LOFAR

LOFAR (LOw Frequency ARray) is a pan-European radio telescope designed to observe the radio universe at VHF frequencies. It is designed, built and operated by ASTRON, the Netherlands Foundation for Radio Astronomy. The LOFAR system is split across multiple sites — known as stations — each of which typically has two arrays of antennas.

The antennas in each of these two arrays are different in design. One design is a vertical 'aerial' which stands about 1.8 m tall, optimised for radio frequencies in the range 30 to 80 MHz. The other design is a large 'tile', with a square area of 5 × 5 m. It is for the higher frequency range of 120 to 240 MHz.

Did you note the gap from 80 to 120 MHz? LOFAR deliberately avoids these frequencies, as this is where commercial and public FM-radio stations broadcast. There is no point trying to listen for faint cosmic radio signals at the same frequency as a high-powered neighbouring radio station.

In addition to a large cluster of LOFAR stations in the Netherlands, there are additional participants in the main LOFAR project: Germany, France, Sweden and the United Kingdom. This map is a closer view than the one posted earlier, and shows the locations of the LOFAR stations (green = complete, yellow = under construction).


KAIRA makes use of the same antenna technology that is used in LOFAR, making it compatible with the LOFAR system. This opens up some exciting prospects of linking the two projects. We'll be looking at these antenna systems soon.

In addition, there have just been some important achievements by the LOFAR project. More on that in the next post!

Putting LOFAR, EISCAT and KAIRA on the map

As one might guess from the name, the Kilpisjärvi Atmospheric Imaging Receiver Array is located in Kilpisjärvi. For those of you who didn't already know, Kilpisjärvi is a small border town located in the top-left-hand corner of Finland. It is usually very easy to find on a map, as it is quite close to the corner of the three countries: Norway, Sweden and Finland.

But possibly less familiar are the related LOFAR and EISCAT projects associated with KAIRA.

This map marks the sites of these project with EISCAT in pale blue and LOFAR in magenta. KAIRA itself is marked in red. At a latitude of +69 degrees north, KAIRA is located well above the Arctic Circle (marked in white), making its association with LOFAR a most northerly one indeed.

There'll be more about LOFAR and EISCAT over the coming weeks, so be sure to visit this weblog again soon.

Twitter

@KairaProject

Did you know that the KAIRA project is now on Twitter? You can follow us there to keep in touch with the latest news. As the summer build commences, we'll use it as a way of keeping everyone informed with reports from the construction site. Short, sharp, to-the-point and very, very up-to-date!

http://twitter.com/KairaProject

SGO rakentaa Kilpisjärvelle radiovastaanotinaseman

An announcement of the project (suomeksi / in Finnish language) has been posted on the University of Oulu web site.

Daily Image

Today, KAIRA receives the honour of being featured as the ASTRON Daily Image!

Every day, ASTRON (the Netherlands Institute for Radio Astronomy) posts an interesting image from the world of radio astronomy. These images vary between famous astronomers, the latest observational results and developments in new instruments and telescopes.

Today it is our turn to be featured, with a report on the deployment of the two test tiles which was carried out last October, and how they have fared so far in the winter conditions.

Mid-winter conditions

Taken in the middle of the day in early January, here are our test tiles in action. In the first picture we look past the snow-depth marker in the direction of the raised tile. Although there is 100 to 150 millimetres of snow on it, the situation remains reasonable.


The ground tile, on the other hand, is completely covered... as we expected. Drifting snow banks up against the side of the tile and covers it in a thick, uneven layer.

We shall continue to monitor the progress of the tiles as the Arctic winter drags on.

The sky is the limit?

The main purpose of the new Kilpisjärvi atmospheric receiver array is to function as a remote station for the VHF incoherent scatter radar of the EISCAT Scientific Association located in Tromsø, Norway. Because the receiver will be constructed using LOFAR hardware, it will have a usable frequency band covering 30-240 MHz, with only a small gap where FM broadcast stations are located (80-120 MHz). Due to the large number of antenna elements, the standard antenna array can receive along 254 narrow beams. KAIRA can be used in a number of different ways:

• Wide band imaging riometer, as a complementary instrument to the IRIS riometer located close by. As a riometer, KAIRA can be used without any radar transmitter to study mesospheric (D region) ion chemistry and the effects of active ionospheric modification experiments (Heating) carried out at EISCAT Tromsø.
• In terms of meteor studies, there are a number of possible transmitters in the vicinity that will allow measurements of specular meteor trails, allowing for accurate orbital element determination. In addition to this, there are several meteor radars close by that might yield usable echos.
• It remains to be seen if actual mesosphere-stratosphere-troposphere (MST) measurements can be done, as the site is located fairly far from the nearest MST radar transmitters. At least mesospheric measurements should be feasible.
• Passive radar using digital radio broadcasts.

In addition to these there are several other possible uses for KAIRA as shown in the figure on the right column of this blog.

There are also several smaller instruments that could be co-located with KAIRA to make the site a truly versatile platform for atmospheric studies. Such installations will be considered together with our collaborators in due course.