Lapland Ice Lanterns

At this time of year, Lappish Ice Lanterns (Jäälyhty in Finnish) are lovely way to decorate paths and outdoor areas around homes. The lanterns are made of ice with a candle and are easy to make. First, you need a bucket. Anything will do, but a plain 10-litre plastic bucket is ideal.

Standard buckets. Just what you need to make the Lappish ice lanterns. Well, that and a cold climate, of course! The exact size is not critical, but these ones hold about 10 litres. (Photo: D. McKay-Bukowski)

This is then filled up with water, leaving a few centimetres to the top (the exact distance is not important, but you just don't want it completely filled). The bucket is then put outside in the snow.

Because it is quite cold at this time of year (typically –15 to –30 degrees C), the water in the bucket will freeze. The bucket should be left out for 4 to 8 hours (depending on the temperature). What is needed is that the water only part freezes. When half frozen, you are left with an "ice bubble" (frozen around the outsides, but still liquid in the centre). That is when you need to bring it back indoors. Note that you should never let the ice completely freeze. It will expand and crack the bucket!

Next, you put the bucket in the sink, upside down. Let some water run over the outside: the ice will slowly start to melt and, with a loud bang, the ice will fall out of the bucket into the sink. Let some water then run onto the top (which was originally the bottom of the bucket). It will melt through the ice and create a hole.

Then tip the ice over and let the remaining water drain out. This leaves an ice shell with a hole in the top.

Tipping the water our of the lantern. Because of the way this one froze, it now has a very thick base. Your hands tend to get very cold doing this! Also, be careful as the wet ice is very slippery too. (Photo: D. McKay-Bukowski)

These ice lantern shells can then be taken back outside. Carefully place a lit candle in it and there you go!

A completed Lapland ice lantern. (Photo: D. McKay-Bukowski)

And that is the lantern!

The ice will protect the candle flame from the wind and the frosted ice will make it beautiful to look at. Because the ice will freeze slightly differently each time, the individual lanterns will all be subtly different. Also, you can colour them, but using not plain water, but the left over water from cooking beetroot or tinted with the dregs of pots of tea.

Some more Lappish ice lanterns in the snow. The two on the left were tinted with some coffee grounds when they were froze, to give an amber-brown tint to the ice. We have several here jsut for decoration and some to illuminate the path to the front door. (Photo: D. McKay-Bukowski)

Of course, in the spring, these lanterns will melt away (but don't forget to clean up the remains of the candles!)

Winter solstice 2012

Another year is almost done and today is the winter solstice. It is also a Friday so, in the tradition of pretty photographs for the end of the week, here is one for that... at the winter solstice too.

Winter solstice at SGO. (Photo: D. McKay-Bukowski)

The photograph was taken looking across the antenna fields; not at KAIRA, but at the Sodankylä Geophysical Observatory. Of course, being in the Arctic the sun does not rise above the horizon, but it is only just below it, giving a strange ethereal twilight above the snowy landscape.

Have a nice weekend (and winter solstice too!)

Routine display of all-sky images

For those of you who have been wondering about the strange plots on the right-hand side of our weblog page, here is the explanation.

These are all-sky radio images, taken using KAIRA. Our array is capable of imaging the entire sky instantaneously. In some ways, you can think of it as a fish-eye lens for radio astronomy. Because of the typical observation mode, we can taken these images regularly and put them on the web for everyone to see. In fact, we are the only LOFAR-based station that we know of that does this on a regular basis. Typically, the images are updated every 9 minutes or so. Here's a recent example:

Along the top of the image is the date (top left) and time (top right). The times are given in Coordinated Universal Time (UTC). Along the bottom are some details of the observation. The "mode" is the "RCU mode" (RCU = Receiver Unit) which specifies which filters are being used and which antenna array is selected. Typically, this is Mode=3 for our low-band antenna array observations. "Sb" is the subband (or receiver channel). Each receiver unit splits the signal up into 512 subbands which are sampled and processed. These all-sky observations are only one subband. The equivalent frequency of this subband is shown at the bottom right.

Around the edge of the plot are the cardinal points (North, East, South, West). Although it might seem that East and West are incorrect, this is actually what you expect when you look up. Imagine lying on your back, looking up. If North is above your head, then East is on your left and West to the right. This is also what you see on conventional star maps.

Because the images are regularly updated, you can watch the radio sources change position with time. The sequence below shows four images, separated by approximately one hour each. As you can see, the position of the radio objects move. This is because the Earth is rotating in the opposite direction. As a result, they appear to be moving around the north celestial pole.

The amount of time it takes for the sources to complete one full circuit is one sidereal day (approx. 23 hours 56 minutes). This is due to the mix between the rotation of the Earth and the orbit of the Earth around the Sun. This also means that for a given time of day, the radio sky will appear at a different position at different times of the year.

Have a very log periodic christmas!

An X-polarized X-mas tree of the future.

With the holidays approaching, the folks at MIT Haystack decided to decorate. This year the Christmas tree is a bit more special than usual. This one can sense radio waves as it doubles as a prototype antenna for SKA. The antenna is developed by Cambridge University for the SKA project and was just recently set up at MIT Haystack so that it can be tested with future receivers developed in the RAPID project.  On the background you can also see the steerable and zenith pointing MIT Haystack ISR antennas.

The lonely road

Roads in Lapland are often long and straight, with very little traffic. Today's photograph shows one such stretch of road between KAIRA and SGO. And with no traffic, it is very easy to stop and wander out into the middle of the road to take such a photograph!

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

Have a nice weekend!

New KAIRA pages

Some of you will no doubt have noticed, but we now have some new pages linked directly through the web log. Above the web log text, you'll see links to general information about the project and also the technical specifications.

The technical specifications list the capabilities of the instrument... very useful for scientists who are thinking of making use of our facility!

KAIRA as a multi-frequency riometer

Photo: Carl-Fredrik Enell

"My name is Malefia Sinor, I’m a student in Lappeenranta University of Technology, in where I am doing a masters thesis in collaboration with Sodankylä Geophysical Observatory. My topic is to search for a parameterized model for the D-region electron density to be used in a multi-frequency riometer data analysis.

"Riometer (relative ionospheric opacity meter) is an instrument used to measure the cosmic HF radio noise absorption that is taking place in the D-region ionosphere (50-90 km). Traditionally, riometers measure the cosmic radio noise only at one or two single frequencies, typically around 40 MHz. Depending on the amount of ionization, the radio signal is absorbed when it passes through the ionosphere. The ionosphere is the partially ionized region of the Earth’s upper atmosphere. It extends from about 60 km to 1000 km. The absorption takes place mainly in the lowest part of the ionosphere, due to collisions between the free electrons and neutral particles.

"KAIRA instrument turns out to be a unique riometer, because of its capability to measure a wide range of different HF frequencies in multiple narrow beams. The multi-frequency capability is the one which makes it possible to invert the electron density since the height profile of the refractive index of the plasma depends on the radio wave frequency for a given electron density profile.

"To share experience and to get an idea about my work, I traveled to Sodankylä. When I arrived, the weather was -20oC (or more), which is for me very cold, I never imagined this kind of weather and I almost couldn’t survive from it for the first time, but peoples at SGO were very helpful. For the last week, I have had an opportunity to attend to the Finnish EISCAT campaign in Tromsø, Norway. After we drove for several hours from Sodankylä to Tromsø, we finally arrived to the EISCAT site. It was ecstatic to see the control room and the receiver when the radar equipments were introduced to us. I’m enjoying my stay on the site, seeing the magical white mountains and the sparkle of the northern lights, and gaining experience of the space physics research in practise."

Winter's day

Today's photograph shows the best light levels that you can expect at this time of year.

The KAIRA site. (Photo: D. McKay-Bukowski)

Signs of winter

Just a nice photograph to finish the week. This one is of the sign as you head past the custom station. In the distance is Saana Mountain.

The sign to Kilpisjärvi. (Photo: D. McKay-Bukowski)

Have a nice weekend!

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)

Kaira Local Pipeline

Today we decided to release the code for our local processing pipeline that we have been working on. We didn't have time to invent a fancy name for it, so just decided to call it the KAIRA Local Pipeline (KLP). You can download it from here: http://www.sgo.fi/~j/klp-1.0.tar.gz. The 1.0 release contains three simple processors: file recorder (to store beamlet data on disk), average power recorder (for e.g., interplanetary scintillation measurements), and a null processor that does nothing (for performance testing the udp packet processing).

While there already exists at least one program (PELICAN) with similar capabilities, we wanted a program that is very simple and allows users get going without learning how to use a larger framework. If you need a sophisticated highly configurable object oriented framework for processing LOFAR data, you should probably be considering PELICAN. If you want something simple and ANSI C based, with minimal supporting utilities and configuration files, you might want to check out KLP.

The hardware needed to run KLP is the similar to what one would have for running ARTERMIS (the pulsar processing pipeline developed at Oxford) or any other local processing pipeline on a LOFAR station. At KAIRA we currently only have one Linux PC with a quad gigabit ethernet interface. This quad gigabit ethernet is connected to the four data lanes coming out of the four RSPs that output the beamformed beamlets. For our current purposes, one machine is enough, but in the future, it would also be possible to install KLP on a Linux cluster and use, e.g., MPI for interprocess communication.

Two possible hardware configurations to run the LOFAR local processing. 

As already said, the software architecture is very simple. There is one process for each lane and there are two threads that work in parallel on the incoming data. The first thread reads the udp packets coming in from the LOFAR RSP, parses them and puts them into a double buffer. Another thread waits for the double buffer to flip and once this happens, it then calls the klp_proc() function that processes the contents of the buffer. All of the underlying threading and synchronization is hidden away from the user, who only has to implement klp_proc().

The software architecture detailing all of the inner workings of KLP. The way to implement your own processing is to define klp_proc() and klp_init() and link it with klp_core.c.  

Mounting snow

Snow levels at KAIRA continue to deepen. Additionally, there is significant drifting in places, which results in raised mounds of it. So far, the arrays are holding up well. There is uniform distribution on the LBA ground planes and snow on tope of HBA tiles is barely exceeding 5 cm due to natural clearing by the wind sheer.

Snow build-up between the LBA mausoleum and the HBA array. (Photo: D. McKay-Bukowski)