Third International VLBI Technology Workshop

RadioNet3 ERATec Engineering Special Session


hosted by the Joint Institute for VLBI in Europe

10 - 13 November 2014, Groningen/Dwingeloo, the Netherlands

There are 10 posters.

Name Title
Beaklini, Pedro P.B. Title: 3C 273 variability at 7 mm: evidence of shocks and precession in the jet
VLBI observations of parsec scale jets in QSOs reveal the presence of discrete components receding from the core at sometimes apparently superluminal velocities. The formation of new components, especially at millimeter wavelengths, can be also identified as flares in single dish light curves. The origin of these components is still under discussion, one of the hypotheses being the formation of shocks that expand and evolve, becoming optically thin first at the higher frequencies. In that case, a delay is expected between the observations of the X and gamma rays emitted when the shock is formed and the maximum in the radio emission of the expanding components. In this work we report four years of observations of 3C 273 at 7 mm obtained with the Itapetinga radio telescope, in Brazil, between 2009 and 2013. We detected a flare in 2010 March that we suggest is the radio counterpart of the gamma-ray flare observed by the Fermi Large Area Telescope in 2009 September, in which the flux density at high energies reached a flux density 50 times higher than its average value. The differences in flare intensities between different frequencies and at different times are explained as a consequence of an increase in the Doppler factor δ, as predicted by the 16-yr precession model proposed by Abraham & Romero (1999). We also discuss other VLBI observable effects of the variation in δ, such as the increase in the formation rate of superluminal components, which we found to be compatible with changes in the Doppler factor.
Bogacki, Wojbor Title: OPTIME - time and frequency dissemination system based on fiber optical network
The OPTIME proposes a solution that allows end users to obtain ultra-precise time and frequency signals without incurring huge costs for the purchase their own atomic clocks, and receive the service related to laboratories generating international atomic time scales, to witch any precise time must be referred.
Bonhoure, Thomas Title:
Giménez de Castro, Guillermo Title: mm VLBI of Solar Bursts
C. Guillermo Gimenez de Castro
Centro de Radio Astronomia e Astrofisica Mackenzie
Universidade Presbiteriana Mackenzie

In recent years, spatially unresolved observations of solar flares at mm- and submm-waves with subsecond time resolution, showed a spiky nature that suggests a source fragmentation. Moreover, focal arrays using a multibeam position determination technique have shown that these sources do lie at different places separated by tens of arcsends. VLBI observations may address the question of the mm-wave sources fragmentation to an unprecedented level. Solar flares VLBI observations were experimentally conducted in 1981 using Dwingeloo and Onsala radio telescopes at dm-waves, looking for the onset of the energy release. We propose now to carry on regular observatons of the impulsive phase of solar flares at mm-waves using facilities now under construction in South America. Combining observations from the Large Latin American Millimeter Array (LLAMA), under construction in the Argentinian Atacama region, with the ALMA array in Chile, we can achieve a spatial resolution of around 0".007 at 50 GHz, i.e. 5 km over the solar surface. In this work we dicsuss the science, the challenges we will face and the expected observational constraints of the Solar Flare mm VLBI observations.
Je, Do-Heung Title: Mm-wave phase calibration signal generator using NLTL comb generator and frequency up-converter
KVN(Korean VLBI Network) is operating 22, 43, 86, 129 GHz simultaneous observation system. Ultra broadband phase calibration(P-cal) system is needed for 4-band simultaneous observation. Conventional P-cal signal generation is limited to 40 GHz band. Therefore I applied frequency up-conversion using PDRO(Phase-locked Dielectric Resonator Oscillator) for 86, 129 GHz P-cal generation. P-cal signal in band lower than 50 GHz is generated using NLTL comb generator without frequency conversion. 86, 129 GHz band P-cal signal is generated using comb generator and frequency up-conversion. I will show P-cal signal’s measured spectrum and phase stability in 22, 43, 86 GHz band.
Kang, Yong-Woo Title: Development of KDS for KVN
KVN Digital Sampler(KDS) has been developed by KASI. The sampler has a sampling frequency of 1024MHz with 2bits/sample. Also we are developing the sampler with 4GHz/sample. I will introduce some progress of the sampler developed and also the sampler development plan for Korean VLBI Network(KVN).
Kirves, Petri Title: Extending the service life of aging VLBI receivers cost effectively
We have refurbished our VLBI receivers with some economical upgrades. In this poster we represent the modifications.

22 GHz receiver - LO swap
43 GHz receiver - LNA replace
86 GHz receiver - LNA replace and back-end re-design
Pinkert, Tjeerd Title: Long haul optical time and frequency distribution in telecommunication networks
T.J. Pinkert 1), C. van Tour 1), E. Dierikx 2), H.Z. Peek 3), R. Smets 4), K.S.E. Eikema 1), and J.C.J. Koelemeij 1),5)

1)LaserLaB, Department of Physics and Astronomy, VU University Amsterdam,
2)VSL, Delft, 3)Nikhef, Amsterdam, 4)SURFnet, Utrecht, 5)OPNT B.V., Amsterdam

We report on a new fibre-optic link for time distribution with (sub-)nanosecond uncertainty and dissemination of the SI second, which has been realized between VSL Delft and Nikhef Amsterdam. We make use of quasi-bidirectional semiconductor optical amplifiers, instead of commonly-used erbium doped fiber amplifiers, to enable bidirectional optical transmission out of the C-band. Such links, based on commercially available White Rabbit Ethernet technology developed at CERN, can be used to augment or surpass time distribution by Global Navigation Satellite Systems, aiming at applications in telecommunication, the electricity grid, finance, and ‘SuperGPS’ positioning.

The performance of a 5 km actively compensated frequency distribution link using semiconductor and erbium-doped fibre amplifiers is also described, which enables state-of-the-art frequency comparisons for tests of fundamental physics in widely separated experiments. This technique can be employed on the 2x317 km optical fibre link between VU Amsterdam and University of Groningen.
Radil, Jan Title: New Photonic Services and Operative Deployment
Modern scientific experiments with unique and expensive instruments, like telescopes, are one of the driving forces behind innovation in various fields and research is nowadays pushing for new features in networks.

Emerging new applications like time and stable frequency transfer, or reproducible experiments using physically distant equipment, were simply not considered when currently used networks were designed.

New kind of services called Photonic Services are able to provide unique features for new and innovative applications whose requirements cannot be met by conventional networks with OEO conversions. Higher and higher data
transmission speeds (even 400 Gb/s and above) cannot solve the issue of such new applications, which relies on a constant delay and minimal jitter within the transmission path. Unique features are Significant differences are
minimal and/or constant latency and jitter, avoiding costly OEO conversions.

We will discuss how Photonic Services may enable these innovations to happen and practical aspects and present examples of real deployment are also considered.
Rastorgueva-Foi, Elizaveta Title: AuScope VLBI array data transport: a case study
AuScope geodetic VLBI array consists of three 12-m telescopes, operated by University of Tasmania (UTas) in coordination with IVS and funded by Australian government. The goal of AuScope VLBI project is to tie Australian geodesy into the international Geospatial Reference Frame and to the International Celestial Reference Frame. In the year 2014, AuScope is scheduled to observe 178 days, as a stand-alone array or as a part of a global geodetic VLBI network. This number is to be increased in the coming years. At present, AuScope date transfer methods vary along the path from physical shipment of Mark5 modules from the remote sites to the coordination center at UTas, to rapid e-transfer from the high-capacity online data storage to the correlator. Many people are involved in this process at different steps. However, the planned upgrade to the next generation broadband receiver system as a part of VGOS project will dramatically increase the recorded data rate in the near future. Taking into account that two of the AuScope antennas are places in the remote locations, these plans create an increasing pressure on the data transfer infrastructure and require optimization of the data flow logistics. New technical solutions are needed, that will unable e-transfer along the whole data path from an antenna to the correlator. An upgrade of local infrastructure will be essential: planned updates are fast optical fiber network connection to the remote stations and implementation of high-speed data buffers at all sites. The experience of AuScope VLBI array may help to find solutions for the data transport problems that will be shortly faced by the global geodetic VLBI network in connection with implementation of the VGOS project.

There are 54 oral presentations.

Name Title
Aben, Guido Title:
Abraham, Zulema Title: mm VLBI with ALMA
LLAMA (Large Latin American Millimeter Array) is a joint initiative involving Argentina and Brazil, aimed initially to the installation of one submillimeter radiotelescope in the Argentinian Andes, at an altitude of about 4800 m and at a distance of about 150 km from ALMA, to be used as single dish and VLBI antenna. The project is already funded; the 12 m antenna, similar to ALMA but with two Nasmyth cabins similar to APEX, was ordered to Vertex, and will be delivered by the end of 2016.The receivers will also be ALMA receivers and will include 6 bands, band 1 (40 GHz), band 3 (100 GHz), band 5, (186 GHz), band 6 (230 GHz), band 7 (345 GHz), and and 9 (675 GHz). These frequency bands will allow us to perform VLBI observations with ALMA and APEX, and participate of the European mm VLBI project and the American "Event Horizon Telescope".
Alef, Walter Title: DBBC3 Development Status
G. Tuccari, W. Alef, A. Bertarini, S. Buttaccio, S. Casey, M. Lindqvist,
P.R. Platania, A. Felke, M. Wunderlich
The Radionet3 JRA project 'DBBC3' is entering the last period of development. The first units of the 4 GHz bandwidth samplers have been developed as well as the Core3 processing boards. The basic operating
modes have been successfully tested and the construction of more units is under way. The system is described together with the expected performance, and an overview of the implementation is presented for data-rates of 32 and 64 Gbps with two examples of their application: a) astronomical for EVN and for the millimeter VLBI network with the EHT (Event Horizon Telescope), and b) geodetic for the VGOS broadband network. The latest measurements and progress will be shown.
Alef (instead of GinoTuccari), Walter Title: AntArr Project: a DBBC3 synthesis array
Abstract: G. Tuccari, W. Alef, S. Buttaccio, M. Wunderlich
A project with an alternative application of the DBBC3 is presented.
A set of antennas operating at frequencies lower than 1 GHz are combined into an array. The individual antenna is covering the broadband frequency range from 10 MHz to 1000 MHz. Moreover dedicated elements can be added to reach still lower frequencies to virtually observe the range down to kHz frequencies. The DBBC3 manages the array operations in a selected portion of the band and synthesize a beam with an innovative approach. The final product of the array is a single station standard VLBI data set. Some antenna and array prototypes have been realized and are under test in two locations.
AMY-KLEIN, Anne Title: Progress towards a metrological fiber wide-area network
In the frame of the REFIMEVE+ project, aiming at disseminating an optical frequency standard to more than 20 laboratories in France, we present the progress made towards a metrological fibre wide-area network.
We are currently developing an optical link of 1500 km using the fibers of the French National Research and Education Network. Using the so-called dark-channel approach, the ultrastable signal is copropagating with data traffic using wavelength division multiplexing. Due to significant reflections and losses along the fibers, which cannot be compensated with bi-directional amplifiers, we have developed some repeater stations for the metrological signal. These remotely-operated stations amplify and filter the ultrastable signal and compensate for the propagation noise. The link is thus composed of a few cascaded spans. It gives the possibility to increase the noise correction bandwidth, which is proportional to the inverse of the fiber length for each span.
We will report on the first implementation of a four-span cascaded link of 1100 km reaching a relative stability of a few 10-19 after 10000 s averaging time.
We will also address the issue of multiple user distribution. We demonstrate a technique which gives the possibility to extract the ultrastable signal along a main link and either directly distribute it to a user or feed a secondary link.
Alternative transfer methods will also be briefly discussed.
Andrianov, Andrey Title: Radioastron primary data processing. Technology and results.
The “Radioastron" space mission is the unique project of Russian Space Agency (Roscosmos) and Russian Academy of Sciences to investigate the Universe at 4 frequencies from decimeter to mm wavelength by means of implementation the VLBI principles with 'Spectr-R' space vehicle. The correlator for Radioastron mission is a part of an ASL (Astro Space Locator) processing application for Windows environment and fully developed at Astro Space Center (ASC) of Lebedev Physical Institute. In this report the main features and operational procedures of ASC correlator are described with the emphasis on the differences to data-processing in the ground VLBI. The time delay and its derivative estimations are clearly formulated as a principle decision of correlation output for the ground-space interferometer data. Efficiency and parameterization of the correlator operations are illustrated on a number of examples.
Beaudoin, Christopher Title: Report on the new VGOS 12m radio telecope at Kokee Park Geophysical Observatory
Under sponsorship through the NASA Space Geodesy Project (SGP), MIT Haystack Observatory is currently engaged in the development of a VGOS signal chain for the Kokee Park Geophysical Observatory located in Kauai, Hawaii. Similar to other VGOS signal chains developed by Haystack, the frontend is based on the QRFH feed and CITCRYO1-12 LNAs; both components that have been developed by the California Institute of Technology. In the backend subsystem, four new RDBE-G components will provide the necessary VLBI digital signal processing infrastructure while a single Mark6 16Gbps data recorder serves as the centralized VLBI data acquisition unit. In this presentation, other new technical developments in regard to this system will also be presented. These developments include those on the Signal Chain Calibration subsystem that incorporates a new reference cable delay measurement system (CDMS), new tuning capabilities of the Haystack UpDown converter design, and a new IEEE 802.3at Power-over-Ethernet compatible VLBI data acquisition (VDAQ) module targeted for general purpose monitor and control infrastructure needs at the generic VLBI station.
Bezrukov, Ilya Title: Data recording system compatible with VGOS
Ilya Bezrukov, Alexandre Salnikov, Yakovlev Vladislav, Andrey Vylegzhanin

The IAA RAS develops data recording system for observations with radio telescopes of small diameter (13m), which are also intended to realize the goals of the international program VLBI-2010.
Main system goals:

1. Recording of 8 data streams in the VDIF format with data speed 2Gbps from each channel;
2. Realizing data transfer to the Data Processing Center at 10 Gbps transfer speed simultaneously with recording and buffering data;
3. Storing observations data up to 20TB size in generic file structure at set of ZFS pools.
Our presentation describes details of this solution based on high-performance COTS (Commercial off-the-shelf) hardware and open-source software such as FreeBSD operating system with ZFS file system. And first results of the experiments.
Boven, Paul Title: Using VLBI to demonstrate long-haul fiber-optic frequency transfer.
Time transfer over fiber optic links opens two exciting possibilities for VLBI. Firstly, it enables the dissemination of an even higher quality clock to observatories, compared to the performance of the H-masers commonly in use. This can improve the sensitivity in e.g. space-based VLBI and astrometry. It will also do away with the need to perform clock-searches. Secondly, it allows to deliver a frequency reference with suitable stability for VLBI, to telescopes that do not have (the budget for) an H-maser. This would make it possible to expand the VLBI arrays with e.g. telecon dishes converted for radio astronomy. An interesting use case of this is the nascent African VLBI Network.

In the Asterics proposal that we recently submitted, we hope to demonstrate the feasibility of using White Rabbit to transfer the WSRT H-maser signal via fiber optics to the Dwingeloo Radio telescope, and measure fringes between these two telescopes.
Bruni, Gabriele Title: Space VLBI: RadioAstron correlation and activities at MPIfR
RadioAstron is the first space-VLBI mission after VSOP, and is managed by
Astro Space Center (Moscow). Scientific observations started in July 2013,
and it is now entering the second observing period offered to the community.
Since October 2013, MPIfR is carrying out the correlation of RadioAstron
imaging key-science projects. A customized DiFX version, designed to
handle space-vlbi data, has been developed and is currently being
merged with the latest DiFX distributed version (dtrunk).
I will illustrate RadioAstron-related correlation activities in Bonn,
and comment the status of the software development.
Capone, Vincenzo Title: Current status and future plans of GÉANT infrastructure.
The GÉANT infrastructure is the backbone that serves all the scientific communities in Europe for their data movement needs and their access to international research and education networks. Along with the physical infrastructure, on the GEANT network are delivered a portfolio of services aimed to best fit the specific needs of the users, including Authentication and Authorization Infrastructure, end-to-end monitoring and performance, advanced network services (dynamic circuits, L2-L3VPN, MD-VPN).
This talk will provide details on the current infrastructure status, as well as the plans for the future European and international connectivity.
Chen, Zhong Title: e-VLBI progress in China
In my presentation,i will give a brief introduction of recent progresses of e-VLBI activities in Chinese VLBI network, such as real-time e-VLBI applications in ChangÉ-3 mission, and IPv6 demostration as well.
Clark, Eric Title: The JPL DSCC VLBI Processor (DVP)
The JPL Deep Space Communications Complex (DSCC) Very Long Baseline Interferometry (VLBI) Processor (the DVP) is the new-generation wideband data acquisition system for VLBI in the Deep Space Network (DSN). The DVP replaced the venerable MarkIV VLBI Data Acquisition System, with much improved capabilities and results. This presentation provides a qualitative description of the DVP and it's applications, including a functional description of the hardware with comparisons to the old system, the status and function of the VLBI Experiment (VEX) file script-builder software, examples of common configuration types, and plans for accommodating more flexible configurations. Also included are results of DVP products used by JPL PI's for astrometry, as well as EVN and Host-Country VLBI science users.
Coulouarn, Tangui Title:
Deller, Adam Title: International LOFAR: VLBI at 140 MHz
With baselines extending to 1200 km (soon to be 2000 km), International LOFAR offers the first opportunity for imaging at
sub-arcsecond resolution at wavelengths >1 m. It is a sensitive instrument (thermal noise < 0.1 mJy in one hour), has excellent
instrumental stability and offers real-time correlation. International LOFAR possesses numerous advantages compared to previous long baseline interferometers operating at this frequency, but even so, calibration of the differential ionosphere remains a steep challenge. By using standard VLBI techniques, a number of impressive science results have already been obtained, but work is underway to tailor the calibration approach specifically to the challenges faced at these frequencies. In this talk, I will describe International LOFAR and its current calibration practices, before highlighting some of the early science results and discussing the calibration strategies planned for the future.
Emrich, Anders Title: VLBI2010 Front-end
A complete front-end compliant with VLBI2010 requirements will be presented on system level.
Two units have been shipped to end users and discussions are on-going with several potential customers.
The Omnisys VLBI2010 front-end is provided as a standard product but minor modifications may be
considered on a case by case basis.
The VLBI2010 front-end is based on the 11-feed, provided by Gapwaves AB, includes features such as
active temperature control of LNA's, with essential control and housekeeping handled by an embedded
computer with ethernet communication. An amplitude and phase calibration system is also provided as a stand-alone unit.
The results from performance tests will be presented, including sensitivity, aperture efficiency, phase
stability as well as from more functional parameters such as dewar leakage etc. Trec is below 15 K
for most of the frequency band with a few narrow peaks of about 25 K. The peaks are due to both standing waves in the front-end but also standing waves in the test set-up. The aperture efficiency is about 70% for most of the band with a few dips down to 60%, calculated over a 120 degree beamwidth. For the MTM reflector system, the aperture efficiency will be higher, according to Grasp simulation. With an active temperature control of the LNA's, these are stable within <10 mK with an ambient temperature change of 15 K and phase drifts are a fraction of a degree.
FUKUZAKI, Yoshihiro Title: New receiving system for VGOS Station in Japan
The Geospatial Information Authority of Japan (GSI) has started a new project for constructing VGOS station in Japan. The construction of the antenna (radio telescope) has been complete and the necessary equipments (Front-end, Back-end, H-maser, and so on) have also been delivered.
New receiving systems have been developed for new antenna. In order to achieve broadband receiving, Eleven feed and Quadruple-Ridged Flared Horn (QRFH) systems are under development. In addition, tri-band feed system has been developed and installed on the new antenna for the compatibility with the legacy S/X band receiving.
In the presentation, the development of the receiving systems will be introduced, and the preliminary result of the measurement of the receiving performance will be briefly reported.
Grange, Yan Title: Network challenges for large interferometric arrays Lofar experience and outlook for the SKA
Hargreaves, Jonathan Title: The JIVE UniBoard Correlator (JUC) firmware
JIVE has developed a field programmable gate array (FPGA) correlator based on the UniBoard hardware. This talk will describe the current and potential future capabilities of the JIVE UniBoard Correlator
Heinselman, Craig Title: The EISCAT_3D phased-array radar for research into the arctic ionosphere
EISCAT_3D is a multi-static phased array radar system dedicated to observations of the Earth’s polar atmosphere in order to study how the atmosphere is coupled to space. The incoherent scatter technique used is based on analysing the signal, which is backscattered from free electrons that are coupled to the ions by ion-acoustic and other plasma waves. The frequency spectrum of the backscattered radio waves contains information on the characteristics of the atmospheric electron, ion and neutral densities and line-of-sight ion velocity and the science return increases with the bandwidth of the back-scattered signal that can be analysed. The time lag after which the back-scattered signal is detected provides altitude information. Incoherent scatter probes the atmosphere over a wide range of altitude (roughly 60 to 1200 km expected for the standard data products).

From a core site, EISCAT_3D transmits pulsed high-power radio waves in a 5 MHz interval around the centre frequency of 233 MHz and measures from multiple sites the time profile of the back-scattered signal within a bandwidth up to 30 MHz. The system consists of up to 10000 antennas, which at the core cite have transmit/receive capability. Each array simultaneously forms up 100 beams. The produced raw data exceed the volume of data from the present EISCAT dish antennas by several orders of magnitude. Data will be combined and processed in real-time, requiring the provision of significant computing and data transport capabilities from relatively remote locations. Networking and long-term data storage solutions are developed with the national e-infrastructures and network providers for research in the Nordic region. Potential technical synergies with radio astronomy lie in e.g. control of arrays and time/clock synchronization, phased array beam-forming and real-time data transfer, though in case of EISCAT_3D this is primarily on-site.

The new radar system will be located on the northern Scandinavian Peninsula with cites in Norway, Sweden and Finland. The European Strategy Forum on Research Infrastructures (ESFRI) selected EISCAT_3D for inclusion in the Roadmap 2008 for Large-Scale European Research Infrastructures and the project is currently in its Preparatory Phase funded within FP7. This presentation is prepared for the EISCAT_3D Project together with Assar Westman and Ingemar Häggström.
Jansweijer, Peter Title: Implementing White Rabbit in your design
Abstract: Distribution of time throughout large infrastructures has been an issue for many decades. In recent years work has been done by the White Rabbit developers community to provide a fully deterministic Ethernet-based network for general purpose data transfer and synchronization at sub-nanosecond accuracy and picoseconds precision for large distributed systems. White Rabbit enhances the Precision Time Protocol (PTP) and is currently the most accurate PTP implementation.
White Rabbit has got the attention of many people, and today the number of users and applications in different fields, worldwide, is increasing.
Following a brief overview of White Rabbit, this talk will explain how to make your own hardware White Rabbit capable. It will mainly focus on the technical aspects of such an implementation.
Jung, Taehyun Jung Title: mm-VLBI phase correction with the KVN and it's recent updates
The Korean VLBI Network (KVN) has been conducting simultaneous multi-frequency VLBI observations at 22/43/86/129 GHz. By applying band-to-band phase transfer, tropospheric phase fluctuations can be effectively calibrated using a multi-frequency receiving system. In this talk, we report the results of phase correction for mm-VLBI observations.
Keimpema, Aard Title: Phasing up the EVN using the SFXC software correlator
Recently a phased array mode has been developed for SFXC, the EVN software
correlator. In this phased array mode the signals from all stations in an
experiment are summed coherently rather than being correlated.
The main applications for this mode are time domain pulsar studies such
as pulsar timing and pulsar searching experiments.

The sensitivity of an accurately phased array scales linearly with the
total collecting area in the array. For the EVN the total collecting
area approaches that of the illuminated area of the Arecibo dish.

The output from the phased array mode can optionally be coherently
de-dispersed before it is written to disk. The output data is stored in either
PSRFITS or filterbank format which are widely supported by pulsar toolkits
such as SIGPROC and PRESTO.
Kettenis, Mark Title: VEX2 Schedule Format Standard
The VEX2 specification committee (Walter Brisken, Ed Himwich, Mark Kettenis, Cormac Reynolds, and Alan Whitney) is nearing the end of development of
the new standard. This talk will cover the rationale for the approach
used, the major features of VEX2, and the transition plan for moving
from VEX1 to VEX2 for operations. Once the transition is complete, the
committee will continue to operate at a lower level of activity to
address any issues that arise.
Koelemeij, Jeroen Title: Methods for data, time and ultrastable frequency transfer through long-haul fiber-optic links
Tightly synchronized time and frequency references are essential for astronomical observations via distributed antenna arrays, such as VLBI. Typical synchronization solutions make use of GPS radio signals and/or stand-alone atomic clocks like hydrogen masers. Recently, several research groups have developed and demonstrated fiber-optic methods for time and frequency distribution over long distances. The unsurpassed stability and accuracy afforded by these methods opens up the perspective of future fiber-optic infrastructure providing high-capacity telecommunication along with atomic clock signals of extremely high quality. A promising approach into this direction is the White Rabbit (WR) protocol developed at CERN, which combines Gigabit Ethernet with time transfer with 1 nanosecond uncertainty over distances up to 10 km. In this talk I will describe a WR link between the cities of Amsterdam and Delft in the Netherlands, aimed at sub-nanosecond time transfer over 2×137 km of installed optical fiber. The link employs bidirectional semiconductor optical amplifiers, and the outcome of a performance comparison with erbium-doped fiber amplifiers is reported. Finally, I will discuss the possibility of implementing WR for (e)VLBI observations in existing dense-wavelength-division-multiplexed networks.
Maat, Peter Title: The LOFAR Clock System
The design and performance of the LOFAR Clock System will be presented
Mishin, Vladimir Title: VGOS GPU Based Software Correlator Design
Igor Surkis, Voytsekh Ken, Yana Kurdubova, Vladimir Mishin, Dmitry Pavlov, Nadezhda Sokolova, Violet Shantyr, Vladimir Zimovsky

The VGOS software correlator is being designed in the IAA RAS. The correlator will be capable to process data at maximum rate of 16 Gb/s from each station and up to 6 stations simultaneously.

The main idea of FX correlator design is using of Graphical Processing Units (GPUs) for Fourier transformation, spectra multiplication and other complex operations. The correlator hardware is based on hybrid blade server cluster. Each of 40 blade servers holds two CPU and two Kepler K20x GPU. Usage of GPUs allows to reduce amount of blade servers required for such high performance correlator.

At present correlator hardware is almost assembled. To test correlator prototype special single baseline test experiment was carried out with following setup: single frequency channel of 512 MHz bandwidth.

Start of VLBI data processing with the new correlator is planned in early 2015.
Nosov, Evgeny Title: Current State of Russian VLBI Broadband Acquisition System
Broadband acquisition system (BRAS) was developed in Institute of Applied Astronomy (IAA RAS) for new two-element radio interferometer. It was shipped to Badary and Zelenchukskaya observatories and was temporary installed on RT-32 antennas for testing. Test observations were successfully performed and the results are presented. Currently the system is ready for use on new 13-meters antennas.
Oyama, Tomoaki Title: A progress report on the development and performance of OCTAVE-DAS and Correlator System
The VLBI observing system (OCTAVE-DAS) and Correlator system has been developed on the basis of the VLBI Standard Hardware Interface (VSI-H) and the VLBI Data Interchange Format (VDIF) specifications. It consists of 1) high speed >8-Gsps 3-bit RF direct analog-to-digital converter (OCTAD) enabling us to acquire not only wide intermediate frequency but also radio frequency up to 50 GHz and have digital base-band converter (DBBC) functions for the VLBI Global Observing System (VGOS), 2) Converters (OCTAVIA and OCTAVIA2) between one 10 GigE port and four 2 giga bites per second (Gbps) input and output ports conformable to VSI-H, and 3) Recorders (OCTADISK and OCTADISK2-VSREC) at a rate of 4.5 Gbps and above 8 Gbps and 4) Gbit realtime hardware XF-type correlators (OCTACOR) and software FX-type correlator systems (OCTACOR2) based on the GICO3. These are connected via 10 GigE networks with VDIF and VSI specifications. These components have been used for the VLBI Exploration of Radio Astrometry (VERA), the Japanese VLBI Network (JVN) and Korea-Japan Joint VLBI Correlator (KJJVC). We will introduce the OCTAVE System and present the results of test broad-band(>8 Gbps) VLBI observations using these systems.
Pantaleev, Miroslav Title: Current development towards wide bandwidth front-ends for VLBI
The talk will present the current development in two areas, both aiming to extend the bandwidth for VLBI observations.

The first area is the ongoing work within the FP7 RadioNet project with contribution from MPIfR, IAF-Fraunhofer, ASTRON and Onsala Observatory. The goal of the particular work package called DIVA Task 1 is to develop 1.5-5.2GHz bandwidth front-end for VLBI. The talk will present details about the LNA, feed development and system integration.

The second area is the ongoing design work for upgrade of the Onsala 20m antenna with receiver for the 4-12.25GHz frequency range. The system will be used in two different modes referred as “Astro-VLBI” and “Geo-VLBI”. In the first mode the system will provide continuous coverage over the 4-12.25GHz frequency range. In the second mode the system is used with tertiary and will cover the S-band and 8-12.25GHz band. The talk will present details on feed-reflector system performance, expected system noise and system integration.
Paragi, Zsolt Title: VLBI in the SKA era
The mid-frequency components of the Square Kilometre Array (SKA-MID,
SKA-SUR) will form a number of tied-array beams for VLBI operations,
to work together with radio telescopes from other VLBI networks at
~GHz frequencies. The full SKA will have very long baselines and will
operate up to ~15 GHz. The talk will describe the main motivations
for and the realization of SKA-VLBI.
Phillips, Chris Title:
Pogrebenko, Sergei Title: Analysis of factors influencing phase noise of VLBI telescopes
Influence of the stations clock Allan variance on the phase noise of VLBI antennas was disentangled from other factors like interplanetary and ionospheric plasma and troposphere using observations of ESA Venus Express spacecraft with several EVN telescopes and ultra-high spectral resolution technique.
Quick, Jonathan Title: VLBI in Africa
Although Africa has only one operational VLBI station (HartebeesthoeK) to date, there are several plans which should add further capacity in the not too distant future. An update on several of these, namely MeerKAT and the AVN, and of future developments at HartRAO will be presented.
Romney, Jonathan Title: Re-Establishing Instrumental Compatibility for HSA and Global VLBI
The VLBA Sensitivity Upgrade project is now complete within the VLBA, ending a 7-year period of development, integration, and extensive

In the High Sensitivity Array (HSA), testing of the GBT and Effelsberg implementations of the same instrumentation, and of the equivalent modes developed at the phased VLA ("Y27"), are all in final stages. Final implementation and testing are currently pending at Arecibo.

Joint VLBA+EVN observations in the "Global cm Network" have already resumed, although some uncertainties remain about compatibility between the VLBA's RDBE and the DBBC now widely used in the EVN. Similarly, observations in the Global 3-mm VLBI array are being planned using mixed instrumentation. For both these global arrays, a reconsideration of the old standard LO frequencies may be warranted to fully exploit new instrumentation, in both the new backend systems, and new receivers.

I will present the capabilities of the new VLBA systems, and the compatible global modes currently well established, but also hope to start a discussion among interested meeting participants on how best to re-establish the old global standards.
Rottmann, Helge Title: The ALMA Phasing Project - Design and Status
Phased ALMA together with a recording data-rate of 64 Gbps will boost the sensitivity of the Event Horizon Telescope, such that the immediate vicinity of the central Black Holes of our and nearby galaxies will become observable by VLBI. We will report on the technical design and the status of the project.
Rudnitskiy, Alexey Title: “Millimetron” mission: space VLBI opportunities and capabilities
“Millimetron” is a 10-meter cooled FIR and sub-mm space observatory. It was approved by Russian Space Agency and is a next project of Astro Space Center of Lebedev Physical Institute after “Radioastron” mission. Its parameters and capabilities will provide very high sensitivity for single-dish and the highest angular resolution for VLBI operational modes. In this report details on the VLBI mode of this challenging mission are presented.
Ruszczyk, Chester Title: Mark 6 - Present Status and Future Plans
The Mark 6 system is currently being deployed at: (1) IVS stations for VGOS observations, (2) some stations in the EVN and other astronomy-VLBI stations, (2) ALMA, for the Alma Phasing Project, and (3) the telescopes of Event Horizon Telescope [not all mutually exclusive, of course]. For VGOS, the Mark 6 supports planned 30-second scans at 8Gbps to a single 8-disk module; for astronomy observations, 16 Gbps continuous recording to four 8-disk modules is supported. We will describe the current state of the present Mark 6 software suite, including new capabilities recently introduced in version 1.1. We will also discuss the integration of Mark 6 into software correlator systems and the planned road map of future Mark 6 capabilities.
Salmon, David Title:
Schnatz, Harald Title: Towards international optical clock comparisons using optical fibers: current status and prospects
By Harald Schnatz and Gesine Grosche

Already 1985 Bjerhammar suggested using the gravitational red-shift of clock frequencies to define the geoid: “The relativistic geoid is the surface nearest to mean sea level on which precise clocks run with the same speed.” However, in 1985 the realization of this idea was a very distant prospect due to the performance of operational microwave clocks. Optical clocks are only now starting to reach the required accuracy for a height resolution at the cm-level. The on-going development of clocks based on optical transitions during the past three decades culminates in today’s availability of optical clocks with orders of magnitude lower instability and uncertainty.
Synchronizing clocks over long distances or transmitting a timing or frequency signal without degrading its performance to the location where it is required will foster novel applications in relativistic geodesy or tests of fundamental physics. E.g. with transportable optical atomic clocks synchronized via fiber optical cable the local gravitational field of the Earth can be mapped on small scale and such a survey will complement satellite mission like GOCE or GRACE.
During the last decade several research groups have explored optical frequency transfer over long-haul fibre links and have demonstrated that such links allow frequency comparisons to be performed at a much higher level of accuracy and stability than that mediated by conventional satellite links. Ultra precise optical atomic clocks in combination with optical links measure geopotential differences between the locations of the clocks providing the most direct possible local measurement of the geoid.
This talk highlights recent achievements of optical frequency transfer and discusses some applications and future prospects.
Shatskaya, Marina Title: Data Processing Center for Space VLBI Projects Implementation.
The issues of implementation and operation of the Data Processing Center for the Radioastron Project as well as the problem of implementation of the Data Center for Millimetron project are considered.
The problems of the organization of the engineering infrastructure of the center are shown. The problems of improving productivity and increasing the volume of the storage of information in the collection and processing of high-speed digital data streams are discussed. Indicators of efficiency in many ways provided the rational organization of the structure of the computer and network complex, communication, storage and processing of large volumes of information. Also the problems of high-speed data required for the exchange of large volumes of astronomical observations are considered.
Spencer, Ralph Title: Phase Stable Interferometers at Jodrell Bank
I will talk about the development of phase stable long baseline radio interferometers at Jodrell Bank, starting with the early work on the MkI-MkIII radio linked interferometer,then MERLIN and more recently the fibre optic linked e-MERLIN. They all rely on the reciprocity property of electromagnetic waves, where 'go and return' signals are used to compensate for changes in the link path to the remote telescope. Comments on how such systems can be used for SKA will also be made.
Stagni, Matteo Title: The Italian VLBI network and the validation of SRT: tests and perspectives
Since the installation of the DiFX software correlator and storage facilities in IRA headquarters in Bologna there has been a series of both national and international enquires and tests to prove the effectiveness of an Italian interferometer involving the antennas of Medicina, Noto and SRT. A series of test cases regarding in particular the placement in operation of the dBBC and Fila 10G hardware will be presented to discuss the strengths and downsides of handling equipment that could improve correlation processes and advance the way data is recorded and stored. Data transfers, formats and correlation issues will be discussed in detail to shed a light on the perspectives of a more efficient process management that would eventually lead to effective science results.
Stranden, Helge Title: VLBI station in Ny-Ålesund, Svalbard soon available through subsea fibreoptic connection
Takefuji, Kazuhiro Title: The first light and fringe with broadband system at NICT
We have been developing the broadband system ( Gala-V ) on the Kashima 34 meter antenna and two compact antennas (1.5 meter). In December in 2013, we curried out the first observation of 6 GHz to the radio sources of 3C273B and W3OH with Gala-V, after 2 Gbps digitized data correlation, we successfully obtained the first fringe both continuum and maser emission between 34 meter and the compact antenna.
Now we have a plan of dual band 6 GHz and 12 GHz observation of methanol maser emission. We will report the progress of our development and observation.
Thostrup Jensen, Henrik Title: Status for NORDUnet network and NSI service
Status for NORDUnet network and NSI service
Tsaruk, Alexey Title: Methods of transfer ultra-stable frequencies to radiotelescope.
Frequency standards using for VLBI have to be extremely phase and frequency stable for coherence losses minimize. Feature of the new radiotelescopes RT13 of VLBI complex "Quasar-KVO" is that the recording and data conversion equipment is located in the elevation cabin of radiotelescope. This requires the transfer of a reference signal to the radiotelescope without insertion phase distortion. Different methods of the reference frequency transmission to the radiotelescope are investigated by the Institute of Applied Astronomy. The experimental results of investigated for transmitting reference signals over RF cable and fiber optic cable are presented.
Verkouter, Harro Title: Herding FPGAs - the UniBoard correlator control system
At JIVE the next generation FPGA based UniBoard correlator is being developed. Being a 'hardware' correlator, it does require some tending to; it does not run itself. In fact, it requires a distributed system to properly operate.

Distributed systems are inherently difficult to write, so after careful consideration we decided to write a control system from scratch, even with only two FTEs available. As it turns out, with the right programming language, this can easily be done.

The Erlang programming language and runtime system was explicitly designed and built to facilitate building, amongst others, reliable, transparent, distributed, soft-realtime monitoring and control systems.

In this talk I would like to elaborate on the Erlang programming language and what it can do for building a (massively) distributed control system.
Wallin, Anders Title: Time Transfer in a Wide Area White Rabbit Network
Time transfer using the White Rabbit Precision Time Protocol (WR-PTP) is demonstrated over a 1000 km optical fiber link using a dedicated channel in the Finnish University Network (FUNET). The maximum instability of time transfer, determined by independent GPS-PPP measurements, was +/-2 ns over a 100 day period. We discuss the performance and limitations of WR-PTP time&frequency transfer in a public NREN.
Weston, Stuart Title: Expanding New Zealand VLBI Capability And The 30m Dish
We describe our current VLBI activities with the 12m dish; but also with the conversion of a former 100-foot (30-m) telecommunication antenna in New Zealand into a radio telescope show the future capabilities. Provide a brief of the specifications of the 30m and describe the telescope control system, telescope networking for VLBI, and telescope maintenance. Plans for RF, front-end and back-end developments based on radio astronomical and VLBI priorities will be outlined.
Xu, Zhijun Title: The Development of Hardware Correlator in SHAO
The hardware correlator have been used in Chinese Chang'E 1,2 and 3 missions. Recently, a hardware correlator based on uniboard has been developed. This article presents the development of hardware correlator at SHAO and some result of the recent Chang'E mission.
Zhang, Juan Title: The Software Correlator Status of Chinese VLBI Network
The paper will introduce the CVN software correlator structure and its current situation. CVN software correlator developed by SHAO has been used in the Chinese lunar exploration projects from CE-1 to CE-3. It is also be used in Crustal Movement Observation Network of China. This software correlator is developed based on language C, MPI and OpenMP, it can work in real-time mode (based on e-VLBI technology) and post-process mode. Besides the basic correlation function, it also has the features of fast fringe search, PCAL extraction, visibility visualization and monitoring, FITS and CVN format output.
Zhang, Xiuzhong Title: The Development of Broadband VLBI Technologies in SHAO
Since several years developing, three groups in SHAO work on the era of broadband VLBI technologies. The progress of developing of Broadband receiver system, data acquisition system will be reported in this paper. The equipment will be prepared for SHAO VGOS station in future.
Zheng, Weimin Title: CVN in Chang’e-3 lunar exploration mission
Chang’E 3 is the first Chinese lunar probe landed on the moon and releasing Yutu rover. The real-time and accuracy requirement to Chinese VLBI Network (CVN) is much higher than the previous. To support this mission, CVN made important upgrades; the new VLBI center and the 65-m Tianma antenna were built in Sheshan of Shanghai suburb. The real-time and high-accuracy VLBI data greatly supported CE-3 mission. To get the high-precision delay results, CVN used the X-band real-time ΔDOR (Differential One-way Range) technique to track the lander. During the circumlunar orbit, VLBI delay residuals after orbit determination was ~0.5ns (5-second integration). Absolute position accuracy of lander using VLBI group delay is approximately 100 meters. The e-VLBI technique reduced the observable turnover time to 15~45 seconds. After landing, using the same beam VLBI observation mode, the phase delay and phase reference mapping methods were used to determine the relative position of Yutu with the accuracy of 1 meter.