UK Astronomers to Build Unique Radio Telescope
UK astronomers are poised for a new era of discovery with the development
of e-MERLIN, the world’s most powerful radio telescope. This ambitious
project will use new technology to connect antennas across the UK,
creating the largest and most sensitive linked network in the world.
The 217km MERLIN radio telescope array, run by The University of
Manchester’s Jodrell Bank Observatory, is to be given a £7.8m upgrade.
This has been made possible by the agreement, announced today, of the
Particle Physics and Astronomy Research Council (PPARC) to continue
funding MERLIN operations, so assuring the future of Jodrell Bank.
Professor Andrew Lyne, Director of the Jodrell Bank Observatory, welcomed
the PPARC announcement:
“The enhancement to MERLIN will give UK astronomers access to one of
the world’s major astronomical research instruments. This development
reflects the proven technical excellence of the University staff and
their world-leading research programmes.”
Dr. Philip Diamond, Director of the MERLIN/VLBI National Facility added:
“In combination with the newly resurfaced 76m Lovell telescope, the
upgrade will give a 30-fold increase in sensitivity. This will enable
the enhanced instrument, called e-MERLIN, to probe far deeper into the
Universe, achieving in one day what would currently take three years
of continuous observation.”
The upgrade is to be funded by the North West Development Agency
(NWDA) and a consortium of three universities — Manchester, UMIST
and Cambridge. The NWDA have agreed in principle to a contribution of
up to £2.5 million, and its Chief Executive, Mike Shields, welcomed
today’s news:
“I am delighted that the NWDA’s funding contribution will help to
secure the future of Jodrell Bank — a longstanding symbol of scientific
endeavour in the North West. This package will not just maintain Jodrell
Bank’s position at the leading edge of world astronomy, but will also
help to maintain the region’s reputation for excellence in the future.”
MERLIN is the UK’s national radio-imaging facility and the only world-
class astronomical facility based solely in the UK. No other radio
facility in the world can routinely match the resolution of the Hubble
Space Telescope. The completion of the new instrument in 2007 will
help keep the UK at the forefront of astronomical research for years
to come.
Radio-astronomy is crucial to the understanding of our Universe
because radio waves penetrate the clouds of dust and gas that hamper
observations at other frequencies. e-MERLIN will have unprecedented
sensitivity and an imaging capability equivalent to viewing a 1p piece
at a distance of 50 miles. It will thus open up new areas of science,
particularly in fields such as extragalactic astronomy and cosmology,
star formation across the Universe and studies of the extreme
conditions around black holes.
The current MERLIN telescope is made up of seven radio-antennas sited
around the UK. Much of the increase in sensitivity created by the
upgrade will be due to the introduction of optical fibre connections
between the antennas. This will allow a far greater proportion of the
radio waves actually collected by the individual antennas to be brought
back to Jodrell Bank than by the existing microwave radio links.
Dr. Diamond thanked Sir Martin Harris, Vice-Chancellor of the
University of Manchester, for playing such a crucial role in putting
together the capital funding package. He warmly welcomed the various
partners involved in the project and also wished to thank the Cheshire
County Council, North West Members of Parliament, and local Councillors
for their great support, without which the project may well not have
come to fruition.
Professor Tom Millar, Head of UMIST’s Astrophysics Group said:
“My colleagues and I are very pleased to be part of this exciting
development and look forward to using e-MERLIN to advance
significantly our research on star formation and the late stages of
stellar evolution.”
Richard Hills, Professor of Radio Astronomy at Cambridge, said:
“This is very good news for the future of UK Radio Astronomy. One of
the MERLIN antennas is located here and we are delighted to be playing
a part in the project. We are very much looking forward to using the
enhanced facility.”
– End of release –
Related images, contact details, background information and links to
further information are given below.
Related images:
* Location of the MERLIN telescopes (109KB)
http://www.jb.man.ac.uk/news/e-MERLIN/merlinmap.jpg
* Location and photographs of the MERLIN telescopes (228KB)
http://www.jb.man.ac.uk/news/e-MERLIN/merlinmap2.jpg
* The 76m Lovell Telescope at Jodrell Bank (1MB)
http://www.jb.man.ac.uk/news/e-MERLIN/Lovell.jpg
* The 32m Telescope at Cambridge (158KB)
http://www.jb.man.ac.uk/news/e-MERLIN/cambridge.jpg
Contact Details:
Jodrell Bank Observatory:
Dr Phil Diamond
Director, MERLIN/VLBI National Facility at Jodrell Bank Observatory
Phone: +44-(0)1477 572625
Mobile: 0776 970 6872
e-mail: pdiamond@jb.man.ac.uk
Professor Andrew Lyne
Director, Jodrell Bank Observatory
Phone: +44-(0)1477 572640
e-mail: agl@jb.man.ac.uk
Dr Tom Muxlow
MERLIN operations team
Phone: +44-(0)1477 572609
e-mail: twbm@jb.man.ac.uk
Dr Simon Garrington
MERLIN operations team
Phone: +44-(0)1477 572607
e-mail: stg@jb.man.ac.uk
The University of Manchester:
Mr Andy Swain
Information Officer
Phone: +44-(0)161 275 2018
e-mail: andy.swain@man.ac.uk
Northwest Development Agency:
Ms Emma Degg
Phone: +44-(0)1925 400295
e-mail: Emma.Degg@nwda.co.uk
The University of Manchester Institute of Science and Technology:
Professor Tom Millar
Professor of Astrophysics
Phone: +44-(0)161-200-3677
e-mail: Tom.Millar@umist.ac.uk
Cambridge University:
Professor Richard Hills
Professor of Radio Astronomy
Phone: +44-(0) 1223 337300
e-mail: r.e.hills@mrao.cam.ac.uk
Background:
The home of the MERLIN network is the Jodrell Bank Observatory which
is part of the Department of Physics and Astronomy of the University of
Manchester. The MERLIN/VLBI National facility based in the observatory
is operated by the University on behalf of the Particle Physics and
Astronomy Research Council (PPARC).
MERLIN, developed 25 years ago from the pioneering experiments in long-
baseline interferometry at Jodrell Bank, was designed to provide sub-
arcsecond resolution at centimetre radio wavelengths. This was primarily
to study in more detail the radio galaxies and quasars imaged by the
Cambridge aperture synthesis arrays. Surpassing its original goals,
both technically and astronomically, it was immediately recognised as
a world-class instrument and many of its initial publications appeared
in Nature. A major upgrade in 1990, in which the resolution was
increased by nearly a factor of 2 and the sensitivity by almost an
order of magnitude, ensured that MERLIN was transformed into a general-
purpose instrument capable of attacking a wider range of astrophysical
problems. Thus, it has remained a world-class astronomical facility;
the only one entirely based within the UK. With its unique sub-arcsecond
resolution matching that of the Hubble Space Telescope (HST), it has
been identified as one of the leading strengths of UK astronomy,
having an extensive user-base from 27 universities and other research
establishments throughout the country.
In order to study the physics of astronomical objects, it is accepted
that observations of similar resolution and sensitivity across the
electromagnetic spectrum are required. However, it had become clear
over the past few years that the sensitivity available at radio
wavelengths was beginning to lag behind that available in other
wavebands. Thus, radio facilities needed to be upgraded to make them
comparable with and complementary to the new observational facilities
in other regions of the electromagnetic spectrum. Thus the timely
increase in the sensitivity of MERLIN will complement the upgrades of
major radio astronomical facilities elsewhere in the world such as that
of the 36 km Very Large Array (VLA) in New Mexico which has just been
funded and will become the EVLA.
Image quality and resolution lie at the heart of MERLIN’s success.
Maintaining its resolution and vastly increasing its sensitivity,
will enable e-MERLIN to carry out unique science. e-MERLIN will
image in detail objects that can now only be glimpsed in the deepest
observations and detect objects previously unseen at radio wavelengths
with unprecedented resolution. It will provide radio images that
complement those from the new generation of optical and sub-mm
telescopes as well as probing regimes of the Universe not visible at
other wavelengths. e-MERLIN will continue to bridge the resolution gap
between the European and American very long baseline arrays (termed
VLBI) and instruments such as the VLA. (Three of the Jodrell Bank
telescopes take part in the European VLBI Network, the EVN. ) Many
of the key problems being attacked by UK astronomers require radio
observations at a sensitivity level that will be provided by e-MERLIN
and with matched resolution to the HST. However, history shows that
when any telescope makes a leap of more than an order of magnitude in
sensitivity, it is the discoveries that could not have been predicted
which turn out to have the greatest impact. For example, it was never
anticipated beforehand that MERLIN would have such a significant
impact on studies of the Hubble Deep Field.
One of the great achievements of radio astronomy over the past two
decades has been the close cooperation between the VLA and MERLIN. Data
from the two arrays have often been combined to produce high-quality,
high-sensitivity images of a great variety of astronomical objects. It
turns out that the data combination is a non-linear process in that
the resulting images are far superior to what one might expect from a
simple combination of the individual images from the two instruments.
This is because of the additional constraints which results from a
combination of the pre-processed data. The implementation of e-MERLIN
will continue this partnership with the enhanced EVLA. With the Lovell
telescope included in MERLIN, the upgraded instruments will have
similar sensitivities at their principal observing frequencies, but
when e-MERLIN data is combined with that from the EVLA the resultant
images will have six times the resolution achievable by the VLA alone.
e-MERLIN will thus enable the creation of one of most significant tools
with which to probe the Universe.
The MERLIN Antennas
There are 7 antennas in MERLIN. Two, the 76m Lovell Telescope and the
25m Mk II telescope are located at Jodrell Bank, some 20 miles south
of Manchester in the Cheshire countryside. When incorporated into the
array, the Lovell Telescope doubles the effective collecting area and
so doubles MERLIN’s sensitivity. Prior to the extensive upgrade which
will be completed in the summer of 2002, the Lovell Telescope could
only be used at the lower MERLIN operating frequencies, but from next
year it will be able to be used at the key operating frequency of
5 GHz and thus give a sensitivity boost to MERLIN well before the
commissioning of e-MERLIN later in the decade.
The oldest antenna in the array is located at Defford, near Great
Malvern, 127 km south from Jodrell Bank. The wire mesh surface of the
dish only allows observations up to 5 GHz, and ideally it would be
replaced by a more modern antenna capable of operation up to 22 GHz.
This part of the original e-MERLIN proposal has had to be dropped for
the time being due to financial constraints.
There are three identical 25m antennas at Pickmere, near Northwich in
Cheshire, Darnhall, south of Winsford in Cheshire and Knockin, near
Oswestry in Shropshire. These are of similar design to those
incorporated into the Very Large Array in New Mexico and can be used
over the full range of MERLIN operating frequencies.
The most recent MERLIN antenna is the 32m at Cambridge. Completed in
1991, it formed a major part of the first upgrade to MERLIN and, by
increasing the overall size of the array to 217km, doubled its
resolution making it comparable to that of the Hubble Space Telescope.
The operational efficiency of the MERLIN array had been improved in the
last few years by the implementation of “frequency flexibility”. All
MERLIN telescopes apart from the Lovell now have an array of receivers
located close to the focus of the telescope which can be moved to the
focal point by remote control. Changes between observations at different
frequencies can thus be made with great ease. This, for example, allows
observations at the highest frequencies, where weather conditions can
effect the results, to be scheduled at short notice when conditions are
optimum.
Linking the antennas into the MERLIN array
Currently the signals from the MERLIN outstations are brought back to
Jodrell Bank for analysis using microwave radio links. Their performance
was substantially increased in the earlier MERLIN upgrade, but is still
limited to returning 30 MHz of bandwidth to Jodrell Bank. This is the
restriction that effectively limits the current performance of MERLIN.
Most of the signal received by the telescopes has to be discarded
prior to transmission due to the limited capacity of the links. The
replacement of these links with those using optical fibres removes
this limitation. It is the greatly increased data bandwidth that will
provide the major part of the massive sensitivity increase of e-MERLIN.
Development of the required optical fibre technology for e-MERLIN is
being carried out by Jodrell Bank engineers and will use bit rates of
30 Gigabits/second. This same technology will also be used for the
future joint European and USA project, ALMA — the Atacama Large
Millimetre Array. ALMA is to be located at a height of 16,400 ft in
the Atacama desert in Chile and optical fibres will link the 64 or
more antennas in the array with the central receiver laboratory.
Similar data transmission systems will be used in future radio
telescope projects such as the “Square Kilometre Array”, so in this
respect, e-MERLIN will act as a prototype system for these future
developments.
Combining the data — the e-MERLIN Correlator
The massive increase in the data returned from the telescopes of the
e-MERLIN array will require a very powerful system to carry out the
required data processing in real time. With each antenna returning over
30 Gigabits of data per second to Jodrell Bank, half a million times
faster than the average home modem, the continuous data rate analysed
by the new correlator will exceed 200 Gigabits per second! The required
data throughput is greater than even the fastest general purpose
processors can achieve, so a special purpose “correlator” will be
required. The costs of designing and implementing such a system are
great and would not be affordable with e-MERLIN funding alone. The
design and construction of the correlator will thus also be an
international project with Jodrell Bank engineers working with those
from Canada and the USA in its design and implementation. It is hoped
that the correlator will be developed in Canada funded by the National
Research Council of Canada, the National Science Foundation of the USA
and ourselves. Versions of the correlator will be then be constructed
both for e-MERLIN and the EVLA project referred to above.
Further Information:
For examples of the astronomical research carried out with the MERLIN
telescope array see the Astronomy Section of the MERLIN/VLBI National
Facility Biennial Report 1999/2000,
http://www.merlin.ac.uk/biennial/astro.html
For more details on the e-MERLIN project see the e-MERLIN summary page,
http://www.merlin.ac.uk/e-merlin/introduction2.html
