Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-12-14
Astronomy and Astrophysics
Astrophysics
12 pages, 11 figures, Accepted for publication in A&A, figures compressed to low resolution; high-resolution version available
Scientific paper
10.1051/0004-6361:20079122
Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity. We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Holographic observations, sampling angular scales between about 5 arcmin and 11 degrees, were obtained of a bright compact source (3C147). These permitted measurement of voltage response patterns for seven of the fourteen telescopes in the array and allowed calculation of the mean cross-correlated power beam. Good sampling of the main-lobe, near-in, and far-side-lobes out to a radius of more than 5 degrees was obtained. A robust empirical beam model was detemined in all polarization products and at frequencies between 1322 and 1457 MHz with 1 MHz resolution. Substantial departures from axi-symmetry are apparent in the main-lobe as well as systematic differences between the polarization properties. Surprisingly, many beam properties are modulated at the 5 to 10% level with changing frequency. These include: (1) the main beam area, (2) the side-lobe to main-lobe power ratio, and (3) the effective telescope aperture. These semi-sinusoidsal modulations have a basic period of about 17 MHz, consistent with the natural 'standing wave' period of a 8.75 m focal distance. The deduced frequency modulations of the beam pattern were verified in an independent long duration observation using compact continuum sources at very large off-axis distances. Application of our frequency-resolved beam model should enable higher dynamic range and improved image fidelity for interferometric observations in complex fields. (abridged)
Braun Robert
Popping Attila
No associations
LandOfFree
The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-662344