Perfect Fit

Here is the final post on the HBA installation which was finished earlier this month. As the project moves from major hardware installation to software and commissioning, reports from Chilbolton will be stopping, so you should expect fewer blog posts in the coming weeks.

Here it is: the last report:

Over the top of each HBA tile, there is a black UV-resistant cover. These are fitted to each tile and held to the ground via elastic rings that connect to the anchor ropes.

A rod is cut into the folded cover edge. An elastic loop is
included.



The elastic loop is knotted to provide the tension and an S-hook is attached.



Richard Whittaker goes around the edge of a cover fitting the loops and S-hooks.

Reaching the field edge

A little more on the HBA installation in Chilbolton (which was finished last week).

This one about the tricky details of using the digger to install the tiles at the edge of the field.

It is at the edge of the field that the use of the tracked digger becomes critical. The LOFAR Chilbolton site is on a slope, which means that to level the field, one needs to cut into the ground at the high end. That in turn leaves a bit of a steep slope to deal with.



In the image, Stuart Keenan, Zabet Ahmadi and Matthew Hambley complete the fitting of a tile by the field edge. John Murray backs up the digger to the higher ground behind the tile.

Droplets

Another beautiful image from Chilbolton:

After a night of light rain, the water droplets bead on the surface of a new HBA tile. Until the tiles have had a chance to wear in a bit, there are some interesting experiments in surface tension to be done. That, and taking photographs for desktop backgrounds.

More on the Owls

Continuing with more posts about Chilbolton wildlife, here's an update on the owls.

For those who were curious about the outcome of the little owl, it seems to have left the nest box now.

Here is another photograph, this time of one of the parents. This owl is perched on the edge of the roof of the control building at the Observatory.

Chilbolton rabbits in the news

Aparantly our Chilbolton rabbits have caught some interest in the press: this Daily Telegraph article "Rabbits Disrupt Project to Map the Universe" appeared today discussing the (completed expected) impact they have on the LOFAR LBAs and the plans put in place to limit the impact on the array (our very own rabbit proof fence).

All 97 HBA tiles installed in Chilbolton

The installation of HBA tiles at the LOFAR Chilbolton site has just been completed. So this is the final status update for the installation. There are still some backdated reports from Chilbolton I will be posting on the blog in the next couple of weeks.

The final status is shown on the below progress map, with today's work being shown with purple:




The final status is:
-- 13 tiles were installed on Friday 2nd July 2010 (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)
-- 10 tiles were installed on Thursday 8th (dark green)
-- 8 tiles were installed on Friday 9th (light blue)
-- 11 tiles were installed on Monday 12th (dark blue)
-- 8 tiles were installed on Tuesday 13th (violet)
-- 7 tiles were installed on Wednesday 14th (purple)

All 97 tiles have now been installed; we this work has been completed two days ahead of schedule. The whole of LOFAR-UK wants to extend their thanks to those who participated in this part of the project. A panoramic view of the completed HBA field in Chilbolton is shown below.



Even though all the LBA and HBA antennas have been installed, the Chilbolton LOFAR station is still far from complete. Work recommences tomorrow with continued RF-electronics work, landscaping around the edges of the antenna fields and installation of the optical fibre from the RF-container to the main observatory building.

HBA progress - 90 tiles installed

Here is another update on the LOFAR-Chilbolton HBA antenna installation. Today's work is marked in violet.




The current status is:


-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)
-- 10 tiles were installed on Thursday 8th (dark green)
-- 8 tiles were installed on Friday 9th (light blue)
-- 11 tiles were installed on Monday 12th (dark blue)
-- 8 tiles were installed on Tuesday 13th (violet)

There are now 90 out of 97 complete in the field. Today work also started on the installation of the RF electronics in the RF container. The sub-rack assemblies have now been put in and cable work is underway. Things are *very* messy at the moment owing to the muddy conditions.

HBA progress - 82 tiles installed

Another map for the LOFAR-Chilbolton HBA antenna installation. Today's progress is marked in dark blue.



The current status is:

-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)
-- 10 tiles were installed on Thursday 8th (dark green)
-- 8 tiles were installed on Friday 9th (light blue)
-- 11 tiles were installed on Monday 12th (dark blue)


We have 82 out of 97 now complete.

HBA progress - 71 tiles installed

Here is the new completion map for the LOFAR-Chilbolton HBA antenna installation. Today's progress is marked in light blue.



The current status is:

-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)
-- 10 tiles were installed on Thursday 8th (dark green)
-- 8 tiles were installed on Friday 9th (light blue)


Today was an extremely hot day. Working with 5x5m black boxes in the direct sunshine was very uncomfortable for the Chilbolton crew. Still, good progress was made. 71 out of 97 now complete.

The view from a balloon

This fantastic image of the Chilbolton LOFAR site was taken from a balloon flight a couple of miles away last night (July 8th). The dish and control rooms are clearly visible, as is the partially completed (the black regions) HBA field. Behind the HBA field is the completed LBA field although, of course, you can't see the individual HBAs from this distance.
Many thanks to Tim Freegarde (Southampton Physics) and friends for providing me with this!

Finishing touches

The HBA tiles are transported onto the field and put in specific places, as marked out by hundreds of survey pegs.


Once the HBA tiles are in their final location a black plastic cover is firmly anchored down over them. Here, Alex Escudero prepares a new cover.


A row of HBA tiles. The undulation is actually deliberate. Each tile has a slight camber in order to prevent water from pooling on the surface.

Still more HBA work

Stuart Keenan hammers an anchor peg into the ground. These anchors are hammered down about 600 to 700 millimetres. The angle is chosen to avoid interfering with underground cabling.



"Geen Problem!" (Dutch for "No problem!") Zabet Ahmadi prepares some cables ready for insertion into the base of and HBA tile.


Eric Petrusma (front left) and Rob D'Alessandro (front right) lift a stack of "lids" onto a tile under preparation. Bjorn Gustavsson (in front of the digger) fastens the lower plastic sheeting to the polystyrene frame. This viewpoint helps show the honeycomb structure within each tile.


John Murray drives the digger down onto the field to start work on tile deployment. In the lower right of the photograph is Eric Petrusma, giving a pretty good idea as to how big the lifting rig is.



Mal Clarke (left) and Jon Eastment repair a damaged cable with a set of careful joins, connections and sealant. The specialist toolkit was provided at short notice by ASTRON to respond to the problems on the site.

HBA progress - 63 tiles installed

Here is the updated completion map for the LOFAR-Chilbolton HBA antenna installation. Today's progress is marked in dark green.




The current status is:

-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)
-- 10 tiles were installed on Thursday 8th (dark green)


Tiles #93 and #94 were difficult to place owing to the proximity of a steep edging bank.

Today they have also done some work around the RF-cabin to improve the pedestrian access and the LBA field has now been completely cleared of left over building materials from its installation work.

Give and take

At times it might seem that the whole LOFAR installation process at Chilbolton is nothing more than moving dirt about. Either putting some in, or taking some out. Of course, there is a *lot* more to it than that. Still...

Take it out! Here Ian Northrop (left) and Harry Smith excavate the area around a pair of HBA signal cables that need checking.


Put it back! Before a tile can go onto the ground, the area must be cleared and any last-minute levelling done with a fine layer of sand. Here, Eric Petrusma (left) and Zabet Ahmadi (right) add and smooth some more sand. In the background, Ian Northrop does some final work on the previously installed tile.

HBA unfolding station

One of the HBA setup areas is known as an "unfolding station". For each batch of tiles that are deployed onto the field, there must be a place where they can be unwrapped, unfolded and fitted out. In this photograph, the tile is being prepared to be lifted onto the unfolding station (which is directly behind the tile and is not visible).




This is the lifting equipment that is used to lift the tile onto the unfolding station.

HBA progress - 53 tiles installed

Here is the updated completion map for the LOFAR-Chilbolton HBA antenna installation. Today's progress is marked in light green.




The current status is:

-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)
-- 8 tiles were installed on Wednesday 7th (light green)


The rework on HBA tile #0 was also completed today. Also, the last tile installed today was the centre tile, which is a dummy load only, and not an actual active tile. We have done a lot of work today in consolidating palettes and clearing the site as we move across the field.

HBA progress - 45 tiles installed.

Here is the updated completion map for the LOFAR-Chilbolton HBA antenna installation. Today's progress is marked in yellow.



The current status is:

-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)
-- 18 tiles were installed on Tuesday 6th (yellow)


HBA tile #0 has been hatched to indicate that problems have been discovered and there is rework that needs to be done. This particular tile should not be considered complete just yet.

Explaining the strange order

There have been a few questions as to why the HBA tiles are being installed in the order that they area. Direct from Chilbolton, here is the reason...

The connectors for each tile are on the south west edge. Because access is needed to make these connections, it is imperative that this side is kept free as the tile is being placed. In the example, the connector location for #64 is shown. If #64 was placed *before* #53, it would then actually be impossible to place #53, as there would be no access to its cable connections. This is why the tiles must be placed starting at the northeast and working south west in any given column.


Then there are the complications. Locations #6, #14, #21, #27, #31, #34 and #44 have problems with the cables (marked with crosses). Until these problems are fixed, we cannot place the tiles at these locations. This then effectively blocks that particular column. So, for example, we placed #12, #22 and #33, but because we cannot place #44, this column is then blocked from further placement.


Then, Tile #C is special. It has not been delivered to site yet. Until it has arrived, it presents another obstacle that we cannot pass.

Furthermore, the digger can only drive down certain columns due to the placement of survey pegs. The digger also has limited reach. Where it is shown at the moment, it can easily reach #69 and #70. And, because we do not want to turn the digger on the field (to preserve the surface), we can only go along the green lines.

And, once you've placed a tile, you can no longer drive passed it. So, if we place #70, we could no longer place #58.

So, following the initial placement from digger track A and B, we have moved the digger to track C, where there is a clear run of tiles that can be installed. While this is going on, repair work is being done on location #31, so after track C is complete we'll be able to reach #20, #31, etc. from the southeast edge.

Due to the various blockages, this is the most efficient way to proceed. Think of it like playing Tetris with an 18-tonne digger and 5m x 5m blocks!

HBA progress - 27 tiles installed

Here is the updated completion map for the LOFAR-Chilbolton HBA antenna installation. Yesterday's progress is marked in orange.



-- 13 tiles were installed on Friday 2nd (red)
-- 14 tiles were installed on Monday 5th (orange)

Some explanation of the strange installation pattern might be helpful. Due to connection limitations, tiles must be installed from northeast to southwest down each of the columns. The choice of columns has been dictated by ongoing work on the cables.

Although there is a good deal of colour on the map now, there is still a long way to go.

HBA antennas

As the HBAs are being installed now we thought you might like a post about what exactly a HBA (high band antenna) consists of. As you'll see they're rather more complex than the LBAs

Each HBA tile is composed of 16 crossed bow-tie antennas in a 4 x 4 grid. This grid is exposed at first, but during the assembly it is covered with polystyrene lids and then a polyurethane cover. Under the entire tile is a wire mesh, which acts as a backplane (like the ground plane wire mesh the LBAs had).

The honey-comb structure which holds the individual antennas.


A shot looking through a still-vertical tile at the 25m dish in the background.

Wet, wet, wet

Well, the spell of perfect weather is officially over. The Dutch, who were obviously feeling homesick, decided to bring some of their North-Sea conditions with them to Chilbolton.

In the pouring rain, Stuart Keenan prepares the lifting rig for the next tile antenna.



Alex Escudero and Stuart Keenan demonstrate the strength of the polystyrene tiles. However, it is suspected they were preparing to use the antenna module as a raft in the event of rising flood waters.




After another downpour, this photograph of droplets on an HBA tile was taken. The 25m dish in the background is apparently the world's largest weather radar... obviously enjoying the conditions too!

HBA progress - 13 tiles installed.

Like we did during the LBA installation week, we will be posting progress updates on days that HBA tiles are installed.

So here is the progress map for the LOFAR HBA antenna installation. Today's progress is marked in red.



Progress so far is:
-- 13 tiles were installed on Friday 2nd July (red)

First HBA tile deployed at Chilbolton!

Starting at 07:30 yesterday (Friday 2nd July 2010), in pretty miserable weather conditions, the first HBA tile was deployed at LOFAR-Chilbolton.

More on the geotextile

To stop the geotextile blowing away, it is nailed into the ground using 4-inch nails and wide washers. At other stations they use pegs (similar to tent pegs)... not possible for the rock solid Chilbolton ground.


Here the team are nailing down a freshly laid sheet of geotextile


The completed field. Ready to accept the first HBA tiles.

Geotextile

The HBA tiles are each 5 x 5 metres in size. They are closely packed, unlike the sparse LBA. However, they do not touch completely. Between any two tiles there is at least a 10 centimetre gap. In order to stop weeds from growing up in these gaps, long sheets of geotextile weed suppressant are placed along the inner intra-tile boundaries.

No, this is not the world's largest toilet roll! Instead, this is a roll of geotextile material, being placed at the field edge. The trolley to carry it has been custom built for this purpose. The crew are Eric Petrusma (left) and Harry Smith.


Here Harry Smith spools out another length of geotextile. Eric Petrusma is in the distance pulling it forward.

Checks and tests

At every stage of the installation work, the processes are being checked, tested and inspected.


Eric Petrusma from Autonational inspects a cable pair. It is important to ensure that the cables are always in good condition.



The 18-tonne digger does a test drive over some geotextile. As we will need to drive the digger over this fabric later, it is important to assess whether or not the tracks damage it in any way. (They don't!)

More work on the HBA cables

Before the HBA tiles can be placed, the cables need to be prepared to accept them. This means that the metal support stakes are removed, the surrounding rubble extracted and the support pipe taken off. They are then set to their final position ready for the next stage of the project. This work is being done by the engineers from Autonational.

Zabet Ahmadi opens up the cable egress points ready for separating and preparing the cables.


Stuart Keenan starts filling in the cables again having set the template to ensure that they are at the correct separation.

Yet another lorry

Another international delivery arrives at the Chilbolton Observatory.