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radboud_current_astronomy_picture [2011/07/18 12:10] (current)
falcke created
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 +====== Radboud Current Astronomy Picture ======
 +===== July 18, 2011: Fire in TV & radio tower seen in LOFAR data =====
 +{{currentpicture:​hoogersmildetoren-tbb.jpg }}
 +On July 15, 2011 the TV & Radio communication tower at Hoogersmilde in the
 +province of Drenthe caught fire and eventually collapsed. This caused
 +a major disruption of TV and radio service in the Netherlands. The
 +tower is located in the same province as the LOFAR radio telescope,
 +which was operational at the time measuring radio emission from cosmic
 +particles for the LOFAR Cosmic Ray Key Science project using the
 +transient buffer boards (TBBs). The TBBs allow one to record raw data
 +from all antenna and do offline processing after an event has
 +happened. The figure shows three radio spectra from low-band antennas
 +(LBAs) in the FM band with 1 kHz resolution right after the fire had
 +started: During the fire the signal strength goes down and then shuts
 +off completely. The data was taken through the side-lobes of the
 +antennas and through a low-pass filter to suppress the FM band, so is
 +highly suppressed, but nonetheless clearly visible.
 +While Hoogersmilde was the strongest source of transmission at
 +low-frequencies,​ it had not caused major problems in LOFAR data since
 +proper measures had been taken to mitigate its radio frequency
 +interference (RFI). In fact, the LBA frequency range is rather free of
 +Credit: H.Falcke, S. ter Veen