Sebastiaan van der Tol

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—LOFAR is a low-frequency radio astronomical array currently under development in The Netherlands. It is designed to produce synthesis images of the most distant celestial objects yet observed. Due to high redshift levels, observations must be at unusually low frequencies (30–240 MHz), over large apertures (100 km), using thousands of antennas. At these(More)
In radio astronomy, cosmic sources are observed which are many orders of magnitude weaker than the telescope system noise level. The necessary sensitivity is achieved by large telescope collecting areas, long integration times, and large bandwidths. In the coming two decades, telescopes are planned which are even one to two orders of magnitude more(More)
The LOFAR astronomical array currently under development in The Netherlands will produce synthesis images of the most distant (and thus oldest) space objects by observing at unusually low frequencies (30-250 MHz) over a large aperture (100 km) using many antennas (on the order of 10,000). This presents some significant challenges for sensor calibration(More)
Radio telescopes based on large phased arrays form an interesting application area for array signal processing. LOFAR is a large low frequency (10Mz–240MHz) array consisting of 13,000 antennas grouped into 50 stations, currently under construction in the Netherlands. Data from a 60-element test station of LOFAR is available to evaluate the performance of(More)
Several low frequency radio astronomy arrays are currently under development. For example the LOFAR array (with 13,000 dipole elements) will operate in the frequency range of 20MHz−240Mhz. At these frequencies the effect of the ionosphere cannot be ignored. Due to the fact that the size of the array is larger than the size of the irregularities in the(More)
—Radio astronomical observations are increasingly contaminated by man-made RF interference (RFI). If these signals are continuously present, then they cannot be removed by the usual techniques of detection and blanking. We have previously proposed a spatial filtering technique, where the impact of the interferer is projected out from the estimated(More)
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