ress Release - Cambridge, January 27, 2004.
Faster, deeper, sharper: thanks to GÉANT, Europe’s radioastronomers
can now observe transient objects at the edge of the
For the first time, astronomers led by
, the European Joint Institute for Very Long Baseline Interferometry,
used GÉANT, the world’s most advanced international research network, to
combine data from radio telescopes in the UK, Sweden and the
Netherlands, generating images of a jet of gas moving at nearly the speed
of light close to the edge of the visible Universe.
Thanks to GÉANT’s bandwidth, Europe’s astronomers got the image they
were looking for in hours, rather than months. Without GÉANT, they would
have had to wait for up to six months to see the result of their labours. And
would have missed most of the show anyway.
Europe’s radio-astronomers have dreamed for some time of transmitting
their data electronically using a network such as GÉANT. GÉANT matters
to them because the ability to electronically combine several radio
telescopes’ data together has the effect of bringing an enormous boost to
the telescopes’ sensitivity and operational reliability. Concretely, this means
they can look deeper into the early Universe - and do so in exquisite detail.
In the experiment, the astronomers created Europe’s - and the world’s - first
electronic Very Long Baseline Interferometer
. VLBI allows radio astronomers to distinguish objects separated by
about 1 milliarcsecond – that’s the equivalent of seeing individual
astronauts on the moon from earth (by comparison, the resolution of the
Hubble space telescope is about fifty times poorer).
Radio interferometry is based upon the principle that the resolution of an
image depends on the size of the
looking at it – and that a very large
eye can be simulated by combining images obtained from several remote
telescopes. In this experiment, the data from the telescopes was combined
to yield an image offering the resolution of a single, 957 km -wide radio
It is a potent technique, allowing astronomers to gaze back to the very edge
of the Universe. But until now, its practitioners faced two serious
challenges, both born of the fact that the data had to be recorded onto tape
and physically shipped to a central location for processing and analysis.
First, the image may be sharp – but it’s very dark. That’s because each
telescope generates enormous amounts of data, most of which is lost (until
last week, there was no way to collect, match and process the tens of
gigabits per second generated directly - and the data tapes used typically
yield an effective bandwidth of only 128 Mbits per second). This seriously
degrades the image’s sensitivity.
"It’s like trying to look up at the stars at
night wearing sunglasses," said Mike Garrett, JIVE’s director. At the edge
of the Universe, only the very brightest objects can be seen at all, and most
of the sky seems dark to VLBI astronomers.
Second, the physical handling of data storage media from various locations
led to months of frustrating delay between an observation and the resulting
image. This can waste precious observing time, since it’s impossible to
know during the observation if all the telescopes are operating as they
should (if one of them didn’t, the time all of them spent on that observation
is irrevocably lost). And it forces VLBI astronomers to treat the cosmos as a
static display. They simply can’t react to the Universe’s sudden events like
gamma-ray bursts or supernova explosions.
The solution is obviously to link the telescopes together through an
electronic network – to do eVLBI, with its potential to realise much higher
data rates, and make analysis in near real time a possibility. But, before
GÉANT, doing this was simply impossible: the required bandwidth simply
wasn’t available (indeed, VLBI in the United States is also still carried out
with data tapes).
In last week’s experiment, three telescopes at the Onsala Space
Observatory in Sweden, the Jodrell Bank Observatory in England and the
Westerbork Radio Observatory in the Netherlands, were connected by
GÉANT to the European VLBI Network’s central processing facility
(operated and developed by JIVE) in Dwingeloo, also in the Netherlands, to
be correlated and processed into a ten-milliarcsecond resolution image of
Blazar 2007+777. Astronomically, the test resulted in a routine image. But
"for someone who spent a lot of time watching telescope data stream
locally on to tape, this was quite an event," said Dr Garrett.
Each telescope was connected to its country’s National Research and
Education Network, and the data routed onwards through GÉANT to
SURFnet, the Dutch research network, for delivery to JIVE.
Telescopes, for obvious reasons, tend to be located in remote areas – but
networks aren’t. The difficulty and expense of building a high bandwidth
network all the way to each telescope is what makes international eVLBI a
We are as delighted as our friends at JIVE at the success of
this first experiment. We look forward to connecting more telescopes
through GÉANT to the eVLBI network as the year progresses,
said Mr Dai
Davies, General Manager of
, which operates GÉANT.
Thanks to GÉANT, radio-astronomers using Europe’s telescopes can look
forward to much more sensitive, sharper images – and will soon be able to
react quickly to the Universe’s many surprises.
The achievement shows how GÉANT can support distributed European
. GÉANT provides the network infrastructure essential to
support the growing number of research projects that use facilities located
in several different countries.
As radio-astronomers are discovering, Europe’s delivery trucks have a
rather low bandwidth compared to GÉANT,
said Dai Davies.
pleased indeed to see GÉANT supporting distributed European research so
successfully. This achievement is a real Big Bang for international
The data rates used for this first test were still quite low (256Mb/sec).
we are aiming for 1Gb/sec on six telescopes by the end of this year," Dr
Garrett said. "We’ll finally be able to take those sunglasses off." With
GÉANT and its successors, DANTE hopes to offer astronomers data
transfer rates of 10 Gb/sec within four years. "We’ll see objects almost ten
times fainter than we can today in incredible detail," Dr Garrett added.
Astronomers will then be able to explore the Universe when it was still a
baby. Dr Garrett explained that the hope was to catch the light of the very
with eVLBI, we may finally see the most famous event in all
of Genesis: the transition from ‘And darkness was upon the face of the
deep’ to ‘Let there be light: and there was light’.
It is at that remote time that the Universe is suspected of having taken on
the basic shape it has today. Many of the heavier chemical elements that
make up our bodies were forged in those first, young stars. With electronic
VLBI, we may in a very real sense be able to witness our own creation.