Lecture's on!

Lectures in progress... today's photograph is of Lassi Roininen, making his presentation as the first talk of the morning.

Lassi in action! (Photo: D. McKay-Bukowski)

Digital painting of the aurora

The last slide of the first KAIRA presentation at the Inverse Problems working group at Luosto was a digital painting, created by the author. Today we are featuring it on the web log for others to enjoy.

Inverse problems working group

This week, the Inverse Problems teams from a few Finnish Universities and Institutes are meeting to have a working group session. This is an opportunity to get together and work on problems that are part of the join collaborations. This meeting takes place at Luosto, Lapland.

Sunshine!

Yesterday we had some sunshine at the institute. This is actually quite unusual for this year as, apart from the darkness, it has been cloudy nearly no stop since October. So, a bit of sunshine features as today's Friday photograph. The photo was taken by Lassi in the early afternoon.

Sunshine at the EISCAT Building and 32m antenna. (Photo: L. Roininen)

Have a nice weekend!

Snowverhang

Depending on the prevailing wind, snow and temperature conditions, it is possible to get some interesting effects with the ice along the KAIRA HBA tile edges. Today's photograph shows such an effect.

Snowverhang on the KAIRA HBA. (Photo: D. McKay-Bukowski)

Although the effect can be seen in the foreground, it was most pronounced further into the snow corridor. (Click on the image for an enlargement.). At the furthest point, the snow was 90 cm overhanging the edge of the HBA tiles.

Note also the way the snow post at the front corner is bending under the snow loading. This is not much, but it does show a general trend of the ice to move across the surface of the HBA array.

KAIRA featured in ASTRON News

ASTRON (the organisation responsible for the LOFAR project) publish a regular news bulletin with all their latest developments, research and discoveries.

And, guess what features in the Winter 2013 edition?

Yes, KAIRA is the cover photograph. There's a full-page article about KAIRA inside (on page 22) as well!   :-)


Link:

• ASTRON news Winter 2013

Sunlit Hamperokken

It is Friday again, and we have a nice photograph to share with you today, submitted by one of our colleagues from the EISCAT facility, just up the road at Romfjordmoen, near Tromsø.

Hamperokken behind the wires of the ionospheric heating facility. (Photo: M. Rietveld)

The image shows the striking peak of 'Hamperokken' lit by the waning sun at 3.00 pm, Thursday 13 February, with some of the HF antennas of the ionospheric heating facility at Ramfjordmoen in the foreground. Taken while Mike Rietveld was digging about 1.5m into the crusty snow to fix some faulty coaxial cable feed lines in preparation for some Heating campaigns in the coming weeks. The unusually large snowfall and subsequent weather in November has caused considerable damage to the coaxial lines.

Thanks Mike for sharing this with us!

Have a good weekend, everyone.

Reindeer high-pass filter

In places around the KAIRA site, the snow has been sufficiently deep that it renders the reindeer fence useless. There are now at least three places where the land dips, but the snow surface remains constant. Thus, the fence (which follows the terrain) dips under the snow surface.

Snow-covered reindeer fence... mind the gap! (Photo: D. McKay-Bukowski)

Incidentally, we've now seen elk foot prints inside the KAIRA site compound.

Snow on the LBA field

Over the last couple of days, we've reported how snow affects the RF performance of the LBA aerials. Today we have some more photographs from #L33 and #L34.

Just a bit deeper here. Note how this aerial has its wires partly
covered, where the others in the background have their guys and
elastics still visible above the snow line. (Photo: D. McKay-Bukowski)

There was about 20 cm of ice along each
receiver wire. (Photo: D. McKay-Bukowski)

Another image of the iced up wire. The snow depth is
approx. 70-75 cm. The HBA array is visible in the
background. (Photo: D. McKay-Bukowski)

Digging down to the ground plane. Notice how the aerial
is leaning. This is due to the ice tension on the wires,
guys and elastics, causing distortion of the LBA aerial.

Snow affecting the RF-performance

Yesterday we showed a plot which indicated strange spectral responses of the LBA aerials #L33 and #L34. Today we show what is causing this strange effect...

Snow.

Each LBA aerial has four wires that descend from the top of the aerial down towards the corner pegs. This is the receiving wires. However, the lower part is just for support and is either nylon or elastic. As long as the snow is below that level, it does not affect the performance of the wires to receive the radio waves.

The wires reach down to approx. 65 cm above the ground. But, if the snow depth exceeds 65 cm, then this partial covering will start to affect the antenna. And this is precisely what happened to aerials #L33 and #L34.

The author inspecting #L34. The snow depth here is 70 cm.

Strange subband responses

Data Monday again. This time we're featuring some subband statistics from KAIRA's Low-Band Antenna (LBA) array.

There are 48 aerials and for each of these there are two polarisations. Thus, there are 96 signals coming back from the array. Each one has its own Receiver Unit (RCU). After filtering, the signals are digitised and split into 512 frequency channels, called subbands. 1-second average power for each subband for each RCU is calculated and recorded. These are the subband statistics and they can be used for form a spectrum for each RCU, to show its performance. We've occasionally shown these before.

However, last week we noticed something a bit odd...

Four of the RCUs were showing low signals. These were numbers 65, 66, 67 and 68. Here's a plot showing them. Also shown in the plot are RCUs 64 and 65 (which are behaving correctly).

KAIRA subband statistics 05-Feb-2014. RCUs 64 & 65
are behaving normally. The others are a bit odd.

The forest of vertical lines towards the left is radio-frequency interference (RFI) from shortwave radio. The two near the right are FM radio stations. We do expect a peak towards 55-60 MHz, which is the best response for the amplifiers and antenna design. However, notice how RCUs 67, 68 and 69 have their peak shifted to the left a bit. And RCU 66 has a double peak.

Very strange.

If we look up the LBA aerial numbers associated with these RCUs, we find that RCUs 66,67 are for LBA #L33. And 68,69 are for LBA #L34. And, if we check the array map, we find that these two aerials are on the southwestern edge of the LBA array.



Well, we've now done some investigations and have found the cause of the problem. But we'll save that for tomorrow. Until then, you can speculate for yourself.  :-)

Air-conditioning fixes

Recently we've had some problems with the KAIRA RF-container air-conditioning again. The problem this time has been that the refrigerant has been too cold and has lost pressure. This has taken a little while to resolve, but we now have fixed the problem. This has been done by heating the airconditioner!

Yes, that's right, we have put in a heating coil which is variably heated according to temperature. Thus, in the bitterly cold winter nights, this coil warms up sufficiently to keep the partial pressure of the refrigerant at sufficiently high pressure to allow the compressor to continue working. It is a tough fix to make, but we hope to have improved reliability again.

Servicing the air-con unit at KAIRA. (Photo: D. McKay-Bukowski)

Toivo explains the changes and the new heating system. (Photo: D. McKay-Bukowski)

Digging out

I need a spanner.

It's in the storage container.

But the storage container has a great pile of ice packed against the door.

So, I'll need to dig it out.

With a shovel.

Which is in the storage container.

:-\

That was the grey storage container (which you can see, complete with snow pile in one of yesterday's photographs). So what are the chances of needing something from the other storage container in the same trip? Well, pretty high, apparently. At least this time I have a shovel. It is a bleak task to have to do it by hand.

Time to dig my way into the other container (Photo: D. McKay-Bukowski)

KAIRA site conditions

Friday again... times for some more photographs. Today, we have the KAIRA site conditions taken on 05-Feb-2014.

Snow around the LBA cable mausoleum. (Photo: D. McKay-Bukowski)

KAIRA's LBA field in the snow. (Photo: D. McKay-Bukowski)

Snow banks around the site driveway and storage. (Photo: D. McKay-Bukowski)

New networking at KAIRA

We've just upgraded the internal network at KAIRA. This should improve the reliability and give us more remote control to individually power-cycle pieces of equipment. It also improves the internal LAN performance. All the changes have been made within the RF-container.

Timo installing some new network equipment. (Photo: D. McKay-Bukowski)

Breakfast at Tähtelä

Busy week this week. So we had a working breakfast in the conference room in the Sodankylä EISCAT building.

Juha, Mikko and Lassi in the EISCAT-building at SGO. (Photo: D. McKay-Bukowski)

Tähteläntie

Today's photograph is taken at the start of Tähteläntie. Tähtelä (Finnish for "place of  stars") is the actual location of Sodankylä Geophysical Observatory. It is a few kilometres south of Sodankylä itself. This here is the start of the road into Tähtelä.

The road to Tähtelä (Photo: D. McKay-Bukowski)