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European VLBI
Network Newsletter Number 22 January 2009 |
The EVN started 2009, International Year of Astronomy (IYA), with a very
nice event: a very successful e-EVN observation with 17 radiotelescopes
participating from five continents. The demo, which was presented to the general
public and to the press during the opening ceremony of the IYA in
indeed a very good illustration of the e-EVN potential, as well as some other achievements
in e-VLBI, is indeed described more in detail in this Newsletter. We should
congratulate the EXPReS team for their success.
The 9th EVN symposium "The role of VLBI in the Golden Age for Radio
Astronomy" which was exemplarly organized by our
IRA (INAF) colleagues in
countries attended the conference and presented extremely interesting VLBI results.
Such results will surely act as an important catalyst inspiring further research with the EVN. It is a pleasure to
thank the excellent work made by the local organizers and the exciting talks
and posters presented by the numerous attendants to the meeting.
Some new very interesting scientific results obtained at the EVN are highlighted
in this issue, such as the observations of methanol in a massive star forming
region in DR21, and the use of such methanol masers in the determination of the
size and mass of our Galaxy. Among the many works on extragalactic research, we
highlight the EVN observations of two Ultra Luminous Infrared Galaxies (ULIRGs) and those of a sample of 27 Seyfert
galaxies.
The EVN CBD met in
I send my best wishes to all VLBI friends (in particular to all EVN
members and users) in this International Year of the Astronomy
!
Rafael Bachiller (OAN,
(This text is
also available on the web at http://www.ira.inaf.it/evn_doc/call.txt)
Observing proposals are invited for the EVN, a
VLBI network of radio telescopes spread throughout
The observations may be conducted with disk
recording (standard EVN) or in real-time (e-VLBI).
The EVN is open to all astronomers. Use of
the Network by astronomers not specialized in the VLBI technique is encouraged.
The Joint Institute for VLBI in Europe (JIVE)
can provide support and advice on project preparation, scheduling, correlation
and analysis. See EVN User Support at http://www.jive.nl.
2009
Session 2 |
May
28 – Jun 18 |
18/21cm,
6cm, 5cm, ... |
2009
Session 3 |
Oct
22 – Nov 12 |
18/21cm,
6cm, 7mm, … |
Proposals received by 1 February 2009 will be
considered for scheduling in Session 2, 2009 or later. Finalization of the planned
observing wavelengths will depend on proposal pressure. Other wavelengths which
may be scheduled in 2009 are 90cm, 50cm, 30cm, 1.3cm, and S/X.
2009
Feb 10 – Feb 11 (start at 13 UTC) 2009
Mar 24 – Mar 25 (start at 13 UTC) 2009
Apr 21 – Apr 22 (start at 13 UTC) 2009
May 19 – May 20 (start at 13 UTC) |
18/21cm,
6cm, 5cm, 1.3cm 18/21cm,
6cm, 5cm, 1.3cm 18/21cm,
6cm, 5cm, 1.3cm 18/21cm,
6cm, 5cm, 1.3cm |
There are three e-VLBI observation classes: general
e-VLBI proposals; triggered e-VLBI proposals; short observations. General and
triggered e-VLBI proposals must be submitted by the February 1 deadline to be
considered for scheduling in the above e-VLBI sessions starting from March
2009.
Requests for short observations may be
submitted up to three weeks prior to any e-VLBI session.
Continuum and spectral line observations can
be carried out.
See http://www.ira.inaf.it/evn_doc/guidelines.html for details
concerning the e-VLBI observation classes and the observing modes.
·
·
Yebes 40-m may join the regular EVN sessions at 1.3cm
and at S/X from March 2009, and may be available at 6 and 5cm from Session II
on.
·
MERLIN is normally available for joint EVN+MERLIN
observations in all standard sessions, for any EVN wavelengths which MERLIN
supports (18/21cm, 6/5cm, 1.3cm). However, due to the e-MERLIN construction
only an incomplete MERLIN array will be available in 2009 due to limited
resources. For updated information please consult the web at http://www.merlin.ac.uk//evn+merlin.html.
Large EVN projects
Most proposals request 12-48hrs observing
time. The EVN Program Committee (PC) also encourages larger projects (>48
hrs); these will be subject to more detailed scrutiny, and the EVN PC may, in
some cases, attach conditions on the release of the data.
The on-line proposal
submission tool Northstar now replaces the
old Latex-email way of submission for all EVN and Global proposals; EMAIL
PROPOSAL SUBMISSION IS NOT POSSIBLE ANYMORE. Global proposals will be forwarded
to NRAO automatically and do not need to be submitted to NRAO separately.
To use Northstar,
people should register (at http://proposal.jive.nl, only for the
first proposal submission), enter the information about the
investigators and the technical specifications of the proposed observations (equivalent
to that previously in the coversheet) using the on-line forms, and upload a
scientific justification in pdf or ps format. The scientific justification should be limited
to 2 pages in length. Up to 2 additional pages with diagrams may be included.
The deadline for submission is 23:59:59 UTC on 1 February 2009.
Further information on Global VLBI, EVN+MERLIN
and e-VLBI observations, and guidelines for proposal submission are available
at: http://www.ira.inaf.it/evn_doc/guidelines.html
The EVN User Guide (http://www.evlbi.org/user_guide/user_guide.html) describes the
network and provides general information on its capabilities.
The current antenna capabilities can be found
in the status tables. For the standard EVN see http://www.evlbi.org/user_guide/EVNstatus.txt. For the e-VLBI
array see http://www.evlbi.org/evlbi/e-vlbi_status.html
The On-line VLBI catalogue (http://db.ira.inaf.it/evn/) lists sources
observed by the EVN and Global VLBI.
Tiziana Venturi - Chairperson of the EVN
Program Committee
In order to test the reliability of this disc interpretation, the 6.7-GHz
methanol masers in DR21(OH)N were re-observed using
the European VLBI Network at the same spectral resolution but with an angular
resolution ten times greater than that of MERLIN (5 mas
compared with 50 mas). In doing this, it was possible
to verify (or otherwise) the velocity curve of the maser disc.
Observations:
DR21(OH)N was observed at 6.7-GHz using the European VLBI Network. The total
observing bandwidth of 0.5 MHz was split into 512 spectral channels, giving a
velocity resolution of 0.04 km/s. A total of 238 minutes were spent on the
target source, leading to an RMS noise level of 60 mJy/beam.
Results:
The positions of 6.7-GHz methanol maser emission centroids
in each spectral channel are shown in Figure
Summary & Future Work:
The images of DR21(OH)N made with the EVN show methanol masers at the same
position, and with a very similar position-velocity curve, to the results of
Harvey-Smith et al. (2008) using MERLIN. This close agreement confirms the
existence of a rotating disc of molecular gas at the position of the ERO3
massive protostar. As an extension of this work, a survey is currently being
carried out of the Cygnus X molecular cloud towards very young massive
protostars that show signatures of outflow in SiO. It
is hoped that this survey will allow a statistical determination of the
frequency with which massive stars form in the 'disc-outflow' scheme.
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Figure 1: Comparison of the positions of 6.7-GHz methanol maser centroids, observed with the EVN (crosses: this paper) and
MERLIN (circles: Harvey-Smith et al. 2008). The maps were registered by
aligning the brightest spectral channel in each data set. |
Figure 2: A comparison of the position-velocity plots of the EVN
(crosses: this paper) and MERLIN (circles: Harvey-Smith et al. 2008) data in DR21(OH)N, showing the general agreement between the two
velocity curves. |
Lisa Harvey-Smith (USYD,
How does our Galaxy look like? What is its
size and mass? The key to these fundamental questions are reliable distances
on a Galactic scale. The most trustworthy and unbiased method is the
trigonometric parallax. Using VLBI techniques for measuring parallaxes of
molecular masers one can obtain very high accuracies up to 10 micro arc
seconds, which translates to an accuracy of better than 10% up to distances
of 10 kpc. This is a 100 fold improvement on Hipparcos, the first dedicated astrometry satellite at optical
wavelengths. ESA's GAIA mission, a future
astrometry satellite to be launched in 2012, will measure parallaxes and
proper motions of one billion stars in the Milky Way with comparable
accuracies. However, the regions traced by the molecular masers are usually
highly obscured by dust and not visible in the optical. Thus the radio
parallaxes will complement the GAIA results in regions like the spiral arms
or the inner Galaxy. The 6.7 GHz transition is exclusively
associated with massive star forming regions, is very strong, stable, and has
small internal motions. Furthermore, it is found several hundred times all
over the Milky Way. This makes the 6.7 GHz transitions an ideal tool for
measuring accurate distances and proper motions. In a pilot study to investigate the
feasibility of high precision astrometry of 6.7 GHz methanol masers with the
EVN we observed eight target sources in five epochs between June 2006 and
March 2008. This resulted, for the first time, in measured parallaxes of 6.7
GHz methanol masers. Preliminary parallax signatures and distance results for
ON1 and L1287 are shown in the figure below. Both regions are well studied
massive star formation regions, where our results solve the distance
uncertainties, give insights to the kinematics of these regions and allow the
determination of important physical properties such as length scales, masses
and luminosities. In our preliminary results we reach accuracies up to 51
micro arc seconds, which still have the potential to be improved. This means
that the 6.7 GHz methanol masers can be successfully added as a new tool to
the astrometric tool bag. |
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Caption: A face on image of our Galaxy
(credit: R. Hurt (SSC), JPL-Caltech, NASA) overlaid with the star forming regions
hosting the methanol masers observed by us placed according to their
kinematic distances (magenta squares). The yellow square marks the position
of the Sun. The top left and right insets show the parallax signatures in
Right Ascension (solid line) and declination (dashed line) of ON1 and L1287,
respectively. |
Kazi L.J. Rygl (1), Andreas Brunthaler (1), Karl M.
Menten (1), Mark J. Reid (2), Huib Jan van Langevelde (3,4),
1 MPIfR,
2 Harvard-Smithsonian CfA, 3 JIVE,
4 Sterrewacht
IRAS 23365+3604 and IRAS 07251-0248 are two
of the most distant Ultra Luminous Infrared Galaxies (ULIRG; L_FIR > 10^12
L_sun) in the local Universe, with expected CCSN
rates of 5 and 8 SN/yr, respectively. Using quasi-simultaneous observations
with the EVN at 6 and The results of this work are available at http://arxiv.org/abs/0812.0760 and will be
published in the proceedings for The 9th European VLBI Network Symposium on
The role of VLBI in the Golden Age for Radio Astronomy and EVN Users Meeting.
An extended version is in preparation.
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Active Galactic Nuclei (AGN) are traditionally
divided in radio quiet (RQ) and radio loud (RL). While the latter are common
targets of VLBI observations, only a few of the most nearby RQ sources have
been imaged at milliarcsecond resolution.
In order to achieve a comprehensive understanding of the broadband properties of
RQ AGN (and eventually clarify the nature of the RL/RQ differences), we are studying
a distance-limited sample of 27 Seyfert galaxies. Literature
VLA observations have revealed radio cores at the milliJansky
level in these galaxies and we have selected 6 targets to be observed with the
EVN at 1.6 and 5 GHz in 2007 session 2 and 2008 session 1.
Despite unfavourable observing conditions, we have been successful in revealing
compact components in 4 out of the 6 sources: NGC 4051, NGC 4388, NGC 4501, and
NGC 5033, three Seyfert galaxies of type 2 (or 1.9)
and one of type 1.5. The flux densities are barely at the milliJansky
level, but thanks to the great sensitivity provided by the 1 Gbps recording rate, these are all solid detections. Further analysis and
accurate review of transfer solution from our phase calibrators will hopefully
improve our images, e.g. confirming the possible jet-like feature visible in
NGC 4388 (see figure).
The results have been presented at the last EVN Symposium in
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Images of NGC 4388 - Top left: An SDSS
optical image of this beautiful Sy2 galaxy; bottom right: our (preliminary)
EVN phase referenced map of its central region. The participating telescopes
are Jb, Wb, Ef, On, Mc, Tr, Sh, |
Marcello
Giroletti (INAF/IRA, Bologna) & Francesca Panessa (INAF/IASF, Rome)
The 9th
European VLBI Network Symposium on "The role of VLBI in the Golden Age for
Radio Astronomy" reached its end on Friday 26 September 2008 at 16:40, as
planned, after the closing speech by Rafael Bachiller,
Chairman of the EVN Consortium Board of Directors.
The
Symposium, sponsored by the Istituto Nazionale di Astrofisica (INAF), RadioNet,
and the Istituto di Radioastronomia, was held in the Conference Centre of the
"Area della Ricerca del Consiglio Nazionale delle Ricerche", Bologna.
More than 140 participants, from 20 different countries (10 of which
non-European) came to
The EVN
Users Meeting was held at the Visitor Centre of the Medicina Radio Observatory.
Participants had a guided tour of the two radio telescopes of the Observatory,
the Northern Cross and the 32-m dish. The day at the Medicina Radio Observatory
ended with the Symposium closing dinner at the restaurant "Aia Cavicchio". The dinner
followed one of the main events of the meeting, the football match, now a
tradition at the EVN Symposium. The local team, the "Local Fats",
beat the "Giant Stars"-team 6 to 2. The referee of the match was from
I like
to finish this report by warmly thanking the members of the SOC and the Local
Organizing Committee for their collaboration. Also many
thanks to the IRA administration, to the technical staff, and to the many
students who generously contributed to the success of the symposium.
The
Proceedings of the 9th European VLBI Network Symposium will be published by
Proceedings of Science (PoS), Sissa,
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Franco Mantovani, SOC Chairman.
In
recent years real-time, long-baseline, radio interferometry over optical networks
has developed from a technical possibility to a mature technique.
Scientifically, real-time operation is more important for long baselines,
with their high spatial resolution, than for short baselines. However, until
recently the required technology has not been readily available. Technical
advances and the explosive increase of connection capacity have now radically
changed the situation. Emerging radio interferometers (e-MERLIN, E-LOFAR,
e-EVN and other e-VLBI arrays) will exploit mixed private/shared networks to
achieve wide-bandwidth real-time operation. Mirroring developments in other
wavebands of astronomy, these new real-time radio instruments are being
optimized to study transient phenomena. Moving data transport to fibre also gives the prospect of rapidly expanding
observing bandwidth and sensitivity as network capacity continues to
increase. Technically and operationally today's e-VLBI instruments serve as
precursors to the real-time Square Kilometer Array. Given recent developments
the time seems ripe to bring all those working on the science and technology
of real-time, long-baseline radio interferometry together to discuss the
state-of-the-art and future prospects. |
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The
conference will be held in
-
Scientific: Applications of
real-time operation to astronomy, geodesy and other applications. How to best
coordinate emerging e-VLBI arrays for best scientific return. Connections to
transient monitoring in other wavebands including Fermi Gamma-Ray Space
Telescope observations.
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Technical: e-VLBI test
experiments, use of new long distance links, development in techniques
including selective packet dropping and novel protocols, the search for higher
bandwidths, network status and monitoring, distributed processing, and future
development.
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Scientific/Technical: Future
technical possibilities of interest in planning future instruments. Desired
technical requirements to fulfill scientific goals, science priorities for
development.
This
workshop is sponsored by the Centro Nacional de Información Geográfica - Instituto Geográfico Nacional (CNIG-IGN)
of
More
information may be found in the web: http://www.oan.es/expres09/
Francisco
Colomer (LOC Chairman; OAN-IGN).
The
second half of 2008 was not eventless in the world of e-VLBI. During the 9th
EVN Symposium the first results from sensitive e-EVN observations were presented, and the great progress in the EXPReS project were
presented. This may have stimulated the PIs' curiosity because there were a
number of e-EVN proposal submitted to the 1st October deadline. Besides the
regular proposals, there was a target of opportunity request in early November
to follow the evolution of a great flare in SS433 at three epochs. These
observations produced a number of technical firsts for the e-EVN.
On 13 November the full e-EVN observed including
was then sent to JIVE as a Multicast datastream. Each
receiving Mark5A at JIVE that is responsible for handling the data from one of
the MERLIN telescopes can subscribe to this stream, which is only sent across
once from Jodrell Bank to JIVE. This was the first time we used this new
feature in an science observation.
On 19 November the observations went in a similar fashion. However, an additional
important milestone was achieved in that experiment. Three of the e-EVN
telescopes, Effelsberg, Onsala and Westerbork
observed and sent data at a full 1024 Mbps during the whole run, without
dropping data packets. We are working on including more telescopes at a full
1024 Mbps in the near future.
In December 2008 there were a number of tests including stations in Asia and
The e-VLBI demonstrations at the IYA
2009 opening went very well. This was a 33-hours observation with 17
telescopes participating from five continents! The stations were ATCA, Mopra,
system temperatures, but we were please to see the jet component to the NW show
up in agreement with the expectations (see movie here). Also shown is the total network
throughput graph for the experiment.
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Note: the full movie can
be watched on the URL: |
The
EXPReS team
One of
our newest developments from late 2008 is the 4G-EXPReS disk recorder. It
records at 4-6 Gbit/s onto an external >=20 TB diskpack using COTS hardware. The system is targeted to record
data from the upcoming digital backend systems with 10 Gbps Ethernet output
such as the DBBC, DBE2 and others.
The
Serial ATA port multiplier (PM) technology is often used in consumer and
corporate systems in place of SAS. SATA PM boards are
commercially available at low cost and they are supported by many modern SATA
controllers.
Based
on the PM technology and a gaming computer, we developed external low-cost diskpack variants that can carry 20 or 10 SATA disks. The diskpack is connected to the computer over one SFF-8470 SAS
multilane ("InfiniBand") cable at rates up
to 12 Gbit/s.
The
recording system can emulate Mark5C control commands and can store network
data in Mark5C, VDIF and other formats. It is
even possible to upgrade Mark5 units so that the same unit can be used in
both Mark5 and 4G-EXPReS modes. Continuous
4 Gbit/s recording over 17 hours is possible using
1.5 TB SATA disks. Recordings longer than 24 hours are possible using two diskpacks. The 2 TB SATA disks released this week allow even
longer recording. The diskpack is easy to carry and easy to ship from stations
that do not yet have 10 Gbps networking. It presents a portable, shippable
solution for high-speed recording and storage for those who do not desire to
set up a traditional distributed network file system. A diskpack
without side covers installed is shown in Figure 1. Current
write rates are in excess of 4 Gbit/s, reaching 6 Gbit/s. With newer motherboards this year we expect 8 Gbit/s rates to be achieved. |
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Jouko Ritakari, Jan Wagner, Guifré Molera, Minttu Uunila and
Ari Mujunen (TKK/Metsähovi
Radio Observatory); and
Simon Casey (Onsala Space Observatory).
In
preparation for the e-VLBI demonstration at the opening of the International
Year of Astronomy, a fringe test with several Asian and Australian stations
took place today. The participating stations were ATCA, Mopra,
We also
were able to transfer formatted data from the 34m Kashima telescope
(dynamically translated from K5 to Mark5B) for the first time at 256 Mb/s.
Hopefully the weather will allow us to see the first fringes during the next
test. |
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Mark Kettenis (JIVE).
On 16
October 2008, it was for the first time that an EVN network monitoring
experiment (NME) was performed at Q-band (
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More
results of the JIVE software correlator, including spectra of the SiO maser source U Her in LCP and RCP, can be found at http://www.evlbi.org/tog/ftp_fringes/N08Q1/index.html
Many thanks to Dave Graham and his colleagues of the
GMVA for their advice on high-frequency VLBI!
Stefanie
Muehle (JIVE).
2008
Session 3: 16 October – 4 November
Wavelengths: 7mm, 13/3.6cm, 6cm, 18cm, 1.3cm
Again,
for this session the main scheduling difficulties arose from the inclusion of
many non-EVN telescopes in the observations, in addition to the restricted use
of the Chinese antennas caused by the CHANG'E mission.
A total of 16 user observations were scheduled; more could have been observed
if the EVN had more disk-packs at its disposal. All except 2 projects with
grades 1.6 or better were scheduled. The 3 antennas of the Russian QUASAR
geodetic network were included in 3 parts of one project. The Yebes 40m
telescope was included for all projects at 13/3.6cm and 1.3cm. Again I
thank the Onsala, Noto and Effelsberg observatories for permitting the
scheduling of a 5th wavelength (7mm) in the session.
Richard
Porcas (EVN Scheduler)
·
THE JOINT INSTITUTE FOR VLBI IN
EUROPE (JIVE) is seeking candidates for fixed-term appointment as SUPPORT
SCIENTIST to be located at JIVE, Dwingeloo, The Netherlands. Deadline:
2 February 2009.
The
Joint Institute for VLBI in Europe (JIVE) operates the 16-station/Gbps MkIV EVN data processor (correlator) to support VLBI
astronomical observations made with the European VLBI Network (EVN). The EVN is
often used in conjunction with the MERLIN interferometer in the
We
invite applications for the position of JIVE Support Scientist. This position
would spend 50% of time on support duties and 50% on the appointee's own
astronomical research. Support responsibilities typically include:
*
assisting EVN users to schedule and analyze VLBI experiments.
*
monitoring network performance through dedicated test observations.
* overseeing the correlation of user experiments: data-quality review,
preparation of PI/station feedback, liaison with users, etc.
* testing new correlator/network features and capabilities.
The
position may also involve other local-service collateral duties, such as
visitor coordination or maintaining aspects of the JIVE computing environment
for visitors.
The
position requires a Ph.D. in astronomy or other relevant field, and a thorough
knowledge of VLBI techniques. Applicants
of any nationality are eligible to apply. A good command of written and spoken
English is essential.
The
appointment is offered for one year in the first instance with the possibility
of an extension up to a total of three years. The appointee will be in the
formal employ of the Netherlands Organization for Scientific Research (NWO).
The position carries a competitive salary plus an excellent package of
secondary benefits, including relocation expenses.
Please
send your application to: Ms D. Verweij; Joint
Institute for VLBI in
Applications
should include a CV and list of publications, together with three letters of
reference, which may be sent separately. All application materials should
arrive by 2 February 2009,
mentioning ref. No JIVE2009/01.
Responses
are preferred by e-mail. Further information can be obtained from Dr. R.M.
Campbell (campbell@jive.nl).
·
THE JOINT INSTITUTE FOR VLBI IN
EUROPE (JIVE) is seeking candidates for fixed-term appointment as DIGITAL ENGINEER
to be located at JIVE, Dwingeloo, The
Netherlands. Deadline: 1 February 2009.
The
Joint Institute for VLBI in Europe (JIVE) operates an advanced purpose-built
supercomputer (correlator) to support astronomical observations made with the
European VLBI Network (EVN). This network of radio telescopes extends well
beyond the boundaries of Europe, including telescopes located as far away as
The
EVN is constantly expanding through the inclusion of new telescopes. In
addition, developments in receiver and networking technology will enable a
large increase in sensitivity of the network. In order to take full opportunity
of these developments, the EVN correlator will need to be replaced. The next
generation EVN correlator will have to provide several hundreds of Teraflops,
comparable to the capacity of the largest current supercomputers.
In 2009 the UniBoard project, led by JIVE, will
start. This project, part of the European Commission-sponsored RadioNet programme, will aim at the creation of a generic
high-performance FPGA-based computing platform. This board will support
several astronomical applications, including a correlator, a pulsar binning
machine and a digital receiver.
JIVE is inviting applicants for the following appointment, becoming available
immediately: Digital Engineer.
This position involves:
- Translation of astronomical demands into system specifications
- Definition of architectural specifications
- Design and implementation of driver software
- (co-) responsibility for development and implementation of firmware
- Definition and execution of tests, both regarding astronomical integrity and
computing performance
We are seeking an individual with an academic level education in digital
engineering, or equivalent experience. He/she should be experienced in design
and development of digital systems, have knowledge of design methods and development tools
and experience with the definition of demands and specifications. We are
seeking someone with a pragmatic attitude, who can function well both in a team
and singly, and with the ambition to look beyond his own responsibility.
A good command of written and spoken English is essential.
The appointment will be based at JIVE in the
Please send your application to: personnel@astron.nl.
Ms D. Verweij; Joint Institute for VLBI in
Applications including a CV should arrive by February 1 2009, mentioning ref.
No. JIVE2008/07. Further information can be obtained
from Arpad Szomoru (szomoru@jive.nl,
+31521596509).
At
JIVE, Jun Yang started as a support
scientist on 1 Nov 2008. Giuseppe Cimo remains at JIVE, but leaves his support scientist
position in the Science Operations & Support group to take up a posdoctoral fellow in VLBI techniques and applications
after 1 Jan 2009. Antonis Polatidis will
shortly depart as a support scientist at JIVE to fill the position of head of
science support for the Radio Observatory at ASTRON, effective 1 Feb 2009.
EVN
Newsletter No. 22.
© 2009 European VLBI Network. Edited by Francisco Colomer (OAN, Spain).