EISCAT-Sodankylä

If you have looked at the map showing the positions of LOFAR, EISCAT and KAIRA, it will be apparent that there is actually three EISCAT sites on the Fenno-Scandinavian mainland. Apart from the transmitter site at Tromsø and the receiver site at Kiruna (home of the EISCAT_3D demonstrator array) there is also an EISCAT site in Finland.

This is actually located at Sodankylä Geophysical Observatory, the institute behind the KAIRA project. Like the Kiruna site, the EISCAT system in Sodankylä is a receiving station (there is no transmitter). The two dishes are copies of each other, built at the same time and deployed to the two sites. They are fully-steerable, 32m-diameter, prime-focus paraboloids. Both are fitted with UHF receivers (although on occasion other receiving systems have been fitted for specific experiements). The photograph shows well the backing structure and counterweights of the Sodankylä dish.

In fact, at the time these were built, there were two other identical dishes built, which were deployed as part of the European VLBI Network in Italy (one at Medicina and one at Noto).

Apart from some of its own unique research projects, the 32m dish at Sodankylä acts as a one of the receivers for bi- or tri-static ionospheric radar observations.

Photo credit: Th. Ulich

Testing SETI with LOFAR

The KAIRA team has learned that LOFAR test observations have coincided with the 3rd observing run of Project Dorothy. The LOFAR station used was the British LOFAR station (UK608), located at Chilbolton, Hampshire. The Project Dorothy observing run was carried out on the early (Euro-) mornings of the 3rd and 4th of March 2011, with the targets being the so-called Kepler planets, identified by the Kepler mission and other related projects. The aim of Project Dorothy is to provide observations on more than 85 of these candidate sources (including KOI 268.01 and KOI 701.03).

For the LOFAR participation, the work carried out was principally for evaluation of the software systems. The latest tests involved pointing at three different places in the sky at once (using the multi-beam capacity), and also testing if data could be taken at 1 Hz frequency resolution across a full band 36 MHz wide. If these tests are successful, it will pave the way for further use of the LOFAR system for SETI observations.

Station UK608 is still being commissioned in certain areas and the opportunity to carry out this work was fortuitous. The LOFAR-UK observations were organised at the last moment to provide additional coverage of these joint US-Japan observations. Although highly experimental, it appears that data has been successfully taken by the radio telescope, which is great news for LOFAR, and a tribute to the team from SEPnet/Oxford University who provided data acquisition system and managed to get the observations scheduled at the last minute.

Additional programmes are planned for the same observing window approximately 24 hours later with the possibility of further follow-up observations.

What this demonstrates is the flexibility of modern digital radio-telescopes like LOFAR, KAIRA, etc. to react to interesting and challenging observing opportunities.

Thanks to LOFAR-UK and Project Dorothy for the above information.

Early-March status

Wow! The year is moving on and the first site image for March has now come in. The photograph featured in this web log post was taken by a member of the KAIRA team on 4^th March 2011. The raised tile is clearly visible on the right, but the ground tile still remains blanketed by snow. It is just possible to make out its position on the left of the photograph behind one of the posts.


We are now entering an interesting time. Temperatures are starting to rise, sometimes even hitting highs of –10 degrees celsius. From a technical point of view, this is a challenging period for the test antennas, as they will be subjected to ever-compacting snow. There is also the chance of localised melting and re-freezing, especially in the places where direct sunlight can strike the black antenna covers and warm them up. These are the sorts of conditions where ice movement can cause significant damage. Only a few months to go and we'll know if this experiment has worked.

But is will also be interesting from a more artistic sense. As the Arctic approaches the equinox, there is, for a few weeks, a semblance of normal day and night. This is accompanied with a great variety of lighting directions and conditions, plenty of sunshine and some still inky-black nights. Being the tail end of winter, the weather is much nicer, with more snow on the ground and less cloud in the sky.

No doubt, there will be some more lovely photographs to come.

Photo credit: Markku Postila

Kiruna dusk

'I once lived in a place ...'

While going through the photographs for the previous weblog entry, I stumbled across this one. It was taken during the late summer at the Kiruna receiver station, which is part of the EISCAT radar er receiver network. At the time, this was also where I was living (I have a tendency to live at observatories). At this time of the day and year, the lights and colours of the sky can be breathtaking. So, as a nice way to finish the week, let's just end with a photograph.

Enjoy.

Crossing borders

KAIRA will be built at Kilpisjärvi (hence the name!). If you have had a look at the map where this is, you will see it is not far from the international border between Norway and Finland.

Ignoring the border guards and customs station for the time being, the crossing into Norway is marked simply and to the point. 'Norge' (which is Norwegian for Norway, of course). The long road then heads on to the distant towns of Skibotn and Lyngen.

Going the other way, you are entering Finland (written in Finnish, English and Sami language) and, of course, this is shown in the livery of the European Union. After all, this is border not just with Finland, but with the entire of the EU.

The settlement of Kilpisjärvi itself is not far from the border, so there is not far to go once you've entered Finland.

However, not far away from the crossing point is the original border marker.

It is nice to see this old border marker from a bygone era.

(Note: I took these photographs at the height of summer 2006. Of course at the time I'm posting this weblog entry, these vistas are completely white.)

Space debris

Space debris is an ever growing environmental problem occurring in space. After over 50 years of space rocket launches, our near space is littered with approximately 10^6 objects larger than 1 cm in diameter, weighing a total of 5500 tons (Nasa ODQN Jan 2010). As the atmosphere is very thin in near-Earth space, these objects do not come down very quickly, causing danger to Earth orbiting spacecraft for tens or hundreds of years to come. Once these objects are in space, there is also a probability that these objects will eventually collide with each other and create even more debris. As the probability of in flight collisions increases as a function of debris in orbit, a catastrophic collisional cascade process that renders regions of near-Earth space unusable is a real risk. This scenario is often referred to as the Kessler syndrome. A video of the evolution of space objects is shown below.

A hypervelocity collision.

EISCAT has been active in space debris measurements for over 10 years, producing hundreds of hours of space debris measurements, covering two major break ups: the Chinese anti-satellite collision and the collision of the Iridium and Cosmos satellites.

Most of the measurements are so called beam-park measurements where the antenna is positioned at a fixed pointing. During a 24-hour period, while the Earth rotates around its axis, a representative statistical sample of debris is measured, containing information on orbital elements of the debris. The time of day provides information on the longitude of the ascending node, while the Doppler shift gives information on the inclination of the object. An example measurement produced after the collision of the Iridium and Cosmos satellites is shown in the figure below.

EISCAT UHF beam park measurement of the Iridium-Cosmos collision
debris clouds. Each point represents a detection of an object passing
the radar beam, the color represents radial Doppler shift. full sized version.

One of the potential uses of the planned EISCAT3D system is to track space objects and space debris. One of the advantages of a phased array system is the capability of observing a large volume of space simultaneously and making interferometric direction angle measurements. This will allow accurate trajectory measurements that can be used for collision avoidance with operational spacecraft, such as the International Space Station or Envisat.

For more information on EISCAT space debris activities can be obtained here.

SKA — Square Kilometer Array (Part 2)

This article follows on from yesterday's discussion of the Square Kilometre Array (SKA) project.

The SKA will operate over a wide range of frequencies (70 MHZ to 10 GHz) and, like KAIRA, it will be split into different antenna arrays to cover these different frequency bands. The reason for this is that there is no single antenna design that can cover the entire frequency range efficiently.

As a result, the SKA will comprise arrays of three types of antenna elements. These arrays are referred to as the SKA-low, SKA-mid and SKA-dish arrays.


The SKA-low array uses simple dipole antennas to cover the frequency range from 70 - 200 MHz. These will be grouped in 100m diameter stations each containing about 90 elements. This system is very similar to the existing LOFAR Low-Band Array layout.

An artist's impression of the SKA-low dipoles. (Image:
SPDO/Swinburne Astronomy Productions)

The SKA-mid array is again LOFAR-like. It will most likely comprise more delicate antennas, assembled into 'tiles', which are then configured into arrays. These tiles cover the medium frequency range from 200 to 500 MHz, with tiles clustered together into circular stations.

An artist's impression of the SKA-mid tile cluster.
(Image: SPDO/Swinburne Astronomy Productions)

The SKA-dish array will have several thousand antennas in the more traditional 'dish' form to cover the frequency range 500 MHz to 10 GHz. The plan is to equip these dishes with focal plane arrays at their focus to increase their field-of-view (a limitation of traditional dishes).

An artist's impression of the SKA high-frequency dishes.
(Image: SPDO/Swinburne Astronomy Productions)

There are lots of links on the Internet about the SKA project. However, the official project web site is: http://www.skatelescope.org/