The eXperimental Development Model (XDM) is a 15-m diameter radio telescope antenna prototype for the Karoo Array Telescope (KAT). It is located at the Hartebeesthoek Radio Astronomy Observatory (HartRAO). It is being used to test technology leading up to development of the Square Kilometer Array (SKA).
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2007 07 10 The camera flash produces an intriguing pattern from the reflective targets on XDM, whose surface shape was being measured by photogrammetry and theodolite.
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2007 07 11 Connecting the rotator system for the feed mounting plate on XDM.
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2007 07 12 An optical camera was mounted on XDM to take measurements for the pointing model. This image captures the first star tracked with this system, Vega. A smiling Margie Campbell is seen as a ghostly reflection in the screen.
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2007 07 13 Margaret Campbell (IST), Robert Crida (KAT) and Henk (IST) test the KAT and IST sections of the antenna control system for XDM.
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2007 07 16 This was a very busy day. Here a laser system is being used to verify the alignment of the feed mounting.
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2007 07 16 Adjusting the feed mounting. A laser reflector is mounted on the feed support legs.
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2007 07 16 Next the encoder offsets were adjusted, using the shadow of the Sun to provide the alignment.
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2007 07 16 As the Sun set, the 1.5GHz EMSS feed and HartRAO receiver were mounted at the prime focus by Pieter Stronkhorst of HartRAO. Photographed as night fell, Jupiter can be seen below the focus assembly.
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2007 07 16 XDM first light with the 1.5GHz receiver occured at 18h 55m SAST when Adriaan Peens_Hough and Clifford Gumede of KAT drove the telescope onto Sagittarius A, while Mike Gaylard of HartRAO ran the data capture program developed by Paul Prozesky. The step between 200 and 300 is signal from the calibration noise diode being injected into the receiver. Between 600 and 700, the telescope scans across Sagittarius A, and then settles back to track it from 850 onwards.
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2007 07 16 The bright radio galaxy Cygnus A can be used as a calibrator source. This drift scan across the source was carried out just after 11pm and shows the shape of the main beam. This was the first extra-galactic object recorded by XDM.
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07 07 17 Daylight photo of the 1.5GHz feed and receiver on XDM.
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2007 07 17 Newly minted radio astronomers Adriaan Peens-Hough and Clifford Gumede write up the night's results and breakfast on astronomers' food - Ouma se Beskuit!
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07 07 17 Breakfast over, Clifford and Adriaan resume testing XDM.
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2007 07 17 The supernova remnant Taurus A housing the Crab pulsar, provided a good morning target. Here a stepping scan has been carried, with positions on the source and at the half power points of the beam in the RA and Dec directions. The symmetry of the pattern indicates good pointing accuracy.
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2007 07 18 A scan across Taurus A is closely watched by Thomas Kusel and Adriaan Peens-Hough.
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2007 07 18 XDM 1.5GHz feed focus adjustment by Jacques Grobler and Pieter Stronkhorst.
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2007 07 18 Drift scan across the Sun at 1420MHz by XDM.
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2007 07 18 Installation of the HartRAO-built 12GHz receiver on XDM.
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2007 07 18 First light with the 12GHz receiver on XDM, with a scan across the Sun followed by tracking on the Sun, then orthogonal scans across it.
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2007 07 18 Orthogonal scans across the Sun at 12GHz with XDM. The calibration signal is the small blip near the beginning.
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2007 07 18 First scans across Venus with XDM at 12GHz. Venus is currently nearby in its orbit. With an angular diameter at the time of 41", its blackbody radiation provides a relatively strong signal.
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2007 07 19 Closeup view of the 12GHz receiver on XDM.
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2007 07 19 The visit by the Critical Design Review Team for the dual polarization L-band receiver provided the opportunity to celebrate XDM's first light as a radio telescope.
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2007 07 31 Isak Theron and Robert Lehmensiek of EMSS test the second generation L-band feed for XDM using the HartRAO radiometry test setup.
Find out more about the SKA and KAT at www.ska.ac.za