstract: Realtime VLBI observation named 'GALAXY' had been carried out between NAO, ISAS and CRL telescope facility. Proposal based observations were made once or twice a month. In realtime VLBI, it is possible to schedule the system dynamically during the observation based on correlated result or new astronomical event. Currently the domestic network enabled 256Mbps observation at frequency 2/5/8/22 GHz depends on telescope combination. On the other hand, 1024Mbps realtime (VL)BI experiment had performed between Kashima 34m and Kashima 26m telescope. Related topics are presented in the meeting.^ | ||
|
Celestial Reference Frame RSC(GAOUA)99 C 03
O. A. Molotaj Astronomical observatory of Kyiv University|Celestial re ference frame RSC(GAOUA)99 C 03 | ||
| Abstract: The frame RSC(GAOUA)99 C 03 comprises positions of 738 radio sources with uncertainties of 212 defining ones which are equal to 0.06 and 0.07 mas in right ascension and declination respectively. The frame axes are aligned to those of the ICRF with accuracy 0.021 mas. | ||
|
Multi-frequency VLBI Observations of the ICRF Source 1823+568
Z. Paragi et al. FOMI Satellite Geodetic Observatory | ||
| Abstract: The Inertial Celestial Reference Frame (ICRF) defining source 1823+568 was observed as a calibrator source in one of our multi-frequency very long baseline interferometry (VLBI) experiments. Imaging of the data taken at 5, 8.4, 15 and 22 GHz reveals that there is a shift in position of the source between these frequencies. The shift of the "radio core" in this object is qualitatively in agreement with predictions of conical jet models developed for radio-loud active galactic nuclei. | ||
|
Differential VLBI Observations of the Lunar Prospector
Y. Kono[1], H. Hanada[2], K. Iwadate[2], H. Araki[2], N. Kawano[2], Y. Koyama[3] , Y. Fukuzaki[4] |[1] GUAS of Japan, [2] National Astronomical Observatory of Japan, [3] CRL, [4] Geographical Survey Institute | ||
| Abstract: VRAD (VLBI radio sources on the Moon and on the relay satellite) mission measures amplitudes of the physical librations and the gravity field of the Moon by differential VLBI. These radio sources are launched in 2003 under SELENE project. We made a preliminary observation of the Lunar Prospector of NASA by using Mizusawa, Kashima and Tsukuba VLBI stations. In this experiments we determined the fringe phase within the accuracy of about 1 degree. This result shows that the observation system for VRAD can determine the fringe phase within the error of 10 degrees and the relative position between the two radio sources within the error of 1 m. | ||
|
EOP Series and Station Positions from VLBI Observations for 1984-1999
Elena Skurikhina Institute of Applied Astronomy, Russian Academy of Sciences | ||
| Abstract: EOP series and station coordinates obtained from VLBI observations since 1984 are presented. The package OCCAM version 3.5 was used for computation. Observations collected from IRIS-A, NEOS-A, CORE-A and CORE-B programs were used for this study. Station positions have been derived for every session and their temporary variations are analyzed. The EOP series since 1984 have been obtained and analyzed, too. Accuracy of EOP obtained from IRIS-A program is about twice worse than for NEOS-A one, the accuracy EOP for CORE-A and CORE-B programs is a few worse than for NEOS-A. For station position, the inner accuracy estimation is the similar for all three programs and averages about 5-10 mm. Coordinate time series for each stations is used to estimate velocity and irregular changes in station position. | ||
|
VLBI in the Deep Space Network: Challenges and Prospects
V. Altunin, G. Resch, D. Rogstad, P. Wolken * JPL/NASA, * AlliedSignal | ||
| Abstract: The purpose of this paper is to highlight the current status and prospects for VLBI in the NASA DSN. Although the prime purpose of the DSN is to support spacecraft operations and space research in deep space, this unique facility is also used on a noninterference basis with flight projects to support radio astronomy experiments. The DSN VLBI capabilities are an integral part of a number of space- and ground-based projects. It includes support of experiments at major radio astronomy VLBI networks (e.g., VLBA, Global VLBI, EVN), Space VLBI co-observing, as well as VLBI geodesy and astrometry programs. The paper will describe for the potential DSN VLBI users 1) DSN VLBI objectives, 2) the current organizational structure and 3) current, and projected capabilities. | ||
|
Geodesy/Astrometry from the VLBA
David Gordon Raytheon ITSS and NASA/GSFC | ||
| Abstract: I will present an overview of the processing of VLBA experiments, problems encountered including the infamous 'southern source' problem , analysis results and comparisons with Mark III results, earlier correlator comparisons, and a preliminary plan for a future Mark IV/VLBA correlator comparison. | ||
|
VLBI Baseline Rates from Simultaneous Solution of Baseline Measurements
with Antenna Offsets
H. B. Iz and B. A. Archinal The U.S. Naval Observatory, Department of Earth Orientation, Washington D.C., USA | ||
| Abstract: At a given site, occasionally a new VLBI antenna has replaced an older one for operational use. Large scale VLBI solutions account for these situations by assuming the motion of the old and new antenna is the same. We alternatively used composite models to estimate baseline rates (for baselines including these antennas) directly from the baseline measurements. Because the baseline lengths are invariant under rotations and translations, the combined solutions are less affected by common systematic effects and consequently simpler than the large scale solutions. We investigated the compatibility of the baseline measurements from different nearby antennas and compared the composite model solutions with the separate solutions for baseline measurements from the a) ALGOPARK to NRAO85-3 and NRAO20, b) GILCREEK to NRAO85-3 and NRAO20, and c) HARTRAO to KAUAI and KOKEE antennas. We also evaluated the gain in efficiency in estimating baseline rates as a result of increased number of observations. | ||
|
Polar Motion from VLBI Observations
Jinling Li and Guangli Wang Shanghai Observatory | ||
| Abstract: VLBI observations are analyzed to yield CRF, TRF and EOP. We show the spectrum of the polar motion series, in which the Markowitz wobble does not appear. Wavelet analysis shows that the relative variation in the amplitude of annual wobble is more obvious than that of Chandler wobble. Secular polar motion is determined by using filter. | ||
| Thursday, February 24 | ||
| 09:00 | Excursion to Fundamentalstation Wettzell Introduction to activities at a fundamental station for geodesy (Schlüter) Visit to VLBI group at 20-m radio telescope (Kilger) Visit to Transportable Integrated Geodetic Observatory (TIGO) (Hase) Visit to the Wettzell Laser Ranging System (WLRS) (Riepl, Schreiber) Visit to the GPS control station (Roettcher, Hessels) Visit to the Time & Frequency Laboratory (Feil) Visit to the seismic and gravity meter station (Stoeger) | |
| 12:00 | End of tour and departure for lunch | |
| 13:30 | Analysis Centers Workshop Axel Nothnagel | |