Abstract
LOFAR is the world’s largest radio telescope by many measures. It combines signals from phased array antenna stations instead of large parabolic dishes. Signals are digitized at a very early stage, making it a software-heavy facility. The signals recorded by the LOFAR stations are sent to the central processing facility at the University of Groningen’s supercomputer centre. The digital back end, named Cobalt, either correlates these data or creates tied-array beams, and stores them on the CEP4 storage cluster for further processing. After that, data are stored at a long term archive, from which users may download them. This lecture introduces LOFAR’s architecture and antenna types, provides a detailed overview of the Cobalt digital back end, and discusses phased array beams to a level that should be sufficient to understand the data reduction procedures discussed elsewhere in this book.
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Notes
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COrrelator and Beam former Application for the LOFAR Telescope.
- 3.
COBALT computes I = |X|2 + |Y |2, Q = |X|2 −|Y |2, \(U=2Re(X\bar {Y})\), \(V=2Im(X\bar {Y})\). Note that V is a negation of its formal definition.
References
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Brentjens, M.A., Mol, J.D. (2018). LOFAR Overview. In: Heald, G., McKean, J., Pizzo, R. (eds) Low Frequency Radio Astronomy and the LOFAR Observatory. Astrophysics and Space Science Library, vol 426. Springer, Cham. https://doi.org/10.1007/978-3-319-23434-2_2
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