Daily Image

27-08-2010
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Array noise temperature when scanning the sky with APERTIF tile as aperture array

Submitter: Laurens Bakker, Bert Woestenburg
Description: As follow up on the daily image of 6/8/2010 where we showed an AA-tile system noise temperature below 50K, we have now reprocessed the data to scan the sky. In the first picture an all sky scan is shown. The plot displays the array noise temperature over scan angle. The large red spot in the upper right corner is RT5. The tile was a bit close to this telescope, due to the fact that we used the existing APERTIF back-end to do these measurements. The large red spot in the lower right corner of the picture turned out to be the sun. As expected a strong increase in the noise temperature is visible near the horizon. Due to the relatively large beam-size of one tile this area is rather extended. A careful look at this picture also reveals the road along the telescopes.

In the second picture the array noise temperature up to a scan angle of 45 degrees is shown. It can be seen that the array noise temperature is around 50K at zenith (the minimum noise temperature in this plot is 47K) and is not increasing too much up to a scan angle of 45 degrees. In the third picture this is further magnified by subtracting the array noise at zenith from the array noise temperature at a certain position. This picture shows that the noise temperature is only increasing by ~10K in most directions (apart from the position of RT5 and the sun). One can also observe that the array noise temperature is not necessarily at a minimum at zenith.
Copyright: ASTRON
 
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