The end of May

Just a photograph to end the week... and the month! Next week will be very exciting as we have the official opening ceremony for the station next Thursday. No doubt there will be many updates to the web log during that time so stay tuned.

Today's photograph was taken on the 28th May. It shows the corner of the HBA nearest the RF-container. To the left are the "barracks" and then Saana. To the right of the HBA is Pikku Malla. There is still a tiny amount of snow left on the site, but it won't last long!

Mosaic panorama of the KAIRA HBA - click to enlarge. (Photo: D. McKay-Bukowski)

Have a nice weekend!

Opening display

In exactly one week from today, KAIRA will be formally opened. Although we have been operating for some time now, all the auxiliary tasks have now been completed and routine operations are now, just that. The event has been timed to exploit the hot Arctic summer, and provide a lead-in to the 100th anniversary of Sodankylä Geophysical Observatory. There are lots of preparations to be done, but also a few interesting things along the way which we'll be sharing.

Today's offering is from a new all-sky display that will feature at the opening ceremony.

The radio sky image is the one that is already familiar to our readers; it often appears on the right-hand side and updates every ten minutes or so. It shows the radio intensity across the sky in false colour. However the foreground of this display is a fish-eye view of the KAIRA site.

Imagine lying on the HBA array, looking up, with full hemispheric vision. Then this is the surrounding landscape you would see. North to the top, East to the right. Saana is to the lower left, the VHF is aligned with the tile join, off to the top right. The panorama was made from a series of images taken by Thomas Ulich a while back. We stitched approx. 40 individual frames together to get the landscape panorama, which was then projected and overlaid over the incoming all-sky images.

The final display has more to it than this, but we're saving that for the opening! It updates continuously, providing a dynamic display of the invisible radio universe overhead.

Observing tips #4 — Keeping watch

Often during observing there are tasks that require a certain amount of time to complete. Sometimes these are things that can be simply left to run and at other times you might need to keep an eye on them. Occasionally, there are also occasions when you want to monitor some system parameter on the computer. This can be easy enough to do once, but often it results in typing the command over and over (or using up-arrow / carriage return).

Let's take disk space on the file system, for instance. This is often done with the 'df' command. Now, to be a bit clever, you could put this in a loop. Here is an example (the '%' is just the prompt).

    % while true ; do df ; done

That runs it a bit fast, so we can add some wait time between iterations

    % while true ; do df ; sleep 2 ; done

Better, but still difficult to read. So, we can clear the terminal each time first.

    % while true ; do clear ; df ; sleep 2 ; done

Although the above works, and is effective, there is a simpler way, that exists on most modern Linux systems... watch!

    % watch df

This does exactly what the above command sequence was doing, but it also prints the current time, the update frequency and the command being run. If you want to monitor more complex commands, simply put them in quotes. Such as:

    % watch "ls -l"

To exit from a 'watch', press CTRL+C. There are plenty of options for it too. Just run it with the '--help' flag as:

    %  watch --help

On most versions you can control the update time, highlight differences from one update to the next, control the formatting or even get it to automatically drop out on an error.

All in all, this is a useful utility and it makes keeping tabs on those long data transfers much easier.

Muonionjoki meltwater

As we were last travelling to the KAIRA site, we encountered a lot of meltwater flooding. In particular the Muonionjoki (Muonio River) was extremely high and had burst its banks in places, spilling out through the surrounding forest. On several occasions we stopped to take some pictures and here is a small selection of them.

Flooded forest near Karesuvanto. (Photo: D. McKay-BukowskI)

In places the water encroached onto the main highway. (Photo: D. McKay-Bukowski)

There were several places where there was water lapping against buildings. (Photo: D. McKay-Bukowski)

Accommodation, tea and camping, but bring your own submarine. (Photo: D. McKay-Bukowski)

The swollen Muonio River. (Photo: D. McKay-Bukowski)

LOFAR Overview Paper

 The following was posted on the ASTRON website today:

The long-awaited LOFAR overview paper has now been accepted for publication in the journal Astronomy & Astrophysics. This paper is intended to serve as a general reference and gives an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. The paper also presents a selection of new results from the commissioning phase of this new radio observatory. Over two years in the making, the paper features 56 pages, 34 figures, and 200 authors. The paper will be published in a forthcoming volume of Astronomy & Astrophysics, but in the meantime copies can be downloaded from the astro-ph archive:
http://arxiv.org/abs/1305.3550
 The release of the paper is well timed of course to take advantage of the tsunami of citations sure to be produced by the flood of science papers expected from the first year of LOFAR regular operations. In addition, this paper will hopefully be the first of many more reference papers detailing the various components of the LOFAR system including the pipelines, archive, and MSSS surveys. 

 
Fromall of us here at KAIRA, well done to the LOFAR team for this epic paper (for an epic project!).

Rocks in our Solar System

There will be a special session at the European Week of Astronomy and Space Science (EWASS 2013) to discuss "Rocks in our Solar System - bridging the gap between meteor, meteorite and asteroid studies".

EWASS 2013 is being held on 8 - 13 July 2013, Logomo Centre, Turku, Finland, and this special session will be held on Friday, 12 July. The session will bring together scientists working on all aspects of Solar System rocky material properties. The topic includes laboratory analysis of meteorites and cosmic dust as well as observations and modeling of both meteoroids and asteroids. The contributions bridging the gap between properties of meteors, meteorites and asteroids are highly welcome.

The session will also focus on recent Chelyabinsk fireball / meteorite fall event in order to put together knowledge acquired from studies of fireball trajectory, orbital analysis, and recovered meteorites.

Abstract submission, registration, and conference programme is available on the EWASS 2013 main page.

Session details: http://www.physics.helsinki.fi/conf/EWASS2013

Kurkiaska at midnight

'Tis Friday again (what, already?!), so it is time to end the week with a nice photo. Today's is from the Kurkiaska hydro-power station, on the Kitinen river, just south of Tähtelä, where the institute is. We took this photograph on our way back from the EISCAT_3D Users' Meeting. As we flew in on the late flight, it meant it was really quite late when we crossed the river... just before midnight in fact. The sun had set (just!) but there was still a blaze of colour on the northern horizon.

Have a nice weekend!

Midnight sunset from Kurkiaska. (Photo: D. McKay-Bukowski)

The Kiruna Demonstrator Array

As we wrote earlier, we went to Kiruna last week as part of the planning for the demonstrator array work. The Kiruna EISCAT Demonstrator Array is a phased array of 48 Yagi antennas, arranged in either a 4×12 grid or 4×6 grid... depending on he configuration. It operates at VHF frequencies and is capable of detecting signals from the VHF transmitter in Tromsø.The demonstrator array was mainly built to be an experimental test bed for the digital receivers and digital beam steering that was proposed in the EISCAT_3D design study. Part of the work that the KAIRA team is carrying out is related to this work.

Curious engineers inspect one of the equipment
cabinets. (Photo: D. McKay-Bukowski)

The view along the array. Note the signal cables run
along the frame. (Photo: D. McKay-Bukowski)

Another view (in the sunshine!). But there is still a bit
of snow on the ground. (Photo: D. McKay-Bukowski)

Ionospheric Scintillation with KAIRA and LOFAR

Yesterday we had a seminar from one of our visiting scientists. The subject was ionospheric scintillation and the speaker was Richard Fallows from ASTRON, Netherlands. The abstract of the presentation was:

 The wide bandwidth of KAIRA (Kilpisjärvi Atmospheric Imaging Receiver Array) and LOFAR (Low Frequency Array) is opening up new perspectives in the study of ionospheric scintillation. Direct observing at station level has enabled observations which combine low-band and high-band modes to cover the full available frequency bandwidth from 10 to 250 MHz. For the first time, the evolution of scintillation from weak to strong scattering regimes has been directly observed in dynamic spectra. "Scintillation arcs", seen previously in two-dimensional power spectra from interstellar scintillation observations, have been noted for the first time using observations of ionospheric scintillation. This offers new methods of studying the plasma structures giving rise to the scintillation.

It was an excellent talk... really interesting, great results and a lively discussion afterwards. Thanks Richard!

Thomas Ulich (standing) introduces the speaker
Richard Fallows (right). Photo: E. Turunen.

That also prompted us to investigate some of the riometry data that we had taken and look at some of the scintillation effects that we see in that. It was certainly good to examine some of the data with an expert at hand to advise us on what we were seeing.

Lappish crisps

Only in Lapland...

Actually, these are really, really good. I'd rank them as my third-favourite flavour ever.  (After Paprika and Salt-&-Vinegar, in case you are wondering.)

Kiruna EISCAT site

Today we just have a photograph from the EISCAT radar receiver site at Kiruna, Sweden. (I used to live here once.)

EISCAT Mottagarstasjon, Kiruna. (Photo: D. McKay-Bukowski)

You're breaking up...

At the end of last week a couple of the KAIRA team went over the the EISCAT site at Kiruna, Sweden. The purpose of the visit was to do a preliminary investigation of the set-up of the EISCAT_3D demonstrator array that is built there. We have a few photographs to share, and they will be posted later this week.

However on  the way there, we crossed a few rivers. As it is now well into spring these are starting to melt and break up. At one crossing, there was a huge jumble of broken ice. It looked quite striking... and quite treacherous too!

Broken ice in the river. (Photo: D. McKay-Bukowski)

And the bridge itself. (Photo: D. McKay-Bukowski)

Data recovery

Some of the data that we take with KAIRA can be exported across a 3G mobile data link. However, some experiments generate such large volumes of data that the only sensible thing to do at this stage si to physically go to the site, copy the data off onto harddrives and then bring them back to the institute.

Data computers used to recover some of our experiment data.

The photo shows a couple of heavy-duty servers which are making copies of some VHF radar data that we took earlier this year.

Random photos from Uppsala

Last week we had the EISCAT_3D users meeting in Uppsala, Sweden. It was a very successful meeting.. and not just because of the talks given on KAIRA!

We have a collection of photographs from various times and stages of the conference. And, although the conference photograph has already been posted on the EISCAT_3D web log, we felt we should share half-a-dozen or so (well, okay, 10 then) as a reminder of what was a very successful meeting.

Thanks to Mikko Orispää for submitting lots of excellent photographs too.

Enjoy!

The aeroplane to Helsinki at Rovaniemi aerodrome. (Photo: D. McKay-Bukowski)

The lovely scenery in downtown Uppsala. (Photo: M. Orispää)

One of the buildings at the university. The meeting was held next door.
(Photo: D. McKay-Bukowski)

The meeting is formally opened by the director, Craig Heinselman.
(Photo: M. Orispää)

A public fountain. Someone had knitted socks for the cherubs!
(Photo: M. Orispää)

Some of the university buildings. (Photo: M. Orispää)

One of the riometry splinter groups. (Photo: M. Orispää)

Checking out the latest electronics. (Photo: M. Orispää)

The wallpaper on my hotel room wall. Can any chemists tell us what
it's all about? (Photo: D. McKay-Bukowski)

Definitely the best image of the meeting. (Photo: M. Orispää)

Meltwater on the KAIRA site

As Spring continues its metamorphosis into Summer, we are continuing to get pools of liquid water forming around the site. These leave beautiful little pools of sparkling light to dazzle the eye and catch the attention (and soak the foot if you accidentally walk in one!)

A pool of meltwater at the lower right, with the snow shrouded HBA array behind it. (Photo: D. McKay-Bukowski).

Have a nice weekend everyone!

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)

Recent Results on Radar Coding and Priors

Two papers by KAIRA-team have been published in the May issue of Inverse Problems and Imaging:

L. Roininen, P. Piiroinen and M. Lehtinen, Constructing Continuous Stationary Covariances as Limits of the Second-Order Stochastic Difference Equations, Inverse Problems and Imaging 7 611-647 (2013).

L. Roininen and M. S. Lehtinen, Perfect pulse-compression coding via ARMA algorithms and unimodular transfer functions, Inverse Problems and Imaging, 7 649-661  (2013).

The first paper discusses strong-weak convergence of probability measures and a certain class of discretisation-invariant Gaussian Markov random fields. These random fields can be used as a priori distributions in Bayesian statistical inversion. Developed formalism can be used whenever regularisation techniques are needed. We use these priors for ionospheric tomography and radar imaging.

The second paper focuses on a control-theoretic study on amplitude and polyphase radar coding. In collaboration with our MIT colleagues, we are working on actual implementation of these coding methods at Haystack Observatory. The methods will be used operationally in the future EISCAT_3D incoherent scatter radar!

Both papers are open-access!

Inverse Problems and Imaging: http://aimsciences.org/journals/home.jsp?journalID=11

First VLBI fringes with KAIRA & DE601

On Monday 13th May 2013, a joint test between three LOFAR-based telescopes (DE601, SE607 and KAIRA) was carried out. The target was the pulsar B0809+74. It was a complicated experiment, as there were numerous non-standard procedures in place, a variety of equipment/computing configurations and the challenges of scheduling and data transport. However, DE601 and KAIRA managed to take a short burst of co-temporal data and we managed to get the data from Kilpisjärvi to the correlator in Bonn, Germany.

Then, late last night, we received an e-mail from our German colleagues, with the news that with less than a minute of data, and with only one LOFAR "lane" (that is, a bandwidth of only 12 MHz), they had made a preliminary detection of fringes!

First-fringes! (Image: O.Wucknitz, MPIfR)

As the project coordinator, Olaf Wucknitz, explains...

The plot shows a delay/fringe-rate spectrum for 21.5 sec of the first data block with only lane 0 (12 MHz bandwidth). This is after correction for geometric delay (ca. 0.2 msec). The residual delay is about 0.5 musec, consistent with expectations for the ionosphere. The colour scale is logarithmic.

Note that the signal looks different than for unpulsed sources. For only one pulse we would have a diagonal line because of dispersion. For no dispersion, we would have a vertical line, because one short pulse does not constrain the rate. Dispersion turns this diagonal. Here we have a number of pulses, which causes the maxima at separations of 1/period in rate. This is because a full turn per period could not be detected. Ionospheric rates should be << 1 Hz, so the central peak is the real one.

It must be stressed that this is only a preliminary detection. There is still a lot of work to be done and additional verification experiments need to be carried out before we can proceed with further observational programmes. However, this is an extremely promising result and we are delighted to have made this much progress so far. Apart from advancing towards an exciting long-baseline science programme, we have also resolved numerous technical issues along the way, thus improving procedures, calibration and technique for all our other measurement campaigns.

KAIRA, Kilpisjärvi, Finland (Photo: D. McKay-Bukowski)

DE601, Effelsberg, Germany (Photo: D. McKay-Bukowski)

Of course, this initial detection is the longest baseline to have achieved this within the LOFAR system... a baseline of some 2185 km!

The location of the two stations: KAIRA (Kilpisjärvi, Finland) and DE601 (Effelsberg, Germany).

Thanks go to all the participants in this work, especially to Olaf Wucknitz (MPIfR, Bonn).

What a surprise!

Yesterday I received something really amazing in the post. At first I was completely puzzled by it:  the package was quite plain, I didn't recognise the handwriting, there was no return address and the previous address was obscured.

The mystery package

So, completely baffled I opened it up to find a book. Wow! It was a book detailing the construction of the LOFAR station in England.

Wow! That was TOTALLY unexpected.

Entitled "The Installation of LOFAR UK608 in Chilbolton", it had entries and photographs from the early days of the project in late 2009, all the way through to the point when I formally left for the current project in Finland, which was in early 2013. Throughout its pages, were not just words and images, but memories of all the challenges and triumphs of that project.

Happy memories. (Hey, there's 'my' blue Land Rover!)

But, the best thing was the dedication in the front of the book...

:-)

As I say, there was no return address or indication of who had organised this or written the dedication, but I am very grateful. It was a fantastic gift and I really appreciate it. It brought back lots of happy memories and I sincerely hope that the LOFAR-UK community has as much fun and success using their LOFAR station as I did in building it.

With thanks,

Derek.

A bright day over KAIRA

Just a photograph of the site today, as the snow continues to slowly melt away from the aerials. Although it looks quite soft, the surface of the snow here is very hard as the snow partially melts and re-freezes.

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

Spectro-polarimetric experiments for remote sensing

Announcement:

Spectro-polarimetric experiments for remote sensing
WG4 Meeting in Helsinki, 19-21 August 2013

Polarised light reflectance measurements are essential to empirically validate physically-based parameterisation, to verify selected theoretical models, to provide ground reference data for the calibration of remote-sensing observations, and to support databases needed for data-analysis techniques. Exploitation of acquired experimental information is a valuable tool in target classification and quantification.

Researchers conducting reflectance measurements or using the measurement data are all invited to attend. The primary focus will be on the polarimetric characterisation of test sites and targets, covering also angular, spatial and spectral aspects. Measurement techniques, modelling, and other use of measurement data will also be discussed, wherever related to polarimetric experiments
 
The conference organisers stated that some travel support is available and that there is no registration fee.

More details can be found at the conference website:

http://www.polarisation.eu/index.php/meetings/spectropolarimetricexperiments

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)

Trained containers

On the site there are a few storage containers, used for spare parts and crates and the like. They are lined up along the north-eastern part of the site.

Containers at theKAIRA site. (Photo: D. McKay-Bukowski)

When caught in the evening sun, the looked a bit like a railway train. The thing is though, the barracks (on the left) is actually an ex-railway carriage.

Snow at sunset

We've had some more snow. And this time it fell during a pretty sunset, making for a lovely photo opportunity.

Snowfall at sunset at KAIRA. (Photo: D. McKay-Bukowski)

Have a nice weekend!

Where the test field once was

Today we just have a nice snoswscape of the field where our LFOAR LBA test aerials had been located. The tracks in the snow are from the snowmobiles that we used to recover the equipment.

It looks very picturesque now, but in a few months, this will be a shifting swamp once more.

Clear field: the now empty test field. (Photo: D. McKay-Bukowski)

Uniform snow depth over the LBA field.

One thing that we are particularly pleased about, is that we had correctly anticipated the snow drift patterns, and had left sufficient space between the low-band antenna (LBA) array and other raised and depressed areas around it (such as the edge of the mound and the HBA array). This means that the snow cover across the field, while deep, remains uniform.

Flat snow over the KAIRA LBA array field. (Photo: D. McKay-Bukowski)

It will be interesting to watch the heating pattern as the season warms up, and see whether the melting is also uniform.

Closing the loop... a fragment from Chelyabinsk

Today at the EISCAT_3D User Meeting, held in Uppsala, we've had a plethora of fascinating presentations and discussions. There has been plenty of interesting information, and we've learned a lot. However, for me at least, the best talk has been given by Maria Gritsevich. Her presentation was entitled "Physical properties of meteoroids based on observations" and discussed a number of meteoroid events as well as some theoretical considerations of such events and where radar observations fit in with the ongoing research effort.

However, what made this presentation special was the reference to the Chelyabinsk meteor event. As our regular readers will remember, we were caught up in the initial investigation of that event, as it was coincidentally on the same day as our observations 2012 DA14. That lead to our team doing that initial work on disassociating the meteor event and the asteroid and the initial trajectory and size calculations.

Since then, many other researchers have become involved in the event and the subsequent detailed analysis. And today's presentation was a good chance to reflect the progress that has been made.

Maria Gritsevich giving the presentation of meteoroid research.

And, to top it off... the speaker had brought in a fragment from the Chelyabinsk event to pass around.

A fragment of the Chelyabinsk event.

It was indeed a strange experience to hold this tiny fragment from such a dramatic event that caused such upheaval on that cold February morning, not so long ago.

The "A" sources

Some of the stars that we see with our own eyes have names, but many are catalogued in some systematic way. One of the first major attempts to do this listed each star according to its brightness within a given constellation. The brightest would be assigned the Greek letter alpha, then the next brightest would be beta, then gamma, and so on. Then, just to mix things up, this would be followed by the constellation's Latin name (in the genitive case, of course!). Thus we have stars such as alpha Orionis or beta Ursae Minoris. Since then, there have been many optical star catalogues made, with combinations of letters, numbers, etc., referring to them by position, brightness or some other criteria.

In the early days of radio astronomy, it was noted that, like its optical counterpart, there were distinct objects in the radio sky. These discreet sources were also labelled along similar lines. The brightest "radio star" in a given constellation would be named by the constellation and the Latin letter, starting with "A" for the brightest, then "B", and so forth.

Because radio astronomy advanced so quickly, this system was only used briefly, before naming radio objects with catalogue numbers or positions, such as 3C273 or PSR B1919+21. However, those first few remain highly significant and are, of course, the brightest. So radio astronomers continue to refer to them by their historic names. Because it is usually only the brightest ones that get this treatment, they are usually just the "A" sources from each constellation. Collectively, they are referred to as the "A-sources" or the "A-team".

We use the positions of the A-sources a lot, so we may as well make the list available to everyone else too. The following parametersare the Right Ascensions and Declinations in decimal degrees and radians for each of these historic radio sources.


Name    RA(deg)     Dec(deg)    RA(rad)     Dec(rad)
Cas A    350.8500     58.8150    6.1234877     1.0265154
Cen A    201.3651    -43.0191    3.5144833    -0.7508252
Cyg A    299.8682     40.7339    5.2336866     0.7109409
For A     50.6730    -37.2093    0.8844107    -0.6494249
Her A    252.7839      4.9926    4.4119122     0.0871371
Hyd A    139.5235    -12.0956    2.4351453    -0.2111072
Ori A     83.8221     -5.3911    1.4629713    -0.0940926
Per A     49.9507     41.5117    0.8718036     0.7245158
Per B     69.2682     29.6705    1.2089587     0.5178480
Pic A     79.9572    -45.7788    1.3955169    -0.7989909
Pup A    126.0292    -42.9967    2.1996239    -0.7504334
Sex A    152.7521     -4.6914    2.6660268    -0.0818802
Sgr A    266.4168    -29.0078    4.6498510    -0.5062818
Tau A     83.6331     22.0145    1.4596727     0.3842255
Vir A    187.7059     12.3911    3.2760865     0.2162659

Coordinates are J2000 equinox; J2000.0 epoch.               

Sources:

• Baars et al., The absolute spectrum of CAS A - an accurate flux density scale and a set of secondary calibrators, A&A, 61, 99, 1977
• Bolton, J.G., Stanley, G.J, and Slee, O.B., Galactic Radiation at Radio Frequencies - VIII, Aust.J.Phys, 7, 1, 109-129, 1953.
• Roger, R.S., et al., The radio emission from the Galaxy at 22 MHz, A&A.sup, 137, 7-19, 1999.
• Scaife, A.M.M, & Heald, G.H., A broadband flux-scale for low-frequency raio telescopes, MNRAS, 423, 1, pp. L30-L34, 2010. 
• Stanley, G.J., and Slee, O.B., Galactic Radiation at Radio Frequencies - II, Aust.J.Phys, 1949.
• van der Tol, S., Bayesian Estimation for Ionospheric Calibration in Radio Astronomy, PhD Thesis, 2009
• SIMBAD online catalogue, http://simbad.u-strasbg.fr/
• LOFAR system catalogue, ASTRON, 2011.

Snow on the north-west face

Following on from yesterday's posting, here is the situation on the north-west face of the high-band antenna (HBA) array. This is the side that takes the brunt of the weather.

Snow on the northwestern edge of the HBA array
at the end of April. (Photo: D. McKay-Bukowski)

The fact that this side is now bathed in sunlight, indicates that we are getting close to "midnight-sun season".

Still a bit of snow on site

Although spring is well advanced now, there is still plenty of snow on the ground. Because it reflects the light so well, it will actually take a while yet to disappear. However, the areas which have been cleared (like the path in from the site entrance to the container) will heat more readily and melt away the ice.

Thus, as shown in this picture, deep snow can exist around the site, but the areas that have been ploughed or driven over clear completely.

Deep snow on either side of the cleared driveway into the site.