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LOFAR as a passive radar

Submitter: Michiel Brentjens
Description: On Febrary 26 2008, the entire sky was observed with the LBA antennae at CS010 at a frequency of 55.052 MHz. The integration time per frame is 1 second and the entire observation lasts for 60 seconds. The movie is played back at double speed. North is up and east is on the left. The zenith is at the centre. The Milky Way runs from NE to SSW. Cas A is ENE of the centre and Cyg A due south.

The bright dot moving from NW to NE is an airplane reflecting the radio waves of television transmitter DR 1 in Fyn, Denmark. Across the image, one can see co-moving dots which change brightness along with the aircraft. This is the point spread function (PSF) of the array.

The slow "flash" in the NW is probably an aircraft making a turn and temporarily reflecting a much larger fraction of the radio waves towards CS010. The short flash above the eastern horizon near the end of the movie is most likely a meteor reflection.

Although LOFAR observations at his precise frequency are likely utterly impossible to calibrate down to the thermal noise, frequencies as little as 10 kHz away from 55.052 MHz are clean.
Copyright: (c) 2008 Michiel Brentjens
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