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."

You can see more images from the Onsala Observatory at the Flickr page.

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.

SETI on TV

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: http://www.bbc.co.uk/iplayer/episode/b00wltbk/The_Search_for_Life_The_Drake_Equation/) there was also a rerun of a Horizon Program on SETI from 2008 (also on iPlayer at: http://www.bbc.co.uk/iplayer/episode/b0094cym/Horizon_20072008_Are_we_Alone_in_the_Universe/). 

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.

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.

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). 

Building LOFAR-Sweden

While in the UK we've completed our LOFAR station and can retreat inside our homes when the icy weather comes, in Sweden, they have just started the construction of their station, at Onsala. The image below is a great snapshot taken today of the preparatory work underway amidst the snow and ice (credit John Conway).

Sweden will be the final one of the 'founding' members (NL, DE, France, UK, Sweden) of the International LOFAR Telescope to construct their station, and we expect full operation of the entire ~40-station array in 2011.

In the meantime, our station at Chilbolton has been taking some observations of the Sun, and should be connected to the Dutch supercomputer/correlator in the very near future, allowing the first high-resolution images utilising the British baseline. More posts coming soon !

Turbo-fans

Here's a rare peek inside one of the signal processing servers. Note the two forced-air heat-sinks on the motherboard. This computer is one of four servers that will be used to control the array of GPU-processors which, in turn, will perform the de-dispersion calculations (see Heavy Duty Computing).

And, yes... when they are running all of these machines make a LOT of noise!

Cable Calibration

In order to form the best possible result out of the LOFAR system, it is essential that we can calibrate for the signal travel-times. This means not only being able to know the direction from whence the signal came, but also how long it takes to travel through every cable and every circuit.

Each cable within the system is carefully manufactured and labelled. The serial number on the cable contains information about its performance and role. For example, the one in the photograph (CHY-0853425-1305090755) is an "C"able from the "H"igh-Band Array, "Y"-polarisation. It is "085" metres long and has a delay of "3425" tenths of a nanosecond. This means that, in laboratory conditions, it takes 342.5 nanoseconds for a signal to travel down this cable.

However, that is in the lab.

Although this is a pretty good measurement, to really get the best performance we need to know the signal delay in the field, now that the cable is in place. Things such as connectors, thermal variations and other deployment factors can contribute to subtle variations in the effective cable length. Calibrating these sorts of things is part of the vital commissioning work that is currently being carried out on the LOFAR Chilbolton station.

Shut the door!

Inside the RF-container lies all the electronics that does the signal processing. Because there is so much of it, and it is so close to the antenna array, it is crucial that it is shielded to prevent interfering signals from escaping from these electronics to feedback into the system.

Now that we've started taking routine calibration and test data, it is important to keep the RF-contain sealed against unwanted radio leaks.

The notice on the door reads: "INTERFERENCE HAZARD - The equipment in this RF-container can disrupt telescope observations. Do not open this door without first checking with the Operations Group."

Heavy Duty Computing

With the main antenna arrays now complete, we are now concentrating on getting the data processing equipment set up. One of the major components of this is the computer system that will perform the de-dispersion calculations. Dispersion is a physical phenomenon where the signals at different frequencies travel at different speeds through a medium. In our case, lower-frequency radio waves travel through the interstellar medium slower than higher-frequency radio waves.

In order to add signals together (for example to analyse the pulses from a pulsar), one must first apply a correction for the dispersion that occurs. Although it is possible to estimate what the dispersion will be, based on our knowledge of the Galaxy, ultimately one has to simply try lots of different dispersion measures.

That means a lot of calculations, which means we need some pretty high powered, specialist computing to do the work. The project to do this for LOFAR is being led by the University of Oxford on behalf of SEPnet.

Caption 1 :  Dispatch from the University of Oxford.

Caption 2 : Aris Karastergiou unloads another GPU-server from the delivery van.

LOFAR HAKU

The RF-Container at the Chilbolton LOFAR station is an adapted shipping container. Because ships and storage facilities can hold many tens of thousands of containers, it is important to be able to identify them. As a result, containers from a given manufacturer are marked with a unique 7-digit serial number (strictly speaking it is a 6-digit code plus a single-digit checksum). Additionally, the serial number is prefixed by a four-letter code to denote the company that built the container (these prefixes always end in the letter "U"). The code for the RF-container at Chilbolton is HAKU2961555.

HAKU is the prefix for containers manufactured by "Container Company Amsterdam BV".

However, HAKU has another meaning.

During the visit from the ionospheric physics group, Derek McKay-Bukowski described the LOFAR system, with its multiple beams, rapid direction-switching and de-dispersion back-end, as an "astronomical search engine". After the presentation, an e-mail was received from Thomas Ulich, asking if we knew what the "HAKU" on the side of the container meant. While we were aware of the container serial number, as explained above, what wasn't known was that "haku" is the Finnish word for "search". Thomas explained that "hakukone" means "search engine" in Finnish; "kone" is engine, and "haku" means "search, fetch, retrieval", but also "quest, trawl".

So our LOFAR container certainly has the correct name!

Ionospheric Visit

Because of the frequencies at which LOFAR observes, an understanding of the ionosphere is crucial to the interpretation of our results. On the other hand, LOFAR also offers a powerful tool for investigating this tenuous layer of the earth's atmosphere.

On 27-28 September 2010, a special meeting was organised by the UK solar-terrestrial physics community (MIST) to celebrate the life and work of the late Prof. Henry Rishbeth (1931-2010). The meeting took place in his home city of Southampton, and celebrated Henry's long commitment to the advancement of ionospheric science. And, on the afternoon of the 28th, a number of the attending physicists visited the LOFAR Chilbolton station. (Photograph by Th. Ulich.)

This post also appears on the STFC RAL website.

LOFAR like arrays for satellite TV and radio

There have been a couple of articles on technology news websites in the last week about the possible use of LOFAR like arrays to receive satellite TV or radio.

Gizmag: New chip could allow antenna arrays to replace satellite dishes

Next Big Future: Virtual Satellite Dish using energy efficient special DSP chip

Seems like an interesting impact of the development of software pointed radio telescopes like LOFAR - to make getting digital radio on your smart phone possible, or remove the need for aiming satellite dishes.

World Space Week at Intech

LOFAR-UK was represented at this year's World Space Week events at the Intech Science Centre and Planetarium near Winchester, Hampshire. Members of SEPnet universities put together some demonstrations of the technology behind LOFAR including radio wave detection, and fibre optic transmission of information.

A LOFAR-UK poster behind a demonstration of fibre optics.

There was an LBA on site. It was put together by an expert member of the student army and good enough to give an idea of the simple materials used, but definitely not going to quite pass inspection to join the array! Unfortunately we don't have any space ground planes at present, so this just shows the central pole, LNA and antenna wires, but we are planning to make a mock up ground plane to improve the demonstration for next time.

SEPnet members demonstrating the transmission of information by fibre optics to a group of school children.

Fibre

Yesterday and Tuesday, the BT engineers were on site to install the network termination equipment (NTE) for the 10 gigabit link. This is the connection equipment that will transmit the data from the main Chilbolton building to the next major network point which is located in Southampton.

Caption 1 : The BT van arrives at the main building at Chilbolton Observatory

Caption 2 : Installed. This is what the connection looks like in the comms room at the observatory.

LOFAR-UK on OU Learn Channel

LOFAR-UK now appears on the OU Learn Channel. In the below video Dr Stephen Serjeant (reader in cosmology at the Open University and a member of LOFAR-UK) talks about the recent opening at Chilbolton about how LOFAR works and the exciting cosmology it will do, along with how the Open University is involved.

Overview Images

Yesterday at Chilbolton, we made use of the trailer-mounted cherry picker. The first image was made from a height of approx. 10 metres above the hard compound at the end of the HBA array. It gives a great view of the HBA, but the LBA is still visible in the distance.

The second image is from the opposite right side, looking back over the LBA, but also with an excellent view of the HBA and 25m dish in the background. It was made from a height of approx. 16 metres.

The final image shows the photographer in action; not a job for anyone with a fear of heights.

LOFAR-UK on ASTRON Image of the Day

The LOFAR-UK Chilbolton Station has appeared again on the ASTRON Daily Image, this time for October 6th 2010.

See LOFAR on BBC Horizon

Bob Nichol was on last night's episode of Horizon explaining how LOFAR can be used to learn about what might have happened before the Big Bang.

View it on iPlayer link.

Watch LOFAR-UK on Sky at Night on iPlayer

You can at the moment watch the report on LOFAR-UK on the Sky at Night on iPlayer. The start of the episode is at this link. The point at which the LOFAR-UK segment starts is here (roughly at the 23 minute mark).

Enjoy.

Transformational Science from a Revolutionary Radio Telescope

Now available on YouTube is the talk "Transformational Science from a Revolutionary Radio Telescope" given by Prof. Rob Fender (Southampton Uni/LOFAR-UK Project Leader) at the LOFAR-UK Chilbolton Opening on Monday 20th September 2010.

LOFAR-UK on Sky at Night

Related to the previous post, LOFAR-UK will also feature in the upcoming episode of Sky at Night after Chris Lintott helped with the LBA installation in June.

LOFAR-UK in Sky at Night Magazine

There is a 6 page article about LOFAR-UK and Chilbolton in the September issue of Sky at Night Magazine.

LOFAR-UK on the main LOFAR website

The main LOFAR website ran a story this week about the Chilbolton Opening.

We are also featured in the ASTRON Daily Image for today.

(After today you can find this and other daily images about Chilbolton by going to the Archive (link at top of the Daily Image page) and searching for "Chilbolton".)

Derek's Talk at the Opening

On Monday I filmed the speech given by Derek McKay-Bukowski (LOFAR-UK Project Manager) at the evening event in the Intech planetarium. Thanks are owed from all of use to Derek for making LOFAR-UK such a success.

Video of Soundbite Interviews

At the opening on Monday I filmed short "soundbite" interviews with many of the scientists involved in LOFAR-UK. The resulting video is a nice summary of the excitement felt within the UK community (and wider) about our involvement in LOFAR.

Video of Ribbon Cutting at Chilbolton

This video shows hi-lights from the part of the LOFAR-UK opening on Monday 20th September 2010 which took place at the Chilbolton Observatory itself. This included a ribbon cutting by Dame Jocelyn Bell-Burnell, and some real time observations of a bright pulsar (as explained by Dr. Aris Karastergiou).

Coverage of the Opening

There has been some online coverage of the opening events on Monday. Here's a collection of links. If you have something to add let me know.

BBC Science Article

Redorbit (Science, Space, Technology and Health News and Information)

Space Daily

Sify News (Indian News)

LOFAR-UK links:

Universities:

Birmingham,
Edinburgh,
Portsmouth,
Southampton,
Sussex

STFC Press Release (which includes a video of the ribbon cutting and the first pulsar observations)

Official LOFAR-UK Opening

Yesterday was a big day for LOFAR-UK. The station at Chilbolton was officially handed over (as per an earlier blog report) and was also officially opened by Dame Jocelyn Bell Burnell in a ribbon cutting ceremony out in the field.


(Picture taken by James West, SEPnet)

This ribbon cutting was followed by real time observations of one of the brightest pulsars in the sky (thanks to Aris Karastergiou from Oxford Univ. who had worked very hard and set up some impressive computing to process the data to show us in real time). Jocelyn seemed very pleased to see the telescope worked, and was very excited particularly about it's potential to detect new transient radio emitters.


(Picture taken by James West, SEPnet)

After the Chilbolton event was a celebratory event held at the nearby Intech Science Centre. Rob Fender (LOFAR-UK PI, Southampton Uni), John Womersley (STFC), Mike Garrett (ASTRON) and Derek McKay-Bukoswki (Chilbolton Station Project Manager) all gave talks, and then Jenny Shipway (Intech Planetarium Manager) gave us a wonderful planetarium show specially adapted to include links to LOFAR science. I think I can speak for most astronomers in the room by saying that we don't get to see planetarium shows very often, and it was a wonderful reminder of the inspirational science behind why most of us got into this game in the first place.

Also we had cake.

(Picture taken by Bob Nichol, Portsmouth).

Well done to everyone involved.

Sign of the times

The finishing touch on the LOFAR field was putting up the sign. On it, apart from the station name (LOFAR-UK Chilbolton) and number (UK608), there are the logos/names of all the contributing organisations.

Official hand over from ASTRON

On the morning of 20th September 2010, just ahead of the official opening, the delegation from ASTRON arrived at Chilbolton Observatory to review the progress and hand over the LOFAR station formally to STFC and LOFAR-UK. Part of this included an inspection of the site and the comments were all extremely positive concerning the professional work done, efficiency of the build and the final presentation and attention to detail. During the handover meeting itself, Corina Vogt (the ASTRON representative) said that the only thing she had to say about the field was "Wow!"

Caption : Corina Vogt, Michiel van Haarlem and Harm Munk at LOFAR Station UK608.

Ready for a new era of British Astronomy

The LOFAR Chilbolton Radio Telescope now stands ready for the official opening, which is due to be held on Monday 20th September 2010. Although the opening is but a single moment in a long programme of construction, installation and commissioning, it is a significant one. And now is a good time to pause and reflect on the past few months and what work has been achieved. To have come so far so quickly has been fantastic and everyone involved in this project should be proud of all that we have accomplished and look forward to the significance and celebration that will follow.


Caption : Looking through the LBA field at sunset. The monolith on the horizon is the RF container and in the distance the silhouette of the 25m dish can be seen.

Replacement Signal Processing Board

During the commissioning work, we discovered that one of the network connections on one of the digital signal processing boards was not working correctly. By exchange modules with others, we could determine that the fault was located in this particular board. As soon as we have completed the detective work, ASTRON were notified and a replacement board was sent out immediately.


Caption: This new board has now arrived and was fitted and initialised. The photograph shows the board as it was being unpacked. The new component is now fully fitted and is working correctly.

Aerial at dusk

This photograph is a close-up shot of one of the low-noise amplifier (LNA) modules that is found at the head of each low-band array (LBA) aerial. This particular one is number #76, the number of which can be discerned in amongst the other code sequences on the bar-coded label.

More commissioning work

With only a few days until the official opening, everyone is really putting in the hours to ensure that as much commissioning work is being accomplished as possible.


Caption: Aris Karastergiou works late into the evening with the configuration of the Local Control Unit in the RF-container.

Front desk

At the front desk at Chilbolton Observatory is Jan Lass. Now, Jan is just great; she is the friendly smile whenever our visitors or colleagues arrive at the site and she ensures that everything remains organised and efficient. Jan has been instrumental in sorting out some of the important contracts that were placed for the LOFAR project and we have only managed to get this far because of her work behind the scenes.

Caption: Many thanks Jan, we really appreciate all you have done for the LOFAR Chilbolton project!

Installing the data processing system

The data processing system for the LOFAR Chilbolton station is being developed by Oxford University. When complete, it will be a large system with multiple server and control computers as well as a small cluster of GPU blades to do the heavy-duty number crunching. As part of the initial commissioning work, a small part of the final system is set up temporarily in the comms room at the Chilbolton Observatory, in order to test the system.


Caption : Aris Karastergiou (left) and Alan Doo at work on the installation of the two GPU blades in the rack on the left. The tangled bundles of cables on the right are NOT part of the LOFAR system!

Checking the polarisation

There are a lot of connections within the system and it is important to check that they are all working. One that is difficult to notice is the polarisation of the signal. In order to test this, a temporary test transmitter is setup, which sends out a low-power signal. This is then used to check that the correct signal is going through the correct chain in the electronics.


Caption : Here is the test aerial. The RF-container can be seen in the background.

Skip nothing

On 2nd September 2010, the skip that was located at the LOFAR field site was removed and brought back to the main Observatory compound. From there, it was loaded with a few more items which needed disposing of from there. However there was very little waste to be removed.


Caption : Here the skip is about to be loaded onto the lorry for the last time before leaving the site.

Setting up the networks

During the work on the LBA and HBA, there was a parallel task of establishing the network connections. These are for within the RF-container itself, but also between the RF-container and the main Observatory building.


Caption : Klaas Stuurwold takes some notes during the network set-up process.

First signals

On 1st September 2010, at 11:38 UTC (12:38 local time), we measured the first signal from the completed LBA array at Chilbolton. These data are from all 192 channels (96 aerials, 2 polarisations each) and show the expected bandpasses from all elements functioning normally. Although not a sky image just yet, this is an important milestone in the development of the project. Thanks go to Menno Norden, Klaas Stuurwold, Henri Meulman and the local commissioning team for their work in getting to this point. However, this is also a moment for everyone involved in any way throughout the entire installation of the LBA. Without your contributions, this would have been impossible. Well done!

Caption 1 : The first signal. Although just a blurry photograph of a computer monitor, this is the first moment where radio signals have been correctly received, amplified, digitised and processed.



Caption 2 : Some of the commissioning team. From left-to-right: Menno Norden, Klaas Stuurwold, Matthew Davies and Alejo Martinez-Sansigre.

HBA testing

Like the Low-Band Array (LBA), the High-Band Array (HBA) also needs to be tested and the commissioning work finished. This means checking the response of the HBA elements and making sure that they respond correctly and give the correct signal output.


Caption 1 : In the event of a problem, an engineer needs to go out onto the array, find the unresponsive tile and repair it.



Caption 2 : Henri Meulman completes the work on one of the HBA tiles. It is possible to see the polystyrene skeleton of the open HBA tile.

LBA-commissioning

On 31-Aug-2010, a crew of three engineers from ASTRON started work on the final RF commissioning work. This meant establishing that all the low-noise amplifiers (LNAs) are functioning and that the signal can be processed through the electronics in the RF-container. Once that work has been done, then we are ready to start testing the system as a telescope.

During this work a number of polarisations were discovered to be not functioning. This is to be expected, as there are often problems with the response of the LNAs or issues with the connections. In total we discovered four polarisations between three aerials that needed attention.

There was one worrying moment when we though the problem might be the cable, not the LNA unit, but the concerns were unfounded. Within a few hours all the systems had been checked and working correctly.



Caption 1: Menno Norden fits a new LNA cap to one of the aerial posts.



Caption 2 : Sarah James reconnects a new LNA cap.



Caption 3 : Henri Meulman uses a Time-Domain Reflectometer to test a cable for possible defects.

Foggy start, fiery finish

Caption 1 : On the 31st August 2010, the Observatory began the day with an eerie start. As the sun rose and started burning off the fog, the shapes of the landscape gradually began to emerge into view. By about 08:00 hours, the fog had vanished.


Caption 2 : 12 hours later on the same day, there was a spectacular sunset, with high cloud and a blaze of sunshine from the western horizon. This photograph was taken from near the camera that points to the LOFAR field, looking back over the Observatory buildings.

Off-road

As part of the final work on the field, the Land Rover was used to travel around the site edge to gather in all the remaining debris and left-over fencing material. This photograph is looking down over the bonnet of the vehicle.

A new vista

This panorama of the LOFAR-Chilbolton field was taken on the morning on 28th August 2010. It shows both LOFAR fields; the solid-packed HBA on the left and the sparse LBA to the right. In the background is the 25m dish at the main Chilbolton Observatory compound. In the picture there are two containers. The blue one directly behind the HBA is the skip where surplus construction materials are stored. It will be removed from the site soon. The other, just beyond the right-hand edge of the HBA field is the RF-container. The main Chilbolton Observatory building is just to the left of the 25m dish.

IT rack

On 27th August 2010, work started on installing the IT equipment in the main building. Here are the first two modules to be added. The top one is the optical fibre patch panel for the 8-core fibre that runs between the LOFAR field and the Main Building. Below it is the 10-Gbit/s network switch.

Good moon rising

On the evening of the 24th August 2010, one of the site security cameras caught this photograph of the moon rising over the LOFAR field. There seem to be three containers in the photograph. The raised one on the left is an WWII ex-RAF water tower. The middle one, with the white box on the side of it, is the RF-container. This is where the bulk of the LOFAR signal processing occurs. The white box is the air-conditioning unit. The battered-looking container on the right is the construction skip, where the surplus and waste materials are temporarily stored.

Compound cleared

As of 24 August 2010, the hard-standing at the end of the LOFAR field has now been completely cleared. It is certainly strange to see it as it was before the construction equipment moved in last March (ref: http://blog.lofar-uk.org/2010/03/ground-works-start-at-chilbolton.html). The white box and dish in the far distance on the right-hand side is the Chilbolton 4.5m ground station.

Data link

On 16th August 2010, the ISDN control line was established. Between the Chilbolton site and the supercomputing centre in Groningen, there is 10 Gbit/s link. However, this link is mono-directional. We can send data to the Netherlands, but there is no way to send data back. For the data itself, this is fine. However, it is also necessary to send back control signals. For the telescope a conventional Internet connection is used. However, for the control of the 10 Gbit/s transmission equipment a second ISDN line is required.

Caption 1 : The lines run through a tunnel on the site. This view is looking down the tunnel in the direction of the termination point, where the BT lines first come onto the site.



Caption 2 : BT engineer fitting the ISDN connection in the room where the terminations are.