Data extraction

There are numerous computers in the RF-container, which handle data processing, control and storage. One of these has now been taken out and has been moved back to SGO for use there in some of our interferometric riometry development work. During the extraction of this data system, we had the side cover of the RF-container signal processing racks off, thus once can see the other computers, network gear, etc.

KAIRA data systems (Photo: D. McKay-Bukowski)

KAIRA site buildings

I took this photograph during a recent trip to KAIRA. The structure on the left if the RF-container. note the large grey panel on the near-side... that is the cowling to protect the airconditioner from snow and ice. The timber structure on the right is the HBA cable mausoleum. This is where additional cable delay line length is placed. Normally on LOFAR systems, this is underground. However at KAIRA both the LBA and HBA arrays have above-ground housing for the extra delay lengths. The other raised building is the site office (known locally as the "barracks").

RF-container and HBA mausoleum, and then the site office. (Photo: D. McKay-Bukowski)

RF-container and the mountains beyond

Recently, Thomas Ulich (SGO Head of Measurements) visited the KAIRA site as part of the maintenance/servicing trip and as a general inspection of the site. During that time, Thomas took a number of good photographs and we'll be featuring those over the next few weeks in amongst our other material.

Today we have the first of these, with a shot looking over the RF-container towards the mountains on the Fenno-Norwegian border. The RF-container contains the signal processing electronics that combines the signals from the KAIRA antennas as well as most of the computing.

KAIRA HBA and RF-container (Photo: Th. Ulich)

kaira05

Recently, we reported on the arrival of a new computer. This `canister mac' has now been installed in the RF-container at KAIRA and is being used for data acquisition. In addition to the computer itself there are two RAID arrays of 28 TB each, which triples the existing capacity of the in-container storage.

The new canister mac (`kaira05') atop the LOFAR
local control unit. (Photo: D. McKay-Bukowski)

The form factor of this machine is difficult so I would not recommend this. Also, the use of MacOSX has been problematic, so we may yet install Linux on this. However these are the tools we've been given and, with a lot of effort, we have managed to get it working at least for the basics. (High-speed processing remains to be tackled).

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)

Repatching the RF-container data network

Recently, we discovered a bit of a problem with the recording of high-speed radar data at KAIRA. We have had some problems with the recording of UDP packets via our local data computer kaira01. As part of the testing for the installation of the new QNAP data recorders, we were also testing the UDP packet reception on not just the QNAP box, but also one of the other KAIRA acquisition machines, kaira03. As this work was being done in the RF-container, we were physically in the container and running the software from there.

During this time, we noticed that simultaneous dropped packets on all four lanes would occur at precisely the moment that the air-conditioning cuts in. Suspecting possible power spikes somehow getting into the network we traced the cables. These turned out to be quite long (two were 7.5 m and the other two were 10 m) and surplus length was coiled in the sub-floor space under the racks close to some of the power distribution cables.

We therefore suspect that some packet loss might have been caused by spikes induced into these cables corresponding to power fluctuations. At the time we were checking this, we also noticed that the cables used were CAT-5, which are only rated to 100 Mbit/s.

We have now replaced all four cables with 3-m CAT-6 cables (rated to 1 Gbit/s). These cables route directly through the signal cable guides on the back of the racks and do not go anywhere near the sub-floor space.

Re-patching work in the RF-container (Photo: D. McKay-Bukowski)

We now see a noticeable improvement in packet reliability, although we still see the occasional lost packet.

KAIRA site conditions 2013.11.25

It is Friday again! But today, instead of a nice photograph, we have a short video for you. Earlier this week there was a pretty heavy snow fall at Kilpisjärvi. Our snow corridors are now about half full and with the wind picking up, there was quite a lot of drift snow banks about. Around midday, we took some video footage of various places around the site and have compiled them into a short video for you to see what KAIRA looks like at this time of year.

Direct link: http://www.youtube.com/watch?v=ut48VSVoFCk


Have a nice weekend!

Sky above, snow beneath

Today we have another photograph of the snow conditions at the KAIRA site:

HBA, RF-container, site office and one of the storage containers.
Oh, and plenty of fresh snow too. (Photo: D. McKay-Bukowski)

Last snow-free day of 2013?

Just a photo today. This shot was taken on what will probably be the last snow-free day of the year. There are snow falls predicted for every day for the remainder of the week.

Last snow-free day of 2013? (Photo: D. McKay-Bukowski)

To the left is the RF-container and HBA cable mausoleum The building behind the Land Cruiser is the site office (or "barracks" as they are sometimes known).

RF-container

Last week, one of the scientists from SGO was en route to Tromsø and passed by the KAIRA site. Today, we feature a couple of photographs that he took of the RF-container. The first image shows the entire container with the mausoleum in front of it.

The KAIRA RF-container. (Photo: C-F Enell)

It is based on a regular international LOFAR RF-container, but with antennas for communications and, of course, the mausoleum for the delay excesses for the HBA array. Additionally, there is a metal cowling on the western side which protects the air-conditioning unit. This metal shield stops ice and snow from jamming up the air-conditioning unit during winter.

Air-conditioning cowling. (Photo: C-F Enell)

RF patch cables and RCUs

Just a neat photograph today... this one was taken on the day of the official opening, looking across the patch cables going into the Receiver Unit (RCU) subracks.

RCUs and patch cables at KAIRA (Photo: J. Keskitalo)

The astute LOFAR observer will know that this is either an RCU mode 3 or mode 4 observation. (Because the led above all the middle input connectors is lit.) Indeed, we observed mode 3 riometry throughout that particular day.

The LOFAR logo

We all know the LOFAR logo...

But who remembers the old one? There used to be an old logo that was used for the LOFAR project. In fact, it can still be found in a few places. And one of these are the front panels of the receiver units.

This photograph is a close-up of one of those in the RF-container of KAIRA.

Close-up of the KAIRA RCU subrack (Photo: J. Keskitalo)

The critical eye

During the KAIRA official opening, we had the honour of having a visit by René Vermeulen, director of the International LOFAR Telescope. Of course we showed him around the facility as part of the general open day and he was most interested in the differences between the KAIRA installation and those of other LOFAR stations. Today's photograph was taken during his inspection of the inside of the RF-container.

The ILT director inspects the KAIRA electronics installation.

Midnight twilight

Glimmers of pink glow illuminate the KAIRA RF-container. This photograph was taken very late at "night".

The KAIRA RF-container. (Photo: D. McKay-Bukowski)

RF-container

Today we just have a nice photograph of the RF-container at the KAIRA site.

The KAIRA RF-container and HBA cable mausoleum. (Photo: D. McKay-Bukowski)

Snow trench

Another photograph of the snow conditions on the site. This one is the path we manually dug through the snow to get to the RF-container and Barracks. At the time this photograph was taken (a couple of weeks ago now), the trench was about 70cm deep. No doubt this will fill up again very quickly.

Snow trench at KAIRA (Photo: D. McKay-Bukowski)

Snow's getting closer

Actually taken a couple of weeks back, but even back then the snowline was descending down the mountain slopes. In the foreground is the RF-container, which houses the KAIRA digital signal processing electronics.

The RF-container at KAIRA, with the HBA mausoleum attached to the front of it. (Photo: D. McKay-Bukowski)

Cable work in the RF-container

We now have installed all the patch cables in the RF-container. These are the 6-metre cables that go from the back of the patch-panel under the false floor and into the signal processing racks.

Under-floor cabling. (Photo. D. McKay-Bukowski)

Close-up of the back of the patch panel. (Photo: D. McKay-Bukowski)

New reel

In the entrance to the RF-container, there are the ends of the cable ducts, where the signal cables emerge from the ground and go into the patch panel. Although the signal path is from outside to in, we actually feed the cables the other way when installing them. As the ducts are getting more and more crowded, we have had to improvise with the installation equipment that we use to do the work.

In this particular case, this meant designing and building a new cable reel. The cables are place on the reel side-by-side (cables for the X and Y polarisations). Although this may not seem like much, it makes a big difference to the work that we do.

The new cable reel, made from scraps of timber, left-over cardboard
and offcuts of agricultural drain. In the background, you can see the
duct entry points and part of the patch panels. (Photo: D. McKay-Bukowski)

RCU boards

The receiver unit (RCU) boards are the first part in the signal processing chain as the signals come into the RF-container. There are 96 of these in total in the KAIRA system (which is the equivalent of a Dutch Remote Station). There is one RCU per polarisation per antenna. Each RCU has three input channels. These are the high-band antennas (HBA), low-band-high (LBH) and low-band-low (LBL). On KAIRA, and other international LOFAR stations, only the HBA and LBH channels are used. These have the signals from the HBA and LBA arrays respectively. The third channel is for even lower frequency antennas (such as 10-30 MHz). At this stage, these antennas have not been realised, although there is some prototype work on this being carried out at the French LOFAR station (FR606, Nançay). On Dutch stations, the second part of the LBA arrays utilise this third channel.

The RCU subracks, with one of the RCU boards pulled out. (Photo: D. McKay-Bukowski)

What this means, is that it is not possible to use the HBA and LBA simultaneously on a given channel. While it is possible to mix and match between the different channel, each individual one is limited to a single input.

On these RCU boards are mostly switches and filters, but this then goes in to the sampler. This is a 12-bit analogue to digital converter, sampling at 160 or 200 megasamples per second (depending on the configuration). Once the signal has been digitised, down-converted and filtered the processing chain is common.