Friday, December 17, 2010

Swedish LOFAR Station Construction

As Rob pointed out a couple of weeks ago, construction of the Swedish LOFAR station is just starting. Making the rounds on the internet this morning is the below beautiful image of the Swedish LOFAR station.
An aerial photograph shows the Onsala LOFAR station site. Credit: Onsala Space Observatory/Västkustflyg

This is how the image is described in the article posted at The Universe Today

"This aerial photograph shows the Onsala LOFAR station site at the lower right. Behind, the white radome of the observatory’s 20-metre telescope and the dish of the 25-meter telescope by the Kattegat shore.
The two circular areas where the LOFAR station’s high-band (snow-covered) and low-band antennas will be placed are already flattened. The cold weather has delayed the next stage in the work, deploying the fibre cables, but the Onsala station should still be fully operational by mid-2011.

Onsala is LOFAR’s northernmost station and will help give the array a close to circular beam. It will also contribute some of the array’s longest baselines."

Thursday, December 16, 2010

Follow SEPnet on Facebook and Twitter

SEPnet - the grouping of South East Physics departments who have contributed signficant funds to LOFAR-UK have launched a new website, and are now also on Facebook, LinkedIn and Twitter.


One of our plans for the LOFAR-UK station is to perform some SETI (Search for Extraterrestrial Intelligence) experiments (hopefully some as part of the remaining Project Dorothy dates). You'll hear more about this in the future.

This is just a quick post to point out that this week on the BBC there was a program about the Drake Equation (still available on iPlayer: there was also a rerun of a Horizon Program on SETI from 2008 (also on iPlayer at: 

Friday, December 10, 2010

Connecting Chilbolton to the LOFAR core

While the installation of hardware at Chilbolton was completed this summer, the LOFAR-UK station is still in a commissioning phase where data quality is being checked, and the full data link to the LOFAR supercomputer at Groningen (in the Netherlands) is being established.

The Chilbolton LOFAR Radio Telescope has two modes of operation, standalone and remote. Remote operation will see the radio telescope controlled by ASTRON in Dwingeloo and data sent to Groningen. Standalone operation (which is already happening - more on that soon) sees the telescope controlled from Chilbolton and the data stored locally.

Data rates from a LOFAR station under remote operation can be over 20-30 TB (that's tera bytes) a day, which is equivalent to about 5000 DVDs. So as you can imagine this kind of data cannot be sent over the normal internet lines and a dedicated path is required. In fact a 10 Gbps (giga bit per second) connection is one of the contracted requirements between LOFAR-UK and ASTRON for hosting a LOFAR station at Chilbolton.

Linking Chilbolton to the Netherlands with this dedicated 10 Gb/s connection (equivalent to adding 100,000 broad band internet users in the small village of Chilbolton in rural Hampshire) turned out to be quite a challenge for LOFAR-UK with a significant amount of effort going into researching the best options (and not to mention that it dominates the cost of the telescope!). The main challenge actually was to get the data to London from where a fast link to Groningen was relatively cheap and easy. Multiple routes to London had to be considered, the main two being via Southampton (to the south of Chilbolton), or via Reading (to the north). Going via Southampton might looks a bit like going in the wrong direction, but it reduces the number of intermediate service providers, thus keeping the cost low.

So while no actual observations have taken place yet combining the Chilbolton station with the main LOFAR core (currently 20 science-ready stations in the Netherlands), this article should explain
why the first connection over the full 10 Gbps link to Groningen (which occurred early last week, with the first full-capacity transmission taking place yesterday) is a significant milestone for LOFAR-UK and something we have all been celebrating.

Throughput tests are currently being conducted and we hope to be able to establish the first data transmission very soon.

Thursday, December 9, 2010

First Image from eMERLIN

Today is an exciting day for UK radio astronomy as eMERLIN has released its first image. This dramatic image shows the Double Quasar. In the image, light from a quasar billions of light years away is bent around a foreground galaxy by the curvature of space. A quasar is a galaxy powered by a super-massive black hole, leading to the ejection of jets of matter moving at almost the speed of light - one of which can be seen arcing to the left in the image.

This is a composite of the new e-MERLIN radio image of the Double Quasar and an earlier Hubble Space Telescope (HST) optical image. The radio emission generated by the black hole as seen with e-MERLIN is visible as the compact bright region superimposed on the (yellow-green) optical emission seen by HST.  
The e-MERLIN image is shown in false-colour with a colour table ranging from blue through red to white, where the colours represent the brightness of the radio emission. The HST image is made from WFPC2 images through two filters: the F555W filter (V-band) is coloured green and the F814W filter (I-band) is coloured red.
Credit: Jodrell Bank Centre for Astrophysics, University of Manchester 

e-MERLIN is an array of seven radio telescopes, spanning 217km, connected by a new optical fibre network to Jodrell Bank Observatory.

 As a radio telescope array eMERLIN of course has many similarities to LOFAR, but to readers familiar with LOFAR there are also several big differences. To start with eMERLIN observes at much higher frequences (shorter wavelengths) than LOFAR. The frequency (or equivalently wavelength) of electromagnetic radiation which can be detected using radio technology stretches all the way from sub-mm radiation (at many GHz) down to the limit set by the ionosphere at 30MHz (many metres in wavelength). eMERLIN detects radiation in three radio bands at roughly 1.5, 5 and 22 GHz, while LOFAR has two bands at much lower frequency (LBA at 30 - 80 MHz and the HBA at 120 - 240 MHz). This change in frequency means that the tecnhology for the antennas is much different. LOFAR as you know uses many dipole antennas all connected together by software for each "station". This would not work for the frequencies observed by eMERLIN which requires each point in the array to be a "traditional" radio antenna (as illustrated above). 

This e-MERLIN image demonstrates the successful transmission of wide-bandwidth digitised signals from all the telescopes remote from Jodrell Bank over the optical fibre network. This initial image, taken at a frequency of roughly 6.5 GHz, has an angular resolution of 50 milli-arcseconds, similar to the resolution of the Hubble Space Telescope. The new system is already approaching 3 times the sensitivity of the previous radio-linked MERLIN telescope. This will result in a very substantial (around a factor 5) further increase in sensitivity. Operations at full sensitivity, (achieved by including the Lovell telescope and upgrades of the bandwidths in the data links) are expected in 2011.

For more details see the press release at Jodrell Bank.

Wednesday, December 8, 2010

Bienvenue LOFAR Nancay

The LOFAR station in Nancay was the latest international station to have it's inaugaration (last week on Dec 2nd). The report of the inauguaration ceremony on the website of the Station de Radioastronomie de Nancay  (and reproduced below) will give all of us in LOFAR-UK a chance to practice our secondary school French on familiar scientific language.

Also another nice image of LBAs in the snow (taken from the Nancay website)

Inauguration du plus grand radiotélescope du monde. La France partenaire de ce réseau européen d'antennes inédit

LOFAR (LOw Frequency ARray), est aujourd’hui le plus grand radiotélescope du monde. La partie Française sera officiellement inaugurée à Nançay le jeudi 2 décembre 2010, lors d'une cérémonie sous le haut patronage de Valérie Pécresse, seront présent les astronomes et ingénieurs représentant les pays partenaires du projet, dont les Pays-Bas. C’est le consortium FLOW, qui coordonne la participation française à LOFAR au nom du CNRS-INSU, de l'Observatoire de Paris et de l'Université d'Orléans - Observatoire des Sciences de l'Univers en région Centre (OSUC). 

LOFAR est un très grand interféromètre basses fréquences (de 30 à 240 MHz), formé d'une cinquantaine de réseaux phasés (groupes d'antennes). Une quarantaine de ces réseaux, totalisant environ 35 000 antennes élémentaires, se trouvent aux Pays-Bas et une dizaine d'autres, environ 16 000 antennes, dans les pays environnants. En France, l'un de ces réseaux (1 600 antennes et leurs 96 récepteurs associés) vient d'être installé à la station de radioastronomie de Nançay (unité de l'Observatoire de Paris, du CNRS et de l'Université d'Orléans) en région Centre.

LOFAR combine électroniquement les signaux de ses antennes réparties sur des milliers de kilomètres à travers l'Europe pour former des images du ciel radio basses fréquences, beaucoup plus sensibles et précises que ce qui existe, dans un grand champ de vue instantané. Par l'utilisation de réseaux phasés déployés à grande échelle et connectés par fibre optique, de techniques numériques de réception du signal et d'un super-ordinateur pour son analyse, LOFAR ouvre la voie vers une nouvelle génération de grands radiotélescopes permettant d'observer plusieurs objets célestes en même temps dans différentes directions. C'est l'un des précurseurs du futur radiotélescope géant SKA (Square Kilometer Array), un projet international programmé pour les années 2020.

Le radiotélescope LOFAR servira une vaste communauté internationale d'astronomes pour l'étude détaillée de l'Univers aux fréquences les plus basses accessibles depuis le sol. LOFAR permettra en effet d'aborder des sujets aussi divers que la formation des premières étoiles et des premiers trous noirs de l'Univers, les galaxies, les amas et grandes structures, le champ magnétique galactique, la cartographie profonde du ciel radio, la détection des rayons cosmiques et des milliers de sources transitoires ou sporadiques (pulsars, explosions d'étoiles, trous noirs, planètes ... et peut-être exoplanètes), ou l'étude du Soleil.

LOFAR a été développé par l'institut ASTRON aux Pays-Bas. Le consortium FLOW, soutenu par l'Agence Nationale de la Recherche, étudie actuellement avec les ingénieurs de la station de radioastronomie de Nançay un projet de développement d'une extension majeure du réseau d'antennes LOFAR de Nançay (projet superstation).