LOFAR - A Multidisciplinary Wide Area Sensor Network
Interfacing the World with a Distributed Supercomputer

Prof. Dr. Heino Falcke


The world breathes, changes, and lives and we want to observe, understand and shape this world. Understanding the dynamic world around and above requires us to obtain, process, and digest an enormous amount of information. This can only by achieved through modern information and communication technology: it requires the construction of Wide Area Sensor Networks (WASN). A WASN consists of an array of geographically distributed sensors which are connected by a self-organizing, partly wireless network and an ultra-high speed backbone to a distributed super computer. All three components are mutually dependent: network and computing resources are constantly fed by a multitude of sensors providing a huge data flow that in turn could only be processed by this special high-throughput networks and computers of the next generation.  LOFAR is the first large scale attempt to implement such a concept in the real world on a large scale, driven by a wide range of user knowledge processing user groups from a variety of disciplines. This includes but is not limited to astronomy, geophysics, meteorology, and agriculture where it will be a major player. LOFAR will open up the next level of distributed computing and networking and provide significant visibility for the technology partners involved.








Schematic view of the LOFAR sensor network.


Table of Contents:

The Basic Concept for a European WASN-Testbed. 1

Wide Area Sensor Networks. 2

A Short History of LOFAR.. 3

Generalization of LOFAR into a WASN.. 4

Key Technologies. 5

Why should one get involved?. 6

What is needed?. 6

Conclusions. 6

LOFAR Organization and Structure. 6

LOFAR Organization and Structure. 7

Who is ASTRON?. 7

Wide Area Sensor Networks

The changing world around and above us provides an enormous amount of information that

*      can be measured through a distributed network of sensors, providing a continuous data stream

*      needs to be channeled to central data bases and monitoring and control units

*      needs to be processed for our information society to understand, predict, and shape our environment.


How can one connect different sets of geographically spread-out sensor arrays to a super computer?


A wide Area Sensor Network needs three basic components:

*      a large number of cheap and robust digital sensors of various kinds,

*      a dedicated high-speed (10Tb/s) network over several hundreds and thousands of kilometers,

*      very high performance central and distributed super computing capabilities.


Each of these areas requires new technologies and research and can form the basis of a next level of information services for science as well as for governments and citizens.


With the huge amount of information being generated by a large set of continuously streaming sensors, a WASN has demands beyond traditional high-bandwidth networks and applications. Different user groups demand different sensors, bandwidths and modes of operations. Currently planned examples of sensors required by different user groups are:

*      radio dipoles for radio astronomy creating a virtual telescope, studying: cosmology, space weather, ionosphere, high-energy particles

*      particle detectors: measuring cosmic ray induced particle showers

*      geophones for monitoring tectonic activity and ground water levels through micro-earthquakes

*      weather stations for real-time weather and storm evolution monitoring

*      microphones for infrasound applications

*      soil, crop, and livestock sensors for enabling precision agriculture










A Short History of LOFAR

The initial driver for LOFAR came from radio astronomy which has a tradition in digitally connected element interferometers and high-bandwidth applications. The idea for LOFAR was to replace a conventional radio telescope with a distributed network (phased array) of simple digitally sampled dipoles. This allows one to realize a telescope completely in software which can point and focus electronically without any moving parts – in fact it can even look in multiple directions and trough data buffering even back in time. At low radio frequencies this is possible with modern technology and would provide up to three orders of magnitude increase in resolution and sensitivity over existing facilities. The idea of and desire for an astronomical Wide Area Sensor Network was born! Within an international consortium of scientific institutes the basic concept and requirements for LOFAR were specified:

*      2x 13,000 small antennas

*      clustered in 100 stations distributed over 350 km in a “log-spiral” configuration

*      >20 Tbit/sec data network  (if full scientific bandwidth)

*      >40 Tflop distributed supercomputer

*      innovative software systems

*      data mining and visualization

*      full and exclusive control via the Internet

*      instantaneous view of the full sky, several simultaneous users.

Now, the LOFAR project is ready to make the next step…



MATLAB Handle Graphics




Artists view of a LOFAR station (center) which can electronically form multiple antenna beams (left & right) for an astronomical application..








Generalization of LOFAR into a WASN

In the course of the R&D for LOFAR the project realized that the genuine nature of their concept went beyond astronomy and fundamental science. As the technical concepts matured the interest from other scientific communities and from commercial parties steadily increased. The main aspects that make the LOFAR project attractive for other fields are:

*      With a dedicated high-speed network and 100 extended stations, additional sensors can be added at only a small additional cost.

*      Digital sensors are a main driver for high-speed networking and supercomputing, exceeding the demands and vision of multi-media applications or computer-to-computer networking.

*      A genuine WASN has never been realized on the scale of LOFAR.


The additional cost for this expansion of LOFAR is the burden of increased flexibility and a wide range of user demands in terms of bandwidth, robustness, interconnectivity, and services. For example, radio astronomy has a high demand on bandwidth and synchronization. Geophones, microphones, weather station have low-bandwidth but may require local pre-processing. Agricultural sensors can be widely distributed and non-stationary (e.g. cows!). High-energy particle detectors for astroparticle physics applications need special triggering and synchronization. All applications may also demand differently spaced network access points. As a result an interdisciplinary knowledge consortium is formed that clusters around a central ICT research and infrastructure, producing fundamental and applied research.



Key Technologies

There are a number of key technologies that need to be developed by various partners in the consortium. Some of the key areas of research and development are

*      low-cost sensors: every user group has defined and design its own set of robust, affordable sensors that can be coupled to the network,

*      generic sensor interface: coupling sensors into the network requires the definition of a generic sensor interface that can accommodate the wide range of sensors envisaged,

*      broad-band data links: given the huge demand for bandwidth a (possibly routerless) optical network has to developed using a combination of existing dark fibers and newly laid connections,

*      IPv6 based protocols: a number of high- and low-bandwidth applications with guaranteed or ad-hoc allocated bandwidth have to communicate with sensors and operators and be integrated in a single network,

*      high performance cluster-computer: central processing requires not only fast number-crunching capabilities (10 Tflop) but also massive data throughput (25 Tbit/s) and buffering capabilities (up to several minutes).

*      embedded software is needed to implement the majority of the WASN functionality, especially the signal processing functions for the various sensor applications, and the handling of the dynamic and self-configuring behavior associated with some of these.

*      adaptive monitoring and autonomous control of the network has to cope with continuously changing environmental conditions, changing hardware configurations, hardware degradation, and changing user demands

*      intelligent web-based user interfaces: with the enormous amount of data being processed, the results have to be stored and then made accessible to a widely distributed user base via ‘traditional’ internet services, making the operation fully transparent, building up and providing access to a large interdisciplinary knowledge base.




















While sensor development and data reduction algorithm will be the prime task of the various research communities and user groups, the remaining technology issues are well posed problems for commercial companies and public-private partnerships are the preferred model.

Why should one get involved?

LOFAR is a unique project that combines some of the most advanced aspects of modern technology and science. As a major international science project it will provide large visibility for all partners involved through:

*      Geographic distribution: football field sized distribution of stations across the northern parts of Germany and the Netherlands together with a central visitor center

*      Scientific excellence: LOFAR will be at the forefront of astronomical research which nowadays guarantees media interest and public fascination for the next decade. LOFAR is probably the only major astronomical facility that can still be realized in the heart of Europe!

*      Education: LOFAR will provide a strong link to students and schools across Europe that can use part of the facility for education and outreach.

*      Next generation networks: stress-testing IPv6 and security issues

*      Other new technology: The WASN concept will have many future applications beyond basic science that can affect everyday life and hence LOFAR will be a trend setter in this area.

*      Testbed: As a testbed LOFAR – driven by the high demands of basic science – allows one to develop and test already now techniques that markets will demand in the coming years.


What is needed?

There are numerous specific tasks for potential partners in the project. Some of those specific to the WASN testbed concept include, but are not limited to:

*      Lay out the LOFAR network on scales of  2, 50, 300 km distance with newly installed fibers (inner region) or using unmanaged dark fibers provided by a partner

*      Provide LOFAR nodes and stations with advanced GbE network equipment, GSM/GPRS links, GPS receivers, etc.

*      Provide various categories of sensors (e.g., measuring environmental parameters)

*      Develop protocols for simultaneous use of these sensors and secure communication protocols (IPv6 based - multitude of sensors, high performance secure transport of heterogeneous data, dynamic behavior through radio links or "ad hoc" behavior of some sensor types)



A wide area sensor network is a new and innovative approach to sensing the physical world. It is a technology that easily drives bandwidth demand to a new level, providing a step beyond GRID. The reason is that here we do not have computers talking to computers, but the real world talking to us! Computers and networks provide the key interface. The real world will always provide more information than we can handle in any virtual world, hence smart information reduction and processing is the key for a WASN. A European testbed, realized through LOFAR, driven by demanding users, will push this technology into a reality.

LOFAR Organization and Structure

The early international LOFAR consortium that initiated the project consists of ASTRON, MIT (Haystack Observatory, US), and the Naval Research Lab (US). Now partners from Australia, Germany, Sweden, and France have joined the efforts or are in the process of doing so.. Connected with the consortium there are several formal collaborations with partners from industry and universities, mainly at the European level. Several tens of M€ of initial funding are already available, including significant contributions from industrial partners.


The LOFAR project has a strong regional backing in the northern Dutch provinces and on a national level. Early 2003 a predominantly Dutch consortium has submitted a 70M€ proposal for funding of a significant part of LOFAR and a large program of ICT related research that uses it. The consortium unites a number of Dutch universities, research institutes, industrial enterprises, and some international partners from Germany and Sweden. The consortium is in principle open for new partners.


ASTRON has set up a professional management structure with a project office and system engineering team to handle the managerial challenges associated with this complex international situation. As of 2003, the total staff involved in LOFAR at ASTRON is 45.



Who is ASTRON?

ASTRON is a knowledge-institute for astronomical instrumentation funded by the Dutch state. The mission of ASTRON, the Netherlands Foundation for Research in Astronomy, is to “make astronomical discoveries happen by providing innovative observing instruments”. As such ASTRON is a technology provider for a very demanding customer base. We have a long standing experience in international projects, through our participation in international instrumentation development.

ASTRON operates the Westerbork Radio Synthesis Telescope. Since 1993, ASTRON has been working towards the next generation radio telescopes: the Square Kilometre Array and LOFAR. The latter will be the first operational facility that utilises massive signal processing, high‑speed data networks and full internet based operations. ASTRON has a Technical Laboratory organised around the competence areas of system engineering, antenna development, RF electronics, digital signal processing, and software/image processing. The Technical Laboratory also carries out major projects for optical, infrared and millimetre instrumentation. ASTRON disseminates its knowledge and expertise to regional SMEs through the SKAIHigh program, sponsored by the Northern provinces and Syntens. To realise its core business ASTRON needs to utilise state‑of‑the‑art and pre‑competitive technologies. For this reason ASTRON seeks partnerships with technology partners in various areas.



Prof. Harvey Butcher (butcher@astron.nl), ASTRON General Director

Dr. Mark Bentum (bentum@astron.nl), FP6 Consortium Coordinator

Prof. Heino Falcke (falcke@astron.nl), Senior Scientist LOFAR & European Coordinator

Dr. Marco de Vos (devos@astron.nl), LOFAR System Engineering Manager


ASTRON, P.O. Box 2, 7990 AA Dwingeloo, The Netherlands
Tel: (+31) (0)521 595 100

Fax: (+31) (0)521 597 332

www.astron.nl or www.lofar.nl