|Description:|| As part of the revision and upgrade of the Westerbork Synthesis Radio Telescope (WSRT), the hardware and software of the telescope control system have been completely redesigned. With that, the WSRT is fully prepared for the new APERTIF era.|
To operate and commission APERTIF properly, the telescope control system should be able to support holography(*). In this mode, one dish tracks a source continuously, while the other scans the same source using a predefined scan pattern. This mode was available in the former WSRT telescope control system, but was not ported to the new system yet. We are glad to report that the holography mode has recently been implemented in the new system as well.
The implementation of the holography mode should of course be verified. How could that be easier, when you just installed Phased Array Feeds in the WSRT dishes? The above images show the 121 receiver chains for dishes RTA and RTB. RTA (left) scans a bright radio source, while RTB (right) tracks it. The scan pattern used here has four points. You can clearly see that the bright source moves through the different receiver chains (or 'pixels') in the left panel. In the right panel, the bright source is in the centre at all times. This shows that the new telescope control system now successfully support holographic measurements.
(*) In radio astronomy, holography is a technique to measure the shape of the dish(es) with the help of a strong celestial point source. It was originally implemented for the WSRT by Hans van Someren Greve.