A detailed radio image of the entire northern sky in the frequency range of 120-168 MHz. That is what the LOFAR Two-metre Sky Survey (LoTTS) aims to achieve.

Published by the editorial team, 9 June 2020

To do that, scientists must observe no less than 3170 pointings for 8 hours each. When they achieve this impressive feat, the scientists will be able to achieve 5” resolution images with a sensitivity of 100 µJy/beam and accomplish the main scientific aims of the survey: to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structures.

An impossible task? ‘We are now a bit over 50 percent of the observations,’ says ASTRON astronomer dr. Timothy Shimwell. Quite an achievement already and one that has been made with a team of about 250 scientists. Shimwell: ‘We’re spread over 20 countries and about 60 institutes.’

Why so many scientists? Because there were quite a few challenges to overcome with different expertises. For example: LOFAR uses supercomputers that handle large data rates, and a large number of specially written algorithms and software.

High-resolution LOFAR High Band Antenna image of the Boötes field, made at 130-169 MHz. The image is a result of the LOFAR Two Metre Sky Survey. (copyright: Wendy Williams)

To what does the ‘Two-metre’ refer? ‘To the 150 MHz-band’, Shimwell explains. So basically, to the bandwidth that LOFAR is surveying. And quite effectively, Shimwell adds. ‘One of LOFAR’s strengths is to map the sky at very low frequencies with very high resolution and sensitivity, within a reasonable amount of time.’

The project started in 2014 and has thus far produced over a hundred scientific papers. And even though the LOFAR Two-metre Sky Survey had passed the halfway mark, it is unknown when it will be finished. Shimwell: ‘Just like everyone else we have to send in proposals to get some time allocated to do our surveys. We generally put in a big proposal and on average get allocated around a thousand hours per six months.’ To put things into perspective: the whole survey will take about 14,000 hours of observations.

Particularly important about the survey is the openness, explains Shimwell: ‘We are trying to ensure that the data we collect become public in the best possible quality. That way, the whole international scientific community can benefit from it.’

On 12 June 2020, LOFAR celebrates its tenth anniversary. The radio telescope is the world’s largest low frequency instrument and is one of the pathfinders of the Square Kilometre Array (SKA), which is currently being developed. Throughout its ten years of operation, LOFAR has made some amazing discoveries. It has been a key part of groundbreaking research, both in astronomy and engineering. Here we feature some – but definitely not all – of these past highlights, with surely more to come in the future.



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Daily image of the week

On June 13-17, the LOFAR Family Meeting took place in Cologne. After two years LOFAR researchers could finally meet in person again. The meeting brings together LOFAR users and researchers to share new scientific results.

Our renewed ‘Melkwegpad’ (Milky Way Path) is finished! The new signs have texts in Dutch on the one side and in English on the other side. The signs concerning planets have a small, 3D printed model of that planet in their centre.
#Melkwegpad @RTVDrenthe

Daily image of the week

The background drawing shows how the subband correlator calculates the array correlation matrix. In the upper left the 4 UniBoard2s we used. The two ACM plots in the picture show that the phase differences of the visibilities vary from 0 to 360 degrees.

Daily image of the week: Testing with the Dwingeloo Test Station (DTS)
One of the key specifications of LOFAR2.0 is measuring using the low- and the highband antenna at the same time. For this measurement we used 9 lowband antenna and 3 HBA tiles.