The 100 meter radio telescope
in Effelsberg, Germany.
As one of the largest telescope dishes on Earth,
it is capable of detecting radio waves that have traveled
billions of years, from the farthest quasars and galaxies.
The larger the collecting area a radio telescope has,
the more sensitive it is to signals from the cosmos,
enabling observations of fainter sources.
Greater telescope size also results in sharper images
with better resolution.
"Obviously there's a limit to the
size of the telescope we can build.
Fortunately we have a trick for that.
It's called interferometry."
Using a technique called interferometry,
multiple telescopes simulate a single, larger telescope.
They observe the same region of sky at the same time, gathering data.
This data is sent to a super-computer called a correlator.
The correlator synchronizes the data for every possible pair
of telescopes, and combines them all to create a single image.
Interferometry can also be done on a scale of thousands of kilometers.
This is called Very Long Baseline Interferometry, or VLBI.
The European VLBI Network is a collaboration of
major radio astronomical institutes in Europe,
as well as Asia and Africa.
With access to 27 telescopes in 13 countries,
the EVN is capable of simulating a telescope up to 10,000 km
in width - nearly as big as the face of the Earth.
With so many stations at such great distances,
the EVN can produce images with better resolution
than the best optical telescopes.
"VLBI gives us fantastic resolution.
In fact the resolution is so good that even in astronomical objects
we can see things move. That is something that is hardly possible
with any other technique."
As with smaller interferometric arrays,
VLBI data is sent from the telescopes to a correlator.
The EVN correlator is located here,
at the Joint Institute for VLBI in Europe, or JIVE, in the Netherlands.
Specially built for this purpose, the correlator is continually
improved to ensure compatibility with upgrades made
at the various telescopes.
Correlator upgrades also enable cutting edge capabilities
to support new astronomical questions, such as when and how
the first galaxies were formed.
In traditional VLBI,
data is sent from the telescopes to the correlator
on magnetic tape or disks.
Shipping disks here from around the world is costly.
They can be damaged or lost in transit, or can be found to have
errors in the data.
Moreover, there is a significant delay from the time of the
observation to the receipt of processed data by the astronomer.
In addition, scheduling VLBI observations typically requires
significant advance coordination among the many institutes that
operate the telescopes.
This limits opportunity for unscheduled observations when
transient events are detected, such as supernovae and other
violent cosmic phenomena.
Until now.
In recent years, JIVE has made numerous updates to the EVN correlator.
The most significant allow for data to be streamed over
fiber optic networks directly to the correlator.
"This technique is called real-time,
or electronic VLBI, or e-VLBI for short.
And we use this technique to stream the data from the telescopes
directly to the correlator, where it's correlated in real-time."
With such fast data delivery and processing, problems at the
telescope stations can be detected and corrected immediately,
saving valuable data.
Astronomers receive their data in a matter of hours, rather than weeks.
Furthermore, procedural changes make it possible to accommodate
observations on short notice, when transient activity is detected.
"Some of the most interesting
astrophysical phenomena are
transient, and many of these are
located at great distances from us.
To study emission from objects like collapsing stars or
accreting black holes, radio astronomers have to arrange
observations with the largest telescopes on a very short notice.
Real-time e-VLBI at the EVN makes this much easier than
before, allowing us to observe many more transient sources.
In the past years, we have been able to investigate a number
of supernovae, which are exploding stars, microquasars that have
highly collimated, relativistic outflows, or even a star that
has been ripped apart by a supermassive black hole."
These upgrades were made possible through the EXPReS project.
Coordinated by JIVE and funded by the European Union,
EXPReS upgraded the correlator for real-time processing.
It also completed much of the "last mile" networking
to connect the telescopes.
"Data from telescopes all over the world is streaming into a
hardware supercomputer which is at the core of our VLBI operations.
And what you see on the screen here is the total data rate
that has been coming into..."(fades)
Now, e-VLBI is a regular service offered by the EVN.
e-VLBI observations have already led to scientific discoveries
that have improved our under-standing of how galaxies form
and evolve.
Improvements in the past few years have made e-VLBI
as good as traditional VLBI
in terms of bandwidth and image resolution.
Today JIVE is working to make it even better.
Major efforts at JIVE are focused on a new correlator platform,
required for increasing data rates planned by the EVN.
JIVE and EVN engineers are using the latest electronics to deliver
the processing power for future radio astronomy observations.
In 2010, JIVE started coordination of the NEXPReS project.
With 14 partner institutes, JIVE is combining the
best of both worlds: the speed and flexibility of e-VLBI,
with the robustness and reliability of disk-based, recorded VLBI.
One main activity of the project addresses network disruptions
to make sure data transport progresses smoothly.
Data integrity is protected by buffering the data
at the telescopes and the correlator.
Related upgrades will improve on-the-fly monitoring and
modification. This will enable automated correlation.
Another NEXPReS activity is to make more efficient use of the
networks with "bandwidth on demand".
"Right now we have static lightpaths for e-VLBI,
which are point-to-point connections.
They're there all the time, whether you use them or not.
So this is not a very efficient use of resources.
So we are developing bandwidth on demand, which makes it possible
to dynamically allocate bandwidth at the times that you need it,
and not at the times that you don't."
Moreover, dedicated lightpaths are limited to 1 gigabit per second.
The EVN is already planning 4 and 10 gigabit per second upgrades.
A third aspect of the project addresses the limited speed
of the existing centralized, hardware-based correlator.
In recent years, JIVE has developed a software correlator,
the basis for an automated, distributed correlator.
By leveraging network and computing resources
that already exist in the EVN, NEXPReS will enable additional
VLBI observations with minimal impact on scarce resources.
The last major challenge to combining traditional and e-VLBI
is in storing and archiving the tremendous amount data
generated in an observation.
A typical EVN experiment generates 12 gigabits of data per second.
That's about the same as one high-quality, feature-length movie
every second for 12 hours.
NEXPReS is developing high-bandwidth, high-capacity
networked storage on demand to accommodate this data.
Radio astronomers around the world will benefit from these
developments in next-generation e-VLBI.
Furthermore, new developments of the EVN technologies
advanced by JIVE are essential for new telescopes.
The high level of automation and distributed architecture
are also feeding into design of the Square Kilometre Array.
Additionally, these developments are crucial for various
planetary science missions such as ESA's Venus Express,
and space-based VLBI telescopes such as RadioAstron.
Work by JIVE is pushing the envelope of Europe's ICT
infrastructure.
"It has been demonstrated that fundamental science has a
healthy impact on the viability of our economy.
And it's not hard to imagine how the techniques that we deploy
in e-VLBI will influence other sciences, education, communication
and even entertainment."
JIVE, forging a path to the future of Radio Astronomy.