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Sample records for vlbi determined baseline

  1. Constraining proposed combinations of ice history and Earth rheology using VLBI determined baseline length rates in North America

    Science.gov (United States)

    Mitrovica, J. X.; Davis, J. L.; Shapiro, I. I.

    1993-01-01

    We predict the present-day rates of change of the lengths of 19 North American baselines due to the glacial isostatic adjustment process. Contrary to previously published research, we find that the three dimensional motion of each of the sites defining a baseline, rather than only the radial motions of these sites, needs to be considered to obtain an accurate estimate of the rate of change of the baseline length. Predictions are generated using a suite of Earth models and late Pleistocene ice histories, these include specific combinations of the two which have been proposed in the literature as satisfying a variety of rebound related geophysical observations from the North American region. A number of these published models are shown to predict rates which differ significantly from the VLBI observations.

  2. Length Variations of European Baselines Derived from VLBI and GPS Observations

    CERN Document Server

    Malkin, Zinovy; Skurikhina, Elena

    2011-01-01

    Results of VLBI and GPS observations were analyzed with goal to investigate differences in observed baseline length derived from both techniques. VLBI coordinates for European stations were obtained from processing of all available observations collected on European and global VLBI network. Advanced model for antenna thermal deformation was applied to account for change of horizontal component of baseline length. GPS data were obtained from re-processing of the weekly EPN (European Permanent GPS Network) solutions. Systematic differences between results obtained with two techniques including linear drift and seasonal effects are determined.

  3. Centimeter repeatability of the VLBI estimates of European baselines

    Science.gov (United States)

    Rius, Antonio; Zarraoa, Nestor; Sardon, Esther; Ma, Chopo

    1992-01-01

    In the last three years, the European Geodetic Very Long Baseline Interferometry (VLBI) Network has grown to a total of six fixed antennas placed in Germany, Italy, Spain and Sweden, all equipped with the standard geodetic VLBI instrumentation and data recording systems. During this period of time, several experiments have been carried out using this interferometer providing data of very high quality due to the excellent sensitivity and performance of the European stations. The purpose of this paper is to study the consistency of the VLBI geodetic results on the European baselines with respect to the different degrees of freedom in the analysis procedure. Used to complete this study were both real and simulated data sets, two different software packages (OCCAM 3.0 and CALC 7.4/SOLVE), and a variety of data analysis strategies.

  4. Systematic Effects in Earth Orientation Parameters Determined by VLBI

    Science.gov (United States)

    Schuh, H.; Heinkelmann, R.

    2015-12-01

    Very Long Baseline Interferometry (VLBI) is the only technique that directly connects on the observation level the realizations of ITRS and ICRS in terms of their orientation. Many applications in spacecraft navigation, fundamental astronomy, astrometry and geosciences depend on the Earth Orientation Parameters (EOP) determined by VLBI. Currently, under the IAG/IAU Joint Working Group on the Theory of Earth Rotation, activities are supported to advance the theory of Earth rotation. Some components of Earth Rotation, such as the free modes like the Free Core Nutation (FCN) are not predictable but rely entirely on the observation through VLBI. In our presentation we investigate the EOP when alternating various VLBI analysis options such as correction models, a priori parameters, and other choices with the aim to detect and quantify possible systematic effects. Our approach is purely empirical: we alternate certain analysis options and assess the differences with respect to the reference solution that adheres to the IERS Conventions (2010) and applies the standard parameterization. For demonstration we analyze the regular International VLBI Service for Geodesy and Astrometry (IVS) sessions IVS-R1 and IVS-R4.The IAG flagship component GGOS (Global Geodetic Observing System) aims to provide the EOP with an accuracy of 1 mm on the Earth surface (about 30 microarcseconds). This accuracy target will be applied as a limit to interpret the significance of the differences obtained in our comparisons.

  5. VLBI TRF determination via Kalman filtering

    Science.gov (United States)

    Soja, Benedikt; Karbon, Maria; Nilsson, Tobias; Glaser, Susanne; Balidakis, Kyriakos; Heinkelmann, Robert; Schuh, Harald

    2015-04-01

    The determination of station positions is one of the primary tasks for space geodetic techniques. Station coordinate offsets are usually determined with respect to a linear coordinate model after removing elastic displacements caused by mass redistributions within the Earth's system. In operational VLBI analysis, the coordinate offsets are estimated in a least-squares adjustment as a constant over the duration of a 24-hour VLBI experiment. Terrestrial reference frames (TRF) are usually derived by adjusting the normal equations that contain the 24-hour constant offsets in order to estimate a linear model, possibly including breaks, for the station positions. We have created a VLBI TRF solution without the assumption of negligible subdaily motion and of linear behavior on longer time scales by applying a Kalman filter. As a preparation for the upcoming VLBI Global Observing System (VGOS), which aims for continuous observations that are available in real-time, a Kalman filter has been implemented into the VLBI software VieVS@GFZ. In addition to the real-time capability, the filter offers the possibility of stochastically modeling the parameters of interest. For station coordinates, changes in a subdaily time frame occur, for instance, from un- or mismodeled geophysical effects. The models for tidal and non-tidal ocean, atmosphere, and hydrology loading are known to have deficiencies and inconsistencies which propagate into the estimated station coordinates. The stochastic model of the Kalman filter can be adapted to take these subdaily effects into account. Comparing the resulting station coordinate time series with daily values from a least squares fit, we have investigated to what extent and in which regions the loading models currently have deficiencies. Due to the high correlation between station height and tropospheric delays, it is possible that errors in one group of parameters are partly absorbed by the other group. To detect problems with correlations and to

  6. VLBI Observations of GNSS Signals on the Baseline Hobart-Ceduna

    Science.gov (United States)

    Hellerschmied, Andreas; Böhm, Johannes; Kwak, Younghee; McCallum, Jamie; Plank, Lucia

    2016-12-01

    Observing GNSS satellites with geodetic VLBI opens a variety of new possibilities, which include promising applications in the field of inter-technique frame ties. Considering GNSS satellites as co-location platforms in space, such observations provide possibilities to directly connect the dynamic GNSS and the kinematic VLBI reference frames, which may result in improved future ITRF realizations. In our research we are trying to apply observation strategies that are commonly used in geodetic VLBI, i.e., the main observables are group delays derived from direct observations of GNSS satellite signals. However, clear strategies for the data acquisition and the geodetic analysis are still missing. To pave the way towards an operational application we established a workflow to plan, correlate, observe, and analyze VLBI observations to GNSS satellites. Based on these processes we carried out several successful experiments on the Australian baseline Hobart-Ceduna in 2015 in which we observed GLONASS and GPS satellites in the L1 and L2 bands. For the first time a connected processing chain from scheduling, to correlation, to data analysis has been realized. In this contribution we introduce our workflow and present first results.

  7. Single baseline GLONASS observations with VLBI: data processing and first results

    Science.gov (United States)

    Tornatore, V.; Haas, R.; Duev, D.; Pogrebenko, S.; Casey, S.; Molera Calvés, G.; Keimpema, A.

    2011-07-01

    Several tests to observe signals transmitted by GLONASS (GLObal NAvigation Satellite System) satellites have been performed using the geodetic VLBI (Very Long Baseline Interferometry) technique. The radio telescopes involved in these experiments were Medicina (Italy) and Onsala (Sweden), both equipped with L-band receivers. Observations at the stations were performed using the standard Mark4 VLBI data acquisition rack and Mark5A disk-based recorders. The goals of the observations were to develop and test the scheduling, signal acquisition and processing routines to verify the full tracking pipeline, foreseeing the cross-correlation of the recorded data on the baseline Onsala-Medicina. The natural radio source 3c286 was used as a calibrator before the starting of the satellite observation sessions. Delay models, including the tropospheric and ionospheric corrections, which are consistent for both far- and near-field sources are under development. Correlation of the calibrator signal has been performed using the DiFX software, while the satellite signals have been processed using the narrow band approach with the Metsaehovi software and analysed with a near-field delay model. Delay models both for the calibrator signals and the satellites signals, using the same geometrical, tropospheric and ionospheric models, are under investigation to make a correlation of the satellite signals possible.

  8. VLBI Observing System for VSOP

    Science.gov (United States)

    Ulvestad, J. S.; Murphy, D. W.

    1996-01-01

    The very long baseline interferometry (VLBI) Space Observatory Program (VSOP) satellite is scheduled for launch in September 1996. This paper describes the VLBI observing system for VSOP and its differences from ground radio telescope VLBI systems.

  9. GPS and CSS Radio Sources and Space-VLBI

    Science.gov (United States)

    Snellen, I.

    2009-08-01

    A short overview is given of the status of research on young extragalactic radio sources. We concentrate on Very Long Baseline Interferometric (VLBI), and space-VLBI results obtained with the VLBI Space Observatory Programme (VSOP). In 2012, VSOP-2 will be launched, which will allow VLBI observations at an unprecedented angular resolution. One particular question VSOP-2 could answer is whether some of the High Frequency Peakers (HFP) are indeed the youngest objects in the family of GPS and CSS sources. VSOP-2 observations can reveal their angular morphology and determine whether any are Ultra-compact Symmetric Objects.

  10. Development of Very Long Baseline Interferometry (VLBI) techniques in New Zealand: Array simulation, image synthesis and analysis

    Science.gov (United States)

    Weston, S. D.

    2008-04-01

    This thesis presents the design and development of a process to model Very Long Base Line Interferometry (VLBI) aperture synthesis antenna arrays. In line with the Auckland University of Technology (AUT) Institute for Radiophysics and Space Research (IRSR) aims to develop the knowledge, skills and experience within New Zealand, extensive use of existing radio astronomical software has been incorporated into the process namely AIPS (Astronomical Imaging Processing System), MIRIAD (a radio interferometry data reduction package) and DIFMAP (a program for synthesis imaging of visibility data from interferometer arrays of radio telescopes). This process has been used to model various antenna array configurations for two proposed New Zealand sites for antenna in a VLBI array configuration with existing Australian facilities and a passable antenna at Scott Base in Antarctica; and the results are presented in an attempt to demonstrate the improvement to be gained by joint trans-Tasman VLBI observation. It is hoped these results and process will assist the planning and placement of proposed New Zealand radio telescopes for cooperation with groups such as the Australian Long Baseline Array (LBA), others in the Pacific Rim and possibly globally; also potential future involvement of New Zealand with the SKA. The developed process has also been used to model a phased building schedule for the SKA in Australia and the addition of two antennas in New Zealand. This has been presented to the wider astronomical community via the Royal Astronomical Society of New Zealand Journal, and is summarized in this thesis with some additional material. A new measure of quality ("figure of merit") for comparing the original model image and final CLEAN images by utilizing normalized 2-D cross correlation is evaluated as an alternative to the existing subjective visual operator image comparison undertaken to date by other groups. This new unit of measure is then used ! in the presentation of the

  11. 40 CFR 1042.825 - Baseline determination.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Baseline determination. 1042.825... Provisions for Remanufactured Marine Engines § 1042.825 Baseline determination. (a) For the purpose of this... not valid. (f) Use good engineering judgment for all aspects of the baseline determination. We may...

  12. Determination of nutation offsets by combining VLBI/GPS-produced normal equations

    Science.gov (United States)

    Kudryashova, Maria; Lambert, Sebastien; Dehant, Veronique; Bruyninx, Carine

    2010-05-01

    Longstanding routing operation of individual geodetic space- and ground-based techniques (like, for instance, VLBI, GNSS, LLR, etc.) revealed their strong and weak aspects. More effective use of these strengths as well as reduction of their weaknesses is possible by incorporating of the information collected by each individual technique into combined products. Such a consistent combination can be performed either by combination at the observational level or at the level of normal equations. We concentrate on the combination of normal equations gathered during VLBI/GPS-data processing. The main goal of this combination is to construct a time series of nutation offsets in the most consistent way. The objective of this presentation is to describe the developed strategy of combination and to present the current status of tits implementation. For the purpose of step-by-step validation of our procedure we use two-month-long time series of normal equations produced from VLBI and GPS observations by means of CALC/SOLVE and BERNESE v.5.0 software, respectively. Earth orientation parameter determination will, in our procedure, benefit from angle and rate observation for a unique estimation.

  13. 215 GHz VLBI observations: Detection of fringes on the 1147 KM baseline Pico Veleta-Plateau de Bure

    NARCIS (Netherlands)

    Greve, A.; Torres, M.; Wink, J. E.; Grewing, M.; Wild, W.; Alcolea, J.; Barcia, A.; Colomer, F.; de Vincente, P.; Gomez-Gonzalez, J.; Lopez-Fernandez, I.; Graham, D. A.; Krichbaum, T. P.; Schwartz, R.; Standke, K. J.; Witzel, A.; Baudry, A.

    1995-01-01

    In a VLBI test experiment between the IRAM 3Om telescope at Pico Veleta,Spain, and one 15-m telescope of the IRAM interferometer on Plateau de Bure, France, we detected fringes at 215 GHz with signal to noise ratios between 6 8 and 10.2. On this 1147km long distance, of 0.28-0.43 milli arcseconds pr

  14. Relative position determination of a lunar rover using high-accuracy multi-frequency same-beam VLBI

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Multi-frequency same-beam VLBI means that two explorers with a small separation angle are simultaneously observed with the main beam of receiving antennas. In the same-beam VLBI, the differential phase delay between two explorers and two receiving telescopes can be obtained with a small error of several picoseconds. The differential phase delay, as the observable of the same-beam VLBI, gives the separation angular information of the two explorers in the celestial sphere. The two-dimensional relative position on the plane-of-sky can thus be precisely determined with an error of less than 1 m for a distance of 3.8×105 km far away from the earth, by using the differential phase delay obtained with the four Chinese VLBI stations. The relative position of a lunar rover on the lunar surface can be determined with an error of 10 m by using the differential phase delay data and the range data for the lander when the lunar topography near the rover and the lander can be determined with an error of 10 m.

  15. Navigation of space VLBI missions: Radioastron and VSOP

    Science.gov (United States)

    Ellis, Jordan

    1993-01-01

    In the mid-1990s, Russian and Japanese space agencies will each place into highly elliptic earth orbit a radio telescope consisting of a large antenna and radio astronomy receivers. Very long baseline interferometry (VLBI) techniques will be used to obtain high resolution images of radio sources observed by the space and ground based antennas. Stringent navigation accuracy requirements are imposed on the space VLBI missions by the need to transfer an ultra-stable ground reference frequency standard to the spacecraft and by the demands of the VLBI correlation process. Orbit determination for the mission will be the joint responsibility of navigation centers in the U.S., Russia, and Japan with orbit estimates based on combining tracking data from NASA, Russian, and Japanese sites. This paper describes the operational plans, the inter-agency coordination, and data exchange between the navigation centers required for space VLBI navigation.

  16. Japanese VLBI Network

    CERN Document Server

    Doi, A; Harada, K; Nagayama, T; Suematsu, K; Sugiyama, K; Habe, A; Honma, M; Kawaguchi, N; Kobayashi, H; Koyama, Y; Murata, Y; Omodaka, T; Sorai, K; Sudou, H; Takaba, H; Takashima, K; Wakamatsu, K; Doi, Akihiro; Fujisawa, Kenta; Harada, Keiichiro; Nagayama, Takumi; Suematsu, Kousuke; Sugiyama, Koichiro; Habe, Asao; Honma, Mareki; Kawaguchi, Noriyuki; Kobayashi, Hideyuki; Koyama, Yasuhiro; Murata, Yasuhiro; Omodaka, Toshihiro; Sorai, Kazuo; Sudou, Hiroshi; Takaba, Hiroshi; Takashima, Kazuhiro; Wakamatsu, Ken-ichi

    2006-01-01

    We present the basic features and the activities of Japanese VLBI network (JVN), a newly-established VLBI network with baselines ranging from 50 to 2560 km spreading across the Japanese islands, and capable of observing at 6.7, 8.4, and 22 GHz. We show a number of results of JVN observations: 8.4-GHz continuum images of a Giga-hertz Peaked Spectrum (GPS) source and radio-loud Narrow-Line Seyfert 1 galaxies (NLS1s), the spatial and velocity structures of water masers in NML Cygni as well as methanol masers in Cep A, and demonstrative observations with the bigradient phase referencing.

  17. Applications of same-beam VLBI in the orbit determination of multi-spacecrafts in a lunar sample-return mission

    Institute of Scientific and Technical Information of China (English)

    GOOSSENS; Sander; KIKUCHI; Fuyuhiko; MATSUMOTO; Koji; HANADA; Hideo

    2010-01-01

    Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLBI,the differential phase delay between the two spacecrafts and the two receiving antennas can be obtained within a small error of several picoseconds. As a successful application,the short-arc orbit determination of several hours for Rstar and Vstar,which are two small sub-spacecrafts of SELENE,has been much improved by using the same-beam VLBI data together with the Doppler and range data. The long-arc orbit determination of several days has also been accomplished within an error of about 10 m with the same-beam VLBI data incorporated. These results show the value of the same-beam VLBI for the orbit determination of multi-spacecrafts. This paper introduces the same-beam VLBI and Doppler observations of SELENE and the orbit determination results. In addition,this paper introduces how to use the same-beam VLBI for a lunar sample-return mission,which usually consists of an orbiter,a lander and a return unit. The paper also offers the design for the onboard radio sources in the lunar sample-return mission,and introduces applications of S-band multi-frequency same-beam VLBI in lunar gravity exploration and applications during all stages in the position/orbit determinations such as orbiting,landing,sampling,ascending,and docking.

  18. Probing the Solar Corona with VLBI

    Science.gov (United States)

    Soja, Benedikt; Sun, Jing; Heinkelmann, Robert; Schuh, Harald; Böhm, Johannes

    2013-04-01

    Radio observations close to the Sun are sensitive to the dispersive effects of the Sun corona. This has been used to determine (among other parameters) the electron density in the corona during solar conjunctions with spacecrafts. Although geodetic Very Long Baseline Interferometry (VLBI) observations close to the Sun have already been performed before 2002 (but suspended afterwards) they have not yet been used for calculations of corona electron densities. Almost 10 years later the International VLBI Service for Geodesy and Astrometry (IVS) decided to schedule twelve 24 hours VLBI sessions in 2011 and 2012 including observations closer than 15 degrees to the heliocenter. Both the recent and the earlier sessions are analysed in order to determine electron densities of the Sun corona. Based on the ionospheric delay corrections derived from two-frequency VLBI measurements, other dispersive effects like instrumental biases and, most important of all, the Earth's ionosphere effects are estimated and then eliminated. The residual delays are used to successfully determine power-law parameters of the electron density of the Sun corona for several of these sessions. In some cases, scheduled observations close to the Sun had failed, making it impossible to derive meaningful results from them. Both, the successful and the lost observations were analysed including external information like Sunspot numbers and flare occurrences. The estimated electron densities were compared to previous models of the Sun corona derived by radio measurements to spacecrafts during solar conjunctions. Our investigations show that it is possible to use geodetic VLBI sessions with observations close to the Sun to determine electron densities of the corona. The success depends on the geometry, i.e. the source position with respect to the Sun, and on the schedule, which can be optimized for such investigations. Unpredictable disturbances at the Sun's surface, such as flares, play also a role. So far

  19. Supernova VLBI

    Science.gov (United States)

    Bartel, N.

    2009-08-01

    We review VLBI observations of supernovae over the last quarter century and discuss the prospect of imaging future supernovae with space VLBI in the context of VSOP-2. From thousands of discovered supernovae, most of them at cosmological distances, ˜50 have been detected at radio wavelengths, most of them in relatively nearby galaxies. All of the radio supernovae are Type II or Ib/c, which originate from the explosion of massive progenitor stars. Of these, 12 were observed with VLBI and four of them, SN 1979C, SN 1986J, SN 1993J, and SN 1987A, could be imaged in detail, the former three with VLBI. In addition, supernovae or young supernova remnants were discovered at radio wavelengths in highly dust-obscured galaxies, such as M82, Arp 299, and Arp 220, and some of them could also be imaged in detail. Four of the supernovae so far observed were sufficiently bright to be detectable with VSOP-2. With VSOP-2 the expansion of supernovae can be monitored and investigated with unsurpassed angular resolution, starting as early as the time of the supernova's transition from its opaque to transparent stage. Such studies can reveal, in a movie, the aftermath of a supernova explosion shortly after shock break out.

  20. 40 CFR 80.90 - Conventional gasoline baseline emissions determination.

    Science.gov (United States)

    2010-07-01

    ... gasoline baseline emissions determination. (a) Annual average baseline values. For any facility of a... gasoline volume of the facility, per § 80.91. (b) Baseline exhaust benzene emissions—simple model. (1) Simple model exhaust benzene emissions of conventional gasoline shall be determined using the following...

  1. (abstract) A VLBI Test of Tropospheric Delay Calibration with WVRs

    Science.gov (United States)

    Linfield, R. P.; Teitelbaum, L. P.; Keihm, S. J.; Resch, G. M.; Mahoney, M. J.; Treuhaft, R. N.

    1994-01-01

    Dual frequency (S/X band) very long baseline interferometry (VLBI) observations were used to test troposphere calibration by water vapor radiometers (WVRs). Comparison of the VLBI and WVR measurements show a statistical agreement (specifically, their structure functions agree) on time scales less than 700 seconds. On longer time scales, VLBI instrumental errors become important. The improvement in VLBI residual delays from WVR calibration was consistent with the measured level of tropospheric fluctuations.

  2. GPS & CSS radio sources and space-VLBI

    OpenAIRE

    Snellen, I. A. G.

    2008-01-01

    A short overview is given of the status of research on young extragalactic radio sources. We concentrate on Very Long Baseline Interferometric (VLBI), and space-VLBI results obtained with the VLBI Space Observatory Programme (VSOP). In 2012, VSOP-2 will be launched, which will allow VLBI observations at an unprecedented angular resolution. One particular question VSOP-2 could answer is whether some of the High Frequency Peakers (HFP) are indeed the youngest objects in the family of GPS and CS...

  3. The use of the Long Baseline Array in Australia for precise geodesy and absolute astrometry

    CERN Document Server

    Petrov, Leonid; Bertarini, Alessandra; Deller, Adam; Pogrebenko, Sergei; Mujunen, Ari

    2008-01-01

    We report the results of a successful 12 hour 22 GHz VLBI experiment using a heterogeneous network that includes radio telescopes of the Long Baseline Array (LBA) in Australia and several VLBI stations that regularly observe in geodetic VLBI campaigns. We have determined positions of three VLBI stations, ATCA-104, Ceduna and Mopra, with an accuracy of 3-30 mm using a novel technique of data analysis. These stations have never before participated in geodetic experiments. We observed 105 radio sources, and amongst them 5 objects which have not previously been observed with VLBI. We have determined positions of these new sources with the accuracy of 2-6 mas. We make conclusion that the LBA network is capable of conducting absolute astrometry VLBI surveys with accuracy better than 5 mas.

  4. Space VLBI and the Radio Reference Frame

    Science.gov (United States)

    Charlot, P.

    2009-08-01

    The current radio reference frame is defined by the VLBI positions of several hundreds of extragalactic sources measured with sub-milliarcsecond accuracy. We discuss whether space VLBI can be used to improve the accuracy of the frame, either directly by conducting absolute astrometric observations using space VLBI baselines, or in an indirect way by making available VLBI images of the reference frame sources with increased angular resolution. The VSOP-2 project, in its present state, is found to have the necessary capabilities for accurate absolute astrometry although there may be limitations due to scheduling constraints. Space VLBI images are essential for pinpointing accurately a stable reference feature within the extended structure of each source. In this respect, the VSOP-2 project may have a significant impact on the definition of the radio reference frame if targeting such reference frame sources on a regular basis.

  5. The future of VLBI has begun!

    CERN Document Server

    van Langevelde, Huib

    2010-01-01

    With the exceptional progress e-VLBI has achieved over the last three years, the VLBI of the future has already started. At least for the EVN, it is argued that at some point all VLBI operations should be done in e-VLBI mode. This ambition is based on the scientific case that is described in the EVN2015 science vision. At the same time, it should be taken into account that the long-term future of radio astronomy is connected to the development of the SKA. The consensus in the community is that there is a scientific case for Very Long Baseline Interferometry in the next decade, and synergy with the technology development for the SKA and its pathfinders should be explored to enhance the VLBI capabilities. It is noteworthy that e- VLBI has been recognised as a SKA pathfinder. Here, I review the progress with e-VLBI, and the options to enhance the sensitivity and operational efficiency of the EVN and global VLBI arrays, including the options for future correlators. In the coming years, through the new NEXPReS eff...

  6. Vienna VLBI Software - Current release and plans for the future

    Science.gov (United States)

    Madzak, M.; Böhm, J.; Böhm, S.; Krásná, H.; Nilsson, T.; Plank, L.; Tierno Ros, C.; Schuh, H.; Soja, B.; Sun, J.; Teke, K.

    2013-08-01

    The Vienna VLBI Software (VieVS) is a geodetic Very Long Baseline Interferometry (VLBI) data analysis software which has been developed at the Vienna University of Technology since 2008. This paper gives an overview about its capabilities, including scheduling and simulation of VLBI observations. The latest release, version 2.1 includes a a graphical user interface. A few results and planned future developments are presented as well.

  7. Very Long Baseline Interferometry Experiment on Giant Radio Pulses of Crab Pulsar toward Fast Radio Burst Detection

    CERN Document Server

    Takefuji, K; Kondo, T; Mikami, R; Takeuchi, H; Misawa, H; Tsuchiya, F; Kita, H; Sekido, M

    2016-01-01

    We report on a very long baseline interferometry (VLBI) experiment on giant radio pulses (GPs) from the Crab pulsar in the radio 1.4 to 1.7 GHz range to demonstrate a VLBI technique for searching for fast radio bursts (FRBs). We carried out the experiment on 26 July 2014 using the Kashima 34 m and Usuda 64 m radio telescopes of the Japanese VLBI Network (JVN) with a baseline of about 200 km. During the approximately 1 h observation, we could detect 35 GPs by high-time-resolution VLBI. Moreover, we determined the dispersion measure (DM) to be 56.7585 +/- 0.0025 on the basis of the mean DM of the 35 GPs detected by VLBI. We confirmed that the sensitivity of a detection of GPs using our technique is superior to that of a single-dish mode detection using the same telescope.

  8. Precise baseline determination for the TanDEM-X mission

    Science.gov (United States)

    Koenig, Rolf; Moon, Yongjin; Neumayer, Hans; Wermuth, Martin; Montenbruck, Oliver; Jäggi, Adrian

    The TanDEM-X mission will strive for generating a global precise Digital Elevation Model (DEM) by way of bi-static SAR in a close formation of the TerraSAR-X satellite, already launched on June 15, 2007, and the TanDEM-X satellite to be launched in May 2010. Both satellites carry the Tracking, Occultation and Ranging (TOR) payload supplied by the GFZ German Research Centre for Geosciences. The TOR consists of a high-precision dual-frequency GPS receiver, called Integrated GPS Occultation Receiver (IGOR), and a Laser retro-reflector (LRR) for precise orbit determination (POD) and atmospheric sounding. The IGOR is of vital importance for the TanDEM-X mission objectives as the millimeter level determination of the baseline or distance between the two spacecrafts is needed to derive meter level accurate DEMs. Within the TanDEM-X ground segment GFZ is responsible for the operational provision of precise baselines. For this GFZ uses two software chains, first its Earth Parameter and Orbit System (EPOS) software and second the BERNESE software, for backup purposes and quality control. In a concerted effort also the German Aerospace Center (DLR) generates precise baselines independently with a dedicated Kalman filter approach realized in its FRNS software. By the example of GRACE the generation of baselines with millimeter accuracy from on-board GPS data can be validated directly by way of comparing them to the intersatellite K-band range measurements. The K-band ranges are accurate down to the micrometer-level and therefore may be considered as truth. Both TanDEM-X baseline providers are able to generate GRACE baselines with sub-millimeter accuracy. By merging the independent baselines by GFZ and DLR, the accuracy can even be increased. The K-band validation however covers solely the along-track component as the K-band data measure just the distance between the two GRACE satellites. In addition they inhibit an un-known bias which must be modelled in the comparison, so the

  9. VLBI real-time analysis by Kalman Filtering

    Science.gov (United States)

    Karbon, Maria; Soja, Benedikt; Nilson, Tobias; Heinkelmann, Robert; Liu, Li; Lu, Ciuxian; Xu, Minghui; Raposo-Pulido, Virginia; Mora-Diaz, Julian; Schuh, Harald

    2014-05-01

    Geodetic Very Long Baseline Interferometry (VLBI) is one of the primary space geodetic techniques. It provides the full set of Earth Orientation Parameter (EOP) and is unique for observing long term Universal Time (UT1) and precession/nutation. Currently the VLBI products are delivered with a delay of about two weeks from the moment of the observation. However, the need for near-real time estimates of the parameters is increasing, e.g. for satellite based navigation and positioning or for enabling precise tracking of interplanetary spacecraft. The goal is thus to reduce the time span between observation and the final result to less than one day. This can be archived by replacing the classical least squares method with an adaptive Kalman filter. We have developed a Kalman filter for VLBI data analysis. This method has the advantage that it is simultaneously possible to estimate stationary parameters, e.g. station positions, and to model the highly variable stochastic behavior of non-stationary parameters like clocks or atmospheric parameters. The filter is able to perform without any human interaction, making it a completely autonomous tool. In this work we describe the filter and discuss its application for EOP determination and prediction. We discuss the implementation of the stochastic models to statistically account for unpredictable changes in EOP. Furthermore, additional data like results from other techniques can be included to improve the performance. For example, atmospheric angular momentum calculated from numerical weather models can be introduced to supplement the short-term prediction of UT1 and polar motion. This Kalman filter will be extended and embedded in the newly developed Vienna VLBI Software (VieVS) as a completely autonomous tool enabling the VLBI analysis in near real-time and providing all the parameters of interest with the highest possible accuracy.

  10. NASA Space Geodesy Program: GSFC data analysis, 1992. Crustal Dynamics Project VLBI geodetic results, 1979 - 1991

    Science.gov (United States)

    Ryan, J. W.; Ma, C.; Caprette, D. S.

    1993-01-01

    The Goddard VLBI group reports the results of analyzing 1648 Mark 3 data sets acquired from fixed and mobile observing sites through the end of 1991, and available to the Crustal Dynamics Project. Two large solutions were used to obtain Earth rotation parameters, nutation offsets, radio source positions, site positions, site velocities, and baseline evolution. Site positions are tabulated on a yearly basis for 1979 to 1995, inclusive. Site velocities are presented in both geocentric Cartesian and topocentric coordinates. Baseline evolution is plotted for 200 baselines, and individual length determinations are presented for an additional 356 baselines. This report includes 155 quasar radio sources, 96 fixed stations and mobile sites, and 556 baselines.

  11. The future of VLBI

    CERN Document Server

    van Langevelde, Huib Jan

    2013-01-01

    Almost two decades after the establishment of the Joint Institute for VLBI in Europe (JIVE), the European VLBI Network is a thriving scientific infrastructure with a significant user community and a healthy proposal pressure. It offers opportunities to address a breadth of important scientific topics, which feature in national and European astronomy roadmaps. Most of these science themes call for further enhancements of the sensitivity and image quality delivered by VLBI networks. The exceptional progress of e-VLBI over the last five years demonstrates how sensitive VLBI should be done in the future. At the same time JIVE is pushing the technology for large capacity correlators that can connect VLBI networks with many elements in real-time. Indeed, many new initiatives to build or outfit telescopes for VLBI are emerging from around the world. The technological VLBI developments have a great synergy with the SKA preparations. This is recognized in the SKA pathfinder role that e-VLBI has in the European VLBI Ne...

  12. The impact of celestial pole offset modelling on VLBI UT1 Intensive results

    CERN Document Server

    Malkin, Zinovy

    2011-01-01

    Very Long Baseline Interferometry (VLBI) Intensive sessions are scheduled to provide operational Universal Time (UT1) determinations with low latency. UT1 estimates obtained from these observations heavily depend on the model of the celestial pole motion used during data processing. However, even the most accurate precession-nutation model, IAU 2000/2006, is not accurate enough to realize the full potential of VLBI observations. To achieve the highest possible accuracy in UT1 estimates, a celestial pole offset (CPO), which is the difference between the actual and modelled precession-nutation angles, should be applied. Three CPO models are currently available for users. In this paper, these models have been tested and the differences between UT1 estimates obtained with those models are investigated. It has been shown that neglecting CPO modelling during VLBI UT1 Intensive processing causes systematic errors in UT1 series of up to 20 microarcseconds. It has been also found that using different CPO models causes...

  13. VLBI Antenna Calibration via GPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to investigate and develop an inexpensive system to determine: 1)VLBI antenna properties such as axis-offset, non-intersection of axis and antenna...

  14. Crustal motion results derived from observations in the European geodetic VLBI network

    Science.gov (United States)

    Haas, Rüdiger; Gueguen, Erwan; Scherneck, Hans-Georg; Nothnagel, Axel; Campbell, James

    2000-10-01

    Geodetic VLBI observations have been performed with the European geodetic VLBI network since early 1990 on a regular basis. The purpose of these observations is to determine crustal motion in Europe and to establish a stable reference frame for other space geodetic techniques. Over the years the size of the network and the number of participating stations has steadily increased. Today, the network extends from the island of Sicily in the south to the island of Spitsbergen/Svalbard in the north and from the Iberian peninsula in the west to the Crimean peninsula in the east. The area covered by the network is affected by two main geodynamic processes which are post-glacial rebound effects in the northern part, and the evolution of the Alps-Apennines orogenic systems in the southern part. With nearly 10 years of VLBI observations the determination of crustal motion in Europe is carried out with high accuracy. Baseline measurements are achieved with an accuracy of a few parts per billion. We compare the evolution of baseline lengths and topocentric station displacements with geophysical models. Strain rates in Europe on a large scale are determined from the results of the VLBI analysis.

  15. Analysis and comparison of precise long-term nutation series, strictly determined with OCCAM 6.1 VLBI software

    CERN Document Server

    Bourda, G; Heinkelmann, R; Schuh, H

    2008-01-01

    The IAU/IUGG Working Group on "Nutation for a non-rigid Earth", led by V\\'eronique Dehant, won the European Descartes Prize in 2003, for its work developing a new model for the precession and the nutations of the Earth. This model (MHB2000, Mathews et al. 2002) was adopted by the IAU (International Astronomical Union) during the General Assembly in Manchester, in 2000. It is based (i) on some improvements for the precession model (with respect to the previous one of Lieske et al. 1977) owing to the VLBI technique, and (ii) on a very accurate nutation model, close to the observations. With this prize, the Descartes nutation project could offer for international scientists some grants, to be used for further improvements of the precession-nutation Earth model. At the IGG (Institute of Geodesy and Geophysics), with the OCCAM 6.1 VLBI analysis software and the best data and models available, we re-analyzed the whole VLBI sessions available (from 1985 till 2005) solving for the Earth Orientation Parameters (EOP). ...

  16. ERP Estimation using a Kalman Filter in VLBI

    Science.gov (United States)

    Karbon, M.; Soja, B.; Nilsson, T.; Heinkelmann, R.; Liu, L.; Lu, C.; Mora-Diaz, J. A.; Raposo-Pulido, V.; Xu, M.; Schuh, H.

    2014-12-01

    Geodetic Very Long Baseline Interferometry (VLBI) is one of the primary space geodetic techniques, providing the full set of Earth Orientation Parameters (EOP), and it is unique for observing long term Universal Time (UT1). For applications such as satellite-based navigation and positioning, accurate and continuous ERP obtained in near real-time are essential. They also allow the precise tracking of interplanetary spacecraft. One of the goals of VGOS (VLBI Global Observing System) is to provide such near real-time ERP. With the launch of this next generation VLBI system, the International VLBI Service for Geodesy and Astrometry (IVS) increased its efforts not only to reach 1 mm accuracy on a global scale but also to reduce the time span between the collection of VLBI observations and the availability of the final results substantially. Project VLBI-ART contributes to these objectives by implementing an elaborate Kalman filter, which represents a perfect tool for analyzing VLBI data in quasi real-time. The goal is to implement it in the GFZ version of the Vienna VLBI Software (VieVS) as a completely automated tool, i.e., with no need for human interaction. Here we present the methodology and first results of Kalman filtered EOP from VLBI data.

  17. VLBI and GPS-based Time-Transfer Using CONT08 Data

    Science.gov (United States)

    Rieck, Carsten; Haas, Ruediger; Jaldehag, Kenneth; Jahansson, Jan

    2010-01-01

    One important prerequisite for geodetic Very Long Baseline Interferometry (VLBI) is the use of frequency standards with excellent short term stability. This makes VLBI stations, which are often co-located with Global Navigation Satellite System (GNSS) receiving stations, interesting for studies of time- and frequency-transfer techniques. We present an assessment of VLBI time-transfer based on the data of the two week long consecutive IVS CONT08 VLBI campaign by using GPS Carrier Phase (GPSCP). CONT08 was a 15 day long campaign in August 2008 that involved eleven VLBI stations on five continents. For CONT08 we estimated the worst case VLBI frequency link stability between the stations of Onsala and Wettzell to 1e-15 at one day. Comparisons with GPSCP confirm the VLBI results. We also identify time-transfer related challenges of the VLBI technique as used today.

  18. Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

    Science.gov (United States)

    Soja, Benedikt; Nilsson, Tobias; Balidakis, Kyriakos; Glaser, Susanne; Heinkelmann, Robert; Schuh, Harald

    2016-12-01

    Terrestrial reference frames (TRF), such as the ITRF2008, are primary products of geodesy. In this paper, we present TRF solutions based on Kalman filtering of very long baseline interferometry (VLBI) data, for which we estimate steady station coordinates over more than 30 years that are updated for every single VLBI session. By applying different levels of process noise, non-linear signals, such as seasonal and seismic effects, are taken into account. The corresponding stochastic model is derived site-dependent from geophysical loading deformation time series and is adapted during periods of post-seismic deformations. Our results demonstrate that the choice of stochastic process has a much smaller impact on the coordinate time series and velocities than the overall noise level. If process noise is applied, tests with and without additionally estimating seasonal signals indicate no difference between the resulting coordinate time series for periods when observational data are available. In a comparison with epoch reference frames, the Kalman filter solutions provide better short-term stability. Furthermore, we find out that the Kalman filter solutions are of similar quality when compared to a consistent least-squares solution, however, with the enhanced attribute of being easier to update as, for instance, in a post-earthquake period.

  19. Determination of a terrestrial reference frame via Kalman filtering of very long baseline interferometry data

    Science.gov (United States)

    Soja, Benedikt; Nilsson, Tobias; Balidakis, Kyriakos; Glaser, Susanne; Heinkelmann, Robert; Schuh, Harald

    2016-06-01

    Terrestrial reference frames (TRF), such as the ITRF2008, are primary products of geodesy. In this paper, we present TRF solutions based on Kalman filtering of very long baseline interferometry (VLBI) data, for which we estimate steady station coordinates over more than 30 years that are updated for every single VLBI session. By applying different levels of process noise, non-linear signals, such as seasonal and seismic effects, are taken into account. The corresponding stochastic model is derived site-dependent from geophysical loading deformation time series and is adapted during periods of post-seismic deformations. Our results demonstrate that the choice of stochastic process has a much smaller impact on the coordinate time series and velocities than the overall noise level. If process noise is applied, tests with and without additionally estimating seasonal signals indicate no difference between the resulting coordinate time series for periods when observational data are available. In a comparison with epoch reference frames, the Kalman filter solutions provide better short-term stability. Furthermore, we find out that the Kalman filter solutions are of similar quality when compared to a consistent least-squares solution, however, with the enhanced attribute of being easier to update as, for instance, in a post-earthquake period.

  20. Determination of the local tie vector between the VLBI and GNSS reference points at Onsala using GPS measurements

    Science.gov (United States)

    Ning, T.; Haas, R.; Elgered, G.

    2015-07-01

    Two gimbal-mounted GNSS antennas were installed on each side of the radome-enclosed 20 m VLBI radio telescope at the Onsala Space Observatory. GPS data with a 1 Hz sampling rate were recorded for five semi-kinematic and four kinematic observing campaigns. These GPS data were analysed together with data from the IGS station ONSA with an in-house Matlab-based GPS software package, using the double-difference analysis strategy. The coordinates of the GNSS antennas on the telescope were estimated for different observation angles of the telescope, at specific epochs, and used to calculate the geodetic reference point of the telescope. The local tie vector between the VLBI and the ONSA GNSS reference points in a geocentric reference frame was hence obtained. The two different types of observing campaigns gave consistent results of the estimated local tie vector and the axis offset of the telescope. The estimated local tie vector obtained from all nine campaigns gave standard deviations of 1.5, 1.0, and 2.9 mm for the geocentric X, Y, and Z components, respectively. The result of the estimated axis offset of the VLBI telescope shows a difference of 0.3 mm, with a standard deviation of 1.9 mm, with respect to a reference value obtained by two local surveys carried out in 2002 and 2008. Our results show that the presented method can be used as a complement to the more accurate but more labour intensive classical geodetic surveys to continuously monitor the local tie at co-location stations with an accuracy of a few millimetres.

  1. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell.

    Science.gov (United States)

    Schüler, Torben; Kronschnabl, Gerhard; Plötz, Christian; Neidhardt, Alexander; Bertarini, Alessandra; Bernhart, Simone; la Porta, Laura; Halsig, Sebastian; Nothnagel, Axel

    2015-07-30

    Geodetic Very Long Baseline Interferometry (VLBI) uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1), the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW) is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate.

  2. Initial Results Obtained with the First TWIN VLBI Radio Telescope at the Geodetic Observatory Wettzell

    Directory of Open Access Journals (Sweden)

    Torben Schüler

    2015-07-01

    Full Text Available Geodetic Very Long Baseline Interferometry (VLBI uses radio telescopes as sensor networks to determine Earth orientation parameters and baseline vectors between the telescopes. The TWIN Telescope Wettzell 1 (TTW1, the first of the new 13.2 m diameter telescope pair at the Geodetic Observatory Wettzell, Germany, is currently in its commissioning phase. The technology behind this radio telescope including the receiving system and the tri-band feed horn is depicted. Since VLBI telescopes must operate at least in pairs, the existing 20 m diameter Radio Telescope Wettzell (RTW is used together with TTW1 for practical tests. In addition, selected long baseline setups are investigated. Correlation results portraying the data quality achieved during first initial experiments are discussed. Finally, the local 123 m baseline between the old RTW telescope and the new TTW1 is analyzed and compared with an existing high-precision local survey. Our initial results are very satisfactory for X-band group delays featuring a 3D distance agreement between VLBI data analysis and local ties of 1 to 2 mm in the majority of the experiments. However, S-band data, which suffer much from local radio interference due to WiFi and mobile communications, are about 10 times less precise than X-band data and require further analysis, but evidence is provided that S-band data are well-usable over long baselines where local radio interference patterns decorrelate.

  3. A Strategic Independent Geodetic VLBI Network for Europe

    Science.gov (United States)

    Dale, Denise; Combrinck, Ludwig; de Witt, Alet

    2014-12-01

    Irregularities of the rotation of the Earth in space are described by the Earth Orientation Parameters (EOPs). An independent EOP network, applying the Very Long Baseline Interferometry (VLBI) technique and using the Vienna VLBI Software (VieVS), are strategically essential for Europe to minimize its reliance on foreign global support in terms of required infrastructure for the realization of such a network. The generation of independent EOPs is already achievable by countries such as the USA, the People's Republic of China, and the Russian Federation due to their large extent of land mass that allows for long baselines in both the North-South and East-West directions and thus allows for accurate determination of all EOPs. These three countries need not rely on foreign partnerships to generate EOPs, as they all have independent geodetic VLBI networks capable of determining EOPs for precise positioning, navigation, and satellite launch/orbital purposes. They also have or are developing independent Global Navigation Satellite Systems (GNSS) constellations; so does the European Union (EU). Accurate EOPs are essential for long-term orbital maintenance of GNSS constellations, leaving the EU GALILEO GNSS vulnerable and reliant on the three superpowers. Generation of accurate EOPs by Europe is not possible due to its much smaller land mass and thus smaller achievable baselines. Even though there are many radio telescopes spread across Europe, these are separated by relatively short distances. The proposed stations that will be used to investigate this independent EOP network for Europe are the WETTZELL radio telescope in Germany, two German owned radio telescopes, TIGOCONC in Concepción, Chile, and OHIGGINS in Antarctica, as well as the HartRAO radio telescope in South Africa.

  4. A Feasibility Study of Space VLBI for Geodesy and Geodynamics

    Science.gov (United States)

    Kulkarni, Madhav Narayan

    1992-01-01

    Space Very Long Baseline Interferometry (VLBI) is an extension of the ground based VLBI to the space. With the launching of two or more Space VLBI satellites in the future, Space VLBI observations will be available for astrometric, geodetic and geodynamic applications. This new technique holds potential for various important applications including monitoring Earth rotation and interconnection of the reference frames used in geodesy and geodynamics. The aim of this feasibility study has been to investigate the possibility of precise estimation of geodetic parameters, with emphasis on the Earth rotation parameters (ERP's), from Space VLBI observations. A brief description of the Space VLBI technique, it's possible applications, and the Space VLBI missions being planned has been given. Estimability analysis to investigate the estimability of geodetic parameters from Space VLBI observations has been carried out and a simplified mathematical model is derived in terms of estimable parameters. Results of sensitivity analysis carried out to study the sensitivity of the Space VLBI observables to the geodetic parameters of interest, including the number of these parameters and random errors in their a priori values, have been presented. Some of the dominant systematic effects including atmospheric refraction, solar radiation pressure and relativistic effects have also been investigated. Simulation studies have been carried out to study the influence of these systematic effects and a priori information on the estimation of the Earth rotation parameters. The results from the simulation studies indicate that it may be possible to use the Space VLBI technique for monitoring Earth rotation and polar motion, only if the orbital systematic effects can be modeled to a high degree of accuracy (or the satellites can be tracked, with high accuracy, independently), and precise a priori information on station coordinates from other sources is used. A brief description of the Space VLBI

  5. Computational Imaging for VLBI Image Reconstruction

    CERN Document Server

    Bouman, Katherine L; Zoran, Daniel; Fish, Vincent L; Doeleman, Sheperd S; Freeman, William T

    2015-01-01

    Very long baseline interferometry (VLBI) is a technique for imaging celestial radio emissions by simultaneously observing a source from telescopes distributed across Earth. The challenges in reconstructing images from fine angular resolution VLBI data are immense. The data is extremely sparse and noisy, thus requiring statistical image models such as those designed in the computer vision community. In this paper we present a novel Bayesian approach for VLBI image reconstruction. While other methods require careful tuning and parameter selection for different types of images, our method is robust and produces good results under different settings such as low SNR or extended emissions. The success of our method is demonstrated on realistic synthetic experiments as well as publicly available real data. We present this problem in a way that is accessible to members of the computer vision community, and provide a dataset website (vlbiimaging.csail.mit.edu) to allow for controlled comparisons across algorithms. Thi...

  6. Complex demodulation in VLBI estimation of high frequency Earth rotation components

    Science.gov (United States)

    Böhm, S.; Brzeziński, A.; Schuh, H.

    2012-12-01

    The spectrum of high frequency Earth rotation variations contains strong harmonic signal components mainly excited by ocean tides along with much weaker non-harmonic fluctuations driven by irregular processes like the diurnal thermal tides in the atmosphere and oceans. In order to properly investigate non-harmonic phenomena a representation in time domain is inevitable. We present a method, operating in time domain, which is easily applicable within Earth rotation estimation from Very Long Baseline Interferometry (VLBI). It enables the determination of diurnal and subdiurnal variations, and is still effective with merely diurnal parameter sampling. The features of complex demodulation are used in an extended parameterization of polar motion and universal time which was implemented into a dedicated version of the Vienna VLBI Software VieVS. The functionality of the approach was evaluated by comparing amplitudes and phases of harmonic variations at tidal periods (diurnal/semidiurnal), derived from demodulated Earth rotation parameters (ERP), estimated from hourly resolved VLBI ERP time series and taken from a recently published VLBI ERP model to the terms of the conventional model for ocean tidal effects in Earth rotation recommended by the International Earth Rotation and Reference System Service (IERS). The three sets of tidal terms derived from VLBI observations extensively agree among each other within the three-sigma level of the demodulation approach, which is below 6 μas for polar motion and universal time. They also coincide in terms of differences to the IERS model, where significant deviations primarily for several major tidal terms are apparent. An additional spectral analysis of the as well estimated demodulated ERP series of the ter- and quarterdiurnal frequency bands did not reveal any significant signal structure. The complex demodulation applied in VLBI parameter estimation could be demonstrated a suitable procedure for the reliable reproduction of

  7. The African VLBI network project

    Science.gov (United States)

    Loots, Anita

    2015-01-01

    The AVN is one of the most significant vehicles through which capacity development in Africa for SKA participation will be realized. It is a forerunner to the long baseline Phase 2 component of the mid-frequency SKA. Besides the 26m HartRAO telescope in South Africa, Ghana is expected to be the first to establish a VLBI-capable telescope through conversion of a redundant 32m telecommunications system near Accra. The most widely used receivers in the EVN are L-band and C-band (5 GHz). L-band is divided into a low band around the hydrogen (HI) line frequency of 1420 MHz, and a high band covering the hydroxyl line frequencies of 1612-1720 MHz. The high band is much more commonly used for VLBI as it provides more bandwidth. For the AVN, the methanol maser line at 6668 MHz is a key target for the initial receiver and the related 12178MHz methanol maser line also seen in star-forming regions a potential future Ku-band receiver. In the potential future band around 22GHz(K-band), water masers in star-forming regions and meg-maser galaxies at 22.235 GHz are targets, as are other radio continuum sources such as AGNs. The AVN system will include 5GHz and 6.668GHz receiver systems with recommendation to partner countries that the first upgrade should be L-band receivers. The original satellite telecommunications feed horns cover 3.8 - 6.4 GHz and should work at 5 GHz and operation at 6.668 GHz for the methanol maser is yet to be verified. The first light science will be conducted in the 6.7 GHz methanol maser band. Telescopes developed for the AVN will initially join other global networks for VLBI. When at least four VLBI-capable telescopes are operational on the continent, it will be possible to initiate stand-alone AVN VLBI. Each country where an AVN telescope becomes operational will have its own single-dish observing program. Capacity building to run an observatory includes the establishment of competent core essential observatory staff in partner countries who can train

  8. High-accuracy same-beam VLBI observations using Shanghai and Urumqi telescopes

    Institute of Scientific and Technical Information of China (English)

    KIKUCHI; Fuyuhiko; KAMATA; Shun’ichi; MATSUMOTO; Koji; HANADA; Hideo

    2009-01-01

    The same-beam VLBI observations of Rstar and Vstar,which were two small satellites of Japanese lunar mission,SELENE,were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle between Rstar and Vstar was less than 0.1 deg,the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms,which was reduced by 1-2 order compared with the former VLBI results. When the separation angle was less than 0.56 deg,the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed,and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft,and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.

  9. High-accuracy same-beam VLBI observations using Shanghai and Urumqi telescopes

    Institute of Scientific and Technical Information of China (English)

    LIU QingHui; PING JingSong; FAN QingYuan; XIA Bo; AN Tao; QIAN ZhiHan; YANG WenJun; ZHANG Hua; WANG Zhen; WANG Na; SHI Xian; KIKUCHI Fuyuhiko; HUANG Qian; KAMATA Shun'ichi; MATSUMOTO Koji; HANADA Hideo; HONG XiaoYu; YU AiLi

    2009-01-01

    The same-beam VLBI observations of Rstar and Vstar, which were two small satellites of Japanese lunar mission, SELENE, were successfully performed by using Shanghai and Urumqi 25-m telescopes.When the separation angle between Rstar and Vstar was less than 0.1 deg, the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms, which was reduced by 1-2 order compared with the former VLBI results.When the separation angle was less than 0.56 deg, the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed, and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft, and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.

  10. Non-linear VLBI station motions and their impact on the celestial reference frame and Earth orientation parameters.

    Science.gov (United States)

    Krásná, Hana; Malkin, Zinovy; Böhm, Johannes

    The increasing accuracy and growing time span of Very Long Baseline Interferometry (VLBI) observations allow the determination of seasonal signals in station positions which still remain unmodelled in conventional analysis approaches. In this study we focus on the impact of the neglected seasonal signals in the station displacement on the celestial reference frame and Earth orientation parameters. We estimate empirical harmonic models for selected stations within a global solution of all suitable VLBI sessions and create mean annual models by stacking yearly time series of station positions which are then entered a priori in the analysis of VLBI observations. Our results reveal that there is no systematic propagation of the seasonal signal into the orientation of celestial reference frame but position changes occur for radio sources observed non-evenly over the year. On the other hand, the omitted seasonal harmonic signal in horizontal station coordinates propagates directly into the Earth rotation parameters causing differences of several tens of microarcseconds.

  11. Space VLBI Mission: VSOP

    Science.gov (United States)

    Murata, Yasuhiro; Hirabayashi, Hisashi; Kobayashi, Hideyuki; Shibata, Katsunori M.; Umemoto, Tomofumi; Edwards, P. G.

    2001-03-01

    We succeeded in performing space VLBI observations using the VLBI satellite HALCA (VSOP satellite), launched in February, 1997 aboard the first M-V rocket developed by ISAS. The mission is led by ISAS and NAO, with the collaborations from CRL, NASA, NRAO, and other institutes and observatories in Europe, Australia, Canada, South-Africa, and China, We succeeded to make a lot of observations and to get the new features from the active galaxies, the cosmic jets, and other astronomical objects.

  12. Application of ray-traced tropospheric slant delays to geodetic VLBI analysis

    Science.gov (United States)

    Hofmeister, Armin; Böhm, Johannes

    2017-02-01

    The correction of tropospheric influences via so-called path delays is critical for the analysis of observations from space geodetic techniques like the very long baseline interferometry (VLBI). In standard VLBI analysis, the a priori slant path delays are determined using the concept of zenith delays, mapping functions and gradients. The a priori use of ray-traced delays, i.e., tropospheric slant path delays determined with the technique of ray-tracing through the meteorological data of numerical weather models (NWM), serves as an alternative way of correcting the influences of the troposphere on the VLBI observations within the analysis. In the presented research, the application of ray-traced delays to the VLBI analysis of sessions in a time span of 16.5 years is investigated. Ray-traced delays have been determined with program RADIATE (see Hofmeister in Ph.D. thesis, Department of Geodesy and Geophysics, Faculty of Mathematics and Geoinformation, Technische Universität Wien. http://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-3444, 2016) utilizing meteorological data provided by NWM of the European Centre for Medium-Range Weather Forecasts (ECMWF). In comparison with a standard VLBI analysis, which includes the tropospheric gradient estimation, the application of the ray-traced delays to an analysis, which uses the same parameterization except for the a priori slant path delay handling and the used wet mapping factors for the zenith wet delay (ZWD) estimation, improves the baseline length repeatability (BLR) at 55.9% of the baselines at sub-mm level. If no tropospheric gradients are estimated within the compared analyses, 90.6% of all baselines benefit from the application of the ray-traced delays, which leads to an average improvement of the BLR of 1 mm. The effects of the ray-traced delays on the terrestrial reference frame are also investigated. A separate assessment of the RADIATE ray-traced delays is carried out by comparison to the ray-traced delays from the

  13. Application of ray-traced tropospheric slant delays to geodetic VLBI analysis

    Science.gov (United States)

    Hofmeister, Armin; Böhm, Johannes

    2017-08-01

    The correction of tropospheric influences via so-called path delays is critical for the analysis of observations from space geodetic techniques like the very long baseline interferometry (VLBI). In standard VLBI analysis, the a priori slant path delays are determined using the concept of zenith delays, mapping functions and gradients. The a priori use of ray-traced delays, i.e., tropospheric slant path delays determined with the technique of ray-tracing through the meteorological data of numerical weather models (NWM), serves as an alternative way of correcting the influences of the troposphere on the VLBI observations within the analysis. In the presented research, the application of ray-traced delays to the VLBI analysis of sessions in a time span of 16.5 years is investigated. Ray-traced delays have been determined with program RADIATE (see Hofmeister in Ph.D. thesis, Department of Geodesy and Geophysics, Faculty of Mathematics and Geoinformation, Technische Universität Wien. http://resolver.obvsg.at/urn:nbn:at:at-ubtuw:1-3444, 2016) utilizing meteorological data provided by NWM of the European Centre for Medium-Range Weather Forecasts (ECMWF). In comparison with a standard VLBI analysis, which includes the tropospheric gradient estimation, the application of the ray-traced delays to an analysis, which uses the same parameterization except for the a priori slant path delay handling and the used wet mapping factors for the zenith wet delay (ZWD) estimation, improves the baseline length repeatability (BLR) at 55.9% of the baselines at sub-mm level. If no tropospheric gradients are estimated within the compared analyses, 90.6% of all baselines benefit from the application of the ray-traced delays, which leads to an average improvement of the BLR of 1 mm. The effects of the ray-traced delays on the terrestrial reference frame are also investigated. A separate assessment of the RADIATE ray-traced delays is carried out by comparison to the ray-traced delays from the

  14. The latest results from the Global mm-VLBI Array

    CERN Document Server

    Hodgson, Jeffrey A; Marscher, Alan P; Jorstad, Svetlana G; Marti-Vidal, Ivan; Bremer, Michael; Lindqvist, Michael; de Vicente, Pablo; Zensus, Anton

    2014-01-01

    The Global mm-VLBI Array (GMVA) is the highest angular resolution imaging interferometer currently available as a common user facility. It is capable of angular resolutions on the order of 40 microarcseconds. Currently 14 stations in the United States and Europe participate in global 3 mm VLBI observations. The GMVA is used for continuum and spectroscopic imaging, probing the central regions of active galaxies and the origin of jets as these regions are typically not observable at longer wavelengths due to synchrotron self-absorption. In early 2012, fringes were detected to the three stations of the Korean VLBI Network (KVN), opening the possibility of extending the baseline coverage of the VLBI array to the East. In these proceedings, we will present recent images from a monitoring program of gamma-ray blazars using the GMVA, including the sources 3C454.3 and 0235+164, and an update of its current status and abilities.

  15. A VLBI variance-covariance analysis interactive computer program. M.S. Thesis

    Science.gov (United States)

    Bock, Y.

    1980-01-01

    An interactive computer program (in FORTRAN) for the variance covariance analysis of VLBI experiments is presented for use in experiment planning, simulation studies and optimal design problems. The interactive mode is especially suited to these types of analyses providing ease of operation as well as savings in time and cost. The geodetic parameters include baseline vector parameters and variations in polar motion and Earth rotation. A discussion of the theroy on which the program is based provides an overview of the VLBI process emphasizing the areas of interest to geodesy. Special emphasis is placed on the problem of determining correlations between simultaneous observations from a network of stations. A model suitable for covariance analyses is presented. Suggestions towards developing optimal observation schedules are included.

  16. VLBI observations of Infrared-Faint Radio Sources

    Science.gov (United States)

    Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

    2006-10-01

    We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

  17. Very Long Baseline Interferometry with the SKA

    CERN Document Server

    Paragi, Zsolt; Reynolds, Cormac; Rioja, Maria; Deller, Adam; Zhang, Bo; Gurvits, Leonid; Bietenholz, Michael; Szomoru, Arpad; Bignall, Hayley; Boven, Paul; Charlot, Patrick; Dodson, Richard; Frey, Sandor; Garrett, Michael; Imai, Hiroshi; Lobanov, Andrei; Reid, Mark; Ros, Eduardo; van Langevelde, Huib; Zensus, J Anton; Zheng, Xing Wu; Alberdi, Antxon; Agudo, Ivan; An, Tao; Argo, Megan; Beswick, Rob; Biggs, Andy D; Brunthaler, Andreas; Campbell, Robert M; Cimo, Giuseppe; Colomer, Francisco; Corbel, Stephane; Conway, John; Cseh, David; Deane, Roger; Falcke, Heino; Gabanyi, Krisztina; Gawronski, Marcin; Gaylard, Michael; Giovannini, Gabriele; Giroletti, Marcello; Goddi, Ciriaco; Goedhart, Sharmila; Gomez, Jose L; Gunn, Alastair; Jung, Taehyun; Kharb, Preeti; Klockner, Hans-Rainer; Kording, Elmar; Kovalev, Yurii Yu; Kunert-Bajraszewska, Magdalena; Lindqvist, Michael; Lister, Matt; Mantovani, Franco; Marti-Vidal, Ivan; Mezcua, Mar; McKean, John; Middelberg, Enno; Miller-Jones, James; Moldon, Javier; Muxlow, Tom; O'Brien, Tim; Pérez-Torres, Miguel; Pogrebenko, Sergei; Quick, Jonathan; Rushton, Anthony P; Schilizzi, Richard; Smirnov, Oleg; Sohn, Bong Won; Surcis, Gabriele; Taylor, Greg; Tingay, Steven; Tudose, Valeriu; van der Horst, Alexander; van Leeuwen, Joeri; Venturi, Tiziana; Vermeulen, Rene; Vlemmings, Wouter; de Witt, Aletha; Wucknitz, Olaf; Yang, Jun

    2014-01-01

    Adding VLBI capability to the SKA arrays will greatly broaden the science of the SKA, and is feasible within the current specifications. SKA-VLBI can be initially implemented by providing phased-array outputs for SKA1-MID and SKA1-SUR and using these extremely sensitive stations with other radio telescopes, and in SKA2 by realising a distributed configuration providing baselines up to thousands of km, merging it with existing VLBI networks. The motivation for and the possible realization of SKA-VLBI is described in this paper.

  18. Radio VLBI and the quantum interference paradox

    CERN Document Server

    Singal, Ashok K

    2016-01-01

    We address here the question of interference of radio signals from astronomical sources like distant quasars, in a very long baseline interferometer (VLBI), where two (or more) distantly located radio telescopes (apertures), receive simultaneous signal from the sky. In an equivalent optical two-slit experiment, it is generally argued that for the photons involved in the interference pattern on the screen, it is not possible, even in principle, to ascertain which of the two slits a particular photon went through. It is argued that any procedure to ascertain this destroys the interference pattern. But in the case of the modern radio VLBI, it is a routine matter to record the phase and amplitude of the voltage outputs from the two radio antennas on a recording media separately and then do the correlation between the two recorded signals later in an offline manner. Does this not violate the quantum interference principle? We provide a resolution of this problem here.

  19. Maser Astrometry with VLBI and the SKA

    CERN Document Server

    Green, James A; Brunthaler, Andreas; Ellingsen, Simon; Imai, Hiroshi; Vlemmings, Wouter; Reid, Mark; Richards, Anita

    2015-01-01

    We discuss the unique opportunities for maser astrometry with the inclusion of the Square Kilometre Array (SKA) in Very Long Baseline Interferometry (VLBI) networks. The first phase of the SKA will enable observations of hydroxyl and methanol masers, positioning the latter to an accuracy of 5 microarcseconds, and the second phase may allow water maser observations. These observations will provide trigonometric distances with errors as small as 1%. The unrivalled sensitivity of the SKA will enable large-scale surveys and, through joint operations, will turn any VLBI network into a fast astrometry device. Both evolved stars and high mass star formation regions will be accessible throughout the (Southern) Milky Way, completing our understanding of the content, dynamics and history of our Galaxy. Maser velocities and proper motions will be measurable in the Local Group of galaxies and beyond, providing new insights into their kinematics and evolution.

  20. VLBI observations of young Type II supernovae

    CERN Document Server

    Pérez-Torres, M A; Marcaide, J M

    2005-01-01

    We give an overview of circumstellar interaction in young Type II supernovae, as seen through the eyes of very-long-baseline interferometry (VLBI) observations. The resolution attained by such observations (best than 1 mas) is a powerful tool to probe the interaction that takes place after a supernova goes off. The direct imaging of a supernova permits, in principle, to estimate the deceleration of its expansion, and to obtain information on the eject and circumstellar density profiles, as well as estimates of the magnetic field intensity and relativistic particle energy density in the supernova. Unfortunately, only a handful of radio supernovae are close and bright enough as to permit their study with VLBI. We present results from our high-resolution observations of the nearby Type II radio supernovae SN1986J and SN2001gd.

  1. Future mmVLBI Research with ALMA: A European vision

    CERN Document Server

    Tilanus, R P J; Zensus, J A; Baudry, A; Bremer, M; Falcke, H; Giovannini, G; Laing, R; van Langevelde, H J; Vlemmings, W; Abraham, Z; Afonso, J; Agudo, I; Alberdi, A; Alcolea, J; Altamirano, D; Asadi, S; Assaf, K; Augusto, P; Baczko, A-K; Boeck, M; Boller, T; Bondi, M; Boone, F; Bourda, G; Brajsa, R; Brand, J; Britzen, S; Bujarrabal, V; Cales, S; Casadio, C; Casasola, V; Castangia, P; Cernicharo, J; Charlot, P; Chemin, L; Clenet, Y; Colomer, F; Combes, F; Cordes, J; Coriat, M; Cross, N; D'Ammando, F; Dallacasa, D; Desmurs, J-F; Eatough, R; Eckart, A; Eisenacher, D; Etoka, S; Felix, M; Fender, R; Ferreira, M; Freeland, E; Frey, S; Fromm, C; Fuhrmann, L; Gabanyi, K; Galvan-Madrid, R; Giroletti, M; Goddi, C; Gomez, J; Gourgoulhon, E; Gray, M; di Gregorio, I; Greimel, R; Grosso, N; Guirado, J; Hada, K; Hanslmeier, A; Henkel, C; Herpin, F; Hess, P; Hodgson, J; Horns, D; Humphreys, E; Kramer, B Hutawarakorn; Ilyushin, V; Impellizzeri, V; Ivanov, V; Julião, M; Kadler, M; Kerins, E; Klaassen, P; Klooster, K van 't; Kording, E; Kozlov, M; Kramer, M; Kreikenbohm, A; Kurtanidze, O; Lazio, J; Leite, A; Leitzinger, M; Lepine, J; Levshakov, S; Lico, R; Lindqvist, M; Liuzzo, E; Lobanov, A; Lucas, P; Mannheim, K; Marcaide, J; Markoff, S; Martí-Vidal, I; Martins, C; Masetti, N; Massardi, M; Menten, K; Messias, H; Migliari, S; Mignano, A; Miller-Jones, J; Minniti, D; Molaro, P; Molina, S; Monteiro, A; Moscadelli, L; Mueller, C; Müller, A; Muller, S; Niederhofer, F; Odert, P; Olofsson, H; Orienti, M; Paladino, R; Panessa, F; Paragi, Z; Paumard, T; Pedrosa, P; Pérez-Torres, M; Perrin, G; Perucho, M; Porquet, D; Prandoni, I; Ransom, S; Reimers, D; Rejkuba, M; Rezzolla, L; Richards, A; Ros, E; Roy, A; Rushton, A; Savolainen, T; Schulz, R; Silva, M; Sivakoff, G; Soria-Ruiz, R; Soria, R; Spaans, M; Spencer, R; Stappers, B; Surcis, G; Tarchi, A; Temmer, M; Thompson, M; Torrelles, J; Truestedt, J; Tudose, V; Venturi, T; Verbiest, J; Vieira, J; Vielzeuf, P; Vincent, F; Wex, N; Wiik, K; Wiklind, T; Wilms, J; Zackrisson, E; Zechlin, H

    2014-01-01

    Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imagin...

  2. VLBI for Gravity Probe B: The Guide Star IM Pegasi

    CERN Document Server

    Bartel, N; Lebach, D E; Ransom, R R; Ratner, M I; Shapiro, I I

    2015-01-01

    We review the radio very long baseline interferometry (VLBI) observations of the guide star, IM Peg, and three compact extragalactic reference sources, 3C 454.3, B2250+194, and B2252+172, made in support of the NASA/Stanford gyroscope relativity mission, GP-B. The main goal of the observations was the determination of the proper motion of IM Peg relative to the distant universe. VLBI observations made between 1997 and 2005 yield a proper motion of IM Peg of -20.83 $\\pm$ 0.09 mas yr$^{-1}$ in RA and -27.27 $\\pm$ 0.09 mas yr$^{-1}$ in dec, in a celestial reference frame of extragalactic radio galaxies and quasars virtually identical to the International Celestial Reference Frame 2 (ICRF2). They also yield a parallax for IM Peg of 10.37 $\\pm$ 0.07 mas, corresponding to a distance of 96.4 $\\pm$ 0.7 pc. The uncertainties are standard errors with statistical and estimated systematic contributions added in quadrature. These results met the pre-launch requirements of the GP-B mission to not discernibly degrade the es...

  3. Automated ambiguity estimation for VLBI Intensive sessions using L1-norm

    Science.gov (United States)

    Kareinen, Niko; Hobiger, Thomas; Haas, Rüdiger

    2016-12-01

    Very Long Baseline Interferometry (VLBI) is a space-geodetic technique that is uniquely capable of direct observation of the angle of the Earth's rotation about the Celestial Intermediate Pole (CIP) axis, namely UT1. The daily estimates of the difference between UT1 and Coordinated Universal Time (UTC) provided by the 1-h long VLBI Intensive sessions are essential in providing timely UT1 estimates for satellite navigation systems and orbit determination. In order to produce timely UT1 estimates, efforts have been made to completely automate the analysis of VLBI Intensive sessions. This involves the automatic processing of X- and S-band group delays. These data contain an unknown number of integer ambiguities in the observed group delays. They are introduced as a side-effect of the bandwidth synthesis technique, which is used to combine correlator results from the narrow channels that span the individual bands. In an automated analysis with the c5++ software the standard approach in resolving the ambiguities is to perform a simplified parameter estimation using a least-squares adjustment (L2-norm minimisation). We implement L1-norm as an alternative estimation method in c5++. The implemented method is used to automatically estimate the ambiguities in VLBI Intensive sessions on the Kokee-Wettzell baseline. The results are compared to an analysis set-up where the ambiguity estimation is computed using the L2-norm. For both methods three different weighting strategies for the ambiguity estimation are assessed. The results show that the L1-norm is better at automatically resolving the ambiguities than the L2-norm. The use of the L1-norm leads to a significantly higher number of good quality UT1-UTC estimates with each of the three weighting strategies. The increase in the number of sessions is approximately 5% for each weighting strategy. This is accompanied by smaller post-fit residuals in the final UT1-UTC estimation step.

  4. Developments of VLBI synthesis mapping.

    Science.gov (United States)

    Jiang, Dongrong; Wan, Tongshan

    1992-12-01

    The authors review the developments of VLBI synthesis mapping. First they give a brief history of VLBI techniques and a summary of some technical parameters frequently used in VLBI synthesis mapping. They then mention problems, namely, (u,v) coverage, correction of errors in visibility data, image quality, GFF (Global Fringe Fitting), field of view, etc. The new developments which are presented include the improvements of (u,v) coverage and angular resolution, Mk III GFF, phase reference mapping, wide field mapping, difference mapping, the potential of space VLBI mapping, mosaicing and non-linear deconvolution.

  5. A model for determining baseline morphometrics of skeletal myofibres

    Directory of Open Access Journals (Sweden)

    Maurice Mars

    2014-02-01

    Full Text Available The minimum diameter method of morphometry (MDM is used to measure and detect changes in myofibre diameters (FD. The MDM is used to identify pathology in skeletal muscle. In such studies, an assumption is made that the mean FD in a particular muscle in both limbs is essentially the same. This study explored this premise to determine the accuracy of MDM as a means of morphometric analysis. Muscle biopsies were obtained from the left (G1 and right (G2 tibialis anterior of four vervet monkeys and from the massaged left (G3 and untreated right (G4 tibialis anterior of four animals. Wax sections were prepared for MDM and FD was measured. Three specimens were re-measured on four occasions. The mean FD of each biopsy from G1 and G2 limbs were compared and the number of measurements necessary to produce a meaningful result determined. Repeated measurement showed a difference of < 3.0% in FD means between the first and three subsequent measurements. There was no significant difference of FD means between G1 and G2, whilst the difference between G3 and G4 was 11.2%. When > 175 FD were measured, the difference from the final mean was less than 2.0%. These data show that, (1 FD data derived from a muscle in an untreated limb can be used as a control for experiment mediated changes of FD in the other, (2 MDM is a reliable means of measuring FD and (3 150–175 FD are needed to provide a dependable result.

  6. Identifying optimal tag-along station locations for improving VLBI Intensive sessions

    Science.gov (United States)

    Kareinen, Niko; Klopotek, Grzegorz; Hobiger, Thomas; Haas, Rüdiger

    2017-01-01

    Very Long Baseline Interferometry (VLBI) is a unique space-geodetic technique capable of direct observation of the Earth's phase of rotation, namely Universal Time (UT1). The International VLBI Service for Geodesy and Astrometry (IVS) conducts daily 1-h Intensive VLBI sessions to determine rapid variations in the difference between UT1 and Coordinated Universal Time (UTC). The main objective of the Intensive sessions is to provide timely UT1-UTC estimates. These estimates are especially crucial for Global Navigation Satellite Systems (GNSS). The monitoring of rapid variations in Earth rotation also provides insight into various geophysical phenomena. There is an ongoing effort to improve the quality of the UT1-UTC estimates from single-baseline Intensive sessions to realise the expected accuracy and to bring them to a better agreement with the 24-h VLBI sessions. In this paper, we investigate the possibility to improve the Intensives by including a third station in tag-along mode to these regularly observed sessions. The impact of the additional station is studied via extensive simulations using the c5++ analysis software. The location of the station is varied within a predetermined grid. Based on actual Intensive session schedules, a set of simulated observations are generated for the two original stations and each grid point. These simulated data are used to estimate UT1-UTC for every Intensive session scheduled during the year 2014 on the Kokee-Wettzell and Tsukuba-Wettzell baselines, with the addition of a third station. We find that in tag-along mode when a third station is added to the schedule we can identify areas where the UT1-UTC estimates are improved up to 67% w.r.t. the original single-baseline network. There are multiple operational VLBI stations in these areas, which could with little effort be included in a tag-along mode to the currently scheduled Intensive sessions, thus providing the possibility to improve the UT1-UTC estimates by extending the

  7. Parallel algorithm of VLBI software correlator under multiprocessor environment

    Science.gov (United States)

    Zheng, Weimin; Zhang, Dong

    2007-11-01

    The correlator is the key signal processing equipment of a Very Lone Baseline Interferometry (VLBI) synthetic aperture telescope. It receives the mass data collected by the VLBI observatories and produces the visibility function of the target, which can be used to spacecraft position, baseline length measurement, synthesis imaging, and other scientific applications. VLBI data correlation is a task of data intensive and computation intensive. This paper presents the algorithms of two parallel software correlators under multiprocessor environments. A near real-time correlator for spacecraft tracking adopts the pipelining and thread-parallel technology, and runs on the SMP (Symmetric Multiple Processor) servers. Another high speed prototype correlator using the mixed Pthreads and MPI (Massage Passing Interface) parallel algorithm is realized on a small Beowulf cluster platform. Both correlators have the characteristic of flexible structure, scalability, and with 10-station data correlating abilities.

  8. VLBI in ASIAA Contribution to Sub-Millimeter VLBI Network

    Science.gov (United States)

    Inoue, M.; Asada, K.; Chen, M. T.; Huang, Y. D.; Chen, C. P.; Matsushita, S.; Ho, P.

    2011-05-01

    A new effort has been launched to perform frontier VLBI studies in Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) with the addition of new staff members. The main targets of the new VLBI group are sub-mm and space VLBI to open new physics on super massive black holes (SMBHs) and related issues. Recent observations shows an exciting possibility to see event horizon of SMBH. To get high quality images of it, additional VLBI stations are essential, and site survey has been planned for a new sub-mm VLBI station somewhere in the world. Collaboration has been also discussed to increase the observing efficiency by providing a tracking station for the VSOP-2 project. To pursue these exciting projects, the group is planning to promote a larger science group in ASIAA.

  9. Methodology for the combination of sub-daily Earth rotation from GPS and VLBI observations

    Science.gov (United States)

    Artz, T.; Bernhard, L.; Nothnagel, A.; Steigenberger, P.; Tesmer, S.

    2012-03-01

    A combination procedure of Earth orientation parameters from Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI) observations was developed on the basis of homogeneous normal equation systems. The emphasis and purpose of the combination was the determination of sub-daily polar motion (PM) and universal time (UT1) for a long time-span of 13 years. Time series with an hourly resolution and a model for tidal variations of PM and UT1-TAI (dUT1) were estimated. In both cases, 14-day nutation corrections were estimated simultaneously with the ERPs. Due to the combination procedure, it was warranted that the strengths of both techniques were preserved. At the same time, only a minimum of de-correlating or stabilizing constraints were necessary. Hereby, a PM time series was determined, whose precision is mainly dominated by GPS observations. However, this setup benefits from the fact that VLBI delivered nutation and dUT1 estimates at the same time. An even bigger enhancement can be seen for the dUT1 estimation, where the high-frequency variations are provided by GPS, while the long term trend is defined by VLBI. The estimated combined tidal PM and dUT1 model was predominantly determined from the GPS observations. Overall, the combined tidal model for the first time completely comprises the geometrical benefits of VLBI and GPS observations. In terms of root mean squared (RMS) differences, the tidal amplitudes agree with other empirical single-technique tidal models below 4 μ as in PM and 0.25 μ s in dUT1. The noise floor of the tidal ERP model was investigated in three ways resulting in about 1 μ as for diurnal PM and 0.07 μ s for diurnal dUT1 while the semi-diurnal components have a slightly better accuracy.

  10. Future directions in VLBI technology

    Science.gov (United States)

    Whitney, A. R.

    Three technology areas are examined to measure their impact on VLBI and the capa bilities that may be offered to VLBI practioners in the near future: VLBI Standard Interface: An international committee has recently agr eed on a standard interface definition for all future VLBI data systems. This s hould, at long last, allow interoperability between various VLBI data systems. New Recording Technologies: Courtesy of large investments by the co mputer industry, moderately priced high-data rate digital recorders that may be suitable for VLBI are on the near horizon. Small arrays of these machines, appr opriately interfaced, promise to support 1-8 Gbps recording over the next few ye ars at an attractive price. e-VLBI: With the advent of optical fiber being laid at a prodigious rate, real-time (or near-real time) VLBI on an international scale is close to b eing a technical possibility. However, questions remain about costs to lease th e necessary bandwidth and to lay the 'last mile' of fiber to remote antennas.

  11. VLBI Data Interchange Format (VDIF)

    Science.gov (United States)

    Whitney, Alan; Kettenis, Mark; Phillips, Chris; Sekido, Mamoru

    2010-01-01

    One important outcome of the 7th International e-VLBI Workshop in Shanghai in June 2008 was the creation of a task force to study and recommend a universal VLBI data format that is suitable for both on-the-wire e-VLBI data transfer, as well as direct disk storage. This task force, called the VLBI Data Interchange Format (VDIF) Task Force, is the first part of a two-part effort, the second of which will address standardization of e-VLBI data-transmission-protocols. The formation of the VDIF Task Force was prompted particularly by increased e-VLBI activity and the difficulties encountered when data arrive at a correlator in different formats from various instruments in various parts of the world. The task force created a streaming packetized data format that may be used for real-time and non-realtime e-VLBI, as well as direct disk storage. The data may contain multiple channels of time-sampled data with an arbitrary number of channels, arbitrary #bits/sample up to 32, and real or complex data; data rates in excess of 100 Gbps are supported. Each data packet is completely self-identifying via a short header, and data may be decoded without reference to any external information. The VDIF task force has completed its work, and the VDIF standard was ratified at the 2009 e-VLBI workshop in Madrid.

  12. Error Modeling and Analysis for InSAR Spatial Baseline Determination of Satellite Formation Flying

    Directory of Open Access Journals (Sweden)

    Jia Tu

    2012-01-01

    Full Text Available Spatial baseline determination is a key technology for interferometric synthetic aperture radar (InSAR missions. Based on the intersatellite baseline measurement using dual-frequency GPS, errors induced by InSAR spatial baseline measurement are studied in detail. The classifications and characters of errors are analyzed, and models for errors are set up. The simulations of single factor and total error sources are selected to evaluate the impacts of errors on spatial baseline measurement. Single factor simulations are used to analyze the impact of the error of a single type, while total error sources simulations are used to analyze the impacts of error sources induced by GPS measurement, baseline transformation, and the entire spatial baseline measurement, respectively. Simulation results show that errors related to GPS measurement are the main error sources for the spatial baseline determination, and carrier phase noise of GPS observation and fixing error of GPS receiver antenna are main factors of errors related to GPS measurement. In addition, according to the error values listed in this paper, 1 mm level InSAR spatial baseline determination should be realized.

  13. Australian geodetic VLBI network (AuScope): present and future.

    Science.gov (United States)

    Titov, Oleg

    2015-04-01

    The Australian geodetic Very Long Baseline Interferometry (VLBI) array (AuScope) consisting of three new 12-meter radio telescopes in Australia (Hobart, Katherine and Yarragadee), and a correlation facility in Perth that started operations in 2011. The daily positions of the AuScope array are estimated with a precision of a few mm, whereas their daily estimates vary within a range of 20-30 mm on the annual scale. This VLBI network also provides a substantial contribution to the improvement of the Celestial Reference Frame in the southern hemisphere. The plans for extension of the network in collaboration with the New Zealand and South Africa VLBI stations during 2015-2020 are discussed in this presentation.

  14. The automatic calibration of Korean VLBI Network data

    CERN Document Server

    Hodgson, Jeffrey A; Zhao, Guang-Yao; Algaba, Juan-Carlos; Yun, Youngjoo; Jung, Taehyun; Byun, Do-Young

    2016-01-01

    The calibration of Very Long Baseline Interferometry (VLBI) data has long been a time consuming process. The Korean VLBI Network (KVN) is a simple array consisting of three identical antennas. Because four frequencies are observed simultaneously, phase solutions can be transferred from lower frequencies to higher frequencies in order to improve phase coherence and hence sensitivity at higher frequencies. Due to the homogeneous nature of the array, the KVN is also well suited for automatic calibration. In this paper we describe the automatic calibration of single-polarisation KVN data using the KVN Pipeline and comparing the results against VLBI data that has been manually reduced. We find that the pipelined data using phase transfer produces better results than a manually reduced dataset not using the phase transfer. Additionally we compared the pipeline results with a manually reduced phase-transferred dataset and found the results to be identical.

  15. The Automatic Calibration of Korean VLBI Network Data

    Science.gov (United States)

    Hodgson, Jeffrey A.; Lee, Sang-Sung; Zhao, Guang-Yao; Algaba, Juan-Carlos; Yun, Youngjoo; Jung, Taehyun; Byun, Do-Young

    2016-08-01

    The calibration of Very Long Baseline Interferometry (VLBI) data has long been a time consuming process. The Korean VLBI Network (KVN) is a simple array consisting of three identical antennas. Because four frequencies are observed simultaneously, phase solutions can be transferred from lower frequencies to higher frequencies in order to improve phase coherence and hence sensitivity at higher frequencies. Due to the homogeneous nature of the array, the KVN is also well suited for automatic calibration. In this paper we describe the automatic calibration of single-polarisation KVN data using the KVN Pipeline and comparing the results against VLBI data that has been manually reduced. We find that the pipelined data using phase transfer produces better results than a manually reduced dataset not using the phase transfer. Additionally we compared the pipeline results with a manually reduced phase-transferred dataset and found the results to be identical.

  16. A possible space VLBI constellation utilizing the stable orbits around the TLPs in the Earth-Moon system.

    Science.gov (United States)

    Liu, Bin; Tang, Jingshi; Hou, Xiyun

    2016-07-01

    Current studies indicate that there are stable orbits around but far away from the triangular libration points .Two special quasi-periodic orbits around each triangular libration points L4 , L5 in the Earth-Moon sys-tem perturbed by Sun are gain , and the stable orbits discussed in this work are ideal places for space colonies because no orbit control is needed. These stable orbits can also be used as nominal orbits for space VLBI (Very Long Baseline Interferometry) stations. The two stations can also form baselines with stations on the Earth and the Moon, or with stations located around another TLP. Due to the long distance between the stations, the observation precision can be greatly enhanced compared with the VLBI stations on the Earth. Such a VLBI constellation not only can advance the radio astronomy, but also can be used as a navigation system for human activities in the Earth-Moon system and even in the solar system. This paper will focus on the navigation constellation coverage issues, and the orbit determination accuracy problems within the Earth-Moon sys-tem and interplanetary space.

  17. Submicrosecond comparison of international clock synchronization by VLBI and the NTS satellite

    Science.gov (United States)

    Hurd, W. J.; Wardrip, S. C.; Bussion, J.; Oaks, J.; Mccaskill, T.; Warren, H.; Whitworth, G.

    1979-01-01

    The intercontinental clock synchronization capabilities of Very Long Baseline Interferometry (VLBI) and the Navigation Technology Satellite (NTS) were compared using both methods to synchronize the Cesium clocks at the NASA Deep Space Net complexes at Madrid, Spain and Goldstone, California. Verification of the accuracy of both systems was examined. The VLBI experiments used the Wideband VLBI Data Acquisition System developed at the NASA Jet Propulsion Laboratory. The NTS Satellites were designed and built by the Naval Research Laboratory used with NTS Timing Receivers developed by the Goddard Space Flight Center. The two methods agreed at about the one-half microsecond level.

  18. Adapting a Cryogenic Sapphire Oscillator for Very Long Baseline Interferometry

    CERN Document Server

    Doeleman, Sheperd; Rogers, Alan; Hartnett, John; Tobar, Michael; Nand, Nitin; 10.1086/660156

    2011-01-01

    Extension of very long baseline interferometry (VLBI) to observing wavelengths shorter than 1.3mm provides exceptional angular resolution (~20 micro arcsec) and access to new spectral regimes for the study of astrophysical phenomena. To maintain phase coherence across a global VLBI array at these wavelengths requires that ultrastable frequency references be used for the heterodyne receivers at all participating telescopes. Hydrogen masers have traditionally been used as VLBI references, but atmospheric turbulence typically limits (sub) millimeter VLBI coherence times to ~1-30 s. Cryogenic Sapphire Oscillators (CSO) have better stability than Hydrogen masers on these time scale and are potential alternatives to masers as VLBI references. Here, We describe the design, implementation and tests of a system to produce a 10 MHz VLBI frequency standard from the microwave (11.2 GHz) output of a CSO. To improve long-term stability of the new reference, the CSO was locked to the timing signal from the Global Positionin...

  19. IVS Working Group 4: VLBI Data Structures

    Science.gov (United States)

    Gipson, John

    2010-01-01

    In 2007 the IVS Directing Board established IVS Working Group 4 on VLBI Data Structures. This note discusses the current VLBI data format, goals for a new format, the history and formation of the Working Group, and a timeline for the development of a new VLBI data format.

  20. DSN Beowulf Cluster-Based VLBI Correlator

    Science.gov (United States)

    Rogstad, Stephen P.; Jongeling, Andre P.; Finley, Susan G.; White, Leslie A.; Lanyi, Gabor E.; Clark, John E.; Goodhart, Charles E.

    2009-01-01

    The NASA Deep Space Network (DSN) requires a broadband VLBI (very long baseline interferometry) correlator to process data routinely taken as part of the VLBI source Catalogue Maintenance and Enhancement task (CAT M&E) and the Time and Earth Motion Precision Observations task (TEMPO). The data provided by these measurements are a crucial ingredient in the formation of precision deep-space navigation models. In addition, a VLBI correlator is needed to provide support for other VLBI related activities for both internal and external customers. The JPL VLBI Correlator (JVC) was designed, developed, and delivered to the DSN as a successor to the legacy Block II Correlator. The JVC is a full-capability VLBI correlator that uses software processes running on multiple computers to cross-correlate two-antenna broadband noise data. Components of this new system (see Figure 1) consist of Linux PCs integrated into a Beowulf Cluster, an existing Mark5 data storage system, a RAID array, an existing software correlator package (SoftC) originally developed for Delta DOR Navigation processing, and various custom- developed software processes and scripts. Parallel processing on the JVC is achieved by assigning slave nodes of the Beowulf cluster to process separate scans in parallel until all scans have been processed. Due to the single stream sequential playback of the Mark5 data, some ramp-up time is required before all nodes can have access to required scan data. Core functions of each processing step are accomplished using optimized C programs. The coordination and execution of these programs across the cluster is accomplished using Pearl scripts, PostgreSQL commands, and a handful of miscellaneous system utilities. Mark5 data modules are loaded on Mark5 Data systems playback units, one per station. Data processing is started when the operator scans the Mark5 systems and runs a script that reads various configuration files and then creates an experiment-dependent status database

  1. Comparison between summing-up algorithms to determine areas of small peaks on high baselines

    Science.gov (United States)

    Shi, Quanlin; Zhang, Jiamei; Chang, Yongfu; Qian, Shaojun

    2005-12-01

    It is found that the minimum detectable activity (MDA) has a same tendency as the relative standard deviation (RSD) and a particular application is characteristic of the ratio of the peak area to the baseline height. Different applications need different algorithms to reduce the RSD of peak areas or the MDA of potential peaks. A model of Gaussian peaks superposed on linear baselines is established to simulate the multichannel spectrum and summing-up algorithms such as total peak area (TPA), and Covell and Sterlinski are compared to find the most appropriate algorithm for different applications. The results show that optimal Covell and Sterlinski algorithms will yield MDA or RSD half lower than TPA when the areas of small peaks on high baselines are to be determined. The conclusion is proved by experiment.

  2. GNSS Single Frequency, Single Epoch Reliable Attitude Determination Method with Baseline Vector Constraint.

    Science.gov (United States)

    Gong, Ang; Zhao, Xiubin; Pang, Chunlei; Duan, Rong; Wang, Yong

    2015-12-02

    For Global Navigation Satellite System (GNSS) single frequency, single epoch attitude determination, this paper proposes a new reliable method with baseline vector constraint. First, prior knowledge of baseline length, heading, and pitch obtained from other navigation equipment or sensors are used to reconstruct objective function rigorously. Then, searching strategy is improved. It substitutes gradually Enlarged ellipsoidal search space for non-ellipsoidal search space to ensure correct ambiguity candidates are within it and make the searching process directly be carried out by least squares ambiguity decorrelation algorithm (LAMBDA) method. For all vector candidates, some ones are further eliminated by derived approximate inequality, which accelerates the searching process. Experimental results show that compared to traditional method with only baseline length constraint, this new method can utilize a priori baseline three-dimensional knowledge to fix ambiguity reliably and achieve a high success rate. Experimental tests also verify it is not very sensitive to baseline vector error and can perform robustly when angular error is not great.

  3. GNSS Single Frequency, Single Epoch Reliable Attitude Determination Method with Baseline Vector Constraint

    Directory of Open Access Journals (Sweden)

    Ang Gong

    2015-12-01

    Full Text Available For Global Navigation Satellite System (GNSS single frequency, single epoch attitude determination, this paper proposes a new reliable method with baseline vector constraint. First, prior knowledge of baseline length, heading, and pitch obtained from other navigation equipment or sensors are used to reconstruct objective function rigorously. Then, searching strategy is improved. It substitutes gradually Enlarged ellipsoidal search space for non-ellipsoidal search space to ensure correct ambiguity candidates are within it and make the searching process directly be carried out by least squares ambiguity decorrelation algorithm (LAMBDA method. For all vector candidates, some ones are further eliminated by derived approximate inequality, which accelerates the searching process. Experimental results show that compared to traditional method with only baseline length constraint, this new method can utilize a priori baseline three-dimensional knowledge to fix ambiguity reliably and achieve a high success rate. Experimental tests also verify it is not very sensitive to baseline vector error and can perform robustly when angular error is not great.

  4. CASA Uno GPS orbit and baseline experiments

    Science.gov (United States)

    Schutz, B. E.; Ho, C. S.; Abusali, P. A. M.; Tapley, B. D.

    1990-01-01

    CASA Uno data from sites distributed in longitude from Australia to Europe have been used to determine orbits of the GPS satellites. The characteristics of the orbits determined from double difference phase have been evaluated through comparisons of two-week solutions with one-week solutions and by comparisons of predicted and estimated orbits. Evidence of unmodeled effects is demonstrated, particularly associated with the orbit planes that experience solar eclipse. The orbit accuracy has been assessed through the repeatability of unconstrained estimated baseline vectors ranging from 245 km to 5400 km. Both the baseline repeatability and the comparison with independent space geodetic methods give results at the level of 1-2 parts in 100,000,000. In addition, the Mojave/Owens Valley (245 km) and Kokee Park/Ft. Davis (5409 km) estimates agree with VLBI and SLR to better than 1 part in 100,000,000.

  5. CASA Uno GPS orbit and baseline experiments

    Science.gov (United States)

    Schutz, B. E.; Ho, C. S.; Abusali, P. A. M.; Tapley, B. D.

    1990-01-01

    CASA Uno data from sites distributed in longitude from Australia to Europe have been used to determine orbits of the GPS satellites. The characteristics of the orbits determined from double difference phase have been evaluated through comparisons of two-week solutions with one-week solutions and by comparisons of predicted and estimated orbits. Evidence of unmodeled effects is demonstrated, particularly associated with the orbit planes that experience solar eclipse. The orbit accuracy has been assessed through the repeatability of unconstrained estimated baseline vectors ranging from 245 km to 5400 km. Both the baseline repeatability and the comparison with independent space geodetic methods give results at the level of 1-2 parts in 100,000,000. In addition, the Mojave/Owens Valley (245 km) and Kokee Park/Ft. Davis (5409 km) estimates agree with VLBI and SLR to better than 1 part in 100,000,000.

  6. U.S. Naval Observatory VLBI Analysis Center

    Science.gov (United States)

    Boboltz, David A.; Fey, Alan L.; Geiger, Nicole; Dieck, Chris; Hall, David M.

    2013-01-01

    This report summarizes the activities of the VLBI Analysis Center at the United States Naval Observatory for the 2012 calendar year. Over the course of the year, Analysis Center personnel continued analysis and timely submission of IVS-R4 databases for distribution to the IVS. During the 2012 calendar year, the USNO VLBI Analysis Center produced two VLBI global solutions designated as usn2012a and usn2012b. Earth orientation parameters (EOP) based on this solution and updated by the latest diurnal (IVS-R1 and IVS-R4) experiments were routinely submitted to the IVS. Sinex files based upon the bi-weekly 24-hour experiments were also submitted to the IVS. During the 2012 calendar year, Analysis Center personnel continued a program to use the Very Long Baseline Array (VLBA) operated by the NRAO for the purpose of measuring UT1-UTC. Routine daily 1-hour duration Intensive observations were initiated using the VLBA antennas at Pie Town, NM and Mauna Kea, HI. High-speed network connections to these two antennas are now routinely used for electronic transfer of VLBI data over the Internet to a USNO point of presence. A total of 270 VLBA Intensive experiments were observed and electronically transferred to and processed at USNO in 2012.

  7. VLBI Radar of the 2012 DA14 Asteroid

    Science.gov (United States)

    Nechaeva, M. B.; Dugin, N. A.; Antipenko, A. A.; Bezrukov, D. A.; Bezrukov, V. V.; Voytyuk, V. V.; Dement'ev, A. F.; Jekabsons, N.; Klapers, M.; Konovalenko, A. A.; Kulishenko, V. F.; Nabatov, A. S.; Nesteruk, V. N.; Putillo, D.; Reznichenko, A. M.; Salerno, E.; Snegirev, S. D.; Tikhomirov, Yu. V.; Khutornoy, R. V.; Skirmante, K.; Shmeld, I.; Chagunin, A. K.

    2015-03-01

    An experiment on VLBI radar of the 2012 DA14 asteroid was carried out on February 15-16, 2011 at the time of its closest approach to the Earth. The research teams of Kharkov (Institute of Radio Astronomy of the National Academy of Sciences of Ukraine), Evpatoria (National Space Facilities Control and Test Center), Nizhny Novgorod (Radiophysical Research Institute), Bologna (Istituto di Radioastronomia (INAF)), and Ventspils (Ventspils International Radioastronomy Center) took part in the experiment. The asteroid was irradiated by the RT-70 planetary radar (Evpatoria) at a frequency of 5 GHz. The reflected signal was received using two 32-m radio telescopes in Medicina (Italy) and Irbene (Latvia) in radiointerferometric mode. The Doppler frequency shifts in bi-static radar mode and interference frequency in VLBI mode were measured. Accuracy of the VLBI radar method for determining the radial and angular velocities of the asteroid were estimated.

  8. When you wish upon a star Future developments in astronomical VLBI

    CERN Document Server

    Garrett, M A

    2003-01-01

    In this paper, I present the likely technological development of VLBI, and its impact on the astronomical community over the next 1-5 years. VLBI is currently poised to take advantage of the rapid development in commercial off-the-shelf (COTS) PC-based products. The imminent deployment of disk-based recording systems will enable Gbps data rates to be achieved routinely by both cm and mm-VLBI networks. This, together with anticipated improvements in collecting area, receiver systems and coherence time is set to transform the performance of VLBI in terms of both baseline and image noise sensitivity. At the same time the feasibility of using fibre based communication networks as the basis for production, real-time VLBI networks will begin. Fantastic new correlator output data rates, and the ability to deal with these via powerful PC clusters promises to expand the typical VLBI field-of-view to scales previously reserved for connected, short baseline interferometers. By simultaneously sampling the summed response...

  9. Submicrosecond comparison of intercontinental clock synchronization by VLBI and the NTS satellite

    Science.gov (United States)

    Hurd, W. J.; Wardrip, S. C.; Bussion, J.; Oaks, J.; Mccaskill, T.; Warren, H.; Whitworth, G.

    1979-01-01

    The intercontinental clock synchronization capabilities of Very Long Baseline Interferometry (VLBI) and the Navigation Technology Satellite (NTS) were compared in May 1978 by using both methods to synchronize the cesium clocks at the NASA Deep Space Net complexes at Madrid, Spain, and Goldstone, California. The VLBI experiments used the Wideband VLBI Data Acquisition System. The Navigation Technology Satellites were used with NTS Timing Receivers developed by the Goddard Space Flight Center. The two methods agreed at about the one-half microsecond level. The VLBI system also obtained long-term stability information on the HP5061A004 cesium standards by measuring delta T/T over four 3- to 4-day intervals, obtaining stability estimates of (1 + or - 1)x10 to the -13th power for the combined timing systems.

  10. Detection of atmospheric pressure loading using very long baseline interferometry measurements

    Science.gov (United States)

    Vandam, T. M.; Herring, T. A.

    1994-01-01

    Loading of the Earth by the temporal redistribution of global atmospheric mass is likely to displace the positions of geodetic monuments by tens of millimeters both vertically and horizontally. Estimates of these displacements are determined by convolving National Meteorological Center (NMC) global values of atmospheric surface pressure with Farrell's elastic Green's functions. An analysis of the distances between radio telescopes determined by very long baseline interferometry (VLBI) between 1984 and 1992 reveals that in many of the cases studied there is a significant contribution to baseline length change due to atmospheric pressure loading. Our analysis covers intersite distances of between 1000 and 10,000 km and is restricted to those baselines measured more than 100 times. Accounting for the load effects (after first removing a best fit slope) reduces the weighted root-mean-square (WRMS) scatter of the baseline length residuals on 11 of the 22 baselines investigated. The slight degradation observed in the WRMS scatter on the remaining baselines is largely consistent with the expected statistical fluctuations when a small correction is applied to a data set having a much larger random noise. The results from all baselines are consistent with approximately 60% of the computed pressure contribution being present in the VLBI length determinations. Site dependent coefficients determined by fitting local pressure to the theoretical radial displacement are found to reproduce the deformation caused by the regional pressure to within 25% for most inland sites. The coefficients are less reliable at near coastal and island stations.

  11. Applying Kalman filtering to investigate tropospheric effects in VLBI

    Science.gov (United States)

    Soja, Benedikt; Nilsson, Tobias; Karbon, Maria; Heinkelmann, Robert; Liu, Li; Lu, Cuixian; Andres Mora-Diaz, Julian; Raposo-Pulido, Virginia; Xu, Minghui; Schuh, Harald

    2014-05-01

    Very Long Baseline Interferometry (VLBI) currently provides results, e.g., estimates of the tropospheric delays, with a delay of more than two weeks. In the future, with the coming VLBI2010 Global Observing System (VGOS) and increased usage of electronic data transfer, it is planned that the time between observations and results is decreased. This may, for instance, allow the integration of VLBI-derived tropospheric delays into numerical weather prediction models. Therefore, future VLBI analysis software packages need to be able to process the observational data autonomously in near real-time. For this purpose, we have extended the Vienna VLBI Software (VieVS) by a Kalman filter module. This presentation describes the filter and discusses its application for tropospheric studies. Instead of estimating zenith wet delays as piece-wise linear functions in a least-squares adjustment, the Kalman filter allows for more sophisticated stochastic modeling. We start with a random walk process to model the time-dependent behavior of the zenith wet delays. Other possible approaches include the stochastic model described by turbulence theory, e.g. the model by Treuhaft and Lanyi (1987). Different variance-covariance matrices of the prediction error, depending on the time of the year and the geographic latitude, have been tested. In winter and closer to the poles, lower variances and covariances are appropriate. The horizontal variations in tropospheric delays have been investigated by comparing three different strategies: assumption of a horizontally stratified troposphere, using north and south gradients modeled, e.g., as Gauss-Markov processes, and applying a turbulence model assuming correlations between observations in different azimuths. By conducting Monte-Carlo simulations of current standard VLBI networks and of future VGOS networks, the different tropospheric modeling strategies are investigated. For this purpose, we use the simulator module of VieVS which takes into

  12. 23 GHz VLBI Observations of SN 2008ax

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Guirado, J C; Pérez-Torres, M A; Ros, E; Shapiro, I I; Beswick, R J; Muxlow, T W B; Pedlar, A; Argo, M K; Immler, S; Panagia, N; Stockdale, C J; Sramek, R A; Van Dyk, S; Weiler, K W

    2009-01-01

    We report on phase-referenced 23 GHz Very-Long-Baseline-Interferometry (VLBI) observations of the type IIb supernova SN 2008ax, made with the Very Long Baseline Array (VLBA) on 2 April 2008 (33 days after explosion). These observations resulted in a marginal detection of the supernova. The total flux density recovered from our VLBI image is 0.8$\\pm$0.3 mJy (one standard deviation). As it appears, the structure may be interpreted as either a core-jet or a double source. However, the supernova structure could be somewhat confused with a possible close by noise peak. In such a case, the recovered flux density would decrease to 0.48$\\pm$0.12 mJy, compatible with the flux densities measured with the VLA at epochs close in time to our VLBI observations. The lowest average expansion velocities derived from our observations are $(1.90 \\pm 0.30) \\times 10^5$ km s$^{-1}$ (case of a double source) and $(5.2 \\pm 1.3) \\times 10^4$ km s$^{-1}$ (taking the weaker source component as a spurious, close by, noise peak, which i...

  13. Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis

    Science.gov (United States)

    Sarti, Pierguido; Abbondanza, Claudio; Petrov, Leonid; Negusini, Monia

    2011-01-01

    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 gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [-3, 73] mm and a net scale increase of 0.3-0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.

  14. Development of an e-VLBI Data Transport Software Suite with VDIF

    Science.gov (United States)

    Sekido, Mamoru; Takefuji, Kazuhiro; Kimura, Moritaka; Hobiger, Thomas; Kokado, Kensuke; Nozawa, Kentarou; Kurihara, Shinobu; Shinno, Takuya; Takahashi, Fujinobu

    2010-01-01

    We have developed a software library (KVTP-lib) for VLBI data transmission over the network with the VDIF (VLBI Data Interchange Format), which is the newly proposed standard VLBI data format designed for electronic data transfer over the network. The software package keeps the application layer (VDIF frame) and the transmission layer separate, so that each layer can be developed efficiently. The real-time VLBI data transmission tool sudp-send is an application tool based on the KVTP-lib library. sudp-send captures the VLBI data stream from the VSI-H interface with the K5/VSI PC-board and writes the data to file in standard Linux file format or transmits it to the network using the simple- UDP (SUDP) protocol. Another tool, sudp-recv , receives the data stream from the network and writes the data to file in a specific VLBI format (K5/VSSP, VDIF, or Mark 5B). This software system has been implemented on the Wettzell Tsukuba baseline; evaluation before operational employment is under way.

  15. Development of Broadband VLBI System and its Application to T&F Transfer

    Science.gov (United States)

    Sekido, Mamoru; Takefuji, Kazuhiro; Ujihara, Hideki; Kondo, Tetsuro; Tsutsumi, Masanori; Miyauchi, Yuka; Kawai, Eiji; Takiguchi, Hiroshi; Hasegawa, Shingo; Ichikawa, Ryuichi; Hanado, Yuko; Koyama, Yasuhiro; Watabe, Ken-ichi; Suzuyama, Tomonari; Amemiya, Masaki; Fukuzaki, Yoshihiro; Komuro, Jun-ichi; Terada, Kenjiro; Namba, Kunitaka; Takahashi, Rumi; Okamoto, Yoshihiro; Ikeda, Takatoshi; Aoki, Tetsuo

    2015-08-01

    We are developing a new broadband VLBI system, named GALA-V, for frequency comparison. Atomic time standards connected to transportable small antennas are compared via broadband VLBI observation with large diameter antenna. Disadvantages of small antenna in sensitivity is compensated (1) by ten times wider frequency range of observation and (2) by joint observation with large diameter antenna. NICT has originally developed broadband feed system (6.5-15GHz) for Kashima 34m radio telescope. The system development and performance evaluation of the Gala-V system are being conducted at NICT (Koganei)- NMIJ (Tsukuba) baseline, where both NICT and NMIJ are institutes of maintaining their UTC.The broadband GALA-V system is designed to be compatible with the VGOS (VLBI2010 Global Observing System), which is the next generation geodetic VLBI system promoted by the IVS. We have successfully made the first VLBI observation between the new Ishioka 13m VGOS antenna of GSI and Kashima 34m antenna. Additionally super broadband VLBI observation over 8GHz bandwidth, and coherent signal synthesis for quite high delay resolution were achieved for the first time in the world. This paper will report recent progress of the broadband system development and results of frequency comparison experiments with the GALA-V system.

  16. Earth's core and inner-core resonances from analysis of VLBI nutation and superconducting gravimeter data

    Science.gov (United States)

    Rosat, S.; Lambert, S. B.; Gattano, C.; Calvo, M.

    2017-01-01

    Geophysical parameters of the deep Earth's interior can be evaluated through the resonance effects associated with the core and inner-core wobbles on the forced nutations of the Earth's figure axis, as observed by very long baseline interferometry (VLBI), or on the diurnal tidal waves, retrieved from the time-varying surface gravity recorded by superconducting gravimeters (SGs). In this paper, we inverse for the rotational mode parameters from both techniques to retrieve geophysical parameters of the deep Earth. We analyse surface gravity data from 15 SG stations and VLBI delays accumulated over the last 35 yr. We show existing correlations between several basic Earth parameters and then decide to inverse for the rotational modes parameters. We employ a Bayesian inversion based on the Metropolis-Hastings algorithm with a Markov-chain Monte Carlo method. We obtain estimates of the free core nutation resonant period and quality factor that are consistent for both techniques. We also attempt an inversion for the free inner-core nutation (FICN) resonant period from gravity data. The most probable solution gives a period close to the annual prograde term (or S1 tide). However the 95 per cent confidence interval extends the possible values between roughly 28 and 725 d for gravity, and from 362 to 414 d from nutation data, depending on the prior bounds. The precisions of the estimated long-period nutation and respective small diurnal tidal constituents are hence not accurate enough for a correct determination of the FICN complex frequency.

  17. VLBI in the service of geodesy 1968-2000: An Onsala perspective

    Science.gov (United States)

    Elgered, G.; Haas, R.

    Very-Long-Baseline Interferometry (VLBI) has been used at the Onsala Space Observatory since 1968. In this paper we summarize the geodetic application of VLBI in terms of the observations so far obtained and the main geodetic results. Estimated time series of intercontinental as well as European baseline lengths are presented. The present facilities include the 20 m radome enclosed radio telescope, several continuously operating GPS receivers, a 21/31 GHz microwave radiometer for studies of the atmospheric excess propagation path due to water vapour, and a gravimetry foundation anchored in the solid granite rock in a laboratory environment. Geodetic VLBI continues to play an important role for the maintenance of the International Terrestrial Reference Frame (ITRF). The international CORE programme has the goal to continuously measure the earth rotation parameters. Over long time scales nutation and UT1 are not possible to estimate reliably from techniques using satellites in orbits around the earth.

  18. Evaluation of current tropospheric mapping functions by Deep Space Network very long baseline interferometry

    Science.gov (United States)

    Sovers, O. J.; Lanyi, G. E.

    1994-01-01

    To compare the validity of current algorithms that map zenith tropospheric delay to arbitrary elevation angles, 10 different tropospheric mapping functions are used to analyze the current data base of Deep Space Network Mark 3 intercontinental very long baseline interferometric (VLBI) data. This analysis serves as a stringent test because of the high proportion of low-elevation observations necessitated by the extremely long baselines. Postfit delay and delay-rate residuals are examined, as well as the scatter of baseline lengths about the time-linear model that characterizes tectonic motion. Among the functions that utilize surface meteorological data as input parameters, the Lanyi 1984 mapping shows the best performance both for residuals and baselines, through the 1985 Davis function is statistically nearly identical. The next best performance is shown by the recent function of Niell, which is based on an examination of global atmospheric characteristics as a function of season and uses no weather data at the time of the measurements. The Niell function shows a slight improvement in residuals relative to Lanyi, but also an increase in baseline scatter that is significant for the California-Spain baseline. Two variants of the Chao mapping function, as well as the Chao tables used with the interpolation algorithm employed in the Orbit Determination Program software, show substandard behavior for both VLBI residuals and baseline scatter. The length of the California-Australia baseline (10,600 km) in the VLBI solution can vary by as much as 5 to 10 cm for the 10 mapping functions.

  19. Determinants of rapid weight gain during infancy: baseline results from the NOURISH randomised controlled trial

    Directory of Open Access Journals (Sweden)

    Mihrshahi Seema

    2011-11-01

    Full Text Available Abstract Background Rapid weight gain in infancy is an important predictor of obesity in later childhood. Our aim was to determine which modifiable variables are associated with rapid weight gain in early life. Methods Subjects were healthy infants enrolled in NOURISH, a randomised, controlled trial evaluating an intervention to promote positive early feeding practices. This analysis used the birth and baseline data for NOURISH. Birthweight was collected from hospital records and infants were also weighed at baseline assessment when they were aged 4-7 months and before randomisation. Infant feeding practices and demographic variables were collected from the mother using a self administered questionnaire. Rapid weight gain was defined as an increase in weight-for-age Z-score (using WHO standards above 0.67 SD from birth to baseline assessment, which is interpreted clinically as crossing centile lines on a growth chart. Variables associated with rapid weight gain were evaluated using a multivariable logistic regression model. Results Complete data were available for 612 infants (88% of the total sample recruited with a mean (SD age of 4.3 (1.0 months at baseline assessment. After adjusting for mother's age, smoking in pregnancy, BMI, and education and infant birthweight, age, gender and introduction of solid foods, the only two modifiable factors associated with rapid weight gain to attain statistical significance were formula feeding [OR = 1.72 (95%CI 1.01-2.94, P = 0.047] and feeding on schedule [OR = 2.29 (95%CI 1.14-4.61, P = 0.020]. Male gender and lower birthweight were non-modifiable factors associated with rapid weight gain. Conclusions This analysis supports the contention that there is an association between formula feeding, feeding to schedule and weight gain in the first months of life. Mechanisms may include the actual content of formula milk (e.g. higher protein intake or differences in feeding styles, such as feeding to schedule

  20. Improved VLBI astrometry of OH maser stars

    CERN Document Server

    Vlemmings, W H T

    2007-01-01

    Aims: Accurate distances to evolved stars with high mass loss rates are needed for studies of many of their fundamental properties. However, as these stars are heavily obscured and variable, optical and infrared astrometry is unable to provide enough accuracy. Methods: Astrometry using masers in the circumstellar envelopes can be used to overcome this problem. We have observed the OH masers of a number of Asymptotic Giant Branch (AGB) stars for approximately 1 year with the Very Long Baseline Array (VLBA). We have used the technique of phase referencing with in-beam calibrators to test the improvements this technique can provide to Very Long Baseline Interferometry (VLBI) OH maser astrometric observations. Results: We have significantly improved the parallax and proper motion measurements of the Mira variable stars U Her, S CrB and RR Aql. Conclusions: It is shown that both in-beam phase-referencing and a decrease in solar activity during the observations significantly improves the accuracy of the astrometric...

  1. VLBI Detections of Parsec-Scale Nonthermal Jets in Radio-Loud Broad Absorption Line Quasars

    CERN Document Server

    Doi, Akihiro; Kono, Yusuke; Oyama, Tomoaki; Fujisawa, Kenta; Takaba, Hiroshi; Sudou, Hiroshi; Wakamatsu, Ken-ichi; Yamauchi, Aya; Murata, Yasuhiro; Mochizuki, Nanako; Wajima, Kiyoaki; Omodaka, Toshihiro; Nagayama, Takumi; Nakai, Naomasa; Sorai, Kazuo; Kawai, Eiji; Sekido, Mamoru; Koyama, Yasuhiro; Asano, Shoichiro; Uose, Hisao

    2009-01-01

    We conducted radio detection observations at 8.4 GHz for 22 radio-loud broad absorption line (BAL) quasars, selected from the Sloan Digital Sky Survey (SDSS) Third Data Release, by a very-long-baseline interferometry (VLBI) technique. The VLBI instrument we used was developed by the Optically ConnecTed Array for VLBI Exploration project (OCTAVE), which is operated as a subarray of the Japanese VLBI Network (JVN). We aimed at selecting BAL quasars with nonthermal jets suitable for measuring their orientation angles and ages by subsequent detailed VLBI imaging studies to evaluate two controversial issues of whether BAL quasars are viewed nearly edge-on, and of whether BAL quasars are in a short-lived evolutionary phase of quasar population. We detected 20 out of 22 sources using the OCTAVE baselines, implying brightness temperatures greater than 10^5 K, which presumably come from nonthermal jets. Hence, BAL outflows and nonthermal jets can be generated simultaneously in these central engines. We also found four...

  2. Baseline configuration for GNSS attitude determination with an analytical least-squares solution

    Science.gov (United States)

    Chang, Guobin; Xu, Tianhe; Wang, Qianxin

    2016-12-01

    The GNSS attitude determination using carrier phase measurements with 4 antennas is studied on condition that the integer ambiguities have been resolved. The solution to the nonlinear least-squares is often obtained iteratively, however an analytical solution can exist for specific baseline configurations. The main aim of this work is to design this class of configurations. Both single and double difference measurements are treated which refer to the dedicated and non-dedicated receivers respectively. More realistic error models are employed in which the correlations between different measurements are given full consideration. The desired configurations are worked out. The configurations are rotation and scale equivariant and can be applied to both the dedicated and non-dedicated receivers. For these configurations, the analytical and optimal solution for the attitude is also given together with its error variance-covariance matrix.

  3. MultiView High Precision VLBI Astrometry at Low Frequencies

    Science.gov (United States)

    Rioja, María J.; Dodson, Richard; Orosz, Gabor; Imai, Hiroshi; Frey, Sandor

    2017-03-01

    The arrival of the Square Kilometer Array (SKA) will revitalize all aspects of Very Long Baseline Interferometry (VLBI) astronomy at lower frequencies. In the last decade, there have been huge strides toward routinely achieving high precision VLBI astrometry at frequencies dominated by tropospheric contributions, most notably at 22 GHz, using advanced phase-referencing techniques. Nevertheless, to increase the capability for high precision astrometric measurements at low radio frequencies (phase-referencing calibrator. The MultiView technique holds the key to compensating for atmospheric spatial-structure errors, by using observations of multiple calibrators and two-dimensional interpolation in the visibility domain. In this paper we present the first demonstration of the power of MultiView using three calibrators, several degrees from the target, along with a comparative study of the astrometric accuracy between MultiView and phase-referencing techniques. MultiView calibration provides an order of magnitude improvement in astrometry with respect to conventional phase referencing, achieving ∼100 μas astrometry errors in a single epoch of observations, effectively reaching the thermal noise limit. MultiView will achieve its full potential with the enhanced sensitivity and multibeam capabilities of SKA and the pathfinders, which will enable simultaneous observations of the target and calibrators. Our demonstration indicates that the 10 μas goal of astrometry at ∼1.6 GHz using VLBI with SKA is feasible using the MultiView technique.

  4. Search for exoplanets and brown dwarfs with VLBI

    Science.gov (United States)

    Katarzyński, K.; Gawroński, M.; Goździewski, K.

    2016-09-01

    The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter's magnetic field (˜9 G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI. However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies. We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different emission scenarios, and found that the radiation induced by moons (process similar to Jupiter-Io interactions) appears to be less efficient than the emission generated by a stellar wind on a planetary magnetosphere. We also estimated hypothetical emission of planets and brown dwarfs located around relatively young and massive main-sequence A-type stars. Our results show that the emission produced by stellar winds could be detected by currently operating VLBI networks.

  5. Millimeter-VLBI with a Large Millimeter-Array: Future Possibilities

    CERN Document Server

    Krichbaum, T P

    2003-01-01

    We discuss possibilities and improvements which could be obtained, if a phased array with a large number (N=50-100) of sub-millimeter antennas - like the planned large southern array (the former LSA, now ALMA) is used for radio-interferometry with very long baselines (VLBI) at millimeter wavelengths. We find that the inclusion of such an instrument in global VLBI network will push the sensitivity and the imaging capabilities of high resolution millimeter interferometry by up to 2 orders of magnitude. This will cause many but todate unforseeable new discoveries.

  6. 1.6 GHz VLBI Observations of SN 1979C: almost-free expansion

    CERN Document Server

    Marcaide, J M; Pérez-Torres, M A; Alberdi, A; Guirado, J C; Ros, E; Weiler, K W

    2009-01-01

    We report on 1.6 GHz Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN 1979C made on 18 November 2002. We derive a model-dependent supernova size. We also present a reanalysis of VLBI observations made by us on June 1999 and by other authors on February 2005. We conclude that, contrary to our earlier claim of strong deceleration in the expansion, SN 1979C has been undergoing almost-free expansion ($m = 0.91\\pm0.09$; $R \\propto t^m$) for over 25 years.

  7. Plate tectonics from VLBI and SLR global data

    Science.gov (United States)

    Harrison, Christopher G. A.; Robaudo, Stefano

    1992-01-01

    This study is based on data derived from fifteen years of observations of the SLR (side-looking radar) network and six years of the VLBI (very long baseline interferometry) network. In order to use all available information VLBI and SLR global data sets were combined in a least squares fashion to calculate station horizontal velocities. All significant data pertaining to a single site contribute to the station horizontal motion. The only constraint on the solution is that no vertical motion is allowed. This restriction does not greatly affect the precision of the overall solution given the fact that the expected vertical motion for most stations, even those experiencing post glacial uplift, is well under 1 cm/yr. Since the average baseline is under 4,000 km, only a small fraction of the station vertical velocity is translated into baseline rates so that the error introduced in the solution by restricting up-down station movement is minimal. As a reference, station velocities were then compared to the ones predicted by the NUVEL-1 geological model of DeMets et al. (1990). The focus of the study is on analyzing these discrepancies for global plate tectonics as well as regional tectonic settings. The method used also allows us not only to derive horizontal motion for individual stations but also to calculate Euler vectors for those plates that have enough stations located on the stable interior like North America, Pacific, Eurasia, and Australia.

  8. Zooming towards the Event Horizon - mm-VLBI today and tomorrow

    CERN Document Server

    Krichbaum, T P; Wagner, J; Rottmann, H; Hodgson, J A; Bertarini, A; Alef, W; Zensus, J A; Marscher, A P; Jorstad, S G; Freund, R; Marrone, D; Strittmatter, P; Ziurys, L; Blundell, R; Weintroub, J; Young, K; Fish, V; Doeleman, S; Bremer, M; Sanchez, S; Fuhrmann, L; Angelakis, E; Karamanavis, V

    2013-01-01

    Global VLBI imaging at millimeter and sub-millimeter wavelength overcomes the opacity barrier of synchrotron self-absorption in AGN and opens the direct view into sub-pc scale regions not accessible before. Since AGN variability is more pronounced at short millimeter wavelength, mm-VLBI can reveal structural changes in very early stages after outbursts. When combined with observations at longer wavelength, global 3mm and 1mm VLBI adds very detailed information. This helps to determine fundamental physical properties at the jet base, and in the vicinity of super-massive black holes at the center of AGN. Here we present new results from multi-frequency mm-VLBI imaging of OJ287 during a major outburst. We also report on a successful 1.3mm VLBI experiment with the APEX telescope in Chile. This observation sets a new record in angular resolution. It also opens the path towards future mm-VLBI with ALMA, which aims at the mapping of the black hole event horizon in nearby galaxies, and the study of the roots of jets ...

  9. [Strategy for determining a baseline in areas of vector interruption for Chagas disease].

    Science.gov (United States)

    Montenegro, Diego; Vera, Mauricio; Zuleta, Liliana; Llanos, Violeta; Junqueira, Angela

    2016-06-01

    Objectives Present a strategy to determine the baseline in endemic areas in the process of vector interruption for Chagas disease (CHD). Methods A social and environmental questionnaire and an entomological survey evaluated the physical conditions of dwellings, the inhabitants' knowledge of CHD, the entomological triatomine indicators and the statistical relationship among these variables. Results Colonization and natural infection with Trypanosoma cruzi exist in Rhodnius prolixus, the principal vector of CHD in Colombia. Colonization was related to palm-thatched houses constructed with adobe or wattle and daub. The Panstrongylus geniculatus vector was found to be colonizing. Almost 50% of the surveyed population associated the term CHD with human disease and 37%, with triatomines. Conclusions R. prolixus can be considered to be the principal vector of T. cruzi in domestic environments and the process of interruption is feasible within the prioritized municipality. New studies are needed to verify the existence of wild populations of R. prolixus that could affect future stages of the process and demonstrate whether P. geniculatus is a factor in the transmission of T. cruzi. These scenarios can be made viable by including the inhabitants throughout the process, since they have been highly sensitive in vector detection inside their houses. The study design presented here can be adapted to other endemic areas of the Region of the Americas.

  10. SWARM: A 32 GHz Correlator and VLBI Beamformer for the Submillimeter Array

    CERN Document Server

    Primiani, Rurik A; Young, André; Patel, Nimesh; Wilson, Robert W; Vertatschitsch, Laura; Chitwood, Billie B; Srinivasan, Ranjani; MacMahon, David; Weintroub, Jonathan

    2016-01-01

    A 32 GHz bandwidth VLBI capable correlator and phased array has been designed and deployed at the Smithsonian Astrophysical Observatory's Submillimeter Array (SMA). The SMA Wideband Astronomical ROACH2 Machine (SWARM) integrates two instruments: a correlator with 140 kHz spectral resolution across its full 32 GHz band, used for connected interferometric observations, and a phased array summer used when the SMA participates as a station in the Event Horizon Telescope (EHT) Very Long Baseline Interferometry (VLBI) array. For each SWARM quadrant, Reconfigurable Open Architecture Computing Hardware (ROACH2) units shared under open source from the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER) are equipped with a pair of ultra-fast Analog-to- Digital Converters (ADCs), a Field Programmable Gate Array (FPGA) processor, and eight 10 Gigabit Ethernet ports. A VLBI data recorder interface designated the SWARM Digital Back End, or SDBE, is implemented with a ninth ROACH2 per quadrant, f...

  11. The deflection of light induced by the Sun's gravitational field and measured with geodetic VLBI

    CERN Document Server

    Titov, O

    2015-01-01

    The Sun's gravitational field deflects the apparent positions of close objects in accordance with the formulae of general relativity. Optical astrometry is used to test the prediction, but only with the stars close to the Sun and only during total Solar eclipses. Geodetic Very Long Baseline Interferometry (VLBI) is capable of measuring the deflection of the light from distant radio sources anytime and across the whole sky. We show that the effect of light deflection is equivalent to the gravitational delay calculated during the reduction of VLBI data. All reference radio sources display an annual circular motion with the magnitude proportional to their ecliptic latitude. In particular, radio sources near the ecliptic pole draw an annual circle with magnitude of 4 mas. This effect could be easily measured with the current precision of the geodetic VLBI data.

  12. 1.3 mm Wavelength VLBI of Sagittarius A*: Detection of Time-Variable Emission on Event Horizon Scales

    CERN Document Server

    Fish, Vincent L; Beaudoin, Christopher; Blundell, Ray; Bolin, David E; Bower, Geoffrey C; Chamberlin, Richard; Freund, Robert; Friberg, Per; Gurwell, Mark A; Honma, Mareki; Inoue, Makoto; Krichbaum, Thomas P; Lamb, James; Marrone, Daniel P; Moran, James M; Oyama, Tomoaki; Plambeck, Richard; Primiani, Rurik; Rogers, Alan E E; Smythe, Daniel L; SooHoo, Jason; Strittmatter, Peter; Tilanus, Remo P J; Titus, Michael; Weintroub, Jonathan; Wright, Melvyn; Woody, David; Young, Ken H; Ziurys, Lucy M

    2010-01-01

    Sagittarius A*, the ~4 x 10^6 solar mass black hole candidate at the Galactic Center, can be studied on Schwarzschild radius scales with (sub)millimeter wavelength Very Long Baseline Interferometry (VLBI). We report on 1.3 mm wavelength observations of Sgr A* using a VLBI array consisting of the JCMT on Mauna Kea, the ARO/SMT on Mt. Graham in Arizona, and two telescopes of the CARMA array at Cedar Flat in California. Both Sgr A* and the quasar calibrator 1924-292 were observed over three consecutive nights, and both sources were clearly detected on all baselines. For the first time, we are able to extract 1.3 mm VLBI interferometer phase information on Sgr A* through measurement of closure phase on the triangle of baselines. On the third night of observing, the correlated flux density of Sgr A* on all VLBI baselines increased relative to the first two nights, providing strong evidence for time-variable change on scales of a few Schwarzschild radii. These results suggest that future VLBI observations with grea...

  13. VLBI-Gaia offsets favour parsec-scale jet direction in Active Galactic Nuclei

    CERN Document Server

    Kovalev, Y Y; Plavin, A V

    2016-01-01

    The data release 1 (DR1) of milliarcsecond-scale accurate optical positions of stars and galaxies was recently published by the space mission Gaia. We analyze the offsets of highly accurate absolute radio (very long baseline interferometry, VLBI) and optical positions of active galactic nuclei (AGN) to check whether a signature of wavelength-dependent parsec-scale structure can be seen. We use in the analysis astrometric positions of thousands of AGNs from the VLBI and Gaia observations as well as reconstructed VLBI images. We have found that there is a statistically significant excess of sources with VLBI-to-Gaia positional offset directions along the jet for a full range of offset values as well as an excess for the direction opposite to the jet if offset values are less than 3 mas. An existence of strong extended parsec-scale optical jet structure in many AGNs is required to explain the observed VLBI-Gaia offsets along the jet direction. The 1-mas offsets in the opposite direction are explained by a non-po...

  14. A Global Terrestrial Reference Frame from simulated VLBI and SLR data in view of GGOS

    Science.gov (United States)

    Glaser, Susanne; König, Rolf; Ampatzidis, Dimitrios; Nilsson, Tobias; Heinkelmann, Robert; Flechtner, Frank; Schuh, Harald

    2017-07-01

    In this study, we assess the impact of two combination strategies, namely local ties (LT) and global ties (GT), on the datum realization of Global Terrestrial Reference Frames in view of the Global Geodetic Observing System requiring 1 mm-accuracy. Simulated Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) data over a 7 year time span was used. The LT results show that the geodetic datum can be best transferred if the precision of the LT is at least 1 mm. Investigating different numbers of LT, the lack of co-located sites on the southern hemisphere is evidenced by differences of 9 mm in translation and rotation compared to the solution using all available LT. For the GT, the combination applying all Earth rotation parameters (ERP), such as pole coordinates and UT1-UTC, indicates that the rotation around the Z axis cannot be adequately transferred from VLBI to SLR within the combination. Applying exclusively the pole coordinates as GT, we show that the datum can be transferred with mm-accuracy within the combination. Furthermore, adding artificial stations in Tahiti and Nigeria to the current VLBI network results in an improvement in station positions by 13 and 12%, respectively, and in ERP by 17 and 11%, respectively. Extending to every day VLBI observations leads to 65% better ERP estimates compared to usual twice-weekly VLBI observations.

  15. Status and plans for the future of the Vienna VLBI Software

    Science.gov (United States)

    Madzak, Matthias; Böhm, Johannes; Böhm, Sigrid; Girdiuk, Anastasiia; Hellerschmied, Andreas; Hofmeister, Armin; Krasna, Hana; Kwak, Younghee; Landskron, Daniel; Mayer, David; McCallum, Jamie; Plank, Lucia; Schönberger, Caroline; Shabala, Stanislav; Sun, Jing; Teke, Kamil

    2016-04-01

    The Vienna VLBI Software (VieVS) is a VLBI analysis software developed and maintained at Technische Universität Wien (TU Wien) since 2008 with contributions from groups all over the world. It is used for both academic purposes in university courses as well as for providing VLBI analysis results to the geodetic community. Written in a modular structure in Matlab, VieVS offers easy access to the source code and the possibility to adapt the programs for particular purposes. The new version 2.3, released in December 2015, includes several new parameters to be estimated in the global solution, such as tidal ERP variation coefficients. The graphical user interface was slightly modified for an improved user functionality and, e.g., the possibility of deriving baseline length repeatabilities. The scheduling of satellite observations was refined, the simulator newly includes the effect of source structure which can also be corrected for in the analysis. This poster gives an overview of all VLBI-related activities in Vienna and provides an outlook to future plans concerning the Vienna VLBI Software.

  16. On the potential of lunar observations in regular geodetic VLBI sessions

    Science.gov (United States)

    Klopotek, Grzegorz; Hobiger, Thomas; Haas, Rüdiger

    2017-04-01

    Artificial radio sources on the surface of the Moon enable us to observe lunar based transmitters with geodetic VLBI. Although during the last years a few dedicated VLBI experiments have already been carried out, the question still remains how and to what extend new information can be derived from observing such targets. Therefore, we perform Monte Carlo simulations using the c5++ software in order to evaluate how the inclusion of lunar observations into regular VLBI schedules would impact classical Earth-related target parameters of geodetic VLBI such as station coordinates and Earth Orientation Parameters, as well as how it would extend the possibilities to determine selenoidic parameters. Our study is based on modified IVS-R1 observing schedules, originally created by the International VLBI Service for Geodesy and Astrometry (IVS) to determine Earth Orientation Parameters, thus representing state-of-the-art VLBI observing programs. Based on our simulations, we demonstrate that an artificial radio source on the surface of the Moon can be located with both, accuracy and precision of better than 50 cm when observed along with quasars in the regular IVS-R1 session schedules. Moreover, we show that geodetic VLBI has the potential to improve our knowledge of lunar physical models and/or help to verify or update lunar ephemerides. We will discuss how the quality and quantity of lunar observations affect the uncertainty of the position of a non-moving artificial radio source located on the surface of the Moon and we highlight the factors limiting the determination of its position. Furthermore, we will reveal the impact of Moon VLBI observations on the determination of the Earth Orientation Parameters and VLBI station positions. We will also test the concept of VLBI lunar observations with simulations that reflect VGOS performance in terms of observation precision, number of scans and future network configurations. Thus, our simulations will provide valuable insights

  17. The "Quasar" Network Observations in e-VLBI Mode Within the Russian Domestic VLBI Programs

    Science.gov (United States)

    Finkelstein, Andrey; Ipatov, Alexander; Kaidanovsky, Michael; Bezrukov, Ilia; Mikhailov, Andrey; Salnikov, Alexander; Surkis, Igor; Skurikhina, Elena

    2010-01-01

    The purpose of the Russian VLBI "Quasar" Network is to carry out astrometrical and geodynamical investigations. Since 2006 purely domestic observational programs with data processing at the IAA correlator have been carried out. To maintain these geodynamical programs e-VLBI technology is being developed and tested. This paper describes the IAA activity of developing a real-time VLBI system using high-speed digital communication links.

  18. VLBI terrestrial reference frame contributions to ITRF2008

    Science.gov (United States)

    Böckmann, Sarah; Artz, T.; Nothnagel, A.

    2010-03-01

    In late 2008, the Product Center for the International Terrestrial Reference Frame (ITRF) of the International Earth Rotation and Reference Systems Service (IERS) issued a call for contributions to the next realization of the International Terrestrial Reference System, ITRF2008. The official contribution of the International VLBI Service for Geodesy and Astrometry (IVS) to ITRF2008 consists of session-wise datum-free normal equations of altogether 4,539 daily Very Long Baseline Interferometry (VLBI) sessions from 1979.7 to 2009.0 including data of 115 different VLBI sites. It is the result of a combination of individual series of session-wise datum-free normal equations provided by seven analysis centers (ACs) of the IVS. All series are completely reprocessed following homogeneous analysis options according to the IERS Conventions 2003 and IVS Analysis Conventions. Altogether, nine IVS ACs analyzed the full history of VLBI observations with four different software packages. Unfortunately, the contributions of two ACs, Institute of Applied Astronomy (IAA) and Geoscience Australia (AUS), had to be excluded from the combination process. This was mostly done because the IAA series exhibits a clear scale offset while the solution computed from normal equations contained in the AUS SINEX files yielded unreliable results. Based on the experience gathered since the combination efforts for ITRF2005, some discrepancies between the individual series were discovered and overcome. Thus, the consistency of the individual VLBI solutions has improved considerably. The agreement in terms of WRMS of the Terrestrial Reference Frame (TRF) horizontal components is 1 mm, of the height component 2 mm. Comparisons between ITRF2005 and the combined TRF solution for ITRF2008 yielded systematic height differences of up to 5 mm with a zonal signature. These differences can be related to a pole tide correction referenced to a zero mean pole used by four of five IVS ACs in the ITRF2005

  19. Gravity-dependent signal path variation in a large VLBI telescope modelled with a combination of surveying methods

    Science.gov (United States)

    Sarti, Pierguido; Abbondanza, C.; Vittuari, L.

    2009-11-01

    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 parts of the telescope’s structure. Triangulation and trilateration on the targets highlight a consistent amount of deformation that biases the estimate of the instrument’s reference point up to 1 cm, depending on the targets’ locations. Therefore, whenever the estimation of accurate local ties is needed, it is critical to take into consideration the action of gravity on the structure. Furthermore, deformations induced by gravity on VLBI telescopes may modify the length of the path travelled by the incoming radio signal to a non-negligible extent. As a consequence, differently from what it is usually assumed, the relative distance of the feed horn’s phase centre with respect to the elevation axis may vary, depending on the telescope’s pointing elevation. The Medicina telescope’s signal path variation Δ L increases by a magnitude of approximately 2 cm, as the pointing elevation changes from horizon to zenith; it is described by an elevation-dependent second-order polynomial function computed as, according to Clark and Thomsen (Techical report, 100696, NASA, Greenbelt, 1988), a linear combination of three terms: receiver displacement Δ R, primary reflector’s vertex displacement Δ V and focal length variations Δ F. Δ L was investigated with a combination of terrestrial triangulation and trilateration, laser scanning and a finite element model of the antenna. The antenna gain (or auto-focus curve) Δ G is routinely determined through astronomical observations. A surprisingly accurate reproduction of Δ G can be obtained with a combination of Δ V, Δ F and Δ R.

  20. Radio sources - Very, Very Long Baseline Interferometry

    Science.gov (United States)

    Roberts, D. H.

    1983-03-01

    With resolution of a thousandth of an arcsecond, the radio technique of Very Long Baseline Interferometry (VLBI) provides astronomers with their highest-resolution view of the universe. Data taken with widely-separated antennas are combined, with the help of atomic clocks, to form a Michelson interferometer whose size may be as great as the earth's diameter. Extraordinary phenomena, from the birth of stars as signaled by the brilliant flashes of powerful interstellar masers to the 'faster-than-light' expansion of the cores of distant quasars, are being explored with this technique. However, earth-bound VLBI suffers from several restrictions due to the location of the component antennas at fixed places on the earth's surface. The use of one or more antennas in space in concert with ground-based equipment will greatly expand the technical and scientific capabilities of VLBI, leading to a more complete and even higher resolution view of cosmic phenomena.

  1. Modernizing the JPL VLBI Correlator

    Science.gov (United States)

    Rogstad, S.; Goodhart, C. E.; Clark, J. E.; Finley, S.; Lanyi, G. E.; White, L. A.; Jacobs, Christopher S.>

    This poster will present the current capabilities of the JPL VLBI Correlator (JVC) and the general architecture of the equipment. In addition, the scientific and navigation uses of the JVC will be enumerated for background purposes. The JVC is a software correlator based on a Beowulf cluster of computers. It replaces a thirty year old correlator based on custom designed digital hardware. General comparisons between the old and new equipment will be made. The JVC makes use of a separate program, SoftC, to do the actual correlations. The JVC manages the sending of data to multiple machines in a Beowulf cluster each running SoftC in parallel on small chunks of the data. The basic architecture of SoftC will also be described.

  2. The RAEGE VLBI2010 radiotelescopes

    Science.gov (United States)

    Sust, Eberhard; López Fernández, José Antonio

    2012-09-01

    The goal of the RAEGE (Red Atlantica Estaciones Geodinamicas Espaciales) project is the establishment of a Spanish-Portuguese network of geodynamical and spatial geodesy stations by the installation and operation of four fundamental geodetic / astronomical stations provided with radio telescopes located at - Yebes, close to Madrid / Spain - Tenerife, Canary Islands / Spain - Santa Maria, Azores Islands / Portugal. VLBI 2010 radiotelescopes are belonging to a new generation of radiotelescopes suitable for high precision geodetical earth observation and measurements, that shall allow to built up a high precision global reference system. The design of the radiotelescopes has been finished by MT Mechatronics in summer 2011 and currently three radiotelescopes are being manufactured. The first one is scheduled for installation in summer 2012 at Yebes Observatory close to Madrid.

  3. Structure Corrections in Modeling VLBI Delays for RDV Data

    Science.gov (United States)

    Sovers, Ojars J.; Charlot, Patrick; Fey, Alan L.; Gordon, David

    2002-01-01

    Since 1997, bimonthly S- and X-band observing sessions have been carried out employing the VLBA (Very Long Baseline Array) and as many as ten additional antennas. Maps of the extended structures have been generated for the 160 sources observed in ten of these experiments (approximately 200,000 observations) taking place during 1997 and 1998. This paper reports the results of the first massive application of such structure maps to correct the modeled VLBI (Very Long Baseline Interferometry) delay in astrometric data analysis. For high-accuracy celestial reference frame work, proper choice of a reference point within each extended source is crucial. Here the reference point is taken at the point of maximum emitted flux. Overall, the weighted delay residuals (approximately equal to 30 ps) are reduced by 8 ps in quadrature upon introducing source maps to model the structure delays of the sources. Residuals of some sources with extended or fast-varying structures improve by as much as 40 ps. Scatter of 'arc positions' about a time-linear model decreases substantially for most sources. Based on our results, it is also concluded that source structure is presently not the dominant error source in astrometric/geodetic VLBI.

  4. Subdaily Earth Rotation Models Estimated From GPS and VLBI Data

    Science.gov (United States)

    Steigenberger, P.; Tesmer, V.; MacMillan, D.; Thaller, D.; Rothacher, M.; Fritsche, M.; Rülke, A.; Dietrich, R.

    2007-12-01

    Subdaily changes in Earth rotation at diurnal and semi-diurnal periods are mainly caused by ocean tides. Smaller effects are attributed to the interaction of the atmosphere with the solid Earth. As the tidal periods are well known, models for the ocean tidal contribution to high-frequency Earth rotation variations can be estimated from space- geodetic observations. The subdaily ERP model recommended by the latest IERS conventions was derived from an ocean tide model based on satellite altimetry. Another possibility is the determination of subdaily ERP models from GPS- and/or VLBI-derived Earth rotation parameter series with subdaily resolution. Homogeneously reprocessed long-time series of subdaily ERPs computed by GFZ/TU Dresden (12 years of GPS data), DGFI and GSFC (both with 24 years of VLBI data) provide the basis for the estimation of single-technique and combined subdaily ERP models. The impact of different processing options (e.g., weighting) and different temporal resolutions (1 hour vs. 2 hours) will be evaluated by comparisons of the different models amongst each other and with the IERS model. The analysis of the GPS and VLBI residual signals after subtracting the estimated ocean tidal contribution may help to answer the question whether the remaining signals are technique-specific artifacts and systematic errors or true geophysical signals detected by both techniques.

  5. Construction of the Korean VLBI Network (KVN)

    CERN Document Server

    Kim, H G; Sohn, B W; Oh, S J; Je, D H; Wi, S O; Song, M G

    2004-01-01

    Korea's new VLBI project to construct the Korean VLBI Network (KVN) started in 2001, as a 7-year project that is fully funded by our government. We plan to build 3 new high-precision radio telescopes of 21-m diameter in 3 places in Korea, which will be exclusively used for VLBI observations. We will install the 2/8, 22 and 43 GHz HEMT receivers within 2007 as a first target, and later we will expand the receiving frequency up to 86 and 129 GHz for astronomical, geodetic, and earth science VLBI research. The millimeter-wave VLBI will be the ultimate goal of KVN. For the front-ends, we are going to install a multi-channel receiver system that employs low-pass filters within a quasi-optical beam transportation system. This receiver system will give reliable phase calibrations for millimeter-wave VLBI as well as enable simultaneous multi-frequency band observations. The hard-disk type new Mark 5 will be used as the main recorder of KVN. We have completed the design of the KVN DAS system of 2 Gsps sampling rate, w...

  6. e-VLBI Development at Haystack Observatory

    Science.gov (United States)

    Whitney, Alan

    Haystack Observatory continues an aggressive program of e-VLBI development, particularly with respect to the use of public (shared) high-speed networds for data transfer. Much of 2002 was spent preparing for a Gbps e-VLBI demonstration experiment using antennas at Westford, MA and Greenbelt, MD; this experiment was succcesully conducted using both near-real-time and real-time data transfers to the Mark 4 correlator at Haystack Observatory, though correlation was not done in real time. In early 2003 a dedicated e-VLBI Gigabit-Ethernet wavelength was establisted between Haystack Observatory and MIT Lincoln Laboratory, giving Haystack easy access to the high-speed Abilene network in the U.S. Also in October 2002, preliminary e-VLBI experiments were conducted between Westford, MA and Kashima, Japan; this set of experiments is continuing with increasing data-rate transfers. These experiments use the Mark 5 system at Westford and the K5 system at Kashima; data is transferred in both directions and correlated at both sites. Preparations are now underway to begin e-VLBI transfers from Wettzell, Germany and Kokee Park, Kauaii for routine daily observation of UT1. Haystack Observatory has recently been awarded a 3-year grant the the National Science Foundation for the development of new IP protocols specifically tailored for e-VLBI and similar applications.

  7. Constraining the Structure of Sagittarius A*'s Accretion Flow with Millimeter-VLBI Closure Phases

    CERN Document Server

    Broderick, Avery E; Doeleman, Sheperd S; Loeb, Abraham

    2011-01-01

    Millimeter wave Very Long Baseline Interferometry (mm-VLBI) provides access to the emission region surrounding Sagittarius A*, the supermassive black hole at the center of the Milky Way, on sub-horizon scales. Recently, a closure phase of 0+-40 degrees was reported on a triangle of Earth-sized baselines (SMT-CARMA-JCMT) representing a new constraint upon the structure and orientation of the emission region, independent from those provided by the previously measured 1.3mm-VLBI visibility amplitudes alone. Here, we compare this to the closure phases associated with a class of physically motivated, radiatively inefficient accretion flow models, and present predictions for future mm-VLBI experiments with the developing Event Horizon Telescope (EHT). We find that the accretion flow models are capable of producing a wide variety of closure phases on the SMT-CARMA-JCMT triangle, and thus not all models are consistent with the recent observations. However, those models that reproduce the 1.3mm-VLBI visibility amplitu...

  8. Dual-frequency VLBI study of Centaurus A on sub-parsec scales

    CERN Document Server

    Müller, Cornelia; Ojha, R; Wilms, J; Böck, M; Edwards, P G; Fromm, C M; Hase, H; Horiuchi, S; Katz, U; Lovell, J E J; Plötz, C; Pursimo, T; Richers, S; Ros, E; Rothschild, R E; Taylor, G B; Tingay, S J; Zensus, J A

    2011-01-01

    Centaurus A is the closest active galactic nucleus. High resolution imaging using Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on sub-parsec scales, providing essential information for jet emission and formation models. Our aim is to study the structure and spectral shape of the emission from the central-parsec region of Cen A. As a target of the Southern Hemisphere VLBI monitoring program TANAMI (Tracking Active Galactic Nuclei with Milliarcsecond Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, and South Africa. The first dual-frequency images of this source are presented along with the resulting spectral index map. An angular resolution of 0.4 mas x 0.7 mas is achieved at 8.4 GHz, corresponding to a linear scale of less than 0.013 pc. Hence, we obtain the highest resolution VLBI image of Cen A, ...

  9. NASA Space Geodesy Program: GSFC data analysis, 1993. VLBI geodetic results 1979 - 1992

    Science.gov (United States)

    Ma, Chopo; Ryan, James W.; Caprette, Douglas S.

    1994-01-01

    The Goddard VLBI group reports the results of analyzing Mark 3 data sets acquired from 110 fixed and mobile observing sites through the end of 1992 and available to the Space Geodesy Program. Two large solutions were used to obtain site positions, site velocities, baseline evolution for 474 baselines, earth rotation parameters, nutation offsets, and radio source positions. Site velocities are presented in both geocentric Cartesian and topocentric coordinates. Baseline evolution is plotted for the 89 baselines that were observed in 1992 and positions at 1988.0 are presented for all fixed stations and mobile sites. Positions are also presented for quasar radio sources used in the solutions.

  10. An accurate position for the black hole candidate XTE J1752-223: re-interpretation of the VLBI data

    Science.gov (United States)

    Miller-Jones, J. C. A.; Jonker, P. G.; Ratti, E. M.; Torres, M. A. P.; Brocksopp, C.; Yang, J.; Morrell, N. I.

    2011-07-01

    Using high-precision astrometric optical observations from the Walter Baade Magellan Telescope in conjunction with high-resolution very long baseline interferometric (VLBI) radio imaging with the Very Long Baseline Array (VLBA), we have located the core of the X-ray binary system XTE J1752-223. Compact radio emission from the core was detected following the state transition from the soft to the hard X-ray state. Its position to the south-east of all previously detected jet components mandated a re-analysis of the existing VLBI data. Our analysis suggests that the outburst comprised at least two ejection events prior to 2010 February 26. No radio-emitting components were detected to the south-east of the core at any epoch, suggesting that the receding jets were Doppler-deboosted below our sensitivity limit. From the ratio of the brightness of the detected components to the measured upper limits for the receding ejecta, we constrain the jet speed β > 0.66 and the inclination angle to the line of sight θ < 49°. Assuming that the initial ejection event occurred at the transition from the hard intermediate state to the soft intermediate state, an initial period of ballistic motion followed by a Sedov phase (i.e. self-similar adiabatic expansion) appears to fit the motion of the ejecta better than a uniform deceleration model. The accurate core location can provide a long time baseline for a future proper motion determination should the system show a second outburst, providing insights into the formation mechanism of the compact object.

  11. Application Of The Climafor Baseline To Determine Leakage: TheCase Of Scolel Te.

    Energy Technology Data Exchange (ETDEWEB)

    De Jong, B.H.J.; Bazan, E. Esquivel; Quechulpa Montalvo, S.

    2007-06-01

    The acceptance of forestry-based project activities tomitigate greenhouse gases emissions has been subjected to a number ofmethodological questions to be answered, of which the most challengingare baseline establishment and identification of and measuring leakage.Here we pose hypotheses for and quantify leakage of the Scolel Te projectin Chiapas, Mexico. In this project small-scale farmers are implementingforestry, agroforestry, and forest conservation activities, with carbonsequestration as one of the goals. The main leakage monitoring domain isdefined as the area owned by the participating farmers or communitiesoutside the area where the specific project activities take place. Thenull-hypothesis (no leakage) is that non-project land owned by the farmeror community will experience the same carbon stock changes as predictedby the regional baseline, specifically developed for the project. Firstwe assessed the most likely causes and sources of leakage that may occurin the project. From this analysis, one type of leakage seems to beimportant, i.e., activity shifting. Second we estimated the leakage of asample of participating farmers and communities. Actual land use was thencompared with expected land use derived from the baseline. The Plan Vivoof each participant, complemented with readily available tools toidentify the main sources and drivers of leakage are used to developsimple leakage assessment procedures, as demonstrated in this paper.Negative leakage was estimated to be negligible in this study.Incorporating these procedures already in the project planning stage willreduce the uncertainties related to the actual carbon mitigationpotential of any forestry project.

  12. Masses of Nearby Supermassive Black Holes with Very-Long Baseline Interferometry

    CERN Document Server

    Johannsen, Tim; Gillessen, Stefan; Marrone, Daniel P; Ozel, Feryal; Doeleman, Sheperd S; Fish, Vincent L

    2012-01-01

    Dynamical mass measurements to date have allowed determinations of the mass M and the distance D of the galactic center black hole Sgr A* as well as those of other nearby supermassive black holes. In the case of Sgr A*, these measurements are limited by a degeneracy between the mass and distance scaling roughly as M ~ D^2. Future very-long baseline interferometric observations will image a bright and narrow ring surrounding the shadow of the supermassive black hole, if its accretion flow is optically thin. In this paper, we show that the combination of dynamical measurements and VLBI imaging of the ring of Sgr A* breaks the degeneracy between mass and distance. We estimate the signal to noise ratio of near-future VLBI arrays consisting of five to six stations and simulate measurements of the mass and distance of Sgr A* using the expected size of the ring image and existing data of stellar ephemerides. We demonstrate that VLBI observations at 1 mm can already improve the error on the mass by a factor of three ...

  13. First 230 GHz VLBI Fringes on 3C 279 using the APEX Telescope

    CERN Document Server

    Wagner, J; Krichbaum, T P; Alef, W; Bansod, A; Bertarini, A; Güsten, R; Graham, D; Hodgson, J; Märtens, R; Menten, K; Muders, D; Rottmann, H; Tuccari, G; Weiss, A; Wieching, G; Wunderlich, M; Zensus, J A; Araneda, J P; Arriagada, O; Cantzler, M; Duran, C; Montenegro-Montes, F M; Olivares, R; Caro, P; Bergman, P; Conway, J; Haas, R; Johansson, J; Lindqvist, M; Olofsson, H; Pantaleev, M; Buttaccio, S; Cappallo, R; Crew, G; Doeleman, S; Fish, V; Lu, R -S; Ruszczyk, C; SooHoo, J; Titus, M; Freund, R; Marrone, D; Strittmatter, P; Ziurys, L; Blundell, R; Primiani, R; Weintroub, J; Young, K; Bremer, M; Sánchez, S; Marscher, A P; Chilson, R; Asada, K; Inoue, M

    2015-01-01

    We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, the phased submillimeter array (SMA), and the SMT of the Arizona Radio Observatory (ARO). We installed VLBI equipment and measured the APEX station position to 1 cm accuracy (1 sigma). We then observed 3C 279 on 2012 May 7 in a 5 hour 230 GHz VLBI track with baseline lengths of 2800 M$\\lambda$ to 7200 M$\\lambda$ and a finest fringe spacing of 28.6 micro-arcseconds. Fringes were detected on all baselines with SNRs of 12 to 55 in 420 s. The correlated flux density on the longest baseline was ~0.3 Jy/beam, out of a total flux density of 19.8 Jy. Visibility data suggest an emission region <38 uas in size, and at least two components, possibly polarized. We find a lower limit of the brightness temperature of the inner jet region of about 10^10 K. Lastly, we find an upper limit of 20% on the linear polarization fraction at a fringe spacing of ~38 uas. With APEX the angul...

  14. Design of VLBI Array in South America

    Science.gov (United States)

    Carrara, E. A.; Abraham, Z.

    1990-11-01

    RESUMEN. Estudiamos la localizaci6n 6ptima de estaciones de \\ ras' en territorlo brasileno. Con una red VLBI de estaciones reales y ficti- cias simulamos observaciones. Se usan los datos generados de estps ex- perimentos para obtener Ia distribuci6n de brillo de radiofuentes fic- ticias por medlo de tecaicas de mapeo bIbrido. Se concluye que l mejor localizaci6n de estacionee'VLBI futuras, tomando en cuenta las estacio- nes de EUA y de Europa, se encuentra en el Norte-Noreste de razll. El analisis de los datos se hizo con los programas de CALTECH, los cuales estan instalados en una computadora VAX del Departamento de Astronomla del Instituto Astron6mico y Geoflsico de la Universidad de Sa"'o Paulo. ABSTRACT: In this work we study the optimum localization for future VLBI stations in the Brazilian territory. With a VLBI network of real and fictitious stations we make simulations of observations. The data generated in these experiments are used to obtain brightness distribution of a fictitious radio source by the hybrid mapping techniques. We conclude that the best localization of a future VLBI station taking into account the addition of US and European Stations, is roughly in North-Northeast sites in Brazil. The analysis of the data is made with the software of CALTECH, which is installed in the VAX computer of the Astronomy Department of Instituto e Geofisico - USP. Key `{` : INSTRUMENTS - INTERFEROMETRY

  15. Search for exoplanets and brown dwarfs with VLBI

    CERN Document Server

    Katarzynski, K; Gozdziewski, K

    2016-01-01

    The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter's magnetic field ($\\sim 9$ G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI. However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies. We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different e...

  16. Applying the theory of general relativity to reducing geodetic VLBI data

    CERN Document Server

    Titov, O

    2015-01-01

    We present an alternate formula for calculating gravitational time delay. We use this formula to reduce geodetic Very Long Baseline Interferometry (VLBI) data, taking into account gravitational effects within the solar system, and to test general relativity. The alternate formula was obtained by expanding the conventional formula in a Taylor series. We show that the gravitational delay can be split into several terms including a term due to the coordinate transformation and terms that are explicitly linked to the light deflection angle. Our formula is compared numerically with the conventional formula, and difference in arrival times within 1 ps are found at 1$^\\circ$ from the Sun for a full range of baseline lengths. We conclude that the standard reduction of geodetic VLBI data for the effects of general relativity is equivalent to displacing the reference radio sources from their original catalogue positions in accordance with the classical light deflection formula across the whole sky.

  17. Radio source stability and geodetic VLBI

    Science.gov (United States)

    Gattano, César; Lambert, Sébastien

    2016-04-01

    The observation of the Earth's rotation by VLBI is conditioned by the celestial reference frame that should be as stable as possible. The selection of the most stable sources therefore constitutes a major step in the construction of a celestial reference frame since their stability prevents time deformation of the axes with time. The assessment of astrometric stability, i.e., the time stability the radiocenter location as detected by the VLBI, is one of the methods that were used in previous ICRF realizations (works of M. Feissel-Vernier and ICRF2). We think the same method should be addressed for the construction of the ICRF3. We analyzed the radio source time series obtained from the analysis of the data from the permanent geodetic VLBI monitoring program of the IVS. We used several utils based on basic statistics and more advanced methods (Allan variance) in order to provide a preliminary classification of sources.

  18. Milky Way Scattering Properties and Intrinsic Sizes of AGN Cores Probed by VLBI Surveys of Compact Extragalactic Radio Sources

    CERN Document Server

    Pushkarev, A B

    2015-01-01

    We have measured the angular sizes of radio cores of active galactic nuclei (AGN) and analyzed their sky distributions and frequency dependencies to study synchrotron opacity in AGN jets and the strength of angular broadening in the interstellar medium. We have used archival very long baseline interferometry (VLBI) data of more than 3000 compact extragalactic radio sources observed at frequencies, $\

  19. VLBI observations of a flared optical quasar CGRaBS J0809+5341

    CERN Document Server

    An, Tao; Paragi, Zsolt; Frey, Sandor; Gurvits, Leonid I; Gabanyi, Krisztina E

    2016-01-01

    A bright optical flare was detected in the high-redshift ($z=2.133$) quasar CGRaBS J0809+5341 on 2014 April 13. The absolute magnitude of the object reached $-30.0$ during the flare, making it the brightest one (in flaring stage) among all known quasars so far. The 15 GHz flux density of CGRaBS J0809+5341 monitored in the period from 2008 to 2016 also reached its peak at the same time. To reveal any structural change possibly associated with the flare in the innermost radio structure of the quasar, we conducted a pilot very long baseline interferometry (VLBI) observation of CGRaBS J0809+5341 using the European VLBI Network (EVN) at 5 GHz on 2014 November 18, about seven months after the prominent optical flare. Three epochs of follow-up KaVA (Korean VLBI Network and VLBI Exploration of Radio Astrometry Array) observations were carried out at 22 and 43 GHz frequencies from 2015 February 25 to June 4, with the intention of exploring a possibly emerging new radio jet component associated with the optical flare. ...

  20. THE APPLICATION OF MULTIVIEW METHODS FOR HIGH-PRECISION ASTROMETRIC SPACE VLBI AT LOW FREQUENCIES

    Energy Technology Data Exchange (ETDEWEB)

    Dodson, R.; Rioja, M.; Imai, H. [International Centre for Radio Astronomy Research, M468, University of Western Australia, 35 Stirling Hwy, Crawley, Western Australia 6009 (Australia); Asaki, Y. [Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuou, Sagamihara, Kanagawa 252-5210 (Japan); Hong, X.-Y.; Shen, Z., E-mail: richard.dodson@icrar.org [Shanghai Astronomical Observatory, CAS, 200030 Shanghai (China)

    2013-06-15

    High-precision astrometric space very long baseline interferometry (S-VLBI) at the low end of the conventional frequency range, i.e., 20 cm, is a requirement for a number of high-priority science goals. These are headlined by obtaining trigonometric parallax distances to pulsars in pulsar-black hole pairs and OH masers anywhere in the Milky Way and the Magellanic Clouds. We propose a solution for the most difficult technical problems in S-VLBI by the MultiView approach where multiple sources, separated by several degrees on the sky, are observed simultaneously. We simulated a number of challenging S-VLBI configurations, with orbit errors up to 8 m in size and with ionospheric atmospheres consistent with poor conditions. In these simulations we performed MultiView analysis to achieve the required science goals. This approach removes the need for beam switching requiring a Control Moment Gyro, and the space and ground infrastructure required for high-quality orbit reconstruction of a space-based radio telescope. This will dramatically reduce the complexity of S-VLBI missions which implement the phase-referencing technique.

  1. Multi-frequency imaging in VLBI

    CERN Document Server

    Likhachev, S

    2004-01-01

    The new technique, multi-frequency imaging (MFI) is developed. In VLBI, Multi-Frequency Imaging (MFI) consists of multi-frequency synthesis (MFS) and multi-frequency analysis (MFA) of the VLBI data obtained from observations on various frequencies. A set of linear deconvolution MFI algorithms is described. The algorithms make it possible to obtain high quality images interpolated on any given frequency inside any given bandwidth, and to derive reliable estimates of spectral indexes for radio sources with continuum spectrum. Thus MFI approach makes it is possible not only to improve the quality and fidelity of the images and also essentially to derive the morphology of the observed radio sources.

  2. The recent progress of Chinese VLBI Network

    Science.gov (United States)

    Zheng, Weimin

    2015-08-01

    At present, Chinese VLBI Network (CVN) consists of 5 antennas (Seshan 25m, Urumqi 25m, Kunming 30m, Miyun 50m and Tianma 65m) and one data processing center in Shanghai Observatory, Chinese academy of sciences. It is a synthetic aperture radio telescope with the equivalent diameter up to 3000 Km. Through e-VLBI (electronic VLBI) technology, CVN is connected by the commuication network. It is a multi-purpose scientific research platform radio for geodesy, astronomy, as well as deep space exploration. In Geodesy, CVN is the component of the Crustal Movement Observation Network of China. Since the year of 2006, more than 20 geodetic domestic observations have been carried out. A set of phase-referencing observations of pulsars with CVN has carried out and got preliminary results. CVN also joined the Chinese lunar exploration Project from 2007 and supported 4 Chang’E series lunar probe missions. In Chang’E-3 mission, using the in-beam VLBI observations, the relative position accuracy of Rover and Lander is up to 1 meter.In recent years, we have updated the facilities of CVN from antenna, receivers, VLBI terminals to correlator. Participation of Tianma 65m antennas increases its performance. In 2012, Shanghai correlator was accepted as the IVS correlator. After upgrade, Shanghai correlator will try to provide the data process service for IVS community from 2015. To drive the construction of the planned VGOS (VLBI2010 Global Observing System) station, at least two VOGS 13m antenna will join CVN in the near future. Construction of the first VOGS antenna in Shanghai hopes to begin this year.The new VLBI correlator and digital terminal are under development. From participation in VGOS, we plan to study the earth rotation especially of high frequency and corresponding geophysical signals, to link China’s regional reference frame to ITRF, and etc. CVN is willing to join the research corporation with IVS, EVN, VLBA and AOV (Asia- Oceania VLBI Group for Geodesy and

  3. The Acceleration of the Barycenter of Solar System Obtained from VLBI Observations and Its Impact on the ICRS

    Science.gov (United States)

    Xu, M. H.

    2016-03-01

    Since 1998 January 1, instead of the traditional stellar reference system, the International Celestial Reference System (ICRS) has been realized by an ensemble of extragalactic radio sources that are located at hundreds of millions of light years away (if we accept their cosmological distances), so that the reference frame realized by extragalactic radio sources is assumed to be space-fixed. The acceleration of the barycenter of solar system (SSB), which is the origin of the ICRS, gives rise to a systematical variation in the directions of the observed radio sources. This phenomenon is called the secular aberration drift. As a result, the extragalactic reference frame fixed to the space provides a reference standard for detecting the secular aberration drift, and the acceleration of the barycenter with respect to the space can be determined from the observations of extragalactic radio sources. In this thesis, we aim to determine the acceleration of the SSB from astrometric and geodetic observations obtained by Very Long Baseline Interferometry (VLBI), which is a technique using the telescopes globally distributed on the Earth to observe a radio source simultaneously, and with the capacity of angular positioning for compact radio sources at 10-milliarcsecond level. The method of the global solution, which allows the acceleration vector to be estimated as a global parameter in the data analysis, is developed. Through the formal error given by the solution, this method shows directly the VLBI observations' capability to constrain the acceleration of the SSB, and demonstrates the significance level of the result. In the next step, the impact of the acceleration on the ICRS is studied in order to obtain the correction of the celestial reference frame (CRF) orientation. This thesis begins with the basic background and the general frame of this work. A brief review of the realization of the CRF based on the kinematical and the dynamical methods is presented in Chapter 2

  4. Effects of illumination functions on the computation of gravity-dependent signal path variation models in primary focus and Cassegrainian VLBI telescopes

    Science.gov (United States)

    Abbondanza, Claudio; Sarti, Pierguido

    2010-08-01

    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 depend on the dimensions and the focal lengths of the telescopes as well as on the feed illumination taper. They hold for any primary focus or Cassegrainian very long baseline interferometry (VLBI) telescope. Earlier investigations usually determined the SPV models assuming a uniform illumination of the telescope mirrors. We prove this hypothesis to be over-simplistic by comparing results derived adopting (a) uniform, (b) Gaussian and (c) binomial illumination functions. Numerical computations are developed for AZ-EL mount, 32 m Medicina and Noto (Italy) VLBI telescopes, these latter being the only telescopes which possess thorough information on gravity-dependent deformation patterns. Particularly, assuming a Gaussian illumination function, the SPV in primary focus over the elevation range [0°, 90°] is 10.1 and 7.2 mm, for Medicina and Noto, respectively. With uniform illumination function the maximal path variation for Medicina is 17.6 and 12.7 mm for Noto, thus highlighting the strong dependency on the choice of the illumination function. According to our findings, a revised SPV model is released for Medicina and a model for Noto is presented here for the first time. Currently, no other VLBI telescope possesses SPV models capable of correcting gravity-dependent observation biases.

  5. The Potential for a Ka-band (32 GHz) Worldwide VLBI Network

    Science.gov (United States)

    Jacobs, C. S.; Bach, U.; Colomer, F.; Garcia-Miro, C.; Gomez-Gonzalez, J.; Gulyaev, S.; Horiuchi, S.; Ichikawa, R.; Kraus, A.; Kronschnabl, G.; Lopez-Fernandez, J. A.; Lovell, J.; Majid, W.; Natusch, T.; Neidhardt, A.; Phillips, C.; Porcas, R.; Romero-Wolf, A.; Saldana, L.; Schreiber, U.; Sotuela, I.; Takeuchi, H.; Trinh, J.; Tzioumis, A.; deVincente, P.

    2012-01-01

    Ka-band (32 GHz, 9mm) Very Long Baseline Interferometric (VLBI) networking has now begun and has tremendous potential for expansion over the next few years. Ka-band VLBI astrometry from NASA's Deep Space Network has already developed a catalog of 470 observable sources with highly accurate positions. Now, several antennas worldwide are planning or are considering adding Ka-band VLBI capability. Thus, there is now an opportunity to create a worldwide Ka-band network with potential for high resolution imaging and astrometry. With baselines approaching a Giga-lambda, a Ka-band network would be able to probe source structure at the nano-radian (200 as) level ( 100X better than Hubble) and thus gain insight into the astrophysics of the most compact regions of emission in active galactic nuclei. We discuss the advantages of Ka-band, show the known sources and candidates, simulate projected baseline (uv) coverage, and discuss potential radio frequency feeds. The combination of these elements demonstrates the feasibility of a worldwide Ka network within the next few years!

  6. The Potential for a Ka-band (32 GHz) Worldwide VLBI Network

    Science.gov (United States)

    Jacobs, C. S.; Bach, U.; Colomer, F.; Garcia-Miro, C.; Gomez-Gonzalez, J.; Gulyaev, S.; Horiuchi, S.; Ichikawa, R.; Kraus, A.; Kronschnabl, G.; hide

    2012-01-01

    Ka-band (32 GHz, 9mm) Very Long Baseline Interferometric (VLBI) networking has now begun and has tremendous potential for expansion over the next few years. Ka-band VLBI astrometry from NASA's Deep Space Network has already developed a catalog of 470 observable sources with highly accurate positions. Now, several antennas worldwide are planning or are considering adding Ka-band VLBI capability. Thus, there is now an opportunity to create a worldwide Ka-band network with potential for high resolution imaging and astrometry. With baselines approaching a Giga-lambda, a Ka-band network would be able to probe source structure at the nano-radian (200 as) level ( 100X better than Hubble) and thus gain insight into the astrophysics of the most compact regions of emission in active galactic nuclei. We discuss the advantages of Ka-band, show the known sources and candidates, simulate projected baseline (uv) coverage, and discuss potential radio frequency feeds. The combination of these elements demonstrates the feasibility of a worldwide Ka network within the next few years!

  7. Determination of Baseline Periods of Record for Selected Streamflow-Gaging Stations in New Jersey for Determining Ecologically Relevant Hydrologic Indices (ERHI)

    Science.gov (United States)

    Esralew, Rachel A.; Baker, Ronald J.

    2008-01-01

    Hydrologic changes in New Jersey stream basins resulting from human activity can affect the flow and ecology of the streams. To assess future changes in streamflow resulting from human activity an understanding of the natural variability of streamflow is needed. The natural variability can be classified using Ecologically Relevant Hydrologic Indices (ERHIs). ERHIs are defined as selected streamflow statistics that characterize elements of the flow regime that substantially affect biological health and ecological sustainability. ERHIs are used to quantitatively characterize aspects of the streamflow regime, including magnitude, duration, frequency, timing, and rate of change. Changes in ERHI values can occur as a result of human activity, and changes in ERHIs over time at various stream locations can provide information about the degree of alteration in aquatic ecosystems at or near those locations. New Jersey streams can be divided into four classes (A, B, C, or D), where streams with similar ERHI values (determined from cluster analysis) are assigned the same stream class. In order to detect and quantify changes in ERHIs at selected streamflow-gaging stations, a 'baseline' period is needed. Ideally, a baseline period is a period of continuous daily streamflow record at a gaging station where human activity along the contributing stream reach or in the stream's basin is minimal. Because substantial urbanization and other development had already occurred before continuous streamflow-gaging stations were installed, it is not possible to identify baseline periods that meet this criterion for many reaches in New Jersey. Therefore, the baseline period for a considerably altered basin can be defined as a period prior to a substantial human-induced change in the drainage basin or stream reach (such as regulations or diversions), or a period during which development did not change substantially. Index stations (stations with minimal urbanization) were defined as streamflow

  8. Determining baselines for human-elephant conflict: A matter of time.

    Science.gov (United States)

    Pozo, Rocío A; Coulson, Tim; McCulloch, Graham; Stronza, Amanda L; Songhurst, Anna C

    2017-01-01

    Elephant crop raiding is one of the most relevant forms of human-elephant conflict (HEC) in Africa. Northern Botswana holds the largest population of African elephants in the world, and in the eastern Okavango Panhandle, 16,000 people share and compete for resources with more than 11,000 elephants. Hence, it is not surprising this area represents a HEC 'hotspot' in the region. Crop-raiding impacts lead to negative perceptions of elephants by local communities, which can strongly undermine conservation efforts. Therefore, assessing trends in conflict levels is essential to developing successful management strategies. In this context, we investigated the trend in the number of reported raiding incidents as one of the indicators of the level of HEC, and assessed its relationship to trends in human and elephant population size, as well as land-use in the study area. For each of these factors, we considered data spanning historical (since the 1970s) and contemporary (2008-2015) time frames, with the aim of comparing subsequent inferences on the drivers of crop raiding and predictions for the future. We find that the level of reported crop raiding by elephants in the eastern Panhandle appears to have decreased since 2008, which seems to be related to the reduction in agricultural land allocated to people in recent years, more than with human and elephant population size. We show that inferences regarding the drivers of HEC and predictions for the future are dependent on the time span of the data used. Although our study represents a first step in developing a HEC baseline in the eastern Panhandle, it highlights the need for additional multi-scale analyses that consider progress in conservation conflict to better understand and predict drivers of HEC in the region.

  9. Vienna SAC-SOS: Analysis of the European VLBI Sessions

    Science.gov (United States)

    Ros, C. T.; Pavetich, P.; Nilsson, T.; Böhm, J.; Schuh, H.

    2012-12-01

    The Institute of Geodesy and Geophysics (IGG) of the Vienna University of Technology as an IVS Special Analysis Center for Specific Observing Sessions (SAC-SOS) has analyzed the European VLBI sessions using the software VieVS. Between 1990 and 2011, 115 sessions have been carried out. The analyzed baselines have lengths ranging from approximately 445 to 4580 km, and they show good repeatabilities, apart from the ones containing station Simeiz. The station velocities have also been investigated. The stations situated in the stable part of Europe have not shown significant relative movements w.r.t. Wettzell, whereas the stations located in the northern areas have the largest vertical motions as a result of the post glacial isostatic rebound of the zone. The stations placed in Italy, around the Black Sea, in Siberia, and near the Arctic Circle show the largest relative horizontal motions because they belong to different geodynamical units.

  10. Towards a four technique GGOS site: VLBI - DORIS compatibility tests at Wettzell

    Science.gov (United States)

    Klügel, Thomas; Didelot, Francois; Kodet, Jan; Kronschnabl, Gerhard; Mähler, Swetlana; Neidhardt, Alexander; Plötz, Christian; Saunier, Jérôme; Schüler, Torben; Walter, Jean-Marc

    2016-04-01

    Within the framework of a Global Geodetic Observing System (GGOS), co-location sites are of special importance for the evaluation and mutual control of the individual geodetic space techniques. At the Geodetic Observatory Wettzell a DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacon could complete the geodetic instrumentation consisting of three Very Long Baseline Interferometry (VLBI) telescopes, two Laser Ranging (LR) systems and a number of multi- Global Navigation Satellite System (GNSS) stations. Integrating all fourth geodetic instrumentation into one site generates new problems with Electromagnetic Compatibility (EMC). While the VLBI system is designed to receive very weak signals from quasars, the DORIS beacon emits strong signals in the UHF frequency band at 401.25 MHz and in the S band at 2036.25 MHz. During the observation of quasars with VLBI there is a high risk of coupling DORIS S band signals into the VLBI receiving chain generating spurious signal and, in the worst case, overloading receiving chain electronics and risking its damage. Before a DORIS beacon is operated at the Geodetic Observatory Wettzell, it must be ensured that it can be operated alongside the VLBI system without any risk of damage or degradation of the measurement. Field tests under different setups were performed to assess the impact of the DORIS signal on the classical geodetic VLBI 20-m and the VGOS 13-m radio telescopes. Different locations on the observatory each at a distance of more than 100 m were occupied by the DORIS antenna. It has been shown that obstacles like buildings or earth mounds attenuate the signal up to 20 dB. However the power received at the input of the Low Noise Amplifiers (LNA) is still at a critical level when the radio telescope points towards the DORIS beacon. The quality of the correlated signals is not or barely affected at long baselines. At local baselines however, the DORIS emission as a common mode signal degrades

  11. VLBI Surveys of Active Galactic Nuclei

    Science.gov (United States)

    Kovalev, Y. Y.

    2009-08-01

    A review is given on the current status and selected results from large VLBI surveys of compact extragalactic radio sources made between 13 cm and 3 mm wavelengths and covering the entire sky. More than 4200 objects are observed and imaged with dynamic ranges from a hundred to several thousand at (sub)parsec scales. Implications to the VSOP-2 project are discussed.

  12. Atmospheric pressure loading parameters from very long baseline interferometry observations

    Science.gov (United States)

    Macmillan, D. S.; Gipson, John M.

    1994-01-01

    Atmospheric mass loading produces a primarily vertical displacement of the Earth's crust. This displacement is correlated with surface pressure and is large enough to be detected by very long baseline interferometry (VLBI) measurements. Using the measured surface pressure at VLBI stations, we have estimated the atmospheric loading term for each station location directly from VLBI data acquired from 1979 to 1992. Our estimates of the vertical sensitivity to change in pressure range from 0 to -0.6 mm/mbar depending on the station. These estimates agree with inverted barometer model calculations (Manabe et al., 1991; vanDam and Herring, 1994) of the vertical displacement sensitivity computed by convolving actual pressure distributions with loading Green's functions. The pressure sensitivity tends to be smaller for stations near the coast, which is consistent with the inverted barometer hypothesis. Applying this estimated pressure loading correction in standard VLBI geodetic analysis improves the repeatability of estimated lengths of 25 out of 37 baselines that were measured at least 50 times. In a root-sum-square (rss) sense, the improvement generally increases with baseline length at a rate of about 0.3 to 0.6 ppb depending on whether the baseline stations are close to the coast. For the 5998-km baseline from Westford, Massachusetts, to Wettzell, Germany, the rss improvement is about 3.6 mm out of 11.0 mm. The average rss reduction of the vertical scatter for inland stations ranges from 2.7 to 5.4 mm.

  13. Combined Earth orientation parameters based on homogeneous and continuous VLBI and GPS data

    Science.gov (United States)

    Thaller, Daniela; Krügel, Manuela; Rothacher, Markus; Tesmer, Volker; Schmid, Ralf; Angermann, Detlef

    2007-06-01

    The CONT02 campaign is of great interest for studies combining very long baseline interferometry (VLBI) with other space-geodetic techniques, because of the continuously available VLBI observations over 2 weeks in October 2002 from a homogeneous network. Especially, the combination with the Global Positioning System (GPS) offers a broad spectrum of common parameters. We combined station coordinates, Earth orientation parameters (EOPs) and troposphere parameters consistently in one solution using technique- specific datum-free normal equation systems. In this paper, we focus on the analyses concerning the EOPs, whereas the comparison and combination of the troposphere parameters and station coordinates are covered in a companion paper in Journal of Geodesy. In order to demonstrate the potential of the VLBI and GPS space-geodetic techniques, we chose a sub-daily resolution for polar motion (PM) and universal time (UT). A consequence of this solution set-up is the presence of a one-to-one correlation between the nutation angles and a retrograde diurnal signal in PM. The Bernese GPS Software used for the combination provides a constraining approach to handle this singularity. Simulation studies involving both nutation offsets and rates helped to get a deeper understanding of this singularity. With a rigorous combination of UT1 UTC and length of day (LOD) from VLBI and GPS, we showed that such a combination works very well and does not suffer from the systematic effects present in the GPS-derived LOD values. By means of wavelet analyses and the formal errors of the estimates, we explain this important result. The same holds for the combination of nutation offsets and rates. The local geodetic ties between GPS and VLBI antennas play an essential role within the inter-technique combination. Several studies already revealed non-negligible discrepancies between the terrestrial measurements and the space-geodetic solutions. We demonstrate to what extent these discrepancies

  14. VLBI observations of four radio quasars at z > 4: blazars or not?

    Science.gov (United States)

    Cao, H. M.; Frey, S.; Gabányi, K. É.; Paragi, Z.; Yang, J.; Cseh, D.; Hong, X.-Y.; An, T.

    2017-01-01

    Blazars are active galactic nuclei (AGN) whose relativistic jets point nearly to the line of sight. Their compact radio structure can be imaged with very long baseline interferometry (VLBI) on parsec scales. Blazars at extremely high redshifts provide a unique insight into the AGN phenomena in the early Universe. We observed four radio sources at redshift z > 4 with the European VLBI Network (EVN) at 1.7 and 5 GHz. These objects were previously classified as blazar candidates based on X-ray observations. One of them, J2134-0419 is firmly confirmed as a blazar with our VLBI observations, due to its relativistically beamed radio emission. Its radio jet extended to ˜10 milli-arcsec scale makes this source a promising target for follow-up VLBI observations to reveal any apparent proper motion. Another target, J0839+5112 shows a compact radio structure typical of quasars. There is evidence for flux density variability and its radio "core" has a flat spectrum. However, the EVN data suggest that its emission is not Doppler-boosted. The remaining two blazar candidates (J1420+1205 and J2220+0025) show radio properties totally unexpected from radio AGN with small-inclination jet. Their emission extends to arcsec scales and the Doppler factors of the central components are well below 1. Their structures resemble that of double-lobed radio AGN with large inclination to the line of sight. This is in contrast with the blazar-type modeling of their multi-band spectral energy distributions. Our work underlines the importance of high-resolution VLBI imaging in confirming the blazar nature of high-redshift radio sources.

  15. Homogenization of atmospheric pressure time series recorded at VLBI stations using a segmentation LASSO approach

    Science.gov (United States)

    Balidakis, Kyriakos; Heinkelmann, Robert; Lu, Cuixian; Soja, Benedikt; Karbon, Maria; Nilsson, Tobias; Glaser, Susanne; Andres Mora-Diaz, Julian; Anderson, James; Liu, Li; Raposo-Pulido, Virginia; Xu, Minghui; Schuh, Harald

    2015-04-01

    Time series of meteorological parameters recorded at VLBI (Very Long Baseline Interferometry) observatories allow us to realistically model and consequently to eliminate the atmosphere-induced effects in the VLBI products to a large extent. Nevertheless, this advantage of VLBI is not fully exploited since such information is contaminated with inconsistencies, such as uncertainties regarding the calibration and location of the meteorological sensors, outliers, missing data points, and breaks. It has been shown that such inconsistencies in meteorological data used for VLBI data analysis impose problems in the geodetic products (e.g vertical site position) and result in mistakes in geophysical interpretation. The aim of the procedure followed here is to optimally model the tropospheric delay and bending effects that are still the main sources of error in VLBI data analysis. In this study, the meteorological data recorded with sensors mounted in the vicinity of VLBI stations have been homogenized spanning the period from 1979 until today. In order to meet this objective, inhomogeneities were detected and adjusted using test results and metadata. Some of the approaches employed include Alexandersson's Standard Normal Homogeneity Test and an iterative procedure, of which the segmentation part is based on a dynamic programming algorithm and the functional part on a LASSO (Least Absolute Shrinkage and Selection Operator) estimator procedure. For the provision of reference time series that are necessary to apply the aforementioned methods, ECMWF's (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis surface data were employed. Special care was taken regarding the datum definition of this model. Due to the significant height difference between the VLBI antenna's reference point and the elevation included in geopotential fields of the specific numerical weather models, a hypsometric adjustment is applied using the absolute pressure level from the WMO

  16. A robust method for pulse peak determination in a digital volume pulse waveform with a wandering baseline.

    Science.gov (United States)

    Jang, Dae-Geun; Farooq, Umar; Park, Seung-Hun; Hahn, Minsoo

    2014-10-01

    This paper presents a robust method for pulse peak determination in a digital volume pulse (DVP) waveform with a wandering baseline. A proposed new method uses a modified morphological filter (MMF) to eliminate a wandering baseline signal of the DVP signal with minimum distortion and a slope sum function (SSF) with an adaptive thresholding scheme to detect pulse peaks from the baseline-removed DVP signal. Further in order to cope with over-detected and missed pulse peaks, knowledge based rules are applied as a postprocessor. The algorithm automatically adjusts detection parameters periodically to adapt to varying beat morphologies and fluctuations. Compared with conventional methods (highpass filtering, linear interpolation, cubic spline interpolation, and wavelet adaptive filtering), our method performs better in terms of the signal-to-error ratio, the computational burden (0.125 seconds for one minute of DVP signal analysis with the Intel Core 2 Quad processor @ 2.40 GHz PC), the true detection rate (97.32% with an acceptance level of 4 ms ) as well as the normalized error rate (0.18%). In addition, the proposed method can detect true positions of pulse peaks more accurately and becomes very useful for pulse transit time (PTT) and pulse rate variability (PRV) analyses.

  17. VLBI observations of 10 CSO candidates: expansion velocities of hot spots

    CERN Document Server

    An, Tao; Yang, Jun; Taylor, Gregory B; Hong, Xiaoyu; Baan, Willem A; Liu, Xiang; Wang, Min; Zhang, Hongbo; Wang, Weihua; Chen, Xi; Cui, Lang; Hao, Longfei; Zhu, Xinying

    2011-01-01

    Observations of ten Compact Symmetric Objects ({\\rm CSO}) candidates have been made with the Very Long Baseline Array at 8.4 GHz in 2005 and with a combined Chinese and European VLBI array at 8.4 GHz in 2009. The 2009 observations incorporate for the first time the two new Chinese telescopes at Miyun and Kunming for international astrophysical observations. The observational data, in combination with archival VLBA data from previous epochs, have been used to derive the proper motions of the VLBI components. Because of the long time baseline of $\\sim$16 years of the VLBI data sets, the expansion velocities of the hot spots can be measured at an accuracy as high as $\\sim$1.3 $\\mu$as yr$^{-1}$. Six of the ten sources are identified as CSOs with a typical double or triple morphology on the basis of both spectral index maps and their mirror-symmetry of proper motions of the terminal hot spots. The compact double source J1324+4048 is also identified as a CSO candidate. Among the three remaining sources, J1756+5748 ...

  18. Greenland Telescope Project --- Direct Confirmation of Black Hole with Sub-millimeter VLBI

    OpenAIRE

    Inoue, M.; Algaba-Marcos, J. C.; Asada, K.; Chang, C.-C.; Chen, M. -T.; Han, J.; Hirashita, H.; P. T. P. Ho; Hsieh, S. -N.; Huang, T; Jiang, H.; Koch, P. M.; Kubo, D. Y.; Kuo, C. -Y.; Liu, B.

    2014-01-01

    A 12-m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline > 9,000 km to achieve an exceptional angular resolution of 20 micro arc sec at 350 GHz, which will enable us ...

  19. Imaging VLBI polarimetry data from Active Galactic Nuclei using the Maximum Entropy Method

    Directory of Open Access Journals (Sweden)

    Coughlan Colm P.

    2013-12-01

    Full Text Available Mapping the relativistic jets emanating from AGN requires the use of a deconvolution algorithm to account for the effects of missing baseline spacings. The CLEAN algorithm is the most commonly used algorithm in VLBI imaging today and is suitable for imaging polarisation data. The Maximum Entropy Method (MEM is presented as an alternative with some advantages over the CLEAN algorithm, including better spatial resolution and a more rigorous and unbiased approach to deconvolution. We have developed a MEM code suitable for deconvolving VLBI polarisation data. Monte Carlo simulations investigating the performance of CLEAN and the MEM code on a variety of source types are being carried out. Real polarisation (VLBA data taken at multiple wavelengths have also been deconvolved using MEM, and several of the resulting polarisation and Faraday rotation maps are presented and discussed.

  20. The Benefits of VLBI Astrometry to Pulsar Timing Array Searches for Gravitational Radiation

    CERN Document Server

    Madison, D R; Cordes, J M

    2012-01-01

    Precisely measured astrometric parameters are integral to successful pulsar timing campaigns. They are commonly measured by fitting the astrometric parameters of a deterministic timing model to a series of pulse times of arrival (TOAs). TOAs measured to microsecond precision over several-year spans can in this way provide astrometric parameters precise to sub-milliarcsecond levels. However, pulsars do not pulsate in a deterministic fashion. Many display significant amounts of red spin noise. Furthermore, a stochastic background of gravitational waves can lead to red noise-like structure in TOAs. We investigate how noise of different spectral types is absorbed by timing models and leads to significant estimation errors in the astrometric parameters. Independent of timing, very long baseline interferometry (VLBI) is capable of providing sub-milliarcsecond astrometric parameters for pulsars. We find that incorporating VLBI astrometric measurements into the timing models of pulsars for which only a couple of year...

  1. Analysis of the Monitoring Model of VLBI Antenna Reference Point%VLBI 天线参考点监测模型与分析

    Institute of Scientific and Technical Information of China (English)

    张津维; 李金岭

    2013-01-01

    The monitoring of the reference point and axis offset of VLBI antenna with high pre-cision is of importance to modeling the spatial variation of delay observations as the changing of antenna orientation, the improvement of determination precision of astrometric and geodetic param-eters such as station and source coordinates and so on. The nowadays ordinary monitoring method of VLBI antenna is mainly based on some special restrictions to the rotation mode of antenna, which would occupy the effective time of operation of the telescope, the efficiency of the monitoring and the precision of determined parameters are limited. By parameterizing the rotation of VLBI antenna and modeling the coordinates of targets fixed on VLBI antenna in the local control network, it is expected to perform automatic monitoring of antenna parameters without any interruption of nor-mal observation operations of the telescope. Some insights and analysis are presented concerning the establishment of monitoring model, the settings of parameters and the selection of constraints to observation equations, which are verified via simulation analysis to be rational and effective. The ef-fects of the number of targets, the number of antenna orientations, the precision of target positioning observations and the selection of target positioning observations on the determination precision of antenna parameters are also analyzed, and some preliminary conclusions are given for reference for readers.%  在不同定向时模型化天线对测量时延的影响、提高台站坐标与源坐标等天测与测地参数的解析精度等方面,高精度监测 VLBI 天线参考点和轴线偏差等参数,具有重要意义。基于对天线旋转模式的特殊限定 VLBI 天线参数的常规监测方式,占用望远镜工作时间,且监测效率低、所得参数精度差。通过参数化 VLBI 天线的旋转运动,及建立天线固连合作目标在局域网中坐标的数学模型,有望

  2. Measurements of the VLBI experiments during the first campaign of the Asian-Pacific space geodynamics (APSG) program

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    During the first campaign of the Asian-Pacific space geodynamics(APSG) program in October 1997, two VLBI experiments were successfully organized and coordinated by the Astrometry and Geodesy VLBI Group of Shanghai Astronomical Observatory, the Chinese Academy of Sciences, cooperated with geodetic VLBI group, GSFC, NASA, USA. Six VLBI stations participated in the experiments, including Seshan and Urumqi station of China, Gilcreek station in Alaska and Kokee station in Hawaii of USA, Kashima station of Japan and Hobart station at Tasmania of Australia. Baseline lengths are from 1 900 to 11 000 km and the mean relative uncertainty of the baseline length measurements is 1.0×10-9. In addition, the rates of the baseline lengths among the six stations and their three-dimensional velocities are solved out via global analysis of the two APSG sessions and the historical observations of the six stations as well as other VLBI observations from the global observation network. These results are appreciable to the studies of the modern crustal movement in the Asian-Pacific region. Especially,an 8 mm/a eastward motion and a 14 mm/a north by northeast motion are detected respectively for Seshan and Urumqi stations relative to the stable part of the Eurasian plate. The motions directly illustrate the effect of the northward movement of Indian plate on the modern crustal motions of the northwestern and the eastern part of China, which is of important significance to the study of the modern crustal motion of China.

  3. Progress on VLBI Ecliptic Plane Survey

    CERN Document Server

    Shu, Fengchun; Jiang, Wu; McCallum, Jamie; Yi, Sang-oh; Takefuji, Kazuhiro; Li, Jinling; Lovell, Jim

    2016-01-01

    We launched the VLBI Ecliptic Plane Survey program in 2015. The goal of this program is to find all compact sources within 7.5 degrees of the ecliptic plane which are suitable as phase calibrators for anticipated phase referencing observations of spacecrafts. We planned to observe a complete sample of the sources brighter than 50 mJy at 5 GHz listed in the PMN and GB6 catalogues that have not yet been observed with VLBI. By April 2016, eight 24-hour sessions have been performed and processed. Among 2227 observed sources, 435 sources were detected in three or more observations. We have also run three 8-hour segments with VLBA for improving positions of 71 ecliptic sources.

  4. On significance of VLBI/Gaia offsets

    CERN Document Server

    Petrov, L

    2016-01-01

    We have cross matched the Gaia Data Release 1 secondary dataset that contains positions of 1.14 billion objects against the most complete to date catalogue of VLBI positions of 11.4 thousand sources, almost exclusively active galactic nuclei. We found 6,064 matches, i.e. 53% radio objects. The median uncertainty of VLBI positions is a factor of 4 smaller than the median uncertainties of their optical counterparts. Our analysis shows that the distribution of normalized arc lengths significantly deviates from Rayleighian shape with an excess of objects with small normalized arc lengths and with a number of outliers. We found that 8% matches have radio optical offsets significant at 99% confidence level. Therefore, we conclude there exists a population of objects with genuine offsets between centroids of radio and optical emission.

  5. SAND: Automated VLBI imaging and analyzing pipeline

    Science.gov (United States)

    Zhang, Ming

    2016-05-01

    The Search And Non-Destroy (SAND) is a VLBI data reduction pipeline composed of a set of Python programs based on the AIPS interface provided by ObitTalk. It is designed for the massive data reduction of multi-epoch VLBI monitoring research. It can automatically investigate calibrated visibility data, search all the radio emissions above a given noise floor and do the model fitting either on the CLEANed image or directly on the uv data. It then digests the model-fitting results, intelligently identifies the multi-epoch jet component correspondence, and recognizes the linear or non-linear proper motion patterns. The outputs including CLEANed image catalogue with polarization maps, animation cube, proper motion fitting and core light curves. For uncalibrated data, a user can easily add inline modules to do the calibration and self-calibration in a batch for a specific array.

  6. Studies of ultracompact jets with space VLBI

    Science.gov (United States)

    Lobanov, Andrei

    Imaging and polarimetry of radio emission on microarcsecond scales provided by VSOP-2 and RadioAstron will offer a range of possibilities for studying ultracompact regions of relativistic jets and extreme vicinity of the central supermassive bodies in AGN. Both missions will address a number of outstanding problems in AGN physics, including the site and the mechanism of jet formation, acceleration of relativistic flows, structure of magnetic field in the vicinity of the central engine of AGN, and the fundamental question of the physical nature of the central massive objects in galaxies. Combining space VLBI observations with variability studies made in the X-ray, and gamma-ray bands will enable locating accurately the sites of high-enenrgy continuum production in AGN. Prospects and potentials of these lines of study with space VLBI will be reviewed.

  7. The VSOP-2 Space VLBI Mission

    Science.gov (United States)

    Hirabayashi, Hisashi; Murata, Yasuhiro; Murphy, David W.

    2002-01-01

    Following the success of the VLBI Space Observatory Program (VSOP), a next generation space VLBI mission, VSOP-2, is currently being planned. Higher observing frequencies, cooled receivers, increased bandwidths and larger telescope diameters will result in gains in resolution and interferometer sensitivity by factors of 10 over the VSOP mission. The use of phase-referencing by fast switching between a calibrator source and the target source is now being studied as this technique allows sources 50-150 times weaker to be observed depending on the frequency band. Such a capability would greatly enhance the VSOP-2 mission. Several other enhancements to the VSOP-2 mission are also presently under investigation including the VSOP-2 spacecraft operating at the same time as a US spacecraft to form what has come to be known as the iARISE (international ARISE) mission.

  8. VLBI2020: From Reality to Vision

    Science.gov (United States)

    Titov, Oleg

    2010-01-01

    The individual apparent motions of distant radio sources are believed to be caused by the effect of intrinsic structure variations of the active galactic nuclei (AGN). However, some cosmological models of the expanded Universe predict that systematic astrometric proper motions of distant quasars do not vanish as the radial distance from the observer to the quasar grows. These systematic effects can even increase with the distance, making it possible to measure them with high-precision astrometric techniques like VLBI. The Galactocentric acceleration of the Solar System barycenter may cause a secular aberration drift with a magnitude of 4 uas/yr. The Solar System motion relative to the cosmic microwave background produces an additional dipole effect, proportional to red shift. We analyzed geodetic VLBI data spanning from 1979 until 2009 to estimate the vector spherical harmonics in the expansion of the vector field of the proper motion of 687 radio sources. The dipole and quadrupole vector spherical harmonics were estimated with an accuracy of 1-5 as/yr. We have shown that over the next decade the geodetic VLBI may approach the level of accuracy on which the cosmological models of the Universe could be tested. Hence, it is important to organize a dedicated observational program to increase the number of measured proper motions to 3000.

  9. Axis Offset Estimation of VLBI Telescopes

    Science.gov (United States)

    Krásná, Hana; Nickola, Marisa; Böhm, Johannes

    2014-12-01

    Axis offset models have to be applied for VLBI telescopes with pointing axes which do not intersect. In this work, we estimated the axis offsets for VLBI antennas in a global adjustment of suitable IVS 24-hour sessions (1984.0-2014.0) with the Vienna VLBI Software (VieVS). In particular, we focused on the two radio telescopes of the Hartebeesthoek Radio Astronomy Observatory (HartRAO) in South Africa. For the older 26-m telescope we compared the estimated axis offset values before (6699.2 ± 0.5 mm) and after (6707.3 ± 0.8 mm) the bearing repair in 2010. A comparison with axis offset estimates from other geodetic techniques, such as GNSS or conventional local survey, was made. The estimated axis offset for the newer 15-m telescope (1495.0 ± 3.4 mm) agrees with the estimated value from the GPS survey in 2007. Furthermore, we assessed the influence of differences in the axis offsets on the estimated geodetic parameters, such as station coordinates or Earth Orientation Parameters.

  10. The East-Asian VLBI Network

    CERN Document Server

    Wajima, Kiyoaki; An, Tao; Baan, Willem A; Fujisawa, Kenta; Hao, Longfei; Jiang, Wu; Jung, Taehyun; Kawaguchi, Noriyuki; Kim, Jongsoo; Kobayashi, Hideyuki; Oh, Se-Jin; Roh, Duk-Gyoo; Wang, Min; Wu, Yuanwei; Xia, Bo; Zhang, Ming

    2015-01-01

    The East-Asian VLBI Network (EAVN) is the international VLBI facility in East Asia and is conducted in collaboration with China, Japan, and Korea. The EAVN consists of VLBI arrays operated in each East Asian country, containing 21 radio telescopes and three correlators. The EAVN will be mainly operated at 6.7 (C-band), 8 (X-band), 22 (K-band), and 43 GHz (Q-band), although the EAVN has an ability to conduct observations at 1.6 - 129 GHz. We have conducted fringe test observations eight times to date at 8 and 22 GHz and fringes have been successfully detected at both frequencies. We have also conducted science commissioning observations of 6.7 GHz methanol masers in massive star-forming regions. The EAVN will be operational from the second half of 2017, providing complementary results with the FAST on AGNs, massive star-forming regions, and evolved stars with high angular resolution at cm- to mm-wavelengths.

  11. VLBI observations of T Tauri S

    CERN Document Server

    Smith, K W; Gödel, M; Conway, J; Benz, Arnold O

    2003-01-01

    We report observations of the T Tauri system at 8.4 GHz with a VLBI array comprising the VLBA, VLA and Effelsberg 100m telescopes. We detected a compact source offset approximately 40 mas from the best infrared position of the T Tau Sb component. This source was unresolved, and constrained to be less than 0.5 mas in size, corresponding to 0.07 AU or 15 R$_{\\odot}$ at a distance of 140 pc. The other system components (T Tau Sa, T Tau N) were not detected in the VLBI data. The separate VLA map contains extended flux not accounted for by the compact VLBI source, indicating the presence of extended emission on arcsecond scales. The compact source shows rapid variability, which together with circular polarization and its compact nature indicate that the observed flux arises from a magnetically-dominated region. Brightness temperatures in the MK range point to gyrosynchrotron as the emission mechanism for the steady component. The rapid variations are accompanied by dramatic changes in polarization, and we record a...

  12. Astrometria diferencial de precision con VLBI el triangulo de Draco (y estudios de SN1993J)

    Science.gov (United States)

    Ros, E.

    1997-11-01

    The Very Long Baseline Interferometry (VLBI) technique provides unprecedented resolutions in astronomy. In this PhD we show progress in the study of high precision phase-delay differential astrometry through observations of the radio source triangle formed by the BL-Lac objects 1803+784 and 2007+777, and the QSO 1928+738, in the Northern constellation of Draco (the Dragon), from observations carried out on 20/21 November 1991 with an intercontinental interferometric array simultaneously at the frequencies of 2.3 and 8.4 GHz. We have determined the angular separations among the three radio sources with submilliarcsecond accuracy from a weighted least squares analysis of the differential phase delay from the three celestial bodies. Our present work introduces important advances with respect to previous astrometric studies, carried out over radio source pairs separated by smaller angular distances. We have consistently modeled the parameters involved in an astrometric VLBI observation, in order to reproduce the differential phase observed for radio sources separated by almost 7o on the sky. We have demonstrated the possibility of phase-connection over these angular distances at 8.4 GHz, even at an epoch of a maximum in the solar activity. After the phase-connection we have corrected the effects of the extended structure of the radio source and of the ionosphere. This last correction is one of the main technical achievements of this thesis: it is possible to remove the ionospheric contribution with independent measurements of the ionosphere total electron content obtained at Global Positioning Systems (GPS) sites the VLBI observing stations. The triangular geometry introduces constraints in parameter space that allow a better estimation of the angular separations among the radio sources. It is possible to test the consistency of the astrometric results through the Sky-Closure, defined as the circular sum of the angular separations of the three radio sources, determined

  13. Prospects for UT1 Measurements from VLBI Intensive Sessions

    Science.gov (United States)

    Boehm, Johannes; Nilsson, Tobias; Schuh, Harald

    2010-01-01

    Very Long Baseline Interferometry (VLBI) Intensives are one-hour single baseline sessions to provide Universal Time (UT1) in near real-time up to a delay of three days if a site is not e-transferring the observational data. Due to the importance of UT1 estimates for the prediction of Earth orientation parameters, as well as any kind of navigation on Earth or in space, there is not only the need to improve the timeliness of the results but also their accuracy. We identify the asymmetry of the tropospheric delays as the major error source, and we provide two strategies to improve the results, in particular of those Intensives which include the station Tsukuba in Japan with its large tropospheric variation. We find an improvement when (1) using ray-traced delays from a numerical weather model, and (2) when estimating tropospheric gradients within the analysis of Intensive sessions. The improvement is shown in terms of reduction of rms of length-of-day estimates w.r.t. those derived from Global Positioning System observations

  14. Parallax of a Mira variable R Ursae Majoris studied with astrometric VLBI

    Science.gov (United States)

    Nakagawa, Akiharu; Kurayama, Tomoharu; Matsui, Makoto; Omodaka, Toshihiro; Honma, Mareki; Shibata, Katsunori M.; Sato, Katsuhisa; Jike, Takaaki

    2016-10-01

    We have measured an annual parallax of the Mira variable R Ursae Majoris (R UMa) with the VLBI Exploration for Radio Astronomy (VERA). From the monitoring VLBI observations over a span of about two years, we detected H2O maser spots in the LSR velocity range from 37 to 42 km s-1. We derived an annual parallax of 1.97 ± 0.05 mas, and this gives a corresponding distance of 508 ± 13 pc. The VLBI maps revealed 72 maser spots distributed in an ˜110 au area around the expected stellar position. Circumstellar kinematics of the maser spots were also revealed by subtracting a systemic motion in the Hipparcos catalog from proper motions of each maser spot derived from our VLBI observations. Infrared photometry was also conducted to measure a K-band apparent magnitude, and we obtained a mean magnitude of mK = 1.19 ± 0.02 mag. Using the trigonometric distance, mK is converted to a K-band absolute magnitude of MK = -7.34 ± 0.06 mag. This result gives a much more accurate absolute magnitude for R UMa than previously provided. We solved a zero-point of the MK-log P relation for the Galactic Mira variables and obtained a relation of MK = -3.52 log P + (1.09 ± 0.14). Other long-period variables, including red supergiants, whose distances were determined with astrometric VLBI, were also compiled to explore the different sequences of the MK-log P relation.

  15. Greenland Telescope (GLT) Project: "A Direct Confirmation of Black Hole with Submillimeter VLBI"

    CERN Document Server

    Nakamura, M; Asada, K; Chen, B; Chen, M -T; Han, J; Ho, P H P; Hsieh, S -N; Huang, T; Inoue, M; Koch, P; Kuo, C -Y; Martin-Cocher, P; Matsushita, S; Meyer-Zhao, Z; Nishioka, H; Nystom, G; Pradel, N; Pu, H -Y; Raffin, P; Shen, H -Y; Tseng, C -Y

    2013-01-01

    The GLT project is deploying a new submillimeter (submm) VLBI station in Greenland. Our primary scientific goal is to image a shadow of the supermassive black hole (SMBH) of six billion solar masses in M87 at the center of the Virgo cluster of galaxies. The expected SMBH shadow size of 40-50 $\\mu$as requires superbly high angular resolution, suggesting that the submm VLBI would be the only way to obtain the shadow image. The Summit station in Greenland enables us to establish baselines longer than 9,000 km with ALMA in Chile and SMA in Hawaii as well as providing a unique $u$--$v$ coverage for imaging M87. Our VLBI network will achieve a superior angular resolution of about 20 $\\mu$as at 350 GHz, corresponding to $\\sim2.5$ times of the Schwarzschild radius of the supermassive black hole in M87. We have been monitoring the atmospheric opacity at 230 GHz since August. 2011; we have confirmed the value on site during the winter season is comparable to the ALMA site thanks to high altitude of 3,200 m and low temp...

  16. The Impact of Frequency Standards on Coherence in VLBI at the Highest Frequencies

    CERN Document Server

    Rioja, M; Asaki, Y; Hartnett, J; Tingay, S

    2012-01-01

    We have carried out full imaging simulation studies to explore the impact of frequency standards in millimeter and sub-millimeter Very Long Baseline Interferometry (VLBI), focusing on the coherence time and sensitivity. In particular, we compare the performance of the H-maser, traditionally used in VLBI, to that of ultra-stable cryocooled sapphire oscillators over a range of observing frequencies, weather conditions and analysis strategies. Our simulations show that at the highest frequencies, the losses induced by H-maser instabilities are comparable to those from high quality tropospheric conditions. We find significant benefits in replacing H-masers with cryocooled sapphire oscillator based frequency references in VLBI observations at frequencies above 175 GHz in sites which have the best weather conditions; at 350 GHz we estimate a 20-40% increase in sensitivity, over that obtained when the sites have H-masers, for coherence losses of 20-10%, respectively. Maximum benefits are to be expected by using colo...

  17. 15 years of VLBI observations of two compact radio sources in Messier 82

    CERN Document Server

    Beswick, R J; Fenech, D; Marti-Vidal, I; McDonald, A R; Muxlow, T W B; Pedlar, A; Riley, J D; Wills, K A

    2006-01-01

    We present the results of a second epoch of 18cm global Very Long-Baseline Interferometry (VLBI) observations, taken on 23 February 2001, of the central kiloparsec of the nearby starburst galaxy Messier 82. These observations further investigate the structural and flux evolution of the most compact radio sources in the central region of M82. The two most compact radio objects in M82 have been investigated (41.95+575 and 43.31+592). Using this recent epoch of data in comparison with our previous global VLBI observations and two earlier epochs of European VLBI Network observations we measure expansion velocities in the range of 1500-2000km/s for 41.95+575, and 9000-11000km/s for 43.31+592 using various independent methods. In each case the measured remnant expansion velocities are significantly larger than the canonical expansion velocity (500km/s) of supernova remnants within M82 predicted from theoretical models. In this paper we discuss the implications of these measured expansion velocities with respect to ...

  18. Probing into the Shadow of Galactic Center Black Hole with Future Sub-millimeter VLBI

    Science.gov (United States)

    Shen, Z.-Q.

    2009-08-01

    Sgr A* is the closest massive black hole candidate with the largest angular size of its Schwarzschild radius (about 10 μas). Unfortunately, Sgr A* is not a suitable target for the next generation space-VLBI mission, VSOP-2, even at its highest frequency of 43 GHz. This is mainly because of its too big (scattering-broadened) apparent size compared to the angular resolution of VSOP-2, which makes space baselines unnecessary for the imaging study of Sgr A*. Rather, recent development of VLBI observations at shorter millimeter wavelengths has led to the firm detection of the intrinsic size of the emission region of Sgr A* (about 1 AU at 86 GHz). Future sub-millimeter VLBI observation is promising in resolving the shadow of Sgr A*, which could be a test of the general relativity in strong field regime. Our simulation demonstrates that visibility analysis can constrain the geometry of radio emitting region surrounding Sgr A*. We are on the verge of resolving the shadow of Sgr A*.

  19. The application of MultiView Methods for High Precision Astrometric Space VLBI at Low Frequencies

    CERN Document Server

    Dodson, R; Asaki, Y; Imai, H; Hong, X -Y; Shen, Z

    2013-01-01

    High precision astrometric Space Very Long Baseline Interferometry (S-VLBI) at the low end of the conventional frequency range, i.e. 20cm, is a requirement for a number of high priority science goals. These are headlined by obtaining trigonometric parallax distances to pulsars in Pulsar--Black Hole pairs and OH masers anywhere in the Milky Way Galaxy and the Magellanic Clouds. We propose a solution for the most difficult technical problems in S-VLBI by the MultiView approach where multiple sources, separated by several degrees on the sky, are observed simultaneously. We simulated a number of challenging S-VLBI configurations, with orbit errors up to 8m in size and with ionospheric atmospheres consistant with poor conditions. In these simulations we performed MultiView analysis to achieve the required science goals. This approach removes the need for beam switching requiring a Control Moment Gyro, and the space and ground infrastructure required for high quality orbit reconstruction of a space-based radio tele...

  20. e-VLBI observations of SS 433 in outburst

    NARCIS (Netherlands)

    Tudose, V.; Paragi, Z.; Trushkin, S.; Soleri, P.; Fender, R.; Garrett, M.; Spencer, R.; Rushton, A.; Burgess, P.; Kunert-Bajraszewska, M.; Pazderski, E.; Borkowski, K.; Hammargren, R.; Lindqvist, M.; Maccaferri, G.

    2008-01-01

    We have observed the X-ray binary SS 433 on November 6, 2008 between 13:48-18:35 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The radio telescopes participating in the experiment were: Medicina, Onsala 25m, Torun, Jodrell Bank MkII and Cambridge. The X-ray binary SS 4

  1. Detectability of Circumstellar SiO Maser Emission on VSOP-2 Baselines

    Science.gov (United States)

    Colomer, F.; Bujarrabal, V.; Ruiz, R. S.; Dodson, R.; Alcolea, J.; Desmurs, J.-F.

    2009-08-01

    We have studied compact circumstellar SiO maser emission at 86 GHz with the Global Millimeter VLBI Array (GMVA), which provides the same spatial resolution as the VSOP-2 to ground baselines at 43 GHz. We present preliminary maps of the emission, estimate the flux and size of the maser spots, and discuss their detectability on baselines from VSOP-2 to ground telescopes.

  2. Combining VLBI and ring laser observations at normal equation level

    Science.gov (United States)

    Schartner, Matthias; Böhm, Johannes; Böhm, Sigrid; Schreiber, Karl Ulrich; Gebauer, André

    2017-04-01

    Observations from ring laser gyroscopes can be used to continuously monitor earth rotation with high resolution and without an external reference frame, which makes them unique in contrast to other techniques like VLBI or GNSS. A combination, however, of ring laser and VLBI data could potentially result in an improved accuracy of estimated earth rotation parameters. In this study, we use observations from the ring laser "G" (Grossring) located at Wettzell (Germany) and combine them with VLBI observations at the normal equation level. The Vienna VLBI and Satellite Software (VieVS) is used to set up the normal equations for each VLBI session as SINEX files. We present combined estimates for polar motion and length of day and assess the impact by the ring laser observations.

  3. The Innermost AGNs with Future mm-VLBI

    CERN Document Server

    Agudo, I; Bach, U; Pagels, A; Sohn, B W; Graham, D A; Witzel, A; Zensus, J A; Gómez, J L; Bremer, M; Grewing, M

    2005-01-01

    The capabilities of the Global mm-VLBI Array are summarized and demonstrated through actual images from our monitoring of extragalactic radio jets. This sensitive 3mm-VLBI interferometer is able to provide images of up to 50 microarcseconds resolution. For the near future, ALMA, the GBT, the LMT, CARMA, SRT, Yebes, Nobeyama and Noto are some of the most sensitive stations suitable to participate in mm-VLBI. This future array, together with the present Global mm-VLBI Array, would achieve 10 times better sensitivities than nowadays. Image fidelity would also largely increased. T he addition of ALMA would improve the (u,v)-coverage for sources with low declination (<20 deg.) and facilitate the VLBI imaging of the Galactic Centre source SgrA*.

  4. Mark 6 16-Gbps Next-Generation VLBI Data System

    Science.gov (United States)

    Whitney, Alan R.; Cappallo, Roger J.; Ruszczyk, Chester A.; SooHoo, Jason; Crew, Geoffrey B.

    2014-12-01

    The Mark 6 VLBI data system has been developed as a next-generation disk-based VLBI data system capable of supporting the goals of VLBI2010 and other very-high-data-rate VLBI applications, with a maximum sustained recording rate of 16 Gbps. Based on COTS data hardware and open-source software, the Mark 6 is designed to transition easily from the widely used Mark 5 system. Its features include a `scatter/gather' gather algorithm to ensure that data recording is not slowed by one or more slow or bad disks. The first field demonstration of a 16 Gbps/station VLBI experiment using Mark 6 in 2012 is reported. Existing Mark 5 systems are upgradeable to Mark 6, and existing Mark 5 SATA modules are upgradeable for compatibility with Mark 6.

  5. The Chinese space millimeter-wavelength VLBI array - a step toward imaging the most compact astronomical objects

    CERN Document Server

    Hong, Xiaoyu; An, Tao; Liu, Qinghui

    2014-01-01

    The Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences (CAS) is studying a space VLBI (Very Long Baseline Interferometer) program. The ultimate objective of the program is to image the immediate vicinity of the supermassive black holes (SMBHs) in the hearts of galaxies with a space-based VLBI array working at sub-millimeter wavelengths and to gain ultrahigh angular resolution. To achieve this ambitious goal, the mission plan is divided into three stages. The first phase of the program is called Space Millimeter-wavelength VLBI Array (SMVA) consisting of two satellites, each carrying a 10-m diameter radio telescope into elliptical orbits with an apogee height of 60000 km and a perigee height of 1200 km. The VLBI telescopes in space will work at three frequency bands, 43, 22 and 8 GHz. The 43- and 22-GHz bands will be equipped with cryogenic receivers. The space telescopes, observing together with ground-based radio telescopes, enable the highest angular resolution of 20 micro-arcsecond...

  6. Assessment of periodic sub-diurnal Earth rotation variations at tidal frequencies through transformation of VLBI normal equation systems

    Science.gov (United States)

    Artz, Thomas; Tesmer Née Böckmann, Sarah; Nothnagel, Axel

    2011-09-01

    We present an empirical model for periodic variations of diurnal and sub-diurnal Earth rotation parameters (ERPs) that was derived based on the transformation of normal equation (NEQ) systems of Very Long Baseline Interferometry (VLBI) observing sessions. NEQ systems that contain highly resolved polar motion and UT1-TAI with a temporal resolution of 15 min were generated and then transformed to the coefficients of the tidal ERP model to be solved for. To investigate the quality of this model, comparisons with empirical models from the Global Positioning System (GPS), another VLBI model and the model adopted by the conventions of the International Earth Rotation and Reference Systems Service (IERS) were performed. The absolute coefficients of these models agree almost completely within 7.5 μ as in polar motion and 0.5 μ s in UT1-TAI. Several bigger differences exist, which are discussed in this paper. To be able to compare the model estimates with results of the continuous VLBI campaigns, where signals with periods of 8 and 6 h were detected, terms in the ter- and quarter-diurnal band were included in the tidal ERP model. Unfortunately, almost no common features with the results of continuous VLBI campaigns or ERP predictions in these tidal bands can be seen.

  7. European VLBI Network: Present and Future

    CERN Document Server

    Zensus, J A

    2015-01-01

    The European VLBI Network is a collaboration of the major radio astronomical institutes in Europe, Asia, South Africa and Puerto Rico. Established four decades ago, since then it has constantly improved its performance in terms made using resolution, data bit-rate and image fidelity with improvements in performance, and the addition of new stations and observing capabilities. The EVN provides open skies access and has over time become a common-user facility. In this contribution we discuss the present status and perspectives for the array in a continuously changing environment, especially in the era of ALMA and with the Square Kilometre Array ante portas.

  8. RAIM Based on Single Baseline Attitude Determination%单基线姿态测量的RAIM算法研究

    Institute of Scientific and Technical Information of China (English)

    窦婧婧; 战兴群; 王博雄

    2011-01-01

    The attitude information of the vehicle could be delivered when satellite navigation receivers are equipped with multiple antennae. This paper explains the principles of a baseline constrained version of the Analytical Resolution Method (ARM). This version of the ARM is optimal by using the integrity confine of the initial integer ambiguities and the known baseline length. Once the integrity combination is fixed, the attitude information can be measured when only two satellites are captured using single differencing (SD) carrier phase equations established in local level frame (LLF). So this algorithm is capable of reducing the search integer space into countable two dimensional discrete points and ambiguity function method (AFM) resolves the ambiguity searching within the analytical solutions space. The Receiver Autonomous Integrity Monitoring (RAIM) is brought into this algorithm, and this method is useful in selecting the healthy satellites and improving AFM method. Engineering aspects of this attitude determination method are also discussed and the method is demonstrated to be effective.%当载体安装有GPS接收机和多个天线时,可以得到其姿态信息(航向角、俯仰角、横滚角);论述了利用载波相位姿态测量的解析法,利用了基线长固定的条件,在整周模糊度初始化时进行粗搜索,利用模糊度函数法进行判断筛选整周模糊度组合,减少了搜索空间;接收机自主完好性监测(RAIM)的概念被引入到姿态测量算法中,有效地剔除问题卫星,改善AFM算法;系统姿态测量结果达0.1标准差,故障卫星可由RAIM检测并剔除;结果表明RAIM算法能有效提高姿态测量结果可靠性.

  9. Response of the Earth system to zonal tidal forcing examined by VLBI based dUT1 variations

    Science.gov (United States)

    Boehm, S.; Schuh, H.

    2011-10-01

    The VLBI group at the Institute of Geodesy and Geophysics of Vienna University of Technology is developing the software VieVS (Vienna VLBI software) for the analysis of geodetic VLBI data. VieVS incorporates the most recent models recommended by the IERS Conventions and in contrast to other VLBI software uses a parameterization with piece-wise linear offsets at integer hours. Thus it provides more flexibility for combination or comparison with time series from other space geodetic techniques or of geophysical origin. We employed this new software to re-process all available geodetic VLBI sessions from 1984 till 2010, suitable for the determination of the Earth rotation parameters (ERP), i.e. dUT1 (UT1-UTC) and the polar motion coordinates xp and yp. Zonal tidal signals with periods from 5 to 35 days in the derived dUT1 long-time series were then used to estimate the so-called zonal response coefficient κ defined by Agnew and Farrell (1978). The frequency dependent zonal response coefficient is an extension to the concept of the Love number k2 which allows for a response of the Earth to tidal forcing, deviating from purely elastic behaviour and thus taking into account effects of ocean tides, a fluid core and mantle anelasticity. A tidally induced change of the rotation rate of the Earth and consequently of dUT1 is proportional to the tide-generating potential through the zonal response coefficient κ. The values estimated for κ for different tidal frequencies from VLBI observations of dUT1 were compared to theory and to the results of previous determinations of κ from observations of space geodetic techniques.

  10. International VLBI Service for Geodesy and Astrometry 2004 Annual Report

    Science.gov (United States)

    Behrend, Dirk (Editor); Baver, Karen D. (Editor)

    2005-01-01

    Contents include the following: Combination Studies using the Cont02 Campaign. Coordinating Center report. Analysis coordinator report. Network coordinator report. IVS Technology coordinator report. Algonquin Radio observatory. Fortaleza Station report for 2004. Gilmore Creek Geophysical Observatory. Goddard Geophysical and Astronomical observatory. Hartebeesthoek Radio Astronomy Observatory (HartRAO). Hbart, Mt Pleasant, station report for 2004. Kashima 34m Radio Telescope. Kashima and Koganei 11-m VLBI Stations. Kokee Park Geophysical Observatory. Matera GGS VLBI Station. The Medicina Station status report. Report of the Mizusawa 10m Telescope. Noto Station Activity. NYAL Ny-Alesund 20 metre Antenna. German Antarctic receiving Station (GARS) O'higgins. The IVS network station Onsala space Observatory. Sheshan VLBI Station report for 2004. 10 Years of Geodetic Experiments at the Simeiz VLBI Station. Svetloe RAdio Astronomical Observatory. JARE Syowa Station 11-m Antenna, Antarctica. Geodetic Observatory TIGO in Concepcion. Tsukuba 32-m VLBI Station. Nanshan VLBI Station Report. Westford Antenna. Fundamental-station Wettzell 20m Radiotelescope. Observatorio Astroonomico Nacional Yebes. Yellowknife Observatory. The Bonn Geodetic VLBI Operation Center. CORE Operation Center Report. U.S. Naval Observatory Operation Center. The Bonn Astro/Geo Mark IV Correlator.

  11. Probing spacetime around Sagittarius A* using modeled VLBI closure phases

    CERN Document Server

    Fraga-Encinas, R; Brinkerink, C; Falcke, H

    2016-01-01

    The emission region and black hole shadow of Sagittarius A*, the supermassive black hole at the Galactic Center, can be probed with millimeter Very Long Baseline Interferometry. Our goal is to probe the geometry of the emitting plasma around Sgr A* by using modeled mm-VLBI closure phase calculations at 1.3 mm and to constrain the observer's inclination angle and position angle of the black hole spin axis. We have simulated images for three different models of the emission of Sgr A*: an orbiting spot, a disk model, and a jet model. The orbiting spot model was used as a test case scenario, while the disk and jet models are physically driven scenarios based on standard three-dimensional general relativistic magnetohydrodynamic simulations of hot accretion flows. Our results are compared to currently available closure phase observational limits. Our results indicate that more models with closer to edge-on viewing angles are consistent with observational limits. In general, jet and disk geometries can reproduce si...

  12. Digital Front End for Wide-Band VLBI Science Receiver

    Science.gov (United States)

    Jongeling, Andre; Sigman, Elliott; Navarro, Robert; Goodhart, Charles; Rogstad, Steve; Chandra, Kumar; Finley, Sue; Trinh, Joseph; Soriano, Melissa; White, Les; hide

    2006-01-01

    An upgrade to the very-long-baseline-interferometry (VLBI) science receiver (VSR) a radio receiver used in NASA's Deep Space Network (DSN) is currently being implemented. The current VSR samples standard DSN intermediate- frequency (IF) signals at 256 MHz and after digital down-conversion records data from up to four 16-MHz baseband channels. Currently, IF signals are limited to the 265-to-375-MHz range, and recording rates are limited to less than 80 Mbps. The new digital front end, denoted the Wideband VSR, provides improvements to enable the receiver to process wider bandwidth signals and accommodate more data channels for recording. The Wideband VSR utilizes state-of-the-art commercial analog-to-digital converter and field-programmable gate array (FPGA) integrated circuits, and fiber-optic connections in a custom architecture. It accepts IF signals from 100 to 600 MHz, sampling the signal at 1.28 GHz. The sample data are sent to a digital processing module, using a fiber-optic link for isolation. The digital processing module includes boards designed around an Advanced Telecom Computing Architecture (ATCA) industry-standard backplane. Digital signal processing implemented in FPGAs down-convert the data signals in up to 16 baseband channels with programmable bandwidths from 1 kHz to 16 MHz. Baseband samples are transmitted to a computer via multiple Ethernet connections allowing recording to disk at rates of up to 1 Gbps.

  13. VLBI Images of 49 Radio Supernovae in Arp 220

    Science.gov (United States)

    Lonsdale, Colin J.; Diamond, Philip J.; Thrall, Hannah; Smith, Harding E.; Lonsdale, Carol J.

    2006-08-01

    We have used a very long baseline interferometry (VLBI) array at 18 cm wavelength to image the nucleus of the luminous IR galaxy Arp 220 at ~1 pc linear resolution, with very high sensitivity. The resulting map has an rms of 5.5 μJy beam-1, and careful image analysis results in 49 confirmed point sources ranging in flux density from 1.2 mJy down to ~60 μJy. Comparison with high-sensitivity data from 12 months earlier reveals at least four new sources. The favored interpretation of these sources is that they are radio supernovae, and if all new supernovae are detectable at this sensitivity, a resulting estimate of the supernova rate in the Arp 220 system is 4+/-2 per year. The implied star formation rate is sufficient to power the entire observed far-infrared luminosity of the galaxy. The two nuclei of Arp 220 exhibit striking similarities in their radio properties, although the western nucleus is more compact, and appears to be ~3 times more luminous than the eastern nucleus. There are also some puzzling differences, and differential free-free absorption, synchrotron aging, and expansion losses may all be playing a role. Comparison with the nearby starburst galaxy M82 supports the hypothesis that the activity in Arp 220 is essentially a scaled-up version of that in M82.

  14. VLBI Images of 49 Radio Supernovae in Arp 220

    CERN Document Server

    Lonsdale, C J; Lonsdale, C J; Smith, H E; Thrall, H; Diamond, Philip J.; Lonsdale, Carol J.; Lonsdale, Colin J.; Smith, Harding E.; Thrall, Hannah

    2006-01-01

    We have used a Very Long Baseline Interferometry (VLBI) array at 18cm wavelength to image the nucleus of the luminous IR galaxy Arp 220 at ~1 pc linear resolution, and with very high sensitivity. The resulting map has an rms of 5.5 microJy/beam, and careful image analysis results in 49 confirmed point sources ranging in flux density from 1.2 mJy down to ~60 microJy. Comparison with high sensitivity data from 12 months earlier reveals at least four new sources. The favored interpretation of these sources is that they are radio supernovae, and if all new supernovae are detectable at this sensitivity, a resulting estimate of the supernova rate in the Arp 220 system is 4 +/- 2 per year. The implied star formation rate is sufficient to power the entire observed far-infrared luminosity of the galaxy. The two nuclei of Arp 220 exhibit striking similarities in their radio properties, though the western nucleus is more compact, and appears to be ~3 times more luminous than the eastern nucleus. There are also some puzz...

  15. Prior determination of baseline minimum alveolar concentration (MAC) of isoflurane does not influence the effect of ketamine on MAC in rabbits.

    Science.gov (United States)

    Gianotti, Giacomo; Valverde, Alexander; Sinclair, Melissa; Dyson, Doris H; Gibson, Thomas; Johnson, Ron

    2012-10-01

    The objective of this study was to compare the effect on the minimum alveolar concentration (MAC) of isoflurane when ketamine was administered either after or without prior determination of the baseline MAC of isoflurane in rabbits. Using a prospective randomized crossover study, 8 adult, female New Zealand rabbits were allocated to 2 treatment groups. Anesthesia was induced and maintained with isoflurane. Group 1 (same-day determination) had the MAC-sparing effect of ketamine [1 mg/kg bodyweight (BW) bolus followed by a constant rate infusion (CRI) of 40 μg/kg BW per min, given by intravenous (IV)], which was determined after the baseline MAC of isoflurane was determined beforehand. A third MAC determination was started 30 min after stopping the CRI. Group 2 (separate-day determination) had the MAC-sparing effect of ketamine determined without previous determination of the baseline MAC of isoflurane. A second MAC determination was started 30 min after stopping the CRI. In group 1, the MAC of isoflurane (2.15 ± 0.09%) was significantly decreased by ketamine (1.63 ± 0.07%). After stopping the CRI, the MAC was significantly less (2.04 ± 0.11%) than the baseline MAC of isoflurane and significantly greater than the MAC during the CRI. In group 2, ketamine decreased isoflurane MAC (1.53 ± 0.22%) and the MAC increased significantly (1.94 ± 0.25%) after stopping the CRI. Minimum alveolar concentration (MAC) values did not differ significantly between the groups either during ketamine administration or after stopping ketamine. Under the study conditions, prior determination of the baseline isoflurane MAC did not alter the effect of ketamine on MAC. Both methods of determining MAC seemed to be valid for research purposes.

  16. The African Very Long Baseline Interferometry Network:The Ghana Antenna Conversion

    CERN Document Server

    Copley, C J; Loots, A; Bangani, S; Cloete, K; Combrinck, L; Gioio, S; Ludick, J; Nicolson, G; Pollak, A W; Pretorius, P; Quick, J F H; Taylor, G; Ebrahim, F; Humphreys, C; Maake, K; Maganane, R; Majinjiva, R; Mapunda, A; Manzini, M; Mogakwe, N; Moseki, A; Qwabe, N; Royi, N; Rosie, K; Smith, J; Schietekat, S; Toruvanda, O; Tong, C; van Niekerk, B; Walbrugh, W; Zeeman, W

    2016-01-01

    The African Very Long Baseline Interferometry Network (AVN) is a pan-African project that will develop Very Long Baseline Interferometry (VLBI) observing capability in several countries across the African continent, either by conversion of existing telecommunications antennas into radio telescopes, or by building new ones. This paper focuses on the conversion of the Nkutunse satellite communication station (near Accra, Ghana), specifically the early mechanical and infrastructure upgrades, together with the development of a custom ambient receiver and digital backend. The paper concludes with what remains to be done, before the station can be commissioned as an operational VLBI station.

  17. VLBI experiment with the Huygens Probe during its descent in the atmosphere of Titan : An evidence for meridional wind

    NARCIS (Netherlands)

    Pogrebenko, Sergei; Gurvits, Leonid; Avruch, Ian; Cimo, Giuseppe; Team, Huygens VLBI Tracking

    Phase-referencing VLBI observations of the Huygens Probe were performed during its descent in the atmosphere of Titan on 14 January 2005 using a global network of 17 radio telescopes. The Probe's position in the Titanographic frame was determined with the accuracy of about 1 km relative to a priori

  18. Influence of prior determination of baseline minimum alveolar concentration (MAC) of isoflurane on the effect of ketamine on MAC in dogs.

    Science.gov (United States)

    Gianotti, Giacomo; Valverde, Alexander; Johnson, Ron; Sinclair, Melissa; Gibson, Thomas; Dyson, Doris H

    2014-07-01

    The objective of this study was to determine if prior measurement of the minimum alveolar concentration (MAC) of isoflurane influences the effect of ketamine on the MAC of isoflurane in dogs. Eight mixed-breed dogs were studied on 2 occasions. Anesthesia was induced and maintained using isoflurane. In group 1 the effect of ketamine on isoflurane MAC was determined after initially finding the baseline isoflurane MAC. In group 2, the effect of ketamine on isoflurane MAC was determined without previous measure of the baseline isoflurane MAC. In both groups, MAC was determined again 30 min after stopping the CRI of ketamine. Plasma ketamine concentrations were measured during MAC determinations. In group 1, baseline MAC (mean ± SD: 1.18 ± 0.14%) was decreased by ketamine (0.88 ± 0.14%; P MAC after stopping ketamine was similar (1.09 ± 0.16%) to baseline MAC and higher than with ketamine (P MAC with ketamine (0.79 ± 0.11%) was also increased after stopping ketamine (1.10 ± 0.17%; P MAC values with ketamine were different between groups (P MAC determination. The MAC of isoflurane during the CRI of ketamine yielded different results when methods of same day (group-1) versus separate days (group-2) are used, despite similar plasma ketamine concentrations with both methods. However, because the magnitude of this difference was less than 10%, either method of determining MAC is deemed acceptable for research purposes.

  19. 我国建筑能耗基准线确定方法探讨%Determination of building energy consumption baseline in China

    Institute of Scientific and Technical Information of China (English)

    朱能; 朱天利; 仝丁丁; 丁研

    2015-01-01

    通过对国内外建筑能耗基准线研究与应用进行梳理,对所涉及的两类基准线明确了其界定及应用。第一类基准线是基于单栋建筑的能耗基准线,用于比较建筑自身能耗的变化;第二类基准线是基于多栋建筑的能耗基准线,用于确定某栋建筑相对于其他建筑的能耗水平。在此基础上分别提出了两类基准线的确定方法,包括明确基准对象、确定指标形式、确定能耗边界及测算基准值。以校园建筑为例验证了上述方法的可行性。%Through sorting out the previous research results and their application of building energy consumption baseline at home and abroad,discusses the definition and application of the two kinds of building energy consumption baseline involved.The first baseline is the energy consumption baseline based on every single building,used in comparison of energy consumption variety of building-self.The second baseline is the energy consumption baseline based on buildings,used in identification of energy consumption level of a building relative to other buildings.Develops the acknowledgement methodology of the two kinds of building energy consumption baseline,including defining the baseline object,determining the index form,measuring the energy consumption boundary and calculating the baseline value.With a case study of campus buildings,verifies the practicability of the methodology developed in this paper.

  20. THE FIRST VERY LONG BASELINE INTERFEROMETRIC SETI EXPERIMENT

    Energy Technology Data Exchange (ETDEWEB)

    Rampadarath, H.; Morgan, J. S.; Tingay, S. J.; Trott, C. M., E-mail: hayden.rampadarath@icrar.org [International Centre for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA (Australia)

    2012-08-15

    The first Search for Extra-Terrestrial Intelligence (SETI) conducted with very long baseline interferometry (VLBI) is presented. By consideration of the basic principles of interferometry, we show that VLBI is efficient at discriminating between SETI signals and human generated radio frequency interference (RFI). The target for this study was the star Gliese 581, thought to have two planets within its habitable zone. On 2007 June 19, Gliese 581 was observed for 8 hr at 1230-1544 MHz with the Australian Long Baseline Array. The data set was searched for signals appearing on all interferometer baselines above five times the noise limit. A total of 222 potential SETI signals were detected and by using automated data analysis techniques were ruled out as originating from the Gliese 581 system. From our results we place an upper limit of 7 MW Hz{sup -1} on the power output of any isotropic emitter located in the Gliese 581 system within this frequency range. This study shows that VLBI is ideal for targeted SETI including follow-up observations. The techniques presented are equally applicable to next-generation interferometers, such as the long baselines of the Square Kilometre Array.

  1. Baseline rationing

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Moreno-Ternero, Juan D.; Østerdal, Lars Peter Raahave

    The standard problem of adjudicating conflicting claims describes a situation in which a given amount of a divisible good has to be allocated among agents who hold claims against it exceeding the available amount. This paper considers more general rationing problems in which, in addition to claims......, there exist baselines (to be interpreted as objective entitlements, ideal targets, or past consumption) that might play an important role in the allocation process. The model we present is able to accommodate real-life rationing situations, ranging from resource allocation in the public health care sector...... to international protocols for the reduction of greenhouse emissions, or water distribution in drought periods. We define a family of allocation methods for such general rationing problems - called baseline rationing rules - and provide an axiomatic characterization for it. Any baseline rationing rule within...

  2. Receiving And Data Acquisition Systems Of Rt-32 For Vlbi Observations / Rt-32 Uztveršanas Un Datu Reģistrācijas Sistēmas Vlbi Novērojumiem

    Science.gov (United States)

    Bezrukovs, Vl.; Shmeld, I.; Nechaeva, M.; Trokss, J.; Bezrukovs, D.; Klapers, M.; Berzins, A.; Lesins, A.; Dugin, N.

    2012-12-01

    Radiotelescope RT-32 is a fully steerable 32-m parabolic antenna located at Irbene and belonging to Ventspils International Radio Astronomy Centre (VIRAC). Currently, the work on upgrading and repair of its receiving hardware and data acquisition systems is of high priority for the VIRAC. One of the main scientific objectives for the VIRAC Radioastronomical observatory is VLBI (very long baseline interferometry) observations in centimetre wavelengths in collaboration with world VLBI networks, such as European VLBI network (EVN), Low Frequency VLBI network (LFVN), and others. During the last years the room in the secondary focus of telescope was reconstructed, and several new receivers were installed. Currently, RT-32 observations are carried out in four different bands: 92 cm, 18 cm, 6 cm, and 2.5 cm. First three of them are already successfully employed in diversified VLBI experiments. The receiver on 2.5 cm band has only one linear polarized chain and is used mainly for the methanol maser single dish observations. The apparatus system of RT-32 is equipped with two independent VLBI data acquisition systems: TN-16, and DBBC in combination with MK5b. Both systems are employed in interferometric observations depending on the purpose of experiment and the enabled radiotelescopes. The current status of RT-32, the availability of its receiving and data acquisition units for VLBI observations and the previous VLBI sessions are discussed. Radioteleskops RT-32 ir Ventspils Starptautiskajam Radioastronomijas Centram (VSRC) piederoša pilnas piedziņas 32 m diametra paraboliskā antena. Pašreiz visaktuālākie VSRC veicamie darbi ir saistīti ar RT-32 uztverošās aparatūras un datu reģistrēšanas sistēmas labošanu un modernizāciju. Viens no radioastronomiskās observatorijas galvenajiem zinātniskajiem uzdevumiem ir sevišķi lielas bāzes interferometriskie (VLBI) novērojumi centimetru viļņu garumu diapazonā sadarbībā ar pasaules VLBI tīkla partneriem, t

  3. VLBI observations of bright AGN jets with KVN and VERA Array (KaVA): Evaluation of Imaging Capability

    CERN Document Server

    Niinuma, Kotaro; Kino, Motoki; Sohn, Bong Won; Akiyama, Kazunori; Zhao, Guang-Yao; Sawada-Satoh, Satoko; Trippe, Sascha; Hada, Kazuhiro; Jung, Taehyun; Hagiwara, Yoshiaki; Dodson, Richard; Koyama, Shoko; Honma, Mareki; Nagai, Hiroshi; Chung, Aeree; Doi, Akihiro; Fujisawa, Kenta; Han, Myoung-Hee; Kim, Joeng-Sook; Lee, Jeewon; Lee, Jeong Ae; Miyazaki, Atsushi; Oyama, Tomoaki; Sorai, Kazuo; Wajima, Kiyoaki; Bae, Jaehan; Byun, Do-Young; Cho, Se-Hyung; Choi, Yoon Kyung; Chung, Hyunsoo; Chung, Moon-Hee; Han, Seog-Tae; Hirota, Tomoya; Hwang, Jung-Wook; Je, Do-Heung; Jike, Takaaki; Jung, Dong-Kyu; Jung, Jin-Seung; Kang, Ji-Hyun; Kang, Jiman; Kang, Yong-Woo; Kan-ya, Yukitoshi; Kanaguchi, Masahiro; Kawaguchi, Noriyuki; Kim, Bong Gyu; Kim, Hyo Ryoung; Kim, Hyun-Goo; Kim, Jaeheon; Kim, Jongsoo; Kim, Kee-Tae; Kim, Mikyoung; Kobayashi, Hideyuki; Kono, Yusuke; Kurayama, Tomoharu; Lee, Changhoon; Lee, Jung-Won; Lee, Sang Hyun; Minh, Young Chol; Matsumoto, Naoko; Nakagawa, Akiharu; Oh, Chung Sik; Oh, Se-Jin; Park, Sun-Youp; Roh, Duk-Gyoo; Sasao, Tetsuo; Shibata, Katsunori M; Song, Min-Gyu; Tamura, Yoshiaki; Wi, Seog-Oh; Yeom, Jae-Hwan; Yun, Young Joo

    2014-01-01

    The Korean very-long-baseline interferometry (VLBI) network (KVN) and VLBI Exploration of Radio Astrometry (VERA) Array (KaVA) is the first international VLBI array dedicated to high-frequency (23 and 43 GHz bands) observations in East Asia. Here, we report the first imaging observations of three bright active galactic nuclei (AGNs) known for their complex morphologies: 4C 39.25, 3C 273, and M 87. This is one of the initial result of KaVA early science. Our KaVA images reveal extended outflows with complex substructure such as knots and limb brightening, in agreement with previous Very Long Baseline Array (VLBA) observations. Angular resolutions are better than 1.4 and 0.8 milliarcsecond at 23 GHz and 43 GHz, respectively. KaVA achieves a high dynamic range of ~1000, more than three times the value achieved by VERA. We conclude that KaVA is a powerful array with a great potential for the study of AGN outflows, at least comparable to the best existing radio interferometric arrays.

  4. Discovery of off-axis jet structure of TeV blazar Mrk 501 with mm-VLBI

    CERN Document Server

    Koyama, S; Giroletti, M; Doi, A; Giovannini, G; Orienti, M; Hada, K; Ros, E; Niinuma, K; Nagai, H; Savolainen, T; Krichbaum, T P; Pérez-Torres, M Á

    2016-01-01

    High-resolution millimeter wave very-long-baseline interferometry (mm-VLBI) is an ideal tool for probing the structure at the base of extragalactic jets in detail. The TeV blazar Mrk 501 is one of the best targets among BL Lac objects for studying the nature of off-axis jet structures because it shows different jet position angles at different scales. The aim of this study is to investigate the properties of the off-axis jet structure through high-resolution mm-VLBI images at the jet base and physical parameters such as kinematics, flux densities, and spectral indices. We performed Very Long Baseline Array (VLBA) observations over six epochs from 2012 February to 2013 February at 43 GHz. Quasi-simultaneous Global Millimeter VLBI Array (GMVA) observations at 86 GHz were performed in May 2012. We discover a new jet component at the northeast direction from the core in all the images at 43 and 86 GHz. The new component shows the off-axis location from the persistent jet extending to the southeast. The 43 GHz ima...

  5. VLBI2010 Receiver Back End Comparison

    Science.gov (United States)

    Petrachenko, Bill

    2013-01-01

    VLBI2010 requires a receiver back-end to convert analog RF signals from the receiver front end into channelized digital data streams to be recorded or transmitted electronically. The back end functions are typically performed in two steps: conversion of analog RF inputs into IF bands (see Table 2), and conversion of IF bands into channelized digital data streams (see Tables 1a, 1b and 1c). The latter IF systems are now completely digital and generically referred to as digital back ends (DBEs). In Table 2 two RF conversion systems are compared, and in Tables 1a, 1b, and 1c nine DBE systems are compared. Since DBE designs are advancing rapidly, the data in these tables are only guaranteed to be current near the update date of this document.

  6. Connecting VLBI and Gaia celestial reference frames

    CERN Document Server

    Malkin, Zinovy

    2016-01-01

    The current state of the link problem between radio and optical celestial reference frames is considered. The main objectives of the investigations in this direction during the next few years are the preparation of a comparison and the mutual orientation and rotation between the optical {\\it Gaia} Celestial Reference Frame (GCRF) and the 3rd generation radio International Celestial Reference Frame (ICRF3), obtained from VLBI observations. Both systems, ideally, should be a realization of the ICRS (International Celestial Reference System) at micro-arcsecond level accuracy. Therefore, the link accuracy between the ICRF and GCRF should be obtained with similar error level, which is not a trivial task due to relatively large systematic and random errors in source positions at different frequency bands. In this paper, a brief overview of recent work on the GCRF--ICRF link is presented. Additional possibilities to improve the GCRF--ICRF link accuracy are discussed. The suggestion is made to use astrometric radio s...

  7. e-VLBI detection of SN2007gr

    Science.gov (United States)

    Paragi, Z.; Kouveliotou, C.; Garrett, M. A.; Ramirez-Ruiz, E.; van Langevelde, H. J.; Szomoru, A.; Argo, M.

    2007-09-01

    We observed the Type Ibc SN2007gr on 6-7 September for 12 hours (21:00-09:00 UTC) at 4.97 GHz with the the European VLBI Network (EVN) using the e- VLBI technique. Participating telescopes were Darnhall, Jodrell Bank (MkII), Medicina, Onsala, Torun and Westerbork (phased array of 14 telescopes). The aggregate bitrate was 256 Mbps, except for Darnhall which contributed with an effective data rate of 128 Mbps due to analog bandwidth restrictions.

  8. Simulation of Local Tie Accuracy on VLBI Antennas

    Science.gov (United States)

    Kallio, Ulla; Poutanen, Markku

    2010-01-01

    We introduce a new mathematical model to compute the centering parameters of a VLBI antenna. These include the coordinates of the reference point, axis offset, orientation, and non-perpendicularity of the axes. Using the model we simulated how precisely parameters can be computed in different cases. Based on the simulation we can give some recommendations and practices to control the accuracy and reliability of the local ties at the VLBI sites.

  9. A VLBI survey at 2.29 GHz

    Science.gov (United States)

    Preston, R. A.; Morabito, D. D.; Williams, J. G.; Faulkner, J.; Jauncey, D. L.

    1985-01-01

    VLBI observations at 2.29 GHz with fringe spacings of about 3 milliarcsec have been performed on 1398 radio sources spread over the entire sky. 917 sources were detected, including 93 percent of the identified BL Lacertae objects, 86 percent of the quasars, and 36 percent of the galaxies. The resulting catalog of compact radio sources is useful for various astrophysical studies and in the formation of VLBI celestial reference frames.

  10. Study of a Bistatic Radar System Using VLBI Technologies for Detecting Space Debris and the Experimental Verification of its Validity

    Science.gov (United States)

    Yajima, Masanobu; Tsuchikawa, Kazutomo; Murakami, Toshiyuki; Katsumoto, Kazuyoshi; Takano, Tadashi

    2007-04-01

    Space debris are increasing around the Earth. The observation of space debris is a key issue for the investigation and monitoring of space environment. But the observation opportunities and the detection ability are limited in existing monostatic radar systems. This paper proposes a bistatic radar which is composed of a transmitting station and a receiving-only station. A carrier wave modulated by PN-PSK signals is used in combination with a VLBI (Very Long Baseline Interferometry) recorder for range measurement between space debris and stations. The receiving radio wave is processed on the basis of VLBI techniques. Accordingly, the system is shown to have significant advantages over a monostatic radar. We actually formed a bistatic radar system, and observed a satellite in order to experimentally verify the validity. The configuration of the system, data analysis and the experimental results are described.

  11. Technical note: Effect of determining baseline plasma urea nitrogen concentrations on subsequent posttreatment plasma urea nitrogen concentrations in 20- to 50-kilogram pigs.

    Science.gov (United States)

    Waguespack, A M; Powell, S; Roux, M L; Frugé, E D; Bidner, T D; Payne, R L; Southern, L L

    2011-12-01

    Plasma urea N (PUN) has been used as an indicator of AA requirements and efficiency of AA utilization in swine. However, PUN concentrations vary among a population of pigs, even a population with a close range of BW and fed the same diet. Thus, pretreatment or baseline PUN concentrations are used as a covariate to reduce variation of posttreatment PUN. However, this procedure increases experimental costs and stress to the pigs. Data from 14 experiments (26 to 28 d in duration) conducted using PUN as a response variable were compiled into 1 data set. Each experiment had 4 to 6 treatments. The purpose of this technical report was to summarize the effect of determining pretreatment baseline PUN concentrations on subsequent posttreatment PUN concentrations in 20- to 50-kg pigs. In all experiments, pigs were fed corn- and soybean meal-based diets and low-CP diets with various AA additions; pigs were assigned to dietary treatments in a randomized complete block design with a minimum of 4 replicates of 3 to 5 pigs each. Before the start of each experiment, all pigs were fed a common diet for a minimum of 3 d. Blood samples were collected from each pig before allotment to dietary treatments (d 0) and at the end of each experiment. The baseline (d 0) PUN was analyzed as a covariate for posttreatment PUN. Data from each experiment were analyzed without and with baseline PUN in the statistical model. In all experiments combined, there were 768 possible treatment comparisons. The covariate baseline PUN was statistically significant (P < 0.10) in 9 of 14 experiments. However, only 8 treatment differences changed statistical significance as a result of analyzing the data with baseline PUN as a covariate. These 8 treatment differences were in 3 experiments. These results indicate that it is not always necessary to determine baseline PUN concentrations when feeding diets with large differences in AA content.

  12. The Tropospheric Products of the International VLBI Service for Geodesy and Astrometry

    Science.gov (United States)

    Heinkelmann, Robert; Schwatke, Christian

    2010-01-01

    The IVS runs two tropospheric products: The IVS tropospheric parameter rapid combination monitors the zenith wet delay (ZWD) and zenith total delay (ZTD) of the rapid turnaround sessions R1 and R4. Goal of the combination is the identification and the exclusion of outliers by comparison and the assessment of the precision of current VLBI solutions in terms of tropospheric parameters. The rapid combination is done on a weekly basis four weeks after the observation files are released on IVS Data Centers. Since tropospheric and geodetic parameters, such as vertical station components, can significantly correlate, the consistency of the ZTD can be a measure of the consistency of the corresponding TRF as well. The ZWD mainly rely on accurate atmospheric pressure data. Thus, besides estimation techniques, modeling and analyst s noise, ZWD reflects differences in the atmospheric pressure data applied to the VLBI analysis. The second product, called tropospheric parameter long-term combination, aims for an accurate determination of climatological signals, such as trends of the atmospheric water vapor observed by VLBI. Therefore, the long-term homogeneity of atmospheric pressure data plays a crucial role for this product. The paper reviews the methods applied and results achieved so far and describes the new maintenance through DGFI.

  13. Direct estimation of tidally induced Earth rotation variations observed by VLBI

    Science.gov (United States)

    Englich, S.; Heinkelmann, R.; BOHM, J.; Schuh, H.

    2009-09-01

    The subject of our study is the investigation of periodical variations induced by solid Earth tides and ocean tides in Earth rotation parameters (ERP: polar motion, UT1)observed by VLBI. There are two strategies to determine the amplitudes and phases of Earth rotation variations from observations of space geodetic techniques. The common way is to derive time series of Earth rotation parameters first and to estimate amplitudes and phases in a second step. Results obtained by this means were shown in previous studies for zonal tidal variations (Englich et al.; 2008a) and variations caused by ocean tides (Englich et al.; 2008b). The alternative method is to estimate the tidal parameters directly within the VLBI data analysis procedure together with other parameters such as station coordinates, tropospheric delays, clocks etc. The purpose of this work was the application of this direct method to a combined VLBI data analysis using the software packages OCCAM (Version 6.1, Gauss-Markov-Model) and DOGSCS (Gerstl et al.; 2001). The theoretical basis and the preparatory steps for the implementation of this approach are presented here.

  14. Enhanced GPS-based GRACE baseline determination by using a new strategy for ambiguity resolution and relative phase center variation corrections

    Science.gov (United States)

    Gu, Defeng; Ju, Bing; Liu, Junhong; Tu, Jia

    2017-09-01

    Precise relative position determination is a prerequisite for radar interferometry by formation flying satellites. It has been shown that this can be achieved by high-quality, dual-frequency GPS receivers that provide precise carrier-phase observations. The precise baseline determination between satellites flying in formation can significantly improve the accuracy of interferometric products, and has become a research interest. The key technologies of baseline determination using spaceborne dual-frequency GPS for gravity recovery and climate experiment (GRACE) formation are presented, including zero-difference (ZD) reduced dynamic orbit determination, double-difference (DD) reduced dynamic relative orbit determination, integer ambiguity resolution and relative receiver antenna phase center variation (PCV) estimation. We propose an independent baseline determination method based on a new strategy of integer ambiguity resolution and correction of relative receiver antenna PCVs, and implement the method in the NUDTTK software package. The algorithms have been tested using flight data over a period of 120 days from GRACE. With the original strategy of integer ambiguity resolution based on Melbourne-Wübbena (M-W) combinations, the average success rate is 85.6%, and the baseline precision is 1.13 mm. With the new strategy of integer ambiguity resolution based on a priori relative orbit, the average success rate and baseline precision are improved by 5.8% and 0.11 mm respectively. A relative ionosphere-free phase pattern estimation result is given in this study, and with correction of relative receiver antenna PCVs, the baseline precision is further significantly improved by 0.34 mm. For ZD reduced dynamic orbit determination, the orbit precision for each GRACE satellite A or B in three dimensions (3D) is about 2.5 cm compared to Jet Propulsion Laboratory (JPL) post science orbits. For DD reduced dynamic relative orbit determination, the final baseline precision for two

  15. Relation between baseline plaque features and subsequent coronary artery remodeling determined by optical coherence tomography and intravascular ultrasound.

    Science.gov (United States)

    Xie, Zulong; Dong, Nana; Sun, Rong; Liu, Xinxin; Gu, Xia; Sun, Yong; Du, Hongwei; Dai, Jiannan; Liu, Youbin; Hou, Jingbo; Tian, Jinwei; Yu, Bo

    2017-01-17

    Atherosclerosis often leads to myocardial infarction and stroke. We examined the influence of baseline plaque characteristics on subsequent vascular remodeling in response to changes in plaque size. Using optical coherence tomography (OCT) and intravascular ultrasound (IVUS), we examined 213 plaques from 138 patients with acute coronary syndrome at baseline and repeated IVUS at the 12-month follow-up. The change in external elastic membrane (EEM) area for each 1 mm2 change in plaque area (i.e., the slope of the regression line) was calculated as a measure of vascular remodeling capacity. In plaques with static positive remodeling, the slope was smaller than in plaques without static positive remodeling. In addition, the slope of the regression line for lesions with a large plaque burden was much smaller than that for lesions with a small plaque burden. Multivariate linear regression analysis showed that diabetes, calcification and static positive remodeling were inversely and independently associated with the level of change in EEM area/change in plaque area. Lesions with a large plaque burden, calcifications or static positive remodeling had less remodeling capacity, and calcification and static positive remodeling were independent predictors of reduced subsequent remodeling. Therefore, calcifications and static positive remodeling could be used as morphological biomarkers to predict decreased subsequent arterial remodeling.

  16. Connecting VLBI and Gaia celestial reference frames

    Directory of Open Access Journals (Sweden)

    Zinovy Malkin

    2016-09-01

    Full Text Available The current state of the link problem between radio and optical celestial reference frames is considered.The main objectives of the investigations in this direction during the next few years are the preparation of a comparisonand the mutual orientation and rotation between the optical it Gaia Celestial Reference Frame (GCRFand the 3rd generation radio International Celestial Reference Frame (ICRF3, obtained from VLBI observations.Both systems, ideally, should be a realization of the ICRS (International Celestial Reference System at micro-arcsecond level accuracy.Therefore, the link accuracy between the ICRF and GCRF should be obtained with similar error level, which is not a trivial taskdue to relatively large systematic and random errors in source positions at different frequency bands.In this paper, a brief overview of recent work on the GCRF--ICRF link is presented.Additional possibilities to improve the GCRF--ICRF link accuracy are discussed.The suggestion is made to use astrometric radio sources with optical magnitude to 20$^m$ rather than to 18$^m$ as currently plannedfor the GCRF--ICRF link.In addition, the use of radio stars is also a prospective method to obtain independent and accurate orientation between the Gaia frame and the ICRF.

  17. Mark 6 Next-Generation VLBI Data System

    Science.gov (United States)

    Whitney, A.; Lapsley, D.

    2012-12-01

    The Mark 6 VLBI data system is being developed by MIT Haystack Observatory as a next-generation disk-based VLBI data system capable of supporting the goals of VLBI2010, with a maximum sustained recording rate of 16 Gbps writing to an array of 32 magnetic disks. The Mark 6 is based on COTS hardware and open-source code and is being designed to transition easily from the widely used Mark 5 system. A successful 16 Gbps per station VLBI demonstration experiment was conducted with Mark 6 in late 2011 as a proof-of-concept. Haystack Observatory is collaborating with the NASA/GSFC High-End Network Computing Group in the selection of high-performance COTS hardware platforms and with Conduant Corporation in the development of a high-performance disk module for Mark 6. Existing Mark 5 systems will be upgradable to Mark 6, and existing Mark 5 SATA modules will be upgradeable for compatibility with Mark 6. The Mark 6 system is projected to be available to the VLBI community in late 2012.

  18. Plan for VLBI observations of close approaches of Jupiter to compact extragalactic radio sources in 2014-2016

    CERN Document Server

    Girdiuk, Anastassia

    2013-01-01

    Very Long Baseline Interferometry is capable of measuring the gravitational delay caused by the Sun and planet gravitational fields. The post-Newtonian parameter $\\gamma$ is now estimated with accuracy of $\\sigma_{\\gamma}=2\\cdot 10^{-4}$ using a global set of VLBI data from 1979 to present (Lambert, Gontier, 2009), and $\\sigma_{\\gamma}=2\\cdot10^{-5}$ by the Cassini spacecraft (Bertotti et. al, 2003). Unfortunately, VLBI observations in S- and X-bands very close to the Solar limb (less than 2-3 degrees) are not possible due to the strong turbulence in the Solar corona. Instead, the close approach of big planets to the line of sight of the reference quasars could be also used for testing of the general relativity theory with VLBI. Jupiter is the most appropriate among the big planets due to its large mass and relatively fast apparent motion across the celestial sphere. Six close approaches of Jupiter with quasars in 2014-2016 were found using the DE405/LE405 ephemerides, including one occultation in 2016. We ha...

  19. Parsec structure and properties of the jet of 3C273. Results of Space VLBI data processing

    Science.gov (United States)

    Chuprikov, A.; Guirin, I.

    2010-01-01

    We present result of processing of data of ground-space VLBI experiment titled W068. Particularly, one part of data of that observational session is successfully processed. These data were obtained on 2000 March 17 between 9:00 UT and 10:30 UT. 10 antennas of American interferometer VLBA (Very Long Baseline Array) and Japan satellite VSOP (VLBI Space Observatory Programme ([4])) were involved into this experiment. Moreover, 27 antennae of VLA (Very Large Array) were used as an additional ground antenna. Data were transferred from archive of the NRAO (National Radio Astronomy Observatory, USA) and processed with the software titled 'Astro Space Locator' (ASL for Windows) (see [1]). The main result of this processing is the image of the quasar titled 3C273 with high resolution and high accuracy. Using this image, we make some conclusions about the radio structure of jet of this object. Our result is not in conflict with other results of processing of the Space VLBI data for 3C273 published earlier with many authors ([5], [6]). We could add some new aspects into that results. The reconstructed images of 3C273 for 6 centimeter wavelength range and values of some parameters of this source are presented.

  20. Evidence for Low Black Hole Spin and Physically Motivated Accretion Models from Millimeter VLBI Observations of Sagittarius A*

    CERN Document Server

    Broderick, Avery E; Doeleman, Sheperd S; Loeb, Abraham

    2010-01-01

    Millimeter very-long baseline interferometry (mm-VLBI) provides the novel capacity to probe the emission region of a handful of supermassive black holes on sub-horizon scales. For Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, this provides access to the region in the immediate vicinity of the horizon. Broderick et al. (2009) have already shown that by leveraging spectral and polarization information as well as accretion theory, it is possible to extract accretion-model parameters (including black hole spin) from mm-VLBI experiments containing only a handful of telescopes. Here we repeat this analysis with the most recent mm-VLBI data, considering a class of aligned, radiatively inefficient accretion flow (RIAF) models. We find that the combined data set rules out symmetric models for Sgr A*'s flux distribution at the 3.9-sigma level, strongly favoring length-to-width ratios of roughly 2.4:1. More importantly, we find that physically motivated accretion flow models provid...

  1. VizieR Online Data Catalog: VLBI Ecliptic Plane Survey: VEPS-1 (Shu+, 2017)

    Science.gov (United States)

    Shu, F.; Petrov, L.; Jiang, W.; Xia, B.; Jiang, T.; Cui, Y.; Takefuji, K.; McCallum, J.; Lovell, J.; Yi, S.-O.; Hao, L.; Yang, W.; Zhang, H.; Chen, Z.; Li, J.

    2017-08-01

    We began observations in the search mode in 2015 February. The participating stations included the three core stations of the Chinese VLBI Network (CVN): seshan25, kunming, and urumqi. Depending on the participating stations, the longest baseline length in each session can be varied from 3200km to 9800km. Our observations were performed at a 2048Mbps data rate, with 16 Intermediate Frequency (IF) channels and 2-bit sampling. The first eight IFs of 32MHz bandwidth were distributed in the range of [8.188, 8.444]GHz, and the remaining eight IFs of 32MHz bandwidth were in the range of [8.700, 8.956]GHz. Table 1: Summary of the VLBI Ecliptic Plane Survey (VEPS) observations in search mode: --------------------------------------------------- Date Dur. Code Stations Number of (Y/M/D) (h) Targets --------------------------------------------------- 2015 Feb 13 24 VEPS01 ShKmUr 293 2015 Feb 14 24 VEPS02 ShKmUr 338 2015 Apr 23 24 VEPS03 UrKv 300 2015 Apr 24 24 VEPS04 ShKmUrKv 400 2015 Aug 10 25 VEPS05 ShKmKvHo 252 2015 Aug 19 25 VEPS06 ShKmKvHo 277 2016 Mar 02 24 VEPS07 ShKmUrKb 333 2016 Mar 11 24 VEPS08 ShKmUrKb 477 2016 May 13 24 VEPS09 ShUrHo 291 2016 May 14 22 VEPS10 ShUrKv 322 2016 Jul 06 24 VEPS11 ShUrKb 307 2016 Sep 02 23 VEPS12 ShUr 424 2016 Sep 03 23 VEPS13 ShKmUr 344 --------------------------------------------------- Sh=Seshan25; Km=Kunming; Ur=Urumqi; Kv=Sejong; Kb=Kashim34; Ho=Hobart26. --------------------------------------------------- We ran two absolute astrometry dual-band VLBA programs that targeted ecliptic plane compact radio sources: the dedicated survey of weak ecliptic plane calibrators with the VLBA BS250 program in 2016 March-May, and the VLBA Calibrator Survey 9 (VCS-9) in 2015 August-2016 September. The International VLBI Service for Geodesy and Astrometry (IVS) runs a number of VLBI observing programs. We made an attempt to improve the coordinates of some VEPS sources detected in the search mode and provide additional measurements of telescope

  2. Search for Binary Black Hole Candidates from the VLBI Images of AGNs

    Indian Academy of Sciences (India)

    Xiang Liu

    2014-09-01

    We have searched the core-jet pairs in the VLBI scales (< 1 kpc), from several VLBI catalogues, and found out 5 possible Binary Black Hole (BBH) candidates. We present here the search results and analyse the candidates preliminarily. We plan to study with multi-band VLBI observation. We also plan to carry out optical line investigation in future.

  3. VLBI Imagings of Kilo-parsec Knot in 3C 380

    CERN Document Server

    Koyama, Shoko; Nagai, Hiroshi; Hada, Kazuhiro; Kameno, Seiji; Kobayashi, Hideyuki

    2012-01-01

    We investigate observational properties of a kilo-parsec scale knot in radio-loud quasar 3C 380 by using two epoch archival data obtained by Very Long Baseline Interferometry (VLBI) at 5 GHz on 1998 July and 2001 April. We succeed in obtaining the highest spatial resolution image of the bright knot K1 located at 732 milliarcseconds, or more than 20 kpc de-projected, downstream from the nucleus three times better than previously obtained highest resolution image by Papageorgiou et al. (2006). Our images reveal, with new clarity, "inverted bow-shock" structure in K1 facing the nucleus and its morphology resembles a conical shock wave. By comparing the two epoch images directly, we explore the kinematics of K1 and obtain the upper limit of apparent velocity, 0.25 mas/yr or 9.8 c of K1 for the first time. The upper limit of apparent velocity is marginally smaller than superluminal motions seen in the core region. Further new epoch VLBI observations are necessary to measure the proper motion at K1.

  4. Imaging an Event Horizon: submm-VLBI of a Super Massive Black Hole

    CERN Document Server

    Doeleman, Sheperd; Backer, Don; Baganoff, Fred; Bower, Geoffrey C; Broderick, Avery; Fabian, Andrew; Fish, Vincent; Gammie, Charles; Ho, Paul; Honma, Mareki; Krichbaum, Thomas; Loeb, Avi; Marrone, Dan; Reid, Mark; Rogers, Alan E E; Shapiro, Irwin; Strittmatter, Peter; Tilanus, Remo; Weintroub, Jonathan; Whitney, Alan; Wright, Melvyn; Ziurys, Lucy

    2009-01-01

    A long standing goal in astrophysics is to directly observe the immediate environment of a black hole with angular resolution comparable to the event horizon. Realizing this goal would open a new window on the study of General Relativity in the strong field regime, accretion and outflow processes at the edge of a black hole, the existence of an event horizon, and fundamental black hole physics (e.g., spin). Steady long-term progress on improving the capability of Very Long Baseline Interferometry (VLBI) at short wavelengths has now made it extremely likely that this goal will be achieved within the next decade. The most compelling evidence for this is the recent observation by 1.3mm VLBI of Schwarzschild radius scale structure in SgrA*, the compact source of radio, submm, NIR and xrays at the center of the Milky Way. SgrA* is thought to mark the position of a ~4 million solar mass black hole, and because of its proximity and estimated mass presents the largest apparent event horizon size of any black hole can...

  5. Localizing Sagittarius A* and M87 on Microarcsecond Scales with Millimeter VLBI

    CERN Document Server

    Broderick, Avery E; Reid, Mark J

    2011-01-01

    With the advent of the Event Horizon Telescope (EHT), a millimeter/sub-millimeter very-long baseline interferometer (VLBI), it has become possible to image a handful of black holes with sub-horizon resolutions. However, these images do not translate into microarcsecond absolute positions due to the lack of absolute phase information when an external phase reference is not used. Due to the short atmospheric coherence time at these wavelengths, nodding between the source and phase reference is impractical. However, here we suggest an alternative scheme which makes use of the fact that many of the VLBI stations within the EHT are arrays in their own right. With this we show that it should be possible to absolutely position the supermassive black holes at the centers of the Milky Way (Sgr A*) and M87 relative to nearby objects with precisions of roughly 1 microarcsecond. This is sufficient to detect the perturbations to Sgr A*'s position resulting from interactions with the stars and stellar-mass black holes in t...

  6. 8.4GHz VLBI observations of SN2004et in NGC6946

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Guirado, J C; Lara, L; Pérez-Torres, M A; Ros, E; Argo, M K; Beswick, R J; Muxlow, T W B; Pedlar, A; Shapiro, I I; Stockdale, C J; Sramek, R A; Weiler, K W; Vinko, J

    2007-01-01

    We report on 8.4GHz Very Long Baseline Interferometry (VLBI) observations of the type II-P supernova SN2004et in the spiral galaxy NGC 6946, made on 20 February 2005 (151 days after explosion). The Very Large Array (VLA) flux density was 1.23$\\pm$0.07 mJy, corresponding to an isotropic luminosity at 8.4GHz of (4.45$\\pm$0.3)$\\times10^{25}$ erg s$^{-1}$ Hz$^{-1}$ and a brightness temperature of (1.3$\\pm$0.3)$\\times10^{8}$ K. We also provide an improved source position, accurate to about 0.5 mas in each coordinate. The VLBI image shows a clear asymmetry. From model fitting of the size of the radio emission, we estimate a minimum expansion velocity of 15,700$\\pm$2,000 km s$^{-1}$. This velocity is more than twice the expected mean expansion velocity estimated from a synchrotron self-absorbed emission model, thus suggesting that synchrotron self-absorption is not relevant for this supernova. With the benefit of an optical spectrum obtained 12 days after explosion, we favor an emission model which consists of two h...

  7. VLBI FOR GRAVITY PROBE B. I. OVERVIEW

    Energy Technology Data Exchange (ETDEWEB)

    Shapiro, I. I.; Lebach, D. E.; Ratner, M. I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bartel, N.; Bietenholz, M. F.; Ransom, R. R. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON, M3J 1P3 (Canada); Lestrade, J.-F. [Observatoire de Paris, Centre National de la Recherche Scientifique, 77 Av. Denfert Rochereau, 75014 Paris (France)

    2012-07-01

    We describe the NASA/Stanford gyroscope relativity mission, Gravity Probe B (GP-B), and provide an overview of the following series of six astrometric and astrophysical papers that report on our radio observations and analyses made in support of this mission. The main goal of this 8.5 year program of differential very long baseline interferometry astrometry was to determine the proper motion of the guide star of the GP-B mission, the RS CVn binary IM Pegasi (IM Peg; HR 8703). This proper motion is determined with respect to compact, extragalactic reference sources. The results are -20.833 {+-} 0.090 mas yr{sup -1} and -27.267 {+-} 0.095 mas yr{sup -1} for, respectively, the right ascension and declination, in local Cartesian coordinates, of IM Peg's proper motion, and 10.370 {+-} 0.074 mas (i.e., 96.43 {+-} 0.69 pc) for its parallax (and distance). Each quoted uncertainty is meant to represent an {approx}70% confidence interval that includes the estimated contribution from systematic error. These results are accurate enough not to discernibly degrade the GP-B estimates of its gyroscopes' relativistic precessions: the frame-dragging and geodetic effects.

  8. Development of a New VLBI Data Analysis Software

    Science.gov (United States)

    Bolotin, Sergei; Gipson, John M.; MacMillan, Daniel S.

    2010-01-01

    We present an overview of a new VLBI analysis software under development at NASA GSFC. The new software will replace CALC/SOLVE and many related utility programs. It will have the capabilities of the current system as well as incorporate new models and data analysis techniques. In this paper we give a conceptual overview of the new software. We formulate the main goals of the software. The software should be flexible and modular to implement models and estimation techniques that currently exist or will appear in future. On the other hand it should be reliable and possess production quality for processing standard VLBI sessions. Also, it needs to be capable of processing observations from a fully deployed network of VLBI2010 stations in a reasonable time. We describe the software development process and outline the software architecture.

  9. 基于卫星DOR信号的VLBI相时延解算方法研究%Method of Calculating VLBI Phase Delay Based on DOR Signal of a Satellite

    Institute of Scientific and Technical Information of China (English)

    陈冠磊; 郑鑫; 陈明; 刘庆会; 戴志强; 吴亚军; 赵融冰

    2012-01-01

    VLBI技术是深空探测中主要的测角手段,其对与视线垂直方向上卫星的轨道和位置变化有很高的灵敏度.基于DOR信号的VLBI观测量一般是群时延,其精度一般为纳秒量级,在约2000 km的基线长度上,月球探测器的位置测量误差达近百米,对深空探测器来说位置测量误差会更大.为了提高卫星测定轨测定位精度,研究了含微小偏倚量的VLBI相时延的解算算法,并利用嫦娥—号△DOR观测数据对连续观测和间断观测时的算法进行了验证.结果表明:两种观测模式下皆可行.经过比较,相时延的随机误差大幅降低.%In deep space exploration, the VLBI technique is a precise method for the angular measurement, which can give the plane-of-sky position information. The group delay of DOR signal can usually be obtained with an accuracy of nanosecond in the VLBI observation. The accuracy of group delay can bring an orbital error of lunar probe about a hundred meters for a baseline of about 2000 kilometers. Especially in the further deep space exploration, the orbital error will be much larger. A method to calculate the small biased phase delay of VLBI is proposed in this paper in order to improve the accuracy of the orbit and position determination. The small biased phase delay is acquired by using the phase delay with ambiguity approaching the middle of bandwidth synthesis group delay of DOR signal. The method both in continuous and discontinuous observation is feasible, proved by processing the data from CE-2 satellite A DOR experiments. The relationship between the group delay and phase delay is discussed. Both of the closure group delay and the closure phase delay of three baselines of SH-BJ, SH-UR and BJ-UR are calculated, and the errors of them are analyzed. The phases of the carrier and the DOR tones are compared to prove the validity of the method. The phase delay's error, especially the random error, can be reduced. The system error will be

  10. Terrestrial gamma radiation dose study to determine the baseline for environmental radiological health practices in Melaka state, Malaysia.

    Science.gov (United States)

    Ramli, Ahmad Termizi; Sahrone, Sallehudin; Wagiran, Husin

    2005-12-01

    Environmental terrestrial gamma radiation dose rates were measured throughout Melaka, Malaysia, over a period of two years, with the objective of establishing baseline data on the background radiation level. Results obtained are shown in tabular, graphic and cartographic form. The values of terrestrial gamma radiation dose rate vary significantly over different soil types and for different underlying geological characteristics present in the study area. The values ranged from 54 +/- 5 to 378 +/- 38 nGy h(-1). The highest terrestrial gamma dose rates were measured over soil types of granitic origin and in areas with underlying geological characteristics of an acid intrusive (undifferentiated) type. An isodose map of terrestrial gamma dose rate in Melaka was drawn by using the GIS application 'Arc View'. This was based on data collected using a NaI(Tl) scintillation detector survey meter. The measurements were taken at 542 locations. Three small 'hot spots' were found where the dose rates were more than 350 nGy h(-1). The mean dose rates in the main population areas in the mukims (parishes) of Bukit Katil, Sungai Udang, Batu Berendam, Bukit Baru and Bandar Melaka were 154 +/- 15, 161 +/- 16, 160 +/- 16, 175 +/- 18 and 176 +/- 18 nGy h(-1), respectively. The population-weighted mean dose rate throughout Melaka state is 172 +/- 17 nGy h(-1). This is lower than the geographical mean dose rate of 183 +/- 54 nGy h(-1). The lower value arises from the fact that most of the population lives in the central area of the state where the lithology is dominated by sedimentary rocks consisting of shale, mudstone, phyllite, slate, hornfels, sandstone and schist of Devonian origin which have lower associated dose rates. The mean annual effective dose to the population from outdoor terrestrial gamma radiation was estimated to be 0.21 mSv. This value is higher than the world average of 0.07 mSv.

  11. Precise geodesy with the Very Long Baseline Array

    CERN Document Server

    Petrov, Leonid; Gipson, John; MacMillan, Dan; Ma, Chopo; Fomalont, Ed; Walker, R Craig; Carabajal, Claudia

    2008-01-01

    We report on a program of regular measurements between 1994 and 2007 which used the Very Long Baseline Array and up to 10 additional stations. One of the goals of these sessions was to monitor positions of the array at 1 millimeter level of accuracy and to tie the VLBA into the International Terrestrial Reference Frame. The large number of stations and the many competing goals made scheduling these sessions manually difficult, and lead to advances in scheduling software. We describe the analysis of these data, which is non-standard, and involves translating the data into a form useful for geodetic VLBI. We also describe several interesting geophysical results including measured station displacement due to crustal motion, earthquakes, and antenna tilt. In terms of both formal errors and observed scatter, these sessions are among the very best geodetic VLBI sessions.

  12. Detection of space debris with VLBI radar technique

    Science.gov (United States)

    Molotov, I.; Konovalenko, A.; Agapov, V.; Sochilina, A.; Lipatov, B.; Molotov, E.; Gorshenkov, Y.

    The possibility of Evpatoria RT-70 planetary radar application for space debris research was tested in two trial experiments for targets at geostationary (GEO) and high-elliptic (HEO) orbits in 2001. The RT-70 has the 200 kW continuous power transmitter at 6-cm wavelength, which was used for radio location of planets. Therefore the bistatic radar system only may be realized for orbital object measurements. The receiving antennas (Bear Lakes RT-64, Svetloe RT-32, Noto RT- 32, Torun RT-32 and Urumqi RT-25) used the standard VLBI equipment for recording of echo-signals, because they have not specialized radar apparatus. Such multi-antennas configuration allows to add the classic radar data with VLBI measurements: radar has the resolution for range and radial velocity, VLBI provides the angle and angular rate. Moreover the VLBI radar may be a tool for 3D- measurements: combination of radar map and VLBI image can result the "radio holography" picture of investigated object. Seven GEO objects were detected in May session and four GEO + two HEO objects - in December session. The uncontrolled axial rotation with 5 - 20 s period was fixed for GEO targets. The first results of processing that carry out at Russia and Canada are presented. It is planned to finally adjust the VLBI radar method and t o start the regular observations under the international program of optical and radar monitoring of the near-Earth space environment that will be partially supported by INTAS-01-0669, RFBR-02-02- 17568 and RFBR-02-02-3108.

  13. e-VLBI observations of Cyg X-3

    Science.gov (United States)

    Tudose, V.; Paragi, Z.; Fender, R.; Spencer, R.; Garrett, M.; Rushton, A.

    2008-04-01

    We observed the X-ray binary Cyg X-3 on April 9th, 2008 for 9.5 hours, between 03:30-13:00 UT, at 5 GHz with the European VLBI Network (EVN) in e-VLBI mode (the data from the radio telescopes are sent over optical fibers in real-time to the correlator for processing). The radio telescopes participating in the experiment were: Cambridge, Medicina, Jodrell Bank MkII, Onsala (25 m), Torun and Westerbork (phased array).

  14. e-VLBI observations of SS 433 in outburst

    Science.gov (United States)

    Tudose, V.; Paragi, Z.; Trushkin, S.; Soleri, P.; Fender, R.; Garrett, M.; Spencer, R.; Rushton, A.; Burgess, P.; Kunert-Bajraszewska, M.; Pazderski, E.; Borkowski, K.; Hammargren, R.; Lindqvist, M.; Maccaferri, G.

    2008-11-01

    We have observed the X-ray binary SS 433 on November 6, 2008 between 13:48-18:35 UT at 5 GHz with the European VLBI Network (EVN) using the e-VLBI technique. The radio telescopes participating in the experiment were: Medicina, Onsala 25m, Torun, Jodrell Bank MkII and Cambridge. The X-ray binary SS 433 is in outburst. Trushkin & Nizhelskij (ATel #1819) reported a major flare already active during the RATAN-600 observations in the 1-22 GHz band on 2008 October 28.

  15. Radio Astronomy Data Transfer and eVLBI using KAREN

    CERN Document Server

    Weston, Stuart; Gulyaev, Sergei

    2011-01-01

    Kiwi Advanced Research and Education Network (KAREN) has been used to transfer large volumes of radio astronomical data between the Radio Astronomical Observatory at Warkworth, New Zealand and various international organizations involved in joint projects and VLBI observations. Here we report on the current status of connectivity and on the results of testing different data transfer protocols. We investigate new UDP protocols such as 'tsunami' and UDT and demonstrate that the UDT protocol is more efficient than 'tsunami' and 'ftp'. We also report on the tests on direct data streaming from the radio telescope receiving system to the correlation centre without intermediate buffering or recording (real-time eVLBI).

  16. Determining barriers to creating an enabling environment in Cambodia: results from a baseline study with key populations and police

    Directory of Open Access Journals (Sweden)

    Mira L Schneiders

    2016-07-01

    Full Text Available Introduction: Cambodian law enforcement's limited acceptance of harm reduction has hindered HIV program effectiveness. With funding from the Australian Department of Foreign Affairs and Trade, FHI 360 supported the Ministry of Interior to implement the Police Community Partnership Initiative (PCPI in Cambodia's capital Phnom Penh. To guide this, FHI 360 conducted a baseline study examining police and key populations’ attitudes and practices towards one another, including fear and occurrence of arrest. Methods: Between December 2012 and January 2013, a cross-sectional survey of 199 police post officers, 199 people who use drugs (PWUD including people who inject drugs (PWID, 199 men who have sex with men (MSM, 200 transgender women (TGW and 200 female entertainment workers (FEW was conducted in five Phnom Penh districts. Eligible participants were ≥18 years, members of a key population from selected hotspots or police officers, deputy chiefs or chiefs. Results: Key populations’ median age was 25 years (IQR: 22–30; 40% had completed only primary school. Police were male (99.5%, with median age 43 years (IQR: 30 to 47, and 45 and 25% high school and university completion rates, respectively. Key populations feared arrest for carrying needles and syringes (67%, condoms (23% and 19% felt afraid to access health services. Close to 75% of police reported body searching and 58% arresting key populations in the past six months for using drugs (64%, selling or distributing drugs (36% or being violent (13%. Self-reported arrests (23% PWUD, 6% MSM, 6% TGW, 12% FEW; p<0.05, being verbally threatened (45% PWUD, 21% MSM, 25% TGW, 27% FEW; p<0.001 and body searched (44% PWUD, 28% MSM, 23% TGW, 8% FEW; p<0.001 was significantly higher among PWUD than other key populations. The majority (94% of police believed arrest was an appropriate solution to reduce HIV and drug use and reported selling sex (88% and carrying needles and syringes (55% as valid reasons

  17. Terrestrial gamma radiation dose study to determine the baseline for environmental radiological health practices in Melaka state, Malaysia

    Energy Technology Data Exchange (ETDEWEB)

    Ramli, Ahmad Termizi; Sahrone, Sallehudin; Wagiran, Husin [Department of Physics, Faculty of Science, Universiti Teknologi Malaysia, 81310 Skudai, Johore Bahru, Johore, Malaysia (Malaysia)

    2005-12-15

    Environmental terrestrial gamma radiation dose rates were measured throughout Melaka, Malaysia, over a period of two years, with the objective of establishing baseline data on the background radiation level. Results obtained are shown in tabular, graphic and cartographic form. The values of terrestrial gamma radiation dose rate vary significantly over different soil types and for different underlying geological characteristics present in the study area. The values ranged from 54 {+-} 5 to 378 {+-} 38 nGy h{sup -1}. The highest terrestrial gamma dose rates were measured over soil types of granitic origin and in areas with underlying geological characteristics of an acid intrusive (undifferentiated) type. An isodose map of terrestrial gamma dose rate in Melaka was drawn by using the GIS application 'Arc View'. This was based on data collected using a NaI(Tl) scintillation detector survey meter. The measurements were taken at 542 locations. Three small 'hot spots' were found where the dose rates were more than 350 nGy h{sup -1}. The mean dose rates in the main population areas in the mukims (parishes) of Bukit Katil, Sungai Udang, Batu Berendam, Bukit Baru and Bandar Melaka were 154 {+-} 15, 161 {+-} 16, 160 {+-} 16, 175 {+-} 18 and 176 {+-} 18 nGy h{sup -1}, respectively. The population-weighted mean dose rate throughout Melaka state is 172 {+-} 17 nGy h{sup -1}. This is lower than the geographical mean dose rate of 183 {+-} 54 nGy h{sup -1}. The lower value arises from the fact that most of the population lives in the central area of the state where the lithology is dominated by sedimentary rocks consisting of shale, mudstone, phyllite, slate, hornfels, sandstone and schist of Devonian origin which have lower associated dose rates. The mean annual effective dose to the population from outdoor terrestrial gamma radiation was estimated to be 0.21 mSv. This value is higher than the world average of 0.07 mSv.

  18. Lorentz symmetry and very long baseline interferometry

    Science.gov (United States)

    Le Poncin-Lafitte, C.; Hees, A.; Lambert, S.

    2016-12-01

    Lorentz symmetry violations can be described by an effective field theory framework that contains both general relativity and the Standard Model of particle physics called the Standard Model extension (SME). Recently, postfit analysis of Gravity Probe B and binary pulsars led to an upper limit at the 10-4 level on the time-time coefficient s¯T T of the pure-gravity sector of the minimal SME. In this work, we derive the observable of very long baseline interferometry (VLBI) in SME and then implement it into a real data analysis code of geodetic VLBI observations. Analyzing all available observations recorded since 1979, we compare estimates of s¯T T and errors obtained with various analysis schemes, including global estimations over several time spans, and with various Sun elongation cutoff angles, and by analysis of radio source coordinate time series. We obtain a constraint on s¯ T T=(-5 ±8 )×10-5 , directly fitted to the observations and improving by a factor of 5 previous postfit analysis estimates.

  19. Lorentz symmetry and Very Long Baseline Interferometry

    CERN Document Server

    Poncin-Lafitte, C Le; lambert, S

    2016-01-01

    Lorentz symmetry violations can be described by an effective field theory framework that contains both General Relativity and the Standard Model of particle physics called the Standard-Model extension (SME). Recently, post-fit analysis of Gravity Probe B and binary pulsars lead to an upper limit at the $10^{-4}$ level on the time-time coefficient $\\bar s^{TT}$ of the pure-gravity sector of the minimal SME. In this work, we derive the observable of Very Long Baseline Interferometry (VLBI) in SME and then we implement it into a real data analysis code of geodetic VLBI observations. Analyzing all available observations recorded since 1979, we compare estimates of $\\bar s^{TT}$ and errors obtained with various analysis schemes, including global estimations over several time spans and with various Sun elongation cut-off angles, and with analysis of radio source coordinate time series. We obtain a constraint on $\\bar s^{TT}=(-5\\pm 8)\\times 10^{-5}$, directly fitted to the observations and improving by a factor 5 pr...

  20. About the Compatibility of DORIS and VLBI Observations

    Science.gov (United States)

    Il'in, Gennady; Smolentsev, Sergey; Sergeev, Roman

    2010-01-01

    We investigated the compatibility of the DORIS and VLBI observations at Badary Observatory. The DORIS beacon stands at 100-m distance from the main radio telescope dish and transmits signals on two frequencies: 2036.25 MHz and 401.25 MHz. The latter frequency is modulated to send messages containing an ID number, timing information, data from the meteorological sensors, and engineering data (e.g., power). Both frequencies affect the S/X band radio telescope receivers. The parameters of the DORIS signals were measured at the outputs of the S/X band intermediate frequency amplifier. It was found that: (1) The level of RFI, produced by the DORIS beacon, practically corresponds to the level of the system (antenna plus receiver) noise signal and does not overload the S/X band receivers. (2) The DORIS 401.25 MHz signal is out of the frequency bands recorded during standard VLBI sessions. As a result, RFI from DORIS does not affect VLBI observations. This conclusion was confirmed after data correlations of actual VLBI observations that were conducted with the DORIS beacon turned on/off.

  1. VLBI data transmission system using multiple IP streams

    Science.gov (United States)

    Uose, Hisao

    We have developed an IP-based data transmission system which can directly replace K4 (ID1) VLBI data recorder. It employs multiple TCP data steams and individual buffers to cope with variable usable bandwidth we encouter when we use shared academic networks. This paper describes the outline of the system and preliminary testing results.

  2. A Radio Detection Survey of Narrow-Line Seyfert 1 Galaxies using Very-Long-Baseline Interferometry at 22 GHz

    CERN Document Server

    Doi, Akihiro; Kono, Yusuke; Yamauchi, Aya; Suzuki, Syunsaku; Matsumoto, Naoko; Tazaki, Fumie

    2016-01-01

    We conducted a high-sensitivity radio detection survey for forty narrow-line Seyfert 1 (NLS1) galaxies using very-long-baseline interferometry (VLBI) at 22 GHz through phase-referencing long-time integration and using a newly developing recorder with a data rate of 8 Gbps, which is a candidate of the next generation VLBI data recording systems for the Japanese VLBI Network. The baseline sensitivity was typically a few mJy. The observations resulted in a detection rate of 12/40 for our radio-selected NLS1 sample; 11 out of the detected 12 NLS1s showed inverted radio spectra between 1.4 and 22 GHz on the basis of the Very Large Array flux densities and the VLBI detections. These high fractions suggest that a compact radio core with a high brightness temperature is frequently associated with NLS1 nuclei. On the other hand, at least half of the sample indicated apparently steep spectra even with the limited VLBI sensitivity. Both the inverted and steep spectrum radio sources are included in the NLS1 population.

  3. Gravitational effects from a series of IVS R&D VLBI-sessions with observations close to the Sun

    Science.gov (United States)

    Heinkelmann, R.; Soja, B.; Schuh, H.

    2015-08-01

    In 2011 and 2012 the IVS observed twelve VLBI research and development (R&D) sessions that include successful observations as angularly close as 3.9° from the heliocenter. Among others, one purpose of these IVS-R&D sessions was to achieve an improvement in the determination of the PPN parameter γ . Besides, by analyzing this specific set of IVS sessions, it was for the first time possible to measure the dispersive effect of the Solar corona with VLBI (Soja et al., 2014). In this work we assess the formal error of the γ-parameter and the contributions of the various terms to the partial derivative of the γ-parameter. Furthermore, we investigate the size of the gravitational delays caused by: (i) Solar monopole field at rest and with approximately linear translation, (ii) rotation of the Solar monopole field, (iii) Solar gravitational field quadrupole expansion, and (iv) Solar higher order term.

  4. An accurate position for the black hole candidate XTE J1752-223: re-interpretation of the VLBI data

    CERN Document Server

    Miller-Jones, J C A; Ratti, E M; Torres, M A P; Brocksopp, C; Yang, J; Morrell, N I

    2011-01-01

    Using high-precision astrometric optical observations from the Walter Baade Magellan Telescope in conjunction with high-resolution very long baseline interferometric (VLBI) radio imaging with the Very Long Baseline Array (VLBA), we have located the core of the X-ray binary system XTE J1752-223. Compact radio emission from the core was detected following the state transition from the soft to the hard X-ray state. Its position to the south-east of all previously-detected jet components mandated a re-analysis of the existing VLBI data. Our analysis suggests that the outburst comprised at least two ejection events prior to 2010 February 26. No radio-emitting components were detected to the south-east of the core at any epoch, suggesting that the receding jets were Doppler-deboosted below our sensitivity limit. From the ratio of the brightness of the detected components to the measured upper limits for the receding ejecta, we constrain the jet speed to be greater than 0.66c and the inclination angle to the line of...

  5. International VLBI Service for Geodesy and Astrometry - Delivering high-quality products and embarking on observations of the next generation

    Science.gov (United States)

    Nothnagel, A.; Artz, T.; Behrend, D.; Malkin, Z.

    2016-09-01

    The International VLBI Service for Geodesy and Astrometry (IVS) regularly produces high-quality Earth orientation parameters from observing sessions employing extensive networks or individual baselines. The master schedule is designed according to the telescope days committed by the stations and by the need for dense sampling of the Earth orientation parameters (EOP). In the pre-2011 era, the network constellations with their number of telescopes participating were limited by the playback and baseline capabilities of the hardware (Mark4) correlators. This limitation was overcome by the advent of software correlators, which can now accommodate many more playback units in a flexible configuration. In this paper, we describe the current operations of the IVS with special emphasis on the quality of the polar motion results since these are the only EOP components which can be validated against independent benchmarks. The polar motion results provided by the IVS have improved continuously over the years, now providing an agreement with IGS results at the level of 20-25 μ as in a WRMS sense. At the end of the paper, an outlook is given for the realization of the VLBI Global Observing System.

  6. International VLBI Service for Geodesy and Astrometry. Delivering high-quality products and embarking on observations of the next generation

    Science.gov (United States)

    Nothnagel, A.; Artz, T.; Behrend, D.; Malkin, Z.

    2017-07-01

    The International VLBI Service for Geodesy and Astrometry (IVS) regularly produces high-quality Earth orientation parameters from observing sessions employing extensive networks or individual baselines. The master schedule is designed according to the telescope days committed by the stations and by the need for dense sampling of the Earth orientation parameters (EOP). In the pre-2011 era, the network constellations with their number of telescopes participating were limited by the playback and baseline capabilities of the hardware (Mark4) correlators. This limitation was overcome by the advent of software correlators, which can now accommodate many more playback units in a flexible configuration. In this paper, we describe the current operations of the IVS with special emphasis on the quality of the polar motion results since these are the only EOP components which can be validated against independent benchmarks. The polar motion results provided by the IVS have improved continuously over the years, now providing an agreement with IGS results at the level of 20-25 μas in a WRMS sense. At the end of the paper, an outlook is given for the realization of the VLBI Global Observing System.

  7. Greenland Telescope Project --- Direct Confirmation of Black Hole with Sub-millimeter VLBI

    CERN Document Server

    Inoue, M; Asada, K; Chang, C -C; Chen, M -T; Han, J; Hirashita, H; Ho, P T P; Hsieh, S -N; Huang, T; Jiang, H; Koch, P M; Kubo, D Y; Kuo, C -Y; Liu, B; Martin-Cocher, P; Matsushita, S; Meyer-Zhao, Z; Nakamura, M; Nishioka, H; Nystrom, G; Pradel, N; Pu, H -Y; Raffin, P A; Shen, H -Y; Snow, W; Srinivasan, R; Wei, T -S; Blundell, R; Burgos, R; Grimes, P; Keto, E; Paine, S; Patel, N; Sridharan, T K; Doeleman, S S; Fish, V; Brisken, W; Napier, P

    2014-01-01

    A 12-m diameter radio telescope will be deployed to the Summit Station in Greenland to provide direct confirmation of a Super Massive Black Hole (SMBH) by observing its shadow image in the active galaxy M87. The telescope (Greenland Telescope: GLT) is to become one of the Very Long Baseline Interferometry (VLBI) stations at sub-millimeter (submm) regime, providing the longest baseline > 9,000 km to achieve an exceptional angular resolution of 20 micro arc sec at 350 GHz, which will enable us to resolve the shadow size of ~40 micro arc sec. The triangle with the longest baselines formed by the GLT, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, and the Submillimeter Array (SMA) in Hawaii will play a key role for the M87 observations. We have been working on the image simulations based on realistic conditions for a better understanding of the possible observed images. In parallel, retrofitting of the telescope and the site developments are in progress. Based on three years of opacity monitori...

  8. Backpack VLBI terminal with subscentimeter capability

    Science.gov (United States)

    Connselman, C. C., III; Shapiro, I. I.; Greenspan, R. L.; Cox, D. B., Jr.

    1980-01-01

    Backpack portable equipment was developed to measure vector baseline from approximately 1 km to 100 km in length with subcentimeter to few centimeter accuracy. The equipment design features as well as the instrumentation specifications are discussed. It is shown that the unit has the following advantages: it is simple in concept; it is reliable in unattended operation; and it is inexpensive (less than $15,000 per unit).

  9. Orbit determination for Chang'E-2 lunar probe and evaluation of lunar gravity models

    Science.gov (United States)

    Li, PeiJia; Hu, XiaoGong; Huang, Yong; Wang, GuangLi; Jiang, DongRong; Zhang, XiuZhong; Cao, JianFeng; Xin, Nan

    2012-03-01

    The Unified S-Band (USB) ranging/Doppler system and the Very Long Baseline Interferometry (VLBI) system as the ground tracking system jointly supported the lunar orbit capture of both Chang'E-2 (CE-2) and Chang'E-1 (CE-1) missions. The tracking system is also responsible for providing precise orbits for scientific data processing. New VLBI equipment and data processing strategies have been proposed based on CE-1 experiences and implemented for CE-2. In this work the role VLBI tracking data played was reassessed through precision orbit determination (POD) experiments for CE-2. Significant improvement in terms of both VLBI delay and delay rate data accuracy was achieved with the noise level of X-band band-width synthesis delay data reaching 0.2-0.3 ns. Short-arc orbit determination experiments showed that the combination of only 15 min's range and VLBI data was able to improve the accuracy of 3 h's orbit using range data only by a 1-1.5 order of magnitude, confirming a similar conclusion for CE-1. Moreover, because of the accuracy improvement, VLBI data was able to contribute to CE-2's long-arc POD especially in the along-track and orbital normal directions. Orbital accuracy was assessed through the orbital overlapping analysis (2 h arc overlapping for 18 h POD arc). Compared with about 100 m position error of CE-1's 200 km×200 km lunar orbit, for CE-2's 100 km×100 km lunar orbit, the position errors were better than 31 and 6 m in the radial direction, and for CE-2's 15 km×100 km orbit, the position errors were better than 45 and 12 m in the radial direction. In addition, in trying to analyze the Delta Differential One-Way Ranging (ΔDOR) experiments data we concluded that the accuracy of ΔDOR delay was dramatically improved with the noise level better than 0.1 ns and systematic errors better calibrated, and the Short-arc POD tests with ΔDOR data showed excellent results. Although unable to support the development of an independent lunar gravity model, the

  10. Baseline characteristics and treatment of patients in prospective comparison of ARNI with ACEI to determine impact on global mortality and morbidity in heart failure trial (PARADIGM-HF).

    Science.gov (United States)

    McMurray, John J V; Packer, Milton; Desai, Akshay S; Gong, Jianjian; Lefkowitz, Martin; Rizkala, Adel R; Rouleau, Jean L; Shi, Victor C; Solomon, Scott D; Swedberg, Karl; Zile, Michael R

    2014-07-01

    To describe the baseline characteristics and treatment of the patients randomized in the PARADIGM-HF (Prospective comparison of ARNi with ACEi to Determine Impact on Global Mortality and morbidity in Heart Failure) trial, testing the hypothesis that the strategy of simultaneously blocking the renin-angiotensin-aldosterone system and augmenting natriuretic peptides with LCZ696 200 mg b.i.d. is superior to enalapril 10 mg b.i.d. in reducing mortality and morbidity in patients with heart failure and reduced ejection fraction. Key demographic, clinical and laboratory findings, along with baseline treatment, are reported and compared with those of patients in the treatment arm of the Studies Of Left Ventricular Dysfunction (SOLVD-T) and more contemporary drug and device trials in heart failure and reduced ejection fraction. The mean age of the 8442 patients in PARADIGM-HF is 64 (SD 11) years and 78% are male, which is similar to SOLVD-T and more recent trials. Despite extensive background therapy with beta-blockers (93% patients) and mineralocorticoid receptor antagonists (60%), patients in PARADIGM-HF have persisting symptoms and signs, reduced health related quality of life, a low LVEF (mean 29 ± SD 6%) and elevated N-terminal-proB type-natriuretic peptide levels (median 1608 inter-quartile range 886-3221 pg/mL). PARADIGM-HF will determine whether LCZ696 is more beneficial than enalapril when added to other disease-modifying therapies and if further augmentation of endogenous natriuretic peptides will reduce morbidity and mortality in heart failure and reduced ejection fraction. © 2014 The Authors. European Journal of Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.

  11. On the monitoring model of reference point of VLBI antenna

    Science.gov (United States)

    Zhang, J.; Li, J.

    2013-08-01

    By parameterizing the rotation of VLBI antenna and modeling in local control network the coordinates of targets fixed on the antenna, it is expected to perform fully automatic monitoring of antenna parameters without any interference to normal operations of the telescope. Some insights and analysis are presented concerning the mathematical monitoring model, the setting of parameters and selection of constraints to the observation equation, which are verified via data simulation analysis to be rational and effective. Some factors which may affect the estimation precision of antenna parameters are analyzed in order to design and develop monitoring procedure, data analysis software and to make necessary preparation to practical application of the new monitoring concept of VLBI antenna.

  12. The Italian VLBI Network: First Results and Future Perspectives

    Science.gov (United States)

    Stagni, Matteo; Negusini, Monia; Bianco, Giuseppe; Sarti, Pierguido

    2016-12-01

    A first 24-hour Italian VLBI geodetic experiment, involving the Medicina, Noto, and Matera antennas, shaped as an IVS standard EUROPE, was successfully performed. In 2014, starting from the correlator output, a geodetic database was created and a typical solution of a small network was achieved, here presented. From this promising result we have planned new observations in 2016, involving the three Italian geodetic antennas. This could be the beginning of a possible routine activity, creating a data set that can be combined with GNSS observations to contribute to the National Geodetic Reference Datum. Particular care should be taken in the scheduling of the new experiments in order to optimize the number of usable observations. These observations can be used to study and plan future experiments in which the time and frequency standards can be given by an optical fiber link, thus having a common clock at different VLBI stations.

  13. Warkworth 12-m VLBI Station: WARK12M

    CERN Document Server

    Gulyaev, Sergei; Weston, Stuart; Palmer, Neville; Collett, David

    2011-01-01

    This report summarizes the geodetic VLBI activities in New Zealand in 2010. It provides geographical and technical details of WARK12M - the new IVS network station operated by the Institute for Radio Astronomy and Space Research (IRASR) of Auckland University of Technology (AUT). The details of the VLBI system installed in the station are outlined along with those of the collocated GNSS station. We report on the status of broadband connectivity and on the results of testing data transfer protocols; we investigate UDP protocols such as 'tsunami' and UDT and demonstrate that the UDT protocol is more efficient than 'tsunami' and 'ftp'. In general, the WARK12M IVS network station is fully equipped, connected and tested to start participating in regular IVS observational sessions from the beginning of 2011.

  14. Optimizing the African VLBI Network for Astronomy and Geodesy

    Science.gov (United States)

    de Witt, A.; Mayer, D.; MacLeod, G.; Combrinck, L.; Petrov, L.; Nickola, M.

    2016-12-01

    The African VLBI Network will be a pan-African network of radio telescopes comprised of converted redundant satellite Earth-station antennas and new purpose-built radio telescopes. The first of these antennas, in Ghana, is currently being converted to a radio telescope and current funding is estimated to permit the conversion of two more antennas in Africa. These antennas will initially be equipped with a 5-GHz and 6.7-GHz receiver and the next receiver likely to be fitted is a 1.4-1.7-GHz receiver. While it would be advantageous for the AVN antennas to be able to participate also in geodetic and astrometric VLBI observations, there is no funding currently for this. In this paper we re-visit the scientific justifications for the AVN in an attempt to optimize the AVN for each science case, both astronomical and geodetic.

  15. International VLBI Service for Geodesy and Astrometry 2012 Annual Report

    Science.gov (United States)

    Baver, Karen D.; Behrend, Dirk; Armstrong, Kyla L.

    2013-01-01

    This volume of reports is the 2012 Annual Report of the International VLBI Service for Geodesy and Astrometry (IVS). The individual reports were contributed by VLBI groups in the international geodetic and astrometric community who constitute the permanent components of IVS. The IVS 2012 Annual Report documents the work of the IVS components for the calendar year 2012, our fourteenth year of existence. The reports describe changes, activities, and progress ofthe IVS. Many thanks to all IVS components who contributed to this Annual Report. With the exception of the first section and parts of the last section (described below), the contents of this Annual Report also appear on the IVS Web site athttp:ivscc.gsfc.nasa.gov/publications/ar2012

  16. Using geodetic VLBI to test Standard-Model Extension

    Science.gov (United States)

    Hees, Aurélien; Lambert, Sébastien; Le Poncin-Lafitte, Christophe

    2016-04-01

    The modeling of the relativistic delay in geodetic techniques is primordial to get accurate geodetic products. And geodetic techniques can also be used to measure the relativistic delay and get constraints on parameters describing the relativity theory. The effective field theory framework called the Standard-Model Extension (SME) has been developed in order to systematically parametrize hypothetical violations of Lorentz symmetry (in the Standard Model and in the gravitational sector). In terms of light deflexion by a massive body like the Sun, one can expect a dependence in the elongation angle different from GR. In this communication, we use geodetic VLBI observations of quasars made in the frame of the permanent geodetic VLBI monitoring program to constrain the first SME coefficient. Our results do not show any deviation from GR and they improve current constraints on both GR and SME parameters.

  17. Comments on "Measuring the Gravity Speed by VLBI"

    OpenAIRE

    Asada, Hideki

    2003-01-01

    Einstein gravity with extra dimensions or alternative gravity theories might suggest that the gravity propagation speed can be different from the light speed. Such a difference may play a vital role in the primordial universe. In recent, Kopeikin and Fomalont claimed the first measurement of the gravity speed by VLBI. However, the measurement has no relevance with the speed of gravity as I had shown before the observation was done. It seems that our conclusion has been established well by re-...

  18. DiFX: A software correlator for very long baseline interferometry using multi-processor computing environments

    CERN Document Server

    Deller, A T; Bailes, M; West, C

    2007-01-01

    We describe the development of an FX style correlator for Very Long Baseline Interferometry (VLBI), implemented in software and intended to run in multi-processor computing environments, such as large clusters of commodity machines (Beowulf clusters) or computers specifically designed for high performance computing, such as multi-processor shared-memory machines. We outline the scientific and practical benefits for VLBI correlation, these chiefly being due to the inherent flexibility of software and the fact that the highly parallel and scalable nature of the correlation task is well suited to a multi-processor computing environment. We suggest scientific applications where such an approach to VLBI correlation is most suited and will give the best returns. We report detailed results from the Distributed FX (DiFX) software correlator, running on the Swinburne supercomputer (a Beowulf cluster of approximately 300 commodity processors), including measures of the performance of the system. For example, to correla...

  19. Constraining the Size of the Dark Region Around the M87 Black Hole by Space-VLBI Observations

    Science.gov (United States)

    Takahashi, Rohta; Mineshige, Shin

    2011-03-01

    In order to examine if the next-generation space very long baseline interferometer (VLBI), such as VSOP-2 (VLBI Space Observatory Programme-2), will make it possible to obtain direct images of the accretion flow around the M87 black hole, we calculate the expected observed images by relativistic ray-tracing simulations under considerations of possible observational errors. We consider various cases of electron temperature profiles, as well various values for the distance, mass, and spin of the M87 black hole. We find it feasible to detect an asymmetric intensity profile around the black hole caused by rapid disk rotation, as long as the electron temperature does not rise steeply toward the black hole, as was predicted by the accretion disk theory and three-dimensional magnetohydrodynamic simulations. Further, we can detect a deficit in the observed intensity around the black hole when the apparent size of the gravitational radius is larger than gsim1.5 μas. In the cases that the inner edge of the disk is located at the radius of the innermost stable circular orbit (ISCO), moreover, even the black hole spin will be measured. We also estimate the required signal-to-noise ratio {R}_SN for achieving the scientific goals mentioned above, finding that it should be at least 10 at 22 GHz. To conclude, direct mapping observations by the next-generation space VLBI will provide us a unique opportunity to provide the best evidence for the presence of a black hole and to test the accretion disk theory.

  20. Millimeter VLBI of NGC 1052: Dynamics

    Directory of Open Access Journals (Sweden)

    Anne-Kathrin Baczko

    2016-10-01

    Full Text Available The LINER galaxy NGC 1052 is an ideal target to study the innermost regions of active galactic nuclei (AGN, given its close distance of about 20 Mpc. The source was observed at 29 epochs from 2005 to 2009 with the Very Long Baseline Array (VLBA at 43 GHz. Here, we present a kinematic study of its twin-jet system from a subset of 9 epochs at 43 GHz carried out in 2005 and 2006, finding a bright central feature as the dynamic center. The resulting mean velocities of β = v / c = 0 . 46 ± 0 . 08 and β = 0 . 69 ± 0 . 02 for the western and eastern jet, respectively, give hints towards higher velocities in the eastern jet.

  1. The AuScope Geodetic VLBI Array

    CERN Document Server

    Lovell, J E J; Reid, P B; McCulloch, P M; Baynes, B E; Dickey, J M; Shabala, S S; Watson, C S; Titov, O; Ruddick, R; Twilley, R; Reynolds, C; Tingay, S J; Shield, P; Adada, R; Ellingsen, S P; Morgan, J S; Bignall, H E; 10.1007/s00190-013-0626-3

    2013-01-01

    The AuScope geodetic Very Long Baseline Interferometry array consists of three new 12 m radio telescopes and a correlation facility in Australia. The telescopes at Hobart (Tasmania), Katherine (Northern Territory) and Yarragadee (Western Australia) are co-located with other space geodetic techniques including Global Navigation Satellite Systems (GNSS) and gravity infrastructure, and in the case of Yarragadee, Satellite Laser Ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) facilities. The correlation facility is based in Perth (Western Australia). This new facility will make significant contributions to improving the densification of the International Celestial Reference Frame in the Southern Hemisphere, and subsequently enhance the International Terrestrial Reference Frame through the ability to detect and mitigate systematic error. This, combined with the simultaneous densification of the GNSS network across Australia will enable the improved measurement of intrapl...

  2. Comparison of Site Velocities Derived from Collocated GPS, VLBI and SLR Techniques at The Hartebeesthoek Radio Astronomy Observatory (Comparison of Site Velocities

    Directory of Open Access Journals (Sweden)

    Munghemezulu C.

    2014-04-01

    Full Text Available Space geodetic techniques provide highly accurate methods for estimating bedrock stability at subcentimetre level. We utilize data derived from Satellite Laser Ranging (SLR, Very Long Baseline Interferometry (VLBI and Global Positioning Systems (GPS techniques, collocated at the Hartebeesthoek Radio Astronomy Observatory, to characterise local plate motion and compare the solutions from the three techniques. Data from the GNSS station were processed using the GAMIT/GLOBK (version 10.4 software, data from the SLR station (MOBLAS-6were processed using the Satellite Laser Ranging Data Analysis Software (SDAS and the VLBI data sets were processed using the Vienna VLBI Software (VieVS software. Results show that there is a good agreement between horizontal and vertical velocity components with a maximum deviation of 1.7 mm/yr, 0.7 mm/yr and 1.3 mm/yr between the North, East and Up velocity components respectively for the different techniques. At HartRAO there is no significant trend in the vertical component and all the techniques used are consistent with the a-priori velocities when compared with each other. This information is crucial in monitoring the local motion variations since geodetic instruments require a very stable base to minimise measurement errors. These findings demonstrate that station coordinate time-series derived with different techniques and analysis strategies provide comparable results.

  3. Pilot VLBI Survey of SiO v=3 J=1--0 Maser Emission around Evolved Stars

    CERN Document Server

    Imai, Hiroshi; Chong, Sze Ning; Nakagawa, Akiharu; Kurayama, Tomoharu; Nakashima, Jun-ichi; Matsumoto, Naoko; Nagayama, Takumi; Oyama, Tomoaki; Mizuno, Shota; Deguchi, Shuji; Cho, Se-Hyung

    2012-01-01

    In this Letter, we report detections of SiO v=3 J=1--0 maser emission in very long baseline interferometric (VLBI) observations towards 4 out of 12 long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections towards WX Psc and T Cep are new ones. We also present successful astrometric observations of SiO v=2 and v=3 J=1--0 maser emissions associated with two stars: WX Psc and W Hya and their position-reference continuum sources: J010746.0+131205 and J135146.8-291218 with the VLBI Exploration of Radio Astrometry (VERA). The relative coordinates of the position-reference continuum source and SiO v=3 maser spots were measured with respect to those of an SiO v=2 maser spot adopted as fringe-phase reference. Thus the faint continuum sources were inversely phase-referenced to the bright maser sources. It implies possible registration of multiple SiO maser line maps onto a common coordinate system with 10 microarcsecond-level accuracy.

  4. A spinning supermassive black hole binary revealed by VLBI data on the jet of S5 1928+738

    CERN Document Server

    Kun, E; Karouzos, M; Britzen, S; Gergely, L Á

    2014-01-01

    Very Long Baseline Interferometry (VLBI) allows for high-resolution and high-sensitivity observations of relativistic jets, that can reveal periodicities of several years in their structure. We perform an analysis of long term VLBI data on the quasar S5 1928+738, confronting it with a geometric model of a helical structure projected on to the plane of the sky. We monitor the direction of the jet axis through its inclination and position angles. We decompose the variation of the inclination of the inner 2 milliarcsecond part of the jet of S5 1928+738 into a periodic term with an amplitude of ~0.89 deg and a linear decreasing trend with rate of ~0.05 deg/yr. We also decompose the variation of the position angle into a periodic term with amplitude of ~3.39 deg and a linear increasing trend with rate of ~0.24 deg/yr. We interpret the periodic components as arising from the orbital motion of a binary black hole inspiraling at the jet base. Corrected values of the mass ratio and separation are derived from the accu...

  5. Radio emission of SN1993J: the complete picture. I. Re-analysis of all the available VLBI data

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Guirado, J C; Perez-Torres, M A; Ros, E

    2010-01-01

    We have performed a complete re-calibration and re-analysis of all the available Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN1993J, following an homogeneous and well-defined methodology. VLBI observations of SN1993J at 69 epochs, spanning 13 years, were performed by two teams, which used different strategies and analysis tools. The results obtained by each group are similar, but their conclusions on the supernova expansion and the shape and evolution of the emitting region differ significantly. From our analysis of the combined set of observations, we have obtained an expansion curve with unprecedented time resolution and coverage. We find that the data from both teams are compatible when analyzed with the same methodology. One expansion index ($m_3 = 0.87 \\pm 0.02$) is enough to model the expansion observed at 1.7\\,GHz, while two expansion indices ($m_1 = 0.925\\pm0.016$ and $m_2 = 0.808\\pm0.004$), separated by a break time, $t_{br} = 390\\pm40$ days, are needed to model the data at th...

  6. Active galactic nuclei cores in infrared-faint radio sources: Very long baseline interferometry observations using the Very Long Baseline Array

    CERN Document Server

    Herzog, Andreas; Norris, Ray P; Spitler, Lee R; Deller, Adam T; Collier, Jordan D; Parker, Quentin A

    2015-01-01

    Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z >~ 2). Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginal...

  7. e-VLBI... a Wide-field Imaging Instrument with milliarcsecond Resolution & microJy Sensitivity

    CERN Document Server

    Garrett, M A

    2004-01-01

    The European VLBI Network (EVN) is in the process of establishing an e-VLBI array in which the radio telescopes and the EVN correlator at JIVE are connected in real-time, via high-speed national fibre optic networks and the pan-European research network, GEANT. This paper reports on recent test results, including the production of the first real-time e-VLBI astronomical image. In a parallel and related development, the field-of-view of VLBI is also expanding by many orders of magnitude, and the first results of deep, wide-field surveys capable of detecting many sources simultaneously are summarised. The detection of sources as faint as 10 microJy should soon be possible in the era of ``Mk5'' and e-VLBI.

  8. A method of mapping compact structure in radio sources using VLBI observations

    Science.gov (United States)

    Cotton, W. D.

    1979-01-01

    A two-part technique is described for determining the angular structure of the compact components of radio sources from VLBI observations. With this technique, the source structure is first approximated, using both amplitudes and closure phases, by a model consisting of circularly symmetric Gaussian components located on a grid of positions on the sky. The second part begins by employing this model to predict the visibility phase corresponding to each observed visibility amplitude; these estimated visibility phases are then adjusted to agree with the observed closure phases. The resulting estimates of the visibility phases and the observed visibility amplitudes are then combined in a direct Fourier transform to produce a 'dirty' source map that is deconvolved via the CLEAN procedure on the basis of the point-source response. Some examples based on data generated from test models are provided.

  9. First results of European VLBI radar observations of space objects

    CERN Document Server

    Molotov, I; Nechaeva, M; Dugin, N; Konovalenko, A A; Falkovich, I; Gorshenkov, Yu N; Liu, X; Volvach, A; Agapov, V; Pushkarev, A B; Titenko, V; Buttacio, S; Rumyantsev, V; Shmeld, I

    2004-01-01

    Since 1999 we carried out seven trial VLBI radar experiments under LFVN project. The aim of this work is to adjust new research technique for investigating the Solar system bodies (planets, asteroids, space debris). It is planned to obtain the information on their movement parameters, proper rotation and structure of surface. The transmitter of Evpatoria RT-70 sounded the space objects. Array of Bear Lakes RT-64, Noto RT-32, Urumqi RT-25, Simeiz RT-22 received the echo-signals. The data were processed with NIRFI-3 Mk-2 correlator in N. Novgorod, Russia and NRTV processor in Noto, Italy. The first results of these experiments are presented.

  10. First results of European VLBI radar observations of space objects

    Science.gov (United States)

    Molotov, I.; Tuccari, G.; Nechaeva, M.; Dugin, N.; Konovalenko, A.; Falkovich, I.; Gorshenkov, Y.; Liu, X.; Volvach, A.; Agapov, V.; Pushkarev, A.; Titenko, V.; Buttacio, S.; Rumyantsev, V.; Shmeld, I.

    Since 1999 we carried out seven trial VLBI radar experiments under LFVN project. The aim of this work is to adjust new research technique for investigating the Solar system bodies (planets, asteroids, space debris). It is planned to obtain the information on their movement parameters, proper rotation and structure of surface. The transmitter of Evpatoria RT-70 sounded the space objects. Array of Bear Lakes RT-64, Noto RT-32, Urumqi RT-25, Simeiz RT-22 received the echo-signals. The data were processed with NIRFI-3 Mk-2 correlator in N. Novgorod, Russia and NRTV processor in Noto, Italy. The first results of these experiments are presented. (astro-ph/0412694)

  11. AuScope VLBI Project and Hobart 26-m Antenna

    Science.gov (United States)

    Lovell, Jim; Dickey, John; Reid, Brett; McCallum, Jamie; Shabala, Stas; Watson, Christopher; Ellingsen, Simon; Memin, Anthony

    2013-01-01

    This is a report on the activities carried out at the three AuScope VLBI observatories and the Hobart 26-m antenna. In 2012 the three AuScope 12-m antennas at Hobart (Hb), Katherine (Ke), and Yarragadee (Yg) completed their first full year of operations as an array. The Hobart 26-m antenna (Ho) continued to make a contribution to IVS, providing overlap with the Hb time series. In total the AuScope antennas and the Hobart 26 m observed for 146 antenna days in 2012. In this report we also briefly highlight our research activities during 2012 and our plans for 2013.

  12. Precise Doppler tracking from the Medicina VLBI station

    Science.gov (United States)

    Ambrosini, R.; Comoretto, G.; Iess, L.; Messeri, A.

    1992-06-01

    The first opposition test of Doppler tracking the Ulysses spacecraft from the Medicina VLBI (Very Long Base Interferometry) station (Italy) proved its capability to perform a systematic search for gravitational waves. In house and JPL (Jet Propulsion Laboratory) data analysis showed that the target Allan variance of 3 x 10(exp -14) at 1000 s, planned for the DSN antennas was also achieved from the station. The main observation campaign during the second opposition phase will last for thirty continuous nights--from mid Feb. to mid Mar. 1992. The main hardware and software features developed for this application, together with some results of the first opposition test, are described.

  13. Active galactic nuclei cores in infrared-faint radio sources. Very long baseline interferometry observations using the Very Long Baseline Array

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

    2015-06-01

    Context. Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z ≳ 2). Aims: Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. Methods: We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Results: Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginally higher VLBI detection fraction than randomly selected sources with mJy flux densities at arcsec-scales. Moreover, our data provide a positive correlation between compactness - defined as the ratio of milliarcsec- to arcsec-scale flux density - and redshift for IFRS, but suggest a decreasing mean compactness with increasing arcsec-scale radio flux density. Based on these findings, we suggest that IFRS tend to contain young AGNs whose jets have not formed yet or have not expanded, equivalent to very compact objects. We found two IFRS that are resolved into two components. The two components are spatially separated by a few hundred milliarcseconds in both cases. They might be components of one AGN, a binary black hole, or the result of gravitational lensing.

  14. Digital Base Band Converter As Radar Vlbi Backend / Dbbc Kā Ciparošanas Sistēma Radara Vlbi Novērojumiem

    Science.gov (United States)

    Tuccari, G.; Bezrukovs, Vl.; Nechaeva, M.

    2012-12-01

    can then allow exploring easily the desired range of search for unknown or not fully determined orbit objects. These features make Radar VLBI personality most useful in the space debris measurements. DBBC sistēma izstrādāta Noto Radioastronomijas institūtā. Sistēmas galvenaisuzdevums - palielināt visa Eiropas VLBI tīkla jutību - realizēts, palielinotvisas novērojamās joslas platumu un pielietojot ciparu signālu apstrādes metodes.Izejas datu plūsma palielināta no 1 līdz 4 Gbps katram radioteleskopam un visasoperācijas, kas saistītas ar signālu apstrādi (frekvences pārveidošana, pastiprinājums,iekšējie ģeneratori, utt.), realizētas digitālā formā, kas ļauj iegūt nozīmīgusuzlabojumus atkārtojamībā, precizitātē, vienkāršībā, nemaz neminot vispārzināmāspriekšrocības, ko nodrošina digitālo tehnoloģiju izmantošana. Maksimālā ieejassignāla frekvenču josla ir 3.5 GHz, un momentānais joslas platums ir līdz 1 GHz uzkatru no astoņiem iespējamajiem RF/IF kanāliem. Šī datu reģistrācijas sistēma irļoti veiktspējīga platforma ne tikai EVN, bet arī citiem radioastronomijas pielietojumiem,un papildus tiek izstrādāta vesela virkne programmatūras pakotņu, kasvēl vairāk paplašina sistēmas funkcionalitāti. Tas ietver PFB (Polifāzes FiltruBanka) uztvērējus "Spectra”, kas piemēroti augstas izšķirtspējas spektroskopijasvajadzībām. Papildus realizēts jaunas programmatūras risinājums, ar mērķiizmantot DBBC sistēmu kā daudzfunkcionālu datu ciparošanas iekārtu, kasizmantojama bistatiskiem radara novērojumiem, tai skaitā arī radara VLBInovērojumiem. Šāda veida novērojumos tiek pētīta kosmisko atlūzu populācija,nodrošinot iespēju detektēt pat centimetra izmēru objektus. Debess apgabalaapstarošanai tiek izmantots jaudīgs raidītājs, un tiek analizēts atbalss signāls, kasatstarojas no zināmiem vai nezināmiem objektiem un tiek uztverts ar vienu vaivairākiem teleskopiem uz Zemes

  15. Plutonium Immobilization Project Baseline Formulation

    Energy Technology Data Exchange (ETDEWEB)

    Ebbinghaus, B.

    1999-02-01

    A key milestone for the Immobilization Project (AOP Milestone 3.2a) in Fiscal Year 1998 (FY98) is the definition of the baseline composition or formulation for the plutonium ceramic form. The baseline formulation for the plutonium ceramic product must be finalized before the repository- and plant-related process specifications can be determined. The baseline formulation that is currently specified is given in Table 1.1. In addition to the baseline formulation specification, this report provides specifications for two alternative formulations, related compositional specifications (e.g., precursor compositions and mixing recipes), and other preliminary form and process specifications that are linked to the baseline formulation. The preliminary specifications, when finalized, are not expected to vary tremendously from the preliminary values given.

  16. 毫米波甚长基线干涉测量的发展与展望%Development and Future Prospects of Millimeter-VLBI

    Institute of Scientific and Technical Information of China (English)

    路如森; 沈志强; T.P.KRICHBAUM

    2011-01-01

    甚长基线干涉测量(VLBI)的出现为天文学研究提供了很高的角分辨率(空间分辨率),为人们认识和理解活动星系核(AGN)现象起到不可替代的作用.毫米波VLBI以其独有的优势正在成为天体物理学研究中最有效的研究工具之一.本文简要回顾了射电干涉测量的发展历程,重点介绍了毫米波VLBI的发展历史与现状,及其在活动星系核研究中的重要作用.展望了未来几年随着大口径毫米波段望远镜以及望远镜阵列的加入,毫米波VLBI的发展和应用前景.%Very Long Baseline Interferomety (VLBI) is a high-resolution imaging technique in radio astronomy.It has made substantial contribution to our understanding of Active Galactic Nuclei (AGN).The progress in VLBI is reviewed focusing on the development at millimeter wavelengths and its applications to AGN studies.Extending this technique to millimeter wavelengths, so-called mm-VLBI,leads to a unique opportunity to directly probe the central regions of AGN with the highest angular resolution in astronomy.Direct imaging of the jet innermost regions is indispensable for answering a number of unresolved fundamental questions regarding the jet formation, acceleration, and collimation.It is also a key to understand how the gravitational effects and magnetic fields (through full polarimetric VLBI observations) play the role in the vicinity of Super Massive Black Holes (SMBH).Such kind of studies are not possible at centimeter wavelengths due to the self-absorption, opacity, Faraday depolarization and scattering (in the case of Sgr A*) effects.In addition, millimeter-VLBI observations also open windows to study new species of spectral lines with unprecedented angular resolutions.The present challenges of millimeter VI.BI are explained and a brief developing history is then described.Recent technical development allows imaging of hundreds of sources at 86GHz with high dynamic range.At even higher frequencies, studies are

  17. High resolution mm-VLBI imaging of Cygnus A

    CERN Document Server

    Boccardi, Bia; Bach, Uwe; Ros, Eduardo; Zensus, J Anton

    2015-01-01

    At a distance of 249 Mpc ($z$=0.056), Cygnus A is the only powerful FR II radio galaxy for which a detailed sub-parsec scale imaging of the base of both jet and counter-jet can be obtained. Observing with VLBI at millimeter wavelengths is fundamental for this object, as it uncovers those regions which appear self-absorbed or free-free absorbed by a circumnuclear torus at longer wavelengths. We performed 7 mm Global VLBI observations, achieving ultra-high resolution imaging on scales down to 90 $\\mu$as. This resolution corresponds to a linear scale of only $\\sim$400 Schwarzschild radii. We studied the transverse structure of the jets through a pixel-based analysis, and kinematic properties of the main emission features by modeling the interferometric visibilities with two-dimensional Gaussian components. Both jets appear limb-brightened, and their opening angles are relatively large ($\\phi_\\mathrm {j}\\sim 10^{\\circ}$). The flow is observed to accelerate within the inner-jet up to scales of $\\sim$1 pc, while lo...

  18. VLBI observations of single stars, spatial resolution and astrometry

    Science.gov (United States)

    Pestalozzi, M.; Benz, A. O.; Conway, J. E.; Gudel, M.; Smith, K.

    VLBI studies can both spatially resolve single dMe stars and measure their positions at submilliarcsecond accuracy. The spatial resolution gives the brightness temperature and allows us to draw co nclusions about the nature of the emitting processes. In particular it is possib le to distinguish between thermal or non-thermal emission. The position accuracy gives better knowledge about the astrometric properties (like proper motion and parallax) especially for nearby stars. In this contribution recent results of c ontinuum VLBI observations towards two dMe stars (YZ CMi and AD Leo) at 8.4 GHz are presented. For YZ CMi an estimate of the size of the coronal emission is giv en (0.98 mas in diameter or 0.7 ±0.3 Rstar above the photosphere where Rstar refers to the photospheric radius). For AD Leo an upper limit is gi ven, i.e. the emitting region is shown to be Pestalozzi et al. 2000 ).

  19. VLBI observations of seven BL Lac objects from RGB sample

    CERN Document Server

    Wu, Zhongzu; Gu, Minfeng; Liu, Yi

    2007-01-01

    We present EVN observations of seven BL Lac objects selected from the RGB sample. To investigate the intrinsic radiation property of BL Lac objects, we estimated the Doppler factor with the VLA or MERLIN core and the total 408 MHz luminosity for a sample of 170 BL Lac objects. The intrinsic (comoving) synchrotron peak frequency was then calculated by using the estimated Doppler factor. Assuming a Lorentz factor of 5, the viewing angle of jets was constrained. The high-resolution VLBI images of seven sources all show a core-jet structure. We estimated the proper motions of three sources with the VLBI archive data, and find that the apparent speed increases with the distance of components to the core for all of them. In our BL Lacs sample, the Doppler factor of LBLs is systematically larger than that of IBLs and HBLs. We find a significant anti-correlation between the total 408 MHz luminosity and the intrinsic synchrotron peak frequency. However, the scatter is much larger than for the blazar sequence. Moreover...

  20. New VLBI2010 scheduling strategies and implications on the terrestrial reference frames.

    Science.gov (United States)

    Sun, Jing; Böhm, Johannes; Nilsson, Tobias; Krásná, Hana; Böhm, Sigrid; Schuh, Harald

    In connection with the work for the next generation VLBI2010 Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry, a new scheduling package (Vie_Sched) has been developed at the Vienna University of Technology as a part of the Vienna VLBI Software. In addition to the classical station-based approach it is equipped with a new scheduling strategy based on the radio sources to be observed. We introduce different configurations of source-based scheduling options and investigate the implications on present and future VLBI2010 geodetic schedules. By comparison to existing VLBI schedules of the continuous campaign CONT11, we find that the source-based approach with two sources has a performance similar to the station-based approach in terms of number of observations, sky coverage, and geodetic parameters. For an artificial 16 station VLBI2010 network, the source-based approach with four sources provides an improved distribution of source observations on the celestial sphere. Monte Carlo simulations yield slightly better repeatabilities of station coordinates with the source-based approach with two sources or four sources than the classical strategy. The new VLBI scheduling software with its alternative scheduling strategy offers a promising option with respect to applications of the VGOS.

  1. Resolving the Base of the Relativistic Jet in M87 at 6Rsch Resolution with Global mm-VLBI

    Directory of Open Access Journals (Sweden)

    Jae-Young Kim

    2016-09-01

    Full Text Available M87 is one of the nearest radio galaxies with a central Super-Massive Black Hole (SMBH and a prominent relativistic jet. Due to its close distance to the observer and the large SMBH mass, the source is one of the best laboratories to obtain strong observational constraints on the theoretical models for the formation and evolution of the AGN jets. In this article, we present preliminary results from our ongoing observational study about the innermost jet of M87 at an ultra-high resolution of ∼50 μ as achieved by the Global Millimeter-Very Long Baseline Interferometry Array (GMVA. The data obtained between 2004 and 2015 clearly show limb-brightened jets at extreme resolution and sensitivity. Our preliminary analysis reveals that the innermost jet expands in an edge-brightened cone structure (parabolic shape but with the jet expansion profile slightly different from the outer regions of the jet. Brightness temperatures of the Very Long Baseline Interferometry (VLBI core obtained from cm- to mm-wavelengths show a systematic evolution, which can be interpreted as the evolution as a function of distance from the BH. We also adopt an alternative imaging algorithm, Bi-Spectrum Maximum Entropy Method (BSMEM, to test reliable imaging at higher angular resolution than provided by the standard CLEAN method (i.e., super-resolution. A demonstration with a VLBA 7 mm example data set shows consistent results with a near-in-time 3 mm VLBI image. Application of the method to the 2009 GMVA data yields an image with remarkable fine-scale structures that have been never imaged before. We present a brief interpretation of the complexity in the structure.

  2. MeqSilhouette : A mm-VLBI observation and signal corruption simulator

    CERN Document Server

    Blecher, Tariq; Bernardi, Gianni; Smirnov, Oleg

    2016-01-01

    The Event Horizon Telescope (EHT) aims to spatially resolve the silhouette (or shadow) of the supermassive black holes in the Galactic Centre (Sgr A$^\\star$) and M87. The primary scientific objectives are to test general relativity in the strong-field regime and to probe accretion and jet-launch physics at event-horizon scales. This is made possible by the technique of Very Long Baseline Interferometry (VLBI) at (sub)millimetre wavelengths, which can achieve angular resolutions of order $\\sim10~\\mu$-arcsec. However, this approach suffers from unique observational challenges, including scattering in the troposphere and interstellar medium; rapidly time-variable source structure in both polarized and total intensity; as well as non-negligible antenna pointing errors. In this, the first paper in a series, we present the MeqSilhouette software package which is specifically designed to accurately simulate EHT observations. It includes realistic descriptions of a number of signal corruptions that can limit the abil...

  3. Stirring the Embers: High-Sensitivity VLBI Observations of GRB 030329

    Energy Technology Data Exchange (ETDEWEB)

    Pihlstrom, Y.M.; Taylor, G.B.; /New Mexico U.; Granot, J.; /KIPAC, Menlo Park; Doeleman, S.; /MIT, Haystack Observ.

    2007-09-24

    We present high-sensitivity Very Long Baseline Interferometry (VLBI) observations 806 days after the {gamma}-ray burst of 2003 March 29 (GRB 030329). The angular diameter of the radio afterglow is measured to be 0:347 {+-} 0:09 mas, corresponding to 0:99 {+-} 0:26 pc at the redshift of GRB 030329 (z = 0:1685). The evolution of the image size favors a uniform external density over an R{sup -2} windlike density profile (at distances of R {approx}> 10{sup 18} cm from the source), although the latter cannot be ruled out yet. The current apparent expansion velocity of the image size is only mildly relativistic, suggesting a nonrelativistic transition time of tNR {approx} 1 yr. A rebrightening, or at least a significant flattening in the flux decay, is expected within the next several years as the counterjet becomes visible (this has not yet been observed). An upper limit of <1.9c is set on the proper motion of the flux centroid.

  4. A VLBI survey of compact Broad Absorption Lines (BAL) quasars with BALnicity Index BI=0

    CERN Document Server

    Ceglowski, M; Roskowinski, C

    2015-01-01

    We present high-resolution observations, using both the European VLBI Network (EVN) at 1.7-GHz, and the Very Long Baseline Array (VLBA) at 5 and 8.4-GHz to image radio structures of 14 compact sources classified as broad absorption line (BAL) quasars based on the absorption index (AI). All source but one were resolved, with the majority showing core-jet morphology typical for radio-loud quasars. We discuss in details the most interesting cases. The high radio luminosities and small linear sizes of the observed objects indicate they are strong young AGNs. Nevertheless, the distribution of the radio-loudness parameter, log(Ri), of a larger sample of AI quasars shows that the objects observed by us constitute the most luminous, small subgroup of AI population. Additionally we report that for the radio-loudness parameter, the distribution of AI quasars and those selected by using the traditional balnicity index (BI), BI quasars differ significantly. Strong absorption is connected with the lower log(Ri), and thus ...

  5. MeqSilhouette : A mm-VLBI observation and signal corruption simulator

    Science.gov (United States)

    Blecher, Tariq; Deane, Roger; Bernardi, Gianni; Smirnov, Oleg

    2016-09-01

    The Event Horizon Telescope (EHT) aims to spatially resolve the silhouette (or shadow) of the supermassive black holes in the Galactic Centre (Sgr A⋆) and M87. The primary scientific objectives are to test general relativity in the strong-field regime and to probe accretion and jet-launch physics at event-horizon scales. This is made possible by the technique of Very Long Baseline Interferometry (VLBI) at (sub)millimetre wavelengths, which can achieve angular resolutions of order ˜10~μ-arcsec. However, this approach suffers from unique observational challenges, including scattering in the troposphere and interstellar medium; rapidly time-variable source structure in both polarized and total intensity; as well as non-negligible antenna pointing errors. In this, the first paper in a series, we present the MEQSILHOUETTE software package which is specifically designed to accurately simulate EHT observations. It includes realistic descriptions of a number of signal corruptions that can limit the ability to measure the key science parameters. This can be used to quantify calibration requirements, test parameter estimation and imaging strategies, and investigate systematic uncertainties that may be present. In doing so, a stronger link can be made between observational capabilities and theoretical predictions, with the goal of maximising scientific output from the upcoming order of magnitude increase in EHT sensitivity.

  6. Determining dynamical parameters of the Milky Way Galaxy based on high-accuracy radio astrometry

    Science.gov (United States)

    Honma, Mareki; Nagayama, Takumi; Sakai, Nobuyuki

    2015-08-01

    In this paper we evaluate how the dynamical structure of the Galaxy can be constrained by high-accuracy VLBI (Very Long Baseline Interferometry) astrometry such as VERA (VLBI Exploration of Radio Astrometry). We generate simulated samples of maser sources which follow the gas motion caused by a spiral or bar potential, with their distribution similar to those currently observed with VERA and VLBA (Very Long Baseline Array). We apply the Markov chain Monte Carlo analyses to the simulated sample sources to determine the dynamical parameter of the models. We show that one can successfully determine the initial model parameters if astrometric results are obtained for a few hundred sources with currently achieved astrometric accuracy. If astrometric data are available from 500 sources, the expected accuracy of R0 and Θ0 is ˜ 1% or higher, and parameters related to the spiral structure can be constrained by an error of 10% or with higher accuracy. We also show that the parameter determination accuracy is basically independent of the locations of resonances such as corotation and/or inner/outer Lindblad resonances. We also discuss the possibility of model selection based on the Bayesian information criterion (BIC), and demonstrate that BIC can be used to discriminate different dynamical models of the Galaxy.

  7. High Frequency Very Long Baseline Interferometry Observations of Active Galactic Nuclei

    Science.gov (United States)

    Bower, Geoffrey Copeland

    Millimeter wavelength very long baseline interferometry (VLBI) provides an excellent tool for the investigation of compact synchrotron sources. The high angular resolution and the decline in synchrotron opacity and lifetime with decreasing wavelength give unprecedented spatial and temporal resolution in active galactic nuclei. We present here a description of the implementation of millimeter VLBI with the 9-element millimeter array at Hat Creek Radio Observatory. We emphasize the technical details of array phasing, calibration and observation. The Hat Creek array was used successfully in 5 VLBI experiments between 1995 and 1997. We tested the technique of total power correction for atmospheric phase fluctuations due to water vapor with two epochs of 3mm λ VLBI observations with the Hat Creek array and with the National Radio Astronomy Observatory (NRAO) Kitt Peak 12m antenna. We reduced the root-mean-square phase by as much as a factor of two and to as low as one radian. The limiting factor was the gain stability of the receivers. We present 7mm λ VLBI observations made with the NRAO Very Long Baseline Array (VLBA) of the compact, nonthermal radio source Sgr A*. We find that the image of Sgr A* is fully consistent with the hypothesis that it is a cyclo-synchrotron source powered by accretion onto a 106Msolar black hole and obscured by a screen of thermal electrons. We find no evidence for any asymmetric structure. We also present a two year study of the gamma-ray blazar 530 with multiple epochs of VLBI imaging at 3 mm, 7 mm, 1.3 cm and 3.6 cm λ. We incorporate flux density monitoring ranging from the radio band to positive correlation over 4 years between the millimeter and gamma-ray flux densities. We also find that a bright millimeter wavelength flare in early 1995 corresponded to the creation of a new parsec-scale jet component. We study the spectra and dynamical evolution of the jet. The jet component appears to decelerate from 7.6 ± 2.2c to 0.95 ± 0.16c

  8. VLBI observations of SN2011dh: imaging of the youngest radio supernova

    CERN Document Server

    Marti-Vidal, I; Paragi, Z; Yang, J; Marcaide, J M; Guirado, J C; Ros, E; Alberdi, A; Perez-Torres, M A; Argo, M K; van der Horst, A J; Garrett, M A; Stockdale, C J; Weiler, K W

    2011-01-01

    We report on the VLBI detection of supernova SN2011dh at 22GHz using a subset of the EVN array. The observations took place 14 days after the discovery of the supernova, thus resulting in a VLBI image of the youngest radio-loud supernova ever. We provide revised coordinates for the supernova with milli-arcsecond precision, linked to the ICRF. The recovered flux density is a factor 2 below the EVLA flux density reported by other authors at the same frequency and epoch of our observations. This discrepancy could be due to extended emission detected with the EVLA or to calibration problems in the VLBI and/or EVLA observations.

  9. A Model for Relation Between Differential Phase Fluctuations of Same-beam VLBI and Separation Angle of Detectors%同波束VLBI 差分相位抖动与角距离的关系模型

    Institute of Scientific and Technical Information of China (English)

    唐明乐; 刘庆会; 贺庆宝; 郑鑫; 吴亚军

    2015-01-01

    在有2个探测器的深空探测中,利用同波束VLBI技术可解算高精度的差分相时延,进而同时提高2个探测器的测定轨精度。但是,差分相时延的解算条件严格,差分相位抖动较大时直接影响解算的成功率。针对这一问题,利用SELENE 两颗小卫星Rstar 和Vstar 的4个测站长达1年的同波束VLBI观测数据,统计得出了差分相位抖动与其对应的角距离的关系模型。该模型的建立,既有利于提高同波束VLBI 差分相时延的解算成功率,又对行星中性大气和电离层掩星观测研究具有重要的参考意义。%In deep-space exploration with two detectors, using the same-beam VLBI tech-nique can get high precision differential phase delay, thus the accuracy of orbit determina-tion can be much improved. However, the conditions of differential phase delay solution are much strict. Differential phase fluctuations may jeopardize the success of resolving differen-tial phase delay. To make it clear, conduct a statistic work of one year’s same-beam VLBI data which are got from two satellites (Rstar and Vstar) in SELENE pro ject. After a series of computing, a model for the relation between differential phase fluctuations φ and corre-sponding separation anglesθof two satellites was drawn. The model is described as a linear equation ofφ=2.69θ+1.09, where, the slope of 2.69 reflects the influence of earth neutral atmosphere and ionosphere, and the intercept of 1.09 deg reflects the effect of thermal noise. This model not only can help to resolve differential phase delay in the same-beam VLBI observation, but also can serve as a reference for the study of planetary atmosphere and ionosphere in occultation observation.

  10. Providing hydrogen maser timing stability to orbiting VLBI radio telescope observations by post-measurement compensation of linked frequency standard imperfections

    Science.gov (United States)

    Springett, James C.

    1994-01-01

    Orbiting VLBI (OVLBI) astronomical observations are based upon measurements acquired simultaneously from ground-based and earth-orbiting radio telescopes. By the mid-1990s, two orbiting VLBI observatories, Russia's Radioastron and Japan's VSOP, will augment the worldwide VLBI network, providing baselines to earth radio telescopes as large as 80,000 km. The challenge for OVLBI is to effectuate space to ground radio telescope data cross-correlation (the observation) to a level of integrity currently achieved between ground radio telescopes. VLBI radio telescopes require ultrastable frequency and timing references in order that long term observations may be made without serious cross-correlation loss due to frequency source drift and phase noise. For this reason, such instruments make use of hydrogen maser frequency standards. Unfortunately, space-qualified hydrogen maser oscillators are currently not available for use on OVLBI satellites. Thus, the necessary long-term stability needed by the orbiting radio telescope may only be obtained by microwave uplinking a ground-based hydrogen maser derived frequency to the satellite. Although the idea of uplinking the frequency standard intrinsically seems simple, there are many 'contaminations' which degrade both the long and short term stability of the transmitted reference. Factors which corrupt frequency and timing accuracy include additive radio and electronic circuit thermal noise, slow or systematic phase migration due to changes of electronic circuit temporal operating conditions (especially temperature), ionosphere and troposphere induced scintillations, residual Doppler-incited components, and microwave signal multipath propagation. What is important, though, is to realize that ultimate stability does not have to be achieved in real-time. Instead, information needed to produce a high degree of coherence in the subsequent cross-correlation operation may be derived from a two-way coherent radio link, recorded and later

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

    Science.gov (United States)

    Abbondanza, Claudio; Sarti, Pierguido; Petrov, Leonid; Negusini, Monia

    2010-05-01

    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 upward by 8.9 mm and 6.7 mm, respectively. The impact on other parameters is negligible. To infer the impact of antenna gravity deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects are changes in VLBI heights in the range [-3,73] mm and a significant net scale increase of 0.3 - 0.8 ppb. This demonstrates the need to include SPV models in routine VLBI data analysis.

  12. VLBI at the highest frequencies - AGN studied with micro-arcsecond resolution

    CERN Document Server

    Krichbaum, T P; Bach, U; Witzel, A; Zensus, J A

    2006-01-01

    Compact galactic and extragalactic radio sources can be imaged with an unsurpassed angular resolution of a few ten micro-arcseconds, adopting the observing technique of global millimeter VLBI. Here we present the Global Millimeter VLBI Array (GMVA) and discuss its present performance. For individual and partially archetypical radio sources with prominent VLBI jets (e.g. 3C120, Cygnus A, M87, 3C454.3, NRAO150),we show and discuss new results obtained with the GMVA. The variety of observed effects range from jet propagation and bending, partial fore-ground absorption in the nucleus, and jet component ejection after major flares to new and very small (15-20 Schwarzschild radii) upper limits to the jet base of M87. We also discuss the future development of mm-VLBI at 3mm and towards shorter wavelengths, and make suggestions for possible improvements.

  13. Present and Future Millimeter VLBI Imaging of Jets in AGN: The Case of NRAO 150

    CERN Document Server

    Agudo, I; Bach, U; Pagels, A; Graham, D; Alef, W; Witzel, A; Zensus, J A; Bremer, M; Grewing, M; Ter"asranta, H

    2005-01-01

    The Global mm-VLBI Array is at present the most sensitive 3 mm-VLBI interferometer and provides images of up to 40 micro-arcsecond resolution. Using this array, we have monitored the rotation of the innermost jet in the quasar NRAO 150, which shows an angular speed of ~ 7 deg./yr. Future 3 mm arrays could include additional stations like ALMA, GBT, LMT, CARMA, SRT, Yebes, Nobeyama and Noto, which would allow to push VLBI at this wavelength to sensitivity and image quality levels comparable to those of present VLBI at centimeter wavelengths. This would improve our knowledge of the accretion systems and the magneto-hydrodynamics of the innermost jets in AGN and microquasars.

  14. Wide-Band Data Transmission System Expected in the Next Generation Space VLBI Mission: VSOP-2

    Science.gov (United States)

    Murata, Yasuhiro; Hirabayashi, Hisashi

    2002-01-01

    Following the success of the VLBI Space Observatory Program (VSOP), a next generation space VLBI mission (VSOP-2) is currently being planned. We expect the data rate of more than 1 Gbps to get more sensitivity. Here we will present: (1) How to sample the data (on board), including the radiation test results which show we can have the 10 Gbps sampler LSI which can use in space; (2) Possibility of the bit rate more than 1 Gbps to downlink the VLBI data. We studied the link budget for the wide band data transmission, and discussed the various ideas which can get more than 1 Gbps; and (3) What kind of VLBI tracking station and recording system will be expected for the VSOP-2 mission? We will present the idea of using normal radio telescopes as a tracking station, and also review the possibility of recording and processing at the tracking stations and correlators.

  15. Pulsar VLBI to Measure Cosmological Rotation and Study Pulsar Emission Regions

    Science.gov (United States)

    Gwinn, C. R.

    2009-08-01

    Pulsars are useful for measuring the rotation of the universe. Also, their emission regions provide interesting laboratories for plasma physics. I describe here how VLBI of pulsars, and the VSOP-2 spacecraft, can contribute to such studies.

  16. Remote Control and Monitoring of VLBI Experiments by Smartphones

    Science.gov (United States)

    Ruztort, C. H.; Hase, H.; Zapata, O.; Pedreros, F.

    2012-12-01

    For the remote control and monitoring of VLBI operations, we developed a software optimized for smartphones. This is a new tool based on a client-server architecture with a Web interface optimized for smartphone screens and cellphone networks. The server uses variables of the Field System and its station specific parameters stored in the shared memory. The client running on the smartphone by a Web interface analyzes and visualizes the current status of the radio telescope, receiver, schedule, and recorder. In addition, it allows commands to be sent remotely to the Field System computer and displays the log entries. The user has full access to the entire operation process, which is important in emergency cases. The software also integrates a webcam interface.

  17. GPU Based Software Correlators - Perspectives for VLBI2010

    Science.gov (United States)

    Hobiger, Thomas; Kimura, Moritaka; Takefuji, Kazuhiro; Oyama, Tomoaki; Koyama, Yasuhiro; Kondo, Tetsuro; Gotoh, Tadahiro; Amagai, Jun

    2010-01-01

    Caused by historical separation and driven by the requirements of the PC gaming industry, Graphics Processing Units (GPUs) have evolved to massive parallel processing systems which entered the area of non-graphic related applications. Although a single processing core on the GPU is much slower and provides less functionality than its counterpart on the CPU, the huge number of these small processing entities outperforms the classical processors when the application can be parallelized. Thus, in recent years various radio astronomical projects have started to make use of this technology either to realize the correlator on this platform or to establish the post-processing pipeline with GPUs. Therefore, the feasibility of GPUs as a choice for a VLBI correlator is being investigated, including pros and cons of this technology. Additionally, a GPU based software correlator will be reviewed with respect to energy consumption/GFlop/sec and cost/GFlop/sec.

  18. Radio Astronomy and eVLBI using KAREN

    CERN Document Server

    Weston, Stuart; Gulyaev, Sergei

    2010-01-01

    Kiwi Advanced Research and Education Network (KAREN) has been used to transfer large volumes of radio astronomical data between the AUT Radio Astronomical Observatory at Warkworth, New Zealand and the international organisations with which we are collaborating and conducting observations. Here we report on the current status of connectivity and on the results of testing different data transfer protocols. We investigate new UDP protocols such as "tsunami" and UDT and demonstrate that the UDT protocol is more efficient than "tsunami" and ftp. We report on our initial steps towards real-time eVLBI and the attempt to directly stream data from the radio telescope receiving system to the correlation centre without intermediate buffering/recording.

  19. Mark 6: A Next-Generation VLBI Data System

    Science.gov (United States)

    Whitney, A. R.; Lapsley, D. E.; Taveniku, M.

    2011-07-01

    A new real-time high-data-rate disk-array system based on entirely commercial-off-the-shelf hardware components is being evaluated for possible use as a next-generation VLBI data system. The system, developed by XCube Communications of Nashua, NH, USA was originally developed for the automotive industry for testing/evaluation of autonomous driving systems that require continuous capture of an array of video cameras and automotive sensors at ~8Gbps from multiple 10GigE data links and other data sources. In order to sustain the required recording data rate, the system is designed to account for slow and/or failed disks by shifting the load to other disks as necessary in order to maintain the target data rate. The system is based on a Linux OS with some modifications to memory management and drivers in order to guarantee the timely movement of data, and the hardware/software combination is highly tuned to achieve the target data rate; data are stored in standard Linux files. A kit is also being designed that will allow existing Mark 5 disk modules to be modified to be used with the XCube system (though PATA disks will need to be replaced by SATA disks). Demonstrations of the system at Haystack Observatory and NRAO Socorro have proved very encouraging; some modest software upgrades/revisions are being made by XCube in order to meet VLBI-specific requirements. The system is easily expandable, with sustained 16 Gbps likely to be supported before end CY2011.

  20. Space VLBI Polarimetry of IDV Sources: Lessons from VSOP and Prospects for VSOP-2

    Science.gov (United States)

    Bach, U.; Krichbaum, T. P.; Bernhart, S.; Impellizzeri, C. M. V.; Kraus, A.; Fuhrmann, L.; Witzel, A.; Zensus, J. A.

    2009-08-01

    To locate and image the compact emission regions in quasars, which are closely connected to the phenomenon of IntraDay Variability (IDV), space VLBI observations are of prime importance. Here we report on VSOP observations of a prominent IDV source, the BL Lac objects S5 0716+714. To monitor their short term variability, these sources were observed with VSOP at 5 GHz in several polarisation sensitive experiments, separated in time by one day to six days, in autumn 2000. Contemporaneous flux density measurements with the Effelsberg 100 m radio telescope were used to directly compare the single dish IDV with changes of the VLBI images. A clear IDV behaviour in total intensity and linear polarization was observed in 0716+714. Analysis of the VLBI data shows that the variations are located inside the VLBI core component of 0716+714. In good agreement with the single-dish measurements, the VLBI ground array images and the VSOP images, both show a decrease in the total flux density of ˜20 mJy and a drop of ˜5 mJy in the linear polarization of the VLBI core. No variability was found in the jet. These findings are supported by VLBA observations of five IDV sources, including 0716+714, in December 2000, that show a similar behaviour. From the variability timescales we estimate a source size of a few micro-arcseconds and brightness temperatures exceeding 1015 K. Independent of whether the interpretation of the IDV seen in the VLBI core is source intrinsic or extrinsic a lower limit of TB > 2×1012 K is obtained by model fitting of the VLBI-core. Our results show that future VSOP2 observations should be accompanied by a single dish monitoring not only to discriminate between source-extrinsic (interstellar scintillation) and source-intrinsic effects but to allow also a proper calibration and interpretation of ultra-high resolution VSOP2 images.

  1. Studies of cosmic plasma using radioastron VLBI observations of giant pulses of the pulsar B0531+21

    Science.gov (United States)

    Rudnitskii, A. G.; Karuppusamy, R.; Popov, M. V.; Soglasnov, V. A.

    2016-02-01

    The structure of the interstellar plasma in the direction of the pulsar in the Crab Nebula is studied using several sets of space-VLBI observations obtained with networks of ground telescopes and the RadioAstron space antenna at 18 and 92 cm. Six observing sessions spanning two years are analyzed. Giant pulses are used to probe the cosmic plasma, making it possible to measure the scattering parameters without averaging. More than 4000 giant pulses were detected. The interferometer responses (visibility functions) on ground and ground-space baselines are analyzed. On the ground baselines, the visibility function as a function of delay is dominated by a narrow feature at zero delay with a width of δ τ ~ 1/B, where B is the receiver bandwidth. This is typical for compact continuum sources. On the ground-space baselines, the visibility function contains a set of features superposed on each other and distributed within a certain interval of delays, which we identify with the scattering time for the interfering rays τ. The amplitude of the visibility function on ground baselines falls with increasing baseline; the scattering disk is partially resolved at 18 cmand fully resolved at 92 cm. Estimates of the scattering angle ? give 0.5-1.3mas at 18 cm and 14.0 mas at 92 cm. The measured values of ? and τ are compared to estimate the distance from the source to the effective scattering screen, which is found at various epochs to be located at distances from 0.33 to 0.96 of the distance from the observer to the pulsar, about 2 kpc. The screen is close to the Crab Nebula at epochs of strong scattering, confirming that scattering on inhomogeneities in the plasma in the vicinity of the nebula itself dominates at these epochs.

  2. Implementation of high precision optical and radiometric LRO tracking data in the orbit determination to supplement the baseline S-band tracking

    Science.gov (United States)

    Mao, D.; Torrence, M. H.; Mazarico, E.; Neumann, G. A.; Smith, D. E.; Zuber, M. T.

    2016-12-01

    LRO has been in a polar lunar orbit for 7 year since it was launched in June 2009. Seven instruments are onboard LRO to perform a global and detailed geophysical, geological and geochemical mapping of the Moon, some of which have very high spatial resolution. To take full advantage of the high resolution LRO datasets from these instruments, the spacecraft orbit must be reconstructed precisely. The baseline LRO tracking was the NASA's White Sands station in New Mexico and a commercial network, the Universal Space Network (USN), providing up to 20 hours per day of almost continuous S-band radio frequency link to LRO. The USN stations produce S-band range data with a 0.4 m precision and Doppler data with a 0.8 mm/s precision. Using the S-band tracking data together with the high-resolution gravity field model from the GRAIL mission, definitive LRO orbit solutions are obtained with an accuracy of 10 m in total position and 0.5 m radially. Confirmed by the 0.50-m high-resolution NAC images from the LROC team, these orbits well represent the LRO orbit "truth". In addition to the S-band data, one-way Laser Ranging (LR) to LRO provides a unique LRO optical tracking dataset over 5 years, from June 2009 to September 2014. Ten international satellite laser ranging stations contributed over 4000 hours LR data with the 0.05 - 0.10 m normal point precision. Another set of high precision LRO tracking data is provided by the Deep Space Network (DSN), which produces radiometric tracking data more precise than the USN S-band data. In the last two years of the LRO mission, the temporal coverage of the USN data has decreased significantly. We show that LR and DSN data can be a good supplement to the baseline tracking data for the orbit reconstruction.

  3. VLBI observations of the CORALZ sample: young radio sources at low redshift

    CERN Document Server

    de Vries, N; Schilizzi, R T; Mack, K -H; Kaiser, C R

    2009-01-01

    Young radio-loud active galactic nuclei form an important tool to investigate the evolution of extragalactic radio sources. To study the early phases of expanding radio sources, we have constructed CORALZ, a sample of 25 compact ($\\theta<2"$) radio sources associated with nearby ($z<0.16$) galaxies. In this paper we determine the morphologies, linear sizes, and put first constraints on the lobe expansion speeds of the sources in the sample. We observed the radio sources from the CORALZ sample with MERLIN at 1.4 GHz or 1.6 GHz, the EVN at 1.6 GHz, and global VLBI at 1.6 GHz and/or 5.0 GHz. Radio maps, morphological classifications, and linear sizes are presented for all sources in the CORALZ sample. We have determined a first upper limit to the expansion velocity of one of the sources, which is remarkably low compared to the brighter GPS sources at higher redshifts, indicating a relation between radio luminosity and expansion speed, in agreement with analytical models. In addition we present further stro...

  4. A VLBI Resolution of the Pleiades Distance Controversy

    CERN Document Server

    Melis, Carl; Mioduszewski, Amy J; Stauffer, John R; Bower, Geoffrey C

    2014-01-01

    Because of its proximity and its youth, the Pleiades open cluster of stars has been extensively studied and serves as a cornerstone for our understanding of the physical properties of young stars. This role is called into question by the "Pleiades distance controversy" wherein the cluster distance of 120.2+/-1.5 pc as measured by the optical space astrometry mission Hipparcos is significantly different from the distance of 133.5+/-1.2 pc derived with other techniques. We present an absolute trigonometric parallax distance measurement to the Pleiades cluster that uses very long baseline radio interferometry. This distance of 136.2+/-1.2 pc is the most accurate and precise yet presented for the cluster and is incompatible with the Hipparcos distance determination. Our results cement existing astrophysical models for Pleiades-age stars.

  5. A Small-Radio-Telescope Network for VLBI

    Science.gov (United States)

    Shaffer, D. B.; Cobb, M. L.

    2004-12-01

    In the last several years, high schools, colleges, universities, and even some private amateur radio astronomers have put some 120 copies of the commercially-available Haystack Small Radio Telescope (SRT) into operation. Haystack Observatory is now working on a new version of the SRT, designed to be used in an interferometer (see paper by Vats and Rogers, this conference). We show how the new SRT, or other similar small radio telescopes, could be adapted for educational and scientific VLBI observations of continuum and OH line sources, with a relatively small additional investment. We propose that one or more large radio telescopes join a network of the small antennas, so that fringes would be readily detected between the large antenna(s) and the small antennas. An 85-foot antenna such as those at PARI or the 40-meter antenna of the Owens Valley Radio Observatory would serve nicely as a base station. Eventually, as data storage and transmission capacity continue to improve, the small antennas should be able to operate on their own. Our emphasis is on a simple, inexpensive VLBI system. The most critical item is good frequency standard. For observations at 21 or 18 cm, a rubidium standard is good enough. (Inexpensive Rb standards can be found on E-bay!) Local time at each station would come from GPS receivers which readily provide sub-microsecond timing accuracy. One-bit data sampling at rates on the order of 10 megasamples per second could be performed with a simple box interfaced to a PC via USB. Sampled data would first be recorded to the PC hard drive, and then sent on CD-ROM or DVD through the mail or by internet to a central correlation facility. Correlation and data analysis for the network would be performed on PCs as well. We suggest an observing scenario comprised of scans that are several minutes long and taken several times per hour during the apparition of a compact source. The total data for the 10-12 hours that a source is "up" for a USA network would

  6. DiFX: A Software Correlator for Very Long Baseline Interferometry Using Multiprocessor Computing Environments

    Science.gov (United States)

    Deller, A. T.; Tingay, S. J.; Bailes, M.; West, C.

    2007-03-01

    We describe the development of an FX-style correlator for very long baseline interferometry (VLBI), implemented in software and intended to run in multiprocessor computing environments, such as large clusters of commodity machines (Beowulf clusters) or computers specifically designed for high-performance computing, such as multiprocessor shared-memory machines. We outline the scientific and practical benefits for VLBI correlation, these chiefly being due to the inherent flexibility of software and the fact that the highly parallel and scalable nature of the correlation task is well suited to a multiprocessor computing environment. We suggest scientific applications where such an approach to VLBI correlation is most suited and will give the best returns. We report detailed results from the Distributed FX (DiFX) software correlator running on the Swinburne supercomputer (a Beowulf cluster of ~300 commodity processors), including measures of the performance of the system. For example, to correlate all Stokes products for a 10 antenna array with an aggregate bandwidth of 64 MHz per station, and using typical time and frequency resolution, currently requires an order of 100 desktop-class compute nodes. Due to the effect of Moore's law on commodity computing performance, the total number and cost of compute nodes required to meet a given correlation task continues to decrease rapidly with time. We show detailed comparisons between DiFX and two existing hardware-based correlators: the Australian Long Baseline Array S2 correlator and the NRAO Very Long Baseline Array correlator. In both cases, excellent agreement was found between the correlators. Finally, we describe plans for the future operation of DiFX on the Swinburne supercomputer for both astrophysical and geodetic science.

  7. The Software Correlator of the Chinese VLBI Network

    Science.gov (United States)

    Zheng, Weimin; Quan, Ying; Shu, Fengchun; Chen, Zhong; Chen, Shanshan; Wang, Weihua; Wang, Guangli

    2010-01-01

    The software correlator of the Chinese VLBI Network (CVN) has played an irreplaceable role in the CVN routine data processing, e.g., in the Chinese lunar exploration project. This correlator will be upgraded to process geodetic and astronomical observation data. In the future, with several new stations joining the network, CVN will carry out crustal movement observations, quick UT1 measurements, astrophysical observations, and deep space exploration activities. For the geodetic or astronomical observations, we need a wide-band 10-station correlator. For spacecraft tracking, a realtime and highly reliable correlator is essential. To meet the scientific and navigation requirements of CVN, two parallel software correlators in the multiprocessor environments are under development. A high speed, 10-station prototype correlator using the mixed Pthreads and MPI (Massage Passing Interface) parallel algorithm on a computer cluster platform is being developed. Another real-time software correlator for spacecraft tracking adopts the thread-parallel technology, and it runs on the SMP (Symmetric Multiple Processor) servers. Both correlators have the characteristic of flexible structure and scalability.

  8. International VLBI Service for Geodesy and Astrometry: General Meeting Proceedings

    Science.gov (United States)

    Vandenberg, Nancy R. (Editor); Baver, Karen D. (Editor)

    2002-01-01

    This volume contains the proceedings of the second General Meeting of the International VLBI Service for Geodesy and Astrometry (IVS), held in Tsukuba, Japan, February 4-7, 2002. The contents of this volume also appear on the IVS Web site at http://ivscc.gsfc.nasa.gov/publications/gm2002. The key-note of the second GM was prospectives for the future, in keeping with the re-organization of the IAG around the motivation of geodesy as 'an old science with a dynamic future' and noting that providing reference frames for Earth system science that are consistent over decades on the highest accuracy level will provide a challenging role for IVS. The goal of the meeting was to provide an interesting and informative program for a wide cross section of IVS members, including station operators, program managers, and analysts. This volume contains 72 papers and five abstracts of papers presented at the GM. The volume also includes reports about three splinter meetings held in conjunction with the GM: a mini-TOW (Technical Operations Workshop), the third IVS Analysis Workshop and a meeting of the analysis working group on geophysical modeling.

  9. The diversity of methanol maser morphologies from VLBI observations

    CERN Document Server

    Bartkiewicz, A; Van Langevelde, H J; Richards, A M S; Pihlström, Y M

    2009-01-01

    We investigate which structures the 6.7 GHz methanol masers trace in the environment of high-mass protostar candidates by observing a homogenous sample of methanol masers selected from Torun surveys. We also probed their origins by looking for associated H II regions and IR emission. We selected 30 methanol sources with improved position accuracies achieved using MERLIN and another 3 from the literature. We imaged 31 of these using the European VLBI Network's expanded array of telescopes with 5-cm (6-GHz) receivers. We used the VLA to search for 8.4 GHz radio continuum counterparts and inspected Spitzer GLIMPSE data at 3.6-8 um from the archive. High angular resolution images allowed us to analyze the morphology and kinematics of the methanol masers in great detail and verify their association with radio continuum and mid-infrared emission. A new class of "ring-like" methanol masers in star--forming regions appeared to be suprisingly common, 29 % of the sample. The new morphology strongly suggests that methan...

  10. Vienna VLBI Software VieVS - status quo and future developments

    Science.gov (United States)

    Böhm, Sigrid; Böhm, Johannes; Krásná, Hana; Madzak, Matthias; Nilsson, Tobias; Plank, Lucia; Tierno Ros, Claudia; Sun, Jing; Teke, Kamil

    2013-04-01

    The Vienna VLBI Software VieVS has been developed by the VLBI group at the Vienna University of Technology since 2008. VieVS is designed for the analysis of geodetic VLBI observation data as well as for scheduling and simulation of different VLBI sessions. The software incorporates the latest IERS Conventions and uses the concept of continuous piecewise linear offsets at integer hours for the parameter setup, consistent with the terms of reference of the GGOS. The current version, 2.0, which was released in 2012, aggregates all modules (i.e. data setup, least squares adjustment, global solution, scheduling, simulation, etc.) within one common graphical user interface. The new interface also offers additional tools to plot estimated parameters and residuals. We present the current status of the software focusing on the capabilities of release 2.0. Furthermore we give an overview of future plans and latest developments, such as the restructuring of the least squares adjustment into a scan wise update of the normal equation system which enables the analysis of sessions with a very large data volume, e.g. VLBI2010 sessions.

  11. Application of Geodetic VLBI Data to Obtaining Long-Term Light Curves for Astrophysics

    Science.gov (United States)

    Kijima, Masachika

    2010-01-01

    The long-term light curve is important to research on binary black holes and disk instability in AGNs. The light curves have been drawn mainly using single dish data provided by the University of Michigan Radio Observatory and the Metsahovi Radio Observatory. Hence, thus far, we have to research on limited sources. I attempt to draw light curves using VLBI data for those sources that have not been monitored by any observatories with single dish. I developed software, analyzed all geodetic VLBI data available at the IVS Data Centers, and drew the light curves at 8 GHz. In this report, I show the tentative results for two AGNs. I compared two light curves of 4C39.25, which were drawn based on single dish data and on VLBI data. I confirmed that the two light curves were consistent. Furthermore, I succeeded in drawing the light curve of 0454-234 with VLBI data, which has not been monitored by any observatory with single dish. In this report, I suggest that the geodetic VLBI archive data is useful to obtain the long-term light curves at radio bands for astrophysics.

  12. Space VLBI polarimetry of IDV sources: Lessons from VSOP and prospects for VSOP2

    CERN Document Server

    Bach, U; Bernhart, S; Impellizzeri, C M V; Kraus, A; Fuhrmann, L; Witzel, A; Zensus, J A

    2008-01-01

    To locate and image the compact emission regions in quasars, which are closely connected to the phenomenon of IntraDay Variability (IDV), space VLBI observations are of prime importance. Here we report on VSOP observations of two prominent IDV sources, the BL Lac objects S5 0716+714. To monitor their short term variability, these sources were observed with VSOP at 5 GHz in several polarisation sensitive experiments, separated in time by one day to six days, in autumn 2000. Contemporaneous flux density measurements with the Effelsberg 100m radio telescope were used to directly compare the single dish IDV with changes of the VLBI images. A clear IDV behaviour in total intensity and linear polarization was observed in 0716+714. Analysis of the VLBI data shows that the variations are located inside the VLBI core component of 0716+714. In good agreement with the single-dish measurements, the VLBI ground array images and the VSOP images, both show a decrease in the total flux density of ~20 mJy and a drop of ~5 mJy...

  13. Impact of Baseline Angiographic Complexities Determined by Coronary Artery Bypass Grafting SYNTAX Score on the Prediction of Outcome After Percutaneous Coronary Intervention.

    Science.gov (United States)

    Nakahashi, Takuya; Sakata, Kenji; Nomura, Akihiro; Yakuta, Yohei; Gamou, Tadatsugu; Terai, Hidenobu; Horita, Yuki; Ikeda, Masatoshi; Namura, Masanobu; Takamura, Masayuki; Kawashiri, Masa-Aki; Yamagishi, Masakazu; Hayashi, Kenshi

    2016-10-01

    Although Synergy Between Percutaneous Coronary Intervention With Taxus and Cardiac Surgery (SYNTAX) score based on angiographic scoring system was developed in patients with previous coronary artery bypass grafting (CABG), few data exist regarding its prognostic utility in patients undergoing percutaneous coronary intervention (PCI). We examined 272 patients with previous CABG (217 men; mean age, 70.4 ± 9.7 years) undergoing PCI. Severity of the coronary anatomy was evaluated using CABG-SYNTAX score. The primary end point of this study was cardiovascular death. The baseline CABG-SYNTAX score ranged from 2 to 53.5, with an average of 26.0 ± 10.2. In the index procedures, PCI for the native coronary accounted for nearly all patients (88%). During follow-up (median 4.1 years), 40 cardiovascular deaths had occurred. In multivariate analysis, age >75 years (hazard ratio [HR] 2.82, 95% CI 1.45 to 5.52), left ventricular ejection fraction SYNTAX score >25 (HR 2.37, 95% CI 1.19 to 5.05) were independent predictors of cardiovascular death. After creating a composite risk score in consideration of identified predictors, the freedom from cardiovascular death at 5 years was 98%, 86%, and 58% in the low (0 to 1), medium (2), and high (3 to 5) scores, respectively (p SYNTAX and composite risk scores were 0.66 and 0.77, respectively (p <0.05). In conclusion, the combination of angiographic and clinical characteristics is useful for risk stratification in patients with previous CABG undergoing PCI.

  14. Observation of the Earth's nutation by the VLBI: how accurate is the geophysical signal

    Science.gov (United States)

    Gattano, César; Lambert, Sébastien B.; Bizouard, Christian

    2016-09-01

    We compare nutation time series determined by several International VLBI Service for geodesy and astrometry (IVS) analysis centers. These series were made available through the International Earth Rotation and Reference Systems Service (IERS). We adjust the amplitudes of the main nutations, including the free motion associated with the free core nutation (FCN). Then, we discuss the results in terms of physics of the Earth's interior. We find consistent FCN signals in all of the time series, and we provide corrections to IAU 2000A series for a number of nutation terms with realistic errors. It appears that the analysis configuration or the software packages used by each analysis center introduce an error comparable to the amplitude of the prominent corrections. We show that the inconsistencies between series have significant consequences on our understanding of the Earth's deep interior, especially for the free inner core resonance: they induce an uncertainty on the FCN period of about 0.5 day, and on the free inner core nutation (FICN) period of more than 1000 days, comparable to the estimated period itself. Though the FCN parameters are not so much affected, a 100 % error shows up for the FICN parameters and prevents from geophysical conclusions.

  15. VLBI observations of helical jets: hints on the nature of radio-jets

    CERN Document Server

    Perucho, M; Lobanov, A P; Agudo, I; Marti-Vidal, I

    2013-01-01

    We make use of VLBI observations of the radio jet in the quasar S5 0836+710 at different frequencies and epochs to study its properties. The jet shows helical structure at all frequencies. The ridge-line of the emission in the jet coincides at all frequencies and epochs, within the errors. We conclude that the helicity is a real, physical structure. Small differences between epochs reveal wave-like motion of the ridge-line transversal to the jet propagation axis. These transversal motions are measured to be superluminal. This unphysical result could correspond to a possible small amplitude oscillation of the ridge-line at the radio-core and to large errors in the determination of the positions. In addition, higher resolution images at 15 GHz show that the ridge-line does not coincide exactly with the centre of the radio jet. At arc-second scales, this powerful jet shows non-collimated, irregular structure and a lack of a hot-spot. Following this collection of evidence, we conclude that the ridge-line could be...

  16. European VLBI Network imaging of 6.7 GHz methanol masers

    CERN Document Server

    Bartkiewicz, Anna; van Langevelde, Huib J

    2016-01-01

    Methanol masers at 6.7 GHz are well known tracers of high-mass star-forming regions. However, their origin is still not clearly understood. We aimed to determine the morphology and velocity structure for a large sample of the maser emission with generally lower peak flux densities than those in previous surveys. Using the European VLBI Network we imaged the remaining sources (17) from a sample of sources that were selected from the unbiased survey using the Torun 32 m dish. Together they form a database of a total of 63 source images with high sensitivity, milliarcsecond angular resolution and very good spectral resolution for detailed studies. We studied in detail the properties of the maser clouds and calculated the mean and median values of the projected size (17.4 au and 5.5 au, respectively) as well as the FWHM of the line (0.373 km s$^{-1}$ and 0.315 km s$^{-1}$ for the mean and median values, respectively), testing whether it was consistent with Gaussian profile. We also found maser clouds with velocit...

  17. Observation of the Earth's nutation by the VLBI: how accurate is the geophysical signal

    Science.gov (United States)

    Gattano, César; Lambert, Sébastien B.; Bizouard, Christian

    2017-07-01

    We compare nutation time series determined by several International VLBI Service for geodesy and astrometry (IVS) analysis centers. These series were made available through the International Earth Rotation and Reference Systems Service (IERS). We adjust the amplitudes of the main nutations, including the free motion associated with the free core nutation (FCN). Then, we discuss the results in terms of physics of the Earth's interior. We find consistent FCN signals in all of the time series, and we provide corrections to IAU 2000A series for a number of nutation terms with realistic errors. It appears that the analysis configuration or the software packages used by each analysis center introduce an error comparable to the amplitude of the prominent corrections. We show that the inconsistencies between series have significant consequences on our understanding of the Earth's deep interior, especially for the free inner core resonance: they induce an uncertainty on the FCN period of about 0.5 day, and on the free inner core nutation (FICN) period of more than 1000 days, comparable to the estimated period itself. Though the FCN parameters are not so much affected, a 100 % error shows up for the FICN parameters and prevents from geophysical conclusions.

  18. 5 year Global 3-mm VLBI survey of Gamma-ray active blazars

    CERN Document Server

    Hodgson, J A; Marscher, A P; Jorstad, S G; Marti-Vidal, I; Lindqvist, M; Bremer, M; Sanchez, S; de Vicente, P; Zensus, J A

    2015-01-01

    The Global mm-VLBI Array (GMVA) is a network of 14 3\\,mm and 7\\,mm capable telescopes spanning Europe and the United States, with planned extensions to Asia. The array is capable of sensitive maps with angular resolution often exceeding 50\\,$\\mu$as. Using the GMVA, a large sample of prominent $\\gamma$-ray blazars have been observed approximately 6 monthly from later 2008 until now. Combining 3\\,mm maps from the GMVA with near-in-time 7\\,mm maps from the VLBA-BU-BLAZAR program and 2\\,cm maps from the MOJAVE program, we determine the sub-pc morphology and high frequency spectral structure of $\\gamma$-ray blazars. The magnetic field strength can be estimated at different locations along the jet under the assumption of equipartition between magnetic field and relativistic particle energies. Making assumptions on the jet magnetic field configuration (e.g. poloidal or toroidal), we can estimate the separation of the mm-wave "core" and the jet base, and estimate the strength of the magnetic field there. The results ...

  19. 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy $\\rm \\gamma$-ray state in 2012

    CERN Document Server

    Akiyama, Kazunori; Fish, Vincent L; Doeleman, Sheperd S; Broderick, Avery E; Dexter, Jason; Hada, Kazuhiro; Kino, Motoki; Nagai, Hiroshi; Honma, Mareki; Johnson, Michael D; Algaba, Juan C; Asada, Keiichi; Brinkerink, Christiaan; Blundell, Ray; Bower, Geoffrey C; Cappallo, Roger; Crew, Geoffrey B; Dexter, Matt; Dzib, Sergio A; Freund, Robert; Friberg, Per; Gurwell, Mark; Ho, Paul T P; Inoue, Makoto; Krichbaum, Thomas P; Loinard, Laurent; MacMahon, David; Marrone, Daniel P; Moran, James M; Nakamura, Masanori; Nagar, Neil M; Ortiz-Leon, Gisela; Plambeck, Richard; Pradel, Nicolas; Primiani, Rurik A; Rogers, Alan E E; Roy, Alan L; SooHoo, Jason; Tavares, Jonathan-Leon; Tilanus, Remo P J; Titus, Michael; Wagner, Jan; Weintroub, Jonathan; Yamaguchi, Paul; Young, Ken H; Zensus, Anton; Ziurys, Lucy M

    2015-01-01

    We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona and Cedar Flat in California. For the first time, we have acquired 230 GHz VLBI interferometric phase information on M87 through measurement of closure phase on the triangle of long baselines. Most of the measured closure phases are consistent with 0$^{\\circ}$ as expected by physically-motivated models for 230 GHz structure such as jet models and accretion disk models. The brightness temperature of the event-horizon-scale structure is $\\sim 1 \\times 10^{10}$ K derived from the compact flux density of $\\sim 1$ Jy and the angular size of $\\sim 40 $ $\\rm \\mu$as $\\sim$ 5.5 $R_{{\\rm s}}$, which is broadly consistent with the peak brightness of the radio cores at 1-86 GHz located within $\\sim 10^2$ $R_{{\\rm s}}$. Our observations occurred in the middle of an enhancement in very-high-energy (VHE) $\\rm \\gamma$-ray flux, presumably originating in the vicinity of the centr...

  20. mm-VLBI Observations of the Active Galaxy 3C 111 in Outburst

    CERN Document Server

    Schulz, Robert; Ros, Eduardo; Krichbaum, Thomas P; Großberger, Christoph; Müller, Cornelia; Mannheim, Karl; Agudo, Iván; Aller, Hugh D; Aller, Margo F

    2013-01-01

    The broad-line radio galaxy 3C 111 exhibited a major flux density outburst in 2007. Here, we present imaging and preliminary kinematic results of the jet, based on three millimetre-VLBI observations at 86 GHz using the Global Millimeter VLBI Array (GMVA) covering one year just after the radio flare. The GMVA data allow us to study this outburst with unprecedented image fidelity at highest (sub-parsec) resolution. On these scales, the outburst is resolved into a complex series of plasma components forming an intriguing bent structure. Within 1 mas from the jet base, ejections vary in position angle and components move with an apparent velocity of ~3.7 c, significantly slower than the maximum velocity observed with cm-VLBI on scales beyond 1 mas.

  1. Acceleration Term at ASL FRING as a Tool to Improve Space VLBI Sensitivity

    Science.gov (United States)

    Kogan, L.; Likhachev, S.; Girin, I.; Ladygin, V.

    2009-08-01

    Astro Space Locator (ASL) a new postcorrelation software has been created recently in Astro Space Center (ASC), Russia. This software is created specifically for space VLBI project such as Radioastron and VSOP. The delay for the ground based VLBI traditionally comprised of two terms: initial delay and its rate of change in time. For space VLBI, taking into account the third term (acceleration) can be required because the satellite orbit may not be known with such a high accuracy as rotation of the Earth. The ASL software solves for all three parameters: delay, fringe rate, and acceleration. In this paper we test this algorithm and demonstrate the advantage of taking into account the acceleration term.

  2. VLBI Observations of the Blazar 1611+343 at 5 GHz

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The gamma-ray blazar 1611+343 was observed with polarization VLBI mode at 5 GHz in February 1999. The total intensity (I) VLBI image of the source shows a core-jet structure. The jet bends eastward at ~ 3 mas south of the core.Four components have been detected from results of fitting, with apparent speeds estimated at 6.7 ±- 0.7, 2.5 ±- 0.3, 4.5 ± 0.5 h-1c for three jet components (taking Ho = 100 h km s- 1 Mpc-1, q0 = 0.5). The polarization (P) VLBI image of 1611±343 displays the polarized configuration in the jet. The mechanism of the curved jet is discussed.

  3. Proceedings of the Sixth General Meeting of the International VLBI Service for Geodesy and Astrometry

    Science.gov (United States)

    Behrend, Dirk (Editor); Baver, Karen D. (Editor)

    2010-01-01

    This volume is the proceedings of the sixth General Meeting of the International VLBI Service for Geodesy and Astrometry (IVS), held in Hobart, Tasmania, Australia, February 7-13, 2010. The contents of this volume also appear on the IVS Web site at http://ivscc.gsfc.nasa.gov/publications/gm2010. The keynote of the sixth GM was the new perspectives of the next generation VLBI system under the theme "VLBI2010: From Vision to Reality". The goal of the meeting was to provide an interesting and informative program for a wide cross-section of IVS members, including station operators, program managers, and analysts. This volume contains 88 papers. All papers were edited by the editors for usage of the English language, form, and minor content-related issues.

  4. Radioecologycal study of 239/240Pu in Bangka Island and Muria Peninsula: Determination of 239/240Pu in marine sediment and seawater as part of baseline data collecting for sitting of candidates of first Indonesia NPP

    Science.gov (United States)

    Suseno, Heny; Wisnubroto, Djarot S.

    2014-03-01

    Radioisotope Pu-239/240 are alpha emitting nuclides important indicators of radioactive contamination of the marine environment. Global fallout is the main source of plutonium in the marine environment. There are very limited study on 239/240Pu in Indonesia coastal environments. The data of this radioisotopes is needed for baseline data of nuclear power plant (NPP) site candidates both in Bangka Island and Muria Peninsula. Bottom sediments play an important role in radioecological studies of the marine environment because a large proportion of radioactive substances entering the sea is adsorbed over time onto suspended particulate matter and deposited in sediments. Plutonium is particle reactive and deposited in marine sediment. Radioisotope 239/240Pu was determinated by alpha spectrometry after radiochemical procedure that was performed in both water and marine sediment from Bangka Island and Muria Peninsula. The sediment baseline of concentration 239/240Pu in Bangka Island and Muria Peninsula were range from 0.013 to 0.021 Bq.kg-1 and 0.018 to 0.024 Bq.kg-1 respectively. The water baseline concentration this isotope were range from 2.73 to 4.05 mBq.m-3 and 2.98 to 4.50 mBq.m-3.

  5. Radioecologycal study of {sup 239/240}Pu in Bangka Island and Muria Peninsula: Determination of {sup 239/240}Pu in marine sediment and seawater as part of baseline data collecting for sitting of candidates of first Indonesia NPP

    Energy Technology Data Exchange (ETDEWEB)

    Suseno, Heny, E-mail: henis@batan.go.id [Radioactive Waste Technology Center - The Indonesian National Nuclear Energy Agency (Indonesia); Wisnubroto, Djarot S. [The Indonesian National Nuclear Energy Agency (Indonesia)

    2014-03-24

    Radioisotope Pu-239/240 are alpha emitting nuclides important indicators of radioactive contamination of the marine environment. Global fallout is the main source of plutonium in the marine environment. There are very limited study on {sup 239/240}Pu in Indonesia coastal environments. The data of this radioisotopes is needed for baseline data of nuclear power plant (NPP) site candidates both in Bangka Island and Muria Peninsula. Bottom sediments play an important role in radioecological studies of the marine environment because a large proportion of radioactive substances entering the sea is adsorbed over time onto suspended particulate matter and deposited in sediments. Plutonium is particle reactive and deposited in marine sediment. Radioisotope {sup 239/240}Pu was determinated by alpha spectrometry after radiochemical procedure that was performed in both water and marine sediment from Bangka Island and Muria Peninsula. The sediment baseline of concentration {sup 239/240}Pu in Bangka Island and Muria Peninsula were range from 0.013 to 0.021 Bq.kg{sup −1} and 0.018 to 0.024 Bq.kg{sup −1} respectively. The water baseline concentration this isotope were range from 2.73 to 4.05 mBq.m{sup −3} and 2.98 to 4.50 mBq.m{sup −3}.

  6. The Fresnel-Fizeau effect and the atmospheric time delay in geodetic VLBI

    CERN Document Server

    M., Kopeikin S

    2015-01-01

    The Fresnel-Fizeau effect is a special relativistic effect that makes the speed of light dependent on the velocity of a transparent, moving medium. We present a theoretical formalism for discussing propagation of electromagnetic signals through the moving Earth atmosphere with taking into account the Fresnel-Fizeau effect. It provides the rigorous relativistic derivation of the atmospheric time delay equation in the consensus model of geodetic VLBI observations which was never published before. The paper confirms the atmospheric time delay of the consensus VLBI model used in IERS Standards, and provides a firm theoretical basis for calculation of even more subtle relativistic corrections.

  7. EVN e-VLBI detections of MAXI J1659-152

    Science.gov (United States)

    Paragi, Z.; van der Horst, A. J.; Granot, J.; Taylor, G. B.; Kouveliotou, C.; Garrett, M. A.; Wijers, R. A. M. J.; Ramirez-Ruiz, E.; Kuulkers, E.; Gehrels, N.; Woods, P. M.

    2010-10-01

    We observed MAXI J1659-152 (Negoro et al. 2010, ATel #2873; Mangano et al. 2010, GCN #11296) following its sub-millimeter and centimeter radio detections (de Ugarte Postigo et al. 2010, GCN #11304; van der Horst et al. 2010, ATel #2874) with the European VLBI Network (EVN) in real-time e-VLBI mode on 30 September 2010, from 13:30 to 18:30 UT at 4.9 GHz. The participating telescopes were Cambridge, Effelsberg, Jodrell Bank (MkII), Hartebeesthoek, Medicina, Onsala, Torun and Westerbork sending data at a rate of ~1024 Mbps to the EVN Data Processor at JIVE.

  8. Intercomparison Study of Time and Frequency Transfer between VLBI and Other Techniques (GPS, ETS8(TCE), TW(DPN) and DMTD)

    CERN Document Server

    Takiguchi, Hiroshi; Kondo, Tetsuro; Ishii, Atsutoshi; Thomas, Hobiger; Ichikawa, Ryuichi; Koyama, Yasuhiro; Takahashi, Yasuhiro; Nakagawa, Fumimaru; Nakamura, Maho; Tabuchi, Ryo; Tsutshiya, Shigeru; Hama, Shinichi; Gotoh, Tadahiro; Fujieda, Miho; Aida, Masanori; Li, Tingyu; Amagai, Jun

    2011-01-01

    We carried out the intercomparison experiments between VLBI and other techniques to show the capability of VLBI time and frequency transfer by using the current geodetic VLBI technique and facilities as the summary of the experiments that we carried out since 2007. The results from the two different types of experiments show that the VLBI is more stable than GPS but is slightly noisier than two new two-way techniques (TW(DPN), ETS8(TCE)), and VLBI can measure the correct time difference as same as ETS8(TCE).

  9. Positioning Reduction of Deep Space Probes Based on VLBI Tracking%深空探测器VLBI跟踪定位归算

    Institute of Scientific and Technical Information of China (English)

    乔书波

    2011-01-01

    以我国嫦娥工程、萤火计划等深空探测计划为背景,通过理论分析、方法研究、软件研发、仿真检验和实测资料解析等,完成了基于VLBI、USB跟踪对欧空局Smart-1环月卫星和火星快车(MEX)卫星,以及我国嫦娥一号(CE-1)、嫦娥二号(CE-2)等卫星的定位归算;在理论模型研究、误差方程建立、法方程条件分析、约束方程选取、仿真数据检验、观测野值规避、参数解算稳定性的保障、实用软件编制和实测资料处理等方面均获得了进展.%In the background of the Chinese Lunar Exploration Project and the Yinghuo Project, through theoretical analysis, algorithm study, software development, data simulation, real data processing and so on, the positioning reductions of the European lunar satellite Smart-1 and Mars Express (MEX) satellite, as well as the Chinese Chang'e-1 (CE-1) and Chang'e-2 (CE-2) satellites are accomplished by using VLBI and USB tracking data in this dissertation. The progress is made in various aspects including the development of theoretical model, the construction of observation equation, the analysis of the condition of normal equation, the selection and determination of the constraint, the analysis of data simulation, the detection of outliers in observations, the maintenance of the stability of the solution of parameters, the development of the practical software system, the processing of the real tracking data and so on. The details of the research progress in this dissertation are written as follows:(1) The algorithm is analyzed concerning the positioning reduction of the deep space-craft based on VLBI tracking data. Through data simulation, it is analyzed for the effects of the bias in predicted orbit, the white noises and systematic errors in VLBI delays, and USB ranges on the positioning reduction of spacecraft. Results show that it is preferable to suppress the dispersion of positioning data points by applying the constraint of

  10. Magic Baseline Beta Beam

    CERN Document Server

    Agarwalla, Sanjib Kumar; Raychaudhuri, Amitava

    2007-01-01

    We study the physics reach of an experiment where neutrinos produced in a beta-beam facility at CERN are observed in a large magnetized iron calorimeter (ICAL) at the India-based Neutrino Observatory (INO). The CERN-INO distance is close to the so-called "magic" baseline which helps evade some of the parameter degeneracies and allows for a better measurement of the neutrino mass hierarchy and $\\theta_{13}$.

  11. Rationing with baselines

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Moreno-Ternero, Juan D.; Østerdal, Lars Peter Raahave

    2013-01-01

    We introduce a new operator for general rationing problems in which, besides conflicting claims, individual baselines play an important role in the rationing process. The operator builds onto ideas of composition, which are not only frequent in rationing, but also in related problems...... such as bargaining, choice, and queuing. We characterize the operator and show how it preserves some standard axioms in the literature on rationing. We also relate it to recent contributions in such literature....

  12. The TDAQ Baseline Architecture

    CERN Multimedia

    Wickens, F J

    The Trigger-DAQ community is currently busy preparing material for the DAQ, HLT and DCS TDR. Over the last few weeks a very important step has been a series of meetings to complete agreement on the baseline architecture. An overview of the architecture indicating some of the main parameters is shown in figure 1. As reported at the ATLAS Plenary during the February ATLAS week, the main area where the baseline had not yet been agreed was around the Read-Out System (ROS) and details in the DataFlow. The agreed architecture has: Read-Out Links (ROLs) from the RODs using S-Link; Read-Out Buffers (ROB) sited near the RODs, mounted in a chassis - today assumed to be a PC, using PCI bus at least for configuration, control and monitoring. The baseline assumes data aggregation, in the ROB and/or at the output (which could either be over a bus or in the network). Optimization of the data aggregation will be made in the coming months, but the current model has each ROB card receiving input from 4 ROLs, and 3 such c...

  13. 建设中的深空测控网甚长基线干涉测量系统%Development of a VLBI System for China's Deep Space Network

    Institute of Scientific and Technical Information of China (English)

    郝万宏; 李海涛; 黄磊; 王宏; 樊敏

    2012-01-01

    In view of relevant CCSDS (Consultative Committee for Space Data Systems) recommendations, this paper describes the VLBI (Very Long Baseline Interferometry) system of China's deep space network, which is under development at the moment, including its system definition and performance requirements, system design and implementation and its design principles and strategies. For a quasar, the delay is determined by correlation of the results of the received signals of two ground stations. For a spacecraft, the delay is determined with a single station by extracting the phases, using a differential method. Finally, the performance of inter-agency cross support with ESA is analyzed.%结合CCSDS(空间数据系统咨询委员会)给出的相关技术标准,介绍了我国目前正在建设的深空测控网甚长基线干涉测量系统,包括系统定义与性能需求,系统的设计与实现等方面.阐述了相关的设计原则和设计思路:对射电源信号,通过将2个测站接收到的同一射电源信号进行互相关的方式求取信号延迟; 对航天器信号,利用对正弦信号的统计处理方法,对正弦相位进行估计再差分求取时延.最后简要分析了与欧空局开展机构间交互支持的性能指标.

  14. SDSSJ143244.91+301435.3 at VLBI: a compact radio galaxy in a narrow-line Seyfert 1

    CERN Document Server

    Caccianiga, A; Anton, S; Ballo, L; Berton, M; Mack, K -H; Paulino-Afonso, A

    2016-01-01

    We present VLBI observations, carried out with the European Very Long Baseline Interferometry Network (EVN), of SDSSJ143244.91+301435.3, a radio-loud narrow-line Seyfert 1 (RLNLS1) characterized by a steep radio spectrum. The source, compact at Very Large Array (VLA) resolution, is resolved on the milliarcsec scale, showing a central region plus two extended structures. The relatively high brightness temperature of all components (5x10^6-1.3x10^8 K) supports the hypothesis that the radio emission is non-thermal and likely produced by a relativistic jet and/or small radio lobes. The observed radio morphology, the lack of a significant core and the presence of a low frequency (230 MHz) spectral turnover are reminiscent of the Compact Steep Spectrum sources (CSS). However, the linear size of the source (~0.5kpc) measured from the EVN map is lower than the value predicted using the turnover/size relation valid for CSS sources (~6kpc). This discrepancy can be explained by an additional component not detected in ou...

  15. Parallax of a Mira variable R Ursae Majoris studied with astrometric VLBI

    CERN Document Server

    Nakagawa, Akiharu; Matsui, Makoto; Omodaka, Toshihiro; Honma, Mareki; Shibata, Katsunori M; Sato, Katsuhisa; Jike, Takaaki

    2016-01-01

    We have measured an annual parallax of the Mira variable R~Ursae~Majoris (R~UMa) with the VLBI exploration for Radio Astronomy (VERA). From the monitoring VLBI observations spanning about two years, we detected H$_2$O maser spots in the LSR velocities ranges from 37 to 42 km\\,s$^{-1}$. We derived an annual parallax of 1.97$\\pm$0.05\\,mas, and it gives a corresponding distance of 508$\\pm$13\\,pc. The VLBI maps revealed 72 maser spots distributed in $\\sim$110 au area around an expected stellar position. Circumstellar kinematics of the maser spots were also revealed by subtracting a systemic motion in the Hipparcos catalog from proper motions of each maser spots derived from our VLBI observations. Infrared photometry is also conducted to measure a $K$ band apparent magnitude, and we obtained a mean magnitude of $m_K$ = 1.19$\\pm$0.02\\,mag. Using the trigonometric distance, the $m_K$ is converted to a $K$ band absolute magnitude of $M_K = -$7.34$\\pm$0.06\\,mag. This result gives a much more accurate absolute magnitud...

  16. Status quo and future plans for the Vienna VLBI Software (VieVS)

    Science.gov (United States)

    Mayer, David; Böhm, Johannes; Böhm, Sigrid; Choliy, Vasyl; Hellerschmied, Andreas; Hofmeister, Armin; Karbon, Maria; Krasna, Hana; McCallum, Jamie; Madzak, Matthias; Nilsson, Tobias; Plank, Lucia; Shabala, Stas; Soja, Benedikt; Sun, Jing; Teke, Kamil

    2014-05-01

    The Vienna VLBI Software (VieVS) has been developed by the VLBI group at the Vienna University of Technology since 2008, and in recent years important contributions have been made by other groups all over the world. The software is written in Matlab which makes it easy for students to get an insight in VLBI processing and which allows short and concise source code. The current version 2.1 of VieVS has improved capabilities in terms of the global solution and the graphical user interface compared to earlier releases. Furthermore, more sophisticated approaches are now available in terms of scheduling VLBI sessions. Presently, we are working on the new version 2.2 which will be released this summer and which will be presented at the 5th VieVS User-Workshop in September 2014. For example, it will be equipped with a source structure simulator, as well as more refined possibilities for scheduling and the global solution. In a test version, we will also provide a graphical user interface built with Qt instead of Matlab.

  17. VLBI, MERLIN and HST observations of the giant radio galaxy 3C 236

    NARCIS (Netherlands)

    Schilizzi, RT; Tian, WW; Conway, JE; Nan, R; Miley, GK; Barthel, PD; Normandeau, M; Dallacasa, D; Gurvits, LI

    2001-01-01

    We present VLBI and MERLIN data at 1.66 and 4.99 GHz on the central component coincident with the nucleus of the giant radio galaxy, 3C 236. The nuclear radio structure is composed of two complexes of emission which are resolved on scales from 1 milli-arcsec (mas) to 1 arcsec. Oscillations with an a

  18. Status and future plans for the Vienna VLBI Software VieVS

    Science.gov (United States)

    Nilsson, T.; Böhm, J.; Böhm, S.; Madzak, M.; Nafisi, V.; Plank, L.; Spicakova, H.; Sun, J.; Tierno Ros, C.; Schuh, H.

    2011-07-01

    The Vienna VLBI Software (VieVS) is a new VLBI analysis software which has been developed at the Institute of Geodesy and Geophysics of the Vienna University of Technology since 2008. In this software, which is written in Matlab, the most recent IERS Conventions and are implemented, and through a graphical user interface it is easy to use. Lately, two new modules have been added to the official version of VieVS. One is a simulation module (VIE_SIM) which allows to create simulated VLBI observations. The other is a global solution module (VIE_GLOB) which can be used for combining several sessions in a global solution in order to derive e.g. a terrestrial and/or a celestial reference frame. In this presentation an overview of VieVS and its current status will be given and its performance will be demonstrated by showing selected results. We also discuss the planned future developments of VieVS. These include the possibility to use external tropospheric delays obtained, e.g. by ray-tracing through numerical weather models, to use external ionospheric corrections from, e.g. GNSS TEC maps, and to implement a Kalman filter solution. We also plan to cover earlier steps in the VLBI data processing chain, like ambiguity resolution, which have not been considered so far in VieVS.

  19. Design and baseline characteristics of a prospective cohort study for determinants of osteoporotic fracture in community-dwelling elderly Japanese men: the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN Study

    Directory of Open Access Journals (Sweden)

    Moon Jong-Seong

    2009-12-01

    Full Text Available Abstract Background Osteoporosis and osteoporotic fracture in men are significant public health problems in an aging society. However, information on male osteoporosis remains impressively lacking, especially for Asians. We designed the Fujiwara-kyo Osteoporosis Risk in Men (FORMEN study as an ancillary study of a cohort study, the Fujiwara-kyo study, to determine risk factors for osteoporotic fractures in Japanese men. Methods/Design Design: A community-based single-centre prospective cohort study with at least a 5-year follow-up Subjects: All the male participants of the Fujiwara-kyo study who were living in the four cities studied, aged 65 years and older, and able to walk without aid from others. Primary outcome: Incidence of osteoporotic fractures including vertebral and clinical non-vertebral fractures. Additional outcomes: Change in bone mineral density (BMD, change in hip geometry, onset of receiving benefits from Long-term Care Insurance (LCI, health-related quality of life, and mortality. Baseline measurements: BMD at the lumbar spine (LS and hip (TH, hip geometry, vertebral deformity assessment, bone turnover markers, physical and cognitive performance, various medical and lifestyle factors, and geriatric psychosocial measures confirmed by interviews based on self-administrated questionnaires. Outcome surveillance: Annual mail surveys and a follow-up survey at the fifth year comprising similar items to the baseline study will be used to determine the outcomes. Receipt of benefits from LCI and mortality will be obtained from the city governments. Current status: The baseline study was conducted for 2174 eligible men, and 2012 completed the study and were eligible for follow-up. Prevalence rates of osteoporosis (BMD 2.5 SD or more below the young adult mean (YAM and low BMD (BMD 1 SD or more below YAM in at least one of LS and TH were calculated to be 4.4% and 41.8%, respectively. The proportion of men with low BMD only at TH showed a

  20. The Improvement of a VLBI Monitoring System%VLBI监控系统的改进∗

    Institute of Scientific and Technical Information of China (English)

    杨文军; 赵融冰; 聂俊

    2015-01-01

    对Mark5B监控系统软件的设计思想、软件功能、通讯机制等几个方面作了介绍。 Mark5B记录系统是当今世界VLBI观测台站中广泛使用的最为先进的记录系统之一,也是VLBI终端系统的重要组成部分。研制Mark5B监控系统软件的主要目的是进一步提高VLBI终端记录系统的可靠性,保障VLBI联测数据有效和高质量。该软件是在Qt开发环境下采用signals/slots的安全类型机制,并在Qt creator IDE上设计图形界面,完成数据采集和网络通信工作。 Mark5B监控系统不仅适用于VLBI天体物理测量观测、 VLBI测地观测,而且适用于中国VLBI网( The Chinese VLBI Network, CVN)联测。%In this paper we mainly discuss the design ideas, functions, communication mechanisms, and related issues of the software of a Mark5B monitoring system, which incorporates a Mark5B recording system. Mark5B recording systems are currently widely used in astronomical observation stations around the world. Mark5B recording systems are among the most advanced terminal recording systems, A Mark5B recording system is an important part of a VLBI terminal system. Our main purpose of developing the software of a Mark5B monitoring system is to improve the reliability of a VLBI terminal system, i. e. to ensure the effectiveness and high quality of VLBI measurement data. The software is designed under the Qt-based development environment and uses the signals/slots as a secure communication mechanism. The graphical interfaces of the software were designed in the Qt Creator IDE. The data collections and network communications of the software are realized in the Qt Creator IDE as well. The Mark5B monitoring system with the software is suitable not only for astrophysical observations but also for VLBI geodetic surveys. The software will be used in the Chinese VLBI Network stations other than the Xinjiang Astronomical Observatory.

  1. Radio emission of SN1993J: the complete picture. I. Re-analysis of all the available VLBI data

    Science.gov (United States)

    Martí-Vidal, I.; Marcaide, J. M.; Alberdi, A.; Guirado, J. C.; Pérez-Torres, M. A.; Ros, E.

    2011-02-01

    We have performed a complete re-calibration and re-analysis of all the available Very-Long-Baseline-Interferometry (VLBI) observations of supernova SN1993J, following an homogeneous and well-defined methodology. VLBI observations of SN1993J at 69 epochs, spanning 13 years, were performed by two teams, which used different strategies and analysis tools. The results obtained by each group are similar, but their conclusions on the supernova expansion and the shape and evolution of the emitting region differ significantly. From our analysis of the combined set of observations, we have obtained an expansion curve with unprecedented time resolution and coverage. We find that the data from both teams are compatible when analyzed with the same methodology. One expansion index (m3 = 0.87 ± 0.02) is enough to model the expansion observed at 1.7 GHz, while two expansion indices (m1 = 0.933 ± 0.010 and m2 = 0.796 ± 0.005), separated by a break time, tbr = 390 ± 30 days, are needed to model the data, at frequencies higher than 1.7 GHz, up to day ~4000 after explosion. We thus confirm the wavelength dependence of the size of the emitting region reported by one of the groups. We also find that all sizes measured at epochs later than day ~4000 after explosion are systematically smaller than our model predictions (i.e., an additional expansion index might be needed to properly model these data). We also estimate the fractional shell width (0.31 ± 0.02, average of all epochs and frequencies) and the level of opacity to the radio emission by the ejecta. We find evidence of a spectral-index radial gradient in the supernova shell, which is indicative of a frequency-dependent ejecta opacity. Finally, we study the distribution and evolution of the azimuthal anisotropies (hot spots) found around the radio shell during the expansion. These anisotropies have intensities of ~20% of the mean flux density of the shell, and appear to systematically evolve during the expansion.

  2. TAPIR--Finnish national geochemical baseline database.

    Science.gov (United States)

    Jarva, Jaana; Tarvainen, Timo; Reinikainen, Jussi; Eklund, Mikael

    2010-09-15

    In Finland, a Government Decree on the Assessment of Soil Contamination and Remediation Needs has generated a need for reliable and readily accessible data on geochemical baseline concentrations in Finnish soils. According to the Decree, baseline concentrations, referring both to the natural geological background concentrations and the diffuse anthropogenic input of substances, shall be taken into account in the soil contamination assessment process. This baseline information is provided in a national geochemical baseline database, TAPIR, that is publicly available via the Internet. Geochemical provinces with elevated baseline concentrations were delineated to provide regional geochemical baseline values. The nationwide geochemical datasets were used to divide Finland into geochemical provinces. Several metals (Co, Cr, Cu, Ni, V, and Zn) showed anomalous concentrations in seven regions that were defined as metal provinces. Arsenic did not follow a similar distribution to any other elements, and four arsenic provinces were separately determined. Nationwide geochemical datasets were not available for some other important elements such as Cd and Pb. Although these elements are included in the TAPIR system, their distribution does not necessarily follow the ones pre-defined for metal and arsenic provinces. Regional geochemical baseline values, presented as upper limit of geochemical variation within the region, can be used as trigger values to assess potential soil contamination. Baseline values have also been used to determine upper and lower guideline values that must be taken into account as a tool in basic risk assessment. If regional geochemical baseline values are available, the national guideline values prescribed in the Decree based on ecological risks can be modified accordingly. The national geochemical baseline database provides scientifically sound, easily accessible and generally accepted information on the baseline values, and it can be used in various

  3. SDSSJ143244.91+301435.3 at VLBI: a compact radio galaxy in a narrow-line Seyfert 1

    Science.gov (United States)

    Caccianiga, A.; Dallacasa, D.; Antón, S.; Ballo, L.; Berton, M.; Mack, K.-H.; Paulino-Afonso, A.

    2017-01-01

    We present very long baseline interferometry (VLBI) observations, carried out with the European Very Long Baseline Interferometry Network (EVN), of SDSSJ143244.91+301435.3, a radio-loud narrow-line Seyfert 1 (RL NLS1) characterized by a steep radio spectrum. The source, compact at Very Large Array resolution, is resolved on the milliarcsec scale, showing a central region plus two extended structures. The relatively high brightness temperature of all components (5 × 106-1.3 × 108 K) supports the hypothesis that the radio emission is non-thermal and likely produced by a relativistic jet and/or small radio lobes. The observed radio morphology, the lack of a significant core, and the presence of a low frequency (230 MHz) spectral turnover are reminiscent of the Compact Steep-Spectrum (CSS) sources. However, the linear size of the source (˜0.5 kpc) measured from the EVN map is lower than the value predicted using the turnover/size relation valid for CSS sources (˜6 kpc). This discrepancy can be explained by an additional component not detected in our observations, accounting for about a quarter of the total source flux density, combined to projection effects. The low core dominance of the source (CD < 0.29) confirms that SDSSJ143244.91+301435.3 is not a blazar, i.e. the relativistic jet is not pointing towards the observer. This supports the idea that SDSSJ143244.91+301435.3 may belong to the `parent population' of flat-spectrum RL NLS1 and favours the hypothesis of a direct link between RL NLS1 and compact, possibly young, radio galaxies.

  4. The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)

    CERN Document Server

    Matsumoto, Naoko; Sugiyama, Koichiro; Kim, Kee-Tae; Kim, Mikyoung; Byun, Do-Young; Jung, Taehyun; Chibueze, James O; Honma, Mareki; Kameya, Osamu; Kim, Jongsoo; Lyo, A-Ran; Motogi, Kazuhito; Oh, Chungsik; Shino, Nagisa; Sunada, Kazuyoshi; Bae, Jaehan; Chung, Hyunsoo; Chung, Moon-Hee; Cho, Se-Hyung; Han, Myoung-Hee; Han, Seog-Tae; Hwang, Jung-Wook; Je, Do-Heung; Jike, Takaaki; Jung, Dong-Kyu; Jung, Jin-seung; Kang, Ji-hyun; Kang, Jiman; Kang, Yong-Woo; Kan-ya, Yukitoshi; Kawaguchi, Noriyuki; Kim, Bong Gyu; Kim, Jaeheon; Kim, Hyo Ryoung; Kim, Hyun-Goo; Kobayashi, Hideyuki; Kono, Yusuke; Kurayama, Tomoharu; Lee, Changhoon; Lee, Jeong Ae; Lee, Jeewon; Lee, Jung-Won; Lee, Sang Hyun; Lee, Sang-Sung; Minh, Young Chol; Miyazaki, Atsushi; Oh, Se-Jin; Oyama, Tomoaki; Park, Sun-youp; Roh, Duk-Gyoo; Sasao, Tetsuo; Sawada-Satoh, Satoko; Shibata, Katsunori M; Sohn, Bong Won; Song, Min-Gyu; Tamura, Yoshiaki; Wajima, Kiyoaki; Wi, Seog-Oh; Yeom, Jae-Hwan; Yun, Young Joo

    2014-01-01

    We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than approximately 650 km corresponding to 100 Mlambda in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~ 5 mas x 2 mas, which corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc. The brightness temperatures of thes...

  5. Long Baseline Neutrino Experiments

    Science.gov (United States)

    Mezzetto, Mauro

    2016-05-01

    Following the discovery of neutrino oscillations by the Super-Kamiokande collaboration, recently awarded with the Nobel Prize, two generations of long baseline experiments had been setup to further study neutrino oscillations. The first generation experiments, K2K in Japan, Minos in the States and Opera in Europe, focused in confirming the Super-Kamiokande result, improving the precision with which oscillation parameters had been measured and demonstrating the ντ appearance process. Second generation experiments, T2K in Japan and very recently NOνA in the States, went further, being optimized to look for genuine three neutrino phenomena like non-zero values of θ13 and first glimpses to leptonic CP violation (LCPV) and neutrino mass ordering (NMO). The discovery of leptonic CP violation will require third generation setups, at the moment two strong proposals are ongoing, Dune in the States and Hyper-Kamiokande in Japan. This review will focus a little more in these future initiatives.

  6. Biofuels Baseline 2008

    Energy Technology Data Exchange (ETDEWEB)

    Hamelinck, C.; Koper, M.; Berndes, G.; Englund, O.; Diaz-Chavez, R.; Kunen, E.; Walden, D.

    2011-10-15

    The European Union is promoting the use of biofuels and other renewable energy in transport. In April 2009, the Renewable Energy Directive (2009/28/EC) was adopted that set a 10% target for renewable energy in transport in 2020. The directive sets several requirements to the sustainability of biofuels marketed in the frame of the Directive. The Commission is required to report to the European Parliament on a regular basis on a range of sustainability impacts resulting from the use of biofuels in the EU. This report serves as a baseline of information for regular monitoring on the impacts of the Directive. Chapter 2 discusses the EU biofuels market, the production and consumption of biofuels and international trade. It is derived where the feedstock for EU consumed biofuels originally come from. Chapter 3 discusses the biofuel policy framework in the EU and major third countries of supply. It looks at various policy aspects that are relevant to comply with the EU sustainability requirements. Chapter 4 discusses the environmental and social sustainability aspects associated with EU biofuels and their feedstock. Chapter 5 discusses the macro-economic effects that indirectly result from increased EU biofuels consumption, on commodity prices and land use. Chapter 6 presents country factsheets for main third countries that supplied biofuels to the EU market in 2008.

  7. Medicina-Noto VLBI observation of SN2013ej

    Science.gov (United States)

    Sokolovsky, K.; Giroletti, M.; Stagni, M.; Nanni, M.; Mahabal, A.

    2013-08-01

    We used the 32m radio telescopes of Istituto di Radioastronomia (INAF-IRA) in Medicina and Noto as a two-element very long baseline interferometer to search for a possible radio counterpart of SN2013ej, a type IIP supernova (CBET #3606, ATel #5228, #5229, #5230, #5237, #5243) in M74. The observations were conducted at 6.7 GHz on 2013 July 31.3 UT, 6 days after the first optical detection reported in CBET #3609.

  8. A VLBI experiment using a remote atomic clock via a coherent fibre link

    Science.gov (United States)

    Clivati, Cecilia; Ambrosini, Roberto; Artz, Thomas; Bertarini, Alessandra; Bortolotti, Claudio; Frittelli, Matteo; Levi, Filippo; Mura, Alberto; Maccaferri, Giuseppe; Nanni, Mauro; Negusini, Monia; Perini, Federico; Roma, Mauro; Stagni, Matteo; Zucco, Massimo; Calonico, Davide

    2017-02-01

    We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks.

  9. Post-Newtonian Treatment of the VLBI Experiment on September 8, 2002

    CERN Document Server

    Kopeikin, S M

    2003-01-01

    Gravitational physics of VLBI experiment conducted on September 8, 2002 and dedicated to measure the speed of gravity is treated in the first post-Newtonian approximation. Explicit speed-of-gravity parameterization is introduced to the Einstein equations to single out the retardation effect associated with the finite speed of gravity in the relativistic time delay of light propagating in the gravitational field of moving Jupiter. Velocity-dependent 1.5 post-Newtonian correction to the Shapiro time delay is derived and compared with our previous result obtained by making use of the post-Minkowskian approximation. We prove that the 1.5 post-Newtonian correction to the Shapiro delay depends on the speed of propagation of gravity c_g that is a directly measurable parameter in the VLBI experiment.

  10. Radio Brightness Temperatures and Angular Dimensions of Recently Predicted Vl-Bi Small-Scale Structures

    Science.gov (United States)

    Opher, R.

    1990-11-01

    RESUMEN. Muestro que analisis recientes publicados de fuentes de radio galacticas y extragalacticas predicen estructuras en pequera escala en fuentes de radio extendidas, remanentes de supernova, vientos protoestelares, nubes moleculares, distorsiones del fondo de 3 K, enanas blancas magnetizadas, estrellas de tipo tardio y el Sol. Discuto las temperatu- ras de brillo de radio de estas estructuras y sus ditnensiones. Muestro que estas estructuras son detectables con las sensibilidades actuales de VLBI (o en el futuro cercano). ABSTRACT. I show that recently published analysis of galactic and extragalactic radio sources make predictions of small-scale structures in extended radio sources, supernovae remnants, protostellar winds, molecu- lar clouds, distortions of the 3 K background, magnetized white dwarf binaries, late-type stars and the sun. I discuss the radio brightness temperatures of these structures and their dimensions. I show that these structures are detectable with present (or near future) VLBI sensitivities. : RADIO SOURCES-EXTENDED

  11. Jet precession in the active nucleus of M81. Ongoing VLBI monitoring

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Brunthaler, A

    2013-01-01

    In a recent publication, we reported results of a multi-frequency VLBI campaign of observations of the Active Galactic Nucleus (AGN) in galaxy M\\,81, phase-referenced to the supernova SN\\,1993J. We were able to extract precise information on the relative astrometry of the AGN radio emission at different epochs and frequencies. We found strong evidence of precession in the AGN jet (i.e., a systematic evolution in the jet inclination at each frequency) coupled to changes in the overall flux density at the different frequencies. In these proceedings, we summarise the main contents of our previous publication and we report on (preliminary) new results from our follow-up VLBI observations, now phase-referenced to the young supernova SN2008iz. We also briefly discuss how these results match the picture of our previously-reported precession model.

  12. High resolution VLBI polarisation imaging of AGN with the Maximum Entropy Method

    CERN Document Server

    Coughlan, Colm P

    2016-01-01

    Radio polarisation images of the jets of Active Galactic Nuclei (AGN) can provide a deep insight into the launching and collimation mechanisms of relativistic jets. However, even at VLBI scales, resolution is often a limiting factor in the conclusions that can be drawn from observations. The Maximum Entropy Method (MEM) is a deconvolution algorithm that can outperform the more common CLEAN algorithm in many cases, particularly when investigating structures present on scales comparable to or smaller than the nominal beam size with "super-resolution". A new implementation of the MEM suitable for single- or multiple-wavelength VLBI polarisation observations has been developed and is described here. Monte Carlo simulations comparing the performances of CLEAN and MEM at reconstructing the properties of model images are presented; these demonstrate the enhanced reliability of MEM over CLEAN when images of the fractional polarisation and polarisation angle are constructed using convolving beams that are appreciably ...

  13. A VLBI experiment using a remote atomic clock via a coherent fibre link

    Science.gov (United States)

    Clivati, Cecilia; Ambrosini, Roberto; Artz, Thomas; Bertarini, Alessandra; Bortolotti, Claudio; Frittelli, Matteo; Levi, Filippo; Mura, Alberto; Maccaferri, Giuseppe; Nanni, Mauro; Negusini, Monia; Perini, Federico; Roma, Mauro; Stagni, Matteo; Zucco, Massimo; Calonico, Davide

    2017-01-01

    We describe a VLBI experiment in which, for the first time, the clock reference is delivered from a National Metrology Institute to a radio telescope using a coherent fibre link 550 km long. The experiment consisted of a 24-hours long geodetic campaign, performed by a network of European telescopes; in one of those (Medicina, Italy) the local clock was alternated with a signal generated from an optical comb slaved to a fibre-disseminated optical signal. The quality of the results obtained with this facility and with the local clock is similar: interferometric fringes were detected throughout the whole 24-hours period and it was possible to obtain a solution whose residuals are comparable to those obtained with the local clock. These results encourage further investigation of the ultimate VLBI performances achievable using fibre dissemination at the highest precision of state-of-the-art atomic clocks. PMID:28145451

  14. Round-Trip System Available to Measure Path Length Variation in Korea VLBI System for Geodesy

    Science.gov (United States)

    Oh, Hongjong; Kondo, Tetsuro; Lee, Jinoo; Kim, Tuhwan; Kim, Myungho; Kim, Suchul; Park, Jinsik; Ju, Hyunhee

    2010-01-01

    The construction project of Korea Geodetic VLBI officially started in October 2008. The construction of all systems will be completed by the end of 2011. The project was named Korea VLBI system for Geodesy (KVG), and its main purpose is to maintain the Korea Geodetic Datum. In case of the KVG system, an observation room with an H-maser frequency standard is located in a building separated from the antenna by several tens of meters. Therefore KVG system will adopt a so-called round-trip system to transmit reference signals to the antenna with reduction of the effect of path length variations. KVG s round-trip system is designed not only to use either metal or optical fiber cables, but also to measure path length variations directly. We present this unique round trip system for KVG.

  15. Deepwater Horizon - Baseline Dataset

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — In 2010, the Deepwater Horizon oil spill occurred in the Gulf of Mexico and the Natural Resources Damage Assessment (NRDA) was initiated to determine the extent of...

  16. Impact of different NWM-derived mapping functions on VLBI and GNSS analysis

    Science.gov (United States)

    Nikolaidou, Thalia; Balidakis, Kyriakos; Nievinski, Felipe; Mendonça, Marco; Santos, Marcelo; Schuh, Harald

    2016-04-01

    In this study, the issue of the tropospheric mapping functions (MF) employed for VLBI and GNSS data analysis is addressed. IERS Conventions (2010) recommend for standard operational solutions, the use of MF based on numerical weather models (NWM) to improve troposphere modeling. The Vienna Mapping Functions 1 (VMF1) map the atmospheric delay from zenith to the line of sight as an elevation dependent function and are capable of better accounting for real weather phenomena compared to MF without NWM input data. However, the spatial resolution of the NWM itself, directly impacts the ability to model atmospheric conditions effectively. Therefore, we employ the UNB-VMF1 which utilize the high resolution model from the Canadian Meteorological Centre based on the Global Deterministic Prediction System (CMC GDPS). The latter, as a modern operational model, contains the latest application of atmospheric physics and parameterizations and is relieved from spatially based systematic effects. For our investigations, we analyze all rapid turnaround VLBI experiments spanning a five year period using the VieVS@GFZ software, as well as the entire data set from IGS sites that observed at the same interval using GAPS: UNB Precise Point Positioning software. Using the independent UNB ray-tracing algorithm we derive hydrostatic and wet "a" coefficients of MF as well as zenith delays from ray-tracing in CMC NWM. The solutions we produced differ only in the choice of the MF. The VLBI and GNSS analysis are fully consistent. The comparison is conducted on both global and local parameters (station positions and velocities, Earth rotation parameters, zenith wet delays and first order tropospheric gradients) between VLBI and GNSS derived products as well as between employing VMF1 (ECMWF operational analysis) and UNB-VMF1 (CMC).

  17. VLBI collimation tower technique for time-delay studies of a large ground station communications antenna

    Science.gov (United States)

    Otoshi, T. Y.; Young, L. E.; Rusch, W. V. T.

    1983-01-01

    A need for an accurate but inexpensive method for measuring and evaluating time delays of large ground antennas for VLBI applications motivated the development of the collimation tower technique. Supporting analytical work which was performed primarily to verify time delay measurement results obtained for a large antenna when the transmitter was at a collimation distance of 1/25 of the usual far field criterion is discussed. Comparisons of theoretical and experimental results are also given.

  18. A 5-GHz Southern Hemisphere VLBI Survey of Compact Radio Sources, 2

    CERN Document Server

    Shen, Z Q; Moran, J M; Jauncey, D L; Reynolds, J E; Tzioumis, A K; Gough, R G; Ferris, R H; Sinclair, M W; Jiang, D R; Hong-Xing, Y; Liang, S G; Edwards, P G; Costa, M E; Tingay, S J; McCulloch, P M; Lovell, J E J; King, E A; Nicolson, G D; Murphy, D W; Meier, D L; Van Ommen, T D; White, G L

    1998-01-01

    We report the results of a 5-GHz southern-hemisphere snapshot VLBI observation of a sample of blazars. The observations were performed with the Southern Hemisphere VLBI Network plus the Shanghai station in 1993 May. Twenty-three flat-spectrum, radio-loud sources were imaged. These are the first VLBI images for 15 of the sources. Eight of the sources are EGRET (> 100 MeV) gamma-ray sources. The milliarcsecond morphology shows a core-jet structure for 12 sources, and a single compact core for the remaining 11. No compact doubles were seen. Compared with other radio images at different epochs and/or different frequencies, 3 core-jet blazars show evidence of bent jets, and there is some evidence for superluminal motion in the cases of 2 blazars. The detailed descriptions for individual blazars are given. This is the second part of a survey: the first part was reported by Shen et al. (AJ 114(1997)1999).

  19. New Zealand pathway towards Asia-Pacific and global e-VLBI research and development

    CERN Document Server

    Gulyaev, Sergei; Weston, Stuart; Thomasson, Peter

    2011-01-01

    Over the past 3 years, Auckland University of Technology has established the first radio astronomical observatory in New Zealand, which, because of its remote geographic location, has quickly become a member of a number of international VLBI networks, in particular the IVS and the LBA. Not only has this added significantly to the observational power in the Pacific and Oceania, but by utilising new fibre connections within New Zealand, and across the Pacific and the Tasman Sea, the New Zealand radio telescopes have now been linked to many in Australia, Asia and the Pacific. Recent astronomical results are presented and plans for widening New Zealand participation in Australasian, Asia-Pacific and global VLBI research and development are outlined. Real-time e-VLBI is a vital part of New Zealand's capability development towards the SKA. The rapid and challenging establishment of New Zealand radio astronomy can serve as a model for the engagement in mega-Science and e-Science by resource-limited institutions and ...

  20. GENJI Programme: Gamma-ray Emitting Notable AGN Monitoring by Japanese VLBI

    CERN Document Server

    Nagai, Hiroshi; Niinuma, Kotaro; Akiyama, Kazunori; Hada, Kazuhiro; Koyama, Shoko; Orienti, Monica; Hiura, Koichiro; Sawada-Satoh, Satoko; Honma, Mareki; Giovannini, Gabriele; Giroletti, Marcello; Shibata, Katsunori; Sorai, Kazuo

    2012-01-01

    We introduce the GENJI program (Gamma-ray Emitting Notable AGN Monitoring by Japanese VLBI), which is a monitoring program of gamma-ray bright AGNs with the VERA array (VLBI Exploration of Radio Astrometry). The GENJI programme aims a dense monitoring at 22 GHz towards the $\\gamma$-ray emitting active galactic nuclei (AGNs) to investigate the radio time variation of the core and possible ejection of new radio component, motion of jets, and their relation with the emission at other wavelengths especially in $\\gamma$-rays. Currently we are monitoring 8 $\\gamma$-ray-emitting notable AGNs (DA 55, 3C 84, M 87, PKS 1510-089, DA 406, NRAO 530, BL Lac, 3C 454.3) about once every two weeks. This programme is promising to trace the trend of radio time variation on shorter timescale than conventional VLBI monitoring programme and to provide complimentary data with them (e.g., MOJAVE, Boston University Blazar Project). In particular, we successfully coordinated quick follow-up observations after the GeV $\\gamma$-ray flar...

  1. VLBI detection of the Galactic black hole binary candidate MAXI J1836-194

    CERN Document Server

    Yang, Jun; Li, Zhixuan; Paragi, Zsolt; Campbell, Robert M; Gurvits, Leonid; Shen, Zhiqiang; Hong, Xiaoyu; Xia, Bo

    2012-01-01

    The X-ray transient MAXI J1836-194 is a newly-identified Galactic black hole binary candidate. As most X-ray transients, it was discovered at the beginning of an X-ray outburst. After the initial canonical X-ray hard state, the outburst evolved into a hard intermediate state and then went back to the hard state. The existing RATAN-600 radio monitoring observations revealed that it was variable on a timescale of days and had a flat or inverted spectrum, consistent with optically thick synchrotron emission, possibly from a self-absorbed jet in the vicinity of the central compact object. We observed the transient in the hard state near the end of the X-ray outburst with the European VLBI Network (EVN) at 5 GHz and the Chinese VLBI Network (CVN) at 2.3 and 8.3 GHz. The 8.3 GHz observations were carried out at a recording rate of 2048 Mbps using the newly-developed Chinese VLBI data acquisition system (CDAS), twice higher than the recording rate used in the other observations. We successfully detected the low-decl...

  2. First geodetic VLBI sessions with the Chinese Deep Space Stations Jiamusi and Kashi

    Science.gov (United States)

    Xu, Dezhen; Dong, Guangliang; Wang, Guangli; Li, Haitao; Jiang, Wu

    2016-11-01

    The first three 24-h S/X dual-band geodetic VLBI sessions using two new Chinese Deep Space Stations (CDSSs), Jiamusi and Kashi, and four Chinese VLBI Stations (CVSs), Beijing, Kunming, Seshan, and Urumqi were conducted with the goal of improving the two CDSSs' positions, which were previously known to a few decimeters. Due to the limited frequency ranges of Jiamusi and Kashi, different but compatible frequencies for bandwidth synthesis were set at the CDSS and CVS stations. This paper presents the scheduling, correlation and fringe fit, and geodetic analysis of the observations. Final estimates of the station positions are obtained from the global solution using 5365 international VLBI sessions from August 3, 1979 through September 29, 2015. Position estimates for Jiamusi are accurate to 23, 35, and 41 mm in the X, Y, and Z directions, respectively, and for Kashi are accurate to 10, 20, and 16 mm. Precisions of the two CDSSs' positions are improved by a factor of 5-10 over previous values, which fully satisfies the requirements of the experiments and makes the first step towards the foundation and maintenance of the time-space reference frame based on the Chinese Deep Space Network (CDSN).

  3. Influence of ocean tides on the diurnal and semidiurnal earth rotation variations from VLBI observations

    Science.gov (United States)

    Gubanov, V. S.; Kurdubov, S. L.

    2015-05-01

    The International astrogeodetic standard IERS Conventions (2010) contains a model of the diurnal and semidiurnal variations in Earth rotation parameters (ERPs), the pole coordinates and the Universal Time, arising from lunisolar tides in the world ocean. This model was constructed in the mid-1990s through a global analysis of Topex/Poseidon altimetry. The goal of this study is to try to estimate the parameters of this model by processing all the available VLBI observations on a global network of stations over the last 35 years performed within the framework of IVS (International VLBI Service) geodetic programs. The complexity of the problemlies in the fact that the sought-for corrections to the parameters of this model lie within 1 mm and, thus, are at the limit of their detectability by all currently available methods of ground-based positional measurements. This requires applying universal software packages with a high accuracy of reduction calculations and a well-developed system of controlling the simultaneous adjustment of observational data to analyze long series of VLBI observations. This study has been performed with the QUASAR software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences. Although the results obtained, on the whole, confirm a high accuracy of the basic model in the IERS Conventions (2010), statistically significant corrections that allow this model to be refined have been detected for some harmonics of the ERP variations.

  4. The Power of (Near Simultaneous Multi-Frequency Observations for mm-VLBI and Astrometry

    Directory of Open Access Journals (Sweden)

    María J. Rioja

    2017-01-01

    Full Text Available Simultaneous or near-simultaneous observations at multiple frequency bands have the potential to overcome the fundamental limitation imposed by the atmospheric propagation in mm-VLBI observations. The propagation effects place a severe limit in the sensitivity achievable in mm-VLBI, reducing the time over which the signals can be coherently combined, and preventing the use of phase referencing and astrometric measurements. We present two demonstrations of the power of (near simultaneous multi-frequency observations with the KVN and VLBA, and our recently developed analysis strategies to enable new measurements at mm-VLBI. The first case comprises simultaneous observations at 22, 43, 87 and 130 GHz of a group of five AGNs, the weakest of which is ∼200 mJy at 130 GHz, with angular separations ranging from 3.6 to 11 degrees, using the KVN. We analysed this data using the Frequency Phase Transfer (FPT and the Source Frequency Phase Referencing (SFPR techniques, which use the observations at a lower frequency to correct those at a higher frequency. The results of the analysis provide an empirical demonstration of the increase in the coherence times at 130 GHz from a few tens of seconds to about twenty minutes, with FPT, and up to many hours with SFPR. Moreover the astrometric analysis provides high precision relative position measurements between two frequencies, including, for the first time, astrometry at 130 GHz. The second case is a variation of the above, whereby adding dedicated wide-band cm-wavelength observations to measure the ionosphere eliminates the need for a second, calibrator, source. This addresses the scarcity of calibrators at mm-VLBI. We dubbed this technique Multi Frequency Phase Referencing (MFPR. We present bona fide astrometrically aligned VLBA images of BL Lacertae at 22 and 43 GHz using MFPR, which, combined with results from conventional phase referencing at cm-wavelengths, suggests the VLBI core has a recollimation shock

  5. Determination of elemental baseline using peltigeralean lichens from Northeastern Canada (Québec): Initial data collection for long term monitoring of the impact of global climate change on boreal and subarctic area in Canada.

    Science.gov (United States)

    Darnajoux, Romain; Lutzoni, François; Miadlikowska, Jolanta; Bellenger, Jean-Philippe

    2015-11-15

    Northeastern Canada is mostly free of anthropogenic activities. The extent to which this territory has been impacted by anthropogenic atmospheric depositions remains to be studied. The main goal of our study was to establish background levels for metals in boreal muscicolous/terricolous macrolichens over non-urbanized areas of northeastern Canada (Québec). Concentrations of 18 elements (Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Cd, and Pb) were determined for three species of the genus Peltigera (Peltigera aphthosa (L.) Willd. s.l., Peltigera neopolydactyla (Gyeln.) Gyeln. s.l., Peltigera scabrosa Th. Fr. s.l.), and Nephroma arcticum (L.) Torss., along a 1080 km south-north transect and along a of 730 km west-east transect. We report that elemental contents in the sampled lichen thalli are very low and similar to background levels found in other studies performed in pristine places (high elevation or remote ecosystems) throughout the world. Overall, our results demonstrate that most of the boreal and subarctic zone of Québec (northeastern Canada) is still pristine. The elemental baseline established in these lichen populations will contribute to monitor metal pollution in boreal and sub-polar ecosystems due to global climate change and future industrial expansion.

  6. Using biofilms and grazing chironomids (Diptera: Chironomidae) to determine primary production, nitrogen stable isotopic baseline and enrichment within wetlands differing in anthropogenic stressors and located in the Athabasca oil sands region of Alberta

    Energy Technology Data Exchange (ETDEWEB)

    Frederick, K.; Ciborowski, J.J. [Windsor Univ., Windsor, ON (Canada); Wytrykush, C.M. [Syncrude Canada Ltd., Edmonton, AB (Canada)

    2009-07-01

    This presentation reported on a study that investigated the effects of oil sands process materials (OSPM) and construction disturbances on primary production and nitrogen stable isotope enrichment in reclaimed and reference wetlands at oil sands mines in the Athabasca basin. Productivity and food web analyses were instrumental in evaluating the succession and viability of reclaimed wetlands. Primary production was estimated through chlorophyll a (Chl a) concentrations and biomass. Carbon (C) and nitrogen (N) stable isotope ratios were used to identify energy sources, storage and the magnitude and direction of energy transfer within food webs. The objectives were to determine primary productivity, the N baseline, and N enrichment from biofilms and grazing invertebrates colonizing artificial substrates immersed in the water column of two OSPM-affected, two constructed reference and two natural reference wetlands. The lower biomass and Chl a concentrations in OSPM-affected and constructed wetlands suggests that both anthropogenic disturbance and OSPM have an adverse effect on primary productivity and overall wetland function.

  7. Relative Astrometry of Compact Flaring Structures in Sgr A* with Polarimetric VLBI

    CERN Document Server

    Johnson, Michael D; Doeleman, Sheperd S; Broderick, Avery E; Wardle, John F C; Marrone, Daniel P

    2014-01-01

    We demonstrate that polarimetric interferometry can be used to extract precise spatial information about compact polarized flares of Sgr A*. We show that, for a faint dynamical component, a single interferometric baseline suffices to determine both its polarization and projected displacement from the quiescent intensity centroid. A second baseline enables two-dimensional reconstruction of the displacement, and additional baselines can self-calibrate using the flare, enhancing synthesis imaging of the quiescent emission. We apply this technique to simulated 1.3-mm wavelength observations of a "hot spot" embedded in a radiatively inefficient accretion disk around Sgr A*. Our results indicate that, even with current sensitivities, polarimetric interferometry with the Event Horizon Telescope can achieve ~5 microarcsecond relative astrometry of compact flaring structures near Sgr A* on timescales of minutes.

  8. Aligning VLBI Images of Active Galactic Nuclei at Different Frequencies

    CERN Document Server

    Croke, S M

    2008-01-01

    Many important techniques for investigating the properties of extragalactic radio sources, such as spectral-index and rotation-measure mapping, involve the comparison of images at two or more frequencies. In the case of radio interferometric data, this can be done by comparing the CLEAN maps obtained at the different frequencies. However, intrinsic differences in images due to the frequency dependence of the radio emission can be distorted by additional differences that arise due to source variability (if the data to be compared is obtained at different times), image misalignment, and the frequency dependence of the sensitivity to weak emission and the angular resolution provided by the observations (the resolution of an interferometer depends on the lengths of its baselines in units of the observing wavelength). These effects must be corrected for as best as possible before multi-frequency data comparison techniques can be applied. We consider the origins for the afore-mentioned factors, outline the standard...

  9. A experiment on radio location of objects in the near-Earth space with VLBI in 2012

    Science.gov (United States)

    Nechaeva, M.; Antipenko, A.; Bezrukovs, V.; Bezrukov, D.; Dementjev, A.; Dugin, N.; Konovalenko, A.; Kulishenko, V.; Liu, X.; Nabatov, A.; Nesteruk, V.; Pupillo, G.; Reznichenko, A.; Salerno, E.; Shmeld, I.; Shulga, O.; Sybiryakova, Y.; Tikhomirov, Yu.; Tkachenko, A.; Volvach, A.; Yang, W.-J.

    An experiment on radar location of space debris objects using of the method of VLBI was carried out in April, 2012. The radar VLBI experiment consisted in irradiation of some space debris objects (4 rocket stages and 5 inactive satellites) with a signal of the transmitter with RT-70 in Evpatoria, Ukraine. Reflected signals were received by a complex of radio telescopes in the VLBI mode. The following VLBI stations took part in the observations: Ventspils (RT-32), Urumqi (RT-25), Medicina (RT-32) and Simeiz (RT-22). The experiment included measurements of the Doppler frequency shift and the delay for orbit refining, and measurements of the rotation period and sizes of objects by the amplitudes of output interferometer signals. The cross-correlation of VLBI-data is performed at a correlator NIRFI-4 of Radiophysical Research Institute (Nizhny Novgorod). Preliminary data processing resulted in the series of Doppler frequency shifts, which comprised the information on radial velocities of the objects. Some results of the experiment are presented.

  10. A Three-decade X-band VLBI Study of 3CR Lobe-dominated Quasar Nuclei

    Directory of Open Access Journals (Sweden)

    Hough David H.

    2013-12-01

    Full Text Available We report X-band VLBI observations of several 3CR lobe-dominated quasar nuclei from 1981 to 2010, mostly obtained with the NRAO VLBA. The goal is to follow flux density outbursts and to fully determine the jet morphology and kinematics on 1-100 pc scales. In 3C207, the core region has flux outbursts at mean intervals of ~7 yr; one of these is actually a double outburst from a stationary true core and a swinging component ~0.5 mas apart. The position angle (PA of the swinging component varies by ~40°, while the PA values of the jet components span ~25°. The jet extends to ~25 mas. Average superluminal speeds are ~10c. One component shows apparent acceleration from 7c to 14c at 2-3 mas from the true core, in a jet recollimation zone that redirects the flow toward PA ~90°. Individual jet components expand until reaching the recollimation zone. In 3C263 and other objects, some of the same phenomena are seen, including ejection of jet components over a range in PA, superluminal motion, and apparent acceleration, but to a lesser degree. Possible physical interpretations involving beaming, orientation, projection, precession, and magnetic effects are discussed.

  11. Hanford Site technical baseline database

    Energy Technology Data Exchange (ETDEWEB)

    Porter, P.E.

    1996-09-30

    This document includes a cassette tape that contains the Hanford specific files that make up the Hanford Site Technical Baseline Database as of September 30, 1996. The cassette tape also includes the delta files that dellinate the differences between this revision and revision 4 (May 10, 1996) of the Hanford Site Technical Baseline Database.

  12. Hanford Site technical baseline database

    Energy Technology Data Exchange (ETDEWEB)

    Porter, P.E., Westinghouse Hanford

    1996-05-10

    This document includes a cassette tape that contains the Hanford specific files that make up the Hanford Site Technical Baseline Database as of May 10, 1996. The cassette tape also includes the delta files that delineate the differences between this revision and revision 3 (April 10, 1996) of the Hanford Site Technical Baseline Database.

  13. MEQSILHOUETTE: a mm-VLBI observation and signal corruption simulator

    Science.gov (United States)

    Blecher, Tariq; Deane, Roger; Bernardi, Gianni; Smirnov, Oleg

    2017-01-01

    The Event Horizon Telescope (EHT) aims to spatially resolve the silhouette (or shadow) of the supermassive black holes in the Galactic Centre (Sgr A⋆) and M87. The primary scientific objectives are to test general relativity in the strong-field regime and to probe accretion and jet-launch physics at event-horizon scales. This is made possible by the technique of very long baseline interferometry at (sub)millimetre wavelengths, which can achieve angular resolutions of order ˜ 10 μ-arcsec. However, this approach suffers from unique observational challenges, including scattering in the troposphere and interstellar medium; rapidly time-variable source structure in both polarized and total intensity; as well as non-negligible antenna pointing errors. In this, the first paper in a series, we present the MEQSILHOUETTE software package which is specifically designed to accurately simulate EHT observations. It includes realistic descriptions of a number of signal corruptions that can limit the ability to measure the key science parameters. This can be used to quantify calibration requirements, test parameter estimation and imaging strategies, and investigate systematic uncertainties that may be present. In doing so, a stronger link can be made between observational capabilities and theoretical predictions, with the goal of maximizing scientific output from the upcoming order of magnitude increase in EHT sensitivity.

  14. Long-baseline Neutrino Oscillation at DUNE

    Science.gov (United States)

    Worcester, Elizabeth; DUNE Collaboration Collaboration

    2017-01-01

    The Deep Underground Neutrino Experiment (DUNE) is a long-baseline neutrino oscillation experiment with primary physics goals of determining the neutrino mass hierarchy and measuring δc P with sufficient sensitivity to discover CP violation in neutrino oscillation. CP violation sensitivity in DUNE requires careful understanding of systematic uncertainty, with contributions expected from uncertainties in the neutrino flux, neutrino interactions, and detector effects. In this presentation, we will describe the expected sensitivity of DUNE to long-baseline neutrino oscillation parameters, how various aspects of the experimental design contribute to that sensitivity, and the planned strategy for constraining systematic uncertainty in these measurements.

  15. 活动星系核VLBI观测的新进展%Progress in the VLBI observation of AGNs

    Institute of Scientific and Technical Information of China (English)

    蒋栋荣

    2003-01-01

    This paper reports some recent progresses in the VLBI observation of the AGNs,specially those in the investigations about the central structure of the AGNs and the low luminosity AGNs.The main goal is to show the importance of the VLBI observations in this field.%介绍了活动星系核(AGN)的VLBI观测的新近展,特别关注其中心结构和低光度的活动星系核.主要目的是强调VLBI观测在该领域的重要性.

  16. Observation VLBI Session RAPL02. the Results of the Data Processing

    Science.gov (United States)

    Chuprikov, A. A.

    Results of processing of data of a VLBI experiment titled RAPL02 are presented. These observations were made in 2011 February with 5 antennas. All 3 antennas of Petersberg's Institute of Applied Astronomy (IAA) were used in this session. These were antennae in Svetloe, in Zelenchuck, and in Badary. Additionally, a 22-m antenna in Puschino as well as a 32-m antenna in Medicina (Italy) were also included into observations. The raw data correlation was made at the software correlator of Astro Space Center. The secondary data processing was made for 3 quasars, 3C273, 3C279, and 3C286.

  17. The Nuclear Structure of 3C84 with Space VLBI (RadioAstron) Observations

    CERN Document Server

    Giovannini, Gabriele; Savolainen, Tuomas; Nagai, Hiroshi; Giroletti, Marcello; Hada, Kazuhiro; Bruni, Gabriele; Hodgson, Jeffrey; Honma, Mareki; Kino, Motoki; Kovalev, Yuri Y; Krichbaum, Thomas; Lee, Sang-Sung; Lobanov, Andrei; Sohn, Bong Won; Sokolovsky, Kirill; Voitsik, Peter; Zensus, J Anton

    2015-01-01

    The radio galaxy 3C84 is a representative of gamma-ray-bright misaligned active galactic nuclei (AGN) and one of the best laboratories to study the radio properties of subparsec scale jets. We discuss here the past and present activity of the nuclear region within the central 1pc and the properties of subparsec-sized components C1, C2 and C3. We compare these results with the high resolution space-VLBI image at 5GHz obtained with the RadioAstron satellite and we shortly discuss the possible correlation of radio emission with the gamma-ray emission.

  18. Multifrequency Study of Giant Radio Pulses from the Crab Pulsar with K5 VLBI Recording Terminal

    CERN Document Server

    Popov, M V; Kondratiev, V I; Bilous, A V; Moshkina, O; Oreshko, V V; Ilyasov, Yu P; Sekido, M; Kondo, T

    2009-01-01

    Simultaneous multifrequency observations of the Crab pulsar giant pulses (GPs) were performed with the 64-m Kalyazin radio telescope at four frequencies 0.6, 1.4, 2.2 and 8.3 GHz using the K5 VLBI recording terminal. K5 terminal provided continuous recording in 16 4-MHz wide frequency channels distributed over 4 frequency bands. Several thousands of GPs were detected during about 6 hours of observations in two successive days in July 2005. Radio spectra of single GPs were analysed at separate frequencies and over whole frequency range. These spectra manifest notable modulation both on large ($\\Delta\

  19. Comparison of VLBI TRF solutions based on Kalman filtering and recent ITRS realizations

    Science.gov (United States)

    Soja, Benedikt; Nilsson, Tobias; Glaser, Susanne; Balidakis, Kyriakos; Karbon, Maria; Heinkelmann, Robert; Gross, Richard; Schuh, Harald

    2016-04-01

    Compared to previous prominent global terrestrial reference frames (TRF) solutions, such as the ITRF2008 or DTRF2008, the current accuracy requirements demand among other things extended parameterization to account for various non-linear signals present in the time series of station coordinates. The next generation of TRFs, built upon geodetic data until the end of 2014, employs different approaches to tackle in particular seasonal variations and post-seismic deformations. The ITRF2014, developed at the International Earth Rotation and Reference Systems Service (IERS) Combination Center (CC) at Institut Géographique National, introduces harmonic, exponential and logarithmic functions to take into account aforementioned effects. In contrast, the ITRS realization of the IERS CC at Jet Propulsion Laboratory is based on Kalman filtering, which allows coordinate variations to be modeled in a stochastic sense besides the parameterized linear and seasonal signals. In our study, we compare these multi-technique TRFs with solutions solely based on VLBI data, including 104 radio telescopes and 4239 VLBI sessions, covering a time span of 34 years. We calculated a VLBI TRF based on the traditional least-squares adjustment of session-wise normal equations, and an ensemble of Kalman filter and smoother solutions with different parameterizations and stochastic models. In particular, we investigate the impact of different process noise levels for station coordinates, the choice of stochastic processes, e.g. random walks, and the application of time- and station-dependent noise models. For instance, we find that the estimation of seasonal signals, while important for predictions, does not affect the filtered coordinate time series when observational data is available. Furthermore, post-seismic deformations after major earthquakes require the process noise to be scaled accordingly. For instance, we detected coordinate differences of up to 5 cm immediately after the Chile 2010

  20. Oscillation Baselining and Analysis Tool

    Energy Technology Data Exchange (ETDEWEB)

    2017-03-27

    PNNL developed a new tool for oscillation analysis and baselining. This tool has been developed under a new DOE Grid Modernization Laboratory Consortium (GMLC) Project (GM0072 - “Suite of open-source applications and models for advanced synchrophasor analysis”) and it is based on the open platform for PMU analysis. The Oscillation Baselining and Analysis Tool (OBAT) performs the oscillation analysis and identifies modes of oscillations (frequency, damping, energy, and shape). The tool also does oscillation event baselining (fining correlation between oscillations characteristics and system operating conditions).

  1. Quivira NWR biological baseline data

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This dataset is biological baseline data for Quivira National Wildlife Refuge as of January 2016. It contains data on species found on the refuge, when and where...

  2. 324 Building Baseline Radiological Characterization

    Energy Technology Data Exchange (ETDEWEB)

    R.J. Reeder, J.C. Cooper

    2010-06-24

    This report documents the analysis of radiological data collected as part of the characterization study performed in 1998. The study was performed to create a baseline of the radiological conditions in the 324 Building.

  3. The parametrization of radio source coordinates in VLBI and its impact on the CRF

    Science.gov (United States)

    Karbon, Maria; Heinkelmann, Robert; Mora-Diaz, Julian; Xu, Minghui; Nilsson, Tobias; Schuh, Harald

    2016-04-01

    Usually celestial radio sources in the celestial reference frame (CRF) catalog are divided in three categories: defining, special handling, and others. The defining sources are those used for the datum realization of the celestial reference frame, i.e. they are included in the No-Net-Rotation (NNR) constraints to maintain the axis orientation of the CRF, and are modeled with one set of totally constant coordinates. At the current level of precision, the choice of the defining sources has a significant effect on the coordinates. For the ICRF2 295 sources were chosen as defining sources, based on their geometrical distribution, statistical properties, and stability. The number of defining sources is a compromise between the reliability of the datum, which increases with the number of sources, and the noise which is introduced by each source. Thus, the optimal number of defining sources is a trade-off between reliability, geometry, and precision. In the ICRF2 only 39 of sources were sorted into the special handling group as they show large fluctuations in their position, therefore they are excluded from the NNR conditions and their positions are normally estimated for each VLBI session instead of as global parameters. All the remaining sources are classified as others. However, a large fraction of these unstable sources show other favorable characteristics, e.g. large flux density (brightness) and a long history of observations. Thus, it would prove advantageous including these sources into the NNR condition. However, the instability of these objects inhibit this. If the coordinate model of these sources would be extended, it would be possible to use these sources for the NNR condition as well. All other sources are placed in the "others" group. This is the largest group of sources, containing those which have not shown any very problematic behavior, but still do not fulfill the requirements for defining sources. Studies show that the behavior of each source can vary

  4. The Subparsec-Scale Structure and Evolution of Centaurus A. II. Continued Very Long Baseline Array Monitoring

    Science.gov (United States)

    Tingay, S. J.; Preston, R. A.; Jauncey, D. L.

    2001-10-01

    We present the results of continued 8.4 GHz Very Long Baseline Array monitoring of the subparsec-scale structure and evolution of Centaurus A, following on from the initial results presented in 1998 by Tingay et al. We include, for the first time, multiepoch VLBI images at 22.2 GHz that show that the jet is linear and well collimated on scales as small as 0.02 pc (~1000rs). Two components in the subparsec-scale jet continue to evolve slowly with a speed of 0.12c. We confirm that an additional component, close to the core, has no significant motion. Some evidence is seen for rapid variations within individual components, as noted dramatically in 1991-1992 by Tingay et al., albeit at a lower level of activity. Both the stationary behavior of the component close to the core and the internal variability of components in the subparsec-scale jet of Centaurus A may be explained as being due to the existence of shocks created in the wake of major component ejections from the nucleus, as simulated by Agudo et al. (published in 2001). Tentative evidence is found to suggest that two subparsec-scale counterjet components are in motion away from the nucleus. The estimated apparent speeds of the jet and counterjet components are consistent with the previously suggested likely jet viewing angle range, 50°-80°. We also compare our Centaurus A images with high-resolution VLBI images of M87 to show that the region of the Centaurus A jet in which collimation likely first occurs lies a factor of 10 below our current resolution limit. Future space VLBI missions at high frequency will be required to resolve this region.

  5. GEOSAT: Combining VLBI, SLR, GPS, and DORIS at the observation level

    Science.gov (United States)

    Helge Andersen, Per; Dähnn, Michael; Fausk, Ingrid; Hjelle, Geir Arne; Kirkvik, Ann-Silje; Mysen, Eirik

    2015-04-01

    GEOSAT is a multi-technique geodetic software that has been under development for about 30 years [P. H. Andersen, "Multilevel arc combination with stochastic parameters". Journal of Geodesy 01/2000; 74(7): 531 - 551]. The last couple of years the development efforts have been headed by a team at the Norwegian Mapping Authority. The GEOSAT software can be used in the analysis of space geodetic data by combining data from VLBI, SLR, GPS and DORIS at the observation level epoch by epoch. As a result technique dependent systematic errors will be visible as anomalous a posteriori residuals, and can be compensated for by introducing technique dependent empirical models. GEOSAT is based on factorized Kalman filters which allow the estimation of stochastic parameters common for several techniques. GEOSAT contributed to the IVS solution used in the upcoming ITRF. In addition to VLBI analysis the software can process SLR and GPS data, while DORIS based analysis is under development. Experiments in combining data from different techniques according to the GEOSAT philosophy are currently being done. This presentation will be a description of how GEOSAT combines data from the different techniques, while at the same time reporting the current state of the project and our plans going forward.

  6. Earth Orientation Parameters from VLBI and GNSS Combined at the Normal Equation Level

    Science.gov (United States)

    Richard, Jean-Yves; Lambert, Sébastien; Bizouard, Christian; Becker, Olivier

    2017-04-01

    Current reference series (C04) of the International Earth Rotation and Reference Systems Service (IERS) are produced by a weighted combination of Earth orientation parameters (EOP) time series built up by combination centers of each technique (VLBI, GNSS, Laser ranging, DORIS). In the future, we plan to produce EOP by a direct combination of the normal equation of the four techniques. We present an intermediate step of this project: a combination of VLBI and GNSS pre-reduced, constraint-free, normal equations with the DYNAMO geodetic analysis software package developed and maintained by the French GRGS (Groupe de Recherche en Géodésie Spatiale). The used normal equations are those produced separately by the IVS and IGS combination centers. Our series cover 2002-2016. The estimation strategy consists of fixing quasar coordinates to their optimal values given by the latest realization of the International Celestial Reference Frame (ICRF), and most of station coordinates to the ITRF 2014 except for stations undergoing strong nonlinear displacements caused by, e.g., postseismic relaxation. These station coordinates are estimated as time series. The resulting EOP series are compared to intra-technique combinations and to the IERS-C04 reference series.

  7. 3C84, BL Lac. Earth based VLBI test for the RADIOASTRON project

    CERN Document Server

    Chuprikov, Andrey; Chibisov, Andrey; Kostenko, Vladimir; Kovalev, Yuri; Graham, Dave; Lobanov, Andrew; Giovannini, Gabriele

    2011-01-01

    Results of processing of data of a VLBI experiment titled RAPL01 are presented. These VLBI observations were made on 4th February, 2010 at 6.28 cm between the 100-m antenna of the Max Planck Institute (Effelsberg, Germany), Puschino 22-m antenna (Astro Space Center (ASC), Russia), and two 32-m antennas of the Istituto di Radioastronomia di Bologna (Bologna, Italy) in Noto and Medicina. 2 well-known sources, 3C84 (0316+413), and BL Lac (2200+420) were included in the schedule of observations. Each of them was observed during 1 hour at all the stations. The Mark-5A registration system was used at 3 European antennae. The alternative registration system known as RDR (RADIOASTRON Data Recorder) was used in Puschino. The Puschino data were recorded in format RDF (RADIOASTRON Data Format). Two standard recording modes designed as 128-4-1 (one bit), and 256-4-2 (two bit) were used in the experiment. All the Mark-5A data from European antennae were successfully converted into the RDF format. Then, the correlation fun...

  8. High frequency VLBI observations of the scatter broadened quasar B2005+403

    CERN Document Server

    Gabanyi, K E; Britzen, S; Krichbaum, T P; Ros, E; Witzel, A; Zensus, J A

    2006-01-01

    The quasar B2005+403 located behind the Cygnus region, is a suitable object for studying the interplay between propagation effects, which are extrinsic to the source and source intrinsic variability. On the basis of VLBI experiments performed at 1.6, 5, 8, 15, 22, and 43GHz between 1992-2003 and parallel multi-frequency monitoring of the total flux density, we investigated the variability of total flux density and source structure. Below 8 GHz, the point-like VLBI source is affected by scatter-broadening of the turbulent interstellar medium, which is located along the line of sight and likely associated with the Cygnus region. We present and discuss the measured frequency dependence of the source size, which shows a power-law with slope of -1.91+/-0.05. From the measured scattering angle at 1GHz of 77.1+/-4.0mas a SM=0.43+/-0.04 m^{-20/3} kpc is derived, consistent with the general properties of the ISM in this direction. The decreasing effect of angular broadening towards higher frequencies allows to study t...

  9. Geochemical baseline studies of soil in Finland

    Science.gov (United States)

    Pihlaja, Jouni

    2017-04-01

    The soil element concentrations regionally vary a lot in Finland. Mostly this is caused by the different bedrock types, which are reflected in the soil qualities. Geological Survey of Finland (GTK) is carrying out geochemical baseline studies in Finland. In the previous phase, the research is focusing on urban areas and mine environments. The information can, for example, be used to determine the need for soil remediation, to assess environmental impacts or to measure the natural state of soil in industrial areas or mine districts. The field work is done by taking soil samples, typically at depth between 0-10 cm. Sampling sites are chosen to represent the most vulnerable areas when thinking of human impacts by possible toxic soil element contents: playgrounds, day-care centers, schools, parks and residential areas. In the mine districts the samples are taken from the areas locating outside the airborne dust effected areas. Element contents of the soil samples are then analyzed with ICP-AES and ICP-MS, Hg with CV-AAS. The results of the geochemical baseline studies are published in the Finnish national geochemical baseline database (TAPIR). The geochemical baseline map service is free for all users via internet browser. Through this map service it is possible to calculate regional soil baseline values using geochemical data stored in the map service database. Baseline data for 17 elements in total is provided in the map service and it can be viewed on the GTK's web pages (http://gtkdata.gtk.fi/Tapir/indexEN.html).

  10. The Extragalactic Lens VLBI Imaging Survey (ELVIS). I. A Search for the Central Image in the Gravitational Lens PMN J1838-3427

    CERN Document Server

    Boyce, E R; Hewitt, J N; Myers, S T; Boyce, Edward R.; Winn, Joshua N.; Hewitt, Jacqueline N.; Myers, Steven T.

    2006-01-01

    The Extragalactic Lens VLBI Imaging Survey (ELVIS) searches for central images of lensed radio quasars, in order to measure the central density profiles of distant galaxies. Here we present sensitive multi-epoch Very Long Baseline Array (VLBA) observations of PMN J1838-3427 at 8 GHz, with a 1 sigma noise level of 38 microJy beam^(-1). Based on the absence of a central image of the background source at this level, we explore the possibilities for the central matter distribution in the lens galaxy. A power-law density profile, rho ~ r^(-gamma), must have gamma > 1.93. Thus the density profile is close to an isothermal profile (gamma = 2) or steeper. The upper limit on any constant-density core in an otherwise isothermal profile is ~< 5 parsecs. We also derive the constraints on models in which the density profile is isothermal on kiloparsec scales, but is allowed to have a different power law in the central ~100 parsecs. If the lens galaxy harbors a supermassive black hole, the galaxy profile is allowed to b...

  11. Studies of circumstellar shells in AGB stars by multifrequency (sub)mm-VLBI observations of maser emission

    Science.gov (United States)

    Colomer, F.; Desmurs, J. F.; Bujarrabal, V.; Baudry, A.; de Vicente, P.; Soria-Ruiz, R.; Alcolea, J.; Diaz-Pulido, A.; Gómez, M.

    2017-03-01

    VLBI observations of maser emission are a basic tool to study the circumstellar envelopes (CSEs) around evolved stars, mainly around AGB and post-AGB stars. The maser lines of water and silicon monoxide are particularly intense. They provide us with high spatial resolution data on the very inner CSEs around AGB stars, including the pulsating layers previous to grain formation and outer regions where the fast expansion characteristic of such envelopes is already present. The analysis of the pumping mechanism of SiO masers and of the physical conditions in the emitting clumps requires accurate maps of the various lines, which show different excitation requirements. A large observational effort is being done to obtain (quasi-)simultaneous multiline data at the highest spatial resolution, using VLBI techniques, which makes possible to compare the relative distribution of the maser lines. We present the state-of-the-art in the field, and discuss preliminary results of SiO masers observed with the Global Millimeter VLBI Array (GMVA) which provide a new view into the physics of these AGB envelopes. The participation of ALMA in these VLBI arrays will boost the study of these masers, at higher frequencies.

  12. How and Why to Do VLBI on GPS

    Science.gov (United States)

    Dickey, J. M.

    2010-01-01

    In order to establish the position of the center of mass of the Earth in the International Celestial Reference Frame, observations of the Global Positioning Satellite (GPS) constellation using the IVS network are important. With a good frame-tie between the coordinates of the IVS telescopes and nearby GPS receivers, plus a common local oscillator reference signal, it should be possible to observe and record simultaneously signals from the astrometric calibration sources and the GPS satellites. The standard IVS solution would give the atmospheric delay and clock offsets to use in analysis of the GPS data. Correlation of the GPS signals would then give accurate orbital parameters of the satellites in the ICRF reference frame, i.e., relative to the positions of the astrometric sources. This is particularly needed to determine motion of the center of mass of the earth along the rotation axis.

  13. Physics Potential of Long-Baseline Experiments

    Directory of Open Access Journals (Sweden)

    Sanjib Kumar Agarwalla

    2014-01-01

    Full Text Available The discovery of neutrino mixing and oscillations over the past decade provides firm evidence for new physics beyond the Standard Model. Recently, θ13 has been determined to be moderately large, quite close to its previous upper bound. This represents a significant milestone in establishing the three-flavor oscillation picture of neutrinos. It has opened up exciting prospects for current and future long-baseline neutrino oscillation experiments towards addressing the remaining fundamental questions, in particular the type of the neutrino mass hierarchy and the possible presence of a CP-violating phase. Another recent and crucial development is the indication of non-maximal 2-3 mixing angle, causing the octant ambiguity of θ23. In this paper, I will review the phenomenology of long-baseline neutrino oscillations with a special emphasis on sub-leading three-flavor effects, which will play a crucial role in resolving these unknowns. First, I will give a brief description of neutrino oscillation phenomenon. Then, I will discuss our present global understanding of the neutrino mass-mixing parameters and will identify the major unknowns in this sector. After that, I will present the physics reach of current generation long-baseline experiments. Finally, I will conclude with a discussion on the physics capabilities of accelerator-driven possible future long-baseline precision oscillation facilities.

  14. Learning to Baseline Business Technology

    Directory of Open Access Journals (Sweden)

    David Gore

    2013-10-01

    Full Text Available bills, sign multi-­‐year contracts, and make purchasing decisions without having an overall technology plan. That plan includes a technology baseline to fully assess existing technology. A CIO's goal is to align IT with business goals. Businesses must know total cost of ownership and the return on investment for all technology purchases and monthly costs. A business must also be able to manage technology assets and best utilize resources across the business. Teaching students to baseline technology will enable them to track and manage costs, discover errors and waste, and consolidate and improve existing technology.

  15. Complex Demodulation in Monitoring Earth Rotation by VLBI: Testing the Algorithm by Analysis of Long Periodic EOP Components

    Science.gov (United States)

    Wielgosz, A.; Brzeziński, A.; Böhm, S.

    2016-12-01

    The complex demodulation (CD) algorithm is an efficient tool for extracting the diurnal and subdiurnal components of Earth rotation from the routine VLBI observations (Brzeziński, 2012). This algorithm was implemented by Böhm et al (2012b) into a dedicated version of the VLBI analysis software VieVs. The authors processed around 3700 geodetic 24-hour observing sessions in 1984.0-2010.5 and estimated simultaneously the time series of the long period components as well as diurnal, semidiurnal, terdiurnal and quarterdiurnal components of polar motion (PM) and universal time UT1. This paper describes the tests of the CD algorithm by checking consistency of the low frequency components of PM and UT1 estimated by VieVS CD and those from the IERS and IVS combined solutions. Moreover, the retrograde diurnal component of PM demodulated from VLBI observations has been compared to the celestial pole offsets series included in the IERS and IVS solutions. We found for all three components a good agreement of the results based on the CD approach and those based on the standard parameterization recommended by the IERS Conventions (IERS, 2010) and applied by the IERS and IVS. We conclude that an application of the CD parameterization in VLBI data analysis does not change those components of EOP which are included in the standard adjustment, while enabling simultaneous estimation of the high frequency components from the routine VLBI observations. Moreover, we deem that the CD algorithm can also be implemented in analysis of other space geodetic observations, like GNSS or SLR, enabling retrieval of subdiurnal signals in EOP from the past data.

  16. Baseline Removal From EMG Recordings

    Science.gov (United States)

    2007-11-02

    a time-varying baseline contamination. Acknowledgements: Work funded by the Departamento de Salud del Gobierno de Navarrra and by a Spanish MEC...Name(s) and Address(es) Departamento de Ingenieria Electra y Electronica Universidad Publica de Navarra Pamplona, Spain Performing Organization Report

  17. La influencia de la rotación terrestre en el método de los arcos aplicado a observaciones VLBI

    Science.gov (United States)

    de Biasi, M. S.; Arias, E. F.

    We analyze the influence of the model or Earth's rotation in the arclength method envisioned to analyze VLBI astrometric observations. We particulary focus in the case of quasi-simultaneous observations.

  18. Use of GPS TEC Maps for Calibrating Single Band VLBI Sessions

    Science.gov (United States)

    Gordon, David

    2010-01-01

    GPS TEC ionosphere maps were first applied to a series of K and Q band VLBA astrometry sessions to try to eliminate a declination bias in estimated source positions. Their usage has been expanded to calibrate X-band only VLBI observations as well. At K-band, approx.60% of the declination bias appears to be removed with the application of GPS ionosphere calibrations. At X-band however, it appears that up to 90% or more of the declination bias is removed, with a corresponding increase in RA and declination uncertainties of approx.0.5 mas. GPS ionosphere calibrations may be very useful for improving the estimated positions of the X-only and S-only sources in the VCS and RDV sessions.

  19. Beyond the usual mapping functions in GPS, VLBI and Deep Space tracking.

    Science.gov (United States)

    Barriot, Jean-Pierre; Serafini, Jonathan; Sichoix, Lydie

    2014-05-01

    We describe here a new algorithm to model the water contents of the atmosphere (including ZWD) from GPS slant wet delays relative to a single receiver. We first make the assumption that the water vapor contents are mainly governed by a scale height (exponential law), and secondly that the departures from this decaying exponential can be mapped as a set of low degree 3D Zernike functions (w.r.t. space) and Tchebyshev polynomials (w.r.t. time.) We compare this new algorithm with previous algorithms known as mapping functions in GPS, VLBI and Deep Space tracking and give an example with data acquired over a one day time span at the Geodesy Observatory of Tahiti.

  20. Space-VLBI with RadioAstron: new correlator capabilities at MPIfR

    CERN Document Server

    Bruni, G; Alef, W; Lobanov, A; Zensus, J A

    2015-01-01

    DiFX is a correlator for VLBI data based on the FX architecture (first Fourier transform and then cross-multiply). DiFX is a free licensed software written in C++, developed and maintened by an international group of programmers. A new DiFX version (dra) has been developed at Max-Planck-Institut f\\"ur Radioastronomie (MPIfR), in order to manage the correlation of a space-based antenna with ground stations. The dra version is running on the High Performance Computer cluster (HPC) in Bonn, and it is used for the data processing of the three AGN imaging RadioAstron Key Science Projects ongoing, based at the MPIfR.

  1. VSOP-2 : a space VLBI mission to image central engines and jet launching regions

    Science.gov (United States)

    Kameno, Seiji; Tsuboi, Masato; Murata, Yasuhiro; Doi, Akihiro; Asaki, Yoshiharu; Mochizuki, Nanako; Hagiwara, Yoshi-Aki; Kino, Motoki; Nagai, Hiroshi; Asada, Keiichi; Inoue, Makoto; Sudou, Hiroshi; Sawada-Satoh, Satoko

    VSOP-2 is a space VLBI program using the spacecraft ASTRO-G to be launched in 2015 by the Japan Aerospace eXploration Agency. The array consisting of a 9-m antenna in orbit and ground radio telescopes offers angular resolutions of 40, 80, and 210 microarcsec at 43, 22, and 8 GHz, respectively. The resolution allows us to image accretion disks and jet launching regions in nearby active galactic nuclei such as M 87. Dual polarization receivers enable full Stokes images at all frequency to illustrate magnetic fields in jets. Phase referencing is capable for astrometry by 60-sec-cycle switching maneuvers. Higher sensitivity than the VSOP (HALCA) is achieved by cooled receivers at 22 and 43 GHz, 1-Gbps wideband downlink, and longer coherent integration. We will introduce the mission overview, observational specifications, and key sciences of the VSOP-2. We call for community's scientific contributions to the mission.

  2. First Results of the VLBI Experiment on Radar Location of the Asteroid 2012 DA14

    Science.gov (United States)

    Nechaeva, M.; Antipenko, A.; Bezrukov, D.; Bezrukovs, Vl.; Dementjev, A.; Dugin, N.; Jekabsons, N.; Khutornoy, R.; Klapers, M.; Konovalenko, A.; Kulishenko, V.; Nabatov, A.; Nesteruk, V.; Pupillo, G.; Reznichenko, A.; Salerno, E.; Shmeld, I.; Skirmante, K.; Tikhomirov, Yu.; Voytyuk, V.

    An international VLBI experiment on radio location of the asteroid 2012 DA14 was organized on 2013 February 15--16, during its flyby close to Earth. The purpose of observations was to investigate and specify orbital parameters of the asteroid, as well as to evaluate its rotation period and other characteristics. The irradiation of the asteroid was performed by the RT-70 transmitter at Evpatoria (Crimea, Ukraine), while the reflected signals were successfully accepted by the two 32 m radio telescopes at Medicina (Bologna, Italy) and Irbene (Ventspils, Latvia). Processing and interpretation of the data were performed both in the Radiophysical Research Institute and in the Ventspils International Radio Astronomy Center. The first results of this experiment are presented and discussed.

  3. High-frequency VLBI Imaging of Sgr A* and VX Sgr

    Science.gov (United States)

    Lu, R.-S.; Krichbaum, T. P.; Zensus, A. J.

    VLBI observations at millimeter wavelengths provide unprecedented high angular resolution and allow to image regions, which are self-absorbed at longer wavelengths. Here we present new results from a multi-frequency VLBA monitoring of SgrA* at 22, 43, and 86 GHz performed on 10 consecutive days in May 2007. We discuss the source structure of Sgr A* through the analysis of the closure phase and closure amplitude, of which the latter improves the calibration accuracy and shows indications of a non-Gaussian brightness distribution at the highest frequency. We also present preliminary maps of the maser emission lines (v=1, J=1-0, and J=2-1) in the circumstellar SiO maser of VX Sgr. This will put new constraints on the kinematics and the pumping mechanisms of SiO masers.

  4. High resolution VLBI polarization imaging of AGN with the maximum entropy method

    Science.gov (United States)

    Coughlan, Colm P.; Gabuzda, Denise C.

    2016-12-01

    Radio polarization images of the jets of Active Galactic Nuclei (AGN) can provide a deep insight into the launching and collimation mechanisms of relativistic jets. However, even at VLBI scales, resolution is often a limiting factor in the conclusions that can be drawn from observations. The maximum entropy method (MEM) is a deconvolution algorithm that can outperform the more common CLEAN algorithm in many cases, particularly when investigating structures present on scales comparable to or smaller than the nominal beam size with `super-resolution'. A new implementation of the MEM suitable for single- or multiple-wavelength VLBI polarization observations has been developed and is described here. Monte Carlo simulations comparing the performances of CLEAN and MEM at reconstructing the properties of model images are presented; these demonstrate the enhanced reliability of MEM over CLEAN when images of the fractional polarization and polarization angle are constructed using convolving beams that are appreciably smaller than the full CLEAN beam. The results of using this new MEM software to image VLBA observations of the AGN 0716+714 at six different wavelengths are presented, and compared to corresponding maps obtained with CLEAN. MEM and CLEAN maps of Stokes I, the polarized flux, the fractional polarization and the polarization angle are compared for convolving beams ranging from the full CLEAN beam down to a beam one-third of this size. MEM's ability to provide more trustworthy polarization imaging than a standard CLEAN-based deconvolution when convolving beams appreciably smaller than the full CLEAN beam are used is discussed.

  5. Mode S Baseline Radar Tracking.

    Science.gov (United States)

    1982-11-01

    range units and 20 azimuth units) overlaying the position of the beacon reports. In the cases analyzed where beacon reports were not radar reinforced ...82/53 j~ C ~ 7 C _ _ _ _ _ _ 4. Title end Su.btitle 5. Neget at. November 1982 MDDE S BASELINE RADAR TRACKIN4G 6. Poelin Orgeuianti.. Cede ACT-100...Ground Clutter 33 Mode S/ARTS III 100-Scan False Radar Track Summary 74 34 Percent Beacon Radar Reinforcement 77 vii INTRODUCTION PURPOSE. The purpose of

  6. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 1. Depth to Bedrock Determinations Using Shallow Seismic Data Acquired in the Straight Creek Drainage Near Red River, New Mexico

    Science.gov (United States)

    Powers, Michael H.; Burton, Bethany L.

    2004-01-01

    In late May and early June of 2002, the U.S. Geological Survey (USGS) acquired four P-wave seismic profiles across the Straight Creek drainage near Red River, New Mexico. The data were acquired to support a larger effort to investigate baseline and pre-mining ground-water quality in the Red River basin (Nordstrom and others, 2002). For ground-water flow modeling, knowledge of the thickness of the valley fill material above the bedrock is required. When curved-ray refraction tomography was used with the seismic first arrival times, the resulting images of interval velocity versus depth clearly show a sharp velocity contrast where the bedrock interface is expected. The images show that the interpreted buried bedrock surface is neither smooth nor sharp, but it is clearly defined across the valley along the seismic line profiles. The bedrock models defined by the seismic refraction images are consistent with the well data.

  7. Geochemical baseline data, Youngs Bay, Oregon, 1974

    Energy Technology Data Exchange (ETDEWEB)

    McMechan, K.J. (ed.); Johnson, V.G.; Cutshall, N.H.

    1975-04-01

    This report comprises one part of a final report to the Alumax Pacific Aluminum Corporation on the Physical, Chemical and Biological Studies of Youngs Bay''. The data reported herein are the product of the geochemical baseline section of the project. The primary objectives of the geochemical study were: to provide a baseline record of fluoride and selected trace metal levels in Youngs Bay bottom sediment, to identify areas that might function as heavy metal traps, to attempt to determine the recent depositional history of sediment in the bay. In addition to these primary objectives, a number of secondary tasks were undertaken during the study. While time did not allow these additional studies to be carried to completion, preliminary results are included herein because of their potential usefulness in assessing the impact of environmental releases of fluoride to aquatic systems in the vicinity of Youngs Bay or elsewhere. This report is made up of two major sections. In the first, a description of sample collection and analytical procedures is followed by a discussion of the baseline results. Obvious vertical and horizontal patterns of elemental distribution are identified and their origins considered. Problems needed further research are also discussed. In the second section, the data are presented in interpretive, graphical form, as well as in tables. 35 refs., 29 figs., 14 tabs.

  8. Efficient Wide Baseline Structure from Motion

    Science.gov (United States)

    Michelini, Mario; Mayer, Helmut

    2016-06-01

    This paper presents a Structure from Motion approach for complex unorganized image sets. To achieve high accuracy and robustness, image triplets are employed and (an approximate) camera calibration is assumed to be known. The focus lies on a complete linking of images even in case of large image distortions, e.g., caused by wide baselines, as well as weak baselines. A method for embedding image descriptors into Hamming space is proposed for fast image similarity ranking. The later is employed to limit the number of pairs to be matched by a wide baseline method. An iterative graph-based approach is proposed formulating image linking as the search for a terminal Steiner minimum tree in a line graph. Finally, additional links are determined and employed to improve the accuracy of the pose estimation. By this means, loops in long image sequences are implicitly closed. The potential of the proposed approach is demonstrated by results for several complex image sets also in comparison with VisualSFM.

  9. SRP Baseline Hydrogeologic Investigation, Phase 3

    Energy Technology Data Exchange (ETDEWEB)

    Bledsoe, H.W.

    1988-08-01

    The SRP Baseline Hydrogeologic Investigation was implemented for the purpose of updating and improving the knowledge and understanding of the hydrogeologic systems underlying the SRP site. Phase III, which is discussed in this report, includes the drilling of 7 deep coreholes (sites P-24 through P-30) and the installation of 53 observation wells ranging in depth from approximately 50 ft to more than 970 ft below the ground surface. In addition to the collection of geologic cores for lithologic and stratigraphic study, samples were also collected for the determination of physical characteristics of the sediments and for the identification of microorganisms.

  10. Ionospheric Response to the Total Solar Eclipse of 22 July 2009 as Deduced from VLBI and GPS Data

    Science.gov (United States)

    Guo, L.; Shu, F. C.; Zheng, W. M.; Kondo, T.; Ichikawa, R.; Hasegawa, S.; Sekido, M.

    2010-01-01

    A total solar eclipse occurred over China at latitudes of about 30 N on the morning of 22 July 2009, providing a unique opportunity to investigate the influence of the sun on the earth's upper ionosphere. GPS observations from Shanghai GPS Local Network and VLBI observations from stations Shanghai, Urumqi, and Kashima were used to observe the response of TEC to the total solar eclipse. From the GPS data reduction, the sudden decrease of TEC at the time of the eclipse, amounting to 2.8 TECU, and gradual increase of TEC after the eclipse were found by analyzing the diurnal variations. More distinctly, the variations of TEC were studied along individual satellite passes. The delay in reaching the minimum level of TEC with the maximum phase of eclipse was 5-10 min. Besides, we also compared the ionospheric activity derived from different VLBI stations with the GPS results and found a strong correlation between them.

  11. Japanese VLBI Network Observations of a Gamma-Ray Narrow-Line Seyfert 1 Galaxy 1H 0323+342

    Indian Academy of Sciences (India)

    Kiyoaki Wajima; Kenta Fujisawa; Masaaki Hayashida; Naoki Isobe

    2014-09-01

    We made simultaneous single-dish and VLBI observations of a gamma-ray narrow-line Seyfert 1 (NLS1) galaxy 1H 0323+342. We found significant flux variation at 8 GHz on a time scale of one month. The total flux density varied by 5.5% in 32 days, corresponding to a variability brightness temperature of 7.0 × 1011 K. We also obtained brightness temperatures of greater than 5.2 × 1010 K from the VLBI images. These high brightness temperatures suggest that the source has nonthermal processes in the central engine. The source structure could be modelled by two elliptical Gaussian components on the parsec scales. The flux of the central component decreases in the same way as the total flux density, showing that the short-term variability is mainly associated with this component.

  12. Long-Baseline Neutrino Experiments

    CERN Document Server

    Diwan, M V; Qian, X; Rubbia, A

    2016-01-01

    We review long-baseline neutrino experiments in which neutrinos are detected after traversing macroscopic distances. Over such distances neutrinos have been found to oscillate among flavor states. Experiments with solar, atmospheric, reactor, and accelerator neutrinos have resulted in a coherent picture of neutrino masses and mixing of the three known flavor states. We will summarize the current best knowledge of neutrino parameters and phenomenology with our focus on the evolution of the experimental technique. We proceed from the first evidence produced by astrophysical neutrino sources to the current open questions and the goals of future research.

  13. Long-Baseline Neutrino Experiments

    Science.gov (United States)

    Diwan, M. V.; Galymov, V.; Qian, X.; Rubbia, A.

    2016-10-01

    We review long-baseline neutrino experiments in which neutrinos are detected after traversing macroscopic distances. Over such distances neutrinos have been found to oscillate among flavor states. Experiments with solar, atmospheric, reactor, and accelerator neutrinos have resulted in a coherent picture of neutrino masses and mixing of the three known flavor states. We summarize the current best knowledge of neutrino parameters and phenomenology, with a focus on the evolution of the experimental technique. We proceed from the first evidence produced by astrophysical neutrino sources to the current open questions and the goals of future research.

  14. Baseline LAW Glass Formulation Testing

    Energy Technology Data Exchange (ETDEWEB)

    Kruger, Albert A. [USDOE Office of River Protection, Richland, WA (United States); Mooers, Cavin [The Catholic University of America, Washington, DC (United States). Vitreous State Lab.; Bazemore, Gina [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Pegg, Ian L. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Hight, Kenneth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Lai, Shan Tao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Buechele, Andrew [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Rielley, Elizabeth [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Gan, Hao [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Muller, Isabelle S. [The Catholic University of America, Washington, DC (United States). Vitreous State Lab; Cecil, Richard [The Catholic University of America, Washington, DC (United States). Vitreous State Lab

    2013-06-13

    The major objective of the baseline glass formulation work was to develop and select glass formulations that are compliant with contractual and processing requirements for each of the LAW waste streams. Other objectives of the work included preparation and characterization of glasses with respect to the properties of interest, optimization of sulfate loading in the glasses, evaluation of ability to achieve waste loading limits, testing to demonstrate compatibility of glass melts with melter materials of construction, development of glass formulations to support ILAW qualification activities, and identification of glass formulation issues with respect to contract specifications and processing requirements.

  15. Single-baseline-interferometry-based Orbit Measurement and Determination Test of GEO Satellite%基于单基线干涉测量的GEO卫星轨道测定与验证

    Institute of Scientific and Technical Information of China (English)

    任天鹏; 曹建峰; 唐歌实; 戴一堂; 陈略; 孙靖; 韩松涛; 路伟涛; 王美

    2016-01-01

    As a kind of passive measurement, the interferometry has a natural advantage to track a non-cooperative spatial target. Through applying a 5.5km-baseline interferometry system, a differential interferometry test is done on a GEO satellite. After introducing group-delay-aided phase delay, the measured noise of the interferometry delay is about 9.4ps (root mean square of the linear fitting residuals in each 300 seconds). Following a differential observation as "2-hour-calibration~13-hour-tracking~2-hour-calibration", the accuracy of the interferometry delay is about 0.267ns (rms). The maximum difference between solved orbit and precise ephemeris is about 35.7km. Results show that the single-baseline interferometry can converge to the solution of GEO satellite orbit, which would bring a high-accuracy orbit even as passive monitoring.%干涉测量具有被动式测量特点,对空间非合作目标轨道监测具有天然优势.利用5.5公里基线干涉测量系统,针对GEO卫星开展了差分干涉测量实验.引入群时延辅助的相时延处理技术,GEO卫星干涉测量噪声约9.4ps.基于"2小时标校-13小时跟踪-2小时标校"的长时差分观测模式,GEO卫星干涉测量误差约0.267ns,定轨解算星历与精密星历最大径向偏差为35.7公里.结果表明,单基线干涉测量可以收敛解算GEO卫星轨道,实现较高精度的GEO卫星轨道被动式监测.

  16. VLBI collimation-tower technique for time-delay studies of a large ground-station communications antenna

    Science.gov (United States)

    Otoshi, T. Y.; Young, L. E.; Rusch, W. V. T.

    1985-01-01

    A need for an accurate but inexpensive method for measuring and evaluating time delays of large ground antennas for VLBI applications motivated the development of the collimation tower technique. Supporting analytical work which was performed primarily to verify time delay measurement results obtained for a large antenna when the transmitter was at a collimation distance of 1/25 of the usual far field criterion is discussed. Comparisons of theoretical and experimental results are also given.

  17. FED baseline engineering studies report

    Energy Technology Data Exchange (ETDEWEB)

    Sager, P.H.

    1983-04-01

    Studies were carried out on the FED Baseline to improve design definition, establish feasibility, and reduce cost. Emphasis was placed on cost reduction, but significant feasibility concerns existed in several areas, and better design definition was required to establish feasibility and provide a better basis for cost estimates. Design definition and feasibility studies included the development of a labyrinth shield ring concept to prevent radiation streaming between the torus spool and the TF coil cryostat. The labyrinth shield concept which was developed reduced radiation streaming sufficiently to permit contact maintenance of the inboard EF coils. Various concepts of preventing arcing between adjacent shield sectors were also explored. It was concluded that installation of copper straps with molybdenum thermal radiation shields would provide the most reliable means of preventing arcing. Other design studies included torus spool electrical/structural concepts, test module shielding, torus seismic response, poloidal conditions in the magnets, disruption characteristics, and eddy current effects. These additional studies had no significant impact on cost but did confirm the feasibility of the basic FED Baseline concept.

  18. Esophageal impedance baseline according to different time intervals

    Directory of Open Access Journals (Sweden)

    Ummarino Dario

    2012-06-01

    Full Text Available Abstract Background The impedance baseline has been shown to reflect esophageal integrity, and to be decreased in patients with esophagitis. However, different methods for the determination of the impedance baseline have not been compared. Methods The median impedance baseline was calculated in 10 consecutive multichannel intraluminal impedance recordings in children with non-erosive reflux disease. All children underwent an endoscopy with a biopsy as part of the clinical work-up to exclude esophagitis. The impedance baseline was obtained both by including and excluding all impedance episodes (IE; reflux, swallows and gas episodes during the full recording, and during the first 1-minute period without an IE every hour (method 1, every 2 hours (method 2 or every 4 hours (method 3. The impedance baseline obtained during the full recording was set at 100%, and the variation (difference in impedance baseline for the different methods and variability (difference in impedance baseline during one analysis period were assessed. Results None of the participants had esophagitis. The mean difference over the six channels between the impedance baseline over the total recording with and without IE was approximately 2.5%, and comparable for each channel (range 0.47% to 5.55%. A mean of 1,028 IEs were excluded in each tracing, and it took between 4 and 24 hours to delete all events in one tracing. The difference in the impedance baseline obtained with and without IEs was mainly caused by the gas episodes in the upper channels and swallows in the lower channels. The median impedance baseline according to the three one-minute analysis methods was comparable to the median impedance baseline according to the 24 hour analysis. Conclusions The automatic determination of the median impedance baseline over the total tracing including IEs is an adequate method. In isolated tracings with numerous IEs, the calculation of the median impedance baseline over one minute

  19. Pinellas Plant Environmental Baseline Report

    Energy Technology Data Exchange (ETDEWEB)

    1997-06-01

    The Pinellas Plant has been part of the Department of Energy`s (DOE) nuclear weapons complex since the plant opened in 1957. In March 1995, the DOE sold the Pinellas Plant to the Pinellas County Industry Council (PCIC). DOE has leased back a large portion of the plant site to facilitate transition to alternate use and safe shutdown. The current mission is to achieve a safe transition of the facility from defense production and prepare the site for alternative uses as a community resource for economic development. Toward that effort, the Pinellas Plant Environmental Baseline Report (EBR) discusses the current and past environmental conditions of the plant site. Information for the EBR is obtained from plant records. Historical process and chemical usage information for each area is reviewed during area characterizations.

  20. TWRS privatization process technical baseline

    Energy Technology Data Exchange (ETDEWEB)

    Orme, R.M.

    1996-09-13

    The U.S. Department of Energy (DOE) is planning a two-phased program for the remediation of Hanford tank waste. Phase 1 is a pilot program to demonstrate the procurement of treatment services. The volume of waste treated during the Phase 1 is a small percentage of the tank waste. During Phase 2, DOE intends to procure treatment services for the balance of the waste. The TWRS Privatization Process Technical Baseline (PPTB) provides a summary level flowsheet/mass balance of tank waste treatment operations which is consistent with the tank inventory information, waste feed staging studies, and privatization guidelines currently available. The PPTB will be revised periodically as privatized processing concepts are crystallized.

  1. Integrated Baseline Review (IBR) Handbook

    Science.gov (United States)

    Fleming, Jon F.; Kehrer, Kristen C.

    2016-01-01

    The purpose of this handbook is intended to be a how-to guide to prepare for, conduct, and close-out an Integrated Baseline Review (IBR). It discusses the steps that should be considered, describes roles and responsibilities, tips for tailoring the IBR based on risk, cost, and need for management insight, and provides lessons learned from past IBRs. Appendices contain example documentation typically used in connection with an IBR. Note that these appendices are examples only, and should be tailored to meet the needs of individual projects and contracts. Following the guidance in this handbook will help customers and suppliers preparing for an IBR understand the expectations of the IBR, and ensure that the IBR meets the requirements for both in-house and contract efforts.

  2. Trinocular Stereo Matching Based on Correlations Between Baselines and Disparities

    Institute of Scientific and Technical Information of China (English)

    GUANYepeng; GUWeikang

    2004-01-01

    Gray correlation technique is utilized to take the multi-peak feature points with gray correlation coefficients less than a certain range of maximal correlation coefficient as a potential candidate matching set. There exists the maximal correlation between the correct disparities and their corresponding baselines. A trinocular stereo matching algorithm is proposed based on correlations between the baselines and disparities. After computing the correlations between the baselines and disparities, the unique matches can be determined by maximal correlation coefficient. It is proved that the algorithm proposed is valid and credible by 3-D reconstruction on two pairs of actual natural stereo images.

  3. Pipeline integrity: ILI baseline data for QRA

    Energy Technology Data Exchange (ETDEWEB)

    Porter, Todd R. [Tuboscope Pipeline Services, Houston, TX (United States)]. E-mail: tporter@varco.com; Silva, Jose Augusto Pereira da [Pipeway Engenharia, Rio de Janeiro, RJ (Brazil)]. E-mail: guto@pipeway.com; Marr, James [MARR and Associates, Calgary, AB (Canada)]. E-mail: jmarr@marr-associates.com

    2003-07-01

    The initial phase of a pipeline integrity management program (IMP) is conducting a baseline assessment of the pipeline system and segments as part of Quantitative Risk Assessment (QRA). This gives the operator's integrity team the opportunity to identify critical areas and deficiencies in the protection, maintenance, and mitigation strategies. As a part of data gathering and integration of a wide variety of sources, in-line inspection (ILI) data is a key element. In order to move forward in the integrity program development and execution, the baseline geometry of the pipeline must be determined with accuracy and confidence. From this, all subsequent analysis and conclusions will be derived. Tuboscope Pipeline Services (TPS), in conjunction with Pipeway Engenharia of Brazil, operate ILI inertial navigation system (INS) and Caliper geometry tools, to address this integrity requirement. This INS and Caliper ILI tool data provides pipeline trajectory at centimeter level resolution and sub-metre 3D position accuracy along with internal geometry - ovality, dents, misalignment, and wrinkle/buckle characterization. Global strain can be derived from precise INS curvature measurements and departure from the initial pipeline state. Accurate pipeline elevation profile data is essential in the identification of sag/over bend sections for fluid dynamic and hydrostatic calculations. This data, along with pipeline construction, operations, direct assessment and maintenance data is integrated in LinaViewPRO{sup TM}, a pipeline data management system for decision support functions, and subsequent QRA operations. This technology provides the baseline for an informed, accurate and confident integrity management program. This paper/presentation will detail these aspects of an effective IMP, and experience will be presented, showing the benefits for liquid and gas pipeline systems. (author)

  4. General relativistic model for experimental measurement of the speed of propagation of gravity by VLBI

    CERN Document Server

    Kopeikin, S M; Kopeikin, Sergei; Fomalont, Ed

    2002-01-01

    A relativistic sub-picosecond model of gravitational time delay in radio astronomical observations is worked out and a new experimental test of general relativity is discussed in which the effect of retardation of gravity associated with its finite speed can be observed. As a consequence, the speed of gravity can be measured by differential VLBI observations. Retardation in propagation of gravity is a central part of the Einstein theory of general relativity which has not been tested directly so far. The idea of the proposed gravitational experiment is based on the fact that gravity in general relativity propagates with finite speed so that the deflection of light caused by the body must be sensitive to the ratio of the body's velocity to the speed of gravity. The interferometric experiment can be performed, for example, during the very close angular passage of a quasar by Jupiter. Due to the finite speed of gravity and orbital motion of Jupiter, the variation in its gravitational field reaches observer on Ea...

  5. Reliability and Stability of VLBI-Derived Sub-Daily EOP Models

    Science.gov (United States)

    Artz, Thomas; Boeckmann, Sarah; Jensen, Laura; Nothnagel, Axel; Steigenberger, Peter

    2010-01-01

    Recent investigations have shown significant shortcomings in the model which is proposed by the IERS to account for the variations in the Earth s rotation with periods around one day and less. To overcome this, an empirical model can be estimated more or less directly from the observations of space geodetic techniques. The aim of this paper is to evaluate the quality and reliability of such a model based on VLBI observations. Therefore, the impact of the estimation method and the analysis options as well as the temporal stability are investigated. It turned out that, in order to provide a realistic accuracy measure of the model coefficients, the formal errors should be inflated by a factor of three. This coincides with the noise floor and the repeatability of the model coefficients and it captures almost all of the differences that are caused by different estimation techniques. The impact of analysis options is small but significant when changing troposphere parameterization or including harmonic station position variations.

  6. Exploring the jet launching region in active galactic nuclei using high-resolution VLBI

    Science.gov (United States)

    Rani, Bindu

    2017-01-01

    The high radio frequency polarization imaging of non-thermal emission from AGN is a direct way to probe the magnetic field strength and structure in the immediate vicinity of SMBHs and is crucial in testing the jet-launching scenario. To explore the magnetic field configuration at the base of jets in blazars, I took advantage of the full polarization capabilities of the GMVA (Global Millimeter VLBI Array). With an angular resolution of 50 micro-arcseconds at 86 GHz, one could reach scales down to 900 Rs (for a 109 solar mass black hole). On sub-mas scales the core and central jet of BL Lac is polarized with the EVPA being aligned well with jet in the North-South jet direction. This suggests a well ordered magnetic field, with its main component being perpendicular to the jet axis. Such a field configuration is consistent with a helical magnetic field in the jet. In this talk, I will show the results of our study on BL Lac.

  7. On the nature of FRB 150418: clues from European VLBI Network and e-MERLIN observations

    CERN Document Server

    Giroletti, M; Garrett, M; Paragi, Z; Yang, J; Hada, K; Muxlow, T W B; Cheung, C C

    2016-01-01

    We investigate the nature of the compact, and possibly variable nuclear radio source in the centre of WISE J0716-19, the proposed host galaxy of fast radio burst, FRB 150418. We observed WISE J0716-19 at 5.0 GHz with the European VLBI Network four times between 2016 March 16 and June 2. At three epochs, we simultaneously observed the source with e-MERLIN at the same frequency. We detected a compact source in the EVN data in each epoch with a significance up to ~8sigma. The four epochs yielded consistent results within their uncertainties, for both peak surface intensity and positions. The mean values for these quantities are I_peak = (115+-9) {\\mu}Jy/beam and r.a. = 07:16:34.55496(7), dec. = -19:00:39.4754(8), respectively. The e-MERLIN data provided ~3-5sigma detections, at a position consistent with those of the EVN data. The presence of emission on angular scales intermediate between the EVN and e-MERLIN is consistent with being null. The brightness temperature of the EVN core is Tb~10^8.5K, close to the v...

  8. 2016 Annual Technology Baseline (ATB)

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Wesley; Kurup, Parthiv; Hand, Maureen; Feldman, David; Sigrin, Benjamin; Lantz, Eric; Stehly, Tyler; Augustine, Chad; Turchi, Craig; O' Connor, Patrick; Waldoch, Connor

    2016-09-01

    Consistent cost and performance data for various electricity generation technologies can be difficult to find and may change frequently for certain technologies. With the Annual Technology Baseline (ATB), National Renewable Energy Laboratory provides an organized and centralized dataset that was reviewed by internal and external experts. It uses the best information from the Department of Energy laboratory's renewable energy analysts and Energy Information Administration information for conventional technologies. The ATB will be updated annually in order to provide an up-to-date repository of current and future cost and performance data. Going forward, we plan to revise and refine the values using best available information. The ATB includes both a presentation with notes (PDF) and an associated Excel Workbook. The ATB includes the following electricity generation technologies: land-based wind; offshore wind; utility-scale solar PV; concentrating solar power; geothermal power; hydropower plants (upgrades to existing facilities, powering non-powered dams, and new stream-reach development); conventional coal; coal with carbon capture and sequestration; integrated gasification combined cycle coal; natural gas combustion turbines; natural gas combined cycle; conventional biopower. Nuclear laboratory's renewable energy analysts and Energy Information Administration information for conventional technologies. The ATB will be updated annually in order to provide an up-to-date repository of current and future cost and performance data. Going forward, we plan to revise and refine the values using best available information.

  9. Physics Potential of Long-Baseline Experiments

    CERN Document Server

    Agarwalla, Sanjib Kumar

    2014-01-01

    The discovery of neutrino mixing and oscillations over the past decade provides firm evidence for new physics beyond the Standard Model. Recently, theta13 has been determined to be moderately large, quite close to its previous upper bound. This represents a significant milestone in establishing the three-flavor oscillation picture of neutrinos. It has opened up exciting prospects for current and future long-baseline neutrino oscillation experiments towards addressing the remaining fundamental questions, in particular the type of the neutrino mass hierarchy and the possible presence of a CP-violating phase. Another recent and crucial development is the indication of non-maximal 2-3 mixing angle, causing the octant ambiguity of theta23. In this paper, I will review the phenomenology of long-baseline neutrino oscillations with a special emphasis on sub-leading three-flavor effects, which will play a crucial role in resolving these unknowns. First, I will give a brief description of neutrino oscillation phenomeno...

  10. 2016 Annual Technology Baseline (ATB) - Webinar Presentation

    Energy Technology Data Exchange (ETDEWEB)

    Cole, Wesley; Kurup, Parthiv; Hand, Maureen; Feldman, David; Sigrin, Benjamin; Lantz, Eric; Stehly, Tyler; Augustine, Chad; Turchi, Craig; Porro, Gian; O' Connor, Patrick; Waldoch, Connor

    2016-09-13

    This deck was presented for the 2016 Annual Technology Baseline Webinar. The presentation describes the Annual Technology Baseline, which is a compilation of current and future cost and performance data for electricity generation technologies.

  11. Atlantic NAD 83 SLA Baseline Points

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains baseline points in ArcGIS shapefile format for the BOEM Atlantic Region. Baseline points are the discrete coordinate points along the...

  12. Atlantic NAD 83 SLA Baseline Points

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains baseline points in ArcGIS shapefile format for the BOEM Atlantic Region. Baseline points are the discrete coordinate points along the...

  13. Atlantic NAD 83 SLA Baseline Tangents

    Data.gov (United States)

    Bureau of Ocean Energy Management, Department of the Interior — This data set contains baseline tangent lines in ArcGIS shapefile format for the BOEM Atlantic Region. Baseline tangent lines are typically bay or river closing...

  14. The MINK methodology: background and baseline. [USA - Midwest Region

    Energy Technology Data Exchange (ETDEWEB)

    Rosenberg, N.J.; Crosson, P.R.; Frederick, K.D.; Easterling, W.E. III; McKenney, M.S.; Bowes, M.D.; Sedjo, R.A.; Darmstadter, J.; Katz, L.A.; Lemon, K.M. (Resources for the Future, Washington, DC (United States))

    1993-06-01

    A four step methodology has been developed for study of the regional impacts of climate change and the possible responses thereto. First the region's climate sensitive sectors and total economy are described (Task A, current baseline). Next a scenario of climate change is imposed on the current baseline (Task B, current baseline with climate change). A new baseline describing the climate sensitive sectors and total regional economy is projected for some time in the future (Task C, future baseline, year 2030) in the absence of climate change. Finally, the climate change scenario is reimposed on the future baseline (Task D, future baseline with climate change). Impacts of the climate change scenario on the current and future regional economies are determined by means of simulation models and other appropriate techniques. These techniques are also used to assess the impacts of an elevated CO[sub 2] concentration (450 ppm) and of various forms of adjustments and adaptations. The region chosen for the first test of the methodology is composed of the four U.S. states of Missouri, Iowa, Nebraska and Kansas. The climate change scenario is the actual weather of the 1930s decade in the MINK region. 'Current' climate is the actual weather of the period 1951-1980. 20 refs., 3 figs., 2 tabs.

  15. The WITCH Model. Structure, Baseline, Solutions.

    Energy Technology Data Exchange (ETDEWEB)

    Bosetti, V.; Massetti, E.; Tavoni, M.

    2007-07-01

    WITCH - World Induced Technical Change Hybrid - is a regionally disaggregated hard link hybrid global model with a neoclassical optimal growth structure (top down) and an energy input detail (bottom up). The model endogenously accounts for technological change, both through learning curves affecting prices of new vintages of capital and through R and D investments. The model features the main economic and environmental policies in each world region as the outcome of a dynamic game. WITCH belongs to the class of Integrated Assessment Models as it possesses a climate module that feeds climate changes back into the economy. In this paper we provide a thorough discussion of the model structure and baseline projections. We report detailed information on the evolution of energy demand, technology and CO2 emissions. Finally, we explicitly quantifiy the role of free riding in determining the emissions scenarios. (auth)

  16. Ultra-trace determination of (90)Sr, (137)Cs, (238)Pu, (239)Pu, and (240)Pu by triple quadruple collision/reaction cell-ICP-MS/MS: Establishing a baseline for global fallout in Qatar soil and sediments.

    Science.gov (United States)

    Amr, Mohamed A; Helal, Abdul-Fattah I; Al-Kinani, Athab T; Balakrishnan, Perumal

    2016-03-01

    The development of practical, fast, and reliable methods for the ultra-trace determination of anthropogenic radionuclides (90)Sr, (137)Cs, (238)Pu, (239)Pu, and (240)Pu by triple quadruple collision/reaction cell inductively coupled plasma mass spectrometry (CRC-ICP-MS/MS) were investigated in term of its accuracy and precision for producing reliable results. The radionuclides were extracted from 1 kg of the environmental soil samples by concentrated nitric and hydrochloric acids. The leachate solutions were measured directly by triple quadrupole CRC-ICP-MS/MS. For quality assurance, a chemical separation of the concerned radionuclides was conducted and then measured by single quadrupole-ICP-MS. The developed methods were next applied to measure the anthropogenic radionuclides (90)Sr, (137)Cs, (238)Pu, (239)Pu, and (240)Pu in soil samples collected throughout the State of Qatar. The average concentrations of (90)Sr, (137)Cs, (238)Pu, (239)Pu, and (240)Pu were 0.606 fg/g (3.364 Bq/kg), 0.619 fg/g (2.038 Bq/kg), 0.034 fg/g (0.0195 Bq/kg), 65.59 fg/g (0.150 Bq/kg), and 12.06 fg/g (0.103 Bq/kg), respectively.

  17. Factors determining the structure of fish assemblages in an Amazonian river near to oil and gas exploration areas in the Amazon basin (Brazil: establishing the baseline for environmental evaluation

    Directory of Open Access Journals (Sweden)

    Igor David Costa

    2015-10-01

    Full Text Available ABSTRACT Determining the significance of biotic and abiotic factors in the structuring of fish assemblages in freshwater environments is an important question in ecology, particularly in view of environmental changes caused by man. In this paper we sought to identify the factors responsible for the composition and abundance of fish species collected with gill nets in six locations near ports in forest clearance areas opened up for oil and natural gas exploration (Petrobras Pedro Moura Base in the Urucu River, during drought and flood cycles. In all, 923 individuals from 23 families and 82 species were collected, totalling a biomass of 182,244 g. The most abundant species during the flood season were Bryconops alburnoides (Kner, 1858 and Dianema urostriatum (Miranda Ribeiro, 1912; in the drought season, the predominant species were Osteoglossum bicirrhosum (Cuvier, 1829 and Serrasalmus rhombeus (Linnaeus, 1766. The species with the greatest biomass during the flood season were Pellona castelnaeana (Valenciennes, 1847, S. rhombeus and Pellona flavipinis (Valenciennes, 1847. During the drought season, the predominant species was O. bicirrhosum. When both periods were analysed together, electrical conductivity, water transparency and dissolved oxygen were the most important factors. The species Hemisorubim platyrhynchos (Valenciennes, 1840, O. bicirrhosum, Chaetobranchus flavenscens Heckel, 1840, Geophagus proximus (Castelnau, 1855 were strongly related to high values of conductivity, pH and water current velocity during the drought season, as well as Serrasalmus altispinis Merckx, Jégu & Santos, 2000, Triportheus albus Cope, 1872, Triportheus angulatus (Spix & Agassiz, 1829 and Brycon melanopterus (Cope, 1872 that were associated with less depth and width in the drought season whereas P. castelnaeana, D. urostriatum, Rhytiodus argenteofuscus Kner, 1858 and Sorubim lima (Bloch & Schneider, 1801 were mainly associated with high transparency and

  18. The Earth's free core nutation: Formulation of dynamics and estimation of eigenperiod from the very-long-baseline interferometry data

    Science.gov (United States)

    Chao, B. F.; Hsieh, Y.

    2015-12-01

    The free-core nutation (FCN) is a rotational normal mode of the Earth's outer core. We derive the equations of motion for FCN w.r.t. both the inertia space F0 and the uniformly rotating frame FΩ, and show that the two sets of equations are invariant in form under the reference frame transformation, as required by physics. The frequency-domain formulation describes the FCN resonance (to nearby tidal signals), which has been exploited to estimate the complex eigenfrequency of FCN, or its eigenperiod P and quality factor Q. On the other hand, our time-domain formulation in terms of temporal convolution describes the response of the free FCN under a (continual) excitation. The convolution well explains the dynamic behaviors of FCN in the observed very-long-baseline interferometry (VLBI) data (in F0), including the undulation of the FCN amplitude and the apparent fluctuations in the period and phase over time, as well as the temporal concurrence of a large phase jump with the near-zero amplitude during ∼ 1998- 2000, in complete analogy to the observed behavior of the Chandler wobble (in FΩ). The reverse, deconvolution process is further exploited to yield optimal estimates for FCN's eigenfrequency using the VLBI data, following the approach of Furuya and Chao (1996) of locating minimum excitation power. While this method is found to be insensitive to Q owing to the short timespan of the data, we obtain the estimate of P = 441 ± 4.5 sidereal days (sd) where the 1-sigma uncertainty is assessed via extensive Monte Carlo simulations. This value is closer to the theoretical value of ∼460 sd predicted by Earth models assuming hydrostatic equilibrium than do the prior estimates (425-435 sd) by the resonance method. The deconvolution process also yields the excitation function as a by-product, the physical sources of which await further studies.

  19. Application of laser ranging and VLBI data to a study of plate tectonic driving forces. [finite element method

    Science.gov (United States)

    Solomon, S. C.

    1980-01-01

    The measurability of changes in plate driving or resistive forces associated with plate boundary earthquakes by laser rangefinding or VLBI is considered with emphasis on those aspects of plate forces that can be characterized by such measurements. Topics covered include: (1) analytic solutions for two dimensional stress diffusion in a plate following earthquake faulting on a finite fault; (2) two dimensional finite-element solutions for the global state of stress at the Earth's surface for possible plate driving forces; and (3) finite-element solutions for three dimensional stress diffusion in a viscoelastic Earth following earthquake faulting.

  20. Combination of Vlbi, GPS and Slr Observations At The Observation Level For The Realization of Terrestrial and Celestial Reference Frames

    Science.gov (United States)

    Andersen, P. H.

    Forsvarets forskningsinstitutt (FFI, the Norwegian Defence Research Establishment) has during the last 17 years developed a software system called GEOSAT, for the analysis of any type of high precision space geodetic observations. A unique feature of GEOSAT is the possibility of combining any combination of different space geode- tic data at the observation level with one consistent model and one consistent strategy. This is a much better strategy than the strategy in use today where different types of observations are processed separately using analysis software developed specifically for each technique. The results from each technique are finally combined a posteriori. In practice the models implemented in the software packages differ at the 1-cm level which is almost one order of magnitude larger than the internal precision of the most precise techniques. Another advantage of the new proposed combination method is that for example VLBI and GPS can use the same tropospheric model with common parameterization. The same is the case for the Earth orientation parameters, the geo- center coordinates and other geodetic or geophysical parameters where VLBI, GPS and SLR can have a common estimate for each of the parameters. The analysis with GEOSAT is automated for the combination of VLBI, SLR and GPS observations. The data are analyzed in batches of one day where the result from each daily arc is a SRIF array (Square Root Information Filter). A large number of SRIF arrays can be combined into a multi-year solution using the CSRIFS program (Com- bination Square Root Information Filter and Smoother). Four parameter levels are available and any parameter can, at each level, either be represented as a constant or a stochastic parameter (white noise, colored noise, or random walk). The batch length (i.e. the time interval between the addition of noise to the SRIF array) can be made time- and parameter dependent. GEOSAT and CSRIFS have been applied in the analysis of selected

  1. SWARM: A Compact High Resolution Correlator and Wideband VLBI Phased Array Upgrade for SMA

    Science.gov (United States)

    Weintroub, Jonathan

    2014-06-01

    A new digital back end (DBE) is being commissioned on Mauna Kea. The “SMA Wideband Astronomical ROACH2 Machine”, or SWARM, processes a 4 GHz usable band in single polarization mode and is flexibly reconfigurable for 2 GHz full Stokes dual polarization. The hardware is based on the open source Reconfigurable Open Architecture Computing Hardware 2 (ROACH2) platform from the Collaboration for Astronomy Signal Processing and Electronics Research (CASPER). A 5 GSps quad-core analog-to-digital converter board uses a commercial chip from e2v installed on a CASPER-standard printed circuit board designed by Homin Jiang’s group at ASIAA. Two ADC channels are provided per ROACH2, each sampling a 2.3 GHz Nyquist band generated by a custom wideband block downconverter (BDC). The ROACH2 logic includes 16k-channel Polyphase Filterbank (F-engine) per input followed by a 10 GbE switch based corner-turn which feeds into correlator-accumulator logic (X-engines) co-located with the F-engines. This arrangement makes very effective use of a small amount of digital hardware (just 8 ROACH2s in 1U rack mount enclosures). The primary challenge now is to meet timing at full speed for a large and very complex FPGA bit code. Design of the VLBI phased sum and recorder interface logic is also in process. Our poster will describe the instrument design, with the focus on the particular challenges of ultra wideband signal processing. Early connected commissioning and science verification data will be presented.

  2. MALDI-TOF Baseline Drift Removal Using Stochastic Bernstein Approximation

    Directory of Open Access Journals (Sweden)

    Howard Daniel

    2006-01-01

    Full Text Available Stochastic Bernstein (SB approximation can tackle the problem of baseline drift correction of instrumentation data. This is demonstrated for spectral data: matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF data. Two SB schemes for removing the baseline drift are presented: iterative and direct. Following an explanation of the origin of the MALDI-TOF baseline drift that sheds light on the inherent difficulty of its removal by chemical means, SB baseline drift removal is illustrated for both proteomics and genomics MALDI-TOF data sets. SB is an elegant signal processing method to obtain a numerically straightforward baseline shift removal method as it includes a free parameter that can be optimized for different baseline drift removal applications. Therefore, research that determines putative biomarkers from the spectral data might benefit from a sensitivity analysis to the underlying spectral measurement that is made possible by varying the SB free parameter. This can be manually tuned (for constant or tuned with evolutionary computation (for .

  3. The LOFAR long baseline snapshot calibrator survey

    CERN Document Server

    Moldón, J; Wucknitz, O; Jackson, N; Drabent, A; Carozzi, T; Conway, J; Kapińska, A D; McKean, P; Morabito, L; Varenius, E; Zarka, P; Anderson, J; Asgekar, A; Avruch, I M; Bell, M E; Bentum, M J; Bernardi, G; Best, P; Bîrzan, L; Bregman, J; Breitling, F; Broderick, J W; Brüggen, M; Butcher, H R; Carbone, D; Ciardi, B; de Gasperin, F; de Geus, E; Duscha, S; Eislöffel, J; Engels, D; Falcke, H; Fallows, R A; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; Grießmeier, J; Gunst, A W; Hamaker, J P; Hassall, T E; Heald, G; Hoeft, M; Juette, E; Karastergiou, A; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Kuper, G; Maat, P; Mann, G; Markoff, S; McFadden, R; McKay-Bukowski, D; Morganti, R; Munk, H; Norden, M J; Offringa, A R; Orru, E; Paas, H; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Reich, W; Röttgering, H; Rowlinson, A; Scaife, A M M; Schwarz, D; Sluman, J; Smirnov, O; Stappers, B W; Steinmetz, M; Tagger, M; Tang, Y; Tasse, C; Thoudam, S; Toribio, M C; Vermeulen, R; Vocks, C; van Weeren, R J; White, S; Wise, M W; Yatawatta, S; Zensus, A

    2014-01-01

    Aims. An efficient means of locating calibrator sources for International LOFAR is developed and used to determine the average density of usable calibrator sources on the sky for subarcsecond observations at 140 MHz. Methods. We used the multi-beaming capability of LOFAR to conduct a fast and computationally inexpensive survey with the full International LOFAR array. Sources were pre-selected on the basis of 325 MHz arcminute-scale flux density using existing catalogues. By observing 30 different sources in each of the 12 sets of pointings per hour, we were able to inspect 630 sources in two hours to determine if they possess a sufficiently bright compact component to be usable as LOFAR delay calibrators. Results. Over 40% of the observed sources are detected on multiple baselines between international stations and 86 are classified as satisfactory calibrators. We show that a flat low-frequency spectrum (from 74 to 325 MHz) is the best predictor of compactness at 140 MHz. We extrapolate from our sample to sho...

  4. Post Auction Coverage Baseline 2.0

    Data.gov (United States)

    Federal Communications Commission — FINAL TELEVISION CHANNEL ASSIGNMENT INFORMATION RELATED TO INCENTIVE AUCTION REPACKING. NOTE: This file provides new baseline coverage and population data for all...

  5. 40 CFR 80.91 - Individual baseline determination.

    Science.gov (United States)

    2010-07-01

    ... refinery engaged in the production of gasoline blendstocks from crude oil and/or crude oil derivatives, and...) Method 1-type data. (i) Method 1-type data shall consist of quality (composition and property data) and... properties and to minimize loss of volatile fractions of the sample. (B) Properties of the retained...

  6. Determining Baseline Stress-Related Hormone Values in Large Cetaceans

    Science.gov (United States)

    2015-09-30

    stress hormone cortisol (N=1; 12 growth layers (GL)). This earplug was extracted from a shipstrike animal in 2007 (>1980s) and housed at the Santa...levels will be transformative for our understanding of the extent of exposure and the potential effect on the health of these animals and offers... exponential research opportunities that simply does not exist with traditional matrices such as blood and blubber and is ideally suited for examining

  7. Structure and flux variability in the VLBI jet of BL Lacertae during the WEBT campaigns (1995--2004)

    CERN Document Server

    Bach, U; Raiteri, C M; Agudo, I; Aller, H D; Aller, M F; Denn, G; Gómez, J L; Jorstad, S; Marscher, A; Mutel, R L; Terasranta, H

    2006-01-01

    BL Lacertae has been the target of several observing campaigns by the Whole Earth Blazar Telescope (WEBT) collaboration and is one of the best studied blazars at all accessible wavelengths. A recent analysis of the optical and radio variability indicates that part of the radio variability is correlated with the optical light curve. Here we present an analysis of a huge VLBI data set including 108 images at 15, 22, and 43 GHz obtained between 1995 and 2004. The aim of this study is to identify the different components contributing to the single-dish radio light curves. We obtain separate radio light curves for the VLBI core and jet and show that the radio spectral index of single-dish observations can be used to trace the core variability. Cross-correlation of the radio spectral index with the optical light curve indicates that the optical variations lead the radio by about 100 days at 15 GHz. By fitting the radio time lags vs. frequency, we find that the power law is steeper than expected for a freely expandi...

  8. Deformation Monitoring of the Submillimetric UPV Calibration Baseline

    Science.gov (United States)

    García-Asenjo, Luis; Baselga, Sergio; Garrigues, Pascual

    2017-06-01

    A 330 m calibration baseline was established at the Universitat Politècnica de València (UPV) in 2007. Absolute scale was subsequently transferred in 2012 from the Nummela Standard Baseline in Finland and distances between pillars were determined with uncertainties ranging from 0.1 mm to 0.3 mm. In order to assess the long-term stability of the baseline three field campaigns were carried out from 2013 to 2015 in a co-operative effort with the Universidad Complutense de Madrid (UCM), which provided the only Mekometer ME5000 distance meter available in Spain. Since the application of the ISO17123-4 full procedure did not suffice to come to a definite conclusion about possible displacements of the pillars, we opted for the traditional geodetic network approach. This approach had to be adapted to the case at hand in order to deal with problems such as the geometric weakness inherent to calibration baselines and scale uncertainty derived from both the use of different instruments and the high correlation between the meteorological correction and scale determination. Additionally, the so-called the maximum number of stable points method was also tested. In this contribution it is described the process followed to assess the stability of the UPV submillimetric calibration baseline during the period of time from 2012 to 2015.

  9. Multi-technique approach for deriving a VLBI signal extra-path variation model induced by gravity: the example of Medicina

    Science.gov (United States)

    Sarti, P.; Abbondanza, C.; Negusini, M.; Vittuari, L.

    2009-09-01

    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.

  10. Determining

    Directory of Open Access Journals (Sweden)

    Bahram Andarzian

    2015-06-01

    Full Text Available Wheat production in the south of Khuzestan, Iran is constrained by heat stress for late sowing dates. For optimization of yield, sowing at the appropriate time to fit the cultivar maturity length and growing season is critical. Crop models could be used to determine optimum sowing window for a locality. The objectives of this study were to evaluate the Cropping System Model (CSM-CERES-Wheat for its ability to simulate growth, development, grain yield of wheat in the tropical regions of Iran, and to study the impact of different sowing dates on wheat performance. The genetic coefficients of cultivar Chamran were calibrated for the CSM-CERES-Wheat model and crop model performance was evaluated with experimental data. Wheat cultivar Chamran was sown on different dates, ranging from 5 November to 9 January during 5 years of field experiments that were conducted in the Khuzestan province, Iran, under full and deficit irrigation conditions. The model was run for 8 sowing dates starting on 25 October and repeated every 10 days until 5 January using long-term historical weather data from the Ahvaz, Behbehan, Dezful and Izeh locations. The seasonal analysis program of DSSAT was used to determine the optimum sowing window for different locations as well. Evaluation with the experimental data showed that performance of the model was reasonable as indicated by fairly accurate simulation of crop phenology, biomass accumulation and grain yield against measured data. The normalized RMSE were 3%, 2%, 11.8%, and 3.4% for anthesis date, maturity date, grain yield and biomass, respectively. Optimum sowing window was different among locations. It was opened and closed on 5 November and 5 December for Ahvaz; 5 November and 15 December for Behbehan and Dezful;and 1 November and 15 December for Izeh, respectively. CERES-Wheat model could be used as a tool to evaluate the effect of sowing date on wheat performance in Khuzestan conditions. Further model evaluations

  11. Causal connection in parsec-scale relativistic jets: results from the MOJAVE VLBI survey

    Science.gov (United States)

    Clausen-Brown, E.; Savolainen, T.; Pushkarev, A. B.; Kovalev, Y. Y.; Zensus, J. A.

    2013-10-01

    We report that active galactic nucleus (AGN) jets are causally connected on parsec scales, based on 15 GHz Very Long Baseline Array (VLBA) data from a sample of 133 AGN jets. This result is achieved through a new method for measuring the product of the jet Lorentz factor and the intrinsic opening angle Γθj from measured apparent opening angles in flux density limited samples of AGN jets. The Γθj parameter is important for jet physics because it is related to the jet-frame sidewise expansion speed and causal connection between the jet edges and its symmetry axis. Most importantly, the standard model of jet production requires that the jet be causally connected with its symmetry axis, implying that Γθj ≲ 1. When we apply our method to the MOJAVE flux density limited sample of radio loud objects, we find Γθj ≈ 0.2, implying that AGN jets are causally connected. We also find evidence that AGN jets viewed very close to the line of sight effectively have smaller intrinsic opening angles compared with jets viewed more off-axis, which is consistent with Doppler beaming and a fast inner spine/slow outer sheath velocity field. Notably, gamma-ray burst (GRB) jets have a typical Γθj that is two orders of magnitude higher, suggesting that different physical mechanisms are at work in GRB jets compared to AGN jets. A useful application of our result is that a jet's beaming parameters can be derived. Assuming Γθj is approximately constant in the AGN jet population, an individual jet's Doppler factor and Lorentz factor (and therefore also its viewing angle) can be determined using two observable quantities: apparent jet opening angle and the apparent speed of jet components.

  12. Addendum to the 2015 Eastern Interconnect Baselining and Analysis Report

    Energy Technology Data Exchange (ETDEWEB)

    Amidan, Brett G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Follum, James D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-06-30

    This report serves as an addendum to the report 2015 Eastern Interconnect Baselining and Analysis Report (Amidan, Follum, and Freeman, 2015). This addendum report investigates the following: the impact of shorter record lengths and of adding a daily regularization term to the date/time models for angle pair measurements, additional development of a method to monitor the trend in phase angle pairs, the effect of changing the length of time to determine a baseline, when calculating atypical events, and a comparison between quantitatively discovered atypical events and actual events.

  13. Multiproject baselines for evaluation of electric power projects

    Energy Technology Data Exchange (ETDEWEB)

    Sathaye, Jayant; Murtishaw, Scott; Price, Lynn; Lefranc, Maurice; Roy, Joyashree; Winkler, Harald; Spalding-Fecher, Randall

    2003-03-12

    Calculating greenhouse gas emissions reductions from climate change mitigation projects requires construction of a baseline that sets emissions levels that would have occurred without the project. This paper describes a standardized multiproject methodology for setting baselines, represented by the emissions rate (kg C/kWh), for electric power projects. A standardized methodology would reduce the transaction costs of projects. The most challenging aspect of setting multiproject emissions rates is determining the vintage and types of plants to include in the baseline and the stringency of the emissions rates to be considered, in order to balance the desire to encourage no- or low-carbon projects while maintaining environmental integrity. The criteria for selecting power plants to include in the baseline depend on characteristics of both the project and the electricity grid it serves. Two case studies illustrate the application of these concepts to the electric power grids in eastern India and South Africa. We use hypothetical, but realistic, climate change projects in each country to illustrate the use of the multiproject methodology, and note the further research required to fully understand the implications of the various choices in constructing and using these baselines.

  14. Life Support Baseline Values and Assumptions Document

    Science.gov (United States)

    Anderson, Molly S.; Ewert, Michael K.; Keener, John F.; Wagner, Sandra A.

    2015-01-01

    The Baseline Values and Assumptions Document (BVAD) provides analysts, modelers, and other life support researchers with a common set of values and assumptions which can be used as a baseline in their studies. This baseline, in turn, provides a common point of origin from which many studies in the community may depart, making research results easier to compare and providing researchers with reasonable values to assume for areas outside their experience. With the ability to accurately compare different technologies' performance for the same function, managers will be able to make better decisions regarding technology development.

  15. Should Studies of Diabetes Treatment Stratification Correct for Baseline HbA1c?

    Directory of Open Access Journals (Sweden)

    Angus G Jones

    Full Text Available Baseline HbA1c is a major predictor of response to glucose lowering therapy and therefore a potential confounder in studies aiming to identify other predictors. However, baseline adjustment may introduce error if the association between baseline HbA1c and response is substantially due to measurement error and regression to the mean. We aimed to determine whether studies of predictors of response should adjust for baseline HbA1c.We assessed the relationship between baseline HbA1c and glycaemic response in 257 participants treated with GLP-1R agonists and assessed whether it reflected measurement error and regression to the mean using duplicate 'pre-baseline' HbA1c measurements not included in the response variable. In this cohort and an additional 2659 participants treated with sulfonylureas we assessed the relationship between covariates associated with baseline HbA1c and treatment response with and without baseline adjustment, and with a bias correction using pre-baseline HbA1c to adjust for the effects of error in baseline HbA1c.Baseline HbA1c was a major predictor of response (R2 = 0.19,β = -0.44,p<0.001.The association between pre-baseline and response was similar suggesting the greater response at higher baseline HbA1cs is not mainly due to measurement error and subsequent regression to the mean. In unadjusted analysis in both cohorts, factors associated with baseline HbA1c were associated with response, however these associations were weak or absent after adjustment for baseline HbA1c. Bias correction did not substantially alter associations.Adjustment for the baseline HbA1c measurement is a simple and effective way to reduce bias in studies of predictors of response to glucose lowering therapy.

  16. Breton Island, Louisiana Baseline (Geographic, NAD83)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Breton Island, Louisiana Baseline (Geographic, NAD83) consists of vector line data that were input into the Digital Shoreline Analysis System (DSAS) version 4.0,...

  17. SSA FITARA Common Baseline Implementation Plan

    Data.gov (United States)

    Social Security Administration — This document describes the agency's plan to implement the Federal Information Technology Acquisition Reform Act (FITARA) Common Baseline per OMB memorandum M-15-14.

  18. NRAO Very Long Baseline Array (VLBA)

    Data.gov (United States)

    Federal Laboratory Consortium — The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It's the world's largest, sharpest, dedicated telescope array. With an eye...

  19. Breton Island, Louisiana Baseline (Geographic, NAD83)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Breton Island, Louisiana Baseline (Geographic, NAD83) consists of vector line data that were input into the Digital Shoreline Analysis System (DSAS) version 4.0,...

  20. Hanford Site technical baseline database. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Porter, P.E.

    1995-01-27

    This report lists the Hanford specific files (Table 1) that make up the Hanford Site Technical Baseline Database. Table 2 includes the delta files that delineate the differences between this revision and revision 0 of the Hanford Site Technical Baseline Database. This information is being managed and maintained on the Hanford RDD-100 System, which uses the capabilities of RDD-100, a systems engineering software system of Ascent Logic Corporation (ALC). This revision of the Hanford Site Technical Baseline Database uses RDD-100 version 3.0.2.2 (see Table 3). Directories reflect those controlled by the Hanford RDD-100 System Administrator. Table 4 provides information regarding the platform. A cassette tape containing the Hanford Site Technical Baseline Database is available.

  1. Confirmation of a conspiracy - Dual-band VLBI maps of the flat-spectrum radio source 2021 + 614

    Science.gov (United States)

    Wittels, J. J.; Shapiro, I. I.; Cotton, W. D.

    1982-01-01

    VLBI observations at 3.6 and 13 cm wavelengths of the flat-spectrum radio source 2021 + 614 reveal two components, separated by about 6.5 + or - 0.6 milli-arcseconds along a position angle of 36 deg + or - 6 deg. The dual-band observations show that the two components have spectral indices of opposite signs, indicating that, as for 0735 + 178 (Cotton et al. 1980), the flat spectrum of 2021 + 614 is a result of the superposition of spectra from individual components, each having a peaked spectrum, presumably due to incoherent electron synchrotron radiation. If this situation is typical, then there is too large a percentage of flat-spectrum sources for the individual components in each to have independent characteristics.

  2. VLBI observations of the RS Canum Venaticorum binary systems UX Arietis and HR 1099 at 1.65 GHz

    Science.gov (United States)

    Mutel, R. L.; Doiron, D. J.; Phillips, R. B.; Lestrade, J. F.

    1984-01-01

    VLBI observations of the RS CVn binaries UX Arietis and HR 1099 have been made at 1.65 GHz using a three-element array with a minimum fringe spacing of 11.5 milli-arcsec. Both sources were found to be unresolved within measurement uncertainties. In both cases, the derived upper limit to the source size was comparable to the overall size of each binary system. The lower limits to the brightness temperature were 1.4 x 10 to the 10th K for UX Arietis and 2.9 x 10 to the 10th K for HR 1099. Simultaneous polarization measurements at the VLA showed 4-8 percent circular polarization and less than 2 percent linear polarization. It is found that the data are consistent with gyrosynchrotron emission from a power-law energy distribution of electrons in a magnetic field B less than or approximately equal to 6 gauss.

  3. VLBI observations of 3C273 at 22 GHz and 43 GHz ; 2, test of Synchrotron Self-Compton process

    CERN Document Server

    Mantovani, F; McHardy, I M; Valerio, C

    1999-01-01

    The VLBI observations at 22 GHz and 43 GHz of the quasar 3C273 obtained during a multi-frequency campaign in late 1992 in the radio, millimetre and X-ray bands allow us to derive the components' angular sizes, their peak fluxes and turnover frequencies. Lower limits to the Doppler factors have been derived by comparing the observed X-ray fluxes with those predicted by the Synchrotron Self-Compton model. Independent estimates of the Doppler factors were obtained through the assumption of the energy equipartition between the particles and the magnetic field. Of the five components used to model the first two milli-arcseconds of the jet, apart from the core, two components are in equipartition and the remaining two, at larger distances from the core, have large Doppler factors and are mainly responsible for the X-ray emission due to the Synchrotron Self-Compton process.

  4. Association of Fetal Heart Rate Baseline Change and Neonatal Outcomes.

    Science.gov (United States)

    Yang, Michael; Stout, Molly J; López, Julia D; Colvin, Ryan; Macones, George A; Cahill, Alison G

    2017-07-01

    Objective The objective of this study was to describe the incidence of baseline change within normal range during labor and its prediction of neonatal outcomes. Materials and Methods This was a prospective cohort of singleton, nonanomalous, term neonates with continuous electronic fetal monitoring and normal baseline fetal heart rate throughout the last 2 hours of labor. We determined baseline in 10-minute segments using Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria. We evaluated baseline changes of ≥ 20 and ≥ 30 bpm for association with acidemia (umbilical cord arterial pH ≤ 7.10) and neonatal intensive care unit (NICU) admission. Finally, we performed a sensitivity analysis of normal neonates, excluding those with acidemia, NICU admission, or 5-minute Apgar bpm; 272 (9.0%) had ≥ 30 bpm. Among normal neonates (n = 2,939), 1,221 (41.5%) had change ≥20 bpm. Acidemia was not associated with baseline change of any direction or magnitude. NICU admission was associated with decrease ≥ 20 bpm (adjusted odds ratio [aOR]: 2.93; 95% confidence interval [CI]: 1.19 - 7.21) or any direction ≥ 20 bpm (aOR: 4.06; 95% CI: 1.46-11.29). For decrease ≥ 20 bpm, sensitivity and specificity were 40.0 and 81.7%; for any direction ≥ 20 bpm, 75.0 and 58.3%. Conclusion Changes of normal baseline are common in term labor and poorly predict morbidity, regardless of direction or magnitude. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  5. Development Of Regional Climate Mitigation Baseline For A DominantAgro-Ecological Zone Of Karnataka, India

    Energy Technology Data Exchange (ETDEWEB)

    Sudha, P.; Shubhashree, D.; Khan, H.; Hedge, G.T.; Murthy, I.K.; Shreedhara, V.; Ravindranath, N.H.

    2007-06-01

    Setting a baseline for carbon stock changes in forest andland use sector mitigation projects is an essential step for assessingadditionality of the project. There are two approaches for settingbaselines namely, project-specific and regional baseline. This paperpresents the methodology adopted for estimating the land available formitigation, for developing a regional baseline, transaction cost involvedand a comparison of project-specific and regional baseline. The studyshowed that it is possible to estimate the potential land and itssuitability for afforestation and reforestation mitigation projects,using existing maps and data, in the dry zone of Karnataka, southernIndia. The study adopted a three-step approach for developing a regionalbaseline, namely: i) identification of likely baseline options for landuse, ii) estimation of baseline rates of land-use change, and iii)quantification of baseline carbon profile over time. The analysis showedthat carbon stock estimates made for wastelands and fallow lands forproject-specific as well as the regional baseline are comparable. Theratio of wasteland Carbon stocks of a project to regional baseline is1.02, and that of fallow lands in the project to regional baseline is0.97. The cost of conducting field studies for determination of regionalbaseline is about a quarter of the cost of developing a project-specificbaseline on a per hectare basis. The study has shown the reliability,feasibility and cost-effectiveness of adopting regional baseline forforestry sectormitigation projects.

  6. Nonintrusive methodology for wellness baseline profiling

    Science.gov (United States)

    Chung, Danny Wen-Yaw; Tsai, Yuh-Show; Miaou, Shaou-Gang; Chang, Walter H.; Chang, Yaw-Jen; Chen, Shia-Chung; Hong, Y. Y.; Chyang, C. S.; Chang, Quan-Shong; Hsu, Hon-Yen; Hsu, James; Yao, Wei-Cheng; Hsu, Ming-Sin; Chen, Ming-Chung; Lee, Shi-Chen; Hsu, Charles; Miao, Lidan; Byrd, Kenny; Chouikha, Mohamed F.; Gu, Xin-Bin; Wang, Paul C.; Szu, Harold

    2007-04-01

    We develop an accumulatively effective and affordable set of smart pair devices to save the exuberant expenditure for the healthcare of aging population, which will not be sustainable when all the post-war baby boomers retire (78 millions will cost 1/5~1/4 GDP in US alone). To design an accessible test-bed for distributed points of homecare, we choose two exemplars of the set to demonstrate the possibility of translation of modern military and clinical know-how, because two exemplars share identically the noninvasive algorithm adapted to the Smart Sensor-pairs for the real world persistent surveillance. Currently, the standard diagnoses for malignant tumors and diabetes disorders are blood serum tests, X-ray CAT scan, and biopsy used sometime in the physical checkup by physicians as cohort-average wellness baselines. The loss of the quality of life in making second careers productive may be caused by the missing of timeliness for correct diagnoses and easier treatments, which contributes to the one quarter of human errors generating the lawsuits against physicians and hospitals, which further escalates the insurance cost and wasteful healthcare expenditure. Such a vicious cycle should be entirely eliminated by building an "individual diagnostic aids (IDA)," similar to the trend of personalized drug, developed from daily noninvasive intelligent databases of the "wellness baseline profiling (WBP)". Since our physiology state undulates diurnally, the Nyquist anti-aliasing theory dictates a minimum twice-a-day sampling of the WBP for the IDA, which must be made affordable by means of noninvasive, unsupervised and unbiased methodology at the convenience of homes. Thus, a pair of military infrared (IR) spectral cameras has been demonstrated for the noninvasive spectrogram ratio test of the spontaneously emitted thermal radiation from a normal human body at 37°C temperature. This invisible self-emission spreads from 3 microns to 12 microns of the radiation wavelengths

  7. GPS dynamic cycle slip detection and correction with baseline constraint

    Institute of Scientific and Technical Information of China (English)

    Liu Zhenkun; Huang Ahunji

    2009-01-01

    When the cycle slips take place in the attitude determination of a moving platform, the precision of the attitude will be impaired badly. A method of cycle slip detection and correction is proposed, which is suitable to the dynamic measurement using GPS carrier phase: the cycle slips detection is first achieved by triple difference observables, then the cycle slips correction is performed with baseline length constraint. The simulation results show that the proposed method is effective to the dynamic cycle slips problem.

  8. Moon-Based INSAR Geolocation and Baseline Analysis

    Science.gov (United States)

    Liu, Guang; Ren, Yuanzhen; Ye, Hanlin; Guo, Huadong; Ding, Yixing; Ruan, Zhixing; Lv, Mingyang; Dou, Changyong; Chen, Zhaoning

    2016-07-01

    Earth observation platform is a host, the characteristics of the platform in some extent determines the ability for earth observation. Currently most developing platforms are satellite, in contrast carry out systematic observations with moon based Earth observation platform is still a new concept. The Moon is Earth's only natural satellite and is the only one which human has reached, it will give people different perspectives when observe the earth with sensors from the moon. Moon-based InSAR (SAR Interferometry), one of the important earth observation technology, has all-day, all-weather observation ability, but its uniqueness is still a need for analysis. This article will discuss key issues of geometric positioning and baseline parameters of moon-based InSAR. Based on the ephemeris data, the position, liberation and attitude of earth and moon will be obtained, and the position of the moon-base SAR sensor can be obtained by coordinate transformation from fixed seleno-centric coordinate systems to terrestrial coordinate systems, together with the Distance-Doppler equation, the positioning model will be analyzed; after establish of moon-based InSAR baseline equation, the different baseline error will be analyzed, the influence of the moon-based InSAR baseline to earth observation application will be obtained.

  9. Automated baseline change detection phase I. Final report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-12-01

    The Automated Baseline Change Detection (ABCD) project is supported by the DOE Morgantown Energy Technology Center (METC) as part of its ER&WM cross-cutting technology program in robotics. Phase 1 of the Automated Baseline Change Detection project is summarized in this topical report. The primary objective of this project is to apply robotic and optical sensor technology to the operational inspection of mixed toxic and radioactive waste stored in barrels, using Automated Baseline Change Detection (ABCD), based on image subtraction. Absolute change detection is based on detecting any visible physical changes, regardless of cause, between a current inspection image of a barrel and an archived baseline image of the same barrel. Thus, in addition to rust, the ABCD system can also detect corrosion, leaks, dents, and bulges. The ABCD approach and method rely on precise camera positioning and repositioning relative to the barrel and on feature recognition in images. In support of this primary objective, there are secondary objectives to determine DOE operational inspection requirements and DOE system fielding requirements.

  10. Magical properties of 2540 km baseline Superbeam Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Umasankar, Sankagiri; Raut, Sushant [Department of Physics, Indian Institute of Technology - I.I.T. Bombay, Mumbai, 400076 Maharashtra (India); Singh, Ravi Shanker [Department of Physics, Barus-Holley building, 184 Hope Street, Brown University, Box 1843, Providence, RI 02912 (United States)

    2010-07-01

    The determination if the neutrino mixing matrix and mass-squared differences is one of the aims of neutrino physics today. This is a complicated affair, owing to the various parameter degeneracies. While the proposed 7500 km long 'magic baseline' experiment simplifies the task considerably, the intense beam required for such an experiment seems futuristic by current standards. As an alternative, we highlight the 'magical' properties of the 2540 km baseline. We propose a Superbeam experiment at this much shorter baseline with a narrow band NuMI-like beam, and demonstrate the ability of this single setup to distinguish between the two mass hierarchies. This, we show, is possible with a moderate exposure and by running the experiment in the neutrino mode only. Our results hold up to fairly small values of the mixing angle {theta}{sub 13} and irrespective of the value of the CP violating parameter. Unlike the magic baseline, it may also be possible to use this setup to measure CP violation in neutrino oscillation experiments. (authors)

  11. Salton Sea sampling program: baseline studies

    Energy Technology Data Exchange (ETDEWEB)

    Tullis, R.E.; Carter, J.L.; Langlois, G.W.

    1981-04-13

    Baseline data are provided on three species of fish from the Salton Sea, California. The fishes considered were the orange mouth corvina (Cynoscion xanthulus), gulf croaker (Bairdiella icistius) and sargo (Anisotremus davidsonii). Morphometric and meristic data are presented as a baseline to aid in the evaluation of any physiological stress the fish may experience as a result of geothermal development. Analyses were made on muscle, liver, and bone of the fishes sampled to provide baseline data on elemental tissue burdens. The elements measured were: As, Br, Ca, Cu, Fe, Ga, K, Mn, Mi, Pb, Rb, Se, Sr, Zn, and Zr. These data are important if an environmentally sound progression of geothermal power production is to occur at the Salton Sea.

  12. Baseline methodologies for clean development mechanism projects

    Energy Technology Data Exchange (ETDEWEB)

    Lee, M.K. (ed.); Shrestha, R.M.; Sharma, S.; Timilsina, G.R.; Kumar, S.

    2005-11-15

    The Kyoto Protocol and the Clean Development Mechanism (CDM) came into force on 16th February 2005 with its ratification by Russia. The increasing momentum of this process is reflected in more than 100 projects having been submitted to the CDM Executive Board (CDM-EB) for approval of the baselines and monitoring methodologies, which is the first step in developing and implementing CDM projects. A CDM project should result in a net decrease of GHG emissions below any level that would have resulted from other activities implemented in the absence of that CDM project. The 'baseline' defines the GHG emissions of activities that would have been implemented in the absence of a CDM project. The baseline methodology is the process/algorithm for establishing that baseline. The baseline, along with the baseline methodology, are thus the most critical element of any CDM project towards meeting the important criteria of CDM, which are that a CDM should result in 'real, measurable, and long term benefits related to the mitigation of climate change'. This guidebook is produced within the frame work of the United Nations Environment Programme (UNEP) facilitated 'Capacity Development for the Clean Development Mechanism (CD4CDM)' Project. This document is published as part of the projects effort to develop guidebooks that cover important issues such as project finance, sustainability impacts, legal framework and institutional framework. These materials are aimed to help stakeholders better understand the CDM and are believed to eventually contribute to maximize the effect of the CDM in achieving the ultimate goal of UNFCCC and its Kyoto Protocol. This Guidebook should be read in conjunction with the information provided in the two other guidebooks entitled, 'Clean Development Mechanism: Introduction to the CDM' and 'CDM Information and Guidebook' developed under the CD4CDM project. (BA)

  13. Neutrino Interactions and Long-Baseline Experiments

    CERN Document Server

    Mosel, Ulrich

    2016-01-01

    The extraction of neutrino mixing parameters and the CP-violating phase requires knowledge of the neutrino energy. This energy must be reconstructed from the final state of a neutrino-nucleus reaction since all long-baseline experiments use nuclear targets. This reconstruction requires detailed knowledge of the neutrino reactions with bound nucleons and of the final state interactions of hadrons with the nuclear environment. Quantum-kinetic transport theory can be used to build an event generator for this reconstruction that takes basic nuclear properties, such as binding, into account. Some examples are discussed that show the effects of nuclear interactions on observables in long-baseline experiments

  14. Verification of the Astrometric Performance of the Korean VLBI Network, using comparative SFPR studies with the VLBA at 14/7 mm

    CERN Document Server

    Rioja, Mar\\'\\ia J; Jung, TaeHyun; Sohn, Bong Won; Byun, Do-Young; Agudo, Iván; Cho, Se-Hyung; Lee, Sang-Sung; Kim, Jongsoo; Kim, Kee-Tae; Oh, Chung Sik; Han, Seog-Tae; Je, Do-Heung; Chung, Moon-Hee; Wi, Seog-Oh; Kang, Jiman; Lee, Jung-Won; Chung, Hyunsoo; Kim, Hyo Ryoung; Kim, Hyun-Goo; Lee, Chang-Hoon; Roh, Duk-Gyoo; Oh, Se-Jin; Yeom, Jae-Hwan; Song, Min-Gyu; Kang, Yong-Woo

    2014-01-01

    The Korean VLBI Network (KVN) is a new mm-VLBI dedicated array with capability for simultaneous observations at multiple frequencies, up to 129 GHz. The innovative multi-channel receivers present significant benefits for astrometric measurements in the frequency domain. The aim of this work is to verify the astrometric performance of the KVN using a comparative study with the VLBA, a well established instrument. For that purpose, we carried out nearly contemporaneous observations with the KVN and the VLBA, at 14/7 mm, in April 2013. The KVN observations consisted of simultaneous dual frequency observations, while the VLBA used fast frequency switching observations. We used the Source Frequency Phase Referencing technique for the observational and analysis strategy. We find that having simultaneous observations results in a superior performance for compensation of all atmospheric terms in the observables, in addition to offering other significant benefits for astrometric analysis. We have compared the KVN astr...

  15. Waste management project technical baseline description

    Energy Technology Data Exchange (ETDEWEB)

    Sederburg, J.P.

    1997-08-13

    A systems engineering approach has been taken to describe the technical baseline under which the Waste Management Project is currently operating. The document contains a mission analysis, function analysis, requirement analysis, interface definitions, alternative analysis, system definition, documentation requirements, implementation definitions, and discussion of uncertainties facing the Project.

  16. How Valid Are the Portland Baseline Essays?

    Science.gov (United States)

    Martel, Erich

    1991-01-01

    Portland, Oregon's "African-American Baseline Essays," widely used in creating multicultural curricula, inaccurately depicts ancient Egyptians as black people and Olmec civilization as derived from African influences. The authors advance racial theories long abandoned by mainline Africa scholars, attribute mystical powers to pyramids,…

  17. Geochemical modelling baseline compositions of groundwater

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Kjøller, Claus; Andersen, Martin Søgaard

    2008-01-01

    Reactive transport models, were developed to explore the evolution in groundwater chemistry along the flow path in three aquifers; the Triassic East Midland aquifer (UK), the Miocene aquifer at Valreas (F) and the Cretaceous aquifer near Aveiro (P). All three aquifers contain very old groundwaters...... of the evolution in natural baseline properties in groundwater....

  18. Solid Waste Program technical baseline description

    Energy Technology Data Exchange (ETDEWEB)

    Carlson, A.B.

    1994-07-01

    The system engineering approach has been taken to describe the technical baseline under which the Solid Waste Program is currently operating. The document contains a mission analysis, function analysis, system definition, documentation requirements, facility and project bases, and uncertainties facing the program.

  19. Rationing in the presence of baselines

    DEFF Research Database (Denmark)

    Hougaard, Jens Leth; Moreno-Ternero, Juan D.; Østerdal, Lars Peter

    2013-01-01

    We analyze a general model of rationing in which agents have baselines, in addition to claims against the (insufficient) endowment of the good to be allocated. Many real-life problems fit this general model (e.g., bankruptcy with prioritized claims, resource allocation in the public health care...

  20. National Cyberethics, Cybersafety, Cybersecurity Baseline Study

    Science.gov (United States)

    Education Digest: Essential Readings Condensed for Quick Review, 2009

    2009-01-01

    This article presents findings from a study that explores the nature of the Cyberethics, Cybersafety, and Cybersecurity (C3) educational awareness policies, initiatives, curriculum, and practices currently taking place in the U.S. public and private K-12 educational settings. The study establishes baseline data on C3 awareness, which can be used…

  1. RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz

    CERN Document Server

    Lobanov, A P; Bruni, G; Kovalev, Y Y; Anderson, J; Bach, U; Kraus, A; Zensus, J A; Lisakov, M M; Sokolovsky, K V; Voytsik, P A

    2015-01-01

    Polarization of radio emission in extragalactic jets at a sub-milliarcsecond angular resolution holds important clues for understanding the structure of the magnetic field in the inner regions of the jets and in close vicinity of the supermassive black holes in the centers of active galaxies. Space VLBI observations provide a unique tool for polarimetric imaging at a sub-milliarcsecond angular resolution and studying the properties of magnetic field in active galactic nuclei on scales of less than 10^4 gravitational radii. A space VLBI observation of high-redshift quasar TXS 0642+449 (OH 471), made at a wavelength of 18 cm (frequency of 1.6 GHz) as part of the Early Science Programme (ESP) of the RadioAstron} mission, is used here to test the polarimetric performance of the orbiting Space Radio Telescope (SRT) employed by the mission, to establish a methodology for making full Stokes polarimetry with space VLBI at 1.6 GHz, and to study the polarized emission in the target object on sub-milliarcsecond scales. ...

  2. PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz

    CERN Document Server

    Karamanavis, V; Krichbaum, T P; Angelakis, E; Hodgson, J; Nestoras, I; Myserlis, I; Zensus, J A; Sievers, A; Ciprini, S

    2016-01-01

    Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106 showing a rapid and strong gamma-ray outburst followed by high and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign covering also the radio, optical, UV, and X-ray bands indicating that the flare was accompanied by a simultaneous outburst at optical/UV/X-rays and a delayed outburst at radio bands. Aims: In the current work we explore the phenomenology and physical conditions within the ultra-relativistic jet of the gamma-ray blazar PKS 1502+106. Additionally, we address the question of the spatial localization of the MeV/GeV-emitting region of the source. Methods: We utilize ultra-high angular resolution mm-VLBI observations at 43 and 86 GHz complemented by VLBI observations at 15 GHz. We also employ single-dish radio data from the F-GAMMA program at frequencies matching the VLBI monitoring. Results: PKS 1502+106 sh...

  3. The soft X-ray properties of AGN from the CJF sample; A correlation analysis between soft X-ray and VLBI properties

    CERN Document Server

    Britzen, S; Campbell, R M; Gliozzi, M; Readhead, A C S; Browne, I W A; Wilkinson, P

    2008-01-01

    Context: We present the soft X-ray properties obtained in the ROSAT All-Sky survey and from pointed PSPC observations for the AGN in the complete flux-density limited Caltech-Jodrell Bank flat spectrum sample (hereafter CJF). CJF is a VLBI survey (VLBA observations at 5 GHz) of 293 AGN with detailed information on jet component motion. Aims: We investigate and discuss the soft X-ray properties of this AGN sample and examine the correlations between X-ray and VLBI properties, test beaming scenarios, and search for the discriminating properties between the sub-samples detected and not detected by ROSAT. Methods: Comparing the observed and the predicted X-ray fluxes by assuming an Inverse Compton (IC) origin for the observed X-rays, we compute the beaming or Doppler factor and contrast the Doppler factors with other beaming indicators derived from the VLBI observations, such as the value of the expansion velocity, and the observed and intrinsic brightness temperature. In addition, we investigate the large-scale ...

  4. Sensor Technology Baseline Study for Enabling Condition Based Maintenance Plus in Army Ground Vehicles

    Science.gov (United States)

    2012-03-01

    and mechanisms are identified. Based on this analysis, baselines sensor technologies are determined to prognosticate these types failure causes early...Current/voltage sensor measured at sensor terminals; Fluid level sensor Excessive slippage and clutch chatter Internal transmission failure ... TYPE Final 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Sensor Technology Baseline Study for Enabling Condition Based Maintenance Plus in

  5. RadioAstron Studies of the Nearby, Turbulent Interstellar Plasma With the Longest Space-Ground Interferometer Baseline

    CERN Document Server

    Smirnova, T V; Popov, M V; Gwinn, C R; Anderson, J M; Andrianov, A S; Bartel, N; Deller, A; Johnson, M D; Joshi, B C; Kardashev, N S; Karuppusamy, R; Kovalev, Y Y; Kramer, M; Soglasnov, V A; Zensus, J A; Zhuravlev, V I

    2014-01-01

    RadioAstron space-ground VLBI observations of the pulsar B0950+08, conducted with the 10-m space radio telescope in conjunction with the Arecibo 300-m telescope and Westerbork Synthesis Radio Telescope at a frequency of 324 MHz, were analyzed in order to investigate plasma inhomogeneities in the direction of this nearby pulsar. The observations were conducted at a spacecraft distance of 330,000 km, resulting in a projected baseline of 220,000 km, providing the greatest angular resolution ever achieved at meter wavelengths. Our analysis is based on fundamental behavior of structure and coherence functions. We find that the pulsar shows scintillation on two frequency scales, both much less than the observing frequency; but modulation is less than 100%. We infer that the scattering is weak, but a refracting wedge disperses the scintillation pattern. The refraction angle of this "cosmic prism" is measured as theta_0=1.1 - 4.4 mas, with the refraction direction being approximately perpendicular to the observer vel...

  6. Coral reef baselines: how much macroalgae is natural?

    Science.gov (United States)

    Bruno, John F; Precht, William F; Vroom, Peter S; Aronson, Richard B

    2014-03-15

    Identifying the baseline or natural state of an ecosystem is a critical step in effective conservation and restoration. Like most marine ecosystems, coral reefs are being degraded by human activities: corals and fish have declined in abundance and seaweeds, or macroalgae, have become more prevalent. The challenge for resource managers is to reverse these trends, but by how much? Based on surveys of Caribbean reefs in the 1970s, some reef scientists believe that the average cover of seaweed was very low in the natural state: perhaps less than 3%. On the other hand, evidence from remote Pacific reefs, ecological theory, and impacts of over-harvesting in other systems all suggest that, historically, macroalgal biomass may have been higher than assumed. Uncertainties about the natural state of coral reefs illustrate the difficulty of determining the baseline condition of even well studied systems.

  7. Measurement of baseline and orientation between distributed aerospace platforms.

    Science.gov (United States)

    Wang, Wen-Qin

    2013-01-01

    Distributed platforms play an important role in aerospace remote sensing, radar navigation, and wireless communication applications. However, besides the requirement of high accurate time and frequency synchronization for coherent signal processing, the baseline between the transmitting platform and receiving platform and the orientation of platform towards each other during data recording must be measured in real time. In this paper, we propose an improved pulsed duplex microwave ranging approach, which allows determining the spatial baseline and orientation between distributed aerospace platforms by the proposed high-precision time-interval estimation method. This approach is novel in the sense that it cancels the effect of oscillator frequency synchronization errors due to separate oscillators that are used in the platforms. Several performance specifications are also discussed. The effectiveness of the approach is verified by simulation results.

  8. Joint Multi-baseline SAR Interferometry

    Directory of Open Access Journals (Sweden)

    S. Tebaldini

    2005-12-01

    Full Text Available We propose a technique to provide interferometry by combining multiple images of the same area. This technique differs from the multi-baseline approach in literature as (a it exploits all the images simultaneously, (b it performs a spectral shift preprocessing to remove most of the decorrelation, and (c it exploits distributed targets. The technique is mainly intended for DEM generation at centimetric accuracy, as well as for differential interferometry. The problem is framed in the contest of single-input multiple-output (SIMO channel estimation via the cross-relations (CR technique and the resulting algorithm provides significant improvements with respect to conventional approaches based either on independent analysis of single interferograms or multi-baselines phase analysis of single pixels of current literature, for those targets that are correlated in all the images, like for long-term coherent areas, or for acquisitions taken with a short revisit time (as those gathered with future satellite constellations.

  9. Dissipative Effect in Long Baseline Neutrino Experiments

    CERN Document Server

    Oliveira, Roberto L N

    2016-01-01

    The propagation of neutrinos in long baselines experiments may be influenced by dissipation effects. Using Lindblad Master Equation we evolve neutrinos taking into account these dissipative effects. The MSW and the dissipative effects may change the probabilities behavior. In this work, we show and explain how the behavior of the probabilities can change due to the decoherence and relaxation effects acting individually with the MSW effect. A new exotic peak appears in this case and we show the difference between the decoherence and relaxation effects in the appearance of this peak. We also adapt the usual approximate expression for survival and appearance probabilities with all possible decoherence effects. We suppose the baseline of DUNE and show how each decoherence parameters change the probabilities analyzing the possible modification using numeric and analytic approach.

  10. Systematic errors in long baseline oscillation experiments

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Deborah A.; /Fermilab

    2006-02-01

    This article gives a brief overview of long baseline neutrino experiments and their goals, and then describes the different kinds of systematic errors that are encountered in these experiments. Particular attention is paid to the uncertainties that come about because of imperfect knowledge of neutrino cross sections and more generally how neutrinos interact in nuclei. Near detectors are planned for most of these experiments, and the extent to which certain uncertainties can be reduced by the presence of near detectors is also discussed.

  11. The Gambia Impact Evaluation Baseline Report

    OpenAIRE

    2015-01-01

    The Government of The Gambia is implementing the Maternal and Child Nutrition and Health Results Project (MCNHRP) to increase the utilization of community nutrition and primary maternal and child health services. In collaboration with the Government, the World Bank is conducting an impact evaluation (IE) to assess the impact of the project on key aspects of maternal and child nutrition and health. The baseline survey for the MCNHRP IE took place between November 2014 and February 2015. It c...

  12. Killer whale industry - Baseline Data Collection of Southern Resident Killer Whale (SRKW) Industry Members

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — SRKW were listed as endangered in 2005. This study collected baseline data about the industry to be able to determine social impacts to the industry as a result of...

  13. The SFXC software correlator for Very Long Baseline Interferometry: Algorithms and Implementation

    CERN Document Server

    Keimpema, A; Pogrebenko, S V; Campbell, R M; Cimó, G; Duev, D A; Eldering, B; Kruithof, N; van Langevelde, H J; Marchal, D; Calvés, G Molera; Ozdemir, H; Paragi, Z; Pidopryhora, Y; Szomoru, A; Yang, J

    2015-01-01

    In this paper a description is given of the SFXC software correlator, developed and maintained at the Joint Institute for VLBI in Europe (JIVE). The software is designed to run on generic Linux-based computing clusters. The correlation algorithm is explained in detail, as are some of the novel modes that software correlation has enabled, such as wide-field VLBI imaging through the use of multiple phase centres and pulsar gating and binning. This is followed by an overview of the software architecture. Finally, the performance of the correlator as a function of number of CPU cores, telescopes and spectral channels is shown.

  14. The First Geodetic VLBI Field Test of LIFT: A 550-km-long Optical Fiber Link for Remote Antenna Synchronization

    Science.gov (United States)

    Perini, Federico; Bortolotti, Claudio; Roma, Mauro; Ambrosini, Roberto; Negusini, Monia; Maccaferri, Giuseppe; Stagni, Matteo; Nanni, Mauro; Clivati, Cecilia; Frittelli, Matteo; Mura, Alberto; Levi, Filippo; Zucco, Massimo; Calonico, Davide; Bertarini, Alessandra; Artz, Thomas

    2016-12-01

    We present the first field test of the implementation of a coherent optical fiber link for remote antenna synchronization realized in Italy between the Italian Metrological Institute (INRIM) and the Medicina radio observatory of the National Institute for Astrophysics (INAF). The Medicina VLBI antenna participated in the EUR137 experiment carried out in September 2015 using, as reference systems, both the local H-maser and a remote H-maser hosted at the INRIM labs in Turin, separated by about 550 km. In order to assess the quality of the remote clock, the observed radio sources were split into two sets, using either the local or the remote H-maser. A system to switch automatically between the two references was integrated into the antenna field system. The observations were correlated in Bonn and preliminary results are encouraging since fringes were detected with both time references along the full 24 hours of the session. The experimental set-up, the results, and the perspectives for future radio astronomical and geodetic experiments are presented.

  15. Radiation Testing of Consumer High-Speed LSI Chips for the Next Space VLBI Mission, VSOP-2

    CERN Document Server

    Wajima, Kiyoaki; Murata, Yasuhiro; Hirabayashi, Hisashi

    2007-01-01

    We performed two types of radiation testing on high-speed LSI chips to test their suitability for use in wideband observations by the Japanese next space VLBI mission, VSOP-2. In the total ionization dose experiment we monitored autocorrelation spectra which were taken with irradiated LSI chips and the source current at intervals up to 1,000 hours from the ionization dose, but we could not see any change of these features for the chips irradiated with dose rates expected in the VSOP-2 mission. In the single event effect experiment, we monitored the cross correlation phase and power spectra between the data from radiated and non-radiated devices, and the source current during the irradiation of heavy-ions. We observed a few tens of single event upsets as discrete delay jumps for each LSI. We estimated the occurrence rate of single events in space as between once a few days to once a month. No single event latch-up was seen in any of the LSIs. These results show that the tested LSIs have sufficient tolerance to...

  16. 烟草野火病菌对细菌杀星的敏感性测定及敏感基线建立%Sensitivity Determination and Sensitivity Baseline Establishment of Pseudomonas syringae pv.tabaci to Streptomycin·Saikuzuo

    Institute of Scientific and Technical Information of China (English)

    陈长卿; 隋原; 杨丽娜; 周洪波; 张文中; 高洁

    2011-01-01

    从黑龙江省和吉林省烟草主要种植区获得烟草野火病菌(Pseudomonas syringae pv.tabaci)菌株61个,采用抑菌圈法对50%细菌杀星WP进行了敏感性测定.结果表明:不同地理来源的烟草野火病菌对细菌杀星敏感性有一定差异,EC50=1.070~1.517 μg/mL,平均1.421μg/mL;黑龙江省鸡西的菌株h28为最敏感菌株,其EC50为1.070μg/mL,而黑龙江宁安菌株h40敏感性最低,其EC50值为1.517 μg/mL.同时确定了两省烟草野火病菌对细菌沙星的敏感基线为1.421μg/mL,可用于对烟草野火病菌对细菌杀星的抗药性监测;烟草野火病菌对细菌杀星未产生抗药性.%The fungicide sensitivity to streptomycin · saikuzuo of sixty one strains of Pseudomonas syringae pv. Tabaci (Pst) from tabacco regions in Heilongjiang and Jilin provinces was determined using the method of inhibition zone. The results showed there were sensitivity differences among the strains, and EC50 value of all strains was lower than 2 μg/mL, which ranged from 1.070 to 1.517 μg/mL, and the av erage value was 1.421 μg/mL. Strains h28( EC50 1.070 μg/mL) from Jixi, Heilongjiang was the most sensitive to the fungicide, but h4O(EC50 1.517 μg/mL) from Ning'an, Heilongjiang was strain of the low est sensitivity. The sensitivity baseline of Pst strains to streptomycin ? saikuzuo was determined as 1.421 μg/mL, which could be used for monitoring resistance of Pst strains to the fungicide. There wasno resistance of Pst strains to the fungicide.

  17. SRP baseline hydrogeologic investigation, Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Bledsoe, H.W.

    1987-11-01

    As discussed in the program plan for the Savannah River Plant (SRP) Baseline Hydrogeologic Investigation, this program has been implemented for the purpose of updating and improving the current state of knowledge and understanding of the hydrogeologic systems underlying the Savannah River Plant (SRP). The objective of the program is to install a series of observation well clusters (wells installed in each major water bearing formation at the same site) at key locations across the plant site in order to: (1) provide detailed information on the lithology, stratigraphy, and groundwater hydrology, (2) provide observation wells to monitor the groundwater quality, head relationships, gradients, and flow paths.

  18. Optimization of the CLIC Baseline Collimation System

    Energy Technology Data Exchange (ETDEWEB)

    Resta-Lopez, Javier; /Oxford U., JAI; Angal-Kalinin, Deepa; /Daresbury; Fernandez-Hernando, Juan; /Daresbury; Jackson, Frank; /Daresbury; Dalena, Barbara; /CERN; Schulte, Daniel; /CERN; Tomas, Rogelio; /CERN; Seryi, Andrei; /SLAC

    2012-07-06

    Important efforts have recently been dedicated to the improvement of the design of the baseline collimation system of the Compact Linear Collider (CLIC). Different aspects of the design have been optimized: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers have also been reviewed to minimize wakefields; in addition, the optics design have been polished to improve the collimation efficiency. This paper describes the current status of the CLIC collimation system after this optimization.

  19. SRP baseline hydrogeologic investigation: Aquifer characterization

    Energy Technology Data Exchange (ETDEWEB)

    Strom, R.N.; Kaback, D.S.

    1992-03-31

    An investigation of the mineralogy and chemistry of the principal hydrogeologic units and the geochemistry of the water in the principal aquifers at Savannah River Site (SRS) was undertaken as part of the Baseline Hydrogeologic Investigation. This investigation was conducted to provide background data for future site studies and reports and to provide a site-wide interpretation of the geology and geochemistry of the Coastal Plain Hydrostratigraphic province. Ground water samples were analyzed for major cations and anions, minor and trace elements, gross alpha and beta, tritium, stable isotopes of hydrogen, oxygen, and carbon, and carbon-14. Sediments from the well borings were analyzed for mineralogy and major and minor elements.

  20. Baseline Response Levels Are a Nuisance in Infant Contingency Learning

    Science.gov (United States)

    Millar, W. S.; Weir, Catherine

    2015-01-01

    The impact of differences in level of baseline responding on contingency learning in the first year was examined by considering the response acquisition of infants classified into baseline response quartiles. Whereas the three lower baseline groups showed the predicted increment in responding to a contingency, the highest baseline responders did…