Moved storage

In order to build the Low-Band Array, the storage containers need to be moved from their original locations. The new location is by the service road that runs along the northern edge of the High-Band Array.

The storage containers in their new locations. Photo: Joona.

These contains have various boxes and parts that are either left-over from the build or are needed for when the main antenna deliveries arrive.

International EISCAT Radar School 2012

From the SGO website...

In the near future the EISCAT Scientific Association will face a major instrumental upgrade with the ESFRI Roadmap project "EISCAT_3D: A European Three-Dimensional Imaging Radar for Atmospheric and Geospace Research."

EISCAT, in co-operation with the Sodankylä Geophysical Observatory, will run a training course for new users of the EISCAT radars, from 27th August to 1st September, 2012 (Monday to Saturday). The training course will be held at Sodankylä, where one of the EISCAT UHF remote sites is located.

The course will cover all essential aspects of the current EISCAT systems, including the science programme. An overview of the existing hardware and software will be provided and future plans will be discussed, with a strong emphasis on EISCAT_3D. The course will have a very strong emphasis on practicals, i.e. work in groups of participants on real data. There will be a dedicated radar experiment for every group, and the groups will then analyse their data and present their results under the guidance of an experienced team of instructors.

The deadline for registration is 12th July 2012.

For more details, see:  http://www.sgo.fi/Events/RS2012/

Trailer mods

To get the LBA grids back to SGO, we needed to modify our trailer. Here are some photographs from that:

The removed trailer cover is inverted. If the lake wasn't
frozen, I'm sure we'd have tried to launch it!

So, for now, it has to be stored in the container.

Then the grids can be loaded onto the trailer.

And finally set off for SGO!

LBA cable routing

In order to get the cables from the LBA area back to the RF-container, we have to work out the best routing. There were several options, but there necessarily needs to be a trade off between the direct route, dodging boulders and so forth.

This adapted photograph shows some of the possible locations for the main ducting, based on some of these considerations. The possible routes are shown in amber. The purple shows the location of the existing HBA cables, which are now fully buried into the ground.

LBA grids for SGO

Half the LBA will be built at KAIRA and the other half near Sodankylä. This means transporting some of the grids back to SGO. To do this we investigated various ways of doing this transport work.

In this photograph, you can see some cut grids in the foreground, ready to be loaded on to the trailer.

Sorting out the woodwork

In order for the LBA to be placed, the left over woodwork from the HBA frameset build needed to be moved.

This was done by the RAL/SGO team by hand.

In no time we had everything cleared up and sorted out ready for the LBA ground works. In the second photograph, the LBA grids are on the left, spare frames in the centre and left-over HBA pallets on the right. All the left-over timber will be re-used to build snow fences to help protect the aerials and tiles.

LBA test aerial and HBA

Just a nice photograph for the weekend. Again, taken by our camera-wielding (but camera-shy himself) summer student, Joona. Don't forget you can click on all the photographs to see larger versions!

LBA test aerial and the HBA in the background. (Photo credit: Joona)

Have a nice weekend!

Summators (mostly) installed!

Here is the final photograph from the HBA summator installation. In the end we installed 48 Y-polarisation units and 42 X-polarisation units. We could not install the last few X-polarisation units, as we did not have a full set of parts. This work will be completed in July when the ASTRON team are back to do the next stage of the RF installation work.

Five of the HBA installation team (minus Joona... who took the photograph!).

A big thank you to all the team for their efforts in getting the job done in such a short time. Owing to the windy weather, it was just as well it was completed soon. But it had stayed dry, which was important... although with the consequence of a lot of static electricy, which meant we were regularly getting zapped!

The weather turns

Despite it being June, the weather wasn't always kind. High winds made life difficult for the installation work. However, the temperatures stayed cool, which was very welcome. We even had some snow as we were installing the last few units.

Only a few HBA tiles to go! (Photo: D. McKay-Bukowski)

In the background, you can see the mountains, but between the site and the mountains is Siilasjärvi, the nearest lake. Its surface, along with most of Kilpisjärvi itself, was still covered with ice.

Tile damage

During the HBA summator installation we discovered one tile lid that was partially fractured. We suspect this was from loading too many people on what may have already been a weak lid. Having found the crack, we removed it and tested to see where it would break and, if so, how. Here is the result.

A fractured tile is subjected to additional pressure.

Overall, the system has held up remarkable well. The LOFAR tiles turn out to survive the Arctic environment very well.

Summator installation revisited

This panorama was taken from the top of the RF-container during the HBA summator installation week. Note the open tiles with the team busily connecting the new units.

HBA summator installation at KAIRA. (Photo credit: D. McKay-Bukowski)

In the background are Saana (left) and Pikku Malla (right). The Lehtinen Barracks are in the left foreground.

HBAs with Saana beyond

Just a nice photograph today. Again, this is one taken by our summer student, Joona.It shows the edge of the HBA tiles with Saana in the background. Despite it being mid-June, there is still a lot of snow on the mountains (and even still a bit on the site itself!).

Saana seen in the distance beyond the HBA tile edges. (Photo credit: Joona)

The photograph was taken during the summator installation week. And, yes, the weather was not going to remain perfect for us throughout!

LBA tests

During the winter of 2011-2012, we set up three test platforms for the LBA aerials. These were located on the tundra to the north west of the HBA.

The test LBA aerial with the HBA in the background. (Photo credit: D. McKay-Bukowski)

Although superficially they look okay, the sparse array, combined with the reduced DSP set and the non-uniform ground plane, make this location for deployment not suitable. However, it was good to see that the antennas themselves had held up okay during the snowy months.

Lying down on the job?

It may look comfortable, but installing the summators was seemingly neck-breaking work. To reach into the tile, you have to lie on your stomach. Your hands are busy connecting cables so you can't support yourself with your arms. And, holding your head out to see what you are doing puts a strain on the neck.

Trying to make the most of the good weather, we had multiple tiles undergoing HBA summator
installation at once. In the background is Saana. (Photo credit: D. McKay-Bukowski)

Add to this the constant climbing up and down off the 2-metre high tiles and by the end of each day we were all exhausted.

Clear skies

During the week we had a team of six on the site: 2 ASTRON engineers, 2 SGO staff, 1 RAL scientist and an SGO summer student. The summer student (Joona) was responsible for many of the photographs that were taken during the week and he was glad to share them with us. So, here's one of his best for ending the week.

Photo credit: Joona

This photo shows the clear skies during the HBA summator installation week (as you'll see later, they weren't always that way!). The array on the left, and the RF-container and barracks on the right. In the far distance are the mountains in Norway. Have a nice weekend!

Installing the summators

To install the summators, the HBA tiles must be opened up.

The team peel back a cover and remove one of the cell lids. (Photo credit: Joona)

Then the cell arc is removed, the summator attached, and the cables connected. Tests are done to check the resistance of the summator, and thus check for any failed circuits.

An ASTRON engineer fits a Y-polarisation summator. Note the test equipment on the cover nearby. (Photo credit: Joona)

There are two summators per tile, so after the X-polarisation summator is done, the adjacent cell is opened to the done the Y-polarisation. Finally, the covers are all put back, and the anchor lines re-attached to the timber frame sets.

RAL and SGO staff re-secure the cover on one of the tiles. (Photo credit: Joona)

It is tricky work. With so many cables, one must be very careful to ensure that no mistakes are made. We had a system of checking and cross-checking each others work to ensure that the installation was error-free.

HBA summators

The HBA (High-Band Antenna) summators are units that reside inside the HBA tiles. They act as analogue beamformers, providing an initial level of control to steer the tile primary beam over the sky.

From front to back: a Mark-I summator, two Mark-II summators and
another summator still in its anti-static bag. (Photo credit: Joona)

There are two designs: the older "Mark-I" design uses a sheet-metal box. They are nominally okay, but in the Netherlands where there are high moisture levels, condensation causes some failures. The newer "Mark-II" design is completely encased in black resin (similar to the LBA low-noise amplifier units). These are more robust. For KAIRA, our installation comprises Mark-I summators for the X-polarisation and Mark-II summators for the Y-polarisation. Normally summators are installed in the tiles as they are assembled in the factory. However due to unit shortages in 2010 and 2011, we had this postponed. This means that the summators must be installed in situ. This work was carried out last week, and we'll be reporting on the work over the next couple of days.

ASTRON arrives

Last week a couple of engineers from ASTRON arrived to install the HBA summators at KAIRA. The next few posts will be from that visit.

Members of the HBA installation team.(Photo credit: Joona Keskitalo)

Flying to KAIRA

This photograph was taken just as we started to get off the aeroplane at Helsinki airport. This is part of the long journey up to KAIRA.

Arrival at Helsinki.

There are two common routes to KAIRA. One is to fly to Helsinki and then fly to Rovaniemi. From there, you can take the Murmansk-bus-service, and get off at Sodankylä before driving from SGO there up to KAIRA. Alternatively, you can fly in via Norway. First to Oslo, then a connecting flight to Tromsø, before driving to the site. This second method is faster, but you don't get to visit the institute at Sodankylä.

LBA location

There have been a number of factors which have influenced the design of the KAIRA array. As a result, it is definitely not a standard layout, as far as regular LOFAR stations are concerned. The primary aim of the station is to satisfy the VHF reception from the EISCAT radar system. This has determined the layout and position of the HBA. The LBA, on the other hand, needs to remain secondary to this and we have tried to work out a suitable configuration that will still allow us to accomplish our complicated scientific requirements.

However, there has been an additional complication: the original LBA field site is simply not stable enough to take the LBA array as originally planned. This has forced a rethink but, in turn, this has actually allowed us to come up with a better solution, that we could not have foreseen before the HBA was built in 2011.

The plan now is to locate the LBA to the south-east of the HBA. This gives a large number of benefits. Firstly, in terms of deployment, this is the easiest area to work with. There are no ground stability issues and there are no problems in terms of vehicle access, which would be the case on the tundra. The new area is also (mostly) in the shadow of the HBA, thus affording additional protection. It is on the raised mound which should also help keep snow levels down.

Proposed area for the KAIRA LBA.

The array area is shown in the following diagram. At this stage the exact placement of individual aerials is not shown, but we will discuss this in another post coming soon.

Arctic trees

Just a nice photograph of some of the trees along the edge of the KAIRA site. Enjoy your weekend!

Trees at the KAIRA site in May.

LBA survey work

Here are some photographs taken from the LBA survey. We used a combination of metal survey tapes, laser levels, laser ranger finders and direct and trilateration measurements.

Measuring and recording another field height.

A path of snow cleared for the laser level.

White board

Ah, a proper white board! This photograph was taken of some quick sketches in the snow, as we planned the grid and triangulation method that we will use for the LBA survey.

A traditional white board.

More snow poles

From the recent blasé comments, I don't think that everyone appreciates how deep (and dangerous) the snow can be. At the leading edges, snow densities are high and depths can reach two metres. In the photograph here, Markkus and Toivo provide a good comparison for scale. The orange posts that they are placing along the array are 3 metres tall.

Posting along the drifts.

When the snow builds up like this, it can crush structures through the sheer weight of it. Packed snow can be quite heavy, as the destructive winter testing in 2011 showed.

Snow clearing re-visited

Another panorama today! This one is taken from the exact opposite end of the site as yesterday's, now looking north. It shows the LBA field clearance in the foreground, about half completed. The stack of grids in the foreground (on which Toivo is standing), are those that will be used for the LBA.

Snow clearing work at KAIRA. (Click to enlarge)

Panorama of the KAIRA site

KAIRA, May 2012. (Click to enlarge)

Today we have a large panorama to share with our readers. This was taken from the top of the RF-container, looking south. In the distance, there is Saana on the left and Pikku Malla on the right. The photograph was taken in mid-May, so there is still heavy snow cover across the site, especially on the leading edges of the array sections, where it has banked up. The building in the left foreground is the so-called "Lehtinen Barracks".

Rise to the HBA

Today, just a nice photograph looking up the slope from the south-east edge of the site towards the HBA.

KAIRA's HBA.

Enjoy!

Snow mobile trail

Along the south east edge of the site, there is a trail that runs along the reindeer fence. This is marked with red-crossed-posts to show the way. There is not much traffic along this path, which runs from Finland to Norway, but there were still a few lines in the snow.

The snow-mobile trail that runs past the KAIRA site.

Note that although the fence is metal, it is nearly 10 metres below the level of the HBA tiles, thus well out of the way and not a problem in terms of reflections into the system.

Snow clearing

The low-band array (LBA) will be located on the expanse of ground to the south of the high-band array (HBA). At the time of the site survey in mid-May, this was still completely covered in snow. We brought in a tractor to clear off the bulk of it and expose some of the rock underneath.

The snow tractor arrives at the site.

Making headway into the deeper parts.

Major snow banks of snow.

With the site mostly clear, natural sunlight heating the dark ground underneath will rapidly melt the remaining snow ready for the work starting on the site in early June.

Kilpisjärvi

Järvi is a Finnish word, which means lake. During May, Kilpisjärvi (the lake) has had a frozen surface. This breaks up during June. However, at the time of the site inspection visit, it was still a solid sheet of ice, with occasional people skiing, or even riding snowmobiles, over the white expanse.

The photograph shows the view of our accommodation, with Pikku Malla in the right-hand background. The lake surface is visible through the still-bare trees.