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Sample records for vlbi slr gps

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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...

  7. Satellite co-locations as a link between SLR, GPS and Low Earth Orbiting (LEO) satellites

    Science.gov (United States)

    Melachroinos, S. A.; Lemoine, F. G.; Chinn, D. S.; Nicolas, J. B.; Zelensky, N. P.; Wimert, J.; Radway, Y.

    2013-12-01

    The procedure applied for the determination of the International Terrestrial Reference Frame (ITRF) requires the combination of all four major techniques of Space Geodesy. This combination is only possibly realized by the introduction of the local-ties between co-located techniques. A local-tie is the lever arm vector between the marker points on the sites where two or more space geodesy instruments operate. The local ties are used as additional observations with proper variances. They are usually derived from local surveys using either classical geodesy or the global navigation satellite systems (GNSS). The Global Positioning System (GPS) plays a major role in the ITRF combination by linking together all the other three techniques SLR, DORIS and VLBI (Altamimi and Collilieux 2009). However, discrepancies between local ties and space geodesy estimates are well known although the reasons for these discrepancies are often not clear. These discrepancies could be either due to errors in local ties and in coordinate estimates or in both. In this study, we use the tracking to G05-35 and G06-36 and one LEO by SLR sites and their combined orbits, earth rotation parameters (ERPs) and station positions in order to establish space-based co-location ties on the stations. The LEO satellite used in this experiment is Jason-2, which carries both GPS and SLR. Therefore from the data-processing point of view the LEO satellite is used as a fast moving station (Thaller et al. 2011). Jason-2 is also equipped with DORIS, but it will be included into another combined analysis. Subsequently, we compare the consistency of our space-based co-locations to the ones from ITRF08 and SLRF08 - IGb08 solutions.

  8. 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.

  9. 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...

  10. J2: An evaluation of new estimates from GPS, GRACE, and load models compared to SLR

    NARCIS (Netherlands)

    Lavallée, D.A.; Moore, P.; Clarke, P.J.; Petrie, E.J.; Van Dam, T.; King, M.A.

    2010-01-01

    Changes in J2, resulting from past and present changes in Earth's climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth's shape observed by GPS. We compare estimates of non-secular J2 changes from

  11. J2: An evaluation of new estimates from GPS, GRACE, and load models compared to SLR

    NARCIS (Netherlands)

    Lavallée, D.A.; Moore, P.; Clarke, P.J.; Petrie, E.J.; Van Dam, T.; King, M.A.

    2010-01-01

    Changes in J2, resulting from past and present changes in Earth's climate, are traditionally observed by Satellite Laser ranging (SLR). Assuming an elastic Earth, it is possible to infer changes in J2 from changes in Earth's shape observed by GPS. We compare estimates of non-secular J2 changes from

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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).

  2. 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.

  3. 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.

  4. SLR 2000

    Science.gov (United States)

    Degnan, John J.

    1994-11-01

    SLR 2000 is a concept for a totally automated subcentimeter SLR system presently being studied at GSFC. If funding permits, a prototype would be installed and tested at the Goddard Geophysical and Astronomical Observatory (GCAO) in FY98 and a small number of automated stations would be fielded by the year 2000. Unlike present systems, the "SLR 2000" system is being designed to: 1) operate autonomously without the need for onsite operators; 2) present no hazards (i.e., optical, electrical, and/or chemical) to personnel in the vicinity or to overflying aircraft; and 3) have a mean time between failures (MTBF) of at least three months. It is assumed that the systems are located at "friendly" sites where some level of security is provided and where certain low level service functions (e.g. commercial power, communications, heat pump service cleaning, etc.) are available or can be contracted for locally on an as-needed basis. The main system consists of two parts - an optical head and electronics rack. The optical head contains the laser transmitter and power supply, transmit/receive switch, optical telescope, tracking angle sensor (intensified CCD camera), detector and power supply, two angular encoders, azimuth and elevation motors, and a protective dome. The optical head mounts directly to the top of a concrete pier which contains the geodetic monument and forms part of the environmental housing for the hardware and servicing personnel. It is equipped with electronic levels for leveling the mount and monitoring its stability.

  5. GPS Position Time Series @ JPL

    Science.gov (United States)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  6. GPS Position Time Series @ JPL

    Science.gov (United States)

    Owen, Susan; Moore, Angelyn; Kedar, Sharon; Liu, Zhen; Webb, Frank; Heflin, Mike; Desai, Shailen

    2013-01-01

    Different flavors of GPS time series analysis at JPL - Use same GPS Precise Point Positioning Analysis raw time series - Variations in time series analysis/post-processing driven by different users. center dot JPL Global Time Series/Velocities - researchers studying reference frame, combining with VLBI/SLR/DORIS center dot JPL/SOPAC Combined Time Series/Velocities - crustal deformation for tectonic, volcanic, ground water studies center dot ARIA Time Series/Coseismic Data Products - Hazard monitoring and response focused center dot ARIA data system designed to integrate GPS and InSAR - GPS tropospheric delay used for correcting InSAR - Caltech's GIANT time series analysis uses GPS to correct orbital errors in InSAR - Zhen Liu's talking tomorrow on InSAR Time Series analysis

  7. Evaluation of CHAMP Satellite Orbit with SLR Measurements

    Institute of Scientific and Technical Information of China (English)

    QIN Xianping; YANG Yuanxi

    2005-01-01

    The technique of Evaluating CHAMP satellite orbit with SLR measurements is presented. As an independent evaluation of the orbit solution, SLR data observed from January 1 to 16, 2002 are processed to compute the residuals after fixing the GFZ's post science orbits solutions. The SLR residuals are computed as the differences of the SLR measurements minus the corresponding distances between the SLR station and the GPS-derived orbit positions. On the basis of the SLR residuals analysis, it is found that the accuracy of GFZ's post science orbits is better than 10 em and that there is no systematic error in GFZ's post science orbits.

  8. Ten years of SLR production in Argentina

    Science.gov (United States)

    Pacheco, A.; Podestá, R.; Yin, Z.; Liu, W.; Actis, E.; Adarvez, S.; Quinteros, J.; Podestá, F.

    2017-07-01

    SLR technique is a proved astro-geodetic art with a significant power to contribute to Earth and Space Sciences. Therefore, scientific applications of SLR System are able to perform multiple tasks in the fields of Astrometry, Geodesy and Geophysics. The results we show here were obtained from satellite observations made at SLR 7406 Station of Observatorio Astronómico Félix Aguilar (OAFA) in San Juan, Argentina. The telescope was installed early on 2006, in concordance with an International Cooperation Agreement between Universidad Nacional de San Juan, Argentina and Chinese Academy of Sciences. In this abstract we show the current research being done with ILRS 7406 station: Length of day (LOD) and Angular velocity of Earth Rotation, calculated weekly; Pole Motion. ILRS7406 is daily surveying Pole coordinates x and y; Tracking SLR to GNSS constellations. SLR System contributes to the adjustment and validation of satellite GALILEO, GPS, GLONASS, and BEIDOU orbits. Our station is nowadays member of the new ITRF 2014 frame, and these past years has been one of the 3 highest producing SLR Stations on the ILRS net, composed of about 40 stations distributed all around the world. The obtained results during this first 10 years of experience are useful to enhance the traditional collaboration between OAFA and international services such as ILRS, IERS and NASA.

  9. 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.

  10. SLR data for the next ITRF

    Science.gov (United States)

    Schillak, Stanislaw; Lejba, Pawel

    2013-04-01

    The determination of the new International Terrestrial Reference Frame (ITRF) have to include all significant effects in the SLR data in the long time period. The presented analysis was based on the results of coordinates determination for the most SLR stations in the period 1983-2011. The geocentric coordinates were computed separately for each station by means of NASA Goddard's GEODYN-II program from monthly arcs of LAGEOS-1 and LAGEOS-2 satellites. These station positions and velocities were transformed to the North, East and vertical components in the reference to ITRF2008 and these components were the base for further analysis. The coordinates for each arc were only accepted if the number of the normal points per SLR station was greater than 50. The results of this analysis show several important systematic biases which should be included in the new ITRF. First of all the SLR stations accuracy is stable from January 1997 up to now and only these data should be used in the new ITRF. The earlier data especially before 1993 have too large biases mainly due to results from only one LAGEOS satellite. The positions for the period 1993-1996 have too large variations for the most stations. The systematic biases are the next problem which should be included in the next ITRF. The problem is especially important for the most accurate stations Zimmerwald (7810) and Herstmoceux (7840), both stations had jump in vertical component due to change interval counter to event timer, 2.5 cm in February 2006 and 1.0 cm in February 2007, respectively. The ITRF coordinates should be determined separately for the data before and after jump. The several systematic biases for the other stations e.g. Matera, Monument Peak, Grasse, Wettzell should be take into account. The comparison with the GPS positions transformed to the SLR reference point is the best verification. The position change due to earthquake is the next important task. The effect of the Concepcion station (7405) position

  11. 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.

  12. 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.

  13. 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.

  14. Combined analysis of GNSS and SLR observations for the GIOVE satellites

    Science.gov (United States)

    Thaller, D.; Steinbach, A.; Dach, R.

    2009-04-01

    The GGSP (Galileo Geodetic Service Provider) is responsible to provide the geodetic basement of the future European GNSS, the Galileo system. The AIUB is one partner of the consortium of seven institutions. In the context of this project, the data of 13 GESS (Galileo Experimental Sensor Stations) are processed together with the GPS data of about 120 IGS sites. Apart from the station coordinates also the satellite orbits, ERPs, and clock corrections are computed. Since the 13 GESS do not only provide GPS data but also track the two first Galileo satellites (i.e., GIOVE-A and GIOVE-B), a combined processing of the GPS and Galileo data using microwave data is possible. Due to the sparse network of GESS the GPS data highly support the Galileo related products (the orbits and satellite clock corrections). Nevertheless, the quality of the GIOVE orbits is limited to about 20 cm. As both GIOVE are equipped with retro-reflector arrays, the satellites are tracked by satellite laser ranging (SLR), as it is already done for some GLONASS satellites and those two GPS satellites equipped with retro-reflectors. The availability of SLR data allows a validation of the satellite orbits determined from GNSS observations. The range residuals show whether there is any systematic difference between the GNSS and SLR system and, thus, may help to improve the orbit modeling for the GIOVE satellites. Furthermore, we will include the SLR tracking data into the orbit determination in order to derive a combined GNSS+SLR orbit. It will be studied whether the inclusion of SLR data shows any significant improvement for the combined orbit compared to the GNSS-only orbit. This study can be seen as a further step toward the combined processing of GNSS and SLR observations for a fully integrated multi-technique data analysis.

  15. Determination of Chinese mobile SLR sites' coordinates

    Institute of Scientific and Technical Information of China (English)

    FENG Chugang; CAI Wusan; ZHU Yuanlan; YANG Fumin

    2003-01-01

    The geocentric coordinates of three mobile sites including Fangshan inBeijing, Urumqi in the Xinjiang Uygur Autonomous Region and Lhasa in Tibet are determined in the ITRF2000 frame by means of both the global SLR data and the mobile (SLR) data obtained by a mobile satellite laser ranging (SLR) apparatus from Aug. 2000 to Dec. 2001. The results showed that the geometrical performance ofChinese SLR network has been significantly improved.

  16. 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...

  17. 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.

  18. Long range geoid control through the European GPS traverse: Final results

    Science.gov (United States)

    Torge, W.; Basic, T.; Denker, H.; Doliff, J.; Wenzel, H.-G.

    1989-01-01

    The European north-south Global Positioning System (GPS)-traverse proposed by IAG SSG 3.88, should control and improve the European geoid. This traverse follows first order leveling lines, included in the United European Leveling Network. From May to August 1986 and in July 1987, the central and northern part of this traverse (approx. 3000 km) was observed using up to four TI 4100 receivers, covering Austria, Federal Republic of Germany, Denmark, Sweden and Norway. Both traverse parts contain 71 stations with distances of about 50 km. In addition, 8 stations have been occupied for overlapping connections, and traverse links were established for connecting the fundamental stations Wettzell (VLBI and SLR) and Onsala (VLBI). Final results show a GPS observation precision of a few cm for loops of some 100 km circumference. After transformation of the GPS results to geoid heights using the leveled heights, comparisons with different existing gravimetric geoid determinations including geopotential models were performed. In addition, new geopotential models complete to degree and order 360 tailored to gravity data in Europe, and gravimetric geoid solutions using 6 x 10' mean gravity anomalies were investigated. The comparison with GPS and leveling yields rms discrepancies of + or - 0.1...0.2 m over 1000 km traverse sections for the best solutions, but a strong slope is existing in Sweden and southern Norway in almost all solutions, which is probably caused by systematic errors in the available gravity data for Scandinavia. This is confirmed by a new geoid computation at the Danish Geodetic Institute where the slope has disappeared. If this new solution is taken for the northern traverse section and the best solution for the central part, the rms discrepancy reduces to approximately + or - 0.2 m over 3000 km. Thus, a + or - 10 (exp 7) relative height accuracy seems to be achievable over long distances with the GPS/leveling and the gravimetric geoid calculation techniques

  19. Local effects of redundant terrestrial and GPS-based tie vectors in ITRF-like combinations

    Science.gov (United States)

    Abbondanza, Claudio; Altamimi, Zuheir; Sarti, Pierguido; Negusini, Monia; Vittuari, Luca

    2009-11-01

    Tie vectors (TVs) between co-located space geodetic instruments are essential for combining terrestrial reference frames (TRFs) realised using different techniques. They provide relative positioning between instrumental reference points (RPs) which are part of a global geodetic network such as the international terrestrial reference frame (ITRF). This paper gathers the set of very long baseline interferometry (VLBI)-global positioning system (GPS) local ties performed at the observatory of Medicina (Northern Italy) during the years 2001-2006 and discusses some important aspects related to the usage of co-location ties in the combinations of TRFs. Two measurement approaches of local survey are considered here: a GPS-based approach and a classical approach based on terrestrial observations (i.e. angles, distances and height differences). The behaviour of terrestrial local ties, which routinely join combinations of space geodetic solutions, is compared to that of GPS-based local ties. In particular, we have performed and analysed different combinations of satellite laser ranging (SLR), VLBI and GPS long term solutions in order to (i) evaluate the local effects of the insertion of the series of TVs computed at Medicina, (ii) investigate the consistency of GPS-based TVs with respect to space geodetic solutions, (iii) discuss the effects of an imprecise alignment of TVs from a local to a global reference frame. Results of ITRF-like combinations show that terrestrial TVs originate the smallest residuals in all the three components. In most cases, GPS-based TVs fit space geodetic solutions very well, especially in the horizontal components (N, E). On the contrary, the estimation of the VLBI RP Up component through GPS technique appears to be awkward, since the corresponding post fit residuals are considerably larger. Besides, combination tests including multi-temporal TVs display local effects of residual redistribution, when compared to those solutions where Medicina TVs

  20. Variability in GPS sources

    NARCIS (Netherlands)

    Jauncey, DL; King, EA; Bignall, HE; Lovell, JEJ; Kedziora-Chudczer, L; Tzioumis, AK; Tingay, SJ; Macquart, JP; McCulloch, PM

    2003-01-01

    Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, similar to10%, vary. Their variability falls

  1. Variability in GPS sources

    NARCIS (Netherlands)

    Jauncey, DL; King, EA; Bignall, HE; Lovell, JEJ; Kedziora-Chudczer, L; Tzioumis, AK; Tingay, SJ; Macquart, JP; McCulloch, PM

    2003-01-01

    Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, similar to10%, vary. Their variability falls

  2. SLR Contribution to Investigation of Polar Motion

    CERN Document Server

    Malkin, Zinovy

    2011-01-01

    SLR technique has being used for determination of ERP during over twenty years. Most of results contributed to IERS are based on analysis of observations of Lageos 1&2 satellites collected at the global tracking network of about 40 stations. Now 5 analysis centers submit operative (with 2-15 days delay) solutions and about 10 analysis centers yearly contribute final (up to 23 years) ERP series. Some statistics related to SLR observations and analysis is presented and analyzed. Possible problems in SLR observations and analysis and ways of its solution are discussed.

  3. 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.

  4. 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.

  5. Study on Reference Datum of Global Vertical Crustal Motion by SLR Techniques%利用卫星激光测距技术研究全球垂直地壳运动的参考基准

    Institute of Scientific and Technical Information of China (English)

    朱新慧; 杨力; 孙付平; 王刃

    2014-01-01

    当前地震、地质灾害等现象的频繁发生,表明对于地壳运动尤其是垂直方向的研究是迫切而必需的,研究垂直地壳运动的一个重要前提就是其参考基准的确立。针对目前国内外对于全球垂直地壳运动参考基准不统一的现状,本文分析了研究该基准的必要性,提出将 ITRF2008框架下获取的卫星激光测距(satellite laser ranging,SLR)的垂向速度场作为全球垂直地壳运动参考基准的方案,论证了该方案的合理性,并分别利用GPS和甚长基线干涉测量技术的速度场数据,求取了各自速度场与 SLR 垂直基准之间的系统差,分析了产生不同大小且方向各异系统差的原因,实现了各速度场与全球垂直地壳运动参考基准的统一。由于该基准包含了较为丰富的地球物理信息,具有可发展、可提高以及直接相对于地球质心等特性,因此,推荐将 ITRF2008框架下 SLR 技术获取的垂向速度场定义为全球垂直地壳运动的参考基准。%It is urgent and necessary to study crustal motion especially in vertical direction along with high frequency happening of Earthquake and geological disasters,while the precondition is to study and establish reference datum of vertical crustal motion.Aiming at the status of disunity of global vertical crustal motion reference datum at home and abroad,its essentiality was analyzed to study global uniform reference datum of vertical crustal motion.The project of global vertical crust motion reference datum was put forward and established through SLR vertical velocity field in ITRF2008 frame,whose rationality was demonstrated too.The systematic bias between other velocity field and SLR vertical datum was resolved by using GPS and VLBI velocity observations,and realized the unity of other velocity field and global vertical crustal motion reference datum.Because of abundant geophysical information,expansibility,advancing and relative to the Earth Center,it is

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. LOD First Estimates In 7406 SLR San Juan Argentina Station

    Science.gov (United States)

    Pacheco, A.; Podestá, R.; Yin, Z.; Adarvez, S.; Liu, W.; Zhao, L.; Alvis Rojas, H.; Actis, E.; Quinteros, J.; Alacoria, J.

    2015-10-01

    In this paper we show results derived from satellite observations at the San Juan SLR station of Felix Aguilar Astronomical Observatory (OAFA). The Satellite Laser Ranging (SLR) telescope was installed in early 2006, in accordance with an international cooperation agreement between the San Juan National University (UNSJ) and the Chinese Academy of Sciences (CAS). The SLR has been in successful operation since 2011 using NAOC SLR software for the data processing. This program was designed to calculate satellite orbits and station coordinates, however it was used in this work for the determination of LOD (Length Of Day) time series and Earth Rotation speed.

  11. SLR-PLUS version 1.0 user's manual

    Science.gov (United States)

    Hill, J. M.

    1982-11-01

    Version 1.0 of Solar Load Ratio heating plus cooling (SLR-PLUS), developed as an advanced passive solar system design and evaluation tool, is discussed. SLR-PLUS maintains the friendly user interface structure developed for the active solar system FCHART program. Users familiar with the FCHART programs and the FCHART/SLR program will find the operation of the SLR-PLUS program very familiar SLR-PLUS differs significantly from its parent program in three major ways. First, SLR-PLUS is strictly for the evaluation of passive solar energy systems. Second, the latest correlations from the Los Alamos National Laboratory serve as the basis to the passive heating analysis used by SLR-PLUS. Finally, SLR-PLUS includes cooling loads imposed by passive systems in the form of an annual cooling load for the building modelled and for the individual passive systems. The present version was developed on an Hewlett-Packard 1000 minicomputer using an RTE-IVB operating system. The present version requires approximately 22K 16-bit words of core with overlays to run. The FORTRAN source code will compile with minor changes on any FORTRAN 77 compiler.

  12. 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.

  13. Mercedes-Benz SLR McLaren Roadster

    Institute of Scientific and Technical Information of China (English)

    Prometheus

    2007-01-01

    在推出SLR McLaren之后,梅赛德斯-奔驰终于发布了最新的SLR McLaren Roadster车型。作为奔驰SLR最新的一款车型,奔驰SLR McLaren Roadster恰到好处地将源自上世纪50年代的奔驰SLR的运动传统与迈凯轮F1车队的最新顶尖赛车科技进行了结合。

  14. 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\

  15. SLR in the framework of the EGSIEM project

    Science.gov (United States)

    Maier, Andrea; Sušnik, Andreja; Meyer, Ulrich; Arnold, Daniel; Dach, Rolf; Jäggi, Adrian; Sośnica, Krzysztof; Thaller, Daniela

    2016-04-01

    This contribution describes the three roles Satellite Laser Ranging (SLR) is playing within the European Gravity Service for the Improved Emergency Management (EGSIEM). The purpose of this Horizon 2020 project is to combine monthly gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE) mission that are derived by different institutions. The combined gravity field product will provide complementary information to traditional products for flood and drought monitoring and forecasting. First, SLR is used to validate Global Navigational Satellite System (GNSS) orbits, which are computed at the Astronomical Institute of the University of Bern. To ensure a consistent set of GNSS products (orbits, Earth rotation parameters, and clocks) a reprocessing campaign was initiated. The reprocessed products are based on the new Empirical CODE Orbit Model, which is used for all orbit products generated at the Center for Orbit Determination in Europe (CODE) from January 4, 2015 onwards. Since the kinematic orbits of GRACE will be based on these orbits, we present an in-depth validation of the GNSS orbits using SLR. Second, SLR to geodetic satellites is crucial for the estimation of the dynamical Earth's flattening term (C20) since this coefficient is degraded by aliasing when derived from GRACE data. We will compare the temporal variation of C20 with external solutions and demonstrate the benefit of involving a larger number of geodetic satellites. The third aspect is based on the fact that the gravity field product delivered by EGSIEM will include GRACE and SLR data. It is thus desirable to establish a reference frame based on both GNSS data and SLR observations. For this purpose it is planned to analyze SLR measurements to GNSS satellites equipped with a retroreflector array and to estimate common parameters such as station coordinates and geocenter coordinates from a combined set of SLR and GNSS data. We will present a workflow how to derive a common

  16. Status of Precise Orbit Determination for Jason-2 Using GPS

    Science.gov (United States)

    Melachroinos, S.; Lemoine, F. G.; Zelensky, N. P.; Rowlands, D. D.; Pavlis, D. E.

    2011-01-01

    The JASON-2 satellite, launched in June 2008, is the latest follow-on to the successful TOPEX/Poseidon (T/P) and JASON-I altimetry missions. JASON-2 is equipped with a TRSR Blackjack GPS dual-frequency receiver, a laser retroreflector array, and a DORIS receiver for precise orbit determination (POD). The most recent time series of orbits computed at NASA GSFC, based on SLR/DORIS data have been completed using both ITRF2005 and ITRF2008. These orbits have been shown to agree radially at 1 cm RMS for dynamic vs SLRlDORIS reduced-dynamic orbits and in comparison with orbits produced by other analysis centers (Lemoine et al., 2010; Zelensky et al., 2010; Cerri et al., 2010). We have recently upgraded the GEODYN software to implement model improvements for GPS processing. We describe the implementation of IGS standards to the Jason2 GEODYN GPS processing, and other dynamical and measurement model improvements. Our GPS-only JASON-2 orbit accuracy is assessed using a number of tests including analysis of independent SLR and altimeter crossover residuals, orbit overlap differences, and direct comparison to orbits generated at GSFC using SLR and DORIS tracking, and to orbits generated externally at other centers. Tests based on SLR and the altimeter crossover residuals provide the best performance indicator for independent validation of the NASAlGSFC GPS-only reduced dynamic orbits. For the ITRF2005 and ITRF2008 implementation of our GPS-only obits we are using the IGS05 and IGS08 standards. Reduced dynamic versus dynamic orbit differences are used to characterize the remaining force model error and TRF instability. We evaluate the GPS vs SLR & DORIS orbits produced using the GEODYN software and assess in particular their consistency radially and the stability of the altimeter satellite reference frame in the Z direction for both ITRF2005 and ITRF2008 as a proxy to assess the consistency of the reference frame for altimeter satellite POD.

  17. RT-3 15 m diameter radiotelescope receiving and recording system for GPS white noise observations (some preliminary results).

    Science.gov (United States)

    Pazderski, E.; Vorbrich, K. K.

    A short introduction explaining the idea of using the large VLBI radio telescope for GPS observations is enclosed. A description of the GPS - RT-3 Receiving and Recording Systems is given. Some GPS - RT-3 observational and computational results are presented.

  18. 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.

  19. Analysis of the GPS Observations of the Site Survey at Sheshan 25-m Radio Telescope in August 2008

    Science.gov (United States)

    Liu, L.; Cheng, Z. Y.; Li, J. L.

    2010-01-01

    The processing of the GPS observations of the site survey at Sheshan 25-m radio telescope in August 2008 is reported. Because each session in this survey is only about six hours, not allowing the subdaily high frequency variations in the station coordinates to be reasonably smoothed, and because there are serious cycle slips in the observations and a large volume of data would be rejected during the software automatic adjustment of slips, the ordinary solution settings of GAMIT needed to be adjusted by loosening the constraints in the a priori coordinates to 10 m, adopting the "quick" mode in the solution iteration, and combining Cview manual operation with GAMIT automatic fixing of cycle slips. The resulting coordinates of the local control polygon in ITRF2005 are then compared with conventional geodetic results. Due to large rotations and translations in the two sets of coordinates (geocentric versus quasi-topocentric), the seven transformation parameters cannot be solved for directly. With various trial solutions it is shown that with a partial pre-removal of the large parameters, high precision transformation parameters can be obtained with post-fit residuals at the millimeter level. This analysis is necessary to prepare the follow-on site and transformation survey of the VLBI and SLR telescopes at Sheshan

  20. Monitoring global climate change using SLR data from LARES and other geodetic satellites

    Science.gov (United States)

    Paolozzi, Antonio; Paris, Claudio; Pavlis, Erricos C.; Sindoni, Giampiero; Ciufolini, Ignazio

    2016-04-01

    The Earth Orientation Parameters (EOP), i.e. the spin axis of the Earth, is influenced by the mass redistribution inside and on the surface of the Earth. On the Earth surface, global ice melting, sea level change and atmospheric circulation are the prime contributors. Recent studies have unraveled the majority of the mysteries behind the Chandler wobble, the annual motion and the secular motion of the pole. The differences from the motion of a pole for a rigid Earth is indeed due to the mass redistribution and transfer of angular momentum among the atmosphere, the oceans and solid Earth. The technique of laser ranging and the use of laser ranged satellites such as LARES along with other techniques such Very Long Baseline Interferometry (VLBI) allow to measure the EOP with accuracies at the level of ~200 μas which correspond to few millimeters at the Earth's surface, while the use of Global Navigation Satellite System (GNSS) data can reach an accuracy even below 100 μas. At these unprecedented high levels of accuracy, even tiny anomalous behavior in EOP can be observed and thus correlated to global environmental changes such as ice melting on Greenland and the polar caps, and extreme events that involve strong ocean-atmosphere coupling interactions such as the El Niño. The contribution of Satellite Laser Ranging (SLR) data such as from the LARES mission and similar satellites to this area is outlined in this paper.

  1. The Parsec-Scale Morphology of Southern GPS Sources

    Science.gov (United States)

    Edwards, P. G.; Tingay, S. J.

    2016-12-01

    Multi-frequency, multi-epoch ATCA observations of a sample of AGN resulted in the identification of nine new candidate Giga-hertz Peaked Spectrum sources. Here, we present Long Baseline Array observations at 4.8 GHz of the four candidates with no previously published VLBI image, and consider these together with previously published VLBI images of the other five sources. We find core-jet or compact double morphologies dominate, with further observations required to distinguish between these two possibilities for some sources. One of the nine candidates, PKS 1831-711, displays appreciable variability, suggesting its GPS spectrum is more ephemeral in nature. We focus in particular on the apparent relationship between a narrow spectral width and `compact double' parsec-scale morphology, finding further examples, but also exceptions to this trend. An examination of the VLBI morphologies high-redshift (z > 3) sub-class of GPS sources suggests that core-jet morphologies predominate in this class.

  2. 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

  3. A morphological and spectral study of GPS galaxies and quasars

    NARCIS (Netherlands)

    Schilizzi, RT; Tschager, W; Snellen, IAG; de Bruyn, AG; Miley, GK; Rottgering, HJA; van Langevelde, HJ; Fanti, C; Fanti, R; Hirabayashi, H; Preston, RA; Gurvits, LI

    2000-01-01

    We have analysed HALCA and global VLBI data for 2021+614, the first of eleven GPS quasars and galaxies to be observed by HALCA. We show that 2021+614 is a compact symmetric object of overall size similar to 40 pc, and confirm that the speed of separation of the two dominant lobes is approximately on

  4. A morphological and spectral study of GPS galaxies and quasars

    NARCIS (Netherlands)

    Schilizzi, RT; Tschager, W; Snellen, IAG; de Bruyn, AG; Miley, GK; Rottgering, HJA; van Langevelde, HJ; Fanti, C; Fanti, R; Hirabayashi, H; Preston, RA; Gurvits, LI

    2000-01-01

    We have analysed HALCA and global VLBI data for 2021+614, the first of eleven GPS quasars and galaxies to be observed by HALCA. We show that 2021+614 is a compact symmetric object of overall size similar to 40 pc, and confirm that the speed of separation of the two dominant lobes is approximately

  5. A morphological and spectral study of GPS galaxies and quasars

    NARCIS (Netherlands)

    Schilizzi, RT; Tschager, W; Snellen, IAG; de Bruyn, AG; Miley, GK; Rottgering, HJA; van Langevelde, HJ; Fanti, C; Fanti, R; Hirabayashi, H; Preston, RA; Gurvits, LI

    2000-01-01

    We have analysed HALCA and global VLBI data for 2021+614, the first of eleven GPS quasars and galaxies to be observed by HALCA. We show that 2021+614 is a compact symmetric object of overall size similar to 40 pc, and confirm that the speed of separation of the two dominant lobes is approximately on

  6. 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...

  7. 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.

  8. GPS Separator

    CERN Multimedia

    2016-01-01

    Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.

  9. Hacking GPS

    CERN Document Server

    Kingsley-Hughes, Kathie

    2005-01-01

    * This is the "user manual" that didn't come with any of the 30 million GPS receivers currently in use, showing readers how to modify, tweak, and hack their GPS to take it to new levels!* Crazy-cool modifications include exploiting secret keycodes, revealing hidden features, building power cords and cables, hacking the battery and antenna, protecting a GPS from impact and falls, making a screen protector, and solar-powering a GPS* Potential power users will take the function and performance of their GPS to a whole new level by hacking into the firmware and hacking into a PC connection with a GPS* Fear not! Any potentially dangerous mod (to the device) is clearly labeled, with precautions listed that should be taken* Game time! Readers can check out GPS games, check into hacking geocaching, and even use a GPS as a metal detector

  10. 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.

  11. 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.

  12. 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.

  13. Improvement of SLR accuracy, a possible new step

    Science.gov (United States)

    Kasser, Michel

    1993-01-01

    The satellite laser ranging (SLR) technology experienced a large number of technical improvements since the early 1970's, leading now to a millimetric instrumental accuracy. Presently, it appears as useless to increase these instrumental performances as long as the atmospheric propagation delay suffers its actual imprecision. It has been proposed for many years to work in multiwavelength mode, but up to now the considerable technological difficulties of subpicosecond timing have seriously delayed such an approach. Then a new possibility is proposed, using a device which is not optimized now for SLR but has already given good results in the lower troposphere for wind measurement: the association of a radar and a sodar. While waiting for the 2-lambda methodology, this one could provide an atmospheric propagation delay at the millimeter level during a few years with only little technological investment.

  14. Functional studies of the gene slr2049 from Synechocystis sp. PCC6803 and its site-directed mutation.

    Science.gov (United States)

    Liu, Bingjun; Chen, Sili; Zhang, Lei

    2015-06-01

    Phycobiliprotein is a homologous family of light-harvesting chromoproteins existing in cyanobacteria, red algae and cryptophytes. Phycobiliprotein is made up of phycobilin and its corresponding apophycobiliprotein, and they are covalently linked by the thioether bond with the bilin lyase. Using the software BLAST, we have found gene slr2049 in Synechocystis sp. PCC6803 homologous to the biliprotein lyase gene cpeS. This paper investigates the protein expressed by gene slr2049 to find the enzymatic activity characteristics. We cloned slr2049 and its related genes cpcB, ho1, and pcyA which are linked with the synthesis of phycocyanin. Special amino acid mutagenesis was performed on slr2049 to construct eight mutants slr2049 (H21S), slr2049 (L23S), slr2049 (A24S), slr2049 (F25S), slr2049 (W72L), slr2049 (G84S), slr2049 (R107S) and slr2049 (Y124S). These mutants were ligated with vectors pEDFDuet-1 and pET-23a to construct pCDF-cpcB-slr2049 wild-type, pCDF-cpcB-slr2049 mutants and pET-ho1-pcyA, for the purpose of protein expression and analysis. The results showed that the wild-type and mutants slr2049 (H21S), slr2049 (L23S), slr2049 (F25S), slr2049 (W72L), slr2049 (G84S), and slr2049 (Y124S) can catalyze CpcB to couple on PCB correctly and the products have unique spectral characteristics. However mutants slr2049 (A24S) and slr2049 (R107S) have no spectral characteristics. Thus, it is suggested that alanine at position 24 and arginine at position 107 are the active sites.

  15. 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.

  16. 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.

  17. 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...

  18. 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.

  19. (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.

  20. 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

  1. The versatile TolC-like Slr1270 in the cyanobacterium Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Oliveira, Paulo; Martins, Nuno M; Santos, Marina; Pinto, Filipe; Büttel, Zsófia; Couto, Narciso A S; Wright, Phillip C; Tamagnini, Paula

    2016-02-01

    Here we report on the functional characterization of the hypothetical protein Slr1270, a TolC homologue in Synechocystis sp. PCC 6803. Analysis of a slr1270 insertion deletion mutant and respective wild-type revealed that the mutant presents increased susceptibility to antibiotics. In addition, a detailed study of the exoproteome showed that Slr1270 mediates protein secretion. Among the protein substrates dependent on Slr1270 function, we found the S-layer structural component. Electron microscopy studies of the slr1270 mutant showed that the S-layer is indeed absent. The requirement of functional Slr1270 for protein secretion and drug resistance mechanisms suggests that Slr1270 plays a role similar to that described for TolC in other bacteria. Additional phenotypic traits could also be observed, including slower growth rates at low temperature, impairment in biofilm formation and increased activity of enzymes detoxifying reactive oxygen species. Furthermore, an increased capacity of outer membrane vesicles (OMVs) formation and release was also found in the slr1270 mutant, a feature that has not yet been observed in bacteria lacking TolC. This work highlights the marked physiological fitness that the TolC-like Slr1270 bestows to the photosynthetic model Synechocystis sp. PCC 6803 and presents a valuable model for studying OMVs formation and release. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  2. 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...

  3. 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.

  4. GPS & Roadpricing

    DEFF Research Database (Denmark)

    Zabic, Martina

    2005-01-01

    I denne artikel præsenteres analysemetoderne og resultaterne fra et eksamensprojekt omhandlende en analyse af GPS kvaliteten i forhold til roadpricing i København. Denne undersøgelse af GPS kvaliteten i forbindelse med roadpricing, er foretaget i tilknytning til det danske AKTA forsøg (www.......akta-kbh.dk), hvor GPS data er indsamlet for 500 biler over en 2-årig periode (2001-2003). Artiklen præsenterer således en analyse af GPS nøjagtigheden med henblik på at undersøge om kvalitet og pålidelighed er tilstrækkelig, til et GPS-baseret roadpricingssystem i København. Ved GPS-baseret roadpricing, udstyres...... med henblik på enhedsomkostningerne skulle være økonomisk realisable til brug i et så omfattende roadpricingssystem. Endvidere vanskeliggøres positionerings forholdene, idet bilen der ønskes positionsbestemt er i bevægelse. Når både satellitterne og GPS modtageren er i bevægelse, reduceres...

  5. GPS & Roadpricing

    DEFF Research Database (Denmark)

    Zabic, Martina

    2005-01-01

    I denne artikel præsenteres analysemetoderne og resultaterne fra et eksamensprojekt omhandlende en analyse af GPS kvaliteten i forhold til roadpricing i København. Denne undersøgelse af GPS kvaliteten i forbindelse med roadpricing, er foretaget i tilknytning til det danske AKTA forsøg (www.......akta-kbh.dk), hvor GPS data er indsamlet for 500 biler over en 2-årig periode (2001-2003). Artiklen præsenterer således en analyse af GPS nøjagtigheden med henblik på at undersøge om kvalitet og pålidelighed er tilstrækkelig, til et GPS-baseret roadpricingssystem i København. Ved GPS-baseret roadpricing, udstyres...... med henblik på enhedsomkostningerne skulle være økonomisk realisable til brug i et så omfattende roadpricingssystem. Endvidere vanskeliggøres positionerings forholdene, idet bilen der ønskes positionsbestemt er i bevægelse. Når både satellitterne og GPS modtageren er i bevægelse, reduceres...

  6. Future global SLR network evolution and its impact on the terrestrial reference frame

    Science.gov (United States)

    Kehm, Alexander; Bloßfeld, Mathis; Pavlis, Erricos C.

    2016-04-01

    SLR is the unique technique that allows determining the geocentre with very high accuracy and contributes to the realization of the scale of a conventional reference frame. In addition, due to the high sensitivity of the SLR-tracked satellites on the Earth's gravitational field, SLR is a crucial technique for determining important geodetic parameters such as Earth Orientation Parameters (EOP) and low-degree spherical harmonics of the Earth's gravitational field model. So far, the distribution of SLR stations has been quite inhomogeneous, especially in the southern hemisphere, mostly due to the lack of land-masses. With the set-up of a new SLR station in Brasilia in 2014 and the transfer of the former TIGO observatory from Concepción (Chile) to La Plata (Argentina) - now known as AGGO Argentinian-German Geodetic Observatory -, the shape of SLR subnetwork in South America has changed significantly. Furthermore, additional SLR stations in India (Mount Abu and Ponmundi), as well as a new station in Hartebeesthoek, are scheduled to start operations in 2016 and they will further improve the global SLR network geometry. In this work, SLR data has been simulated in order to determine the influence of the changing SLR network geometry on the geodetic parameters such as a global terrestrial reference frame, EOP and the low-degree harmonics of the Earth's gravitational field. The simulations have been performed for different network geometries as well as different satellites. In this investigation, a special emphasis is placed on the improvement of the geocentric realization of a global SLR-derived reference frame.

  7. 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.

  8. 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

  9. Variability of GPS Radio Sources at 5 GHz

    Indian Academy of Sciences (India)

    Lang Cui; Xiang Liu; Jun Liu

    2011-03-01

    We carry out flux monitoring on a sample of 169 Gigahertz Peaked Spectrum (GPS) radio sources at 5 GHz and find that about one-third of them show considerable Inter-Month Variability (IMV), and these IMV phenomena are likely to be caused by interstellar scintillation (ISS). Furthermore, we find that those showing IMV tend to be point-like or core-jet structures at VLBI scale.

  10. Modifications to the FCHART/SLR version 2. 0 program

    Energy Technology Data Exchange (ETDEWEB)

    Hill, J. M.

    1981-07-01

    A number of errors have been detected in the FCHART/SLR computer code as it pertains to the thermal performance of passive solar energy systems. Along with minor coding changes, major revisions in the code have been made to improve the computer models used to predict the effects of overhangs on incident solar radiation and the radiation absorbed in attached sunspaces. Modifications to the code were also made to improve the handling of mullions and to reduce the effort required to describe the placement of overhangs. The theoretical basis of these changes, along with the associated alterations to the code, are given. For the cases examined, the program as modified now agrees to within 15% of published LANL passive system performance correlations. This new code has been designated as Version 2.1 and is presently operational at SSEC.

  11. 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.

  12. 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.

  13. 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

  14. GPS Composite Clock Analysis

    OpenAIRE

    Wright, James R.

    2008-01-01

    The GPS composite clock defines GPS time, the timescale used today in GPS operations. GPS time is illuminated by examination of its role in the complete estimation and control problem relative to UTC/TAI. The phase of each GPS clock is unobservable from GPS pseudorange measurements, and the mean phase of the GPS clock ensemble (GPS time) is unobservable. A new and useful observability definition is presented, together with new observability theorems, to demonstrate explicitly that GPS time is...

  15. Determination of SLR station coordinates on the basis of tracking 45 GNSS satellites: benefits for future ITRF realizations

    Science.gov (United States)

    Sośnica, Krzysztof; Bury, Grzegorz; Zajdel, Radosław; Kaźmierski, Kamil; Drożdżewski, Mateusz

    2017-04-01

    The SLR station coordinates and SLR-derived Earth Rotation Parameters (ERPs) are typically derived on the basis of SLR tracking of four spherical geodetic satellites: two LAGEOS and two Etalons. Between 2014 and 2016, the International Laser Ranging Service (ILRS) initiated four intensive SLR tracking campaigns for Galileo and three campaigns devoted to tracking all GNSS spacecraft. As a result, the number of SLR observations and the number of tracked GNSS satellites have dramatically increased allowing for determining SLR station coordinates and ERPs solely on the basis of SLR tracking of GNSS satellites. This paper shows, for the first time, the solution in which the SLR station coordinates, geocenter motion, and ERPs are determined using the SLR observations to 26 GLONASS, 14 Galileo, 2 BeiDou IGSO, 2 BeiDou MEO, and 1 QZSS satellite. We compare the SLR station coordinate stability derived from GNSS-based results to the LAGEOS-only solution and from a combined 'SLR to GNSS+LAGEOS' solution. We address the issues related to the GNSS orbit determination using sparse SLR data and the issues related to handling range biases in the GNSS solutions. We found that the coordinate stability of those SLR stations which provide a large number of GNSS observations can remarkably be improved. The Length-of-day parameter can be derived from SLR-GNSS solutions with a much better accuracy than from the LAGEOS-only solutions. Finally, we show that the SLR tracking of GNSS satellites improves the consistency between SLR and GNSS solutions, and thus, can be beneficial for the future ITRF realizations.

  16. A novel periplasmic protein (Slr0280) tunes photomixotrophic growth of the cyanobacterium, Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Dong, Liang-Liang; Li, Qing-Dong; Wu, Dong; Sun, Ya-Fang; Zhou, Ming; Zhao, Kai-Hong

    2016-01-10

    Cyanobacteria are among the main contributors to global photosynthesis and show a high degree of metabolic plasticity. Synechocystis sp. PCC 6803 can grow under photoautotrophic, photomixotrophic or photoheterotrophic conditions. We have characterized a novel periplasmic protein (Slr0280) that tunes the photomixotrophic growth of Synechocystis sp. PCC 6803. Slr0280 is a multi-domain protein consisting mainly of β-sheets. Several proteins that interact with Slr0280 were identified via bacterial two-hybrid screening. Slr0280 may interact through its DUF2233 domain with partners that participate in sugar metabolism, thereby coordinating the respective regulations. When slr0280 was deleted, the mutant grew more slowly than wild-type in the presence of glucose, which is ascribed to the down-regulation of glycolysis, glycogen catabolism, oxidative pentose phosphate pathway, Calvin cycle and glucose utilization. A positive regulation of Slr0280 on these sugar catabolic enzymes was confirmed by transcript (qPCR) analyses. Based on these findings, we proposed a speculative model that Slr0280 plays a coordinating regulatory role in sugar metabolism. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Jason-2 systematic error analysis in the GPS derived orbits

    Science.gov (United States)

    Melachroinos, S.; Lemoine, F. G.; Zelensky, N. P.; Rowlands, D. D.; Luthcke, S. B.; Chinn, D. S.

    2011-12-01

    Several results related to global or regional sea level changes still too often rely on the assumption that orbit errors coming from station coordinates adoption can be neglected in the total error budget (Ceri et al. 2010). In particular Instantaneous crust-fixed coordinates are obtained by adding to the linear ITRF model the geophysical high-frequency variations. In principle, geocenter motion should also be included in this computation, in order to reference these coordinates to the center of mass of the whole Earth. This correction is currently not applied when computing GDR orbits. Cerri et al. (2010) performed an analysis of systematic errors common to all coordinates along the North/South direction, as this type of bias, also known as Z-shift, has a clear impact on MSL estimates due to the unequal distribution of continental surface in the northern and southern hemispheres. The goal of this paper is to specifically study the main source of errors which comes from the current imprecision in the Z-axis realization of the frame. We focus here on the time variability of this Z-shift, which we can decompose in a drift and a periodic component due to the presumably omitted geocenter motion. A series of Jason-2 GPS-only orbits have been computed at NASA GSFC, using both IGS05 and IGS08. These orbits have been shown to agree radially at less than 1 cm RMS vs our SLR/DORIS std0905 and std1007 reduced-dynamic orbits and in comparison with orbits produced by other analysis centers (Melachroinos et al. 2011). Our GPS-only JASON-2 orbit accuracy is assessed using a number of tests including analysis of independent SLR and altimeter crossover residuals, orbit overlap differences, and direct comparison to orbits generated at GSFC using SLR and DORIS tracking, and to orbits generated externally at other centers. Tests based on SLR-crossover residuals provide the best performance indicator for independent validation of the NASA/GSFC GPS-only reduced dynamic orbits. Reduced

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  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. 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.

  10. 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...

  11. 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

  12. Successful operation of a cooperative SLR station of China and Argentina in San Juan

    Institute of Scientific and Technical Information of China (English)

    HAN YanBen; E ALONSO; XIANG QingGe; HUANG DongPing; YIN ZhiQiang; LIU WeiDong; E ACTIS; R PODESTA; WANG TanQiang; GUO TangYong; QU Feng; A M PACHECO; AA GONZALEZ

    2008-01-01

    We introduced the observations and researches using a Satellite Laser Ranging (SLR) system with high precision,which was designed and made in China and installed in the Observatory of San Juan Uni-versity,Argentina,the capability of the system and the achievement of the cooperative procedure be-tween China and Argentina.The SLR station in San Juan,set up by China and Argentina,is quite sig-nificant for improving the distribution of SLR stations and enhancing the orbital coverage of the whole earth.Since the SLR system started to work in the Observatory of San Juan University in the beginning of 2006,the operation is rather good,and rich data with high precision have been obtained.Further plan of the cooperation for the near future is also presented.

  13. GINFEST: Geodetic Intercomparison Network for Evaluating Space Techniques

    Science.gov (United States)

    Ashkenazi, Vidal

    Details are given of a geodetic network connecting the major radio telescopes and SLR facilities in Western and Central Europe, which is to be used in a co-location exercise involving VLBI, CERI, SLR and GPS observations, with the aim of evaluating the relative accuracies and system biases of these geodetic space observation techniques.

  14. 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

  15. 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

  16. GPS for land surveyors

    CERN Document Server

    Van Sickle, Jan

    2008-01-01

    The GPS SignalGlobal Positioning System (GPS) Signal StructureTwo ObservablesPseudorangingCarrier Phase RangingBiases and SolutionsThe Error BudgetDifferencingThe FrameworkTechnological ForerunnersVery Long Baseline InterferometryTransitNavstar GPSGPS Segment OrganizationGPS ConstellationThe Control SegmentReceivers and MethodsCommon Features of GPS ReceiversChoosing a GPS ReceiverSome GPS Surveying MethodsCoordinatesA Few Pertinent Ideas About Geodetic Datums for GPSState Plane CoordinatesHeightsGPS Surveying TechniquesStatic GPS SurveyingReal-Time Kinematic (RTK) and Differential GPS (DGPS)T

  17. 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.

  18. 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*.

  19. 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.

  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. 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

  2. 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.

  3. Impact of Swarm GPS receiver updates on POD performance

    Science.gov (United States)

    van den IJssel, Jose; Forte, Biagio; Montenbruck, Oliver

    2016-05-01

    The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard GPS receivers deliver high-quality data with an almost continuous data rate. However, the receivers show a slightly degraded performance when flying over the geomagnetic poles and the geomagnetic equator, due to ionospheric scintillation. Furthermore, with only eight channels available for dual-frequency tracking, the amount of collected GPS tracking data is relatively low compared with various other missions. Therefore, several modifications have been implemented to the Swarm GPS receivers. To optimise the amount of collected GPS data, the GPS antenna elevation mask has slowly been reduced from 10° to 2°. To improve the robustness against ionospheric scintillation, the bandwidths of the GPS receiver tracking loops have been widened. Because these modifications were first implemented on Swarm-C, their impact can be assessed by a comparison with the close flying Swarm-A satellite. This shows that both modifications have a positive impact on the GPS receiver performance. The reduced elevation mask increases the amount of GPS tracking data by more than 3 %, while the updated tracking loops lead to around 1.3 % more observations and a significant reduction in tracking losses due to severe equatorial scintillation. The additional observations at low elevation angles increase the average noise of the carrier phase observations, but nonetheless slightly improve the resulting reduced-dynamic and kinematic orbit accuracy as shown by independent satellite laser ranging (SLR) validation. The more robust tracking loops significantly reduce the large carrier phase observation errors at the geomagnetic poles and along the geomagnetic

  4. SLR Station Recovery, Center of Frame Motion, and Time Varying Gravity

    Science.gov (United States)

    Zelensky, Nikita P.; Lemoine, Frank G.; Chinn, Douglas S.; Melachroinos, Stavros; Wiser Beall, Jennifer; Larson, Jordan D.

    2012-01-01

    Weekly station position estimates, beginning with 1993, are derived from the ITRF2008-based SLR processing of up to four satellites: Lageos 1, Lageos2, Starlette, and Stella. Helmert parameters obtained from c omparison of weekly SLR station positions and the a-priori SLRF2008 station complement are evaluated for geocenter motion and scale. Two me thods for modeling time varying gravity are employed in the SLR satel lite POD processing, with GGM03S serving as the static gravity field. Both methods forward model atmosphere gravity derived from 6-hour ECM WF pressure data. The standard approach applies an annual 20x20 field estimated from 4 years of GRACE data, and the IERS2003 recommended linear rates for C20, C30, C40, C21, and S21. The alternate approach us es a new set of low-order/degree 4x4 coefficients estimated weekly fr om SLR & DORIS processing to 10 satellites from 1993-2012. This exper imental tvg4x4 model has been shown to improve the TOPEX, Jason-1, and Jason-2 altimeter satellite orbits,. In this paper we apply the more detailed time-variable gravity modeling to the SLR satellite POD pro cessing and subsequent reference frame analyses. For this study we will evaluate the orbit differences (periodic and secular) for the satel lites concerned, characterize the impact on the station coordinate solutions, and the impact on reference frame parameters (geocenter and s cale).

  5. 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.

  6. Precipitable Water Vapor Estimates in the Australian Region from Ground-Based GPS Observations

    Directory of Open Access Journals (Sweden)

    Suelynn Choy

    2015-01-01

    Full Text Available We present a comparison of atmospheric precipitable water vapor (PWV derived from ground-based global positioning system (GPS receiver with traditional radiosonde measurement and very long baseline interferometry (VLBI technique for a five-year period (2008–2012 using Australian GPS stations. These stations were selectively chosen to provide a representative regional distribution of sites while ensuring conventional meteorological observations were available. Good agreement of PWV estimates was found between GPS and VLBI comparison with a mean difference of less than 1 mm and standard deviation of 3.5 mm and a mean difference and standard deviation of 0.1 mm and 4.0 mm, respectively, between GPS and radiosonde measurements. Systematic errors have also been discovered during the course of this study, which highlights the benefit of using GPS as a supplementary atmospheric PWV sensor and calibration system. The selected eight GPS sites sample different climates across Australia covering an area of approximately 30° NS/EW. It has also shown that the magnitude and variation of PWV estimates depend on the amount of moisture in the atmosphere, which is a function of season, topography, and other regional climate conditions.

  7. AK枪族再添新丁:阿森纳SLR106、SLR107系列步枪大检阅

    Institute of Scientific and Technical Information of China (English)

    韦志俊; 王猛; 耿嘉

    2008-01-01

    伴随着美国民用市场对AK系列步枪的热捧,一些公司纷纷通过各种渠道以组装生产的形式推出自己的AK类型产品,如本刊2008年8(下)期介绍的韦格步枪。美国阿森纳(Arsenal)公司是保加利亚阿森纳公司的分公司,而保加利亚一直使用苏式武器,有此便利条件,美国阿森纳公司当然不甘落后,最近推出了自己的AK类型产品——SLR106系列和SLR107系列。

  8. 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...

  9. 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.

  10. 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.

  11. 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.

  12. 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...

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. The role of Slr0151, a tetratricopeptide repeat protein from Synechocystis sp. PCC 6803, during Photosystem II assembly and repair

    Directory of Open Access Journals (Sweden)

    Anna eRast

    2016-05-01

    Full Text Available The assembly and repair of photosystem II (PSII is facilitated by a variety of assembly factors. Among those, the tetratricopeptide repeat (TPR protein Slr0151 from Synechocystis sp. PCC 6803 (hereafter Synechocystis has previously been assigned a repair function under high light conditions (Yang et al., 2014, J. Integr. Plant Biol. 56, 1136-50. Here, we show that inactivation of Slr0151 affects thylakoid membrane ultrastructure even under normal light conditions. Moreover, the level and localization of Slr0151 are affected in a variety of PSII-related mutants. In particular, the data suggest a close functional relationship between Slr0151 and Sll0933, which interacts with Ycf48 during PSII assembly and is homologous to PAM68 in Arabidopsis thaliana. Immunofluorescence analysis revealed a punctate distribution of Slr0151 within several different membrane types in Synechocystis cells.

  18. Centimeter-level precise orbit determination for the HY-2A satellite using DORIS and SLR tracking data

    Science.gov (United States)

    Kong, Qiaoli; Guo, Jinyun; Sun, Yu; Zhao, Chunmei; Chen, Chuanfa

    2017-01-01

    The HY-2A satellite is the first ocean dynamic environment monitoring satellite of China. Centimeter-level radial accuracy is a fundamental requirement for its scientific research and applications. To achieve this goal, we designed the strategies of precise orbit determination (POD) in detail. To achieve the relative optimal orbit for HY-2A, we carried out POD using DORIS-only, SLR-only, and DORIS + SLR tracking data, respectively. POD tests demonstrated that the consistency level of DORIS-only and SLR-only orbits with respect to the CNES orbits were about 1.81 cm and 3.34 cm in radial direction in the dynamic sense, respectively. We designed 6 cases of different weight combinations for DORIS and SLR data, and found that the optimal relative weight group was 0.2 mm/s for DORIS and 15.0 cm for SLR, and RMS of orbit differences with respect to the CNES orbits in radial direction and three-dimensional (3D) were 1.37 cm and 5.87 cm, respectively. These tests indicated that the relative radial and 3D accuracies computed using DORIS + SLR data with the optimal relative weight set were obviously higher than those computed using DORIS-only and SLR-only data, and satisfied the requirement of designed precision. The POD for HY-2A will provide the invaluable experience for the following HY-2B, HY-2C, and HY-2D satellites.

  19. GPS Separator HD

    CERN Multimedia

    2016-01-01

    Footage of the 70 degree ISOLDE GPS separator magnet MAG70 as well as the switchyard for the Central Mass and GLM (GPS Low Mass) and GHM (GPS High Mass) beamlines in the GPS separator zone. In the GPS20 vacuum sector equipment such as the long GPS scanner 482 / 483 unit, faraday cup FC 490, vacuum valves and wiregrid piston WG210 and WG475 and radiation monitors can also be seen. Also the RILIS laser guidance and trajectory can be seen, the GPS main beamgate switch box and the actual GLM, GHM and Central Beamline beamgates in the beamlines as well as the first electrostatic quadrupoles for the GPS lines. Close up of the GHM deflector plates motor and connections and the inspection glass at the GHM side of the switchyard.

  20. GPS Satellite Simulation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The GPS satellite simulation facility consists of a GPS satellite simulator controlled by either a Silicon Graphics Origin 2000 or PC depending upon unit under test...

  1. GPS Control Segment

    Science.gov (United States)

    2015-04-29

    Luke J. Schaub Chief, GPS Control Segment Division 29 Apr 15 GPS Control Segment Report Documentation Page Form ApprovedOMB No. 0704-0188...00-2015 4. TITLE AND SUBTITLE GPS Control Segment 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT...Center, GPS Control Segment Division,Los Angeles AFB, El Segundo,CA,90245 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S

  2. 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...

  3. 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.

  4. 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.

  5. 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.

  6. GLOBAL POSITIONING SYSTEM (GPS

    Directory of Open Access Journals (Sweden)

    Celalettin Karaali

    1996-02-01

    Full Text Available Use of GPS is becoming more widespread on surveying engineering. Especially, preference to GPS is increased by getting accuracy of order of milimeter, making observation on every weather forecast, without requiring intervisibility between station. Besides, developing new observation techniques and technologies in GPS increased its use in deformation easurements, monitoring crustal movements, mapping precise geoid maps, detail surveying, etc.

  7. 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.

  8. Jason-1 and Jason-2 POD Using GPS

    Science.gov (United States)

    Melachroinos, Stavros; Lemoine, Frank G.; Zelensky, Nikita P.; Rowlands, David D.; Luthcke, Scott B.; Beckley, Brian D.

    2012-01-01

    The Jason-2 satellite, launched in June 2008, is the latest follow-on to the successful Jason-1 altimetry satellite mission launched in December 7, 2001. Both, Jason-2 and Jason-1 are equipped with a GPS dual-frequency receiver, a laser retroreflector array, and a DORIS receiver for precise orbit determination (POD). A series of dynamic and reduced-dynamic Jason-2 orbits computed at NASA GSFC, based on GPS-only data and the std0905 standards, have been completed till cy74through cycle 74 using the IGS05 framework. These orbits, now publicly available, have been shown to agree radially at 1 cm RMS with the GSFC std0905 SLR/DORIS orbits and in comparison with orbits produced by JPL, ESA and CNES. In this paper, we describe the implementation of the IGS08 and repro1 framework for the Jason-2 and Jason-1 GPS POD processing with the NASA GSFC GEODYN software. . In our updated GPS POD, ambiguity fixing and updated time variable and static gravity fields. We also evaluate the implementation of non-tidal and degree-1 loading displacement as forward modeling to the tracking stations. Reduced-dynamic versus dynamic orbit differences are used to characterize the remaining force model errors and TRF instability. In particular, we assess their consistency radially and the stability of the altimeter satellite reference frame in the North/South direction as a proxy to assess the consistency of the reference frame.

  9. Jason-1 and Jason-2 POD Using GPS

    Science.gov (United States)

    Melachroinos, Stavros; Lemoine, Frank G.; Zelensky, Nikita P.; Rowlands, David D.; Luthcke, Scott B.; Beckley, Brian D.

    2012-01-01

    The Jason-2 satellite, launched in June 2008, is the latest follow-on to the successful Jason-1 altimetry satellite mission launched in December 7, 2001. Both, Jason-2 and Jason-1 are equipped with a GPS dual-frequency receiver, a laser retroreflector array, and a DORIS receiver for precise orbit determination (POD). A series of dynamic and reduced-dynamic Jason-2 orbits computed at NASA GSFC, based on GPS-only data and the std0905 standards, have been completed till cy74through cycle 74 using the IGS05 framework. These orbits, now publicly available, have been shown to agree radially at 1 cm RMS with the GSFC std0905 SLR/DORIS orbits and in comparison with orbits produced by JPL, ESA and CNES. In this paper, we describe the implementation of the IGS08 and repro1 framework for the Jason-2 and Jason-1 GPS POD processing with the NASA GSFC GEODYN software. . In our updated GPS POD, ambiguity fixing and updated time variable and static gravity fields. We also evaluate the implementation of non-tidal and degree-1 loading displacement as forward modeling to the tracking stations. Reduced-dynamic versus dynamic orbit differences are used to characterize the remaining force model errors and TRF instability. In particular, we assess their consistency radially and the stability of the altimeter satellite reference frame in the North/South direction as a proxy to assess the consistency of the reference frame.

  10. UT/CSR analysis of earth rotation from Lageos SLR data

    Science.gov (United States)

    Tapley, B. D.; Eanes, R. J.; Schutz, B. E.

    1986-01-01

    The 1983-1984 data collected by NASA and stations participating in the Crustal Dynamics Project from satellite laser ranging (SLR) systems are used to generate solutions for the earth polar motion. Solutions obtained using the MERIT Lageos standard data set are compared to operational results based on quick-look data and generated in near real-time, and the capability of Lageos SLR for the determination of earth orientation parameters (EOP) with high temporal resolution is investigated. Finally, the sensitivity of the MERIT campaign results to the number of tracking stations and to changes in the MERIT standard model is evaluated. It is concluded that the departures from the IAU/IUGG MERIT standards do not significantly change the solution and that solutions accurate at the 2 milliarcsec level can be maintained with a network of fewer than 10 appropriately selected stations.

  11. GPS Scintillation Analysis.

    Science.gov (United States)

    2007-11-02

    Rev. 2-89) Prescribed by ANSI Std. Z39-1 298-102 TABLE OF CONTENTS 1. INTRODUCTION 1 2. GPS COMPARISON WITH ALL-SKY IMAGES OVER AGUA VERDE...Depletions from 1 October 1994 2 3. GPS data from Agua Verde, Chile on the night of 1 October 1994 3 4. PL-SCINDA display of GPS ionospheric...comparison of GPS measurements with GOES8 L-band scintillation data, are discussed. 2. GPS COMPARISON WITH ALL-SKY IMAGES OVER AGUA VERDE, CHILE As

  12. GPS Control Segment Improvements

    Science.gov (United States)

    2015-04-29

    Systems Center GPS Control Segment Improvements Mr. Tim McIntyre GPS Product Support Manager GPS Ops Support and Sustainment Division Peterson...DATE 29 APR 2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE GPS Control Segment Improvements 5a. CONTRACT...ORGANIZATION NAME(S) AND ADDRESS(ES) Air Force Space Command,Space and Missile Systems Center, GPS Ops Support and Sustainment Division,Peterson AFB,CO,80916 8

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Zero-difference and single-difference precise orbit determination for LEO using GPS

    Institute of Scientific and Technical Information of China (English)

    PENG DongJu; WU Bin

    2007-01-01

    Various methods for precise orbit determination (POD) of low earth orbiters (LEO) are briefly introduced in this paper. Based on the software named SHORD-III developed by our institute, single-difference (SD) and zero-difference (ZD) dynamic POD based on LEO carrying an on-board GPS receiver is mainly discussed. The approaches are tested using real GRACE data (November 5-25, 2002) and independently validated with Satellite Laser Ranging (SLR) measurements over the same 21 days. Comparisons with the scientific orbits provided by GFZ indicate that the SD POD RMS accuracy can achieve 5, 10 and 6 cm in radial, along and cross the track, and the ZD POD RMS accuracy can achieve 4, 8 and 4 cm in radial, along and cross the track. SLR validation shows that SD POD accuracy is better than 8 cm in distance, and ZD POD accuracy is better than 6 cm.

  2. GPS Modernization Update

    Science.gov (United States)

    2014-06-01

    space vehicles currently set healthy • 6 GPS IIA, 12 GPS IIR , 7 GPS IIR -M, 5 GPS IIF – 5 additional satellites in residual status, 1 in test status...Advisory Board Final.pptx S P A C E A N D M I S S I L E S Y S T E M S C E N T E R Legacy GPS IIA/ IIR • Single Frequency (L1) • Coarse...acquisition (C/A) code • Y-Code (L1Y & L2Y) GPS IIR -M • 2nd Civil Signal (L2C) • M-Code (L1M & L2M) GPS IIF • 3rd civil signal (L5) • 2 Rb + 1 Cs

  3. 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).

  4. 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.

  5. 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).

  6. 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.

  7. 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.

  8. 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.

  9. Advanced GPS Technologies (AGT)

    Science.gov (United States)

    2015-05-01

    V Air Force Research Laboratory ••• Advanced GPS Technologies (AGT) Integrity *Service *Excellence 1 May 2015 Kevin Slimak Program Manager...2015 2. REPORT TYPE 3. DATES COVERED 00-00-2015 to 00-00-2015 4. TITLE AND SUBTITLE Advanced GPS Technologies (AGT) 5a. CONTRACT NUMBER 5b...DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES Presented at the GPS Partnership

  10. 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

  11. GPS Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Global Positioning System (GPS) Test Facility Instrumentation Suite (GPSIS) provides great flexibility in testing receivers by providing operational control of...

  12. 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.

  13. The Effect of Seasonal and Long-Period Geopotential Variations on the GPS Orbits

    Science.gov (United States)

    Melachroinos, Stavros A.; Lemoine, Frank G.; Chinn, Douglas S.; Zelensky, Nikita P.; Nicholas, Joseph B.; Beckley, Brian D.

    2013-01-01

    We examine the impact of using seasonal and long-period time-variable gravity field (TVG) models on GPS orbit determination, through simulations from 1994 to 2012. The models of time-variable gravity that we test include the GRGS release RL02 GRACE-derived 10-day gravity field models up to degree and order 20 (grgs20x20), a 4 x 4 series of weekly coefficients using GGM03S as a base derived from SLR and DORIS tracking to 11 satellites (tvg4x4), and a harmonic fit to the above 4 x 4 SLR-DORIS time series (goco2s_fit2). These detailed models are compared to GPS orbit simulations using a reference model (stdtvg) based on the International Earth Rotation Service (IERS) and International GNSS Service (IGS) repro1 standards. We find that the new TVG modeling produces significant along, cross-track orbit differences as well as annual, semi-annual, draconitic and long-period effects in the Helmert translation parameters (Tx, Ty, Tz) of the GPS orbits with magnitudes of several mm. We show that the simplistic TVG modeling approach used by all of the IGS Analysis Centers, which is based on the models provided by the IERS standards, becomes progressively less adequate following 2006 when compared to the seasonal and long-period TVG models.

  14. Improvement of the software Bernese for SLR data processing in the Main Metrological Centre of the State Time and Frequency Service

    Science.gov (United States)

    Tsyba, E.; Kaufman, M.

    2015-08-01

    Preparatory works for resuming operational calculations of the Earth rotation parameters based on the results of satellite laser ranging data processing (LAGEOS 1, LAGEOS 2) are to be completed in the Main Metrology Centre Of The State Time And Frequency Service (VNIIFTRI) in 2014. For this purpose BERNESE 5.2 software (Dach & Walser, 2014) was chosen as a base software which has been used for many years in the Main Metrological Centre of the State Time and Frequency Service to process phase observations of GLONASS and GPS satellites. Although in the BERNESE 5.2 software announced presentation the possibility of the SLR data processing is declared, it has not been fully implemented. In particular there is no such an essential element as corrective action (as input or resulting parameters) in the local time scale ("time bias"), etc. Therefore, additional program blocks have been developed and integrated into the BERNESE 5.2 software environment. The program blocks are written in Perl and Matlab program languages and can be used both for Windows and Linux, 32-bit and 64-bit platforms.

  15. 超乎想像Mercedes-benz McLaren SLR Stirling Moss

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    在我印象里,Benz车外表通常都比较低调、内敛.有时甚至显得有些沉闷。不过这款超跑却张扬得令你不得不张大嘴巴.它的样子太漂亮了.太张扬了.太彪悍了!这款新车被命名为SLR Stirling Moss,是以1955年驾驶Benz 300 SLR取得佳绩的英国传奇车手Stirling Moss的名字命名的。

  16. Tectonic Plate Parameters Estimated in the International Terrestrial Reference Frame ITRF2008 Based on SLR Stations

    Directory of Open Access Journals (Sweden)

    Kraszewska Katarzyna

    2016-10-01

    Full Text Available This paper concerns an analysis of the accuracy of estimated parameters Ω(Φ, Λ, ω which define the tectonic plate motions. The study is based on the velocities of station positions published by ITRF2008 for Satellite Laser Ranging (SLR technique. The Eurasian, African, North American and Australian plates were used in the analysis. Influence of the number and location of stations on the plate surface on estimation accuracy of the tectonic plate motion parameters was discussed. The results were compared with the APKIM 2005 IGN model. In general, a remarkable concurrence agreement between our solutions and the APKIM 2005 model was found.

  17. 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...

  18. Multi-technique combination of space geodesy observations: Impact of the Jason-2 satellite on the GPS satellite orbits estimation

    Science.gov (United States)

    Zoulida, Myriam; Pollet, Arnaud; Coulot, David; Perosanz, Félix; Loyer, Sylvain; Biancale, Richard; Rebischung, Paul

    2016-10-01

    In order to improve the Precise Orbit Determination (POD) of the GPS constellation and the Jason-2 Low Earth Orbiter (LEO), we carry out a simultaneous estimation of GPS satellite orbits along with Jason-2 orbits, using GINS software. Along with GPS station observations, we use Jason-2 GPS, SLR and DORIS observations, over a data span of 6 months (28/05/2011-03/12/2011). We use the Geophysical Data Records-D (GDR-D) orbit estimation standards for the Jason-2 satellite. A GPS-only solution is computed as well, where only the GPS station observations are used. It appears that adding the LEO GPS observations results in an increase of about 0.7% of ambiguities fixed, with respect to the GPS-only solution. The resulting GPS orbits from both solutions are of equivalent quality, agreeing with each other at about 7 mm on Root Mean Square (RMS). Comparisons of the resulting GPS orbits to the International GNSS Service (IGS) final orbits show the same level of agreement for both the GPS-only orbits, at 1.38 cm in RMS, and the GPS + Jason2 orbits at 1.33 cm in RMS. We also compare the resulting Jason-2 orbits with the 3-technique Segment Sol multi-missions d'ALTimétrie, d'orbitographie et de localisation précise (SSALTO) POD products. The orbits show good agreement, with 2.02 cm of orbit differences global RMS, and 0.98 cm of orbit differences RMS on the radial component.

  19. Spin axis orientation of Ajisai determined from Graz 2 kHz SLR data

    Science.gov (United States)

    Kucharski, D.; Otsubo, T.; Kirchner, G.; Koidl, F.

    2010-08-01

    The Graz 2 kHz Satellite Laser Ranging (SLR) measurements allow determination of the spin axis orientation of the geodetic satellite Ajisai. The high repetition rate of the laser makes it possible to determine the epoch time when the laser is pointing directly between two corner cube reflector (CCR) rings of the satellite. Identification of many such events during a few (up to 3) consecutive passes allows to state the satellite orientation in the celestial coordinate system. Six years of 2 kHz SLR data (October 2003-October 2009) delivered 331 orientation values which clearly show precession of the axis along a cone centered at 14 h56 m2.8 s in right ascension and 88.512° in declination (J2000.0 celestial reference frame) and with an half-aperture angle θ of 1.405°. The spin axis precesses with a period of 117 days, which is equal to the period of the right ascension of the ascending node of Ajisai's orbit. We present a model of the axis precession which allows prediction of the satellite orientation - necessary for the envisaged laser time transfer via Ajisai mirrors.

  20. GPS derived Crustal Deformation and Strain determination in India

    Directory of Open Access Journals (Sweden)

    Abhay P. Singh,

    2011-06-01

    Full Text Available The theory of Plate tectonics has revolutionized the way thinking about the processes of Earth. According to this theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The edges of these plates, where they move against each other, are sites of intense tectonic activity, suchas earthquakes, volcanism, and mountain building. It is well known that Indian Plate is currently moving in the northeast direction, while the Eurasian Plate is moving north. This is causing the Indian and Eurasian Plate to deform at the point of contact besides its interior. Modern geophysical and space geodetic techniques such asseismology and GPS (Global Positioning system, have become important tools in the study of the deformation in the Earth due to tectonic processes, leading to earthquakes. Geodesy has provided an important role for plate tectonics study with high temporal resolution of the plate movements, particular from space technologies such as GPS and VLBI. The Global Positioning System (GPS provides accurate measurements of the rate of displacement of crustal. Indeed, the GPS velocity field can only be compared to finite strain if one assumes adeformation mechanism and that the style of deformation has been the same over long periods of geological time. For study of crustal deformation National Center of Mineralogy and Petrology, University of Allahabad, Allahabad installed highly efficient and accurate LEICA GRX1200 Pro receiver at Ghoorpur near to Allahabad. This instrument is also equipped withMET3A sensor to record pressure, temperature, humidity at regular interval of 30 second. The Latitude and longitude of the GPS sites is 25.21N, 81.28E.

  1. Slr1670 from Synechocystis sp. PCC 6803 is required for the re-assimilation of the osmolyte glucosylglycerol

    Directory of Open Access Journals (Sweden)

    Philipp Savakis

    2016-08-01

    Full Text Available When subjected to mild salt stress, the cyanobacterium Synechocystis sp. PCC 6803 produces small amounts of glycerol through an as of yet unidentified pathway. Here, we show that this glycerol is a degradation product of the main osmolyte of this organism, glucosylglycerol (GG. Inactivation of ggpS, encoding the first step of GG-synthesis, abolished de novo synthesis of glycerol, while the ability to hydrolyze exogenously supplied glucoslylglycerol was unimpaired. Inactivation of glpK, encoding glycerol kinase, had no effect on glycerol synthesis. Inactivation of slr1670, encoding a GHL5-type putative glycoside hydrolase, abolished de novo synthesis of glycerol, as well as hydrolysis of GG, and led to increased intracellular concentrations of this osmolyte. Slr1670 therefore presumably displays GG hydrolase activity. A gene homologous to the one encoded by slr1670 occurs in a wide range of cyanobacteria, proteobacteria and archaea. In cyanobacteria, it co-occurs with genes involved in GG-synthesis.

  2. Aircraft landing using GPS

    Science.gov (United States)

    Lawrence, David Gary

    The advent of the Global Positioning System (GPS) is revolutionizing the field of navigation. Commercial aviation has been particularly influenced by this worldwide navigation system. From ground vehicle guidance to aircraft landing applications, GPS has the potential to impact many areas of aviation. GPS is already being used for non-precision approach guidance; current research focuses on its application to more critical regimes of flight. To this end, the following contributions were made: (1) Development of algorithms and a flexible software architecture capable of providing real-time position solutions accurate to the centimeter level with high integrity. This architecture was used to demonstrate 110 automatic landings of a Boeing 737. (2) Assessment of the navigation performance provided by two GPS-based landing systems developed at Stanford, the Integrity Beacon Landing System, and the Wide Area Augmentation System. (3) Preliminary evaluation of proposed enhancements to traditional techniques for GPS positioning, specifically, dual antenna positioning and pseudolite augmentation. (4) Introduction of a new concept for positioning using airport pseudolites. The results of this research are promising, showing that GPS-based systems can potentially meet even the stringent requirements of a Category III (zero visibility) landing system. Although technical and logistical hurdles still exist, it is likely that GPS will soon provide aircraft guidance in all phases of flight, including automatic landing, roll-out, and taxi.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. COMPARISON BETWEEN POSTERIOR TO ANTERIOR MOBILIZATION AND TRACTION SLR ON PAIN AND NEURODYNAMIC MOBILITY IN PATIENTS OF LOW BACK PAIN

    Directory of Open Access Journals (Sweden)

    Singh Varun

    2014-02-01

    Full Text Available Background : Low back pain is one of the most prevalent condition . According to the American Association of Orthopaedic Surgeons about 80 percent of people will have at least one bout with back pain during their lifetime . Various treatments methods have been used like traction SLR , posterior to anterior mobilization etc, but no study was done to compare the effects of posterior to anterior mobilization and traction SLR technique in reducing pain and increasing neurodynamic mobility in patients of low back pain. Purpose of study : To find out the effectiveness of traction SLR and posterior to Anterior mobilization in decreasing pain and increasing neurodynamic mobility of low back pain patients. Method : 20 subjects were taken as per selection criteria which included both male and female between the age of 25 to 45 years. They were randomly divided into two groups, group A (n=10 subjects received traction SLR and group B (n=10 received posterior to anterior mobilization. Range Of Motion and VAS were taken as outcome measurement parameters. Result: Comparison was made between pre and post reading within group using related t – test and between groups by using unrelated t-test for statistical analysis. Result showed statistically significant improvement between pre and post intervention VAS score for both group A and B. Result showed a statistically significant improvement between pre and post intervention ROM in for both Group A and B. Result shows statistically non significant difference between Group A and B in ROM and VAS scores. Conclusion: Traction SLR and posterior to anterior mobilization are effective in improving ROM and pain in patients suffering from low back pain. However there was no statistically significant difference between Traction SLR and posterior to anterior mobilization in improving Pain and ROM in patients suffering from low back pain.

  10. 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-...

  11. GPS Activities at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Behrend, Dirk

    2002-11-19

    The Alignment Engineering Group of the Stanford Linear Accelerator Center (SLAC) started to use RTK (real-time kinematic) GPS equipment in order to perform structure mapping and GIS-related tasks on the SLAC campus. In a first step a continuously observing GPS station (SLAC M40) was set up. This station serves as master control station for all differential GPS activities on site and its coordinates have been determined in the well-defined global geodetic datum ITRF2000 at a given reference epoch. Some trials have been performed to test the RTK method. The tests have proven RTK to be very fast and efficient.

  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. 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.

  14. 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.

  15. 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

  16. SLR-induced temporal and spatial changes in hotspots to storms along the Catalan coast

    Science.gov (United States)

    Jiménez, Jose A.; Sanuy, Marc; Valdemoro, Herminia

    2017-04-01

    any significant increasing trend, this does not imply that storm-induced coastal hazards will not change. Thus, SLR will induce a series of long-term changes in coastal areas that although not directly affecting storminess will modify the coastal resilient capacity and, thus, changing coastal storm risks. To provide long-term predictions of hotspot, we have assessed the long-term SLR influence on erosion and inundation risks. To do this, an equilibrium-based approach has been adopted in which background SLR-induced shoreline retreat and beach vertical response are assessed for different SLR scenarios. Obtained values are used to predict future coastal morphology and to compute the resilient capacity for each beach at any time horizon. With this information, future erosion and inundation risks and corresponding new spatial distributions of coastal hotspots are calculated for selected probabilities. Obtained results show a significant increase in hotspots along the coast, with most of the changes concentrated in areas with small accommodation space and dominated by mild slope shorefaces. The extension of the new hotspots seems to indicate than unless land planning is considered as a tool for risk reduction, massive protection need to be implemented in certain areas.

  17. HlSST and SLR - bridging the gap between GRACE and GRACE Follow-on

    Science.gov (United States)

    Weigelt, Matthias; Jäggi, Adrian; Meyer, Ulrich; Arnold, Daniel; Grahsl, Andrea; Sosnica, Krysztof; Dahle, Christoph; Flechtner, Frank

    2017-04-01

    GRACE is undoubtedly one of the most important sources to observe mass transport on global scales. Numerous applications have shown the validity and impact of using its data. Within the EGSIEM project GRACE gravity field solutions from various processing centers are processed and combined to further increase the spatial and temporal resolution. However, it is expected that GRACE will not continue to observe mass variations from space till its successor GRACE Follow-on will be operational. Thus there is a need for an intermediate technique that will bridge the gap between the two missions and will allow 1) for a continued and uninterrupted time series of mass observations and 2) to compare, crossvalidate and link the two time series. Here we will focus on the combination of high-low satellite-to-satellite tracking (hlSST) of low-Earth orbiting satellites by GNSS in combination with SLR. SLR is known to provide highest quality time-variable gravity for the very low degrees (2-5). HlSST provides a higher spatial resolution but at a lower precision in the very low degrees. Thus it seems natural to combine these two techniques and their benefit has already been demonstrated in the past. Here we make use of the lessons learned within the EGSIEM project and focus on various aspects of combination such as the optimal strategy and relative weighting schemes. We discuss also the achievable spatial and temporal resolutions of different satellite scenarios, such as e.g. using Swarm satellites in combination with Sentinel and/or single GRACE satellites, and present the potential and limitations for geophysical applications.

  18. 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

  19. The hazard of Sea Level Rise (SLR) in Greece: from scientific knowledge towards risk awareness of main actors

    Science.gov (United States)

    Dandoulaki, Miranda; Karymbalis, Efthimios; Yorgos, Melissourgos; Skordili, Sophia; Valkanou, Kanella

    2014-05-01

    A natural hazard that is expected to affect coastal areas in the near future is Sea-Level Rise (SLR) due to climate change. According to recent reports the eustatic sea-level rise caused by global warming will reach approximately 18-59 cm by the year 2100. Potential impacts of future sea-level rise include coastal erosion, frequent and intensified cyclonic activity and associated storm surge flooding that may affect the coastal zones, saltwater intrusion into groundwater aquifers, the inundation of ecologically significant wetlands, and threats to cultural and historical resources, as well as to infrastructure. The identification of sensitive sections of coasts and the assessment of potential impacts of SLR on these is therefore a fundamental, yet initial, step towards their protection. Greece has the most extensive coastline among all Mediterranean countries with most of the socio-economic activities concentrated along the coastal zone. Almost all big urban centres are coastal ones and the same stands for a great part of infrastructure (ports, airports, roads, electricity and telecommunications network etc). As a result, the impacts of a potential rise of the sea level are expected to seriously affect the entire country. The paper examines the vulnerability to SLR of coastal zones in Greece; however its main focus is how knowledge can lead to policy making and the protection of coastal areas. The main actors in respect to protection from SLR in Greece are identified and there is an attempt to pin point how the knowledge is communicated and shared between them. Barriers, bridges and gaps are detected as regards how information and knowledge lead to risk awareness and finally to the implementation of protection policies. A main finding of the paper is that SLR risk is far from becoming a policy priority in Greece, although steps are taken for addressing impacts attributed to SLR such as coastal erosion. In order to address this risk, there are many potential

  20. 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.

  1. 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.

  2. 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.

  3. 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)

  4. 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.

  5. 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.

  6. GPS Metric Tracking Unit

    Science.gov (United States)

    2008-01-01

    As Global Positioning Satellite (GPS) applications become more prevalent for land- and air-based vehicles, GPS applications for space vehicles will also increase. The Applied Technology Directorate of Kennedy Space Center (KSC) has developed a lightweight, low-cost GPS Metric Tracking Unit (GMTU), the first of two steps in developing a lightweight, low-cost Space-Based Tracking and Command Subsystem (STACS) designed to meet Range Safety's link margin and latency requirements for vehicle command and telemetry data. The goals of STACS are to improve Range Safety operations and expand tracking capabilities for space vehicles. STACS will track the vehicle, receive commands, and send telemetry data through the space-based asset, which will dramatically reduce dependence on ground-based assets. The other step was the Low-Cost Tracking and Data Relay Satellite System (TDRSS) Transceiver (LCT2), developed by the Wallops Flight Facility (WFF), which allows the vehicle to communicate with a geosynchronous relay satellite. Although the GMTU and LCT2 were independently implemented and tested, the design collaboration of KSC and WFF engineers allowed GMTU and LCT2 to be integrated into one enclosure, leading to the final STACS. In operation, GMTU needs only a radio frequency (RF) input from a GPS antenna and outputs position and velocity data to the vehicle through a serial or pulse code modulation (PCM) interface. GMTU includes one commercial GPS receiver board and a custom board, the Command and Telemetry Processor (CTP) developed by KSC. The CTP design is based on a field-programmable gate array (FPGA) with embedded processors to support GPS functions.

  7. GPS satellite surveying

    CERN Document Server

    Leick, Alfred; Tatarnikov, Dmitry

    2015-01-01

    THE MOST COMPREHENSIVE, UP-TO-DATE GUIDE ON GPS TECHNOLOGY FOR SURVEYING Three previous editions have established GPS Satellite Surveying as the definitive industry reference. Now fully updated and expanded to reflect the newest developments in the field, this Fourth Edition features cutting-edge information on GNSS antennas, precise point positioning, real-time relative positioning, lattice reduction, and much more. Expert authors examine additional tools and applications, offering complete coverage of geodetic surveying using satellite technologies. The past decade has seen a major evolut

  8. GPS, su datum vertical.

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available La introducción de la metodología GPS en aplicaciones topográficas y geodésicas pone en notoria evidencia la clásica separación de sistemas de referencia en horizontal y vertical. Con GPS el posicionamiento es tridimensional, pero el concepto de altura difiere del clásico. Si se desea utilizar la información altimétrica debe contemplarse la ondulación del geoide.

  9. Identification of a New Target slr0946 of the Response Regulator Sll0649 Involving Cadmium Tolerance in Synechocystis sp. PCC 6803.

    Science.gov (United States)

    Sun, Tao; Xu, Le; Wu, Lina; Song, Zhongdi; Chen, Lei; Zhang, Weiwen

    2017-01-01

    Survival of photosynthetic cyanobacteria is challenged by environmental contaminations like heavy metals. Among them, deciphering the regulatory mechanisms for cadmium (Cd) in cyanobacteria would facilitate the construction of Cd-resistant strains. In this study, the DNA-Affinity-Purified-chromatin immunoprecipitation assay was employed to identify the direct targets of Sll0649, which was a Cd(2+)-related response regulator identified in our previous work in model cyanobacteria Synechocystis sp. PCC 6803. As a result, the promoter region of slr0946 encoding the arsenate reductase was enriched fourfolds by quantitative real time PCR analysis. Further, deletion of slr0946 led to a sensitive phenotype to Cd(2+) stress compared with the wild type (WT) and the sensitive phenotype of Δslr0946 could be rescued by complementation assay via introducing slr0946 back into Δslr0946. Finally, individually overexpression of slr0946 as well as two Cd(2+)-related genes identified priviously (i.e., sll1598 and slr0798) in WT could significantly improve the tolerance of Synechocystis sp. PCC 6803 to Cd(2+). This study provided a better understanding of the tolerance mechanism to Cd(2+) in cyanobacteria and also feasible strategies for tolerance modifications to heavy metals in the future.

  10. GPS Imaging of Solid Earth's Flex and Flow: A New Paradigm

    Science.gov (United States)

    Blewitt, G.; Hammond, W. C.; Kreemer, C.

    2015-12-01

    Geodetic GPS data analysis has gone through several paradigm shifts since the 1980s. Initially GPS was used in relative positioning mode to leverage and densify the existing global VLBI network. In the 1990s the new paradigm was to analyze GPS as a self-contained system, in which the global network of GPS stations and satellite orbits could be estimated simultaneously. Computational resources limit this approach to a few hundred stations (n ~ 100), with O(n4) computational complexity. Since the last decade, the new paradigm is to estimate GPS orbits first, followed by precise point positioning of single stations with O(n) complexity. This allows for parallel processing of an unlimited number of stations. The Nevada Geodetic Laboratory currently updates GPS time series for over 13,500 stations every week, a number that has been doubling every ~3 years. In some parts of the world, the inter-station distance between GPS stations that we process is now approaching ~10 km. This now brings us to a new paradigm, "GPS Imaging," for which we use thousands of GPS stations in different continents to generate smooth, yet detailed maps of vertical land motion. Our prototype images show that the striking, first-order signal in North America and Europe is large scale uplift and subsidence from mantle flow driven by Glacial Isostatic Adjustment. Thus we are imaging deep Earth processes with unprecedented scope, resolution and accuracy. At regional scales, the images reveal that anthropogenic lithospheric processes can dominate vertical land motion in extended regions. We have developed prototype techniques that form a foundation to make "GPS Imaging" operational: (1) an automatic, robust estimator of station velocity that is insensitive to prevalent step discontinuities, outliers, seasonality, and heteroscedasticity; (2) a realistic estimate of the velocity errors based on subsampling; (3) a filter of common-mode noise that is globally seamless; (4) a median spatial filter to

  11. The membrane bound LRR lipoprotein Slr, and the cell wall-anchored M1 protein from Streptococcus pyogenes both interact with type I collagen.

    Directory of Open Access Journals (Sweden)

    Marta Bober

    Full Text Available Streptococcus pyogenes is an important human pathogen and surface structures allow it to adhere to, colonize and invade the human host. Proteins containing leucine rich repeats (LRR have been identified in mammals, viruses, archaea and several bacterial species. The LRRs are often involved in protein-protein interaction, are typically 20-30 amino acids long and the defining feature of the LRR motif is an 11-residue sequence LxxLxLxxNxL (x being any amino acid. The streptococcal leucine rich (Slr protein is a hypothetical lipoprotein that has been shown to be involved in virulence, but at present no ligands for Slr have been identified. We could establish that Slr is a membrane attached horseshoe shaped lipoprotein by homology modeling, signal peptidase II inhibition, electron microscopy (of bacteria and purified protein and immunoblotting. Based on our previous knowledge of LRR proteins we hypothesized that Slr could mediate binding to collagen. We could show by surface plasmon resonance that recombinant Slr and purified M1 protein bind with high affinity to collagen I. Isogenic slr mutant strain (MB1 and emm1 mutant strain (MC25 had reduced binding to collagen type I as shown by slot blot and surface plasmon resonance. Electron microscopy using gold labeled Slr showed multiple binding sites to collagen I, both to the monomeric and the fibrillar structure, and most binding occurred in the overlap region of the collagen I fibril. In conclusion, we show that Slr is an abundant membrane bound lipoprotein that is co-expressed on the surface with M1, and that both these proteins are involved in recruiting collagen type I to the bacterial surface. This underlines the importance of S. pyogenes interaction with extracellular matrix molecules, especially since both Slr and M1 have been shown to be virulence factors.

  12. Semantic enrichment of GPS trajectories

    NARCIS (Netherlands)

    Graaff, de Victor; Keulen, van Maurice; By, de Rolf

    2012-01-01

    Semantic annotation of GPS trajectories helps us to recognize the interests of the creator of the GPS trajectories. Automating this trajectory annotation circumvents the requirement of additional user input. To annotate the GPS traces automatically, two types of automated input are required: 1) a co

  13. 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...

  14. 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...

  15. 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.

  16. 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.

  17. 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...

  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. First Attempt of Orbit Determination of SLR Satellites and Space Debris Using Genetic Algorithms

    Science.gov (United States)

    Deleflie, F.; Coulot, D.; Descosta, R.; Fernier, A.; Richard, P.

    2013-08-01

    We present an orbit determination method based on genetic algorithms. Contrary to usual estimation methods mainly based on least-squares methods, these algorithms do not require any a priori knowledge of the initial state vector to be estimated. These algorithms can be applied when a new satellite is launched or for uncatalogued objects that appear in images obtained from robotic telescopes such as the TAROT ones. We show in this paper preliminary results obtained from an SLR satellite, for which tracking data acquired by the ILRS network enable to build accurate orbital arcs at a few centimeter level, which can be used as a reference orbit ; in this case, the basic observations are made up of time series of ranges, obtained from various tracking stations. We show as well the results obtained from the observations acquired by the two TAROT telescopes on the Telecom-2D satellite operated by CNES ; in that case, the observations are made up of time series of azimuths and elevations, seen from the two TAROT telescopes. The method is carried out in several steps: (i) an analytical propagation of the equations of motion, (ii) an estimation kernel based on genetic algorithms, which follows the usual steps of such approaches: initialization and evolution of a selected population, so as to determine the best parameters. Each parameter to be estimated, namely each initial keplerian element, has to be searched among an interval that is preliminary chosen. The algorithm is supposed to converge towards an optimum over a reasonable computational time.

  2. Zoom lens design for 10.2-megapixel APS-C digital SLR cameras.

    Science.gov (United States)

    Sun, Wen-Shing; Chu, Pu-Yi; Tien, Chuen-Lin; Chung, Meng-Feng

    2017-01-20

    A zoom lens design for a 10.2-megapixel digital single-lens reflex (SLR) camera with an advanced photo system type-C (APS-C) CCD image sensor is presented. The proposed zoom lens design consists of four groups of 3× zoom lenses with a focal length range of 17-51 mm. In the optimization process, 107 kinds of Schott glass combined with 26 kinds of plastic materials, as listed in Code V, are used. The best combination of glass and plastic materials is found based on the nd-Vd diagram. The modulation transfer function (MTF) was greater than 0.509 at 42  lp/mm, the lateral chromatic aberration was less than 5 μm, the optical distortion was less than 1.97%, and the relative illumination was greater than 80.05%. We also performed the tolerance analysis with the 2σ (97.7%) position selected and given tolerance tables and results for three zooming positions, which made the design more practical for manufacturing.

  3. 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.

  4. 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.

  5. Indoor Positioning Using GPS Revisited

    DEFF Research Database (Denmark)

    Kjærgaard, Mikkel Baun; Blunck, Henrik; Godsk, Torben

    2010-01-01

    It has been considered a fact that GPS performs too poorly inside buildings to provide usable indoor positioning. We analyze results of a measurement campaign to improve on the understanding of indoor GPS reception characteristics. The results show that using state-of-the-art receivers GPS...... low signal-to-noise ratios, multipath phenomena or bad satellite constellation geometry. We have also measured the indoor performance of embedded GPS receivers in mobile phones which provided lower availability and accuracy than state-of-the-art ones. Finally, we consider how the GPS performance...

  6. Comparison of ENVISAT's Attitude Simulation and Real Optical and SLR Observations in order to Refine the Satellite Attitude Model

    Science.gov (United States)

    Silha, J.; Schildknecht, T.; Pittet, J.; Bodenmann, D.; Kanzler, R.; Karrang, P.; Krag, H.

    2016-09-01

    The Astronomic Institute of the University of Bern (AIUB) in cooperation with other three partners is involved in an ESA study dedicated to the attitude determination of large spacecraft and upper stages. Two major goals are defined. First is the long term prediction of tumbling rates (e.g. 10 years) for selected targets for the future Active Debris Removal (ADR) missions. Second goal is the attitude state determination in case of contingencies, when a short response time is required between the observations themselves and the attitude determination. One of the project consortium partners, Hypersonic Technology Goettingen (HTG), is developing a highly modular software tool ιOTA to perform short- (days) to long-term (years) propagations of the orbit and the attitude motion of spacecraft in space. Furthermore, ιOTA's post-processing modules will generate synthetic measurements, e.g. light curves, SLR residuals and Inverse Synthetic Aperture Radar (ISAR) images that can be compared with the real measurements. In our work we will present the first attempt to compare real measurements with synthetic measurements in order to estimate the attitude state of tumbling satellite ENVISAT from observations performed by AIUB. We will shortly discuss the ESA project and ιOTA software tool. We will present AIUB's ENVISAT attitude state determined from the SLR ranges acquired by the Zimmerwald SLR station. This state was used as the initial conditions within the ιOTA software. Consequently the attitude of satellite was predicted by using ιOTA and compared with the real SLR residuals, as well with the high frame-rate light curves acquired by the Zimmerwald 1-m telescope.

  7. Adaptive Missile Guidance Using GPS

    Directory of Open Access Journals (Sweden)

    Pallavi Sharad Rupnar

    2013-05-01

    Full Text Available The name adaptive means we can guide any missile using GPS in any critical conditions. GPS guided missiles, using the exceptional navigational and surveying abilities of GPS, after being launched, could deliver a warhead to any part of the globe via the interface of the onboard computer in the missile with the GPS satellite system.GPS allows accurate targeting of various military weapons including ICBMs, cruise missiles and precision-guided munitions. Artillery projectiles with embedded GPS receivers able to withstand accelerations of 12,000 G have been developed for use in 155mm.GPS guided weapons, with their technological advances over previous, are the superior weapon of choice in modern days

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. The potential use of fiducial ground networks.

    Science.gov (United States)

    Bianco, G.

    1991-12-01

    Collocation of space geodetic techniques will play an important role for precision orbit determination of ARISTOTELES. The FLINN network concept is ideal for defining and maintaining an highly precise conventional terrestrial reference frame by means of collocated SLR, VLBI and GPS stations. The proposed, "on-line" ARISTOTELES GPS tracking network should be supported by an extended, "off-line" tracking network with several selected FLINN sites, in order to include the ARISTOTELES mission within a standard, high accuracy conventional terrestrial reference system.

  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. 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.

  2. 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 ...

  3. 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.

  4. 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...

  5. 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.

  6. Standardization of GPS data processing

    Energy Technology Data Exchange (ETDEWEB)

    Park, Pil Ho

    2001-06-15

    A nationwide GPS network has been constructed with about 60 permanent GPS stations after late 1990s in Korea. For using the GPS in variety of application area like crustal deformation, positioning, or monitoring upper atmosphere, it is necessary to have ability to process the data precisely. Now Korea Astronomy Observatory has the precise GPS data processing technique in Korea because it is difficult to understand characteristics of the parameters we want to estimate, resolve the integer ambiguity, and analyze many errors. There are three reliable GPS data processing software in the world ; Bernese(University of Berne), GIPSY-OASIS(JPL), GAMIT(MIT). These software allow us to achieve millimeter accuracy in the horizontal position and about 1 cm accuracy vertically even for regional networks with a diameter of several thousand kilometers. But we established the standard of GPS data processing using Bernese as main tool and GIPSY{sub O}ASIS as side.

  7. Update on GPS Modernization Efforts

    Science.gov (United States)

    2015-06-02

    SPACE AND MISSILE SYSTEMS CENTER , GPS constellation consists of 24+ satellites orbiting the earth at - 10,900 nautical miles (Medium Earth Orbit , MEO...estimates instantaneous state of GPS constellation PUBLICALL Y RELEASABLE 4 Civil Cooperation • 1 + Bill ion civil & commercial users worldwide...Observatory • PNT EXCOMS • GPS Partnership Council Maintenance/Security Spectrum 38 Satellites I 31 Set Healthy Baseline Constellation : 24 Satellites

  8. Military GPS User Equipment (MGUE)

    Science.gov (United States)

    2015-04-29

    Space and Missile Systems Center Military GPS User Equipment (MGUE) Lt Col James “Mutt” Wilson Program Manager 29 Apr 15 Information contained in...SUBTITLE Military GPS User Equipment (MGUE) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK...SUPPLEMENTARY NOTES Presented at the GPS Partnership Council 2015 (GPSPC15), held April 29 to May 1, 2015, at the Los Angeles AFB, CA. 14. ABSTRACT

  9. 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

  10. Hastighedskort for Danmark vha. GPS

    DEFF Research Database (Denmark)

    Andersen, Ove; Lahrmann, Harry; Torp, Kristian

    2011-01-01

    Hastighed på vejnettet er en central metrik indenfor trafikplanlægning og trafikoptimering. I denne artikel beskrives, hvorledes et hastighedskort for hele Danmark er skabt udelukkende vha. GPS data. To tilgangsvinkler til at beregne hastigheder vha. GPS data er præsenteret. Dette er hhv. en punk...... foretages med et beskedent budget er uvist....

  11. Evidential recovery from GPS devices

    Directory of Open Access Journals (Sweden)

    Brian Cusack

    Full Text Available Global Positioning Systems (GPS have become more affordable, are now widely used in motor vehicles and in other frequently used applications. As a consequence GPS are increasingly becoming an important source of evidential data for digital forensic investigations. This paper acknowledges there are only disparate documents for the guidance of an investigator when extracting evidence form such systems. The focus of this paper is to provide the technical details of recovering artifacts from four GPS currently available to the New Zealand market. Navman brand GPS are used, following a forensically robust process. The steps of the process are described, results analysed and the associated risks are discussed. In addition, the paper discusses techniques related to the visual presentation of evidence suitable for Google Maps. Automation attempts to speed up the analysis to visualization steps are also included. The outcome is a road map that may assist digital forensic investigators develop GPS examination strategies for implementation in their own organizations.

  12. Spaceborne GPS receiver antenna phase center offset and variation estimation for the Shiyan 3 satellite

    Directory of Open Access Journals (Sweden)

    Gu Defeng

    2016-10-01

    Full Text Available In determining the orbits of low Earth orbit (LEO satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset (PCO and phase center variations (PCVs are gradually becoming a major limiting factor for continued improvements to accuracy. Shiyan 3, a small satellite mission for space technology experimentation and climate exploration, was developed by China and launched on November 5, 2008. The dual-frequency GPS receiver payload delivers 1 Hz data and provides the basis for precise orbit determination within the range of a few centimeters. The antenna PCO and PCV error characteristics and the principles influencing orbit determination are analyzed. The feasibility of PCO and PCV estimation and compensation in different directions is demonstrated through simulation and in-flight tests. The values of receiver antenna PCO and PCVs for Gravity Recovery and Climate Experiment (GRACE and Shiyan 3 satellites are estimated from one month of data. A large and stable antenna PCO error, reaching up to 10.34 cm in the z-direction, is found with the Shiyan 3 satellite. The PCVs on the Shiyan 3 satellite are estimated and reach up to 3.0 cm, which is slightly larger than that of GRACE satellites. Orbit validation clearly improved with independent k-band ranging (KBR and satellite laser ranging (SLR measurements. For GRACE satellites, the average root mean square (RMS of KBR residuals improved from 1.01 cm to 0.88 cm. For the Shiyan 3 satellite, the average RMS of SLR residuals improved from 4.95 cm to 4.06 cm.

  13. Spaceborne GPS receiver antenna phase center offset and variation estimation for the Shiyan 3 satellite

    Institute of Scientific and Technical Information of China (English)

    Gu Defeng; Lai Yuwang; Liu Junhong; Ju Bing; Tu Jia

    2016-01-01

    In determining the orbits of low Earth orbit (LEO) satellites using spaceborne GPS, the errors caused by receiver antenna phase center offset (PCO) and phase center variations (PCVs) are gradually becoming a major limiting factor for continued improvements to accuracy. Shiyan 3, a small satellite mission for space technology experimentation and climate exploration, was developed by China and launched on November 5, 2008. The dual-frequency GPS receiver payload delivers 1 Hz data and provides the basis for precise orbit determination within the range of a few centime-ters. The antenna PCO and PCV error characteristics and the principles influencing orbit determi-nation are analyzed. The feasibility of PCO and PCV estimation and compensation in different directions is demonstrated through simulation and in-flight tests. The values of receiver antenna PCO and PCVs for Gravity Recovery and Climate Experiment (GRACE) and Shiyan 3 satellites are estimated from one month of data. A large and stable antenna PCO error, reaching up to 10.34 cm in the z-direction, is found with the Shiyan 3 satellite. The PCVs on the Shiyan 3 satellite are estimated and reach up to 3.0 cm, which is slightly larger than that of GRACE satellites. Orbit validation clearly improved with independent k-band ranging (KBR) and satellite laser ranging (SLR) measurements. For GRACE satellites, the average root mean square (RMS) of KBR resid-uals improved from 1.01 cm to 0.88 cm. For the Shiyan 3 satellite, the average RMS of SLR resid-uals improved from 4.95 cm to 4.06 cm.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. 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...

  19. 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.

  20. 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

  1. 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...

  2. 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...

  3. 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.

  4. 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...

  5. 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.

  6. 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...

  7. 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.

  8. De GPS al mapa

    Directory of Open Access Journals (Sweden)

    Esteban Dörries

    2016-03-01

    Full Text Available Las coordenadas Lambert obtenidas a partir de mediciones con equipos GPS de mano, llamados a veces navegadores, en ciertos casos confunden al usuario, por diferir claramente de su posición real al ser graficadas en un mapa del Instituto Geográfico Nacional (IGN: Esto puede resolverse con suficiente exactitud mediante una transformación de Molodensky, seguida de la correspondiente proyección cartográfica. Sin embargo, los tres parámetros necesarios para la transformación, supuestamente válidos para Costa Rica, se encuentran en muchas variantes y producen obviamente resultados diferentes. En este trabajo se analizan los fundamentos del problema y sus posibles soluciones, culminando con un estudio comparativo de ocho casos, que permite seleccionar los valores más adecuados para los parámetros.

  9. 75 FR 8928 - Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800 Interface Control Working Group (ICWG...

    Science.gov (United States)

    2010-02-26

    ... Department of the Air Force Announcement of IS-GPS-200, IS-GPS-705, IS-GPS-800Interface Control Working Group... an Interface Control Working Group (ICWG) teleconference meeting for document/s IS-GPS-200E (NAVSTAR GPS Space Segment/Navigation User Interfaces), IS-GPS-705A (NAVSTAR GPS Space Segment/User Segment...

  10. Measurements of Interferometer Parameters at Reception of GLONASS and GPS Signals

    Directory of Open Access Journals (Sweden)

    Nechaeva M.

    2016-10-01

    Full Text Available The present paper deals with the calibration method of interferometers with antennas having a small effective area, on the quasinoise signals of GLONASS and GPS navigation satellites. Algorithms for calculation of antenna coordinates and instrumental delay from the analysis of correlation interferometer response to signals of satellites in the near field of the instrument were reviewed. The method was tested in VLBI experiments on interferometers with medium and large baselines that included radio telescopes of NIRFI and VIRAC. The values of the antenna coordinates and instrumental delay with an error within the limits of one discrete were obtained. The sources of measurement errors and ways to improve the accuracy of results were analysed.

  11. 两行根数辅助的SLR单站定轨%Two Line Element Aided Orbit Determination Using Single Station SLR Data

    Institute of Scientific and Technical Information of China (English)

    梁智鹏; 刘承志; 范存波; 孙明国

    2012-01-01

    It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data generated by performing diffuse-reflection SLR to the orbital space debris are therefore ineffective for orbit improvement.We propose a method to resolve the singularity in the observation distribution. Since the initial orbits of space debris such as the two line elements (TLE) exist prior to the SLR tracking, we use it to simulate observations from other SLR sites. We combine the simulated and actual observations with a proper weight to fit an orbit, thus resolving the singularity in the observation distribution. We then propagate the fitted orbit forward in time to validate against the precision ephemeris derived from the international laser ranging service (ILRS).The method is implemented and applied to the satellite Ajisai. Using the single-station SLR data of five passes in one day and corresponding TLE as the initial orbit, we fit the orbit and the generated predictions. The predicted position error is less than 40 meter in five-day span, significantly improved over the initial SGP4 propagated orbit. The method's potential application to space debris orbit improvement is also discussed.%单站测距资料定轨的困难限制了漫反射SLR (Satellite Laser Ranging)测距资料的应用.为此,提出利用两行根数模拟多站SLR测距资料作为辅助,实现单站SLR测距资料定轨的方法.该方法对卫星Ajisai单站SLR测距资料定轨并生成5d预报轨道,误差小于40 m,实现利用单站测距资料的轨道改进,验证了方法的可行性.

  12. 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

  13. Hastighedskort for Danmark vha. GPS

    DEFF Research Database (Denmark)

    Andersen, Ove; Lahrmann, Harry; Torp, Kristian

    2011-01-01

    Hastighed på vejnettet er en central metrik indenfor trafikplanlægning og trafikoptimering. I denne artikel beskrives, hvorledes et hastighedskort for hele Danmark er skabt udelukkende vha. GPS data. To tilgangsvinkler til at beregne hastigheder vha. GPS data er præsenteret. Dette er hhv. en....... Opsummeret anses den turbaseret for at beregne det mest akkurate estimat, men metoden er meget datakrævende. Det er derfor nødvendigt at have den punktbaserede at falde tilbage på. Generelt mangler metoder til beregning af hastigheder vha. GPS data at blive valideret. Hvordan en sådan validering kan...

  14. 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...

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Scintillation-Hardened GPS Receiver

    Science.gov (United States)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  7. Scintillation-Hardened GPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A Communications, Navigation, and Networking reConfigurable Testbed (CoNNeCT) experiment is proposed to improve the performance of GPS during geomagnetic storms....

  8. The role of key amino acids in the photoactivation pathway of the Synechocystis Slr1694 BLUF domain.

    Science.gov (United States)

    Bonetti, Cosimo; Stierl, Manuela; Mathes, Tilo; van Stokkum, Ivo H M; Mullen, Katharine M; Cohen-Stuart, Thomas A; van Grondelle, Rienk; Hegemann, Peter; Kennis, John T M

    2009-12-08

    BLUF (blue light sensing using FAD) domains belong to a novel group of blue light sensing receptor proteins found in microorganisms. We have assessed the role of specific aromatic and polar residues in the Synechocystis Slr1694 BLUF protein by investigating site-directed mutants with substitutions Y8W, W91F, and S28A. The W91F and S28A mutants formed the red-shifted signaling state upon blue light illumination, whereas in the Y8W mutant, signaling state formation was abolished. The W91F mutant shows photoactivation dynamics that involve the successive formation of FAD anionic and neutral semiquinone radicals on a picosecond time scale, followed by radical pair recombination to result in the long-lived signaling state in less than 100 ps. The photoactivation dynamics and quantum yield of signaling state formation were essentially identical to those of wild type, which indicates that only one significant light-driven electron transfer pathway is available in Slr1694, involving electron transfer from Y8 to FAD without notable contribution of W91. In the S28A mutant, the photoactivation dynamics and quantum yield of signaling state formation as well as dark recovery were essentially the same as in wild type. Thus, S28 does not play an essential role in the initial hydrogen bond switching reaction in Slr1694 beyond an influence on the absorption spectrum. In the Y8W mutant, two deactivation branches upon excitation were identified: the first involves a neutral semiquinone FADH(*) that was formed in approximately 1 ps and recombines in 10 ps and is tentatively assigned to a FADH(*)-W8(*) radical pair. The second deactivation branch forms FADH(*) in 8 ps and evolves to FAD(*-) in 200 ps, which recombines to the ground state in about 4 ns. In the latter branch, W8 is tentatively assigned as the FAD redox partner as well. Overall, the results are consistent with a photoactivation mechanism for BLUF domains where signaling state formation proceeds via light-driven electron

  9. Continuous professional development for GPs

    DEFF Research Database (Denmark)

    Kjaer, N K; Steenstrup, A P; Pedersen, L B

    2014-01-01

    randomly chosen Danish GPs. RESULTS: Focus groups: CPD activities are chosen based on personal needs analysis, and in order to be professionally updated, to meet engaged colleagues and to prevent burnout. GPs also attend CPD to assess their own pre-existing level of competence. CPD activities need...... by topics strengthening their professional capacity and preventing burnout. There would seem to be no need for a mandatory system....

  10. Global Positioning Systems Directorate: GPS Update

    Science.gov (United States)

    2015-04-29

    Council Maintenance/Security Spectrum 39 Satellites /31 Set Healthy Baseline Constellation : 24 Satellites • All Level l and Level II...Department of Transportation • Federal Aviation Administration Satellite Block GPS IIA GPS IIR GPS IIR-M GPS IIF Constellation Department of...segment - India- IRNSS UNCLASSIFIED/APPROVED FOR PUBLIC RELEASE 3 UNCLASSIFIED/APPROVED FOR PUBLIC RELEASE GPS Constellation Status SPACE AND

  11. Geocenter variations derived from a combined processing of LEO- and ground-based GPS observations

    Science.gov (United States)

    Männel, Benjamin; Rothacher, Markus

    2017-08-01

    GNSS observations provided by the global tracking network of the International GNSS Service (IGS, Dow et al. in J Geod 83(3):191-198, 2009) play an important role in the realization of a unique terrestrial reference frame that is accurate enough to allow a detailed monitoring of the Earth's system. Combining these ground-based data with GPS observations tracked by high-quality dual-frequency receivers on-board low earth orbiters (LEOs) is a promising way to further improve the realization of the terrestrial reference frame and the estimation of geocenter coordinates, GPS satellite orbits and Earth rotation parameters. To assess the scope of the improvement on the geocenter coordinates, we processed a network of 53 globally distributed and stable IGS stations together with four LEOs (GRACE-A, GRACE-B, OSTM/Jason-2 and GOCE) over a time interval of 3 years (2010-2012). To ensure fully consistent solutions, the zero-difference phase observations of the ground stations and LEOs were processed in a common least-squares adjustment, estimating all the relevant parameters such as GPS and LEO orbits, station coordinates, Earth rotation parameters and geocenter motion. We present the significant impact of the individual LEO and a combination of all four LEOs on the geocenter coordinates. The formal errors are reduced by around 20% due to the inclusion of one LEO into the ground-only solution, while in a solution with four LEOs LEO-specific characteristics are significantly reduced. We compare the derived geocenter coordinates w.r.t. LAGEOS results and external solutions based on GPS and SLR data. We found good agreement in the amplitudes of all components; however, the phases in x- and z-direction do not agree well.

  12. Loss of the SPHF homologue Slr1768 leads to a catastrophic failure in the maintenance of thylakoid membranes in Synechocystis sp. PCC 6803.

    Directory of Open Access Journals (Sweden)

    Samantha J Bryan

    Full Text Available BACKGROUND: In cyanobacteria the photosystems are localised to, and maintained in, specialist membranes called the thylakoids. The mechanism driving the biogenesis of the thylakoid membranes is still an open question, with only two potential biogenesis factors, Vipp1 and Alb3 currently identified. METHODOLOGY/PRINCIPAL FINDINGS: We generated a slr1768 knockout using the pGEM T-easy vector and REDIRECT. By comparing growth and pigment content (chlorophyll a fluoresence of the Δslr1768 mutant with the wild-type, we found that Δslr1768 has a conditional phenotype; specifically under high light conditions (130 µmol m(-2 s(-1 thylakoid biogenesis is disrupted leading to cell death on a scale of days. The thylakoids show considerable disruption, with loss of both structure and density, while chlorophyll a density decreases with the loss of thylakoids, although photosynthetic efficiency is unaffected. Under low light (30 µmol m(-2 s(-1 the phenotype is significantly reduced, with a growth rate similar to the wild-type and only a low frequency of cells with evident thylakoid disruption. CONCLUSIONS/SIGNIFICANCE: This is the first example of a gene that affects the maintenance of the thylakoid membranes specifically under high light, and which displays a phenotype dependent on light intensity. Our results demonstrate that Slr1768 has a leading role in acclimatisation, linking light damage with maintenance of the thylakoids.

  13. 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.

  14. 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...

  15. 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. ...

  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. 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.

  18. 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.

  19. 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

  20. 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...

  1. 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, ...

  2. 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.

  3. 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.

  4. GPS/INS Sensor Fusion Using GPS Wind up Model

    Science.gov (United States)

    Williamson, Walton R. (Inventor)

    2013-01-01

    A method of stabilizing an inertial navigation system (INS), includes the steps of: receiving data from an inertial navigation system; and receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites; calculating a phase wind up correction; correcting at least one of the finite number of carrier phase observables using the phase wind up correction; and calculating a corrected IMU attitude or velocity or position using the corrected at least one of the finite number of carrier phase observables; and performing a step selected from the steps consisting of recording, reporting, or providing the corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position. A GPS stabilized inertial navigation system apparatus is also described.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. Inversion of GPS meteorology data

    Directory of Open Access Journals (Sweden)

    K. Hocke

    Full Text Available The GPS meteorology (GPS/MET experiment, led by the Universities Corporation for Atmospheric Research (UCAR, consists of a GPS receiver aboard a low earth orbit (LEO satellite which was launched on 3 April 1995. During a radio occultation the LEO satellite rises or sets relative to one of the 24 GPS satellites at the Earth's horizon. Thereby the atmospheric layers are successively sounded by radio waves which propagate from the GPS satellite to the LEO satellite. From the observed phase path increases, which are due to refraction of the radio waves by the ionosphere and the neutral atmosphere, the atmospheric parameter refractivity, density, pressure and temperature are calculated with high accuracy and resolution (0.5–1.5 km. In the present study, practical aspects of the GPS/MET data analysis are discussed. The retrieval is based on the Abelian integral inversion of the atmospheric bending angle profile into the refractivity index profile. The problem of the upper boundary condition of the Abelian integral is described by examples. The statistical optimization approach which is applied to the data above 40 km and the use of topside bending angle profiles from model atmospheres stabilize the inversion. The retrieved temperature profiles are compared with corresponding profiles which have already been calculated by scientists of UCAR and Jet Propulsion Laboratory (JPL, using Abelian integral inversion too. The comparison shows that in some cases large differences occur (5 K and more. This is probably due to different treatment of the upper boundary condition, data runaways and noise. Several temperature profiles with wavelike structures at tropospheric and stratospheric heights are shown. While the periodic structures at upper stratospheric heights could be caused by residual errors of the ionospheric correction method, the periodic temperature fluctuations at heights below 30 km are most likely caused by atmospheric waves (vertically

  10. Location - Global Positioning System (GPS) Photos

    Data.gov (United States)

    Army Corps of Engineers, Department of the Army, Department of Defense — Digital photos tagged with GPS location information. The St. Paul District maintains a digital library of over 10,000 GPS photos. Photos are often associated with...

  11. GPS Attitude Determination for Launch Vehicles Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Toyon Research Corporation proposes to develop a family of compact, low-cost GPS-based attitude (GPS/A) sensors for launch vehicles. In order to obtain 3-D attitude...

  12. GPS operations at Olkiluoto in 2011

    Energy Technology Data Exchange (ETDEWEB)

    Koivula, H.; Kallio, U.; Nyberg, S.; Jokela, J.; Poutanen, M. [Finnish Geodetic Institute, Masala (Finland)

    2012-06-15

    The Finnish Geodetic Institute has studied crustal deformations at Olkiluoto, Kivetty and Romuvaara in co-operation with Posiva Oy since 1995. At Olkiluoto a total of 32 GPS campaigns have been carried out at inner network since 1995 and 17 campaigns at outer network since 2003. Kivetty and Romuvaara were not measured in 2011. In the Olkiluoto inner network 80 percent of the estimated change rates are smaller than 0.10 mm/a. One third of the change rates are statistically significant. They are mainly related to the Olkiluoto permanent station (GPS1) and to the pillars GPS6 and GPS13. The change rates related to GPS6 are not realistic due to the site-specific changes affecting the time series. The maximum change rate (-0.20 mm/a {+-} 0.05 mm/a) is related to GPS13. The time series of GPS13 is half the length of other pillars and therefore, the change rates are more uncertain. In the Olkiluoto outer network the maximum and statistically significant change rate is between GPS1-GPS11 (0.39 mm/a {+-} 0.06 mm/a). Pillar GPS12 was not observed this year. The change rates of baselines GPS1-GPS14 and GPS1-GPS15 are first time statistically significant. The change rates indicate a small movement of the GPS1 pillar. The baseline GPS1-GPS11 crosses an old fracture zone locating in the direction of the Eurajoensalmi, which might be a reason for the deformation. On the other hand, the Onkalo excavations in the vicinity of the Olkiluoto permanent station (GPS1) may cause some movement. Electronic distance measurements have been performed at Olkiluoto at the baseline GPS7-GPS8 using the Mekometer since 2002. The measurements have been carried out simultaneously with GPS campaigns. Based on 19 measurements in 10 years, the trends of the two time series seems to be similar. Due to unmodelled or dismodelled geometrical offsets and the scale difference between GPS measurements and EDM there is about 0.3 mm difference between distances GPS7-GPS8 derived from GPS measurements and EDM

  13. Cadmium triggers an integrated reprogramming of the metabolism of Synechocystis PCC6803, under the control of the Slr1738 regulator

    Directory of Open Access Journals (Sweden)

    Aude Jean-Christophe

    2007-10-01

    Full Text Available Abstract Background Cadmium is a persistent pollutant that threatens most biological organisms, including cyanobacteria that support a large part of the biosphere. Using a multifaceted approach, we have investigated the global responses to Cd and other relevant stresses (H2O2 and Fe in the model cyanobacterium Synechocystis PCC6803. Results We found that cells respond to the Cd stress in a two main temporal phases process. In the "early" phase cells mainly limit Cd entry through the negative and positive regulation of numerous genes operating in metal uptake and export, respectively. As time proceeds, the number of responsive genes increases. In this "massive" phase, Cd downregulates most genes operating in (i photosynthesis (PS that normally provides ATP and NADPH; (ii assimilation of carbon, nitrogen and sulfur that requires ATP and NAD(PH; and (iii translation machinery, a major consumer of ATP and nutrients. Simultaneously, many genes are upregulated, such as those involved in Fe acquisition, stress tolerance, and protein degradation (crucial to nutrients recycling. The most striking common effect of Cd and H2O2 is the disturbance of both light tolerance and Fe homeostasis, which appeared to be interdependent. Our results indicate that cells challenged with H2O2 or Cd use different strategies for the same purpose of supplying Fe atoms to Fe-requiring metalloenzymes and the SUF machinery, which synthesizes or repairs Fe-S centers. Cd-stressed cells preferentially breakdown their Fe-rich PS machinery, whereas H2O2-challenged cells preferentially accelerate the intake of Fe atoms from the medium. Conclusion We view the responses to Cd as an integrated "Yin Yang" reprogramming of the whole metabolism, we found to be controlled by the Slr1738 regulator. As the Yin process, the ATP- and nutrients-sparing downregulation of anabolism limits the poisoning incorporation of Cd into metalloenzymes. As the compensatory Yang process, the PS breakdown

  14. The Present and Future of an SLR System Built Under the Cooperation between China and Argentina%用于中阿合作的卫星激光测距(SLR)系统的现状和未来

    Institute of Scientific and Technical Information of China (English)

    刘卫东; A.A.Gonzalez; 韩延本; R.Podesta; 王谭强; E.Actis; E.Alonso; 赵励民; 刘承志; A.M.Pacheco

    2009-01-01

    简要介绍了用于中国科学院国家天文台与阿根廷San Juan大学合作观测与研究的一个高精度卫星激光测距(SLR)系统.该望远镜口径为60cm的SLR系统由中国研制,于2005年秋被运往阿根廷,安装在阿根廷国立San Juan大学天文台,San Juan大学建立了观测室.准备了工作条件.该系统于2006年2月底完成调试并开始运行.在过去的两年阃,该系统保持了良好的工作状态,由于San Juan具有良好的天气条件,该系统取得了丰富的高精度观测资料.国际激光测距服务认为该仪器的工作对国际激光测距系统是重要的,希望对其增加白天测距的功能.文章也简单介绍了该SLR站未来升级改造和发展的计划.

  15. Diagnosing dementia with confidence by GPs.

    NARCIS (Netherlands)

    Hout, H.P.J. van; Vernooij-Dassen, M.J.F.J.; Stalman, W.A.B.

    2007-01-01

    BACKGROUND: Earlier reports suggest limited clinical reasoning and substantial uncertainty of GPs in assessing patients suspected of dementia. OBJECTIVE: To explore the predictors of GPs to decide on the presence and absence of dementia as well as the predictors of diagnostic confidence of GPs.

  16. The SMS-GPS-Trip-Method

    DEFF Research Database (Denmark)

    Reinau, Kristian Hegner; Harder, Henrik; Weber, Michael

    2015-01-01

    This article presents a new method for collecting travel behavior data, based on a combination of GPS tracking and SMS technology, coined the SMS–GPS-Trip method. The state-of-the-art method for collecting data for activity based traffic models is a combination of travel diaries and GPS tracking...

  17. Diagnosing dementia with confidence by GPs.

    NARCIS (Netherlands)

    Hout, H.P.J. van; Vernooij-Dassen, M.J.F.J.; Stalman, W.A.B.

    2007-01-01

    BACKGROUND: Earlier reports suggest limited clinical reasoning and substantial uncertainty of GPs in assessing patients suspected of dementia. OBJECTIVE: To explore the predictors of GPs to decide on the presence and absence of dementia as well as the predictors of diagnostic confidence of GPs. DESI

  18. INS/GPS Integration Architectures

    Science.gov (United States)

    2010-03-01

    to maintain the mean code tracking error close to zero. RF FILTER I/Q DEMOD SAMPLING CORRELATION AND INTEGRATION SQUARE LAW DETECTION kth...Q(t) INERTIAL SENSORS OTHER SENSORS CORRELATOR BANK (n) x ′ˆ Figure 2.9: Code tracking information flow diagram for GPS-based navigator. The

  19. Recent GPS Results at SLAC

    Energy Technology Data Exchange (ETDEWEB)

    Behrend, Dirk; Imfeld, Hans L.; /SLAC

    2005-08-17

    The Alignment Engineering Group (AEG) makes use of GPS technology for fulfilling part of its above ground surveying tasks at SLAC since early 2002. A base station (SLAC M40) has been set up at a central location of the SLAC campus serving both as master station for real-time kinematic (RTK) operations and as datum point for local GPS campaigns. The Leica RS500 system is running continuously and the GPS data are collected both externally (logging PC) and internally (receiver flashcard). The external logging is facilitated by a serial to Ethernet converter and an Ethernet connection at the station. Internal logging (ring buffer) is done for data security purposes. The weatherproof boxes for the instrumentation are excellent shelters against rain and wind, but do heat up considerably in sun light. Whereas the GPS receiver showed no problems, the Pacific Crest PDL 35 radio shut down several times due to overheating disrupting the RTK operations. In order to prevent heat-induced shutdowns, a protection against direct sun exposure (shading) and a constant air circulation system (ventilation) were installed. As no further shutdowns have occurred so far, it appears that the two measures successfully mended the heat problem.

  20. Contents of GPS Data Files

    Energy Technology Data Exchange (ETDEWEB)

    Sullivan, John P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Carver, Matthew Robert [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Norman, Benjamin [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-12-09

    There are no very detailed descriptions of most of these instruments in the literature – we will attempt to fix that problem in the future. The BDD instruments are described in [1]. One of the dosimeter instruments on CXD boxes is described in [2]. These documents (or web links to them) and a few others are in this directory tree. The cross calibration of the CXD electron data with RBSP is described in [3]. Each row in the data file contains the data from one time bin from a CXD or BDD instrument along with a variety of parameters derived from the data. Time steps are commandable but 4 minutes is a typical setting. These instruments are on many (but not all) GPS satellites which are currently in operation. The data come from either BDD instruments on GPS Block IIR satellites (SVN41 and 48), or else CXD-IIR instruments on GPS Block IIR and IIR-M satellites (SVN53-61) or CXD-IIF instruments on GPS block IIF satellites (SVN62-73). The CXD-IIR instruments on block IIR and IIR(M) satellites use the same design.

  1. Optimal Preprocessing Of GPS Data

    Science.gov (United States)

    Wu, Sien-Chong; Melbourne, William G.

    1994-01-01

    Improved technique for preprocessing data from Global Positioning System receiver reduces processing time and number of data to be stored. Optimal in sense that it maintains strength of data. Also increases ability to resolve ambiguities in numbers of cycles of received GPS carrier signals.

  2. Animal Tracking ARGOS vs GPS

    Science.gov (United States)

    Robinson, P. W.; Costa, D.; Arnould, J.; Weise, M.; Kuhn, C.; Simmons, S. E.; Villegas, S.; Tremblay, Y.

    2006-12-01

    ARGOS satellite tracking technology has enabled a tremendous increase in our understanding of the movement patterns of a diverse array of marine vertebrates from Sharks to marine mammals. Our current understanding has moved from simple descriptions of large scale migratory patterns to much more sophisticated comparisons of animal movements and behavior relative to oceanic features. Further, animals are increasingly used to carry sensors that can acquire water column temperature and salinity profiles. However, a major limitation of this work is the spatial precision of ARGOS locations. ARGOS provides 7 location qualities that range from 3,2,1,0,A,B,Z and correspond to locations with a precision of 150m to tens of kilometers. Until recently, GPS technology could not be effectively used with marine mammals because they did not spend sufficient time at the surface to allow complete acquisition of satellite information. The recent development of Fastloc technology has allowed the development of GPS tags that can be deployed on marine mammals. Here we compare the location quality and frequency derived from standard ARGOS PTTs to Fastloc GPS locations acquired from 11 northern elephant seals, 5 California and 5 Galapagos sea lions and 1 Cape and 3 Australian fur seals. Our results indicate that GPS technology will greatly enhance our ability to understand the movement patterns of marine vertebrates and the in-situ oceanographic data they collect.

  3. 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

  4. Integrated navigation of aerial robot for GPS and GPS-denied environment

    Science.gov (United States)

    Suzuki, Satoshi; Min, Hongkyu; Wada, Tetsuya; Nonami, Kenzo

    2016-09-01

    In this study, novel robust navigation system for aerial robot in GPS and GPS- denied environments is proposed. Generally, the aerial robot uses position and velocity information from Global Positioning System (GPS) for guidance and control. However, GPS could not be used in several environments, for example, GPS has huge error near buildings and trees, indoor, and so on. In such GPS-denied environment, Laser Detection and Ranging (LIDER) sensor based navigation system have generally been used. However, LIDER sensor also has an weakness, and it could not be used in the open outdoor environment where GPS could be used. Therefore, it is desired to develop the integrated navigation system which is seamlessly applied to GPS and GPS-denied environments. In this paper, the integrated navigation system for aerial robot using GPS and LIDER is developed. The navigation system is designed based on Extended Kalman Filter, and the effectiveness of the developed system is verified by numerical simulation and experiment.

  5. Goddard Geophysical and Astronomical Observatory

    Science.gov (United States)

    Figueroa, Ricardo

    2013-01-01

    This report summarizes the technical parameters and the technical staff of the VLBI system at the fundamental station GGAO. It also gives an overview about the VLBI activities during the report year. The Goddard Geophysical and Astronomical Observatory (GGAO) consists of a 5-meter radio telescope for VLBI, a new 12-meter radio telescope for VLBI2010 development, a 1-meter reference antenna for microwave holography development, an SLR site that includes MOBLAS-7, the NGSLR development system, and a 48" telescope for developmental two-color Satellite Laser Ranging, a GPS timing and development lab, a DORIS system, meteorological sensors, and a hydrogen maser. In addition, we are a fiducial IGS site with several IGS/IGSX receivers. GGAO is located on the east coast of the United States in Maryland. It is approximately 15 miles NNE of Washington, D.C. in Greenbelt, Maryland.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  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. 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.

  14. 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...

  15. 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

  16. 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.

  17. 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.

  18. 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).

  19. 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.

  20. Integrated Kinematic Analysis of GPS and Fault Slip Data in the Eastern California Shear Zone, Walker Lane and Sierra Nevada

    Science.gov (United States)

    Hammond, W. C.; Thatcher, W.

    2001-12-01

    The Sierra Nevada (SN) microplate moves roughly N50?W with respect to North America (NA), around an Euler pole that lies in the Pacific (PA) basin to the west and south. Its motion is indicative of processes governing the deformation of the Walker Lane and Eastern California Shear Zone, accommodating east to west expansion of the Basin and Range and approximately 25% of PA/NA dextral shear. To date, estimates for the location of the SN/NA pole obtained by GPS, VLBI and geologic data differ by at least 30 degrees [e.g. Argus and Gordon, 1996; Hearn and Humphreys, 1998]. The difference between these poles may, in part, be attributable to the type of data used in the analyses. The GPS determined velocity field potentially contains artifacts of the earthquake cycle such as recoverable elastic deformation preceded by slip at depth, fault creep, and viscoelastic relaxation following earthquakes on block bounding faults. We use Global Positioning System (GPS), fault strike and slip rate data to constrain the kinematics of the eastern boundary of the Sierra Nevada (SN) microplate, and western Basin and Range province of western North America. Data include previously published GPS measurements [Bennet et al., 1998; Thatcher et al., 1999; Gan et al., 2000; Svarc et al., submitted manuscript 2001], recently collected GPS data, and recently compiled fault maps of Nevada and California that include fault strike, slip sense and slip rate estimates. GPS velocities are refined with the Quasi Observation Combination Analysis algorithm of Dong et al. From these data we constrain the spatial variation in the rate and style of deformation throughout the region, and identify components of the deformation that are relevant to interaction of the PA/NA transform margin and Basin and Range extension. Using two-dimensional viscoelastic finite elements we derive kinematic models representative of the instantaneous (GPS) time scale, in preparation for future modeling of the longer term

  1. 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 ...

  2. 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).

  3. 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.

  4. 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 ...

  5. 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...

  6. 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.

  7. 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...

  8. 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...

  9. 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...

  10. 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).

  11. 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 ...

  12. 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*.

  13. 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!

  14. 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.

  15. 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.

  16. 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.

  17. 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...

  18. 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!

  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. INDOOR LOCALIZATION SOLUTION FOR GPS

    OpenAIRE

    Shreyanka B. Chougule; Dr.Sayed Abdulhayan

    2017-01-01

    GPS technology is used for positioning application and it is highly reliable and accurate when used outdoor. Due to multipath propagation, signal attenuation and blockage its performance is limited in indoor and dense urban environment. As a solution, technologies like Apple’s iBeacon, Radio-frequency identification (RFID), Ultrasonic and Wireless Fidelity (Wi-Fi) access points are used to improve performance in Indoor environment. We are having a look at all these technologies which are mean...

  1. Ionospheric Scintillation Effects on GPS

    Science.gov (United States)

    Steenburgh, R. A.; Smithtro, C.; Groves, K.

    2007-12-01

    . Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

  2. GPS-Aided Video Tracking

    Directory of Open Access Journals (Sweden)

    Udo Feuerhake

    2015-08-01

    Full Text Available Tracking moving objects is both challenging and important for a large variety of applications. Different technologies based on the global positioning system (GPS and video or radio data are used to obtain the trajectories of the observed objects. However, in some use cases, they fail to provide sufficiently accurate, complete and correct data at the same time. In this work we present an approach for fusing GPS- and video-based tracking in order to exploit their individual advantages. In this way we aim to combine the reliability of GPS tracking with the high geometric accuracy of camera detection. For the fusion of the movement data provided by the different devices we use a hidden Markov model (HMM formulation and the Viterbi algorithm to extract the most probable trajectories. In three experiments, we show that our approach is able to deal with challenging situations like occlusions or objects which are temporarily outside the monitored area. The results show the desired increase in terms of accuracy, completeness and correctness.

  3. 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

  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. 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

  6. 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

  7. Applications of GPS technologies to field sports.

    Science.gov (United States)

    Aughey, Robert J

    2011-09-01

    Global positioning system (GPS) technology was made possible after the invention of the atomic clock. The first suggestion that GPS could be used to assess the physical activity of humans followed some 40 y later. There was a rapid uptake of GPS technology, with the literature concentrating on validation studies and the measurement of steady-state movement. The first attempts were made to validate GPS for field sport applications in 2006. While GPS has been validated for applications for team sports, some doubts continue to exist on the appropriateness of GPS for measuring short high-velocity movements. Thus, GPS has been applied extensively in Australian football, cricket, hockey, rugby union and league, and soccer. There is extensive information on the activity profile of athletes from field sports in the literature stemming from GPS, and this includes total distance covered by players and distance in velocity bands. Global positioning systems have also been applied to detect fatigue in matches, identify periods of most intense play, different activity profiles by position, competition level, and sport. More recent research has integrated GPS data with the physical capacity or fitness test score of athletes, game-specific tasks, or tactical or strategic information. The future of GPS analysis will involve further miniaturization of devices, longer battery life, and integration of other inertial sensor data to more effectively quantify the effort of athletes.

  8. Confirmation of gravitationally induced attitude drift of spinning satellite Ajisai with Graz high repetition rate SLR data

    Science.gov (United States)

    Kucharski, Daniel; Kirchner, Georg; Otsubo, Toshimichi; Lim, Hyung-Chul; Bennett, James; Koidl, Franz; Kim, Young-Rok; Hwang, Joo-Yeon

    2016-02-01

    The high repetition rate Satellite Laser Ranging system Graz delivers the millimeter precision range measurements to the corner cube reflector panels of Ajisai. The analysis of 4599 passes measured from October 2003 until November 2014 reveals the secular precession and nutation of Ajisai spin axis due to the gravitational forces as predicted by Kubo (1987) with the periods of 35.6 years and 116.5 days respectively. The observed precession cone is oriented at RA = 88.9°, Dec = -88.85° (J2000) and has a radius of 1.08°. The radius of the nutation cone increases from 1.32° to 1.57° over the 11 years of the measurements. We also detect a draconitic wobbling of Ajisai orientation due to the 'motion' of the Sun about the satellite's orbit. The observed spin period of Ajisai increases exponentially over the investigated time span according to the trend function: T = 1.492277·exp(0.0148388·Y) [s], where Y is in years since launch (1986.6133), RMS = 0.412 ms. The physical simulation model fitted to the observed spin parameters proves a very low interaction between Ajisai and the Earth's magnetic field, what assures that the satellite's angular momentum vector will remain in the vicinity of the south celestial pole for the coming decades. The developed empirical model of the spin axis orientation can improve the accuracy of the range determination between the ground SLR systems and the satellite's center-of-mass (Kucharski et al., 2015) and enable the accurate attitude prediction of Ajisai for the laser time-transfer experiments (Kunimori et al., 1992).

  9. Precise Orbit Solution for Swarm Using Space-Borne GPS Data and Optimized Pseudo-Stochastic Pulses

    Directory of Open Access Journals (Sweden)

    Bingbing Zhang

    2017-03-01

    Full Text Available Swarm is a European Space Agency (ESA project that was launched on 22 November 2013, which consists of three Swarm satellites. Swarm precise orbits are essential to the success of the above project. This study investigates how well Swarm zero-differenced (ZD reduced-dynamic orbit solutions can be determined using space-borne GPS data and optimized pseudo-stochastic pulses under high ionospheric activity. We choose Swarm space-borne GPS data from 1–25 October 2014, and Swarm reduced-dynamic orbits are obtained. Orbit quality is assessed by GPS phase observation residuals and compared with Precise Science Orbits (PSOs released by ESA. Results show that pseudo-stochastic pulses with a time interval of 6 min and a priori standard deviation (STD of 10−2 mm/s in radial (R, along-track (T and cross-track (N directions are optimized to Swarm ZD reduced-dynamic precise orbit determination (POD. During high ionospheric activity, the mean Root Mean Square (RMS of Swarm GPS phase residuals is at 9–11 mm, Swarm orbit solutions are also compared with Swarm PSOs released by ESA and the accuracy of Swarm orbits can reach 2–4 cm in R, T and N directions. Independent Satellite Laser Ranging (SLR validation indicates that Swarm reduced-dynamic orbits have an accuracy of 2–4 cm. Swarm-B orbit quality is better than those of Swarm-A and Swarm-C. The Swarm orbits can be applied to the geomagnetic, geoelectric and gravity field recovery.

  10. GPS in Travel and Activity Surveys

    DEFF Research Database (Denmark)

    Nielsen, Thomas Alexander Sick; Hovgesen, Henrik Harder

    2004-01-01

    The use of GPS-positioning as a monitoring tool in travel and activity surveys opens up a range of possibilities. Using a personal GPS device, the locations and movements of respondents can be followed over a longer period of time. It will then be possible to analyse how the use of urban spaces...... are embedded in the wider context of activity patterns (work, school etc.). The general pattern of everyday itineraries, including route choice and time spent at different locations ?on the way? can also be analysed. If the personal GPS device is combined with an electronic questionnaire, for example...... area. The paper presents the possibilities in travel and activity surveys with GPS and electronic questionnaires. Demonstrative mapping of test data from passive GPS registration of Copenhagen respondents is presented. The different survey possibilities given a combination of GPS and PDA based...

  11. 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...

  12. 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.

  13. Part 4: GPS Telemetry Detection Rates (GPS Test Collar Sites), GCS NAD 83 (2015)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Bias correction in GPS telemetry data-sets requires a strong understanding of the mechanisms that result in missing data. We tested wildlife GPS collars in a variety...

  14. Part 2: GPS Telemetry Detection Rates (Northern Arizona GPS Test Collar Data), GCS NAD 83 (2015)

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — Bias correction in GPS telemetry data-sets requires a strong understanding of the mechanisms that result in missing data. We tested wildlife GPS collars in a variety...

  15. Miniaturized GPS/MEMS IMU integrated board

    Science.gov (United States)

    Lin, Ching-Fang (Inventor)

    2012-01-01

    This invention documents the efforts on the research and development of a miniaturized GPS/MEMS IMU integrated navigation system. A miniaturized GPS/MEMS IMU integrated navigation system is presented; Laser Dynamic Range Imager (LDRI) based alignment algorithm for space applications is discussed. Two navigation cameras are also included to measure the range and range rate which can be integrated into the GPS/MEMS IMU system to enhance the navigation solution.

  16. The estimation method of GPS instrumental biases

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A model of estimating the global positioning system (GPS) instrumental biases and the methods to calculate the relative instrumental biases of satellite and receiver are presented. The calculated results of GPS instrumental biases, the relative instrumental biases of satellite and receiver, and total electron content (TEC) are also shown. Finally, the stability of GPS instrumental biases as well as that of satellite and receiver instrumental biases are evaluated, indicating that they are very stable during a period of two months and a half.

  17. Determination of Vessel Attitudes Using GPS

    Institute of Scientific and Technical Information of China (English)

    王书寅; 周丰年; 金建霞; 吴敬文

    2002-01-01

    With the development of GPS carrier wave phase technology, it becomes possible that the height accuracy of centimeter level is got by GPS RTK technology. Vessel attitudes are very important parameters in marine survey. In this paper, they were determined by 4 GPS receivers. At the same time, the arithmetic and procedure of vessel attitude determining were given. Based on an experiment, some useful conclusions were obtained and the corresponding methods were put forward to improve the accuracy.

  18. The GPS Laser Retroreflector Array Project

    Science.gov (United States)

    Merkowitz, Stephen M.

    2012-01-01

    Systematic co-location in space through the precision orbit determination of GPS satellites via satellite laser ranging will contribute significantly towards improving the accuracy and stability of the international terrestrial reference frame. NASA recently formed the GPS Laser Retroreflector Array Project to develop and deliver retroreflectors for integration on the next generation of GPS satellites. These retroreflectors will be an important contributor to achieving a global accuracy of 1.0 mm and 0.1 mm/year stability in the international terrestrial reference frame. We report here the current status of the GPS Laser Retroreflector Array Project.

  19. GPS operations at Olkiluoto in 2009

    Energy Technology Data Exchange (ETDEWEB)

    Kallio, U.; Nyberg, S.; Koivula, H.; Jokela, J.; Poutanen, M.; Ahola, J. (Finnish Geodetic Institute, Masala (Finland))

    2010-06-15

    The GPS based deformation studies have been made at the investigation areas of Posiva since 1995, when the network of ten GPS pillars was established at Olkiluoto. One pillar in the investigation area belongs to the Finnish permanent GPS network, FinnRef. 28 GPS measurement campaigns have been carried out at Olkiluoto since 1995. According to the time series of the GPS results 1/3 of the baselines at Olkiluoto have statistically significant change rates. However, the observed movements are smaller than +-0.20 mm/a. There are five pillars, which have statistically significant horizontal velocities at Olkiluoto. These local velocity components are small but taking into account the standard deviations the largest velocity components seems to be reliably determined. At Olkiluoto a baseline for electronic distance measurements (EDM) was built in 2002. The baseline has been measured using EDM instruments in connection to the GPS observations. Changes in he difference between the GPS and EDM results indicate the systematic change in GPS results. No corrections based on only one baseline were not applied to GPS vectors. The GPS network at Olkiluoto was extended in 2003. The new pillars were built close to Kuivalahti village and on a small island of Iso Pyrekari. According to the geological evidence it is expected that a fracture zone is located between the new stations, thus enabling the determination of possible deformations along the fracture zone. The new pillars have been observed since 2003 and now we have computed the first deformation analysis from the six years data. Four new permanent stations will be established in summer 2010 at Olkiluoto. We have automated the processing of the campaign data by using the Bernese processing engine (BPE) together with our own Perl scripts. The local crustal deformations have been studied in GeoSatakunta project, too. This GPS network is located in Cities of Pori and Rauma and their neighbouring municipalities. Two new pillars

  20. Evaluating GPS Data in Indoor Environments

    Directory of Open Access Journals (Sweden)

    MOTTE, H.

    2011-08-01

    Full Text Available With the latest generation of ultra-sensitive GPS-receivers, satellite signals can often be picked up even indoors, resulting in (inaccurate indoor GPS-localization. A covered position will therefore no longer be characterized by the absence of satellite signals, creating the need for another way of categorizing this data as potentially inaccurate. This paper describes the use of GPS-based localization in an indoor environment. Only high level, generally available, GPS-data (NMEA-0183 GNSS-subset are taken into account. Applications of ubiquitous location awareness, where the use of several RTLS (Real Time Location System combinations is feasible, may benefit from this information to discriminate between GPS and other available localization data. A quality indicating parameter is readily available in GPS-data; the DOP (Dilution Of Precision data field, which indicates the accuracy of the GPS localization based on the current satellite geometry. However since in indoor environments the roof and possible overlying floors often cause more signal attenuation compared to (outer walls or windows, the probability of a better reception of 'low' orbiting satellite signals increases, giving rise to an unjustified good horizontal DOP value. Standard NMEA-0183 GPS strings are therefore analyzed in search of other indicators for malicious GPS-data.

  1. GOCE gradiometer validation by GPS

    Science.gov (United States)

    Visser, P. N. A. M.

    The upcoming European Space Agency (ESA) Gravity Field and Steady-State Ocean Circular Explorer (GOCE) mission, foreseen to be launched in 2007 (status: July 2006) will carry a highly sensitive gradiometer, consisting of three orthogonal pairs of ultra-sensitive accelerometers. A challenging calibration procedure has been developed to calibrate the gradiometer not only pre-launch by a series of on-ground tests, but also after launch by making use of on-board cold-gas thrusters to provoke a long series of gradiometer shaking events which will provide observations for its calibration. In addition, a number of quick-look post-launch methods has been designed and will be implemented that aim at validating the calibration of the gradiometer instrument and at the same time support the operations of the satellite. These methods are based on (1) comparison with the best available global gravity field models, (2) upward continuation of high-precision ground-based gravity field data over certain geographical areas, and (3) use of GPS Satellite-to-Satellite Tracking (SST) observations. The focus of this paper is on the third method. An assessment has been made of how well the gradiometer observations can be validated by a combination with GPS tracking observations of GOCE. It was found by a detailed simulation study that the most important parameters, the scale factors of the diagonal gravity gradient components, can be determined with an accuracy better than 0.004, provided a nominal behavior of the gradiometer and GPS instruments.

  2. Chip Advancer For GPS Receiver

    Science.gov (United States)

    Meehan, Thomas K.; Srinivasan, Jeffrey M.; Thomas, J. Brooks

    1989-01-01

    Instrument errors made negligible. For each integration interval, both delay and rate of change of delay initialized to small fraction of chip - for example, to order of 10 to the negative 7th power - thereby making feedback control and extraction of delay highly accurate and flexible. With appropriate selection of sampling rate relative to chip rate, commensurability errors reduced to extremely small levels. In Global Positioning System (GPS) receiver, pseudorandom code sequence generated by simple digital logic incorporating effects of time, delay, and rate of change of delay. Flexibility in starting time and sum interval very useful in aligning correlation interval with beginnings and endings of data bits.

  3. 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.

  4. 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.

  5. The Southeastern Sicily GPS network

    Directory of Open Access Journals (Sweden)

    F. Broccio

    1995-06-01

    Full Text Available The area located between Catania and Syracuse (Southeastern Sicily, characterised by the presence of the Simeto-Scordia-Lentini graben, was affected in the past by a strong seismicity as proved by the occurrence of seismic events strong enough to reach the XI degree of the MCS scale. In particular the January 11 th, 1693 (l = XI MCS earthquake with a magnitude over 7.5 (estimated, caused huge damage and a great loss of human lives. Following the last seismic event which occurred on December 13th, 1990 (Ml = 5.4 which caused heavy damage and many victims in the Catania-Syracuse area, a geodetic Global Positioning System network (GPS was set up with the aim of monitoring ground movements in one of the Italian areas subjected to high seismic risk, This "pace geodesy technique supplies high precision measurements and represent, a powerful new tool for investigating both regional stress fields and the evolution of local tectonic areas. The GPS network will allow the detection of ground movements with a centimetric accuracy through repeated surveys in time. The results obtained in two surveys carried out il1 1991 al1d 1993, are described in this paper.

  6. Application of real-time GPS to earthquake early warning

    National Research Council Canada - National Science Library

    Richard M. Allen; Alon Ziv

    2011-01-01

      Real-time GPS can provide static-offset observations during an earthquake Real-time GPS provides a robust constrain on magnitude for warnings GPS networks should be used as a companion to seismic...

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. 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 ...

  15. GPS queues with heterogeneous traffic classes

    NARCIS (Netherlands)

    Borst, Sem; Mandjes, Michel; Uitert, van Miranda

    2002-01-01

    We consider a queue fed by a mixture of light-tailed and heavy-tailed traffic. The two traffic classes are served in accordance with the generalized processor sharing (GPS) discipline. GPS-based scheduling algorithms, such as weighted fair queueing (WFQ), have emerged as an important mechanism for a

  16. Effect of GPS errors on Emission model

    DEFF Research Database (Denmark)

    Lehmann, Anders; Gross, Allan

    n this paper we will show how Global Positioning Services (GPS) data obtained from smartphones can be used to model air quality in urban settings. The paper examines the uncertainty of smartphone location utilising GPS, and ties this location uncertainty to air quality models. The results presented...

  17. Stigma and GPs' perceptions of dementia

    NARCIS (Netherlands)

    Gove, D.; Downs, M.; Vernooij-Dassen, M.; Small, N.

    2016-01-01

    OBJECTIVES: General practitioners (GPs) are crucial to improving timely diagnosis, but little is reported about how they perceive dementia, and whether their perceptions display any elements of stigma. The aim of this study was to explore how GPs' perceptions of dementia map onto current

  18. Factors predicting trust between GPs and OPs

    NARCIS (Netherlands)

    A.P. Nauta; J. von Grumbkow (Jasper)

    2001-01-01

    textabstractPURPOSE: To study possible differences in trust between general practitioners (GPs) and occupational physicians (OPs) and the explanatory factors for trust. Insight into the factors predicting trust can improve programmes for stimulating the co-operation of GPs and OPs.

  19. An assisted GPS support for GPS simulators for embedded mobile positioning

    Science.gov (United States)

    Kashyap, Pradeep; Samant, Abhay; Sagiraju, Phani K.; Akopian, David

    2009-02-01

    During recent years, location technologies have emerged as a research area with many possible applications in wireless communications, surveillance, military equipment, etc. Location Based Services (LBS) such as safety applications have become very popular. For example, US Federal Communication Commission Enhanced 911 (E911) Mandate seeks to provide emergency services personnel with location information that will enable them to dispatch assistance to wireless 911 callers much more quickly. Assisted GPS (A-GPS) is an extension of the conventional Global Positioning System (GPS) which increases start-up sensitivity by as much as 25dB relative to conventional GPS and reduces start times to less than six seconds. In A-GPS assistance data is delivered to the receiver through communication links. This paper addresses the generation of the assistance for GPS simulators for testing A-GPS receivers. The proposed approach is to use IP-based links and location support standards for assistance delivery avoiding network-specific signaling mechanisms so that GPS receiver developers can use this information for testing A-GPS capabilities using basic GPS simulators. The approach is implemented for the GPS simulator developed by the National InstrumentsTM.

  20. Using GPS for studying pastoral mobility

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine

    2017-01-01

    geographer familiar with satellite remote sensing and GIS, I pondered how these relatively new technologies could be combined with classic ethnographic fieldwork, which we also use in human geography. I decided to use handheld GPS devices for tracking the pastoralists and their herds. My study was, as far...... as I know, the first one to use GPS for studying pastoral mobility. A total of 10 pastoralists were trained in using a GPS and asked to map their movements. This information was combined with satellite imagery on one hand and qualitative interviews on the other. This case study provides an account...... of the practical aspects of using GPS, taking the reader to the heart of some methodological issues that arose in the course of the research. The case sheds light on the particular challenges in using GPS for eliciting information about pastoral mobility. Thinking about such challenges leads to more general...

  1. 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

    A digital base band converter (DBBC) system has been developed by the Istituto di Radioastronomia (Noto, Italy) for increasing the sensitivity of European VLBI Network (EVN) by expanding the full observed bandwidth using numerical methods. The output data rate of this VLBI-backend is raised from 1 to 4 Gbps for each radiotelescope. All operations related to the signal processing (frequency translation, amplification, frequency generation with local oscillators, etc.) are transferred to the digital domain, which allows - in addition to well-known advantages coming from digital technologies - achieving better repeatability, precision, simplicity, etc. The maximum input band of DBBC system is 3.5 GHz, and the instantaneous bandwidth is up to 1 GHz for each radio frequency/intermediate frequency (RF/IF) out of the eight possible. This backend is a highly powerful platform for other radioastronomy applications, and a number of additional so-called personalities have been developed and used. This includes PFB (polyphase filter bank) receivers and Spectra for high resolution spectroscopy. An additional new development with the same aim - to use the DBBC system as a multi-purpose backend - is related to the bi-static radar observations including Radar VLBI. In such observations it is possible to study the population of space debris, with detection of even centimetre class fragments. A powerful transmitter is used to illuminate the sky region to be analyzed, and the echoes coming from known or unknown objects are reflected to one or more groundbased telescopes thus producing a single-dish or interferometric detection. The DBBC Radar VLBI personality is able to realize a high-resolution spectrum analysis, maintaining in the central area the echo signal at the expected frequency including the Doppler shift of frequency. For extremely weak signals a very large integration time is needed, so for this personality different input parameters are provided. The realtime information

  2. Surveying co-located space geodesy techniques for ITRF computation

    Science.gov (United States)

    Sarti, P.; Sillard, P.; Vittuari, L.

    2003-04-01

    We present a comprehensive operational methodology, based on classical geodesy triangulation and trilateration, that allows the determination of reference points of the five space geodesy techniques used in ITRF computation (i.e.: DORIS, GPS, LLR, SLR, VLBI). Most of the times, for a single technique, the reference point is not accessible and measurable directly. Likewise, no mechanically determined ex-center with respect to an external and measurable point is usually given. In these cases, it is not possible to directly measure the sought reference points and it is even less straightforward to obtain the statistical information relating these points for different techniques. We outline the most general practical surveying methodology that permits to recover the reference points of the different techniques regardless of their physical materialization. We also give a detailed analytical approach for less straightforward cases (e.g.: non geodetic VLBI antennae and SLR/LLR systems). We stress the importance of surveying instrumentation and procedure in achieving the best possible results and outline the impact of the information retrieved with our method in ITRF computation. In particular, we will give numerical examples of computation of the reference point of VLBI antennae (Ny Aalesund and Medicina) and the ex-centre vector computation linking co-located VLBI and GPS techniques in Medicina (Italy). A special attention was paid to the rigorous derivation of statistical elements. They will be presented in an other presentation.

  3. Tropospheric Parameters and Subdaily EOP From Combinations of Independent Space Geodetic Data

    Science.gov (United States)

    Thaller, D.; Krügel, M.; Rothacher, M.; Angermann, D.; Schmid, R.; Tesmer, V.

    2004-12-01

    The space geodetic techniques GPS, VLBI, SLR and DORIS contribute to the determination of several geodetic parameters (e.g. site positions, Earth orientation parameters (EOP), tropospheric parameters) providing valuable information to study various geophysical processes. Due to the different strengths of the techniques it can be expected that the parameters benefit from a combination. The VLBI campaign CONT02, initiated by the IVS, provides 15~days of continuous VLBI measurements. Therefore, this data set is well-suited for the combination with other techniques. Especially the combination with other microwave techniques like GPS provides the opportunity to estimate common tropospheric parameters in addition to station coordinates and EOP. For the studies presented here, free daily normal equations were generated for GPS and VLBI using identical models and the same parameterization to avoid any inconsistencies. Additionally, the normal equation of a 14-day SLR solution is included to investigate primarily reference frame related aspects. The work focusses on the combination of tropospheric parameters and EOP with a high resolution in time: solutions with one and two hour resolution of the parameters were compared to decide whether a higher time resolution is more appropriate to describe the time-dependent behavior of these parameters. For the validation of the tropospheric parameters independent data sets of water vapor radiometers are used, and the EOP are compared with a subdaily model derived from altimetry. Special attention has to be addressed to the tropospheric parameters from GPS, because they are sensitive to the physical characteristics of the antenna and the antenna environment. The comparison with VLBI-derived tropospheric parameters shows that absolute antenna phase center corrections should be used instead of relative models. Similarly, if a radome is installed at the antenna, the tropospheric zenith delay estimates change significantly. As no phase

  4. 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

  5. GPS Precision Timing at CERN

    CERN Document Server

    Beetham, C G

    1999-01-01

    For the past decade, the Global Positioning System (GPS) has been used to provide precise time, frequency and position co-ordinates world-wide. Recently, equipment has become available specialising in providing extremely accurate timing information, referenced to Universal Time Co-ordinates (UTC). This feature has been used at CERN to provide time of day information for systems that have been installed in the Proton Synchrotron (PS), Super Proton Synchrotron (SPS) and the Large Electron Positron (LEP) machines. The different systems are described as well as the planned developments, particularly with respect to optical transmission and the Inter-Range Instrumentation Group IRIG-B standard, for future use in the Large Hadron Collider (LHC).

  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. 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.

  8. 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.

  9. 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.

  10. 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...

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. GPS Radio Occultation as Part of the Global Observing System for Atmosphere

    Science.gov (United States)

    Mannucci, Anthony J.; Ao, C. O.; Iijima, B. A.; Wilson, B. D.; Yunck, T. P.; Kursinski, E. R.

    2008-01-01

    Topics include: The Measurement (Physical retrievals based on time standards), GPS Retrieval Products, Retrievals and Radiances: CLARREO Mission, GPS RO and AIRS, GPS RO and Microwave, GPS RO and Radiosondes, GPS/GNSS Science, and Conclusions.

  16. Evaluating the Effect of Global Positioning System (GPS) Satellite Clock Error via GPS Simulation

    Science.gov (United States)

    Sathyamoorthy, Dinesh; Shafii, Shalini; Amin, Zainal Fitry M.; Jusoh, Asmariah; Zainun Ali, Siti

    2016-06-01

    This study is aimed at evaluating the effect of Global Positioning System (GPS) satellite clock error using GPS simulation. Two conditions of tests are used; Case 1: All the GPS satellites have clock errors within the normal range of 0 to 7 ns, corresponding to pseudorange error range of 0 to 2.1 m; Case 2: One GPS satellite suffers from critical failure, resulting in clock error in the pseudorange of up to 1 km. It is found that increase of GPS satellite clock error causes increase of average positional error due to increase of pseudorange error in the GPS satellite signals, which results in increasing error in the coordinates computed by the GPS receiver. Varying average positional error patterns are observed for the each of the readings. This is due to the GPS satellite constellation being dynamic, causing varying GPS satellite geometry over location and time, resulting in GPS accuracy being location / time dependent. For Case 1, in general, the highest average positional error values are observed for readings with the highest PDOP values, while the lowest average positional error values are observed for readings with the lowest PDOP values. For Case 2, no correlation is observed between the average positional error values and PDOP, indicating that the error generated is random.

  17. GPS radio interferometry of travelling ionospheric disturbances

    Science.gov (United States)

    Afraimovich, E. L.; Palamartchouk, K. S.; Perevalova, N. P.

    1998-01-01

    This paper presents some results investigating the new possibilities of radio interferometry of Travelling Ionospheric Disturbances (TIDs) that are based on exploiting standard measurements of transionospheric radio signal characteristics and coordinate-time measurements using dual-frequency multichannel receivers of the Global Positioning System (GPS). A Statistical Angle-of-arrival and Doppler Method for GPS radio interferometry (SADM-GPS) is proposed for determining the characteristics of the TIDs dynamics by measuring variations of GPS phase derivatives with respect to time and spatial coordinates. These data are used to calculate corresponding values of the velocity vector, in view of a correction for satellite motions based on the current information available regarding the angular coordinates of the satellites. Subsequently, velocity and direction distributions are constructed and analyzed to verify the hypothesis of whether there is a predominant displacement. If it exists, then the pattern can be considered to be travelling, and the mean travel velocity can be determined from the velocity distribution. Through a computer simulation it was shown that multi-satellite GPS radio interferometry in conjunction with the SADM-GPS algorithm allows the detection and measurement of the velocity vector of TIDs in virtually the entire azimuthal range of possible TID propagation directions. The use of the proposed method is exemplified by an investigation of TIDs during the solar eclipse of 9 March 1997, using the GPS-radio interferometer GPSINT at Irkutsk.

  18. NASA's GPS tracking system for Aristoteles

    Science.gov (United States)

    Davis, E. S.; Hajj, G.; Kursinski, E. R.; Kyriacou, C.; Meehan, T. K.; Melbourne, William G.; Neilan, R. E.; Young, L. E.; Yunck, Thomas P.

    1991-12-01

    NASA 's Global Positioning System (GPS) tracking system for Artistoteles receivers and a GPS flight receiver aboard Aristoteles is described. It will include a global network of GPS ground receivers and a GPS flight receiver aboard Aristoteles. The flight receiver will operate autonomously; it will provide real time navigation solutions for Aristoteles and tracking data needed by ESOC for operational control of the satellite. The GPS flight and ground receivers will currently and continuously track all visible GPS satellites. These observations will yield high accuracy differential positions and velocities of Aristoteles in a terrestrial frame defined by the locations of the globally distributed ground work. The precise orbits and tracking data will be made available to science investigators as part of the geophysical data record. The characteristics of the GPS receivers, both flight and ground based, that NASA will be using to support Aristoteles are described. The operational aspects of the overall tracking system, including the data functions and the resulting data products are summarized. The expected performance of the tracking system is compared to Aristoteles requirements and the need to control key error sources such as multipath is identified.

  19. National 2000' GPS control network of China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An accurately unified national GPS network with more than 2500 stations, named "National 2000' GPS Control Network", signed the epoch 2000.0, has been established by integrating the existing six nationwide GPS networks of China set up by different departments with different objectives. This paper presents the characteristics of the existing GPS networks, summarizes the strategies in the integrated adjustment of the GPS network, including functional model, stochastic model as well as the adjustment principle modification. By modifying the adjustment strategies according to the characteristics of the existing GPS networks and under the support of the IGS stations, the accuracy of the integrated national GPS network is greatly improved. The datum differences among the sub networks disappear, the systematic error influences are weakened, and the effects of the outliers on the estimated coordinates and their variances are controlled. It is shown that the average standard deviation for the horizontal component is smaller than 1.0 cm, the vertical component is smaller than 2.0 cm, and the three-dimensional (3-D) position of geocenter coordinates is smaller than 3.0 cm. The exterior checking accuracy for the 3-D position is averagely better than 1.0 cm.

  20. Seasonal Effects on GPS PPP Accuracy

    Science.gov (United States)

    Saracoglu, Aziz; Ugur Sanli, D.

    2016-04-01

    GPS Precise Point Positioning (PPP) is now routinely used in many geophysical applications. Static positioning and 24 h data are requested for high precision results however real life situations do not always let us collect 24 h data. Thus repeated GPS surveys of 8-10 h observation sessions are still used by some research groups. Positioning solutions from shorter data spans are subject to various systematic influences, and the positioning quality as well as the estimated velocity is degraded. Researchers pay attention to the accuracy of GPS positions and of the estimated velocities derived from short observation sessions. Recently some research groups turned their attention to the study of seasonal effects (i.e. meteorological seasons) on GPS solutions. Up to now usually regional studies have been reported. In this study, we adopt a global approach and study the various seasonal effects (including the effect of the annual signal) on GPS solutions produced from short observation sessions. We use the PPP module of the NASA/JPL's GIPSY/OASIS II software and globally distributed GPS stations' data of the International GNSS Service. Accuracy studies previously performed with 10-30 consecutive days of continuous data. Here, data from each month of a year, incorporating two years in succession, is used in the analysis. Our major conclusion is that a reformulation for the GPS positioning accuracy is necessary when taking into account the seasonal effects, and typical one term accuracy formulation is expanded to a two-term one.

  1. Briefing highlights space weather risks to GPS

    Science.gov (United States)

    Tretkoff, Ernie

    2011-07-01

    Solar storms, which are expected to increase as the Sun nears the most active phase of the solar cycle, can disrupt a variety of technologies on which society relies. Speakers at a 22 June briefing on Capitol Hill in Washington, D. C., focused on how space weather can affect the Global Positioning System (GPS), which is used in a wide range of industries, including commercial air travel, agriculture, national security, and emergency response. Rocky Stone, chief technical pilot for United Airlines, noted that GPS allows more aircraft to be in airspace, saves fuel, and helps aircraft move safely on runways. “Improvements in space weather forecasting need to be pursued,” he said. Precision GPS has also “changed the whole nature of farming,” said Ron Hatch, Director of Navigation Systems, NavCom Technology/John Deere. GPS makes it possible for tractors to be driven in the most efficient paths and for fertilizer and water to be applied precisely to the areas that most need them. Space weather-induced degradation of GPS signals can cause significant loss to farms that rely on GPS. Elizabeth Zimmerman, Deputy Associate Administrator for the Office of Response and Recovery at the Federal Emergency Management Agency (FEMA), described how FEMA relies on GPS for disaster recovery. The agency is developing an operations plan for dealing with space weather, she said.

  2. 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

  3. 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.

  4. 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...

  5. 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

  6. 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, $\

  7. 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.

  8. Mining significant semantic locations from GPS data

    DEFF Research Database (Denmark)

    Cao, Xin; Cong, Gao; Jensen, Christian S.

    2010-01-01

    With the increasing deployment and use of GPS-enabled devices, massive amounts of GPS data are becoming available. We propose a general framework for the mining of semantically meaningful, significant locations, e.g., shopping malls and restaurants, from such data. We present techniques capable...... of extracting semantic locations from GPS data. We capture the relationships between locations and between locations and users with a graph. Significance is then assigned to locations using random walks over the graph that propagates significance among the locations. In doing so, mutual reinforcement between...

  9. Mining significant semantic locations from GPS data

    DEFF Research Database (Denmark)

    Cao, Xin; Cong, Gao; Jensen, Christian S.

    2010-01-01

    With the increasing deployment and use of GPS-enabled devices, massive amounts of GPS data are becoming available. We propose a general framework for the mining of semantically meaningful, significant locations, e.g., shopping malls and restaurants, from such data. We present techniques capable...... of extracting semantic locations from GPS data. We capture the relationships between locations and between locations and users with a graph. Significance is then assigned to locations using random walks over the graph that propagates significance among the locations. In doing so, mutual reinforcement between...

  10. 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.

  11. GPS: El sistema de posicionamiento global

    National Research Council Canada - National Science Library

    Juan Gilberto Serpas; Manuel Ramírez N; Franklin de Obaldía

    2016-01-01

    El Sistema de Posicionamiento Global (GPS, por sus siglas en inglés) se ha convertido, en la actualidad, en una herramienta invaluable para el posicionamiento de puntos sobre la superficie terrestre...

  12. Using GPS for studying pastoral mobility

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine

    2017-01-01

    In 1997 I embarked on a PhD to study mobility amongst nomadic pastoralists in Senegal. Previous studies had largely been conducted by anthropologists who through ethnographic fieldwork followed the nomadic pastoralists for long periods of time and did their own sketches of the movements. As a human...... as I know, the first one to use GPS for studying pastoral mobility. A total of 10 pastoralists were trained in using a GPS and asked to map their movements. This information was combined with satellite imagery on one hand and qualitative interviews on the other. This case study provides an account...... of the practical aspects of using GPS, taking the reader to the heart of some methodological issues that arose in the course of the research. The case sheds light on the particular challenges in using GPS for eliciting information about pastoral mobility. Thinking about such challenges leads to more general...

  13. Global Positioning System (GPS) Energetic Particle Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Energetic particle data from the CXD and BDD instrument on the GPS constellation are available to the space weather research community. The release of these data...

  14. Earth Rotation Parameter Estimation by GPS Observations

    Institute of Scientific and Technical Information of China (English)

    YAO Yibin

    2006-01-01

    The methods of Earth rotation parameter (ERP) estimation based on IGS SINEX file of GPS solution are discussed in detail. There are two different ways to estimate ERP: one is the parameter transformation method, and the other is direct adjustment method with restrictive conditions. By comparing the estimated results with independent copyright program to IERS results, the residual systemic error can be found in estimated ERP with GPS observations.

  15. Integrating GPS with Dead Reckoning Sensors

    DEFF Research Database (Denmark)

    Cederholm, Jens Peter

    2000-01-01

    A vehicle positioning system comprising a GPS receiver, a digital compass, and an odometer was tested on a 2.8-km stretch in Aalborg, Denmark. The system, which merges observations from the three instruments using a Kalman filter, has an update rate of 1 Hz and is intended for use in both urban...... and rural areas. The filtered positions follow the travelled route closely. A simulation suggests that the system will work even when the GPS coverage is insufficient....

  16. En Billig GPS Data Analyse Platform

    DEFF Research Database (Denmark)

    Andersen, Ove; Christiansen, Nick; Larsen, Niels T.

    2011-01-01

    Denne artikel præsenterer en komplet software platform til analyse af GPS data. Platformen er bygget udelukkende vha. open-source komponenter. De enkelte komponenter i platformen beskrives i detaljer. Fordele og ulemper ved at bruge open-source diskuteres herunder hvilke IT politiske tiltage, der...... organisationer med et digitalt vejkort og GPS data begynde at lave trafikanalyser på disse data. Det er et krav, at der er passende IT kompetencer tilstede i organisationen....

  17. En Billig GPS Data Analyse Platform

    DEFF Research Database (Denmark)

    Andersen, Ove; Christiansen, Nick; Larsen, Niels T.;

    2011-01-01

    Denne artikel præsenterer en komplet software platform til analyse af GPS data. Platformen er bygget udelukkende vha. open-source komponenter. De enkelte komponenter i platformen beskrives i detaljer. Fordele og ulemper ved at bruge open-source diskuteres herunder hvilke IT politiske tiltage, der...... organisationer med et digitalt vejkort og GPS data begynde at lave trafikanalyser på disse data. Det er et krav, at der er passende IT kompetencer tilstede i organisationen....

  18. Offset detection in GPS coordinate time series

    Science.gov (United States)

    Gazeaux, J.; King, M. A.; Williams, S. D.

    2013-12-01

    Global Positioning System (GPS) time series are commonly affected by offsets of unknown magnitude and the large volume of data globally warrants investigation of automated detection approaches. The Detection of Offsets in GPS Experiment (DOGEx) showed that accuracy of Global Positioning System (GPS) time series can be significantly improved by applying statistical offset detection methods (see Gazeaux et al. (2013)). However, the best of these approaches did not perform as well as manual detection by expert analysts. Many of the features of GPS coordinates time series have not yet been fully taken into account in existing methods. Here, we apply Bayesian theory in order to make use of prior knowledge of the site noise characteristics and metadata in an attempt to make the offset detection more accurate. In the past decades, Bayesian theory has shown relevant results for a widespread range of applications, but has not yet been applied to GPS coordinates time series. Such methods incorporate different inputs such as a dynamic model (linear trend, periodic signal..) and a-priori information in a process that provides the best estimate of parameters (velocity, phase and amplitude of periodic signals...) based on all the available information. We test the new method on the DOGEx simulated dataset and compare it to previous solutions, and to Monte-Carlo method to test the accuracy of the procedure. We make a preliminary extension of the DOGEx dataset to introduce metadata information, allowing us to test the value of this data type in detecting offsets. The flexibility, robustness and limitations of the new approach are discussed. Gazeaux, J. Williams, S., King, M., Bos, M., Dach, R., Deo, M.,Moore, A.W., Ostini, L., Petrie, E., Roggero, M., Teferle, F.N., Olivares, G.,Webb, F.H. 2013. Detecting offsets in GPS time series: First results from the detection of offsets in GPS experiment. Journal of Geophysical Research: Solid Earth 118. 5. pp:2169-9356. Keywords : GPS

  19. GPS (Global Positioning System) Range Applications Study.

    Science.gov (United States)

    1982-12-31

    Portability + + All; Improved Due to Fewer Resources * Availabilty - + All; (-) Small Satellite Window, (+) Better MTMF * Data Timeliness 0 0 GPS APPLICABILITY...calculations to maxi- mum and minimum values based on the spread evidenced in his- torical range usage . 7-23 THE ANALYTIC SCIENCES CORPORATION accuracy... Availabilty 0 + Less Reliance on Older Equipment a Data Timeliness + 0 Labor Intensive Optics for Velocity GPS APPLICABILITY HIGH HIGH Accuracy and Coverage in

  20. Global Positioning System III (GPS III)

    Science.gov (United States)

    2015-12-01

    Military Operations in Urban Terrain; Defense-Wide Mission Support; Air Mobility; and Space Launch Orbital Support. For military users, the GPS III...program provides Precise Positioning Service (PPS) to military operations and force enhancement. It also provides increased anti-jam power to the earth ...to be modified . On January 31, 2016, USD(AT&L) signed the GPS III revised APB. This Change 1 to the APB was due to both cost and schedule breaches

  1. Analysis list: Gps2 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available Gps2 Embryonic fibroblast + mm9 http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Gps...2.1.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/target/Gps2.5.tsv http://dbarchive.biosciencedb...c.jp/kyushu-u/mm9/target/Gps2.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/mm9/colo/Gps2.Embryonic_fibr

  2. {WiFi GPS} based Combined positioning Algorithm

    OpenAIRE

    Zirari, Soumaya; Canalda, Philippe; Spies, François

    2010-01-01

    International audience; If nowadays, positioning becomes more and more accurate, and covers better and better a territory (indoor and outdoor), it remains territories where traditional (and basic) positioning system (GPS, gsm or WiFi) and hybrid ones (GPS-gsm, GPS-WiFi, GPS-WiFi-gsm,...) are insufficient and requires research investment treating combined positioning. In this paper we propose a GPS-WiFi combined positioning algorithm, based on trilateration technique. Real experiments and othe...

  3. GPS in Pedestrian and Spatial Behaviour Surveys

    DEFF Research Database (Denmark)

    Nielsen, Thomas Alexander Sick; Hovgesen, Henrik Harder

    The planning of the environment for pedestrians can be improved by using the newest gps tools for monitoring changes in human activity patterns in time and space. Using a personal GPS device, the locations and movements of respondents can be followed over a longer period of time. It will then be ......The planning of the environment for pedestrians can be improved by using the newest gps tools for monitoring changes in human activity patterns in time and space. Using a personal GPS device, the locations and movements of respondents can be followed over a longer period of time....... It will then be possible to analyse how the use of urban spaces are embedded in the wider context of activity patterns (work, school etc.). The general pattern of everyday itineraries, including route choice and time spent at different locations ?on the way? can also be analysed.    If the personal GPS device is combined...... position in the urban area. Thus a new form of integration between research into activity patterns and urban places will be possible.    The paper presents the possibilities in spatial behaviour and pedestrian surveys with GPS and electronic questionnaires. Demonstrative mapping of test data from passive...

  4. Geomagnetic storm effects on GPS based navigation

    Directory of Open Access Journals (Sweden)

    P. V. S. Rama Rao

    2009-05-01

    Full Text Available The energetic events on the sun, solar wind and subsequent effects on the Earth's geomagnetic field and upper atmosphere (ionosphere comprise space weather. Modern navigation systems that use radio-wave signals, reflecting from or propagating through the ionosphere as a means of determining range or distance, are vulnerable to a variety of effects that can degrade the performance of the navigational systems. In particular, the Global Positioning System (GPS that uses a constellation of earth orbiting satellites are affected due to the space weather phenomena.

    Studies made during two successive geomagnetic storms that occurred during the period from 8 to 12 November 2004, have clearly revealed the adverse affects on the GPS range delay as inferred from the Total Electron Content (TEC measurements made from a chain of seven dual frequency GPS receivers installed in the Indian sector. Significant increases in TEC at the Equatorial Ionization anomaly crest region are observed, resulting in increased range delay during the periods of the storm activity. Further, the storm time rapid changes occurring in TEC resulted in a number of phase slips in the GPS signal compared to those on quiet days. These phase slips often result in the loss of lock of the GPS receivers, similar to those that occur during strong(>10 dB L-band scintillation events, adversely affecting the GPS based navigation.

  5. Calibración del retardo ionosférico en observaciones astrométricas y geodésicas a partir de observaciones GPS

    Science.gov (United States)

    Brunini, C.; Kleusberg, A.; Arias, E. F.; de Biasi, M. S.

    Los parámetros astrométricos y geodésicos de precisión se determinan hoy mediante la observación con técnicas espaciales (VLBI, GPS y LSR). Las técnicas VLBI y GPS operan en la banda de microondas y en ella la ionósfera terrestre es dispersiva. Las señales que provienen de las radiofuentes y de los satélites atraviesan la ionósfera, donde el índice de refracción difiere de la unidad en una cantidad que es proporcional a la densidad de electrones libres e inversamente proporcional al cuadrado de la frecuencia de la onda portadora. Actualmente el International GPS Service for Geodynamics (IGS) mantiene operacional una red global integrada por más de 50 estaciones equipadas con receptores GPS de alta performance; las observaciones diarias son accesibles a los usuarios mediante ftp. La posibilidad de utilizar estas observaciones en un monitoreo continuo de la ionósfera fue señalada por diversos autores, razón por la cual en los últimos años se ha invertido un significativo esfuerzo en la producción de mapas ionosféricos regionales y globales. En el presente trabajo se utilizan 28 estaciones cuyas observaciones mapean la mayor parte de la ionósfera global. Los resultados obtenidos demuestran la posibilidad de obtener mapas ionosféricos globales con una resolución de medio día y con una precisión de (1.5 nseg (rms)). Dichos mapas proveen valores medios globales para el intervalo ajustado. Los residuos del ajuste por mínimos cuadrados constituyen una señal a partir de la cual pueden estudiarse mejor las variaciones geográficas de la ionósfera y las componentes estadísticas de su variación temporal.

  6. 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.

  7. Combined GPS/GLONASS Precise Point Positioning with Fixed GPS Ambiguities

    Science.gov (United States)

    Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

    2014-01-01

    Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF. PMID:25237901

  8. Combined GPS/GLONASS precise point positioning with fixed GPS ambiguities.

    Science.gov (United States)

    Pan, Lin; Cai, Changsheng; Santerre, Rock; Zhu, Jianjun

    2014-09-18

    Precise point positioning (PPP) technology is mostly implemented with an ambiguity-float solution. Its performance may be further improved by performing ambiguity-fixed resolution. Currently, the PPP integer ambiguity resolutions (IARs) are mainly based on GPS-only measurements. The integration of GPS and GLONASS can speed up the convergence and increase the accuracy of float ambiguity estimates, which contributes to enhancing the success rate and reliability of fixing ambiguities. This paper presents an approach of combined GPS/GLONASS PPP with fixed GPS ambiguities (GGPPP-FGA) in which GPS ambiguities are fixed into integers, while all GLONASS ambiguities are kept as float values. An improved minimum constellation method (MCM) is proposed to enhance the efficiency of GPS ambiguity fixing. Datasets from 20 globally distributed stations on two consecutive days are employed to investigate the performance of the GGPPP-FGA, including the positioning accuracy, convergence time and the time to first fix (TTFF). All datasets are processed for a time span of three hours in three scenarios, i.e., the GPS ambiguity-float solution, the GPS ambiguity-fixed resolution and the GGPPP-FGA resolution. The results indicate that the performance of the GPS ambiguity-fixed resolutions is significantly better than that of the GPS ambiguity-float solutions. In addition, the GGPPP-FGA improves the positioning accuracy by 38%, 25% and 44% and reduces the convergence time by 36%, 36% and 29% in the east, north and up coordinate components over the GPS-only ambiguity-fixed resolutions, respectively. Moreover, the TTFF is reduced by 27% after adding GLONASS observations. Wilcoxon rank sum tests and chi-square two-sample tests are made to examine the significance of the improvement on the positioning accuracy, convergence time and TTFF.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Excellent observation of China SLR in southern hemisphere%中国SLR在南半球观测取得良好进展

    Institute of Scientific and Technical Information of China (English)

    韩延本; 刘卫东; E.; Actis; R.; Podesta; 王谭强; 瞿锋

    2007-01-01

    本文简要介绍了用中国研制的人造卫星激光测距仪(SLR),安装在阿根廷与San Juan大学天文台开展SLR合作观测与研究的意义,以及这个SLR系统的指标和性能.该仪器系统于2006年初在阿根廷国立San Juan大学天文台工作以来,进展良好,取得了观测数量丰富、精度高的优良结果.该合作的进展状况和未来的发展设想也在文中做了介绍.

  15. 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.

  16. 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.

  17. GPS Space Service Volume: Ensuring Consistent Utility Across GPS Design Builds for Space Users

    Science.gov (United States)

    Bauer, Frank H.; Parker, Joel Jefferson Konkl; Valdez, Jennifer Ellen

    2015-01-01

    GPS availability and signal strength originally specified for users on or near surface of Earth with transmitted power levels specified at edge-of-Earth, 14.3 degrees. Prior to the SSV specification, on-orbit performance of GPS varied from block build to block build (IIA, IIRM, IIF) due to antenna gain and beam width variances. Unstable on-orbit performance results in significant risk to space users. Side-lobe signals, although not specified, were expected to significantly boost GPS signal availability for users above the constellation. During GPS III Phase A, NASA noted significant discrepancies in power levels specified in GPS III specification documents, and measured on-orbit performance. To stabilize the signal for high altitude space users, NASA DoD team in 2003-2005 led the creation of new Space Service Volume (SSV) definition and specifications.

  18. Very long-period GPS waveforms. What can GPS bring to Earth seismic velocity models?

    Science.gov (United States)

    Kelevitz, K.; Houlie, N.; Nissen-Meyer, T.; Boschi, L.; Giardini, D.; Rothacher, M.

    2014-12-01

    It is now admitted that high rate GPS observations can provide reliable surface displacement waveforms. For long-period (T > 5s) transients, it was shown that GPS and seismometer (STS-1) displacements are in agreement at least for vertical component [Houlié et al., 2011]. We propose here to supplement existing long-period seismic networks with high rate (>= 1Hz) GPS data in order to improve the resolution of global seismic velocity models. We aim at extending the use of GPS measurements beyond the range of STS-1 in the low frequency end (T>1000s). We present the results of the processing of 1Hz GPS records of the Hokkaido, Sumatra and Tohoku earthquakes (25th of September, 2003, Mw = 8.3; 26th of December, 2004, Mw = 8.9; 11th of March, 2011, Mw = 9.1, respectively). 3D waveforms phase time-series have been used to recover the ground motion histories at the GPS sites. Through the better resolution of inversion of the GPS phase observations, we determine displacement waveforms of periods ranging from 30 seconds to 1300 seconds for a selection of sites. We compare inverted GPS waveforms with STS-1 waveforms, superconducting gravity waveforms and synthetic waveforms computed using 3D global wave propagation with SPECFEM. We find that the GPS waveforms are in agreement with the SPECFEM synthetic data and are able to fill the period-gap between the broadband seismometer STS-1 data and the normal mode period range detected by the superconducting gravimeters. References: Houlié, N., G. Occhipinti, T. Blanchard, N. Shapiro, P. Lognonne, and M. Murakami (2011), New approach to detect seismic surface waves in 1Hz-sampled GPS time series, Scientific reports, 1, 44.

  19. GPS Remote Sensing Measurements Using Aerosonde UAV

    Science.gov (United States)

    Grant, Michael S.; Katzberg, Stephen J.; Lawrence, R. W.

    2005-01-01

    In February 2004, a NASA-Langley GPS Remote Sensor (GPSRS) unit was flown on an Aerosonde unmanned aerial vehicle (UAV) from the Wallops Flight Facility (WFF) in Virginia. Using direct and surface-reflected 1.575 GHz coarse acquisition (C/A) coded GPS signals, remote sensing measurements were obtained over land and portions of open water. The strength of the surface-reflected GPS signal is proportional to the amount of moisture in the surface, and is also influenced by surface roughness. Amplitude and other characteristics of the reflected signal allow an estimate of wind speed over open water. In this paper we provide a synopsis of the instrument accommodation requirements, installation procedures, and preliminary results from what is likely the first-ever flight of a GPS remote sensing instrument on a UAV. The correct operation of the GPSRS unit on this flight indicates that Aerosonde-like UAV's can serve as platforms for future GPS remote sensing science missions.

  20. Ionospheric irregularities at Antarctic using GPS measurements

    Indian Academy of Sciences (India)

    Sunita Tiwari; Amit Jain; Shivalika Sarkar; Sudhir Jain; A K Gwal

    2012-04-01

    The purpose of this work is to study the behaviour of the ionospheric scintillation at high latitude during geomagnetically quiet and disturbed conditions which is one of the most relevant themes in the space weather studies. Scintillation is a major problem in navigation application using GPS and in satellite communication at high latitudes. Severe amplitude fading and strong scintillation affect the reliability of GPS navigational system and satellite communication. To study the effects of the ionospheric scintillations, GPS receiver installed at Antarctic station Maitri (Geog. 70.76°S; 11.74°E) was used. The data is collected by using GISTM 4004A, NOVATEL’S GPS receiver during March 2008. Studies show that percentage occurrence of phase scintillation is well correlated with geomagnetic activity during the observation period. The result also shows that very intense scintillations can degrade GPS based location determination due to loss of lock of satellites. These findings indicate that the dependence of scintillations and irregularity occurrence on geomagnetic activity is associated with the magnetic local time (MLT). Large number of patches are reported and their activity depends on the magnetic activity index.

  1. Uav Onboard GPS in Positioning Determination

    Science.gov (United States)

    Tahar, K. N.; Kamarudin, S. S.

    2016-06-01

    The establishment of ground control points is a critical issue in mapping field, especially for large scale mapping. The fast and rapid technique for ground control point's establishment is very important for small budget projects. UAV onboard GPS has the ability to determine the point positioning. The objective of this research is to assess the accuracy of unmanned aerial vehicle onboard global positioning system in positioning determination. Therefore, this research used UAV onboard GPS as an alternative to determine the point positioning at the selected area. UAV is one of the powerful tools for data acquisition and it is used in many applications all over the world. This research concentrates on the error contributed from the UAV onboard GPS during observation. There are several points that have been used to study the pattern of positioning error. All errors were analyzed in world geodetic system 84- coordinate system, which is the basic coordinate system used by the global positioning system. Based on this research, the result of UAV onboard GPS positioning could be used in ground control point establishment with the specific error. In conclusion, accurate GCP establishment could be achieved using UAV onboard GPS by applying a specific correction based on this research.

  2. Applying GPS to check horizontal control quality

    Directory of Open Access Journals (Sweden)

    Jakub Vincent

    2004-03-01

    Full Text Available GPS technologies can also be used for check quality in available horizontal point set with coordinates CJ of the frame S-JTSK. When survey and setting-out tasks should be performed in certain area, one can found in it allways some points of the fundamental and detail state controls. To use these points for some actual aims, it is necessary to investigate their compatibility (among the point mark positions and the point coordinate of control points. This can be done using GPS surveying that may be at the same time employed to determine the new point in the relevant area.Principle of quality investigatingf an existing control is founded on determination of point coordinates CJt from GPS measurements. Then, based on discrepancies among the "official" netpoint coordinates CJ and coordinates CJt "given by GPS", it can be estimated the degree and the real compatibility dislocations in the network structure of the existing points.Realisation procedure for the introduced investigation is demonstrated on GPS checking (by SOKKIA STRATUS receivers horizontal control for reconstruction of a railway bridge on river Bodrog in East Slovakia.It can be shown from the results in Table 3, that points P3 and P7 are useless due to their incompatibility (inconsistency in the inspected point set. For other 7 points (Table 7 the average measure of incompatibility reads 9.8 mm that make possible applying these points for precise setting-out

  3. GPS-GRAVIMETRIC GEOID DETERMINATION IN EGYPT

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The main objective of this study is to improve the geoid byGPS/leveling data in Egypt.Comparisons of the gravimetric geoid with GPS/leveling data have been performed.On the basis of a gravimetric geoid fitted to GPS/leveling by the least square method,a smoothed geoid was obtained.A high-resolution geoid in Egypt was computed with a 2.5′×2.5′ grid by combining the data set of 2 600 original point gravity values,30″×30″ resolution Digital Terrain Model (DTM) grid and the spherical harmonic model EGM96.The method of computation involved the strict evaluation of the Stokes integral with 1D-FFT.The standard deviation of the difference between the gravimetric and the GPS/leveling geoid heights is ±0.47 m.The standard deviation after fitting of the gravimetric geoid to the GPS/leveling points is better than ±13 cm.In the future we will try to improve our geoid results in Egypt by increasing the density of gravimetric coverage.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Testing Rtk GPS System In Urban Areas

    Science.gov (United States)

    Pirti, A.; Ata, E.

    RTK GPS is provided with cm accuracy and real time surveying system. For providing this conditions, the reference is necessary for high accuracy position. Because this sta- tion is transmitted the corrections to the other receivers. At the some time this system is required common satellites on the receiver to compute integer ambiguity solution. In addition to the conditions, the data transmission device's range is very important. Although RTK GPS technique has a lot of advantages, many problems meet in prac- tice. One of the most important problem in RTK system, which is very useful and reliable in the rural areas, uses in the urban areas. We search this article, how influence RTK GPS applications on satellite numbers, multipath, data transmission device's range capability and etc. in the urban areas.

  9. Using GPS for studying pastoral mobility

    DEFF Research Database (Denmark)

    Adriansen, Hanne Kirstine

    2017-01-01

    In 1997 I embarked on a PhD to study mobility amongst nomadic pastoralists in Senegal. Previous studies had largely been conducted by anthropologists who through ethnographic fieldwork followed the nomadic pastoralists for long periods of time and did their own sketches of the movements. As a human...... geographer familiar with satellite remote sensing and GIS, I pondered how these relatively new technologies could be combined with classic ethnographic fieldwork, which we also use in human geography. I decided to use handheld GPS devices for tracking the pastoralists and their herds. My study was, as far...... as I know, the first one to use GPS for studying pastoral mobility. A total of 10 pastoralists were trained in using a GPS and asked to map their movements. This information was combined with satellite imagery on one hand and qualitative interviews on the other. This case study provides an account...

  10. Airborne gravimetry, altimetry, and GPS navigation errors

    Science.gov (United States)

    Colombo, Oscar L.

    1992-01-01

    Proper interpretation of airborne gravimetry and altimetry requires good knowledge of aircraft trajectory. Recent advances in precise navigation with differential GPS have made it possible to measure gravity from the air with accuracies of a few milligals, and to obtain altimeter profiles of terrain or sea surface correct to one decimeter. These developments are opening otherwise inaccessible regions to detailed geophysical mapping. Navigation with GPS presents some problems that grow worse with increasing distance from a fixed receiver: the effect of errors in tropospheric refraction correction, GPS ephemerides, and the coordinates of the fixed receivers. Ionospheric refraction and orbit error complicate ambiguity resolution. Optimal navigation should treat all error sources as unknowns, together with the instantaneous vehicle position. To do so, fast and reliable numerical techniques are needed: efficient and stable Kalman filter-smoother algorithms, together with data compression and, sometimes, the use of simplified dynamics.

  11. The covariance of GPS coordinates and frames

    CERN Document Server

    Lachièze-Rey, M

    2006-01-01

    We explore, in the general relativistic context, the properties of the recently introduced GPS coordinates, as well as those of the associated frames and coframes. We show that they are covariant, and completely independent of any observer. We show that standard spectroscopic and astrometric observations allow any observer to measure (i) the values of the GPS coordinates at his position, (ii) the components of his [four-]velocity and (iii) the components of the metric in the GPS frame. This provides to this system an unique value both for conceptual discussion (no frame dependence) and for practical use (involved quantities are directly measurable): localisation, motion monitoring, astrometry, cosmography, tests of gravitation theories. We show explicitly, in the general relativistic context, how an observer may estimate its position and motion, and reconstruct the components of the metric. This arises from two main results: the extension of the velocity fields of the probes to the whole (curved) spacetime; a...

  12. GPS and Mobile Multisensor Mapping System

    Institute of Scientific and Technical Information of China (English)

    Zhang Ke-fei; Xiao Ben-lin

    2003-01-01

    The latest development and evolution of surveying and mobile mapping technologies opens new avenues for the acquisition, update, fast and online processing of data. Currently mobile mapping systems are supported by a series of advanced technologies, including GPS and Inertial Navigation Systems (INS), imaging sensors of high-resolution CCD, SAR, multispectral and hyperspectral sensors, portable computers and highly intelligent processing/automation algorithms. This paper outlines recent developments of micro-GPS technology and integrated mapping systems, including accuracy,integration with GIS and communication techniques. The definition and history of the Mobile Mapping System(MMS) is reviewed and briefly outlined. Advancements in low-cost, micro-GPS technologies are emphasised.Some new advancements of the current MMS will be reviewed to demonstrate recent progress and future trends of development. A few commercial MMSs are also assessed.

  13. 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...

  14. 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.

  15. 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.

  16. 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...

  17. 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...

  18. 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). ...

  19. 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.

  20. GPS-SNO: computational prediction of protein S-nitrosylation sites with a modified GPS algorithm.

    Directory of Open Access Journals (Sweden)

    Yu Xue

    Full Text Available As one of the most important and ubiquitous post-translational modifications (PTMs of proteins, S-nitrosylation plays important roles in a variety of biological processes, including the regulation of cellular dynamics and plasticity. Identification of S-nitrosylated substrates with their exact sites is crucial for understanding the molecular mechanisms of S-nitrosylation. In contrast with labor-intensive and time-consuming experimental approaches, prediction of S-nitrosylation sites using computational methods could provide convenience and increased speed. In this work, we developed a novel software of GPS-SNO 1.0 for the prediction of S-nitrosylation sites. We greatly improved our previously developed algorithm and released the GPS 3.0 algorithm for GPS-SNO. By comparison, the prediction performance of GPS 3.0 algorithm was better than other methods, with an accuracy of 75.80%, a sensitivity of 53.57% and a specificity of 80.14%. As an application of GPS-SNO 1.0, we predicted putative S-nitrosylation sites for hundreds of potentially S-nitrosylated substrates for which the exact S-nitrosylation sites had not been experimentally determined. In this regard, GPS-SNO 1.0 should prove to be a useful tool for experimentalists. The online service and local packages of GPS-SNO were implemented in JAVA and are freely available at: http://sno.biocuckoo.org/.

  1. A GPS Receiver for Lunar Missions

    Science.gov (United States)

    Bamford, William A.; Heckler, Gregory W.; Holt, Greg N.; Moreau, Michael C.

    2008-01-01

    Beginning with the launch of the Lunar Reconnaissance Orbiter (LRO) in October of 2008, NASA will once again begin its quest to land humans on the Moon. This effort will require the development of new spacecraft which will safely transport people from the Earth to the Moon and back again, as well as robotic probes tagged with science, re-supply, and communication duties. In addition to the next-generation spacecraft currently under construction, including the Orion capsule, NASA is also investigating and developing cutting edge navigation sensors which will allow for autonomous state estimation in low Earth orbit (LEO) and cislunar space. Such instruments could provide an extra layer of redundancy in avionics systems and reduce the reliance on support and on the Deep Space Network (DSN). One such sensor is the weak-signal Global Positioning System (GPS) receiver "Navigator" being developed at NASA's Goddard Space Flight Center (GSFC). At the heart of the Navigator is a Field Programmable Gate Array (FPGA) based acquisition engine. This engine allows for the rapid acquisition/reacquisition of strong GPS signals, enabling the receiver to quickly recover from outages due to blocked satellites or atmospheric entry. Additionally, the acquisition algorithm provides significantly lower sensitivities than a conventional space-based GPS receiver, permitting it to acquire satellites well above the GPS constellation. This paper assesses the performance of the Navigator receiver based upon three of the major flight regimes of a manned lunar mission: Earth ascent, cislunar navigation, and entry. Representative trajectories for each of these segments were provided by NASA. The Navigator receiver was connected to a Spirent GPS signal generator, to allow for the collection of real-time, hardware-in-the-loop results for each phase of the flight. For each of the flight segments, the Navigator was tested on its ability to acquire and track GPS satellites under the dynamical

  2. GPS for large-scale aerotriangulation

    Science.gov (United States)

    Rogowksi, Jerzy B.

    The application of GPS (Global Positioning System) measurements to photogrammetry is presented. The technology of establishment of a GPS network for aerotriangulation as a base for mapping at scales from 1:1000 has been worked out at the Institute of Geodesy and Geodetical Astronomy of the Warsaw University of Technology. This method consists of the design, measurement, and adjustment of this special network. The results of several pilot projects confirm the possibility of improving the aerotriangulation accuracy. A few-centimeter accuracy has been achieved.

  3. Arctic tides from GPS on sea ice

    DEFF Research Database (Denmark)

    Kildegaard Rose, Stine; Skourup, Henriette; Forsberg, René

    The presence of sea-ice in the Arctic Ocean plays a significant role in the Arctic climate. Sea ice dampens the ocean tide amplitude with the result that global tidal models which use only astronomical data perform less accurately in the polar regions. This study presents a kinematic processing...... of Global Positioning System (GPS) buoys placed on sea-ice at five different sites north of Greenland for the study of sea level height and tidal analysis to improve tidal models in the Central Arctic. The GPS measurements are compared with the Arctic tidal model AOTIM-5, which assimilates tide...

  4. Volcano deformation and subdaily GPS products

    Science.gov (United States)

    Grapenthin, Ronni

    Volcanic unrest is often accompanied by hours to months of deformation of the ground that is measurable with high-precision GPS. Although GPS receivers are capable of near continuous operation, positions are generally estimated for daily intervals, which I use to infer characteristics of a volcano’s plumbing system. However, GPS based volcano geodesy will not be useful in early warning scenarios unless positions are estimated at high rates and in real time. Visualization and analysis of dynamic and static deformation during the 2011 Tohokuoki earthquake in Japan motivates the application of high-rate GPS from a GPS seismology perspective. I give examples of dynamic seismic signals and their evolution to the final static offset in 30 s and 1 s intervals, which demonstrates the enhancement of subtle rupture dynamics through increased temporal resolution. This stresses the importance of processing data at recording intervals to minimize signal loss. Deformation during the 2009 eruption of Redoubt Volcano, Alaska, suggested net deflation by 0.05 km³ in three distinct phases. Mid-crustal aseismic precursory inflation began in May 2008 and was detected by a single continuous GPS station about 28 km NE of Redoubt. Deflation during the explosive and effusive phases was sourced from a vertical ellipsoidal reservoir at about 7-11.5 km. From this I infer a model for the temporal evolution of a complex plumbing system of at least 2 sources during the eruption. Using subdaily GPS positioning solutions I demonstrate that plumes can be detected and localized by utilizing information on phase residuals. The GPS network at Bezymianny Volcano, Kamchatka, records network wide subsidence at rapid rates between 8 and 12 mm/yr from 2005-2010. I hypothesize this to be caused by continuous deflation of a ˜30 km deep sill under Kluchevskoy Volcano. Interestingly, 1-2 explosive events per year cause little to no deformation at any site other than the summit site closest to the vent. I

  5. DATA PROCESSING FOR GPS PRECISE POINT POSITIONING

    Institute of Scientific and Technical Information of China (English)

    HUCong-wei; CHENWu; GAOShah; CHENYong-qi; DINGXiao-li

    2005-01-01

    In the data processing of the precise point positioning (PPP), the un-difference method is commonly used. However, GPS measurements can be differenced with satellites or different observation epochs. In theory,these differencing approaches should be mathematically equivalent. The positioning performance of different PPP data models, including un-difference (UD), satellite difference (SD), time difference (TD) and time-satellite difference (TSD), is examined using the 24 h GPS observation. The positioning accuracy, convergence of ambiguity, and tropspheric delay estimation with these four models are compared with each other.

  6. Investigation on Tidal Components in GPS Coordinates

    Science.gov (United States)

    Araszkiewicz, Andrzej; Bogusz, Janusz; Figurski, Mariusz

    2009-01-01

    This paper presents analyses on the GPS coordinates from sub-diurnal solutions of EPN data provided by Warsaw Military University of Technology. The aim of this research is to investigate the way the tidal models used in Bernese software (solid Earth and ocean tides as well) fit to the individual conditions of EPN stations. The 1-hour solution technique of GPS data processing was utilized to obtain coordinates of above 70 EPN stations. Additionally several Polish permanent sites with clearly seen oscillations were examined. This processing technique allowed us to recognize diurnal and sub-diurnal residual oscillations which could be next utilized for validation of the tidal models.

  7. A Bridge Deflection Monitoring with GPS

    Science.gov (United States)

    Figurski, M.; Gałuszkiewicz, M.; Wrona, M.

    2007-01-01

    This paper introduces results of investigation carried on by The Applied Geomatics Section in Military University of Technology. Research includes possibilities of monitoring dynamic behavior of a bridge using high rate GPS data. Whole event was executed with collaboration of The Road and Bridge Management and The Warsaw Geodesy Company. Interdisciplinary approach with this project allows authors to get reliable information about investigating constructions and their respond for true traffic loading detected by GPS receivers. Way of compute data and used software (TRACK) are also shown in this paper.

  8. Dual RF Astrodynamic GPS Orbital Navigator Satellite

    Science.gov (United States)

    Kanipe, David B.; Provence, Robert Steve; Straube, Timothy M.; Reed, Helen; Bishop, Robert; Lightsey, Glenn

    2009-01-01

    Dual RF Astrodynamic GPS Orbital Navigator Satellite (DRAGONSat) will demonstrate autonomous rendezvous and docking (ARD) in low Earth orbit (LEO) and gather flight data with a global positioning system (GPS) receiver strictly designed for space applications. ARD is the capability of two independent spacecraft to rendezvous in orbit and dock without crew intervention. DRAGONSat consists of two picosatellites (one built by the University of Texas and one built by Texas A and M University) and the Space Shuttle Payload Launcher (SSPL); this project will ultimately demonstrate ARD in LEO.

  9. Precise orbit determination for Jason-1 satellite using on-board GPS data with cm-level accuracy

    Institute of Scientific and Technical Information of China (English)

    PENG DongJu; WU Bin

    2009-01-01

    The joint US/French Jason-1 satellite altimeter mission, launched from the Vandenberg Air Force Base on December 7, 2001, continues the time series of centimeter-level ocean topography observations as the follow-on to the highly successful T/P radar altimeter satellite. Orbit error especially the radial orbit error is a major component in the overall budget of all altimeter satellite missions, in order to continue the T/P standard of observations. Jason-1 has a radial orbit error budget requirement of 2.5 cm. in this work, two cycles (December 19, 2002 to January 7, 2003) of the Jason-1 on-board GPS data were processed using the zero-difference (ZD) dynamic precise orbit determination (POD) technique. The resulting Jason-1 orbit accuracy was assessed by comparison with the precise orbit ephemeris (POE)produced by JPL, orbit overlaps and SLR residuals. These evaluations indicate that the RMS radial accuracy is in the range of 1-2 cm.

  10. A New GPS System for Continuous Deformation Monitoring

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper presents a multi-antenna GPS based system developed for localcontinuous deformation monitoring. Due to a large number of points that needs to be monitored,the standard approaches of using permanent GPS receiver arrays will cause high cost. Iteventually becomes the limiting factor for large-scale use of GPS in these application areas.Multi-antenna GPS system allows a number of GPS antennas to be linked to one GPS receiverby a specially designed electronic component, i.e. the so-called GPS multi-antenna switch(GMS), The receiver takes data sequentially from each of the antennas attached to thereceiver. A distinctive advantage of the approach is that one GPS receiver can be used tomonitor more than one point. The cost per monitored point (i. e. the expenses of hardware)istherefore significantly reduced.

  11. An Analysis of Local Tie Vectors' Temporal Evolution and Site Stability at Medicina Observatory through Terrestrial and GPS-based Observations

    Science.gov (United States)

    Abbondanza, C.; Vittuari, L.; Sarti, P.; Negusini, M.

    2007-07-01

    The observatory of Medicina (Italy) hosts a co-location between GPS and VLBI, whose eccentricity vector has been re-measured several times once since 2001. As a result, the co-located site is now provided with a series of nearly annual local tie vectors produced by means of terrestrial and GPS-based observations. This work aims at summarising the results of a systematic analysis of the whole set of local ties produced so far and highlighting at the same time their temporal evolution. As such, the application of algebraic tools focussed on deformation detections can benefit the analysis of the local tie temporal variations and at the same time that one of the "geodynamical" stability of the co-located site. Nevertheless, just like in any other problem of deformation detection, such an analysis would ask for a reproducible local datum, according to which the relative displacements among the points have to be referred to. The application of algebraic projection theory to the local tie oriented-networks will be carried out in order to select a "common and fully reproducible" datum onto which the network solutions will be projected and discuss possible displacements within the re-measured networks.

  12. Analysis list: GPS2 [Chip-atlas[Archive

    Lifescience Database Archive (English)

    Full Text Available GPS2 + hg19 http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/GPS2.1.tsv http:...//dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/GPS2.5.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/target/GP...S2.10.tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/GPS2..tsv http://dbarchive.biosciencedbc.jp/kyushu-u/hg19/colo/.gml ...

  13. 78 FR 67132 - GPS Satellite Simulator Control Working Group Meeting

    Science.gov (United States)

    2013-11-08

    ... Department of the Air Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Space and Missile Systems Center, Global Positioning Systems (GPS) Directorate, Air Force, DoD. ACTION: Meeting notice..., 2013 Vol. 78 No. 206. This new meeting notice is to inform GPS simulator manufacturers, who supply...

  14. 77 FR 70421 - GPS Satellite Simulator Control Working Group Meeting

    Science.gov (United States)

    2012-11-26

    ... Department of the Air Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Space and Missile Systems Center, Global Positioning Systems (GPS) Directorate, Department of the Air Force, DoD. ACTION: Meeting Notice. SUMMARY: This meeting notice is to inform GPS simulator manufacturers, who supply products...

  15. 78 FR 63459 - GPS Satellite Simulator Control Working Group Meeting

    Science.gov (United States)

    2013-10-24

    ... Force GPS Satellite Simulator Control Working Group Meeting AGENCY: Department of the Air Force. ACTION: Meeting Notice. SUMMARY: This meeting notice is to inform GPS simulator manufacturers, who supply products to the Department of Defense (DoD), and GPS simulator users, both government and DoD contractors...

  16. Sensing and Classifying Impairments of GPS Reception on Mobile Devices

    DEFF Research Database (Denmark)

    Blunck, Henrik; Kjærgaard, Mikkel Baun; Toftegaard, Thomas Skjødeberg

    2011-01-01

    Positioning using GPS receivers is a primary sensing modality in many areas of pervasive computing. However, previous work has not considered how people’s body impacts the availability and accuracy of GPS positioning and for means to sense such impacts. We present results that the GPS performance...

  17. A GPS-Based Decentralized Control Method for Islanded Microgrids

    DEFF Research Database (Denmark)

    Golsorkhi, Mohammad; Lu, Dylan; Guerrero, Josep M.

    2017-01-01

    , GPS timing technology is utilized to synchronize the DERs to a common reference frame, rotating at nominal frequency. In addition, an adaptive Q-f droop controller is introduced as a backup to ensure stable operation during GPS signal interruptions. In the context of the common reference frame, even...... with respect to GPS interruptions....

  18. GPSIM: A Personal Computer-Based GPS Simulator System

    Science.gov (United States)

    Ibrahim, D.

    Global Positioning Systems (GPS) are now in use in many applications, ranging from GIS to route guidance, automatic vehicle location (AVL), air, land, and marine navigation, and many other transportation and geographical based applications. In many applications, the GPS receiver is connected to some form of intelligent electronic system which receives the positional data from the GPS unit and then performs the required operation. When developing and testing GPS-based systems, one of the problems is that it is usually necessary to create GPS-compatible geographical data to simulate a GPS operation in real time. This paper provides the details of a Personal Computer (PC)-based GPS simulator system called GPSIM. The system receives user way-points and routes from Windows-based screen forms and then simulates a GPS operation in real time by generating most of the commonly used GPS sentences. The user-specified waypoints are divided into a number of small segments, each segment specifying a small distance in the direction of the original waypoint. The GPS sentence corresponding to the geographical coordinates of each segment is then sent out of the PC serial port. The system described is an invaluable testing tool for GPS-based system developers and also for people training to learn to use GPS-based products.

  19. Low-cost implementation of Differential GPS using Arduino

    OpenAIRE

    Svaton, Martin

    2016-01-01

    The thesis proposes the low-cost solution of Differential GPS using Arduino as a Master Control Unit. The thesis provides the methods of GPS position augmentation, which is available for varied applications such as drones or autonomous lawnmowers operated in a private sector. Used methods of GPS positioning accuracy improvements are based on a Satellite-Based Augmentation System (SBAS) and pseudorange residuals.

  20. The Evolution of Global Positioning System (GPS) Technology.

    Science.gov (United States)

    Kumar, Sameer; Moore, Kevin B.

    2002-01-01

    Describes technological advances in the Global Positioning System (GPS), which is also known as the NAVSTAR GPS satellite constellation program developed in 1937, and changes in the nature of our world by GPS in the areas of agriculture, health, military, transportation, environment, wildlife biology, surveying and mapping, space applications, and…