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| radboud_current_astronomy_picture [2011/07/18 12:10] – created falcke | radboud_current_astronomy_picture [2019/09/19 15:01] (current) – removed nelemans |
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| ====== Radboud Current Astronomy Picture ====== | |
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| ===== July 18, 2011: Fire in TV & radio tower seen in LOFAR data ===== | |
| {{currentpicture:hoogersmildetoren-tbb.jpg }} | |
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| 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. | |
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| 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 | |
| RFI. | |
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| ---- | |
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| Credit: H.Falcke, S. ter Veen | |
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